The role of metal oxides supported on extracted aluminium catalysts in the co-pyrolysis of cotton fabric and polypropylene wastes for bio-oil production

Biomass is an alternative renewable energy source that can reduce dependency on fossil fuels. Biomass can be converted into carbon-based liquid fuel or bio-oil, which is environmentally friendly via heterogeneous catalytic process. The management of textile and plastic waste remains a critical environmental challenge, as conventional disposal methods generate greenhouse gases, toxic emissions, and persistent pollutants. Although pyrolysis offers a promising solution, its large-scale application is limited by poor product quality from individual feedstocks, low catalyst efficiency and stability, and the underutilization of industrial waste as a sustainable catalyst source. This study aims to investigate on the synthesized metal oxides supported on extracted aluminium (EA) derived from industrial sludge as catalyst in the reaction to produce bio-oil via co-pyrolysis of cotton fabric waste (CFW) and polypropylene plastic waste (PPW). The catalysts were developed as chromium-extracted aluminium (CE) and chromium/titanium-extracted aluminium (CTE). The catalyst was prepared via wet impregnation method at various metal loadings (5-20 wt.%) and heat treated at calcination temperatures between 400 °C to 800 °C and calcination time of 2 h to 6 h. Several characterization techniques were carried out including N₂ adsorption desorption, scanning electron microscopy-energy dispersive x-ray (SEM-EDX), x-ray diffraction (XRD), ammonia temperature-programmed desorption (NH₃-TPD), x-ray fluorescence (XRF), gas chromatography-mass spectrometry (GC-MS), and Fourier Transformed Infra-Red (FTIR). The catalysts activities were evaluated in a fixed bed reactor at different operating conditions including temperature (450 °C to 650 °C), time (15 min to 75 min), CFW/PPW ratio (80:20, 60:40, 50:50, 40:60, 20:80) and feedstock to-catalyst (F/C) ratio (2:1, 1:1, 1:1.5, 1:2). The results have revealed good catalytic activities, where 15CE-600-5 and CTE21-700-5 achieved highest bio-oil yield of 74.6% and 87.6%, respectively in co-pyrolysis of CFW and PPW. The reusability study shows that these catalysts can be regenerated for two cycles, where CTE21-700-5 could maintain better activity at 70.2% and 59.5% of bio-oil yield, compared to 15CE-600-6 that could be attributed to its higher surface areas. The best catalyst CTE21-700-5 achieved highest bio-oil yield of 87.6% at best operating conditions of 550 °C, 60 min, 50:50 CFW/PPW ratio, 1:1 F/C ratio and reusability for two cycles. The kinetic study revealed the co-pyrolysis of CFW/PPW with CTE21-700-5 catalyst was describe by 0.5 order with activation energy of 47.25 kJ/mol and pre-exponential factor of 1.19×103s-1. The study concludes that the reusability heterogeneous catalyst synthesized via affordable and environmentally friendly method could effectively catalysed reaction to produce bio-oil from co-pyrolysis of CFW and PPW at moderate operating conditions.