异丁烷/丁烯烷基化分子筛催化剂的失活研究进展

分子筛催化剂在催化异丁烷/丁烯烷基化中具有良好的应用前景,但易失活,需频繁再生。系统总结分子筛催化剂在异丁烷/丁烯烷基化反应中的研究进展,认为烯烃低聚物覆盖活性位、堵塞分子筛孔道是催化剂失活的直接原因。论述了分子筛性能及烷基化反应条件对分子筛失活的影响,指出具有合适B酸强度和数量、易于丁烯低聚物脱附、利于扩散的分子筛催化剂是未来的研究方向。     

异丁烷/丁烯烷基化反应的固体酸催化剂研究进展

概述了沸石分子筛、固体超强酸、杂多酸、酸性树脂等常用的固体酸催化剂在异丁烷/丁烯烷基化反应中的应用,并对固体酸催化剂存在的问题和应用前景进行了展望。     

异丁烷与丁烯烷基化反应用新分子筛催化剂的研究

探讨了六方沸石分子筛催化剂对异丁烷与丁烯烷基化反应的催化活性。实验确定了烷基化反应的温度、反应时间、异丁烷与丁烯摩尔比及反应压力对丁烯转化率及目的产物Ｃ０８ 的选择性的影响。并对各种参数的影响进行了简要分析。在适宜反应条件下,丁烯的转化率达到９８％ ,对Ｃ０８ 的选择性接近９３ ％ 。还进行了催化剂的物性测定,利用红外光谱和ＴＰＤ 氨脱附表征了催化剂表面酸中心性质及酸强度。测定结果表明,该催化剂具有大的比表面积,较多的酸中心和较高的酸强度,因而对异丁烷与丁烯的烷基化具有较高的催化活性。     

异丁烷与丁烯烷基化反应用新分了筛催化剂的研究

探讨了六方沸石分子筛催化剂对异丁烷与丁烯烷基化反应的催化活性,。实验确定了烷基化反就的工,以应时间,异丁烷与丁烯尔比及反应压力对丁烯转化率及目的产物Ｃ＾０８的选择性的影响。     

离子液体催化异丁烷/丁烯烷基化反应的研究进展

简要介绍了用于异丁烷/丁烯烷基化反应的传统烷基化催化剂和固体酸催化剂的优缺点。阐述了离子液体的性质及其催化异丁烷/丁烯烷基化反应的可能。综述了用于异丁烷/丁烯烷基化反应的氯铝酸离子液体,包括常规氯铝酸离子液体催化剂、改性的氯铝酸离子液体催化剂和复合离子液体催化剂。同时指出了这些催化剂存在的问题。着重强调了非氯铝酸离子液体在催化异丁烷/丁烯烷基化反应中的优势特点及其最新研究进展。     

分子筛催化异丁烷与正丁烯烷基化反应性能

以Y、β、MCM-41和EU-1分子筛为活性组分制备异丁烷与正丁烯烷基化反应催化剂,并利用NH_3-TPD和N_2物理吸附-脱附对催化剂进行表征。结果表明,HY分子筛催化剂的总酸量最大,MCM-41分子筛催化剂的总酸量最小,Hβ和HEU-1分子筛催化剂总酸量适中,Hβ分子筛催化剂平均孔径最大,而大孔径有利于分子扩散。对分子筛催化异丁烷与正丁烯反应的催化性能进行研究,结果表明,Hβ分子筛催化剂的失活速率最低,正丁烯异构化率最低,生成的烷基化油辛烷值达85.2,对Hβ分子筛催化剂进行Pt元素改性后催化剂的失活速率降低。     

异丁烷丁烯烷基化工艺技术应用进展

介绍了氢氟酸烷基化、硫酸烷基化、离子液体烷基化、固体酸烷基化等异丁烷丁烯烷基化技术特点以及工业应用情况。分析指出尽管硫酸烷基化工艺存在废酸处理、设备腐蚀等问题,但就安全性和易操作性而言硫酸烷基化技术仍是现阶段生产烷基化油技术路线中最好的选择。复合离子液体在异丁烷丁烯烷基化反应中显示出比硫酸和氢氟酸更高的催化活性,是另一个可供选择的生产高质量烷基化油的技术路线。异丁烷丁烯固体酸烷基化技术相比于其他液体烷基化工艺从本质上实现了安全、环保,是未来异丁烷丁烯烷基化技术的发展方向。     

氟化铵改性HUSY分子筛催化异丁烷/1-丁烯烷基化反应的研究

利用氟化铵溶液对HUSY分子筛进行改性,采用扫描电镜、X射线衍射、N2吸附-脱附、NH_3-程序升温脱附等方法对改性前后分子筛的形貌特征、晶相结构、孔道结构和酸性等进行表征,并考察了氟化铵处理时间对分子筛催化异丁烷/1-丁烯烷基化性能的影响。结果表明,氟化铵改性后分子筛的基本骨架结构得以保持,比表面积和微孔孔容减小,介孔孔容增加,中强酸与弱酸量的比值增大。HUSY经氟化铵溶液处理5 min后,其异丁烷/1-丁烯烷基化性能大幅度提高。     

异丁烷丁烯烷基化工艺技术应用进展

介绍了氢氟酸烷基化、硫酸烷基化、离子液体烷基化、固体酸烷基化等异丁烷丁烯烷基化技术特点以及工业应用情况。分析指出尽管硫酸烷基化工艺存在废酸处理、设备腐蚀等问题,但就安全性和易操作性而言硫酸烷基化技术仍是现阶段生产烷基化油技术路线中最好的选择。复合离子液体在异丁烷丁烯烷基化反应中显示出比硫酸和氢氟酸更高的催化活性,是另一个可供选择的生产高质量烷基化油的技术路线。异丁烷丁烯固体酸烷基化技术相比于其他液体烷基化工艺从本质上实现了安全、环保,是未来异丁烷丁烯烷基化技术的发展方向。     

稀土La改性X分子筛催化异丁烷/丁烯烷基化反应

采用液相离子交换法,通过改变交换和焙烧次数制备了5种不同浓度稀土La改性的X分子筛催化剂,使用连续进料的固定床反应器评价其催化异丁烷/丁烯烷基化反应的性能,分析了分子筛物相结构的变化,考察了分子筛的酸性. 结果表明,催化剂制备过程对催化剂结构和性能影响显著,La3+改性后X分子筛结晶度下降,但酸度显著增强,随La3+交换次数增加,分子筛的B酸量增多,L酸量减少;5种催化剂中,焙烧前离子交换2次、焙烧后再交换3次、再焙烧所制催化剂催化性能最佳,丁烯的初始转化率为89.94%, C8收率可达66.71%,这归因于酸性增加加快了氢负离子转移,降低了碳正离子上发生重复烷基化的可能性,抑制了大分子生成. 反应温度和烯烃空速对反应影响显著,温度从80℃升至100℃,副反应裂解生成的C5?C7从9.64%增加到36.74%;丁烯进料空速从0.1 h?1降至0.05 h?1时,低聚生成的C9+从7.2%增至31%.     

Beta分子筛改性对催化苯和乙烯烷基化反应的影响

苯和乙烯烷基化反应是重要的乙苯生产途径,Beta分子筛是该过程的重要催化剂。苯和乙烯烷基化反应是一个酸中心催化过程,因此Beta分子筛的表面酸性与催化反应性能之间有密切联系。对工业Beta分子筛进行浸Mg、高温水蒸汽处理和高温焙烧等改性处理,考察改性方法对Beta分子筛酸性及催化苯和乙烯烷基化性能的影响,结果表明,浸Mg改性能增加分子筛总酸量,但酸强度降低,导致催化活性降低,苯和乙烯烷基化反应主要发生在分子筛强酸中心;高温水蒸汽处理后,分子筛酸强度分布基本不变,但总酸量降低,导致乙烯转化率降低;高温焙烧处理导致分子筛结晶度下降,催化活性下降。     

TUN, IMF and -SVR Zeolites; Synthesis, Properties and Acidity

The effect of synthesis conditions on the preparation and properties of three novel zeolites TUN, IMF, and -SVR was investigated and compared with MFI. X-ray powder diffraction, infrared spectroscopy, chemical analysis, sorption measurements, and scanning electron microscopy were employed to characterize the textural and chemical properties of these zeolites. FTIR spectroscopy in combination with pyridine as probe molecule was used to describe the type, concentration and acid strength of these zeolites. Zeolite -SVR was synthesized with Si/Al ratios higher than 100 in contrast with TUN and IMF having Si/Al ratios about 20–30, respectively. TUN, MFI and IMF zeolites exhibit similar concentrations of Brønsted and Lewis acid sites and also similar acid strength of Brønsted sites. In contrast, the presence of one vacancy/unit cell in the case of -SVR zeolite substantially changes its acidic properties. Generally, zeolites TUN and IMF exhibit similar acidic properties in terms of acid strength and Brønsted to Lewis acid site ratio like MFI and due to their slightly larger pores higher activities in catalytic reactions are expected.     

A study on the dimerization of 1-butene over Beta zeolite

New restrictions on gasoline in some part of the world implies that oxygenates such as MTBE and aromatics should be replaced by other high-octane components. The dimerization of 1-butene, which is a step in the production of “Green” gasoline, is evaluated under liquid phase reaction conditions over acidic Beta zeolites synthesized with different synthesis time. There are substantial differences between Beta zeolites obtained at synthesis times 96 and 240 h leading to different physico-chemical properties and, furthermore, catalytic performances. More acidic Beta zeolites lead to higher yields to light olefins while less acidic samples produce more oligomers, i.e. C₁₂–C₁₄ fraction. Interestingly, it was also observed that strong acid sites catalyze cracking reactions, while the weak ones, oligomerization.     

Isobutane/1-butene alkylation on LaNaY catalysts modified by alkali and alkaline-earth cations

The effect of incorporating alkali and alkaline-earth cations into La exchanged NaY zeolites on the alkylation of isobutane with 1-butene has been investigated. The strength of the acid sites of the LaMNaY (M = Group I A and Group II A elements) catalysts do not change significantly, while the density of acidic sites decrease in the order of Na > K > Rb > Cs in the alkali Group I A elements and Ba > Mg > Ca > Sr in the alkaline-earth Group II A elements. The LaBaNaY catalyst has a higher density of acid sites than expected based on the electronegativity of Ba among the Group II A elements . A higher yield of alkylation and oligomerization products and also a higher amount of carbonaceous deposit were observed on the LaMNaY catalysts with a lower density of acidic sites except for LaBaNaY . Thermal gravimetric and differential thermal analysis indicate that the carbonaceous material could be located on the pore mouth and inside the pores of the zeolite. The carbonaceous material on the pore mouth can be desorbed before 300°C, while that in the zeolite pore is more difficult to be removed and a series of reactions such as dehydrogenation, aromatization and polymerization may take place during a temperature-programmed oxidation process. The diffusion of oligomerization products from the zeolite pore appears to be a slow step. The accumulation of these products in the zeolite pores is believed to be the main factor for the catalyst deactivation.     

The Role of Acid Strength of Zeolites in Liquid-Phase Alkylation of Benzene with Ethylene

The role of acid strength of zeolites in liquid-phase alkylation of benzene with ethylene was studied over β, MCM-22, and USY zeolites by means of adsorbing NH₃ at different temperatures. The strong acid sites are active centers, while the weak acid sites are inactive. The selectivity behavior of the strong acid sites varies with the relative acid strength as well as the types of the zeolites.     

Study of the conversion of aromatic hydrocarbons on EMT-type zeolite: Influence of the partial substitution of Al by Ga

(Al,Ga)EMT-type zeolites (Al:Ga = 1:0, 0.75:0.25 and 0.5:0.5) were prepared and tested as catalysts in the gas-phase toluene–methanol alkylation and toluene–trimethylbenzene transalkylation. Various techniques including XRD, N₂ sorption, MAS NMR and SEM were used to monitor the physico-chemical properties of these solids. The results revealed a high purity and crystallinity of the materials, and that the Ga atoms are entirely incorporated into the framework. The ammonia TPD measurements indicated that the isomorphous substitution of aluminium by gallium leads to a decrease of both acidic strength and acid sites concentration. The catalytic performances of the EMT-type solids in the conversion of methylaromatic hydrocarbons were correlated with their acid properties. Thus, the less acidic (Al,Ga)EMT samples exhibited a lower activity, but a higher selectivity towards the xylenes formation by comparison with (Al)EMT.     

NMR Study on the Acidity of TS-1 Zeolite

The acidic properties of TS-1 and Silicalite-1 zeolites have been investigated by the solid-state MAS NMR technique capable of in situ sample pretreatment. As shown by a combination of the ³¹P MAS NMR and ¹H MAS NMR techniques with trimethylphosphine, not only Brønsted acid sites but also Lewis acid sites exist in the TS-1 zeolites. Moreover, TS-1 zeolite is more acidic compared with Silicalite-1. The ¹H, ²⁹Si MAS NMR spectra and the resonance related to Brønsted acid species in the ³¹P MAS NMR spectra demonstrate clearly that the presence of titanium in the framework results in the formation of a new hydroxy group, titanols, which is more acidic than silanols of Silicalite-1. The ³¹P MAS NMR measurements also illustrate convincingly the existence of at least two different Lewis acid species on the TS-1 zeolites. The conversion of propylene oxide into methoxypropanol catalyzed by TS-1 or Silicalite-1 zeolite in methanol solution as a test reaction has also been described. With the increase of titanium in zeolite, TS-1 appears to have a higher activity during the reaction of propylene oxide to methoxypropanol.     

Reduction of nitrogen dioxide by propene over acidic mordenites: influence of acid site concentration, formation of by-products and mechanism

The reduction of nitrogen dioxide to nitrogen by propene was studied over a variety of acidic mordenite zeolites differing in their Si : Al ratio and thus, in their concentration of acid sites. The formation of by-products was monitored applying an ion–molecule reaction (IMR) mass spectrometer. It was found that at fixed conditions the yield of nitrogen increases with increasing concentration of acid sites, confirming that acid sites are the active catalytic centres in the reaction. Apart from nitrogen and nitric oxide, acrylonitrile and ammonia are formed as nitrogen containing gas-phase products in the reaction. In separate experiments, it was shown that acrylonitrile is hydrolysed by water over the acidic zeolites to yield ammonia and acrylic acid. When acrylonitrile is used as reducing agent for nitrogen dioxide, formation of nitrogen is strongly enhanced in the presence of water. Water also has a promoting effect on the formation of nitrogen in the reaction between nitrogen dioxide and propene. Acrylonitrile and its product of hydrolysis, ammonia, are considered to be intermediates of nitrogen dioxide reduction to nitrogen by propene over acidic zeolites.     

稀土杂原子沸石合成条件对甲苯烷基化反应的影响

利用硝酸镧、硅酸和硫酸铝为原料，用正丁胺作模板剂合成［La］-AlZSM-5沸石。XRD和晶胞参数测定表明, 镧原子进入沸石骨架,部分取代了铝原子。考察了不同合成条件对甲苯烷基化反应的影响。实验结果表明，在凝胶碱度较低,晶化时间80 h,模板剂C₄H₁₁N/SIO₂为0.045条件下,合成的沸石催化剂性能最佳。［La］-AlZSM-5沸石催化剂具有很高的活性和选择性。当甲苯转化率为21.07％时,对乙基甲苯选择性达94.81％。