Effect of novel Ni2P-loaded catalysts on algal pyrolysis bio-oil

Abstract

This study focused on conversion of algal biomass to bio-oil through in-situ catalytic fast pyrolysis. In particular, novel Ni2P-loaded and unmodified (zeolite, activated carbon and chicken manure biochar) catalysts were evaluated to determine their effect on in-situ upgrading of algal pyrolysis products. Among the catalysts evaluated, Ni2P-loaded zeolite achieved the highest bio-oil hydrocarbon (34.97 %) and calorific value (32.66 MJ/kg), and the lowest O/C (0.075) and N/C (0.074) ratios. There was a 137 % increase of the aliphatic hydrocarbon fraction and a 72 % increase of the biochar specific surface area (SSA) with the loading of Ni2P to zeolite. Additionally, unfavourable major oxygen- and nitrogen-containing compound, phytol and tetradecanamide, decreased seven- and six-fold, respectively, compared to the non-catalytic baseline case. Ni2P-loaded biochar achieved a reduction in the bio-oil acidity from a pH of 4.52–6.78 and a 41 % decrease of the carboxylic acids content. Biochar produced from the zeolite formulations exhibited especially favourable sorbent quality with SSA greater than 500 m2/g. According to the proposed catalytic mechanism, the generation of n-heptadecane and hexadecanamide may be due to the decomposition of phytol and tetradecanamide, and the catalytic activity was correlated to the pore size of the catalyst (22.22 Å). Direct addition reactions were the dominant pathway in the formation of liquid hydrocarbons. These results suggest that it is feasible to develop an in-situ multi-catalyst system to achieve high-quality bio-oil production. Thus, the development of novel Ni2P-loaded catalysts addressed a promising approach for biomass conversion into hydrocarbon-rich products with low risk to the environment.