Patent Description:
<CIT>discloses the production of a fuel additive by selective hydrogenation of a C4 stream, followed by isomerization of <NUM>-butene to <NUM>-butene and hydration of <NUM>-butene to butanol.

<NPL>, discloses another process for producing fuel additives by selective hydrogenation of C4 hydrocarbons, isomerization and production of butanol by hydration of butenes, e.g. isobutene, <NUM>-butene.

<CIT>discloses the production of butanol as fuel additive by hydration of butenes, and states that since the hydration rate of <NUM>-butene is higher than that of <NUM>-butene, <NUM>-butene can be isomerized to <NUM>-butene. Commercial gasoline, which is fuel for internal combustion engines, is a refined petroleum product that is typically a mixture of hydrocarbons (base gasoline), additives, and blending agents. Additives and blending agents, for example octane boosters, are added to the base gasoline to enhance the performance and the stability of gasoline.

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 (e.g., C<NUM>-C<NUM> hydrocarbons). The effluent can then be separated into individual olefins (for example, ethylene, propylene, and C<NUM> hydrocarbons) 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. 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> kilopascals, greater than <NUM> kilopascals, greater than <NUM> kilopascals, 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.

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 invention is a method of producing a fuel additive according to claim <NUM>.

Particular embodiments of the method of the invention are found in dependent claims <NUM> to <NUM>.

These and other features and characteristics are more particularly described below.

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.

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 <NUM>-butanol, <NUM>-butanol, tert-butyl alcohol, C<NUM>-dimer, or a combination thereof. For example, the final fuel additive products can have levels of the C<NUM>-dimer comprising trimethylpentane, di-isobutylene, <NUM>,<NUM>,<NUM> trimethylpentane, <NUM>,<NUM>,<NUM> trimethylpentane, or a combination thereof in an amount of <NUM>% by weight to <NUM>% by weight, based on the total weight of the fuel additive product (e.g., the total weight of the fuel additive product is <NUM>% by weight), 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 in the fuel additive product can be present in an amount of <NUM> to <NUM>% by weight, for example, <NUM> to <NUM>% by weight, based on the total weight of the fuel additive product. 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, ethylene and propylene products can be produced along with the fuel additive, thus maximizing the efficiency and productivity of the process.

The method disclosed herein can provide a process for producing a fuel additive with a minimal number of components. For example, the inclusion of a hydrogenation unit, for example, a selective hydrogenation unit in the method can transform the butadiene components to <NUM>-butene and <NUM>-butene together with the utilization of isobutylene without the inclusion of a butadiene unit or a MTBE unit in the method. The method of making a fuel additive as disclosed can have increased efficiency by eliminating the inert n-butane and isobutane from the streams that are used as feedstocks for the hydration unit. Elimination of the use of these materials can increase efficiency by minimizing the amount of material to be recycled from the method. The method can produce fuel additives, for example, alcohol fuel additives, for example, C<NUM> fuel additives, from mixed crude hydrocarbon feedstocks, for example, C<NUM> hydrocarbons, from cracking units, such as steam cracking units with minimum capital expenditures and maximum production of the fuel additive with even further increased efficiency.

The method disclosed herein can provide a novel design for utilization and transformation of crude hydrocarbons from a cracking unit recycle stream as a feedstock to maximize production of the fuel additive. The method includes the use of selective hydrogenation units, distillation units, and hydration units for the maximum production of the fuel additive.

The method of making a fuel additive herein includes passing a feed stream of crude hydrocarbons through a first hydrogenation unit. The crude hydrocarbons include C<NUM> hydrocarbons. The first hydrogenation unit can be a selective hydrogenation unit. This hydrogenation unit converts the butadiene (BD) present in the feed stream to <NUM>-butene and <NUM>-butene, forming a first process stream. The first process stream is passed through a distillation unit, which separates the first process stream into component hydrocarbons. The reduction of butadiene and the maximization of butenes in the feed stream can increase desirable product specifications of the fuel additive, for example, the octane number. A <NUM>-butene stream is withdrawn from the distillation unit and passed through a second hydrogenation unit to convert <NUM>-butene to <NUM>-butene. A <NUM>-butene stream is withdrawn from the second hydrogenation unit and passed through a separation unit to separate and isolate <NUM>-butene. The <NUM>-butene stream is passed through a hydration unit to produce the fuel additive, for example, a mixed alcohols fuel additive, for example, a C<NUM> alcohol fuel additive. Recycle streams from within the process can be used to produce ethylene and propylene as secondary products. Accordingly, 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 can include passing a raw material stream through an olefin production unit, for example, a hydrocarbon cracking unit, for example, a catalytic and/or steam cracking unit. The raw material stream can comprise hydrocarbons, for example, C<NUM> hydrocarbons. Additional hydrocarbons, for example, C<NUM> and C<NUM> hydrocarbons, can also be fed to the olefin production unit. A feed stream can then be withdrawn from the olefin production unit. The feed stream produced by the olefin production unit can comprise propylene, ethyl acetylene, vinyl acetylene, propadiene, <NUM>, <NUM>-butadiene, <NUM>, <NUM>-butadiene, isobutylene, cis-<NUM>-butene, trans-<NUM>-butene, <NUM>-butene, isobutane, n-butane, propene, or a combination thereof. The total C<NUM> olefin content of the feed stream when withdrawn from a steam cracking unit can be greater than or equal to <NUM>% by weight based on the total weight of the feed stream (e.g., the total weight of the feed stream is <NUM>% by weight), and the feed stream can comprise greater than or equal to <NUM>% by weight isobutylene, based on the total weight of the feed stream. The total C<NUM> olefin content of the feed stream when withdrawn from a fluid catalytic cracking unit can be greater than or equal to <NUM>% by weight based on the total weight of the feed stream. The feed stream can comprise greater than or equal to <NUM>% by weight isobutane and n-butane based on the total weight of the feed stream, for example, isobutylene in an amount of <NUM>-<NUM>% by weight, olefins in an amount of <NUM>-<NUM>% by weight, and saturated hydrocarbons in an amount of <NUM>-<NUM>% by weight, based on the total weight of the feed stream.

The feed stream will then be passed through a first hydrogenation unit, for example, a selective hydrogenation unit. The first hydrogenation unit converts butadiene to <NUM>-butene and <NUM>-butene. The feed stream entering the first hydrogenation unit can comprise less than or equal to <NUM>% by weight butadiene, for example, less than or equal to <NUM>% by weight butadiene, for example, less than or equal to <NUM>% by weight butadiene, based on the total weight of the feed stream (e.g., the total weight of the feed stream is <NUM>% by weight). The first hydrogenation unit can convert butadiene present in the feed stream to <NUM>-butene, cis-<NUM>-butene and trans-<NUM>-butene. The conversion rate from butadiene to <NUM>-butene, cis-<NUM>-butene and/or trans-<NUM>-butene can be greater than or equal to <NUM>% by weight (e.g., greater than or equal to <NUM>% by weight of butadiene present in the feed stream, based on the total weight of the butadiene present in feed stream, is converted to <NUM>-butene, cis-<NUM>-butene and/or trans-<NUM>-butene), for example, greater than or equal to <NUM>% by weight, for example, greater than or equal to <NUM>% by weight. The first hydrogenation unit can also convert propylene, methyl acetylene, and propadiene present in the process stream to their corresponding alkanes or alkenes, as appropriate. Tertiary butyl catechol and/or hydrogen can be added to the feed stream prior to passing through the first hydrogenation unit.

The first 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 feed stream to <NUM>-butene and <NUM>-butene. The first two reactor stages 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 thereof. The catalyst can be the same for the first two reactor stages. Hydrogen can be injected into the feed 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 <NUM>-butene to <NUM>-butene. 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 <NUM>-butene is being lost to <NUM>-butene. A first process stream can then be withdrawn from the 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 gauge (psig) and kiloPascals (kPa).

The first process stream is then passed through a distillation unit, for example, a kinetic distillation unit. An overhead pressure in the distillation unit can be <NUM> to <NUM> kPa and a reflux temperature can be <NUM>-<NUM>. This distillation unit separates the first process stream into component hydrocarbons. A <NUM>-butene stream is withdrawn from the distillation unit. A temperature within the distillation unit can be <NUM> to <NUM>, for example, <NUM> to <NUM>. A pressure within the distillation unit can be <NUM> kPa to <NUM> kPa, for example, <NUM> kPa to <NUM> kPa, for example, <NUM> kPa to <NUM> kPa.

The <NUM>-butene stream withdrawn from the distillation unit is passed through a second hydrogenation unit. The <NUM>-butene stream can comprise n-butane, <NUM>-butene, and <NUM>-butene. The second hydrogenation unit converts <NUM>-butene present in the <NUM>-butene stream to <NUM>-butene. Pressure in the second hydrogenation unit can be <NUM> to <NUM> kPa and a reflux temperature can be <NUM>-<NUM>. A portion of the <NUM>-butene stream can then be withdrawn from the second hydrogenation unit and recycled back to the distillation unit. The <NUM>-butene stream can comprise <NUM>-butene and n-butane. A portion of the <NUM>-butene stream is passed through a separation unit together with the isobutylene stream. A temperature within the distillation unit can be <NUM> to <NUM>, for example, <NUM> to <NUM>. A pressure within the distillation unit can be <NUM> kilopascals to <NUM> kilopascals, for example, <NUM> kilopascals to <NUM> kilopascals, for example, <NUM> kilopascals to <NUM> kilopascals. The separation unit separates and isolates <NUM>-butene and isobutylene. A separated <NUM>-butene stream and isobutylene stream is withdrawn from the separation unit and passed through a hydration unit.

The hydration unit hydrates the isobutylene stream and a second stream (comprising butenes) to produce a fuel additive, for example, an alcohol fuel additive, for example, a mixed alcohols fuel additive, for example, a C<NUM> alcohol fuel additive. The <NUM>-butene stream entering the hydration 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 based on the total weight of the <NUM>-butene stream (e.g., the total weight of the <NUM>-butene stream is <NUM>% by weight). The fuel additive product is withdrawn from the hydration unit via a product stream. Water is fed to the hydration unit via a water stream. The hydration unit can comprise an oscillating baffle reactor, a fixed bed reactor, a membrane integrated reactor, isothermal multi-tubular reactor, or a combination thereof. The hydration unit can convert butene present in the process stream to butanol. For example, <NUM>-<NUM>% by weight of the butene present in the <NUM>-butene stream, based on the total weight of the butene present in the <NUM>-butene stream, can be converted to butanol within the hydration unit. The <NUM>-butene stream can be contacted with water and a catalyst within the hydration unit. For example, the catalyst can comprise phosphoric acid, hypophosphorous acid, sulfonic ionexchange resin, super acid resins niobium oxide, or a combination thereof. Water and butene can be present within the hydration unit in a molar ratio of <NUM>-<NUM> mole of water to <NUM> mole of butene, for example, <NUM> mole of water to <NUM> mole of butene. A temperature within the hydration unit can be <NUM> to <NUM>, for example, <NUM> to <NUM>. A pressure within the hydration unit can be <NUM> kPa to <NUM>,<NUM> kPa, for example, <NUM> kPa to <NUM>,<NUM> kPa, for example, <NUM> kPa.

The fuel additive product can comprise <NUM>-butanol, <NUM>-butanol, tert-butyl alcohol, C<NUM>-dimer, or a combination thereof. For example, the C<NUM>-dimer can comprise di-isobutylene, <NUM>,<NUM>,<NUM> trimethylpentane, <NUM>,<NUM>,<NUM> trimethylpentane, or a combination thereof. 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, for example greater than or equal to <NUM>% by weight, based on the total weight of the fuel additive product (e.g., the total weight of the fuel additive product is <NUM>% by weight). An octane number of the fuel additive product can be greater than or equal to <NUM> according to the Anti-Knock Index, 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>.

The octane number is a standard measurement used to gauge 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 ("RON") and the Motor Octane Number ("MON") and dividing by two, e.g., (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>, 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 auto-ignition 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 the test method ASTM D-<NUM>. Reid vapor pressure is measured in kilopascals and represents a relative pressure to atmospheric pressure since ASTM D-<NUM> measures the gauge 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 generally cannot be pumped when vapor is present in the fuel line, and winter starting can 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, <NUM> kilopascals to <NUM> kilopascals, for example, <NUM> kilopascals 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.

A recycle stream, e.g., a hydrocarbon recycle stream, can be withdrawn from the hydration unit as a purge stream and recycled to the raw material stream and/or the olefin production unit, such as a steam cracker unit. The recycle stream can comprise butene, isobutane, n-butane, isobutylene, or a combination thereof. The recycle stream can optionally be passed through a recycle hydrogenation unit prior to returning to the raw material stream. The recycle hydrogenation unit can convert the <NUM>-butene and <NUM>-butene present in the recycle stream to n-butane and isobutane. For example, greater than or equal to <NUM>% by weight of butene present in the hydrocarbon recycle stream, based on the total weight of the butene present in the hydrocarbon recycle stream, can be converted to butane within the recycle hydrogenation unit (e.g., the total weight of the butene present in the hydrocarbon recycle stream is <NUM>% by weight). The hydrocarbon recycle stream can also be used to produce secondary products such as ethylene and propylene via a hydrocarbon cracking unit.

Additional recycle streams can be withdrawn from within the process. For example, an iso-stream comprising isobutane and/or isobutylene can be withdrawn from the distillation unit. The iso-stream can comprise greater than or equal to <NUM>% by weight isobutane and/or isobutylene, based on the total weight of the iso-stream (e.g., the total weight of the iso-stream is <NUM>% by weight). A butane stream comprising n-butane and/or isobutane can be withdrawn from the distillation unit and/or the separation unit. The iso-stream and/or the butane stream can be recycled back to the raw material stream and/or the cracking unit (in a manner similar to the hydrocarbon recycle stream). The iso-stream and/or the butane stream can be fed directly to the hydration unit as additional feedstock for production of the fuel additive product. The iso-stream and/or the butane stream can also be used to produce secondary products such as ethylene and propylene via a hydrocarbon cracking unit.

A more complete understanding of the components, processes, and apparatuses disclosed herein can be obtained by reference to the accompanying drawings. These figures (also referred to herein as "FIG. " ) are merely schematic representations 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> can include passing a raw material stream <NUM> comprising hydrocarbons through a hydrocarbon cracking unit <NUM>. For example, the hydrocarbon cracking unit <NUM> can be a steam cracking and/or catalytic cracking unit.

A feed stream <NUM> is withdrawn from the cracking unit <NUM>. The feed stream <NUM> comprises C<NUM> hydrocarbons. The feed stream <NUM> is passed through a first hydrogenation unit <NUM>, for example, a selective hydrogenation unit. The first hydrogenation unit <NUM> can be a selective butadiene hydrogenation unit and can comprise multiple reactors in series. This hydrogenation unit <NUM> converts butadiene present in the feed stream <NUM> to <NUM>-butene and <NUM>-butene.

A first process stream <NUM> is withdrawn from the first hydrogenation unit <NUM> and passed through a distillation unit <NUM> (e.g., kinetic distillation column <NUM>). This distillation unit <NUM> separates the first process stream <NUM> into component hydrocarbons. A <NUM>-butene stream <NUM> is withdrawn from the distillation unit <NUM> and passed through a second hydrogenation unit <NUM>.

The second hydrogenation unit <NUM> converts <NUM>-butene present in the stream <NUM> to <NUM>-butene. A <NUM>-butene stream <NUM> is withdrawn from the second hydrogenation unit <NUM> and can be recycled back to the distillation unit <NUM>. A portion of the <NUM>-butene stream is passed through a separation unit <NUM> via stream <NUM>. The separation unit <NUM> separates and isolates <NUM>-butene.

A separated <NUM>-butene stream <NUM> is withdrawn from the separation unit <NUM> and passed through a hydration unit <NUM>. The hydration unit <NUM> hydrates the <NUM>-butene stream <NUM> to produce a fuel additive <NUM>, for example, an alcohol fuel additive. The fuel additive <NUM> is withdrawn from the hydration unit <NUM>. Water is fed to the hydration unit <NUM> via stream <NUM>. It is noted that the hydration unit can take the form of an oscillating baffle reactor, a fixed bed reactor, a fluidized bed reactor, a membrane integrated reactor, or combinations thereof.

A hydrocarbon recycle stream <NUM> can be withdrawn from the hydration unit <NUM> and recycled back to the raw material stream <NUM> and/or the cracking unit <NUM>. The recycle stream <NUM> can be passed through an additional (e.g., a third) hydrogenation unit <NUM> prior to returning to the raw material stream <NUM>. An iso-stream <NUM> comprising isobutane and/or isobutylene is also withdrawn from the distillation unit <NUM>. A butane stream <NUM> comprising n-butane and/or isobutane can further be withdrawn from the distillation unit <NUM>.

The iso-stream <NUM> and/or the butane stream <NUM> can be recycled back to the raw material stream <NUM> and/or the cracking unit <NUM> (in a manner similar to the hydrocarbon recycle stream <NUM>). The iso-stream <NUM> and/or the butane stream <NUM> can also be used to produce secondary products such as ethylene and propylene.

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

Simulations were conducted using Aspen Plus and Pro/II <NUM> (chemical engineering computer software programs) for the distillation unit <NUM> of the present method. The results from the simulation are presented in Table <NUM>. As shown in <FIG>, Stream <NUM> (e.g., similar to first process stream <NUM> from <FIG>) represents the stream entering the distillation unit <NUM> and Streams <NUM>-<NUM> represent product streams being withdrawn from the unit <NUM>. This can be seen in <FIG>, where Stream <NUM> (S1) is entering the distillation unit <NUM> and Streams <NUM>-<NUM> (S2, S3, S4, and S5) are being withdrawn from the distillation unit <NUM>. Temperature for each Stream S1-S5 is given in degrees Celsius, pressure is given in kilograms per square centimeter ("kg/cm<NUM>"), and flowrate is given in kilogram-moles per hour ("kg-mol/hr"). The fractional compositions of the Streams S1-S5 are also provided by mole % (mole % is based on the total moles of the respective Stream S1 to S5 - e.g., the mole % of isobutane of Stream S1 is based on the total moles of Stream S1).

Stream <NUM>, Stream S4 and/or Stream S5 (e.g., similar to iso-stream <NUM> and/or butane stream <NUM> from <FIG>) can be sent to the hydration unit <NUM>, and Stream S3 (e.g., similar to <NUM>-butene stream <NUM> from <FIG>) is a stream that includes no or trace amounts of isobutylene (e.g., Stream <NUM> has <NUM> mole % isobutylene, as shown in Table <NUM> above), and can be sent to the second hydrogenation unit <NUM>, as discussed above in conjunction with <FIG>.

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)" is 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.

The modifier "about" used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., includes the degree of error associated with measurement of the particular quantity). The notation "± <NUM>%" means that the indicated measurement can be from an amount that is minus <NUM>% to an amount that is plus <NUM>% of the stated value. The terms "front", "back", "bottom", and/or "top" are used herein, unless otherwise noted, merely for convenience of description, and are not limited to any one position or spatial orientation. "Optional" or "optionally" means that the subsequently described event or circumstance can or cannot occur, and that the description includes instances where the event occurs and instances where it does not. Unless defined otherwise, technical and scientific terms used herein have the same meaning as is commonly understood by one of skill in the art to which this invention belongs. A "combination" is inclusive of blends, mixtures, alloys, reaction products, and the like. In a list of alternatively useable species, "a combination thereof" means that the combination can include a combination of at least one element of the list with one or more like elements not named. Also, "at least one of" means that the list is inclusive of each element individually, as well as combinations of two or more elements of the list, and combinations of at least one element of the list with like elements not named.

As used herein, the term "C# hydrocarbons" or "C#" wherein "#" is a positive integer, describes hydrocarbons having # carbon atoms. Accordingly, the term "C<NUM> hydrocarbons" describes hydrocarbons having <NUM> carbon atoms.

Claim 1:
A method of producing a fuel additive (<NUM>), comprising:
passing a feed stream (<NUM>) comprising C<NUM> hydrocarbons through a first hydrogenation unit (<NUM>) producing a first process stream (<NUM>), wherein the feed stream (<NUM>) comprises methyl acetylene, propylene, <NUM>, <NUM>-butadiene, <NUM>, <NUM>-butadiene, isobutylene, cis-<NUM>-butene, trans-<NUM>-butene, <NUM>-butene, isobutane, n-butane, or a combination thereof, and wherein at least a portion of the butadiene present in the feed stream (<NUM>) is converted to <NUM>-butene and <NUM>-butene within the first hydrogenation unit (<NUM>);
passing the first process stream (<NUM>) through a distillation unit (<NUM>);
withdrawing a <NUM>-butene stream (<NUM>) from the distillation unit (<NUM>);
withdrawing an iso-stream (<NUM>) from the distillation unit (<NUM>), wherein the iso-stream (<NUM>) comprises isobutane and isobutylene;
passing the <NUM>-butene stream (<NUM>) through a second hydrogenation unit (<NUM>) producing a <NUM>-butene stream (<NUM>, <NUM>);
passing at least a first portion of the <NUM>-butene stream (<NUM>) through a separation unit (<NUM>) producing a separated <NUM>-butene stream (<NUM>); and
passing the separated <NUM>-butene stream (<NUM>) and a water stream (<NUM>) through a hydration unit (<NUM>) producing the fuel additive (<NUM>).