Catalystic Pyrolysis for the Production of Stable Phenol Rich Bio-Oil from Wood Biomass

Abstract

Biomass studies over the last two decades shows its use as an alternate source for the production of chemicals and fuels. This can help in reducing our load on the conventional hydrocarbon use and be shared with renewable sources such as forest and agricultural wastes. In Saskatchewan, there is abundant availability of wood waste from the timber industry; hence wood can be used as biomass raw material for the production of bio-chemicals. Pyrolysis is the most promising technology for the conversion of biomass into liquids. In this research, wood pellets obtained from a lumber company were used as the feed for pyrolysis to produce a phenol-rich stable bio-oil. Usually, after the bio-oil production, catalytic cracking is done to produce valuable products. In this research, the aim was to produce phenol-rich bio-oil in single step. The experiments were carried out in three phases; Phase I: Parametric study, Phase II: optimized conditions and best-suited catalyst for stable phenol rich bio-oil and Phase III: kinetic study of the process. Experiments were performed in a packed bed reactor under varying temperatures (400,500, 6000C), acidic catalysts (H-ZSM-5, γ-alumina and silica alumina), feed size (0.71, 0.85, 1, 1.18 and 1.44mm) and catalyst weights (1g and 2g). For the kinetic study, experiments were carried out at varying residence times (0, 30, 60 and 90 minutes). Products were collected and analyzed in three phases: bio-oil, gas and char. Gas Chromatography - Mass Spectroscopy (GC-MS) and online GC equipment was used to analyze bio-oil and gases respectively. Significant in phenol derivatives is observed with the use of acid catalyst along with the reduction of oxygenates or sugars. The reduction in sugar content shows the stabilization of bio-oil as the amount of free radicals is reduced hence polymerization of undesired products can be avoided thus increasing the bio-oil shelf life. Catalyst acidity, strength and number of acid sites showed a significant effect on yield of phenol derivatives in bio-oil. Kinetic study of wood catalytic pyrolysis was performed in a batch reactor; component content data was obtained at increasing time intervals and temperatures. The gases were analyzed with the help of GC and carbon content in char was analyzed by sending samples to the Saskatchewan Research Centre (SRC) in Saskatoon. Using the ultimate analysis of wood and carbon in char, carbon conversion was calculated. The rate of reaction can be expressed by a 2 order kinetic model with an activation energy of 17104.04 J/mol and a preexponential factor of 0.000567/s. Statistical analysis was also carried out using the physical and chemical properties of the catalysts. Using MINITAB, a statistical model for the yield of phenol derivatives was determined for 1g and 2g acidic catalysts. The analysis for second resolution interaction model shows the main effect of pore volume, surface area and number of acid site on phenol derivatives yield. Also, interactions of these factors help to understand the effect on phenol yield. The predicted yield from these models and experimental yield gave overall AAD of 7% that shows a good agreement with the model.