银负载硅基气凝胶催化剂及催化还原对硝基苯酚性能研究

Silica aerogel-supported silver catalyst catalyzed reduction of p-nitrophenol

研究了以正硅酸四乙酯和3-氨丙基三乙氧基硅烷为共硅源,乙腈为溶剂,采用溶胶-凝胶法和常压干燥制备得到块状的二氧化硅气凝胶,并利用简单的浸渍法得到银负载二氧化硅气凝胶。为了得到块状结构,使用异氟尔酮二异氰酸酯对湿凝胶做了交联,氨丙基三乙氧基硅烷提供的氨基和异氰酸酯发生聚合反应增强气凝胶骨架。通过X射线衍射、透射电镜、傅里叶变换红外光谱和比表面积等技术对催化剂性质做了测试。分析结果表明,银纳米粒子为纯FCC结构,平均粒径为6.03～9.24 nm。将制备的2种催化剂在过量硼氢化钠存在下催化对硝基苯酚还原为对氨基苯酚,并使用紫外分光光度法测试。结果显示,制备的催化剂有良好的效果,还原时间少于3 min。

Silver-silica aerogel catalysts were synthesized through the impregnation of monolithic silica aerogel by silver ni-trate alcoholic solution.Monolithic silica aerogels were prepared by sol-gel process via the ambient drying process.TEOS(tetraethyl orthosilicate)and APTES[(3-aminopropyl)triethoxysilane]were used as co-precursors and acetonitrile was used as solvent.In this work,isophorone diisocyanate crosslinked with wet gels for maintaining the gel blocky structure and keeping the aerogel integrated.The amino groups provided by APTES can react with diisocyanate conformally coated on the surface of silica aerogel network.The prepared Ag/SiO2 aerogel catalysts were characterized by X-ray diffraction(XRD),transmission electron microscopy(TEM),fourier transform infrared spectroscopy(FT-IR)and Brunauer-Emmett-Teller(BET)etc..Analysis results showed that as-prepared catalysts are pure FCC silver,the average particle size of silver nanoparticle was in the range of 6.03~9.24 nm.The two kind of catalysts were used for the catalyzed reduction of p-nitrophenol(PNP)with excess amount of NaBH4 in aqueous solutions.UV spectrophotometry(UV-vis)was used to monitor the reduction of p-nitrophenol to p-aminophenol(PAP)with the Ag/SiO2 aerogel catalysts.The results revealed that the as-synthesized Ag/SiO2 aerogel cataly-sts had well catalytic performance.The reduction time of PNP to PAP was less than 3 min for each catalyst.