Olefin trimerization

Abstract

This disclosure relates to a process and a production unit used to catalytically manufacture olefin trimers from olefin monomers, and wherein the olefin dimers are recycled after the dimerization reaction and reacted with olefin monomers in an addition reaction.

Description

Olefin trimerization TECHNICAL FIELD This disclosure relates to the processing of olefins, in particular to the production of olefin trimers from olefin monomers with high selectivity. BACKGROUND Current methods for polymerizing olefins typically produce a mixture of olefin polymers with poor selectivity for any particular polymer. Producing a desired polymer species from such mixtures requires complex separation techniques. Therefore, it would be beneficial to find a process that yields a desired olefin polymer with high selectivity, rather than a mixture of polymers, and in which olefin monomers are efficiently converted into the desired polymers. US4544791 describes a two-reactor process that produces 75% dimers and 15% trimers from C4 monomers. Document WO2007 / 091862 describes a method for preparing olefin trimers. Isododecenes are isobutene trimers that can be produced by an isobutene oligomerization reaction. These trimers have previously been produced in small quantities as unwanted byproducts in the isooctene process, but in isooctene production, their quantity is typically suppressed by the use of an oxygen-containing moderator. However, because olefin trimers can be considered an interesting product in their own right, the challenge arises of how to direct the selectivity of isobutene predominantly toward trimers without generating and separating isooctenes (dimers) or heavier oligomers (tetramers and higher polymers). Acid-catalyzed oligomerization of isobutene generally yields a broad distribution of oligomers as isobutene conversion increases. Therefore, previous procedures have not been efficient in producing isobutene trimers, i.e., isododecenes. This disclosure relates to a procedure that achieves high olefin conversion while simultaneously producing a rich trimer product with a selectivity exceeding 90%. Therefore, one objective of this disclosure is to provide products, processes, and systems to alleviate the disadvantages discussed above. In particular, this disclosure aims to provide a process and a production unit that can be used to manufacture olefin trimers from olefin monomers with high selectivity. SUMMARY The scope of protection sought for various embodiments of the invention is set out in the attached claims. This document describes a process for manufacturing olefin trimers, comprising: feeding a reactor containing a dimerization catalyst feed: olefin monomer and at least one oxygen-containing moderator; to operate the reactor at a selected temperature in the range of 40-140 °C and a selected pressure in the range of 10-40 bar to carry out catalytic dimerization reactions between olefin monomers and olefin dimers, and addition reactions between olefin monomers and olefin dimers; to remove an outlet stream from the reactor; and distilling the reactor outlet stream to separate at least one lighter product comprising olefin dimers and one heavier bottom product comprising olefin trimers; wherein At least a portion of the lighter product is recycled to the reactor to provide a recycle feed; the olefin monomers are fed to the reactor predominantly as a fresh olefin monomer feed. The amount of fresh olefin monomer feed and recycle feed fed to the reactor are controlled so that the mass ratio of olefin monomers to olefin dimers entering the reactor is selected in the range 1:8-1:15. and where the catalytic reactions are carried out under operating conditions where the olefins remain in the liquid phase. One advantage of the present process is the selectivity of the polymerization reactions (dimerization and addition reactions) for olefin trimers. Another advantage is that the present process allows for the manufacture of olefin trimers even in a single reactor system, thus simplifying the production procedure. Because the dimers produced in the reactor can be recycled back to the reactor after distillation along with other lighter components, no additional separation technique is required to remove lighter components such as dimers from the olefin trimer product. Therefore, the present process achieves simultaneous recovery of olefin trimers and recycling of reactive species. Alternatively, a plurality of reactor vessels can be used instead of a single reactor unit, allowing for even greater control to optimize the selectivity of the procedure for trimer production. The use of a plurality of reactor vessels is also compatible with the single-step distillation described above. Furthermore, the procedure is flexible, allowing for the recovery of olefin dimers and olefin trimers as separate product streams. It is also possible to implement the present invention with two distillation columns, as will be described later. This document also describes a production unit, which is suitable and configured to carry out the above procedure, comprising: a. at least one reactor unit configured to receive an acid catalyst; b. at least one distillation column configured to separate isooctene from isododecene; c. at least one reactor feed conduit in fluid connection with the reactor unit or reactor units, and at least one olefin monomer tank; d. at least one reactor outlet stream conduit in fluid connection with the reactor unit or units, and the distillation column; e. at least one recycle conduit in fluid connection with the distillation column and the reactor unit or units; and f. a bottom product conduit in fluid connection with the distillation column and a bottom product tank. BRIEF DESCRIPTION OF THE FIGURES The invention will be described in greater detail by means of non-limiting preferred embodiments with reference to the accompanying figures. Figure 1 shows the composition of a bottoms product obtained using the present procedure with recycled olefin dimers. Nearly 90% conversion of monomers to trimers was achieved. Figure 2 shows the composition of a comparative background product obtained when using a "single-use" experimental design, i.e., without recycling olefin dimers. Figure 3 shows an embodiment of production unit 100. Figure 4 shows another embodiment of production unit 100. DETAILED DESCRIPTION The expression oxygen-containing moderator refers to a compound that contains oxygen, such as an oxygenated compound or a compound containing oxygen, carbon, and hydrogen. As used herein, the expression "comprising" includes the broader meanings of "including", "containing" and "comprising", as well as the more restricted expressions "consisting of" and "consisting only of". In one embodiment, the procedure is carried out on an industrial scale, and preferably as a continuous process. In one embodiment, the steps of the process are carried out in the sequence identified in any aspect, embodiment, or claim. In another embodiment, any step of the process specified to be carried out with a product or intermediate compound obtained in a step of the preceding process is carried out directly with the product or intermediate compound, i.e., without additional, optional, or auxiliary processing steps that could chemically or physically alter the product or intermediate compound between such two consecutive steps. In the context of the present invention, the term "reactor feed" refers to any feed entering the reactor. For simplicity, when at least one component, such as an olefin monomer, is fed to the reactor through multiple feeds, "olefin monomer reactor feed" or "olefin monomer reactor feed" may, in such cases, mean the total feed of said olefin monomers into the reactor. The terms "fresh olefin monomer feed" and "fresh olefin monomer" refer to olefin monomers that are newly added, i.e., not recycled, and are fed into the reactor to provide a source of olefin monomers to supplement the amount consumed during catalytic reactions within the reactor. These monomers are removed from the reactor primarily as a recovered or consumed dimer or trimer product. The fresh olefin monomers are fed in sufficient quantity to maintain the mass ratio of monomers to dimers at a desired level. Therefore, when olefin trimer production is carried out as a continuous process, fresh monomers that have not previously entered the reactor are fed through the reactor feed line, and the olefin trimers are removed from the process as a reaction product. In one embodiment, the olefin monomers are fed to the reactor predominantly as a fresh olefin feed, i.e., fresh olefin monomers constitute more than 50% by weight of the total olefin monomers entering the reactor. In another embodiment, at least 55% by weight, 60% by weight, 70% by weight, 80% by weight, or 90% by weight of the olefin monomers entering the reactor are fresh. In one embodiment, the recycling feed comprises unreacted olefin monomers. The term reactor refers to a reactor, such as at least one reactor unit or at least one reactor vessel, in which catalytic reactions take place. The reactor may comprise at least one catalyst bed and openings for introducing fluids into the reactor and removing fluids from the reactor. An olefin is a compound consisting of at least hydrogen and carbon, and having at least one double bond between two carbon atoms. Olefins suitable for the present process contain two or more carbon atoms and may be linear or branched. A preferred olefin monomer in the present invention is isobutene. A mixture of olefins can also be used in the present process and fed to the reactor, such as a mixture of olefin monomers, olefin dimers, and heavier polymers, or a mixture containing olefins with a variable number of carbon atoms and double bonds. In one embodiment, a feed comprising a mixture of olefins is fed to the reactor as a mixed feed. In the context of the present invention, a mixed feed or a mixed monomer feed means olefins having different numbers of carbon atoms, or a mixture of olefin isomers having the same number of carbon atoms, as well as combinations thereof. In one embodiment, the mixed feed comprises C4-C5 olefins. In another embodiment, the mixed feed comprises olefins having C4 carbon atoms + / - 1. In one embodiment, reactive components that are lighter than C4 olefins are removed from the feed entering the reactor to facilitate the distillation of the reaction products. In one embodiment, the olefin monomer feed comprises at least one of the following: C4 olefins, C5 olefins, a mixed feed of C4 and C5 olefins, isobutene, 1-butene, cis-2-butene, trans-2-butene; and optionally at least one of the inerts, n-butane, i-butane, butadiene, distillation fraction or any mixture thereof. In another embodiment, the olefin monomer feed, or the mixed feed, comprises or essentially consists of isobutene and at least one of C4 olefins, C5 olefins, a mixed feed of C4 and C5 olefins, 1-butene, cis-2-butene, trans-2-butene, inerts, n-butane, i-butane, butadiene, distillation fraction, or any mixture thereof. In a preferred embodiment, isobutene is the main component of the mixed feed. In one embodiment, the amount of non-reactive components such as inerts, n-butane, i-butane in the reactor outlet stream, which comes out of the reactor, is so low that they do not significantly hinder the separation of olefin dimers and olefin trimers in the distillation step. One advantage of using a mixed feed in this process is that the removal of inert materials is efficient and does not significantly affect product yield. When using mixed feeds in this process, very little reactive monomer remains in the reactor outlet stream due to the high monomer conversion per pass, and consequently, very little monomer is lost in the inert removal step. The reactor outlet stream, which is extracted from the reactor, contains at least olefin dimers and olefin trimers and, optionally, smaller amounts of olefin monomers, moderator and inerts. Figure 3 illustrates an implementation of a production unit 100 to carry out the present procedure. The production unit 100 comprises a reactor unit 110 and a distillation column 210. Olefin monomers are fed to the reactor from a tank 410 through a reactor feed line 420, which in Fig. 3 is in fluid communication with a first recycle feed 220 and a second recycle feed 230. From the reactor unit 110, the reaction products are transferred to the distillation column 210 through a reactor outlet stream line 120. From the distillation column 210, a first recycle line 220 transfers lighter products comprising at least one olefin monomer, diluent, and moderator back to the reactor unit 110. A second recycle line 230 transfers a stream composed predominantly of olefin dimers back to the reactor unit 110.A heavier bottoms product comprising olefin trimers is conveyed from the distillation column through a bottoms product conduit 250 to a bottoms product tank 510. Inerts can optionally be removed solely through an inerts removal conduit 240. In the embodiment of Fig. 3, the recycle feed consists of two recycle feeds routed through the first recycle duct 220 and the second recycle duct 230 to reactor unit 110. In Fig. 3, the recycle ducts are shown as if they were fluidly connected to the reactor feed duct 420 that accesses reactor unit 110. Alternatively, the recycle ducts can be connected to reactor unit 110 through separate openings in reactor unit 110. Instead of the two recycling lines 220, 230 described above, a single recycling feed line can also be used. In this embodiment, the single recycling line recycles both the olefin dimers and olefin monomers, and optionally the moderator, back to the reactor. In one embodiment, the olefin monomer 410 reservoir is configured to provide a mixed feed. In another embodiment, the olefin monomer reservoir 410 is configured to provide seamless communication to a plurality of reactor units, or reactor vessels. If a plurality of reactor vessels are provided in series, preferably the olefin monomers are fed to the first reactor vessel in a series, and optionally, the later reactor vessels receive feed only from the reactor outlet stream line of a preceding reactor vessel. Figure 4 illustrates another embodiment of the production unit 100, in which a mixed feed is preferably used. In this embodiment, the production unit 100 comprises a reactor unit 110 and a distillation column 210. Fresh olefins are fed to the reactor from a tank 410 through a reactor feed line 420, which in Figure 4 is in fluid communication with the first recycle feed line 220, a second recycle feed line 230, and an optional dimer feed line 430. From the reactor unit 110, the reaction products are transferred to the distillation column 210 through a reactor outlet stream line 120. From distillation column 210 a first recycling conduit 220 transfers lighter products comprising at least one olefin monomer, diluent and moderator, back to reactor unit 110.A second recycle line 230 transfers a stream composed predominantly of olefin dimers back to unit 110 of the reactor. A heavier bottoms product comprising olefin trimers is conveyed from the distillation column through a bottoms product line 250 to a bottoms product tank 510. Inerts can be optionally removed through an inerts removal line 240. Figure 4 also shows optional heat exchangers 310 that can be used to recover heat from the outlet streams leaving the distillation column and to preheat the outlet stream line 120 from the reactor before it enters the distillation column. In Fig. 4, olefin dimers are removed from the distillation column via the second recycling conduit 230 which is fluidly connected to one side of the distillation column to provide a side stream.Preferably, the side stream is taken from the distillation column as a steam outlet stream, which is condensed after heat recovery in the heat exchanger and before entering reactor unit 110 as a recycle feed. As shown in Fig. 4, the bottom product duct 250 can be routed through an optional heat exchanger 310 to heat the reactor outlet stream duct 120 before the stream enters the distillation column. In one embodiment, an olefin monomer feed, preferably a high-purity olefin monomer feed, is fed to a reactor unit, which in the embodiments of Fig. 3 and Fig. 4 is a single reaction vessel. Alternatively, a reactor unit comprising a plurality of reactor vessels may be used. Unit 110 of the reactor contains a dimerization catalyst, which catalyzes the formation of olefin dimers in a dimerization reaction between two olefin monomers and the formation of olefin trimers in an addition reaction between olefin monomers and olefin dimers. Additionally, a small amount of heavier olefin oligomers may be formed. The reaction product is conveyed as an outlet stream 120 from the reactor to the distillation column 210, which separates unreacted inerts, olefin monomers, and olefin dimers from a heavier bottoms product containing at least olefin trimers and, optionally, compounds with a higher boiling point than olefin dimers.An optional 310 heat exchanger can be used to recover heat from the bottom product containing olefin trimers and to use the recovered heat to heat the reactor outlet stream before it enters the distillation column. In the implementation shown in Figures 3 and 4, the moderator can be added to the reactor along with the olefin monomer feed through the reactor feed line 420, along with the recycle feed line 220, 230 from the distillation column to the reactor unit, or through a separate inlet (not shown) directly to the reactor. It is preferable to feed the moderator along with a reactor feed line entering the reactor, such as reactor feed line 420 or recycle line 220, 230, to ensure thorough mixing. In one embodiment, fresh monomers are fed to the reactor as a high-purity monomer feed. The high-purity olefins preferably have a purity of at least 95 wt%. The use of high-purity olefins is particularly advantageous in single-column systems because it results in a reaction product feed containing only a small amount of components with boiling points overlapping with olefin dimers or olefin trimers. Once the olefin stream has passed through the reactor unit(s), the resulting reactor outlet stream is directed to a distillation column that separates the unreacted olefins (primarily dimers) as a lighter product from the olefin trimers, which are withdrawn as the bottoms product. Preferably, the lighter product is substantially free of olefin monomers, indicating a high conversion rate. In one embodiment, the process parameters are selected such that the single-use conversion rate of the olefin monomers is at least 96%, resulting in a lighter product that contains mainly dimers and only a small amount of olefin monomers.Since the monomers are consumed almost entirely in the catalytic conversion, controlling the reactor feeds is easier, as the monomers are added to the feed almost exclusively through the fresh olefin monomer feed, and only a small amount of monomers may be present in the recycled dimer feed. If the lighter product contains dissolved gases, these can be separated from the lighter product using methods known in the art. In one embodiment, the lightest product does not contain olefin trimers. The separation of olefin trimers can be controlled by distillation parameters. In the present process, olefin trimers accumulate in the bottoms product during distillation and are removed from the process. Consequently, the recycle feed contains olefin dimers, whereas olefin trimers are preferably not present in the recycle feed in a significant quantity. In one embodiment, the bottoms product contains less than 15 wt% of olefin tetramers and optionally at least 80 wt% of olefin trimers, based on the total weight of the bottoms product. In another embodiment, the bottoms product contains less than 12 wt% of olefin tetramers and optionally at least 80 wt% of olefin trimers, based on the total weight of the bottoms product. Instead of 80 wt%, the amount of olefin trimers in the bottoms product may also be at least 85 wt% or at least 88 wt%. In one embodiment, the single-use conversion rate of olefin monomers is at least 60%, at least 70%, at least 80%, at least 90%, at least 95%, or at least 96%, and optionally, the selectivity for the production of olefin trimers is at least 85% or at least 90%, expressed as the weight percent of olefin monomers. In the context of the present invention, the term diluent means any inert agent or an agent that is less reactive than the olefins in the present process. The addition of diluent to the reactor thus reduces the concentration of olefins in the reactor; the catalytic conversion rate of olefins in the process can be controlled by selecting an appropriate amount of diluent. In one embodiment, the recycle feed can be withdrawn from one side of the first distillation column as a side recycle stream. In one embodiment, this recycle feed comprises both olefin monomers and olefin dimers. In another embodiment, the recycle feed comprises olefin dimers. Therefore, the withdrawal position of the side recycle stream can be selected so that the dimers are at least partially removed from the distillation column, while the recycle feed does not contain a significant amount of heavier or lighter compounds. In the implementation shown in Figure 4, the monomer-containing product and the lighter dimer-containing product can be mixed with the fresh olefin stream before entering the reactor. The amount of recycled feeds and the amount of fresh olefin can be controlled so that the mass ratio of olefin monomers to olefin dimers in the feeds entering the reactor remains at a desired level. The optional dimer feed line 430 can also be used to feed dimers to the reactor, thereby achieving even greater control over the process. The embodiments described in this document are suitable for the selective production of trimers from olefin monomers and allow control of the olefin feeds and the moderator so that the selectivity of the catalytic reactions promotes the formation of olefin trimers. The moderator is applied to slightly suppress reaction rates and ensure a prolonged catalyst life. A favorable moderator quantity is specific to the target main product and can be selected by someone experienced in the technique by analyzing the reaction products and the procedural conditions. For the production of olefin trimers, a favorable quantity is considerably less than that used in the production of olefin dimers. The moderator can be recycled back to the reactor from the distillation column along with the recycle feed containing olefin monomers. Surprisingly, the inventors found that, unlike isooctene production, a separate solvent is not required in the present process, which is optimized for producing olefin trimers. Therefore, in one embodiment, the present process is operated without an additional solvent. In one embodiment, the olefin feed to the reactor comprises isobutene and recycled olefins (mainly isooctenes) recovered after the feed has passed through the reactor. The present process is advantageous because, in a preferred embodiment, it can be carried out without a diluent. Prior processes designed primarily for the production of olefin dimers require the use of a diluent, making the process uneconomical, especially when using feeds with high purity and concentration.Advantageously, due to the high conversion rate of olefin monomers in the present procedure, the removal of inerts does not cause a significant loss of unreacted olefin monomers, thus improving the efficiency of the procedure and enhancing the removal of inerts. Instead of using a single reactor unit, the reactor unit can be sized and distributed across separate vessels. By increasing the number of reactor vessels and beds, the reaction conditions are easier to control, and consequently, a nearly complete single-step conversion of an olefin monomer, such as isobutene, can be achieved. Thermal control of the adiabatic temperature rise is also easier when using multiple reactor units. In one embodiment, the reactor unit is composed of a plurality of reaction vessels arranged as a reactor in series or a reactor in parallel, or a combination thereof. In one embodiment, the reactor comprises more than one reactor vessel, such as two, three, four, or five reactor vessels, each containing at least one reactor bed. The use of more than one reactor vessel is advantageous because it allows for more precise temperature control and enables the separate control of the amount of moderator and catalyst in each reactor vessel. The feed temperature can be controlled between reactor vessels using temperature control units that can cool or heat the feed. In one embodiment, the reaction conditions, such as temperature and pressure, are essentially the same in each reactor vessel. When multiple reactor vessels are used as a reactor unit instead of a single reactor vessel, each reactor vessel contains a dimerization catalyst, preferably an acidic ion-exchange resin catalyst. Preferably, the same catalyst is used in each reactor vessel. Preferably, the amount of catalyst is kept low in the first reactor vessel and increases in subsequent reactor vessels downstream of the process. By limiting the amount of catalyst in the first reactor vessel(s), for example, the temperature is easier to control and the reaction conditions can be more easily maintained within the selected ranges.For example, olefins can be kept in the liquid phase when multiple reactor vessels are used and the olefin stream is cooled between vessels, making it easier to maintain the mass ratio of olefin monomers to olefin dimers at the desired level. Preferably, beyond the feed to the first reactor vessel, no further olefins are fed to subsequent reactor vessels during the process; that is, the feed olefin mixture is not supplemented with additional olefins as it flows through the reactor vessels. When multiple reactor vessels are used, each with a single reactor bed, the amount of catalyst can be increased within the reactor vessels.In a multiple reactor configuration, the upstream reactor vessels contain more catalyst than the downstream reactor vessels. In one embodiment, a multiple reactor configuration comprises 3 or 4 reactor vessels. In a reactor unit containing a plurality of reactor vessels, the volume of the reactor vessels may increase from the first reactor vessel to the subsequent reactor vessel in the downstream direction. In one embodiment, the volume of the first and second reactor vessels is substantially the same. In another embodiment, the volume of the third and fourth reactor vessels is substantially the same. In yet another embodiment, the volume of the third and fourth reactor vessels is substantially identical to each other, but their volume is greater than the volume of the first or second reactor vessels, wherein the first and second reactor vessels may have substantially identical volumes. In one embodiment, the oxygen-containing moderator is an oxygenated compound, such as demineralized water or tert-butyl alcohol (TBA). Alternatively or additionally, the moderator comprises an alcohol formed within the reactor as a result of a reaction between water and an olefin. Accordingly, e.g., 2-butanol can be formed from isobutene within the reactor. Once the olefin stream has passed through the reactor unit, the resulting reactor outlet stream is directed to a distillation column, which separates unreacted olefins (mainly isooctene) and the moderator component as a lighter product from the olefin trimers, which are removed as the bottom product. The olefin monomer may be present as a minor species in the lighter product, which is primarily composed of olefin dimers. Since the monomers are almost completely consumed in the catalytic conversion, controlling the feed composition within the reactor is easier, as monomers are added only through the addition of fresh olefin monomers. If the lighter product contains dissolved gases, these can be removed using standard methods. The moderator can circulate in the recycling reactor loop along with lighter components and is supplemented to maintain its quantity at a substantially constant level. The moderator is preferably used in an amount exceeding the potential water content of the fresh olefin feed or the recycling feed, which could also serve as a source of oxygenated compounds but is insufficient on its own for the present invention. The moderator can be fed to the reactor by mixing it with a feed entering the reactor, such as a reactor feed comprising fresh olefin monomers. Alternatively, the moderator can be mixed with the recycled olefin dimer stream before mixing with the fresh olefin monomers. The use of added moderator in the present process is advantageous because it improves the selectivity for trimer production. At least a portion of the olefin dimers separated during distillation can be recycled back to the reactor. Alternatively or additionally, an external source of olefin dimers, preferably isooctene, is fed to the reactor with olefin monomers. In one embodiment, the reactor outlet stream is distilled to separate the olefin dimers, which are then recycled back to the reactor. In one embodiment, the components that have not reacted in the reactor are separated as a distillate in a distillation column. The distilled components can be removed from the process or recycled to the reactor. In one embodiment, the present procedure is a continuous process. Advantageously, the present procedure allows the process to be run for extended periods, even months, without interruption for maintenance. Prior art procedures have used batch procedures at laboratory scale, which are unsuitable for industrial-scale use due to instability issues. In particular, when using multiple reactor vessels, the trimerization process is effectively controlled in the present procedure, and the continuous process can be run for a prolonged period. The term dimerization catalyst, or simply catalyst, refers to a catalyst that catalyzes the dimerization of olefin monomers into olefin dimers and an addition reaction between olefin dimers and olefin monomers to yield olefin trimers. In one embodiment of the present process, the majority of the feed entering the reactor contains olefin dimers, and the amount of olefin monomers is kept quite low. Consequently, the reactor conditions in the present invention are selected such that the dimerization catalyst catalyzes a reaction in which an olefin dimer formed in the reactor preferably reacts with an olefin monomer, thereby forming an olefin trimer. In a preferred embodiment, the reactor contains a single catalyst. Preferably, the reactor does not contain two different catalysts, where the first catalyst is specific for dimerization reactions between two monomers but does not catalyze a reaction between a monomer and a dimer, and the second catalyst is specific for reactions between a monomer and a dimer but does not catalyze a dimerization reaction between two monomers. Therefore, the present procedure offers the advantage of being simpler compared to previous systems using multiple catalysts. In one embodiment, water is not removed from the reactor or from the lighter product obtained from the distillation column. In one embodiment, the catalytic reactions are carried out under operating conditions where the olefins remain in the liquid phase and, optionally, where the moderator also remains in the liquid phase. Preferably, at least the temperature and pressure of the reactor(s) are selected such that the olefins are in the liquid phase within the reactor. An advantage of keeping at least the olefins in the liquid phase is that reactor control can be easier to achieve than in a process involving gaseous olefins. In one embodiment, fresh olefin monomers are fed into the reactor, and the fresh olefin monomers comprise olefins having four carbon atoms, preferably isobutene. In one embodiment, olefin dimers are recycled to the reactor by mixing the recycle feed with fresh olefin monomers before introducing the combined feed into the reactor. In another embodiment, the olefin dimers are mixed with the reactor feed before the combined mixture enters the reactor. Mixing the olefin dimers with the reactor feed is advantageous because it ensures effective mixing before contact with the first catalyst. Furthermore, it allows for the dissipation of potential temperature differences between the two feeds. In one embodiment, the recycled feed contains at least 95% by weight of olefin dimers. In one embodiment, the recycle feed contains less than 5 wt% of olefin trimers, preferably less than 3 wt%, 2 wt%, or 1 wt%. Keeping the amount of olefin trimers in the recycle feed low further improves the selectivity of the process for olefin trimer production and prevents the formation of olefin oligomers with more than three monomer units. In preferred embodiments, the mass ratio of olefin monomers to olefin dimers in the reactor feed is at least approximately 1:50, 1:40, 1:30, 1:20, 1:15, 1:14, 1:13, 1:12, 1:11, 1:10, 1:9, 1:8, 1:7, 1:6, 1:5, 1:4, 1:3, or 1:2. In a more preferred embodiment, the feed mass ratio expressed as the mass ratio of olefin monomers to olefin dimers in the feeds entering the reactor is selected from the range 1:8–1:15 or 1:8–1:10. The use of an excess of olefin dimers in the amounts specified above directs the catalytic reaction towards the formation of olefin trimers without significantly decreasing the conversion rate of the monomers. In one embodiment, the selectivity for the production of olefin trimers is at least approximately 85%, preferably approximately 90%, expressed as the weight percent based on the olefin monomers. Depending on the process conditions, a selectivity of even approximately 99% can be achieved. A selectivity of at least 85% means that at least 85% of the olefin monomers are used in the catalytic conversion when olefin dimers and olefin trimers are formed. In one embodiment, the single-use conversion rate of olefin monomers is at least 60%, at least 70%, at least 80%, at least 90%, at least 95%, or at least 96%. In one embodiment, the dimerization catalyst is an acid catalyst, preferably a strongly acidic ion exchange resin catalyst, most preferably a macro-network acid ion exchange resin catalyst. In one embodiment, the catalyst is solid. In one embodiment, the catalyst catalyzes the dimerization reaction of two olefin monomers and the addition reaction of an olefin monomer and an olefin dimer. Advantageously, the present process uses a catalyst and a moderator to improve the selectivity of the process for trimer formation. Previously, it was assumed that moderators such as tert-butanol or alcohols only promoted dimer formation, and that the presence of water in the reactor led to the formation of alcohols or ethers, thereby inhibiting the formation of trimers and oligomers. Consequently, polar compounds such as alcohols or ethers have been pre-treated from the olefin feedstocks before they enter the reactor. In one embodiment, the moderator comprises water, demineralized water, alcohol, tert-butyl alcohol, or any combination thereof. In one embodiment, the amount of moderator is selected from the range of 0.01–0.5 wt% of the total feed to the reactor, preferably from the range of 0.1–0.4 wt%, and more preferably from the range of 0.2–0.3 wt%. The total feed to the reactor comprises all feeds introduced into the reactor. In one embodiment, the temperature inside the reactor is selected from the range of 40-140 °C, preferably from the range of 50-130 °C, more preferably from the range of 60-120 °C. In a preferred embodiment, the pressure inside the reactor is selected from the range of 15-35 bar, more preferably from the range of 20-30 bar. In a preferred embodiment, the reactor is operated at 50–130 °C and 15–35 bar, 50–130 °C and 20–30 bar, 60–120 °C and 15–35 bar, or 60–120 °C and 20–30 bar. Preferably, the reactor operating conditions are selected such that the olefin monomers and olefin dimers are in the liquid phase within the reactor. In one embodiment, the residence time of the feed passing through the reactor is 0.25–2 L / h expressed as the weight hour space velocity (WHSV), preferably 0.25–0.4 L / h. Weight hour space velocity (WHSV) is defined as the weight of fresh feed flowing per unit weight of dry catalyst per hour. In one embodiment, distillation is carried out at a selected pressure in the range of 1.8-2 bar and a Tmax of 250 °C. In one embodiment, the process further comprises recovering heat from at least one feed obtained from the distillation column. In one embodiment of the process, the recovered heat is used to heat the reactor outlet stream before it enters the distillation column. In another embodiment, the heat is used to heat the reactor feed before it enters the reactor. In one embodiment, the distillation column is a non-reactive distillation column that does not contain catalytic material or a reactive zone, and in which the olefins do not undergo any significant chemical reaction. Therefore, the non-reactive distillation column differs, for example, from reactive distillation columns that have a reactive or catalytic zone that chemically converts the feed components, in particular olefin monomers, olefin dimers, or olefin trimers. In one embodiment, the distillation is carried out using two distillation columns in series. This embodiment can be advantageous, particularly when using a mixed feed that has components with boiling points that may be lower than the boiling points of olefin dimers, or that contains inerts that have a lower boiling point than olefin dimers. Therefore, the inerts can be effectively removed using the two-column distillation configuration, and their enrichment can be avoided. When two distillation columns are used, in the first distillation column, the light inerts are removed, and optionally, one of the olefin monomers, diluent, and moderator are separated and recycled to the reactor. Meanwhile, the olefin dimers and heavier optional compounds are removed as a bottom intermediate and fed to a second distillation column. This second column separates at least one of the olefin dimers, diluent, and moderator for recycling back to the reactor, and the olefin trimers and heavier optional compounds are recovered as a bottom product. In a two-column distillation process, the olefin dimers can optionally be recovered from a recycle feed to the second distillation column. In one embodiment, the chemical reactions are carried out in a single reactor. In this embodiment, recycled olefin dimers are fed into the same reactor where the olefin monomers are dimerized by the dimerization catalyst. The olefin trimers obtained from the distillation column contain olefin polymers formed by polymerizing three olefin monomers together. The olefin monomer components that form the trimers can be, in one embodiment, chemically identical olefin monomers, such as a certain type of C4 olefin like isobutene, or the trimers can contain at least one lighter or heavier olefin monomer component with a different number of carbon atoms, or an olefin monomer having the same number of carbon atoms but varying in the number of double bonds and / or degree of isomerization. In one embodiment, the reactor is not a trickling bed reactor. In one embodiment, the catalytic reactions are carried out in a different unit from where the distillation takes place. Therefore, in one embodiment, the reactions are not carried out in a catalytic distillation column. In one embodiment, the distillation column is operated in an environment in which no dimerization or oligomerization of the olefins occurs. In one embodiment, the present process is carried out without the addition of any additional solvent and / or inert agent. Advantageously, with this process, the dimer itself can serve as a rate-controlling agent for the chemical conversion. Additionally, the moderator can be recycled back into the reactor to control the catalytic conversion rate. Figures 3 and 4 provide an embodiment of production unit 100 suitable for carrying out the procedure of the first aspect. The production unit optionally contains a heat recovery unit, a heat transfer unit and / or a heater unit. A heating unit can be arranged in the production unit so that it heats at least one of: the reactor feed line, the reactor outlet stream line before it enters the distillation column, and the distillation column reboiler. When using multiple reactor vessels, a heat recovery unit or a cooling unit can be placed between the reactor vessels. The heat recovered from the feed moving from one reactor vessel to the next can preferably be used in heating units of the production unit to improve process economy. In one embodiment of the production unit, the reactor comprises a plurality of reactor vessels, wherein each downstream reactor unit contains a greater amount of acid catalyst than the preceding upstream reactor vessel. In one embodiment, the production unit further comprises at least one heat exchange unit configured to recover heat from the bottom product containing olefin trimers and use it to heat the reactor outlet stream before it enters the first distillation column. In one embodiment, the production unit further comprises a first recycling conduit configured to recycle at least one of the olefin monomers, diluent, and modifier through a first recycling conduit to at least one reactor, and a second recycling conduit configured to recycle olefin dimers to at least one reactor. EXAMPLES The following examples are provided to further illustrate the claimed invention and should not be construed as limiting the scope of the invention, which is determined by the claims. To the extent that specific materials are mentioned, it is merely for illustrative purposes and is not intended to limit the invention. A person skilled in the art may develop equivalent means or reactants without exercising inventive step and without departing from the scope of the invention. It should be understood that many variations of the processes described herein may be made while remaining within the scope of the present invention. An example implementation of the present procedure was carried out using isobutene: Feed recycling procedure = 0.12 and TBA moderator content 0.37 wt% in the total feed to the reactor section. There were three reactors in series, each with an outlet temperature of 90 °C. The catalyst was an acidic ion exchange resin (5.2 mmol eq / g of acid). RESULT: Bottom product composition: 0.0% dimers, 89.2% trimers, 10.8% tetramers, based on the total weight of the bottom product. The results are shown in Fig. 1. In a comparative example under experimental conditions similar to the above, the reaction section was run in a one-time manner with the same isobutene feed and isobutane solvent (50% by weight) and a similar TBA moderator content. RESULT: Bottom product composition: 68% dimers, 23% trimers, 9% tetramers by weight of the total bottom product weight. The results of the analysis are shown in Fig. 2. Although the dimer content in a single-use operation can be further minimized by decreasing the TBA moderator dosage in the feed, the tetramer content will simultaneously increase, and eventually, even higher oligomers will appear. Therefore, substantial trimer selectivity requires both the procedure configuration with the characteristics described in this disclosure and an appropriate moderator dosage. The foregoing has illustrated several exemplary embodiments of the present invention. These embodiments are used simply to explain selected aspects or steps that may be used in implementing the present invention.

Claims

1. A process for manufacturing olefin trimers, characterized in that it comprises: feeding a reactor containing a dimerization catalyst, which is a feed of olefin monomers comprising at least one of the following: C4 olefins, C5 olefins, a mixed feed of C4 and C5 olefins, isobutene, 1-butene, cis-2-butene, 1-tan-2-butene, and at least one oxygen-containing moderator comprising water, demineralized water, tert-butyl alcohol, or any combination thereof; operating the reactor at a temperature selected from the range 40-140 °C and a pressure selected from the range 10-40 bar to carry out catalytic dimerization reactions between olefin monomers and olefin dimers,and addition reactions between olefin monomers and olefin dimers; withdrawing an outlet stream from the reactor; and distilling the outlet stream from the reactor to separate at least a lighter product comprising olefin dimers and a heavier bottoms product comprising olefin trimers; wherein at least a portion of the lighter product is recycled to the reactor to provide a recycle feed, the olefin monomers are fed to the reactor predominantly as a fresh olefin monomer feed, the amount of the fresh olefin monomer feed and the recycle feed fed to the reactor are controlled so that the mass ratio of olefin monomers to olefin dimers entering the reactor is selected in the range 1:8-1:15,and wherein the catalytic reactions are carried out under operating conditions in which the olefins remain in the liquid phase.

2. The process of claim 1, characterized in that fresh olefin monomers are fed to the reactor, and the fresh olefin monomers comprise olefins having four carbon atoms, preferably isobutene.

3. The process of claim 1 or 2, characterized in that the olefin monomer feed comprises at least one of the following: inerts, n-butane, i-butane, butadiene, distillation fraction, or any mixture thereof.

4. The process of any one of claims 1-3, wherein the olefin dimers are recycled to the reactor by mixing the recycle feed with fresh olefin monomers before feeding the combined feed to the reactor.

5. The method of any one of claims 1-4,wherein the mass ratio of olefin monomers to olefin dimers is selected from the range 1:8-1:

10.

6. The process of any one of claims 1-5, wherein the selectivity for the production of olefin trimers is at least 85%, preferably at least 90%, expressed as the weight percent based on the olefin monomers.

7. The process of any one of claims 1-6, wherein the single-use conversion rate of the olefin monomers is at least 60%, at least 70%, at least 80%, at least 90%, at least 95%, or at least 96%.

8. The process of any one of claims 1-7, wherein the dimerization catalyst is a strongly acidic ion-exchange resin catalyst, most preferably a macro-network acid ion-exchange resin catalyst.

9. The method of claim 1, wherein the amount of the moderator is selected from the range of 0, 0.-0,5% by weight of the total feed to the reactor, preferably from the range of 0.1-0.4% by weight, more preferably from the range of 0.2-0.3% by weight.

10. The method of any of claims 1-9, characterized in that the operating temperature of the reactor is selected from the range of 50-130 °C, more preferably from the range of 60-120 °C.

11. The method of any of claims 1-10, characterized in that the operating pressure of the reactor is selected from the range of 15-35 bar, more preferably from the range of 20-30 bar.

12. The method of any of claims 1-11, wherein the residence time of the feed passing through the reactor is 0.25-2 L / h expressed as the weight space velocity per hour (WHSV), preferably 0.25-0.4 L / h.

13. The procedure of any of claims 1-12,wherein the distillation is carried out at a selected pressure in the range of 1.8–2 bar, and at a maximum temperature (Tmax) of 250 °C.

14. The process of any one of claims 1–13, wherein the recycle feed contains at least 95% by weight of olefin dimers.

15. A use of a production unit configured to carry out the process of claims 1–14.comprising: a. at least one reactor unit configured to receive an acid catalyst; b. at least one distillation column configured to separate isooctene from isododecene; c. at least one reactor feed line in fluid connection with the reactor unit and an olefin monomer tank; d. at least one reactor outlet line in fluid connection with the reactor unit and the distillation column; e. at least one recycle line in fluid connection with the distillation column and the reactor unit; and f. a bottoms product line in fluid connection with the distillation column and a bottoms product tank.

16. The use of a production unit of claim 15, wherein the reactor unit comprises a plurality of reactor vessels,and wherein each of the downstream reactor vessels contains a greater quantity of acid catalyst than the preceding upstream reactor vessel.

17. The use of a production unit of claim 16, the production unit further comprising at least one heat exchange unit configured to recover heat from at least one conduit of the distillation column.

18. The use of a production unit of any one of claims 15-17, wherein the production unit comprises a first recycling conduit configured to recycle at least one of the olefin monomers, diluent, and modifier through a first recycling conduit into at least one reactor, and a second recycling conduit configured to recycle olefin dimers to the at least one reactor unit.

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