Enhancement in the aromatic yield from the catalytic fast pyrolysis of rice straw over hexadecyl trimethyl ammonium bromide modified hierarchical HZSM-5

Abstract

Modified H-type ZSM-5 (HZSM-5) catalysts were prepared using hexadecyl trimethyl ammonium bromide (CTAB) as mesopore templates to enhance the activity for the catalytic fast pyrolysis of rice straw for aromatics compounds. A certain quantity of CTAB added into the HZSM-5 (HZ) forming hierarchical structure exhibited an improvement in the yield of the aromatics and a decrease in the yield of coke in comparison with that of bare HZ. In contrast, excessive CTAB addition resulted in a decrease in aromatic yield and an increase in coke yield. The effects of crystallinity, textural properties, morphological structure and acidity distribution on the production of aromatic compounds were measured by XRD, BET, TEM and NH3-TPD. The good crystallinity, small amount of mesopore formation and highest total acidity discovered in HZ-0.01 (the mole ratio of CTAB/SiO2 is 0.01) provided the highest aromatic compound yield of 26.8% and the lowest coke yield of 39.2%.