Photocatalytic Oxidation Of Isopropanol Research Articles

Understanding structure-function relationships in HZSM-5 zeolite catalysts for photocatalytic oxidation of isopropyl alcohol

The HZSM-5 molecular sieves are a kind of special photocatalyst with photocatalytic activity, while their relationship between structure and function has been a matter of debate. Here, we report that for HZSM-5, the distinguished transformation of coordination environment derived from the removal of tetrahedral framework aluminium by thermal treatment will result in a considerable change in photocatalytic behaviours. The established NMR analysis combined with the theoretical calculations demonstrates the formation of extra-framework aluminium (EFAL) upon calcinations. This leads to a changed reaction path of photocatalytic oxidation of isopropyl alcohol in gas-phase over calcined HZSM-5 catalysts. DFT calculation results show the formed of EFAL species can increase the interaction energy between reactant molecules and zeolites which affords an outstanding photocatalytic reactivity and a controllable photocatalytic selectivity in the oxidation of isopropyl alcohol. This clearly indicates that the framework aluminium (FAL) species are responsible for acetone formation, while the EFAL species are apt to promote the deep mineralization of isopropyl alcohol to inorganic CO2. This study provides new understanding in the issue of photocatalysis for zeolite molecular sieves.

Influence of the triblock copolymer P123 and phosphorous on the physico-chemical properties of TiO 2

Nanocrystalline TiO 2 powders with a high specific surface area (up to 335 m 2/g) were synthesized by a combination of sol–gel and solvothermal syntheses. The influence of the TiO 2 framework template, the triblock copolymer P123, and the framework stabilizer, phosphorous (P) in the form of phosphoric acid (H 3PO 4), on the photocatalytic oxidation of isopropanol was studied. As-prepared samples were characterized by means of X-ray powder diffraction (XRD), thermogravimetric analysis (TG-DTA), measurements of the specific surface area ( s BET), field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The photocatalytic activity under UV (ultraviolet) irradiation of the as-prepared samples was measured by monitoring the degradation of the isopropanol in the gaseous medium. The application of P123 increased the specific surface area of the samples; furthermore, the addition of phosphorous inhibited the particle growth during the thermal treatment and stabilized the anatase crystal phase at higher annealing temperatures (up to 900 °C), thus leading to a higher photocatalytic activity. However, when P123 and phosphorous were used together the specific surface area was increased and an improvement in the photocatalytic oxidation was observed.

In Situ Coating of Flame-Made TiO2 Particles with Nanothin SiO2 Films

Rutile TiO2 particles made by flame spray pyrolysis (FSP) were coated in a single step with SiO2 layers in an enclosed flame reactor. This in situ particle coating was accomplished by a hollow ring delivering hexamethyldisiloxane (HMDSO) vapor (precursor to SiO2) through multiple jets in swirl cross-flow to Al-doped nanostructured rutile TiO2 aerosol freshly made by FSP of a solution of titanium tetraisopropoxide and aluminum sec-butoxide in xylene. The as-prepared powders were characterized by (scanning) transmission electron microscopy (STEM and TEM), energy dispersive X-ray analysis, X-ray diffraction, nitrogen adsorption, electrophoretic mobility, DC plasma optical emission (DCP-OES), and Fourier transform infrared (FT-IR) spectroscopy. The coating quality was assessed further by the photocatalytic oxidation of isopropyl alcohol to acetone. The effect of HMDSO injection point and vapor concentration on product particle morphology was investigated. The titania particles were uniformly SiO2-coated with controlled and uniform thickness at a production rate of about 30 g h(-1) and exhibited limited, if any, photoactivity. In contrast, spraying and combusting equivalent mixtures of the above Si/Al/Ti precursors in the above reactor (without delivering HMDSO through the hollow ring) resulted in particles segregated in amorphous (SiO2) and crystalline (TiO2) domains which exhibited high photocatalytic activity.

Catalysis by heteropolyacids—ix. Photocatalytic oxidation of isopropyl alcohol to acetone under oxygen using tetrabutylammonium decatungstate

Homogeneous photocatalytic oxidation of isopropyl alcohol by tetrabutylammonium decatungstate (Bu 4N) 4[W 10O 32] in acetonitrile using O 2 as a reoxidizing reagent has been studied. The photocatalysis is interpreted on the basis of a rapid redox cycle between 2 e-reduced species and the oxidized species of decatungstate; O 2 as a reoxidizing reagent is converted to water. The catalytic activity and the mechanism of the redox cycle of decatungstate are in contrast to those of Keggin-type heteropolytungstic acids. When the concentration of isopropyl alcohol is lowered by prolonged irradiation, pale yellow precipitates are produced by side reactions due to electron transfer from the counter-ion Bu + 4 to the decatungstate.

Photo-assisted electrochemical oxidation of isopropanol to acetone on a chemically modified electrode

The photocatalytic oxidation of isopropanol, as sensitized by photoexcited quinone derivatives which are chemically bound on a carbon electrode, has been observed. The quantum efficiency for the photosensitized reaction of bound quinones to that of quinone in solution is compared. From the observation of photocurrents, when bound quinones on glassy carbon are photolyzed, it is concluded that some of the excited molecules of the chemically bound quinones react with isopropanol and are not quenched during the lifetime of the excited state at the carbon electrode surface.

Photo-assisted electrochemical oxidation of isopropanol to acetone on a chemically modified electrode

The photocatalytic oxidation of isopropanol, as sensitized by photoexcited quinone derivatives which are chemically bound on a carbon electrode, has been observed. The quantum efficiency for the photosensitized reaction of bound quinones to that of quinone in solution is compared. From the observation of photocurrents, when bound quinones on glassy carbon are photolyzed, it is concluded that some of the excited molecules of the chemically bound quinones react with isopropanol and are not quenched during the lifetime of the excited state at the carbon electrode surface.

The Effect of Phthalocyanines Added to ZnO on the Photocatalytic Oxidation of Isopropyl Alcohol

The Effect of Phthalocyanines Added to ZnO on the Photocatalytic Oxidation of Isopropyl Alcohol

Photoadsorption and photocatalysis at rutile surfaces: II. Photocatalytic oxidation of isopropanol

The photocatalytic oxidation of isopropanol has been studied in a specially designed rotating reaction vessel affording good contact between the incident uv light and the powdered photocatalyst. It has been shown that when TiO 2 (rutile) is illuminated with light of wavelength λ > 300 nm in the presence of isopropanol vapor and oxygen at 300 K, the primary organic oxidation product is acetone. When isopropanol is present as a presorbed layer, the kinetics of the evolution of acetone into the gas phase can be studied as a displacement process. The behavior is discussed in detail with reference to the adsorption isotherms of isopropanol, acetone and water on rutile, and the effect which one component exerts upon the adsorption of the other components. Isopropanol and water are both capable of displacing acetone from the surface. The formation of acetone cannot be sustained in the absence of oxygen, and it is concluded that oxygen photoadsorption is a precursor to the photooxidation. Reaction schemes are discussed.