In depth study of propane dehydrogenation: different effects of bimetallic catalysts

Propylene is a colorless gas at room temperature, which is flammable, toxic, insoluble in water and widely used As a very important chemical raw material, propylene is mainly used to prepare polypropylene, isopropene, acetone, propylene oxide and other compounds At the same time, it is also used to produce some chemical raw materials, synthetic resin and synthetic rubber With the development of industrialization in the world, propylene prepared by the methods of petroleum steam cracking and catalytic cracking can not meet the increasing demand At the same time,

the consumption of petroleum resources makes the contradiction between propylene supply and demand increasingly prominent Therefore, it is of great practical significance to develop an economic and environmental non oil route to increase propylene production At present, propane dehydrogenation is a promising way to produce propylene on a large scale For example, the commercial direct dehydrogenation of propane (DDP) is limited by the thermodynamic equilibrium, the conversion rate of DDP is difficult to improve, the catalyst is easy to inactivate, and the thermodynamic driving force of propane dehydrogenation is small, so the reaction process needs a lot of energy Compared with direct dehydrogenation, oxidative dehydrogenation of propane has the characteristics of less than zero enthalpy change, exothermic reaction and low energy consumption,

which can overcome the limitation of thermodynamic equilibrium and extend the practical life of catalyst As a mild oxidant, CO2 can change its dehydrogenation pathway in the oxidative dehydrogenation of propane At the same time, CO2 can increase the conversion of substrate by consuming H2 Recently, Professor Jingguang g Chen, Department of chemical engineering, Columbia University, studied the catalytic effect of Ceria Supported Bimetallic Catalyst on the reaction of propane with carbon dioxide Generally speaking, there are two ways of reaction between propane and carbon dioxide, one is oxidative dehydrogenation of propane (co2-odhp, formula 1),

the other is dry gas reforming of propane (DRP, formula 2) The two ways occur together in the reaction, but their conversion rate to propane is very different Therefore, it is important to know which way the catalyst mainly catalyzes the reaction of propane and carbon dioxide in the reaction to improve the conversion rate of propane It is found that the reaction of propane and Carbon Dioxide Catalyzed by Fe 3Ni is mainly Co 2-odhp, while Ni 3pt is mainly DRP This achievement was published in Table 1 of natural communication (DOI: 10.1038 / s41467-018-03793-w) under the title of "combining CO2 reduction with proactive hydrogenation over biological catalysts" (photo source: Nat Commun 2018, 9, 1398) firstly, the catalysts of fe3ni, fe3pt and ni3pt supported on CeO2 were prepared by equal volume impregnation, and the catalytic effect of these catalysts on the reaction of carbon dioxide and propane was investigated in a continuous reactor The results show that although Fe3 alone has no catalytic effect on the reaction, fe3ni bimetallic catalyst shows good catalytic activity and selectivity; compared with fe3ni, fe3pt containing noble metal has lower catalytic activity, and its selectivity and stability are not as good as fe3ni; the combination of Ni and Pt will improve the selectivity of catalyst to DRP pathway In addition, it was found by XANES that under reaction conditions, Ni and PT are in the form of simple substance, while Fe is in the form of oxidation in fe3ni catalyst Figure 1 XANES map of catalyst (photo source: Nat Commun 2018, 9, 1398) In addition,

in order to further understand the two reaction pathways of carbon dioxide and propane, the author calculated the fracture energy of C-H bond and C-C bond through DFT It is found that the fracture of C-C bond tends to occur on the surface of ni3pt, while the fracture of C-H bond tends to occur on the surface of fe3ni and FeO / Ni Figure 2 DFT calculation results of catalyst catalytic reaction of carbon dioxide and propane (photo source: Nat Commun 2018, 9, 1398) Full text author: Gomez, Elaine, kattel, Shyam, Yan, binhang, Yao, Siyu, Liu, Ping, Chen, Jingguang g corresponding author: Professor Chen Jingguang