Enhancing the catalytic activity of Au/TS-1 in cellulose pyrolysis via alkali metal modification: A comprehensive study

The ever-increasing global energy demand and growing environmental concerns have underscored the significance of biomass utilization. Catalytic pyrolysis of biomass, especially cellulose, into value-added chemicals and liquid fuels presents a sustainable solution. Herein, Au/TS-1 catalysts modified with four alkali metal carbonates (Na, K, Rb and Cs) were synthesized and evaluated on-line in cellulose catalytic pyrolysis. The results reveal that alkali modification impacts the structural properties of catalyst. It leads to a reduction in the relative content of framework titanium, modifies the pore structure (decreases specific surface area and converts micropores to mesopores), alters the acid site distribution (introduces medium-strong acid sites), and affects the Au particle dispersion (enhances dispersion and reduces particle size). In catalytic activity tests, alkali-modified Au/TS-1 catalysts exhibited enhanced performance. Notably, Rb-Au/TS-1 and Cs-Au/TS-1 showed significant increases in the selectivity for oxygen-containing compound. Specifically, furan selectivity is enhanced upon modification with Rb and Cs, while Na and K promote carbon chain cyclization in ketone formation. Moreover, aldehyde compounds are newly generated after the modification process. This study provides valuable insights for optimizing alkali-modified Au/TS-1 catalysts in cellulose catalytic pyrolysis, thereby facilitating the conversion of biomass-to-chemicals and liquid fuels.