Study On The Performance Of Low-mercury Catalysts And Supporter During Production Of PVC

At present, the craft to synthesis PVC mainly uses the raw materials of acetylene and catalysts of Hg C l2(10-12%wt) loaded on the activated carbon. Hg C l2 easily decompose in the process of reaction, then it can pass into air to damage the human health and environment. So, international- law restricted Hg to be used. So, to study and develop the low mercury catalyst becomes extremely urgent.In this paper, (?)3.5×6 coal activated carbon as carrier, the new low mercury catalysts has been produced by the method of static isometric impregnation; we screen 3 types of new catalyst C1( K?Zn?Fe?B and Hg chloride) C2( Ba?C u?Al and Hg chloride) C3(K?Ca?Al?Fe and Hg chloride) to detect its performance; Then, the catalytic activity of different catalysts were detected by catalytic converter. We study the impact of reaction temperature?atmosphere flow ratio and mixed gas flow to acetylene conversion. Using HC l and different concentration HNO3 to modify the activated carbon, we study the effect of modifying carriers on Hg C l2 adsorption performance and the conversion of acetylene. The AC and low mercury catalysts has been characterized by IR?Beohms titration method ?SEM/TEAM and BET.Experimental results shown that the new catalyst 3 has the better catalytic effect, the conversion rate and selectivity of acetylene is 99%?97% respectively on the 130?. AC using HC l to wash has little role in its surface chemical properties through the analysis of IR, the oxygenic groups have carbonyl?carboxyl?radical?ester and etc; The content of oxygenic groups was determined by Beohms titration method. The surface functional groups existed in AC pretreated with different concentration of nitric acid, were partly transformed into carboxyl and radical. The total acid ?carboxyl and radical content of AC with 20% HNO3 pretreated reached into Max,it`s 6.93mmol?2.26 mmol and 1.22 mmol respectively. O xygen-containing functional groups have effectively improved the absorption performance of Hg C l2, meanwhile, electronic absorption performance can weaken the bond energy of intermolecular reaction, it has co-catalysis effect on the reaction. AC with HC l treatment can reduce the contents of ash and have neat s urface; it has not good for catalysts absorption in the support at too high or low concentration of HNO3 by the analysis of SEM. Results of BET test shown that AC with 20%HNO3 pretreated has the optimum average pore size(18.31nm) and specific surface area(1321 m2·g-1). The test results of new catalysts performance shown that new catalysts3 has better catalytic effect, the conversion ratio and selectivity of acetylene is 99% ?97% at 130?.Synthetic reaction of VCM was analyzed by thermodynamics and kinetics; Conversion ratio of acetylene is 99.9998% at the temperature of 25 degrees through theoretical calculation, with the temperature increasing, Conversion ratio continuously decreased! Equilibrium constant of main reaction is 4.696, the side effect is and 58.34 respectively, compared with the main reaction, it's below the 104 orders of magnitude; Results of dynamic study shown that HC l has priority to adsorb in Hg C l2 than C2H2; in the role of Hg C l2 catalysts, HC l can be dissociated and then add to the C2H2; Cu C l2 and Al C l3 played role in the aid of catalysts and reducing the loss weight ratio of Hg C l2; through the experiment, activation energy of composite catalysts is 59.78 k J/mol far below the values of theoretical calculation.