The application of EPR to the study of acetylene removal and deactivation reactions over Pd-based ethylene purification catalysts

摘要

The selective catalytic hydrogenation of simple alkynes to alkenes over palladium will display significant variations in both activity and selectivity with time. These changes have been associated with the accumulation of hydrocarbon species at the active site and on the surrounding support. The identification of these active sites for hydrogenation and by-product formation is the subject of considerable debate and research. This reaction has been investigated usign flow reactor studies and classic isotopic labelling experiments that have led to a postulated mechanism for alkyne hydrogenation. However the unique identification of the surface intermediates in the main and by-product reactions has not been achieved. In this paper it is proposed that these surface intermediates in catalytic hydrogenation have some free radical character and a methodology has been developed to investigate this concept.