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Applied Catalysis B, Environmental (v.64, #1-2)
Effect of silica on the catalytic destruction of chlorinated organics over V2O5/TiO2 catalysts by S. Albonetti; S. Blasioli; A. Bruno; J. Epoupa Mengou; F. Trifirò (pp. 1-8).
In the present work, the contribution of silica doping to the catalytic activity of V2O5/TiO2 based catalysts in the decomposition of chlorinated organic materials and on the formation of possible by by-products was investigated. The influence of vanadium loading on surface structures of differently supported materials has been systematically investigated by XRD, BET, Raman spectroscopy and H2-TPR. These studies demonstrated that the V2O5 supported on either TiO2/WO3 or TiO2/WO3/SiO2 is very active for the oxidation of o-DCB, a probe molecule for aromatic compounds which is present in flue gas. Silica was found to form a highly dispersed amorphous phase on the support surface, which strongly affects the structural degradation phenomena, delaying the collapse of surface area, that is particularly significant at high vanadium content. The presence of silica on the support influences the distribution of VOx species. Since it was demonstrated that support surfaces predominantly covered with highly dispersed vanadium lead to high activity, in spite of the lower ability of SiO2 to spread metal oxides, the higher stability of silica containing materials, while preserving surface area, favors vanadium dispersion and leads to superior catalytic performance.
Keywords: Vanadia; Titania; Silica effect; Chlorinated destruction; SCR catalyst; Dichloromaleic anhydride
Carbon-coated anatase for oxidation of methylene blue and NO by Takafumi Matsunaga; Michio Inagaki (pp. 9-12).
Carbon-coated TiO2 photocatalysts were prepared from the powder mixtures of TiO2/PVA of 90/10 in mass at a temperature of 500–1000°C for 1h in high purity nitrogen gas flow. Carbon-coated TiO2 prepared at low temperatures as 600°C, of which carbon content was 5.5mass%, was shown to be applicable for NO gas oxidation, a little higher activity than the original anatase powder. For the photodecomposition of methylene blue in water, however, the one heated at 800°C showed the highest activity among the samples used, even better than the original anatase without carbon coating. The crystalliinity of anatase phase was shown to be important factor for the application to whether contaminants in water or gaseous ones even in carbon-coated TiO2 photocatalysts.
Keywords: Carbon coating; Photocatalysts; Methylene blue; NO
Reaction mechanism and kinetics of NO x reduction by methane on In/ZSM-5 under lean conditions by Teuvo Maunula; Juha Ahola; Hideaki Hamada (pp. 13-24).
Indium supported on ZSM-5 was investigated as a promising catalyst for NO x reduction by methane under lean conditions. Indium on protonated H-ZSM-5 showed a higher activity in dry conditions while indium on unprotonated ZSM-5 with a high loading of 7.3% prepared by ion exchange had a higher activity in the presence of 8% water. NO2 in feed promoted the methane oxidation and NO x reduction. In situ FTIR analysis revealed on In/ZSM-5 the presence of inhibiting compounds at lower temperatures and many carbonaceous surface compounds. In the reaction initiation conditions, the surface coverage of nitrogen containing carbonaceous compounds and any adsorbed species were low. It is proposed that the formation of NO2, partially oxidized methane surface derivatives and actual surface reductants containing NC or NH bondings are crucial in NO reduction. Intrazeolitic InO+ was proposed to be the active catalytic site in NO reduction. Free In2O3, detected by XRD and XPS, has possibly a promoting effect on the reactions. A micro kinetic model, including the surface intermediates, was derived for an In/ZSM-5 catalyst by the NOCH4O2 experiments where the reactant concentrations, space velocity and temperature were varied. The adsorbed H2NCO intermediate, formed in the reaction between NO2 and partially oxidized methane, was proposed to act as an actual NO reductant in the reaction mechanism and kinetic equations. The model was able to follow measured responses and predict the dynamic performance in NOCH4O2 reactions quantitatively in usual steady state lean conditions. Adsorbed oxygen and NO2 were simulated to exist with higher coverage on active sites in reaction conditions. Gas and adsorbed compounds were simulated as a function of reactor length in different unmeasured conditions, which simulations can be used as a tool in catalyst reactor design.
Keywords: Nitrogen oxides; Selective catalytic reduction; Methane; Indium; ZSM-5
Simultaneous removal of NO x and soot on Pt–Ba/Al2O3 NSR catalysts by Lidia Castoldi; Roberto Matarrese; Luca Lietti; Pio Forzatti (pp. 25-34).
The potentiality of a typical Pt–Ba/Al2O3 NSR catalyst in the simultaneous removal of particulate matter (soot) and NO x is investigated in this work, and compared with that of a Pt/Al2O3 sample. The behaviour of the catalyst in the soot combustion and NO x removal has been separately analyzed by means of temperature programmed oxidation (TPO) experiments, isothermal combustions and transient response method (TRM), respectively. The results show that in presence of only oxygen, soot oxidation occurs slowly even at a temperature as high as 400°C. On the other hand, the presence of NO greatly increases the rate of soot conversion, which becomes significant at 350°C. The capability of the Pt–Ba/Al2O3 and Pt/Al2O3 catalysts to accomplish the removal of NO x in the absence and in the presence of soot was investigated under cycling conditions, i.e. alternating lean-rich phases according to the typical NSR strategy. It has been found that the Pt–Ba/Al2O3 sample is able to simultaneously remove both soot and NO x, as opposite to the Pt/Al2O3 catalyst which effectively performs the soot oxidation but is not able to remove gas phase NO x to a significant extent. The presence of soot does not significantly affect the activity in the NO x reduction of the Pt–Ba/Al2O3 catalyst. The comparable level of activity in the soot combustion which is observed between the Pt/Al2O3 and the Pt–Ba/Al2O3 sample in spite of the fact that the ternary sample accomplishes the removal of NO x in the gas phase has been tentatively ascribed to specific oxidizing properties of the stored nitrate species.
Keywords: Combined soot and NO; x; removal; Pt–Ba/Al; 2; O; 3; catalysts; Nitrogen storage-reduction catalysts; Catalytic soot oxidation
Importance of the lifetime of oxygen species generated by N2O decomposition for hydrocarbon activation over Fe-silicalite by Evgenii V. Kondratenko; Javier Pérez-Ramírez (pp. 35-41).
Transient isotopic studies in the Temporal Analysis of Products (TAP) reactor evidenced a clear mechanistic regularity between methane and propane for N2O reduction over Fe-silicalite in the temperature range of 623–773K. The lifetime of the oxygen species generated by N2O decomposition on extraframework iron sites was found to be crucial for alkane oxidation. When N2O and CH4 or C3H8 were pulsed together over Fe-silicalite, oxygen species deposited on iron sites effectively activated the hydrocarbon. However, these oxygen species become inactive for alkane oxidation if the pulses of N2O and the alkane were separated by more than 0.1s. Transient studies have indicated that C3H8 is more efficient for N2O reduction than CH4, as expected from the facilitated activation of the CH bond upon increasing the carbon number in alkanes. The performance derived from the TAP reactor agrees well with experiments under flow conditions at ambient pressure.
Keywords: N; 2; O decomposition; N; 2; O reduction; Iron silicalite; Oxygen species; C; 3; H; 8; CH; 4; Mechanism; TAP reactor
Characteristics of copper ion exchanged mordenite catalyst deactivated by HCl for the reduction of NO x with NH3 by Jin Woo Choung; In-Sik Nam (pp. 42-50).
The deactivation characteristics of copper ion exchanged mordenite type zeolite catalyst (CuHM) by HCl for the reduction of NO x, particularly from an incinerator with NH3, have been investigated over a fixed bed flow reactor system. X-ray absorption near edge spectroscopy (XANES), extended X-ray absorption fine structure (EXAFS), synchrotron radiation X-ray diffraction (SR-XRD), X-ray photoelectron spectroscopy (XPS), and temperature programmed desorption (TPD) have been employed to illustrate the deactivation mechanism of CuHM by HCl due to the formation of the deactivation precursor through the reaction between HCl and Cu on the catalyst surface. Cu2Cl(OH)3 has been identified as the precursor for the present reaction system and can also be converted to CuCl2·2H2O during the course of the reaction, particularly at high reaction temperature. XANES and EXAFS analyses reveal that the oxidation state of Cu ion on CuHM catalyst is mainly divalent, regardless of the degree of the catalyst deactivation. However, XPS study provides evidence for an increase of the content of Cu(I) ion on the surface of the catalyst deactivated at 450°C for 110h. Moreover, CuCl2·2H2O that forms on the catalyst surface during the course of the reaction evaporates at a reaction temperature higher than 350°C. It eventually converts to CuCl and then it may evaporate to the bulk gas stream and/or introduce a copper ion onto the zeolite surface again through solid-state ion exchange.
Keywords: Selective catalytic reduction of NO; x; Deactivation of CuHM by HCl; Cu content; XANES; EXAFS; XPS; SR-XRD; TPD
Influence of manganese oxide on the activity of Pt/Al2O3 catalyst for CO and n-hexane oxidation by B. Grbic; N. Radic; B. Markovic; P. Stefanov; D. Stoychev; Ts. Marinova (pp. 51-56).
The influence of low loadings of MnO x on the catalytic activity for n-hexene and CO oxidation over highly dispersed Pt on alumina catalysts has been investigated. The applied deposition–precipitation method allows Mn to be deposited on the Pt containing egg-shell volume. The catalyst samples were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and selective CO chemisorption. Platinum influences the dispersion of deposited MnO x. The dispersion of the MnO x phase is higher on Pt containing samples than on Al2O3. The Pt decoration by Mn is reflected by a low CO uptake and the Pt oxidation state (Pt2+). The addition of Mn lowers the catalytic activity for CO oxidation. This is attributed to a change of the Pt sites such that adsorption of CO is less favorable. The activity of the catalysts in the oxidation of n-hexane showed a significant improvement with addition of MnO x. A light-off shift by about 40°C was observed. This improvement is attributed to the formation of Mn–Pt oxide like species that primarily weakens the Pt–O bond.
Keywords: Pt/Al; 2; O; 3; catalyst; Manganese oxide; Deep oxidation; n; -Hexane; CO
Enhanced photocatalytic disinfection of indoor air by Amit Vohra; D.Y. Goswami; D.A. Deshpande; S.S. Block (pp. 57-65).
A silver ion doped TiO2 based photocatalyst, with improved destruction of airborne microbes, has been developed. The performance of the silver ion doped photocatalyst is demonstrated using a catalyst coated filter in a recirculating air experimental facility. Bacillus cereus, Staphylococcus aureus, Escherichia coli, Aspergillus niger, and MS2 Bacteriophage have been used as indexes to demonstrate the high disinfection efficiency of the enhanced photocatalysis process. The microbial destruction performance of the enhanced photocatalyst is found to be an order of magnitude higher than that of a conventional TiO2 photocatalyst. The process of enhanced photocatalysis can thus be used effectively against high concentrations of airborne microorganisms, making it an attractive option as a defense against bio-terrorism.
Keywords: Photocatalysis; Disinfection; Indoor air; Airborne microorganisms; Silver ions
Increasing the value of dilute acetic acid streams through esterification by V. Ragaini; C.L. Bianchi; C. Pirola; G. Carvoli (pp. 66-71).
Dilute acetic acid (AA) streams (4.5–15%, w/w) were used in an extractive esterification with 2-ethyl-1-hexanol, exploiting the different solubilities of acetic acid and acetic ester in water. The main advantage of the process is the simultaneous water purification and production of an ester having a good commercial value. The new method proposed has the purposes to save the costs arising from the treatment of the waste water and utilize in chemical synthesis the acetic acid otherwise eliminated. The performed reaction is a three-phase system which Amberlyst 15 was used as acid catalyst in. It was clearly demonstrated that the reaction takes place in the organic phase and not in the aqueous one and a conversion of about 70% can be reached. A simplified mathematical model was also proposed.
Keywords: Acetic acid recovery; Water purification; Esterification reaction; Mathematical model; Extractive esterification
MnO x-CeO2 mixed oxides for the low-temperature oxidation of diesel soot by Kirill Tikhomirov; Oliver Kröcher; Martin Elsener; Alexander Wokaun (pp. 72-78).
TG-FTIR and flow reactor experiments were performed to study soot oxidation on MnO x-CeO2 mixed oxide catalysts in model diesel exhaust gas (10% O2, 5% H2O, 1000ppm NO, balance N2). The ignition temperature in TG-FTIR experiments for a 1:20 mixture of soot and catalyst was found to be ∼280°C, which is significantly lower than for the individual oxides.It was found that NO is oxidized over the catalyst to NO2, which is stored on the catalyst as nitrate at low temperatures. At higher temperatures the nitrates decompose, releasing NO2 to the gas phase which acts as the oxidizing agent for soot. The nitrate storage capacity of MnO x-CeO2 is three to five times higher than that of the individual oxides resulting in a major contribution of the released NO2 to the soot oxidation process. This explains the strong synergistic effect of manganese and cerium in the mixed oxide on the soot oxidation.Adding SO2 to the model gas resulted in a deactivation of the catalyst, which is traced to the loss of the NO oxidation activity. The sulphates could be decomposed by heating the catalyst under reducing as well as oxidizing conditions. However, the initial activity of the catalyst could not be restored.
Keywords: Diesel soot oxidation; Manganese cerium mixed oxides; NO; x; storage catalyst
Photocatalytic oxidation of gas-phase methyl tert-butyl ether and tert-butyl alcohol by Sergei Preis; John L. Falconer; Raquel del Prado Asensio; Nuria Capdet Santiago; Anna Kachina; Juha Kallas (pp. 79-87).
Adsorbed methyl tert-butyl ether (MTBE) and tert-butyl alcohol (TBA) were oxidized at room temperature by transient photocatalytic oxidation (PCO) on TiO2 and Pt-TiO2 catalysts; carbon dioxide, water, and acetone were the main gas-phase products. TBA oxidized faster than MTBE. Reaction products such as formic acid, which remained on the surface, were characterized by temperature-programmed desorption (TPD) and oxidation (TPO). The TiO2 catalyst was not a good oxidation catalyst in the dark, but both TBA and MTBE decomposed to form 2-methyl-1-propene (2-MP) during TPD, and MTBE decomposed much faster. The Pt/TiO2 catalysts had higher complete oxidation rates during PCO. Continuous-flow PCO of gas-phase MTBE and TBA was also carried out at 333–453K on TiO2, and carbon dioxide, water, and acetone formed. Product distributions differed during transient and continuous-flow PCO because reaction products were displaced from the surface by reactants or other products. Continuous PCO of TBA proceeded faster in humid air than dry air, but MTBE oxidation was less sensitive to humidity. The TiO2 catalyst was stable during continuous PCO of MTBE, TBA, and acetone above 373K, but gradually lost activity below 373K; the catalyst could be regenerated by UV irradiation in the absence of gas-phase VOCs.
Keywords: Photocatalytic oxidation; Methyl; tert; -butyl ether; tert; -Butyl alcohol; Titanium dioxide
An investigation of NO x storage on Pt–BaO–Al2O3 by G. Zhou; T. Luo; R.J. Gorte (pp. 88-95).
A series of samples containing 5 or 20wt% BaO on γ-Al2O3 with different loadings of Pt were prepared and examined for their NO2 adsorption properties using temperature programmed desorption (TPD), temperature programmed reduction (TPR) and X-ray diffraction (XRD). For calcination at 873K or above, BaO/Al2O3 formed BaAl2O4. While carbonates were found to be unstable on the aluminate phase, NO2 reacted with the aluminate to form bulk Ba(NO3)2 and Al2O3, even at room temperature. With BaO/Al2O3, reaction to form the nitrate required slightly higher temperatures because of the need to displace CO2; however, pulsing NO2 over pure Ba(CO3) showed rapid reaction to form CO2 and NO in the gas phase, along with Ba(NO3)2, at 573K. The decomposition temperature for Ba(NO3)2 shifted by more than 100° when TPD was carried out in vacuum rather than in a carrier gas, showing that re-equilibration with the gas phase is important in the decomposition process. The addition of Pt had a minimal effect on the thermal stability of the nitrates but was essential for the reduction of the nitrate in H2. Since a relatively small amount of Pt was sufficient to cause the complete reduction of the Ba(NO3)2 phase at temperatures below 400K, it appears that the nitrates must be extremely mobile within the Ba-containing phase. Finally, trapping studies of NO2 at 573K, with or without 10% CO2 in the gas phase, showed no measurable difference between BaO/Al2O3 and BaAl2O4, with or without CO2.
Keywords: NO; x; Barium aluminate; Barium oxide; Barium carbonate; Temperature programmed desorption
Microemulsion-prepared Ni catalysts supported on cerium-lanthanum oxide for the selective catalytic oxidation of ammonia in gasified biomass by S. Nassos; E. Elm Svensson; M. Nilsson; M. Boutonnet; S. Järås (pp. 96-102).
Nickel (Ni) catalysts supported on cerium-lanthanum oxide were prepared by two different preparation techniques and have been tested in the temperature range of 500–750°C for selective catalytic oxidation of ammonia to nitrogen in gasified biomass. The two different catalyst preparation methods used are the conventional and the microemulsion (water-in-oil). The effect on catalytic activity of different Ni loadings was also tested in combination with the preparation method.Catalyst characterisation was focused on BET and XRD analysis. Cordierite monoliths were used in a tubular quartz reactor for the purpose of the activity tests. For simulating the gasified biomass fuel, 400ppm NH3 was added to the fuel. Water was also present during the activity tests, which were carried out at fuel rich conditions. Results showed that the microemulsion-prepared catalysts obtained higher performance than the conventional ones, with the best catalyst reaching 98% ammonia conversion and 99% nitrogen selectivity at 750°C. The more the Ni supported on the catalyst, the higher the catalytic activity. Constant conversion and negligible carbon deposition were two other important characteristics for the microemulsion-prepared catalysts.
Keywords: Microemulsion; Selective catalytic oxidation; Gasified biomass; Ammonia conversion; Nitrogen selectivity
NO reduction by hydrocarbons and oxygenated compounds in O2 excess over a Pt/Al2O3 catalyst by Emmanuel Joubert; Xavier Courtois; Patrice Marecot; Daniel Duprez (pp. 103-110).
A 1% Pt/Al2O3 catalyst was prepared by wet impregnation of a δ-alumina with an aqueous solution of Pt(NH3)2(NO2)2. Metal particle sizes were centered around 20nm. Twenty-seven reducers (12 hydrocarbons and 15 oxygenated compounds) were tested in NO reduction in O2 excess while keeping the same experimental conditions (inlet gas: 5% O2 and 5% H2O; space velocity: 14,100h−1; same temperature program from 150 to 600°C). To compare the reducers between them, two criteria were used: (i) the catalyst behaviour at the maximum NO x conversion, and (ii) the efficiencies in NO x conversion and N2, N2O, NO2 production taking into account the temperature integrated performances of the reducers between 150 and 600°C. Among the hydrocarbons tested, cyclic C6 compounds show the highest efficiency in NO x conversion while, among the oxygenated compounds, diols and particularly butane-diols are the most efficient reducers. However, the selectivity to N2 is extremely dependent on the structure of the molecule. For instance, cyclohexadiene is very selective to N2 while aromatics are not. Moreover, the position of the two OH groups in diols can largely control the selectivity: butane-1,3-diol is very selective to N2 while butane-1,4-diol produces a great amount of N2O. The best ten reducers in terms of NO x reduction efficiency are: cyclohexadiene, 292>butane-1,4-diol, 234>benzene, 221>butane-1,3-diol, 212>cyclohexene, 209>propane-1,3-diol, 161>propene, 153≈propan-1-ol, 149>ethanol, 124>propanoic acid, 114. If these data are coupled with a criterion of selectivity, cyclohexadiene, butane-1,3-diol, propan-1-ol, propanoic acid and to a lesser extent ethanol would be the best candidates for the selective NO x reduction.
Keywords: Catalytic NO reduction; Pt/alumina catalyst; Hydrocarbons; C6 hydrocarbons; Cyclohexadiene; Aromatics; Oxygenated compounds; Diols; Butane-1,3-diol; Alcohols; Aldehydes; Ketones; Carboxylic acids
Proton and electron wave-particles in chemical and physical environments by Costas G. Vayenas; Alexandros D. Katsaounis (pp. 111-120).
The energy equations resulting from the dual particle-wave nature of protons, neutrons and/or electrons are used, in conjunction with the necessary relativistic corrections, to obtain an analytical expression for the gravitational constant, G, in terms of h, ɛ, c, and the proton mass mp. The analytically computed value of G=6.676×10−11m3/(kgs2) is in excellent (within 0.04%) agreement with experiment. The stability of nuclei, also of chemical molecules, is analyzed by the same approach and the energies of formation of the He nucleus (−27.1MeV), and the H2 molecule (−4.52eV) are computed analytically with high accuracy, without any typical quantum mechanical treatment. The unification of strong interactions, gravitational and electrostatic forces is also demonstrated and discussed.
Keywords: Wave-particles; Gravitational constant; Nuclei stability
Solar photo-Fenton treatment—Process parameters and process control by W. Gernjak; M. Fuerhacker; P. Fernández-Ibañez; J. Blanco; S. Malato (pp. 121-130).
Photo-Fenton experiments were performed using alachlor as a model compound (initial concentration 100mg/L) in a compound parabolic collector solar pilot-plant. Three process parameters were varied following a central composite design without star points (temperature 20–50°C, iron concentration 2–20mg/L, illuminated volume 11.9–59.5% of total).Under all experimental conditions, complete alachlor degradation, mineralisation of chloride and 85–95% mineralisation of dissolved organic carbon (DOC) was achieved. An increase in temperature, iron concentration and illuminated volume from minimum to maximum value reduced the time required for 80% degradation of initial DOC by approximate factors of 5, 6 and 2, respectively. When process parameter changes were made simultaneously, these factors multiplied each other, resulting in degradation times between 20 and 1250min.Models were designed to predict the time necessary to degrade 50 or 80% of the initial DOC applying response surface methodology (RSM). Another model based on the logistic dose response curve was also designed, which predicted the whole DOC degradation curve over time very well. The three varied process parameters (temperature, iron concentration and illuminated volume) were independent variables in all the models.Mass balances of hydrogen peroxide consumption showed that the same amount of hydrogen peroxide was always needed to degrade a certain amount of DOC regardless of variations in the process parameters within the range applied.Possible applications of the models developed for automatic process control are discussed.
Keywords: Photo-Fenton; Advanced oxidation processes; Wastewater treatment; Solar energy; Response surface methodology
Mechanism and efficiency of atrazine degradation under combined oxidation processes by Claudia L. Bianchi; Carlo Pirola; Vittorio Ragaini; Elena Selli (pp. 131-138).
The mechanism of atrazine degradation in aqueous phase was investigated under sonolysis at 20kHz, ozonation, photolysis at 254nm and photocatalysis in the presence of TiO2, employed either separately or in combination. Ozonation and photocatalysis induced atrazine de-alkylation, followed by slower de-chlorination, while direct photolysis at 254nm produced very efficient de-chlorination. Simultaneous sonolysis had beneficial effects on ozonation and photocatalysis, especially by increasing the rate of photocatalytic de-alkylation, and no effect on the unimolecular photolytic de-chlorination of atrazine. Although complete atrazine mineralization could not be attained, because of the stability of the s-triazine ring toward oxidation, atrazine degradation and overall detoxification, as related to the disappearance of chlorinated by-products, proceeded at the highest rate when photolysis at 254nm was combined with ozonation.
Keywords: Atrazine degradation; Ozonation; UV irradiation; Photocatalysis; Ultrasound
Photoelectrocatalytic reduction of CO2 in LiOH/methanol at metal-modified p-InP electrodes by Satoshi Kaneco; Hideyuki Katsumata; Tohru Suzuki; Kiyohisa Ohta (pp. 139-145).
The photoelectrochemical reduction of CO2 at metal-modified p-InP photoelectrodes was investigated in the LiOH/methanol-based electrolyte. Lead, silver, gold, palladium, copper and nickel were evaluated as deposition metals. With lead, silver, gold and copper-modified p-InP photocathodes, the main products from CO2 were carbon monoxide and formic acid. Maximum current efficiency of carbon monoxide was obtained at silver-modified p-InP photoelectrode ( rf=80.4%). On palladium-deposited p-InP electrode, the reduction product was only carbon monoxide. With nickel-deposited p-InP photoelectrode, hydrocarbons (methane and ethylene) were obtained with low Faradaic efficiencies 0.7% and 0.2%, in addition of the formations of CO and formic acid, respectively. The distribution of reduction products in the photoelectrochemical reduction of CO2 in methanol at metal-modified p-InP photocathodes may be roughly associated with the catalytic property of metallic electrode in the electrochemical CO2 reduction in methanol. This research may contribute to applications in the photochemical conversion and storage of solar energy.
Keywords: Photoelectrochemical reduction of CO; 2; p-Type semiconductor; Metal-modified p-InP; Methanol-based electrolyte; Solar energy conversion
Room temperature oxidation of carbon monoxide over copper oxide catalyst by Unnikrishnan R. Pillai; Sarojini Deevi (pp. 146-151).
Carbon monoxide oxidation has been studied over different oxides of copper as well as a copper oxide sample obtained from precipitation. Room temperature oxidation of carbon monoxide to carbon dioxide has been achieved for the first time over unsupported copper oxide catalyst prepared by a controlled heating of precipitated copper hydroxide after activation of the catalyst in a redox environment. It is found that drying and calcination of the precipitated hydroxide are crucial parameters that affect the catalyst performance dramatically. Experimental results indicate that the active phase is a metastable non-stoichiometric form of copper oxide formed during the treatment of the oxide in a redox environment. This species loses its activity upon exposure to the outside atmosphere due to absorption of moisture. Nevertheless, the activity can be regained by an activation step.
Keywords: Copper oxide; Carbon monoxide oxidation; Precipitation; Room temperature catalyst