Research Of Low Mercury Catalyst For Hydrochlorination Of Acetylene

Now high mercury catalysts were used for hydrochlorination of acetylene for thepreparation of vinyl chloride in industry, but mercuric chloride is easy to sublimate loss.Thus it is urgent to develop a new low mercury catalyst to replace the traditional highmercury catalyst.Activated carbon from coconut shell was taken as the supports in the paper. Lowmercury catalysts were prepared under different conditions by incipient impregnation andthe mass fraction of HgCl2decreased from10%of the support mass to4.5%.Catalystsactivities were tested in a fixed-bed reactor and characterized by N2absorption and TGThe optimum process conditions of hydrochlorination of acetylene reaction were discussed.The influence of different impregnation conditions, supports, additives, additives ratio,drying conditions, activation conditions on the catalyst performance were analyzed. Themain conclusions are as follows:(1) The mercuric chloride and compound fertilizer (containing cerium chloride andpotassium chloride) at the mole ratio of1:1was in the impregnating solution of pH1. Afterimpregnating in70℃for6h and vacuum drying in170℃for14h, the catalyst wasactivated in hydrogen chloride at150℃for2h. The better reaction temperature ofhydrochlorination of acetylene was170℃, hydrogen chloride and acetylene ratio was1.1:1, acetylene airspeed was24h–1. Activity test of the new low-mercury catalystshowed that the acetylene conversion rate can reach more than98%, the selectivity wasover99%, which meet the industrial requirements.(2) TG results showed that sublimation rate of mercuric chloride in low mercurycatalyst was significantly lower than that in high mercury catalyst by adding the compoundadditive. The reason was that coordination action of mercuric chloride and compoundadditive could well contribute to the reaction and improve catalyst activity and thermalstability, and the catalyst life may be extended. Results of mercury determination afterreaction showed that the compound additive could inhibit the sublimation loss of mercuric chloride and improve thermal stability in the reaction. Gas chromatography analysis resultsshowed that activity of the catalyst that took coconut shell activated carbon as the supportwas higher than that took coal activated carbon as the support of catalyst.The reason wasthat the specific surface area of the coconut shell activated carbon is bigger and thus itcould more effective absorb active component.