Reaserch On K~+ Modified Heteropolyacid And Its Application In Oxidation Of Methacrolein

Methyl methacrylate（MMA）is an important chemical raw material,which has a broad application prospect in the innovative and high technology fields such as liquid crystal display light guide plate and bio-medical functional materials.The ethylene carbonylation is a low-cost and environmentally-friendly method of producing MMA.At present,only BASF’production technology has achieved industrialization at home and abroad.Oxidation of methacrolein（MAL）to produce methacrylic acid（MAA）is an important step in the synthesis of MMA by ethylene carbonylation.In view of the low conversion and selectivity of the heteropoly acid catalyst currently used in this reaction,and the key technical issues involved in the industrial scale-up process,this paper carried out the following research work.Firstly,K⁺modified KCsCuNH₄PAV heteropoly acid catalysts were prepared using KNO₃,KHCO₃,and KOH,respectively.The effects of KNO₃,KHCO₃ and KOH as K⁺source modified heteropolyacids on the microstructure and catalytic performance of the catalyst were studied.The catalysts were characterized by FT-IR,XRD,BET,SEM,TEM,TG,NH₃-TPD and H₂-TPR.The characterization results showed that the introduction of KNO₃ as a source of K⁺into the heteropolyacid can change the micro-morphology of the catalyst,and increase the specific surface area.The introduction of KOH as a source of K⁺into heteropolyacid can promote the formation of the internal porous catalysts.The results of three catalysts activity evaluations show that the conversion rate of the heteropolyacid catalyst modified by KNO₃ was the highest,the heteropolyacid catalyst modified by KOH has the highest selectivity,and moderate catalytic activity.Therefore,in this paper,follow-up research were conducted on KOH modified heteropoly acid catalyst.Secondly,the preparation conditions of KCsCuNH₄PAV catalyst were optimized and the optimal roasting temperature,roasting time and particle size were obtained.Moreover,the experimental conditions for the activity evaluation of the catalyst were investigated,and it was found that under the condition of MAL:O₂:H₂O:N₂=1:4:10:14,it showed a conversion of 84.5%and a selectivity of 90.7%at 320℃.The stability of the catalyst was evaluated,and the result showed that the activity of the catalyst did not decrease significantly after 100 hours of operation.Finally,the kinetics of MAL oxidation by KCsCuNH₄PAV catalyst was investigated.The reaction order,reaction rate constant and activation energy were obtained,and the expression of reaction rate equation was determined.r_MAL=-8681.9e^{-（59.74/RT）}p_MAL^1.16-116.7e^{-（49.48/RT）}p_MAL^0.97...