An investigation of the impact of niobia loading on platinum catalysts for sour medium-temperature shift reaction

Abstract

The increasing demand to reduce pollutant emissions, coupled with the declining availability of mineral resources, has heightened the need for technologies that maximize the use of existing resources. Waste gasification is an interesting way to meet this demand, as it enables the production of hydrogen. However, in this gasification process, in addition to hydrogen, carbon monoxide is generated in considerable concentrations, making it necessary to adjust the CO/H₂ ratio through the water-gas shift reaction. In addition the gasification of industrial and urban waste can contain significant concentrations of sulfur that act as a poison for traditional catalysts. As a result, there is an ongoing search for sulfur-tolerant catalysts that can prevent deactivation and eliminate the need for a desulfurization step. Building on the promising results of the Pt/Nb₂O₅ catalyst, new catalysts containing niobia were investigated to assess the impact of niobia loading in the support. In this series of catalysts, increasing the niobium content only leads to higher activity if it does not reduce the niobium surface coverage. Additionally, smaller platinum particle sizes are found to be more favorable for better performance in the water-gas shift reaction. However, the use of Al₂O₃-Nb₂O₅ supports did not impart properties to the platinum catalysts comparable to those of the Pt/Nb₂O₅ catalyst. These catalysts exhibited lower catalytic activity and did not provide sulfur tolerance, regardless of the niobium content. The interaction between platinum and niobia may not have been strong enough to produce the same synergy observed in the Pt/Nb₂O₅ system.