Trimerization of isobutene over cation exchange resins: Effect of physical properties of the resins and reaction conditions

Oligomerization of isobutene has been investigated using several cation exchange resins in order to produce triisobutenes that are useful feedstock for heavy alkylates and neo-acids. Trimers selectivity increases with increasing isobutene conversion. High isobutene conversion is obtained at high temperature and low space velocity by using macroporous cation exchange resins that have high concentration of sulfonic acid groups. Under selected conditions (viz., isobutene WHSV: 10 h⁻¹; temperature: 70 °C; catalyst: Amberlyst-35), the isobutene is quantitatively oligomerized with higher than or equal to 70% selectivity for trimers. The wet resin catalysts containing water or ethanol are very stable for the oligomerization up to about 70 h contrary to the gradual decrease in the conversion with dehydrated catalysts.     

Trimerization of Isobutene Over Solid Acid Catalysts

Oligomerization of isobutene is a very promising reaction not only for the production of isobutene oligomers such as trimers but also for the separation of isobutene from C₄ mixtures. Several solid acid catalysts have been applied for the continuous oligomerization of isobutene in liquid phase. This review analyzes the trimerization of isobutene over various solid acid catalysts such as zeolites, oxides (zirconias and titanias) and acid resins. Trimers selectivity increases with increasing isobutene conversion, irrespective of catalysts such as zeolites and acid resins. Very stable operation with high trimers selectivity is accomplished with WO _x /ZrO₂ catalyst having tetragonal zirconia or various zeolite catalysts with high Lewis acid site-to-Brønsted acid site ratio (LA/BA ratio). For a good performance, acid resins should be macroporous and strong acid (sulphonic acid group) with high acid concentration. Inorganic catalysts are superior to acid resins because the deactivated inorganic materials can be regenerated by simple calcination. The WO _x /ZrO₂ catalyst may be applied to a commercial process because about several thousand tons of isobutene can be oligomerized per one ton of zirconia catalyst in a catalytic cycle without regeneration. The oligomerization of isobutene may be improved further because the reaction has been started only recently and no research has been done for the optimization of the reaction and catalysts. It is expected to develop a new inorganic catalyst having suitable acidity, LA/BA ratio and phase, etc. by further research. The isobutene trimers, with or without hydrogenation, may be used for various purposes, and the importance of this trimerization reaction will be increased considering the expected surplus of isobutene due to the banned use of methyl-tert-butyl ether.     

Highly Selective Dimerization and Trimerization of Isobutene to Linearly Linked Products by Using Nickel Catalysts

The unique linear linkage of isobutene to generate highly valuable C₈ precursors for plasticizers is feasible by using special nickel catalysts. (4‐Cyclooctene‐1‐yl)(1,1,1,5,5,5‐hexafluoro‐2,4‐acetylacetonato)nickel and aluminum‐alkyl‐activated nickel acetylacetonates produce isobutene dimers with high selectivities of up to 95 %. Moreover, selectivity for the head‐to‐head products (2,5‐dimethylhexenes) is remarkably high at up to 99 %. Additionally, novel C₁₂ isobutene trimers are also formed with a very high selectivity of up to 99 % for the linear linkage. The trimer structure (2,5,8‐trimethylnonenes) reflects the stepwise characteristic of the reaction mechanism. Pathways of insertion and activation and the deactivation processes of the catalyst are discussed in detail.     

Pyrolysis of methyl tert-butyl ether (MTBE). 2. Theoretical study of decomposition pathways

The thermal decomposition pathways of MTBE have been investigated using the G3B3 method. On the basis of the experimental observation and theoretical calculation, the pyrolysis channels are provided, especially for primary pyrolysis reactions. The primary decomposition pathways include formation of methanol and isobutene, CH4 elimination, H2 elimination and C-H, C-C, C-O bond cleavage reactions. Among them, the formation channel of methanol and isobutene is the lowest energy pathway, which is in accordance with experimental observation. Furthermore, the secondary pyrolysis pathways have been calculated as well, including decomposition of tert-butyl radical, isobutene, methanol and acetone. The radicals play an important role in the formation of pyrolysis products, for example, tert-butyl radical and allyl radical are major precursors for the formation of allene and propyne. Although some isomers (isobutene and 1-butene, allene and propyne, acetone and propanal) are identified in our experiment, these isomerization reaction pathways occur merely at the high temperature due to their high activation energies. The theoretical calculation can explain the experimental results reported in part 1 and shed further light on the thermal decomposition pathways.     

Aqueous suspension polymerization of isobutene initiated by 1,2-C6F4[B(C6F5)2]2

Lewis acidic, chelating diborane 1 forms stable oxonium acids 2 in the presence of excess MeOH or water. Diborane 1 is shown to be an effective co-initiator for the suspension polymerization of isobutene in aqueous media at sufficiently low temperatures. Poly(isobutene) or butyl rubber is obtained at moderate to high conversion and with Mw < 200 K and PDI approximately 2 under these conditions.     

热稳定性能良好的磺化聚醚砜酮催化剂

采用磺酸化的方法制备了一种热稳定性能良好的新型固体酸树脂催化剂——磺化聚醚砜酮树脂(S-PPESK),并应用在异丁烯的低聚反应中.S-PPESK在较低的温度条件下对异丁烯的低聚反应表现出了很高的催化活性和二聚反应选择性.对S-PPESK的热稳定性能采用预处理的方法进行了测试,结果显示它的预处理温度高达180 ℃,与商业磺酸树脂的预处理温度相比高出约40 ℃. S-PPESK在异丁烯的低聚反应中表现出了良好的催化活性、优良的二聚反应选择性和很好的热稳定性能,其应用前景广泛.     

Isobutene hydroformylation in catalytic systems based on rhodium compounds and polyelectrolytes

The catalytic properties of water-soluble systems based on rhodium complexes and polyelectrolytes in isobutene hydroformylation were studied. All of the catalytic systems exhibited an unexpectedly high activity under the conditions where homogeneous hydroformylation virtually did not occur in the presence of conventional rhodium catalysts. A stable catalytic system based on acacRh(CO)₂-PEG complex was proposed, allowing isobutene hydroformylation to be performed with a high activity under mild conditions. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 705–707, April, 1999.     

Beta沸石上合成对叔丁基苯酚和2,4—二叔丁基苯酚

首次在三相条件下,在Ｂｅｔａ沸石催化剂上研究了苯酚与异丁烯烷基化合成对叔丁基苯酚和２,４－二叔丁基苯酚。通过对Ｈｂｅｔａ沸石高温焙烧和吡啶中毒试验研究了烷基化反应活性和选择性的变化规律;用ＮＨ３－ＴＰＤ和Ｐｙ－ＩＲ测定了试样的酸量和酸种类,结果表明Ｈｂｅｔａ沸石具有很好的烷基化活性,苯酚的转化率可达９２％,经１１２３Ｋ焙烧后苯酚转化率为８８％,对叔丁基苯酚和２,４－二叔丁基苯酚的选择性分别为７０～７５％和１４～２０％,中等强度的Ｂｒｎｓｔｅｄ酸是苯酚与异丁烯烷基化反应的活性中心。粘合剂含量低于３０％对烷基化活性基本无影响     

Skeletal Isomerization of <Emphasis Type="Italic">n</Emphasis>-butenes over Solid Acid Catalysts

Conversion reactions of n-butenes over zeolites and amorphous catalysts have been investigated to deduce the factor that determines the selectivity for the skeletal isomerization producing isobutene. The effects of pore structure and acid site concentration on the selectivity for the skeletal isomerization are discussed on various catalysts. The pore structures of FER and CLI zeolites induce the distant locations of butene molecules, accelerating monomolecular skeletal isomerization. On the other hand, acid site concentration determines the preferred reaction path of n-butenes on amorphous catalysts. Oligomerization followed by cracking that produces various hydrocarbons is suppressed on the catalyst with low acid site concentration, resulting in high selectivity for isobutene. The feasibility of monomolecular skeletal isomerization on zeolites and amorphous catalysts is confirmed by its reversibility with high selectivity.     

Skeletal isomerization of butene over natural ferrierite

The conversion of butenes to isobutene was compared on chemically modified natural and synthetic H-ferrierite catalysts. The proper balance of extra-framework species together with properly chosen reaction conditions allowed 100% isobutene selectivity.     

MCM-49分子筛催化剂上1-丁烯的骨架异构化反应

 采用动态和静态水热合成法合成了不同Si/Al比的MCM-49分子筛,并考察了合成分子筛对1-丁烯骨架异构化反应的催化性能. 结果表明,除目的产物异丁烯外,主要副产物为丙烯和戊烯,产物中没有检测到C6以上的副产物. 异丁烯收率随着反应温度的升高、分子筛晶粒的增大和1-丁烯分压的降低而升高. NH3-TPD 结果表明,随着分子筛Si/Al比的增加,分子筛的酸中心数减少,导致副产物选择性下降,异丁烯选择性升高. 根据反应结果讨论了异丁烯及副产物形成的机理.     

异丁烷在钼酸锌上的催化氧化脱氢

研究了钼酸锌对异丁烷氧化脱氢反应的催化作用,考察了原料气中烷氧体积比、N₂及水蒸汽对反应结果的影响.提高反应原料气中的烷氧体积比能够提高异丁烯选择性,但也会降低异丁烷的转化率.原料气中加入N₂不利于反应;而加入水蒸汽可提高异丁烯选择性.催化剂表面主要是弱酸中心,对反应有利.     

CATALYTIC OXYDEHYDROGENATION OF ISOBUTANE OVER LITHIUM-BASED OXIDES

研究了一些锂基氧化物对异丁烷的催化氧化脱氢作用，其中Ｌｉ２ＳｎＯ３显示出优良的催化性质，Ｌｉ２ＭｎＯ３，ＬｉＦｅ５Ｏ８和ＬｉＡｌ５Ｏ８对异丁烯的选择性较差，而Ｌｉ２ＣｅＯ３，ＬｉＦｅＯ２和ＬｉＺｎＯ２在反应条件下不稳定。系列ＬｉＳｎＯ催化剂的ＣＯ２ＴＰＤ分析表明，当ＳｎＯ２转化为Ｌｉ２ＳｎＯ３时，在表面形成了碱中心，它有利于异丁烯从催化剂表面脱附。Ｏ２ＴＰＤ和Ｈ２ＴＰＤ结果表明，此时吸附的氧物种数量降低，异丁烯的深度氧化受到抑制。Ｌｉ２ＳｎＯ３中晶格氧物种的活性对异丁烷催化氧化脱氢可能是适宜的，但不利于深度氧化。     

异丁烯在Mo—Te氧化物催化剂上的脉冲反应研究

用IR和XRD法研究了Mo-Te氧化物催化剂结构与组成的关系。结果表明，该催化剂由MoO3和Te2MoO7组成，后者随Te加入量的增加而增加，考察了异丁烯在该催化剂上的脉冲反应活性，发现异丁烯转化率和甲基丙烯醛的选择性与Te2MoO7组分有关，反应可能包含丙种不同的氧物种。     

Room temperature olefins oligomerization over sulfated titania

Oligomerization reaction was carried out at room temperature using sulfated titania as catalyst. Total isobutene conversion was obtained with high stability for a long period of time. In case of deactivation, total reactivation of the catalyst was reached.     

甲基叔丁基醚(MTBE)的合成

介绍了甲醇、异丁烯合成甲基叔丁基醚的催化剂、热力学、动力学。综述了合成ＭＴＢＥ的主要原料异丁烯的生产过程，并总结了甲醇、异丁醇和甲醇、叔丁醇合成ＭＴＢＥ的研究开发进展。参考文献１６篇。     

Gas-Phase Synthesis of Ethyl tert-Butyl Ether (ETBE) on H-ZSM-5 Catalyst in Continuous Fixed-Bed and Fluidized-Bed Reactors

The gas-phase synthesis of ETBE from ethanol and isobutene has been carried out over a H-ZSM-5 catalyst in two types of continuous-flow catalytic reactors, fixed-bed and fluidized-bed. We have studied the influence of temperature, molar ratio ethanol/isobutene and weight hourly space velocity on the yield of ETBE.     

Adsorptive separation of isobutene and isobutane on Cu3(BTC)2

The metal organic framework material Cu3(BTC)2 (BTC = 1,3,5-benzenetricarboxylate) has been synthesized using different routes: under solvothermal conditions in an autoclave, under atmospheric pressure and reflux, and by electrochemical reaction. Although the compounds display similar structural properties as evident from the powder X-ray diffraction (XRD) patterns, they differ largely in specific surface area and total pore volume. Thermogravimetric and chemical analysis support the assumption that pore blocking due to trimesic acid and/or methyltributylammoniummethylsulfate (MTBS) which has been captured in the pore system during reaction is a major problem for the electrochemically synthesized samples. Isobutane and isobutene adsorption has been studied for all samples at different temperatures in order to check the potential of Cu3(BTC)2 for the separation of small hydrocarbons. While the isobutene adsorption isotherms are of type I according to the IUPAC classification, the shape of the isobutane isotherm is markedly different and closer to type V. Adsorption experiments at different temperatures show that a somewhat higher amount of isobutene is adsorbed as compared to isobutane. Nevertheless, the differential enthalpies of adsorption are only different by about 5 kJ/mol, indicating that a strong interaction between the copper centers and isobutene does not drive the observed differences in adsorption capacity. The calculated breakthrough curves of isobutene and isobutane reveal that a low pressure separation is preferred due to the peculiar shape of the isobutane adsorption isotherms. This has been confirmed by preliminary breakthrough experiments using an equimolar mixture of isobutane and isobutene.     

Acetone adsorption on hydroxylated silica gel: Correlation of sorption isotherms and IR spectra

The synthesis of MTBE from methanol and isobutene has been carried out over a ZSM-5 based catalyst, in two types of continuous flow catalytic reactors, fixed-bed and fluidized-bed. We have studied the influence of the molar ratio methanol to isobutene, the temperature and the weight hourly spatial velocity (WHSV) on the yield of MTBE.