Iron salt catalytic pyrolysis of biomass: Influence of iron salt type

To improve on existing pyrolytic products and understand the role played by the anion during catalytic pyrolysis with iron salts, different iron salt types were studied for biomass pyrolysis. The results demonstrate that iron salts promoted the cracking of biomass, decreased the precipitation temperature of the volatiles, and increased the production of char and hydrogen. Specifically, the addition of Fe(NO3)3 increased the gas yield and promoted the degree of graphitization and meso-porosity of biochar. The use of FeCl2 and FeCl3 led to a high selectivity (85.74%) for the production of ketone-rich oil, a highly developed micropore-dominated biochar with a surface area of 505 m2/g, and a hydrogen-rich gas (33.68 vol %). When Fe2(SO4)3 was used, acid-dominated oil with 73.85% selectivity was obtained. The pyrolysis behavior and properties of the product depended on the degree of hydrolysis during impregnation and the in-situ-produced iron microcrystalline structure (nitride, oxide, or carbide). [Display omitted] •Iron salts were used to promote the catalytic pyrolysis of biomass.•Fe(NO3)3 catalytic pyrolysis led to sustainable porous graphite from biomass.•Use of FeCl2 and FeCl3 led to microporous large specific surface areas.•Use of FeCl2 and FeCl3 led to high proportion of ketones among the volatiles.•Iron salts cracked biomass, released hydrogen, and trapped carbon atoms in biochar.