Effects of plastics as hydrogen donor on catalytic pyrolysis of cellulose to produce monocyclic aromatics

Hierarchical ZSM-5 (Z-40) was synthesized via a simple two-step hydrothermal crystallization without using any organic template. Low-density polyethylene (LDPE) as hydrogen donor was added into the catalytic pyrolysis of cellulose to enhance deoxygenation and the formation of BTX (benzene, toluene, xylene). Cellulose and LDPE showed the strongest synergistic effect at a feed ratio of 1, and the obtained experimental BTX yield (22.9 %) was 52.7 % higher than the theoretical yield (15 %). Co-catalytic pyrolysis (CCP) of two polymers followed similar cracking behavior to CCP of their pyrolysis vapor model compounds (furfural and n -octane), mainly including pyrolysis, catalytic cracking of pyrolysis fragments in external surface and hydrocarbons pool reactions of small cracking fragments in the internal micropores of zeolite. Z-40 showed better catalytic performance than the commercial ZSM-5 (higher BTX yield and less coke deposition) due to the appropriate acidic properties and distinctive pore structure. The optimal condition for CCP of cellulose/LDPE was temperature at 550 °C, feed ratio at 1:1 and catalyst/feed ratio at 2:1, and the achieved BTX yield reached 24.5 % with high BTX selectivity of 86.7 %. This work provided a cost-effective method for synthesis of ZSM-5 and production of high value-added BTX via a green non-oil route.