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Applied Catalysis B, Environmental (v.107, #1-2)

Contents Continued (pp. i).

Editorial Board (pp. i).

Contents (pp. co4).

Editorial Board (pp. co2).

Characterization and photocatalytic performance in air of cementitious materials containing TiO₂. Case study of formaldehyde removal by Aurélie Hadj Aïssa; Eric Puzenat; Arnaud Plassais; Jean-Marie Herrmann; Claude Haehnel; Chantal Guillard (pp. 1-8).

Display Omitted• Cementitious materials used as matrix for TiO2 photocatalyst. • TiO2 surface coverage was determined from TiO2 Raman mapping. • UV absorbance of TiO2 was achieved by diffuse reflectance spectroscopy. • Good correlation between degradation rate and TiO2 surface coverage and UV absorbance of TiO2.This article demonstrates that photocatalytically self-cleaning mortars and concretes can additionally contribute to the elimination of volatile organic compounds (VOC's) present in indoor and outdoor atmospheres. Formaldehyde was chosen as a representative VOC air pollutant. Titania (PC-105 from Millennium Chemicals) was added in a white Portland Cement (Société Ciment Calcia) to prepare mortar samples according to a normalized methodology. A normalized steady-state was chosen after aging the samples for three months. The distribution of titania at the exposed surface of the mortar sample was quantitatively examined, using Raman spectroscopy mapping and diffuse reflectance spectroscopy. Interestingly, when varying the weight percentage of titania (with respect to the cement weight) between 0 and 10wt%, it was demonstrated that the “occurrence rate” (or presence probability) of 100% in TiO₂ at the surface of the mortar was already reached at 5wt% TiO₂. Direct linear correlation between UV-absorptance and Raman spectroscopy mapping spectroscopy was obtained. In parallel, the photocatalytic removal of formaldehyde, performed in a dynamic flow reactor with an in-line photoacoustic analytic spectrometer was established by the curve rate r= f(TiO₂ wt%). Since concretes and mortars are solids which can be considered as “breathing materials”, which absorb and/or adsorb many compounds, it was carefully and quantitatively determined what part of formaldehyde was adsorbed and/or absorbed by the mortar, either in the dark or under UV. The real and true photocatalytic nature of the disappearance reaction relative to UV-irradiated TiO₂ let us conclude that, in addition to their photocatalytic self-cleaning properties, such cementitious materials can possibly contribute to the elimination of atmospheric VOC's which may come in contact with them.

Keywords: Titania; Cementitious materials; Photocatalysis; Raman spectroscopy mapping; Diffuse reflectance spectroscopy; Formaldehyde

Enhanced Cu activity in catalytic ozonation of clofibric acid by incorporation into ammonium dawsonite by Mohammad S. Yalfani; Sandra Contreras; Jordi Llorca; Francesc Medina (pp. 9-17).

Display Omitted• Dawsonite-incorporated Cu presents high activity in catalytic ozonation. • The contribution of dissolved Cu²⁺ in ozonation is not significant. • Cu appears as Cu(I) within the structure of ammonium dawsonite. • The reaction at initial pH 10 results to highest efficiency and lowest Cu loss.Clofibric acid (CFA) degradation by ozonation in the presence of Cu-dawsonites was studied. Cu-dawsonite materials were synthesized via co-precipitation of Al(NO₃)₃ and Cu(NO₃)₂ by (NH₄)₂CO₃ at pH 7.5–8.0. The as-synthesized and the calcined samples were characterized using XRD, FTIR, N₂-physisorption, TEM and XPS techniques. The CFA degradation was carried out using the as-synthesized and the calcined Cu-dawsonites, dissolved Cu²⁺ and CuO supported on Al₂O₃. The heterogeneous as-synthesized Cu-dawsonite catalysts showed more efficient performance with respect to the other catalysts, despite of significant Cu leaching detected at the end of the reactions. The reactions carried out using the homogeneous dissolved Cu²⁺ (in the concentration range of the leached Cu) indicated low contribution of dissolved Cu²⁺ in the mineralization of CFA and its intermediates; the efficiency was mainly devoted to the activity of Cu incorporated in the dawsonite structure. Characterization of Cu-dawsonites revealed a possibility of Cu localization in the NH₄⁺ position, which is higher exposed to leaching than that of Al. The reaction performed at initial pH 10 (pH higher than pH_PZC of as-synthesized Cu-dawsonite) resulted to a higher TOC and COD reduction after 2h compared with the reaction at pH 3.7. Also lowest Cu leaching was obtained under these conditions. Enhanced activity of Cu incorporated into the structure of dawsonite in the catalytic ozonation of CFA is probably due to the presence of Cu(I) located in the structure of dawsonite revealed by XPS. Some of the main intermediates have been identified by HPLC–MS suggesting three routes for CFA destruction by ozonation using Cu-dawsonite including, C₁–O and C₄–Cl bond breaking and aromatic ring cleavage.

Keywords: Catalytic ozonation; Cupper; Dawsonite; Clofibric acid

Preparation, characterisation and N₂O decomposition activity of honeycomb monolith-supported Rh/Ce_0.9Pr_0.1O₂ catalysts by Verónica Rico-Pérez; Sonia Parres-Esclapez; María José Illán-Gómez; Concepción Salinas-Martínez de Lecea; Agustín Bueno-López (pp. 18-25).

.Display Omitted• Flash calcination (impregnated monoliths are introduced in a previously heated furnace) is better than ramp calcination. • Flash calcination improves the distribution of active phases on the cordierite substrate. • Flash calcination produces smaller Rh particles and better noble metal–CePr mixed oxide interaction. • Flash calcination improves the reduction of surface Rh–Ce–Pr entities. • Flash calcination improves the catalytic activity for N₂O decomposition.Rh/Ce_0.9Pr_0.1O₂ active phases have been loaded by sequential impregnation into cordierite honeycomb monoliths following the procedure (i) Ce+Pr nitrates impregnation+calcinations and (ii) Rh nitrate impregnation+calcination. The supported catalysts have been characterised by XRD, Raman Spectroscopy, SEM–EDS, TEM–EDS and H₂-TPR, and tested for N₂O decomposition. Rh is selectively attached to the mixed oxide Ce_0.9Pr_0.1O₂, being 0.2wt.% the optimum content of Rh. The calcination procedure significantly affects the supported catalyst features. The best catalyst was prepared by flash calcination (introducing the impregnated monolith in a previously heated furnace). Flash calcination yields smaller Rh particles and lowers the temperature for surface Rh–Ce–Pr entities reduction in comparison to ramp calcination, improving both the distribution of active phases on the cordierite substrate and the catalytic activity for N₂O decomposition.

Keywords: N; ₂; O decomposition; Rh; Ceria; Mixed oxide; Honeycomb monolith; Cordierite

Formation and removal of Ba-carbonates or carboxylates on Pt/BaO/γ-Al₂O₃ lean NO_x traps by Saurabh S. Chaugule; Vincent F. Kispersky; Joshua L. Ratts; Aleksey Yezerets; Neal W. Currier; Fabio H. Ribeiro; W. Nicholas Delgass (pp. 26-33).

Display Omitted► CO₂ can store either as carbonates or carboxylates depending on the Ba loading. ► Carbonates are more stable than carboxylates in a reducing atmosphere. ► Nitrates replace all carbonates and carboxylates in absence of CO₂ in the gas phase. ► In CO₂, carbonates/carboxylates could not be fully replaced by NO_x. ► In fast NO_x storage with CO₂, nitrates compete with carbonates/carboxylates.In addition to feed composition, the NO_x storage capacity (NSC) of a Pt/BaO/γ-Al₂O₃ lean NO_x trap (LNT) also depends on the chemical state of Ba prior to the start of the lean NO_x exposure phase during which the NSC is measured. This state of Ba is a result of the history of the trap's cyclic exposures to lean and rich conditions and is a function of the feed composition and the time intervals of the exposures. We have systematically investigated the role of adsorbed CO₂ on the NO_x sorption process on traps with 20, 8 and 4wt.% Ba. This was accomplished through a sequence of NO_x storage and regeneration cycles with CO₂ and H₂O in the feed followed by purge in Ar and then by NO_x storage and regeneration without CO₂ and H₂O at 300°C. The amount of pre-adsorbed CO₂ released during NO_x storage upon the introduction of NO₂+O₂ correlated well with the amount of NO_x stored on the trap with 20wt.% Ba but not on the traps with 8 and 4wt.% Ba loadings. These results were further investigated in DRIFTS sequential adsorption experiments for CO₂, NO₂+O₂, H₂ or NO₂+O₂, CO₂, H₂ at 300°C. The DRIFTS experiments showed that, similar to bulk vs. surface nitrate formation on samples with high vs. low Ba loading, CO₂ adsorption forms either carbonates or carboxylates on high vs. low Ba loadings, respectively. Regeneration by H₂ removed all NO_x adsorbates and any carboxylates, but not the carbonates. Thus, the formation of carbonates slows the NO_x storage process as NO_x must compete with pre-adsorbed carbonates for adsorption sites after regeneration. In addition, comparison between the NO_x breakthrough curves with 7% CO₂ in the lean feed and with pre-adsorbed CO₂ on the catalyst showed that the NO_x storage before the slip occurs was intimately related to the oxygen spillover from Pt to the surrounding Ba and competition between CO₂ and NO_x for adsorption sites. These findings provide insights to further improve the LNT formulations by using optimum Ba loadings and dispersions targeted at increasing the zero NO_x slip time after each fuel rich pulse.

Keywords: NO; _x; storage; Barium carbonate; Barium carboxylate; DRIFTS; Lean NO; _x; trap; NSR

Quantitative room-temperature mineralization of airborne formaldehyde using manganese oxide catalysts by Meera A. Sidheswaran; Hugo Destaillats; Douglas P. Sullivan; Joern Larsen; William J. Fisk (pp. 34-41).

.Display Omitted• Synthesis of manganese oxide-based catalysts (nsutite and cryptomelane/manjiroite). • High surface area and porosity, and small crystal size. • Efficient removal of indoor formaldehyde. • Complete mineralization of formaldehyde. • High activity maintained after processing up to 400m³ of formaldehyde-laden air.Manganese oxide-based catalysts have been synthesized and tested for the abatement of formaldehyde, an ubiquitous indoor pollutant which is not effectively eliminated by most air cleaning technologies. Catalysts were prepared by co-precipitation of MnSO₄ and NaMnO₄ followed by curing at 100, 200 and 400°C. Characterization was performed using X-ray diffractometry (XRD), porosimetry, scanning electron microscopy (SEM), and inductively coupled plasma-mass spectrometry (ICP-MS). Diffractograms of samples treated at 100 and 200°C matched those of nsutite and cryptomelane/manjiroite structures, with high BET surface area (up to 149m²g⁻¹) and small particle size (<50nm), while curing at 400°C yielded pyrolusite with lower effective surface area. Room temperature catalytic oxidation of airborne formaldehyde was studied by supporting the catalyst on a particulate filter media placed in a flow system, under stable upstream formaldehyde concentrations between 30 and 200ppb. Two different face velocities ( v=0.2 and 50cms⁻¹) were studied to evaluate the oxidation efficiency under different flow regimes using formaldehyde-enriched laboratory air at 25–30% relative humidity. Results showed consistent single-pass formaldehyde oxidation efficiency greater than 80% for the synthesized catalysts, which remained active over at least 35 days of continuous operation at v=0.2cms⁻¹ and were able to process up to 400m³ of air at v=50cms⁻¹ without appreciable deactivation. Operation under high relative humidity (>90% RH) produced only a small reversible reduction in formaldehyde removal. Most significantly, 100% mineralization yields were verified by quantifying CO₂ formation downstream of the catalyst for upstream formaldehyde concentrations as high as 6ppm and a face velocity of v=13cms⁻¹. In contrast, a filter loaded with commercially available MnO₂ did not remove appreciable amounts of formaldehyde at v=50cms⁻¹, and yielded <20% initial removal when operated at a very low face velocity ( v=0.03cms⁻¹). Due to the relatively low costs of synthesis and deployment of these catalysts, this technology is promising for maintaining low indoor formaldehyde levels, enabling energy-saving reductions of building ventilation rates.

Keywords: Manganese oxide catalysts; Room-temperature oxidation; Mineralization; Indoor air; Formaldehyde

Spontaneous oxidative degradation of indigo carmine by thin films of birnessite electrodeposited onto SnO₂ by M. Zaied; E. Chutet; S. Peulon; N. Bellakhal; B. Desmazières; M. Dachraoui; A. Chaussé (pp. 42-51).

Display Omitted► Study of spontaneous reactivity of birnessite towards indigo carmine, a toxic dye. ► Rapid degradation and mineralisation without energy supply. ► Importance of agitation on the degree of mineralisation. ► Highlighting the good spontaneous reactivity of a non-toxic material. ► Interest of using thin layer for understanding mechanism at solid–liquid interfaces.This paper describes the successful use of thin films of birnessite to remediate aqueous solutions containing indigo carmine (IC) dye. This latter is one of the oldest and most important dyes used and released in the effluents of many industries, such as textile, paper and plastics. Moreover, this anionic dye belongs to a highly toxic class of dyes (indigoïd). We show that thin films of birnessite, electrodeposited onto a cheap transparent semiconductor substrate (SnO₂), can totally discolor the IC solutions at room temperature after only 1h in the best conditions. The mass spectrometry analyses reveal the presence of intermediate reaction products ( m/ z=226amu, m/ z=244amu and m/ z=216amu) during interaction confirming the real degradation of dye. Moreover, nitrate and ammonium ions are quantified showing that thin films of birnessite can degrade totally (mineralise) and spontaneously more than 60% of indigo carmine into these mineral species after 24h in the best conditions. These results confirm that birnessite thin films appear as a very interesting material for the development of a simple and ecological method of wastewater remediation.

Keywords: Layered manganese oxide; Dye; Mass spectroscopy; Remediation; Mineralisation

Photocatalytic oxidation of methyl ethyl ketones over sol–gel mesoporous and meso-structured TiO₂ films obtained by EISA method by N. Arconada; Y. Castro; A. Durán; V. Héquet (pp. 52-58).

The photocatalytic behaviour of mesoporous and meso-structured TiO₂ films was studied by heterogeneous oxidation of Methyl Ethyl Ketones (MEK). Textural properties of the catalysts (pore volume, pore size distribution and specific and exposed surface areas) are key features to explain the photocatalytic efficiency.Display Omitted• Mesoporous and meso-structured TiO₂ films were obtained by sol–gel/EISA method. • F127/RH 20–70 and Brij58/RH 50 were the only meso-structured resulting coatings. • MEK degradation rates depend on C₀ concentration and textural properties of the films. • The highest photocatalytic activities were obtained for films Brij58 at RH 20/50.This work reports the influence of the meso-structure of TiO₂ films in the photocatalytic oxidation of methyl ethyl ketone. Five types of TiO₂ films were prepared combining the sol–gel route with the Evaporation Induced Self-Assembly (EISA) method. Sols were prepared from titanium tetrachloride (TiCl₄) using different types of pore generating agents. Films characterisation was performed by Fourier Transform Infrared Spectroscopy (FTIR), Grazing X-ray diffraction (GXRD), X-ray diffraction of small angle and Transmission Electron Microscopy (FE-SEM). Environmental Ellipsometric Porosimetry (EEP) studies were performed to obtain the adsorption/desorption isotherms and calculate porous size distribution, pore volume and specific surface area ( S_s) of the films. Kinetic of MEK photocatalytic oxidation data were modelled by Langmuir–Hinshelwood equation and the adsorption and kinetics constants ( k and K) were calculated. Better results of MEK degradation were obtained for the Brij58 films deposited at relative humidity (RH) of 20% and 50%. The results are correlated with the porosity properties of the films.

Keywords: TiO; ₂; anatase films; Sol–gel; Evaporation induced self assembly method (EISA); Mesoporous order of the films; MEK degradation

Effect of glycol on the formation of active species and sulfidation mechanism of CoMoP/Al₂O₃ hydrotreating catalysts by Thanh Son Nguyen; Stéphane Loridant; Lorentz Chantal; Thierry Cholley; Christophe Geantet (pp. 59-67).

Display Omitted• Effect of triethyleneglycol (TEG) impregnated on oxidic catalysts on the HDS performance. • TEG enhanced the formation of heteropolyanion entities by redissolution/redispersion of the active species. • Effect of retardation of the additive on the sulfidation followed by Raman and XAS spectroscopy.The present work is focused on the role of an organic promoter (triethyleneglycol – TEG) on the activity of hydrotreating catalysts. By impregnating such compound on oxidic industrial catalyst, an enhancement of the catalytic activity in the HDS conversion of 4,6-DMDBT as well as SRGO HDS was obtained. Using several physico-chemical techniques and in situ characterization (Raman, XAS), it was found that TEG affected the coordination of Co and Mo in the oxidic species. During the activation procedure, the presence of TEG slows down the sulfidation and allows the genesis of more active “CoMoS” species.

Keywords: Hydrotreating catalyst; Sulphidation; Additive; TEG; Raman spectroscopy; QEXAFS; 27Al NMR

C₂–C₄ light olefins from bioethanol catalyzed by Ce-modified nanocrystalline HZSM-5 zeolite catalysts by Jiandong Bi; Min Liu; Chunsan Song; Xiangsheng Wang; Xinwen Guo (pp. 68-76).

Display Omitted► Ce modified nanocrystalline HZSM-5 was used to convert bioethanol into C₂-C₄ light olefins. ► Ce modification leads to the increase in the ratio of Brőnsted acid sites to Lewis acid sites. ► Both Ce³⁺ and Ce⁴⁺ species present over the surface of catalyst samples after Ce modification. ► The ratio of Ce³⁺ to Ce⁴⁺ can be adjusted by Ce content and calcination temperature. ► Ce modification improves the stability and product distribution.Conversion of bioethanol into bulk chemicals besides ethylene is a promising process in which the stability of catalyst and the selectivity of products are important. In this study, a series of Ce-modified nanocrystalline HZSM-5 catalysts were prepared and their catalytic performance in the conversion of bioethanol into C₂–C₄ light olefins was investigated in a fixed-bed reactor at 400°C under atmospheric pressure. The results show that the stability of catalyst and the distribution of products depend strongly on the content of cerium and the calcination temperature; both cerium content and calcination temperature affect not only the acid properties of the tested catalyst samples but also the composition of cerium species (Ce³⁺/Ce⁴⁺) as revealed by XPS. Among the tested catalyst samples, the catalyst with 5wt% cerium loading and 520°C calcination temperature exhibits the best stability and selectivity to C₃–C₄ light olefins.

Keywords: Bioethanol; Transformation; Light olefins; Ce-modified; Nanocrystalline HZSM-5

Innovative visible light-activated sulfur doped TiO₂ films for water treatment by Changseok Han; Miguel Pelaez; Vlassis Likodimos; Athanassios G. Kontos; Polycarpos Falaras; Kevin O'Shea; Dionysios D. Dionysiou (pp. 77-87).

Display Omitted► The synthesis of S–TiO₂ films by a novel sol–gel method. ► The significant shift of the optical absorption edge toward the visible region. ► The markedly enhanced EPR intensity under visible light illumination. ► The effective degradation of MC-LR under visible light irradiation using S–TiO₂ film.Visible light-activated sulfur doped TiO₂ nanocrystalline films were synthesized by a sol–gel method based on the self-assembly technique with nonionic surfactant to control nanostructure and an inorganic sulfur source (i.e., H₂SO₄). The films were characterized by UV–vis diffuse reflectance, XRD, TEM, Raman, AFM, ESEM, XPS, FT-IR, EDX, EPR and porosimetry. The results showed that the physicochemical properties of the films, such as BET surface area, porosity, crystallite size and pore size distribution could be controlled by the calcination temperature. The highest surface area, smallest crystallite size and narrow pore size distribution were obtained for sulfur doped TiO₂ films calcined at 350°C, which exhibit very smooth surface with minimal roughness (<1nm). The optical absorption edge of sulfur doped TiO₂ was red shifted with indirect bandgap energy of 2.94eV. Sulfur species distributed uniformly throughout the films were identified both as S²⁻ ions related to anionic substitutional doping of TiO₂ as well as S⁶⁺/S⁴⁺ cations, attributed mainly to the presence of surface sulfate groups. EPR measurements revealed a sharp signal at g=2.004, whose intensity correlated with the sulfur content and most importantly was markedly enhanced under visible light irradiation, implying the formation of localized energy states in the TiO₂ band gap due to anion doping and/or oxygen vacancies. In terms of photocatalytic activity, films calcined at 350°C were the most effective for the degradation of hepatotoxin microcystin-LR (MC-LR) under visible light irradiation, while films calcined at 400°C and 500°C degraded MC-LR to a lower extent, following the evolution of the sulfur content with calcination temperature. The photocatalytic activity of the sulfur doped TiO₂ film was stable during three consecutive experiments under visible light irradiation, confirming the mechanical stability and reusability of the doped nanostructured thin film photocatalysts.

Keywords: Nonionic surfactant; Sol–gel method; Microcystin-LR; Dip-coating; Sulfur doped; Visible light; TiO; ₂; Photocatalysis; Cyanotoxins; Water treatment

Effects of biomass inorganics on rhodium catalysts: I. Steam methane reforming by Reetam Chakrabarti; Joshua L. Colby; Lanny D. Schmidt (pp. 88-94).

Display Omitted► Steam methane reforming was used to study effect of inorganics on Rh catalysts. ► Inorganics deposited on the catalyst (1 inorganic atom/5 atoms Rh). ► Sulfur showed strongest poisoning effects, but also partial regeneration. ► Ca, Mg, and Si, showed negligible effect on methane conversion.Inorganic elements in biomass present a major challenge for large-scale application of catalytic processing. Rhodium-based catalysts have been shown to gasify lignocellulosic biomass to syngas with high selectivities by reactive flash volatilization. In this research, the effect of inorganics commonly found in biomass, Na, K, Ca, Mg, Si, P, and S, on rhodium catalysts was investigated using steam methane reforming (SMR) as a model system. SMR was carried out at 700°C on a heated fixed bed of 2.5wt% Rh/α-Al₂O₃ catalysts. The inorganics were uniformly deposited on the catalyst (1 inorganic atom/5 rhodium atoms), followed by performance testing and characterization through H₂ chemisorption, SEM, XPS and XRD. Phosphorus, potassium and sulfur decreased the methane conversion the most (>15%) among the inorganics studied. No significant deactivation was observed upon doping with calcium, magnesium and silicon. Phosphorus and sulfur strongly reduced the dispersion of the rhodium catalyst. Addition of phosphorus and potassium caused formation of carbon-based structures, and phosphorus also increased the rhodium binding energies by 0.6eV in the XPS spectrum, indicating rhodium oxidation.

Keywords: Inorganics; Rhodium catalysts; Steam methane reforming; Poisoning/deactivation

Synthesis of graphitic mesoporous carbons with high surface areas and their applications in direct methanol fuel cells by Jing Qi; Luhua Jiang; Suli Wang; Gongquan Sun (pp. 95-103).

Display Omitted► A novel graphitic mesoporous carbon (GMC) was synthesized. ► The GMC was used as the support to prepare a PtRu/GMC catalyst. ► The PtRu/GMC has excellent activity and stability for MOR under DMFC operating conditions. ► This approach provides a simple route to synthesize graphitic mesoporous carbons.A graphitic mesoporous carbon (denoted as GMC) was synthesized using resorcinol and formaldehyde as carbon precursors and iron nitrate as a graphitization catalyst. The GMC was characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy (TEM), and nitrogen adsorption. The results show that the GMC has a mesoporous structure and a high surface area of 403 m²g⁻¹, and particularly, a well-defined graphitic framework. Using the GMC as the support, a PtRu/GMC was synthesized to act as an electrocatalyst for the methanol oxidation reaction (MOR). A counterpart with Vulcan^® XC-72 (denoted as XC) as the support was prepared for comparison. TEM images show that PtRu nanoparticles are distributed uniformly on the carbon supports for both electrocatalysts. The electrochemical activity of the PtRu/GMC toward the MOR is slightly higher than that of the PtRu/XC in both half cell and single cell measurements. The 1500h stability test of a single cell suggests that the PtRu/GMC is excellent stable.

Keywords: Graphitic carbon; Electrocatalyst; Stability; Methanol electro-oxidation reaction; Direct methanol fuel cell

Clean production of glucose from polysaccharides using a micellar heteropolyacid as a heterogeneous catalyst by Mingxing Cheng; Tian Shi; Hongyu Guan; Shengtian Wang; Xiaohong Wang; Zijiang Jiang (pp. 104-109).

Display Omitted► Assembly of HPAs into a micellar system with Brønsted acidity, confirming the conversion of cellulose into sugars. ► Overcoming the diffusion in this solid–solid reaction and promoting the reaction rate by HPA micellar catalyst. ► Easy handling of this catalyst.Hydrolysis of polysaccharides into glucose was performed over a micellar heteropolyacid (HPA) catalyst [C₁₆H₃₃N(CH₃)₃]H₂PW₁₂O₄₀ (abbreviated as C₁₆H₂PW). This micellar heterogeneous catalyst exhibited high selectivity and activity in the hydrolysis of polysaccharides, such as starch and cellulose. Hydrolysis velocities of starch and cellulose were 0.019 and 0.006g/h at 120°C and 170°C, respectively. The results demonstrated that C₁₆H₂PW is an effective catalyst for the production of glucose and can be reused.

Keywords: Polyoxometalate; Micellar catalysis, Polysaccharides; Hydrolysis; Glucose

Aqueous degradation of diclofenac by heterogeneous photocatalysis using nanostructured materials by C. Martínez; M. Canle L.; M.I. Fernández; J.A. Santaballa; J. Faria (pp. 110-118).

Display Omitted► A detailed mechanism is proposed for the photocatalytic degradation of diclofenac. ► The efficacy of nanostructured materials, including composites MWCNT–TiO₂ is discussed. ► The mechanism of action of MWCNT–TiO₂ composites is analyzed. ► The effects of the variables affecting the process are discussed.The photocatalytic degradation of diclofenac (DIC), 2-[2′, 6′-(dichlorophenyl)amino]phenylacetic acid is investigated under near UV–Vis and UV irradiation, using commercial TiO₂ P25, synthesized TiO₂ (anatase and rutile) and functionalized multi-walled carbon nanotube (MWCNT_ox): anatase (10-MWCNT_ox–TiO₂) suspensions as catalysts. Factors affecting the kinetics of the process, such as the type and load of photocatalyst, and the presence of dissolved O₂, or addition of H₂O₂ as co-oxidant have been compared. The degradation under UV irradiation is more effective than under near UV–Vis. Optimal conditions for a complete removal were obtained using synthesized anatase (0.5gL⁻¹) and 50% O₂ (v/v) under UV irradiation, with rate constants ca. 0.9min⁻¹ (half-life time ca. 0.8min). Eight photoproducts were observed from DIC photodegradation, mainly corresponding to photocyclisation (2-(8-chloro-9H-carbazol-1-yl)acetic acid, 1-chloro-8-methyl-9H-carbazole), decarboxylation (2,6-dichloro-N-o-tolylbenzenamine) and dehalogenation.

Keywords: Persistent organic pollutants (POPs); Pharmaceuticals and personal care products (PPCPs); Heterogeneous photocatalysis; Carbon nanotubes; Diclofenac; Reaction mechanisms

Two routes for mineralizing benzene by TiO₂-photocatalyzed reaction by Thuan Duc Bui; Akira Kimura; Suguru Higashida; Shigeru Ikeda; Michio Matsumura (pp. 119-127).

Display Omitted► Muconaldehyde as well as phenol is an initial product produced from benzene in TiO₂-photocatalyzed reaction. ► Benzene is mineralized on TiO₂-photocatalyst by two parallel pathways via muconaldehyde and via phenol. ► Concentration of muconaldehyde produced is low because it is rapidly oxidized on TiO₂ photocatalyst; in the initial stage of the reaction, most of CO₂ is produced via muconaldehyde.When benzene was oxidized on TiO₂-photocatalysts, muconaldehyde as well as phenol was identified as a product. Muconaldehyde was not produced from phenol, indicating that muconaldehyde and phenol are produced as initial stable intermediates by independent pathways. The amount of muconaldehyde produced in the reaction solution was low because it was rapidly oxidized on the photocatalyst. The contributions of the two pathways to the mineralization of benzene were analyzed by isotopic tracing methods using labeled benzene (¹³C₆H₆) and labeled phenol (¹³C₆H₅OH). The results showed that a larger part (60–70%) of benzene is initially converted to muconaldehyde. The percentage was dependent on the properties of TiO₂ powders. It was also found that anatase-form powders show higher activity for oxidation of benzene than rutile powders do, whereas rutile-form powders show higher activity for oxidation of phenol than anatase powders do.

Keywords: TiO; ₂; photocatalysis; Benzene; Muconaldehyde; Phenol; Ring-opening; Isotopic tracing method

Carbon-doped TiO₂ coating on multiwalled carbon nanotubes with higher visible light photocatalytic activity by Ye Cong; Xuanke Li; Yun Qin; Zhijun Dong; Guanming Yuan; Zhengwei Cui; Xiaojun Lai (pp. 128-134).

Proposed mechanism of synergistic enhancement of visible light photocatalytic activity in carbon-doped TiO₂ coating on MWCNTs.Display Omitted► Carbon-doped titanium dioxide (TiO₂) coatings on multiwalled carbon nanotubes were prepared as a photocatalyst. ► Uniform and fine well-dispersed TiC and/or TiO₂ coatings are formed on the surface of MWCNT template. ► The TiO₂ coating contacts closely with MWCNTs via chemistry bond. ► MWCNTs may act as support, absorbent, photo-generated transfer station and carbon-doping source to narrow the band gap of TiO₂.Carbon-doped titanium dioxide (TiO₂) coating on multiwalled carbon nanotubes (MWCNTs) was prepared by oxidation of titanium carbide (TiC) coated MWCNTs. The structure, morphology and surface chemistry states of the TiO₂ coating on MWCNTs were characterized by XRD, SEM, HRTEM and XPS. The results suggest that the TiO₂ coated MWCNTs keep the similar morphology and length with the pristine MWCNTs. The TiO₂ coating, composed of homogeneous nanosized particles, contacts closely with MWCNTs via chemistry bond and Ti–O–C bonds are found. The visible light photocatalytic activity of the prepared photocatalyst was evaluated by decomposition of methylene blue aqueous solution. A probable mechanism of TiO₂ and MWCNTs on the enhancement of visible light performance is proposed. It suggests that MWCNTs play key roles, which may act as a support, absorbent, photo-generated transfer station and carbon-doping source.

Keywords: Carbon nanotubes; Titanium dioxide; Carbon-doping; Photocatalysis; Mechanism

Conversion of triose sugars with alcohols to alkyl lactates catalyzed by Brønsted acid tin ion-exchanged montmorillonite by Jiacheng Wang; Yoichi Masui; Makoto Onaka (pp. 135-139).

Tin ion-exchanged montmorillonite (Sn-Mont), a heterogeneous, recyclable, strong Brønsted acid, demonstrated a high catalytic activity and selectivity for the conversion of two trioses (DHA and GLA) with alcohols into the corresponding alkyl lactates in excellent yields with the production of water as the main by-product.Display Omitted• Tin ion-exchanged montmorillonite efficiently promotes the dehydration of triose sugars. • Brønsted acidic sites function as major active sites. • Dihydroxyacetone and glyceraldehyde are both suitable substrates. • Various alkyl lactates are obtained in excellent yields of 89–97%. • The heterogeneous catalyst can be reused for several times without loss of activity.We describe the Brønsted acid catalysis of tin ion-exchanged montmorillonite (Sn-Mont), which is easily prepared by the ion-exchange of naturally occurring sodium montmorillonite (Na-Mont) with an aqueous tin tetrachloride solution, for the conversion of two trioses, i.e., dihydroxyacetone (DHA) and glyceraldehyde (GLA), in alcohols to afford the corresponding alkyl lactates. For the conversion of DHA with methanol, the product distribution closely depends on the substrate concentrations, reaction temperatures, and reaction times. Under the optimized reaction conditions, an almost quantitative yield of methyl lactate is obtained with the production of water as the exclusive side-product. Additionally, the montmorillonite catalyst is easily recovered from the reaction mixture by filtration, and reused without any loss in activity. Sn-Mont also demonstrates a high activity for the conversion of DHA with higher alcohols, such as EtOH, nPrOH, and nBuOH, to the corresponding alkyl lactates in 89–93% yields.

Keywords: Brønsted acid catalysis; Tin ion-exchanged montmorillonite; Triose sugars; Dihydroxyacetone; Glyceraldehyde; Alkyl lactate; Dehydration

Influence of gold particle size on the photocatalytic activity for acetone oxidation of Au/TiO₂ catalysts prepared by dc-magnetron sputtering by Bogdan Cojocaru; Ştefan Neaţu; Elena Sacaliuc-Pârvulescu; Francis Lévy; Vasile I. Pârvulescu; Hermenegildo Garcia (pp. 140-149).

Display Omitted► dc reactive sputtering deposition provides Au/TiO₂ photocatalysts with controlled nanoparticle size and layer thickness. ► Photocatalytic activity of Au/TiO₂ strongly depends on the gold loading and titania crystal phase. ► Calcination of the catalysts at 400°C produces only a slight increase of the conversion.Two series of Au/TiO₂ materials with different gold content have been prepared by dc-magnetron sputtering on ceramic shaped pure anatase or Degussa P25 TiO₂. The time of deposition was varied between 1 and 20min in order to obtain different thickness and nanoparticle size of the gold films. For comparison samples with Au loadings in the range 0.3–0.9wt% were prepared using the deposition–precipitation methodology. The obtained materials were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), DR-UV-Vis and atomic force and scanning electron microscopy techniques. The photocatalytic activity was checked in the photo-oxidation of acetone under both UV and visible irradiation conditions. Several factors were found to influence the photoactivity. An optimal Au content corresponding to a maximum activity is observed and attributed to the occurrence of adequate titania surface coverage and Au particle size. The support plays an important role and it was found that pristine anatase on which gold (average particle size 7.7nm) was deposed by dc-reactive sputtering exhibits the maximum of the activity. Samples prepared by dc-sputtering were more active than samples prepared by deposition–precipitation method. Also, the photocatalysts prepared using dc-reactive sputtering showed activity under both UV and visible light irradiation, while those prepared using the deposition–precipitation technique are active only under UV light. The most likely mechanism of gold activation of titania is that upon light absorption, gold nanoparticles inject electrons into the titania conduction band.

Keywords: Titania; Photocatalysis; dc-magnetron gold sputtering

Photocatalytic activity of metal oxides—The role of holes and OH radicals by Mu Yao Guo; Alan Man Ching Ng; Fangzhou Liu; Aleksandra B. Djurišić; Wai Kin Chan (pp. 150-157).

Display Omitted► Dominant mechanism of photocatalytic dye degradation is the direct charge transfer. ► OH radicals play a minor role in photocatalytic dye degradation on metal oxides. ► No correlation exists between BET surface area, ROS generation and dye degradation.We have studied the photocatalytic activity of different metal oxide nanoparticles (TiO₂, ZnO, and MgO) on four different dyes in solution, ambient and vacuum environments. The metal oxide materials considered generated different reactive oxygen species in aqueous solutions and exhibited different photocatalytic activity. We found no correlation between the photocatalytic activity and superoxide ion generation. The presence of the OH radicals contributed to the dye degradation, but the extent of this contribution was dependent on the chemical structure of the dye. The predominant degradation mechanism was found to be direct charge transfer from the metal oxide semiconductor for the experimental conditions considered in this study.

Keywords: Photocatalysis; TiO; ₂; ZnO; MgO

Copper loaded hydroxyapatite catalyst for selective catalytic reduction of nitric oxide with ammonia by Hassib Tounsi; Samir Djemal; Carolina Petitto; Gérard Delahay (pp. 158-163).

Display Omitted► Cu-Hap catalysts prepared by ion exchange in solution. ► Catalysts for the SCR of NO by NH₃ under oxidizing atmosphere. ► Cu-Hap catalysts were active in the NH₃-SCR process. ► Highly dispersed CuO clusters on Ca-Hap surfaces were responsible for the activity at temperatures below 250°C.Copper loaded hydroxyapatite prepared by ion exchange were characterized by XRD, FTIR, BET, UV–vis, H₂-TPR and evaluated in the selective catalytic reduction of NO by NH₃ under oxidizing atmosphere. The Cu-Hap catalysts, without the libethenite phase presence, have been found to be active, and selective in the NH₃-SCR process. The highly dispersed CuO clusters on Ca-Hap surfaces were responsible for the NO conversion in the low temperature range in the NO-SCR with NH₃. The presence of 2.5% of H₂O in the feed mixture strongly affects the NO conversion in the whole temperature range.

Keywords: DeNOx; Ammonia; Hydroxyapatite; Copper

A novel highly selective and stable Ag/MgO-CeO₂-Al₂O₃ catalyst for the low-temperature ethanol-SCR of NO by Lilian Valanidou; Christodoulos Theologides; Antonis A. Zorpas; Petros G. Savva; Costas N. Costa (pp. 164-176).

Display Omitted► Novel catalyst has been developed with excellent activity, stability and selectivity. ► Highest N2 and CO2 selectivities, ever reported, obtained in the present work. ► Excellent stability in the presence of water and sulphur dioxide in the feed. ► Formation of NO_x species on small Ag clusters observed for the first time ever. ► Novel catalyst shows possible formation of active intermediate species on support.The selective catalytic reduction of NO by ethanol under strongly oxidizing conditions (ethanol-SCR) in the wide-temperature range of 150–400°C has been studied over Ag supported on a series of metal oxides (e.g., MgO, Y₂O₃, CuO, CeO₂, SiO₂, MgO-CeO₂-Al₂O₃). The Ag/MgO, Ag/CeO₂ and Ag/Al₂O₃ solids showed the best catalytic behavior with respect to N₂ and CO₂ yield and the widest temperature window of operation compared with the other single metal oxide-supported Ag solids. An optimum 25wt% MgO-25wt% CeO₂-Al₂O₃ support composition was found in terms of specific reaction rate of N₂ production (mol N₂/g_cats) and CO₂ selectivity. High NO conversions (60–90%), N₂ selectivities (95–99%) and CO₂ selectivities (>97%) were also obtained in the 150–400°C range at a GHSV of 40,000h⁻¹ with the low 0.1wt% Ag loading and using a feed stream of 0.05vol% NO, 0.1vol% ethanol, 5vol% O₂, 5vol% H₂O and He as balance gas. Moreover, the latter catalytic system exhibited a high stability in the presence of 50ppm SO₂ in the feed stream. N₂ selectivity values higher than 98% and CO₂ selectivities higher than 97% were obtained over the 0.1wt% Ag/MgO-CeO₂-Al₂O₃ catalyst in the 150–400°C range in the presence of water and SO₂ in the feed stream. The above-mentioned results led to the submission of a patent application for the commercial exploitation of Ag/MgO-CeO₂-Al₂O₃ catalyst towards a new NO_x control technology in the low-temperature range of 150–250°C using ethanol as reducing agent. DRIFTS studies after adsorption of NO, and transient titration of the adsorbed surface intermediate NO_x species with H₂ experiments, have revealed some preliminary important information towards the understanding of basic mechanistic issues of the present catalytic system (e.g., number and location of possible active NO_x intermediate species).

Keywords: Ethanol-SCR; Lean de-NO; _x; NO reduction; DRIFTS; Supported-Ag

Gas-phase dehydration of glycerol over silica–alumina catalysts by Yong Tae Kim; Kwang-Deog Jung; Eun Duck Park (pp. 177-187).

Display Omitted► Gas-phase dehydration of glycerol was examined over silica–alumina catalysts. ► The glycerol conversion depends on the total amount of acid sites. ► The acrolein yield increases with the concentration of the Brønsted acid sites. ► The 1-hydroxyacetone yield increases with the concentration of the Lewis acid sites. ► The acrolein selectivity increases with the water content of the feed.The gas-phase dehydration of glycerol was conducted over silica–alumina catalysts with different Si/Al molar ratios. For comparison, SiO₂ and η-Al₂O₃ were also examined. A variety of techniques, X-ray diffraction (XRD), temperature-programmed desorption of ammonia (NH₃-TPD), temperature-programmed oxidation (TPO) with mass spectroscopy (MS), infrared spectroscopy (FT-IR) after the adsorption of pyridine or glycerol, solid-state²⁹Si and²⁷Al magic-angle spinning nuclear magnetic resonance (MAS/NMR) spectroscopy, Raman spectroscopy, and CHNS analysis, were employed to characterize the catalysts. The initial glycerol conversion at 315°C was strongly dependent on the total amount of acid sites over the silica–aluminas. The acrolein yield was proportional to the concentration of the Brønsted acid sites, whereas the 1-hydroxyacetone yield was proportional to the concentration of the Lewis acid sites. Among the tested catalysts, Si_0.8Al_0.2O_x showed the highest acrolein selectivity during the initial 2h of the reaction. As long as the molar ratio between water and glycerol was in the range 2–11, the acrolein selectivity increased significantly with the water content of the feed.

Keywords: Dehydration; Glycerol; Acrolein; Silica–alumina; Acidity

Photocatalysis and photoelectrocatalysis using (CdS-ZnS)/TiO₂ combined photocatalysts by Maria Antoniadou; Vasileia M. Daskalaki; Nikolaos Balis; Dimitris I. Kondarides; Christos Kordulis; Panagiotis Lianos (pp. 188-196).

Display Omitted► Composite CdS-ZnS photocatalysts are combined with TiO₂. ► Application in photocatalysis or photoelectrocatalysis processes. ► Production of hydrogen or electricity. ► Composite photocatalysts are more efficient than pure CdS or ZnS.Powdered composite CdS-ZnS photocatalysts of variable composition have been synthesized by a co-precipitation method and were used as photocatalysts to produce hydrogen and as photoelectrocatalysts to produce electricity. Results of catalyst characterization show that composite sulphide photocatalysts form solid solutions and that their band gap energy can be tuned between that of ZnS (3.5eV) and that of CdS (2.3eV) by varying Cd (or Zn) content. The composite materials can photocatalytically produce substantial quantities of molecular hydrogen in the presence of sulphide–sulfite ions as sacrificial electron donors. Photocatalytic performance is significantly improved when small amounts of Pt crystallites are deposited on the photocatalyst surface. The rate of hydrogen production over the Pt-free CdS-ZnS powders depends on Cd (or Zn) content and is generally much higher for the composite materials than for pure CdS or ZnS. Pure semiconductors were found to be very poor photocatalysts under the present experimental conditions. Furthermore, two specific photocatalyst compositions, i.e., 67% and 25% CdS, gave maximum hydrogen production rates. An analogous behavior was observed when the same powders were used to make photoanode electrodes since both the rate of hydrogen ion reduction and the current flow are proportional to the number of photogenerated electrons. Composite CdS-ZnS photocatalysts were also applied by successive ionic layer absorption and reaction on TiO₂ films deposited on FTO electrodes. The obtained materials were used as photoanodes in a two-compartment photoelectrocatalysis cell filled with a basic electrolyte and with ethanol as sacrificial electron donor (fuel). The (CdS-ZnS)/TiO₂ photoanodes demonstrated a qualitatively similar behavior as CdS-ZnS photocatalysts. Thus 75%CdS–25%ZnS over TiO₂ was a better electrocatalyst than 100%CdS over TiO₂. When CdS-ZnS photocatalysts were combined with titania, they mainly functioned as visible-light-photosensitizers of this large band-gap semiconductor.

Keywords: CdS; ZnS; TiO; ₂; Photocatalysis; Hydrogen; Photoelectrocatalysis; Photoelectrochemical cells; Photofuel cells

Fe-containing nickel phosphate molecular sieves as heterogeneous catalysts for phenol oxidation and hydroxylation with H₂O₂ by M.N. Timofeeva; Zubair Hasan; A.Yu. Orlov; V.N. Panchenko; Yu.A. Chesalov; I.E. Soshnikov; Sung Hwa Jhung (pp. 197-204).

.Display Omitted► Fe-containing nickel phosphate molecular sieves (Fe-VSB-5) were synthesized at pH 7.3 under microwave irradiation. ► Textural and acid–base properties of Fe-VSB-5 were examined. ► Fe-VSB-5 materials show interesting catalytic behaviour in hydroxylation of phenol and wet phenol oxidation with H₂O₂ at pH of reaction medium 8.2.Fe-containing nickel phosphate molecular sieves (Fe-VSB-5) were hydrothermally synthesized in weak basic conditions under microwave irradiation and characterized by SEM, XRD, N₂-adsorption/desorption, DRS-UV–vis, and FT-IR spectroscopy using PhCN and CDCl₃ as probe molecules. The catalytic activity of Fe-VSB-5 was tested for the phenol hydroxylation and wet phenol oxidation with H₂O₂. The increase in iron content in Fe-VSB-5 leds to an increase in the reaction rates. The increases in activity can be explained by the role of the Fe species, which increases the generation of radicals. The Fe-VSB-5 samples were stable against the leaching out of Fe ions. The catalytic activity of Fe-VSB-5 was compared to the catalytic activity of traditional Fe-containing materials.

Keywords: Nickel phosphate molecular sieves VSB-5; Hydrogen peroxide; Phenol; Oxidation; Hydroxylation

New insights into the mechanism of photocatalytic reforming on Pd/TiO₂ by Hasliza Bahruji; Michael Bowker; Philip R. Davies; Fabien Pedrono (pp. 205-209).

Display Omitted► Relative hydrogen evolution rates depend upon the “hydrogen stoichiometry”. ► Products of the photocatalytic reforming determined by mass spectrometry. ► Four rules derived predicting hydrogen stoichiometry of a molecule. ► Photocatalytic reforming rates equivalent for all the molecules studied. ► Benzyl alcohol poisons the photocatalyst.Using sunlight to generate hydrogen from biomass is a promising and environmentally benign route to converting waste products into fuel but the practical application of the technology requires a photocatalyst and the development of suitable materials for this task has been hampered by an incomplete understanding of the photocatalytic mechanism. By exploring the effect of molecular structure on the rate of hydrogen evolution from a variety of alcohols over Pd/TiO₂ catalysts, a few simple rules are derived that predict the relative rates of photocatalytic reforming and the dominant reaction products; the latter being confirmed by mass spectrometry. In general, for an alcohol C_xH_yOH, decarbonylation dominates with the formation of CO₂ and a hydrocarbon C x₋₁. For diols and triols, alkyl fragments generally scavenge hydrogen and desorb as alkanes but in cases where competition for hydrogen occurs between alkyl fragments, for example iso-propanol, some reaction of alkyl groups to CO₂ and H₂ is evident. Methylene groups are always oxidised.

Keywords: Photocatalysis; Methanol reforming; TiO; ₂; Alcohol; Hydrogen production; Water splitting

Electrochemical promotion of the CO₂ hydrogenation reaction on composite Ni or Ru impregnated carbon nanofiber catalyst-electrodes deposited on YSZ by Vicente Jiménez; Carmen Jiménez-Borja; Paula Sánchez; Amaya Romero; Evangelos I. Papaioannou; Demetrios Theleritis; Stamatios Souentie; Susanne Brosda; José Luis Valverde (pp. 210-220).

(Top) Electrochemical promotion of sample Ni_imp CNF on Ni_sput catalyst-electrode deposited on YSZ following application of −1.30V. Condition: T=390°C,PCO2=1kPa,PH2=5.6kPa, F_T=100ml/min. Open circuit potential=0.005V. (Bottom) Representative SEM images of the composite catalyst-electrode containing a mixture of 2wt% YSZ and 98wt% Ni impregnated CNF deposited on YSZ after exposure to 450°C in air.Display Omitted► For the first time Ni and Ru impregnated carbon nanofibers (CNF) deposited on an oxygen ion conducting solid electrolyte have been used as catalyst-electrodes for NEMCA (non-Faradaic electrochemical modification of catalytic activity) application. ► Ni and Ru impregnated CNF electrodes are stable in oxidizing and reducing gas compositions up to 450°C and exhibit satisfactory electronic conductivity to serve as electrodes. ► In the CO₂ hydrogenation reaction the selectivity to CH₄ was found 20–40% for Ni catalysts and 76% for the Ru catalysts. ► Electrochemical promotion (NEMCA) was obtained for the CO₂ hydrogenation on these CNF electrodes.Ni and Ru impregnated carbon nanofibers (CNFs) have been for the first time successfully applied to an Y₂O₃-stabilized ZrO₂ (YSZ) solid electrolyte to form a catalyst-electrode cell. The catalytic and electrocatalytic properties of this composite Ni or Ru CNFs have been investigated in the CO₂ hydrogenation reaction under atmospheric pressure and at temperatures 200–440°C. The only products observed are methane and CO under open circuit and electrochemical promotion conditions. Ni based catalyst-electrodes show methane selectivity up to 55% at 300°C, while the Ru based catalyst exhibits selectivity up to 75% at 390°C. Negative applied potential enhances mildly the hydrogenation rate and the selectivity to CH₄ in the case of Ni catalyst-electrodes. Ru based catalyst exhibit under negative applied potential an enhanced hydrogenation rate with no further remarkable improvement of methane selectivity.

Keywords: CO; ₂; hydrogenation; Ni and Ru impregnated; Carbon nanofibers; Electrochemical promotion

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Applied Catalysis B, Environmental (v.107, #1-2)