Kinetic equations and models of cyclohexene hydrocarbomethoxylation catalyzed by the RuCl3 and RuCl3/NaCl system

Abstract

Based on the kinetic data obtained earlier, the authors propose an improved mechanisms of cyclohexene hydrocarbomethoxylation and side reactions in the presence of RuCl3 and RuCl3/NaCl system. The mechanisms are complemented by ligand exchange reactions leading to deactivation of ruthenium complexes under CO effect. The paper shows that in the presence of RuCl3/NaCl catalytic system, the target product, methyl cyclohexanecarboxylate, is generated in two catalytic cycles: with the participation of neutral ruthenium complexes and anionic sodium-ruthenium complexes. In the presence of RuCl3, Ru(OCH3)Cl(CH3OH)4 is assumed to be a key intermediate, in the presence of RuCl3/NaCl system—Na[Ru(OCH3)Cl2(CH3OH)3]. For both catalysis cases, kinetic equations of fractional-rational form were obtained, which contain RuCl3 concentration and CO pressure in denominators. The obtained kinetic equations are consistent with the previously established first orders of reaction for cyclohexene and NaCl, the extreme dependences of reaction rate on CO pressure, and the nonlinear rate dependence on RuCl3 concentration with a constant value attainment. Based on the complete data sets on the effect of CO pressure as well as cyclohexene, RuCl3 and NaCl concentrations on the initial reaction rate, kinetic models of hydrocarbomethoxylation was developed.