Polyvinyl chloride (PVC) is one of the top five common plastics, widely used in industrial and agricultural production as well as in daily life.
Currently there are two main methods of making PVC: one is the acetylene route, which employs acetylene as the raw material, whose reaction with hydrogen chloride catalyzed by mercuric chloride forms vinyl chloride monomer. This method uses mercuric chloride as a catalyst, which presents the problem of mercury pollution, and largely have been rendered obsolete in foreign countries. The other method is the ethylene route, in which dichloroethane is obtained by direct chlorination of ethylene and oxychlorination. Dichloroethane is converted to vinyl chloride monomer by thermal cracking. This process is widely used in foreign countries.
Since our country has a scarcity of ethylene but is relatively abundant in calcium carbide resources, the PVC production is still mainly based on the calcium carbide route (acetylene produced using calcium carbide), which exerts an enormous strain on environmental protection. Therefore, researchers have been using unremitting efforts to find a catalyst to replace the mercuric chloride catalyst. It is known that compounds having copper, tin, bismuth, lanthanum, barium, cadmium, palladium, gold, or platinum can catalyze the chlorination reaction of acetylene using hydrogen chloride, but the cost of palladium, gold, platinum and other precious metals are too high, while the catalytic effect of the compounds containing copper, tin, bismuth, lanthanum, or barium, etc., are not as good as that of mercuric chloride. Therefore, the mercuric chloride catalyst has not been replaced.
Chinese invention patent application number 2010101492109 disclosed a method for making vinyl chloride using acetylene and ammonium chloride, which uses barium chloride or lanthanum chloride as the catalyst, with a certain degree of success.
Chinese invention patent application number 2010101491801 disclosed a method of making vinyl chloride through acetylene dichloroethane catalytic reforming. This method uses carbon-supported barium chloride as the catalyst and produces vinyl chloride through acetylene dichloroethane catalytic reforming, which achieved good results.
However, it is noticed in simulated industrial operations that catalysts obtained through regular impregnation method have large crystals with an uneven size distribution. The catalyst has poor adhesion with the substrate and is easy to fall off. The catalytic effect and catalyst stability cannot satisfy the requirements for industrial applications.
Therefore, there is an urgent need to provide a catalyst for vinyl chloride preparation that meets the requirements on catalyst activity and stability for industrial operations.