CO2氛围中低碳烷烃制烯烃催化剂的研究进展

CO₂作为温和的氧化剂有效抑制了低碳烷烃催化转化过程中深度氧化的发生,然而其广泛应用还依赖于高效、高稳定性催化剂的研究与开发。本文就近年来国内外有关利用CO₂作为氧化剂在低碳烷烃催化转化反应方面的研究成果进行了综述,主要涉及甲烷氧化偶联制乙烯和乙烷催化剂;乙烷氧化脱氢制乙烯催化剂、丙烷氧化脱氢制丙烯催化剂和丁烷氧化脱氢制丁烯催化剂,分析讨论了CO₂作为氧化剂的作用和作用机制,并提出了研究展望。     

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。     

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。     

催化乙烷脱氢制乙烯催化剂研究新进展

乙烷蒸汽裂解过程能耗高,并排放大量CO_2和NO_x,亟待开发乙烷制备乙烯的新反应途径。近年来美国页岩气的大量开采提供了丰富的乙烷资源。通过选择性活化C-H键将乙烷直接转化为高附加值的乙烯产品是页岩气资源高效利用的新途径。本文综述了催化乙烷脱氢制乙烯催化剂研究的最新进展,介绍了近年来催化乙烷脱氢制乙烯的催化剂研究进展,并详述了反应机理,最后对未来研究前景进行了展望。     

丙烷制丙烯制备技术及安全性分析

低碳烷烃催化转化制烯烃一直是石油化工领域的研究热点，它将成为新世纪石油化工技术研究开发的重点之一。其中乙烷脱氢制乙烯、丙烷脱氢制丙烯是两个主要的研究方向。但是，乙烷催化脱氢反应条件苛刻，能耗高，反应严格地受到热力学平衡的限制，就目前催化剂水平，c：（乙烯和乙烷）单程收率只能在25％左右徘徊，离工业化甚远，     

Cr/SSZ-13催化二氧化碳氧化乙烷脱氢反应的研究

通过脱氢反应将低碳烷烃转化为同碳数的烯烃是烷烃高值化利用和烯烃原料多元化的重要途径。烷烃氧化脱氢制烯烃的反应具有不受反应平衡限制、积炭少、反应温度低等优点,一直是研究的热点。通过利用浸渍法制备不同铬（Cr）负载量的Cr_x/SSZ-13系列催化剂,采用氮气物理吸附、氨程序升温脱附（NH₃-TPD）、二氧化碳程序升温脱附（CO₂-TPD）、氢气程序升温还原（H₂-TPR）、紫外-可见吸收光谱（UV-Vis）以及高角度环形暗场-扫描透射电镜（HAADF-STEM）与耦合能谱分析（EDX-Mapping）等方法对催化剂进行了物性表征,并用微型固定床反应器评价催化剂对乙烷氧化脱氢制乙烯的催化性能,最终建立了Cr/SSZ-13催化剂的构效关系。研究发现,当n（二氧化硅）/n（氧化铝）=10时,Cr_1.5/SSZ-13-10催化剂上含有丰富的Cr³⁺物种,其中配位不饱和Cr³⁺是优异的脱氢活性位,有利于二氧化碳氧化乙烷脱氢反应的进行。因此,Cr_1.5/SSZ-13催化剂在650 ℃时表现出优异的催化性能,即二氧化碳转化率和乙烷转化率分别达到26.41%和53.2%,乙烯产率为38.83%。     

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...     

逆水煤气变换耦合乙烷脱氢高选择性制备乙烯反应的研究进展

综述了近年来国内外有关利用逆水煤气变换耦合乙烷脱氢制备乙烯反应的研究状况,讨论了该反应的历程和机理。文献表明,担载型铬氧化物、含铬分子筛、纳米氧化物粒子等具有较好的催化活性,CO2的主要作用是通过逆水煤气变换来消除乙烷脱氢产物H2,并与表面积炭反应提高乙烷转化率及催化剂稳定性。反应的关键是选择适宜的催化剂。     

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.     

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。     

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.     

Oxidative Dehydrogenation of Ethane Over Zirconia‐Supported Lithium Chloride Catalysts

A series of Li‐doped catalysts on zirconia or sulfated zirconia were prepared and investigated in the catalytic reaction of ethane oxidative dehydrogenation into ethylene. It is found that zirconia and sulfated zirconia supports prepared by different methods show varying nature and thus influence the catalytic performance of their supported Li catalysts in this reaction. Li catalysts doped on the sulfated zirconia prepared by a two‐step method can exhibit high ethane conversion, selectivity towards ethylene and ethylene yield as well as a stable catalytic performance. The Li precursors also affect the catalytic behavior. LiCl doped on sulfated zirconia can give high ethane conversion and ethylene selectivity. Addition of transitional and lanthanide metal oxides to the LiCl/SZ system significantly improves the activity and yield of ethylene in the oxidative dehydrogenation of ethane. Among the oxides studied, NiO and Nd₂O₃ demonstrate the best promoting effect in terms of catalytic conversion and ethylene yield.     

国内外乙烯生产工艺的研究现状与展望

通过介绍乙烷脱氢,催化裂解,甲烷氧化偶联和甲醇转化及生物质乙醇脱水制乙烯等方法,阐述了乙烯制备的工业进展,并与传统催化裂解方法相比较,说明了其优缺点;分析了生物质乙醇脱水制乙烯原理与方法,生物质乙醇的来源,与其脱水制乙烯的优点以及国内外研究现状和发展前景。     

负载型杂多酸催化乙烷氧化脱氢反应的起燃特性

研究了负载在SiO₂ 上的杂多酸催化剂的乙烷氧化脱氢活性 .发现在乙烷氧化脱氢反应中存在一个活性起燃温度 ,当反应温度高于此温度时 ,反应以气相自由基反应为主 .杂多酸的酸性与乙烷在杂多酸表面的吸附有关 ,酸性越强 ,引发自由基反应的起燃温度越高     

Optimization of ODHE membrane reactor based on mixed ionic electronic conductor using soft computing techniques

This work presents the optimization of the operating conditions of a membrane reactor for the oxidative dehydrogenation of ethane. The catalytic membrane reactor is based on a mixed ionic–electronic conducting material, i.e. Ba_0.5Sr_0.5Co_0.8Fe_0.2O_δ−3, which presents high oxygen flux above 750 °C under sufficient chemical potential gradient. Specifically, diluted ethane is fed into the reactor chamber and air (or diluted air) is flushed to the other side of the membrane. A framework based on Soft Computing techniques has been used to maximize the ethylene yield by simultaneously varying five operation variables: nominal reactor temperature (Temp); gas flow in the reaction compartment (QHC); gas flow in the oxygen-rich compartment (QAir); ethane concentration in the reaction compartment (%C₂H₆); and oxygen concentration in oxygen-rich compartment (%O₂). The optimization tool combines a genetic algorithm guided by a neural network model. This shows how the neural network model for this particular problem is obtained and the analysis of its behavior along the optimization process. The optimization process is analyzed in terms of: (1) catalytic figures of merit, i.e., evolution of yield and selectivity towards different products and (2) framework behavior and variable significance. The two experimental areas maximizing the ethylene yield are explored and analyzed. The highest yield reached in the optimization process exceeded 87%.     

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。     

Comparison of behaviour of rare earth containing catalysts in the oxidative dehydrogenation of ethane

Catalyst promotion by addition of either La and Sm to MgO or Na aluminate to Sm₂O₃ and La₂O₃ has been investigated for the oxidative dehydrogenation of ethane in the temperature range 550–700°C. With all unpromoted and promoted catalysts, the selectivity to ethylene is strongly enhanced by the temperature, the highest values being obtained at 700°C. Sm₂O₃ is the most active among the bulk oxides, while samarium addition to MgO results in higher surface area, but does not enhance the catalytic activity. Ethylene productivity on La₂O₃ promoted MgO samples is higher than with pure La₂O₃, Sm₂O₃ and MgO, not only due to the stabilising effect of La on MgO surface area, but also due to a higher intrinsic activity. With both bulk oxides and rare earth promoted MgO, the selectivity to ethylene strongly increases by decreasing the O₂/C₂H₆ feed ratio, while it is quite unaffected by ethane conversion and catalyst composition, in agreement with the hypothesis that the main role of catalyst in the experimental conditions investigated is to produce ethyl radicals which are converted in the gas phase to CO and C₂H₄. When La₂O₃ is modified by the addition of sodium aluminate the catalytic behaviour significantly changes, likely due to a different, mostly heterogeneous reaction mechanism. On aluminate promoted lanthana, ethane is converted to ethylene with higher yields which do not depend on the feed ratio. Moreover, only CO₂ is produced as by-product, the formation of CO being quite negligible.     

Oxidative dehydrogenation of ethane and propane over Mn-based catalysts

The catalytic performances of Mn-based catalysts have been investigated for the oxidative dehydrogenation of both ethane (ODE) and propane (ODP). The results show that a LiCl/MnO_x/PC (Portland cement) catalyst has an excellent catalytic performance for oxidative dehydrogenation of both ethane and propane to ethylene and propylene, more than 60% alkanes conversion and more than 80% olefins selectivity could be achieved at 650°C. In addition, the results indicate that Mn-based catalysts belong to p-type semiconductors, the electrical conductivity of which is the main factor in influencing the olefins selectivity. Lithium, chlorine and PC in the LiCl/MnO_x/PC catalyst are all necessary components to keep the excellent catalytic performance at a low temperature. This revised version was published online in July 2006 with corrections to the Cover Date.