Assessment of the Catalytic Performance of Ceria-Copper-Titania Nanocomposites for CO2 Reduction by the Dry-Reforming of Methane

Abstract

Fossil fuel extraction and exploitation contribute significantly to global warming by increasing greenhouse gas emissions, primarily, carbon dioxide (CO2) and methane (CH4). Efforts to mitigate CO2 emissions include controlling discharge concentrations, promoting green energy economies, and developing methods for capturing, storing, and utilizing atmospheric CO2. The Dry Reforming of Methane (DRM) process is recognized for its ability to simultaneously convert CO2 and CH4 into value-added precursors for chemicals and fuels via catalysed pathways. To address challenges related to supported nickel catalyst designs, this work explored the preparation, post-modification, and characterization of a series of eleven CeO2TiO2-CuxO nanocomposites to understand property-performance relationships. The supports were prepared with 70:20:10 Ce:Ti:Cu starting mol ratios using sol-gel assisted-solvothermal process. The synthesis involved adjusting reaction parameters including the myristic acid/acetic acid ratio (0-0.06) of structure directing and complexing agents, hydrothermal treatment duration (12-36 h), and the calcination temperature (300-500 °C). Ni impregnation post-synthesis was done at 10%wt of calcined support using the Chelation Coupled Impregnation (CCI) method with H4EDTA as the chelating agent. Various characterization techniques were employed, including Powder X-ray Diffraction (PXRD), Scanning Electron Microscopy (SEM), and Temperature-Programmed H2 Reduction (TPR) and CO2/NH3 Desorption (TPD) measurements to assess the redox and acid-base properties of the impregnated catalyst supports. SEM-EDS revealed preserved morphology and uniform Ni distribution for impregnated catalyst supports. Those calcined at 300 °C (i-E2, i-E4, i-E5, and i-E7) demonstrated suitable acidity, basicity, and reducibility for the DRM reaction, however, were not sufficiently active for very low-temperature DRM (up to 300 °C). Catalysts calcined at 500 °C were selected for further DRM tests, considering the substantial impact of calcination temperature on activation energy barrier for CO2 conversion in DRM. Catalysts i-E1 and i-E3 exhibited the most significant CO2 and CH4 conversions and CO yields over the 12-hour reaction period, consistent with chemisorption studies. Thermal stability was confirmed post DRM, with slight alterations in crystallite sizes indicating coking on all catalysts. Coking after DRM was evident using SEM-EDS and XRD.

Date of Award	7 May 2024
Original language	American English
Supervisor	Maguy Abi Jaoude (Supervisor)