Catalytic co-pyrolysis of cotton stalks and ground film plastic using fishbone-based metal catalysts: Enhanced production of olefins and aromatics

A comprehensive understanding of the catalytic co-pyrolysis mechanism of cotton stalks (CS) and ground film plastics (GFP) is essential for efficient joint treatment in areas with high agricultural and plastic waste coverage. This study investigated the effects of CS/GFP ratios, fishbone-based catalysts (FC), FC catalysts loaded with various transition metals, and process optimization on bio-oil. Notably, the selectivity toward oxygen-containing compounds decreased from 100.00 % (CS/GFP (1:0)) to 31.87 % (CS/GFP (1:2)), while olefin selectivity increased from 0.00 % to 35.14 % under the same ratio comparison. The selectivity of aromatics was enhanced from 7.85 % (without catalyst (NC)) to 36.85 % (FC), while the selectivity of others decreased from 38.45 % (NC) to 15.19 % (FC), suggesting that the catalyst is effective in arylation and deoxygenation. Among the transition-metal-loaded FC catalysts, 10Ni/FC exhibited the best deoxygenation performance, followed by 20Fe/FC and 10Cu/FC. The selectivity of oxygenated compounds decreased from 38.45 % (NC) to 3.01 % (20Fe/HAP), 3.55 % (10Cu/HAP) and 1.06 % (10Ni/HAP), respectively. Using 20Fe/FC and 10Cu/FC, olefin selectivity increased to 71.60 % and 67.12 %, with selectivity on C6–C12 olefins reaching 95.61 % and 71.93 %, respectively. The 20Fe/FC catalyst exhibited superior bond-breaking capability, while 10Cu/FC displayed low polymerization and moderate aromatization capabilities. Furthermore, aromatic hydrocarbon selectivity improved by 1.46 times with 10Cu/FC and 11.23 times with 10Ni/FC, with the latter achieving 97.90 % selectivity for monocyclic aromatic hydrocarbons. This study provides an innovative waste treatment strategy for the production of olefins and aromatic hydrocarbons, reducing waste and facilitating energy recovery.