Study On Nonmercuric Catalysis For The Hydrochlorination Of Acetylene

Hydrogenchlorination of acetylene is an important reaction in the industry, and mercuric chloride is the most common and effective catalyst. However, the toxicity of mercuric chloride becomes the hidden danger to the environment and human health, and thus non-mercury catalysts are needed urgently in industry to replace mercury-containing catalyst.In this paper, gold catalysts or bimetallic catalysts of rare earth and gold were prepared by the incipient impregnation using gold chloride or gold chloride and rare earth chloride as precursors, and activated carbon from coconut shell and with different pore structure as supports. The catalysts were used for the reaction of hydrochlorination of acetylene. The main work and conclusions are as follows:(1) The pore structure of support directly affected the accivity of catalyst. The microporous structure with too narrow channel was easy to be blocked by active components, which decreased surface area and thus the catalytic activity. An appropriate pore structure was conducive to the dispersion of the active components as well as the spread of the reactants and products, and thus leading to high activity. The catalyst with mesoporous structure was more stabile, but easy to produce by-product of ethylene dichloride. A large number of Au3+could be reduced to Au0 if the catalysts were prepared at higher temperatures, lowering the activity of the catalysts.(2) The active gold species in the samples dried under vacuum at room temperature were more, and the catalytic activity and stability of the catalysts were better than those of the samples dried at 180℃. The reason was that, under such conditions the active gold species of high valence could be dispersed with smaller size in the channels of support, which increased the reaction activity.(3) Gold catalysts doping with La and Sm could inhibit the reaction of hydrochlorination of acetylene, while those dopping with Ce could significantly promote the reaction, with nearly doubled reaction activity. However, no significant role of Nd in the catalyst could be observed in the reaction. The greater the initial activity of the bimetallic catalyst of rare earth and gold, the faster is the inactivation rate. The introduction of rare earth in the catalysts could enhance the reduction temperature of gold species with high valence and thus the catalytic activity.