Effect of Solvents on the Structure and Properties of Mesoporous SiO2 Supported Phosphotungstic Acid

HPW/BMMs catalyst was prepared by supported phosphotungstic acid on mesoporous SiO2 with two different mesoporous structures via impregnation method, and characterized by means of XRD, FTIR, nitrogen adsorption- desorption, TG and SEM. The effects of solvents, such as water, ethanol, acetone and acetonitrile, on the structure and properties of supported phosphotungstic acid were systematically investigated. The results showed that the mesoporous structures of BMMs were maintained in the catalysts synthesis process, however, the mesopores order degree, surface area and pore volume of the catalysts (HPW/BMMs) decreased as the increase of HPW loading. A new HPW species in HPW/BMMs appeared at lower loadings and disappeared as the increasing of HPW amount. In addition, the influence of aqueous solution on the Keggin structure of HPW in HPW/BMMs was remarkable, al- though the HPW crystal remained intact with the uniform dispersion. The acid density of the catalyst synthesis in water with 40% HPW loading (40HPW/BMMs-WA) was up to 1.381 μmol/m 2 . In contrast, when acetonitrile was used as solvent, the Keggin structure of HPW was more likely to be maintained, but the HPW crystal phase was se- verely destroyed with a low dispersing inside the mesoporous channels. In comparison, the effects of ethanol and