Nickel-Tungsten Co-Doped Carbon Catalyst Catalyzed Hydrogenolysis Of Cellulose For The Preparation Of Ethylene Glycol

Ethylene glycol（EG）is an important industrial raw material for the production of polyester fibres,antifreeze and cosmetics,as a solvent and surfactant,and is consumed in huge quantities.The traditional synthesis process of ethylene glycol is mainly based on non-renewable petroleum and coal as raw materials,which does not meet the carbon peaking and carbon neutrality goals.Cellulose is the most abundant polysaccharide in nature,and its use as a raw material can effectively reduce dependence on fossil fuels.In this paper,a series of nickel-tungsten co-doped multifunctional catalysts were prepared using cellulose as the raw material and wood-based carbon as the carrier,and the constitutive relationship between the catalyst structure and its catalytic hydrogenolysis of cellulose for the preparation of ethylene glycol was investigated.The study is divided into three main parts as follows:（1）The carbon carrier was prepared using glucose as the source,and the multifunctional catalyst Ni-WO_X-GC_T-R_T was prepared by load nickel and tungsten by impregnation.The effect law of different reduction temperatures on the preparation of ethylene glycol catalyzed by hydrogenolysis of cellulose with Ni-WO_X-GC_T-R_T catalyst was investigated.As the reduction temperature increased from 300℃to 600℃,the W species in the catalyst were reduced from WO₂ to monomeric W,and the proportion of W⁶⁺and W⁵⁺gradually decreased and the proportion of W⁴⁺and W⁰⁺gradually increased.9%Ni-6%WO_X-GC₈₀₀-R₄₀₀ catalyst with rich W⁵⁺and Ni⁰⁺resulted in 100%conversion of cellulose and 63.6%yield of ethylene glycol under optimal conditions.The optimal catalysts showed 72% cellulose conversion and 39% ethylene glycol yield after five cycles.（2）To address the deficiencies of the poor recycling performance of the catalysts in the previous chapter,this chapter uses a one-step method to prepare highly stable Ni-WO_X-GC_T catalysts,and the effects of W⁵⁺and Br（?）nsted acid content on ethylene glycol selectivity were investigated by varying the W load to modulate the W⁵⁺and Br（?）nsted acid content.With the increase of W load the degree of polymerization of WO_X species increased,and the polymerized state of WO_X provided a large amount of polytungstate species,which increased the content of Br（?）nsted acid,then facilitated the hydrolysis of cellulose to glucose and laid a good foundation for the subsequent reaction.In addition,the increase of W load promoted the reduction of WO_X,which increased the content of W⁵⁺,thus promoting the production of acetal alcohol.Finally,Ni⁰⁺provided the hydrogenation active site to promote the hydrogenation of acetal alcohol to ethylene glycol.With the synergistic interaction between great Br（?）nsted acid,W⁵⁺and Ni⁰⁺active sites,the 9%Ni-12%WO_X-GC₇₀₀ catalyst showed catalytic performance with 100%cellulose conversion and 65%ethylene glycol yield under optimal conditions.Conversion of cellulose and yield of ethylene glycol were well maintained at 87%and54.9%respectively after six cycles of the optimum catalyst.（3）The Ni-WC-GC_T catalysts were prepared by further increasing the carbonisation temperature and W load during the catalyst preparation.It was shown that in the presence of metal Ni,with the increase of the carburization temperature and W load,the catalyst underwent carburization reaction during the preparation process,resulting in the W species undergoing the change of WO_X→W→WC morphology,and this change affected the valence and specific surface area of metal W,which directly affected the catalytic performance.9%Ni-13.5%WC-GC₈₅₀catalyst showed good catalytic activity,and the conversion of cellulose is 100%and the yield of ethylene glycol is 69.2%under the optimum conditions.The conversion of cellulose and ethylene glycol yield after six cycles of the optimum catalyst were 84% and 58.4% respectively.