Comparison of non-catalytic and catalytic fast pyrolysis of pomegranate and grape marcs under vacuum and inert atmospheres

Abstract Pomegranate marcs (PM) and grape marcs (GM) were pyrolysed in a fixed bed reactor to investigate the effects of pyrolysis temperature (400, 500 and 600 °C), heating rate (300 and 700 °C/min) and pyrolysis atmosphere (nitrogen (N 2 ) and vacuum (25 kPa)) on product yields and properties. Maximum bio-oil yields were obtained at a pyrolysis temperature of 500 and 600 °C for PM and GM, respectively, with a heating rate of 700 °C/min under vacuum in a non-catalytic procedure. The results show that the pyrolysis of PM yields more bio-oil (43.7 wt%) than that of the GM (27.4 wt%). Therefore, an analysis of variance (ANOVA) was performed to investigate pyrolysis parameters on the yields of the bio-oil and gas products. To study the catalytic upgrading of the pyrolysis vapors, biomass samples were pyrolysed at 500 °C using 10 wt% Aluminum-MCM-41 (Al-MCM-41) as a catalyst. The yields and the quality of the bio-oil and gas were influenced using the Al-MCM-41. Based on the GC–MS results, the composition of pyrolysis oil was significantly affected by the presence of a catalyst. The formation of oxygenated compounds and fatty acids was inhibited by the Al-MCM-41, while the formation of aromatic hydrocarbons was promoted. In addition, the HHV (higher heating value) of the bio-oils and the yield of syngas increased using a catalyst. It was observed that the PM and GM bio-oils could be used as a substitute for fossil fuels to generate heat and chemicals and that syngas yields could be enhanced using a catalyst.