H-ZSM5 Catalyzed Co-Pyrolysis of Biomass and Plastics

TLDR

The study investigates co‑pyrolysis of agricultural plastics and biomass to produce drop‑in fuels and assess whether blending enhances aromatic yield. Catalytic fast pyrolysis at 650 °C with H‑ZSM5 was performed on mixtures of switchgrass, cellulose, xylan, lignin and PET, PP, HDPE, LDPE, PS, and product distributions were quantified by py‑GC/MS to compare yields against individual feedstocks and additive expectations. The blends, especially those containing PE, PP, and PET, showed higher total aromatic yields and altered selectivity compared to the individual biomass or plastic pyrolysis.

Abstract

This study aims to address two important problems vital to agriculture: disposal of agricultural plastics and production of drop-in fuels from biomass via co-pyrolysis of both feedstocks. Mixtures of biomass (switchgrass, cellulose, xylan, and lignin) and plastic (polyethylene terephthalate (PET), polypropylene (PP), high density polyethylene (HDPE), low density polyethylene (LDPE), and polystyrene (PS)) were subjected to catalytic fast pyrolysis (CFP) at 650 °C in the presence of H-ZSM5. A micro-pyrolyzer coupled with GC/MS (py-GC/MS) was utilized to evaluate desired mixes and product distribution. Yields of the aromatic compounds typically observed as catalytic pyrolysis products including toluene, ethylbenzene, p-xylene, o-xylene, naphthalene, and 2-methylnaphthalene and their sum were tracked. The carbon yield of products from CFP of mixtures of biomass and plastic were compared with that of biomass alone, plastic alone, and the calculated arithmetic sum of yield values expected if there was no chemical interaction between the two feedstocks. The latter provides insights as to whether a synergetic effect occurred that enhanced the selectivity to aromatics of the blend or just the additive sum of the individual products. It was found that in several cases conversion enhancement occurred for the mixture, with the aliphatic polymers (PE and PP) and PET generally providing the biggest increase in total aromatic yields. Changes in selectivity for the production of individual aromatic compounds were also observed in the blends compared with the biomass or plastics alone.