Heterogenization of Heteropolyacid with Metal-Based Alumina Supports for the Guaiacol Gas-Phase Hydrodeoxygenation

Because of the global necessity to decrease CO(2) emissions, biomass-based fuels have become an interesting option to explore; although, bio-oils need to be upgraded, for example, by catalytic hydrodeoxygenation (HDO), to reduce oxygen content. This reaction generally requires bifunctional catalysts with both metal and acid sites. For that purpose, Pt-Al(2)O(3) and Ni-Al(2)O(3) catalysts containing heteropolyacids (HPA) were prepared. HPAs were added by two different methods: the impregnation of a H(3)PW(12)O(40) solution onto the support and a physical mixture of the support with Cs(2.5)H(0.5)PW(12)O(40). The catalysts were characterized by powder X-ray diffraction, Infrared, UV-Vis, Raman, X-ray photoelectron spectroscopy and NH(3)-TPD experiments. The presence of H(3)PW(12)O(40) was confirmed by Raman, UV-Vis and X-ray photoelectron spectroscopy, while the presence of Cs(2.5)H(0.5)PW(12)O(40) was confirmed by all of the techniques. However, HPW was shown to strongly interact with the supports, especially in the case of Pt-Al(2)O(3). These catalysts were tested in the HDO of guaiacol, at 300 °C, under H(2) and at atmospheric pressure. Ni-based catalysts led to higher conversion and selectivity to deoxygenated compound values, such as benzene. This is attributed to both a higher metal and acidic contents of these catalysts. Among all tested catalysts, HPW/Ni-Al(2)O(3) was shown to be the most promising, although it suffered a more severe deactivation with time-on-stream.