Catalytic cracking of tar model compounds over char-based catalysts

Catalytic cracking of biomass pyrolysis tar model compounds was conducted in a fixed bed reactor using char and metal-impregnated char (Ni-char, Zn-char) as the catalyst. The catalytic effect of the catalysts on the model compounds (n-heptane, cyclohexane, toluene, thiophene and pyridine) was investigated. The catalytic cracking caused the higher non-condensable gas yield and the lower total tar yield, especially for the Ni-char catalyst. The supported nickel on the Ni-char catalyst was existed in the form of Ni, and the Zn was existed in the form of ZnO on the Zn-char catalyst. NH3-TPD desorption results revealed that the catalyst acidity decreased in the order of Ni-char > Zn-char > Char, which is in accordance with the catalytic activity. The final catalytic effect of the Nichar catalyst on different tar model compounds is mainly determined by the structure of the compounds. The FTIR analysis results of the products obtained from catalytic cracking the model compounds over Ni-char catalyst showed that the hydrogenation reaction usually occurred when n-heptane was cracked, the ring-opening and reforming reactions mainly occurred when cyclohexane and toluene were cracked, while the thiophene and pyridine were changed little.