Catalytic pyrolysis of biomass in molten salt: Effects of ZnCl2, CaCl2 and NiCl2 on bio-oil and gas production

Utilizing carbon-neutral biomass reduces reliance on fossil fuels and lowers carbon emissions. Although thermochemical conversion is efficient, it consumes feedstock for heat, reducing biomass conversion efficiency. Molten salts can enhance reactions and store solar energy; consequently, the coupling of solar energy with molten-salt-assisted biomass thermochemical conversion has attracted significant attention. This study evaluated bio-oil and gas production characteristics from biomass, cellulose, and lignin via conventional and catalytic pyrolysis (the latter using ZnCl 2 , CaCl 2 , and NiCl 2 ) in molten salts. Analysis of the pyrolysis gases and bio-oil revealed the effects of molten salts and catalysts on product generation from biomass, cellulose, and lignin, and suggested potential reaction mechanisms. Results show molten salts and catalysts boost hydrogen intensity: conventional pyrolysis of biomass in molten salts raises it by up to 62.50%, and catalytic pyrolysis by up to 172.67%. Molten salts and catalysts also reduce bio-oil peak area. Catalysts promote deep decomposition, reducing oxygen-containing compounds in detectable volatile compounds. Ni catalysts promote dehydration-condensation, consuming the most water but producing the least H 2 . Zn catalysts promote dehydration, dehydrogenation, and in-situ water reforming, greatly reducing bio-oil oxygenates; and polycondensation releases large-scale H 2 . Ca catalysts show pronounced decarboxylation and dehydrogenation, with feedstock-dependent performance.