Synthesis Of Acylic Acid(Methyl Ester)by Aldol Condensation Over Supported Catalysts

Acrylic acid?methyl ester?with unsaturated double bond and carboxyl structure,can be derived into acrylic acid and ester polymers they are an important chemical intermediate,widely used in coatings,super absorbent resins?SAP?,adhesives and new electronic materials?photoresist?.With the rapid growth of social economy and the improvement of people's awareness of environmental protection,it is particularly important to develop a route of synthesizing acrylic acid?methyl ester?with green,sustainable and atomic economy.At present,the industrial production of acrylic acid?methyl ester?mainly adopts propylene two-step oxidation method.Propylene is the main source of petroleum.On the one hand,a large amount of oil exploitation leads to the excessive consumption of non-renewable resources,resulting in environmental pollution.On the other hand,the high price of oil leads to the increase of the production cost of acrylic acid?methyl ester?and the loss of product price competitive advantage.With the rapid development of coal chemical industry and coal chemical technology in China,coal-based chemical products are developing rapidly,and methanol acetic acid and other chemical raw materials are too saturated.Therefore,it is of great significance to study a method for synthesizing acrylic acid?methyl ester?using coal-based chemical products as raw materials,using acetic acid?methyl ester?and formaldehyde?methanol?.In this paper,various supported catalysts were prepared for the synthesis of acrylic acid?methyl ester?,and the relationship between catalyst structure,physicochemical properties and catalytic effect was discussed by combining the characterization and catalytic performance of catalysts.The content and innovation of this thesis are as follows:1.SiO₂-supported V-P-O catalysts was prepared by the incipient-wetness impregnation method for the synthesis of acrylic acid?methyl ester?by the aldol condensation reaction of methanol and acetic acid in an oxygen atmosphere.The effects of catalysts loading,P/V molar ratio and process parameters on catalytic activity were investigated.The catalysts were characterized by XRD,XPS,BET,CO₂?NH₃?-TPD,Raman and Pyridine-IR techniques.The SiO₂-supported V-P-O catalysts were composed of VOPO₄ and?VO?₂P₂O₇ phases.Both the acidic and alkaline sites were co-present in the catalysts.The vanadium species catalyzed the oxidation of methanol to formaldehyde.The V-P-O?20-30 wt%?/SiO₂ catalysts with a P/V mole ratio of 2:1exhibited higher catalytic activity for the formation of acrylic acid and methyl acrylate with a total selectivity of ca.28%at 380°C.Methanol can be an alternative to formaldehyde for the synthesis of both acrylic acid and methyl acrylate through the aldol condensation reaction.2.The catalysts SiW/SiO₂,PW/SiO₂ and PMo/SiO₂ were prepared by the traditional impregnation method for the synthesis of acrylic acid via the aldol condensation reaction of acetic acid and formaldehyde.The effects of the active component loading,the calcination temperature and the optimum temperature on the catalytic reaction were investigated.Among them,tripolyformaldehyde is used as the source of formaldehyde,so as to reduce the influence of water on the catalytic reaction process of aldol condensation and improve the catalytic reaction activity.In addition,the repeatability and stability of catalyst were studied,and the deactivation of catalyst was discussed.Comparison of silica aerogel-supported SiW/PW/PMo catalysts shows that PW/SiO₂ catalyst with 30 wt%loading and calcinated at 450°C provides the best performance for the condensation of acetic acid and formaldehyde.Increasing reaction temperature from 340 to 400°C leads to the best acrylic acid selectivities of 87.1–84.2%at the formaldehyde conversions of 35.7–45.2%.The acidic and basic sites of catalysts,especially the weak ones,are of vital importance to the synthesis of acrylic acid via the aldol condensation of acetic acid and formaldehyde.3.Nano WO₃ was first prepared by hydrothermal method,and then supported nano WO₃ catalyst was prepared by impregnation method for the synthesis of methyl acrylate by the aldol condensation reaction of methyl acetate and formaldehyde.The effects of hydrothermal reaction time,hydrothermal reaction temperature,and amount of modifier on the particle size of nano WO₃ particles and the acidity and alkalinity of the catalyst were investigated.Then,the activity test of WO₃/SiO₂ catalyst was conducted to study the WO₃/SiO₂ catalyst influence of surface structure and acid-base strength on catalytic activity.It was found that the smaller the particle size of WO₃ nanoparticles and the higher the alkali content of the catalysts were beneficial to the catalytic activity.When the hydrothermal reaction temperature was 160°C,the hydrothermal reaction time was 6 h,and the catalytic reaction temperature was 400°C with sodium oxalate as an auxiliary agent,the selectivity of methyl acrylate 95.3%and the conversion of formaldehyde 10.3%.