Study On The Molding Of Catalyst For The Oxidation Of Methylacrolein To Methylacrylic Acid

Methacrylic acid（MAA）is a kind of organic chemical material with wide application and large consumption.MAA is mainly used in organic synthesis and polymer preparation.The solid waste and strong acid pollution of acetone cyanohydrin method are serious,and the cost of the whole process is high,and the atomic utilization rate is low.In the green and clean chemical trend has been gradually eliminated.At present,MAA is mainly prepared by oxidation of methacrolein（MAL）.Keggin type P-Mo-V heteropoly acid with oxidability and acidity is commonly used as catalyst.The main reason is that heteropoly acid has the advantages of acidity and oxidation reduction.However,it still has the disadvantages of small specific surface area,low MAA selectivity and low yield.By adding binders in the process of catalyst preparation,the surface structure,acidity and oxidizability of heteropoly acid were regulated,so as to improve the catalytic performance.In this paper,the effects of different binders,proportions and average molecular weights of polyethylene glycol（PEG）on the structure,acidity and oxidizability were studied with Cs Cu_0.1（NH₄）_0.3H_2.5PMo₁₁VO₄₀as the base catalyst.Finally,the catalytic performance of ethanol kneading catalyst was studied.Firstly,the catalysts with included PEG,polyvinyl alcohol,starch,tetraethyl orthosilicate,silane coupling agent and sodium silicate,etc were used to study the influence of different binders on the structure,specific surface area and chemical states of vanadium of the catalyst.By comparison,the results showed that the specific surface area,pore volume and acidity of catalysts prepares with inorganic silicon-containing binders all reduced,and these performance of the catalyst with organic binders,especially PEG and starch increased all.The structure and performance of the catalyst are affected by the degree of decomposition of the binder and the existence of the decomposition in the calcination process.Among all the catalysts with binders,the catalyst with PEG showed good catalytic performance.Then,the influence of molecular weight of PEG on the structure,oxidizability and acidity of catalyst was investigated.It was found that when molecular weight was 400g/mol,the selectivity of MAA and the conversion of MAL were improved.Then the optimal content of PEG400 was studied.The results showed that with the increased of PEG content,the specific surface area and acidity increased first and then decreased.when the mass of PEG was 5%of H₄PMo₁₁VO₄₀,the catalyst activity was best.When the feedstock gas MAL,air and N₂were 4.8 vol%,59.5 vol%and 35.7 vol%respectively,and the reaction temperature was 290oC,the MAA yield reached 68%.The addition time period of PEG and the solvent to dissolve it have influence on the structure and property of catalyst.The structure and activity of ethanol-soluble PEG kneading catalyst were investigated.The results showed that the presence of water would lead to the decrease of catalyst activity in the process of kneading the catalyst with water dissolved PEG.The catalysts for kneading ethanol were investigated.It was found that when the amount of ethanol was 40%of the mass of catalyst powder,the catalyst showed better selectivity.