Na-W-Mn-Zr-S-P/SiO_2催化剂上乙烷氧化脱氢反应

研究了甲烷氧化偶联六组分Na-W-Mn-Zr-S-P/SiO_2催化剂对乙烷氧化脱氢反应的催化性能.考察了不同原料气配比、温度和空速等条件下的催化剂活性.讨论了催化剂中S或P组分的含量对催化活性的影响.实验结果表明,S和P元素的加入可以提高催化剂的活性.660℃时六组分催化剂上乙烷的转化率为65.2%,乙烯的选择性为83.2%,此时得到的乙烯收率最高.乙烷与氧气比的增加有利于提高乙烯的选择性.较低反应温度时,空速的增加可以抑制碳氧化物(CO,CO_2)的生成,提高乙烯选择性.     

MoVTeNbOx催化剂应用于乙烷氧化脱氢制乙烯的研究进展

乙烷氧化脱氢制乙烯是非常有应用前景的乙烯生产途径，MoVTeNbO_x催化剂具有活性高、氧化还原能力强等特点，是当前低碳烷烃氧化脱氢的研究热点。本工作系统综述了MoVTeNbO_x复合金属氧化物在乙烷氧化脱氢制乙烯反应中的应用研究情况，包括催化剂晶相结构与活性中心、催化剂制备和催化乙烷转化的影响因素及反应性能优化提升等方面。研究多金属氧化物催化剂活性中心的调控策略，实现各组分氧化物相互作用的最优化，优化制备条件，通过助剂调控策略提高催化剂氧化还原能力及表面V⁵⁺含量，进而提高乙烷氧化脱氢活性和运行稳定性，为催化剂的规模化生产和工业应用奠定基础，是当前的主要研究方向。最后展望了MoVTeNbO_x复合金属氧化物催化剂在氧化脱氢领域的发展前景。     

乙烷催化氧化脱氢制乙烯研究进展

乙烯是一种重要的有机化工原料,它是衡量一个国家化学工业发展水平的指标之一。目前,乙烯生产方法有很多,其中乙烷氧化催化脱氢法过程简单,但反应温度高,能耗高。讨论乙烷氧化脱氢催化剂的研究进展,展望了发展前景。     

乙烷催化氧化脱氢制乙烯催化剂研究进展

介绍了目前几种乙烯的制备技术,认为使用乙烷催化氧化脱氢来制乙烯的方法较好.分析了乙烷催化氧化脱氢制乙烯机理,叙述了此方法反应过程中使用的4类催化剂,即过渡金属氧化混合物类、碱金属及碱土金属类、稀土类和贵金属类,分别介绍了它们的研究进展情况,其中过渡金属氧化催化剂中的氧化镍类在较低的反应温度下有较高的选择性,且原料来源丰...     

乙烷脱氢催化剂研究进展

乙烯是重要的有机化工原料,随着乙烯需求量的不断增加以及石油资源的日益匮乏,乙烷脱氢已成为乙烯增产的重要途径。乙烷脱氢制乙烯受到越来越多的关注,乙烷脱氢催化剂逐步改善。本文首先介绍了近年来国内外乙烷脱氢制乙烯的研究现状,然后从催化剂制备方法、性能以及应用等方面对乙烷催化脱氢催化剂和乙烷氧化脱氢催化剂的研究进行了总结,并对其进行了系统分类。催化脱氢是低碳烷烃转化为烯烃的有效途径,烯烃选择性高,受到热力学平衡限制,能耗较高。氧化脱氢由于氧化剂的引入打破了热力学平衡限制,能够有效抑制焦炭的生成,减少能量消耗。然而,深度氧化反应难于控制,乙烯的选择性低。因此,选取合适的催化脱氢催化剂,尽可能提高乙烷单程转化率、降低能耗是乙烷脱氢的关键。     

PtSn-Mg(Zn)AlO催化剂应用于乙烷脱氢反应研究

采用阴离子交换法合成了一系列不同Zn和Pt含量的PtSn-Mg(Zn)AlO催化剂用于乙烷脱氢反应。实验结果表明,在水滑石载体中掺杂少量的Zn对乙烷脱氢反应有明显影响。当Zn含量为2%（质量）时Pt基催化剂活性性能最优,在550℃时乙烷初始转化率达到27.1%,2 h平均转化率为21.6%。BET和SEM结果表明PtSn-Mg(Zn)AlO催化剂比PtSn-MgAlO催化剂比表面积更大,TEM结果显示,PtSn-Mg(Zn)AlO催化剂和PtSn-MgAlO催化剂的金属颗粒的平均直径分别为（1.49±0.31）nm 和（2.0±0.23）nm,说明Zn的掺杂在一定程度上改变了催化剂的结构,能减小Pt颗粒的尺寸,更好地分散Pt颗粒,从而改善乙烷催化脱氢反应性能。此外,考察温度对乙烷脱氢反应性能影响,发现温度越高乙烷初始转化率越高,但催化剂越易失活;考察Pt负载量对乙烷脱氢反应性能的影响,发现增加Pt含量并不能使乙烷转化率得到相应倍数的增加,即增加Pt含量反而使Pt的利用率降低了,因此适量降低PtSn-Mg(2-Zn)AlO催化剂中Pt含量对研究乙烷脱氢反应有深远意义。     

PtSn-Mg(Zn)AlO催化剂应用于乙烷脱氢反应研究

采用阴离子交换法合成了一系列不同Zn和Pt含量的PtSn-Mg (Zn) AlO催化剂用于乙烷脱氢反应。实验结果表明,在水滑石载体中掺杂少量的Zn对乙烷脱氢反应有明显影响。当Zn含量为2%(质量)时Pt基催化剂活性性能最优,在550℃时乙烷初始转化率达到27.1%,2 h平均转化率为21.6%。BET和SEM结果表明PtSn-Mg(Zn) AlO催化剂比PtSn-MgAlO催化剂比表面积更大,TEM结果显示,PtSn-Mg(Zn) AlO催化剂和PtSn-MgAlO催化剂的金属颗粒的平均直径分别为(1.49±0.31) nm和(2.0±0.23) nm,说明Zn的掺杂在一定程度上改变了催化剂的结构,能减小Pt颗粒的尺寸,更好地分散Pt颗粒,从而改善乙烷催化脱氢反应性能。此外,考察温度对乙烷脱氢反应性能影响,发现温度越高乙烷初始转化率越高,但催化剂越易失活;考察Pt负载量对乙烷脱氢反应性能的影响,发现增加Pt含量并不能使乙烷转化率得到相应倍数的增加,即增加Pt含量反而使Pt的利用率降低了,因此适量降低PtSn-Mg(2-Zn) AlO催化剂中Pt含量对研究乙烷脱氢反应有深远意义。     

乙烷氧化脱氢与乙酸乙烯酯的联合生产

正本发明涉及生产乙烯和醋酸乙烯(VAM)的集成方法,包括在第一反应区中在氧化脱氢催化剂存在下使包括乙烷和任选乙烯的气流与含氧气流接触。活性脱氢条件,以产生包括乙烷、乙烯、乙酸和水以及任选的其他化合物的第一产品流,在第一分离区中将所述第一产品流分离成包括乙酸和任选水和第     

煤氧化的基础研究

作者从反应化学的观点评述了在较高温度下煤的氧化反应。在气相反应中,煤主要经历与液相反应(自由基反应)完全不同的脱氢反应机     

乙烷催化氧化脱氢制乙烯反应及其催化剂的研究进展

综述了国内外有关乙烷氧化催化脱氢反应及其催化剂的研究工作     

Oxidative dehydrogenation of ethane over mixed metal oxide catalysts: Autothermal or cooled tubular reactor design?

A kinetic model consistent with experimentally measured reaction orders for the oxidative dehydrogenation of ethane (ODHE) over a MoVTeNbO catalyst is developed and applied to compare autothermal and multi-tubular reactor designs for the same. The results suggest that autothermal reactor configurations are more favorable compared to multi-tubular ones for this highly exothermic reaction, and become even more so with increasing active site density. A bifurcation analysis based on ignition and extinction behavior is presented as a function of adiabatic temperature rise (varied by altering the feed ethane to oxygen molar ratio) and catalyst active site density (varied by altering the pre-exponential factor), thereby providing additional insights into strategies for successful scale-up of ODHE reactors. These strategies for the design of viable reactor configurations may be more broadly applicable to high temperature catalytic partial oxidation reactions currently in practice or under consideration in the context of large-scale processes for chemical production.     

Acetylene formation during the catalytic oxidative dehydrogenation of ethane over Pt-coated monoliths at short contact times

Short contact time monolithic reactors have been examined for the production of ethylene by oxidative dehydrogenation over a supported Ptcatalyst. The results so far suggest that these reactors may revolutionize the way chemical synthesis is conducted, but many questions remain. This paper addresses the co-production of acetylene. Under some conditions, acetylene is produced as a by-product during the oxidative dehydrogenation of ethane. This acetylene formation appears to be due to homogeneous reactions since the acetylene production increases at higher reaction temperatures and under conditions where there is little available surface area for radical quenching. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of hydrogen combustion reaction on the dehydrogenation of ethane in a fixed-bed catalytic membrane reactor

A two-dimensional non-isothermal mathematical model has been developed for the ethane dehydrogenation reaction in a fixed-bed catalytic membrane reactor. Since ethane dehydrogenation is an equilibrium reaction, removal of produced hydrogen by the membrane shifts the thermodynamic equilibrium to ethylene production. For further displacement of the dehydrogenation reaction, oxidative dehydrogenation method has been used. Since ethane dehydrogenation is an endothermic reaction, the energy produced by the oxidative dehydrogena-tion method is consumed by the dehydrogenation reaction. The results show that the oxidative dehydrogenation method generated a substantial improvement in the reactor performance in terms of high conversions and significant energy saving. It was also established that the sweep gas velocity in the shell side of the reactor is one of the most important factors in the effectiveness of the reactor.     

Free-radical reactions involved in C1-C3 hydrocarbons interaction with oxide catalysts

Experimental proofs of a free radical mechanism in methane oxidative coupling, with homolytic rupture of the C---H bond are given. High concentrations of free radical sites are produced by mechanical milling of SiO₂. A study of C₁---C₃alkanes interaction with these sites allows to simulate the, processes of alkanes oxidation and oxidative dehydrogenation. The reactivity of ethane and propane is higher than that of methane in accordance with the Polanyi-Semenov rule. Oxidative dehydrogenation of ethane is studied on Cd-containing zeolites. CH₄, C₂H₆ and C₃H₈ oxidative dehydrogenation by O₂ or CO₂ is studied on a MNO/SiO₂ catalyst. The initiation of radical reactions of hydrocarbons on Cl-containing catalysts proceeds via chlorine atoms generation.     

Oxidative dehydrogenation of ethane over alkali‐metal doped sulfated zirconia catalysts

Alkali‐metal doped sulfated zirconia catalysts were tested for the oxidative dehydrogenation of ethane into ethene. The effects of metal precursor compounds and acidic anion promoters on the catalytic activity in this reaction were studied. It was found that sulfation of zirconia increases the selectivity of ethane towards ethene. Lithium‐, sodium‐, and potassium‐doped sulfated zirconia catalysts showed quite different activities in this reaction. Sulfated zirconia doped with lithium catalysts were found to be effective for the oxidative dehydrogenation of ethane, giving over 90% selectivity to ethene and 25% ethene yield at 650 °C. © 1999 Society of Chemical Industry     

Kinetics and mechanism of the oxidative dehydrogenation of ethane over Li/Dy/Mg/O/(Cl) mixed oxide catalysts

The microkinetic reaction network of the oxidative dehydrogenation of ethane to ethene over Li/Dy/Mg/O and Li/Dy/Mg/O/Cl catalysts was investigated. With Li/Dy/Mg/O catalysts, the reaction kinetics is compatible with a heterogeneous-homogeneous radical based reaction mechanism. The formation of ethyl radicals on the surface is concluded to be the rate-determining step. In contrast, the reaction kinetics for Li/Dy/Mg/O/Cl is in line with a purely surface catalyzed reaction mechanism. However, also in this case, alkane activation is rate determining.     

Kinetic modelling of the gas phase ethane and propane oxidative dehydrogenation

Gas phase thermal and oxidative dehydrogenation of ethane and propane are explored experimentally and mikrokinetically. Kinetic data for the elementary reactions postulated were adopted from the literature. The results show that oxygen plays a dominating role in the primary activation of the alkanes by producing an HO₂ and a hydrocarbon radical. The kinetic sequences developed predict satisfactorily conversion and products yields for ethane and propane oxidative dehydrogenation.     

逆水煤气变换耦合乙烷脱氢反应中载体对氧化铬催化剂性能的影响

研究了在逆水煤气变换耦合乙烷脱氢反应中担载型氧化铬催化剂的活性,考察了多种载体对于催化剂反应性能的影响。结果表明,不同的载体所担载的氧化铬催化剂具有不同的催化性能。其中二氧化硅担载的氧化铬催化剂具有较高的乙烷转化率和乙烯选择性,在700℃时分别达到30.7%和96.5%。CO₂的作用是通过与H₂反应促进乙烷脱氢、并减少催化剂表面积炭。运用XRD、TPR、 XPS、UV-DRS和微量吸附量热技术对催化剂体相与表面结构、表面酸性和铬物种价态等进行了表征,结果显示催化剂表面酸中心适当的强度、数量和分布有利于乙烷的活化和催化转化,Cr³⁺和Cr⁶⁺物种是反应的活性中心。     

The importance of heterogeneous and homogeneous reactions in oxidative coupling of methane over chloride promoted oxide catalysts

The formation of ethene from ethane and methane in a silica reactor has been studied both in the presence and in the absence of chloride-containing catalysts. Some homogeneous conversion of ethane to ethene occurs in the gas phase through direct dehydrogenation, oxidative dehydrogenation, and, when HCl is present, chlorine radical induced reactions. Methyl chloride is detected in the gas phase but has no influence on the conversion of ethane to ethene. It is shown that under typical catalytic conditions, when a chloride-modified catalyst is used, ethane is mostly produced in the catalyst bed.