Haruna Ibrahim, Ephraim Gaska Kefas, Abubakar M. Ali
The sustainable production of platform chemicals from lignocellulosic biomass offers a viable alternative to petroleum-based processes. This study investigated the synthesis of acetaldehyde from Acacia auriculiformis waste leaf biomass via zinc chloride (ZnCl2)-catalysed thermal hydrolysis under mild reaction conditions. Pulverized leaf biomass (30 g; 250-300 μm) was hydrolysed in water using ZnCl2 catalyst loadings of 0.5-1.5 wt.% at 40-80 °C for 30 min under atmospheric pressure. The products were analysed by gas chromatography–mass spectrometry (GC-MS), while duplicate experiments were conducted to evaluate reproducibility. The effects of reaction temperature and catalyst loading were further assessed using two-way analysis of variance (ANOVA). The highest acetaldehyde yield of 13.34% based on the recovered product (649.73 mg/g biomass) was obtained at 60 °C and 0.5 wt.% ZnCl2. Increasing the catalyst loading beyond 0.5 wt.% reduced acetaldehyde formation, indicating the promotion of competing secondary reactions. The process exhibited excellent reproducibility, with relative standard deviations ranging from 0.98 to 1.30%. ANOVA showed that catalyst loading was the most influential factor, contributing. Although the acetaldehyde yield was lower than those reported for conventional ethanol- and ethylene-based processes, the present method operates under exceptionally mild conditions using renewable waste biomass as the feedstock. This study demonstrates that ZnCl2-catalysed thermal hydrolysis provides a simple, reproducible, and sustainable pathway for acetaldehyde production while promoting biomass valorisation and reduced energy consumption.