Screening of different zeolite-based catalysts for gas-phase selective photooxidation of propan-2-ol (original) (raw)
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Photocatalytic properties of zeolite-based materials for the photoreduction of methyl orange
Applied Catalysis A-general, 2006
Novel photocatalytic materials have been prepared by incorporation of TiO 2 , a transition metal and, heteropolyacid (HPA) in the zeolite structure. These materials have been characterized using XRD, UV-vis diffuse reflectance spectroscopy and elemental analysis. The photocatalytic activity of the materials in visible light has been evaluated for photoreduction of methyl orange solution in the presence of a sacrificial electron donor 1:40 ethanol-water mixture. The material Zeo-Y/TiO 2 /Co 2+ /HPA photoreduces methyl orange effectively to the extent of about 4.11 mg/g TiO 2 and shows better photocatalytic activity as compared to Zeo-Y/TiO 2 /HPA, indicating the role of transition metal ions. The improved photocatalytic properties in the visible region could be due to the combined effect of transition metal ions and HPA, while these constituents along with the zeolite framework are also likely to contribute towards delay in charge recombination. #
Structural and Photocatalytic Properties of TiO2/Zeolite Synthesized using Sol-Gel Method
ALCHEMY, 2019
Titanium dioxide (TiO2) is supported into natural zeolite to enhance its photocatalytic activity. TiO2/zeolite is synthesized using sol-gel method at composition ratio of 5:95; 10:90; 20:80 and 30:70%. Structural properties are measured by X-ray diffraction showed TiO2/zeolite in various composition has characteristic of anatase and modernite phase. The energy dispersive spectroscopy characterization shows TiO2/zeolite containing Ti element which indicates that TiO2is successfully supported into natural zeolite. Vibration mode of Infrared and Raman spectra tend shifted to higher wavenumber as increasing of TiO2 content indicating the higher energy vibration due to molecular interaction between TiO2 and zeolite. Photocatalytic activity test toward methylene blue degradation shows that TiO2/zeolite has higher activity than TiO2 and zeolite itself.Keywords: Photocatalyst, titanium dioxide, zeolite
Photocatalyzed oxidation in zeolite cages
1998
A new concept of room temperature selective oxidation of ole®ns, alkyl substituted benzenes and alkanes by electron transfer from the hydrocarbon to the oxygen molecule induced by irradiation with visible light is shown. The hydrocarbon radical cation±O 2 charge-transfer pair is generated inside the cavities of alkali or alkaline-earth ion-exchanged zeolites, in which the large electrostatic ®eld stabilizes the highly polar charge-transfer states of hydrocarbon±O 2 collisional pair and allows to control the pathways of further transformation. High selectivities to useful products are obtained using this approach. #
Beta zeolite supported sol–gel TiO2 materials for gas phase photocatalytic applications
Journal of Hazardous Materials, 2011
Beta zeolite supported sol-gel TiO 2 photocatalytic materials were prepared according to a sol-gel route in which high specific surface area Beta zeolite powder was incorporated into the titanium isopropoxide sol during the course of the sol-gel process. This led to an intimate contact between the zeolite surface and the TiO 2 precursors, and resulted in the anchorage of large amounts of dispersed TiO 2 nanoparticles and in the stabilization of TiO 2 in its anatase form, even for high TiO 2 wt. contents and high calcination temperatures. Taking the UV-A photocatalytic oxidation of methanol as gas phase target reaction, high methanol conversions were obtained on the Beta zeolite supported TiO 2 photocatalysts when compared to bulk sol-gel TiO 2 , despite lower amounts of TiO 2 within the photoactive materials. The methanol conversion was optimum for about 40 wt.% TiO 2 loading and calcination temperatures of 500-600 • C.
The Journal of Physical Chemistry C, 2018
Two series of V-containing BEA zeolite catalysts, V x SiBEA(I) and V x SiBEA(II), were prepared by a two-step postsynthesis preparation procedure which consists, in the first step, in the dealumination of TEABEA zeolites by a treatment with nitric acid solution to obtain SiBEA zeolites with a Si/Al atomic ratio of 1000 and then, in the second step, in bringing SiBEA into contact with an aqueous NH 4 VO 3 solution with different concentrations at a pH of 2.7. After 3 days, the solids were recuperated from the reaction mixtures: (1) on a sinter funnel and washed several times with distilled water to obtain the V x SiBEA(I) series and (2) in a rotating evaporator under vacuum via a membrane pump to obtain the V x SiBEA(II) series. The combined use of H 2-temperatureprogrammed reduction, diffuse reflectance (DR) UV−vis, Fourier transform infrared (FTIR), 51 V magic-angle spinning (MAS) NMR, electron paramagnetic resonance (EPR), and X-ray photoelectron spectroscopy allows determining the nature and environment of vanadium in both series of V-containing SiBEA zeolites after different treatments. The characterization of V x SiBEA(I) and V x SiBEA(II) series reveals the formation of various forms of vanadium species depending on the V content and conditions applied upon preparation of each series of V-containing SiBEA zeolites. As evidenced by DR UV−vis and 51 V MAS NMR in the V x SiBEA(I) series, vanadium was present mainly as mononuclear framework pseudo-tetrahedral V(V) species. In contrast, in the V x SiBEA(II) series, vanadium was present as mononuclear framework pseudo-tetrahedral and polynuclear extraframework pseudo-octahedral V(V) species. As shown by EPR, the oxidation state of V species easily changes upon calcinations in oxygen, outgassing under vacuum at 773 K and treatment with hydrogen at a high temperature (873 K). The presence of Brønsted and Lewis acidic centers was evidenced in both V x SiBEA(I) and V x SiBEA(II) series by FTIR spectroscopy with pyridine used as a probe molecule. The catalytic activity tests in propene epoxidation revealed that the highly dispersed mononuclear framework pseudo-tetrahedral V(V) species are responsible for high selectivity to propene oxide, whereas polynuclear extra-framework pseudo-octahedral V(V) species catalyzed mainly total oxidation. The V x SiBEA(I) series of catalysts with vanadium, present mainly as mononuclear framework pseudo-tetrahedral V(V) species, show lower turn over frequency values than the V x SiBEA(II) series in which vanadium is present as both mononuclear framework pseudotetrahedral V(V) species and polynuclear extra-framework pseudo-octahedral V(V). It thus demonstrates that apart from highly dispersed isolated vanadium species, the availability of vanadium species to reagents also plays an important role in the gas-phase propene epoxidation.
Applied Catalysis A: General, 1996
The catalytic behavior in propane oxidative dehydrogenation to propylene of V-containing silicalite-1, silicalite-2, ZSM-5 and boralite, prepared either by direct hydrothermal synthesis or by consecutive impregnation with ammonium vanadate of the zeolites in the acid form is reported. Results show that selectivity to propylene depends on the V content and is comparatively higher in samples prepared by direct hydrothermal synthesis than in those prepared by impregnation, but the concentration of propane and the propane to oxygen ratio considerably affect the results. At higher reaction temperatures the presence of weak acid sites due to vanadium ions induces the formation of aromatics. The formation of the latter is enhanced in V-containing boralite and ZSM-5 samples. Maximum selectivities to propylene up to 80-85% are obtained, but only at low propane or oxygen conversion (around 5%).
Solar-based photoreduction of methyl orange using zeolite supported photocatalytic materials
Solar Energy Materials and Solar Cells, 2007
A new class of novel photocatalysts has been prepared by supporting TiO 2 on the zeolite matrix by various routes of synthesis. Different transition metals like cobalt, nickel, and ruthenium have been incorporated in these photocatalysts, alongwith molybdenum based heteropolyacid (HPA) to improve the photocatalytic activity of these materials. Photoreduction of methyl orange under solar radiation was compared with photoreduction in presence of artificial visible light illumination to evaluate their photocatalytic activity. The quantity of methyl orange photoreduced by the cobalt containing photocatalyst was about 2.40 mg/g of TiO 2 under the influence of sunlight as compared to 4.111 mg/g of TiO 2 under artificial visible light illumination. However, the efficiency of the photocatalyst is high as compared to P25 TiO 2 under solar light (0.508 mg/g of TiO 2 ). The high photocatalytic activity of these materials is due to the synergistic effect of incorporation of transition metals in combination with TiO 2 and HPA supported by the zeolite matrix. These materials are being evaluated for photocatalytic water splitting. r
IOP Conference Series: Materials Science and Engineering
Anatase phase of Titanium dioxide (TiO2) is a wide bandgap semiconductor which is active as photocatalyst material under ultraviolet light irradiation. Vanadium dopant has reported to enhance its photocatalytic properties toward visible light irradiation. However, vanadium doped TiO2 has several limitations for further practical application such as its low surface area and difficult in recycling due to its superfine particle. Supporting this material into porous and large surface material like zeolite material supposed to improve its photocatalytic properties. In this research, vanadium doped TiO2 (Ti0.997V0.003O2) photocatalyst was supported on Indonesian natural Zeolite using sonochemical method to study the structural and optical properties of supported photocatalyst. Ti0.997V0.003O2 was loaded into zeolite at various concentration ranging from 10 to 30 % w/w. The X-Ray Diffraction (XRD) data showed that Ti0.997V0.003O2/Zeolite at various concentrations have characteristic of anatase, rutile and mordenite phase structure. Infrared spectra showed the typical vibrational mode of TiO2 and mordenite phase. The sharp peak at 1370 cm-1 which is attributed to the lattice vibration of TiO2 became weaker due to vanadium dopant. The Raman spectra showed that the anatase vibration mode position shifted to higher wavenumber caused by the interaction between Ti0.997V0.003O2 and zeolite. Diffuse Reflectance Spectroscopy (DRS) data revealed that 15% of Ti0.997V0.003O2 on Zeolite has the highest visible light absorption and the lowest band gap energy (2.77 eV or 447 nm) in comparison to the others composition.
Oxidative Dehydrogenation of Propane over Vanadium-Containing Faujasite Zeolite
Molecules
Oxidative dehydrogenation (ODH) of light alkanes to olefins—in particular, using vanadium-based catalysts—is a promising alternative to the dehydrogenation process. Here, we investigate how the activity of the vanadium phase in ODH is related to its dispersion in porous matrices. An attempt was made to synthesize catalysts in which vanadium was deposited on a microporous faujasite zeolite (FAU) with the hierarchical (desilicated) FAU as supports. These yielded different catalysts with varying amounts and types of vanadium phase and the porosity of the support. The phase composition of the catalysts was confirmed by X-ray diffraction (XRD); low temperature nitrogen sorption experiments resulted in their surface area and pore volumes, and reducibility was measured with a temperature-programmed reduction with a hydrogen (H2-TPR) method. The character of vanadium was studied by UV-VIS spectroscopy. The obtained samples were subjected to catalytic tests in the oxidative dehydrogenation o...