Kinetics of the Deactivation of Metallic Palladium Catalyst in the Oxidative Esterification Reaction

Abstract

It was reported by the authors that methyl formate was formed selectively from methanol and oxygen in the liquid phase by suspended metallic palladium catalyst. But remarkable deactivation was observed in the liquid phase contrary to the gas phase reaction. The deactivated catalyst could only be regenerated by treating it with air, and other gases such as nitrogen or hydrogen were not effective.
Based on the experimental results, a model of deactivation was proposed. This model included the activation with oxygen of the vacant active sites which were formed by the desorption of reaction products and the deactivation of some sites. Kinetic treatment of the model showed good coincidence with the experimental results in the range of reaction temperatures 30-60°C and of oxygen pressures 0.1-0.7 atm.
The rate equations of the formation of methyl formate and of the deactivation of active sites are as follows: 1.07 x 10-6 exp (3840/R T) Pch ITT rt(methyl formate), 2X0 2 (1+ 2.0 x 10-19 exp (23200/R T)) PchCaT r (deactivation)= 1.16 x 10-1 exp (2720/R T)