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Applied Catalysis A, General (v.409-410, #)
A critical analysis of the experimental evidence for and against a formate mechanism for high activity water-gas shift catalysts by Robbie Burch; Alexandre Goguet; Frédéric C. Meunier (pp. 3-12).
Display Omitted► The contribution of IR-observable formates to the WGS is minor. ► IR-seen formates are main reaction intermediates only for very low activity catalysts. ► Published FTIR data cannot be used to elucidate the main reaction mechanism. ► Operando FTIR work must be analysed using accurate quantitative methods.An in-depth analysis of the evidence for and against a formate-based mechanism for the water-gas shift reaction has shown that with very few exceptions the published results cannot be used to provide any mechanistic information either for or against a formate model. Where reliable quantitative data are available, these show unequivocally that for all high activity catalysts the contribution of IR-observable formate to the production of CO2 is only of minor importance. It is found that the formates seen by IR typically account for less than about 10–15% of the total WGS reaction products. The formates observed by IR were potentially the main reaction intermediates only in the case of very low activity catalysts. For the high activity catalysts that are of interest for current fuel cell applications it is clear that the major contribution of a formate mechanism is yet to be proven. The current published in situ/operando FTIR data relating to formates cannot be used to elucidate the main reaction mechanism nor for deriving improved catalytic formulations.
Keywords: Water-gas shift; In situ; Operando; FTIR; Formate; Spectator
Conversion of cellulose into renewable chemicals by supported metal catalysis by Hirokazu Kobayashi; Tasuku Komanoya; Samar K. Guha; Kenji Hara; Atsushi Fukuoka (pp. 13-20).
Display Omitted► Supported metal catalysis for the conversion of cellulose. ► Synthesis of sorbitol under hydrolytic hydrogenation conditions. ► Hydrolytic activity of supported metal catalysts. ► Direct use of the cellulose hydrolysate for the production of chemicals.Conversion of biomass to renewable chemicals and fuels has received significant attention as a means to the sustainable society. The most abundant biomass is cellulose, which is produced from carbon dioxide and water using sunlight; however, the efficient chemical transformation of cellulose has remained a challenge because of its persistent property. Among heterogeneous catalysts, supported metal catalysts have been pointed out as an attractive choice to promote the transformation of cellulose due to their tunable activity and durability. In fact, they have been used for the conversion of cellulose to monomeric sugar derivatives based on various strategies. This article provides an overview of the conversion of cellulose by supported metal catalysts into platform chemicals in the biorefinery.
Keywords: Supported metal catalyst; Heterogeneous catalysis; Cellulose; Sugar alcohol; Ethylene glycol; Glucose
Studies on partial hydrogenation of 1,5,9-cyclo-dodecatriene towards cyclo-dodecene by J. Gaube; W. David; R. Sanchayan; N. Wuchter; H.-F. Klein (pp. 21-27).
Display Omitted► Cyclododecene yields >90% are obtained at very low hydrogenation rates of cyclododecatriene. ► Dense coverage by CDT/CDD prevents readsorption of CDE. ► The preference for CDT/CDD is due to adsorption via two double bonds. ► A fully consistent hypothesis for the reaction course of this complicated hydrogenation is given.The selective hydrogenation of 1,5,9- cis, trans, trans-cyclo-dodecatriene (1,5,9- ctt-CDT) towards cyclo-dodecene (CDE) depends strongly on the pressure of hydrogen, respectively the hydrogenation rate. High yields of CDE (>90%) can only be reached at extremely low hydrogen pressure. In order to elucidate this exceptional reaction performance the course of reaction has been studied for a wide range of hydrogen pressure,0.01>pH2>2.5MPa, taking into consideration data of other research groups. The CDT hydrogenations were discontinuously carried out in liquid phase on Pd/Al2O3 at T=353K.The resulting hypothesis of this study is that the very low reaction rate at lowpH2 is necessary in order to realize a dense surface coverage of 1,5,9-CDT and 1,5-cyclo-dodecadiene (CDD) isomers where these molecules show adsorption on Pd via two double bonds so that readsorption of formed CDE and subsequent hydrogenation to cyclo-dodecane (CDA) is hardly possible.On the whole this new hypothesis on the reaction course of CDT hydrogenation gives a sound and fully consistent view on this rather complicated reaction.
Keywords: Hydrogenation; 1,5,9-Cyclo-dodecatriene; Cyclo-dodecene; Kinetics
Heats of adsorption of linear CO species adsorbed on reduced Fe/Al2O3 catalysts using the AEIR method in diffuse reflectance mode by Julien Couble; Daniel Bianchi (pp. 28-38).
Display Omitted► Quantitative studies using diffuse reflectance mode. ► Adsorption equilibrium infrared spectroscopy method using DRIFT. ► Heat of adsorption of linear CO species on Fe2+ and Fe° sites of Fe/Al2O3. ► Impact of Cads species from the CO dissociation on the adsorbed CO species.IR spectra in diffuse reflectance mode are quantitatively exploited to determine the heats of adsorption of two linearly adsorbed CO species formed on Fe2+ and Fe° sites (denotedLFe2+ and LFe° CO species) of reduced x% Fe/Al2O3 (wt%, x=1 and 5) catalysts according to the AEIR procedure developed previously using the IR transmission mode. The IR transmission properties of iron containing catalysts are limited particularly for high iron loadings favoring the use of the diffuse reflectance mode. The heats of adsorption of theLFe2+ CO species linearly vary with the coverage of the sites fromELFe2+(1)=45kJ/mol toELFe2+(0)=66kJ/mol at coverage 1 and 0, respectively. These values are modified by the presence of neither Fe° sites nor carbonaceous adsorbed species. The heats of adsorption of the LFe° CO species on a C-free iron surface (for adsorption temperature Ta<456K), linearly vary with its coverage fromELFe°(1)=79kJ/mol toELFe°(0)=105kJ/mol at high and low coverages. For Ta>456K, the CO dissociation overlaps the CO adsorption equilibrium leading to a C-containing iron surface. The presence of carbonaceous species has no significant impact on the heat of adsorption of the LFe° species at high coverages whereas it increases significantly that at low coverages:ELFe°(0)=120kJ/mol. Considering reduced iron supported catalysts, the AEIR method is particularly useful because it allows the determination of the individual heats of adsorption of two adsorbed CO species that can be simultaneously present on the surface for high iron loadings. The study confirms that quantitative exploitations of DRIFT spectra are available for well designed experimental conditions offering an alternative for solid catalysts with low IR transmission properties.
Keywords: Quantitative DRIFT; AEIR method; CO adsorption; Iron catalysts; Heats of adsorption
Reduction of nitrate on active carbon supported Pd-Cu catalysts by J. Trawczyński; P. Gheek; J. Okal; M. Zawadzki; M.J. Ilan Gomez (pp. 39-47).
Display Omitted► Wetness impregnation or catalytic reduction (CR) for catalyst preparation. ► Pd-Cu/C catalyst for nitrate reduction in water. ► Preparation method affects on the catalyst activity ► Preparation method does not affect on catalyst selectivity. ► Properties of Pd-Cu/C prepared by CR depend on Cu/Pd ratio and metals content.Bimetallic Pd-Cu catalysts supported on active carbon were tested for nitrate reduction in water. The catalysts were prepared either by successive incipient wetness impregnation or catalytic reduction and were characterized by HRTEM, XRD, TPR-H2 and H2-chemisorption. The method of preparation exerts an influence on the activity of Pd-Cu catalysts for nitrate reduction, but the effect on their selectivity to ammonia is negligible. The Cu/Pd atomic ratio and total metal content affect both activity and selectivity of the catalysts prepared by chemical reduction.
Keywords: Nitrate hydrogenation; Pd-Cu catalysts; Active carbon
Chemistry of the oxidation of acetic acid during the homogeneous metal-catalyzed aerobic oxidation of alkylaromatic compounds by Walt Partenheimer (pp. 48-54).
Display Omitted► Chemistry of the aerobic oxidation of acetic acid is described. ► Roles of Co, Mn, Br catalysts are given. ► Methods of reduction of acetic acid oxidation are given. ► Multinuclear complexes provide efficient pathways.Acetic acid is the solvent used for the commercial production of five aromatic acids from polyalkylbenzenes using homogeneous aerobic oxidation. The most important catalysts are mixtures of cobalt(II) and manganese(II) acetates. The co-oxidation of the acetic acid to carbon dioxide and carbon monoxide, denoted CO x, is one of the economic disadvantages of the processes. Understanding the chemistry of the oxidation of acetic acid can led to reduction in these greenhouse gases. This paper assembles and summarizes the organic, free-radical and coordination chemistry detailing how the various products from the oxidation of acetic acid form. It is suggested that the initiation of the acetic acid occurs primarily through the thermal decomposition of cobalt(III) acetate. This leads to three families of by-products starting from the oxidation of methanol, succinic acid and glycolic acid. Carbon monoxide forms by decarbonylation of many of these intermediates. Concerted reactions via polynuclear cobalt and manganese complexes provides efficient mechanistic pathways to these intermediates and by-products. The chemistry presented for the oxidation of the acetic acid is consistent with known optimization methods which are used to reduce acetic acid loss.
Keywords: Autoxidation; Dioxygen; Cobalt; Manganese; Terephthalic acid; Acetic acid
Catalytic reduction of NO by CO over copper-oxide supported mesoporous silica by Archana Patel; Pradeep Shukla; Thomas Rufford; Shaobin Wang; Jiuling Chen; Victor Rudolph; Zhonghua Zhu (pp. 55-65).
Display Omitted► Structure directed CuO catalyst loading on mesoporous silica based support. ► Silica support with 3D pore structure type facilitates higher reactant adsorption. ► Higher catalyst–support interactions within 2D pore structure favor CuO activity.Copper oxide supported on four different types of mesoporous silica (SBA-15, MCM-41, MCM-48 and KIT-6) were prepared and examined for catalytic reduction of NO with CO in the temperature range of 250–500°C. Their structural and chemical properties were characterized by N2 adsorption, low angle and wide angle X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), FTIR and temperature programmed reduction (TPR). H2-TPR revealed that MCM-41 and SBA-15 tend to possess a higher quantity of reducible copper species in contrast to MCM-48 and KIT-6. CuO supported on MCM-41 and SBA-15 exhibited higher activity in catalytic reduction of NO than CuO supported on MCM-48 and KIT-6. The superior catalytic activity was attributed to homogeneous dispersion of CuO and availability of the reducible copper ions in the channels of mesoporous materials.
Keywords: Nitric oxide; Catalytic reduction; Mesoporous silica; Copper oxide
Direct decomposition of NO into N2 and O2 over Ba3Y3.4Sc0.6O9 by Kazuya Goto; Tatsumi Ishihara (pp. 66-73).
Display Omitted► Ba3Y4O9, which has an oxygen-deficient layered structure is stabilized by Sc doping. ► Ba3Y3.4Sc0.6O9 showed highest NO decomposition activity at 1123K. ► NO conversion to N2 attained values of 92% in spite of its low surface area. ► TAP analysis suggests that the direct decomposition of NO proceeded via N2O.Effects of dopant on direct decomposition of nitric oxide (NO) over Ba3Y4O9 were investigated and it was found that Sc is partially substituted Ba3Y3.4Sc0.6O9 catalyst shows a high NO decomposition activity (N2 yield: 92%) at 1123K among the examined dopants. Sc is considered to contribute to the stabilization of the Ba3Y4O9 crystal phase and also form the intrinsic oxygen defects. This catalyst was active in NO decomposition in the presence of O2 and maintained its high activity at high space velocity values. Fourier transform infrared spectroscopy (FT-IR) measurement suggests that initial adsorption state of NO is a bent-type NO−. Moreover, the rate-determining step for NO decomposition seems to be the coupling of the NO species adsorbed on the surface. Doping with Sc effectively weakened the adsorption of NO species, resulting in the increased reactivity. FT-IR and temporal analysis of products (TAP) measurements suggested that N2O may be an intermediate species in NO decomposition.
Keywords: Direct decomposition; NO decomposition; Ba; 3; Y; 3.4; Sc; 0.6; O; 9
Effect of extra-framework cesium on the deoxygenation of methylester over CsNaX zeolites by Tanate Danuthai; Tawan Sooknoi; Siriporn Jongpatiwut; Thirasak Rirksomboon; Somchai Osuwan; Daniel E. Resasco (pp. 74-81).
Display Omitted► Methyl octanoate, a model FAME, can be effectively converted without added H2 over CsNaX. ► Decarbonylation and deacetalization yield heptenes and hexenes as main products. ► Basicity generated by extra-framework Cs determines product selectivity. ► Without Cs, decarbonylation is quickly lost and undesired products are obtained.The deoxygenation of methyl octanoate has been investigated over Cs-containing NaX zeolite catalysts at atmospheric pressure with He carrier gas and methanol as a co-feed. By varying the preparation procedures, different amounts of extra-framework Cs were left on the catalyst. The presence of extra-framework Cs affects the acid–basic characteristics of the catalysts and consequently their activity, stability, and particularly the product selectivity. That is, when the amount of extra-framework Cs increases, the corresponding increase in basicity enhances decarbonylation activity as well as catalyst stability. In this case, the deoxygenation of methyl octanoate on CsNaX catalysts was found to yield heptenes and hexenes as main products via surface decomposition of octanoate-like species. When the amount of extra-framework Cs was reduced, the hexene yield readily increased. The enhancement in hexene production can be ascribed to both, a decreased basicity that reduces decarbonylation and to a greater space available within the zeolite cavity for formation of a rather bulky cyclic-like intermediate that leads to hexene. In addition, weakly acidic sites, generated after the excess Cs was removed, resulted in relatively higher yield of inner-olefin product. When Cs was not present in the catalyst (i.e., NaX), other products such as aromatics and coupling compounds were observed. These compounds are less desirable for transportation fuel applications.
Keywords: Deoxygenation; Decarbonylation; Methylesters; Biofuels; CsNaX; Basicity; Cesium
Esterification of camphene over heterogeneous heteropoly acid catalysts: Synthesis of isobornyl carboxylates by Augusto L.P. de Meireles; Kelly A. da Silva Rocha; Ivan V. Kozhevnikov; Elena V. Gusevskaya (pp. 82-86).
Display Omitted► The catalyst was prepared by supporting of H3PW12O40 on silica (PW/SiO2). ► PW/SiO2 is active in liquid-phase esterification of camphene with C2–C6 fatty acids. ► Commercially important fragrance monoterpenoids were obtained in excellent yields. ► The catalyst is truly heterogeneous and does not undergo PW leaching.Silica supported H3PW12O40 (PW), the strongest heteropoly acid in the Keggin series, is an active and environmentally friendly solid acid catalyst for liquid-phase esterification of camphene, a renewable biomass-based substrate, with C2, C4 and C6 short-chain fatty acids. The reaction provides isobornyl carboxylates, useful as fragrances, in virtually 100% selectivity and 80–90% yield. The reaction is equilibrium-controlled and occurs under mild conditions with a catalyst turnover number of up to 3000. The use of hydrocarbon solvent prevents PW from leaching to allow easy catalyst recovery. The catalyst can be reused several times without loss of activity and selectivity.
Keywords: Biomass-based feedstock; Esterification; Camphene; Heterogeneous acid catalysis; Heteropoly acid
Towards atomic level vanadium doping of TiO2 via liquid-phase atomic layer deposition by Yaodong Shen; Thelese R.B. Foong; Xiao Hu (pp. 87-90).
Display Omitted► A new, liquid-phase atomic layer deposition has enabled atomic level doping of TiO2. ► Vanadium doping of TiO2 via L-ALD results in redshift of band edge by up to 55nm. ► Up to 500% increase of visible light photocatalytic activity is seen in the V-doped TiO2.Vanadium-doping of TiO2 at the atomic level was achieved via a liquid phase atomic layer deposition (L-ALD) method. UV–vis absorption edge of vanadium-doped TiO2 has been red-shifted ∼55nm into visible light region. Photocatalytical assessment reveals that the degradation rate of methylene blue (MB) for vanadium-doped TiO2 under visible light illumination was enhanced by up to 500% compared to the undoped TiO2. This improvement was believed to be attributed to the atomic level doping of the L-ALD method.
Keywords: Atomic force microscopy (AFM); Crystalline oxide; Atomic layer epitaxy
Dimethyl ether steam reforming under daily start-up and shut-down (DSS)-like operation over CuFe2O4 spinel and alumina composite catalysts by N. Shimoda; H. Muroyama; T. Matsui; K. Faungnawakij; R. Kikuchi; K. Eguchi (pp. 91-98).
Display Omitted► The Cu-Fe spinel and γ-alumina composite catalyst was prepared by mechanical mixing. ► The catalyst stability for DME SR under DSS-like operation was evaluated. ► No degradation was observed after the cooling–heating process in O2 atmosphere. ► The catalyst was degraded by cooling–heating process in steam atmosphere.The durability of the CuFe2O4 spinel and γ-Al2O3 composite catalysts for steam reforming of dimethyl ether (DME) was evaluated at 375°C for 120h under the daily start-up and shut-down (DSS) operation. No degradation could be observed for the catalyst subjected to the cooling–heating process in O2 atmosphere. On the other hand, the catalyst performance was significantly degraded by the cooling–heating process in steam atmosphere due to the deactivation of the acid sites on γ-Al2O3 for DME hydrolysis reaction, leading to the loss of DME steam reforming activity. The higher amount of coke formation was also observed over the catalysts exposed to steam during the cooling–heating process, as compared with the catalysts exposed to O2 or without DSS operation. The degraded catalyst could be recovered by the heat treatment in air at 375°C, since the active sites of γ-Al2O3 were regenerated and the coke deposits were removed. Interestingly, the catalytic activity of the regenerated catalysts for methanol steam reforming was higher than the fresh one because of an increase in the metal surface area of Cu species after the regeneration treatment.
Keywords: Steam reforming; Dimethyl ether; CuFe; 2; O; 4; spinel-type oxide; DSS operation; Regeneration
RhCl(TPPTS)3 encapsulated into the hexagonal mesoporous silica as an efficient heterogeneous catalyst for hydroformylation of vinyl esters by N. Sudheesh; Amit K. Chaturvedi; Ram S. Shukla (pp. 99-105).
Display Omitted► RhCl(TPPTS)3 complex was in situ encapsulated into the hexagonal mesoporous silica. ► Active and selective for hydroformylation of vinyl esters. ► Detail investigation on vinyl acetate hydroformylation. ► Catalyst was regenerated and recycled.RhCl(TPPTS)3 (TPPTS=m-trisulphonato triphenyl phosphine) was in situ encapsulated into the mesopores of hexagonal mesoporous silica (HMS) by in situ method. The catalyst was characterized by P-XRD,31P-CPMAS NMR, FT-IR, N2 adsorption, TGA, TEM and ICP techniques. These characterization confirmed the encapsulation and heterogenization of RhCl(TPPTS)3. The synthesized heterogeneous catalyst evaluated for hydroformylation of vinyl esters gave 100% conversion and high selectivity to iso-aldehyde. Vinyl acetate was subjected as a representative vinyl ester for detailed investigations. The performance of the catalyst in terms of conversion and selectivity depended on the studied parameters: amount of the catalyst, substrate, partial pressure of CO and H2, and temperature. Recyclability aspects of the heterogenized catalyst are investigated.
Keywords: Hexagonal mesoporous silica; Hydroformylation; Vinyl esters; Recycling; Heterogeneous catalyst
Monitoring the catalytic synthesis of glycerol carbonate by real-time attenuated total reflection FTIR spectroscopy by V. Calvino-Casilda; G. Mul; J.F. Fernández; F. Rubio-Marcos; M.A. Bañares (pp. 106-112).
Display Omitted► In situ real-time ATR-FTIR spectroscopy monitors glycerol carbonate synthesis. ► Co3O4 nanoparticles hierarchically dispersed on ZnO microparticles act as catalysts. ► ATR-FTIR spectroscopy reveals differences in reactivity of the catalysts. ► ATR-FTIR monitoring provides thorough molecular information on the reaction mechanism. In situ Attenuated Total Reflectance FTIR spectroscopy was used to study the carbonylation of glycerol with urea. Cobalt oxide nanoparticles, Co3O4, hierarchically dispersed on zinc oxide microparticles, ZnO, were used as catalysts. The present work demonstrates that in situ real-time attenuated total reflection ATR-FTIR spectroscopy is a valuable tool for monitoring reaction progress and analyzing the reaction mechanism of the synthesis of glycerol carbonate. ATR-FTIR spectroscopy during the carbonylation reaction of glycerol with urea reveals differences in reactivity of various Co3O4/ZnO catalysts, and in particular demonstrates that the first (fast) step in the conversion of glycerol with urea is the formation of glycerol urethane, whereas the consecutive conversion to glycerol carbonate is relatively slow. In addition, possible interactions of the catalytically active sites with in particular the product glycerol carbonate were also evaluated. Interactions of the 2-hydroxyethyl chain of the product with the surface of the catalysts were identified, suggesting product inhibition might be of relevance to the reaction kinetics.
Keywords: Glycerol; Urea; Glycerol carbonate; Biomass; ATR-FTIR spectroscopy
Methanol dehydration to dimethyl ether in a platelet milli-reactor filled with H-ZSM5/SiC foam catalyst by Yu Liu; Seetharamulu Podila; Dinh Lam Nguyen; David Edouard; Patrick Nguyen; Charlotte Pham; Marc Jacques Ledoux; Cuong Pham-Huu (pp. 113-121).
Display Omitted► SiC foam supported H-ZSM5 zeolite as catalyst. ► Catalysts for methanol dehydration into dimethylether in a platelet millireactor. ► Foam structure allows the low diffusion problem and mixing efficiency. ► No deactivation was observed as a function of time on stream.Milli-structured reactors and process miniaturization have received an over increasing scientific interest during the last decades for the development of new generation of catalytic systems, which can find application in several catalytic processes. Here we report the development of a platelet milli-structured reactor filled with ceramic SiC foam with open porosity, high mixing efficiency, fully accessible surface area and low pressure drop. The SiC support was coated with a homogeneous layer of H-ZSM5 zeolite acting as an active phase for the catalytic dehydration of methanol into dimethyl ether. This hybrid catalyst shows an excellent and stable dehydration activity even at high space velocity due to the foam structure with high reactants mixing efficiency and better effective surface area. The low diffusion length of the foam strut also provide a high escaping of the product reducing secondary reaction and also carbonaceous residue deposit the catalyst and thus, no deactivation was observed for a long-term test.
Keywords: Milli-structured reactor; ZSM-5/SiC catalyst; Silicon carbide foam; Dimethyl ether; Methanol dehydration
Photocatalytic stability of organic phosphonates and phosphates on TiO2 nanoparticles by Angelika Bachinger; Guido Kickelbick (pp. 122-132).
Display Omitted► The photocatalytic degradation of organophosphonates on TiO2 nanoparticles is studied. ► The organic moieties are degraded while phosphate stays on the particle surface. ► The remaining phosphate enhances the photocatalytic activity of the particles.The stability of organic phosphonates and phosphates anchored to TiO2 under photocatalytic conditions was studied by illumination of modified particles with UV light. Spectroscopic characterization of the particles after different illumination intervals revealed that the organic moieties were completely degraded, while the Ti–O–P bond was stable, leaving phosphate species on the particles’ surface after illumination. The presence of degradation intermediates after moderate illumination times, identified by13C CPMAS NMR, indicated a sequential degradation of the organic species. Furthermore, the kinetics of the degradation reactions were studied by means of infrared spectroscopy under different conditions. Phosphate anchoring groups were found to result in faster degradation of organic moieties compared to phosphonate coupling groups. Degradation kinetics were moderately slowed down in the absence of water, indicating a co-existence of hydroxyl radical initiated degradation and direct hole oxidation.
Keywords: Organic phosphonates; TiO; 2; nanoparticles; Photocatalytic degradation; Photocatalytic activity
Microwave assisted rapid conversion of carbohydrates into 5-hydroxymethylfurfural catalyzed by mesoporous TiO2 nanoparticles by Saikat Dutta; Sudipta De; Astam K. Patra; Manickam Sasidharan; Asim Bhaumik; Basudeb Saha (pp. 133-139).
Display Omitted► Self-assembled mesoporous TiO2: high surface area, Lewis acidity. ► Conversion of carbohydrates into liquid transportation fuels. ► 5-Hydroxymethylfurfural (HMF) production. ► Microwave assisted nanocatalysis. ► Sustainable chemistry: high catalytic efficiency.Energy efficient and sustainable process for the production of 5-hydroxymethylfurfural (HMF) from carbohydrates is highly demanding. Here, direct conversion of carbohydrates into HMF has been investigated over self-assembled mesoporous TiO2 nanoparticles (NPs) catalyst. Monosachharidesd-fructose andd-glucose, disaccharides sucrose, maltose, cellobiose were successfully converted into HMF with variable yields in both aqueous and organic mediums under microwave-assisted heating conditions. The effects of solvent polarity, microwave absorbing ability, catalyst loading, reaction time, and substrate variations on the HMF yields have been studied. Pyridine-IR and NH3-TPD analyses confirmed the presence of Lewis acidic sites, whereas N2 sorption analysis revealed high BET surface area for the self-assembled mesoporous TiO2 nanomaterials synthesized by using sodium salicylate as template. High surface area, Lewis acidity and uniform nanosphere-like particle morphology are responsible for high catalytic activity in the dehydration of carbohydrate substrates over this mesoporous TiO2 nanomaterial, whereas commercially available TiO2 is almost inactive for this dehydration reaction under similar conditions. The higher microwave energy absorbing ability (tan δ) of the DMSO and NMP resulted in higher HMF yield in organic solvents than water. Catalyst life-time analysis suggested that mesoporous TiO2 NPs catalysts can be recycled for four catalytic cycles without appreciable loss of its catalytic activity.
Keywords: Mesoporous titania; Carbohydrates; Microwave catalysis; 5-Hydroxymethylfurfural; Sustainable chemistry
Design of improved hydrocracking catalysts by increasing the proximity between acid and metallic sites by J. Francis; E. Guillon; N. Bats; C. Pichon; A. Corma; L.J. Simon (pp. 140-147).
Display Omitted► Enhanced performances of hydrocracking catalyst. ► Increased proximity between acid and hydrogenating functions. ► Nickel impregnation on zeolite powder. ► Squalane hydrocracking catalytic tests.A new approach was undertaken to increase the bifunctionality of USY zeolite based catalyst. Nickel metallic phase was first impregnated onto USY zeolite and composite catalysts NiMo/[γ-Al2O3+(Ni)/USY] were prepared from these zeolites. Catalytic properties in toluene hydrogenation and squalane (2,6,10,15,19,23-hexamethyltetracosane) hydrocracking (HCK) were investigated.Enhanced conversion and middle distillate (MD) selectivity was obtained for catalysts on which nickel has been impregnated on the zeolite powder. These enhancements are ascribed to an increased proximity between the hydrogenation/dehydrogenation (H/DH) function and the acid sites resulting in a more efficient synergy between these two functions.
Keywords: Hydrocracking; Squalane; Zeolite; Nickel; Metal sulfide; Proximity
Effect of chiral ionic liquids on palladium-catalyzed Heck arylation of 2,3-dihydrofuran by Rafał Roszak; Anna M. Trzeciak; Juliusz Pernak; Nina Borucka (pp. 148-155).
Display Omitted► Heck arylation of 2,3-dihydrofuran catalyzed by phosphorus-free palladium catalyst. ► The promoting effect of pyridinium ILs on the yield of the cross-coupling product. ► Application of new chiral ILs as co-catalyst in the Heck reaction. ► Effect of anionic part of ILs on the yield of the Heck reaction.It is demonstrated that a relatively small amount of IL (IL=ionic liquid) can dramatically affect conversion in the Heck arylation of 2,3-dihydrofuran with iodobenzene, catalyzed by Pd(OAc)2 in DMF as a solvent. In all reactions, 2-phenyl-2,3-dihydrofuran (3) was obtained as the main product, and conversion increased even up to 10 times when pyridinium salts with 1-butyl-4-methylpyridinium cation were applied. In a 1:1 mixture of DMF and H2O as solvent, the addition of ILs led to a remarkable deactivation of the catalyst, and this effect was most visible in the presence of imidazolium salts containing a 1-butyl-3-methylimidazolium cation. The influence of the anionic part of ILs on the reaction course was tested using a series of morpholinium salts and, depending on the anion, conversion varied from 0.4% to even 100%. When morpholinium salts with chiral anions were used, e.e. values of up to 10% were obtained, which is the highest value for the Heck reaction involving IL as a chirality source.
Keywords: Homogeneous catalysis; Palladium; Heck reaction; Asymmetric catalysis; Ionic liquids
Polypyrrole-modified graphitized carbon black as a catalyst support for methanol oxidation by Sang Soo Jeon; Won Bae Han; Hyeun Hwan An; Seung Soon Im; Chong Seung Yoon (pp. 156-161).
Display Omitted► The surface of the graphitized carbon black (GCB) was modified by polypyrrole. ► Carbonization of polypyrrole led to nitrogen doping of the GCB surface. ► The nitrogen doping allowed uniform loading of Pt catalysts on the GCB surface. ► The Pt-loaded GCB support was applied to electro-oxidation of methanol. ► The surface modification enhanced the catalytic activity and the CO-tolerance.Surface-modified graphitized carbon black (GCB) was produced through carbonization of polypyrrole (Ppy) on the GCB surface to be used as a catalyst support for Pt nanoparticles in electro-oxidation of methanol. The Ppy modification led to the enhancement of the catalytic activity for the Pt catalysts. The improvement is largely attributed to uniform dispersion of the Pt nanoparticles as the Ppy modification appears to reduce the agglomeration of the Pt nanoparticles. The chronoamperometry and the accelerated cycling tests indicated that the Ppy modification did not improve the long-term stability of the GCB support for Pt.
Keywords: Fuel cells; Graphitized carbon black; Methanol electro-oxidation
Nano n-propylsulfonated γ-Fe2O3 as magnetically recyclable heterogeneous catalyst for the efficient synthesis of β-phosphonomalonates by Sara Sobhani; Zahra Pakdin Parizi; Nasrin Razavi (pp. 162-166).
Display Omitted► In this paper, nano n-propylsulfonated γ-Fe2O3 (NPS-γ-Fe2O3) was synthesized. ► NPS-γ-Fe2O3 was synthesized directly by ring opening reaction of 1,3-propanesultone. ► NPS-γ-Fe2O3 is a new sulfonated nanomagnetic iron oxide. ► NPS-γ-Fe2O3 was applied as a new catalyst for the synthesis of β-phosphonomalonates. ► NPS-γ-Fe2O3 was isolated from the reaction mixture by magnetic decantation.Nano n-propylsulfonated γ-Fe2O3 as a new sulfonated nanomagnetic iron oxide was synthesized directly through ring opening reaction of 1,3-propanesultone with nano magnetic γ-Fe2O3 and used as magnetically recyclable heterogeneous catalyst for the efficient one-pot synthesis of β-phosphonomalonates. The catalyst was easily isolated from the reaction mixture by magnetic decantation using an external magnet and reused at least five times without significant degradation in the activity.
Keywords: Nanomagnetic iron oxide; Heterogeneous catalyst; β-phosphonomalonates; 1,3-propanesultone
Decomposition of 4-phenoxyphenol to aromatics over palladium catalyst supported on activated carbon aerogel by Hai Woong Park; Ung Gi Hong; Yoon Jae Lee; In Kyu Song (pp. 167-173).
.Display Omitted► Decomposition of 4-phenoxyphenol to aromatics was carried out. ► Palladium catalyst supported on activated carbon aerogel (Pd/ACA-H3PO4-1.0) was used. ► Palladium catalyst supported on commercial activated carbon (Pd/AC) was also tested. ► Pd/ACA-H3PO4-1.0 showed a better catalytic performance than Pd/AC.Carbon aerogel (CA) was prepared by a sol–gel polymerization of resorcinol and formaldehyde, and a series of activated carbon aerogels (ACA-H3PO4- X, X=0, 0.5, 1.0, 2.0, and 3.0) were prepared by a chemical activation using different amount of phosphoric acid ( X represented weight ratio of H3PO4 with respect to CA). Palladium catalysts were then supported on activated carbon aerogels (Pd/ACA-H3PO4- X, X=0, 0.5, 1.0, 2.0, and 3.0) by an incipient wetness impregnation method for use in the decomposition of 4-phenoxyphenol to aromatics. 4-Phenoxyphenol was used as a lignin model compound for representing 4-O-5 linkage of lignin. Cyclohexanol, benzene, and phenol were mainly produced by the decomposition of 4-phenoxyphenol. Conversion of 4-phenoxyphenol and total yield for main products (cyclohexanol, benzene, and phenol) were closely related to the average palladium particle size of Pd/ACA-H3PO4- X. Conversion of 4-phenoxyphenol and total yield for main products increased with decreasing average palladium particle size of Pd/ACA-H3PO4- X. Among the catalysts tested, Pd/ACA-H3PO4-1.0 with the smallest average palladium particle size showed the highest conversion of 4-phenoxyphenol and total yield for main products. Conversion of 4-phenoxyphenol and total yield for main products over Pd/ACA-H3PO4-1.0 were much higher than those over palladium catalyst supported on commercial activated carbon (Pd/AC).
Keywords: Activated carbon aerogel; Pd catalyst; Lignin; C–O bond; 4-Phenoxyphenol
Carbon support treatment effect on Ru/C catalyst performance for benzene partial hydrogenation by Cristiane Zanutelo; Richard Landers; Wagner Alves Carvalho; Antonio José Gomez Cobo (pp. 174-180).
Display Omitted► Commercial activated carbon submitted to different treatments. ► Catalytic performance of the system Ru/C is influenced for functional groups. ► Carbonyl groups decrease the activity and selectivity of the reaction. ► Carboxylic groups leads active catalysts and the highest yield of cyclohexene.Ru/C catalysts were prepared from commercial activated carbon submitted to different treatments. The catalysts were prepared by incipient wetness impregnation, through an aqueous solution of the precursor RuCl3· xH2O. After impregnation, some catalysts were submitted to direct reduction treatment under H2 flow at the temperature of 150°C, in order to evaluate the effects of activation. The supports were characterized by N2 adsorption, Boehm and potentiometric titration. The X-ray photoelectron spectroscopy was used to study the supports and catalysts surfaces, while scanning electron microscopy allowed us to determine the chemical composition and observe the catalysts morphology. Ru/C catalysts performance was evaluated within the hydrogenation reaction of benzene in liquid phase, using a Parr reactor. The reaction was conducted under total pressure of 5.0MPa of H2, at a temperature of 100°C with water in the reaction medium. The obtained results indicate that the Ru/C system catalytic performance is influenced for determined functional groups present on the activated carbon surface. The carbonyl groups decrease the activity and selectivity of the reactions, while an increase of the carboxylic groups leads to more active catalysts and the highest yield of cyclohexene.
Keywords: Hydrogenation; Benzene; Ruthenium; Activated carbon; Cyclohexene
Effect of transition metal additives on the catalytic stability of Mo/HZSM-5 in the methane dehydroaromatization under periodic CH4–H2 switch operation at 1073K by Yuebing Xu; Jide Wang; Yoshizo Suzuki; Zhan-Guo Zhang (pp. 181-193).
Display Omitted► Promotional effects of eight metal additives on the activity and stability of Mo/HZSM-5. ► Only Fe addition improves the activity stability at the tested severe condition. ► Fe-induced carbon nanotube formation is the origin of the promotional effect. ► Direct and indirect effects on suppression of accumulation of the surface coke.Eight 0.5wt%M–5wt%Mo/HZSM-5 catalysts (M=Cr, Mn, Fe, Co, Cu, Zn, Ru or Pd) prepared by co-impregnation method were tested for the non-oxidative methane dehydroaromatization at a practically required severe condition of 1atm, 1073K and 10,000mL/g/h in periodic CH4–H2 switch operation mode. The aim was to investigate promotional effects of these transition metal additives on the activity and stability of Mo/HZSM-5 and find out a really effective promoter for the title catalytic system. While Fe, Co, Ru and Pd additions were found to enhance the catalyst's CH4 conversion activity, only Fe was observed to remarkably improve the activity stability, and therefore another two Fe-modified catalysts with 0.3 and 1.0wt% of Fe were prepared and tested to make further confirmation. Ascribed to the second group of metal additives, Cr, Mn, Cu and Zn additions exhibited little influence on the CH4 conversion activity, and Cr and Mn caused even slight decreases in the activity stability. Similar tests were also conducted with the samples of 0.5wt%M/HZSM-5s to confirm the negligibly low activities of all but Pd metal additive themselves. Then, all spent catalyst samples were subjected to TPO, TG, SEM and BET measurements to gain an insight into the promotion mechanisms of Fe additive. Consequently, the TPO and TG measurements revealed that the addition of all metals except Ru enhanced coke accumulation and only Fe induced the formation of a new type of coke. Well consistently, the SEM observations confirmed considerable amounts of carbon nanotubes formed in all Fe-containing spent samples, whereas no single carbon nanotube in all other spent samples. Furthermore, the BET measurements also confirmed that all Fe-containing spent samples had obviously higher BET surface areas and micropore volumes than all other spent catalyst samples. While all these, in addition to the test results, strongly suggest that the promotional effect of Fe additive is closely related to Fe-induced carbon nanotube formation and growth at the tested condition, three possible promotion effects were proposed in the article to explain all observations.
Keywords: Methane dehydroaromatization; Mo/HZSM-5; Metal additives; Carbon nanotube
Effect of Ir crystallographic site on the catalytic performance of Ir-substituted barium hexaferrites for N2O decomposition by Yanyan Zhu; Xiaodong Wang; Yan Zhang; Junhu Wang; Yanqiang Huang; Charles Kappenstein; Tao Zhang (pp. 194-201).
Display Omitted► The crystallographic sites of Ir in barium hexaferrites were identified. ► Ir preferentially occupied the octahedral sites. ► The occupation follows the order of 2a, 12k, and 4f2 as increasing Ir content. ► Ir ions in 4f2 sites in the mirror plane were more active for N2O decomposition.Ir-substituted barium hexaferrites (BaIr xFe12− xO19, x≤0.6) were prepared using the carbonates route and investigated for high-concentration N2O decomposition. It was found that BaIr xFe12− xO19 offered a better dispersion of iridium by incorporating Ir into the hexaferrite structure. The crystallographic sites of Ir in BaIr xFe12− xO19 were identified through the analysis of Fe occupancy in the matrix by sensitive57Fe Mössbauer spectroscopy. Framework iridium preferentially occupied the octahedral sites in the order of 2a, 12k, and 4f2 as increasing x value. When x=0.1 and 0.4, the substitution of Ir for Fe3+ occurred in the 2a and 12k sites in the rigid spinel block with a comparable N2O decomposition activity, while this substitution in the 4f2 sites in the mirror plane at x=0.6 resulted in a remarkable enhancement of activity. Ir ions in the octahedral 4f2 sites in the loosely packed mirror plane were highly active for N2O decomposition.
Keywords: Ir; Crystallographic site; Mössbauer spectroscopy; N; 2; O decomposition
Optimization of the synthesis conditions for LaNiO3 catalyst by microwave assisted citrate method for hydrogen production by Ahmed Galal; Nada F. Atta; Shimaa M. Ali (pp. 202-208).
Display Omitted► LaNiO3 perovskite was prepared by microwave-assistant citrate method. ► Hexagonal distorted rhombohedral perovskite phase of LaNiO3forms. ► Microwave power and time of synthesis affected perovskite electrocatalytic activity. ► Highest rate for HER obtained with microwave power of 720W. ► Catalyst has dimensions ranging from 18nm to 32nm.LaNiO3 was prepared by microwave assisted citrate method. The effect of the synthesis condition such as, the operating microwave power and the microwave irradiation time, on structural, surface and catalytic properties was investigated by XRD, SEM, Tafel linear polarization and impedance measurements. The XRD results suggested successful incorporation of Ni3+ at the La3+ cations sites confirming the formation of the hexagonal distorted rhombohedral perovskite phase of LaNiO3 at all the investigated microwave operating powers and irradiation times. The average particle size ranges between 18 and 32nm. The largest surface area ( ca. 25m2g−1) and the highest catalytic activity for LaNiO3 prepared by the microwave assistant-citrate method toward the hydrogen evolution reaction (HER) were obtained at an operating microwave power of 720W and increased by increasing the microwave irradiation time. In addition, the reaction order, the activation energy and the reaction mechanism were identified.
Keywords: Perovskites; Catalysis; Nanoparticles; Hydrogen evolution; Microwave synthesis
Mineralization of volatile organic compounds (VOCs) over the catalyst CuO–Co3O4–CeO2 and its applications in industrial odor control by Shouichi Somekawa; Toshiya Hagiwara; Kyoko Fujii; Masayuki Kojima; Tsutomu Shinoda; Kazuhiro Takanabe; Kazunari Domen (pp. 209-214).
Display Omitted► Scale-up of catalytic system for the industrial application of VOC degradation. ► Use of non-noble-metal mixed oxide Cu–Co–Ce–Ox as active catalyst. ► Pelletizing study of various metal oxides. ► Performance of odor elimination under scaled-up conditions. ► kinetic analysis of total oxidation to carbon dioxide.Volatile organic compounds (VOCs) present at ppm levels were decomposed over the catalyst CuO–Co3O4–CeO2 (Cu:Co:Ce=10:45:45 in mol) in an attempt to scale up for industrial odor control. In addition to enhancing the catalytic activity, CuO–Co3O4 and CeO2 helped, respectively, to maintain the strength of the pelleted catalysts and inhibit their sintering. Using toluene as a VOC model compound, kinetic analysis of the total oxidation to carbon dioxide was conducted. The odor emitted from paint-drying processes could be eliminated effectively using CuO–Co3O4–CeO2 (Cu:Co:Ce=10:45:45) pelleted catalysts (188ml) in a large-scale system.
Keywords: CuO–Co; 3; O; 4; –CeO; 2; Oxidation of toluene; Kinetics; Odor degradation; Pelletizing
Enhanced visible light photocatalytic activity of novel polymeric g-C3N4 loaded with Ag nanoparticles by Lei Ge; Changcun Han; Jing Liu; Yunfeng Li (pp. 215-222).
Display Omitted► The Ag/g-C3N4 showed remarkably enhanced photocatalytic activity. ► The Ag content had great influence on the photocatalytic activity. ► The interfaces between g-C3N4 and Ag nanoparticles were revealed by HRTEM. ► Photocatalytic mechanism was proposed and confirmed by PL spectra.Novel polymeric g-C3N4 photocatalysts loaded with noble metal Ag nanoparticles were prepared via a facile heating method. The obtained Ag/g-C3N4 composite products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflection spectra (DRS) and photoluminescence spectra (PL). The photocatalytic activities of Ag/g-C3N4 samples were investigated based on the decomposition of methyl orange and hydrogen evolution under visible light irradiation. The XPS results revealed that it was the metallic Ag0 deposited on polymeric g-C3N4 samples. The Ag/g-C3N4 photocatalysts exhibited significantly enhanced photocatalytic performance for the degradation of methyl orange and hydrogen production compared with pure g-C3N4. The optimal Ag content was determined to be 1.0wt%, and the corresponding hydrogen evolution rate was 10.105μmolh−1, which exceeded that of pure g-C3N4 by more than 11.7 times. The enhanced photocatalytic performance could be attributed to the synergic effect between Ag and g-C3N4, which promoted the migration efficiency of photo-generated carriers. The proposed mechanism for the enhanced visible light photocatalytic activity of g-C3N4 modified by a small amount of Ag was further confirmed by photoluminescence spectroscopy.
Keywords: g-C; 3; N; 4; Photocatalysis; Functional; Semiconductors
Unique catalytic performance of mesoporous molecular sieves containing zeolite units in transformation of m-xylene by R.J. Balasamy; T. Odedairo; S. Al-Khattaf (pp. 223-233).
Display Omitted► The effect of mesoporous materials containing ZSM-5 is reported for transformation of m-xylene. ► The presence of mesopores led to a high p-xylene selectivity. ► p-Xylene selectivity follows the order: ZSM-5E Z/48M-4, E Z/41M-4 (transalkylation)> E Z/48M-3, E Z/41M-3 (disproportionation).
Keywords: p-Xylene; m-Xylene transformation; Composite materials
Physicochemical, surface and catalytic properties of nanosized copper and manganese oxides supported on cordierite by G.A. El-Shobaky; H.G. El-Shobaky; Abdelrahman A.A. Badawy; Y.M. Fahmy (pp. 234-238).
Display Omitted► Cordierite is devoted with high thermal stability and low thermal expansion coefficient. ► Cordierite is commonly used as a catalyst support for a variety of transition metals. ► CuO, Mn2O3 and a mixture of both on cordierite are active solids for CO oxidation. ► Temperature of heat treatment may modify the catalytic activity of supported catalysts. ► The activity of individual and binary supported oxides may be different from each other.Nanosized CuO, Mn2O3 and a mixture of both oxides supported on cordierite were prepared by wet impregnation followed by calcination at 350–700°C. The prepared sampled were characterized by using XRD, EDX, nitrogen adsorption at −196°C and CO-oxidation by O2 at 250°C. The results revealed that heating the supported mixed oxides at temperatures starting from 500°C resulted in a solid–solid interaction between some of CuO and Mn2O3 yielding copper manganite (CuMn2O4) the amount of which increased by heating at 700°C. EDX investigation showed that the surface concentration of copper and manganese species in individual supported oxides loaded on cordierite much decreased by increasing the calcination temperatures. Opposite trends manifested in case of mixed oxides supported solids. The BET-surface areas and catalytic activity were much increased by loading individual oxides and/or a mixture of both oxides on cordierite support material. The activity of binary oxides supported on cordierite was found to increase progressively by increasing their calcination temperature within 350–700°C, opposite to the individual oxide supported catalyst.
Keywords: CO-oxidation; Copper oxide; Manganese oxide; Copper manganite; Cordierite
Transesterification of sunflower oil over MoO3 supported on alumina by T.M. Sankaranarayanan; A. Pandurangan; M. Banu; S. Sivasanker (pp. 239-247).
Display Omitted► MoO3 supported on γ-Al2O3 is active for the transesterification of sunflower oil. ► Catalyst is most active when calcined at 950K; 16% MoO3 is preferred loading. ► The catalyst is also active for converting oil containing free fatty acids. ► The catalyst is suitable for use in a fixed-bed reactor with continuous operation.Samples of MoO3/γ-Al2O3 with different MoO3 loadings (8, 12 and 16wt%) calcined at different temperatures (800, 950 and 1100K) have been used in the transesterification of sunflower oil with methanol. Activity was the highest when the samples were calcined at 950K, the most active catalyst being 16%MoO3–Al2O3. XRD and Raman spectroscopy reveal the presence of many Mo-phases, such as dispersed surface molybdenum specie, bulk MoO3 and Al2(MoO4)3 in the samples. The influence of various parameters, such as Mo-loading, calcination temperature, reaction temperature and mole ratio of reactants (methanol:oil), on the reaction is presented. The reaction studies have been carried out both in a batch reactor and in a fixed-bed flow reactor. The studies reveal that a sound fixed-bed continuous transesterification process for the production of biodiesel can be designed using MoO3–Al2O3.
Keywords: Transesterification; Biodiesel; Mo–alumina; FAME; Sunflower oil
Highly durable Pt cathode catalysts for polymer electrolyte fuel cells; coverage of carbon black-supported Pt catalysts with silica layers by Sakae Takenaka; Hiroshi Matsumori; Hideki Matsune; Masahiro Kishida (pp. 248-256).
Display Omitted► Coverage of carbon black-supported Pt metal with silica layers (SiO2/Pt/CB). ► SiO2/Pt/CB cathode catalyst for oxygen reduction in fuel cells. ► Coverage of Pt/CB with silica inhibits Pt metal growth under cathode conditions. ► Coverage with silica does not decrease the catalytic activity of Pt/CB.Carbon black-supported Pt (Pt/CB) catalysts that have been used at the cathode in state of the art polymer electrolyte fuel cell (PEFC) were covered with silica layers to improve the durability of the Pt catalysts under PEFC cathode conditions. The durability of silica-coated Pt/CB to potential cycling between 0.6 and 0.9V (vs. reversible hydrogen electrode (RHE)) was strongly dependent on the thickness of the silica layers, i.e., the durability of Pt/CB improved after coverage with thick silica layers. However, the coverage of the whole surface of the Pt/CB catalysts with silica layers produced electrochemically inactive Pt catalysts. Silica-coated Pt/CB catalysts with an optimal silica layer thickness showed similar activity for the oxygen reduction reaction compared to Pt/CB catalysts without a silica coating, and they had excellent durability at the cathode in a PEFC single cell. Coverage with silica layers improved the durability of the Pt/CB cathode catalysts without a decrease in the catalytic activity for the oxygen reduction reaction.
Keywords: Carbon black-supported Pt electrocatalysts; Polymer electrolyte fuel cell; Cathode catalyst durability; Silica-coating
Solvothermal synthesis of Fe–C codoped TiO2 nanoparticles for visible-light photocatalytic removal of emerging organic contaminants in water by Xiaoping Wang; Yuxin Tang; Ming-Yian Leiw; Teik-Thye Lim (pp. 257-266).
Display Omitted► Solvothermal synthesis of visible-light photoresponsive Fe–C codoped TiO2. ► Photocatalytic degradation and mineralization of bisphenol A and clofibric acid. ► Toxicity evolution of the solutions containing pollutants in the course of photocatalytic process. ► Proposed photocatalytic mechanisms over the Fe/C–TiO2 under visible light and UV irradiation.Anatase Fe/C–TiO2 nanoparticles were synthesized by a facile solvothermal method. The results showed that Fe was incorporated into TiO2 lattice by substituting Ti4+, while C was present in the form of carbonate species on the surface. Fe3+ dopants could introduce a new dopant energy level into TiO2 band gap while the carbonate species served as photosensitizer. Both of them were responsible for the visible-light photocatalytic activity of the Fe/C–TiO2. In addition, the presence of Fe dopants and carbonate species could favor the formation of surface hydroxyl groups, and inhibit recombination of photo-generated electrons and holes. Moreover, the Fe/C–TiO2 displayed larger surface area than C–TiO2 and Fe–TiO2. The synergistic effects of Fe and C codoping into TiO2 resulted in improved photocatalytic activities of Fe/C–TiO2 for degradation of bisphenol A (BPA) and clofibric acid (CA) as compared to C–TiO2, Fe–TiO2 and P25 under visible light and simulated solar light irradiation. The toxicities of BPA solutions gradually decreased throughout BPA mineralization. The photocatalytic activity of the Fe/C–TiO2 was maintained effectively even after several cyclic experiments. Finally, the possible photocatalytic mechanisms over the Fe/C–TiO2 under visible light and UV irradiation were proposed.
Keywords: Fe–C codoping; Carbonate species; Photocatalytic degradation; Toxicity
Unexpected events in sulfated zirconia catalyst during glycerol-to-acrolein conversion by Fabrizio Cavani; Stefania Guidetti; Cristian Trevisanut; Elena Ghedini; Michela Signoretto (pp. 267-278).
Display Omitted► Sulfated zirconia catalysts deactivate during glycerol dehydration into acrolein. ► The catalytic behavior of sulfated zirconia is affected by sulfate loading. ► Accumulation of heavy compounds is not the main reason for deactivation. ► Deactivation is mainly due to the self-reduction of S(VI) and to the loss of S. ► With catalysts having high S loading, O2 co-feeding limits catalyst deactivation.The aim of the work was the analysis of the phenomena occurring during glycerol dehydration in the presence of sulfated zirconia used as solid acid catalysts; the attention was focused on catalyst deactivation. A close correlation between the sulfate content and catalytic behavior was found. In addition to the accumulation of carbon residues on the catalyst surface, there were other phenomena contributing to catalyst deactivation: (i) the self-reduction of sulfuric into sulfurous groups – an event which occurred, however, only in samples with the higher S content under anaerobic conditions – and (ii) the leaching of S from catalysts, due to the hydrolysis of sulfate groups and the formation of volatile esters. These findings are of general interest in relation to both the transformation of glycerol into acrolein by means of gas-phase dehydration and the use of sulfated zirconia catalysts for high-temperature, acid-catalyzed reactions.
Keywords: Glycerol dehydration; Acrolein; Sulfated zirconia; Catalyst deactivation