Characterization of bio-oil yield from catalytic pyrolysis of Zea mays indentata corncob

Abstract

In this study, the effect of zinc oxide catalyst on the quality of bio-oil from catalytic pyrolysis of Zea mays indentata corncob in a fixed bed reactor at optimum bio-oil yield condition was determined. Non-catalytic pyrolysis was carried out in the temperature range of 450 – 600 oC and residence time range of 20 – 35 mins, according to D-optimal design of Design Expert software (version 13.0.1), to determine the optimum condition for bio-oil yield. Catalytic pyrolysis was carried out at the optimum condition for bio-oil yield with biomass to catalyst (b/c) weight ratios in the range 97.5/2.5 - 90/10, according to mixture methodology formulation of Design Expert Software (version 13.0.1). Elemental composition and the basic fuel properties of the bio-oils at optimum bio-oil yields conditions, including viscosity, pH value, ash content and flash point, were determined and compared with those of non-catalytic pyrolysis bio-oil. The highest bio-oil yield (44.94 wt.%) from non-catalytic pyrolysis was obtained at the temperature of 550 ℃ and residence time of 25 minutes. The highest bio-oil yield (37.45 wt.%) from catalytic pyrolysis at the optimum temperature (550 ℃) was obtained at biomass/catalyst ratio of 90/10. Catalytic pyrolysis bio-oils possessed higher carbon and hydrogen at b/c ratios of 96.67/3.33, 92.5/7.5 and 96.67/3.33. but lower oxygen and sulphur at 96.67/3.33, 92.5/7.5 and 90/10 than non-catalytic pyrolysis bio-oil. The use of catalyst reduced the viscosity, ash content (at b/c ratios of 96.67/3.33 and 97.5/2.5), and increased the pH value of bio-oils (at b/c ratios of 95/5 and 90/10). Catalytic pyrolysis improved the quality of pyrolysis bio-oil and can be moderately blended with petroleum diesel to power internal combustion engines.