Catalytic cracking mechanisms of tar model compounds

Abstract

B3LYP/6-31G(d, p) method was used to investigate the catalytic cracking mechanism of biomass tar model compound. Phenol, toluene and benzene were selected as the tar model compounds and CaO was selected as the catalyst. The pathways of tar compound radical absorbed by CaO were determined firstly through comparing enthalpy changes of the absorption, and then Mulliken population changes were analyzed. The results show that the absorption of tar model compound radical and CaO is an exothermic reaction. Formation of C—O—Ca is more easily than that of C—Ca—O and formation of Caromatic—Caromatic—Ca—O is more easily than that of Caromatic—C(O)—Ca—O. The C—C bond Mulliken populations in tar model compound radicals are reduced by 11.9%, 10.5% and 15.5% in the case of a hydrogen atom removed, and those are 15.7%, 14.3% and 16.3% in the case of two hydrogen atoms removed through the absorption of CaO. Catalytic ability of CaO acting on the tar model compound is in an order of phenol>benzene>toluene.