疏水改性磺化泡沫二氧化硅固体酸性能研究

Study on solid acid performance of hydrophobic modified sulfonated foam silica

文章采用巯基丙基三甲氧基硅烷(MPTMS)对介孔泡沫二氧化硅(mesocellular silica foam,MCF)进行接枝磺化,制备了Pr-SO3H/MCF固体酸催化剂,并考察了苯基三甲氧基硅烷疏水改性对苯甲酸甲酯合成的影响。采用氮气吸附脱附(BET)、透射电子显微镜(transmission electron microscope,TEM)、接触角、元素分析仪等手段对催化剂进行表征。结果表明,苯基三甲氧基硅烷改性后的Ph/Pr-SO3H/MCF催化剂,比表面积略有降低,疏水性明显提高。由于苯环与苯环之间形成π-π键,增加了对反应物苯甲酸的吸附能力,在催化剂表面形成了高浓度苯甲酸微区,从而增加了酯化反应速率。同时由于表面的疏水性使得副产物水快速排出催化剂表面,避免催化剂水合,提高了催化剂的耐水性及稳定性。

In this paper,Pr-SO3H/MCF solid acid catalyst was prepared by graft sulfonation of mesocellular silica foam(MCF)with mercaptopropyltrimethoxysilane(MPTMS)and the impact of co-derivatisation with phenyltrimethoxysilane groups to impart hydrophobicity to the catalyst for synthesis of methyl benzoate was investigated.The textural and structural properties of catalyst were studied using nitrogen adsorption-desorption(BET),transmission electron microscope(TEM),contact angle and elemental analyzer.The results show that the phenyltrimethoxysilane modified Ph/Pr-SO3H/MCF catalyst has a slightly lower specific surface area and a significantly improved hydrophobicity.Because of the formation ofπ-πbond between benzene rings,the adsorption capacity of benzoic acid is increased,and a high concentration of benzoic acid microzone is formed on the surface of catalyst,thus increasing the esterification reaction rate.At the same time,due to the hydrophobicity of the surface,the by-product water is quickly discharged from the catalyst surface,avoiding the hydration of the catalyst and improving the water resistance and stability of the catalyst.