Patent Description:
Climate change and on-going energy transition make mandatory to replace fossil carbon-based fuels in chemical production and recycled processes to a more environmentally friendly decarbonized source of energy. Transforming natural gas into valuable chemicals requires elevated temperature, often higher than <NUM> and even up to <NUM> and are often endothermic. The energy needed is, therefore, high and not often environmentally friendly, as it is demonstrated by the common use of fired heated reactors. Several studies have been undertaken to reduce the burden imposed by these (harsh) reaction conditions.

The study of <NPL>) describes the use of magnetic nanoparticles as heating agents to improve the energy efficiency of reactions performed at high temperature, as the heat can be then directly and homogeneously transferred to the medium without the need for heating the reactor walls. This was applied in the hydrodeoxygenation of ketones. However, in such system, relatively low temperatures up to <NUM> were reached and the reaction is exothermic.

In the study of<NPL>), a conventional fired reactor was replaced by an electric-resistance-heated reactor. A laboratory-scale reactor based on FeCrAl alloy tube having a diameter of <NUM> and coated with a <NUM>-µm-nickel-impregnated washcoat was used to carry out steam methane reforming. As the heat source and the wall of the tube are one, it is possible to minimize the loss of heat and then to render more efficient and more economical the process of steam methane reforming. Temperatures with a maximum of <NUM> were reached with this kind of reactor.

In the study of <NPL>), a ceramic tube, having an outer diameter of <NUM> and made of a perovskite derivative, is used as the electrolyte. By applying a voltage and hence a current across the electrolyte, hydrogen can be selectively extracted from methane and steam. The perovskite derivative is supplemented with nickel nanoparticles to provide the catalyst necessary to the reaction.

In the study of<NPL>), electromagnetic induction heating of catalytic heterogeneous processes was used and has been demonstrated as bringing several advantages in terms of process intensification, energy efficiency, reactor setup simplification and safety issues coming from the use of radiofrequency. Temperatures ranging between <NUM> and <NUM> in reactors having <NUM> of inner diameter can be reached using Ni<NUM>Co<NUM> pellets as heat mediators in a continuous-flow fixed-bed reactor.

<CIT> describes a method for producing hydrogen and high quality coke which comprises passing inert solid particles as a relatively dense mass downwardly through an elongated reaction zone, applying an electrical voltage of <NUM> to <NUM> volts per inch across at least a portion of said solids mass in said reaction zone, said voltage being sufficient to raise the temperature of said solids to <NUM> to <NUM> F due to their resistance to the flow of electricity without causing substantial electrical spark discharges through said solids mass, downwardly withdrawing thus heated solids from said reaction zone, preheating a hydrocarbon feed by heat exchange with said withdrawn solids and introducing said preheated feed into and upwardly through said reaction zone in the form of an upwardly moving gasiform stream, said feed contacting said heated solids and being converted to light vapors including a substantial portion of hydrogen and carbon which deposits on said solids, heat exchanging hot vapors withdrawn from said reaction zone with inert solids in a heating zone, circulating at least a portion of the solids withdrawn from the reaction zone and previously heat exchanged with said feed to said heating zone, passing solids from said heating zone to said reaction zone as solids feed thereto, and recovering at least a portion of the solids withdrawn from the reaction zone as product and recovering hydrogen gas and light vapors from the upper portion of said reaction zone.

<CIT> describes a process for converting hydrocarbons to produce lower boiling hydrocarbons and solid coke particles of a size larger than fluidizable size which comprises passing coke agglomerates down through a hot fluidized bed of coke particles, introducing hydrocarbon oil feed into said fluidized bed to crack the hydrocarbon oil, passing cracked vaporous products overhead, removing coke agglomerates from said fluid bed and passing them down through a heat exchanger zone in counter-current contact with said withdrawn cracked vaporous products to cool said cracked vaporous products and to heat said coke agglomerates while condensing and depositing higher boiling hydrocarbons from said cracked vaporous products on said coke agglomerates, withdrawing resulting cracked vaporous products as product, recirculating the so treated coke agglomerates a number of times through said heat exchange zone to deposit hydrocarbons and through said hot fluidized coke bed to coke the deposited high boiling hydrocarbons and to increase the size of the coke agglomerates, withdrawing coke agglomerates of increased size as product from the system. These examples show that progress exists in the field of transforming fossils sources into valuable chemicals with the perspective to diminish the impact onto the climate. However, this progress has not been developed to a large scale as it is rather limited to the laboratory environment.

With regards to this matter, the Shawinigan process, described in <CIT>, relates to a process to prepare hydrocyanic acid from ammonia using in a fluidized bed reactor made of high temperature-resistant silica glass and comprising conductive carbon particles, such as coke and/or petroleum coke. The principle resides in that the electricity is used to heat the conductive carbon particles which can maintain the fluidized bed at a temperature sufficient to transform ammonia into hydrocyanic acid, which is then recovered from the outgoing gas coming off the fluidized bed. The inner diameter of the reactor tube was <NUM>. A temperature ranging between <NUM> and <NUM>, sufficient to perform the requested reaction, can be reached by using such conductive carbon particles.

The disclosure of <CIT> described a fluidized-bed reactor made of silicon carbide for preparing granular polycrystalline silicon at the industrial level. The fluidized-bed reactor is heated using a heating device which is placed in an intermediate jacket between the outer wall of the reactor tube and the inner wall of the reactor vessel. Such intermediate jacket comprises an insulation material and is filled or flushed with an inert gas. It was found that the use of sintered silicon carbide (SSiC) having a SiC content <NUM>% by weight as the main element of the reactor tube with a high purity SiC coating deposited by chemical vapour deposition allowed reaching high temperature up to <NUM> without the tube being corroded. It was also found that using siliconized silicon carbide (SiSiC) as the main element of the reactor tube without any surface treatment, such as the deposition of a coating layer, led to the tube being corroded.

<CIT> discloses cracking heaving hydrocarbons in a fluidized bed in the presence of steam wherein the heat can be provided by electrically heated resistance rods.

On the other hand, the disclosure of <NPL>, relates to fluidized-bed reactor made in graphite and susceptible to perform reaction such as the hydrocracking of hydrocarbons, the pyrolysis of organics, the production of elemental phosphorus or the chlorination of zirconium oxide. Operation at temperatures up to about <NUM> appears possible. However, it is not certain that on the long-term perspective, the graphite material used to design the fluidized-bed reactor can resist to such harsh reaction conditions. Indeed, in the study of <NPL>), it has been shown that graphite corrodes under conditions involving steam and elevated temperature, for instance between <NUM> and <NUM>. Also, as shown in the study of <NPL>), the graphite is susceptible to carbon oxidation reaction, which impacts in its activity as an electrode by restricting notably the voltage that can be applied to it.

The present disclosure aims to provide a large-scale solution to one or more of the problems encountered in the prior art that is suitable for application in the industry, such as the chemical industry. The present disclosure aims to contribute to the replacement of the use of fossil carbon-based fuels heating devices in fluidized bed reactors. The present invention provides a solution to conduct endothermic steam cracking of hydrocarbons into hydrogen, ethylene, propylene, butadiene and single ring aromatics.

According to a first aspect, the invention provides for a process to perform steam cracking reaction of hydrocarbons having at least two carbons, said process comprising the steps of:.

the process is remarkable in that at least <NUM> wt. % of the particles based on the total weight of the particles of the bed are electrically conductive particles and have a resistivity ranging from <NUM> Ohm. cm to <NUM> Ohm. cm at <NUM> and in that the step c) of heating the fluidized bed is performed by passing an electric current through the fluidized bed; and in that the electrically conductive particles of the bed comprise one or more non-metallic resistors selected from silicon carbide, molybdenum disilicide or a mixture thereof.

Surprisingly, it has been found that the use of electrically conductive particles, such as silicon carbide, mixed oxides and/or mixed sulphides, said mixed oxides and/or said mixed sulphides being ionic or mixed conductor, namely being doped with one or more lower-valent cations, in one or more fluidized bed reactors which are electrified, allows maintaining a temperature sufficient to carry out a steam cracking reaction of hydrocarbons requesting high-temperature conditions such as temperature reaction ranging from <NUM> to <NUM> without the need of any external heating device. The use of at least <NUM> wt. % of electrically conductive particles within the particles of the bed allows minimizing the loss of heat when a voltage is applied. Thanks to the Joule effect, most, if not all, the electrical energy is transformed into heat that is used for the heating of the reactor medium.

In a preferred embodiment, the volumetric heat generation rate is greater than <NUM> MW/m<NUM> of fluidized bed, more preferably greater than <NUM> MW/m<NUM>, in particular, greater than <NUM> MW/m<NUM>.

In a preferred embodiment, the at least one fluidized bed reactor comprises a vessel and is devoid of heating means located around or inside the vessel.

For example, the content of electrically conductive particles is ranging from <NUM> wt. % to <NUM> wt. % based on the total weight of the particles of the bed; preferably, from <NUM> wt. % to <NUM> wt. %, more preferably from <NUM> wt. % to <NUM> wt. %, even more preferably from <NUM> wt. % to <NUM> wt. % and most preferably from <NUM> wt. % to <NUM> wt.

For example, the content of electrically conductive particles based on the total weight of the bed is at least <NUM> wt. % based on the total weight of the particles of the bed; preferably, at least <NUM> wt. %, more preferably, at least <NUM> wt. %; even more preferably at least <NUM> wt. %; and most preferably at least <NUM> wt. % or at least <NUM> wt. % or at least <NUM> wt. % or at least <NUM> wt.

For example, the electrically conductive particles have a resistivity ranging from <NUM> to <NUM> Ohm. cm at <NUM>, preferably ranging from <NUM> to <NUM> Ohm. cm at <NUM>; more preferably ranging from <NUM> to <NUM> Ohm. cm at <NUM> and most preferably ranging from <NUM> to <NUM> Ohm. cm at <NUM>
For example, the electrically conductive particles have a resistivity of at least <NUM> Ohm. cm at <NUM>; preferably of at least <NUM> Ohm. cm at <NUM>, more preferably of at least <NUM> Ohm. cm at <NUM>; even more preferably of at least <NUM> Ohm. cm at <NUM>, and most preferably of at least <NUM> Ohm. cm at <NUM>.

For example, the electrically conductive particles have a resistivity of at most <NUM> Ohm. cm at <NUM>; preferably of at most <NUM> Ohm. cm at <NUM>, more preferably of at most <NUM> Ohm. cm at <NUM>; even more preferably of at most <NUM> Ohm. cm at <NUM>, and most preferably of at most <NUM> Ohm. cm at <NUM>.

The selection of the content of electrically conductive particles based on the total weight of the particles of the bed and of the electrically conductive particles of a given resistivity influences the temperature reached by the fluidized bed. Thus, in case the targeted temperature is not attained, the person skilled in the art may increase the density of the bed of particles, the content of electrically conductive particles based on the total weight of the particles of the bed and/or select electrically conductive particles with a lower resistivity to increase the temperature reach by the fluidized bed.

For example, the density of the bed of particles is expressed as the void fraction. Void fraction or bed porosity is the volume of voids between the particles divided by the total volume of the bed. At the incipient fluidisation velocity, the void fraction is typically between <NUM> and <NUM>. The void fraction can increase up to <NUM> in fast fluidised beds with lower values at the bottom of about <NUM> and higher than <NUM> at the top of the bed. The void fraction can be controlled by the linear velocity of the fluidising gas and can be decreased by recycling solid particles that are recovered at the top and send back to the bottom of the fluidized bed, which compensates the entrainment of solid particles out of the bed.

The void fraction VF is defined as the volume fraction of voids in a bed of particles and is determined according to the following equation: <MAT>.

For example, the void fraction of the bed is ranging from <NUM> to <NUM>; preferably ranging from <NUM> to <NUM>, more preferably from <NUM> to <NUM>. To increase the density of the bed of particles, the void fraction is to be reduced.

For example, the particles of the bed have an average particle size ranging from <NUM> to <NUM> as determined by sieving according to ASTM D4513-<NUM>, preferably ranging from <NUM> to <NUM> and more preferably ranging from <NUM> to <NUM> or from <NUM> to <NUM>.

Determination by sieving according to ASTM D4513-<NUM> is preferred. In case the particles have an average size of below <NUM> the determination of the average size can also be done by Laser Light Scattering according to ASTM D4464-<NUM>.

For example, the electrically conductive particles of the bed have an average particle size ranging from <NUM> to <NUM> as determined by sieving according to ASTM D4513-<NUM>, preferably ranging from <NUM> to <NUM> and more preferably ranging from <NUM> to <NUM>.

The electrically conductive particles of the bed comprise one or more non-metallic resistors selected from silicon carbide, molybdenum disilicide or a mixture thereof.

For example, the electrically conductive particles of the bed are or comprise a non-metallic resistor being silicon carbide.

For example, the electrically conductive particles of the bed comprise a mixture of a non-metallic resistor being silicon carbide and electrically conductive particles different from silicon carbide. The presence of electrically conductive particles different from silicon carbide in the bed is optional. It can be present as a starting material for heating the bed since it was found that the resistivity of silicon carbide at room temperature is too high to start the heating of the bed. Alternatively to the presence of electrically conductive particles different from silicon carbide, it is possible to provide heat to the reactor for a defined time to start the reaction.

For example, the silicon carbide is selected from sintered silicon carbide, nitride-bounded silicon carbide, recrystallised silicon carbide, reaction bonded silicon carbide and any mixture thereof. The type of silicon carbide material is selected according to the required heating power necessary for supplying the reaction heat of the steam cracking.

For example, the electrically conductive particles of the bed comprise a mixture of a non-metallic resistor being silicon carbide and electrically conductive particles different from silicon carbide and the electrically conductive particles of the bed comprises from <NUM> wt. % to <NUM> wt. % of silicon carbide based on the total weight of the electrically conductive of the bed; preferably, from <NUM> wt. % to <NUM> wt. %, more preferably from <NUM> wt. % to <NUM> wt. %, even more preferably from <NUM> wt. % to <NUM> wt. % and most preferably from <NUM> wt. % to <NUM> wt.

For example, the electrically conductive particles of the bed comprise a mixture of a non-metallic resistor being silicon carbide and electrically conductive particles different from silicon carbide and the said electrically conductive particles different from silicon carbide are one or more carbon-containing particles and/or one or more mixed oxides being doped with one or more lower-valent cations and/or one or more mixed sulphides being doped with one or more lower-valent cations; with preference, the carbon-containing particles are selected from graphite, carbon black, coke, petroleum coke and/or any mixture thereof.

For example, the electrically conductive particles of the bed comprise one or more mixed oxides being ionic conductor, namely being doped with one or more lower-valent cations; with preference, the mixed oxides are selected from:.

Examples of one or more mixed sulphides are.

With preference, the degree of substitution in the one or more mixed oxides doped with one or more lower-valent cations and having a cubic fluorite structure is between <NUM> and <NUM> atom% based on the total number of atoms present in the one or more oxides having a cubic fluorite structure, preferably between <NUM> and <NUM> atom%, more preferably between <NUM> and <NUM> atom%.

With preference, the degree of substitution in the one or more mixed oxides doped with one or more lower-valent cations is between <NUM> and <NUM> atom% based on the total number of atoms present in the one or more ABO<NUM>-perovskites with A and B tri-valent cations, in the one or more ABO<NUM>-perovskites with A bivalent cation and B tetra-valent cation or in the one or more A<NUM>B<NUM>O<NUM>-pyrochlores with A trivalent cation and B tetra-valent cation respectively, preferably between <NUM> and <NUM> atom%, more preferably between <NUM> and <NUM> atom%.

With preference, the degree of substitution in the one or more mixed sulphides doped with one or more lower-valent cations and having a cubic fluorite structure is between <NUM> and <NUM> atom% based on the total number of atoms present in the one or more oxides having a cubic fluorite structure, preferably between <NUM> and <NUM> atom%, more preferably between <NUM> and <NUM> atom%.

With preference, the degree of substitution in the one or more mixed sulphides doped with one or more lower-valent cations is between <NUM> and <NUM> atom% based on the total number of atoms present in the one or more ABS<NUM> structures with A and B tri-valent cations, in the one or more ABS<NUM> structures with A bivalent cation and B tetra-valent cation or in the one or more A<NUM>B<NUM>S<NUM> structures with A trivalent cation and B tetra-valent cation respectively, preferably between <NUM> and <NUM> atom%, more preferably between <NUM> and <NUM> atom%.

For example, the electrically conductive particles of the bed comprise one or more metallic alloys; with preference, one or more metallic alloys are selected from Ni-Cr, Fe-Ni-Cr, Fe-Ni-Al or a mixture thereof.

With preference, when said metallic alloy comprises at least chromium, the chromium content is at least <NUM> mol. % of the total molar content of said metallic alloy comprising at least chromium, more preferably at least <NUM> mol. %, even more preferably at least <NUM> mol. %, most preferably at least <NUM> mol. Advantageously yet, the iron content in the metallic alloys is at most <NUM>% based on the total molar content of said metallic alloy, preferably at most <NUM> mol. %, more preferably at most <NUM> mol. %, even more preferably at most <NUM> mol.

For example, the electrically conductive particles of the bed comprise a mixture of a non-metallic resistor being silicon carbide and one or more carbon-containing particles different from silicon carbide wherein the carbon-containing particles different from silicon carbide is or comprises graphite particles; with preference, said graphite particles have an average particle size ranging from <NUM> to <NUM> as determined by sieving according to ASTM D4513-<NUM>, more preferably ranging from <NUM> to <NUM> and most preferably ranging from <NUM> to <NUM>.

For example, the said steam cracking reaction is conducted at a temperature ranging from <NUM> to <NUM>, preferably from <NUM> to <NUM>, more preferably from <NUM> to <NUM> and most preferably from <NUM> to <NUM>.

For example, the said steam cracking reaction is performed at a pressure ranging between <NUM> MPa and <NUM> MPa, preferably between <NUM> MPa and <NUM> MPa.

In an embodiment, said process comprises a step of pre-heating with a gaseous stream said fluidized bed reactor before conducting said steam cracking reaction in the fluidized bed reactor; with preference, said gaseous stream is a stream of inert gas and/or has a temperature comprised between <NUM> and <NUM>. The said embodiment is of interest when the carbon-containing particles of the bed and/or the electro-resistive material has too high resistivity at room temperature to start the electro-heating of the bed.

For example, the said steam cracking of a hydrocarbon stream is conducted in presence of a dilution stream and is performed at a weight hourly space velocity of said reaction stream comprised between <NUM>-<NUM> and <NUM>-<NUM>, preferably comprised between <NUM>-<NUM> and <NUM>-<NUM>, more preferably comprised between <NUM>-<NUM> and <NUM>-<NUM>, even more preferably comprised between <NUM>-<NUM> and <NUM>-<NUM>. The weight hourly space velocity is defined as the ratio of mass flow of reaction stream to the mass of solid particulate material in the fluidized bed.

The hydrocarbon feedstock for the present process is selected from ethane, liquefied petroleum gas, naphtha, gasoils and/or whole crude oil.

For example, the fluid stream provided in step b) comprises a hydrocarbon feedstock.

Liquefied petroleum gas (LPG) comprises mainly propane and butanes. Petroleum naphtha or naphtha is defined as the hydrocarbons fraction of petroleum having a boiling point from <NUM> up to <NUM>. It is a complex mixture of linear and branched paraffins (single and multibranched), cyclic paraffins and aromatics having carbons numbers ranging from <NUM> to about <NUM> carbons atoms. Light naphtha has a boiling range from <NUM> to <NUM> and comprises C5 to C6 hydrocarbons, while heavy naphtha has a boiling range from <NUM> to <NUM> and comprises C7 to about C11 hydrocarbons. Gasoils have a boiling range from about <NUM> to <NUM>, and comprise C10 to C22 hydrocarbons, including essentially linear and branched paraffins, cyclic paraffins and aromatics (including mono-, naphtho- and poly-aromatic). Heavier gasoils (like atmospheric gasoil, vacuum gasoil, atmospheric residua and vacuum residua), having boiling ranges above <NUM> and C20+ hydrocarbons including essentially linear and branched paraffins, cyclic paraffins and aromatics (including mono-, naphtho- and poly-aromatic) are available from atmospheric or vacuum distillations units.

In particular, the cracking products obtained in the present process may include one or more of ethylene, propylene and benzene, and optionally hydrogen, toluene, xylenes, and <NUM>,<NUM>-butadiene.

In a preferred embodiment, the outlet temperature of the reactor may range from <NUM> to <NUM>, preferably from <NUM> to <NUM>, more preferably from <NUM> to <NUM>, more preferably from <NUM> to <NUM>.

In a preferred embodiment, the residence time of the hydrocarbon feedstock in the fluidised bed section of the reactor where the temperature is between <NUM> and <NUM>, may range from <NUM> to <NUM> seconds, preferably from <NUM> to <NUM> seconds.

In a preferred embodiment, the steam cracking reaction performed on the hydrocarbon feedstock is done in presence of dilution steam in a ratio of <NUM> to <NUM> steam per kg of hydrocarbon feedstock, preferably from <NUM> to <NUM> steam per kg of hydrocarbon feedstock, more preferably in a ratio from <NUM> to <NUM> steam per kg of hydrocarbon feedstock, to obtain cracking products as defined above.

In a preferred embodiment, the reactor outlet pressure may range from <NUM> to <NUM> MPa, preferably from <NUM> to <NUM> MPa, more preferably may be about <NUM> MPa. Lower operating pressure results in more light olefins yield and reduced coke formation. The lowest pressure possible is accomplished by (i) maintaining the output pressure of the reactor as close as possible to atmospheric pressure at the suction of the cracked gas compressor (ii) reducing the partial pressure of the hydrocarbons by dilution with steam (which has a substantial influence on slowing down coke formation).

Effluent from the pyrolysis furnaces contains unreacted feedstock, desired olefins (mainly ethylene and propylene), hydrogen, methane, a mixture of C4's (primarily isobutylene and butadiene), pyrolysis gasoline (aromatics in the C6 to C8 range), ethane, propane, di-olefins (acetylene, methyl acetylene, propadiene), and heavier hydrocarbons that boil in the temperature range of fuel oil (pyrolysis fuel oil). This cracked gas is rapidly quenched to <NUM>-<NUM> to stop the pyrolysis reactions, minimize consecutive reactions and to recover the sensible heat in the gas by generating high-pressure steam in parallel transfer-line heat exchangers (TLE's). In gaseous feedstock-based plants, the TLE-quenched gas stream flows forward to a direct water quench tower, where the gas is cooled further with recirculating cold water. In liquid feedstock-based plants, a pre-fractionator precedes the water quench tower to condense and separate the fuel oil fraction from the cracked gas. In both types of plants, the major portions of the dilution steam and heavy gasoline in the cracked gas are condensed in the water quench tower at <NUM>-<NUM>. The water-quench gas is subsequently compressed to about <NUM> MPa-<NUM> MPa in <NUM> or <NUM> stages. Between compression stages, the condensed water and light gasoline are removed, and the cracked gas is washed with a caustic solution or with a regenerative amine solution, followed by a caustic solution, to remove acid gases (CO<NUM>, H<NUM>S and SO<NUM>). The compressed cracked gas is dried with a desiccant and cooled with propylene and ethylene refrigerants to cryogenic temperatures for the subsequent product fractionation: front-end de-methanization, front-end de-propanization or front-end de-ethanization.

For example, the step of heating the fluidized bed is performed by passing an electric current at a voltage of at most <NUM> V through the fluidized bed, preferably at most <NUM> V, more preferably at most <NUM> V, even more preferably at most <NUM> V, most preferably at most <NUM> V, even most preferably at most <NUM> V.

For example, said process comprises a step of pre-heating with a gaseous stream said fluidized bed reactor before conducting said steam cracking reaction in the fluidized bed reactor; with preference, said gaseous stream is a stream of inert gas and/or has a temperature comprised between <NUM> and <NUM>.

For example, wherein the at least one fluidized bed reactor provided in step a) comprises a heating zone and a reaction zone and wherein the fluid stream provided in step b) is provided to the heating zone and comprises diluent gases, the step c) of heating the fluidized bed to a temperature ranging from <NUM> to <NUM> to conduct the steam cracking reaction of a hydrocarbon feedstock comprises the following sub-steps:.

The step c) provides that the steam cracking reaction is performed on a hydrocarbon feedstock which implies that a hydrocarbon feedstock is provided.

For example, wherein the heating zone and the reaction zone are mixed (i.e. the same zone); the fluid stream provided in step b) comprises a hydrocarbon feedstock.

For example, wherein the heating zone and the reaction zone are separated zones, the fluid stream provided in step b) to the heating zone is devoid of a hydrocarbon feedstock. For example, wherein the process comprises providing at least one fluidized bed reactor being a heating zone and at least one fluidized bed reactor being a reaction zone, the fluid stream provided in step b) to the heating zone is devoid of a hydrocarbon feedstock and the fluid stream provided in step b) to the reaction zone comprises a hydrocarbon feedstock.

It is understood that the hydrocarbon feedstock is provided to the reaction zone and that when the heating zone is separated from the reaction zone, no hydrocarbon feedstock is provided to the heating zone. It is understood that in addition to the hydrocarbon feedstock provided to the reaction zone, steam can be provided to the reaction zone in order to reach the recommended steam to hydrocarbon ratio in the reaction zone as described above.

According to a second aspect, the invention provides an installation to perform steam cracking reaction, according to the first aspect, said installation comprises at least one fluidized bed reactor comprising:.

the installation is remarkable in that at least <NUM> wt. % of the particles of the bed based on the total weight of the particle of the bed are electrically conductive and have a resistivity ranging from <NUM> Ohm. cm to <NUM> Ohm. cm at a temperature of <NUM>; and in that the electrically conductive particles of the bed comprise one or more non-metallic resistors selected from silicon carbide, molybdenum disilicide or a mixture thereof.

Advantageously, at least one fluidized bed reactor is devoid of heating means located around or inside the reactor vessel. For example, all the fluidized bed reactors are devoid of heating means. When stating that at least one of the fluidized bed reactors is devoid of "heating means", it refers to "classical' heating means, such as ovens, gas burners, hot plates and the like. There are no other heating means than the at least two electrodes of the fluidized bed reactor itself.

For example, the fluidizing gas is one or more diluent gases.

For example, the at least one reactor vessel has an inner diameter of at least <NUM>, preferably at least <NUM>, more preferably at least <NUM>.

With preference, the reactor vessel comprises reactor wall made of materials which are corrosion-resistant materials and advantageously said reactor wall materials comprise nickel (Ni), SiAlON ceramics, yttria-stabilized zirconia (YSZ), tetragonal polycrystalline zirconia (TZP) and/or tetragonal zirconia polycrystal (TPZ).

With preference, one of the electrodes is the reactor vessel or the gas distributor and/or said at least two electrodes are made in stainless steel material or nickel-chromium alloys or nickel-chromium-iron alloys.

For example, the at least one fluidized bed reactor comprises a heating zone and a reaction zone, one or more fluid nozzles to provide a hydrocarbon feedstock to the reaction zone, and optional means to transport the particles of the bed from the reaction zone back to the heating zone.

For example, the installation comprises at least two fluidized bed reactors connected one to each other wherein at least one reactor of said at least two fluidized bed reactors is the heating zone and at least another reactor of said at least two fluidized bed reactors is the reaction zone. With preference, the installation comprises one or more fluid nozzles arranged to inject a hydrocarbon feedstock to the at least one fluidized bed reactor being the reaction zone, means to transport the particles of the bed from the heating zone to the reaction zone when necessary and optional means to transport the particles from the reaction zone back to the heating zone. This configuration is remarkable in that a given particle bed is common to at least two fluidized bed reactors.

For example, the at least one fluidized bed reactor is a single one fluidized bed reactor wherein the heating zone is the bottom part of the fluidized bed reactor while the reaction zone is the top part of the fluidised bed reactor. With preference, the installation comprises one or more fluid nozzles to inject a hydrocarbon feedstock between the two zones. The diameter of the heating zone and reaction zone can be different in order to accomplish optimum conditions for heating in the bottom zone and optimum conditions for methane conversion in the top zone. Particles can move from the heating zone to the reaction zone by entrainment and the other way around from the reaction zone back to the heating zone by gravity. Optionally, particles can be collected from the upper heating zone and transferred by a separate transfer line back to the bottom heating zone.

For example, the at least one fluidized bed comprises at least two lateral zones being an outer zone and an inner zone wherein the outer zone is surrounding the inner zone, with the outer zone being the heating zone and the inner zone being the reaction zone. In a less preferred configuration, the outer zone is the reaction zone and the inner zone is the heating zone. With preference, the installation comprises one or more fluid nozzles to inject a hydrocarbon feedstock in the reaction zone.

According to a third aspect, the invention provides the use of a bed comprising particles in at least one fluidized bed reactor to perform a process of steam cracking of hydrocarbons having at least two carbons according to the first aspect, the use is remarkable in that at least <NUM> wt. % of the particles of the bed based on the total weight of the particles of the bed are electrically conductive and have a resistivity ranging from <NUM> Ohm. cm to <NUM> Ohm. cm at a temperature of <NUM>; and in that the electrically conductive particles of the bed comprise one or more non-metallic resistors selected from silicon carbide, molybdenum disilicide or a mixture thereof.

For example, the use comprises heating the bed comprising particles to a temperature ranging from <NUM> to <NUM> in a first reactor, transporting the heated particle bed from the first reactor to a second reactor and providing a hydrocarbon feedstock to the second reactor; with preference, at least the second reactor is a fluidized bed reactor and/or at least the second reactor is devoid of heating means; more preferably, the first reactor and the second reactor are fluidized bed reactors and/or the first and the second reactor are devoid of heating means. For example, the second reactor is devoid of electrodes.

According to a fourth aspect, the invention provides the use of an installation comprising at least one fluidized bed reactor to perform a steam cracking reaction, remarkable in that the installation is according to the second aspect. With preference, the use of an installation at least one fluidized bed reactor to perform a steam cracking reaction in a process according to the first aspect.

The particular features, structures, characteristics or embodiments may be combined in any suitable manner, as would be apparent to a person skilled in the art from this disclosure, in one or more embodiments.

For the disclosure, the following definitions are given:
The terms "comprising", "comprises" and "comprised of" as used herein are synonymous with "including", "includes" or "containing", "contains", and are inclusive or open-ended and do not exclude additional, non-recited members, elements or method steps. The terms "comprising", "comprises" and "comprised of' also include the term "consisting of".

The recitation of numerical ranges by endpoints includes all integer numbers and, where appropriate, fractions subsumed within that range (e.g. <NUM> to <NUM> can include <NUM>, <NUM>, <NUM>, <NUM>, <NUM> when referring to, for example, a number of elements, and can also include <NUM>, <NUM>, <NUM> and <NUM>, when referring to, for example, measurements). The recitation of endpoints also includes the recited endpoint values themselves (e.g. from <NUM> to <NUM> includes both <NUM> and <NUM>).

Conventional steam crackers are complex industrial facilities that can be divided into three main zones, each of which has several types of equipment with very specific functions:.

Conventional steam cracking is carried out in tubular reactors in direct-fired heaters (furnaces). Various vessel sizes and configurations can be used, such as a coiled tube, U-tube, or straight tube layouts. Tube diameters range from <NUM> to <NUM>. Each furnace comprises a convection zone in which the waste heat is recovered and a radiant zone in which cracking takes place.

The present invention provides a process to perform a steam cracking reaction of hydrocarbons having at least two carbons, said process comprising the steps of:.

the process is remarkable in that at least <NUM> wt. % of the particles based on the total weight of the particles of the bed are electrically conductive and have a resistivity ranging from <NUM> Ohm. cm to <NUM> Ohm. cm at of <NUM>, in that the electrically conductive particles of the bed comprise one or more non-metallic resistors selected from silicon carbide, molybdenum disilicide or a mixture thereof, and in that the step c) of heating the fluidized bed is performed by passing an electric current through the fluidized bed.

The solid particulate material in the fluidized bed reactor is typically supported by a porous plate, a perforated plate, a plate with nozzles or chimneys, known as a distributor. The fluid is then forced through the distributor up and travelling through the voids between the solid particulate material. At lower fluid velocities, the solids remain settled as the fluid passes through the voids in the material, known as a packed bed reactor. As the fluid velocity is increased, the particulate solids will reach a stage where the force of the fluid on the solids is enough to counterbalance the weight of the solid particulate material. This stage is known as incipient fluidization and occurs at this minimum fluidization velocity. Once this minimum velocity is surpassed, the contents of the reactor bed begin to expand and become fluidized. Depending on the operating conditions and properties of solid phase various flow regimes can be observed in such reactors. The minimum fluidization velocity needed to achieve bed expansion depends upon the size, shape, porosity and density of the particles and the density and viscosity of the upflowing fluid.

<NPL>) reads that four different categories of fluidization based on the mean particle have been differentiated by Geldart that determine the fluidization regimes:.

Fluidization may be broadly classified into two regimes (<NPL>): homogeneous fluidization and heterogeneous fluidization. In homogeneous or particulate fluidization, particles are fluidized uniformly without any distinct voids. In heterogeneous or bubbling fluidization, gas bubbles devoid of solids are distinctly observable. These voids behave like bubbles in gas-liquid flows and exchange gas with the surrounding homogeneous medium with a change in size and shape while rising in the medium. In particulate fluidization, the bed expands smoothly with substantial particle movement and the bed surface is well defined. Particulate fluidization is observed only for Geldart-A type particles. A bubbling fluidization regime is observed at much higher velocities than homogeneous fluidization, in which distinguishable gas bubbles grow from the distributor, may coalesce with other bubbles and eventually burst at the surface of the bed. These bubbles intensify the mixing of solids and gases and bubble sizes tend to increase further with a rise in fluidization velocity. A slugging regime is observed when the bubble diameter increases up to the reactor diameter. In a turbulent regime, bubbles grow and start breaking up with the expansion of the bed. Under these conditions, the top surface of the bed is no longer distinguishable. In fast fluidization or pneumatic fluidization, particles are transported out of the bed and need to be recycled back into the reactor. No distinct bed surface is observed.

Fluidized bed reactors have the following advantages:.

Heat can be produced by passing an electrical current through a conducting material that has sufficiently high resistivity (the resistor) to transform electricity into heat. Electrical resistivity (also called specific electrical resistance or volume resistivity, is an intrinsic property independent of shape and size) and its inverse, electrical conductivity; is a fundamental property of a material that quantifies how strongly it resists or conducts electric current (SI unit of electrical resistivity is the ohm-meter (Ω·m) and for conductivity Siemens per meter (S/m)).

When electricity is passed through a fixed bed of electrically conducting particulate solids, having a sufficient resistivity, the bed offers resistance to the flow of current; this resistance depends on many parameters, including the nature of the solid, the nature of the linkages among the particles within the bed, the bed voidage, the bed height, the electrode geometry, etc. If the same fixed bed is fluidized by passing gas, the resistance of the bed increases; the resistance offered by the conducting particles generates heat within the bed and can maintain the bed in isothermal conditions (termed an electrothermal fluidized bed or electrofluid reactor). In many high-temperature reactions, electrofluid reactors offer in situ heating during the reaction and are particularly useful for operating endothermic reactions and hence save energy because no external heating or transfer of heat is required. It is a prerequisite that at least part of the solid particulate material is electrically conducting but non-conducting solid particulates can be mixed and still result in enough heat generation. Such non-conducting or very high resistivity solids can play a catalytic role in the chemical conversion. The characteristics of the bed material determine the resistance of an electrothermal fluidized bed furnace; as this is a charge resistor type of heat generation, the specific resistivity of the particles affects the bed resistance. The size, shape, composition, and size distribution of the particles also influence the magnitude of the bed resistance. Also, when the bed is fluidized, the voids generated between the particles increases the bed resistance. The total resistance of the bed is the sum of two components, e.g. the electrode contact-resistance (i.e., the resistance between the electrode and the bed) and the bed resistance. A large contact-resistance will cause extensive local heating in the vicinity of the electrode while the rest of the bed stays rather cool. The following factors determine the contact-resistance: current density, fluidization velocity, type of bed material, electrode size and the type of material used for the electrodes. The electrode compositions can be advantageously metallic like iron, cast iron or other steel alloys, copper or a copper-based alloy, nickel or a nickel-based alloy or refractory like metal, intermetallics or an alloy of Zr, Hf, V, Nb, Ta, Cr, Mo, W or ceramic-like carbides, nitrides or carbon-based like graphite. The area of contact between the bed material and the electrodes can be adjusted, depending on the electrode submergence and the amount of particulate material in the fluidized bed. Hence, the electrical resistance and the power level can be manipulated by adjusting these variables. Advantageously, to prevent overheating of the electrodes compared to the fluidised bed, the resistivity of the electrode should be lower (and hence the joule heating) than of the particulate material of the fluidized bed. In a preferred embodiment, the electrodes can be cooled by passing a colder fluid inside or outside the electrodes. Such fluids can be any liquid that vaporises upon a heating, gas stream or can be a part of the colder feedstock that first cools the electrode before entering the fluidised bed.

Bed resistance can be predicted by the ohmic law. The mechanism of current transfer in fluidized beds is believed to occur through current flow along continuous chains of conducting particles at low operating voltages. At high voltages, a current transfer occurs through a combination of chains of conducting particles and arcing between the electrode and the bed as well as particle-to-particle arcing that might ionize the gas, thereby bringing down the bed resistance. Arcing inside the bed, in principle, is not desirable as it would lower the electrical and thermal efficiency. The gas velocity impacts strongly the bed resistance, a sharp increase in resistance from the settled bed onward when the gas flow rate is increased; a maximum occurred close to the incipient fluidization velocity, followed by a decrease at higher velocities. At gas flow rates sufficient to initiate slugging, the resistance again increased. Average particle size and shape impact resistance as they influence the contacts points between particles. In general, the bed resistivity increases <NUM> to <NUM> times from a settled bed (e.g. <NUM> Ohm. cm for graphite) to the incipient fluidisation (<NUM> Ohm. cm for graphite) and <NUM> to <NUM> times from a settled bed to twice (<NUM> Ohm. cm for graphite) the incipient fluidisation velocity. Non or less-conducting particles can be added to conducting particles. If the conducting solid fraction is small, the resistivity of the bed would increase due to the breaking of the linkages in the chain of conducting solids between the electrodes. If the non-conducting solid fraction is finer in size, it would fill up the interstitial gaps or voidage of the larger conducting solids and hence increase the resistance of the bed.

In general, for a desired high heating power, a high current at a low voltage is preferred. The power source can be either AC or DC. Voltages applied in an electrothermal fluidized bed are typically below <NUM> V to reach enough heating power. The electrothermal fluidized bed can be controlled in the following three ways:.

The wall of the reactor is generally made of graphite, ceramics (like SiC), high-melting metals or alloys as it is versatile and compatible with many high-temperature reactions of industrial interest. The atmosphere for the reaction is often restricted to the neutral or the reducing type as an oxidising atmosphere can combust carbon materials or create a non-conducting metal oxide layer on top of metals or alloys. The wall and/or the distribution plate itself can act as an electrode for the reactor. The fluidized solids can be graphite, carbon, or any other high-melting-point, electrically conducting particles. The other electrodes, which is usually immersed in the bed, can also be graphite or a high-melting-point metal, intermetallics or alloys.

It may be advantaged to generate the required reaction heat by heating the conductive particles and/or catalyst particles in a separate zone of the reactor where little or substantially no feedstock hydrocarbons are present, but only diluent gases. The benefit is that the appropriate conditions of fluidization to generate heat by passing an electrical current through a bed of conductive particles can be optimized whereas the optimal reaction conditions during hydrocarbon transformation can be selected for the other zone of the reactor. Such conditions of optimal void fraction and linear velocity might be different for heating purposes and chemical transformation purposes.

In an embodiment of the present disclosure, the installation comprises of two zones arranged in series namely a first zone being a heating zone and a second zone being a reaction zone, where the conductive particles and catalyst particles are continuously moved or transported from the first zone to the second zone and vice versa. The first and second zones can be different parts of a fluidized bed or can be located in separate fluidized beds reactors connected one to each other.

In the said embodiment, the process to perform steam cracking reaction of hydrocarbons having at least two carbons said process comprising the steps of:.

wherein at least <NUM> wt. % of the particles based on the total weight of the particles of the bed are electrically conductive particles and have a resistivity ranging from <NUM> Ohm. cm to <NUM> Ohm. cm at <NUM> wherein the electrically conductive particles of the bed comprise one or more non-metallic resistors selected from silicon carbide, molybdenum disilicide or a mixture thereof. , wherein the at least one fluidized bed reactor provided in step a) comprises a heating zone and a reaction zone and wherein the fluid stream provided in step b) is provided to the heating zone and comprises diluent gases and the step c) of heating the fluidized bed to a temperature ranging from <NUM> to <NUM> to conduct the steam cracking reaction of a hydrocarbon feedstock comprises the following sub-steps:.

For example, the diluent gases can be one or more selected from steam, hydrogen, carbon dioxide, argon, helium, nitrogen and methane.

For example, the at least one fluidized bed reactor is at least two fluidized bed reactors connected one to each other wherein at least one of said at least two fluidized bed reactors is the heating zone and at least another of said at least two fluidized bed reactors is the reaction zone. With preference, the at least one fluidized bed reactor being the heating zone comprises gravitational or pneumatic transport means to transport the particles from the heating zone to the reaction zone and/or the installation comprises means arranged to inject a hydrocarbon feedstock to the at least one fluidized bed reactor being the reaction zone. The installation is devoid of means to inject a hydrocarbon feedstock to the at least one fluidized bed reactor being the heating zone.

For example, the at least one fluidized bed reactor is a single one fluidized bed reactor wherein the heating zone is the bottom part of the fluidized bed reactor while the reaction zone is the top part of the fluidised bed reactor. With preference, the installation comprises means to inject a hydrocarbon feedstock and/or diluent between the two zones. The diameter of the heating zone and reaction zone can be different in order to accomplish optimum conditions for heating in the bottom zone and optimum conditions for hydrocarbon conversion in the top zone. Particles can move from the heating zone to the reaction zone by entrainment and the other way around from the reaction zone back to the heating zone by gravity. Optionally, particles can be collected from the upper heating zone and transferred by a separate transfer line back to the bottom heating zone.

The step c) provides that the steam cracking reaction is performed on a hydrocarbon feedstock which implies that a hydrocarbon feedstock is provided. It is understood that the hydrocarbon feedstock is provided to the reaction zone and that when the heating zone is separated from the reaction zone then, with preference, no hydrocarbon feedstock with at least two carbons is provided to the heating zone. It is understood that in addition to the hydrocarbon feedstock provided to the reaction zone, steam can be provided to the reaction zone in order to reach the recommended steam to methane ratio in the reaction zone. When the heating zone and the reaction zone are mixed (i.e. the same zone); the fluid stream provided in step b) comprises a hydrocarbon feedstock.

It is a specific embodiment of the present invention that the distance between the heat sources, being the hot particulate material and the feedstock is significantly reduced because of the small size of the particulates and the mixing of the particulates in the vaporous fluidising stream, compared to steam crackers coils having typically <NUM> to <NUM> internal diameter requiring large temperature gradients to concur the large distance that heat has to travel.

To achieve the required temperature necessary to carry out the steam cracking reaction, at least <NUM> wt. % of the particles based on the total weight of the particles of the bed are electrically conductive and have a resistivity ranging from <NUM> Ohm. cm to <NUM> Ohm. cm at <NUM>.

For example, the content of electrically conductive particles based on the total weight of the bed is at least <NUM> wt. % based on the total weight of the particles of the bed; preferably, at least <NUM> wt. %, more preferably,- at least 20wt. %; even more preferably at least <NUM> wt. %; and most preferably at least <NUM> wt. % or at least <NUM> wt. % or at least <NUM> wt. % or at least <NUM> wt.

For example, the electrically conductive particles have a resistivity ranging from <NUM> to <NUM> Ohm. cm at <NUM>, preferably ranging from <NUM> to <NUM> Ohm. cm at <NUM>; more preferably ranging from <NUM> to <NUM> Ohm. cm at <NUM> and most preferably ranging from <NUM> to <NUM> Ohm. cm at <NUM>.

For example, the electrically conductive particles have a resistivity of at least <NUM> Ohm. cm at <NUM>; preferably of at least <NUM> Ohm. cm at <NUM>, more preferably of at least <NUM> Ohm. cm at <NUM>; even more preferably of at least <NUM> Ohm. cm at <NUM>, and most preferably of at least <NUM> Ohm. cm at <NUM>.

For example, the particles of the bed have an average particle size ranging from <NUM> to <NUM> as determined by sieving according to ASTM D4513-<NUM>, preferably ranging from <NUM> to <NUM> and more preferably ranging from <NUM> to <NUM>.

The electrical resistance is measured by a four-probe DC method using an ohmmeter. A densified power sample is shaped in a cylindrical pellet that is placed between the probe electrodes. Resistivity is determined from the measured resistance value, R, by applying the known expression ρ = R × A / L, where L is the distance between the probe electrodes typically a few millimetres and A the electrode area.

The electrically conductive particles of the bed can exhibit electronic, ionic or mixed electronic-ionic conductivity. The ionic bonding of many refractory compounds allows for ionic diffusion and correspondingly, under the influence of an electric field and appropriate temperature conditions, ionic conduction.

The electrical conductivity, σ, the proportionality constant between the current density j and the electric field E, is given by <MAT> where ci is the carrier density (number/cm<NUM>), µi the mobility (cm<NUM>/Vs), and Ziq the Charge (q= <NUM> × <NUM>-<NUM> C) of the ith charge carrier. The many orders of magnitude differences in σ between metals, semiconductors and insulators generally result from differences in c rather than µ. On the other hand, the higher conductivities of electronic versus ionic conductors are generally due to the much higher mobilities of electronic versus ionic species.

The most common materials that can be used for resistive heating can be subdivided into nine groups:.

A first group of metallic alloys, for temperatures up to <NUM>-<NUM>, is constituted by Ni-Cr alloys with low Fe content (<NUM>-<NUM> %), preferably alloy Ni-Cr (<NUM> % Ni, <NUM> % Cr) and (<NUM> % Ni, <NUM> % Cr). Increasing the content of Cr increases the material resistance to oxidation at high temperature. A second group of metallic alloys having three components are Fe-Ni-Cr alloys, with maximum operating temperature in an oxidizing atmosphere to <NUM>-<NUM> but which can be conveniently used in reducing atmospheres or Fe-Cr-AI (chemical composition <NUM>-<NUM> % Cr, <NUM>-<NUM> % Al and Fe balance) protecting against corrosion by a surface layer of oxides of Cr and Al, in oxidizing atmospheres can be used up to <NUM>-<NUM>. Silicon carbide as non-metallic resistor can exhibit wide ranges of resistivity that can be controlled by the way they are synthesized and presence of impurities like aluminium, iron, oxide, nitrogen or extra carbon or silicon resulting in non-stoichiometric silicon carbide. In general silicon carbide has a high resistivity at low temperature but has good resistivity in the range of <NUM> to <NUM>. In an alternative embodiment, the non-metallic resistor can be devoid of silicon carbon, and/or can comprise molybdenum disilicide (MoSi<NUM>), nickel silicide (NiSi), sodium silicide (Na<NUM>Si), magnesium silicide (Mg<NUM>Si), platinum silicide (PtSi), titanium silicide (TiSi<NUM>), tungsten silicide (WSi<NUM>) or a mixture thereof.

Graphite and amorphous carbon (like coke, petroleum coke, and/or carbon black) have rather low resistivity values, with a negative temperature coefficient up to about <NUM> after which the resistivity starts to increase.

Many mixed oxides and/or mixed sulphides being doped with one or more lower-valent cations, having in general too high resistivity at low temperature, become ionic or mixed conductors at high temperature. The following circumstances can make oxides or sulphides sufficient conductors for heating purposes: ionic conduction in solids is described in terms of the creation and motion of atomic defects, notably vacancies and interstitials of which its creation and mobility is very positively dependent on temperature. Such mixed oxides or sulphides are ionic or mixed conductor, namely being doped with one or more lower-valent cations. Three mechanisms for ionic defect formation in oxides are known: (<NUM>) Thermally induced intrinsic ionic disorder (such as Schottky and Frenkel defect pairs resulting in non-stoichiometry), (<NUM>). Redox-induced defects and (<NUM>) Impurity-induced defects. The first two categories of defects are predicted from statistical thermodynamics and the latter form to satisfy electroneutrality. In the latter case, high charge carrier densities can be induced by substituting lower valent cations for the host cations. Mixed oxides and/or mixed sulphides with fluorite, pyrochlore or perovskite structure are very suitable for substitution by one or more lower-valent cations.

Several sublattice disordered oxides or sulphides have high ion transport ability at increasing temperature. These are superionic conductors, such as LiAlSiO<NUM>, Li<NUM>GeP<NUM>S<NUM>, Li3. <NUM>Si<NUM>P<NUM>. <NUM>O<NUM>, NaSICON (sodium (Na) Super Ionic CONductor) with the general formula Na<NUM>+xZr<NUM>P<NUM>-xSixO<NUM> with <NUM> < x < <NUM>, for example Na<NUM>Zr<NUM>PSi<NUM>O<NUM> (x = <NUM>), or sodium beta alumina, such as NaAl<NUM>O<NUM>, Na<NUM>. <NUM>Al<NUM><NUM><NUM>, and/or Na<NUM>. <NUM>Li<NUM>. <NUM>Al<NUM>. <NUM>O<NUM>.

High concentrations of ionic carriers can be induced in intrinsically insulating solids and creating high defective solids. Thus, the electrically conductive particles of the bed comprise one or more mixed oxides being ionic or mixed conductor, namely being doped with one or more lower-valent cations, and/or one or more mixed sulphides being ionic or mixed conductor, namely being doped with one or more lower-valent cations. With preference, the mixed oxides are selected from one or more oxides having a cubic fluorite structure being at least partially substituted with one or more lower-valent cations, preferentially selected from Sm, Gd, Y, Sc, Yb, Mg, Ca, La, Dy, Er, Eu; and/or from one or more ABO<NUM>-perovskites with A and B tri-valent cations, being at least partially substituted in A position with one or more lower-valent cations, preferentially selected from Ca, Sr, or Mg, and comprising at least one of Ni, Ga, Co, Cr, Mn, Sc, Fe and/or a mixture thereof in B position; and/or from one or more ABO<NUM>-perovskites with A bivalent cation and B tetra-valent cation, being at least partially substituted with one or more lower valent cations, preferentially selected from Mg, Sc, Y, Nd or Yb in the B position or with a mixture of different B elements in the B position; and/or from one or more A<NUM>B<NUM>O<NUM>-pyrochlores with A trivalent cation and B tetra-valent cation being at least partially substituted in A position with one or more lower-valent cations, preferentially selected from Ca or Mg, and comprising at least one of Sn, Zr and Ti in B position.

With preference, the one or more mixed sulphides are selected from one or more sulphides having a cubic fluorite structure being at least partially substituted with one or more lower-valent cations, preferentially selected from Sm, Gd, Y, Sc, Yb, Mg, Ca, La, Dy, Er, Eu; and/or from one or more ABS<NUM> structures with A and B tri-valent cations, being at least partially substituted in A position with one or more lower-valent cations, preferentially selected from Ca, Sr, or Mg, and comprising at least one of Ni, Ga, Co, Cr, Mn, Sc, Fe and/or a mixture thereof in B position; and/or from one or more ABS<NUM> structures with A bivalent cation and B tetra-valent cation, being at least partially substituted with one or more lower-valent cations, preferentially selected from Mg, Sc, Y, Nd or Yb in the B position or with a mixture of different B elements in the B position; and/or from one or more A<NUM>B<NUM>S<NUM> structures with A trivalent cation and B tetra-valent cation being at least partially substituted in A position with one or more lower-valent cations, preferentially selected from Ca or Mg, and comprising at least one of Sn, Zr and Ti in B position.

With preference, the degree of substitution in the one or more mixed oxides doped with one or more lower-valent cations and having a cubic fluorite structure is between <NUM> and <NUM> atom % based on the total number of atoms present in the one or more oxides or sulphides having a cubic fluorite structure, in the one or more ABOs-perovskites with A and B tri-valent cations, in the one or more ABO<NUM>-perovskites with A bivalent cation and B tetra-valent cation or in the one or more A<NUM>B<NUM>O<NUM>-pyrochlores with A trivalent cation and B tetra-valent cation respectively, preferably between <NUM> and <NUM> atom %, more preferably between <NUM> and <NUM> atom%.

With preference, the degree of substitution in the one or more mixed sulphides doped with one or more lower-valent cations and having a cubic fluorite structure is between <NUM> and <NUM> atom % based on the total number of atoms present in the one or more ABS<NUM> structures with A and B tri-valent cations, in the one or moreABS<NUM>structures with A bivalent cation and B tetra-valent cation or in the one or more A<NUM>B<NUM>S<NUM> structures with A trivalent cation and B tetra-valent cation respectively, preferably between <NUM> and <NUM> atom %, more preferably between <NUM> and <NUM> atom%.

Said one or more oxides having a cubic fluorite structure, said one or more ABO<NUM>-perovskites with A and B tri-valent cations, said one or more ABO<NUM>-perovskites with A bivalent cation and B tetra-valent cation or said one or more A<NUM>B<NUM>O<NUM>-pyrochlores with A trivalent cation and B tetra-valent cation being at least partially substituted with lower valent cations, said one or more sulphides having a cubic fluorite structure, said one or more ABS<NUM> structures with A and B tri-valent cations, said one or more ABS<NUM> structures with A bivalent cation and B tetra-valent cation, said one or more A<NUM>B<NUM>S<NUM> structures with A trivalent cation and B tetra-valent cation being at least partially substituted with lower valent cations also means that the same element, being a high-valent cation, can be reduced in the lower-valent equivalent, for example, Ti(IV) can be reduced in Ti(lll) and/or Co(lll) can be reduced in Co(ll) and/or Fe(lll) can be reduced in Fe(ll) and/or Cu(ll) can be reduced in Cu(I).

Phosphate electrolytes such as LiPO<NUM> or LaPO<NUM> can also be used as electrically conductive particles.

Metallic carbides, transition metal nitrides and metallic phosphides can also be selected as electrically conductive particles. For example, metallic carbides are selected from iron carbide (Fe<NUM>C), molybdenum carbide (such as a mixture of MoC and Mo<NUM>C). For example, said one or more transition metal nitrides are selected from zirconium nitride (ZrN), tungsten nitride (such as a mixture of W<NUM>N, WN, and WN<NUM>), vanadium nitride (VN), tantalum nitride (TaN), and/or niobium nitride (NbN). For example, said one or more metallic phosphides are selected from copper phosphide (Cu<NUM>P), indium phosphide (InP), gallium phosphide (GaP), sodium phosphide Na<NUM>P), aluminium phosphide (AIP), zinc phosphide (Zn<NUM>P<NUM>) and/or calcium phosphide (Ca<NUM>P<NUM>).

It is a preferred embodiment of the present invention, the electrically conductive particles that exhibit only sufficiently low resistivity at a high temperature can be heated by external means before reaching the high enough temperature where resistive heating with electricity overtakes or can- be mixed with a sufficiently low resistivity solid at a low temperature so that the resulting resistivity of the mixture allows to heat the fluidized bed to the desired reaction temperature.

For example, the electrically conductive particles of the bed are or comprise silicon carbide. For example, at least <NUM> wt. % of the electrically conductive particles based on the total weight of the electrically conductive particles of the bed are silicon carbide particles and have a resistivity ranging from <NUM> Ohm. cm to <NUM> Ohm. cm at of <NUM>.

In the embodiment wherein the electrically conductive particles of the bed comprise silicon carbide, the person skilled in the art will have the advantage to conduct a step of pre-heating with a gaseous stream said fluidized bed reactor before conduct said endothermic reaction in the fluidized bed reactor. Advantageously, the gaseous stream is a stream of inert gas, i.e., nitrogen, argon, helium, methane, carbon dioxide, hydrogen or steam. The temperature of the gaseous stream can be at least <NUM>, or at least <NUM>, or at least <NUM>, or at least <NUM>, or at least <NUM>, or at least <NUM>, or at least <NUM>, or at least <NUM>, or at least <NUM>. Advantageously, the temperature of the gaseous stream can be comprised between <NUM> and <NUM>, for example between <NUM> and <NUM> or between <NUM> and <NUM>. Said gaseous stream of inert gas can also be used as the fluidification gas. The pre-heating of the said gaseous stream of inert gas is performed thanks to conventional means, including using electrical energy. It is not necessary that the temperature of the gaseous stream used for the preheating of the bed reaches the temperature reaction.

Indeed, the resistivity of silicon carbide at ambient temperature is high, to ease the starting of the reaction, it may be useful to heat the fluidized bed by external means, as with preference the fluidized bed reactor is devoid of heating means. Once the bed is heated at the desired temperature, the use of a hot gaseous stream may not be necessary.

However, in an embodiment, the electrically conductive particles of the bed comprise a mixture of silicon carbide particles and electrically conductive particles different from silicon carbide particles.

The pre-heating step may be also used in the case wherein electrically conductive particles different from silicon carbide particles are present in the bed. For example, it may be used when the content of silicon carbide in the electrically conductive particles of the bed is more than <NUM> wt. % based on the total weight of the particles of the bed, for example, more than <NUM> wt. %, for example, more than <NUM> wt. %, for example, more than <NUM> wt. %, for example, more than <NUM> wt. %, for example, more than <NUM> wt. However, a pre-heating step may be used whatever is the content of silicon carbide particles in the bed.

In the embodiment wherein the electrically conductive particles of the bed comprises a mixture of silicon carbide particles and electrically conductive particles different from silicon carbide particles, the electrically conductive particles of the bed may comprise from <NUM> wt. % to <NUM> wt. % of silicon carbide particles based on the total weight of the electrically conductive particles of the bed; preferably, from <NUM> wt. % to <NUM> wt. %, more preferably from <NUM> wt. % to <NUM> wt. %, even more preferably from <NUM> wt. % to <NUM> wt. % and most preferably from <NUM> wt. % to <NUM> wt.

For example, the electrically conductive particles of the bed comprise a mixture of silicon carbide particles and electrically conductive particles different from silicon carbide particles and the electrically conductive particles of the bed comprises at least <NUM> wt. % of silicon carbide particles based on the total weight of the electrically conductive particles of the bed; preferably at least <NUM> wt. %, more preferably at least <NUM> wt. %, even more preferably at least <NUM> wt. % and most preferably at least <NUM> wt.

In an embodiment, the electrically conductive particles of the bed may comprise from <NUM> wt. % to <NUM> wt. % of electrically conductive particles different from silicon carbide particles based on the total weight of the electrically conductive particles of the bed; preferably, from <NUM> wt. % to <NUM> wt. %, more preferably from <NUM> wt. % to <NUM> wt. %, even more preferably from <NUM> wt. % to <NUM> wt. % and most preferably from <NUM> wt. % to <NUM> wt.

However, it may be interesting to keep the content of electrically conductive particles different from silicon carbide particles quite low in the mixture. Thus, in an embodiment, the electrically conductive particles of the bed comprise a mixture of silicon carbide particles and electrically conductive particles different from silicon carbide particles and electrically conductive particles of the bed comprises from <NUM> wt. % to <NUM> wt. % of electrically conductive particles different from silicon carbide based on the total weight of the electrically conductive particles of the bed; preferably, from <NUM> wt. % to <NUM> wt. %, more preferably, from <NUM> wt. % to <NUM> wt. %, and even more preferably, from <NUM> wt. % to <NUM> wt.

For example, the electrically conductive particles of the bed comprise a mixture of silicon carbide particles and carbon-containing particles different from silicon carbide particles and the said carbon-containing particles different from silicon carbide particles are particles selected from graphite, carbon black, coke, petroleum coke and/or any mixture thereof. For example, the said carbon-containing particles different from silicon carbide particles are or comprise graphite.

Thus, in an embodiment, the electrically conductive particles are a combination of silicon carbide particles and graphite particles. Such electrically conductive particles, upon the electrification of the fluidized bed reactor, will heat up and because of their fluidification, will contribute to the raise and/or to the maintaining of the temperature within the reactor. The Joule heating of such carbon-containing material allows accelerating the heating of the reactant and/or of the other particles that are present within the fluidized bed reactor.

When graphite is selected, it can preferably be flake graphite. It is also preferable that the graphite has an average particle size ranging from <NUM> to <NUM> as determined by sieving according to ASTM D4513-<NUM>, preferably from <NUM> to <NUM>, more preferably ranging from <NUM> to <NUM> and most preferably ranging from <NUM> to <NUM>.

The presence of carbon-containing particles different from silicon carbide particles in the bed allows applying the process according to the disclosure with or without the pre-heating step, preferably without the pre-heating step. Indeed, the carbon-containing particles, upon the electrification of the fluidized bed reactor, will heat up and because of their fluidification, will contribute to raise and/or to maintain the desired temperature within the reactor.

For example, the silicon carbide is selected from sintered silicon carbide, nitride-bounded silicon carbide, recrystallised silicon carbide, reaction bonded silicon carbide and any mixture thereof.

Sintered SiC (SSiC) is a self-bonded material containing a sintering aid (typically boron) of less than <NUM>% by weight.

Recrystallized silicon carbide (RSiC), a high purity SiC material sintered by the process of evaporation - condensation without any additives.

Nitride-bonded silicon carbide (NBSC) is made by adding fine silicon powder with silicon carbide particles or eventually in the presence of a mineral additive and sintering in a nitrogen furnace. The silicon carbide is bonded by the silicon nitride phase (Si<NUM>N<NUM>) formed during nitriding.

Reaction bonded silicon carbide (RBSC), also known as siliconized silicon carbide or SiSiC, is a type of silicon carbide that is manufactured by a chemical reaction between porous carbon or graphite with molten silicon. The silicon reacts with the carbon forming silicon carbide and bonds the silicon carbide particles. Any excess silicon fills the remaining pores in the body and produces a dense SiC-Si composite. Due to the left-over traces of silicon, reaction bonded silicon carbide is often referred to as siliconized silicon carbide. The process is known variously as reaction bonding, reaction sintering, self-bonding, or melt infiltration.

In general, high purity SiC particles have resistivity above <NUM> Ohm. cm, whereas sintered, reaction bonded and nitride-bonded can exhibit resistivities of about <NUM> to <NUM> depending on the impurities in the SiC phase. Electrical resistivity of bulk polycrystalline SiC ceramics shows a wide range of resistivity depending on the sintering additive and heat-treatment conditions (<NPL>; <NPL>). SiC polytypes with high purity possess high electrical resistivity (><NUM><NUM> Ω. cm) because of their large bandgap energies. However, the electrical resistivity of SiC is affected by doping impurities. N and P act as n-type dopants and decrease the resistivity of SiC, whereas Al, B, Ga, and Sc act as p-type dopants. SiC doped with Be, O, and V are highly insulating. N is considered as the most efficient dopant for improving the electrical conductivity of SiC. For N doping of SiC (to decrease resistivity) Y<NUM>O<NUM> and Y<NUM>O<NUM>-REM<NUM>O<NUM> (REM, rare earth metal = Sm, Gd, Lu) have been used as sintering additives for the efficient growth of conductive SiC grains containing N donors. N-doping in SiC grains were promoted by the addition of nitrides (AIN, BN, Si<NUM>N<NUM>, TiN, and ZrN) or combinations of nitrides and Re<NUM>O<NUM> (AlN-REM<NUM>O<NUM> (REM = Sc, Nd, Eu, Gd, Ho, and Er) or TiN-Y<NUM>O<NUM>).

The terms "bottom" and "top" are to be understood in relation to the general orientation of the installation or the fluidized bed reactor. Thus, "bottom" will mean greater ground proximity than "top" along the vertical axis. In the different figures, the same references designate identical or similar elements.

<FIG> illustrates a prior art fluidized bed reactor <NUM> comprising a reactor vessel <NUM>, a bottom fluid nozzle <NUM> for the introduction of a fluidizing gas and a hydrocarbon feedstock, an optional inlet <NUM> for the material loading, an optional outlet <NUM> for the material discharge and a gas outlet <NUM> and a bed <NUM>. In the fluidized bed reactor <NUM> of <FIG> the heat is provided by preheating the feedstock by combustion of fossil fuels using heating means <NUM> arranged for example at the level of the line that provide the reactor with the fluidizing gas and the hydrocarbon feedstock.

The installation of the present disclosure is now described with reference to <FIG>. For sake of simplicity, internal devices known by the person in the art that are used in fluidized bed reactors, like bubble breakers, deflectors, particle termination devices, cyclones, ceramic wall coatings, thermocouples, etc.. are not shown on the illustrations.

<FIG> illustrates a first installation with a fluidized bed reactor <NUM> where the heating and reaction zone are the same. The fluidized bed reactor <NUM> comprises a reactor vessel <NUM>, a bottom fluid nozzle <NUM> for the introduction of a fluidizing gas and a hydrocarbon feedstock, an optional inlet <NUM> for the material loading, an optional outlet <NUM> for the material discharge and a gas outlet <NUM>. The fluidized bed reactor <NUM> of figure <NUM> shows two electrodes <NUM> submerged in the bed <NUM>.

<FIG> illustrates an embodiment wherein at least one fluidized bed reactor <NUM> comprises a heating zone <NUM> and a reaction zone <NUM> with the heating zone <NUM> is the bottom zone and the reaction zone <NUM> is on top of the heating zone <NUM>. One or more fluid nozzles <NUM> to provide a hydrocarbon feedstock to the reaction zone from a distributor <NUM>. As it can be seen on <FIG>, the one or more fluid nozzles <NUM> can be connected to a distributor <NUM> to distribute the hydrocarbon feedstock inside the bed <NUM>.

<FIG> illustrates an installation wherein at least one fluidized bed reactor <NUM> comprises at least two lateral zones with the outer zone being the heating zone <NUM> and the inner zone being the reaction zone <NUM>. The heated particles of the bed <NUM> from the outer zone are transferred to the inner zone by one or more openings <NUM> and mixed with the hydrocarbon feedstock and/or steam. At the end of the reaction zone the particles are separated from the reaction product and transferred to the heating zone.

<FIG> illustrates the installation that comprises at least two fluidized bed reactors (<NUM>, <NUM>) connected one to each other wherein at least one fluidized bed reactor is the heating zone <NUM> and one at least one fluidized bed reactor is the reaction zone <NUM>.

The present invention provides for an installation to be used in a process to perform a steam cracking reaction, said installation comprises at least one fluidized bed reactor (<NUM>, <NUM>, <NUM>, <NUM>) comprising:.

wherein at least <NUM> wt. % of the particles of the bed based on the total weight of the particles of the bed <NUM> are electrically conductive and have a resistivity ranging from <NUM> Ohm. cm to <NUM> Ohm. cm at <NUM> and wherein the electrically conductive particles of the bed comprise one or more non-metallic resistors selected from silicon carbide, molybdenum disilicide or a mixture thereof.

For example, one electrode is a submerged central electrode or two electrodes <NUM> are submerged within the reactor vessel <NUM> of at least one reactor (<NUM>, <NUM>, <NUM>).

For example, the reactor vessel <NUM> has an inner diameter of at least <NUM>, or at least <NUM>; or at least <NUM>. Such large diameter allows to carry out the chemical reaction at an industrial scale, for example at a weight hourly space velocity of said reaction stream comprised between <NUM>-<NUM> and <NUM>-<NUM>, preferably comprised between <NUM>-<NUM> and <NUM>-<NUM>, more preferably comprised between <NUM>- <NUM> and <NUM>-<NUM>, even more preferably comprised between <NUM>-<NUM> and <NUM>-<NUM>. The weight hourly space velocity is defined as the ratio of mass flow of reaction stream to the mass of solid particulate material in the fluidized bed.

The at least one fluidized bed reactor (<NUM>, <NUM>, <NUM>) comprises at least two electrodes <NUM>. For example, one electrode is in electrical connection with the outer wall of the fluidized bed reactor, while one additional electrode is submerged into the fluidized bed <NUM>, or both electrodes <NUM> are submerged into the fluidized bed <NUM>. Said at least two electrodes <NUM> are electrically connected and can be connected to a power supply (not shown). It is advantageous that said at least two electrodes <NUM> are made of carbon-containing material. The person skilled in the art will have an advantage that the electrodes <NUM> are more conductive than the particle bed <NUM>.

For example, at least one electrode <NUM> is made of or comprises graphite; preferably, all or the two electrodes <NUM> are made of graphite. For example, one of the electrodes is the reactor vessel, so that the reactor comprises two electrodes, one being the submerged central electrode and one being the reactor vessel <NUM>.

For example, the at least one fluidized bed reactor comprises at least one cooling device arranged to cool at least one electrode.

During use of the fluidized bed reactor, an electric potential of at most <NUM> V is applied, preferably at most <NUM> V, more preferably at most <NUM> V, even more preferably at most <NUM> V, most preferably at most <NUM> V, even most preferably at most <NUM> V, or at most <NUM> V.

Thanks to the fact that the power of the electric current can be tuned, it is easy to adjust the temperature within the reactor bed.

The reactor vessel <NUM> can be made of graphite. In an embodiment, it can be made of electro-resistive material that is silicon carbide or a mixture of silicon carbide and one or more carbon-containing materials.

With preference, the reactor vessel <NUM> comprises reactor wall made of materials which are corrosion-resistant materials and advantageously said reactor wall materials comprise nickel (Ni), SiAlON ceramics, yttria-stabilized zirconia (YSZ), tetragonal polycrystalline zirconia (TZP) and/or tetragonal zirconia polycrystal (TPZ). SiAlON ceramics are ceramics based on the elements silicon (Si), aluminium (Al), oxygen (O) and nitrogen (N). They are solid solutions of silicon nitride (Si<NUM>N<NUM>), where Si-N bonds are partly replaced with Al-N and AI-O bonds.

For example, the reactor vessel <NUM> is made of an electro-resistive material that is a mixture of silicon carbide and one or more carbon-containing materials; and the electro-resistive material of the reactor vessel <NUM> comprises from <NUM> wt. % to <NUM> wt. % of silicon carbide based on the total weight of the electro-resistive material; preferably, from <NUM> wt. % to <NUM> wt. %, more preferably from <NUM> wt. % to <NUM> wt. %, even more preferably from <NUM> wt. % to <NUM> wt. % and most preferably from <NUM> wt. % to <NUM> wt.

For example, the reactor vessel <NUM> is made of an electro-resistive material that is a mixture of silicon carbide and one or more carbon-containing materials; and the one or more carbon-containing materials are selected from graphite, carbon black, coke, petroleum coke and/or any mixture thereof; with preference, the carbon-containing material is or comprises graphite.

For example, the reactor vessel <NUM> is not conductive. For example, the reactor vessel <NUM> is made of ceramic.

For example, the at least one fluidized bed reactor (<NUM>, <NUM>, <NUM>, <NUM>) comprises a heating zone <NUM> and a reaction zone <NUM>, one or more fluid nozzles <NUM> to provide a fluidizing gas to at least the heating zone from a distributor <NUM>, one or more fluid nozzles <NUM> to provide a hydrocarbon feedstock to the reaction zone from a distributor <NUM>, and means <NUM> to transport the particles from the heating zone <NUM> to the reaction zone <NUM> when necessary, and optional means <NUM> to transport the particles from the reaction zone <NUM> back to the heating zone <NUM>.

For example, as illustrated in <FIG>, the at least one fluidized bed reactor is a single one fluidized bed reactor <NUM> wherein the heating zone <NUM> is the bottom part of the fluidized bed reactor <NUM> while the reaction zone <NUM> is the top part of the fluidised bed reactor <NUM>; with preference, the installation comprises one or more fluid nozzles <NUM> to inject a hydrocarbon feedstock between the two zones (<NUM>, <NUM>) or in the reaction zone <NUM>. The fluidized bed reactor <NUM> further comprises optionally an inlet <NUM> for the material loading, optionally an outlet <NUM> for the material discharge and a gas outlet <NUM>. With preference, the fluidized bed reactor <NUM> is devoid of heating means. For example, the electrodes <NUM> are arranged at the bottom part of the fluidized bed reactor <NUM>, i.e. in the heating zone <NUM>. For example, the top part of the fluidised bed reactor <NUM>, i.e. the reaction zone <NUM>, is devoid of electrodes. Optionally, the fluidized bed reactor <NUM> comprises means <NUM> to transport the particles from the reaction zone <NUM> back to the heating zone <NUM>; such as by means of a line arranged between the top part and the bottom part of the fluidized bed reactor <NUM>.

For example, as illustrated in <FIG>, the installation comprises at least two lateral fluidized bed zones (<NUM>, <NUM>) connected one to each other wherein at least one fluidized bed zone <NUM> is the heating zone and at least one fluidized bed zone <NUM> is the reaction zone. For example, the heating zone <NUM> is surrounding the reaction zone <NUM>. With preference, the installation comprises one or more fluid nozzles <NUM> arranged to inject a hydrocarbon feedstock and/or steam to the at least one reaction zone <NUM> by means of a distributor <NUM>. The fluidized bed zones (<NUM>, <NUM>) further comprise optionally an inlet <NUM> for the material loading and a gas outlet <NUM>. With preference, the at least one fluidized bed zone being the heating zone <NUM> and/or the at least one fluidized bed zone being the reaction zone <NUM> is devoid of heating means. For example, the at least one fluidized bed zone being the reaction zone <NUM> shows optionally an outlet <NUM> for the material discharge. One or more fluid nozzles <NUM> provide a fluidizing gas to at least the heating zone from a distributor <NUM>. With one or more inlet devices <NUM>, heated particles are transported from the heating zone <NUM> to the reaction zone <NUM>, and with one or more means <NUM> comprising downcomers, the separated particles are transported from the reaction zone <NUM> back to the heating zone <NUM>. The fluidization gas for the heating zone <NUM> can be an inert diluent, like one or more selected from steam, hydrogen, carbon dioxide, methane, argon, helium and nitrogen. In such configuration the fluidization gas for the heating zone can also comprise air or oxygen in order to burn of deposited coke from the particles.

For example, as illustrated in <FIG>, the installation comprises at least two fluidized bed reactors (<NUM>, <NUM>) connected one to each other wherein at least one fluidized bed reactor <NUM> is the heating zone <NUM> and at least one fluidized bed reactor <NUM> is the reaction zone <NUM>. With preference, the installation comprises one or more fluid nozzles <NUM> arranged to inject a hydrocarbon feedstock and/or steam to the at least one fluidized bed reactor <NUM> being the reaction zone <NUM>. The fluidized bed reactors (<NUM>, <NUM>) further comprise optionally an inlet <NUM> for the material loading and a gas outlet <NUM>. With preference, the at least one fluidized bed reactor <NUM> being the heating zone <NUM> and/or the at least one fluidized bed reactor <NUM> being the reaction zone <NUM> is devoid of heating means. For example, the at least one fluidized bed reactor <NUM> being the reaction zone <NUM> shows optionally an outlet <NUM> for the material discharge. By means of the inlet device <NUM> heated particles are transported from the heating zone <NUM> to the reaction zone <NUM> when necessary, and by means of device35 the separated particles after the reaction zone are transported from the reaction zone back to the heating zone. The fluidization gas for the heating zone can be an inert diluent, like one or more selected from steam, hydrogen, carbon dioxide, methane, argon, helium, and nitrogen. In such configuration the fluidization gas for the heating zone can also comprise air or oxygen in order to burn of deposited coke from the particles.

For example, the at least one fluidized bed reactor <NUM> being the heating zone <NUM> comprises at least two electrodes <NUM> whereas the at least one fluidized bed reactor <NUM> being the reaction zone <NUM> is devoid of electrodes.

For example, the at least two fluidized bed reactors (<NUM>, <NUM>) are connected one to each other by means <NUM> suitable to transport the particles from the heating zone <NUM> to the reaction zone <NUM>, such as one or more lines.

For example, the at least two fluidized bed reactors (<NUM>, <NUM>) are connected one to each other by means <NUM> suitable to transport the particles from the reaction zone <NUM> back to the heating zone <NUM>, such as one or more lines.

In one embodiment, the steam cracking reaction does not require any catalytic composition. For example, the said steam cracking reaction is conducted at a temperature ranging between <NUM> and <NUM>, preferably between <NUM> and <NUM>.

For example, the said steam cracking reaction is conducted in presence of a reaction stream and is performed at a weight hourly space velocity of said reaction stream comprised between <NUM>-<NUM> and <NUM>-<NUM>, preferably comprised between <NUM>-<NUM> and <NUM>-<NUM>, more preferably comprised between <NUM>-<NUM> and <NUM>-<NUM>, even more preferably comprised between <NUM>-<NUM> and <NUM>-<NUM>.

Claim 1:
A process to perform steam cracking reaction of hydrocarbons having at least two carbons, said process comprising the steps of:
a) providing at least one fluidized bed reactor comprising at least two electrodes and a bed comprising particles;
b) putting the particles of the bed in a fluidized state by passing upwardly through the said bed a fluid stream, to obtain a fluidized bed;
c) heating the fluidized bed to a temperature ranging from <NUM> to <NUM> to conduct the steam cracking reaction of a hydrocarbon feedstock; and
d) optionally, recovering the cracking products of the reaction;
characterized in that at least <NUM> wt.% of the particles based on the total weight of the particles of the bed are electrically conductive particles and have a resistivity ranging from <NUM> Ohm.cm to <NUM> Ohm.cm at <NUM>, in that the step c) of heating the fluidized bed is performed by passing an electric current through the fluidized bed; and in that the electrically conductive particles of the bed comprise one or more non-metallic resistors selected from silicon carbide, molybdenum disilicide or a mixture thereof.