Dehydroaromatization of methane over noble metal loaded Mo/H-ZSM-5 zeolite catalysts

Themba E Tshabalala,Neil J Coville,James A Anderson,Michael S Scurrell

doi:10.1007/s13203-021-00274-y

Abstract

Dehydroaromatization of methane (MDA) reaction was investigated over platinum modified Mo/H-ZSM-5 catalysts which were pre-carbided at 750 °C. The influence of platinum on the catalytic performance and product selectivity of Mo/H-ZSM-5 catalysts for the MDA reaction at 700 °C were studied. The presence of platinum led to a slight decrease in methane conversion from 7.5 to 4.2%. Aromatic selectivities above 90% were obtained with catalysts containing low platinum loadings (0.5 and 1.0 wt.%), with benzene being the most prominent product. A decrease in coke selectivity and coke deposits was noted with the platinum modified Mo/H-ZSM-5 zeolite catalysts. A comparative study was performed to compare platinum, palladium and ruthenium promoted Mo/H-ZSM-5 zeolite catalysts with un-promoted Mo/H-ZSM-5. The ruthenium promoted catalyst proved to be superior in catalytic performance, with a higher methane conversion obtained than that found for platinum promoted and palladium promoted Mo/H-ZSM-5 catalysts. Benzene selectivity of about 60% was obtained for ruthenium and palladium promoted Mo/H- ZSM-5 catalysts and the total aromatic selectivity was maintained at 90%. TGA results showed a total reduction of 50% by weight of carbon deposited on the promoted Mo/H-ZSM-5 catalyst.Graphic abstract

Highlights

The demand for highly marketable products from refineries has grown and this has put pressure on the effective utilization of fossil fuel sources and low valued hydrocarbons
The decrease in surface area may be associated with the location of metal particles on/in the zeolite. These results suggest that the platinum species are too small to modify structural properties of the H-ZSM-5 zeolite; if the metal particles are located in the pores of the zeolites they show an insignificant effect on the surface area [31, 32]
The XRD results illustrated the same intensity for all samples, which implies that the structure of H-ZSM-5 zeolite remained intact after Mo and Pt impregnation (Fig. 1)

Summary

Introduction

The demand for highly marketable products from refineries has grown and this has put pressure on the effective utilization of fossil fuel sources and low valued hydrocarbons. The adsorption of CO on platinum-free Mo/H-ZSM-5 samples showed no band (at 2160 cm−1 region) of the CO adsorbed on the molybdenum species (Fig. 4). The effect of platinum loading on the catalytic performance of Mo/H-ZSM-5 zeolite catalysts on the MDA reaction was investigated.

Results

Conclusion