钌催化剂上苯加氢制环己烯的影响因素

综述了钌催化剂上苯选择性加氢的反应机理、催化剂制备过程中前躯体、制备方法、载体、添加剂(水,有机添加剂,无机添加剂)对催化剂催化性能的影响和反应过程中温度、压力、搅拌速率、催化剂用量及反应时间等对苯转化率、环己烯选择性和环己烯收率的影响。     

钌催化苯选择加氢制环己烯的研究进展

介绍了钌催化苯选择加氢制环己烯这一经济、安全、高效的环己烯制备新工艺的研究进展,着重介绍了液相法苯选择加氢制环己烯钌系催化剂的研究及其对苯液相选择加氢制环己烯反应的各种影响,指出钌催化刘应用于苯液相选择加氢制环己烯一般选择反应温度为150℃～190℃,压力4MPa～5MPa,加入助催化剂及添加剂可以提高环己烯的收率．钌催化苯液相选择加氢制环己烯的反应是一个非常复杂的四相(水、气、油、固)反应体系,对这个四相复杂反应体系的深入研究,有助于找出加快环己烯从催化剂表面脱附的方法,进一步提高环己烯的收率．     

环己烷气相氧化脱氢催化剂的研究进展

为了尽可能多地获得环己烯和充分利用苯选择加氢反应的副产物环己烷,环己烷氧化脱氢反应在近 20 年内得到迅速发展.环己烷氧化脱氢反应催化剂体系的选择对于获得较高的环己烯产率和选择性、较低的氧化脱氢反应温度以及最优的反应路径尤为重要.详细阐述了阳离子沸石催化剂、复合金属氧化物催化剂以及贵金属丝网催化剂等在环己烷氧化脱氢制取...     

用催化剂表面修饰以进行苯选择加氢制环己烯的研究

1 前言常规的气相苯催化加氢反应,苯环大π键一经打开就全部加氢到底,产物中只能获得环己烷而极难得到选择加氢产物环己烯。生成环己烷的反应从热力学上看远比生成环己烯的反应容易进行很多,并且环己烯也非常容易进一步加氢生成环己烷。但催化剂的表面经修饰剂作用后可根本改变其性能,从而改进催化活性及选择性,或实现常规方法不可能实现的反应,获得不易得到的产物。在经表面修饰的催化剂上进行苯加氢反应可获得选择加氢产物环     

苯选择加氢制环己烯在钌基催化体系中的技术进展

环己烯是一种非常重要的有机化工原料,苯选择加氢制环己烯是获取高产量环己烯的最佳途径。长期以来科研工作者们都致力于开发出具有高选择性高收率制环己烯的钌基催化反应体系,然而环境因素使其在工业上大规模应用受到了限制,因此有必要对该领域进一步的深入研究。绿色催化是当下研究的热点之一,开发具有负载少钌且无需反应添加剂的高亲水性催化剂的这一趋势在今后的绿色化学发展中势必加强,因此苯选择加氢制环己烯的技术开发是一项极富有经济意义与科研挑战性的课题。本文从苯选择加氢的反应工艺技术、发展历程、钌基催化剂的反应体系组成以及反应机理等方面,系统介绍了苯选择性加氢制备环己烯的技术进展。     

Selective hydrogenation of benzene to cyclohexene catalyzed by Ru supported catalysts: Influence of the alkali promoters on kinetics, selectivity and yield

The selective hydrogenation of benzene to cyclohexene in the presence of Ru supported catalysts has been investigated in a tetraphase slurry reactor at 423 K, at 5 MPa of pressure, in the presence of two liquid phases: benzene and an aqueous solution of ZnSO₄ (0.6 mol l⁻¹). A study of the influence of the transport phenomena on the reactivity of the catalyst has been carried out. But no correlation between Carberry and Wheeler–Weisz numbers and the selectivity of the catalysts has been found. The main features of the catalysts are the strong dependence between the catalysts preparation procedure and their activity and selectivity. The best results have been observed with Ru/ZrO₂ catalysts. The influence of the bases employed in the precipitation of the catalysts precursor has also been investigated. KOH is the most effective, yield of 41% and initial selectivity of 80% of cyclohexene has been observed.     

Efficient catalysts with controlled porous structure obtained by anodic oxidation under spark-discharge

The anodic oxidation under spark discharge (ANOF technique) is presented as a promising alternative for the preparation of catalytic oxide layers on metallic supports. The influence of the substrate (Al, Ti, and Mg), electrolyte composition and the treatment time to obtain egg-shell catalysts with tailor-made properties for the effective oxydehydrogenation (ODH) of cyclohexane to cyclohexene is studied. Chromium, molybdenum and nickel were chosen as precursors for active species in order to obtain catalysts able to perform the substrate oxidation by electrophilic (chromium oxide), nucleophilic (molybdena) or both kind of oxygen species (nickel oxide). It was found that compared to nickel oxide, the chromium oxide containing egg-shell catalyst was less selective while the molybdenum oxide showed very high selectivity, but lower activity. The intrinsic activity of nickel containing egg-shell catalysts is an order of magnitude higher than that of a classic alumina supported nickel oxide catalyst obtained by impregnation. The selectivity to the intermediate cyclohexene is also favored on the egg-shell catalyst with a regular pore structure. Moreover, the selectivity performance of the catalysts can be improved by designing catalysts with shorter pores.     

钼磷酸催化环己醇脱水制备环己烯

研究了钼磷酸催化环己醇脱水制备环己烯的反应,考察了不同催化剂、催化剂用量、反应温度、反应时间、重复使用的催化剂对反应的影响。结果表明,环己醇用量20 g,钼磷酸用量为环己醇的1%,在190~200℃反应50 min时,环己烯收率达83.4%,催化剂可重复使用。     

C6~C8烯烃水合催化剂的研究进展

环己烯、正己烯、正辛烯等C₆~C₈烯烃是重要的化工原料,用途广泛。综述了环己烯及正己烯,正辛烯等C₆~C₈烯烃水合催化剂的研究进展。环己烯水合法制备环己醇是一种绿色制备工艺,其催化剂由最初的硫酸、磺酸等均相催化剂逐渐向分子筛等非均相催化剂过渡,其中HZSM-5分子筛以其高选择性、高活性成为工艺上常用的催化剂。环己烯间接水合法合成环己醇的途径具有高选择性,高转化率,低能耗的优点,其催化剂的研究也处在一个高速发展阶段。正己烯、正辛烯水合催化剂的研究较少。未来离子液体等新型水合催化剂将会成为环己烯水合制备环己醇的研究重点。     

席夫碱钼(Ⅵ)配合物催化合成环氧环己烷

以合成的水杨醛缩2-氨甲基吡啶席夫碱钼配合物([MoO_2(L_1)(EtOH)])、邻羟基苯乙酮缩2-氨甲基吡啶席夫碱钼配合物([MoO_2(L_2)(EtOH)])、2-吡啶甲醛缩邻氨基酚席夫碱钼配合物([MoO_2(L_3)(EtOH)])为催化剂,研究了叔丁基过氧化氢(TBHP)作氧化剂时3种配合物在制备环氧环己烷中的催化活性。3种席夫碱配合物中[MoO_2(L_3)(EtOH)]的催化活性最高。详细考察了反应时间、温度、催化剂用量、氧化剂用量对环己烯转化率、环氧产物选择性的影响,筛选出了席夫碱钼催化剂最佳的反应条件:70℃,10 mg[MoO_2(L_3)(EtOH)],n(环己烯)∶n(叔丁基过氧化氢)=1∶2,反应5 h,环己烯的转化率为77.2%,环氧环己烷选择性99%,产率为77.2%。催化剂重复使用性实验表明,该席夫碱配合物具有较高的稳定性。     

苯部分加氢制环己烯钌基催化剂研究进展

环己烯是重要的化工原料及中间体,广泛应用于合成纤维及其他工业领域。介绍了苯部分加氢制环己烯的技术路线,该技术路线具有安全环保和节能高效的特点,其中,催化反应体系是该技术的关键要素。重点概述了近年来对液相苯部分加氢催化体系中钌基催化剂的研究,包括催化剂前驱体、催化剂制备方法、载体、助催化剂以及添加剂对催化剂性能和产物选择性等的影响。介绍了已工业化的旭化成和神马集团的苯部分加氢工艺。环己烯的市场前景广阔,苯部分加氢工艺是一条经济效益高的工艺路线,实现催化体系的突破对于该工艺至关重要,但存在催化剂成本高、易失活和环己烯收率低的问题。     

Selective hydrogenation of benzene to cyclohexene using a suspended Ru catalyst in a mechanically agitated tetraphase reactor

The reactivity on unsupported Ru based catalyst in benzene selective hydrogenation to cyclohexene has been studied. The reaction has been carried out in a tetraphase slurry reactor at 423 K, at 5 MPa, in the presence of two liquid phases: benzene and an aqueous solution of ZnSO₄ 0.6 mol l⁻¹. A detailed study of the influence of the transport phenomena on the reactivity of the catalyst has been carried out. No correlation has been found between the characteristic numbers of Weeler–Weisz and of Carberry mass transport at external liquid/solid interface or into the catalyst pores for both benzene and hydrogen and the selectivity of the catalyst. The main features of the catalysts are the strong dependence between the catalysts preparation procedure and their activity and selectivity. In particular the influence of the alkaline or the earth alkaline hydroxide, employed in the precipitation of the Ru precursor, on the selectivity, has been studied. Hydrogen chemisorption measurements indicate that the amount of weakly adsorbed hydrogen depends on the nature of the base employed in the precipitation step.     

Synthesis, characterization of high Ti-containing Ti-MCM-41 catalysts and their activity evaluation in oxidation of cyclohexene and epoxidation of higher olefins

A series of titanium rich isomorphous substituted Ti MCM-41 and HMS materials have been synthesized with different Si/Ti ratios. The highest amount of Ti incorporated in synthesis gel is in TiMCM-41 (Si/Ti = 10). Whereas for TiHMS catalysts, Ti is incorporated up to Si/Ti = 50 successfully without forming any extra framework TiO₂. Cyclohexene epoxidation reaction with dry tert-butyl hydroperoxide (TBHP) as an oxidant has been studied to evaluate the catalytic properties of Ti substituted mesoporous catalysts. The effect of molar ratio of substrate:oxidant in this reaction has been studied and high conversion, high selectivity were achieved at 2: 1 molar ratio with TiMCM-41 (Si/Ti =25). Dry TBHP (in dichloromethane) and chloroform were found as good oxidant and solvent system for this reaction. Pure siliceous mesoporous silica and low `Ti' substituted mesoporous silicas were found to be efficient catalysts for oxidation of cyclohexene. An interesting variation of the selectivity from allylic oxidation to epoxidation during oxidation of cyclohexene was observed with an increase in the Ti amount in the mesoporous framework. The allylic oxidation of cyclohexene has been carried out using molecular oxygen as an oxidant and in the presence of a small amount of TBHP as initiator. Siliceous HMS materials gave better conversion compared to MCM-41 type of materials and other conventional silicas like silica gel, fumed silica etc. in allylic oxidation of cyclohexene. Epoxidation of higher cyclic olefins like cyclooctene, cyclododecene, cis-cyclododecene and linear olefins 1-Heptene, cis-2-hexene, 1-undecene was carried out over TiMCM-41 (Si/Ti = 25). Ti substituted mesoporous catalysts were characterized by elemental analysis, XRD, FTIR, UVDRS, ²⁹SiMASNMR, BET surface area and pore size distribution techniques.     

Photocatalytic cyclohexane oxidehydrogenation on sulphated MoOx/γ-Al2O3 catalysts

The photocatalytic oxidative dehydrogenation of cyclohexane on sulphated MoO_x/γ-Al₂O₃ catalysts has been studied in a two-dimensional fluidized bed photoreactor. The influence of Mo loading at similar sulphate content and the effect of catalyst preparation method have been investigated.Considering the influence of Mo loading at similar sulphate content, the highest photoactivity at 2.4 SO₄ wt% was found at MoO₃ loading of 8 wt%. Selectivity to cyclohexene was 100%, irrespective of the Mo content.At fixed MoO_x content, in particular at 50% of theoretical monolayer coverage, the preparation method of catalysts strongly affected the photocatalysts performances, showing in addition a slight decrease in selectivity to cyclohexene due to side-production of benzene. All the catalysts showed a similar equivalent band gap energy. Thermogravimetric analysis evidenced the presence of surface sulphate species of different thermal stabilities. A linear correlation of photoactivity with the surface sulphates amount of lower thermal stability has been found for all sub-monolayer MoO_x sulphated catalysts. The neighboring of surface sulphates to octahedral polymolybdate species appears to be a key parameter for the photoactivity of the catalysts.The catalyst selectivity was related to surface acidity. Higher acidity resulted in increased cyclohexene dark adsorption and consequently in enhanced benzene formation.     

阳离子交换树脂催化合成丙烯酸环己酯

以丙烯酸和环己烯为原料,磺酸基苯乙烯系强酸性阳离子交换树脂为催化剂合成丙烯酸环己酯,考察了反应温度、催化剂用量、烯酸摩尔比、反应时间对酯化反应的影响.结果表明,合成丙烯酸环己酯的最佳条件为:反应温度85℃,催化剂质量分数5%,n(酸)∶n(烯)=2∶1,反应时间5h.在最佳工艺条件下,环己烯转化率为87.2%,丙烯酸环...     

苯选择性加氢Ru/TiO_2催化剂载体晶型效应研究

以不同晶型的TiO_2为载体采用化学还原浸渍法制备了三种Ru/TiO_2催化剂,并利用X射线衍射(XRD)、N_2吸附-脱附、透射电镜(TEM)、NH_3程序升温脱附(NH_3-TPD)和傅里叶变换红外光谱(FTIR)等表征手段研究了催化剂的物理化学性质,考察了其在苯选择性加氢反应中的催化性能。结果表明:苯选择性加氢活性与Ru/TiO_2催化剂的Ru粒子分散度有关,Ru粒子分散度越高,催化活性越高;而环己烯选择性与Ru/TiO_2催化剂的酸量呈负相关,Ru/TiO_2-P催化剂的酸量最低,对环己烯的吸附量最低,在相同转化率下苯加氢生成环己烯的选择性最高。动力学分析表明,苯加氢生成环己烯的反应速率常数(k_1)与环己烯加氢生成环己烷的反应速率常数(k_2)的比值与环己烯收率呈近似正相关。     

PS负载acac系列钼配合物的合成、表征及其催化性能

以二乙烯苯交联的大孔聚苯乙烯树脂(PS)为载体,首次制备了高分子配体PS-(OCH2CH2)n-acac(n=0,1,2),并在其上组装入了Mo活性中心而成为催化剂--PS-(OCH2CH2)n-acac-Mo(n=0,1,2);用红外光谱分别对高分子配体及催化剂的结构进行了表征.XPS表征证实催化剂中钼以Mo(Ⅵ)价态存在,此外还对催化剂可能存在的结构进行了分析.实验检测了PS-(OCH2CH2)n-acac-Mo (n=0,1,2)在以n(t-BuOOH)=0.1 mol计,n( (◇)):n(t-BuOOH)=3:1,溶剂用量～10 mL,反应温度～80℃,时间～60 min条件下的催化性能.结果表明,在大孔PS载体上,活性组分与载体间增加2个-(OCH2CH2)-距离的臂长,对催化剂催化性能无明显影响;PS-(OCH2CH2)n-acac-Mo催化剂(n=0,1,2)催化环己烯环氧化活性和选择性优异,其中以PS-acac-Mo催化剂最优,环氧环己烷收率在99.5%以上.用于环己烯环氧化反应经循环使用5次后,t-BuOOH转化率仍高达99%以上,催化选择性并未发现明显减低,仍保持在99%以上.     

Effect of the support on the selective hydrogenation of benzeneover ruthenium catalysts. 1. Al2O3 and SiO2

The effect of the support on the liquid phase selective hydrogenation of benzene to cyclohexene over Ru catalysts was studied. Catalysts were prepared using RuCl₃ as precursor and characterized by hydrogen chemisorption, XPS and TPR. The reaction was carried out at 373 K and 2 MPa using a stirred tank reactor. It was found that the catalytic activity is not influenced by the Ru dispersion. More electron-deficient Ru species are present on Al₂O₃ than on SiO₂. The electronic state of Ru affects the selectivity to cyclohexene.     

Epoxidation of Cyclohexene with Air over the Composite Catalysts of Mn-mont Coordinated with Ligands

The catalytic activity of the composite catalysts of Mn-mont (where mont represents montmorillonite) coordinated with ligands for the epoxidation of cyclohexene by air under Mukaiyama conditions was studied. The composite catalysts were characterized by atomic absorption spectroscopic analysis, elemental analysis, fourier transform infrared spectra, diffuse reflectance ultraviolet visible spectra, X-ray photoelectron spectroscopy, powder-X-ray-diffraction, and scanning electron microscopy measurements. The effects of various reaction conditions on the catalytic reaction were studied. Experimental results indicated that the catalysts performed excellent activity for the epoxidation of cyclohexene by air. Repeated runs indicate that the catalyst is stable for 3 cycles. The composite catalysts of Mn-mont coordinated with ligands are economical and environmentally friendly for the epoxidation of cyclohexene.     

环己醇催化脱水制环己烯WO3/MxOy催化剂的研究

分别以SiO₂、γ-Al₂O₃和TiO₂为载体，偏钨酸铵为WO₃前驱体，等体积浸渍法制得WO₃质量分数为12%的WO₃/SiO₂、WO₃/γ-Al₂O₃和WO₃/TiO₂三种催化剂，考察了环己醇脱水制备环己烯的催化剂活性和选择性。采用X 射线衍射、N₂吸附、NH3程序升温脱附和CO₂程序升温脱附等手段对催化剂进行表征，并与催化活性、选择性及稳定性关联。结果表明，催化剂平均孔径大，有利于降低反应物和产物的内扩散阻力，可提高环己醇转化率和环己烯选择性；孔径大小相近的前提下，酸中心量大有利于脱水反应的进行，可提高环己醇转化率；催化剂表面碱强度大、碱中心数多，有良好的抗积炭性能，因而催化剂的稳定性较好。负载WO₃质量分数为12%的WO₃/TiO₂催化剂在反应温度170 ℃和环己醇空速2.7 h^-1的条件下，环己醇转化率可达100%，环己烯选择性可达97%以上，具有良好的稳定性。