The Effects Of Support On Catalytic Performance Of Ni-based Catalysts For Hydrotreatment Of Bio-oil

Fast pyrolysis of biomass is an effective technology for producing bio-oil.However, the obtained bio-oil possess complex compositions and some deleteriousproperties, such as high viscosity, acidity, low heating value, low chemical a ndthermal stability, as well as immiscibility with traditional crude oils. So it requiresupgrading to realize its application in transportation fuels. Many kinds of catalystswere used for bio-oil upgrading. In this paper, we chosed Ni-based catalysts andstudied the effects of support on their catalytic performance.Bimetal mixed oxides Al2O3-SiO2, Al2O3-TiO2, TiO2-SiO2and TiO2-ZrO2wereprepared by co-precipitation. Nickel catalysts based on these bimetal mixed oxideswere tested through hydrodeoxygenation (HDO) process of guaiacol. The effects ofsupport, solvent, reaction temperature and pressure on guaiacol conversion andproduct distributions were studied. The coke resistance, recyclability of catalyst andreaction mechanism for guaiacol HDO were also discussed. The results showed thatthe activities of Ni/TiO2-ZrO2were obviously better than that of the others under thesame reaction conditions. The conversion of guaiacol over Ni/TiO2-ZrO2catalyst was100%and the selectivity for cyclohexane was as high as86.4%under theoptimization condition of300℃, initial H2pressure of4MPa and solvent ofdecalin.However, about71.2%liquid product was yielded when Ni/TiO2-ZrO2wasused for bio-oil upgrading under the same condition. In additional, coke and polymerswas observed.Because basic supports have a better performance of anti-coking, a series ofnickel-based catalysts were prepared by impregnation method using basic MgO,MgO-Al2O3and MgO/SBA-15supports and characterized by BET, SEM, XRD andCO2-TPD. The products obtained from bio-oil hydrogenation in supercritical ethanolover these catalysts were investigated by GC-MS,13C NMR and FT-IR technology.With the preferred20%Ni/MgO catalyst, the saturated alkane functional group of thebio-oil was increased from12.9%to53.5%. C=C double bond, carbonyl, carboxylfunctional groups were reduced at different levels.Ni/SiO2-ZrO2catalyst, which had a good performance for guaiacolhydrodeoxygenation, was used in bio-oil hydrogenation in supercritical ethanol. Theeffects of Ni loadings, variable mass ratios of ethanol to bio-oil (E/B) and reaction temperature on product distributions were studied. Upgraded oil with the best productproperties were obtained by catalyst with20%Ni loading and E/B=4/1at280℃.After upgrading, the saturated alkane functional group increased largely, the contentof cyclopentanones, polyols and esters also increased, the acids decreased to0.86%,the aldehydes almost removed and macromolecular aromatic compounds significantlyreduced. This upgrading process includes a variety of reactions, such ashydrogenation, cracking, alcoholysis, esterification, condensation and so on.