Study On Catalytic Hydrodeoxygenation Reactivity Of Guaiacol

With the increasing consumption of fossil energy,the global will face major energy and environment problems in the future.Lignin can be used as an effective and alternative energy source due to its abundant reserves,renewability and similar to petroleum in terms of hydrocarbon content.Therefore,the study of catalytic hydrodeoxygenation of lignin is of great significance for the utilization of lignin.In addition,the process of first hydrogenation saturation and deoxidation of lignin can effectively separate the product from water and reduce the production cost.In this thesis,guaiacol as a model compound,and the supported nickel catalyst was used to study the feasibility and reaction of guaiacol for hydrogenation and deoxygenation.Using guaiacol as raw material,the effects of process conditions on the hydrogenation activity of Ni/γ-Al₂O₃ catalyst and the role of hydrogen in deoxidation were investigated.The results show that the reaction temperature and space velocity are the main factors affecting the hydrogenation activity of Ni/γ-Al₂O₃ catalyst.When the reaction temperature is in the range of120-200°C,guaiacol is mainly hydrosaturated,and the product is mainly 2-Methoxycyclohexanol.When the reaction temperature is higher than 200°C,guaiacol is mainly subjected to hydrodeoxygenation reaction,and the product is mainly cyclohexane.When guaiacol is firstly hydrogenated at low temperature and then dehydrogenated,the main reaction product is cyclohexene or benzene,and the yield increases with increasing temperature.The supported nickel-based catalysts were prepared by different pretreatment methods（reduction,sulfurization,phosphating）,and the hydrodeoxygenation reaction was carried out with guaiacol as raw material,and the reaction route was also explored.The results show that the HDO reaction pathway of guaiacol on Ni₂P/γ-Al₂O₃ and Ni/γ-Al₂O₃ catalysts:guaiacol is hydro-saturated first and converted to 2-methoxycyclohexanol and cyclohexanol.Then 2-methoxycyclohexanol and cyclohexanol are deoxidated to produce cyclohexane and other substances.The HDO reaction pathway on Ni S/γ-Al₂O₃ catalyst:Guaiacol is directly hydrodeoxygenated to produce phenols and benzene,and some products are hydrosaturated and converted into cyclohexane.Under the same conditions(such as 320℃、3MPa、2h^-1、H₂/Feed=300),the Ni₂P/γ-Al₂O₃ catalyst has the better effect on catalyzing the hydrodeoxygenation of guaiacol to produce saturated hydrocarbons,and the hydrocarbon selectivity is 92.82%.The Ni/γ-Al₂O₃ catalyst is the second,and the hydrocarbon selectivity is83.94%.The Ni S/γ-Al₂O₃ catalyst is the worst,and the hydrocarbon selectivity is 936.36%.The Ni₂P/Nb₂O₅-Al₂O₃ catalyst was prepared by distributed impregnation.The effect of Nb₂O₅ on the hydrodeoxygenation activity of the catalyst Ni₂P/Al₂O₃ catalyst was investigated.The results show that the introduction of proper amount of Nb₂O₅can increase the pore size of the catalyst and the weak acid or strong acid content of the catalyst.The introduction of Nb₂O₅affects the activity of Ni₂P/γ-Al₂O₃ catalyst for guaiacol.The high loading of Nb₂O₅ can modify the deoxidation of Ni₂P/Al₂O₃ catalyst.At low loading,it produces the inhibitory effect on the reaction of guaiacol using the Ni₂P/γ-Al₂O₃ catalyst.