5-18: Screening of catalyst for mild deoxygenation of algal bio-oil

Hydrothermal liquefaction of algae biomass is considered to be favourable conversion process as it avoids the biomass-drying expenses. Crude bio-oil produced from liquefaction of microalgae is rich in fatty acids and can be used as potential feedstock for advanced biofuel. However, microalgal bio-oil tends to be viscous, tar-like, and contains significant amount of oxygen. Thus, the bio-oil needs to be upgraded before it could be used as drop-in fuel. However, complete upgradation to drop-in fuel can be expensive. Consequently, developing mild hydrotreatment strategies to produce refinery compatible bio-oil is desirable.

Our lab has been working on screening catalysts that fit for mild hydrotreatment for this application. Catalysts are selected based upon their selectivity, cost effectiveness, and their performance in aqueous media. We use fatty acid as model compounds to screen several transition metal catalysts on different support and found Ni/ZrO₂ seemed to be promising. The catalyst showed excellent selectivity for converting palmitic acid to pentadecane in aqueous phase. Three other fatty acids, stearic, oleic, and linoleic acid were also compared to illustrate the effect of fatty acid saturation on the conversion rate and products selectivity. Saturated fatty acid was observed to be more effectively deoxygenated to hydrocarbon than unsaturated fatty acid. The main organic product was the paraffin with one carbon less than the precursor fatty acid. At constant temperature and pressure, the conversion rate is 100% with selectivity of paraffin above 90%. We will be verifying the activity of this catalyst on crude bio-oil in our next phase studies.