Preparation Of Magnesium Oxide Supported Gold And Palladium Alloy Catalyst And Their Catalytic Performance

As an important fine chemical intermediate product,benzaldehyde has extremely broad application prospects in the fields of medicine,perfume,pesticides,and dyes.In the traditional industrial production of benzaldehyde,method of chlorinated and hydrolysis of toluene is the most common.However,this method requires a large amount of acid,alkali and chlorine gas,which brings serious environmental pollution and equipment corrosion problems.The benzaldehyde product contains a small amount of residual chlorine,and the product can not be used in food,medical and other fields.Therefore,it is of great significance to develop a green,environmentally friendly,efficient and sustainable catalyst and catalytic system for the oxidation of benzyl alcohol to benzaldehyde.This work is based on the premise of summarizing the work of previous generations,designing a new type of catalyst,Using modified magnesium oxide as support,precious metal nano-gold particles,precious metal nano-gold palladium particles as active centers,Starting from the catalyst support and the active center of the noble metal catalyst,the effect of the catalyst in the catalytic oxidation of benzyl alcohol under different reaction conditions is explored.（1）Using oxygen as the oxidant and o-xylene as the solvent,the catalyst is applied to the liquid phase oxidation of benzyl alcohol.Firstly,the differences in the catalytic performance of the nano-Au catalysts prepared by the impregnation method,the deposition-precipitation method and the chemical reduction method are compared,and it is determined that the catalyst prepared by the chemical reduction method has higher activity.Afterwards,the influence of the amount of protective agent,support alkalinity,and catalyst loading on the performance of the catalyst was studied.And by adjusting the reaction conditions such as the amount of catalyst,oxygen pressure,reaction time,reaction temperature to explore the catalytic performance of the catalyst.The best effect is under the reaction conditions of 1 m L benzyl alcohol,50 mg Au/MgO-X catalyst,10 m L o-xylene as solvent,115°C,0.7 MPa O₂,and reaction time of 4 h.The conversion rate of benzyl alcohol is 42.6%,The selectivity of benzaldehyde is 92.8%.（2）Using oxygen as the oxidant,the catalyst was applied to the liquid phase oxidation of benzyl alcohol without any additional solvent.The gold-palladium alloy catalyst was prepared by chemical reduction method.The study found that under the same support conditions,the catalytic activity of the gold-palladium alloy catalyst was significantly improved compared with the nano-gold catalyst and the nano-palladium catalyst.Afterwards,the effects of reaction temperature,oxygen pressure,and catalyst dosage on the activity of the catalyst were studied.When the amount of catalyst is 100 mg and the reaction is carried out at 120°C for 3 h,the conversion of benzyl alcohol is 49.5%,and the selectivity of benzaldehyde is 94.7%.The cycle test shows that the catalyst has good stability and can still maintain good catalytic activity after being recycled for 4 times.