Study On Preparation Of Propionaldehyde Process By Ethylene Carbonylation

As an important industrial product and raw material,propionaldehyde is the intermediate of many chemical products,which is widely used in paint,plastic,rubber,medicine,pesticide and other industries.In the process of industrial production of propionaldehyde,ethylene carbonylation method is often used.At present,the domestic production scale of propionaldehyde cannot reach the market demand.Propionaldehyde mostly relies on imports,which limits the production of downstream products of propionaldehyde and restricts the development of industries highly dependent on propionaldehyde.Therefore,the development and research of propionaldehyde production process has a good development prospect and market application value.In this paper,based on the method of ethylene carbonylation to produce propionaldehyde.Firstly,the batch reaction was used to explore the reaction conditions,the effects of reaction temperature,reaction pressure,initial concentration of rhodium catalyst and addition amount of triphenylphosphine on the reaction were investigated by batch reaction experiments,the optimum conditions were determined as follows: the feed molar ratio of carbon monoxide,ethylene and hydrogen was 1:1:1.08,the temperature of the reaction system was controlled at 85-90℃,the pressure of the reaction system was controlled at 1.30-1.40 MPa,the initial concentration of rhodium was controlled at 150 ppm,and the dosage of triphenylphosphine was 5wt% of the solvent propionaldehyde.At the same time,the influence of water in the reaction system was investigated.According to the reaction results and the coordination chemistry theory,it was concluded that the impurity water occupied the active site of the reactant of rhodium catalyst through the coordination effect with rhodium,which hindered the carbonylation of ethylene.And then,using the parameters obtained from the batch reaction to carry out continuous reaction to produce propionaldehyde,the effect of the residence time of the continuous reaction on the conversion of ethylene and the selectivity of propionaldehyde was studied,and the optimal residence time was 1 h.The stability of rhodium catalyst was investigated under the conditions of molar ratio of carbon monoxide,ethylene and hydrogen 1:1:1.08,reaction pressure 1.3 MPa,reaction temperature 85℃,rhodium catalyst concentration 120 ppm,triphenylphosphine addition 5wt% of the solvent propionaldehyde.It was found that the ethylene conversion rate was maintained at about 86% and the propionaldehyde selectivity was maintained at about 99.5%,indicating that the catalyst has good stability.Finally,using temperature and rhodium catalyst concentration as variables,the reaction kinetics were investigated with the help of batch reaction experiments in a high-pressure reactor,and the relationship between the reaction pressure and time was obtained.Through the analysis and calculation of the time pressure curve,the correlation coefficient of the kinetic equation was obtained.Finally,the kinetic equation and the apparent activation energy Ea were obtained,and E_a was 64.0kJ/mol.