Preparation and characterization of multicomponent porous materials prepared by the sol-gel process

An experimental strategy was developed to obtain transparent Si- Al- Ti- Ni- Mo and Si- Zr- Ti- Ni- Mo sols via the sol- gel process. The sol was prepared from Si( OEt) (4) ( TEOS), Al( OBus) (3) ( OBus: C2H5CH( CH3) O), Ti( OEt) (4) ( OEt: OCH2CH3), Zr( OPrn) (4) ( OPrn: OCH2CH2CH3). In both cases nickel nitrate hexahydrate ( Ni( NO3) (2) center dot 6H(2)O) and ammonium heptamolybdate tetrahydrate (( NH4) 6Mo7O24 center dot 4H(2)O) were the Ni and Mo sources, respectively. The sols were characterized by Fourier Transform Infrared Spectroscopy ( FTIR). Assignments of the simultaneous formation of the Si- O- Al, Si- O- Ti, Si- O- Ni, and Si- O- Zr bonds were done. The sols were polymerized at room temperature ( 293 K) to obtain gels, and these were dried at 423K and calcined at 573, 853 and 893K in air. The characterization techniques used were small- angle X- ray scattering ( SAXS), X- ray diffraction ( XRD), scanning electron microscopy ( SEM), and Si-29 and Al-27 magic angle spinning nuclear magnetic resonance ( MAS NMR). The density of the solids was measured following ASTM method D- 4892 and the porosity and surface area were determined byN(2) adsorption/ desorption isotherms. The corresponding average pore diameters were evaluated using the BJH, HK, and DA methods.