Impact of Rutile TiO2 Morphology on the Physiochemical and Catalytic Properties of Ru Supported Catalysts in CO2 Methanation

Abstract

This study explores the synthesis and characterization of Ru catalysts supported on various TiO₂ supports, with a focus on understanding the influence of TiO₂ morphology on the catalytic performance in CO₂ methanation. TiO₂ supports were synthesized via a hydrothermal method with varying HCl concentrations, resulting in different crystallite sizes and morphologies. The introduction of Ru to these supports, followed by calcination, was shown to affect the crystallite size and surface characteristics, with significant variations in pore structure and surface area. Nitrogen adsorption-desorption isotherms revealed diverse porosity profiles, and H₂-temperature programmed reduction (H₂-TPR) experiments indicated variations in the reduction behavior and reducibility of the Ru catalysts, particularly highlighting the anomalous reducibility of the Ru/TiO₂-4 sample. Catalytic activity tests for CO₂ methanation were conducted over a temperature range of 200 to 400°C. The results showed that the TiO₂ morphology plays a crucial role in determining catalytic performance. Specifically, the Ru/TiO₂-2.5 catalyst exhibited the highest CO₂ conversion and CH₄ selectivity among the hydrothermally synthesized TiO₂ supports. The study found that change in TiO₂ pore structure, particularly in the TiO₂-4 support, led to a significant decrease in catalytic efficiency. Furthermore, the Ru/TiO₂-2.5 and Ru/TiO₂-r catalyst showed competitive performance relative to Ru/P25, a commonly reported optimal support in literature. However, the Ru/P25-cal catalyst displayed diminished activity, attributed to a substantial loss in surface area and pore volume due to high-temperature calcination.