Showing papers by "Zi Gao published in 2000"
TL;DR: In this paper, hollow spheres of zeolite have been fabricated through a layer-by-layer technique using polystyrene spheres as templates and Nanozeolites as building blocks, followed by calcination.
158 citations
TL;DR: In this article, Al 2 O 3 -promoted sulfated zirconia (SZA-3) was used to stabilize the surface sulfate complex on the oxides and increase the number of catalytically effective acid sites on the catalysts.
131 citations
TL;DR: In this paper, a coprecipitation method was used to synthesize catalysts for the hydroxylation of phenol, Fe−Si−O, Fe-Mg−O and Fe−Mg-O complex oxides.
Abstract: Novel catalysts for the hydroxylation of phenol, Fe–Si–O, Fe–Mg–O and Fe–Mg–Si–O complex oxides, have been synthesized by a coprecipitation method. X‐ray diffraction studies show that MgFe2O4 crystallites with spinel structure are formed in Fe–Mg–Si–O and Fe–Mg–O complex oxides and the crystallite size of the metal oxide or complex oxide is reduced after addition of Si. In the hydroxylation of phenol with hydrogen peroxide, Fe‐based complex oxides exhibit high activities after a short induction period. The phenol conversion is improved when silicon is introduced into the Fe‐based complex oxides, and formation of MgFe2O4 crystals with spinel structure in the catalysts increases the diphenol selectivity. The addition of a little acetic acid to the reaction liquid can shorten the induction period effectively. Under the same reaction conditions, phenol conversion and diphenol selectivity over the Fe–Mg–Si–O catalyst are close to those over TS‐1, and furthermore, the reaction time is more than ten times shorter as compared to TS‐1. The reaction mechanism of the hydroxylation of phenol on the catalysts has been studied, and a free‐radical mechanism initiated by the formation of phenoxy free radicals is suggested.
58 citations
TL;DR: In this article, a novel and flexible technique to synthesize bimodal porous materials with ordered macropores whose walls are composed of microporous zeolites by self-assembly of nanocrystals of silicalite-1 and ZSM-5 was reported.
Abstract: This study reports a novel and flexible technique to synthesize bimodal porous materials with ordered macropores whose walls are composed of microporous zeolites by self-assembly of nanocrystals of silicalite-1 and ZSM-5. The materials prepared by this novel technique are well crystalline and possess uniform macropores interconnected in three dimensions through windows.
44 citations
TL;DR: In this article, the authors investigated the catalytic decomposition of dichlorodifluoromethane (CFC-12) in the presence of water vapor over a series of pure and WO 3 -promoted metal oxides.
Abstract: Catalytic decomposition of dichlorodifluoromethane (CFC-12) in the presence of water vapor was investigated over a series of pure and WO 3 -promoted metal oxides. Although pure TiO 2 , SnO 2 and Fe 2 O 3 showed less activity for the decomposition of CFC-12, obvious enhancement in activity was actualized by supporting WO 3 on them using Ti(OH) 4 , Sn(OH) 4 and Fe(OH) 3 as support precursors. The decomposition activity depended on the calcination temperature obviously and attained to a maximum as the content of WO 3 reached its utmost dispersion capacity on different supports. The 95% conversion temperature of WTi, WSn and WFe catalysts prepared by optimum conditions were 260°C, 315°C and 345°C, respectively. CO 2 was the main-product and no CO was detected as by-product. The selectivity to by-product CFC-13 on WO 3 -modified metal oxides was much lower than on unmodified metal oxides and it also exhibited a coverage-dependent effect. The catalytic activity of WO 3 /TiO 2 , WO 3 /SnO 2 and WO 3 /Fe 2 O 3 all remained steady for 120 h on stream.
30 citations
01 Jan 2000
TL;DR: In this article, the authors investigated the catalytic decomposition of dichlorodifluoromethane CFC-12 in the presence of water vapor over a series of pure and WO -promoted metal oxides.
Abstract: Catalytic decomposition of dichlorodifluoromethane CFC-12 in the presence of water vapor was investigated over a series of pure and WO -promoted metal oxides. Although pure TiO , SnO and Fe O showed less activity for the
24 citations
TL;DR: In this article, a novel procedure was developed to prepare nickel oxide supported silica pillared zirconium phosphates whose surface areas and d-spacings are 125-198 m2/g and 2.1-2.3 nm respectively.
Abstract: A novel procedure was developed to prepare nickel oxide supported silica pillared zirconium phosphates whose surface areas and d-spacings are 125-198 m2/g and 2.1-2.3 nm respectively, whereas the samples prepared by conventional method only have surface areas less than 20 m2/g and d-spacings 1.8 nm. X-Ray diffraction (XRD), N2 adsorption and temperature programmed reduction (TPR) indicated that the materials obtained by the new method have better nickel oxide dispersion than those obtained by the conventional method.
2 citations
TL;DR: In this paper, a new solid superacid catalyst of persulfate modified Al2O3-ZrO2 has been prepared for the first time; it displays extraordinarily high catalytic activity and stability for the isomerization of n-butane.
Abstract: A new solid superacid catalyst of persulfate modified Al2O3–ZrO2 has been prepared for the first time; it displays extraordinarily high catalytic activity and stability for the isomerization of n-butane.