Molecular-level understanding of support effects on the regenerability of Ru-based catalysts in the sulfur-poisoned methanation reaction

摘要

The production of synthetic natural gas-SNG-from dry biomass currently involves a costly and energy-inefficient low-temperature gas cleaning step, needed to remove various sulfur-containing poisons from syngas generated from wood gasification before the sulfur-sensitive methanation step. Here we explore the use of Ru-based methanation catalysts in an alternative process, where the low-temperature gas cleaning step is omitted and the syngas from the gasifier is used directly for methanation. In this process, methanation is carried out in the presence of organic and inorganic sulfur species and is followed by periodic oxidative regeneration of the poisoned catalyst. In situ diffuse reflectance infrared Fourier transform spectroscopy and Ru K-edge X-ray absorption spectroscopy were employed to understand the mechanism of deactivation of Ru nanoparticles on two different supports: Al2O3 and SiO2. The efficiency of the regeneration is higher when Ru nanoparticles are supported on SiO2, on which only a small amount of unstable sulfate species is formed and Ru nanoparticles are more stable against sintering during oxidative regeneration due to a "passivation" effect of the adsorbed sulfur species. (C) 2019 Elsevier Inc. All rights reserved.