Research On The Selective Catalytic Reduction Of Biomass Aromatic Aldehydes To Aromatic Alcohols By Alkali (earth) Metal Salts

With the dwindling fossil resources and people's increasing demand for energy,to prepare fuels and chemicals using renewable resources to replace petrochemical resources is one of the focuses of sustainable chemistry.Biomass constituted by carbon,hydrogen,and oxygen,is a sustaniable organic carbon resource with abundant reserves on the earth,which can be synthesized from photosynthesis of plants.Biomass-derived liquid fuel realized zero emissions of CO₂,leading to less harmful to environment.Biomass platform molecules such as furfural,furfuryl alcohol,5-hydroxymethylfurfural,2,5-bis?hydroxymethyl?-furan,cinnamaldehyde,cinnamyl alcohol and 3-phenylpropanol derived from biomass are considered as important substitutes to petrochemical-basic chemical raw materials.In this paper,using hydrosilanes as hydrogen donor and alkali?earth?metal salt as catalysts to convert biomass aromatic aldehydes?furfural,5-hydroxymethylfurfural and cinnamaldehyde?into alcohols is discussed.The details are listed as follow:?1?Selective hydrogenation of unsaturated compounds is mainly carried out by using high-pressure hydrogen in the presence of a precious or transition metal catalyst.Here,we describe a benign approach to efficiently catalyze the hydrogenation of furfural?FUR?to furfuryl alcohol?FFA?over commercially available cesium carbonate using lowtoxic and cheap polymethylhydrosiloxane?PMHS?as hydrogen source.Good to excellent FFA yields??90%?could be obtained at 25-80oC by appropriate control of the catalyst dosage,reaction time,and the hydride amount.FUR-to-FFA hydrogenation was clarified to follow a pseudo-first order kinetics with low apparent activation energy of 20.6 k J/mol.Mechanistic insights manifested that PMHS was redistributed to H₃Si Me,which acted as the active silane for the hydrogenation reactions.Importantly,this catalytic system was able to selectively reduce a wide range of aromatic aldehydes to the corresponding alcohols in good yields of 81-99%at 25-80oC in 2-6 h.?2?Catalytic reduction of 5-hydroxymethylfurfural?HMF?,deemed as one of important biomass-based platform molecules,is a very promising pathway for upgrading of biomass to biofuels and value-added chemicals.Conventional hydrogenation of HMF was mainly carried out in the presence of precious metal catalysts with high-pressure hydrogen.Here,a highly efficient,green and simple catalytic system composed of K₂CO₃,Ph₂Si H₂,and bio-based solvent2-methyltetrahydrofuran?MTHF?was developed to be efficient for the reduction of HMF.After reacting at 25°C for 2 h,HMF could be completely converted to 2,5-bis?hydroxymethyl?furan?BHMF?in a good yield of 94%.Moreover,a possible reaction pathway was proposed,where siloxane in situ formed via hydrosilylation was found to be the key species responsible for the high reactivity.?3?The calcined egg shell was used for catalyzing the reduction of cinnamaldehyde.The optimal calcined conditions of egg shell were comfirmed?900oC&2 h?.A remarkable cinnamyl alcohol of 97%was reached at 30oC by appropriately controlling reaction parameter including the dosage of catalyst,reaction time and dosage of hydrosilane.Moreover,A good yield of3-phenylpropanol reached to 87%could be achieved by prolonging the reaction reaction time to48 h at 80oC.The reaction mechanism was explicitly validated by control experimental and DFT calculation.We also prepared porous calcium oxide using stearic acid as a template to modify egg shells,which could be utilized to catalyze the reduction of cinnamaldehyde,affording high cinnamyl alcohol yield of 97%yield at 30oC for 1 h.