Preparation And Properties Of Hydrodeoxygenation Catalyst Supported With Metal Phosphide

Coal tar is one of the main by-products in the pyrolysis process of coal.With the rapid development of modern coal chemical technology in China,its output has been increasing year by year.With the fluctuation of international oil prices and the enhancement of human environmental awareness,the production of gasoline and diesel by hydrogenation of coal tar has been quietly shifting to the production of various high value-added chemical products.This new utilization method overcomes the high-value phenolic compounds contained in such tars in conventional production and is burned as fuel oil without being sufficiently effectively used.The use of these phenolic compounds to produce BTX chemical products through hydrorefining will greatly enhance the utilization value of coal tar.Therefore,this paper prepared a supported metal phosphide catalyst around this idea,and characterized it by H₂-TPR,XRD,N₂ adsorption and desorption,and also used 4-methylphenol,medium and low temperature coal tar fraction phenol oil as raw material.The effects of hydrodeoxygenation performance and reaction conditions of various catalysts on catalyst conversion and selectivity were systematically investigated.The following research results have been achieved:The hydrogenation catalyst is prepared by using the nitrate of each metal as the raw material of the hydrogenation active metal component by the equal volume impregnation method,and the series of hydrodeoxygenation catalysts are prepared by changing the metal phosphide type of the catalyst and different assistants.The effects of different metal phosphides and modified metal species on the morphology,phase and structure of the catalysts were investigated by catalyst characterization.The experimental results show that the optimal activity of SiO₂ loading different metal phosphide catalysts for the hydrodeoxygenation of 4-methylphenol is Ni₂P/SiO₂,and the main hydrodeoxygenation pathway is direct hydrodeoxygenation（DDO）.The aromatics in the product have higher selectivity and lower hydrogenation saturation.Compared with the Ni₂P/SiO₂ catalyst,MoP/SiO₂ and CoP/SiO₂ have lower selectivity and conversion of the target products.Different Ni/P molar ratios will produce different active phases.When Ni/P is gradually increased,the amount of active phase Ni₂P in the Ni₂P/SiO₂ catalyst increases gradually.When Ni/P=1.5,the catalyst conversion rate and target product selectivity to reach maximum.As the loading increases from 10%to 40%,the hydrodeoxygenation activity of the Ni₂P/SiO₂ catalyst and the selectivity of the target product increase first and then decrease.Different metal modified Ni₂P/SiO₂ catalysts have improved the hydrodeoxygenation activity.After the addition of the modified metal Ce,the conversion rate of the raw material4-methylphenol is over 80%,and the aromatic hydrocarbon selectivity is 85%.Under the modification of metal Ce,when Ni/P=1.5 and the loading is 30%,the Ni₂P/SiO₂ catalyst has higher hydrodeoxygenation activity and metal active component dispersion.The phenolic oil fraction of medium and low temperature coal tar was hydrodeoxygenated with a preferred catalyst.The effect of hydrogenation process conditions on hydrodeoxygenation of distillate oil was investigated.The results show that the products are mainly aromatic hydrocarbons,and the hydrodeoxygenation effect is obvious.In addition,the elevated temperature is favorable for the deoxidation reaction,and the phenolic compound is directly removed from the oxygen-containing functional group,so that the conversion of the feedstock oil and the selectivity of the product aromatic hydrocarbon increase;the lower space velocity makes the contact time of the feedstock oil and the catalyst increase,The reaction effect is enhanced,and the conversion rate of the feedstock oil is increased.