Synthesis Of Copper-Based Catalysts And Their Selective Catalytic Aerobic Oxidation Of Alcohols

The selective oxidation of alcohols is an important oxidation reaction and the corresponding carbonyl compounds such as aldehydes and ketones are important intermediates and raw materials in many fields.The traditional production process has many problems,such as generating a large amount of pollutants,low utilization rate of atoms,high cost,poor safety factor and so on.It is no longer corresponds to today’s trend of green and sustainable development of production,therefore,it is necessary to develop an efficient,green and economic production process.A galactose oxidase exists in nature,which uses molecular oxygen as an oxidant and can catalyze the oxidation of alcohol with high efficiency and selectivity.It has been widely concerned because of its mild reaction conditions and high selectivity.In the process of simulating bionics,Cu（I）/TEMPO/NMI homogeneous alcohol catalytic system with high efficiency and selectivity was developed.On this basis,considering the recycling of catalysts,a series of heterogeneous catalysts based on Cu₂O have been developed to catalyze the aerobic oxidation of alcohols under mild conditions.The main contents include the following three parts:In the first part,a heterogeneous catalytic system was developed with Cu-Cu₂O/MO₂（M=Mo,W）as catalyst,2,2,6,6-tetramethylpiperidine-N-oxyl（TEMPO）and N-methylimidazole（NMI）as co-catalysts for the selective oxidation of benzyl alcohol.Under the same reaction conditions,the catalytic activity order of the catalysts is Cu-Cu₂O/Mo O₂>Cu-Cu₂O/WO₂>Cu-Cu₂O.The causes of the difference in catalyst activity were analyzed by ultraviolet photoelectron spectroscopy（UPS）,X-ray photoelectron spectroscopy（XPS）and electrochemistry.It is revealed that the increase of catalyst activity is due to the electron transfer caused by the difference of work function,which increases the electron density of active center and changes the energy band structure of catalyst,thus promoting the catalytic activity.In addition,the acidic sites on the surface of the substrate（MO₂）can promote the catalytic reaction.For benzyl alcohol,allyl alcohol,heterocyclic alcohol and other substrates,the system showed excellent catalytic performance.Simple reducing heat treatment can effectively improve the stability of the catalyst.The catalyst has no obvious activity loss after six cycles of recycling.Simple reducing heat treatment can effectively improve the stability of the catalyst.The activity of the catalyst has not decreased significantly after six times of recycling.In the second part,based on the first part,the Cu-Cu₂O/Mo S₂ catalytic system was developed using Mo S₂ as the support and used it for the selective oxidation of benzyl alcohol.Under optimal conditions,Cu-Cu₂O/Mo S₂ has higher catalytic activity and stability than Cu-Cu₂O/Mo O₂,and there is no significant decreased of activity after five cycles.The reason for the better catalytic activity of Cu-Cu₂O/Mo S₂ was studied by spectroscopic and electrochemical techniques.The results showed that Mo S₂ also promoted the catalytic reaction by regulating the electron density and band structure of the active center.In the third part,the Cu-Cu₂O/Y₂O₃ catalytic system was designed and synthesized by introducing low function material（Y₂O₃）.The specific effect of the work function of the introduced material on the activity of the catalyst was investigated by spectroscopic technique,and the interaction within the catalyst was studied,which provided a new idea for the rational design of the catalyst.