Catalytic fast pyrolysis of biomass with noble metal-like catalysts to produce high-grade bio-oil: Analytical Py-GC/MS study

Abstract

Four kinds of noble metal-like catalysts W2C/AC, W2N/AC, Mo2C/AC and Mo2N/AC were prepared and used for catalytic fast pyrolysis of biomass to upgrade the fuel properties of biomass pyrolysis vapors. Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) experiments were performed to analyze the volatile pyrolytic products in pyrolysis vapors. Effects of catalyst, pyrolysis temperature and catalyst-to-biomass ratio on the pyrolytic product distribution were examined thoroughly. Actual yields of major pyrolytic products were determined by an external calibration method. Results showed that tungsten-based catalysts performed better than molybdenum-based catalysts, and W2C/AC possessed comparable performance to Pd/AC catalyst. From the pyrolysis of biomass and its single component, W2C/AC and W2N/AC catalysts exhibited promising capability to promote the decomposition of lignin to generate monomeric phenolic compounds, especially stable phenolics. Meanwhile, they would also affect the holocellulose pyrolysis by decreasing anhydrosugars and linear aldehydes, while increasing furans, cyclopentanones and linear ketones. As for an overall effect, catalysis by W2C/AC and W2N/AC catalysts was capable to convert those undesirable pyrolytic products (containing aldehyde group, CC bond or carboxyl group) through decarbonylation, hydrogenation, decarboxylation and other reactions, and thus decrease the instability, acidity and oxygen content of pyrolytic products for obtaining high-grade bio-oil.