Formation of the surface of Pt-Ni-Cr/C catalysts under reducing conditions

Abstract

The mutual influence of metals in processes of reduction of mono-, bi-, and trimetallic Pt-Ni-Cr catalysts on the Sibunite (C) carbon support during the hydrogenation—dehydrogenation reactions was studied using XPS, TEM, and temperature-programmed reduction (TPR). The TEM data on the phase composition of the catalysts are consistent with the established valence states of metals and their behavior during the TPR process. It is found that in calcined Pt/C samples, the main fraction of platinum exists in the form of electron-deficient Ptδ+ particles, and their treatment with hydrogen does not lead to a significant reduction of platinum to the metallic state Pt0. The introduction of nickel into the catalyst reduces the concentration of electron-deficient platinum Ptδ+ particles, whereas the addition of chromium results in an increase in the concentration of these particles even in the samples subjected to the reduction treatment.