Study On Causes And Control Methods Of Polymer Formation In The Process Of Dimerization Of Acetylene

Chloroprene rubber (CR) is an important variety of synthetic rubber, and it not only has excellent light resistance, anti-aging, acid resistance, heat resistance and oil resistance and other properties, but also has good mechanical properties and electrical properties, moreover, its overall performance is better than that of the natural rubber and other synthetic rubber. Currently, the main production methods of chloroprene rubber include acetylene process and butadiene-based. Because of security concerns, most manufacturers in different countries have abandoned the acetylene method, but use the butadiene method.Throughout development status and trends of the production of chloroprene rubber with acetylene, obviously, the technical difficulties of the acetylene method in China are the low catalytic efficiency, poor selectivity, high polymer in the production process of vinylacetylene (MVA). Therefore, this technology innovation focuses on improving acetylene conversion, MVA selectivity and reducing the polymer and other byproducts in the production process of vinylacetylene.In this paper, the relevant mechanism of acetylene dimerization reaction was summarized and analyzed, and the causes of polymer formation were determined, which were occurred by trimerization, tetramerization, and high-polymerization of acetylene activated by the catalyst CuCl. The impact factors of polymer formation were analyzed. The result showed that the polymer formation in the production process of vinylacetylene was related to the amount of the main catalyst, type and amount of cosolvent, acidity of catalyst, reaction temperature and airspeed of acetylene. The optimal conditions were as follows: main catalyst CuCl 35%-40%, the cosolvent and the main catalyst, molar ratio control in 1:1, hydrochloric acid 0.2% -0.4%, airspeed of acetylene 350-400 acetylene gas m3/ catalyst m3﹒h-1, the reaction temperature 80℃, in which the formation of polymer was relatively low, only 2.73%.Meanwhile, according to reaction mechanism and the factors affecting the formation of polymer, in this paper, some control methods of polymer formation in the process of dimerization of acetylene were put forward. Those methods were: separating the polymer and the catalyst system using organic ether, balancing acid acidity of the catalyst using organic carboxylic, preventing the depth of polymerization of acetylene using polymerization inhibitor. The results showed that using organic ether to separate the polymer and the catalyst system, the polymer production per catalyst was decreased from 2.73% to 0.63%, using organic carboxylic to balance acid acidity of the catalyst system, the polymer production per catalyst was decreased from 2.73% to 1.78%, using both of organic ether and organic carboxylic, the polymer production was decreased to 0.28%, and the reaction temperature could be reduced to 70℃, using inhibitor combined with organic solvents, polymer formation was also controlled, but the result was not obvious, only 0.5%.