Degradation Of 2-propanol Research Articles

Photocatalytic Degradation of 2-Propanol under Irradiation of Visible Light by Nanocrystalline Titanium(IV) Oxide Modified with Rhodium Ion Using Adsorption Method

Abstract Using adsorption method, a small amount of rhodium ion (Rh3+) was loaded on nanocrystalline titanium(IV) oxide (TiO2) with various physical properties prepared by HyCOM and subsequent calcinations at various temperatures. In photocatalytic degradation of 2-propanol under visible light irradiation, Rh3+-modified HyCOM-TiO2 samples exhibited higher levels of activity than did nitrogen-doped TiO2 sample and showed a volcano-like tendency with calcination temperature, suggesting that the balance of surface area and crystallinity of TiO2 is important in an Rh3+/TiO2 photocatalyst.

Photocatalytic activities of Ba2RBiO6 (R = La, Ce, Nd, Sm, Eu, Gd, Dy) under visible light irradiation

We succeeded in synthesizing Ba2RBiO6 (R = La, Ce, Nd, Sm, Eu, Gd, and Dy) with a double-perovskite structure. Its photocatalytic activities were then investigated for a degradation of methylene blue (MB) solution and gaseous 2-propanol (IPA). High photocatalytic activities were observed under visible light irradiation and also a rare earth dependence of photocatalytic activities in the IPA degradation. We carried out first-principle calculations of the band structure based on the all-electron Full-potential Linear Augmented Plane-Wave (FLAPW) method and discuss the relationship between the high photocatalytic activities and the band structure in this paper.

Preparation, characterization and photocatalytic activity of TiO2 impregnated with the heteropolyacid H3PW12O40: Photo-assisted degradation of 2-propanol in gas–solid regime

Both commercial and home prepared TiO2 samples impregnated with tungstophosphoric acid (H3PW12O40) were prepared and used for the photo-assisted degradation of 2-propanol in gas–solid regime. The characterization results evidenced a good coverage of the polyoxometalate (POM) onto the surface of both types of TiO2 samples along with a marginal effect of the presence of ethanol or HCl during the POM impregnation step on the specific surface area, porosity, morphology, crystallinity and acidity of the samples. Propene was the main intermediate product found in 2-propanol photocatalytic degradation by using the samples containing POM as the photocatalyst, whereas propanone was mainly obtained when the photocatalyst was bare TiO2. Acetaldehyde was also an intermediate product and its amount was always significantly smaller with respect to propanone and propene (when formed). Carbon dioxide and water were the ultimate oxidation products. The selectivity to propene has been attributed to the acidity of the POM supported samples.

Comparison of the photocatalytic degradation of 2-propanol in gas–solid and liquid–solid systems by using TiO 2–LnPc 2 hybrid powders

Photocatalytic degradation of 2-propanol was carried out as a probe reaction both in gas–solid and in liquid–solid systems in the presence of TiO 2 both bare and impregnated with lanthanide (Sm, Gd, Ho) bis-phthalocyanines (LnPc 2) used as sensitizers. Continuous and batch photo-reactors, irradiated with an equal flux of photons, were used in gas–solid and in liquid–solid systems, respectively. Propanone and acetaldehyde were the main intermediates found in both systems during 2-propanol oxidation, whereas carbon dioxide and water were the final oxidation products exclusively in the gas–solid regime. The photocatalysts exhibited significantly higher activity in the liquid–solid system than in the gas–solid one. Samples impregnated with the sensitizers were apparently more photoactive than bare TiO 2. The highest photoactivity was shown by the 1.85 HoPc 2–TiO 2 sample.

Simple Design of Hydrophobic Zeolite Material by Modification Using TEFS and its Application as a Support of TiO2 Photocatalyst

Through the simple process using alkoxide reagent containing fluorine, triethoxyfluorosilane (TEFS), hydrophobic mesoporous silica material (HMS) was prepared. The surface modified HMS have still maintained its mesoporous structure and large surface area and showed considerable hydrophobic property compared with non-modified HMS. Moreover the surface modified HMS was applied as a support of TiO2 photocatalyst with the aim of the efficient degradation of organic pollutant in water. Due to the hydrophobic property, the fine TiO2 photocatalyst particles were generated on the modified HMS and both the adsorption properties and photocatalytic activities for the degradation of 2-propanol diluted in water were dramatically increased.

Photo-assisted degradation of 2-propanol in gas–solid regime by using TiO 2 impregnated with heteropolyacid H 3PW 12O 40

Commercial and home prepared TiO 2 samples impregnated with tungstophosphoric acid (H 3PW 12O 40) were used for the photo-assisted degradation of 2-propanol in gas–solid regime. The characterization results evidenced a good coverage of the polyoxometalate (POM) onto the surface of TiO 2 along with a marginal effect of the presence of the POM on the specific surface area, morphology and cristallinity of the samples. Propene was the main intermediate product revealed in 2-propanol photocatalytic degradation by using as photocatalysts the samples containing the POM, whereas propanone was mainly obtained when the photocatalysts was bare TiO 2, both commercial or home prepared. Acetaldehyde was also found as an intermediate product along with traces of isopropyl ether, mesityl oxide and isobutyl-methyl-ketone that were also detected as gaseous products in all the runs. Carbon dioxide and water were the ultimate oxidation products.

FTIR study of photocatalytic degradation of 2-propanol in gas phase with different TiO2 catalysts

The photocatalytic efficiency of different TiO2 catalysts in the degradation of 2-propanol in gas phase has been studied. The obtained efficiencies have been compared considering the distribution of rutile–anatase phases, surface area, particle size, distribution of surface hydroxyl groups and Brönsted or Lewis acid centres. The catalysts used were Degussa-P25 (TiO2-P25), Hombikat, Millennium, Kemira and s/g-TiO2, a catalyst prepared by a sol–gel method.The best photocatalytic behaviours have been obtained with those catalysts with higher surface area and the presence of only anatase phase (Hombikat and Millennium). A progressive deactivation of TiO2-P25 and s/g-TiO2 has been observed during the photocatalytic process.FTIR studies indicated that degradation mechanisms depended on the catalyst employed. Deactivation processes observed in TiO2-P25 have been correlated with the formation of carboxylates.

Exposed crystal surface-controlled TiO 2 nanorods having rutile phase from TiCl 3 under hydrothermal conditions

Size-, shape-, and phase structure-controlled synthesis of TiO 2 nanocrystallites has long been one of the main themes in TiO 2 research. Many synthetic techniques have been utilized in the preparation of TiO 2 nanocrystals, among which hydrothermal treatment has been drawing much attention because it directly produces well-crystallized nanocrystallities of a wide range of compositions of crystal phases within a short reaction time. In this study, we carried out hydrothermal growth of rutile TiO 2 rods by using aqueous titanium trichloride (TiCl 3) solutions containing NaCl. Uniform ultrafine rutile TiO 2 particles were obtained, and developed crystal faces were observed by TEM, SEM, XRD, and specific surface area measurements. The obtained rutile fine particles showed high levels of activity for degradation of 2-propanol and acetaldehyde under UV irradiation compared to the activity levels of anatase fine particles (ST-01) developed for environmental clean-up. The surface chemistry of the rutile TiO 2 particles was also investigated. From photodeposition of Pt and PbO 2, we suggest that the (1 1 0) face provides reductive sites and that the (1 1 1) face provides oxidative sites. These results indicate that the crystal faces facilitate the separation of electrons and holes, resulting in improvement of photocatalytic activity.

Improvement of photocatalytic behavior of chemical-vapor-synthesized TiO2 nanopowders by post-heat treatment

Abstract Anatase-type TiO2 nanopowders less than 10 nm in average diameter were synthesized by a chemical vapor synthesis method. The TiO2 nanopowders showed very poor photocatalytic properties, in spite of their large surface area. With subsequent heat treatment of the TiO2 powders, their photocatalytic properties determined by measuring the degradation of 2-propanol were improved at temperatures up to 600 °C and then diminished along with formation of a rutile phase. This improvement in the photocatalytic properties of TiO2 nanopowders was attributed to both a morphology change and a change in the electronic surface characteristics of TiO2 particles during heat treatment.

Efficient adsorption and photocatalytic degradation of organic pollutants diluted in water using the fluoride-modified hydrophobic titanium oxide photocatalysts: Ti-containing Beta zeolite and TiO 2 loaded on HMS mesoporous silica

Using the F − media, the hydrophobic zeolite and mesoporous silica can be synthesized. These hydrophobic porous materials exhibit the high ability for the adsorption of organic compounds diluted in water and become the useful supports of photocatalyst. The hydrophobic Ti-Beta(F) zeolite prepared in the F − media exhibited high efficiency than the hydrophilic Ti-Beta(OH) zeolite prepared in OH − media for the liquid-phase photocatalytic degradation of 2-propanol diluted in water to produce CO 2 and H 2O. The TiO 2 loaded on the hydrophobic mesoporous silica HMS(F) (TiO 2/HMS(F)), which was synthesized using tetraethyl orthosilicate, tetraethylammonium fluoride as the source of the fluoride and dodecylamine as templates, also exhibited the efficient photocatalytic performance for the degradation. The amount of adsorption of 2-propanol and the photocatalytic reactivity for the degradation increased with increasing the content of fluoride ions on these photocatalysts. The efficient photocatalytic degradation of 2-propanol diluted in water on Ti-Beta(F) zeolite and TiO 2/HMS(F) mesoporous silica can be attributed to the larger affinity for the adsorption of propanol molecules on the titanium oxide species depending on the hydrophobic surface properties of these photocatalysts.

Photocatalytic behaviour of metal-loaded TiO 2 aqueous dispersions and films

Titanium dioxide nanoparticles loaded with Ce, Co, Eu, Sm, W and Yb species were prepared by coprecipitation in mild conditions using TiCl 4 as precursor with the aim to enhance the photocatalytic activity, especially under visible light irradiation. The photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), specific surface area (SSA) determination and UV–Vis diffuse reflectance spectroscopy. The photocatalytic activity of the powders of pure and loaded TiO 2 was investigated by employing the photodegradation of 4-nitrophenol as probe reaction in a liquid–solid system. Loading with suitable amounts of W, Co and Sm resulted in a significant improvement of the photoreactivity of TiO 2. This beneficial effect was attributed to an increased separation of the photogenerated electron–hole pairs. Some samples were more photoactive than commercial powders employed in the same experimental conditions. Films of TiO 2 loaded with the metals that yielded the best photocatalytic responses were prepared by the dip-coating technique. The photoactivity of the films was tested by evaluating the rate of degradation of 2-propanol in a gas–solid system. An enhancement of the photocatalytic efficiency was obtained in the presence of W and Sm.

Photocatalytic degradation of 2-propanol by using Pt/TiO2 prepared by microemulsion technique

Abstract The photocatalytic degradation of 2-propanol was studied by using platinum, titania, and platinum loaded on titania as photocatalysts. In this study, the catalysts were prepared by microemulsion technique, which gives ultrafine particles in the range of 3–5 nm. Each synthesized photocatalyst was suspended in an aqueous solution of 2-propanol, and the solution was photoirradiated by an 11 W low pressure mercury lamp. The results showed a negligible activity of platinum and a relatively low activity of titania in the degradation of 2-propanol, but a significantly high activity of platinum loaded on titania was observed. The effects of the influencing factors, including initial concentration of 2-propanol, catalyst dosage, initial pH, and dissolved oxygen, were studied. The results revealed that the most efficient degradation of 2-propanol was achieved in a highly acidic region, and the degradation rate increased with both catalyst dosage and initial concentration of 2-propanol. The dissolved oxygen was found to have a significant influence affecting the photocatalytic degradation of 2-propanol since it acts as an electron scavenger and is responsible for producing hydroxyl radical. Acetone was detected as an intermediate during the photocatalytic reaction of 2-propanol.

2-Propanol photodegradation over lead niobates under visible light irradiation

Abstract Two binary lead niobates, viz. Pb3Nb2O8 and Pb3Nb4O13, had been developed as visible-light-sensitive photocatalysts. Their physical characteristics were examined by techniques such as XRD, UV–vis reflectance spectroscopy and SEM; the photocatalytic activities of several samples were investigated for 2-propanol degradation in gas phase. Compared to pure Nb2O5, the hybridization of Pb 6s2 and O 2p6 orbitals notably pushed up the position of the valence band top, and narrowed the band gap of lead niobates. Due to the appropriate crystal structure and energy band structure, Pb3Nb4O13 performed much better than Pb3Nb2O8 for 2-propanol photodegradation. Different preparation methods were also adopted to prepare the Pb3Nb4O13 samples. Compared to the solid-state reaction method (SSR), the co-precipitation method (CP) created a high homogeneity in the precursor powder, which notably decreased the calcination temperature required for crystal formation. The so-obtained Pb3Nb4O13(CP) photocatalyst possesses much greater surface area than its Pb3Nb4O13(SSR) counterpart, and exhibited notably improved photocatalytic activity for 2-propanol degradation as a result.

Effect of nitrogen-plasma surface treatment to the enhancement of TiO 2 photocatalytic activity under visible light irradiation

A visible-light-active commercial TiO 2 powder was prepared by thermal nitrogen-plasma processing as the surface treatment. The photoactivity of the treated TiO 2 samples was evaluated in the photocatalytic degradation of gaseous 2-Propanol (IPA) in a batch reactor. XPS analysis showed that oxygen vacancies formed in the lattice of the treated TiO 2 particles and no nitrogen peaks were detected. With increasing the treating time, the visible absorbance and oxygen vacancies were increased but the surface area of treated sample was decreased. The photodegradation rate of IPA under visible light illumination depended strongly on the treating time of the catalyst, and the photoactivity of the treated sample was higher than that of plain TiO 2. From the results of reaction rate constant and mineralization yield of IPA, it was found that the TiO 2 powders treated for 30 min demonstrated the highest photocatalytic activity among all samples. This high visible light photoactivity was ascribed to an intermediate level of visible absorbance as well as optimal oxygen vacancies after the thermal nitrogen-plasma surface treatment.

Design of TiO 2-SiC photocatalyst using TiC-SiC nano-particles for degradation of 2-propanol diluted in water

TiO 2 photocatalyst deposited on SiC (TiO 2-SiC) was prepared by a calcination of nano-particles of TiC-SiC precursor obtained by a carbothermic reduction of SiO 2-TiO 2. The formation of the mixture of well-crystallized anatase and rutile phases of TiO 2 was observed on the calcined TiO 2-SiC photocatalyst, while amorphous TiO 2 species was main component on the TiO 2-SiO 2 photocatalyst prepared by a conventional sol–gel method. From the measurement on the water adsorption ability of photocatalysts, the TiO 2-SiC photocatalyst exhibited the hydrophobic surface property in comparison with TiO 2-SiO 2 and commercial TiO 2 powder (P-25) photocatalysts. Under UV-light irradiation, the TiO 2-SiC photocatalyst decomposed 2-propanol diluted in water into acetone, CO 2, and H 2O, and finally acetone was also decomposed into CO 2 and H 2O. The TiO 2-SiC photocatalyst exhibited the higher photocatalytic reactivity than TiO 2-SiO 2 photocatalyst prepared by the sol–gel method. Well-crystallized TiO 2 phase deposited on SiC and the hydrophobic surface of SiC support are important factors for the enhancement of photocatalytic reactivity for degradation of organic compounds in the liquid phase reaction.

Preparation of bimetal incorporated TiO2 photocatalytic nano-powders by flame method and their photocatalytic reactivity for the degradation of diluted 2-propanol

Abstract Bimetal incorporated TiO2 photocatalysts (FeZn–TiO2) prepared by a flame method showed high photocatalytic activity for the degradation of 2-propanol dissolved in water as compared with mono-metal incorporated or unincorporated TiO2. By using this flame method, parameters such as uniform particle size, crystallinity as well as the anatase and rutile phase ratio (anatase/rutile) could be controlled without calcination of the catalysts at high temperatures, the parameters being important to achieve a high photocatalytic activity. The presence of a small amount of bimetals such as Fe and Zn plays a vital role as a catalyst in the formation of highly crystalline, small and uniform size particles with defined anatase/rutile phase ratio of around 60/40, this being similar to that of P-25 which is well known as a highly active photocatalyst.

Effect of dissolved oxygen and lanthanide ions in solution on TiO2 photocatalytic oxidation of 2-propanol

The photocatalytic degradation of 2-propanol in D2O solution under UV irradiation was investigated. The conversion yield from 2-propanol to acetone was studied by 1H-NMR measurements. The study was carried out to elucidate effects of O2 in the reaction medium and lanthanide ion modification on the TiO2 surface. Under aerobic conditions, acetone formation was clearly increased in comparison with anaerobic conditions. On the modification of TiO2 with lanthanide ion, the conversion yield decreased with the increase in the ionic radius. Yb3+ ion modification increased the acetone formation by approx. 5% in comparison with the unmodified case. Appreciably large effects of the counter ion in lanthanide salts were also observed. The role of OH˙ radical formation in the first step of photocatalysis was emphasized in the experimental results.

Preparation and photocatalytic activity of titania particulate film with mesostructured silica as binder

TiO 2 (titania) particulate films with mesostructured silica (SiO 2) as binder were prepared by drying glass substrate coated with an aqueous mixture of titania particles, tetramethoxysilane (TMOS) and cetyltrimetylammonium bromide (CTAB) at appropriate temperature. X-ray diffraction (XRD) and IR absorption measurements on the obtained films revealed the formation of titania particles/silica composite thin film. XRD patterns at low angle region on these films indicated silica binder has well-ordered lamellar type mesostructure. These films show characteristic properties on both high absorption ability and photocatalytic activity to oxidative degradation of gaseous 2-propanol.

Development of Visible Light Sensitive TiO<sub>2</sub> Photocatalysts and Their Sensitization Using Fe<sup>3+</sup> Ions

Titanium dioxide photocatalysts are promising substrates for photodegradation of pollutants in water and air, but show photocatalytic activities only under UV light. To utilize a wider range of incident wavelengths such as solar light, development of photocatalysts active under visible light is very important. Chemically modified titanium dioxide photocatalysts were prepared containing anatase phase with S (S4+) substituted for some lattice Ti atoms or N substituted for some lattice O atoms. These catalysts showed strong absorption of visible light and high activities for degradation of 2-propanol in aqueous solution and partial oxidation of adamantane under irradiation at wavelengths longer than 440 nm. The oxidation states of the S and N atoms incorporated into the TiO2 particles were determined to be mainly S4+ and N3− from XPS spectra, respectively. The photocatalytic activities of S- or N-doped TiO2 photocatalysts with adsorbed Fe3+ ions were markedly improved for oxidation of 2-propanol compared to those of S- or N-doped TiO2 without Fe3+ ions under a wide range of incident wavelengths, including UV light and visible light. The photocatalytic activity reached maximum with 0.90 wt% Fe3+ ions adsorbed on S-doped TiO2, and 0.36 wt% Fe3+ ions on N-doped TiO2. Furthermore, redox treatment of S- or N-doped TiO2 photocatalysts with adsorbed Fe3+ ions by reduction with NaBH4 followed by air oxidation resulted in further improvements in photocatalytic activities. In this case, the optimum amounts of Fe3+ were 2.81 and 0.88 wt% on the surfaces of S- and N-doped TiO2 photocatalysts, respectively.

Preparation of Nano-Sized TiO<sub>2</sub> Photocatalysts by a Multi-Gelation Method and Their Application to the Degradation of 2-Propanol Diluted in Water

TiO2 photocatalysts prepared by a novel multi-gelation method showed good photocatalytic activity for the degradation of 2-propanol diluted in water by the control of parameters such as particle size, surface area, crystallinity, pore-volume, pore-diameter as well as anatase and rutile phase composition by changing the number of pH swings during preparation. In particular, with this method the phase transition from anatase to rutile at higher pH swing times can be controlled and high purity and uniformity of the TiO2 particles which leads to higher photocatalytic activity of the particles can be achieved. From our experimental results, it has been observed that TiO2 catalysts prepared by this unique multi-gelation method, i.e., adopting variations in the pH swing, significantly shows higher photocatalytic activity for the degradation of 2- propanol diluted in water. It can be considered a viable alternative over existing commercial methods for the preparation of photofunctional catalysts.