Study On The Aldol Condensation Of Methyl Acetate With Formaldehyde Over Ba-Al Supported Catalysts

Methyl acrylate are important intermediate for the synthesis of various coatings,rubber,leather,medical,adhesives and polymers,which is widely used in many aspects.In recent years,it is necessary for acrylic acid and its ester to be demanded.Propylene oxidation is the main way of acrylic acid and its ester in production,which mainly includes propylene one-step oxidation method and propylene two-step oxidation method.The production of propylene oxidation raw materials mainly depends on the cracking and cracking of petroleum products.As we all know,China is a country with more coal and less oil,and using methyl acetate and formaldehyde as raw materials to produce methyl acrylate through the condensation of hydroxyl aldehyde is an economic and environmental friendly green synthetic process route to replace oil with coal.At present,how to efficiently produce methyl acrylate from methyl acetate and formaldehyde is still a research hotspot,and the design and preparation of highly active catalysts are particularly important.Previous research results showed that the alumina catalyst had good catalytic activity,but there were problems such as poor catalyst stability and fast deactivation rate,etc.According to literature reports,the presence of electron transfer in composite metal oxides can improve the deactivation of the catalyst due to carbon deposition.Therefore,in this paper,we focus on the barium and alumina as the main active components,through doping the third component to design and preparation of high activity and high stability of composite oxide catalyst.We prepared Mg O-Al₂O₃ complex,Ce O₂-Al₂O₃ complex,Zr O₂-Al₂O₃ complex,Al PO₄ and other catalyst carriers by co-precipitation method.In a fixed-bed reactor,the catalytic performance of the catalyst support for the condensation of methyl acetate with formaldehyde hydroxyl aldehyde to prepare methyl acrylate was investigated.The effects of the molar ratio of P to Al in Ba/Al PO₄ catalyst and the loading amount of Ba on the catalytic performance were investigated.The experimental results show that compared with Mg O-Al₂O₃ complex,Ce O₂-Al₂O₃complex and Zr O₂-Al₂O₃ complex,the catalytic activity of Al PO₄ is obviously better than the above three kinds of composite oxides,and the catalytic activity and stability are the best when the molar ratio of P to Al of Ba/Al PO₄ catalyst is 1,the calcination temperature is 500°C,and the barium salt load is 15wt%.The characterization results showed that when the molar ratio of P to Al in Ba/Al PO₄ catalyst was 1,the catalyst surface had the most active sites of weak acids and weak bases and the most amount of acid and base,which was conducive to the condensation reaction of hydroxyl aldehyde.Theγ-Zr-Al₂O₃ catalyst successfully prepared by the evaporation induced self-assembly method,which further improves the catalytic performance of theγ-Al₂O₃catalyst support.Theγ-Zr-Al₂O₃ catalyst support was synthesized from aluminum isopropanol by mixing zirconium nitrate into the alumina bulk phase.The effects of the molar ratio of Al to Zr in Ba/γ-Zr-Al₂O₃ catalyst and the loading amount of Ba on the catalytic performance were investigated.The experimental results showed that when the molar ratio of Al to Zr of Ba/γ-Zr-Al₂O₃ was 75 and the load of barium salt was 15wt%,the catalytic activity was the best.The conversion rate of methyl acetate was 24.7%,and the selectivity of target product methyl acrylate was 91.5%.It is shown that doping appropriate amount of zirconium can increase the amount of alkali on the catalyst surface and inhibit the formation of carbon on the catalyst surface,thus reducing the deactivation rate of the catalyst.The best catalytic effect of catalyst 15wt%Ba/γ-Zr-Al₂O₃ was selected,and the synthesis route was optimized from the reaction temperature,injection speed and raw material ratio,and the optimal reaction conditions were finally determined.In conclusion,15wt%Ba/γ-Zr-Al₂O₃ catalyst with excellent catalytic performance were prepared from the perspective of improving the activity and stability of the catalyst,which will provide a reference for the development of methyl acetate and formaldehyde hydroxyl aldehyde condensation to prepare methyl acrylate catalyst.