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UBC Theses and Dissertations

Vapour phase partial oxidation of pyrolysis oil model compounds in presence of vanadia-titania catalyst Ramachandran, Anuradha


Pyrolysis oil obtained from biomass has complex chemistry with more than 300 compounds. The utilization of pyrolysis oil as a transportation fuel is challenged by the high water and oxygen content in the pyrolysis oil. In this study, an alternate approach to improve the economic viability of pyrolysis oil is explored by employing oxidative catalysis to convert bio-oil ketones and alcohols to carboxylic acids. Due to bio-oil’s complex chemistry, this study examined two representative compounds from alcohol and ketone functional groups: ethanol (ETH) and hydroxyacetone (HAC). The model compounds were subjected to partial oxidation in presence of vanadium pentaoxide on titanium dioxide (V/TiO₂) support. The effect of temperature, oxygen ratio in the feed, and weight hourly space velocity (WHSV) on conversion, selectivity, and yield from the oxidation reaction were investigated in a packed bed reactor. Partial oxidation of HAC in presence of V/TiO₂ produced lactic acid, acetic acid, and formic acid. 92.8% conversion was achieved at 473K, O₂/HAC molar ratio = 1.5 at WHSV of 1100 cm³·min⁻¹·gcat⁻¹. Temperature, O₂/HAC and WHSV was found to impact the conversion of HAC and yield of LA. The overall reaction followed second-order kinetics and the activation energy was estimated to be 31.35 kJ·mol⁻¹. Acetic acid (AA), acetaldehyde, CO₂, and CO were identified as the major products from partial oxidation of ethanol in V/TiO₂ catalyst. Complete conversion of ETH was achieved at higher temperatures (>523K) and low WHSV conditions (<250 cm³·min⁻¹·gcat⁻¹). Only temperature and WHSV were identified as variables with significant influence on the conversion of ETH and yield of AA. A first-order rate law was used to describe overall kinetics and the activation energy was estimated to be 76.03kJ·mol⁻¹. The influence of acetic acid in the feed mixture was also investigated. The conversion of HAC and ETH in presence of acetic acid decreased slightly. However, the selectivity and yield of desired acids were similar to the reaction of aqueous HAC and ETH alone. This work successfully demonstrated the selective oxidation of model compounds with alcohol and ketone functional groups to carboxylic acid in presence of V/TiO₂ catalysts.

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