Process for the controlled oligomerization of butenes

Abstract

The selective dimerization of isoolefins such as isobutylene or isopentane or mixtures thereof can be carried out in a system comprising a series of fixed bed reactors and catalytic distillation reactors. The system can pass the fixed bed reactor effluent to the downstream reactors without intermediate separation of the desired product from unreacted components. It has been found that high selectivity to dimers can be achieved even without intermediate separation of the desired product from unreacted components between reactors. In addition, embodiments provide for the use of a partitioned wall column to recover high purity dimer product, thereby reducing unit element count and site size.

Description

Background Technology

[0001] To meet fuel blending requirements, such as octane number or vapor pressure requirements, smaller olefin molecules can be modified to produce longer-chain molecules. Alternatively, smaller olefin molecules can be etherified to increase the oxygen content of the molecule and the resulting fuel blend.

[0002] A common method for modifying smaller olefin molecules, such as C2 to C5 olefins, is oligomerization. Isobutylene has significant commercial value in many applications. For example, isobutylene is one of the comonomers in butyl rubber. Isobutylene can also be oligomerized to produce compounds that can be used as chemical feedstocks for further reactions or for gasoline blending. Diisobutylene (isobutylene dimer) has particular commercial value in a variety of applications. For example, diisobutylene can be used as a feedstock for alkylation reactions or as an intermediate in the preparation of detergents. Diisobutylene can also be hydrogenated to pure isooctane (2,2,4-trimethylpentane), which is highly preferred in gasoline blending.

[0003] Oligopolymerization involves contacting an olefin with a catalyst to produce a longer-chain molecule. Oligomers can consist of two or more constituent olefin molecules. For example, dimerization is a type of oligopolymerization limited to combinations of only two olefin molecules. If the olefin feed contains only one type of olefin, a dimer product is formed. If the olefin feed contains two or more different olefins or olefin isomers, a codimer product may also be formed.

[0004] Specifically, C4 olefin dimerization is widely used to produce isooctene, an intermediate that can be hydrogenated to produce isooctane, a high-value gasoline blending additive. Several representative olefin dimerization reactions are shown below:

[0005]

[0006] U.S. Patent Nos. 3,960,978 and 4,021,502 disclose a gas-phase olefin oligomerization method, wherein C2 to C5 olefins, fed as pure olefins or a mixture with alkanes, undergo oligomerization via contact with a zeolite fixed catalyst bed. Examples of U.S. Patent Nos. 4,242,530, 4,375,576, 5,003,124, 7,145,049, 6,335,473, 6,774,275, 6,858,770, 6,936,742, 6,995,296, 7,250,542, 7,288,693, 7,319,180, and 6,689,9 Other oligomerization methods are disclosed in U.S. Patent Application Publications Nos. 27, 6,376,731, 5,877,372, 4,331,824, 4,100,220, and U.S. Patent Application Publications Nos. 20080064911, 20080045763, 20070161843, 20060030741, 20040210093, and 20040006252. Acidic resin catalysts can also be used in a variety of other petrochemical processes, including ether formation, olefin hydration, esterification, and epoxidation, as described in U.S. Patent Nos. 4,551,567 and 4,629,710.

[0007] Methods for oligomerizing olefins on such resin catalysts require periodic shutdown of the oligomerization unit to replace and / or regenerate the catalyst. Furthermore, such solid-state catalytic processes may require additives (such as “selectivators” or “moderators”, used interchangeably herein) to enhance the catalyst’s selectivity for dimers, where additives can lead to unwanted acid parabolic substances (deactivating the catalyst) and byproducts, and may also require complex separation processes to remove additives and / or byproducts from the resulting product stream.

[0008] In any type of oligomerization reaction, the activity of the oligomerization catalyst can decrease dramatically due to poisoning, scaling, and coking, often caused by impurities present in the olefin feed stream. Furthermore, various additives and impurities that may be present in the olefin feed can participate in side reactions, leading to the formation of undesirable byproducts. For example, the presence of n-butene in the isobutylene oligomerization process for producing isooctene dimers can lead to the formation of undesirable C8 codimers. The formation of C8 codimers can adversely affect the operator in two main ways. First, it reduces the effective yield of the target C8 dimer product, thereby increasing the feed and operating costs of the dimerization reactor. Second, it may require additional costs associated with separating and removing the C8 codimer from the product.

[0009] Oligomerization additives, such as reaction modifiers, may also participate in undesirable side reactions with olefins or dimer products. Modifiers are typically added to oligomerization reactions to improve dimer selectivity by limiting the extent of oligomerization to the dimer stage. Suitable modifiers include oxygen-containing compounds such as water, primary, secondary, and tertiary alcohols, as well as ethers. However, as a compromise for achieving high dimer selectivity, some modifiers may react with olefins or dimer products to form heavy oxygen-containing compounds, such as MSBE. A representative reaction in which olefins react with modifiers to form heavy oxygen-containing compounds is shown below:

[0010]

[0011] Similar to other types of side reactions, the reaction of moderating agents to generate heavy oxygen-containing compounds such as MSBE may also reduce the yield of C8 dimer products and require additional separation costs to maintain the desired product purity. Summary of the Invention

[0012] On one hand, embodiments of this document relate to a method for the dimerization of olefins and / or isoolefins. The method may include feeding an oxygen-containing reaction modifier and a mixed hydrocarbon feed into a fixed-bed reactor containing an oligomerizing catalyst. In some embodiments, the mixed hydrocarbon feed may include isobutylene and optionally one or more of isobutane, n-butane, 1-butene, and 2-butene. In the fixed-bed reactor, the method may include reacting isobutylene under oligomerizing conditions to form a reaction effluent comprising the reaction modifier, isobutylene dimer, unreacted isobutylene, any high-boiling oxygen-containing reaction byproducts formed, and any unreacted isobutane, n-butane, 1-butene, and 2-butene. Following effluent recovery and without component separation, the method comprises feeding the reaction effluent into a second fixed-bed reactor containing an oligomerizing catalyst and reacting isobutylene in the second fixed-bed reactor under oligomerizing conditions to form additional isobutylene dimers, recovering a second reaction effluent comprising a reaction modifier, isobutylene dimers, any oxygen-containing high-boiling reaction byproducts formed, and any unreacted isobutane, n-butane, 1-butene, and 2-butene. Following recovery of the second reaction effluent and without intermediate component separation, the method comprises feeding the second reaction effluent into a catalytic distillation reactor having a reactive distillation zone containing an oligomerizing catalyst. Meanwhile, within the catalytic distillation reactor, the method includes: reacting unreacted isobutene in the second reaction effluent to form additional isobutene dimers; separating the dimers and any oxygen-containing high-boiling-point reaction byproducts recovered as bottom fractions from isobutane, n-butane, and any unreacted isobutene, 1-butene, and 2-butene recovered as top fractions.

[0013] In another aspect, embodiments of this document relate to a method for the dimerization of olefins and / or isoolefins. The method may include feeding an oxygen-containing reaction modifier and a mixed hydrocarbon feed into a fixed-bed reactor containing an oligomerizing catalyst. In some embodiments, the mixed hydrocarbon feed may include C4 hydrocarbons, C5 hydrocarbons, or a mixture of C4 and C5 hydrocarbons. Each of the mixed hydrocarbons may each include an isoolefin, a n-olefin, an isoalkanes, and a n-alkanes. In the fixed-bed reactor, the method may include reacting the isoolefins under oligomerizing conditions to form a reaction effluent comprising the reaction modifier, isoolefin dimers, unreacted isoolefins, any high-boiling oxygen-containing reaction byproducts formed, and any unreacted isoalkanes, n-alkanes, and n-olefins. Following effluent recovery and without component separation, the method includes feeding the reaction effluent into a second fixed-bed reactor containing an oligomerizing catalyst, and reacting the isoolefins in the second fixed-bed reactor under oligomerizing conditions to form additional isoolefin dimers, recovering a second reaction effluent containing a reaction regulator, isoolefin dimers, any oxygen-containing high-boiling reaction byproducts formed, and any unreacted isoalkanes, n-alkanes, and n-olefins. Following recovery of the second reaction effluent and without intermediate component separation, the method includes feeding the second reaction effluent into a catalytic distillation reactor having a reactive distillation zone containing an oligomerizing catalyst. Simultaneously within the catalytic distillation reactor, the method includes: reacting the unreacted isoolefins in the second reaction effluent to form additional isoolefin dimers; separating the dimers and any oxygen-containing high-boiling reaction byproducts recovered as bottom fractions from the isoalkanes, n-alkanes, and any unreacted isoolefins and n-olefins recovered as top fractions.

[0014] In some embodiments, the oligomerizing catalyst contained in each of the fixed-bed reactor, the second fixed-bed reactor, and the reactive distillation zone comprises a sulfonic acid catalyst. In other embodiments, the oligomerizing catalyst contained in each of the fixed-bed reactor, the second fixed-bed reactor, and the reactive distillation zone comprises a phosphoric acid catalyst.

[0015] In some embodiments, the oxygen-containing reaction modifier used is selected from the group consisting of methanol, ethanol, propanol, isopropanol, and mixtures thereof. In other embodiments, water or C4 alcohols such as isobutanol or tert-butanol may be used additionally or optionally as the reaction modifier.

[0016] In several embodiments, the bottom fraction recovered from the catalytic distillation reactor may include a reaction regulator and isobutylene trimer. The method may also include separating the bottom fraction in a partition wall distillation column to recover the top fraction, a side-take fraction containing isobutylene dimer, and the bottom fraction containing isobutylene trimer. In some embodiments, the side-take fraction contains more than 95% by weight of isobutylene dimer.

[0017] Multiple embodiments also provide the recovery and reuse of oxygen-containing reaction modifiers and / or oxygen-containing reaction byproducts as reaction modifiers within one or more of a fixed-bed reactor, a second fixed-bed reactor, and a catalytic distillation reactor.

[0018] In another aspect, embodiments of this document relate to a system for the selective dimerization of olefins and / or isoolefins. The system includes a feed line for conveying an oxygenated compound reaction regulator from an oxygenated compound reaction regulator supply system. The system also includes a feed line for conveying a mixed hydrocarbon feed from a mixed hydrocarbon supply system. The supply system may include tanks or upstream processing units to produce such feeds, as well as pumps, valves, and other associated equipment. The mixed hydrocarbon feed may include C4 hydrocarbons, C5 hydrocarbons, or a mixture of C4 and C5 hydrocarbons, and the mixed hydrocarbons used may include isoolefins, n-olefins, isoalkanes, and n-alkanes. The system also includes a fixed-bed reactor containing an oligomerizing catalyst, configured to receive the mixed hydrocarbon feed and the oxygenated compound reaction regulator and to react the isoolefins in the fixed-bed reactor under oligomerizing conditions to form a reaction effluent comprising the reaction regulator, isoolefin dimers, unreacted isoolefins, any high-boiling oxygenated compound reaction byproducts formed, and any unreacted isoalkanes, n-alkanes, and n-olefins. A flow line is provided for conveying the reaction effluent from a fixed-bed reactor to a second fixed-bed reactor containing an oligomerizing catalyst without intermediate component separation. The second fixed-bed reactor is configured to react unreacted isoolefins under oligomerizing conditions to form additional isoolefin dimers and to produce a second reaction effluent comprising a reaction modifier, isoolefin dimers, any oxygen-containing high-boiling reaction byproducts formed, and any unreacted isoalkanes, n-alkanes, and n-olefins. The system also includes a flow line for conveying the second reaction effluent from the second fixed-bed reactor to a catalytic distillation reactor having a reactive distillation zone containing an oligomerizing catalyst without component separation. This catalytic distillation reactor is configured to simultaneously: react the unreacted isoolefins in the second reaction effluent to form additional isoolefin dimers; and separate the dimers and any oxygen-containing high-boiling reaction byproducts recovered as bottom fractions from the isoalkanes, n-alkanes, and any unreacted isoolefins and n-olefins recovered as top fractions.

[0019] The oligomerizing catalyst included in each of the fixed-bed reactor, the second fixed-bed reactor, and the reactive distillation zone in the embodiment system may include a sulfonic acid catalyst. The oligomerizing catalyst included in each of the fixed-bed reactor, the second fixed-bed reactor, and the reactive distillation zone in other embodiment systems may include a phosphoric acid catalyst.

[0020] In embodiments where the bottom fraction also contains a reaction regulator and an isoolefin trimer, the system may further include a partition wall distillation column for separating the bottom fraction and recovering the top fraction, the side-take fraction containing the isoolefin dimer, and the bottom fraction containing the isoolefin trimer. Attached Figure Description

[0021] Figure 1 This is a simplified process flow diagram of a system for the dimerization and / or oligomerization of olefins according to an embodiment of this document.

[0022] Figure 2 This is a simplified process flow diagram of a system for the dimerization and / or oligomerization of olefins according to the embodiments described herein.

[0023] Figure 3 This is a simplified process flow diagram of a system for the dimerization and / or oligomerization of olefins according to the embodiments described herein. Detailed Implementation

[0024] The embodiments described herein generally involve the dimerization and / or oligomerization of olefins. In some embodiments of this disclosure, C4 olefins, such as 1-butene, 2-butene, and / or isobutene, undergo a controlled dimerization or oligomerization process in a tandem reactor configuration, a portion of which includes a catalytic distillation reactor system, wherein the reaction is carried out under mild conditions in the presence of oxygen-containing compounds such as alcohols.

[0025] As used in the embodiments disclosed herein, the term "catalytic distillation reactor system" and similar terms refer to a system for reacting compounds simultaneously or together and using fractionation to separate reactants and products. In some embodiments, the catalytic distillation reactor system may include a conventional catalytic distillation column reactor, wherein the reaction and distillation occur simultaneously under boiling conditions. In other embodiments, the catalytic distillation reactor system may include a distillation column combined with at least one side reactor, wherein the side reactor may operate as a liquid-phase reactor or a boiling-point reactor. Both of the described catalytic distillation reactor systems are preferred for separation relative to a conventional liquid-phase reaction, and the catalytic distillation column reactor may have advantages such as reduced unit number, lower capital costs, increased catalyst productivity per pound of catalyst, efficient heat removal (the heat of the reaction can be absorbed into the heat of vaporization of the mixture), and potential for shifting equilibrium. A partitioned-wall distillation column may also be used, wherein at least one section of the partitioned-wall column contains catalytic distillation structures, and the partitioned-wall distillation column is referred to herein as a "catalytic distillation reactor system".

[0026] The hydrocarbon feed to one or more reactors may include a purified isoolefin stream, such as a feed stream containing isobutene, isopentene, or a mixture thereof. In other embodiments, the hydrocarbon feed to one or more reactors may include a purified n-olefin stream, such as a feed stream containing 1-butene, 2-butene, 1-pentene, 2-pentene, or a mixture thereof. In other embodiments, the hydrocarbon feed may include C4-C5, C4, or C5 light naphtha fractions. When present in the mixture, tertiary olefins, such as isobutene and isopentene, are more reactive than n-olefin isomers and preferentially react (dimerization, oligomerization, or etherification). The alkanes and isoalkanes in the C4-C5 light naphtha fraction may include n-butane, n-pentane, isobutane, isopentane, or a mixture thereof, which may act as a diluent in the reactor.

[0027] In some embodiments, a C4-containing hydrocarbon stream, such as a C4 naphtha fraction, a C4-C5 naphtha fraction, or a C4-C6 naphtha fraction, can be fed into a reactor for the hydroisomerization of 1-butene to 2-butene, thereby allowing the separation of isobutene from the straight-chain olefin 2-butene, and, if desired, providing an isobutene-rich mixture. Hydroisomerization can be carried out in a fixed-bed reactor as well as in a catalytic distillation reaction system. For example, in some embodiments, a feed containing 1-butene, 2-butene, isobutene, n-butane, and isobutane can be fed into a catalytic distillation reaction system containing at least one hydroisomerization catalyst bed for the simultaneous hydroisomerization of 1-butene to 2-butene and the fractionation of isobutane and isobutene recovered as overhead fractions from heavier hydrocarbons (including n-butane and 2-butene) in the feed stream recovered as bottom fractions. The feed and catalyst positions can be positioned to preferentially contact 1-butene with the hydroisomerization catalyst. For example, hydrocarbons can be fed below the hydroisomerization catalyst, allowing 1-butene to distill upwards into the catalyst bed while 2-butene distills downwards away from the catalyst bed. In other embodiments, the hydroisomerization effluent from a fixed-bed reactor can be fed into a conventional distillation column to produce similar overhead and bottom fractions.

[0028] The resulting bottoms fraction (comprising 2-butene and n-butane) may be depleted of 1-butene, isobutane, and isobutene. For example, depending on the severity of the distillation conditions used, the bottoms fraction may contain less than 1% by weight of 1-butene, isobutane, and isobutene in total; less than 0.5% by weight in other embodiments; less than 0.1% by weight in other embodiments; and less than 500 ppm of 1-butene, isobutane, and isobutene in yet another embodiment.

[0029] The overhead fraction (including isobutene and isobutane) may also contain some unreacted 1-butene. In some embodiments, the overhead fraction may contain less than 1000 ppm of 1-butene; in other embodiments less than 500 ppm; in other embodiments less than 250 ppm; in other embodiments less than 100 ppm; and in yet another embodiment less than 50 ppm of 1-butene.

[0030] According to the implementation scheme described herein, the top fraction can then be reacted to form the desired dimerization and / or oligomerization products, such as C8 to C16 hydrocarbons.

[0031] Regardless of whether the feed is pretreated to produce the desired olefin fraction, such as purified isobutylene, the methods disclosed herein can include any number of reactors, including catalytic distillation reactor systems (both upflow and downflow). The use of catalytic distillation reactor systems prevents the accumulation of fouling and heavy catalyst poisons from the feed in one or more reaction zones. Additionally, clean reflux continuously washes the catalytic distillation structure within the reaction zones. These factors combined provide a long catalyst lifetime. The heat of the reaction causes the liquid to evaporate, and the resulting vapor is condensed in an overhead condenser to provide additional reflux.

[0032] Other reactors that can be used in the embodiments disclosed herein may include conventional fixed-bed reactors, boiling point reactors, and pulsed-flow reactors, wherein the reactant streams and product streams can be co-current or counter-current. In addition to capturing at least a portion of the heat of reaction through evaporation, boiling point reactors and pulsed-flow reactors can also provide continuous washing of the catalyst, thereby allowing for improved reactor temperature distribution compared to conventional fixed-bed reactors. Reactors that can be used in the embodiments disclosed herein can be used as standalone reactors or in combination with one or more reactors of the same or different types.

[0033] Any type of reactor can be used to carry out the reactions described herein. Examples of reactors suitable for carrying out reactions involving olefins and / or isoolefins according to embodiments herein may include distillation column reactors, wall-separated distillation column reactors, conventional tubular fixed-bed reactors, bubble-cap column reactors, slurry reactors with or without distillation columns, pulsed-flow reactors, catalytic distillation columns in which a slurry solid catalyst flows downward along the column, or any combination of these reactors. Multi-reactor systems that can be used in the embodiments disclosed herein may include multiple reactors in series and / or multiple reactors in parallel. Those skilled in the art will recognize that other types of reactors may also be used.

[0034] Reactors that can be used in the embodiments disclosed herein may include any physical device or a combination of two or more devices, including reactors and reactor systems as described above. One or more reactors may have multiple internal devices for gas-liquid separation and gas / liquid transport. The reaction zone within one or more reactors may include a “wettable” structure and / or packing. Wettable structures and packings that can be used in the embodiments disclosed herein may include a variety of distillation structures and packing materials, which may be catalytic or non-catalytic. Suitable wettable structures and packings may include, for example, random or haphazard distillation packings, which are: catalytically inert haphazard packings containing high porosity and maintaining a relatively large surface area, such as Bell saddles (ceramic), Raschig rings (ceramic), Raschig rings (steel), Pall rings (metal), Pall rings (plastic, e.g., polypropylene), etc. A suitable wettable structure is also a monolithic structure containing multiple independent vertical channels and constructed from various materials (such as plastics, ceramics, or metals) (where the channels are typically square). Other geometries may also be used.

[0035] Other materials that promote the distribution of liquids and vapors can also be used, including demisters, defrosters, or other linear or multifilament structures. Such multifilament structures can include one or more of glass fiber, steel, Teflon, polypropylene, polyethylene, polyvinylidene fluoride (PVDF), polyester, or other various materials, and can be braided (or co-braided, where more than one type of filament or thread structure is used), woven, non-woven, or any other type of multifilament structure. Structures including multifilament threads, structures comprising woven glass fiber cloth elements, and high-surface-area stainless steel structured packings, as typically used in demister services, are preferred.

[0036] The reactor system according to the embodiments disclosed herein may include one or more reaction zones. In some embodiments, one or more fixed-bed reactors may be used for the initial conversion of olefins and / or isoolefins, which may be followed by a catalytic distillation column to supplement the conversion and separate heavier reaction products from unreacted feed components.

[0037] The main oligomer products are dimers and trimers of olefins and / or isoolefins. For example, isobutylene can oligomerize to form C8 or C6 compounds. 12 Tertiary olefins. In some embodiments, the C4 oligomer has 8 to 16 carbon atoms and corresponds to an oligomer prepared from a C4 olefin. The reactions described herein can be configured to increase selectivity toward the C8 dimer. Similarly, when using a C5 starting material, the oligomer product can be a C10, C15, or C20 olefin, and when using a mixed starting material, the codimer and cotrimer can, for example, be in the range of C9 to C19.

[0038] Oxygen-containing modifiers can be used to influence the selectivity of oligomerization reactions for dimer products. Oxygen-containing modifiers that can be used in the embodiments disclosed herein may include water, as well as tertiary alcohols and ethers. For example, oxygen-containing modifiers may include at least one of the following: water, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, tert-butanol, methyl tert-butyl ether, and ethyl tert-butyl ether. Mixtures of alcohols or mixtures of one or more alcohols and water may also be used. In some embodiments, the weight ratio of the mixed C4 to the oxygen-containing compound may be from 5:1 to 2:1.

[0039] Oligopolymerization reactions in the presence of oxygen-containing moderating agents can simultaneously produce oligomers (such as dimers and trimers of isoolefins or n-olefins) and various oxygen-containing byproducts resulting from the reaction of the moderating agent with olefins, isoolefins, or isoolefin oligomers such as dimers or trimers. For example, oxygen-containing oligopolymerization byproducts may include C5-C... 16 Ethers and C5-C 12 Alcohols. In some embodiments, C4 olefins can react with a moderating agent to form secondary ethers, such as methyl tert-butyl ether or methyl sec-butyl ether, which may be undesirable.

[0040] Oligopolymerization of olefins and isoolefins can be carried out in a partially liquid phase in the presence of an acidic cationic resin catalyst in a straight-through reaction or in a catalytic distillation reaction in which both gas and liquid phases are present, as well as in a simultaneous reaction / distillation reaction. The catalyst used in the oligomerization reactor according to the embodiments described herein may include acidic resins such as AMBERLYST 15 (available from DuPont) or related fuming sulfuric acid-derived resins, and may include phosphoric acid-derived catalysts, such as those industrially known as SPA (solid phosphoric acid) catalysts. Sulfonic acid catalysts, such as macroporous strongly acidic cationic sulfonic acid catalysts based on polystyrene divinylbenzene sulfonate, and other catalysts may also be used.

[0041] In some embodiments, the resin catalyst can be tuned to have low reactivity with oxygen-containing moderators. For example, appropriate crosslinking and acid functionality of the acidic resin catalyst can provide reduced reactivity with oxygen-containing moderators, thereby providing reduced downstream purification needs for oxygen-containing byproducts that may be generated by catalysts with higher oxygen-containing reactivity. In existing C4 dimerization schemes, the fixed-bed reaction is carried out in stages to increase selectivity toward the C8 dimer, including intermediate separation between reactors to minimize the reaction of the C8 dimer to form trimers in subsequent reactors. The inventors have discovered that, by appropriate dimerization reaction conditions and the appropriate use of selectors or moderators in each reactor, the need for intermediate separators such as butanizers can be minimized or eliminated while still achieving high-olefin and / or isoolefin conversion. Therefore, in some embodiments, the effluent from the first reactor can be fed directly to the second reactor without intermediate component separation.

[0042] Following the reaction in an upstream reactor, such as a fixed-bed reactor, the effluent from the last reactor can be fed into a catalytic distillation column reactor to separate the reaction products, while simultaneously targeting the further conversion of isobutylene or other C4 to C5 olefins. In some embodiments, the catalytic distillation column reactor can be used to target the complete conversion of light olefins and isoolefins. The embodiments described herein envision continuing dimerization in the catalytic distillation column reactor.

[0043] The resulting dimer can, for example, be used as a feedstock for the production of various chemicals such as herbicides and pesticides. In other embodiments, the dimer can be fed into an alkylation system, where it can dissociate into olefins and react with alkanes to produce alkylates within the gasoline boiling range. The dimer can also be hydrogenated to form gasoline-range hydrocarbons such as isooctane, isononane, and other hydrocarbons. In yet another embodiment, a stream containing the dimer can be used as a gasoline-range hydrocarbon blending feedstock without hydrogenation or alkylation.

[0044] The operating conditions within a catalytic distillation reactor system for dimerizing isoolefins, as described above, can include temperatures and pressures sufficient to a) recover unreacted C4 and / or C5 hydrocarbons, water, and other light components as overhead vapor fractions, b) achieve the desired reactivity of the isoolefins on the catalyst, and c) recover the dimer as a bottom liquid fraction. Therefore, the temperature within the reaction zone can be closely correlated with the pressure, the combination of which provides boiling for olefins and / or isoolefins and water within one or more reaction zones. Higher temperatures may be required for the C5 feedstock (compared to the C4 feedstock) and in the section of the column below the reaction zone, thereby providing separation of the dimer from the unreacted feed compounds.

[0045] The temperature in a column is determined by the boiling point of the liquid mixture present at any given pressure. The temperature in the lower part of the column will reflect the composition of the material in that section, and this temperature will be higher than the temperature of the overhead product; that is, at constant pressure, a change in temperature indicates a change in the composition within the column. To change the temperature, the pressure within the column can be changed. Therefore, temperature control in the reaction zone is achieved by increasing the heat (the reaction is exothermic) (which only causes more boiling). By increasing the pressure, the temperature will rise, and vice versa. Even when using a distillation column reactor, some of the olefins and / or isoolefins may remain unconverted and may leave the column with the overhead distillate.

[0046] Dimers, oligomers, and any ether byproducts (depending on the alcohol used) (the highest boiling point substances) are removed from the distillation column reactor as bottom fractions. Top fractions may contain modifiers, unreacted olefins and / or isoolefins, and any light, inert components in the feed such as butane and pentane.

[0047] Now for reference Figure 1 A simplified process flow diagram of a system for oligomerization (dimerization) of olefins and / or isoolefins according to embodiments disclosed herein is shown. Although the following description is for mixed C4 feeds, the system can be similarly used to process mixed C4 / C5 feeds or mixed C5 feeds.

[0048] Hydrocarbon feed, such as raffinate from a butadiene separation process (RAFF-1), containing isoolefins such as isobutene and one or more of isobutane, 1-butene, butadiene, n-butane, and 2-butene, can be fed into reactor 10 via flow line 101, such as a fixed-bed reaction system containing a catalyst suitable for oligomerization. In some embodiments, the butadiene in the feed can be limited to less than 3000 ppm via an upstream process such as hydrogenation. Reaction modifiers, such as one or more alcohols, can also be fed into reactor 10 via flow line 400. Optionally and / or additionally, additional modifiers can be fed into reactor 10 via flow line 304; such additional modifiers can be derived from downstream or upstream alcohol recovery systems, such as, for example... Figure 3 As shown in the image.

[0049] In reactor 10, isobutylene reacts in the presence of a catalyst contained in the reaction zone to convert a portion of the isobutylene and n-olefins into oligomers (including isobutylene dimers). The effluent 105 from reactor 10 can then be combined with additional reaction modifiers (e.g., oxygen-containing compounds) and fed into reactor 20, which also contains a catalyst suitable for the oligomerization reaction. In reactor 20, isobutylene reacts in the presence of a catalyst contained in the reaction zone to convert a portion of the isobutylene into additional oligomers (including isobutylene dimers) besides those produced in reactor 10. In some embodiments, feeding effluent 105 into reactor 20 can be done without an intermediate separator step.

[0050] The effluent 204 from reactor 20 can then be fed into catalytic distillation column 30. If desired or necessary, additional modifier 301 can be fed directly into catalytic distillation column 30. The feed from the effluent of reactor 30 can be introduced into a catalytic distillation column below the reaction zone containing a catalyst suitable for oligomerization. Heavier reaction products can be distilled downwards, while isobutylene and lighter components distill upwards into the reaction zone, where isobutylene and / or other olefins react in the presence of a catalyst contained in the reaction zone to convert a portion of the isobutylene into oligomers (including isobutylene dimers).

[0051] The overhead distillate 306 from the catalytic distillation reactor 30 may include unreacted C4 molecules (such as n-butane, 2-butene, 1-butene, and isobutene) and unreacted alcohols such as methanol, and is sent to one or more downstream processes, such as alcohol extraction and recovery, alkylation, isomerization, or metathesis processes.

[0052] As a side reaction, the moderating agent may react with a portion of at least one of the isoolefins and any 1-butene present in the reaction zone to form oxygen-containing oligomerizing byproducts, such as methyl sec-butyl ether. Simultaneously with the oligomerization reaction, the oligomers, including dimers and trimers, as well as the heavy reaction byproducts, are distilled downwards and can be recovered as a bottom fraction via flow line 206, while isobutane and any unreacted alcohols, isobutenes, and 1-butenes (if present and unreacted) can be distilled upwards and recovered via top flow line 306.

[0053] The bottom distillate 206 of the catalytic distillation column may include dimers and trimers produced via reactions in reactors 10, 20, and 30, and can be used as feedstock for multiple downstream processes. For example, the resulting dimer fraction can be used as feedstock for the production of a variety of chemicals, such as herbicides and pesticides. In other embodiments, the dimer may be fed into an alkylation system, where it can dissociate into olefins and react with alkanes to produce alkylates within the gasoline boiling range. The dimer may also be hydrogenated to form gasoline-range hydrocarbons, such as octane, nonane, and other hydrocarbons. In yet another embodiment, the dimer-containing stream can be used as a gasoline-range hydrocarbon blending feedstock without hydrogenation or alkylation.

[0054] Optionally, if desired, the bottom distillate 206 can then be further separated, such as in one or more distillation columns, such as fractionation columns 40 and 50, as... Figure 1 As shown. The bottom distillate 206 of the catalytic distillation column (which includes dimers and trimers as well as oxygenated compounds with higher boiling points) can be sent to the first fractionation column 40. The overhead product stream 401, which may include any unreacted feed components (such as C4 or C5 olefins and isoolefins), as well as inert components (such as butane or isobutane), and light oxygenated compounds (such as methanol) and any lighter ethers formed therefrom (such as MTBE and MSBE), can be recycled to reactors 10 and / or 20 as an oxygenated compound modifier 400. A portion of the overhead product stream 401 can also be removed via flow line 402 or used as a fuel blend.

[0055] The bottom product stream 402 from column 40 (which may contain isobutylene dimers and trimers) can be fed directly as export-grade product as a fuel blend, fed into downstream hydrogenation processes, or further fractionated (e.g., in column 50). Column 50 can separate the bottom product 402 into an overhead dimer (isooctene) stream 501 and a C12+ fraction 504 (which includes trimers of olefins and / or isoolefins and higher oligomers).

[0056] Figure 1 A separation system comprising two distillation columns is shown, producing a dimer as the column top product 501. In other embodiments, such as Figure 2 As shown, a single partition wall distillation column 60 can be used to separate the bottom product stream 206 of the catalytic distillation column 30 into the top product stream 401, the dimer stream 501, and the heavy distillate stream 504.

[0057] Figure 3 It shows a kind of Figure 2 The system includes an alcohol recovery system 80, which can be used to separate the overhead product 306 from the distillation column reactor into a recycle alcohol stream 304 and a hydrocarbon fraction 802 including unreacted C4-C5 olefins, unreacted C4-C5 isoolefins and inert components.

[0058] As mentioned above, the dimerization and oligomerization reactions are exothermic. If necessary, an interstage cooler can be provided to control or moderate the temperature of the effluent fed from reactor 10 to reactor 20.

[0059] Although Figure 1-3 The system is illustrated as comprising two fixed-bed reactors, but more or fewer reactors may be used. In such embodiments, the feeding of oxygen-containing compounds and / or alcohols can be carried out in stages to achieve the desired selectivity in dimerization and / or etherification reactions.

[0060] As described above, the embodiments described herein can utilize acidic catalysts with extremely high selectivity for oligomers. The conversion of lower oxygen-containing compound modifiers into heavier oxygen-containing compound byproducts can provide advantageous processing. For example, having few or no heavy oxygen-containing compounds (such as MTBE, MSBE) and even heavier oxygen-containing compound byproducts can allow the dimer and oligomer products to be used directly in the separation section (whether it is in a partition wall column or multiple distillation columns) after recovery without further component separation.

[0061] In some implementations, methanol can be used, for example, as an oxygen-containing compound regulator. When used, methanol can react to form, for example, MTBE and MSBE, and the corresponding amylene ethers. Methanol can be recovered from the overhead distillate of the catalytic distillation reactor, and the overhead distillate can be fed to an alcohol recovery zone. Since water can be used to separate and recover methanol, the methanol recycled to the reactor may contain some water.

[0062] In some embodiments, the oxygen-containing reaction moderator may be or may include tert-butanol. In some embodiments, as described above, recycled methanol may contain water, which can react with, for example, isobutylene to form tert-butanol. Tert-butanol has been found to form azeotropes with C8 olefins and can therefore be recovered along with the dimer product stream. The use of C5 olefins in the feed has been found to help break down the azeotropes and can allow the use of side-take distillates (such as...) Figure 2 and 3 (As shown) to more cleanly recover dimer products.

[0063] In embodiments with highly selective / low oxygen-containing reactive catalysts, it has been found that tert-butanol may have little or no reactivity with olefins and isoolefins. In such embodiments, the alcohol recovery section can be omitted from the process because the oxygen-containing compounds recovered from the overhead distillate of the isolation wall column can be recycled back to the reactor to continue to be used as a reaction moderator.

[0064] Ethanol, when used, can be recovered from the overhead and bottom distillates of a catalytic distillation column. Therefore, an alcohol recovery section is likely desirable when using ethanol.

[0065] It has also been found that propanol and isopropanol have little or no reactivity relative to highly selective / low-oxygen-content reactive catalysts. In such embodiments, C3 alcohols can be recovered in the bottom distillate of the catalytic distillation reactor and then in the top distillate of the first distillation column or in the top distillate of the partition wall distillation column. In such embodiments, the alcohol can be recovered in the top distillate of the partition wall distillation column and can be recycled back to the reactor for continued use as a reaction moderator.

[0066] When using heavier moderating agents (e.g., propanol, isopropanol, tert-butanol), the overhead distillate from a catalytic distillation column may consist only of unreacted light hydrocarbon feed components. Recovery of the oxygen-free C4 stream allows the catalytic distillation column overhead stream to be recycled for downstream processes (with little or no additional treatment before use), such as in the alkylation zone to convert isobutane to octane, and other readily conceivable downstream uses.

[0067] As described above, in some embodiments, the catalyst used in the oligomerization reaction zone can be selected to have low oxygen-containing compound reactivity, thereby producing fewer oxygen-containing compound byproducts. Optionally or additionally, the oxygen-containing compound moderator used can have low reactivity relative to the selected catalyst. Advantageously, the systems and methods described herein can advantageously use C3 and heavier alcohols as reaction moderators, thereby minimizing or eliminating the need for alcohol separation of the overhead distillate stream from the catalytic distillation column.

[0068] As described above, C4 olefins, consisting of isobutene, 1-butene, and 2-butene, derived from a hydrocarbon feedstock, are mixed with a portion of C1 to C4 alcohols and / or water. Any C1 to C4 alcohol and water, or a combination of alcohol and water, can be used for the controlled oligomerization process. The mixed C4 and alcohol mixture is then fed to a fixed-bed reactor containing an oligomerizing acidic catalyst, where a controlled oligomerization reaction occurs to form C8, C12, and C16 olefins. To moderate the reaction and improve the selectivity for C8 olefin formation, the C1 to C4 alcohols and / or water act as moderating or selecting agents. Depending on the C4 olefin conversion, one or two reactors are operated in series to improve the overall butene conversion. The effluent from the oligomerization reactor is fed to a catalytic distillation column containing an oligomerizing catalyst. Depending on the type of alcohol, alcohol recovery can be carried out in the overhead or bottom product of the catalytic distillation column. The bottoms from the catalytic distillation are then fed to a fractionation step consisting of a partitioned-wall column to separate the alcohols, oxygenated compounds, and water from the C8, C12, and C16 olefins. Depending on the amount of C12 and C16 olefins produced, the partitioned wall in the column may be off-center or in the center. The tops from the partitioned-wall column, consisting primarily of the recovered alcohols and some oxygenated compounds, are then returned to the reactor and catalytic distillation to control the oligomerization reaction. A side-dip fraction of high-purity C8 olefins is taken from the right side of the partitioned-wall column; for example, in some embodiments, the side-dip fraction may contain more than 90% by weight of C8 olefins, in other embodiments more than 95% by weight of C8 olefins, and in still other embodiments more than 98% by weight of C8 olefins. While the above description primarily pertains to the C4 fraction, methods using C5 or mixed C4 / C5 feeds can also be operated to produce side-dip fractions with similar dimer purity. Depending on the type of alcohol, if it is relatively light, it can be fractionated from the overheads of the catalytic distillation column and recovered by countercurrent washing with water followed by further fractionation to separate the alcohol. The recovered alcohol from the fractionation step is then recycled to the reactor and the catalytic distillation column. Make-up alcohol is fed as needed.

[0069] One advantage over existing technologies is the minimal production of ethers (such as MTBE, MSBE, ETBE, and ESBE), which allows for greater flexibility in terms of oxygen-containing compound requirements. Suitable alcohols can be tailored to the process based on equipment requirements. Furthermore, using a partition wall distillation column in the subsequent heavy distillate fractionation step can reduce the number of units and required space compared to conventional column sequences.

[0070] While this disclosure includes a limited number of embodiments, those skilled in the art who benefit from it will understand that other embodiments can be conceived without departing from the scope of this disclosure. Therefore, the scope should be limited only by the appended claims.

Claims

1. A method for the dimerization of olefins and / or isoolefins, the method comprising: An oxygen-containing reaction regulator and a mixed hydrocarbon feed are fed into a fixed-bed reactor containing an oligomer catalyst, wherein the mixed hydrocarbon feed comprises isobutene and optionally one or more of isobutane, n-butane, 1-butene, and 2-butene. Isobutylene is reacted in the fixed-bed reactor under oligomerization conditions to form a reaction effluent comprising a reaction regulator, isobutylene dimer, unreacted isobutylene, any oxygen-containing high-boiling reaction byproducts formed, and any unreacted isobutane, n-butane, 1-butene, and 2-butene. Without component separation, the reaction effluent is fed into a second fixed-bed reactor containing an oligomerizing catalyst; The unreacted isobutylene is reacted in the second fixed-bed reactor under oligomerization conditions to form additional isobutylene dimers, and a second reaction effluent is recovered, the second reaction effluent comprising a reaction regulator, isobutylene dimers, any oxygen-containing high-boiling-point reaction byproducts formed, and any unreacted isobutane, n-butane, 1-butene, and 2-butene. Without component separation, the second reaction effluent is fed into a catalytic distillation reactor having a reactive distillation zone containing an oligomer catalyst; Simultaneously within the catalytic distillation reactor: The unreacted isobutylene in the second reaction effluent is reacted to form additional isobutylene dimers; The dimer and any oxygen-containing high-boiling-point reaction byproducts recovered as bottom fractions are separated from the isobutane, n-butane, and any unreacted isobutene, 1-butene, and 2-butene recovered as top fractions. The bottom fraction further comprises a reaction regulator and isobutylene trimer, and the method further comprises separating the bottom fraction in a partition wall distillation column to recover the top fraction, the side fraction containing the isobutylene dimer, and the bottom fraction containing the isobutylene trimer.

2. The method of claim 1, wherein the oligomerizing catalyst contained in each of the fixed-bed reactor, the second fixed-bed reactor, and the reactive distillation zone comprises a sulfonic acid catalyst.

3. The method according to claim 1, wherein the oxygen-containing compound reaction modifier is selected from the group consisting of methanol, ethanol, propanol, isopropanol, and combinations thereof.

4. The method of claim 1, wherein the side fraction comprises more than 95% by weight of isobutylene dimer.

5. The method of claim 1, wherein one or both of the bottom fraction from the isolation wall distillation column and the top fraction from the isolation wall distillation column contain oxygen-containing byproducts or contain a reaction regulator, the method further comprising: The reaction regulator or oxygen-containing byproduct is recovered from one or both of the bottom fraction from the isolation wall distillation column and the top fraction from the isolation wall distillation column. and The recovered regulator or oxygen-containing byproduct is recycled to one or more of the fixed-bed reactor, the second fixed-bed reactor, and the catalytic distillation reactor.

6. The method according to claim 1, further comprising: A mixture of C4 hydrocarbons, including isobutene, 1-butene, 2-butene, isobutane, and n-butane, is fed into a hydroisomerization reactor. The 1-butene in the C4 hydrocarbon mixture is hydroisomerized to form additional 2-butene; The C4 hydrocarbon mixture is fractionated to obtain a top fraction containing isobutene and isobutane and a bottom fraction containing 2-butene and n-butane. and The bottom fraction containing 2-butene and n-butane is fed into the fixed-bed reactor as the mixed hydrocarbon feed.

7. A method for the dimerization of olefins and / or isoolefins, the method comprising: An oxygen-containing reaction regulator and a mixed hydrocarbon feed are fed into a fixed-bed reactor containing an oligomer catalyst. The mixed hydrocarbon feed comprises C4 hydrocarbons, C5 hydrocarbons, or a mixture of C4 and C5 hydrocarbons, each of which includes an isoolefin, a n-olefin, an isoalkanes, and a n-alkanes. Isoolefins are reacted in the fixed-bed reactor under oligomerization conditions to form a reaction effluent comprising a reaction regulator, isoolefin dimers, unreacted isoolefins, any oxygen-containing high-boiling reaction byproducts formed, and any unreacted isoalkanes, n-alkanes, and n-olefins. Without component separation, the reaction effluent is fed into a second fixed-bed reactor containing an oligomerizing catalyst; The unreacted isoolefins are reacted in the second fixed-bed reactor under oligomerization conditions to form additional isoolefin dimers, and a second reaction effluent is recovered, the second reaction effluent comprising a reaction regulator, isoolefin dimers, any oxygen-containing high-boiling-point reaction byproducts formed, and any unreacted isoalkanes, n-alkanes, and n-olefins. Without component separation, the second reaction effluent is fed into a catalytic distillation reactor having a reactive distillation zone containing an oligomer catalyst; Simultaneously within the catalytic distillation reactor: The unreacted isoolefins in the second reaction effluent are reacted to form additional isoolefin dimers; The dimer and any oxygen-containing high-boiling-point reaction byproducts recovered as bottom fractions are separated from the isoalkanes, n-alkanes, and any unreacted isoolefins and n-olefins recovered as top fractions. The bottom fraction further comprises a reaction regulator and an isoolefin trimer, and the method further comprises separating the bottom fraction in a partition wall distillation column to recover the top fraction, the side fraction containing the isoolefin dimer, and the bottom fraction containing the isoolefin trimer.

8. The method of claim 7, wherein the oligomerization catalyst included in each of the fixed-bed reactor, the second fixed-bed reactor, and the reactive distillation zone comprises a sulfonic acid catalyst.

9. The method according to claim 7, wherein the oxygen-containing compound reaction modifier is selected from the group consisting of methanol, ethanol, propanol, isopropanol, and combinations thereof.

10. The method of claim 7, wherein the side fraction comprises more than 95% by weight of an isoolefin dimer.

11. The method of claim 7, wherein one or both of the bottom fraction from the isolation wall distillation column and the top fraction from the isolation wall distillation column contain oxygen-containing byproducts or contain a reaction regulator, the method further comprising: The reaction regulator or oxygen-containing byproduct is recovered from one or both of the bottom fraction from the isolation wall distillation column and the top fraction from the isolation wall distillation column. and The recovered regulator or oxygen-containing byproduct is recycled to one or more of the fixed-bed reactor, the second fixed-bed reactor, and the catalytic distillation reactor.

12. A system for the selective dimerization of olefins and / or isoolefins, said system comprising: A feed line for conveying oxygenated compound reaction regulators from an oxygenated compound reaction regulator supply system; A feed line for conveying a mixed hydrocarbon feed from a mixed hydrocarbon supply system, the mixed hydrocarbon feed comprising C4 hydrocarbons, C5 hydrocarbons, or a mixture of C4 and C5 hydrocarbons, each of the mixed hydrocarbons comprising isoolefins, n-olefins, isoalkanes, and n-alkanes; A fixed-bed reactor containing an oligomerization catalyst, the fixed-bed reactor being configured to receive the mixed hydrocarbon feed and the oxygen-containing compound reaction modifier and to react isoolefins in the fixed-bed reactor under oligomerization conditions to form a reaction effluent, the reaction effluent comprising the reaction modifier, isoolefin dimers, unreacted isoolefins, any high-boiling-point reaction byproducts of the formed oxygen-containing compounds, and any unreacted isoalkanes, n-alkanes, and n-olefins; A flow line is used to provide the reaction effluent from the fixed-bed reactor to a second fixed-bed reactor without intermediate component separation. The second fixed-bed reactor contains an oligomerization catalyst and is configured to react the unreacted isoolefins under oligomerization conditions in the second fixed-bed reactor to form additional isoolefin dimers, and to recover a second reaction effluent comprising a reaction regulator, isoolefin dimers, any oxygen-containing high-boiling-point reaction byproducts formed, and any unreacted isoalkanes, n-alkanes, and n-olefins. A flow line for conveying the second reaction effluent from the second fixed-bed reactor to a catalytic distillation reactor without component separation, the catalytic distillation reactor having a reactive distillation zone containing an oligomer catalyst and configured to: The unreacted isoolefins in the second reaction effluent are reacted to form additional isoolefin dimers; The dimer and any oxygen-containing high-boiling-point reaction byproducts recovered as bottom fractions are separated from the isoalkanes, n-alkanes, and any unreacted isoolefins and n-olefins recovered as top fractions. The bottom fraction further comprises a reaction regulator and an isoolefin trimer. The system also includes a partition wall distillation column for separating the bottom fraction and recovering the top fraction, the side fraction containing the isoolefin dimer, and the bottom fraction containing the isoolefin trimer.

13. The system of claim 12, wherein the oligomer catalyst included in each of the fixed-bed reactor, the second fixed-bed reactor, and the reactive distillation zone comprises a sulfonic acid catalyst.

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