Supercritical ethanol-assisted catalytic upgrading of bio-tar using mesoporous SBA-15 supported Ni-based catalysts

Abstract

The bio-tar transformation was conducted utilizing Ni-based catalysts supported on mesoporous SBA-15 within a supercritical ethanol environment. This approach aimed to facilitate the synthesis of biofuels and/or value-added chemical compounds, including alkyl phenols and aromatics. The characterization of the catalysts was accomplished by X-ray diffraction (XRD), N2-sorption, temperature programmed reduction (TPR), Transmission electron microscope (TEM), and Fourier Transform Infrared (FT-IR) techniques. Among the examined catalysts, namely SBA-15, Ni/SBA-15, Ni–Mo/SBA-15, and Mg–Ni–Mo/SBA-15, Mg–Ni–Mo/SBA-15 emerged as the catalyst demonstrating the most pronounced activity for the hydrodeoxygenation (HDO) of bio-tar to produce high-quality liquid products (Total Acid Number (TAN): 3.4 mgKOHg−1, oxygen content: 11.0 wt%, Higher heating value (HHV): 36.7 MJkg−1). The effect of reaction temperature (275–350 °C) and time (0–120 min) on the upgrading of bio-tar over Mg–Ni–Mo/SBA-15 was investigated in a one-pot process. The acids, aldehydes, and oxygenated phenols underwent complete conversion into chemically more stable compounds such as aromatics and alkyl phenols at 325 °C for a 120 min holding time. In particular, the oxygenated phenols found in the bio-tar underwent a complete transformation into alkyl phenols within the liquid products.