Study On Catalysts For The Gas Phase Oxidation Of Methacrolein To Methacrylic Acid

Methyl methacrylate (MMA) is one of the most important organic materials, and there is large demand in domestic and international market. The traditional preparation method of MMA has lots of limitation such as high cost, huge pollution, and virulent raw materials. So it's necessary to search a new green route to replace the ACH route. Isobutene oxidation route is believed to be one of the most ideal technologies with its lower cost, lower pollution and higher economic benefit.The key step of Isobutene oxidation route is to develop the catalysts of the selective oxidation of MAL to MAA.Researchers find the P-Mo heteropolyacids catalysts have quite good activity on the oxidation reaction in 1970's, and the catalysts performance is continuously improved.In this research, various types of P-Mo-V-Cu-Cs-Sb heteropolyacid catalyst supported on SiO₂ were prepared. The influence of factors such as chemical composition, preparation methods and reaction conditions on the activity of catalyst was investigated in detail to find a better performance catalyst and the suitable reaction condition. And the catalysts structure is characterized by IR, XRD and BET.The results show that the primary structure of the catalyst is Keggin structure and there is difference in the second structure of the catalyst with the different chemical composition. The spcific surface area has great influence oncatalysts activities. The larger ratio surface area the catalysts have, the higher activity the catalysts perform. And the reaction condition also effect the catalysts activities. The pentaerythritol-added PMonViCuosCso.sSboj supported on SiC>2 has a high activity for oxidation of MAL to MAA with a conversion of 87.9% for MAL, a selectivity of 47.7% for MAA and a yield of 41.9% for MAA while the reaction condition is controlled at 300 °C with reactants proportion as MAL:O2:H2O:N2=1:3:9:12 and SV=1005 h"1.