Interaction mechanism of cellulose pyrolysis over alumina-coupled Ce-Zr catalysts for aldehyde–ketone compounds

Aldehydes and ketones are regarded as important precursors for hydrocarbon fuel production due to their structural stability and ease of hydrodeoxygenation. In this study, a composite metal catalyst was constructed using alumina as the matrix and Zr and Ce as the active components, which was applied to catalyze the rapid pyrolysis of cellulose for the preparation of aldehydes and ketones. The synergistic roles of metal elements and the transformation pathway of aldehydes and ketones were elucidated, along with the influence of process parameters on product distribution and catalyst structure on activity and coke formation. The results demonstrate that the bimetallic alumina-supported catalyst outperformed the single-metal counterpart, with Zr-Ce/α-Al 2 O 3 showing higher aldehyde and ketone selectivity than Zr-Ce/γ-Al 2 O 3 due to two additional acid sites. Under in-situ pyrolysis at 450 °C and a 1:3 feedstock-to-catalyst ratio, 76 % selectivity to aldehydes and ketones was achieved. ZrO 2 and CeO 2 regulated the acidic sites of alumina and provided lattice oxygen, while the alumina support, in turn, enhanced the catalytic activity of the active metals. The co-precipitated catalyst, with higher BET surface area and stronger acidity, enabled a lower dosage and exhibited greater CeO 2 reducibility. Furfural was identified as the main product of catalytic pyrolysis. Under limited acid sites, it could be converted to 2-methylfuran via hydrogenation or to butanone through ring-opening. Excessive acidity promoted its oxygen addition, leading to acetic acid, which was subsequently ketonized to acetone. In addition, FTIR of the spent catalyst revealed oxygen in coke deposits mainly existed as bound water.