Phosphorus doped biochar as a deoxygenation and denitrogenation catalyst for ex-situ upgrading of vapors from microwave-assisted co-pyrolysis of microalgae and waste cooking oil

High oxygen and nitrogen issues should be addressed to upgrade microalgae pyrolytic oil. In this study, phosphorus-doped (P-doped) biochar was acquired and applied to the catalytic microwave co-pyrolysis of Chlorella and waste cooking oil (WCO). The effects of catalyst-to-feedstock ratio and Chlorella-to-WCO ratio on the product yields and distributions were studied, and the maximum selectivity of hydrocarbons (92.22%), in which 52.35% was mono-aromatics, as well as the highest content of H2 (35.26%) were obtained. During the process, the nitrogenous and oxygenated compounds were effectively removed by 88.8% and 83.2%, respectively. Moreover, P-doped biochar recycling usage resulted in lower production of aromatics and syngas (H2 and CO). The characterization of P-doped biochar helped reveal the catalytic conversion mechanism. The current study offered a potential approach of converting microalgae and WCO into light hydrocarbons by converting nitrogenous and oxygenated compounds.

Automated summary

In this study, phosphorus-doped biochar was used as a catalyst for the catalytic microwave co-pyrolysis of Chlorella and waste cooking oil. The results showed that phosphorus-doped biochar effectively removed nitrogenous and oxygenated compounds, and achieved the highest selectivity of hydrocarbons and H2 production. Reusing phosphorus-doped biochar resulted in lower production of aromatics and syngas.