Shape selectivity of zeolite catalysts for the hydrodeoxygenation of biocrude oil and its model compounds

The influence of catalyst pore size and shape selectivity on the catalytic hydrodeoxygenation (HDO) of biocrude oil has been investigated by comparing the activity of nickel catalysts on the supports of different pore sizes towards model compounds of increasing size. The catalysts (Ni/Beta and Ni/Y) with 3-dimensional structure containing 12 x 12-ring channels show a higher hydrogenation activity for phenanthrene compared to 10 x 10-ring and 12 x 8-ring channel catalysts (Ni/ZSM-5 and Ni/MOR), while only Ni/Y, possessed the largest pore limiting diameter (7.4 Å), displays a good hydrogenation activity for pyrene (6.7 Å), the model compound with the largest critical diameter studied in this work. While all catalysts display a good HDO activity for guaiacol conversion, the 10 × 10-ring channel catalyst (Ni/ZSM-5) exhibit a lower cyclohexane formation rate compared to catalysts containing 12-ring channels when the residence time was reduced, which could be attributed to the small pore diameter (5.0 Å) of ZSM-5 that restricts the diffusion of guaiacol (~4.9 Å). In addition, the Ni/Beta and Ni/ZSM-5 were also tested in HDO of biocrude oil. Ni/Beta catalyst displays higher conversion and high yield of cycloalkanes compared to Ni/ZSM-5, which confirms that the selection of catalyst support has a significant influence on the product distribution in HDO of biocrude.