Dry reforming of ethane over titania-based catalysts for higher selectivity and conversion to syngas

Abstract

Ethane, one of the key components of shale gas, is a valuable feedstock for the production of syngas (CO + H₂) via the CC bond cleavage during dry reforming of ethane (DRE) reaction. Selective catalysts are needed to direct this reaction pathway against the competing CH bond cleavage for ethylene formation. In this study, Fe, V and Rh oxides supported on TiO₂ catalysts were prepared by impregnation method. The catalysts were tested for DRE with the main target of enhancing selectivity to syngas (CO and H₂) and reducing byproducts (methane and ethylene) formation. The catalysts were characterized using X-ray diffraction, scanning electron microscopy, NH₃/CO₂ temperature programmed desorption and H₂-temperature programmed reduction. Temperature programmed oxidation was utilized to characterize the coke contents of the spent catalysts. The catalysts were evaluated for DRE reaction in a fixed-bed reactor at the temperature range from 500 °C to 650 °C and CO₂/ethane ratio from 2:1 to 10:1 (mol/mol). It was found that ethane conversion over the three catalysts increased in the order Rh/TiO₂ > Fe/TiO₂ > V/TiO₂. Rh/TiO₂ catalyst exhibited > 99 % ethane conversion, 36 % and 61 % yields of H₂ and CO, respectively, at 650 °C and CO₂/ethane ratio of 5.0. The high conversion of ethane was mainly attributed to the enhanced dispersion of Rh oxides on the TiO₂ support coupled with the balanced surface acidic and basic sites. The Rh catalyst facilitated CC bond dissociation of ethane thereby forming methyl intermediates which then reacted with adsorbed CO₂, thereby enhancing higher syngas production during DRE reaction.