PROCESS FOR SIMULTANEOUSLY CRACKING HEAVY HYDROCARBONS INTO LIGHT OILS AND PRODUCING HYDROGEN, AND LIGHT OILS AND HYDROGEN WHEN SO PRODUCED

Abstract: A process for simultaneously cracking a heavy hy­ drocarbons to form light oils and producing hydrogen is described, which comprises (a) a first step 1 wherein steam 3 and heavy hydrocarbons 4 are simultaneously contacted with a bed 2 of a catalyst in a reduced state and containing iron in the form of iron oxide to produce hydrogen, cracked gases, and cracked light oils, to con­ vert the reduced-state catalyst into an oxidized-state catalyst, and to deposit coke on the catalyst, (b) a second step 8 wherein a bed 9 of the oxidized-state catalyst with coke deposited thereon is contacted with an oxygen-containing gas 10 to partially combust the coke on the catalyst, to convert the oxidized-state ca­ talyst into a reduced-state catalyst, and to fix a sulfur compound contained in the coke as iron suifide with a part of the reduced-state catalyst; and (c) a third step 13 wherein a bed 14 of a catalyst obtained from the first step 1 or second step 8, the major portion of the catalyst being recycled between the first step 1 and second step 8, is contacted with an oxygen-containing gas 15 at a temperature of from 600 to 1,000°C to effect roasting and gasification of iron sulfide in the catalyst.

Description: "PROCESS FOR SIst1ULTAN3DOUSLY CRACKING HEAVY HYDROCARBONS INTO LIGHT OILS AND PRODUCING HYDROGEN, AND LIGHT OILS AND HYDROGEN WHEN SO PRODUCEDn The present invention relates to a process for simultaneously cracking heavy hydrocarbons to form light oils and producing hydrogen. More particularly, it relates to a process for producing hydrogen, cracked gases, and cracked light oils by contacting steam and heavy hydrocarbons simultaneously with catalyst particles containing iron in a reduced state. Some of the present inventors have previously proposed a process for catalytically cracking vacuum residual oil and other heavy hydrocarbons into light oils in the presence of a laterite catalyst, wherein the coke deposited on the catalyst is combusted in a reducing atmosphere to reduce the iron oxide in the catalyst, and then the reduced catalyst is contacted with steam to produce hydrogen (see U.S. Patents 4,224,140 and 4,298,460) As a result of further extensive study on the foregoing process, it has been found that when a catalyst containing iron in a reduced state is used, a reaction involving cracking of heavy hydrocarbons into cracked gasses and light oils and coking and a steam-iron reaction of iron in a reduced state and steam simultaneously proceeds even at relatively low temperature, e.g., 500 to 6000C. On the basis of the foregoing findings, some of the inventors further proposed a simplified process for simultaneously cracking heavy hydrocarbons into cracked gases and light oils and producing hydrogen, comprising a first step wherein steam and heavy hydrocarbons are simultaneously contacted with a catalyst containing iron in a reduced state to produce hydrogen, cracked gases, and cracked light oils and at the same time, to effect oxidation of the iron in a reduced state, contained in the catalyst and deposition of coke on the catalyst, and a second step wherein the catalyst containing iron in an oxidized state, withthe coke deposited thereon, is contacted with an oxygen-containing gas insufficient for achieving complete combustion of the coke, to partially combust the coke on the catalyst and simultaneously reduce the oxidized iron in the catalyst, thus regenerating the catalyst (see U.S. Serial No. 191,617 filed September 29, 1980). This process is hereinafter explained in detail. The catalyst used in the process can be prepared by pulverizing, kneading, granulating and calcining materials having a very high iron content, such as natural ores containing iron in the form of hydroxide, oxide or carbonate (e.g., laterite, magnetite, siderite, limonite and hematite), or chemical compositions of iron oxides, hydroxides or carbonates, or mixtures thereof with inorganic materials, such as alumina, silica, magnesia, calcium hydroxide, and nickel oxide, and natural ores, e.g., garnierite, dolomite and limestone. To have high catalytic activity, these catalyst particles preferably have a specific surface area of from 0.1 to 30 m2/g, and for use in a fluidized bed, the catalyst particles preferably have a mean diameter of from 60 to 600 t. When the iron (Fe) content of the catalyst is below 30% by weight, only a small amount of hydrogen can be produced. It is, therefore, essential for the catalyst to contain at least 30% by weight Fe. The Fe content preferably does not exceed 70% by weight because otherwise bogging (i.e., sintering and agglomeration of catalyst particles) occurs during the reduction of the catalyst in the second step. The term "in an oxidized state and "in a reduced state" are used herein as a relative measure of the degree of reduction of iron oxides in the catalyst particles. The degree of reduction (R) of the catalyst particles can be represented by the following formula: : gram-atoms of oxygen combined with the Fe in the catalyst R =[1 - -------------------------------------] x 100% 3/2 x (gram-atoms of Fe in the catalyst) If R1, which is the degree of reduction of the catalyst at the end of the first step, is smaller than R2, which is the degree of reduction of the catalyst at the end of the second step, the invention achieves its object, and the greater te difference between R2 and R1, the greater the amount of hydrogen that will be generated per given amount of catalyst recycled to the first step. In this process, therefore, a catalyst having a degree of reduction of R1 is referred to as a catalyst in an oxidized state (or as an oxidized-state catalyst), whereas the catalyst having a degree of reduction of R2 is referred to as a catalyst in a reduced state (or as a reduced-state catalyst). Both R1 and R2 are preferably greater than 11.1%; R2 is preferably in the range of from 12 to 50%, and more preferably in the range of from 15 to 40%. Hereinafter the process will be explained in further detail with reference to the accompanying drawing. In the first step 1 of the process, a catalyst bed 2 composed of catalyst particles in a reduced state, which are introduced thereinto through a catalyst transfer pipe 6, is maintained at a temperature of from 500 to 8000C and a pressure (gauge pressure) of from 0 to 15kg/cm2, and steam 3 and heavy hydrocarbons 4 are introduced into the catalyst bed 2 from the bottom thereof to form a fluidized bed where the steam-iron reaction (a reaction to generate hydrogen by contacting steam with iron (Fe) or iron oxide (FeO) and simultaneous cracking heavy hydrocarbons are performed. Heavy hydrocarbons which can be cracked to light oils with advantage by the process include relatively inexpensive high-boiling residual oils having more than 10% by weight Conradson carbon such as atmospheric residual oil, vacuum residual oil, solvent-deasphalting residues, tar sand, and sale oil. The steam introduced into the catalyst bed causes the steam-iron reaction with the iron in a reduced state (i.e., Fe or FeO), contained in the catalyst, generating hydrogen and at the same time, oxidizing the iron in the catalyst into iron oxides (i.e., FeO or Fe304). The heavy hydrocarbons are catalytically cracked into cracked gases, cracked light oils and coke. The thus-formed coke deposits on the surface of the catalyst particles. About 30 to 50% of the sulfur contained in.the heavy hydrocarbons is distributed into the coke. The amount of the coke deposited on the catalyst increases with the content of Conradson carbon in the heavy hydrocarbons and with the progress of the cracking reaction. For the purpose of the process, the amount of the coke deposited is preferably from 2:toy58 by weight, and more preferably from 4 to 12% by weight, based on the weight of the catalyst. If the amount of the coke deposited is too small, the ironoxides in the catalyst are not reduced adequately in the second step 8, and to provide a good heat balance for the reaction system, additional heat must be supplied in great quantity from an external source. On the other hand, if the amount of the coke deposited on the catalyst is too high, the catalytic activity of the catalyst is decreased and the reaction between the steam and the reduced-state iron is inhibited to decrease the amount of hydrogen generated. Catalyst in a reduced state is converted into catalyst in an oxidized state by the steam. At this time, a part of iron sulfide present in the catalyst, i.e., iron sulfide resulting from the reaction of sulfur with Fe, FeO or Fe at the second step 8, is converted into iron oxides and hydrogen sulfide. It is, however, not desirable from an economic standpoint to decompose all the iron sulfide resulting from the reaction because to do so requires a large quantity of steam. The coke on the catalyst reacts with steam to a slight extent to generate hydrogen, carbon monoxide, and carbon dioxide, but this reaction is insignificant at a temperature longer than 800"C. The amount of heavy hydrocarbons supplied to the first step is properly determined depending on the amount of coke deposited and the amount of catalyst particles recycled to the first step, and the amount of steam supplied is properly selected depending on the degree of reduction of the catalyst, the desired amount of hydrogen generated, and the amount of catalyst particles recycled to the first step. Hydrogen, hydrogen sulfide, cracked gases such as methane, ethane, ethylene, C3 fractions, and C4 fractions, and cracked oils generated in the first step, and uncracked heavy hydrocarbons, steam and so forth are discharged from the top 5 of the first step 1 in the form of a gas and vapor. The thus discharged gas is introduced into a scrubbing column or a distillation column (not shown) where it is first separated into uncracked heavy hydrocarbons and cracked products. The uncracked heavy hydrocarbons are returned and mixed with a feed stock, heavy hydrocarbons, and again subjected to the cracking reaction. The hydrogen, cracked gases, cracked light oil and so forth are separated and recovered by known refining steps as a gaseous mixture which contains hydrogen as the major component, and, additionally, methane, ethane, ethylene, C3 fractions, C4 fractions, and hydrogen sulfide (H2S). This gaseous mixture can be separated into high purity hydrogen and hydrogen sulfide, and propane, butane and other light hydrocarbon gases by suitable means, such as distillation, an amine absorption method, a pressure swing adsorption method [PSA method Csee, for example, CEP, January (1976), pp. 44-49)] and a cryogenic processing [see, for example, CEP, September (1969), pp..78-83], which may be used alone or in combination with each other. For example, the mixture can first be freed of C3 and C4 fractions by distillation or absorption, then freed of H2S by amine absorption, and then freed of hydrogen and light hydrocarbon gases such as methane, ethane, and ethylene by the pressure swing adsorption method of cryogenic processing. The cracked light oil is fed to the refining step where it is separated into a naphtha fraction, a kerosine fraction, a gas oil fraction, etc., which are desulfurized in a desulfurization step to provide the desired end products. The oxidized-state catalyst with the coke formed in the first step deposited thereon is transferred to second step 8 through a transfer pipe 7. A catalyst bed 9 is maintained in a fluidized state by introducing thereinto an oxygen-containing gas 10, e.g., air. The coke deposited on the catalyst is partially combusted with oxygen insufficient for complete combustion of.the coke. The catalyst bed 9 is maintained at a temperature of from 750 to 9500C and a pressure of from 0 to 15 kg/cm2G, and is held in a reducing atmosphere produced by CO gas generated by partial combustion of the coke. The amount of oxygen in the oxygen-containing gas is preferably such that the mole ratio of oxygen supplied to coke deposited on the catalyst (coke supplied from the transfer pipe 7) (O2/C) is from 0.1 to 0.6, with the range of from 0.2 to 0.4 being particularly preferred. The coke deposited and CO gas generated by partial combustion of coke react with the catalyst in an oxidized state to form the catalyst in a reduced state. That is, the iron oxide in the catalyst is reduced. The residence time of each of the catalyst and gas, the amount of coke deposited, the amount of oxygen being introduced, and so forth are properly determined so that the degree of reduction of the catalyst is maintained in.the above described range of from 12 to 50%. The coke deposited on the catalyst reacts with the oxygen in the oxygen-containing gas and the oxygen in the catalyst to form gases such as carbon monoxide (CO) and carbon dioxide (CO2) Simultaneously, sulfur compounds contained in the coke are gasified into H2S, COS, SOx, etc. These gaseous sulfur compounds are captured by Fe,FeO and Fe304 in the reduced-state catalyst and are converted into iron sulfide. Therefore, the sulfur content of a large quantity of waste gas 11 discharged from the second step can be significantly reduced. As the reaction temperature is increased (e.g., to more than 7500C), the above described reactions such as partial combustion of coke, reduction of catalyst, and capture of sulfur proceed faster. It is preferred, however, that the reaction temperature does not exceed 9500C, because otherwise bogging occurs among catalyst particles, undesirably making the fluidization and transfer of catalyst to another step difficult. It is, therefore, preferred to perform the reaction at a temperature between 7500C and 950CC. The temperature can be maintained in this range by the partial combustion of coke. It is to be understood that to avoid the possibility that the heat balance in the reaction system may be upset, the system may be cooled or heated by a conventional external or internal means. For example, cooling can be achieved simply using a boiler type fluidized bed, and for heating, it is convenient to use a method in which torch oil (which may be the same as or different from the heavy hydrocarbon feedstock) is supplied directly to the catalyst bed 9. The amount of heat generated in the reaction system can also be controlled by changing the amount of oxygen in the oxygencontaining gas 10, although care must be taken so that the mole ratio of 02/C is kept within the above defined range. The waste gas 11 resulting from the reduction reaction and partial combustion of coke is generally discharged from step 8, e.g., after recovery of differential pressure energy by means such as a conventional gas expander, and of heat energy by means such as a conventional CO boiler, it is discharged outside the reaction system. Irrespective of the fact that the coke having a high sulfur content is burned with air, for example, the sulfur content of the resulting waste gas 11 is low, since the reduced-state catalyst in step 8 has the action of fixing sulfur compounds as iron sulfide. It is therefore possible to discharge the waste gas directly into the atmosphere without application of a desulfuri ration treatment. The catalyst freed of coke and rendered to a reduced state is returned to the first step through a catalyst transfer pipe 6. In accordance with the process, while effecting reduction and regeneration of the catalyst simultaneously with combustion and gasification of coke in a high temperature reducing atmosphere, the sulfur compounds which are distributed in the coke during the cracking reaction of heavy hydrocarbons and the coking reaction react with the iron in the catalyst, forming iron sulfide. It has been found, however, that when the catalyst is used while recycling for a long period of time, iron sulfide gradually accumulates in the catalyst, causing the problem that the amount of hydrogen generated is reduced. In order to prevent the accumulation of iron sulfide, it has been proposed to use a method of converting iron sulfide into hydrogen sulfide and iron oxide with steam. This method, however, is not always economy c-ally advantageous becuase it needs a large amount of steam because of the equiliblium of reaction. The object of the invention.is to provide a process which overcomes the above described defects and permits the cracking of heavy hydrocarbons into light oils and to produce hydrogen industrially very advantageously. The present invention, therefore, provides a process for simultaneously cracking heavy hydrocarbons to form light oils and producing hydrogen, which comprises: a first step wherein steam and heavy hydrocarbon are simultaneously contacted with a catalyst in a reduced state, containing at least 30% by weight iron (Fe) in the form of iron oxide, at a temperature of from 500 to 8000C to produce hydrogen, cracked gases, and cracked light oils, to convert the reduced-state catalyst into an oxidized-state catalyst, and to deposit coke on the catalyst; and a second step wherein the oxidized-state catalyst with the coke deposited thereon is contacted with an oxygencontaining gas insufficient for achieving complete com- bustion of the coke, at a temperature of from 750 to 9500C to partially combust the coke on the catalyst, to convert the oxidized-state catalyst into a reduced-state catalyst, and to fix sulfur compounds contained in the coke as iron sulfide with a part of the reduced-state catalyst, which process is characterized in that: (1) a major portion of the catalyst is recycled between the first step and second step; and (2) there is provided a third step wherein a part of the catalyst is contacted with an oxygencontaining gas at a temperature of from 600 to 1,000 C to effect roasting and gasification of iron sulfide in the catalyst. The drawing is a schematic illustration of an embodiment of the process of the invention. The reference to a catalyst containing at least 30% by weight iron (Fe)" as used herein assumes that the catalyst has been prepared by suitable means suchrascalcination in a conventional oxidizing atmosphere; thus the term refers to a catalyst which, when most of iron in the catalyst is in the form of Foe,03' contains at least 30% by weight of iron (Fe). The first step and second step of the process of the invention are as described hereinbefore. In addition to the first step and second step, the process of the invention further includes a third step wherein roasting and gasification of iron sulfide in the catalyst formed to the second step 8 is perfomred. The catalyst to be supplied to the third step may be either of the catalyst which is reduced and regenerated in the second step 8 and the catalyst with coke deposited thereon which is formed in the first step 1. then catalyst from the second step is introduced into the third step, since reduced iron (Fe, FeO) in the catalyst is oxidized at the roasting step, the amount of hydrogen formed at the first step 1 is reduced in proportion to the oxidized amount of the reduced iron. On the other hand, when the catalyst from the first step is introduced into the third step, combustion of coke on the catalyst occurs, and this leads to a decrease in the degree of reduction of the catalyst in the second step 8 and then, to a reduction in the amount of hydrogen formed at the first step 1. Introduction of the catalyst with coke deposited thereon from the first step into the third step is industrially advantageous becasue the combustion amount of coke can be reduced by properly selecting roasting conditions in the third step as described hereinafter. The process of the invention is hereinafter described in detail with reference to the drawing schematically illustrating an embodiment thereof wherein the catalyst is recycled between the second step and third step. This is also applicable to the other embodiment of the invention wherein the catalyst is recycled between the first step and third step. Also, the catalyst which has been subjected to the roasting and gasification treatment at the third step can be returned either to the first step or to the second step with the same results. As described above, a major portion of the catalyst is recycled between the first step 1 and the second step 8, and a part of the catalyst is introduced into the third step 13 through a pipe 12. In the third step 13, a catalyst bed 14 is a fluidized bed which is formed by an oxygen-containing gas (e.g., air) and/or steam 15 at a temperature of from 600 to 1,000 C and a pressure of from 0 to 15 kg/cm2G. Into the catalyst bed 14 the oxygen-containing gas (or a mixture of thereof with steam) is introduced in a quantity sufficient for combustion of iron sulfide in catalyst particles formed in the second step to produce iron oxide and gaseous sulfur compounds. The amount of oxygen or mixture of oxygen and steam in the gas introduced is properly determined depending on the amount of iron sulfide in the catalyst particles, the amount of residual coke on the catalyst, and the amount of the catalyst recycled. It is preferred, however, that the combustion is performed by a method which permits the coke deposited on the catalyst to remain in as large an amount as possible. The reason for this is that the coke on the catalyst contributes to the above described reduction of iron oxide in the second step, and therefore to the fomration of hydrogen. The rate of oxidative roasting of iron sulfide and the rate of combustion of coke markedly vary depending on the temperature and the amount of oxygen introduced. For example, when the amount of oxygen introduced at a roasting temperature of 7000C is 70 mole% of the theoretical oxygen amount for complete combustion of iron sulfide and coke, percent desulfurization of iron sulfide is about 72% by weight, whereas the rate of combustion of coke is only 35% by weight. If the roasting temperature is raised to 8000C, percent desulfurization of iron sulfide is increased only slightly, i.e., to about 75% by weight, whereas percent combustion of coke is increased to about 53% by weight. Moreover, if the amount of oxygen introduced is increased to 100 mole% of the theoretical oxygen amount for complete combustion, percent desulfurization of iron sulfide is about 85% by weight and percent combustion of coke is about 708 by weight, at a roasting temperature of 700"C. In the third step as described above, it is preferred to perform the roasting at a relatively low temperature and in a reducing atmosphere for the prevention of loss of coke. Particularly preferably the roasting is performed at a temperature of from 600 to 800"C, with an amount of oxygen introduced of from 60 to 100 mole% of the theoretical oxygen amount for complete combustion of iron sulfide and coke. Admixture of steam with the oxygen-containing gas permits the convesion of a part of the sulfur of iron sulfide into hydrogen sulfide. This is advantageous for the recovery of sulfur compounds in the waste gas from the third step 13 as elemental sulfur. The amount of the catalyst fed to the third step is determined depending on the sulfur content of the heavy hydrocarbons. That is, as described above, the sulfur compounds in the hydrocarbons which have been distributed into the coke are fixed as iron sulfide in the second step. The fixed iron sulfide is gradually accumulated in the catalyst while the catalyst is recylced. Thus, the amount of the catalyst recycled and roasted in the third step can be proportional to the amount of iron sulfide produced, and can be mainly determined by the sulfur content of the heavy hydrocarbons. For example, even when the sulfur content of the heavy hydrocarbon feed is about 5 wt%, it is sufficient to recycle about 10 wt% of the catalyst recycled between the first step 1 and the second step 8 to the third step 13. The catalyst which has been roasted is returned to the second step 8 through a pipe 17 and/or to the first step 1 (the transfer pipe is not shown). The waste gas 16 from the third step 13 contains high concentrations of gaseous sulfur compounds e.g., SOx, and after desulfurization with a sulfur recovery apparatus utilizing a combination of the Clauss reaction and Scott reaction, a sulfuric acid production system, and other usual desulfurization apparatuses, is discharged outside the system. As discussed in the foregoing, the process of the invention permits the advantageous production light cracked oils and hydrogen by catalytic cracking of inexpensive heavy hydrocarbons, and at the same time, the collection of 30 to 50% of the sulfur in the heavy hydrocarbons feed as high concentration gaseous sulfur compounds which can be easily recovered. Thus the process of the invention is industrially very useful. Below Examples, and Comparative Example are described to illustrate the invention in greater detail. In these Examples, the symbol "N" used for "uni" and "cm3" means that the volume indicated is at standard pressure and temperature. EXAMPLE i Cracking was continuously performed while recycling the catalyst according to the flow diagram shown in the drawing. Steps First Step: A cracking column made of stainless steel; inner diameter: 12.7 cm; height: 160 cm Second Step: A regenerating column made of stainless steel; inner diameter: 15.1 cm; height: 180 cm Third Step: A roasting column made of stainless steel; inner diameter: 5.0 cm; height 100 cm Feedstock Kuwait Vacuum Residual Oil Specific Gravity (15"C/4"C) 1.020 Residual Carbon (wt) 21.1 Sulfur (wt%) 5.1 Catalyst - A laterite ore containing 55.1 wtt Fe, 1.26 wt% Ni, 2.6 wt% MgO, 4.7 wt% SiO2, and 2.81 wt% A1203 was ground, kneaded, granulated, and calcined at 1,160"C for 3 hours to make catalyst particles. The catalyst had a mean diameter of 0.2 mm and a specific surface area 2 of 3.2 m /g. Operation Conditions Cracking Column: Catalyst 13 kg Feedstock Supplied 4.0 kg/hr Steam Supplied 2.0 kg/hr Temperature 5400C Pressure 1 kg/cm2 Regenerating Column: Catalyst 20 kg Air Supplied 2.5 Nm3/hr Feedstock Supplied 0.06 kg/hr Temperature 8500C Pressure 1 kg/cm2 Roasting Column: Catalyst 1.0 kg Air Supplied 0.5 Nm3/hr Temperature 750"C Pressure 1 kg/cm2 Catalyst Recycled ¯ ¯¯¯¯¯¯¯ Between Cracking Column and Regenerating Column 20 kg/hr Between Regenerating Column and Roasting Column 1 kg/hr The cracking was performed stably for a long period of time under the foregoing conditions. During the operation, a sample was taken at each step and analyzed. The results are shown in Table 1. Table 1 Cracking Column ¯ Yield of Gas (dry base) 842.7 NQ/hr Gas Composition H2 71.2 vol% H2S 1.3 vol CH4 10.9 vol% C2 Fraction 7.8 vol% C3 Fraction 4.7 vol% C4 Fraction 2.4 vol% Yield of Naphtha Fraction 4.0 wt% Yield of Kerosine Fraction 2.6 wt% Yield of Gas Oil Fraction 2.9 wt% Yield of Vacuum Gas Oil Fraction 26.4 wt% Yield of Coke 13.1 wt% Cracking Ratio of Feedstock 61.4 wt% Regenerating Column Gases Generated 3.1 Nm3/hr Gas Composition CO 17.6 vol% CO2 15.8 vol% H2S + SO, 94.9 ppm Roasting Column Gases Generated 0.45 Nm3/hr Concentration of SOx in Gas 7.7 vol% EXAMPLE 2 Using the heavy hydrocarbons feedstock and catalyst as set forth below, cracking was performed in the same manner as in Example 1 except that the catalyst was recycled between the first step and the third step at a rate of 1 kg/hr and between the first step and the second step at a rate of 20 kg/hr. Heavy Hydrocarbon Feedstock Specific Gravity (150C/4"C) 1.0440 Residual Carbon (wt%) 24.17 Sulfur (wt%) 5.62 Catalyst ¯¯ A laterite ore containing 57.4 wt% Fe, 1.21 wt Ni, 0.78 wt% WIgO, 2.69 wt SiO2 and 6.59 wt% A1203 was ground, kneaded, granulated, andcalcined to form a catalyst. The catalyst had a mean diameter of 0.2 mm and a specific surface area of 1.40 m2/g. The cracking could be. performed stably for a long period of time. During the operation, a sample was taken at each step and analyzed. The results are shown in Table 2 below. Table 2 Cracking Column Yield of Gases (dry base) 968.4 NQ/hr Gas Composition H2 74.4 vol% H2S 0.4 vol% CH4 10.0 vol% C2 Fraction 7.0 vol% C3 Fraction 4.2 vol C4 Fraction 2.-S vol% Yield Naphtha Fraction 7.3 wt% Kerosine Fraction 2.8 wt% Gas Oil Fraction 5.5 wt Vacuum Gas Oil Fraction 23.3 wt% Coke 14.3 wt% Cracking Ratio of Feedstock 63.1 wt% Regenerating Column Waste Gas 2.9 Nm3/hr Gas Composition CO 19.2 vol% CO2 14.2 vol% H2S + sox 90.9 ppm Roasting Column Waste Gas 0.51 Nm3/hr Concentration of SOx in Gas 8.3 vol% COMPARATIVE EXAMPLE Cracking was performed in the same manner as described in Example but eliminating the roasting column in the third step. The feedstock, columns, operation conditions and catalyst used were same as those used in the first and second steps of Example. After operation for 50 hours, a sample was taken at each step and analyzed. The results obtained are shown in Table 3 below. Table 3 Cracking Column Yield of Gas (dry base) 710 NQ/hr Gas Composition H2 67.6 vol% H2S 1.5 vol% CH4 13.1 vol% C2 Fraction 9.0 vol% C3 Fraction 5.8 vol% C4 Fraction 3.0 vol% Yield of Naphtha Fraction 5.8 wt% Yield of Kerosine Fraction 2.5 wtt Yield of Gas Oil Fraction 3.2 wt% Yield of Vaccum Gas Oil Fraction 25.9 wt% Yield of Coke 14.1 wt% Cracking Ratio of Feedstock 59.0 wt Regenerating Column Gases Generated 3.3 Nm3/hr Gas Composition CO 16.4 vol% CO2 17.2 vol% H25 + SO, 120 ppm As apparent from the results shown in Table 2, the yield of hydrogen gas is reduced by about 20% as compared with the yield in Example. This is due to the accumulation of iron sulfide in the catalyst. While the invention has been described in detail and with refernece to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the scope thereof.

Claims: Claims: 1. A process for simultaneously cracking heady hydrocarbons to form light oils and producing hydrogen, which comprises a first step (1) wherein steam (3) and heavy hydrocarbons (4) are simultaneously contacted with a catalyst in a reduced state, containing at least 3Oc,b by weight iron in the form of iron oxide, at a temperature of from 500 to 800 C, to produce hydrogen, cracked gases, and cracked light oils, to convert the reduced-state catalyst, and to deposit coke on the catalyst, and a second step (8) wherein the oxidized-state catalyst with the coke deposited thereon is contacted with an oxygen-containing gas (10) insufficient for achieving complete combustion of the coke, at a temperature of from 750 to 950 C, to partially combust the coke on the catalyst, to convert the oxidized-state catalyst into a reduced-state catalyst, and to fix a sulfur compound contained in the coke as iron sulfide with a part of the reduced-state catalyst, which process is characterized in that: (1) a major portion of the catalyst is recycled between the first step (1) and second step (8); and (2) there is provided a third step (13) wherein a part of the catalyst is contacted with an oxygencontaining gas (15) at a temperature of from 600 to 1,000 C to effect roasting and gasification of iron sulfide in the catalyst. 2. A process as claimed in Claim 1, wherein the catalyst to be roasted in the third step (13) is obtained from the first step (1), and after roasting and gasification of iron sulfide, it is returned to the second step, first step, or both the first and second steps. 3. A process as claimed in Claim 1, wherein the catalyst to be roasted in the third step (13) is obtained from the second step (8), and after roasting and gasification of iron sulfide, it is returned to the second step (8), or first step (1), or both the first and second steps (2,8), 4. A process as claimed in any preceding claim wherein the oxygen-containing gas (15) supplied to the third step (13) contains steam. 5. A process as claimed in any preceding claim, wherein the roasting and gasification of the third step (13) is performed in a reducing atmosphere. 6. A process as claimed in any preceding claim, wherein the temperature in the third step (13) is from 600 to 800 C. 7. A process as claimed in any preceding claim, wherein the quantity of oxygen in the oxygen-containing gas (15) supplied to the third step (13) is from 60 to 100 mole of the theoretical amount necessary for complete combustion of the iron sulfide and coke. 8. Light oils when produced by a process as claimed in any preceding claim. 9. Hydrogen when produced by a process as claimed in any preceding claim.

Inventors: HIDETAKA, OHSE, SHIROU, AIZAWA C/O NIPPON MINING COMPANY LTD., TADASHI, MURAKAMI C/O NIPPON MINING COMPANY LTD., TERUO, SUZUKA C/O NIPPON MINING COMPANY LTD., YASUSHI, ISHIBASHI C/O NIPPON MINING COMPANY LTD., YUKIO, INOUE C/O NIPPON MINING COMPANY LTD.
Applicants: RESEARCH ASSOCIATION FOR RESIDUAL OIL PROCESSING
Application year: 1982
Main classification: C10G11
IPC codes: B01J23, C10G11