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Applied Catalysis B, Environmental (v.69, #3-4)

Editorial Board (pp. i).

IFC Editorial Board (pp. co2).

Effects of surface fluorination of TiO₂ on photocatalytic oxidation of gaseous acetaldehyde by Hwajin Kim; Wonyong Choi (pp. 127-132).

Surface fluorinated TiO₂ (F-TiO₂) shows interesting photocatalytic behaviors that are distinguished from bare TiO₂ in many ways. The effects of surface fluorination of TiO₂ on the photocatalytic oxidation (PCO) of acetaldehyde under the ambient air conditions were investigated in this study. Both bare TiO₂ and F-TiO₂ films were compared for the adsorption and degradation of acetaldehyde. The surface fluorination of TiO₂ markedly inhibited the adsorption of acetaldehyde and the total amount of CH₃CHO adsorbed on F-TiO₂ was as low as 30% of that on bare TiO₂. However, the PCO rate constant for CO₂ production was highly enhanced with F-TiO₂ on the contrary. The total amount of CH₃CHO adsorbed on the photocatalyst films could be quantitatively converted into CO₂. The first-order rate constant for the photocatalytic generation of CO₂ increased by 2.5 times upon the surface fluorination of TiO₂. The effects of surface fluorination on the dark adsorption of acetaldehyde and the PCO kinetics were compared and discussed in detail. The present study demonstrates that the enhanced PCO activity with F-TiO₂ is also observed at the F-TiO₂/air interface while the similar phenomenon was previously observed at the F-TiO₂/water interface. The enhanced PCO activities of F-TiO₂ might be apparently masked by the hindered adsorption of substrates on F-TiO₂ but the PCO kinetics on F-TiO₂ is indeed much faster than that on bare TiO₂.

Keywords: Photocatalysis; Surface fluorinated TiO; ₂; Acetaldehyde degradation; Photocatalytic oxidation kinetics; Air purification

Room temperature visible light oxidation of CO by high surface area rutile TiO₂-supported metal photocatalyst by Florence Bosc; André Ayral; Nicolas Keller; Valérie Keller (pp. 133-137).

Visible light-active rutile TiO₂ with a high surface area of 200m²/g was obtained by a low-temperature sol–gel synthesis, based on a long aging duration of a titania sol to stabilize the rutile phase. Decorated by an adequate amount of metallic nanoparticles, this non-doped TiO₂ displays high and stable performances for the on-stream room temperature oxidation of CO by visible light photocatalysis.

Keywords: Supported catalysts; Photooxidation; Environmental chemistry; Rutile; Sol–gel; Platinum particles; Charge transfer

Low temperature preparation and visible light photocatalytic activity of mesoporous carbon-doped crystalline TiO₂ by Wenjie Ren; Zhihui Ai; Falong Jia; Lizhi Zhang; Xiaoxing Fan; Zhigang Zou (pp. 138-144).

A visible-light-active TiO₂ photocatalyst was prepared through carbon doping by using glucose as carbon source. Different from the previous carbon-doped TiO₂ prepared at high temperature, our preparation was performed by a hydrothermal method at temperature as low as 160°C. The resulting photocatalyst was characterized by XRD, XPS, TEM, nitrogen adsorption, and UV–vis diffuse reflectance spectroscopy. The characterizations found that the photocatalyst possessed a homogeneous pore diameter about 8nm and a high surface area of 126m²/g. Comparing to undoped TiO₂, the carbon-doped TiO₂ showed obvious absorption in the 400–450nm range with a red shift in the band gap transition. It was found that the resulting carbon-doped TiO₂ exhibits significantly higher photocatalytic activity than the undoped counterpart and Degussa P25 on the degradation of rhodamine B (RhB) in water under visible light irradiation ( λ>420nm). This method can be easily scaled up for industrial production of visible-light driven photocatalyst for pollutants removal because of its convenience and energy-saving.

Keywords: Photocatalysis; Titanium dioxide; Degradation; Preparation; Low temperature

Catalytic conversion of commingled polymer waste into chemicals and fuels over spent FCC commercial catalyst in a fluidised-bed reactor by Y.-H. Lin; M.-H. Yang (pp. 145-153).

A commingled post-consumer polymer (CPW#1) was pyrolysed over spent fluid catalytic cracking (FCC) commercial catalyst (ECat-1) using a laboratory fluidised-bed reactor operating isothermally at ambient pressure. The influence of reaction conditions including catalyst, temperature, ratios of commingled polymer to catalyst feed and flow rates of fluidising gas was examined. The conversion for spent FCC commercial catalyst (82.7wt%) gave much higher yield than silicate (only 14.2wt%) and the highest yield (nearly 87wt%) was obtained for ZSM-5. Greater product selectivity was observed with ECat-1 as a recycled catalyst with about 56wt% olefins products in the C₃–C₇ range. The selectivity could be further influenced by changes in reaction conditions. Valuable hydrocarbons of olefins and iso-olefins were produced by low temperatures and short contact times used in this study. It is also demonstrated that the use of spent FCC commercial catalyst and under appropriate reaction conditions can have the ability to control both the product yield and product distribution from polymer degradation, potentially leading to a cheaper process with more valuable products.

Keywords: Polymer waste; Fluidised-bed reactor; Catalyst; Pyrolysis; Selectivity

The importance of Fe loading on the N₂O reduction with NH₃ over Fe-MFI: Effect of acid site formation on Fe species by Kou Sugawara; Takeshi Nobukawa; Masanori Yoshida; Yoshihiro Sato; Kazu Okumura; Keiichi Tomishige; Kimio Kunimori (pp. 154-163).

Effect of the loading amount of Fe over ion-exchanged Fe-MFI catalysts on the catalytic performance of N₂O reduction with NH₃ was investigated, and the results indicated that the turnover frequency (TOF) was almost constant in the Fe/Al range between 0.05 and 0.40. The activity of N₂O+NH₃ reaction was much lower than that of N₂O+CH₄ reaction over Fe-MFI (Fe/Al=0.40), and the preadsorption of NH₃ decreased drastically the activity of N₂O+CH₄ reaction. The temperature-programmed desorption (TPD) of NH₃ showed the formation of stronger acid sites on Fe-MFI (Fe/Al=0.24 and 0.40), and the amount of the acid sites agrees well with the desorption amount O₂ in O₂-TPD in the low temperature range. The acid sites gave a 3610cm⁻¹ peak (Brønsted acid) in FTIR observation. These results suggest that the acid sites were formed on the bridge oxide ions in binuclear Fe species. Adsorbed NH₃ on the strong acid sites inhibited N₂O dissociation, which can be related to the low activity of N₂O+NH₃ reaction over Fe-MFI with high Fe loading.

Keywords: N; ₂; O reduction; Ammonia; Methane; Fe-MFI; Acid sites

Hydroxyapatite photocatalytic degradation of calmagite (an azo dye) in aqueous suspension by M. Pratap Reddy; A. Venugopal; M. Subrahmanyam (pp. 164-170).

The hydroxyapatite (HAP) is prepared by precipitation method and examined for the photocatalytic degradation of calmagite, a toxic and non-biodegradable azo-dye compound. The physicochemical properties of hydroxyapatite material were characterized using BET surface area, XRD, FT-IR, and SEM analysis. The FT-IR analysis of the hydroxyapatite revealed that the peak intensity due to absorbance of surface PO₄³⁻ group centered at wave number 1030cm⁻¹ is drastically decreased upon exposure to UV for 1h. The study includes dark adsorption experiments at different pH conditions, influence of the amount of catalyst, and effect of pH on photocatalytic degradation of dye, chemical oxygen demand (COD) removal, biological oxygen demand (BOD₅) increase and SO₄²⁻ and NO₃⁻ ions evolution during the degradation. At optimum photocatalytic experimental conditions the same is compared with commercial degussa P-25 TiO₂. The photocatalytic treatment significantly reduced the COD (92% removal) and increased the BOD₅/COD ratio to 0.78. Considerable evolution of SO₄²⁻ (8.5mgL⁻¹) and NO₃⁻ (12.2mgL⁻¹) ions are achieved during the degradation process, thus reflecting the usefulness of the hydroxyapatite photocatalytic treatment in calmagite removal in wastewater.

Keywords: Hydroxyapatite; Photocatalysis; Calmagite; Biodegradability; Degradation

Effects of hydrothermal temperature and time on the photocatalytic activity and microstructures of bimodal mesoporous TiO₂ powders by Jiaguo Yu; Guohong Wang; Bei Cheng; Minghua Zhou (pp. 171-180).

Bimodal nanocrystalline mesoporous TiO₂ powders with high photocatalytic activity were prepared by a hydrothermal method using tetrabutylorthotitanate (TiO(C₄H₉)₄, TBOT) as precursor. The as-prepared TiO₂ powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and N₂ adsorption–desorption measurements. The photocatalytic activity of the as-prepared TiO₂ powders was evaluated by the photocatalytic degradation of acetone (CH₃COCH₃) under UV-light irradiation at room temperature in air. The effects of hydrothermal temperature and time on the microstructures and photocatalytic activity of the TiO₂ powders were investigated and discussed. It was found that hydrothermal treatment enhanced the phase transformation of the TiO₂ powders from amorphous to anatase and crystallization of anatase. All TiO₂ powders after hydrothermal treatment showed bimodal pore-size distributions in the mesoporous region: one was intra-aggregated pores with maximum pore diameters of ca. 4–8nm and the other with inter-aggregated pores with maximum pore diameters of ca. 45–50nm. With increasing hydrothermal temperature and time, the average crystallite size and average pore size increased, in contrast, the Brunauer-Emmett-Teller (BET) specific surface areas, pore volumes and porosity steadily decreased. An optimal hydrothermal condition (180°C for 10h) was determined. The photocatalytic activity of the prepared TiO₂ powders under optimal hydrothermal conditions was more than three times higher than that of Degussa P25.

Keywords: Bimodal; Nanocrystalline; Mesoporous; TiO; ₂; powders; Photocatalytic activity; Acetone; Hydrothermal temperature; Hydrothermal time

Thermal stability and catalytic activity of flame-made silica–vanadia–tungsten oxide–titania by Rainer Jossen; Martin C. Heine; Sotiris E. Pratsinis; Steve M. Augustine; M. Kamal Akhtar (pp. 181-188).

Vanadia (0.9 or 2wt.%) and silica (0–5wt.%) doping of flame-made tungsten oxide–titania nanostructured catalyst powders (anatase, 100m²/g, 10wt.% WO₃) is investigated. The effect of dopants on structural and chemical properties of these powders were analyzed by nitrogen adsorption, X-ray diffraction (XRD), temperature programmed reduction (TPR), transmission electron microscopy (TEM) and Raman spectroscopy. After calcination for 20h at 700°C in air, the thermally most stable composite powder conserved its specific surface area (SSA) to 90m²/g and its anatase content to 96wt.%. Tungsten oxide and vanadia form thin polymeric layers (∼1nm) on the surface of the titania support. Adding silica improves the thermal and crystal stability of the catalysts even at higher reactor temperatures. As a result both NO conversion and the rate of selective catalytic reduction (SCR) with NH₃ were increased.

Keywords: Flame spray pyrolysis; DeNO; _x; Titania; Tungsten oxide; Vanadia; Silica

Photocatalytic oxidation of methanol using titania-based fluidized beds by Ryan J. Nelson; Christopher L. Flakker; Darrin S. Muggli (pp. 189-195).

Experiments determined methanol removal and catalyst elutriation rates during photocatalytic oxidation (PCO) of fluidized and packed beds of various titania-based catalysts. The study developed elutriation-resistant catalysts in which TiO₂ was precipitated from solution (p-TiO₂), or was coated on an Al₂O₃ support (TiO₂/Al₂O₃) and compared them to Degussa P-25 TiO₂. Although Degussa P-25 TiO₂ oxidized methanol effectively, it elutriated at a rate that was two orders of magnitude greater than those of p-TiO₂ and TiO₂/Al₂O₃. In addition, TiO₂/Al₂O₃ removed methanol at a significantly greater rate than did P-25, with p-TiO₂ being the least active. Fluidized beds produced greater PCO rates than did packed beds of P-25 and TiO₂/Al₂O₃. Fluidization enhancers, such as vibration and incorporation of a static mixer, improved the performance of the P-25 fluidized bed, but did not change the effectiveness of TiO₂/Al₂O₃ or p-TiO₂. The activity of TiO₂/Al₂O₃ decreased with increasing calcination temperature (over the temperature range 673–873K). The optimum TiO₂ loading for TiO₂/Al₂O₃ was 30wt.%.

Keywords: Attrition; Catalysis; Fluidization; Photochemistry; Photocatalytic oxidation; Vibration

Wet air oxidation in a catalytic membrane reactor: Model and industrial wastewaters in single tubes and multichannel contactors by Eduard Emil Iojoiu; Sylvain Miachon; Emmanuel Landrivon; John C. Walmsley; Henrik Ræder; Jean-Alain Dalmon (pp. 196-206).

Recent results on catalytic wet air oxidation applied to a membrane contactor are presented that give new insight following a series of previous publications. Model and industrial effluents are treated in both single tube and multichannel catalytic systems. Characterisation of the catalytic material (solid analyses, electron microscopy, EDS and EPMA) is carried out, in order to determine the catalyst distribution. Catalytic results show performances heavily dependent on the nature of the effluent and the operating conditions, and to a lesser extent on the catalytic membrane characteristics. At 80°C, an industrial effluent is oxidised at a membrane surface related rate of 3.8mmol/s/m². This result is achieved using a membrane containing about 0.1wt.% Pt. This allows a revised and improved technico-economical evaluation of the Watercatox process.

Keywords: Catalytic wet air oxidation; Wastewater; Platinum; Membrane reactor; Multichannel system

Green approach for the preparation of biodegradable lubricant base stock from epoxidized vegetable oil by Piyush S. Lathi; Bo Mattiasson (pp. 207-212).

A novel process for the production of biodegradable lubricant-based stocks from epoxidized vegetable oil with a lower pour point via cationic ion-exchange resins as catalysts was developed. This involves two steps, first, ring-opening reactions by alcoholysis followed by esterification of the resultant hydroxy group in the first step.The ring-opening reaction of epoxidized soybean oil with different alcohols such as n-butanol, iso-amyl alcohol and 2-ethylhexanol was carried out in presence of Amberlyst 15 (Dry) as a catalyst; identity of products was confirmed by IR and NMR. Pour points of the products were observed in the range of −5 to −15°C. The hydroxy group of ring-opening product of n-butanol was further reacted with acetic anhydride in presence of catalyst Amberlyst 15 (Dry), which was previously used to carry out ring-opening reaction by alcoholysis and identity of the resulting product was confirmed by IR. Pour point of the resulting product was observed to be −5°C.

Keywords: Bio-lubricants; Epoxidized soybean oil; Cationic ion-exchange resins

Toluene oxidation on Pd catalysts supported by CeO₂–Y₂O₃ washcoated cordierite honeycomb by Meng-Fei Luo; Mai He; Yun-Long Xie; Ping Fang; Ling-Yun Jin (pp. 213-218).

A novel CeO₂–Y₂O₃ (CY) washcoat on cordierite honeycomb was prepared by an impregnation method, which was used as a support to prepare a Pd catalyst. A model reaction of the complete combustion of toluene was conducted to evaluate the performance of the developed Pd/CY catalyst. The CY washcoat support and the Pd/CY catalyst were characterized by XRD, Raman spectroscopy, H₂-TPR and SEM techniques. The results show that compared with conventional washcoat the CY washcoat has better adhesion and higher vibration- and heat-resistance. The CY washcoat can anchor well Pd onto the cordierite honeycomb substrate. The formation of a CeO₂–Y₂O₃ solid solution and the steady present of PdO occur at high calcination temperatures, resulting in a better thermal stability. On a Pd/CY catalyst calcined at 500°C, a 99% of toluene conversion was obtained at 210°C, and it was stable for reaction time up to 30h.

Keywords: Cordierite honeycomb; CY washcoat; Toluene combustion

Effect of ceria–zirconia ratio on the interaction of CO with PdO/Al₂O₃–(Ce_x–Zr1−_x)O₂ catalysts prepared by sol–gel method by Gabriela Pérez-Osorio; Felipe Castillón; Andrey Simakov; Hugo Tiznado; Francisco Zaera; Sergio Fuentes (pp. 219-225).

The current work is devoted to study of CO interaction with PdO/Al₂O₃–(Ce_x–Zr1−_x)O₂ catalysts. Ceria–zirconia–alumina supports with different Ce/Zr ratio were prepared by sol–gel technique. The FT-IR characterization of CO adsorbed at −120 and 25°C on oxidized and reduced samples revealed that Ce/Zr ratio modifies the surface properties of support and oxidation state of palladium. The catalyst with Ce/Zr molar ratio 0.5/0.5 was characterized with the highest ability to stabilize palladium in oxide state and the highest activity to oxidize CO. Redox treatment of catalysts improves their catalytic activity.

Keywords: Palladium oxide; Al; ₂; O; ₃; –(Ce; _x; –Zr; 1−; _x; )O; ₂; CO adsorption; In situ; FT-IR; Catalytic CO oxidation

Effect of dopants on the performance of CuO–CeO₂ catalysts in methanol steam reforming by Joan Papavasiliou; George Avgouropoulos; Theophilos Ioannides (pp. 226-234).

Steam reforming of methanol was carried out over a series of doped CuO–CeO₂ catalysts prepared via the urea–nitrate combustion method. XRD analysis showed that at least part of the dopant cations enter the ceria lattice. The addition of various metal oxide dopants in the catalyst composition affected in a different way the catalytic performance towards H₂ production. Small amounts of oxides of Sm and Zn improved the performance of CuO–CeO₂, while further addition of these oxides caused a decrease in catalyst activity. XPS analysis of Zn- and Sm-doped catalysts showed that increase of dopant loading leads to surface segregation of the dopant and decrease of copper oxide dispersion. The addition of oxides of La, Zr, Mg, Gd, Y or Ca lowered or had no effect on catalytic activity, but led to less CO in the reaction products. Noble-metal modified catalysts had slightly higher activity, but the CO selectivity was also significantly higher.

Keywords: Copper oxide; Cerium oxide; Hydrogen production; Methanol; Steam reforming; Combustion method

Microwave-assisted desulfurization of NO_x storage-reduction catalyst by Masaya Ibe; Sinue Gómez; Kinga A. Malinger; Paul Fanson; Steven L. Suib (pp. 235-239).

The activity of NO_x storage-reduction (NSR) catalysts is greatly reduced by sulfur poisoning, caused by the SO₂ present in the exhaust stream. Desorption of sulfur species from poisoned NSR catalysts occurs at temperatures in excess of 600°C using reducing atmospheres and conventional heating. In this work, microwave (MW) heating has been used to promote desulfurization of poisoned NSR catalysts. The experiments were carried out by heating the catalyst with MW radiation and using hydrogen as the reducing gas. Desorption of H₂S at 200°C was observed. Desorption at even lower temperatures (150°C) was observed when water was introduced to the system. In the presence of water, sulfur species desorbed as both H₂S and SO₂. An overall reduction of sulfur species of about 60% was obtained. The use of MW heating proves to be an efficient way to achieve regeneration of poisoned NSR catalysts.

Keywords: Microwave; Desulfurization; NSR catalyst

Alkali deactivation of high-dust SCR catalysts used for NO_x reduction exposed to flue gas from 100MW-scale biofuel and peat fired boilers: Influence of flue gas composition by Åsa Kling; Christer Andersson; Åse Myringer; David Eskilsson; Sven G. Järås (pp. 240-251).

Deactivation of vanadium–titanium deNO_x SCR (selective catalytic reduction) catalysts in high-dust position have been investigated in three 100MW-scale boilers during biofuel and peat combustion. The deactivation of the catalyst samples has been correlated to the corresponding flue gas composition in the boilers. Too investigate the effect on catalyst deactivation a sulphate-containing additive was sprayed into one of the furnaces. Increased alkali content on the SCR catalyst samples decreased the catalytic deNO_x activity. The study has shown a linear correlation between exposure time in the boilers and alkali concentration (mainly potassium) on the samples. The results imply that mainly alkali in ultra fine particles (<100nm) in the flue gas increased the alkali accumulation on the catalyst samples. Low correlation was found between particles larger than 100nm and the catalyst deactivation. It was not possible to decrease the deactivation of the catalyst samples by the sulphate-containing additive. Although the additive had an effect in sulphating potassium chloride to potassium sulphate, it did not decrease the amount of potassium in ultra fine particles or the deactivation of the catalyst samples.

Keywords: Selective catalytic reduction; Nitrogen oxides; Combustion; Biofuel; Alkali; Potassium; Particles; Deactivation

Non-isothermal bioreactors in enzymatic remediation of waters polluted by endocrine disruptors: BPA as a model of pollutant by N. Diano; V. Grano; L. Fraconte; P. Caputo; A. Ricupito; A. Attanasio; M. Bianco; U. Bencivenga; S. Rossi; I. Manco; L. Mita; G. Del Pozzo; D.G. Mita (pp. 252-261).

The bioremediation of waters polluted by Bisphenol A, taken as a model for endocrine disruptors, has been pursued by means of catalytic membranes in bioreactors operating under isothermal and non-isothermal conditions. Laccase from Trametes versicolor was immobilized on nylon membranes grafted with Glycidyl Methacrylate and using Phenylendiamine as spacer. The behaviour of the catalytic membrane was studied as a function of BPA concentration. Affinities of immobilized laccase towards BPA were found to increase with average temperature and under non-isothermal conditions. Percentage increases of enzyme activity, proportional to the applied temperature differences, were found to decrease with the increase of BPA concentrations. Interestingly, the highest levels of BPA biodegradation occurred at the lowest concentrations, in other words those present in wastewaters given the small water solubility of this compound. The results are discussed in terms of the process of thermodialysis by considering the additional BPA fluxes towards the immobilized enzymes driven by the temperature gradients.

Keywords: Water bioremediation; Endocrine disruptors; Bisphenol A; Immobilized laccase; Bioreactors

Adsorption and reactions of ethanol and ethanol–water mixture on alumina-supported Pt catalysts by M. Dömök; M. Tóth; J. Raskó; A. Erdőhelyi (pp. 262-272).

The formation of surface species in the ethanol–water interaction and the reforming of ethanol have been investigated on Pt/Al₂O₃ catalysts and for comparison on the support. By means of infrared spectroscopy it was found that on Pt/Al₂O₃ not only adsorbed ethanol, different types of ethoxy species but also traces of acetaldehyde and a significant amount of acetate groups were detectable on the surface. The latter species were stable even at 700K. The gas phase analysis of the ethanol-dosed surface showed at higher temperature considerable amount of ethylene in the case of Al₂O₃ and hydrogen in the case of Pt/Al₂O₃.In the ethanol+water reaction the selectivity of H₂ and CO₂ formation at 723K decreased in time, while that of ethylene increased. This trend was attenuated by increasing the following parameters: water concentration, metal loading and reaction temperature. It was assumed that this behavior of Pt/Al₂O₃ in the ethanol+water reaction can be attributed to the formation of surface acetate groups which hindered the reaction on the metal, although these species were located rather on the support.

Keywords: Ethanol dehydration; Ethanol dehydrogenation; Steam reforming of ethanol; Surface ethoxide; Acetate formation; Pt/Al; ₂; O; ₃; catalyst

Corrigendum to “Photocatalytic oxidation of multicomponent solutions of herbicides: Reaction kinetics analysis with explicit photon absorption effects” [Appl. Catal. B: Environ. 68 (2006) 171–180] by Bea Toepfer; Alexander Gora; Gianluca Li Puma (pp. 273-273).

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Applied Catalysis B, Environmental (v.69, #3-4)