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Applied Catalysis B, Environmental (v.57, #1)
Photosensitized degradation of ethyl parathion pesticide in aqueous solution of anthracene modified photoactive dextran by Maria Nowakowska; Monika Sterzel; Szczepan Zapotoczny; Emilia Kot (pp. 1-8).
The photosensitized oxidation of parathion-ethyl (PTE) pesticide in the aqueous solution of anthracene substituted dextran (DXA) was investigated. The phototransformation of PTE was found to be significantly enhanced in the presence of DXA. The suggested mechanisms of reactions involve photoinduced electron transfer process as a primary photophysical step. DXA polymer plays a role of environmentally friendly photosensitizer since after the reaction it undergoes decomposition.
Keywords: Polymeric photosensitizer; Photodegradation; Pesticide; Parathion; Photoinduced electron transfer
Photocatalysis of CFC degradation by titanium dioxide by K. Tennakone; K.G.U. Wijayantha (pp. 9-12).
CFC is photodegraded by only hard UV radiation (UV-C) in the upper atmosphere. We have found that fine crystallites of TiO2 catalyse photodecomposition of dichlorodifluoromethane at much longer wavelengths (365–366nm), which is band gap absorption region of the TiO2 crystallites. Oxidation products detected are fluoride and chloride ions, and chlorine. Experiments are conducted in the gaseous phase, using TiO2 supported on glass plates. Implication of the findings on atmospheric CFC degradation are discussed.
Keywords: Chlorofluorocarbons; Photocatalysis CFC photocatalytic degradation; Titanium dioxide
NO x trapping and soot combustion on BaCoO3− y perovskite: LRS and FTIR characterization by V.G. Milt; M.A. Ulla; E.E. Miró (pp. 13-21).
The BaCoO3− y perovskite-type mixed oxide is studied for both trapping of NO x and combustion of diesel soot. The starting material consists of a stoichiometric mixture of Ba and Co nitrates. Different crystalline phases are obtained when the solids are calcined at different temperatures (ranging from 400 to 1000°C). After 400°C calcination Ba(NO3)2 and Co3O4 crystalline phases are formed, while after calcination at 700°C the BaCoO3 stoichiometric perovskite is obtained. However, when the temperature is increased to 1000°C, the structure loses oxygen and perovskite BaCoO2.74 is formed. The solids calcined at 700 and 1000°C show high NO x adsorption capacity, the latter being more effective. This solid shows weak IR bands in the 800cm−1 frequency region associated with the perovskite structure. After the catalyst interacts with NO x, new bands associated with bulk nitrates and surface NO3− species are observed. Signals associated with surface N-bounded species of the OBaNO2 type could be masked by the intense Ba(NO3)2 signals. LRS characterization is in agreement with XRD and FTIR results. The Raman signal at 716cm−1 is associated with the BaCoO2.74 structure while a broad signal at 607cm−1 appears in samples containing BaCoO3 and BaCoO2.94 phases. Nitrates formed upon NO+O2 treatments show high thermal stability under He atmosphere up to 490°C. However, reductive treatments either under H2 atmosphere or with soot particles cause decomposition of the nitrates at temperatures lower than 400°C. A reaction scheme is proposed involving the participation of perovskite structures, Co3O4, Ba(NO3)2, BaO and metallic Co particles.The catalyst under study favors the reaction between the soot particles and the trapped NO x species making this system promising for the simultaneous abatement of both contaminants. The addition of K decreases the soot combustion temperature.
Keywords: BaCoO; 3−; y; perovskite; Diesel pollutants; NO; x; trapping; Soot combustion; Catalytic trap
Photocatalytic degradation of 2-chlorophenol by Co-doped TiO2 nanoparticles by M.A. Barakat; H. Schaeffer; G. Hayes; S. Ismat-Shah (pp. 23-30).
The photocatalytic degradation of 2-chlorophenol (2-CP) in aqueous solution was studied using Co-doped TiO2 nanoparticles catalyst. The catalyst samples were synthesized by a sol–gel technique from TiCl4 with different concentrations of Co(III) dopant and calcination temperatures. The typical composition of the prepared Co-doped TiO2 was Ti1− xCo xO2, where x values ranged from 0.004 to 0.14. Several analytical tools, such as X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area measurement, X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray analysis (EDAX), were used to investigate the nanoparticles structure, size distribution, and composition. The catalytic activity of the prepared nanoparticles was measured in a batch photoreactor containing appropriate solutions of 2-CP with UV irradiation of 100W. High performance liquid chromatography (HPLC) was used for analyzing the concentration of 2-CP in solution at different time intervals during the photodegradation experiment. Parameters affecting the photocatalytic process such as catalyst crystallinity, light absorption efficiency, concentration of the catalyst and the dopant, solution pH, and 2-CP concentration have been investigated.Results obtained revealed that Co-doped TiO2 showed high activity for UV-photocatalytic degradation of 2-CP. The surface area of the catalyst was measured to be 39.7m2g−1. The photodegradation process was optimized by using 10mg/L Co-doped TiO2 with Co doping concentration of 0.036, after 3h irradiation. The efficiency values of the 2-CP photodegradation were 93.4% and 96.4% at solution pH of 9 and 12, respectively. The photodegradation follows a pseudo-first-order reaction and the observed rate constant values change with the 2-CP concentration. The optical absorption properties of the samples were also measured. The presence of Co ions in the TiO2 structure caused a significant absorption shift towards the visible region. The photodegradation efficiency matched the maximum light absorption efficiency.
Keywords: 2-Chlorophenol; Photocatalytic degradation; Nanoparticle
Silicoaluminophosphate molecular sieves as a hydrocarbon trap by S.P. Elangovan; M. Ogura; Y. Zhang; N. Chino; T. Okubo (pp. 31-36).
Silicoaluminophosphate molecular sieves with AFI, AFO, AEL and CHA topologies have been investigated as a hydrocarbon trap by studying the temperature programmed desorption of toluene. The pore diameter is increased in the following order: SAPO-34 ( dp=0.38nm)
Keywords: Cold start; Hydrocarbon trap; Silicoaluminophosphate; Vehicle emission
Iron phthalocyanine supported on silica or encapsulated inside zeolite Y as solid photocatalysts for the degradation of phenols and sulfur heterocycles by Mercedes Alvaro; Esther Carbonell; Mercedes Esplá; Hermenegildo Garcia (pp. 37-42).
The photocatalytic activity of iron phthalocyanine adsorbed on silica (FePc/SiO2) or encapsulated within NaY zeolite (FePc@NaY) towards the degradation of two model compounds using hydrogen peroxide as oxidant has been determined. It was found that while FePc/SiO2 exhibits higher intrinsic activity than FePc@NaY for the degradation of phenol in water, FePc/SiO2 cannot be used as heterogeneous photocatalyst in organic solvents due to self-degradation and/or desorption of the iron phthalocyanine from the silica surface to the solution. Thus, for the oxidative photodegradation of benzothiophene in acetonitrile using FePc/SiO2 as photocatalyst (a model reaction with importance in the fuel industry), the silica becomes colorless and without possibility of reuse. In contrast, FePc@NaY, in where iron phthalocyanine is permanently immobilized inside the zeolite pores, can be recovered by filtration after the photodegradation of benzothiophene in acetonitrile and reused.
Keywords: Iron phthalocyanine; Zeolite encapsulated photocatalyst; Ship-in-a-bottle synthesis; Degradation of benzothiophene
Highly active and selective CuO x/CeO2 catalyst prepared by a single-step citrate method for preferential oxidation of carbon monoxide by Gregorio Marbán; Antonio B. Fuertes (pp. 43-53).
This work describes a novel citrate procedure to prepare highly active and selective copper oxide–ceria catalysts for the preferential oxidation of CO in the presence of hydrogen. At the conditions studied, the prepared catalysts are very active and selective at temperatures around 160°C, even though suffer from slow deactivation during reaction, which is ascribed to the progressive loss of active sites by copper oxide reduction. In spite of this, the catalytic activity of these catalysts is comparable to or higher than that of the most active catalysts reported in literature. Cobalt and manganese oxide-based catalysts prepared by the same procedure present a much lower catalytic activity than that of the copper oxide-based catalyst. The catalysts are formed by small arrangements of ceria crystals (2–40 crystals per particle) of nanometric size (4–10nm), partially covered by XRD amorphous clusters of copper oxide. The presence of copper oxide reduces the normal growing of the ceria crystals during calcination and induces the agglomeration of such crystals. Raman spectroscopy was used to study the catalytic activity-related structural characteristics of the catalysts. Only ceria-related peaks were detected in the Raman spectra. The parameters of the main peak (at ∼450–464cm−1) were found to depend on the crystal size and on the extent of copper oxide covering of the ceria surface. On the other hand, the relation existing between the area of the second peak (at ∼585–598cm−1) and the amount of oxygen vacancies permitted to analyse their effect on the activity of the catalysts prepared at different conditions.
Keywords: Fuel cell; Preferential CO oxidation; Ceria; Copper oxide; Citrate; Raman; XRD
Photocatalytic degradation of azo-dyes reactive black 5 and reactive yellow 145 in water over a newly deposited titanium dioxide by Abdelkahhar Aguedach; Stephan Brosillon; Jean Morvan; El Kbir Lhadi (pp. 55-62).
Reactive black 5 (RB5) and reactive yellow (RY145), two azo-dyes, were degraded by using UV-irradiated TiO2 coated on non-woven paper. The adsorption capacity of the photocatalyst was studied at natural pH and at various pHs of the aqueous solutions of azo-dyes. It can be stated that pH is a very important parameter in dye adsorption. The silica binder played an important role in decreasing the pzc of the coated TiO2. The effect of initial dye concentration and pH on photocatalyst degradation was studied. The rate of degradation was modeled by the Langmuir Hinselwood equation only in acid pH zone. A direct correlation between pH, adsorption and rate of degradation was found. The discoloration and complete mineralization of the two dyes could be achieved. The by-products of the photocatalytic degradation were biodegradable and non-toxic for bacteria from activated sludge. These results suggest that UV-irradiated TiO2 coated on non-woven paper may be considered as an adequate process for the discoloration and detoxification of the treatment of diluted colored textile wastewater.
Keywords: Photocatalysis; Supported photocatalyst; Water treatment; Azo-dyes; Dye removal; RB5; RY145
Distinct roles of copper in bimetallic copper–rhodium three-way catalysts deposited on redox supports by X. Courtois; V. Perrichon (pp. 63-72).
Copper (4.7%)–rhodium (0–2000ppm) catalysts deposited on three supports with different oxygen storage capacity (OSC) were tested under three-way catalytic cycling conditions using a low frequency and large composition fluctuations. The reducibility by hydrogen was also studied for all the catalysts in order to assess their OSC. Alumina (Al), ceria–alumina (CeAl) and ceria–zirconia (CeZr) were selected as supports. Both copper and rhodium metals favour the reduction of CeAl and CeZr at low temperature. The catalytic activity of rhodium in CO, NO and C3H6 conversion in presence of oxygen is less influenced by the oxygen mobility of the support. However the OSC of the supports allow to attenuate or even suppress the effects of the composition fluctuations and thus improves the conversion at high temperatures. For monometallic copper catalysts, copper participates in the regulation of the oxidant/reducer ratio and is determinant if the support OSC is insufficient. Moreover, the interaction between copper and the mobile oxygen of the support greatly favours the CO oxidation at low temperature, whereas it has less influence on C3H6 oxidation and disfavours the NO reduction at low temperature. No synergetic effect was observed for the bimetallic CuRh catalysts. In this case, the activity is ruled by the metal or the association metal-support, which is the most active in each temperature range. The association “copper-support exhibiting mobile oxygen� is the most active for CO conversion. NO reduction depends mainly on the rhodium content, especially at low temperature, and C3H6 conversion is a little improved by rhodium addition.
Keywords: Oxygen storage capacity; Alumina; Three-way catalysts