Patent Description:
When used in high compression internal combustion engines, gasoline has the tendency to "knock. " Knocking occurs when combustion of the air/fuel mixture in the cylinder does not start off correctly in response to ignition because one or more pockets of air/fuel mixture pre-ignite outside the envelope of the normal combustion front. Antiknocking agents, also known as octane boosters, reduce the engine knocking phenomenon, and increase the octane rating of the gasoline.

Hydrocarbon cracking processes are important conversion processes used in petroleum refineries. For example, fluid catalytic cracking (FCC) is widely used to convert the high-boiling, high-molecular weight hydrocarbon fractions of petroleum crude oils to more valuable gasoline, olefinic gases, and other products. Thermal cracking of naphtha and gas oil is also widely used in the petrochemical industry to produce a variety of olefins and aromatics. For example, hydrocarbon feed stocks can be mixed with steam and subjected to elevated temperatures (e.g., <NUM>-<NUM>) in a steam cracker furnace wherein the feed stock components are cracked into various fractions. The effluent of the steam cracker can contain a gaseous mixture of hydrocarbons, for example, saturated and unsaturated olefins and aromatics (C1-C35). The effluent can then be separated into individual olefins (for example, ethylene, propylene and C4's) and pyrolysis gasoline. Recycle streams of crude hydrocarbons are often formed as byproducts during these cracking processes.

The presence of isobutylene, butadiene, <NUM>-butene, <NUM>-butene, and other components within the crude hydrocarbon streams can allow for the formation of valuable alcohols and fuel additives. Such alcohols can include methanol, which is commonly used as a gasoline octane booster. However, the conversion of crude hydrocarbon streams to fuel additive products can often be inefficient and costly. Furthermore, the final product specifications for such alcohols can be undesirable and can fail to meet market quality requirements. For example, alcohol products can have high levels of impurities, high Reid vapor pressures, e.g., greater than <NUM> pounds per square inch (psi) (greater than <NUM> kilopascals), and low octane numbers (e.g., <NUM> Research Octane Number (RON)), all of which correlate with poor product quality. Any improvement in these specifications and/or the efficiency of the process can provide a more valuable fuel additive product. For instance, a process for producing sec-butanol and sec-butyl tert-butyl ether and possibly tert-butyl alcohol from hydrocarbon mixtures containing butane, such as occur in crude oil production or crude oil refining has been described in <CIT>.

Thus, there is a need for an efficient method of producing fuel additives that can make use of crude hydrocarbon streams and produce final products with low impurities and high performance specifications.

Disclosed, in various embodiments, are methods of producing fuel additives.

The methods of producing a fuel additive include the steps as defined in independent claims <NUM> and <NUM>.

The following is a brief description of the drawings wherein like elements are numbered alike and which are presented for the purposes of illustrating the exemplary embodiments disclosed herein and not for the purposes of limiting the same. <NUM> is a schematic diagram representing a unit sequence for producing fuel additives.

Disclosed herein is an efficient method of producing fuel additives that can make use of crude hydrocarbon streams and produce final products with low impurities and high performance specifications. For example, the method disclosed herein can provide a unique sequence of unit operations that converts crude hydrocarbons into valuable fuel additives, such as alcohol fuel additives. This unique sequence can significantly improve the efficiency of the process, thereby reducing total capital costs. The final fuel additive products can have levels of trimethylpentane of <NUM> weight % to <NUM> weight%, based on the total weight of the fuel additive, high octane numbers (e.g., greater than or equal to <NUM> RON, or greater than or equal to <NUM> RON), and low Reid vapor pressures of greater than or equal to <NUM> Kilopascals. For example, the trimethylpentane can be present in an amount of <NUM> to <NUM> weight percent, for example, <NUM> to <NUM> weight %. Any one or all of these properties can correlate with high performance and high market value. The method disclosed herein can also produce secondary products along with the fuel additive product. For example, both propylene and methyl tertiary butyl ether (MTBE) products can be produced along with the fuel additive, thus maximizing the efficiency and productivity of the process.

The method disclosed herein can utilize <NUM>-butene with traces of <NUM>-butene, e.g., , in amounts of less than or equal to <NUM> weight percent to maximize the amount of trimethylpentane (e.g., <NUM>-butanol and tertbutyl alcohol (TBA)) in the final fuel additive product, which can be used to produce propylene. To achieve a maximum increase in the production of <NUM>-butene from a butadiene component present in the C4 hydrocarbon feed stream, isomerization occurs by passing the feed stream through an isomerization unit leaving traces of butadiene that can be less than or equal to <NUM>% by weight, for example, less than or equal to <NUM>% by weight, for example, less than or equal to <NUM>% by weight. A MBTE synthesis unit is inserted in the process to convert isobutylene through a reaction with a methanol stream to produce MTBE. The method can produce a fuel additive containing a maximum volume of alcohols, for example, mixed alcohols, for example, C4 alcohols, with a minimum amount of butadiene, e.g., less than or equal to <NUM>% by weight in the feed stream.

The method disclosed herein includes passing a stream of crude hydrocarbons through a MTBE unit producing a first process stream. The MTBE unit can convert isobutylene present in the feed stream to a MTBE product. The first process stream is then passed through a selective hydrogenation unit. This selective hydrogenation unit can convert the butadiene present in the first process stream to <NUM>-butene and produce a second process stream. The second process feed stream is then passed through an isomerization unit, for example, a hydroisomerization unit, which can convert the <NUM>-butene present in the second process stream to <NUM>-butene. A third process stream taken from the isomerization unit is then passed through a hydration unit to produce a fuel additive, for example, an alcohol fuel additive, such as a mixed alcohol fuel additive, such as a C4 alcohol fuel additive. The maximization of <NUM>-butene in the process increases desirable product specifications, such as octane number. Optionally, a bottom stream of the isomerization unit can be passed through a metathesis unit in order to produce propylene as a secondary product. The present process can maximize product quality for a fuel additive product while also producing additional secondary products in an efficient manner.

The method disclosed herein includes passing a feed stream through an olefin production unit, for example, a hydrocarbon cracking unit, for example, a catalytic and/or steam cracking unit, such that a source of the feed stream includes a product of an olefin cracking process and/or an olefin production process. The feed stream comprises C4 hydrocarbons. Additional hydrocarbons, for example, C2 and C3 hydrocarbons, can also be fed to the olefin production unit. The feed stream is then withdrawn from the olefin production unit as a crude C4 hydrocarbon stream. The process stream produced by the olefin production unit can comprise ethyl acetylene, vinyl acetylene, <NUM>, <NUM>-butadiene, <NUM>, <NUM>-butadiene, isobutylene, cis-<NUM>-butene, trans-<NUM>-butene, <NUM>-butene, isobutane, n-butane, or a combination comprising at least one of the foregoing.

The feed stream is then passed through a MTBE unit producing a first process stream. Methanol can be fed through the MTBE unit via a methanol stream. The MTBE unit can convert isobutylene present in the process stream to a MTBE product. This MTBE product can be withdrawn from the MTBE unit via an MTBE product stream. The purity of the MTBE product can be greater than or equal to <NUM> %. The conversion rate from isobutylene to MTBE within the MTBE unit can be greater than or equal to <NUM>%, for example, greater than or equal to <NUM>%, for example, greater than or equal to <NUM>%. The first process stream is then withdrawn from the MTBE unit with reduced isobutylene content. For example, the first process stream exiting the MTBE unit can comprise less than or equal to <NUM> % by weight isobutylene. A temperature within the MTBE unit can be <NUM> to <NUM>. A pressure within the MTBE unit can be <NUM> kiloPascals to <NUM> kiloPascals, for example, <NUM> kiloPascals to <NUM> kiloPascals, for example, <NUM> kiloPascals to <NUM> kiloPascals, for example, <NUM> kiloPascals to <NUM> kiloPascals, for example, <NUM> kiloPascals to <NUM> kiloPascals. The reaction can be carried out in a fixed bed reactor where the temperature can be maintained at a temperature of <NUM> to <NUM> and the pressure can be maintained at a pressure of <NUM> to <NUM> kiloPascals.

The first process stream exiting the MTBE unit is then passed through a selective hydrogenation unit. For example, the selective hydrogenation unit can be a selective butadiene hydrogenation unit. The process stream entering the hydrogenation unit can comprise less than or equal to <NUM>% by weight butadiene, for example, less than or equal to <NUM>% by weight, for example, less than or equal to <NUM>% by weight. The hydrogenation unit can convert butadiene present in the process stream to <NUM>-butene. The yield from butadiene to <NUM>-butene can be greater than or equal to <NUM>% and from butadiene to butene <NUM> greater that <NUM>%. It is to be noted, however that the selectivities can be shifted to either butene-<NUM> or butene-<NUM> depending on the requirements of the various downstream units. The selective hydrogenation unit can comprise multiple reactors in series, for example, the unit can comprise three reactor stages. The first two reactor stages can convert butadiene present in the first process stream to <NUM>-butene. The first two reactors can comprise a selective hydrogenation catalyst. For example, the hydrogenation catalyst can comprise palladium with an aluminum base. The hydrogenation catalyst can comprise platinum, rhodium, palladium, ruthenium, cobalt, nickel, copper, or a combination comprising at least one of the foregoing. The catalyst can be the same for the first two reactors. Hydrogen can be injected into the first process stream prior to passing through the first reactor stage.

Final hydrogenation reaction of di-olefins to a desired product of mono-olefin can be achieved in the third reactor. Carbon monoxide can be injected into the third reactor to attenuate the catalyst and minimize the isomerization reaction from butene-<NUM> to butene-<NUM>. During normal operations, the desired carbon monoxide injection rate can be <NUM> parts per million of the feed stream to the third reactor. The rate can be increased if too much butene-<NUM> is being lost to butene-<NUM>. The first process stream is then withdrawn from the selective hydrogenation unit. Operation conditions for the selective hydrogenation unit are shown in Table <NUM>. Temperature is reported in degrees Celsius and pressure in pounds per square inch gage and kiloPascals.

The first process stream exiting the hydrogenation unit is then passed through an isomerization unit, for example, a hydroisomerization unit to produce a second process stream. This isomerization unit can convert the <NUM>-butene present in the second process stream to <NUM>-butene. For example, greater than or equal to <NUM>% of any <NUM>-butene present in the first process stream can be converted to <NUM>-butene within the isomerization unit. Typical reactor inlet temperatures can be <NUM> to <NUM>, for example, <NUM> to <NUM>. Typical reactor pressures are <NUM> to <NUM> barg (<NUM> to <NUM> kPa), for example, <NUM> to <NUM> barg (<NUM> to <NUM> kPa). The second process stream can then be withdrawn from the isomerization unit with maximized <NUM>-butene content. For example, the process stream exiting the isomerization unit can comprise greater than or equal to <NUM>% by weight <NUM>-butene.

The second process stream exiting the isomerization unit is then passed through a hydration unit to produce a third process stream and a fuel additive, for example, an alcohol fuel additive, such as a mixed alcohol fuel additive, such as a C4 alcohol fuel additive. The second process stream entering the hydration unit can comprise less than or equal to <NUM>% butadiene by weight, for example, less than or equal to <NUM>% by weight, for example, less than or equal to <NUM>% by weight. The fuel additive product is withdrawn from the hydration unit via a product stream. Water can be fed to the hydration unit via a water stream. Operating conditions of the hydration unit can include a temperature of <NUM> to <NUM> and a pressure of <NUM> to <NUM> barg (<NUM> to <NUM>,<NUM> kPa) with a liquid hourly space velocity (LHSV) of <NUM> to <NUM> v/v/hr and a water to butenes molar ratio of <NUM> to <NUM>:<NUM>. The hydration unit can comprise an oscillating baffle reactor, a fixed bed reactor, a membrane integrated reactor, or a combination comprising at least one of the foregoing. The hydration unit can convert butene present in the second process stream to butanol. For example, greater than or equal to <NUM>% of the butene present in the feed stream can be converted to butanol within the hydration unit.

The fuel additive product comprises <NUM>-butanol, tert-butyl alcohol, di-isobutene, dimers of <NUM>-butene, dimers of <NUM>-butene, dimers of isobutene, or a combination comprising at least one of the foregoing. The fuel additive product can comprise greater than or equal to <NUM>% by weight trimethylpentane, for example, greater than or equal to <NUM>% by weight, for example, greater than or equal to <NUM>% by weight. An octane number of the fuel additive product can be greater than or equal to <NUM>, for example, greater than or equal to <NUM>, for example, greater than or equal to <NUM>, for example, greater than or equal to <NUM>, for example, greater than or equal to <NUM> according to the Anti-Knock Index, for example, greater than or equal to <NUM>.

The octane number is a standard measurement used to gage the performance of an engine or fuel. The higher the octane number, the more compression the fuel is able to withstand before igniting. Fuels with higher octane ratings are generally used in high performance gasoline engines that need higher compression ratios. Fuels with lower octane numbers can be desirable for diesel engines because diesel engines do not compress the fuel, but rather compress only air and then inject fuel into the air which is heated by compression. Gasoline engines rely on ignition of air and fuel compressed together as a mixture, which is ignited at the end of the compression stroke using spark plugs. As a result, high compressibility of fuel is a consideration for gasoline engines.

The Anti-Knock Index is measured by adding the research octane number and the motor octane number and dividing by two, i.e., (RON+MON)/<NUM>. The Research Octane Number is determined by running the fuel in a test engine at a speed of <NUM> revolutions per minute with a variable compression ratio under controlled conditions, and comparing the results with those for mixtures of iso-octane and n-heptane. Motor Octane Number is determined by testing a similar test engine to that used in determining the Research Octane Number but at a speed of <NUM> revolutions per minute with a preheated fuel mixture, higher engine speed, and variable ignition timing. Depending on the composition, the Motor Octane Number can be about <NUM> to <NUM> octanes lower than the Research Octane Number. The research octane number can be greater than or equal to <NUM>, for example, greater than or equal to <NUM>, for example, greater than or equal to <NUM>. The motor octane number can be greater than or equal to <NUM>, for example, greater than or equal to <NUM>, for example, greater than or equal to <NUM>, for example, greater than or equal to <NUM>. Higher octane ratings can give higher amounts of energy needed to initiate combustion. Fuels with higher octane ratings are less prone to autoignition and can withstand a greater rise in temperature during the compression stroke of an internal combustion engine without auto-igniting.

Reid vapor pressure is used to measure the volatility of gasoline defined as the absolute vapor pressure exerted by a liquid at <NUM> as determined by ASTM D-<NUM>. This measures the vapor pressure of gasoline volatile crude oil, and other volatile petroleum products, except for liquefied petroleum gases. Reid vapor pressure is measured in kiloPascals and represents a relative pressure to atmospheric pressure since ASTM D-<NUM> measures the gage pressure of the sample in a non-evacuated chamber. High levels of vaporization are desired for winter starting and operation and lower levels are desirable in avoiding vapor lock during summer heat. Fuel cannot be pumped when vapor is present in the fuel line and winter starting will be difficult when liquid gasoline in the combustion chambers has not vaporized. This means that the Reid vapor pressure is changed accordingly by oil producers seasonally to maintain gasoline engine reliability.

The Reid vapor pressure of the fuel additive product can be less than or equal to <NUM> kiloPascals, for example, less than or equal to <NUM> kiloPascals, for example, less than or equal to <NUM> kiloPascals. The Reid vapor pressure can vary during winter and summer conditions such that the pressure can be at the higher end of the values during the winter and at the lower end of the values during the summer. The fuel additive product can also comprise less than or equal to <NUM>% by weight impurities such as diene. For example, the fuel additive product can comprise less than or equal to <NUM>% by weight of butylene dimers.

A recycle stream, e.g., a hydrocarbon recycle stream, is withdrawn from the hydration unit and recycled to the initial feed stream and/or the olefin production unit, such as a steam cracker unit. The recycle stream can comprise isobutane, n-butane, isobutylene, or a combination comprising at least one of the foregoing. The recycle stream can be optionally passed through a hydrogenation unit prior to returning to the feed stream.

An additional stream (with the same composition as the third process stream entering the hydration unit) can be withdrawn from the isomerization unit and passed through a metathesis unit to produce propylene as a secondary product. The metathesis reactor has a design gauge pressure of <NUM> barg (<NUM> kPa) and a design temperature of <NUM>. The de-ethylenizer condenser has a shell design gauge pressure of <NUM> barg (<NUM> kPa) and a tube design of <NUM> barg (<NUM> kPa). The shell ad tube design temperature is -<NUM>.

The de-propylenizer condenser has a shell design gauge pressure of <NUM>. barg (<NUM> kPa) and a tube design of <NUM> barg (<NUM> kPa). The shell design temperature and the tube design temperature is <NUM>. The de-ethylenizer and de-propylenizer reboilers have a shell design gauge pressure of <NUM> bar (<NUM> kPa) and <NUM> (<NUM> kPa) bar, respectively. The tube design gage pressure for the same equipment and units is <NUM> barg (<NUM> kPa) and <NUM> barg (<NUM> kPa), respectively. The de-ethylenizer and de-propylenizer reboilers have a tube design temperature of <NUM>. The de-ethylenizer and de-propylenizer reboilers have a shell design temperature of <NUM> and <NUM> respectively. The de-ethylenizer column and the de-propylenizer columns have a design gauge pressure of <NUM> barg (<NUM> kPa) and <NUM> barg (<NUM> kPa), respectively. The de-ethylenizer column and the de-propylenizer column have a design temperature of <NUM> and <NUM> respectively.

The metathesis unit can have the same operating conditions as the hydration unit. The metathesis unit can convert normal butylene and ethylene to polymer grade propylene via metathesis. The two equilibrium reactions that can take place are metathesis and isomerization. Propylene is formed by the metathesis of ethylene and <NUM>-butene, and <NUM>-butene is isomerized to <NUM>-butene as <NUM>-butene is consumed in the metathesis reaction. Ethylene can be fed to the metathesis unit via an ethylene stream. The propylene product can be withdrawn from the metathesis unit via a propylene product stream. The propylene product can have a purity of greater than or equal to <NUM>%, for example, greater than or equal to <NUM>%.

A more complete understanding of the components, processes, and apparatuses disclosed herein can be obtained by reference to the accompanying drawings. The figure (also referred to herein as "FIG. ") is merely a schematic representation based on convenience and the ease of demonstrating the present disclosure, and are, therefore, not intended to indicate relative size and dimensions of the devices or components thereof and/or to define or limit the scope of the exemplary embodiments. Although specific terms are used in the following description for the sake of clarity, these terms are intended to refer only to the particular structure of the embodiments selected for illustration in the drawings, and are not intended to define or limit the scope of the disclosure. In the drawings and the following description below, it is to be understood that like numeric designations refer to components of like function.

Referring now to <FIG>, this simplified schematic diagram represents a unit sequence <NUM> used in a method for producing fuel additives. The sequence <NUM> includes passing a first feed stream <NUM> comprising hydrocarbons through a hydrocarbon cracking unit <NUM>. For example, the hydrocarbon cracking unit <NUM> can be a steam cracking and/or a catalytic cracking unit.

A second feed stream <NUM> is then withdrawn from the cracking unit <NUM>. The second feed stream <NUM> comprises C4 hydrocarbons. The C4 hydrocarbons can be present in an amount of <NUM> to <NUM> weight %, for example, <NUM> to <NUM> weight %. The second feed stream <NUM> is then passed through an MTBE unit <NUM>. Methanol can be fed through the MTBE unit <NUM> via stream <NUM>. The MTBE unit <NUM> can convert isobutylene present in the second feed stream <NUM> to an MTBE product <NUM>. This MTBE product <NUM> can be withdrawn from the MTBE unit <NUM>.

A first process stream <NUM> is then withdrawn from the MTBE unit <NUM>, now comprising a reduced isobutylene content. The first process stream <NUM> is then passed through a selective hydrogenation unit <NUM>. The selective hydrogenation unit <NUM> can optionally be a selective butadiene hydrogenation unit and can comprise multiple reactors in series. This selective hydrogenation unit <NUM> can convert butadiene present in the first process stream <NUM> to <NUM>-butene.

A second process stream <NUM> is then withdrawn from the hydrogenation unit <NUM> and passed through an isomerization unit <NUM>, for example, a hydroisomerization unit. This isomerization unit <NUM> can convert the <NUM>-butene present in the second process stream <NUM> to <NUM>-butene.

A third process stream <NUM> is then withdrawn from the isomerization unit <NUM> and passed through a hydration unit <NUM> to produce a fuel additive <NUM>, for example, an alcohol fuel additive, for example, a mixed alcohols fuel additive, for example, a C4 fuel additive. The fuel additive <NUM> can be withdrawn from the hydration unit <NUM>. Water can be fed to the hydration unit via stream <NUM>.

A recycle stream <NUM> is then withdrawn from the hydration unit <NUM> and recycled to the feed stream <NUM> and/or the cracking unit <NUM>. Optionally, the recycle stream <NUM> can be passed through another hydrogenation unit <NUM> prior to returning to the feed stream <NUM>.

A bottom stream <NUM> can be withdrawn from the isomerization unit <NUM> and passed through a metathesis unit <NUM> to produce propylene as a secondary product. Ethylene can be fed to the metathesis unit <NUM> via stream <NUM>. The propylene product can be withdrawn from the metathesis unit <NUM> via product stream <NUM>.

The following examples are merely illustrative of the method of treating pyrolysis gasoline disclosed herein and are not intended to limit the scope hereof. Unless otherwise stated, the examples were based upon simulations.

In general, the invention may alternately comprise, consist of, or consist essentially of, any appropriate components herein disclosed. The invention may additionally, or alternatively, be formulated so as to be devoid, or substantially free, of any components, materials, ingredients, adjuvants or species used in the prior art compositions or that are otherwise not necessary to the achievement of the function and/or objectives of the present invention. The endpoints of all ranges directed to the same component or property are inclusive and independently combinable (e.g., ranges of "less than or equal to <NUM> wt%, or <NUM> wt% to <NUM> wt%," is inclusive of the endpoints and all intermediate values of the ranges of "<NUM> wt% to <NUM> wt%," etc.). Disclosure of a narrower range or more specific group in addition to a broader range is not a disclaimer of the broader range or larger group. "Combination" is inclusive of blends, mixtures, alloys, reaction products, and the like. Furthermore, the terms "first," "second," and the like, herein do not denote any order, quantity, or importance, but rather are used to denote one element from another. The terms "a" and "an" and "the" herein do not denote a limitation of quantity, and are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. "Or" means "and/or. " The suffix "(s)" as used herein is intended to include both the singular and the plural of the term that it modifies, thereby including one or more of that term (e.g., the film(s) includes one or more films). Reference throughout the specification to "one embodiment", "another embodiment", "an embodiment", and so forth, means that a particular element (e.g., feature, structure, and/or characteristic) described in connection with the embodiment is included in at least one embodiment described herein, and may or may not be present in other embodiments. In addition, it is to be understood that the described elements may be combined in any suitable manner in the various embodiments.

Claim 1:
A method of producing a fuel additive, comprising:
passing a first feed stream (<NUM>) comprising C4 hydrocarbons through an olefin production unit (<NUM>);
withdrawing a second feed stream (<NUM>) comprising C4 hydrocarbons from the olefin production unit;
passing the second feed stream (<NUM>) comprising C4 hydrocarbons through a methyl tertiary butyl ether unit (<NUM>) producing a first process stream (<NUM>);
passing the first process stream (<NUM>) through a selective hydrogenation unit (<NUM>) producing a second process stream (<NUM>);
passing the second process stream (<NUM>) through an isomerization unit (<NUM>) producing a third process stream (<NUM>);
passing the third process stream (<NUM>) through a hydration unit (<NUM>) producing the fuel additive (<NUM>) and a recycle stream (<NUM>), wherein the fuel additive (<NUM>) comprises <NUM>-butanol, tert-butyl alcohol, di isobutene, dimers of <NUM>-butene, dimers of <NUM>-butene, dimers of isobutene, or a combination comprising at least one of the foregoing; and
recycling withdrawing the recycle stream (<NUM>) from the hydration unit (<NUM>) and recycling it to the first feed stream (<NUM>) and/or the olefin production unit (<NUM>) .