Study On Design And Performance Of The Catalyst For Hydrogenolysis Of 5-hydroxymethylfurfural Into 2,5-dimethylfuran

As the second-generation liquid biofuel,2,5-dimethylfuran has several outstanding features of convenient transportation and storage,high combustion efficiency,moisture-resistance,low energy consumption for separation and purification and excellent explosion-proof performance.If produced on a large scale,2,5-dimethylfuran will become a promising liquid fuel to replace the traditional fossil fuels,which could effectively solve many problems such as greenhouse effect,sea level rising,and environmental pollution which are caused by the large-scale use of fossil energy.At present,2,5-dimethylfuran is mainly produced by the catalytic hydrogenation of 5-hydroxymethylfurfural.This article focuses on the following aspects:development of a process route for dehydration of fructose to 5-hydroxymethylfurfural in a low boiling point solvent system;optimization of the reaction system for 2,5-dimethylfuran prepared from fructose as a one-pot method;synthesis of new hydrogenation catalysts for the production of 2,5-dimethylfuran from 5-hydroxymethylfurfural;optimization of reaction conditions to obtain the best product yield;characterization of the microstructure of those catalysts;investigation of the catalyst reuse;study of reaction pathway of 5-hydroxymethylfurfural hydrogenation to produce 2,5-dimethylfuran.This article developed a process for efficiently preparing 5-hydroxymethylfurfural in a low boiling point solvent which uses fructose as a raw material.Tetrahydrofuran was confirmed as the best solvent for the reason that it could form a biphasic reaction system with fructose aqueous solution.Dodecylbenzenesulfonic acid was determined as the acid dehydration catalyst for its best catalytic and surfactant performance for fructose dehydration.In the tetrahydrofuran and fructose aqueous solution two-phase system with dodecylbenzenesulfonic acid as the catalyst and surfactant,92.5%yield of 5-hydroxymethylfurfural was obtained at 140? after 30 min.An efficient catalysis system composed of AlCl3,H2SO4 and H3PO4 acid mixture and Ru/AC by using N,N-dimethylformamide as the solvent was developed for the one-pot conversion of fructose to 2,5-dimethylfuran.As a result,the highest 66.3 mol%yield of 2,5-dimethylfuran was obtained at 200? and 1.5 MPa H2 pressure.5 wt%Ru50Co50/rGO catalyst was prepared by co-precipitation method.In the solvent of tetrahydrofuran with Ru50Co50/rGO as the catalyst,a yield of 2,5-dimethylfuran as high as 92.4%was obtained at 200? for 2 h.Reduced graphene oxide have three advantages:the metal component Ru nanoparticles were mainly distributed on the outer surface of reduced graphene oxide that could reduce the diffusion resistance;the reduced graphene oxide carrier contained many oxygen-containing functional groups making it highly hydrophilic,which would promote the contact between carrier and 5-hydroxymethylfurfural;the conjugate effect between the reduced graphene oxide carrier and the furan ring in 5-hydroxymethylfurfural by ?-? interaction,which would promote the adsorption of 5-hydroxymethylfurfural and accelerate the rate of hydrogenolysis reaction.XRD,XPS,HRTEM,Raman,and BET characterization showed that the main reasons for the high catalytic hydrogenation activity of Ru50Co50/rGO catalyst were the extremely high metal dispersion and the formation of RuCo alloys.1 wt%Ru50Re50/TiO2 catalyst was prepared by the impregnation method.In the solvent of tetrahydrofuran with Ru50Re50/TiO2 as the catalyst,the highest 93.5%yield of 2,5-dimethylfuran was obtained at 200? for 4 h.BET,XRD,XPS,and HRTEM characterization indicated that the main reasons for its high catalytic hydrogenation activity were the extremely high dispersion of the metal active component,the strong interaction between the metal and carrier,and the synergistic effects between the metal components Ru and Re.5 wt%Ru-NOMC catalyst was prepared by the embedding method.In the solvent of tetrahydrofuran with Ru-NOMC as the catalyst,a maximum of 93.0%yield of 2,5-dimethylfuran was obtained at 200? for 4 h.The Ru-NOMC catalyst has extremely high recyclability.After being used for 5 times,the yield of the 2,5-dimethylfuran was only reduced by 1%.XRD,XPS,BET,and HRTEM characterization indicated that the nitrogen element has a strong adsorption on Ru metal particles and can improve the dispersibility of metal component;Ru metal nanoparticles were embedded in the carbon skeleton that caused the low metal dispersibility of Ru-NOMC catalyst.5-hydroxymethylfurfural,5-methy lfurfural,5-methylfurfuryl alcohol,2,5-dimethylolfuran,furfural,and furfuryl alcohol were used as the reaction substrates to study the reaction path of 5-hydroxymethylfurfural hydrogenolysis to 2,5-dimethylfuran by Ru-NOMC catalyst.First of all,the methylol group on 5-hydroxymethylfurfural hydrogenolysis to 5-methylfurfural,and then 2,5-dimethylfuran was finally obtained after hydrogenation and hydrogenolysis reaction.Ru-PDMS-F127 catalyst was prepared with polydimethylsiloxane as carrier.During the preparation process,a thin carbon film formed on the catalyst surface that could prevent oxidation and loss of the active metal component Ru.Nitrobenzene hydrogenation was selected to test the reaction hydrogenation activity of Ru-PDMS-F127 catalyst.In the tetrahydrofuran and water two-phase system with Ru-PDMS-F127 as the catalyst,85.7%yield of cyclohexylamine was obtained at 100? for 60 min.HRTEM,HAADF-STEM and FI-IR characterization indicated that the serious agglomeration of Ru metal nanoparticles,the low loading of the active component Ru,and the high hydrophobicity which was caused by the rare oxygen-containing functional groups on the surface,that was not conducive to the contact between the hydrogenation substrate and the catalyst surface,were the main reasons of the poor hydrogenation reactivity of Ru-PDMS-F127 catalyst to the hydrogenation of 5-hydroxymethylfurfural and other substrates.