Selective Hydrodeoxygenation Of Sorbitol Catalyzed By Ru-Mo Catalyst To Produce C5-C6 Alkane

C5-C6 isomerized alkanes are non-straight alkanes with no water absorption,high octane number,no corrosion and swelling,etc.They can also be mixed with traditional gasoline in a high proportion,which can significantly reduce the emission of soot particles,NO_x and CO and other pollutants in gasoline tail gas,and become the ideal clean fuel for gasoline engines.At present,the industrial production of C5-C6 isomerized alkanes is still from the fractionation of naphtha,and then the precious metal catalyst palladium is converted into high octane fuel in automobiles.However,this kind of industrial production is confronted with many problems,such as limited oil resources,high production cost,low safety performance,neither sustainable development nor environmental protection,etc.So developing a sustainable path is imperative.n-hexane is a common six-carbon chain straight chain liquid alkanes,high purity n-hexane widely used in spices,medicine,food,textile and electronic cleaning agent.High purity（99.5%or more）n-hexane can not be produced in China temporarily.Foreign countries are also dependent on petroleum resources,from petroleum fractionation catalytic purification.From the perspective of biomass,in current studies,n-hexane can be prepared by one-step catalyst using lignin,glucose,sorbitol and other raw materials,but the yield and selectivity of n-hexane are very low at present,so it is necessary to develop a high purity n-hexane from biomass energy.The purpose of this study is to explore the process of selective hydrogenation of the C-O bond of sugar alcohols into corresponding C5-C6 isomeric alkanes and high purity n-hexane.The catalytic properties of molybdenum base catalyst and molybdenum carbide base catalyst were studied with sorbitol as model compound.Non-noble metal molybdenum catalysts Ni Mo O₄,Cu Mo O₄,Co Mo O₄,Mo Fe O₄ and noble metal Ru-based catalysts Ru Mo O₃,Ru WO₃,Ru Al₂O₃,Ru Fe₂O₃,Ru Mn O₂,Ru Cr₂O₃,Ru V₂O₅,Ru Mg O were prepared by sol-gel method.The physicochemical properties of Ru Mo C,Ru Mo₂C,Mo₂N and Mo P catalysts were analyzed by XRD,XPS,BET,HR-TEM,H₂-TPR and FTIR.The effects of reaction temperature,reduction temperature.1、Bifunctional catalysts with selective hydrogenolysis of sorbitol C-O bond and rearrangement of C-C bond were screened from the above non-noble molybdenum based catalysts and noble ruthenium based catalysts.Ni Mo O₄ was used as the catalyst for hydrogenhydrolysis and isomerization of sorbitol.Under the conditions of reduction temperature of 500℃,reaction temperature of 280℃and pressure of 1.0 MPa,the product contained about 93.7%C5-C6 alkanes,and the isomerization rate of C5-C6 alkanes reached51.7%.The results indicate that Ni Mo O₄ breaks C-O and C-C bonds,and C-C bonds rearrange themselves.In Ni-Mo O_x,Ni and Mo O_x play a synergistic role and inhibit the transition fracture of C-O bond.2、There are various types of carbon-oxygen bonds,including C-O and C=O,including alcohol hydroxyl group,carboxyl group,ether bond,ester group,etc.Ru Mo C reacts with reactants containing different types of C-O bond,such as ethylene glycol,tetrahydrofurfuryl alcohol,lactic acid,levulinic acid,1,2,6-hexitriol,sorbitol,etc.The bond breaking mechanism of Ru Mo C is investigated.Ru in Ru Mo C has strong ability to break C-O bonds and C-C bonds.However,in actual products,products are basically transformed into alkanes corresponding to reactants.For example,sorbitol is used as raw material,the yield of C6 alkanes is up to 94.0%,and the selectivity of n-hexane is up to 99.1%.This indicated that Mo C had a selective inhibition effect on Ru,and the reason why the selectivity could not be further improved might be that there were partially oxidized Mo O_x on the surface of Mo C,which had a certain rearrangement isomerization effect on the hydrolysis of sorbitol.3、The influence of multiple reaction parameters on the experiment was explored.For the reaction of generating C5-C6 isomerized alkanes,the reaction performance,XRD,XPS and other related characterization evaluation showed that the best reaction temperature for the catalytic activity of Ni Mo O₄ catalyst was 280℃.To C1-C2 alkanes,too low a temperature to exert the activity of the catalyst.The optimal reaction pressure is 1.0 MPa,too low pressure is not conducive to the forward reaction,and too high pressure inhibits the isomerization ability of the catalyst and generates straight-chain alkanes.For the reaction to generate n-hexane,the optimal reaction temperature is 240℃and the optimal reaction concentration is 20%.Although the sorbitol with low concentration can obtain n-hexane with higher yield and selectivity,the low concentration is not conducive to industrial production because of the low utilization of equipment.If the concentration is too high,the conversion rate of sorbitol will be low,and the carbonization of sorbitol that cannot react will form carbon deposition on the catalyst,reducing the activity of the catalyst.