Optimization of products obtained from the pressurized pyrolysis of biomass using response surface methodology and their characterizations

In this study, pressurized pyrolysis experiments of St. John?s wort biomass sample were performed in a fixed bed reactor. Influence of temperature, pressure and heating rate on biomass pyrolysis were investigated and optimum parameters were obtained by Response Surface Methodology (RSM). Pyrolysis experiments were performed at the temperatures of 400; 450; 500; 550 and 600 °C, at the heating rates of 150; 300; 450; 600 and 750 °C/min and at the pressures of 1; 11; 21; 31 and 41 bars. The yields of bio-oils and chars were analysed by response surface methodology, the ANOVA analysis were carried out and a model was formed with the conditions that have an effect on the yields. Also, optimizations of yields were carried out. Regarding to these optimizations, the optimum bio-oil yield was estimated as 32,98% at a temperature of 513,13 °C, at a heating rate of 489,40 °C/min and a pressure at 1 bar. Optimum char yield was estimated as 41,23%, at a temperature of 400 °C, at a heating rate of 150 °C/min and a pressure at 41 bars. Bio-oils obtained at different pyrolysis temperatures and pressures were analysed by GC/MS and also their viscosities were measured. Regarding to GC/MS analysis, comparatively less ring polycyclic aromatic hydrocarbons (PAH?s) in bio-oils like Naphthalene, Phenanthrene, Anthracene were formed with increasing pressures. Morphology of the chars obtained at different pressures were analysed by SEM. Char pore size was increased with increasing pressures. In addition, elemental analysis and BET analysis of the char samples were also performed. Key Words: St. John?s wort, Pressurized Pyrolysis, Response Surface Methodology, Bio-oil, Char