Selective hydrodeoxygenation of guaiacol and bio-oil to cycloalkanes over Ni-based catalysts supported on altered Hβ zeolite

Abstract

The high oxygen content and low calorific value of bio-oil make it unsuitable for direct production of high energy density fuels. To address this issue, the C-O-C, C-O-H, and C-C bonds in the oxygenated compounds of bio-oil can be modified through hydrodeoxygenation (HDO) reaction. In this study, we synthesized a series of efficient Ni-CoOx/Hβ-u catalysts by impregnating Hβ molecular sieve modified with urea under mild conditions. The catalytic HDO performance of these catalysts was evaluated using guaiacol and dealkalized lignin oil as substrates. The results indicate that the Ni-15CoOx/Hβ-u catalyst demonstrated superior activity. The suitable specific surface area and pore volume of the Ni-15CoOx/Hβ-u catalysts, as well as uniformly dispersed metal particles on their surface, increased the number of active sites available for HDO. Additionally, the presence of defective sites on the CoOx surface and acidic sites on the catalyst facilitate the breaking of intermediate C-O bonds (deoxygenation) and dehydration reactions. Utilizing the Ni-15CoOx/Hβ-u catalysts, guaiacol was completely converted to cyclohexane with 100% selectivity (at 180 °C, 1.0 MPa H₂, 40 min). Furthermore, the phenolic compounds in bio-oil could also be transformed into cycloalkanes via the HDO process. These findings suggest that the Ni-15CoOx/Hβ-u catalyst has the potential to effectively hydrodeoxygenate bio-oil under mild reaction conditions.