Preparation And Hydrodeoxygenation Activity Of Ni(Co)-P-B Amorphous Catalysts

Due to the increasing demand for global energy, there are serious concerns over the dwindling storage of fossil fuels and its association with environmental problems such as haze and global warming, the development of a new renewable and sustainable fuel to complement fossil fuels is of great importance. Bio-oil has received much attention as a abundant potential candidate because of its advantages such as renewability, zero CO2 net emission. However, crude bio-oil contains many oxygenated compounds such as phenols, acids and furans, high oxygen content resulting in a low combustion value, which required removal of the oxygen from the bio-oil via hydrodeoxygenation(HDO) to upgrade its quality, thus reach the standards of alternative fuel.Amorphous catalyst, possessing a unique structure and have displayed excellent properties for catalytic HDO. Hence, Ni(Co)–P–B amorphous catalyst was synthesized using a facile chemical reduction method. By adding(NH4)2SO4 and Na3C6H5O7 as buffer agent to restrain the pH volatility of the solution thus regulating the reduction rate of the preparation of Ni(Co)-P-B catalysts. The effects of P/B molar ration on the catalytic activity in the HDO of p-cresol were studied, with the increase of P/B molar ratio in the raw material, the Br?nsted acid sites and Pn+ relative content on the catalyst surface increased. The deoxygenation degree was high to 97.4% with a seslectivty of 91.2% methylcyclohexane at 225 °C(4.0 MPa) within 1 h. The dominant HDO reaction pathway was hydrogenation-dehydration, which effectively decreased both the aromatic content in the product and the reaction temperature. The HDO activity of catalyst mainly depend on the Co(Ni)0 and Pn+ molar ratio on the catalyst surface, synergistic effect of B and P, and the surface area.Considering the water as a destined product of HDO influence the catalytic activity, and graphene oxide(GO) shows a good hydrophilicity, this hydrophilic GO can be transformed to hydrophobic reduced GO(RGO) by chemical reduction method. In order to eliminate the negative effect of water to further enhance the catalytic stability, this study aiming to introduce the GO in the catalyst preparation process. Hydrophobic Ni(Co)-P-B-O/RGO and unsupported Ni(Co)-P-B-O were prepared by a one-step chemical reduction method and their activities were tested using p-cresol as a model compound. Consequently, p-cresol conversion on Ni(Co)-P-B-O reached 99.9% and 99.3% at 225 °C(4.0 MPa) within 1 h, but considerable oxygen-containing compounds were observed in the products, leading to a low deoxygenation degree. After load the RGO, the deoxygenation degree on Ni(Co)-P-B-O/RGO from 55.5% and 66.4% increased to 99.9% and 99.2% under the same conditions, respectively. This is due to its large specific surface area and better hydrophobic properties. The hydrophobicity hindered the absorption of water to supply more active sites for oxygen-containing compounds in the liquid-phase HDO reaction and reduce the loss of the active sites, thus enhance the HDO catalytic properties of catalyst.