Conversion Of 5-HMF Into DMF And C₅/C₆ Alkanes Over Metal-Acid Catalyst

With the decrease of fossil reducing,and environmental problem which was triggered by the fossil utilization became severely,so it was extremely urgent to explore the new sustainable energy to realized the sustainable development of society.Biomass was utilized for producing high-quality chemicals because of its wide distribution,abundance,and renewable.Among those high-quality biofuels,2,5-dimethylfuran(DMF)as a renewable oxygen-contained fuel,which showed high energy density,high octane number and high boiling point compared to ethanol,and it was efficient to improve the combustion performance.C5/C6 alkanes as the important gasoline components can improve the volatile properties and octane number.Cellulose accounts for 40-50%in the three components of lignocellulose(cellulose,hemicellulose,ligin).To realize the utilization of cellulose has great significance for research during the last decades.5-Hydroxymethylfurfural(HMF),as a compound by dehydration of saccharides and hydrolysis of cellulose.which was used to converted to DMF and C5/C6 alkanes can provide the theoretical support.In our work,We used n-butanol system to explore the HMF hydrogenolysis to DMF by metal-acid Ru-MoOx/C catalyst,through the crystal phase stucture,grain size,reducing property and acidity characterization,we verified the electron transferring between Ru and MoOx,which promoted the synergistic effect of particles and increased the hydrogenolysis activity of HMF.For the characterization of NH3-TPD,with the increasing of MoOx loadings,the total acid was enhanced,which promoted the furan ring opening,and this phenomenon provided the idea to prepared C5/C6 alkanes.In the optimum condition,the DMF selectivity was 79.8%(5%Ru-10%MoOx/C catalyst,1800C,1.5 Mpa,1 h).Next,we explored the condition of HMF hydrodeoxygenation to C5/C6 alkanes.The 2%Ru-20%MoOx/C was selected as the catalytic type.In the optimum conditions,the C5/C6 alkanes selectivity was 67.4%.(300 ?,4 MPa,4 h).Next,we investigated the Ru-MoOx/C catalyst regenerability on the optimum condition of HMF hydrogenolysis to DMF(180 ?,1.5 Mpa,1 h).The catalyst was effective and stable during the first three run.After the third run,the DMF selectivity was decreased gradually,which indicated the catalyst deactivated during the tests.After regeneration,this catalyst activity could be recovered.Through the characterization tests,we found the cause of deactivation was probably attributed to the agglomeration of carbon support and deposit of carbonaceous species like humins,which leaded to the decrease of surface area and blocked the active site.Moreover,we explored the reaction network of HMF hydrodeoxygenation to C5/C6 alkanes.HMF was to form 2,5-Furandimethanol(DHMF)by the hydrogenolysis of aldehyde group due to Ru adsorb H2 to dissociate to H over the Ru-MoOx/C catalyst.Since MoOx can accept electronic pair and acted as Lewis acid,DHMF could be converted to DMF by two steps of dehydroxylation over the acid site,5-methyl-2-firfuryl alcohol(MFA)was a key precursor to produce DMF.When increased the temperature and pressure,the DMF would be opened furan ring to produce 2,5-hexanedione and 2,5-hexanediol,and then hydrodeoxygenation to C5/C6 alkanes.Interestingly,over 10%MoOx/C catalyst,the result revealed that it was a different reaction pathway via the first step of dehydroxylation in the presence of aldehyde group to produce 5-Methylfurfural(5-MF)over the acid site,and 5-MF was difficult to further hydrogenolysis to DMF due to lack Ru metal site.Last,based on the above results,due to the metal catalysts was expensive,we decided to explore the new catalytic type.The Mo2C had been reported has the similar property of precious metal,so we investigated the catalytic activity of Mo2C catalyst to convert HMF to DMF.Under the different temperature of reducing,the species was different.Through the XRD tested,the diffraction peak was variational during the different reducing temperature.In the optimum condition,the DMF selectivity was 47.5%(180 ?,3 Mpa,6 h).Although the result was unsatisfactory,there was some rooms to improve the yield in the subsequent experiment.