Research On The Synthesis Of 3-HPA From Formaldehyde And Acetaldehyde By One Step Using A Combined Catalyst Fixed-bed Process

The development and production of 1,3-PDO were briefly described in this paper,and the technics and catalyst of the synthesis of 3-HPA and acrolein, which were the materials of 1,3-PDO,were studied.The condensation of formaldehyde with acetaldehyde was used to synthesiz acrolein in this paper. The method has many advantages such as more easy to get raw materials, having high catalytic efficiency.But for the long production line through two alone steps,the operation is complex and much easy to contact the toxic acrolein, which can be harmful to the peaple'health,so in this paper,the synthesis of 3-HPA through the combined catalyst fixed-bed process from formaldehyde and acetaldehyde is designed and researched.This paper involved these synthetic reactions,the synthesis of acrolein from formaldehyde and acetaldehyde,and the synthesis of 3-HPA and the combined catalytic process of the fomer two.For these reactions,the preparation of catalysts and the effect of reaction technics on the reaction performance are discussed respectively.Thus,it can provide academic reference for the practical industrial production and for the scientific research in the future.For the synthesis of acrolein,the effect of catalyst including the method of catalyst preparation,suport,active components and its content on the reaction performance and the effect of the reaction technics including reaction temprature, space velocity and molar ratio on the reaction performance are researched respectively in this paper.Through comparation of the effect of catalyst preparations such as coprecipitation,impregnation and metal oxides only on the reaction performance,it concludes that impregnation is more suitable for the aldol condensation reaction,so Impregnation was selected to prepare catalyst.Then through comparation of the effect of different suport such as 7-Al₂O₃,SiO₂,ZSM-5,4A and 5A zeolite on the reaction performance,it concludes that SiO₂ is more suitable for the aldol condensation reaction,so SiO₂ was selected as the suport of catalyst.Based on the impregnation and the suport SiO₂,the active components and its content were investigated respectively,then it concludes that 4%MgO/SiO₂ was considered as the optimum catalyst.Based on the catalyst 4%MgO/SiO₂,the effect of temperature,space velocity,molar ratio of reactants and MgO mass fraction on the reaction performance was investigated.An optimum result of 78.35%selectivity,44.25%yield of acrolein and 56.48%conversation of acetaldehyde was obtained at temperature 300℃, space velocity 2.0h^-1,molar ratio of formaldehyde to acetaldehyde 2:1.For the synthesis of 3-HPA,strong acidic resin and chelating resin 850 were selected from kinds of resins as catalysts of acrolein hydration.When strong acidic resin was used in acrolein hydration,the reaction required a low temperature to proceed,and had a higher conversion,but with lower selectivity. In a continuous reaction method,a optimum result of 28.72%yield and 68.72% selectivity of 3-HPA was obtained at temperature 60℃,space velocity 9.0h^-1.In a fixed-bed continuous reactor,while using chelating resin 850 in hydration,the conversion rate was 58.85%and the selectivity of 3-HPA was more than 92%,so its yield could be 54.39%.The data of conversion and selectivity show that such resin is more suitable for 3-HPA industrial productions.For the synthesis of 3-HPA from formaldehyde and acetaldehyde through two combined catalytic reaction-bed,the reaction conditions of the first reaction-bed was kept as same as the synthesis of acrolein,and then change the reaction conditions of the second reaction-bed.The effect of temperature,space velocity,and molar ratio of reactants on the reaction performance was investigated.When strong acidic resin was used in acrolein hydration,an optimum result of 43.02%yield of 3-HPA and 56.54%conversation of acetaldehyde was obtained at temperature 60℃,space velocity 9.0h^-1,molar ratio of formaldehyde to acetaldehyde 2:1.When chelating resin 850 was used in acrolein hydration,a optimum result of 39.64%yield of 3-HPA and 75.78% conversation of acetaldehyde was obtained at temperature 70℃,space velocity 5.0h^-1,molar ratio of formaldehyde to acetaldehyde 2:1.in comparation with the two acid catalyst,when strong acidic resin was used,43.02%yield of 3-HPA was abtained and when chelating resin 850 was used,39.64%yield of 3-HPA was abtained.So for combined reaction-bed reaction,the data of conversion and field show that strong acidic resin is more suitable for 3-HPA industrial productions.