Reaction Mechanism Of Acetylene Hydrochlorination On Cu-based Catalyst

In this paper, the reaction mechanism of acetylene hydrochlorination inCu-based catalyst was studied using the density functional theory (DFT). Thedeactivation mechanism of Cu-based catalyst and some factors which influencethe reaction were also discussed. The conclusions derived from this studywould clarify the experimental design of non-noble metal catalyst with highperformance.The calculation results showed that the two C atoms of C2H2and Cu atomform a compound structure via a ?-? coordination bond. The ? electron of C2H2transfers to the unoccupied molecular orbital of Cu2+, thus the C?C bond isweaken. The activated C2H2react with the catalyst and intermediatechlorovinyl is produced. The intermediate adsorbs HCl on the Cu site, they willgenerate vinyl chloride and the catalyst recovers to the former structure. A sidereaction would be occurred via the acetylene adsorbed on the catalyst alonewhen there is short of HCl, the by-product of dichloroethylene was formed.There are two reasons for the deactivation of the catalyst. In the main reaction,the intermediate is the complex structure with chlorovinyl and catalyst which isreduced partially, the desorption of chlorovinyl and catalyst needs some energy,so the active site of Cu catalyst would be occupied and the catalytic activitywould decrease if HCl can't adsorb on the intermediate. In the side reaction,the catalyst is reduced to elemental copper and the activity is lost.What's more, the electropositivity of the active site in different coppersalt is different, larger the electropositivity, higher the catalytic activity. Whengraphene doped with N or P, the structure become more stable because theelectronegativity of the N atom is high, and the adsorption energy between thecatalyst and graphene is amplified. The reaction rate constants and theactivation free energy can also be influenced by N/P doping. The catalyst isamorphous on the supporter, it would generate different kinds of cluster, theatomic average binding energy, the atomic average adsorption energy and thecharge of the atom are all related with the structure of the cluster. The activities of the cluster decrease with the number of the atoms in the clusterbecause the relatively less atomic average charge.