Hydrodeoxygenation of guaiacol via rice husk char supported Ni based catalysts: The influence of char supports

Six different treatments were carried out on the pyrolyzed and raw rice husks, including hydrothermal carbonization (HI), pyrolysis-acidification (PAI), pyrolysis-steam activation (PSI), pyrolysis (PI), pyrolysis-impregnation-steam activation (PIS) and acidification-pyrolysis (API). The modified chars were used as the supports for Ni-based catalysts, and activated carbon (AC) was used as the comparison. In situ vapour-phase hydrodeoxygenation (HDO) of guaiacol was performed at atmospheric and low temperature. The effect of different char catalysts on the HDO activity of guaiacol was investigated. The physical and chemical properties of the catalysts were characterised by BET, XRD, SEM, H2-TPR, NH3-TPD, etc. The mass transfer process of char heterogeneous catalyst was analysed. The results showed that the catalyst 20Ni/RH-HI obtained a medium-strong acidity and a smallest grain size, and achieved the highest HDO ratio of 55.28% and BTX selectivity of 7.56%. BTX (benzene, toluene and xylene), phenols and cyclohexanones were the main products, indicating that most of hydrogenolysis occurred on the Caromatic-OH and O–CH3 skeleton. And small part of hydrogenolysis was on the phenyl-ring. The HDO activity was determined by the pore structure, acidity and active metal grain size of the char catalysts.