The Study Of Highly Efficient Catalysts For Oxidation Of Benzyl Alcohol And Oxygen

Benzaldehyde,the product of the selective oxidation of benzyl alcohol,is the most commonly used aromatic aldehyde in industry,and it is widely used in perfumes,dyes,pesticides,and pharmaceuticals.In traditional industrial production,toluene chlorinated hydrolysis is generally used to prepare benzaldehyde.However,this method has disadvantages such as complex production steps and serious chlorine pollution,which limit its application.Oxygen or air is a green and economical oxidant.Using it as an oxidant to catalyze the selective oxidation of benzyl alcohol to prepare benzaldehyde is a green and economical synthetic route.Therefore,the development of a highly efficient and recyclable oxidation catalyst for benzyl alcohol with air or oxygen as the oxidant has important research significance.The main research content and results of the paper are as follows:1.We improved the conventional deposition and precipitation method,and discussed the influence of preparation conditions,support and loading on the structure of the catalyst,the actual loading of Ru component,the catalytic activity,and the thermal stability of the catalyst was also investigated.The results show that the nitrogen roasting link in the preparation process is the key to the preparation of the catalyst.The catalytic activity of the Ru-based catalyst prepared when the calcination temperature is 300 ℃ is the best.At this time,the actual loading of Ru component is close to the theoretical loading and the Ru particles are uniformly dispersed.The catalytic activity of Ru-based catalysts showed a decreasing trend with the increase of heat treatment temperature.Combined with the characterization results of the catalyst,it is indicated that the dehydration and decomposition of Ru(OH)x component caused by high-temperature calcination is the main reason for the decrease of catalyst activity.2.We prepared a series of Mn-Fe composites by co-precipitation method,adjusted the composites by changing the Mn/Fe ratio and calcination temperature,and investigated their catalytic performance for the oxidation of benzyl alcohol and oxygen.The results show that the Mn-Fe composites with Mn/Fe =1 has the best catalytic activity,reacting for 4 h in an oxygen atmosphere at 80 ℃ to achieve 83.1%benzyl alcohol conversion and nearly 100% benzaldehyde selectivity.At the same time,the catalyst has good cycle stability.Based on the characterization results,the possible reaction mechanism of the Mn-Fe composites catalyzed by the oxidation of benzyl alcohol and oxygen was proposed.The catalyst activity reduced by high temperature calcination treatment.Based on the characterization results,it is speculated that the decrease in the specific surface area and surface Oβ/O of the catalyst caused by the high-temperature calcination is the main reason for the decrease in its catalytic activity.At the same time,we used an improved deposition precipitation method to prepare a Ru-based catalyst with Mn-Fe composites as a carrier,and investigated its catalytic performance for the oxidation of benzyl alcohol and oxygen.Combined with the catalyst characterization results,considering that the preparation method changes the carrier composition during the catalyst preparation process,the Ru-based catalyst was prepared by the co-precipitation method,and the effect of Ru content on the catalytic performance of the catalyst and the catalytic activity.of each component in the catalyst were studied.The results show that the 2wt% Ru(OH)x/Mn-Fe(Mn/Fe = 3)prepared by the co-precipitation method has good catalytic activity,reacting for 1 h under an oxygen atmosphere at 80 ℃ to reach a conversion rate of 97% benzyl alcohol and nearly 100% benzaldehyde selectivity.The combined characterization results indicate that its high activity is related to the high catalytic activity and large specific surface area of the support material.