Preparation Of Bifunctional Catalyst And Optimization Of Reaction Condition In Methanol Liquid Phase Oxidation

In recent years,China's coal based methanol industry has been developing rapidly,resulting in over capacity of methanol.Methanol can be converted to high value-added chemicals methyl formate.The production of methyl formate has already been industrialized,and the capacity can not meet the demand.The traditional process has high energy consumption and no environmental protection.Therefore,with methanol as reactant and green clean oxygen as oxidant,a supported bifunctional catalyst with both oxidation active site and acid active site of L acid can be prepared to produce methyl formate directly by selective oxidation of methanol in liquid phase.The catalytic effect is good.This method reduces the steps,reduces energy consumption and green efficiency.The catalyst can be recovered and reused through centrifugation and filtration.In this paper,the carrier ?-Al2O3 is prepared by roasting the pseudo boehmite.The Pd/?-Al2O3 and bimetal Pd-Au/?-Al2O3 catalyst are prepared by the sol-gel method to prepare the Pd/?-Al2O3 and bimetallic Pd-Au/?-Al2O3 catalysts supported on Pd and Au of precious metals by the sol-gel method.The catalysts are characterized by XRD,XPS,BET and TEM.The catalytic performance is evaluated,the reaction conditions are optimized and the reproducibility of the catalyst is tested.The results are as follows:1.The Pd/?-Al2O3 catalyst is prepared by sol-gel method,and the Pd particles are uniform,with an average of 6.85 nm.The catalytic performance of Pd/?-Al2O3 catalyst is evaluated and the reaction conditions are optimized.The reactant is 5mL anhydrous methanol,the optimal load of Pd is 2wt%,the optimal dosage of 2wt%Pd/?-Al2O3 is 40 mg,the optimum temperature is 150?,the optimal pressure is 2 MPa,and the optimal time is 2 h.At this time,the conversion gets 50.51%and the selectivity gets 66.46%.The yield is 33.56%,and the reusability of the catalyst is tested for 5 times.Not only the conversion,but also the selectivity have decreased.This indicates that the catalyst is reused in general.2.The Pd-Au/?-Al2O3 catalyst is prepared by sol-gel method,and the size of the alloy is uniform with an average of 7.3 nm.The catalytic performance of Pd-Au/?-Al2O3 catalyst is evaluated and the reaction conditions are optimized.The reactant is 5 mL anhydrous methanol.The optimal load of catalyst is 2wt%Pd-lwt%Au,the optimal dosage of 2wt%Pd-lwt%Au/?-Al2O3 is 20 mg,the optimal temperature is 150?,the optimal pressure is 1.5 MPa,and the optimal time is 2 h.At this time,the conversion rate of methanol is 62.11%and the selectivity of methyl formate is 68.14.The yield of methyl formate is 42.32%,and the reusability of the catalyst is tested for 5 times.After 5 times,the conversion changed little,the selectivity changed little.The yield of methyl formate has changed from 42.32%to 40.54%,indicating that the catalyst had excellent reusing performance.