Catalytic Conversion Of Furfural And Its Derivatives To ?-valerolactone

Catalytic converison of biomass to platform chemicls and bio-fuels is a green method to solve the problem of energy crisis and improve deteriorated environment.?-Valerolactone(GVL),featuring unique physicochemical properties,has wide applications in the field of fuel,food and chemical industry.Hence,selective catalytic conversion biomass to this chemcial becomes a hot research topic in recent years.Currently,the major difficulties and technical bottleneck focus on the reduction of levulinic acid/levulinate esters.There are two types of hydrogenation technology for the reduction of carbonyl group upon levulinic acid/levulinate esters,direct and transfer hydrogenation.The former is conducted in the presence of molecular hydrogen,but some drawbacks such as excessive hydrogenation of substrate,safety of process and high cost of catalyst limit this stragety partly.So,the latter becomes an attractive alternative.Despite high ?-valerolactone yield can be obtain using formic acid as a green hydrogen source,problems such as corrosion issue of apparatus,high cost of the catalyst and harsh reaction conditions also restrict this method.Alcohols,an neutral hydrogen donor,can overcome above disadvantages and becomes an ideal alternative for the reduction of levulinic acid/levulinate esters.In this study,based on the relationship between active site of the catalyst and the cascade reaction type of substrate,a series of catalysts with adjustable physicochemical peoperties were desigened and applied for conversion of furfural,levulinic acid and levulinate esters to ?-valerolactone.The detailed work are listed as follows:(1)According to the raction types of the ?-valerolactone formation process,ZrPO-X catalysts,possessing adjustable physicochemical properties,were desigened and employed for conversion of butyl levulinate to ?-valerolactone using isopropanol as hydrogen donor.Intensive characterization demonstrates that the physicochemical properties,particularly hydrophobicity,the molar ratio of Br?nsted acid and Lewis acid,Lewis acid strength can be subtly tuned via adjustment of the molar proportion of phosphorous and zirconium,which is responsible for excellent transfer hydrogenation activity.Experimental results show that 98.1% butyl levulinate conversion and 95.7% ?-valerolactone yield can be obtained with ZrPO-1.00 at 483 K after 2.0 h.This ZrPO-1.00 catalyst exhibits high stability and direct recyclability for at least ten cycles,and also can be regenerated by calcination under air.(2)Based on the analysis of the pathway of conversion biomass to ?-valerolactone,furfural,as the bridge for connecting biomass and ?-valerolactone,was employed as the raw substrate for ?-valerolactone production using ZrPO-X as the catalyst and isopropanol as the hydrogen donor.Experimental results demonstrate that ZrPO-1.50 catalyst shows the best catalytic acitivty,100% furfural conversion coupled with yields of 54.8% ?-valerolactone,16.4% isopropyl levulinate and 71.4% total products can be achieved at 483 K after 5.0 h.Characterization results reveal that organic compounds deposited on the surface of ZrPO-1.50 is responsible for deactivation after first cycle.But this deactivated catalyst can be used for three cycles after calcination under air,the change of acidic properties caused by decreased surface area is responsible for the loss activity of regenerated ZrPO-1.50 catalyst.(3)According to the in-depth understanding of MPV reduction coupled with the unique structure of basic metal carbonate,a series of basic metal(Ni,Mg,Zr,Pb,Zn)carbonates were employed for catalytic conversion ethyl levulinate to ?-valerolactone using isopropanol as the hydrogen donor.Experimental and characterization results demonstrates that an intensive synergistic effect between acid(Mn+)and base(-OH)sites is respondible for the reduction of carbonyl groups of levulinate esters,and showing more than 80.0% of the value of hydrogen donor utilization.Among these materials,basic zirconium carbonate exhibits the best catalytic activity,giving complete ethyl levulinate conversion and a 96.3% ?-valerolactone yield at 453 K within 3.0 h.This optimized catalyst can be used at leasted four cycles without obvious loss of conversion.(4)A series of Co@CN materials were prepared by calcination of ZIF-67 precursor under various conditions and employed for transfer hydrogenation of ethyl levulinate to ?-valerolactone using isopropanol as hydrogen donor.Characterization results demonstrate the metallic cobalt nanoparticles were formed during the process of calcination and protected by the graphitic carbon,which promoting the antioxidant ability of cobalt nanoparticles.The support possesses adjustable basic sites due to the existence of nitrogen element.Experimential results demonstrate that the catalytic activity is closely related with the calcination conditons,and an intensive cooperation was obersverd between C,N and metallic cobalt nanoparticles.Among these materials,Co@CN-Ar-973 shows the best activity,complete ethyl levulinate conversion and 98.9% ?-valerolactone yield can be obtained at 433 K after 1.5 h.This catalyst can be separated by external magnetic field and used at least ten cycles.These novel catalytic systems,employed in this doctoral dissertation,have guiding significance for value-added utilization of bio-chemials and provide a new strategy for biomass refinery.