Stereospeci c Polymerization of 1, 3-butadiene in an Environment Friendly Solvent: Kinetic Studies

Abstract

In PBR-II plant of RIL-VMD, polybutadiene is manufactured using nickel based catalyst system consisting of nickel naphthenate [catalyst], boron triuoride etherate [promoter], triethylaluminium [co-catalyst]. The detailed kinetic data of the reaction were not provided by the licensor of PBR-II plant. Moreover, the kinetics of nickel based system is not readily available in the open literature. Hence, in this work, effect of nickel based Ziegler-Natta catalyst system on polymerization of 1, 3- butadiene and its detailed kinetics in an environment friendly solvent system (toluene: heptane 50:50) was studied. And it was found that ratio of promoter to co-catalyst is one of important parameters governing the polymerization. Polymerization is 1st order with respect to monomer concentration as well as catalyst concentration in case of both the catalyst systems. The overall rate constant was found to be 1.462 min-1 mol-1 for nickel based catalyst system. The activation energy of the polymerization based on this catalyst system was found to be 14.5kcal mol-1. Besides, PBR-I plant of RIL-VMD utilizes benzene as the solvent for the polymerization of 1, 3 -butadiene using cobalt based catalyst system. The cobalt catalyst system comprises of cobalt octanoate [catalyst], diethylaluminium chloride [co-catalyst] and water [promoter]. Benzene is a carcinogenic solvent which leads to Hematoxin that is linked to increased incidence of leukaemia in humans. So, in this study an attempt was taken to study the 1, 3-butadiene polymerization kinetics in non-carcinogenic cyclohexane solvent so that plant could be benefited while changing over the existing solvent to non-carcinogenic one. From this study, the following conclusions can be made. Polymerization is 1st order with respect to monomer concentration as well as catalyst concentration The overall rate constant was found to be 0.68 min-11mol-1 for cobalt based catalyst system. The activation energy of the polymerization based on this catalyst system was found to be 13.7kcal mol-1.