Evaluation of zeolite catalysts on product distribution and synergy during wood-plastic composite catalytic pyrolysis

The catalytic pyrolysis of poplar wood-polypropylene composite (WPP) over different zeolite catalysts (HZSM-5, HBeta, HY, and HUSY) was investigated to obtain the influence of zeolite properties on both product distribution and synergistic effect using Py-GC/MS. The yield of aromatics was in the order: HZSM-5 > HY > HBeta > HUSY. HZSM-5 facilitated the formation of monomethyl aromatics, whereas HBeta and HY tended to promote the formation of polymethyl aromatics due to the larger pore size. The coke yield of HZSM-5 (6.4%) was much lower than those of other zeolites tested (11.4–20.2%), suggesting that the pore size of a zeolite was mainly responsible for coke formation during WPP pyrolysis. The strong synergistic effects between poplar and polypropylene in WPP pyrolysis were observed with all the zeolite catalysts tested as the experimental and calculated product distribution was significantly different. The synergistic effect over HZSM-5 zeolite promoted the selectivity for polyaromatics instead of mono aromatics, whereas the mono aromatics yield was increased by 28% for HBeta and 15% for HY zeolite. Our findings suggest that the catalytic pyrolysis of wood-plastic composites over the zeolite catalyst with suitable pore size and acidity might provide a viable and efficient route to generate hydrocarbons.