Shedding light: Nitroaromatic compounds on gold nanoparticles (3 wt %) supported on ZrO2 can be reduced directly to the corresponding azo compounds when illuminated with visible light or ultraviolet ...light at 40 °C (see picture). The process occurs with high selectivity and at ambient temperature and pressure, and enables the selection of intermediates that are unstable in thermal reactions.
A novel three-dimensionally ordered macroporous (3DOM) Co/ZrO2 catalyst with mesoporous walls was obtained. The 3DOM Co/ZrO2 catalyst showed less aggregation of Co3O4 particles, better dispersion and ...higher reducibility, which led to the more cobalt surface active sites for the Fischer–Tropsch synthesis reaction, and further displayed an excellent catalytic activity. Display omitted
► 3DOM Co/ZrO2 catalyst was prepared. ► More surface cobalt species dispersed on the 3DOM Co/ZrO2 catalyst. ► 3DOM Co/ZrO2 catalyst showed excellent catalytic performance for the FTS. ► The bimodal mesopores and macropores structure of the 3DOM is related to selectivity.
A three-dimensionally ordered macroporous (3DOM) ZrO2 support with mesoporous walls was prepared using colloidal crystal PS spheres as templates and was used to prepare the 3DOM Co/ZrO2 catalyst via incipient wetness impregnation method to support active metal cobalt on zirconia with 3DOM structure. Two other cobalt catalysts supported on zirconia materials with different pore structure were also prepared as references. The N2 adsorption/desorption, XRD, SEM, TEM, TPR, hydrogen chemisorptions and XPS techniques were used to characterize the support and (or) catalyst. The 3DOM zirconia support with interconnected networks of spherical voids was beneficial to the dispersion of Co species with less aggregation. The as-obtained 3DOM Co/ZrO2-3 catalyst showed good dispersion and high reducibility of cobalt species, which led to more cobalt surface active sites and thus an excellent catalytic performance for the Fischer–Tropsch synthesis (FTS) reaction. The hydrocarbons selectivity of the catalyst greatly depended on the pore structure of the 3DOM ZrO2 support. The macropores, which provided channels for rapid molecular transportation, were in favor of the enhancement of C5+ selectivity. However, the small pores within the walls of 3DOM entities limited the diffusion efficiency of the reactants/products and contributed to the selectivity of methane.
The Cu–ZnO hollow spheres, where CuO nanocrystals were dispersed in the shell of ZnO nanoparticals, were synthesized by using highly uniform and monodispersed Cu-embedded carbon spheres as ...sacrificial templates via a simple route under hydrothermal conditions. The morphology and structure of the spheres were characterized by FTIR, XRD, SEM, TEM and N2 adsorption–desorption. It was suggested that the OH and C=O groups in the surface of the Cu-embedded carbon spheres facilitated the adsorption of Zn2+ in the aqueous solution, giving rise to the final CuO–ZnO hollow structure after these Zn2+-adsorbed spheres were calcined in air. Moreover, the photoluminescence (PL) study showed that the as-prepared CuO–ZnO hollow spheres and the annealed counterpart exhibited strong and dramatically weakened emissions, respectively. This remarkably different photoluminescent behavior afforded the evidence regarding the oxygen vacancy defects in the CuO–ZnO hollow spheres.
CuO–ZnO hollow spheres were obtained using Cu-embedded carbon spheres as template, and the photoluminescent spectra afforded the evidence regarding the oxygen vacancies in the hollow spheres. Display omitted
► A approach was presented to prepare carbon spheres in a high yield. ► The fabrication of CuO–ZnO hollow spheres was a simple route. ► The photoluminescence afforded the evidence of the oxygen vacancies in the hollows. ► The synthetic approach might be applicable to preparing other hollow structures.
Gold was loaded onto porous nanocomposite of ZrO
2 and silicate by deposition–precipitation. The resulting Au/ZrO
2-nanocomposites are found to be superior catalysts for removal of formaldehyde from ...indoor air at moderate temperature by oxidation. They have large specific surface areas and allow the gold to be adequately dispersed as small nanoparticles (NPs). According to the analysis of transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS), in the as-prepared catalyst, gold was well dispersed and in an oxidized state of Au
3+; and it was reduced to metallic crystals (Au
0) during its use as catalyst. The temperature programmed desorption (TPD) results show that gold species in the two states strongly adsorb HCHO molecules at ambient temperature. The adsorbed HCHO molecules convert rapidly into formate species, as observed by the infrared spectra. The temperature programmed surface reaction (TPSR) study reveals that at temperatures below 450
K, the HCHO oxidation involves reaction between adsorbed formate species and adsorbed oxygen molecules. This explains why the gold species in both states are the active sites for HCHO oxidation, and also indicates that HCHO adsorption on the gold species and oxygen adsorption on the support are crucial steps for the oxidation.
Gold was loaded onto porous nanocomposite of ZrO
2 and silicate by deposition–precipitation. The resulting Au/ZrO
2-nanocomposites are superior catalysts for oxidizing formaldehyde from indoor air at moderate temperature. The analysis of temperature program desorption and temperature program surface reaction reveals that HCHO molecules strongly adsorb on the gold species in the samples at ambient temperature and convert rapidly into formate species, which react with adsorbed oxygen molecules.
Nickel catalysts supported on different acid-treated clays were prepared by the impregnation method in order to investigate the effect of the pore structures of supports on the dispersion and the ...chemical states of nickel species, and thus on the carbon depositions resulted from the dissociation of the CO molecules adsorbed on different active nickel sites. The catalysts and supports were characterized by the X-ray diffraction (XRD), the transmittance electron microscopy (TEM), the H2 temperature-programmed reduction (H2-TPR), the nitrogen adsorption–desorption, and the thermogravimetry and differential thermal analysis (TG-DTA). The CO methanation performance of the catalyst was investigated at a temperature range from 300 °C to 500 °C. The results indicated that the dispersion and the states of the nickel species on the support were influenced strongly by the pore structures of the acid-treated clays, and only the mesopores composed by partly damaged clay layers were conducive to forming the active nickel species, and thus reducing the deposition of the inactive carbon and improving the stability of the catalyst. The carbon species deposited on different active sites was slightly different in the oxidative properties when it was oxidized in air. A fraction of aluminum in the clays was leached out by acid, which decreased the possibility of forming the spinel phase of nickel aluminate in the catalyst. The highly dispersed nickel species showed little relevance to the high activity of the catalyst, but it exhibited a strong relation to the nickel sites from the bulk nickel species.
The nickel species grows into larger nickel particles on the surface of the raw clay layers due to no space confinement. The size of the nickel particles dispersed on the mesopore structure composed by the partly damaged clay layers is moderate at a high nickel loading because of the confinement effect of the structure. The clay layers completely collapse into almost uniform clay fragments when the acid concentration is high. The confinement effect of such a pore structure is weak so that the nickel particles usually grow larger on such a support. Display omitted
•An interconnected mesoporous structure composed by partly damaged clay layers was obtained by the hydrothermal treatment.•The interconnected mesopores had the confinement effect and were conducive to the dispersion of nickel species.•The interconnected porous structure reduced the deposition of inactive carbon.•The carbon species deposited on different active sites was slightly different in chemical properties.
A new composite structure with superior photocatalytic activity for phenol decomposition was prepared by reaction between TiOSO4 and a synthetic layered clay laponite. The high photocatalytic ...activity resulted from the unique structure of the composite, in which anatase nanocrystals were attached on leached laponite fragments. The new materials are distinctly different from the conventional TiO2-pillared clays in structure, which are microporous solids with small TiO2 particles (a few nanometers in size) as pillars. The large number of the anatase crystals (the active sites) and better accessibility to the sites by UV light and reactant molecules are the major factors enhancing the photocatalytic activity. Important structural properties of the porous composites, such as specific surface area, pore structure, and size of the anatase crystals, were tailored by modulating the Ti/clay ratio and the hydrothermal synthesis temperatures. The performance of the catalysts is related to their structural features, and it is found that the catalytic activity increased with increasing size of the anatase crystals in the catalysts, specific surface area, and mesopore size.
A series of one-dimensional (1D) zirconia/alumina nanocomposites were prepared by the deposition of zirconium species onto the three-dimensional framework of boehmite nanofibers formed by dispersing ...boehmite nanofibers into butanol solution. The materials were calcined at 773 K and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption/desorption, and infrared emission spectroscopy (IES). The results demonstrated that when the molar percentage X = 100*Zr/(Al + Zr) > 30%, extremely long ZrO2/Al2O3 composite nanorods with evenly distributed ZrO2 nanocrystals on the surface were formed. The stacking of such nanorods gave rise to a new kind of macroporous material without the use of any organic space filler/template or other specific technologies. The mechanism for the formation of long ZrO2/Al2O3 composite nanorods was proposed in this work.
This study focuses on acid activated beidellite and its adsorption ability for the herbicide simazine. After acid activation, the non-silicon atoms, such as Al, Mg, and Fe, which are located in the ...octahedral sheet, and sodium ions between the clay mineral layers were leached from the parent clay mineral. The basal spacing increased after acid activation. The acid activated beidellites were used to remove simazine from water. The simazine molecules can enter into the destroyed alumino silicate interlayer spaces and can be adsorbed from contaminated water.
The Pt, Au and Pd catalysts supported on zirconia were prepared by the colloid deposition method. The catalytic activities of the catalysts for the hydrochlorination of 4-phenyl-1-butene were ...investigated under the irradiation of visible light, taking hydrochloric acid as the sources of chloride and hydrogen. The catalysts exhibited superior activities under the irradiation, giving rise to 4-phenylbutyl chloride and 4-phenyl-2-butenol, but they were almost inactive without the irradiation. Ethanol was unfavorable to the reaction. In addition to 4-phenylbutyl chloride, 2,3-dimethylstyrene was the by-product on the Pt and Au catalysts, and the isomerization from 4-phenyl-1-butene to benzene-1-butenyl occurred on the Pd/ZrO
2
catalyst in ethanol solution.
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