硅气凝胶制备及其作为催化剂载体在甲烷部分氧化反应中的应用

采用超临界干燥(SCD)法和以溶剂置换、表面改性为基础的常压干燥(APD)法分别制得二氧化硅气凝胶.采用N2低温物理吸附脱附法、红外光谱(FT-IR)、X射线衍射(XRD)实验和扫描电子显微镜(SEM)等手段对两种方法制备的气凝胶的理化性能进行了表征.结果表明:SCD法和APD法制备的二氧化硅气凝胶的比表面积分别为1 016和846 m2/g,最可几孔径分别位于孔径大小14.5和11.5 nm处.SCD法制备的二氧化硅气凝胶的孔径分布范围和较大孔的数量均较APD法制备的要宽和多.而以两种方法制备的二氧化硅气凝胶为载体,硝酸镍为镍源,采用浸渍法制备的二氧化硅气凝胶负载镍催化剂中,镍均以极微小的颗粒形式高度分散于二氧化硅气凝胶载体上.对甲烷部分氧化(POM)制合成气反应,用两种方法(SCD和APD)制备的二氧化硅气凝胶载体为基础的负载镍催化剂对产物一氧化碳和氢气的选择性相差不大,但甲烷转化率则呈现明显的差异.

Preparation of Silica Aerogel and Its Application in Partial Oxidation of Methane to Syngas as Catalyst Carrier

The silica aerogel was prepared by supercritical drying(SCD) and ambient pressure drying(APD) based on solvent exchanging and surface modification.The properties of the silica aerogel were determined by the N2 physical adsorption-desorption,FT-IR spectrum,XRD and SEM.The result showed that the specific surface areas of silica aerogel derived from SCD and APD were up to 1 016 and 846 m2/g,and the most probable pore size were mainly distributed around 14.5 and 11.5 nm,respectively.The range of the distribution of the pores in the silica aerogel prepared by SCD was wider than that prepared by APD.And the silica aerogel derived from SCD also had more big pores.The silica aerogel prepared by different methods was used as catalyst carrier to be impregnated with nickel using nickel nitrate.The nickel was highly dispersed in the silica aerogel catalyst.In the partial oxidation of methane(POM) reaction,the conversion of the methane in the reaction of POM catalyzed by both kind of silica aerogel(derived from SCD and APD) was evidently different while the CO and H2 selectivity were nearly the same during the period of reaction.