An in situ FTIR-drifts study on bimetallic CDRM catalysts

Abstract

The purpose of this research was to gain a deeper insight into the difference between the micro-structural and kinetic properties of two bimetallic catalysts, i.e. 0.3Pt10Ni/Al2O3 and 0.2Pt15Ni/Al2O3, which have been previously studied and shown to have different kinetic behaviors in CDRM reaction. In this context, CO characterization, CO-TPD, CO2 and CH4 adsorption and in situ reaction experiments by using FTIR-DRIFTS system were conducted. CO characterization studies conducted at room temperature revealed that dispersion of Ni on the sample containing higher amount of Pt, i.e. 0.3Pt10Ni, was better than that on the 0.2Pt15Ni sample. CO adsorption experiments performed at 300 °C showed that the lower Ni:Pt ratio of the 0.3Pt10Ni sample resulted in a higher extent of reduction. FTIR-DRIFTS-CO-TPD experiments revealed that CO species adsorb in linear fashion were more thermally stable on 0.3Pt-10Ni sample than the ones adsorbed on 0.2Pt15Ni sample. Furthermore, more multicentered CO species remaining on the surface of 0.2Pt15Ni sample after desorption indicates that decrease in the Ni:Pt ratio causes a decrease in thermal stability of these species. CO2 adsorption experiments conducted at 300 °C revealed that more formate species were formed on 0.3Pt10Ni sample indicating its higher activity in CO2 utilization. In the CH4 adsorption experiments, CO formation was observed on both samples showing that the support also has a role in the course of the CDRM reaction. Due to the lower dispersion of 0.2Pt15Ni sample, there formed fewer amounts of formate species on this sample. In situ reaction tests revealed that more gaseous CO and more formate type species were formed on 0.3Pt10Ni sample. Differences in the CO adsorption behavior, CO2 utilization and CH4 adsorption characteristics of the two samples proves the previous findings on the two catalysts indicating there are significant differences among two samples in terms of the CDRM reaction pathways on them.