Influence of Deposition Order and Thermal History in Sequential Ni-Co Impregnation on Catalyst Performance for Dry Reforming of Methane
Document Type
Thesis
Degree Name
Master of Science (MS)
Department
Chemistry
Date of Award
9-1-2026
Abstract
Dry reforming of methane (DRM) offers a promising route for the simultaneous utilization of methane (CH₄) and carbon dioxide (CO₂), two major greenhouse gases, to produce synthesis gas (H₂ and CO). However, catalyst deactivation due to carbon deposition and metal sintering remains a significant challenge to the commercialization of DRM technologies. In this study, the influence of metal deposition order and thermal history during sequential impregnation on the structure and performance of Ni–Co/Al₂O₃ catalysts was investigated. Sequentially impregnated catalysts were prepared by depositing either Ni followed by Co (Ni-first) or Co followed by Ni (Co-first) onto γ-Al₂O₃ via incipient wetness impregnation. Intermediate calcination temperatures (T₁ = 120, 300,500 and 800 °C) were introduced after deposition of the first metal to examine the effects of thermal treatment on catalyst evolution before addition of the second metal. The catalysts were characterized using N₂ physisorption (BET), scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM/EDS), H₂ temperature-programmed reduction (H₂-TPR), CO₂ temperature-programmed desorption (CO₂-TPD), and thermogravimetric analysis (TGA). Catalytic performance was evaluated during DRM at 800 °C and long-term stability testing at 600 °C. BET results indicated that all catalysts maintained relatively high surface areas with only moderate decreases at elevated intermediate calcination temperatures, suggesting that textural changes were not the primary factor governing catalytic performance. SEM/EDS analysis confirmed uniform metal dispersion across the catalyst surface for both impregnation sequences. H₂-TPR results showed that Ni-first catalysts exhibited greater low-temperature reducibility, indicating a higher proportion of readily reducible metal species, whereas increasing intermediate calcination temperature strengthened metal–support interactions and promoted the formation of more strongly bound species. CO₂-TPD analysis revealed that Co-first catalysts possessed a higher concentration of medium and strong basic sites, indicating enhanced CO₂ adsorption and activation capabilities. DRM testing demonstrated that catalyst performance was strongly influenced by both impregnation order and thermal history. Although Ni-first catalysts exhibited greater reducibility, Co-first catalysts achieved higher CH₄ and CO₂ conversions and lower carbon deposition, highlighting the importance of CO₂ activation and carbon removal in determining overall DRM performance. Among the catalysts investigated, Co-first catalysts prepared at intermediate calcination temperatures exhibited the most favorable balance between activity, stability, and resistance to coking. TGA analysis confirmed lower carbon accumulation on Co-first catalysts compared with their Ni-first counterparts. The results indicate that catalyst reducibility alone is insufficient to predict DRM activity and that enhanced basicity and oxygen mobility can play a more dominant role in sustaining catalytic performance. This work demonstrates that sequential impregnation combined with thermal history control provides an effective strategy for tailoring the physicochemical properties of Ni–Co catalysts for DRM applications. The findings highlight the critical role of synthesis history in governing catalyst structure, CO₂ activation, carbon resistance, and overall catalytic performance.
Advisor
Ben Jang
Subject Categories
Chemistry | Physical Sciences and Mathematics
Recommended Citation
Quarm, Jonathan, "Influence of Deposition Order and Thermal History in Sequential Ni-Co Impregnation on Catalyst Performance for Dry Reforming of Methane" (2026). Electronic Theses & Dissertations. 1397.
https://lair.etamu.edu/etd/1397
