WO2007091862A1

WO2007091862A1 - Preparation method of light olefin trimers and production of heavy alkylates by using thereof

Info

Publication number: WO2007091862A1
Application number: PCT/KR2007/000706
Authority: WO
Inventors: Sung-Hwa Jhung; Jong-San Chang; Ji Woong Yoon; Tae-Jin Kim; Dae Hyun Choo; Hee-Du Lee
Original assignee: Korea Research Institute Of Chemical Technology
Priority date: 2006-02-09
Filing date: 2007-02-09
Publication date: 2007-08-16
Also published as: KR100784118B1; KR20070080865A

Abstract

The present invention relates to a preparation method of olefin trimers, and more particularly, to a preparation method of isobutene trimers that are useful as precursors for heavy alkylates or neo acids, performed in such a manner that a macroporous cation exchange resin in hydrogen form is used as a catalyst and the olefin conversion is higher than 60%. Furthermore, the present invention relates to a preparation method of heavy alkylates by hydrogenating olefin trimers thus formed.

Description

PREPARATION METHOD OF LIGHT OLEFIN TRIMERS AND PRODUCTION OF HEAVY ALKYLATES BY USING THEREOF

Technical Field

[1] The present invention relates to a preparation method of olefin trimers useful as precursors for heavy alkylates or neo acids. More particularly, present invention relates to a preparation method of olefin trimers, with high throughput and purity, by tuning the pore-structure of acid catalysts and by increasing olefin conversion. Background Art

[2] The oligomerization reaction of olefins has been carried out by using acid catalysts such as supported phosphoric acid, and olefin dimers have been generally obtained for gasoline additive after hydrogenation of the dimers (USP 6689927, 6284938).

[3] Alkylates have been prepared by the alkylation of olefins with paraffins in the presence of sulfuric acid or hydrofluoric acid (Catalysis Today, 49, 193, 1999); however, the method has a severe disadvantage of environmental problem and corrosion due to the usage of the liquid acids. Heavy alkylates with C or more carbons are obtained by the alkylation in low content of 5-10%, and are used as prime solvent or diesel additive to increase the cetane-number of diesel fuel. Therefore, development of a new process to produce heavy alkylate is necessary because the productivity is limited by conventional methods.

[4] Recently, several oligomerization methods to prepare trimers are reported. Olefin trimerization has been mainly carried out by using solid acid catalysts such as heteropoly acid (JP 2005015383), zirconia (JP 2005015384), zeolite called Al-TS-I (USP 6914165) and sulfated titania (J. Molecular Catalysis A, 228, 333, 2005). Ionic liquids are also used for the reaction (CN 1379005).

[5] A few examples have also been reported to utilize cation exchange resins for the oligomerization. It has been claimed that a cation exchange resin can be used in a dimerization (USP 2005/011911 IAl). USP 5789643 taught that oligomerization could be catalyzed by zeolites, aluminas and ion exchange resins. Tetramers or pentamers could be obtained by the oligomerization of pre-formed dimers with ion exchange resins (US 6239321).

[6] Moreover, an ion exchange resin called Amberlyst-15 was used in the oligomerization of isobutene (Catalysis Today, 100, 463, 2005). However, the conversion was less than 40% and dimers rather than trimers were the main products.

[7] Hence, there is no finding to use cation exchange resins in the olefin trimerization.

Furthermore, no result is reported to get olefin trimers by adjusting physical properties of ion exchange resins or optimizing olefin conversion. [8] Therefore, there remains a need in the art for the development of a novel process for preparing olefin trimers by using solid acid catalysts such as ion exchange resins.

Disclosure of Invention

Technical Problem [9] The present inventors have made intensive researches to overcome the shortcomings described above, and as a result, found a novel trimerization process in which a macroporous cation exchange resin is used in the reaction and the olefin conversion is higher than 60%. Moreover, a heavy alkylate is obtained by the hy- drogenation of trimers that are derived from the trimerization. [10] Accordingly, the object of this invention is to provide a process for producing olefin trimers with high trimers selectivity, high throughput and long catalyst life. Moreover, this invention is also to provide a method for producing a heavy alkylate by the hy- drogenation of the trimers thus obtained.

Technical Solution

[11] The present invention is directed to a novel process for preparing olefin trimers by oligomerization of olefins, wherein macroporous cation exchange resins are used as catalysts and the olefin conversion is higher than 60%. The present invention is also directed to a process for preparing heavy alkylates by the hydrogenation of olefin trimers thus obtained. Olefin trimers can be effectively prepared by using macroporous cation exchange resins, rather than gel-type cation exchange resins without internal surface area, that have high internal surface area, due to pores (>5nm) even in dried state, and maintaining the olefin conversion high, preferably higher than 60 %. [12] The present invention will be described in more detail as follows:

[13] The olefins described in this invention are any olefins composed of C 2 or higher carbon, preferentially to be C 3 or C 4 unsaturated hydrocarbons, and more preferentially to be butenes (C 4 H 8 ) and isobutene is the most suitable olefin.

[14] The oligomerization temperature does not have any limitation; however, the preferential temperature is from room temperature to 120 °C. The reaction rate should be low when the temperature is too low, whereas, the conversion at high temperature is not high, due to the exothermal oligomerization reaction, and the resin catalyst can be degraded if the temperature is too high. The reaction temperature of 50-100 °C is more suitable.

[15] The oligomerization reaction can be performed both in batch mode and continuous mode, and the latter method is suitable for mass production of oligomers. The continuous mode is operated well by using a fixed bed reactor, and the reactants can be flown upward or downward. [16] It is advisable to use a solvent to control the heat of reaction because the oligomerization reaction is very exothermic. Moreover, a solvent is helpful to transport reactants and products easily. As a solvent, hydrocarbons such as C -C paraffins can be used. More preferably, isobutane, n-butane, pentanes, hexanes, octanes, nonanes or decanes can be used. Cyclohexane can also be utilized as a solvent. The reactant/ solvent ratio can be any value between 1/100 and 100/1 (wt/wt), and it is preferable to maintain the ratio between 1/10 and 10/1 because of the operation convenience and high productivity. Inert gases such as nitrogen, argon, carbon dioxide and helium can be used as a diluent instead of an organic solvent. It is good to flow the reactant and the inert gas upward when diluent is used in a fixed bed reactor.

[17] Any macroporous cation exchange resins can be used in the oligomerization reaction if the resin is in a hydrogen form. The pore size of macropore should be larger than 5 nm even in dried form as described in Reactive and functional polymers, 35, 7, 1997. The catalyst stability is low when the pore size is too large, whereas the diffusion of reactants and products are difficult or deactivation of the catalyst is too fast if the pore size is too small. On the other hand, gel-type ion exchange resins without macropore have the drawback of low reactivity and rapid deactivation.

[18] The resins to support hydrogen ion can be any composition, and the resins composed of styrene and divinylbenzene copolymers are suitable. As the content of di- vinylbenzene increases the stability of catalyst increases due to the increased degree of crosslinkings. However, the diffusion of reactants and products will be difficult. The content of divinylbenzene should be 2-98% of the total content of divinylbenzene and styrene. The cation exchange resins should have functional group of sulfonic acid (-SO H) because the acidity is high when the hydrogen ion exists in the form of sulfonic acid.

[19] As the oligomerization reaction rate is high when the concentration of hydrogen ion is high, the cation exchange resins should have at least 2-equivalent H7kg-resin. More preferably, the hydrogen ion concentration is at least 3-equivalent H7kg-resin. The hydrogen ion concentration of 4-6 equivalent HVkg-resin is most preferable.

[20] Any commercial cation exchange resins can be utilized as long as the resins are macroporous and hydrogen form. Amberlyst-35, Amberlyst-DT and Diaion-PK-228 are some of the examples that can be used easily. Amberlyst-35 is the most suitable catalyst because the concentration of sulfonic acid is high. Moreover, any synthetic cation exchange resins can be used for the reaction.

[21] Cation exchange resins can be used in any state such as water-containing form, dried form, alcohol-containing form and acetone-containing form. The alcohol- or acetone-containing form can be obtained by solvent exchange of water with alcohol or acetone. Alcohol- or acetone-containing resin is more suitable because the catalytic performance in the earlier stage of reaction is more stable and the catalyst life is longer than any other state. This may be due to the fact that the reactants are organics similar to the alcohols or acetone incorporated in the cation resins.

[22] Granular catalyst is suitable for the reaction even though no specific size and morphology are mandatory. Catalyst with size greater than 0.1 mm is more suitable, and the size of 0.2-1.0 mm is most suitable for the operation ability and low pressure drop.

[23] Olefin conversion does not have any limitation as long as the conversion is higher than 60%. More preferably, the conversion should be higher than 90% because the selectivity of olefin trimers increases with increasing olefin conversion. If the conversion is too low the formation of impurities such as olefin dimers cannot be avoided, whereas olefin tetramers can be increased slightly when the olefin conversion is too high.

[24] The productivity is low and the concentration of high molecular weight impurity is high when the flow rate or space velocity of reactant is too low. On the other hand, the olefin conversion and trimers selectivity are low if the space velocity is too high. The suitable space velocity, based on the olefin WHSV (weight hourly space velocity), is 2-100 h^"1, and more preferably the velocity is 10-50 h^"1.

[25] The trimers that obtained from the olefin oligomerization can be utilized directly for the production of chemicals such as neo-acid or can be converted to heavy alkylate by hydrogenation. Heavy alkylates containing C or higher carbons are obtained by hy- drogenation of the olefin trimers that are prepared by this invention. The hydrogenation is described only briefly because hydrogenation is conducted relatively easily in the presence of a precious metal or nickel as described in 'Fine chemicals through heterogeneous catalysis, Wiley- VCH, 2001, pp. 351-426'. The hydrogenation for heavy alkylate can be performed with any conventional reactors such as a fixed bed reactor and a continuous stirred reactor. Hydrogenation catalyst can be selected from any supported catalysts such as Pd/C, Pd/alumina, Pd/silica, Pd/silica-alumina, Pt/C, Pt/alumina, Pt/silica, Pt/silica-alumina, Ru/C, Ru/alumina, Ru/silica, Ru/ silica-alumina, Ni/C, Ni/alumina, Ni/silica, Ni/silica-alumina. Or, the mixed catalysts containing two or more of above mentioned catalysts can be applicable. Furthermore supported mixed catalyst that containing two or more metals from Pd, Pt, Ru, Ni can be used for the hydrogenation. The hydrogenation reaction can be carried out in any phase such as liquid- or gas-phase and any concentration of hydrogen is affordable as long as the total amount of hydrogen is higher than the stoichiometric amount that is needed for the hydrogenation. Brief Description of the Drawings [26] Fig. 1 represents the change of conversion and selectivities with reaction time in the isobutene oligomerization, obtained in Example 1.

[27] Fig. 2 represents the dependence of trimers selectivity on the isobutene conversion, obtained in Example 5. Mode for the Invention

[28] The following specific examples are intended to be illustrative of the invention and should not be construed as limiting the scope of the invention as defined by appended claims.

[29] EXAMPLE 1

[30] The oligomerization reaction of isobutene was carried out at 70 °C by using a fixed bed reactor containing 2 g of dried Amberlyst-35 (size: 0.2 1.0mm, average diameter: 0.5 mm) and by flowing n-butane and isobutene (1:1 wt ratio) upward. The flow rates of hydrocarbons were controlled by mass flow controllers and the isobutene flow rate was adjusted for the isobutene WHSV (weight hourly space velocity) to be 10 h^"1. The reaction temperature was maintained constant by using a liquid circulator. Circulated water at fixed temperature absorbs extra heat generated from the oligomerization reaction. The isobutene conversion was calculated by the analysis of gas-phase effluent by using a GC. The isobutene conversion was cross-checked by measuring the total flow rates of n-butane and isobutene with mass flow meters. The liquid product, after trapping using a cold trap, was analyzed by a GC for the composition of dimers, trimers and tetramers. As shown in Table 1, the isobutene conversion and trimers selectivity were 99.4% and 75.5 wt%, respectively, through the reaction of 70 h. The dimers selectivity and tetramers selectivity were maintained low of 9.4 wt% and 15.1 wt %, respectively. Detailed reaction conditions and reaction results are summarized in Table 1.

[31] EXAMPLE 2

[32] The oligomerization reaction was carried out as Example 1, except that ethanol- containing catalyst was used instead of dried catalyst. Ethanol-containing Amberlyst- 35 was prepared from water-containing catalyst by replacing water with ethanol. The used catalyst was 2 g based on the dried catalyst, and the isobutene WHSV was 50 h^"1 instead of 10 h^"1. Even though 2 h of reaction time was needed for the steady state reaction, the isobutene conversion and trimers selectivity were satisfactory after 12 h of reaction. Detailed reaction conditions and reaction results are summarized in Table 1.

[33] EXAMPLE 3

[34] The oligomerization reaction was carried out as Example 1, except that water- containing catalyst was used instead of dried catalyst. Water-containing Amberlyst-35 was used as-received from the maker. The catalyst was 2 g based on the dried catalyst, and the isobutene WHSV was 80 h^"1 instead of 10 h^"1. Even though 2 h of reaction time was needed for the steady state reaction, the isobutene conversion and trimers selectivity were satisfactory after 1O h of reaction. Detailed reaction conditions and reaction results are summarized in Table 1.

[35] EXAMPLE 4

[36] The oligomerization reaction was carried out as Example 3, except that ethanol- containing Amberlyst-DT catalyst was used instead of water-containing Amberlyst-35 catalyst. Ethanol-containing Amberlyst-DT was prepared from water-containing catalyst by replacing water with ethanol. The catalyst was 2 g based on the dried catalyst, and the isobutene WHSV was 50 h^" instead of 80 h^" . Even though 2 h of reaction time was needed for the steady state reaction, the isobutene conversion and trimers selectivity were higher than 50% after 12 h of reaction. Detailed reaction conditions and reaction results are summarized in Table 1.

[37] EXAMPLE 5: Dependence of trimers selectivity on conversion

[38] The oligomerization reaction was carried out as Example 3 except that process parameters such as temperature, space velocity and catalyst amount were changed to reach the isobutene conversion of 40%- 100%. The trimers selectivity increased with the isobutene conversion as shown in Fig. 2. It can be known that isobutene conversion should be higher than 60% for the trimers selectivity higher than 50%.

[39] EXAMPLE 6: Hvdrogenation reaction

[40] Ten(lO) grams of trimers, obtained in Example 1 and purified with distillation, were loaded in a continuous stirred reactor. Cyclohexane (90 g) was added as a solvent. Catalyst basket containing 0.5 g of Pd (5%)/C was mounted on the stirring shaft. The reactor temperature was maintained at 100 °C and the reactor pressure was raised to 10 atm by using hydrogen. The hydrogenation reaction was started by the onset of agitation, and the reactor pressure was maintained constant (10 atm) by using a back pressure regulator. After reaction for 1 h, the product was separated from cyclohexane by distillation. The conversion of olefins to paraffins was higher than 99% and a heavy alkylate was successfully obtained.

[41] COMPARATIVE EXAMPLE 1

[42] The oligomerization reaction was carried out as Example 3, except that water- containing Amberlyst-31 catalyst was used instead of water-containing Amberlyst-35 catalyst. Amberst-31 catalyst was gel-type ion exchange resin without macropore, and was used as received. The catalyst was 2 g based on the dried catalyst, and the isobutene WHSV was 50 h^" instead of 80 h^" . Contrary to other Examples, the isobutene conversion was less than 5 % and the trimers selectivity was less than 20%. Accordingly, the main product was dimers (C 8 ) instead of trimers (C 12 ). Detailed reaction conditions and reaction results are summarized in Table 1.

[43] [Table 1] Reaction conditions for oligomerization and reaction results. [44]

Industrial Applicability

[45] As described above, the present process for preparing olefin trimers is performed by use of macroporous cation exchange resins in hydrogen form and maintaining the isobutene conversion higher than 60% because the trimers selectivity increases with increasing isobutene conversion. The olefin trimers thus obtained can be used for preparing neo-acid or can be hydrogenated to heavy alkylate that is used for prime solvent or diesel additive.

Claims

[1] A preparation method of olefin trimers, wherein a macroporous cation exchange resin is used as an acid catalyst and the olefin conversion is maintained higher than 60%.

[2] The preparation method according to claim 1, wherein reaction temperature is 50

~ 100 °C and olefin space velocity, weight hourly space velocity, is 2 ~ 100 h^"1.

[3] The preparation method according to claim 1, wherein said cation exchange resins have acid sites composed of functional group of -SO H.

[4] The preparation method according to claim 1, wherein said cation exchange resins have hydrogen ion exchange capacity higher than 2-equivalent/kg-resin.

[5] The preparation method according to claim 4, wherein said cation exchange resins have hydrogen ion exchange capacity higher than 4-equivalent/kg-resin.

[6] The preparation method according to claim 1, wherein said olefin conversion is higher than 90%.

[7] The preparation method according to claim 1, wherein said olefin is isobutene.

[8] A preparation method of heavy alkylates by hydrogenation of olefin trimers that are obtained according to any one of claims 1 to 7. [9] The preparation method according to claim 8, wherein hydrogenation catalyst is composed of one or more catalysts selected from supported Pd, Pt, Ru and Ni catalysts and hydrogenation agent is hydrogen.