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Applied Catalysis B, Environmental (v.103, #3-4)
Selective adsorption of dibenzothiophene by functionalized metal organic framework sorbents by Fan Shi; Maha Hammoud; Levi T. Thompson (pp. 261-265).
Display Omitted► Synthesized MOF-5 supported adsorbents while preserving high surface areas. ► Adsorbents possessed high capacities and selectivities for organosulfur compounds. ► Could be developed for military and commercial desulfurization applications.The adsorption of organosulfur compounds directly from liquid fuels has potential advantages over hydrodesulfurization processes including higher efficiencies and lower costs. A series of sorbents was prepared by decomposing Mo(CO)6 onto MOF-5, and evaluated for the selective adsorption of dibenzothiophene from solutions containing i-octane, naphthalene and/or benzene. The resulting materials had Mo loadings up to 20wt%, surface areas in excess of 1800m2/g and pore size distributions that were very similar to those for the parent MOF-5. Other than features for MOF-5, there was no evidence of crystalline domains larger than 50nm in the X-ray diffraction patterns, although, Mo(CO)6 typically decomposes into Mo carbide and/or oxycarbide species under the conditions employed. These materials possessed strong affinities for the adsorption of dibenzothiophene in the absence and presence of the types of aromatic compounds typically found in transportation fuels. Sulfur uptakes at breakthrough approached 0.5mmolS/g which corresponded to surface coverages of ∼4%. With further development, these materials could be used to remove sulfur from gasoline, diesel and military logistics fuels.
Keywords: Adsorptive desulfurization; Mo carbide functionalized MOF-5; Dibenzothiophene
Amino-functionalized and acid treated multi-walled carbon nanotubes as supports for electrochemical oxidation of formic acid by Sankaran Murugesan; Kirby Myers; Vaidyanathan (Ravi) Subramanian (pp. 266-274).
Schematic representation of a two-step functionalization process performed over MWNTs. The first step involves a treatment of the MWNTs using a mixed acid (TMWNTs). The second step involves treatment of the TMWNTs using an amine (TAMWNTs). A direct one-step treatment of the MWNT using amines to form AMWNT is also shown.Display Omitted► A simple two-step functionalization of MWNT. ► Very efficient utilization of Pt over functionalized MWNT. ► Improved formic acid electro-oxidation compared to other supports.We report a simple two-step process to functionalize multi-walled carbon nanotubes, first using mixed acid treatment and then an amine treatment. The treated nanotubes have been characterized using thermo gravimetric analysis and Fourier transform infrared spectroscopy. The treated multi-walled carbon nanotubes can be used as a support for Pt electrodeposition. Potentiodynamic scans in acidified chloroplatinic acid solution result in the formation of polycrystalline Pt deposits on the treated multi-walled carbon nanotubes. Field emission-scanning electron microscopy and high resolution transmission electron microscopy have been used to further analyze the Pt deposits. The Pt deposits are well dispersed over the functionalized supports. Particularly, amino functionalized and acid treated multi-walled carbon nanotubes shows the smallest Pt size of about 10nm with a predominantly Pt (111) basal plane orientation. CO oxidation studies show that the Pt deposits on all forms of multi-walled carbon nanotubes (untreated and treated) demonstrates higher electrochemical activity than traditional Vulcan carbon support. Formic acid oxidation was used as a probe reaction to evaluate electrocatalytic activity. Pt utilization, defined as, amount of active Pt sites per unit mass of Pt deposited, is highest when amino functionalize multi-walled carbon nanotubes is used as a support.
Keywords: Multi-walled carbon nanotubes; Functionalization; Platinum; Formic acid; Electrocatalytic activity
Catalytic oxidation of toluene over binary mixtures of copper, manganese and cerium oxides supported on γ-Al2O3 by Saleh M. Saqer; Dimitris I. Kondarides; Xenophon E. Verykios (pp. 275-286).
Display Omitted► Combustion activity of mixed oxide catalysts depends on M xO y type, loading and composition. ► Activity of optimized catalysts is higher than that of single-component counterparts. ► Enhancement of activity is due to the increased reducibility of active M xO y phases.The catalytic oxidation of toluene has been investigated over binary mixtures of copper, manganese and cerium oxides supported on high surface area γ-Al2O3 in comparison with the corresponding single metal oxide components. Catalysts were synthesized with the impregnation method and were characterized with respect to their specific surface area (BET method), phase composition and mean crystallite size (XRD technique), reducibility (H2-TPR) and adsorption/desorption characteristics toward toluene (TPD followed by TPO). Results obtained using a feed composition consisting of 1000ppm toluene in air showed that the catalytic performance of mixed oxide catalysts can be improved significantly by proper selection of metal oxide (M xO y) loading and composition. The intrinsic activity of optimized catalysts, measured under differential reaction conditions, was found to be significantly higher compared to that of their single-component counterparts. This has been attributed to the better dispersion of the active M xO y phases, their increased reducibility (reactivity of surface oxygen), and their lower tendency to form coke deposits under reaction conditions. Addition of a second VOC (propane) or water vapor in the feed affected differently the activity of optimized-mixed oxide catalysts. As a general trend, inhibition by the presence of propane was more pronounced for CeO2-containing samples whereas the presence of H2O affected mainly the CuO x-containing catalysts. It is concluded that the VOC oxidation activity of Al2O3-supported mixed oxide catalysts is determined by the reducibility of the dispersed active phases, which may be controlled by proper selection of M xO y nature, loading and composition.
Keywords: Toluene; VOC; Metal oxide; Manganese oxide; Copper oxide; Cerium oxide; Total oxidation; TPR; TPD; TPO
The effect of microwave operation parameters on the electrochemical performance of Pt/C catalysts by Shuqin Song; Jinchao Liu; Jianying Shi; Hong Liu; Vasiliki Maragou; Yi Wang; Panagiotis Tsiakaras (pp. 287-293).
Display Omitted► Higher heating efficiency of pulse mode of microwave irradiation vs continuous mode. ► Suitable amount of carbon black into ethylene glycol accelerates heating process. ► Irradiation time and operation mode can affect significantly Pt/C performance. ► Pt/C via pulse microwave mode presents higher activity for alcohol electrooxidation.In the present work, the effect of the microwave operation parameters on the heating behaviour of ethylene glycol (EG) solution and thereafter on the physicochemical and electrochemical properties of Pt/C catalysts have been investigated. It was found that the heating efficiency of the pulse mode (PM) of microwave irradiation is higher than that of the continuous mode (CM). The addition of suitable amount of carbon black into EG system can accelerate the heating process of EG solution, while excessive carbon black decreases the heating rate of EG solution. Moreover, the irradiation time and operation mode can significantly affect the performance of Pt/C catalysts. It was found that Pt/C catalyst prepared in the pulse microwave mode of 10s-ON/10s-OFF for 5 pulses, showed the best electrocatalytic activity towards methanol and ethanol electrooxidation with an electrochemical surface area of 111.7m2g−1 and a peak current density of methanol and ethanol electro-oxidation of 20.9mAcm−2 and 26.7mAcm−2, respectively.
Keywords: Microwave heating; Continuous microwave; Pulse microwave; Carbon supported Pt catalyst; Alcohol electro-oxidation
Photocatalytic degradation of emerging contaminants in municipal wastewater treatment plant effluents using immobilized TiO2 in a solar pilot plant by N. Miranda-García; S. Suárez; B. Sánchez; J.M. Coronado; S. Malato; M. Ignacio Maldonado (pp. 294-301).
Display Omitted► Development of a new sol to cover a borosilcate glass spheres. ► Coupling the new catalyst in a CPC reactor. ► Application of this system in treatment of emerging contaminants present in urban wastewater.This article reports on degradation using TiO2 immobilized on glass spheres of 15 emerging contaminants (ECs) at low concentrations in simulated and real Municipal Wastewater Treatment Plant (MWTP) effluents. A sol containing titanium isopropoxide, commercial P25 and polyethylene glycol (PEG) was prepared, and a layer of the photoactive precursor was immobilized on glass spheres by dip-coating. The raw materials and the xerogels were characterized by N2 adsorption/desorption, XRD and TGA-DTA. The xerogel showed the TiO2 anatase, rutile and brookite crystal phases characteristic of the reference materials. The diffraction pattern showed no modification of the crystal size from incorporation of the PEG. Two different TiO2 anatase crystal sizes were identified, which was attributed to the different TiO2 precursors used in the synthesis route. Degradation of the emerging contaminants (acetaminophen, antipyrine, atrazine, carbamazepine, diclofenac, flumequine, hydroxybiphenyl, ibuprofen, isoproturon, ketorolac, ofloxacin, progesterone, sulfamethoxazole and triclosan), at an initial concentration of 100μgL−1 each was determined by ultra-performance liquid chromatography (UPLC-UV) and mineralization was monitored by measuring the dissolved organic carbon (DOC). The experiments were performed in a pilot compound parabolic collector (CPC) solar plant at the Plataforma Solar of Almeria (Spain). 85% of the compounds were degraded within 120min of illumination time depending on the water. The results show the potential application of this technology as a good alternative to suspension systems for the treatment of polluted water.
Keywords: Emerging contaminants; Immobilized TiO; 2; PEG; Real wastewater; Solar photocatalysis; TiO; 2; sol
Ethanol dehydration to ethylene on acid carbon catalysts by J. Bedia; R. Barrionuevo; J. Rodríguez-Mirasol; T. Cordero (pp. 302-310).
Display Omitted► Gas phase ethanol dehydration to ethylene over acid carbon catalysts has been studied. ► The catalysts were obtained by chemical activation of olive stone waste with H3PO4. ► The presence of oxygen increases the ethanol conversion and avoids deactivation. ► Conversion and selectivity remain constant when water vapor is added to the reactor.Gas phase ethanol decomposition over acid carbon catalysts has been studied. The acid carbon catalysts were obtained by chemical activation of olive stone with phosphoric acid, without needing additional oxidative treatments. Different impregnation ratios, between 0.5 and 2, and activation temperatures, in the interval 400–800°C, were used for the preparation of the carbons. Impregnation ratio shows more influence in the porous structure development than that observed for the activation temperature. XPS analyses reveal that the amount of stable phosphorus remaining over the carbon surface after the washing process increases with both activation temperature and impregnation ratio. FTIR spectra confirm the presence of surface phosphorus in form of phosphate and polyphosphate groups. XPS analyses suggest the existence of C–O–PO3 and C–PO3 surface groups that present acid character and of C3PO and C3P type. The increase of the activation temperature results in an increase in the proportion of C3PO and C3P surface groups. The catalytic decomposition of ethanol over the activated carbons yields mainly dehydration products, mostly ethylene with lower amounts of diethyl ether. In absence of oxygen the catalysts suffer a progressive deactivation. However, the presence of oxygen produces a significant increase of the ethanol conversion without any significant change in the selectivity of reaction and avoids deactivation of the catalysts under the operation conditions studied. The results suggest that oxygen inhibits coke deposition on the acid active sites. Ethanol conversion remains practically constant and selectivity does not change when water vapor is added to the reactor feed in concentration similar to that of bio-ethanol.
Keywords: Biorefinery; Bio-ethanol; Dehydration; Ethylene; Acid activated carbon; Deactivation
Self-assembly of HPW on Pt/C nanoparticles with enhanced electrocatalysis activity for fuel cell applications by Deli Wang; Shanfu Lu; Yan Xiang; San Ping Jiang (pp. 311-317).
Display Omitted► Water-soluble HPW was immobilized on the surface of Pt/C nanoparticles by self-assemble technique. ► The assembled HPW has shown high stability on Pt/C. ► The HPW assembled Pt/C catalyst has shown higher catalyst utilization efficiency and electrocatalytic activities than pristine Pt/C.We report here a novel method to immobilize water soluble tungstophosphoric acid (H3PW12O40, HPW) on Pt/C nanoparticles via the electrostatic interaction between the negatively charged HPW and the positively charged functional groups of chitosan which has been attached to Pt/C nanoparticles to provide positively charged sites for the self-assembly of HPW. The HPW assembled Pt/C catalysts (donated as Pt/C-chitosan-HPW) were characterized by XRD, FTIR, TGA, zeta potential, and X-ray photoelectron spectroscopy (XPS). The results indicate that HPW assembled on chitosan-functionalized Pt/C is very stable and Pt/C-chitosan-HPW catalyst has a higher utilization efficiency as compared to that of pristine Pt/C catalyst. Electrochemical activity of Pt/C-chitosan-HPW catalysts for methanol oxidation and oxygen reduction reaction (ORR) is significantly higher than that of Pt/C catalysts without assembled HPW. The enhanced electrocatalytic activities of HPW assembled Pt/C catalysts are most likely due to the synergistic effect between assembled HPW and Pt/C nanoparticles and the presence of HPW leads to a downward shift in the d-band center of Pt catalyst and facilitates the oxidative removal of COads poisoning species for methanol oxidation and desorption of Oads species for ORR on Pt catalysts.
Keywords: Tungstophosphoric acid; Electrocatalysis; Fuel cells; Immobilization
Effect of additional B-site transition metal doping on oxygen transport and activation characteristics in La0.6Sr0.4(Co0.18Fe0.72X0.1)O3− δ (where X=Zn, Ni or Cu) perovskite oxides by Nandita Lakshminarayanan; Hyunkyu Choi; John N. Kuhn; Umit S. Ozkan (pp. 318-325).
Display Omitted► Improved oxygen vacancy generation with B-site doping in LSCF perovskites. ► Characterization of surface properties with methanol as a probe molecule. ► Oxygen activation studied by methane oxidation and CO2 TPO. ► B-site substitution with Zn improves oxygen activation and mobility.The bulk structure, surface characteristics and catalytic properties of perovskite-type oxides with the formula La0.6Sr0.4(Co0.18Fe0.72X0.1)O3− δ with X=Zn, Ni and Cu have been investigated. With additional B-site doping with divalent cations, the oxygen vacancy generation properties were significantly enhanced, while still maintaining a stable perovskite structure. The Zn-doped sample showed the best performance and was further characterized for surface structure and properties. CO2 TPD and methane oxidation experiments were conducted to gauge the oxygen activation and oxygen mobility and the Zn-doped catalyst showed improved performance over the baseline La0.6Sr0.4Co0.2Fe0.8O3− δ catalyst, making it a potential SOFC cathode catalyst.
Keywords: Perovskite-type mixed conductor; Solid oxide fuel cell cathode; Divalent doping; Methanol Chemisorption
Effect of B and Sn on Ni catalysts supported on pure- and on WO3/MoO3-modified zirconias for direct CH4 conversion to H2 by Ruth L. Martins; Maria. A.S. Baldanza; André L. Alberton; Sonia M.R. Vasconcelos; Silvia F. Moya; Martin Schmal (pp. 326-335).
Display Omitted► Hydrogen on Ni catalysts supported on pure or WO3/MoO3-modified zirconias. ► Ni–B and Ni–Sn bimetallic catalysts are different after exposed to methane at 773K. ► All catalysts, except for Ni–Sn, after 8h of methane exposure concentrated carbon filaments. ► MoO3 and WO3 modified zirconias led to different morphologies of graphite. ► Sn increased Ni dispersion and diminishing Ni ensemble inhibiting carbon deposition.Methane cracking for hydrogen production was studied over monometallic/bimetallic Ni catalysts supported on pure or WO3/MoO3-modified zirconias. The catalysts were reduced easily with methane at 773K, indicating that regeneration studies can be performed without using hydrogen. Ni–B and Ni–Sn bimetallic catalysts presented different behaviors when exposed to methane at 773K. The former, because of its low thermal stability, behaved as a well dispersed phase with small nickel crystallites, while the latter behaved as a bimetallic catalyst. For all catalysts, except for Ni–Sn, the metallic particles, after 8h of methane exposure at 773K, were mostly concentrated at the tip of the carbon filaments, whereas zirconia surface was found to be free from these filaments. Additionally, our results suggest that the presence of Sn does not improve catalytic performance for hydrogen production by methane cracking, considering the catalytic systems under study. Rather, adding Sn seems to inhibit access to Ni sites, which are necessary for the C–H bond activation of methane and then for the nucleation of carbon species.
Keywords: Hydrogen production; Methane cracking; Ni/Ni-alloy catalysts; Carbon nanofibers
Electrochemical promotion of the SO2 oxidation over thin Pt films interfaced with YSZ in a monolithic electropromoted reactor by A. Hammad; S. Souentie; E.I. Papaioannou; S. Balomenou; D. Tsiplakides; J.C. Figueroa; C. Cavalca; C.J. Pereira (pp. 336-342).
Display Omitted► The effect of electrochemical promotion of catalysis on the SO2 oxidation was studied. ► Pt catalyst layers deposited on YSZ were used in a monolithic electropromoted reactor. ► Positive potential application caused an increase of up to 200% in the catalytic rate. ► Faradaic efficiency values up to 30 were obtained under HSV as high as 3×104h−1.The effect of electrochemical promotion of catalysis on the SO2 oxidation reaction was investigated over thin (∼40nm) Pt catalyst electrodes interfaced with YSZ, in a monolithic electrochemically promoted (MEP) reactor equipped with five or twenty-two electrocatalytic plates. A mildly oxidizing gas mixture was used at temperatures from 330 to 370°C and flowrates between 1 and 30Lmin−1.It was found that positive potential application, i.e. O2− supply to catalyst surface, can cause an increase of up to 200% in the catalytic oxidation rate of SO2 with Faradaic efficiency values up to 30 at flowrates as high as 30Lmin−1 which corresponds to 3×104h−1 space velocity or 0.1s residence time.The results show the strong potential of MEP reactors for practical applications of the electrochemical promotion of catalysis (EPOC) effect, in gas treatment units and chemical synthesis and destruction processes.
Keywords: SO; 2; oxidation; EPOC; NEMCA effect; Pt thin films; MEPR; Electropromoted reactors
Influence of support surface basicity and gold particle size on catalytic activity of Au/γ-AlOOH and Au/γ-Al2O3 catalyst in aerobic oxidation of α,ω-diols to lactones by Jie Huang; Ying Wang; Jiaming Zheng; Wei-Lin Dai; Kangnian Fan (pp. 343-350).
Display Omitted► γ-AlOOH and γ-Al2O3 are used as support for the gold-supported catalysts in the green oxidation of diols to lactones. ► The catalytic activity of Au/AlT catalysts is very high, and 1,4-butanediol can be totally consumed in very short time. ► The activities of the as-prepared catalysts are higher than that of Au/TiO2, Au/FeO x and Au/commercial-γ-Al2O3. ► With strong basic sites on the surface, Au/γ-AlOOH shows high activity even though its gold particle size is much larger than Au/γ-Al2O3. ► The small gold particle size and the basicity of the support are all contributable to the excellent activity.Gold catalysts on inert support γ-AlOOH and γ-Al2O3 were used as catalysts for selective aerobic oxidation of α,ω-diols to the corresponding lactones. The support crystal phase and basicity can be adjusted by calcination. Support calcined at below 573K is in the γ-AlOOH phase and when calcined at above 773K it is in the form of γ-Al2O3. There are only weak or medium basic sites on γ-Al2O3, while γ-AlOOH has strong or medium basic sites. Both support surface acidic–basic properties and gold particle size have influence on the activity and selectivity of the catalysts. Highly active catalysts can be obtained on both of the support, and from the characterization results it was found that the strong basic sites of γ-AlOOH were beneficial for the reaction, while selectivity would be sacrificed due to the hydrolysis of the product or further oxidation to acids under basic conditions. By loading gold onto γ-Al2O3, average gold particle size small as 3.8nm can be obtained and it gives higher activity and selectivity than Au/γ-AlOOH.
Keywords: Gold catalyst; Basicity; Particle size; Aluminum oxide; Green oxidation
Tailoring the phase composition and morphology of Bi-doped goethite–hematite nanostructures and their catalytic activity in the degradation of an actual pesticide using a photo-Fenton-like process by Andreja Gajović; Adrián M.T. Silva; Ricardo A. Segundo; Saso Šturm; Boštjan Jančar; Miran Čeh (pp. 351-361).
Display Omitted► Tailoring the iron-based catalysts’ morphology by the addition of Bi to the structure. ► The catalytic activity related to the crystal phases and morphology of the catalysts. ► Homogenous mixture of hematite and BiFeO3 nanoparticles shows the best performance. ► The catalysts were stable in terms of metal leaching under the conditions employed. ► The hydroxyl radicals seem to be produced at the catalyst surface.The influence of adding bismuth on the phase composition and morphology of goethite–hematite nanostructures was investigated with the aim to develop an active and stable heterogeneous catalyst for the degradation of an actual pesticide with the photo-Fenton-like process. The iron-based nanostructures were prepared by the hydrothermal treatment of solutions containing both iron and bismuth salts precipitated at high pH by two different methods: co-precipitation and separate precipitation. The tailoring of the aspect ratio of the goethite nanorods is achieved by varying the bismuth content in the preparation method. An increase of the Bi content in the reaction induced the crystallization of hematite nanoplates, while the addition of 20% of bismuth salt gives a monodispersed, homogenous mixture of hematite and BiFeO3 nanocrystallites.The degradation of an actual pesticide, containing metalaxyl as the active compound, was studied using the prepared nanostructured materials in a photo-Fenton-like process. It was shown that both the morphology and the phase composition have an important role in the catalytic activity. Samples prepared by the hydrothermal treatment after the co-precipitation showed a higher activity than samples prepared by separate precipitation. Among the samples that contain goethite, the elongated goethite nanorods prepared by co-precipitation with 3.5% Bi showed the highest initial activity, while the best results in the degradation of metalaxyl were obtained in the case of the material prepared with 20% of Bi. The studied catalysts were stable with regard to metal leaching under the conditions employed.
Keywords: Goethite; Hematite; Bismuth; HRTEM; Photo-Fenton-like process; Pesticides
Highly active N-doped-CNTs grafted on Fe/C prepared by pyrolysis of dicyandiamide on Fe2O3/C for electrochemical oxygen reduction reaction by Chang Hyuck Choi; Seung Yong Lee; Sung Hyeon Park; Seong Ihl Woo (pp. 362-368).
.Display Omitted► N-doped CNTs grafted on carbon Vulcan are synthesized. ► The catalyst shows high activity towards electro-oxygen reduction reaction (ORR). ► Increasing pyrolysis temperature assists the doping of nitrogen into carbon. ► ORR activity is proportional to the amount of nitrogen doped.Non-noble electro-catalysts were synthesized by pyrolyzing dicyandiamide (DCDA) on carbon supported iron oxide at 700°C, 800°C and 900°C. The effects of pyrolysis temperature on electrochemical properties towards oxygen reduction reaction (ORR) were investigated. After pyrolysis, newly generated carbon arising from DCDA was observed in all the catalysts. Especially at 900°C, carbon nanotubes (CNTs) were grown catalyzed by Fe2O3/C. Pyrolysis of DCDA at higher temperatures increased ORR activity significantly. The catalyst exhibiting the best performance towards ORR was Fe2O3/C pyrolyzed with DCDA at 900°C. EDX and XPS experiments revealed that nitrogen atoms from DCDA were doped into carbon and the amount of doped nitrogen increased with increasing temperature. The reason for high reactivity towards oxygen reduction reaction is due to nitrogen doped CNTs grown on Vulcan carbon support. The reactivity increased as the amount of doped nitrogen increased.
Keywords: CNT-grafted Carbon; Nitrogen doped carbon; Fuel Cell Cathode; Oxygen reduction reaction
Influence of sulfation on iron titanate catalyst for the selective catalytic reduction of NO x with NH3 by Fudong Liu; Kiyotaka Asakura; Hong He; Wenpo Shan; Xiaoyan Shi; Changbin Zhang (pp. 369-377).
Display Omitted► Structure change of sulfated FeTiO x was the main reason for its activity variation. ► The sulfate was mainly formed on iron sites in a chelating bidentate conformation. ► The L–H pathway was cut off due to the inhibition of NO x adsorption by sulfation. ► The E–R pathway could proceed at high temperatures, leading to high SO2 durability. ► FeTiO x can be used without SO2 or with SO2 if reaction temperature exceeds 250°C.Iron titanate catalyst (FeTiO x) is a potential candidate for the substitution of conventional V2O5–WO3 (MoO3)/TiO2 and Fe/Cu-zeolite catalysts for the selective catalytic reduction (SCR) of NO x with NH3 because of its high SCR activity and N2 selectivity in the medium temperature range. Due to the presence of small amount of SO2 in typical diesel exhaust derived from combustion of sulfur-containing fuels, it is very important to investigate the influence of sulfation on SCR activity, catalyst structure and reaction mechanism. After sulfation under the SCR condition, the surface area and pore volume of FeTiO x catalyst decreased to a certain extent due to the formation of sulfate species. According to the characterizations of FeTiO x catalyst using X-ray diffraction, X-ray absorption fine structure spectroscopy, and in situ diffuse reflectance infrared Fourier transform spectroscopy of SO2+O2 treatment, the sulfate species mainly formed on iron sites in a chelating bidentate conformation, resulting in the enhancement of Brønsted acidity and Lewis acid strength simultaneously. NH3 adsorption was greatly enhanced in the high temperature range, while NO x adsorption was severely inhibited due to the stronger acidity of sulfate species. The operation temperature window of the sulfated catalyst shifted ca. 50°C towards high temperature range accordingly. The reaction mechanism study shows that the Langmuir–Hinshelwood reaction pathway was cut off by the sulfation process, resulting in the activity loss at low temperatures; only Eley–Rideal reaction pathway between adsorbed NH3 species and gaseous or weakly adsorbed NO dominated in the SCR reaction, which made this catalyst resistant to SO2 poisoning at relatively high temperatures.
Keywords: Selective catalytic reduction; Iron titanate catalyst; Sulfation; Sulfate species; Langmuir–Hinshelwood reaction pathway; Eley–Rideal reaction pathway
Microwave assisted synthesis of fine chemicals in solvent-free conditions over mesoporous zirconium phosphate by Apurba Sinhamahapatra; Narottam Sutradhar; Biplab Roy; Provas Pal; Hari C. Bajaj; Asit Baran Panda (pp. 378-387).
Display Omitted► Microwave assisted synthesis of mesoporous zirconium phosphate (m-ZrP). ► m-ZrP is an efficient catalyst for fine chemicals under microwave irradiation. ► 98% conversion with 99% selectivity of chalcone was obtained in 10min. ► The developed procedure is convenient, economical and time efficient.Synthesis of various industrially important fine chemicals under microwave irradiation (MWI) in solvent-free conditions over mesoporous zirconium phosphate (m-ZrP) is reported. m-ZrP is synthesized by MWI in basic medium using a precursor solution of zirconium carbonate complex as zirconium source and CTAB as a pore-directing agent. MWI time and MWI power were found to have significant influence on the textural properties of synthesized m-ZrP. Microscopic analyses of the synthesized m-ZrP indicate the presence of worm like pores with spherical morphology. DRIFT analysis of pyridine adsorbed m-ZrP and NH3-TPD measurements indicate the presence of appreciable amount of Brönsted acid sites. Synthesized m-ZrP exhibits high catalytic activity towards Claisen–Schmidt condensation reaction in solvent-free conditions under microwave irradiation. The m-ZrP showed high activity towards other acid catalyzed reactions such as Friedel–Craft benzylation, Pechmann condensation and carbonyl group protection reaction, and also for the synthesis of benzo-xanthenes in solvent-free conditions under MWI. The catalytic activity of m-ZrP is substantially higher than that of conventional layered ZrP. The synthesized catalysts are re-usable for at least five times after regeneration, without losing their catalytic activity significantly.
Keywords: Zirconium phosphate; Mesoporous; Solid acid catalyst; Microwave irradiation; Fine chemicals; Claisen–Schmidt reaction
Preparation of highly dispersed and ultrafine Pd/C catalyst and its electrocatalytic performance for hydrazine electrooxidation by Yan Liang; Yue Zhou; Juan Ma; Jiayue Zhao; Yu Chen; Yawen Tang; Tianhong Lu (pp. 388-396).
Display Omitted► The addition of ethylenediamine–tetramethylene phosphonic acid (EDTMP) can decrease significantly the reduction potential of PdII species and directly translate PdII species in EDTMP–PdII complex into Pd0 in the presence of NaBH4. ► Spherical Pd nanoparticles are highly dispersed on the carbon support in the presence of EDTMP. ► Electrochemical measurements indicated the resulting Pd/C catalyst possessed a significant electrocatalytic effect for hydrazine oxidation under the strong acidic conditions.The highly dispersed and ultrafine carbon supported Pd nanoparticles (Pd/C) catalyst was synthesized by NaBH4 reduction method in the presence of ethylenediamine-tetramethylene phosphonic acid (EDTMP) ligand. The formation of the ultrafine Pd nanoparticles can be attributed to the avoidance of Pd(OH)2 precipitation and the decrease in the reduction potential of PdII species in EDTMP–PdII complex during the preparation of Pd/C catalyst. Electrochemical measurements indicated the resulting Pd/C catalyst possessed a significant electrocatalytic performance for hydrazine oxidation under the strong acidic conditions, indicating that the Pd/C catalyst has potential application in fabrication of acidic direct hydrazine fuel cell.
Keywords: Direct hydrazine fuel cell; Complex; Pd/C catalyst; Hydrazine electrooxidation; Electrocatalytic activity
Characterization of active sites of Pd/Al2O3 model catalysts with low Pd content by luminescence, EPR and ethane hydrogenolysis by Aleksey A. Vedyagin; Alexander M. Volodin; Vladimir O. Stoyanovskii; Ilya V. Mishakov; Dmitrii A. Medvedev; Alexander S. Noskov (pp. 397-403).
Display Omitted► Pd/Al2O3 catalysts in the Pd concentration range of 0.02–1.0wt.% are studied. ► Laser-induced luminescence is used for investigation of the catalysts ► Spin probes for characterization of Pd/Al2O3 active sites are suggested. ► The activity in ethane hydrogenolysis and CO oxidation is studied. ► Surface donor sites are shown to be important for Pd stabilization.Spectroscopic (laser-induced luminescence (LIL) and EPR) and catalytic (ethane hydrogenolysis) techniques were used for characterization of the active sites of Pd/Al2O3 catalysts. These techniques have high sensitivity and make it possible to study the catalysts with Pd concentrations as low as 0.02–0.03wt.%. It was found by EPR using spin probes that the electron donor sites of the support are modified by the deposited palladium. It was found by LIL that the Pd deposition has a substantial effect on the state of hydroxyls on the Al2O3 surface. The obtained results indicate that at Pd concentrations 0.5wt.% or lower supported Pd does not form PdO phase. Instead, it is stabilized in the form of atomically dispersed ion clusters. The possible role of the Al2O3 donor sites in stabilization of such clusters is discussed.
Keywords: Pd catalysts; CO oxidation; Active sites; EPR; Laser induced luminescence
New catalysts for biodiesel additives production by Maciej Trejda; Katarzyna Stawicka; Maria Ziolek (pp. 404-412).
Display Omitted► Niobium species in NbSBA-15 enhance the effectiveness of active centres formation. ► Presence of niobium stabilizes the sulphur containing modifier. ► Niobiosilicate effectively directs the esterification of glycerol towards triacetylglycerol. ► Active phase is not leached during the reaction allowing reuse of the catalysts.Mesoporous silicate and metallosilicate (Al or Nb) materials of SBA-15 type were prepared in the presence of MPTMS, i.e. (3-mercaptopropyl)trimethoxysilane, and hydrogen peroxide. The samples prepared were characterised by different techniques (N2 adsorption/desorption, XRD, XRF, elemental analysis, thermal analysis, FTIR, UV–Vis) and applied as catalysts in glycerol esterification with acetic acid. The impact of different factors such as temperature, glycerol to acetic acid molar ratio, and metal concentration on the course and yield of glycerol esterification was examined. The role of niobium in the formation of sulphonic species was considered and discussed. The most important finding is that niobium source present in the SBA-15 synthesis gel together with MPTMS and H2O2 improves the efficiency of –SH oxidation towards sulphonic species and increases the stability of the modifier (oxidised MPTMS), which results in increased activity and selectivity of the catalysts to triacetylglycerol in esterification of glycerol.
Keywords: Glycerol; Esterification; Niobium; SBA-15; MPTMS
Effect of aging on the NO x storage and regeneration characteristics of fully formulated lean NO x trap catalysts by Yaying Ji; Vencon Easterling; Uschi Graham; Courtney Fisk; Mark Crocker; Jae-Soon Choi (pp. 413-427).
.Display Omitted► This study concerns the effect washcoat composition on LNT aging characteristics. ► Aged catalysts exhibited decreased efficiency for NO x storage and regeneration. ► Aging resulted in segregation of Pt and Ba due to Pt sintering. ► Sulfur accumulation in the washcoat was also observed. ► A high Pt loading was beneficial for catalyst activity after aging.In order to elucidate the effect of washcoat composition on lean NO x trap (LNT) aging characteristics, fully formulated monolithic LNT catalysts containing varying amounts of Pt, Rh and BaO were subjected to accelerated aging on a bench reactor. Subsequent catalyst evaluation revealed that in all cases aging resulted in deterioration of the NO x conversion as a consequence of impaired NO x storage and NO x reduction functions, while increased selectivity to NH3 was observed in the temperature range 250–450°C. Elemental analysis, H2 chemisorption and TEM data revealed two main changes which account for the degradation in LNT performance. First, residual sulfur in the catalysts, associated with the Ba phase, decreased catalyst NO x storage capacity. Second, sintering of the precious metals in the washcoat occurred, resulting in decreased contact between the Pt and Ba, and hence in less efficient NO x spillover from Pt to Ba during NO x adsorption, as well as decreased rates of reductant spillover from Pt to Ba and reverse NO x spillover during catalyst regeneration. For the aged catalysts, halving the Pt loading from 100 to 50g/ft3 was found to result in a significant decrease in overall NO x conversion, while for catalysts with the same 100g/ft3 Pt loading, increasing the relative amount of Pt on the NO x storage components (BaO and La-stabilized CeO2), as opposed to an Al2O3 support material (where it was co-located with Rh), was found to be beneficial. The effect of Rh loading on aged catalyst performance was found to be marginal within the range studied (10–20g/ft3), as was the effect of BaO loading in the range 30–45g/L.
Keywords: Lean NO; x; trap; NO; x; storage; NO; x; reduction; Catalyst aging; Precious metal sintering
Structural characterization and photocatalytic activity of B2O3/ZrO2–TiO2 mesoporous fibers by L.Y. Zhu; X.Q. Wang; G.H. Zhang; Q. Ren; D. Xu (pp. 428-435).
Display Omitted► The B2O3/ZrO2–TiO2 mesoporous fibers using mixed precursor solutions were achieved by dry-spinning method with steam treatments. ► The introduction of B2O3 endows the mesoporous fibers with higher surface area and stronger surface acid sites. ► The macroscopic paper is fabricated by a conventional paper-making process and can be manipulated more easily in practical applications than the forms of powder and film.The formation of B2O3/ZrO2–TiO2 mesoporous fibers using mixed precursor solutions were achieved without any templates by dry-spinning method with novel steam heat-treatment. The samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), N2 adsorption, UV–vis diffuse reflectance and Fourier transformation infrared (FTIR) spectroscopy. Although calcination at 800°C, the mesoporous fibers exhibit higher surface area (∼80m2/g) than pure ZrO2–TiO2 fibers and the only ZrTiO4 phase was observed. The pyridine adsorption on ZrO2–TiO2 sample indicates the presence of stronger surface acid sites. Such properties bring about that the mesoporous oxide system possesses higher efficiency and durable activity stability for photodegradation of methyl orange and phenol than P25 TiO2. In addition, the macroscopic paper form for the resulting materials is more beneficial for practical applications than traditional catalysts forms.
Keywords: B; 2; O; 3; /ZrO; 2; –TiO; 2; Mesoporous fiber; Photocatalytic activity; Fiber paper
Solvothermal preparation of Sn4+ doped anatase TiO2 nanocrystals from peroxo-metal-complex and their photocatalytic activity by Yin Zhao; Jia Liu; Liyi Shi; Shuai Yuan; Jianhui Fang; Zhuyi Wang; Meihong Zhang (pp. 436-443).
Display Omitted► Sn4+ doped anatase TiO2 nanocrystal with dopant level up to 10mol% was prepared. ► Interaction between [M(OH4)(OH2)2]0 unite and reaction solvents determines the crystalline phase. ► Increase in band gap is caused by Sn4+ ions modify anatase electronic structure.The Sn4+ doped anatase TiO2 nanocrystals with various amounts of dopant Sn4+ ions were prepared from peroxo-metal-complex precursor by solvothermal method and characterized by XRD, TEM, HRTEM, XPS, ICP-AES and UV–vis spectrophotometer. The experimental results indicated that the dopant Sn4+ substituted Ti4+ in the lattice of TiO2, which reflected in the lattice expansion in both a- and c-direction and change of the binding energy. All the Sn4+ doped TiO2 nanocrystal samples appeared to be anatase evenly with dopant level up to 10mol%. The effect of dopant Sn4+ ions and reaction solvents on physicochemical properties of the obtained Sn4+ doped anatase TiO2 nanocrystals had been discussed. In addition, the growth mechanism and microstructure evolution of Sn4+ doped anatase TiO2 nanocrystals had been suggested. The photocatalytic activity of the Sn4+ doped anatase TiO2 nanocrystals was tested by the degradation of phenol. Compared with the undoped TiO2 sample, the enhanced photocatalytic activity of the Sn4+ doped anatase TiO2 nanocrystals could be attributed to modification of the optical properties and surface state by doping the optimum concentration of Sn4+ ions.
Keywords: TiO; 2; nanocrystals; Anatase; Solvothermal; Sn; 4+; doping; Photocatalytic activity
Palladium supported on alginate/ionic liquid highly porous monoliths: Application to 4-nitroaniline hydrogenation by C. Jouannin; I. Dez; A.-C. Gaumont; J.-M. Taulemesse; T. Vincent; E. Guibal (pp. 444-452).
SEM-EDX analysis of highly porous monolith supporting Cyphos IL-101 for Pd immobilization and its application to the hydrogenation of nitroaniline.Display Omitted► Synthesis of new Pd catalyst supported on ionic liquid/alginate composite. ► Highly porous monolith catalysts for flow-through application (recirculation mode). ► Application to nitroaniline hydrogenation using formate as the hydrogen donor. ► The flow rate is important for optimizing the catalytic effect. ► SEM–EDX analysis and characterization of supported Pd catalyst.A catalytic system was designed in the form of highly porous monoliths (HPM) in order to be used in a continuous flow column reactor. This catalyst system was composed of an ionic liquid and a transition metal catalyst supported on a biopolymer matrix. Alginate was used as a natural support for immobilizing Cyphos IL-111 (an alkylphosphonium ionic liquid) and for Pd binding. The supported catalyst was efficiently used for the hydrogenation of 4-nitroaniline in the presence of either sodium formate or formic acid as the hydrogen donor. The catalytic HPM was elaborated using a combined procedure of solution icing and freeze-drying. The HPM could be used in a fixed-bed column system under “forced flux” (and recycling mode). The hydrogenation reaction, studied with solution recycling through the HPM, was mainly influenced by the flow rate in the column, the excess of hydrogen donor, the pH of the solution and the type of acid used for pH control (poisoning effect of chloride ions), but was poorly influenced by temperature. The hydrogenation reaction, in the single-pass mode, showed breakthrough curves of higher catalytic activity for HCOONa as hydrogen donor than for HCOOH.
Keywords: Alginate; Phosphonium ionic liquid; Palladium; Hydrogenation; Sodium formate; Formic acid; Catalysis
Continuous syntheses of highly dispersed composite nanocatalysts via simultaneous co-precipitation in supercritical water by Xiaole Weng; Jingyi Zhang; Zhongbiao Wu; Yue Liu; Haiqiang Wang; Jawwad A. Darr (pp. 453-461).
Display Omitted► Homogenous co-precipitation in supercritical water yielded highly dispersed products. ► Much better sintering behaviors for the CHFS made products were obtained. ► The CHFS route yielded very high dispersion and interaction of active species. ► The CHFS made three-way catalysts (TWCs) had excellent catalytic activities.Nanosized Ce0.6Zr0.3La0.05Y0.05O2− δ/γ-Al2O3(CZA) composite supports were prepared in one step using a novel continuous hydrothermal flow synthesis (CHFS) route and a conventional co-precipitation route, followed by 10h heat-treatments at 1000°C in air (to simulate accelerated ageing). HAADF STEM and HR-TEM results indicated that the sample made via CHFS route (i.e., simultaneous co-precipitation in supercritical water, denoted as sc-CZA) had homogenously dispersed CZ particles on alumina support whilst that made via conventional co-precipitation route (denoted as co-CZA sample) had a strong segregation between CZ and alumina. As a consequence of these structural and morphological properties, better sintering behaviors upon accelerated ageing and lesser grain growth of CZ particles were obtained. The sc-CZA sample was then used as supports for syntheses of three-way catalysts (TWCs), in which Pd active species were added via either directly co-precipitating (in the CHFS reactor) or simply wet impregnating Pd2+ onto the support to form composite nanocatalysts. Catalytic measurements revealed that the former had yielded a significantly higher three-way catalytic activity than the latter, attributing to its much higher dispersion of Pd species and stronger interaction between Pd and CZA support.
Keywords: Abbreviations; CHFS; continuous hydrothermal flow synthesis; sc; sample was synthesized via CHFS route; co; sample was synthesized via conventional co-precipitation route; wi; sample was synthesized via wet impregnation route; CZ; Ce; 0.6; Zr; 0.3; La; 0.05; Y; 0.05; O; 2−; δ; CZA; Ce; 0.6; Zr; 0.3; La; 0.05; Y; 0.05; O; 2−; δ; /γ-Al; 2; O; 3; PdCZA; 1.5; wt% Pd/Ce; 0.6; Zr; 0.3; La; 0.05; Y; 0.05; O; 2−; δ; supported on γ-Al; 2; O; 3; CZA1000; CZA sample aged in air at 1000; °C for 10; h to simulate accelerated ageingThree-way catalysts; Co-precipitation; Supercritical water; Nano; Composite catalysts
The influence of synthesis method on the properties of iron contained N doped TiO2 photocatalysts by Peilin Zhang; Shu Yin; Tsugio Sato (pp. 462-469).
Display Omitted► By simply altering the synthesis sequence, Fe status in the final products could be controlled, which showed great influence on property and photocatalytic activity. ► The statuses of Fe in the products were distinguished by XPS analysis, and the observation of Fe–N peak in the sample prepared by 2-step method confirmed the co-doping of Fe into the TiO2− xN y. ► The photocatalytic activities in deNO x experiment revealed the negative effect of Fe co-doping and the positive effect of Fe2O3 coupling, which provided a clue to design high-activity photocatalyst.Fe contained TiO2− xN y were prepared by two different methods to control the status of Fe in the final products. By a 1-step hydrothermal method, Fe and N co-doped TiO2 which showed similar crystalline phases, photo absorption properties and specific surface areas to TiO2− xN y were formed. However, the Fe and N co-doping caused the decrease in photocatalytic activity, due to the formation of lattice vacancy. On the other hand, by a 2-step hydrothermal method, TiO2− xN y/Fe2O3 composites were formed, which showed superior visible light absorption ability to TiO2− xN y regardless the decrease in specific surface areas. The excellent deNO x abilities of TiO2− xN y/Fe2O3 composites may be due to the heterogeneous electron transfer from TiO2− xN y to Fe2O3 to retard the quick recombination of photoinduced electrons and holes.
Keywords: Photocatalyst; Visible-light; Co-doping; Coupling; Iron; Nitrogen; deNO; x
Photoassisted degradation of pentachlorophenol in a simulated soil washing system containing nonionic surfactant Triton X-100 with La–B codoped TiO2 under visible and solar light irradiation by J.W. Liu; R. Han; H.T. Wang; Y. Zhao; Z. Chu; H.Y. Wu (pp. 470-478).
Display Omitted► Novel remediation method to soil washing system containing the chlorinated pollutant. ► Synthesized La–B–TiO2 with high visible light absorption and a modified surface. ► Formed monolayer by hydrophobic interactions between TX-100 and sites on catalyst. ► Remarkable capturing of the target PCP in superficial monolayer on catalyst. ► Efficient decomposition of implanted pollutant under visible and solar light.A novel method to remediate soil washing contaminants was developed through the utilization of La–B codoped TiO2 (La–B–TiO2) nanoparticle in the photocatalysis of a simulated complex system containing hydrophobic pentachlorophenol (PCP) and nonionic surfactant Triton X-100 (TX-100) under visible and solar light irradiation. The photocatalyst synthesized by the sol–gel hydrothermal process exhibited excellent visible light photocatalytic activity and a modified surface. The investigation of the adsorption kinetics and isotherms showed that the distribution of PCP between the catalyst surface and the bulk solution significantly depended on the initial TX-100 concentration ( CTX-0). The formed superficial reactive monolayer at CTX-0 ranging from 0.023 to 0.23mM by the dramatic hydrophobic interactions between the TX-100 moiety and hydrophobic sites on the La–B–TiO2 could remarkably capture the target pollutant. The PCP implanted into the hydrophobic space could be removed effectively in the photocatalysis process induced by visible and solar light, ascribing to the facile availability of PCP to the photo-yielded oxidative radicals on the La–B–TiO2 surface. Additionally, the preferential decomposition of the incorporated PCP, rather than the TX-100, facilitated the removal of the target contaminant and the recycling of the surfactant, which is beneficial to the practical application of this technique under mild and natural light sources.
Keywords: Photocatalysis; Hydrophobic chlorinated pollutant; Hydrophobic adsorption; Modified nanoparticle