Low-temperature ethanol dehydration toward ethylene over Pd–Ce-modified spherical silica catalysts under oxygen co-feeding

Low-temperature ethanol dehydration toward ethylene under oxygen co-feeding was investigated over palladium- and ceria-modified spherical silica particle (SSP) catalysts in the temperature range of 150–350°C. The study examined how Pd, Ce, and their combined modification affected ethanol conversion, product distribution, short-term time-on-stream behavior, and carbon deposition. At a fixed EtOH/O 2 molar ratio of 2.0, Pd/Ce/SSP gave the highest ethylene yield among the catalysts tested at 200°C, reaching 59.3% ethanol conversion and 16.0% ethylene yield. However, CO 2 and acetaldehyde were also formed with yields of 38.3% and 5.3%, respectively, showing that acetaldehyde- and CO 2 -forming pathways competed with ethanol dehydration under oxygen co-feeding. Thus, oxygen co-feeding promoted low-temperature ethanol conversion but also introduced a selectivity trade-off through CO 2 formation. The 12 h time-on-stream test showed short-term retention of conversion and ethylene yield, while TGA/DTG analysis of the spent catalyst gave an estimated carbonaceous accumulation of 1.07 wt%. Characterization results suggest that the mesoporous SSP support helped preserve accessible surface area, while Pd/Ce modification shifted the main H 2 -TPR reduction feature to lower temperature and retained weak acid sites. Overall, Pd/Ce/SSP is better viewed as a proof-of-concept catalyst for oxygen-assisted low-temperature ethanol conversion toward ethylene, with suppression of CO 2 formation remaining the main challenge for further catalyst and feed-composition optimization.