Gas-solid catalytic dehydrogenation of propane and butanes to olefins

Abstract

Catalytic dehydrogenation is an effective route to convert light alkanes to monoolefins with the same carbon number and H2. 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 H2 and olefins. The olefins enter to the gas phase directly without adsorption. The widely used supported Pt and CrOx catalysts 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 (Ga2O3/ZnO and ZnO/Nb2O5), 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.