Production of Valuable Aromatics from the Hydrodeoxygenation of Guaiacol and Real Bio-Oil over Ni-Nb/HZSM-5 under Supercritical Ethanol

Ni metal-impregnated HZSM-5 (30) (HZ) and Nb₂O₅ (Nb) catalysts were employed to achieve high aromatic yields from the HDO of guaiacol in supercritical ethanol. Optimizing the HZ-to-Nb ratio showed the synergistic effect of Nb toward the breaking of Ar-O-Me, Ar-OH linkages, and converting guaiacol into alkyl phenol. In addition, HZ showed its synergy toward the conversion of the produced alkyl phenols into aromatics. Compared to pure HZ, the highest aromatic contents (26.12%) were obtained for Nb/HZ (30:70), with a 93.8% conversion of guaiacol. This phenomenon might be due to an optimization of the Lewis and Brønsted acidic sites. The production of aromatics increased with Ni-loaded Nb/HZ owing to the improvement in the H₂-generation potential of the catalysts, which were 34.75 and 47.46% for 10Ni-Nb/HZ and 15Ni-Nb/HZ, respectively. However, only 28.82% of aromatics were obtained using the 10Ni/HZ catalyst. Additionally, the HDO results of real bio-oil showed the remarkable conversion of phenolic oxygenates into respective hydrocarbons with the 15Ni-Nb/HZ catalyst. A gate-to-gate LCA approach identified the fact that the present process contributed 11.86 kg of CO₂ equiv to produce 1 kg of hydrocarbon-enriched organic phase (OP) within 20 years. Over 100 years, the current process showed a GWP of 9.87 kg CO₂ equiv/kg OP, including a direct contribution of 0.05 kg CO₂ equiv/kg OP.