Decomposition Of 2-propanol Research Articles

Formation of crystalline TiO 2−xN x and its photocatalytic activity

Amorphous precursors to nitrogen-doped TiO 2 (NTP) and pure TiO 2 (ATP) powders were synthesized by hydrolytic synthesis and sol–gel method (SGM), respectively. Corresponding crystalline phases were obtained by thermally induced transformation of these amorphous powders. From FT-IR and XPS data, it was concluded that a complex containing titanium and ammonia was formed in the precipitate stage while calcination drove weakly adsorbed ammonium species off the surface, decomposed ammonia bound on surface of precipitated powder and led to substitution of nitrogen atom into the lattice of TiO 2 during the crystallization. The activation energies required for grain growth in amorphous TiO 2− x N x and TiO 2 samples were determined to be 1.6 and 1.7 kJ/mol, respectively. Those required for the phase transformation from amorphous to crystalline TiO 2− x N x and TiO 2 were determined to be 129 and 142 kJ/mol, respectively. A relatively low temperature was required for the phase transformation in NTP sample than in ATP sample. The fabricated N-doped TiO 2 photocatalyst absorbed the visible light showing two absorption edges; one in UV range due to titanium oxide as the main edge and the other due to nitrogen doping as a small shoulder. TiO 2− x N x photocatalyst demonstrated its photoactivity for photocurrent generation and decomposition of 2-propanol (IPA) under visible light irradiation ( λ ⩾ 4 2 0 nm ).

Sulfated Alumina Catalysts: Consequences of Sulfate Content and Source

Consequences of the loading level of sulfate ions (3, 6, and 10-wt%) as well as the source of sulfate (H2SO4 or (NH4)2SO4) on the structural, textural, and surface acid–base properties as well as the impacts on catalytic activity towards 2-propanol conversions on γ-Al2O3 and on aluminum hydroxide gel is described. Structural investigations of the catalysts by XRD revealed that the sulfation processes do not remarkably affect the γ-phase of alumina irrespective of the sulfate content or source. N2-adsorption at 77 K indicated that sulfated gel catalysts exhibit the highest S BET areas and, in general, S BET for all catalysts were found to decrease with the increase of sulfate content, such a decrease is more pronounced for the 10% loaded catalysts. Pyridine adsorption as followed by FTIR indicated that sulfation of alumina increases the strength of its Lewis acid sites and creates Bronsted acidity in the case of highly loaded catalysts. The catalytic decomposition of 2-propanol in the gas phase indicated that, amongst all the catalysts investigated, the 6% loaded ones exhibited 100% activity (2-propanol conversion) and the highest propene (dehydration product) selectivity.

Ag+‐Inserted NbO2F as a Novel Photocatalyst.

AbstractFor Abstract see ChemInform Abstract in Full Text.

NO reduction with CH 4 or CO on Pt/ZrO 2–CeO 2 catalysts

Catalytic properties of platinum supported on ZrO 2–CeO 2 were studied in the NO reduction by CO or CH 4 as a reducing agent. The catalysts were characterized by means of N 2 adsorption, SEM, XRD, TPR and 2-propanol decomposition. Pt/CeO 2 catalyst showed a higher surface area than the Pt/ZrO 2–CeO 2 and Pt/ZrO 2 catalysts. All samples showed irregular shape and cumulus size. The PtO 2 reduction causes spill over of hydrogen onto the support inducing a concurrent reduction of platinum oxide and the ceria-rich support. The monoclinic and tetragonal phases of the ZrO 2 and the cubic phase of the CeO 2 were identified in the catalysts. 2-Propanol reaction on ZrO 2 sample showed high selectivity towards propene, this is due to the acid properties of this material. The reduction of the NO was dependent of the reducing agent on the catalysts. When CH 4 was used for NO reduction, the catalysts that contain zirconia in the support showed the highest catalytic activity. The NO reduction with CO produced a shift to higher temperature, on this reaction the ceria-content catalysts showed the best catalytic activity. The highest selectivity toward N 2 was showed when CH 4 was used as a reduction agent for the NO reduction. While, the highest N 2 yield was observed on Pt/ZrCe-70 catalysts for both reactions.

Ag+-Inserted NbO2F as a Novel Photocatalyst

The insertion of Ag(+) into NbO(2)F narrowed the band gap from 3.2 eV (NbO(2)F) to 3.0 eV (Ag-NbO(2)F), which shifted the light absorption edge from the UV light region to the near-violet light region. The photocatalytic activities of NbO(2)F and Ag-NbO(2)F were evaluated by the decomposition of gaseous 2-propanol (IPA) under 400-530 and 300-400 nm light irradiations. Ag-NbO(2)F could decompose IPA to CO(2) via acetone under both irradiation conditions. The value of the quantum efficiency was of the same order under both 400-530 and 300-400 nm light irradiations, which suggested the complete hybridization of the Ag4d and O2p orbitals in the valence band of Ag-NbO(2)F resulted in the 400-530 nm light sensitivity. The density of states calculations also supported the complete mixing of Ag4d and O2p.

Template-free Hydrothermal Synthesis of High Surface Area Nitrogen-doped Titania Photocatalyst Active under Visible Light

Abstract The nanofibrous ammonium titanate (NH4)2Ti3O7−xNx was hydrothermally synthesized by a new method proposed here from titanium oxysulfate precursor in a NH4OH solution under hydrothermal conditions at 393 K without any extra templates. The calcination of the as-synthesized material at 673 K produced nitrogen-doped titania (TiO2−xNx) with anatase phase, which absorbed visible light and had an extremely high surface area (377 m2g−1). This material showed an excellent photocatalytic activity in decomposition of 2-propanol under visible light irradiation.

Nitrogen-doped titanium dioxide photocatalysts for visible response prepared by using organic compounds

In order to utilize visible light in photocatalytic reactions, nitrogen atoms were doped in commercially available photocatalytic TiO2 powders by using an organic compound such as urea and guanidine. Analysis by X-ray photoelectron spectroscopy (XPS) indicated that N atoms were incorporated into two different sites of the bulk phase of TiO2. A significant shift of the absorption edge to a lower energy and a higher absorption in the visible light region were observed. These N-doped TiO2 powders exhibited photocatalytic activity for the decomposition of 2-propanol in aqueous solution under visible light irradiation. The photocatalytic activity increased with the decrease of doped N atoms in O site, while decreased with decrease of the other sites. Degradation of photocatalytic activity based on the release of nitrogen atoms was observed for the reaction in the aqueous suspension system.

Visible Light Sensitive Photocatalysts, Nitrogen-Doped Ta2O5Powders

The photocatalytic activities of nitrogen-doped Ta2O5 powders, Ta2O5-xNx (x = 0.10, 0.17, 0.24, 0.35) were evaluated by the decomposition of gaseous 2-propanol (IPA) under visible (Vis) and ultraviolet (UV) light irradiations with the same absorbed photon number (1.4 × 1014 quanta·cm-2·sec-1). Ta2O5-xNx could decompose IPA under both Vis and UV light irradiations, and its photocatalytic activity depended on the dopant concentration and the wavelength of the irradiated light. The values of photonic efficiency decreased with increasing the degree of x when irradiating with both Vis and UV lights.

Characteristics of photocatalytic oxidation of gaseous 2‐propanol using thin‐film TiO2 photocatalyst

AbstractThis work presents a photocatalysis‐based method to treat and purify air because of its broad applicability to common, oxidizable, air contaminants. The effect of oxygen content, temperature, water vapor, and 2‐propanol concentration on the TiO2 surface was investigated. The rate of 2‐propanol decomposition increased with increasing the oxygen content, but was reduced at temperatures higher than 100°C. When water vapor concentration was in the range of 10–355 mmol m−3, the rate of 2‐propanol decomposition was proportional to the water content. However, an opposite result was observed at a higher concentration of water vapor. 2‐Propanol was photooxidized to acetone, and eventually to carbon dioxide and water. The kinetic model of 2‐propanol photooxidation was successfully developed by the competitive Langmuir–Hinshelwood rate form, incorporating the inhibition effect coming from the formation of acetone. Copyright © 2004 Society of Chemical Industry

Physicochemical and catalytic characterization of non-hydrothermally synthesized Mg-, Ni- and Mg–Ni-saponite-like materials

Saponite-like materials with Mg 2+ or Ni 2+ ions and their mixture in the octahedral sheet were non-hydrothermally synthesized. Their protonic forms were prepared through deammoniation or by treatment with HCl. The products were characterized by physical methods, gas-phase adsorption of amines and the catalytic transformation of 2-propanol and cumene via pulse and flow methods. The materials have a `house-of-card' texture composed of platelets with small lateral dimensions and exhibit a high surface area and pore volume. Subsequent deammoniation resulted in the formation of non-framework Ni 2+ and possibly Mg 2+ ions. Mg-saponite, prepared in this way, shows predominantly non-framework species formed by tetrahedrally coordinated Al 3+ ions whereas its acid-treated counterpart contains Al 3+ in both framework and non-framework positions. Deammoniated Ni-saponite exhibits a peculiar catalytic behaviour, which manifests itself in the fact that the activity in the 2-propanol decomposition in a pulse experiment is low while under flow conditions it becomes the most active. This is ascribed to generation during the reaction of new acidic centres due to the dissociative adsorption of produced water on site pairs formed by coordinatively unsaturated non-framework Ni 2+ and framework oxygen ions. Cumene conversion tests confirm this explanation. The high activity and stability of acid-treated Mg-saponite in cumene dealkylation underlines its potential use for high-temperature acid-catalyzed reactions. The Brønsted acidity of the saponite-like materials is related to their layer charge, cation exchange capacity and diminished with increasing Ni content, whereas the Lewis acidity increased. Both the gas-phase amine chemisorption and catalytic tests provide the same order of protonic acidity: Mg > MgNi > Ni. The origin of the acidic sites from deammoniation or HCl treatment is discussed.

Role in photocatalysis and coordination structure of metal ions adsorbed on titanium dioxide particles: a comparison between lanthanide and iron ions

The effect of simply adsorbed Sm, Eu, and Yb ions on TiO 2 (Ln/TiO 2) and Fe ions adsorbed onto TiO 2 (Fe/TiO 2) was examined from the photocatalytic decomposition of adenosine 5′-triphosphate (ATP) as an anionic substance, 2-propanol as a neutral substance, and methylene blue (MB) as a cationic substance. The amount of ATP disappearing in 40 min of reaction in the presence of Ln/TiO 2 increases in the order Ln=Sm<Eu<Yb. For 2-propanol, the photocatalytic activities of Ln/TiO 2 catalysts were similar to that of unmodified TiO 2 (u-TiO 2) catalyst. For MB, the photocatalytic activities of Ln/TiO 2 catalysts were less than that of u-TiO 2 catalyst. By contrast, Fe/TiO 2 catalyst was excellent in photocatalytic decomposition of ATP, 2-propanol, and MB. The photocatalytic activity of Yb/TiO 2-C calcined at 500 °C for 1 h was reduced for ATP, a reduced slightly for 2-propanol, and increased for MB compared with Yb/TiO 2. Photocatalytic activities of Fe/TiO 2-C for ATP, 2-propanol, and MB were all less than for Fe/TiO 2. The local structure around the lanthanide ions on TiO 2 particles was revealed by EXAFS measurement. The structure of the Yb atom in Yb/TiO 2-C was composed of the YbO bonds as in Yb 2O 3, rather than YbCl bonds in Yb/TiO 2.

Preparation of novel TiP 2O 7 carbon composite using ion-exchanged resin (C467) and evaluation for photocatalytic decomposition of 2-propanol

TiP 2O 7 carbon composite photocatalyst was successfully prepared by using ion-exchanged resin (C467) containing amino phosphate by metal ion-exchanged carbothermal reduction (MIER-CTR) method using TiCl 3 and TiCl 4. During the carbonization process in nitrogen, the pre-oxidation (300–350 °C) in air is essential for producing homogeneously dispersed TiP 2O 7 on the carbon matrix. In the absence of pre-oxidation, the resin was melted. The carbonization temperature 500 °C was found to be suitable for producing single phase TiP 2O 7 with higher yields. Powder X-ray diffraction (XRD) and Raman spectroscopic results suggest the formation of TiP 2O 7, while X-ray diffraction results reveal that the crystallite size was less than 35 nm. UV-Vis studies show that the band gap of TiP 2O 7 was 3.32 eV. The TiP 2O 7 carbon composite catalyst was applied for the photocatalytic decomposition of 2-propanol at 30 °C using a mercury lamp (365 nm).

Zeta potential and photocatalytic activity of nitrogen doped TiO2 thin films

Nitrogen doped TiO2 films were fabricated by annealing anatase TiO2 films in gaseous NH3. Nitrogen atoms in these films were substitutionaly introduced into oxygen sites of TiO2 lattice. We have evaluated the zeta potential of these films and have found that it became negative with the amount of nitrogen doping. The photocatalytic decomposition of gaseous 2-propanol was examined under light-limited conditions, and the quantum yield (QY) was estimated while illuminating with ultraviolet (UV) and visible light (VIS). The QY values for the nitrogen doped TiO2 film were 15.4% (UV) and 0.41% (VIS), whereas those for the pure TiO2 film were 18.4% (UV) and 0% (VIS). In addition, the photocatalytic decomposition of ethylamine ions (CH3CH2NH3+) was evaluated in an aqueous solution under UV illumination in a light-rich condition. Consequently, the decomposition rate of the nitrogen doped TiO2 for aqueous ethylamine ions was higher than that of the pure TiO2 because the surface of the nitrogen doped TiO2 film was negatively charged and cationic ethylamine ions were efficiently adsorbed on its surface. The surface structure and the band structure of the nitrogen doped TiO2 are discussed in this paper.

TiP2O7 Fine Particle for Photocatalytic Decomposition of 2-Propanol

TiP2O7 Fine Particle for Photocatalytic Decomposition of 2-Propanol

Carbonaceous deposits on alumina as catalysts and supports

Studies of carbonaceous deposits, intercalated within alumina pores, were carried out from the point of view of their catalytic activity for a number of reactions of alkyl-substituted benzenes. Alumina was not active for ammoxidation of ethylbenzene and m-xylene as well as oxidative dehydrogenation of ethylbenzene until certain amount of the deposit was generated on acid sites of alumina surface. Carbonaceous deposits formed during reactions of decomposition of 2-propanol and hexafluoro-2-propanol were used as supports for platinum catalysts for hydrosilylation of allyl chloride and 1-octene to result in excellent selectivity. Precursor of carbonaceous deposit formed from hexafluoro-2-propanol has been identified and scheme of the deposit formation was proposed.

Cumene cracking functionalities on sulfided Co(Ni)Mo/TiO 2-SiO 2 catalysts

Cumene cracking reaction was carried out on pure support as well as sulfided Mo, CoMo, and NiMo catalysts in a plug flow micro-reactor at 400 °C and atmospheric pressure. Catalytic activity was studied as a function of Mo content, promoter content (Co, Ni), and support composition [Ti/(Ti+Si)=0.0, 0.15, 0.30, 0.45, 0.70, 1.0]. Surface acid–base properties of pure supports were measured with 2-propanol decomposition, showed that the supports were acidic in nature, the acidic character increases with increasing TiO 2 content in SiO 2. Techniques used for characterization were BET specific surface area (SSA), pore volume, X-ray diffraction, CO 2 chemisorption, and low temperature oxygen chemisorption (LTOC). CO 2 chemisorption on sulfided catalysts showed a strong decrease in the amount of CO 2 adsorption as a function of metal loading. The sulfided-supported catalysts exhibited better cracking activity in presence of hydrogen, which suggests that sulfided molybdenum phases were responsible for cumene cracking activity. The LTOC and catalytic activity results showed similar trends with variation of molybdenum content which indicated that the cracking activity of Mo and CoMo catalysts has significant contribution from the supported phases. The cumene cracking activity over supported catalysts is attributed to the Brønsted (S–H) sites like sulfhydryl groups. Variation of support composition strongly affects the catalytic cracking activity which decreases with increasing TiO 2 content in SiO 2.

Effects on solid basicity for sodium metal and metal oxide occluded NaX zeolites

Zeolite NaX, containing occluded sodium metal and oxide clusters at loadings of 0.25, 1, and 3 sodium species per supercage, were prepared via controlled thermal decomposition of impregnated sodium azide and sodium acetate salts, respectively. In addition, occluded sodium oxide clusters were prepared by oxidation of the supported sodium metal clusters in air at 513 K. Adsorption microcalorimetry of carbon dioxide was used to indicate the strength and number of surface base sites created by incorporation of these sodium species into the NaX supercages. For similar loadings of sodium species, the strength of the CO 2 adsorption sites for zeolites that contained occluded sodium metal clusters was greater than for the zeolites containing occluded sodium oxide clusters prepared by both methods. While the number of CO 2 adsorption sites for both supported sodium oxide catalysts were similar at identical sodium loadings, the heats of adsorption for sites created via the oxidation of supported sodium metal clusters were higher than those prepared via the decomposition of sodium acetate. The decomposition of 2-propanol, used as a probe of the acido-basic character of the surface, indicated that loadings of sodium species of one or greater per supercage produced catalysts with greater than 90% selectivity to the base catalyzed product acetone, compared to 24% selectivity over the unmodified NaX zeolite. At near steady-state conditions for the range of loadings investigated, the rate of acetone production increased linearly with increasing occluded sodium content for all catalysts investigated. A linear relationship between the rate of acetone formation and the total uptake of carbon dioxide was also found. The rate of acid catalyzed propene production reached a minimum for catalysts with loadings near two sodium species per supercage. Higher loadings resulted in an increase in the acid catalyzed propene production, presumably due to the incorporation of acid–base pairs that result from incomplete decomposition of the supported azide.

Development of a novel photocatalytic reaction system for oxidative decomposition of volatile organic compounds in water with enhanced aeration

A novel photocatalytic reaction system, composed of solution and gas spaces that are divided by a thin Teflon film and titanium(IV) oxide (TiO 2)-coated mesh or cloth, for the treatment of contaminated aqueous solutions was developed to be operated with enhanced aeration without bubbling of air in the solution. First, the photocatalytic activities of TiO 2 particles immobilized on two kinds of support material, stainless steel mesh (SSM) and fiberglass cloth (FGC), were investigated for photocatalytic oxidation of 2-propanol, as a model volatile organic compound, dissolved in aerated aqueous solution. The TiO 2 particles immobilized on both support materials exhibited photocatalytic activity to oxidize 2-propanol into acetone and carbon dioxide (CO 2), and the activity levels of the TiO 2 particles immobilized on the two kinds of support materials were comparable. Presumably due to the presence of a small amount of metal species originating in SSM that might work as reduction catalysts, molecular hydrogen (H 2) was also liberated on the TiO 2-immobilized SSM. Results of analysis of weight loss after photoirradiation suggested that the stability of the TiO 2-immobilized FGC was better than that of the TiO 2-immobilized SSM. On the basis of these results, FGC was employed in construction of a photocatalytic reactor equipped with an oxygen (O 2)-permeable Teflon membrane in order to make oxygen pass from a gas space to a solution space and to keep the surface of the immobilized TiO 2 photocatalyst, facing an aqueous solution containing volatile organic compounds, saturated with dissolved O 2. From the results of photocatalytic oxidative decomposition of 2-propanol, it was clarified that the surfaces of TiO 2 particles could be sufficiently supplied with O 2 from the gas space through the membrane to accelerate the oxidation.

Nitrogen-Concentration Dependence on Photocatalytic Activity of TiO2-xNx Powders

The oxidation power of the TiO2-xNx powders with low nitrogen concentrations (<0.02) was evaluated by the decomposition of gaseous 2-propanol (IPA) under the same absorbed photon number, 1.4 × 1014 quanta·cm-2·s-1, of visible (Vis) or ultraviolet (UV) light. Regardless of the x value, the quantum yield values from irradiating with Vis light was lower than with UV light, which suggests that the isolated narrow band formed above the valence band is responsible for the Vis light response in the present nitrogen doped TiO2. In addition, increasing the nitrogen concentration when irradiating with UV light lowered the quantum yields, indicating that the doping sites could also serve as recombination sites.

The structure and catalytic activity of the double oxide system Cu-Mn-O/MgF 2

The paper presents the results of a study on the structure and catalytic activity of MgF 2 supported binary copper and manganese oxides, prepared using a co-impregnation procedure, contrasted to the data obtained for Cu/MgF 2 and Mn/MgF 2. The catalysts were characterised by means of BET, X-ray diffraction (XRD), temperature-programmed reduction (TPR) and infrared (IR) methods. The results proved the presence of CuMn 2O 4 type spinel structures in the mixed systems CuO and MnO x supported on MgF 2, forming already at 400 °C. The activity of the mixed copper-manganese oxides and single metal oxides supported on MgF 2 has been studied in the reactions of 2-propanol decomposition, cyclohexene dehydrogenation, oxidation of CO and reduction of NO by C 3H 6. The double oxide systems were found more effective than the catalysts obtained on the basis of individual oxides.