Promoting hydrocarbon production from fatty acid pyrolysis using transition metal or phosphorus modified Al-MCM-41 catalyst

Abstract

Oleaginous biomass conversion to liquid hydrocarbon biofuels has emerged as an effective solution to the energy crisis and environmental problems. In this process, the removal of oxygenated compounds will directly affect the effectiveness of subsequent biofuel applications. Herein, deoxygenation of oleic acid by catalytic cracking was conducted using five various elements (La, Ni, P, Zr and Ce) modified Al-MCM-41. The related characterizations were carried out for these catalysts, including N2 physisorption, XRD, XPS, pyridine-FTIR and NH3-TPD techniques. The results showed the mesoporous structure of Al-MCM-41 was maintained after different modifications, and these catalysts greatly improved the hydrocarbons content and physiochemical properties of biofuels. The modified catalysts tended to facilitate the decarbonylation pathway and showed high selectivity to alkane and aromatic hydrocarbons. Besides, La/Al-MCM-41 presented excellent anti-coking activity. Ni/Al-MCM-41 showed both high dehydrogenation and deoxygenation activities. The Zr modification and Ce modification had a promotion effect in the deoxidizing activity of the catalyst, owing to the formation of oxophilic metal oxides. Noteworthily, P/Al-MCM-41 displayed the best deoxidizing performance due to its high Brönsted acidity, which caused the highest hydrocarbons content (82.30 %) and the lowest fatty acids content (around 0 %) of the biofuel. Moreover, the resulting biofuel had not only low oxygen content (3.88 wt.%) and acid value (5.47 mgKOH g−1) but also a high calorific value (44.50 MJ kg−1), which could be processed into green diesel. Hence, the catalytic cracking of fatty acid over P/Al-MCM-41 has excellent potential to produce high-quality renewable fuels.