丙烷和丁烷气固相催化脱氢制烯烃

Gas-solid catalytic dehydrogenation of propane and butanes to olefins

催化脱氢是将低碳烷烃转化为同碳数单烯烃和氢气的有效途径.本文介绍了国内外近年来丙烷、丁烷气固相催化脱氢制烯烃在反应机理、催化剂和反应器等方面的研究进展.催化脱氢制烯烃是转化率受热力学平衡限制的较强的吸热反应,反应和产物的分离都需要消耗大量的能量,优化操作条件,在保证脱氢选择性和装置长周期安全稳定运行的前提下,尽可能提高烷烃的单程转化率,是降低整个过程能耗的关键.在烷烃脱氢反应过程中,一个烷烃分子相邻两个C上的两个H原子同时吸附在同一个活性位上,活性位将两者拉近并相互吸引形成H_2,是导致C–H键断裂和烯烃形成的决定性因素,形成的烯烃直接进入气相.催化剂方面,负载型Pt和CrOx催化剂已得到广泛应用,本文介绍了其制备方法、活性组分的存在形态、载体和助剂、催化剂的失活与再生、以及使用中需要注意的问题;此外,还讨论了新近报道的负载型Ni、NiSn和Sn催化剂,Ga_2O_3/ZnO、ZnO/Nb_2O_5、其他混合和/或复合氧化物催化剂,以及金属硫化物催化剂的性能特点.反应器方面,固定床、移动床和循环流化床均有应用,其中循环流化床可实现连续反应再生、高温再生剂可高效为吸热的脱氢反应供热,是最适合烷烃脱氢的反应器.以"环保型金属氧化物催化剂+并流循环流化床反应器"为核心的ADHO烷烃脱氢技术,有望为企业提供一种新的高效、低耗的技术选择.

Catalytic dehydrogenation is an effective route to convert light alkanes to monoolefins with the same carbon number and H_2. In this paper the research progress in the reaction mechanism, catalyst and reactor for propane/butane dehydrogenation in recent years has been introduced. Catalytic dehydrogenation of alkanes is a strong endothermic reaction and its conversion for single pass is limited by the thermodynamic equilibrium. Both the reaction and the product separation consume a large amount of energy. Improving the conversion of alkanes for single pass by optimizing the operating conditions, on the basis of guaranteeing the high selectivity to olefins and the long-term safety and stability of the unit operation, is the key to reduce energy consumption for the whole process. During the dehydrogenation of alkanes, two H atoms bonded with two adjacent C atoms adsorb on the same active site, and the active site draws the two H atoms closer to attract each other, leading to the scission of C–H bonds to form H_2 and olefins. The olefins enter to the gas phase directly without adsorption. The widely used supported Pt and Cr Oxcatalysts have been introduced systematically, including the preparation methods, existing state of active components, carriers, additives, deactivation and regeneration, as well as problems encountered in application. At the same time, the newly reported catalysts, such as supported metal catalysts（Ni, NiSn and Sn）, metal oxide catalysts（Ga_2O_3/Zn O and Zn O/Nb_2O_5）, other mixed metal oxides and/or composite metal oxides catalysts, as well as metal sulfide catalysts have also been discussed briefly.Furthermore, the performances of packed-bed, moving-bed and circulating fluidized-bed reactors have been analyzed comparatively. The circulating fluidized-bed reactor is optimal due to its continuous reaction and catalyst regeneration and the efficient heat supplying for the endothermic dehydrogenation by high-temperature regenerated catalyst. The ADHO process, based on environment-friendly metal oxide catalyst coupled with cocurrent circulating fluidized-bed reactor, offers a novel high-efficiency and low-consumption dehydrogenation technology for the chemical industry.