Catalytic upgrading of coal tar coupling with methanol using model compound over hierarchal ZSM-5 for increasing light aromatic production under atmosphere pressure

Abstract

A new route for upgrading coal tar to aromatics was investigated. o-Cresol as model compound was investigated the coupling reaction of coal tar with methanol. ZSM-5 zeolite by 0.3 mol L−1 NaOH treatment showed the best catalytic performances due to higher Brønsted acid sites and larger mesopores. Compared with cresol as sole reactants, mixing methanol significantly promoted the production of aromatics and restrained coke deposition through methylation and hydrogen transfer. Higher yield of aromatics was obtained with increasing methanol/cresol molar ratio, indicating that more aromatic hydrocarbons were produced via providing methyl groups rather than active hydrogen from methanol. Moreover, the types of aromatic hydrocarbons could be tuned by alkylation of methylbenzene with methanol. Main products were toluene, xylene and trimethylbenzene due to the effect of steric hindrance of larger molecules of polymethylbenzene.