Photodegradation Of 2-propanol Research Articles

Physicochemical properties and photocatalytic activity in the 2-propanol degradation of transition metals (Zr, Zn or Nb) doped TiO2 solids

For improving the photocatalytic activity of titania under UV or sunlight (SL) irradiations in the gaseous phase degradation of 2-propanol, M−TiO2 catalysts were synthesized by the sol–gel method (with M = Zr, Zn and Nb) and characterized by various techniques. It was found that the solids show only the diffraction peaks of TiO2 anatase phase with high surface area and porosity. The type of transition metal affects the physicochemical properties and photocatalytic activity of M−TiO2 catalysts which were found more active and more selective to CO2 using UV illumination. Only the Nb-TiO2 solid was less active than TiO2. However, 0.5 % Zr-TiO2 sample was the most efficient catalyst for the photodegradation of 2-propanol with 58 % as 2-propanol maximum conversion to CO2 (54.4 %) and acetone (45.6 %) under UV. This is attributed to its high surface area and porosity, reduced particle size and low band gap energy.

Photodegradation of 2-propanol in gas phase over zirconium doped TiO2: Effect of Zr content

The photocatalytic activity in the 2-propanol degradation, under UV and sunlight (SL)-type irradiations, of a series of Zr-TiO2materials, prepared using the sol–gel method, with a Zr content ranging from 0.25 to 1 wt%, was evaluated in this work. The physicochemical properties of the solids were characterized using X-ray diffraction, BET and porosity measurements, IR, UV–vis, Photoluminescence and X-ray photoelectron spectroscopy. The XRD data showed that the TiO2 was stabilized as anatase phase in all the samples and that the incorporation of Zr4+ into TiO2 lattice has led to a decrease of the crystallite size. The BET analysis confirmed that the addition of zirconium onto TiO2 support affected the surface area which increases with the increase of Zr4+ content. The UV-DRS spectra showed that, the incorporation of zirconium into TiO2 lattice leads to a slight decrease of the band gap energy of TiO2. The results of the photocatalytic test showed an enhancement on the photocatalytic activity of TiO2, in the 2 propanol degradation, by the doping with a low amount of zirconium. All the samples were found more active under UV illumination than under SL. In all cases, the highest efficiency in the 2-propanol photodegradation was observed for the 0.5% Zr-TiO2 sample and was essentially related to its lowest optical band gap energy.

Photocatalytic Degradation of 2-propanol Over TiO2-based Thin Films in a Simulated Pilot Microreactor

Background: Microreactor devices have attracted increasing attention over the last years due to their high surface-to-volume ratio, which ensures a high heat and mass transfer, short molecular diffusion distance and greater spatial illumination homogeneity compared to the traditional reactors. Objective: The aim of this study was to model the kinetics of photo-degradation of 2-propanol over TiO2-based thin films in a gas-phase batch-reactor and simulate their performance in a microreactor device. Methods: The reaction was carried out in a gas-phase batch-reactor, assessing the reactivity of singlelayer nitrogen (N)-doped TiO2 and a bilayer consisting of N-doped TiO2 as a bottom layer and copper (Cu)-doped TiO2 as a top layer. The kinetics of the photocatalytic process was modelled by Langmuir– Hinshelwood (LH) model. The constants obtained from the LH model were used to simulate the performance of the photocatalysts in a microreactor, operating in a continuous flow mode and investigating the effect of the volumetric flow rate (Q), initial concentration of pollutant (Co), number of microchannels (n) and microchannel length (l) on the photo-degradation of 2-propanol. Results: N-Cu-TiO2 exhibited a higher reactivity but a lower adsorption ability towards the target pollutant compared to N-TiO2. To maximize and leverage the advantages of a microreactor, optimal operating conditions for a continuous flow mode, at a steady-state, should be moderately low Q and Co, long l and n that minimizes flow maldistribution in parallel. Conclusion: The findings in this work could serve as a basis to design and fabricate efficient microreactors for the removal of VOC in air purification applications.

Titania-decorated copper oxide nanophotocatalyst powder: A stable and promoted photocatalytic active system

In this work, the synthesis of the CuO-Cu2O nanocomposites decorated with TiO2 nanoparticles was performed by chemical-thermal oxidation and subsequently by the sol–gel method. The X-ray diffraction (XRD) analysis and field emission scanning electron microscopy (FESEM) showed using different furnace atmospheres lead to the formation of nanocomposites with variable components content with a mixture of special morphology. The Energy Dispersive X-Ray Analysis (EDX) confirmed the existence of Ti, Cu, and O elements in the composite material. The X-ray photoelectron spectroscopy (XPS) data suggest the presence of CuO and Cu2O species in addition to the TiO2 phase in the as-prepared composite samples. Transmission electron microscopy (TEM) and UV–vis spectroscopy indicated the successful fabrication of multiple heterostructures of TiO2 and copper oxides components. The assessment of gas-phase photocatalytic performance in the 2-propanol photodegradation under both UV and visible light irradiation was done through the measurement of the reaction rate and quantum efficiency. The composite photocatalysts demonstrated about 2.5 times more active photocatalytic behavior in gas phase photo-oxidation compared with the pure CuO-Cu2O and titania because of the simultaneous presence of different copper oxide types in the structure and TiO2 nanoparticles as a surface decorated part. A cascade-type mechanism was also proposed for the photocatalytic behavior of the system. Furthermore, the stability of the specimens was proved during the photocatalytic reaction.

High-yield and low-cost method to synthesize large-area porous g-C3N4 nanosheets with improved photocatalytic activity for gaseous nitric oxide and 2-propanol photodegradation

A high-yield and low-cost method was developed for preparing graphitic carbon nitride (g-C3N4) with high photocatalytic activity. A trace amount of glyoxal-treated melamine was used as the precursor for g-C3N4. Glyoxal played a remarkable role in the thermal condensation of g-C3N4 as it improved the yield, inhibited the grain growth, and increased the specific surface area (up to 119 m2 g−1). The yield of g-C3N4 obtained with this method was 10 times higher than that in the traditional method. SEM, TEM, and EPR results showed that the prepared photocatalysts have a porous nanosheet structure with nitrogen vacancy defects. The photocatalytic activity of the obtained g-C3N4 was estimated by using it for the photodegradation of gaseous nitric oxide (NO) and isopropyl alcohol (IPA) under visible light (λ > 420 nm). The photocatalytic activity of the porous g-C3N4 nanosheets was well improved as compared with that of bulk g-C3N4. The addition of trace amounts of glyoxal improved the photocatalytic activity remarkably, so this method could open up a new channel for the development of low-cost, high-activity g-C3N4 photocatalysts for green chemistry.

Study of 2-Propanol Photocatalytic Degradation on Surface of Phase-Ratio-Controlled TiO2 Nanoparticles

The crystal form of TiO2 is a crucial focus of research on the photocatalytic degradation of gaseous pollutants by TiO2-based composite photocatalysts. To explore the synergistic effect of mixed crystalline TiO2 on gaseous organic-pollutant photocatalytic degradation, we synthesized a series of TiO2 nanoparticles with controllable phase ratios. We explored the role of the TiO2 phase ratio on the photocatalytic activity and degradation pathway in the photodegradation of 2-propanol (IPA). We estimated the crystallite size and crystal proportions of anatase and rutile by X-ray diffraction. We used the Brunauer–Emmett–Teller method to calculate the specific surface area and Fourier transform infrared spectroscopy to characterize the surface chemistry of the samples. Our results show the photocatalytic activities of pure anatase and the sample with 8.6% rutile to be much better than those of the samples with a phase junction and pure rutile. As such, anatase is the better option for the study of photodegradation design and preparation of gas-phase organic pollutants.

Constructing hydrogen bond based melam/WO3 heterojunction with enhanced visible-light photocatalytic activity

Hydrogen bond based visible-light-response heterojunction photocatalyst Melam/WO3 (MW) has been fabricated for the first time by facile planetary milling treatment. Fourier transform infrared spectroscopy (FTIR) and Thermogravimetric (TG) analysis reveal the formation of hydrogen bonds (NH···O) between melam and WO3. As compared to WO3, the MW not only complete decomposes acetaldehyde, but also shows 10 times and 12 times higher photocatalytic activity for photo-degradation of 2-propanol and photo-generation of H2O2, respectively, under the visible-light irradiation. X-ray photoelectron spectroscopy suggests that the potential difference between N and O (N+H⋯O−) in the heterojunction provides the driving force for the charge transfer from WO3 to melam. Furthermore, hydrogen bonds offer an ultrafast electron pathway for heterojunction. This study demonstrates that hydrogen bond based heterojunction could be a promising approach for developing a new photocatalyst with efficient visible-light photocatalytic activity.

Ag-loaded mesoporous Pb3Nb2O8 photocatalysts with enhanced activity under visible-light irradiation

Mesoporous Pb3Nb2O8 photocatalysts were synthesized by the evaporation-induced self-assembly (EISA) method. Ag was deposited on the surface of mesoporous Pb3Nb2O8 by a facile photoreduction process. The as-prepared samples were characterized by TG-DSC, XRD, N2 adsorption, HR-TEM and UV-Vis spectroscopy. The results revealed that mesoporous Pb3Nb2O8 has a large specific surface area and uniform pore size distribution both before and after Ag deposition. The photodegradation of 2-propanol and acetaldehyde gas under visible-light (λ > 420 nm) irradiation was employed to evaluate the photocatalytic activities of the samples. The results showed that the photocatalytic activity of mesoporous Pb3Nb2O8 is greatly improved by the Ag co-catalyst. These mesoporous Pb3Nb2O8 exhibit photocatalytic activities as much as 41 times higher when compared with the Pb3Nb2O8 prepared by the solid state reaction method. The content of loaded Ag ranged from 0.5% to 5% (Ag2SO4). The optimal loading was determined to be 1% corresponding the highest photocatalytic activity. These results clearly indicate that the activity of Pb3Nb2O8 can be improved to obtain an outstanding performance for the photodegradation of organic pollutants.

E-beam evaporated TiO2 and Cu-TiO2 on glass: Performance in the discoloration of methylene blue and 2-propanol oxidation

TiO2 and Cu-TiO2 thin films were deposited by e-beam evaporation and then annealed at 350 and 500°C. Their structure, surface morphology and optical properties were studied by X-ray diffraction, scanning electron microscopy, cross-sectional TEM, UV–vis, FT-IR spectroscopy and X-ray absorption spectroscopy. A single-phase source material was used for the first time in the deposition process, thus avoiding preferential evaporation of Cu with respect to TiO2, and resulting in an even concentration of Cu in the doped films. The photocatalytic activity was evaluated by degradation of pre-adsorbed methylene blue (MB) in dry conditions and gaseous 2-propanol in oxygen atmosphere under visible and simulated solar light, respectively. Results suggested that high surface hydroxylation of the as-deposited films is an important factor for MB oxidation occurring through a dye-sensitized mechanism activated by visible light absorption. Conversely, the rate of photodegradation of 2-propanol is enhanced in annealed samples due to the greater crystallinity and less electron-hole recombination, with the TiO2 annealed at 500°C being the most efficient photocatalyst. However, Cu-doped samples resulted the most active samples during the degradation of MB under visible radiation. Finally, the performance at increasing thickness (250, 500, 1000, up to 2000nm) was tested for the most reactive films revealing a marked rise in photocatalytic activity up to 1000nm.

Gas phase 2-propanol degradation using titania photocatalysts: Study of the quantum efficiency

A series of TiO2 samples, prepared by a microwave assisted method followed by spray drying and subjected to further calcination, were tested in gas-phase photodegradation of 2-propanol under UV and Sunlight-type illumination conditions. Samples were characterized using X-ray diffraction, porosimetry, UV–vis and Photoluminescence spectroscopies. This physico-chemical characterization was completed with the in-situ analysis of the sample behavior under illumination conditions using infrared spectroscopy. The photochemical behavior of the samples was analyzed through their reaction rate and particularly efficiency parameters, the later measured as both the apparent and true quantum efficiency. To calculate the efficiency in quantitative basis we carried out a complete analysis of the light-matter interaction in the reaction system as well as the chemical response of the catalysts measuring reaction activity and selectivity. The study measures the differences observed among the most common (including the apparent and true quantum efficiency) approximations used to calculate the efficiency parameter providing evidence that they can differ in a factor of 2–4 and shows that optimum performance in our titania-based catalysts is obtained in presence of anatase-rutile interface contact. However, the analysis of the true quantum efficiency demonstrates that this is not exclusively based in the well-known effect of such interface in charge recombination but also depends critically on the variation of the optical properties of the catalytic solids through the series.

SrTiO3-based perovskites: Preparation, characterization and photocatalytic activity in gas–solid regime under simulated solar irradiation

Strontium titanate-based perovskites have been prepared in the presence of Y and Co with the aim to substitute Sr and Ti, respectively, in the ST crystalline structure. The obtained samples have been characterized by XRD, Raman spectroscopy, FE-SEM, XPS and tested as photocatalysts in two gas–solid regime reactions: (i) 2-propanol complete mineralization and (ii) propene partial oxidation, using a system simulating solar irradiation. All the tested samples resulted active as photocatalysts but with significant differences. The lattice substitution of Sr by Y displays a beneficial effect on the 2-propanol photodegradation. Conversely, the partial presence of cobalt on the ST surface, as Co-oxide nanodispersed clusters with a dominant Co(II) phase, plays a substantial detrimental effect on the photo-degradation process of 2-propanol, but favours the photocatalytic partial oxidation of propene to propene oxide.

Surface modification by loading alkaline hydroxides to enhance the photoactivity of WO3

Surface modification on WO3 was carried out by loading KOH, NaOH and CsOH to study the influence of surface interactions on photocatalytic activity of this material. Photodegradation of 2-propanol, methanol, ethanol, acetone and propane in gas phase under visible light irradiation shows loading of KOH, NaOH and CsOH on WO3 enhanced the photodegradation rate about 4 and 3 times respectively. Loading of KOH on TiO2 were carried out for comparison and the results showed enhancement of photoactivity by KOH loading for WO3 which was much higher than that of TiO2. Increasing the rate of the photocatalytic reaction is attributed to compensation of the high tendency of WO3 for H+ donation and making multi-electron O2 reduction by loading of KOH on the surface.

2-Propanol Photodegradation over Bi<sub>5</sub>AgM<sub>4</sub>O<sub>18</sub> (M=Nb and Ta) Powders under Visible-Light Irradiation

Bi5AgM4O18 (M=Nb and Ta) photocatalysts with 3.07-3.55eV of band gaps and layered perovskite-like structures showed activities for 2-propanol degradation in gas phase. Due to the appropriate crystal structure and energy band structure, Bi5AgNb4O18 performed much better than Bi5AgTa4O18 for 2-propanol photodegradation.

Hard Template Synthesis of Mesoporous and Nanocrystalline Alkali Metal Niobates with Enhanced Photocatalytic Performance

A nanocasting method using SBA-15 as a hard template was adopted to prepare mesoporous nanocrystalline ANbO3 (A = Li, Na, and K) samples. The characteristics of samples werecharacterized by techniques such asXRD, N2-sorption measurement, HRTEM and UVDRS. It was found that thealkality of the alkali metals could have profound impacts on the synthesis andthe physical properties of samples. The Li, Na, and K precursors can reacteasily with the siliceous template, and the reactivity varies with the alkalityof the alkali metal. The synthesis of KNbO3 is unsuccessful because of the high alkality ofK. The templated LiNbO3 andNaNbO3 consist of single crystalline nanoparticles that generate interparticle mesoporosity. The LiNbO3andNaNbO3 samples showed notably enhanced photocatalytic activitiesfor 2-propanol photodegradation in comparison to the counterparts prepared bythe solid state reaction.

The effects of NaNbO3 particle size on the photocatalytic activity for 2-propanol photodegradation

The effects of NaNbO3 particle size on the photocatalytic activity were investigated by taking gaseous 2-propanol photodegradation as a model reaction. By varying the loading amount of precursors onto mesoporous SBA-15, nanocrystalline NaNbO3 samples with particle sizes ranging from 3 to 50 nm were successfully synthesized. The particle size and surface area value of templated NaNbO3 change systematically with the change in loading amount of the precursors. The physicochemical characteristics of the samples were examined by techniques such as XRD, SEM, TEM, Raman spectroscopy, and UV-visible diffuse reflectance spectroscopy. The optimum NaNbO3 particle size for the highest photocatalytic activity was found to be 30 nm. The current study also revealed that the NaNbO3 photocatalyst is structure sensitive for 2-propanol photodegradation. The density of active sites on the sample surface decreases as the particle size decreases. Competing effects of factors such as the surface area, changes in electronic structure, defect density, and concentration of reaction active sites determine the optimum particle size of NaNbO3.

Hard Template Synthesis of Nanocrystalline NaNbO3 with Enhanced Photocatalytic Performance

A nanocasting method using SBA-15 as a hard template was adopted to prepare nanocrystalline NaNbO3. The templated NaNbO3 consists of single crystalline nanoparticles about 8 nm. The nanocrystalline NaNbO3 sample showed remarkably enhanced photocatalytic activity for 2-propanol photodegradation in comparison to the counterpart prepared by the solid state reaction.

N-TiO2 Photocatalysts highly active under visible irradiation for NOX abatement and 2-propanol oxidation

N-doped TiO2 powders were prepared by two different sol–gel methods. Samples were characterised by X-ray diffraction (XRD), BET specific surface area measurements (SSA), scanning electron microscopy (SEM), diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and Electron Paramagnetic Resonance (EPR). XPS measurements revealed a signal at 400eV assignable to nitrogen in the form of TiNO. EPR signals are attributed to molecular NO trapped with cavities/defects possibly interacting with oxygen vacancies. The photocatalytic activity under UV and visible light was determined following the abatement of NOx and the photodegradation of 2-propanol in gas–solid systems. N-doped TiO2 showed a higher activity compared with the pristine commercial and home prepared samples under visible light irradiation. A good photoactivity in the abatement of both NOx and 2-propanol is also observed for mechanical dispersions of N-TiO2 in CaCO3 serving as a model in view of perspective application in photocatalytically active construction and architectural materials.

Zn,Al hydrotalcites calcined at different temperatures: Preparation, characterization and photocatalytic activity in gas–solid regime

Layered double hydroxides (LDH) containing zinc and aluminium within the brucite-like layers and carbonate as the interlayer anion have been used as precursors for the preparation of mixed metal oxides by calcination. Zinc oxide and the ZnAl 2O 4 spinel were formed with different degree of crystallinity depending of two parameters, i.e., the Zn 2+/Al 3+ molar ratio and the calcination temperature (500–800 °C) of the LDH precursor. A pure spinel phase was obtained to remove ZnO upon a basic post-treatment in NaOH solution of the samples calcined at 800 °C. All the samples were tested for the photodegradation of 2-propanol in gas–solid regime. All the samples resulted active as heterogeneous photocatalysts. The photocatalytic activity increased by increasing the Zn 2+/Al 3+ molar ratio and the calcination temperature of the solids.

Synthesis, characterization and photocatalytic performance of VDyO x composite under visible light irradiation

A VDyO x (V 2O 5/DyVO 4) composite photocatalyst was prepared using a simple solution method. The powders were characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) method, Raman spectroscopy (Raman), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), UV–vis diffuse reflectance spectroscopy (DRS), and photoluminescence (PL) spectroscopy. Visible light-induced photocatalytic activities of the powders were evaluated by the degradation of acetone. Results generally show that the binary semiconductors V 2O 5/DyVO 4 with matching band potentials exhibit better photocatalytic properties compared with those of the single phase V 2O 5 or DyVO 4. An acetone conversion of 91.6% was achieved over V 1.5Dy 1O x composite photocatalyst under visible light irradiation. Effective electron–hole separation in the two semiconductors is believed to be mainly responsible for the increased photocatalytic performance of composites. The performance of the VDyO x composite catalyst can be further improved by loading a small amount of Pt. In addition, the Pt doped V 1.5Dy 1O x catalyst was also proven to be efficient in the photodegradation of 2-propanol and benzene.

2-propanol photodegradation over molybdates: effects of chemical compositions and electronic structures

A new kind of photocatalysts, ABi(MoO4)2 (A = Na, Ag), were prepared by a traditional solid-state reaction method. The samples were characterized by x-ray diffraction, UV–Vis diffuse reflectance spectroscopy, N2 adsorption–desorption measurement and scanning electron microscopy. The results showed that ABi(MoO4)2 (A = Na, Ag) were all crystallized in a tetragonal system with the space group I41/a. However, the substitution of A1+ cations with different elemental compositions imposed significant effects on their electronic structures and photocatalytic performance. The photocatalytic activities were evaluated by photo-oxidation of gaseous 2-propanol. It was found that NaBi(MoO4)2 showed a higher activity than AgBi(MoO4)2. Theoretically, calculated band structures and density of states by the plane-wave density functional theory revealed that the different photophysical and photocatalytic properties of ABi(MoO4)2 (A = Na, Ag) can possibly be ascribed to their different electronic structures.