Detailed assessment of hematite-promoted pyrolysis of corn straw: Gas products, reaction characteristics and thermo-kinetics

The promoting effect of hematite on the pyrolysis of corn straw was investigated. Hematite significantly increased the production of CO2, CO, and H2 during the fluidization roasting process, while its effect on CH4 was unremarkable. Control experiments using quartz verified the promotion effect of hematite. Specifically, hematite promoted both active pyrolysis and polycondensation reactions of corn straw but did not remarkably affect its dehydration. By promoting the ring-opening reactions and continuous cracking of macromolecular intermediates, hematite allowed for higher yields of CO2, CO, H2, alcohols, phenols, esters, and ethers. Hematite also promoted the reforming reactions between CO2 and CH4, as well as between H2O and CH4, resulting in an insignificant increase in CH4 production. In the polycondensation stage, hematite exerted a notable deoxidation effect, inducing the conversion of oxygenated compounds into benzene series through processes such as cyclization and aromatization, while generating small molecule products. Hematite played a vital catalyst role in this process, as no significant reforming reaction occurred at this stage in the absence of hematite. Moreover, kinetic analysis demonstrated that hematite changed the reaction mechanism in the active pyrolysis stage and lowered the apparent activation energy by about 80 kJ/mol, thereby confirming its kinetic promotion effect.