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Applied Catalysis A, General (v.447-448, #)
Effect of support on V2O5 catalytic activity in chlorobenzene oxidation by Chiraz Gannoun; Romain Delaigle; Damien P. Debecker; Pierre Eloy; Abdelhamid Ghorbel; Eric M. Gaigneaux (pp. 1-6).
Display Omitted► TiO2, TiO2–SO42−, TiO2–CeO2 and TiO2–SO42−–CeO2 are prepared by sol gel route. ► Active vanadia is deposited on these aerogel supports by impregnation route. ► Vanadia based catalysts are tested in chlorobenzene oxidation. ► Cerium containing catalysts considerably improved catalytic properties at 400°C. ► Sulfate containing samples improved catalytic properties in the range 200–300°C.The present paper investigates the influence of the direct incorporation of ceria in TiO2 aerogels support (sulfated and unsulfated) prepared by a sol–gel route on the catalytic properties of vanadia based materials in the total oxidation of chlorobenzene. ICP-AES, N2 physisorption, XRD, DRIFTS, Raman spectroscopy, XPS, H2-TPR and NH3-TPD were employed for catalyst characterization. This study demonstrated that cerium oxide is present as CeO2 form at the catalyst surface, which can improve the catalyst redox properties and so enhance the catalytic activity at high temperature (400°C). Besides, sulfate containing vanadia–titania samples (doped or not with ceria) had their catalytic performances considerably improved (due to sulfates) at lower temperatures (range 200–300°C). This is due to an increased global acidity and higher reactivity of redox sites thanks to the superficial interaction between (i) vanadia and sulfate, and (ii) when ceria is present, between ceria and sulfate leading to higher efficiency of catalysts in the chlorobenzene oxidation.
Keywords: Aerogel; Sulfate; Cerium; Vanadia–titania; Chlorobenzene oxidation
Metalloporphyrins as cytochrome P450 models for chlorhexidine metabolite prediction by Vinicius Palaretti; Joicy Santamalvina dos Santos; Débora Fernandes Costa Guedes; Luiz Alberto Beraldo de Moraes; Marilda das Dores Assis (pp. 7-13).
Display Omitted► Chlorhexidine (CHX) is prone to degradation in the presence of metalloporphyrins. ► p-Chloroaniline (pCA) is the main product from CHX catalytic degradation. ► The results show the strong possibility of pCA formation when CHX is ingested.The catalytic oxidation of chlorhexidine (CHX, a strong microbicidal agent) mediated by ironporphyrins has been investigated by using hydrogen peroxide, mCPBA, tBuOOH, or NaOCl as oxidant. All of these oxygen donors yielded p-chloroaniline (pCA) as the main product. The higher pCA yields amounted to 71% in the following conditions: catalyst/oxidant/substrate molar ratio of 1:150:50, aqueous medium, FeTMPyP as catalyst. The medium pH also had a strong effect on the pCA yields; in physiological pH, formation of this product was specially favored in the presence of the catalysts, with yields 58% higher than those achieved in control reactions. This provided strong evidence that CHX is metabolized to pCA upon ingestion.
Keywords: Biomimetic models; Metalloporphyrins; Cytochrome P450; Chlorhexidine
Improving carbon retention in biomass conversion by alkylation of phenolics with small oxygenates by Lei Nie; Daniel E. Resasco (pp. 14-21).
Display Omitted► Alkylation is an efficient method to retain C from small oxygenates in liquid fraction of bio-oil. ► m-Cresol alkylation activity follows the sequence 2-propanol>propylene>1-propanol. ► A hydrogenation/alkylation two-stage process is proposed to utilize small aldehydes and ketones. ► The combination Pt–Fe/SiO2+H-beta was found to be effective for the two-stage process.Alkylation of phenolics with alcohols is an efficient way to retain carbon from small oxygenates in the liquid products of pyrolysis bio-oil. In this contribution, we have investigated the alkylation of m-cresol with several alkylating agents over H-Beta zeolite. The alkylation activity follows the sequence 2-propanol>propylene>1-propanol. In all cases, propylene is the actual alkylation agent since the alcohols dehydrate at a faster rate than the rate of alkylation. A two-stage process is proposed to convert fractions of bio-oil rich in small aldehydes and ketones together with phenolics. In the first stage, aldehydes and ketones are selectively hydrogenated to alcohols. In the second stage, the resulting alcohols alkylate the phenolic compounds and get incorporated into the upgraded liquid. To illustrate this concept, two consecutive catalyst beds have been used. The first bed contains a metal catalyst for the selective hydrogenation. Among several catalysts investigated, Cu/SiO2 and Pt–Fe/SiO2 were found to exhibit good selectivity to hydrogenate the aldehyde and ketone, respectively, while preserving the aromatic ring of the phenolic compound. The second bed contains an H-Beta zeolite for the alkylation stage.
Keywords: Biofuels; Cresol alkylation; Acetone and propanal hydrogenation
Alloyed Ni-Fe nanoparticles as catalysts for NH3 decomposition by Søren Bredmose Simonsen; Debasish Chakraborty; Ib Chorkendorff; Søren Dahl (pp. 22-31).
Display Omitted► Non-noble metal Ni-Fe alloy catalysts for NH3 decomposition. ► Promising catalysts for high temperature NH3 decomposition. ► Structural sensitivity: increasing activity for decreasing particle sizes. ► Of various support oxides: Al2O3-based support materials give the best performance.A rational design approach was used to develop an alloyed Ni-Fe/Al2O3 catalyst for decomposition of ammonia. The dependence of the catalytic activity is tested as a function of the Ni-to-Fe ratio, the type of Ni-Fe alloy phase, the metal loading and the type of oxide support. In the tests with high temperatures and a low NH3-to-H2 ratio, the catalytic activity of the best Ni-Fe/Al2O3 catalyst was found to be comparable or even better to that of a more expensive Ru-based catalyst. Small Ni-Fe nanoparticle sizes are crucial for an optimal overall NH3 conversion because of a structural effect favoring the smallest particles in terms of catalytic activity per active site. Compared with SiO2, ZrO2 and TiO2, the support materials Al2O3 or Mg-Al-spinel give the highest performance in the high temperature range.
Keywords: Catalysis; NH; 3; decomposition; Nickel-iron alloy; Hydrogen storage; Hydrogen production; Fuel cell
Deoxygenation of propionic acid on heteropoly acid and bifunctional metal-loaded heteropoly acid catalysts: Reaction pathways and turnover rates by Mshari A. Alotaibi; Elena F. Kozhevnikova; Ivan V. Kozhevnikov (pp. 32-40).
Display Omitted► Propionic acid deoxygenation studied at 250–400°C in H2 or N2. ► HPA catalysed ketonisation to 3-pentanone at 250–300°C in N2. ► Pd and Pt decarbonylated propionic acid to ethene in H2 but had no effect in N2. ► Cu hydrogenated CO bond to yield propanal and 1-propanol. ► The turnover rate of propionic acid conversion follows the order: Pd>Pt>Cu.Reaction pathways of the gas-phase deoxygenation of propionic acid in the presence of heteropoly acid and bifunctional metal-loaded heteropoly acid catalysts were investigated in a fixed-bed reactor at 250–400°C in flowing H2 or N2. Silica-supported H3PW12O40 (HPW) and bulk acidic salt Cs2.5H0.5PW12O40 (CsPW), both in H2 and in N2, exhibited ketonisation activity between 250 and 300°C to yield 3-pentanone, CsPW being more selective than HPW. At 400°C, HPW and CsPW were active for decarbonylation and decarboxylation of propionic acid to yield ethene and ethane, respectively. Loading Pd or Pt onto CsPW greatly enhanced decarbonylation in flowing H2 but had little effect in N2. Similar performance exhibited Pd/SiO2 and Pt/SiO2, giving almost 100% selectivity to ethene in H2. These results are consistent with hydrodeoxygenation of propionic acid on Pd and Pt, suggesting that hydrogenolysis of CC bond plays essential role. In contrast to the Pd and Pt catalysts, Cu catalysts, Cu/CsPW and Cu/SiO2, were both active in hydrogenation of CO bond to yield propanal and 1-propanol. Turnover rates of propionic acid conversion on metal catalysts followed the order Pd>Pt>Cu for both CsPW-supported and silica-supported metal catalysts.
Keywords: Deoxygenation; Ketonisation; Propionic acid; Heteropoly acid; Metal catalysts; Heterogeneous catalysis
A comparative study of bulk and 3DOM-structured Co3O4, Eu0.6Sr0.4FeO3, and Co3O4/Eu0.6Sr0.4FeO3: Preparation, characterization, and catalytic activities for toluene combustion by Kemeng Ji; Hongxing Dai; Jiguang Deng; Xinwei Li; Yuan Wang; Baozu Gao; Guangmei Bai; Chak Tong Au (pp. 41-48).
Display Omitted► 3DOM-structure and bulk Co3O4, Eu0.6Sr0.4FeO3, and Co3O4/Eu0.6Sr0.4FeO3 are prepared. ► Porous samples are higher than bulk samples in Oads content and better reducibility. ► The porous samples exhibit higher catalytic performance than the bulk samples. ► There is a synergistic effect between Co3O4 and Eu0.6Sr0.4FeO3. ► Catalytic activity is governed by Oads content, reducibility, and synergistic action.Three-dimensionally ordered macroporous (3DOM) and bulk Co3O4, Eu0.6Sr0.4FeO3 (ESFO), and 3 wt% Co3O4/Eu0.6Sr0.4FeO3 (3Co3O4/ESFO) were fabricated using the PMMA-templating (3DOM-Co3O4 and 3DOM-ESFO), citric acid-assisted hydrothermal (Co3O4-bulk and ESFO-bulk), and incipient wetness impregnation (3Co3O4/3DOM-ESFO and 3Co3O4/ESFO-bulk) methods, respectively. Physicochemical properties of these materials were characterized by means of various techniques, and their catalytic activities were evaluated for toluene combustion. Compared to the nonporous Co3O4 and ESFO samples, the 3DOM-Co3O4, 3DOM-ESFO, and 3Co3O4/3DOM-ESFO samples exhibited higher oxygen adspecies concentrations and better low-temperature reducibility. The 3Co3O4/3DOM-ESFO sample showed the best catalytic activity for toluene combustion, giving the T50% and T90% of 251 and 269°C at 20,000mL/(gh), respectively. The apparent activation energies of these samples were in the range of 72–88kJ/mol. We believe that the higher oxygen adspecies concentration, better low-temperature reducibility, and synergistic action between Co3O4 and 3DOM-structured ESFO were responsible for the excellent catalytic performance of 3Co3O4/3DOM-ESFO.
Keywords: Three-dimensionally ordered macroporous perovskite-type oxide; Supported cobalt oxide catalyst; Toluene combustion; Synergistic action
New palladium catalysts on polyketone prepared through different smart methodologies and their use in the hydrogenation of cinnamaldehyde by Anna Maria Raspolli Galletti; Luigi Toniolo; Claudia Antonetti; Claudio Evangelisti; Claudia Forte (pp. 49-59).
Display Omitted► Polyketone has been employed for the first time as support for Pd nanoparticles. ► Three different synthetic approaches were adopted. ► The hydrogenation of cinnamaldehyde to hydrocinnamaldehyde was studied. ► The catalysts showed high stability and recyclability. ► The performances are related to Pd nanoparticles morphology.For the first time, polyketone (poly-3-oxotrimethylene, PK) has been employed as support for Pd nanoparticles. Three different approaches have been adopted: (i) reduction of Pd(OAc)2 in EtOH under microwave irradiation, (ii) hydrothermal reduction of the same precursor in EtOH or n-BuOH employing traditional heating and (iii) vaporization of Pd metal through metal vapour synthesis. These supported systems have been characterized by solid state NMR, TEM, ICP, XPS, BET and tested in the selective hydrogenation of cinnamaldehyde (CAL) to hydrocinnamaldehyde (HCAL) as probe reaction. Their catalytic performances have been compared in relation to their preparation procedure and morphology. It is remarkable that these catalysts do not show significant leaching even after several catalytic recycles, thus indicating their high stability and recyclability, ascribed to a stabilizing capacity of this particular polymeric support.
Keywords: Pd nanoparticles; Polyketone; Cinnamaldehyde; Hydrocinnamaldehyde
One-pot solvothermal synthesis of mixed Cu-Ce-O x nanocatalysts and their catalytic activity for low temperature CO oxidation by Driss Mrabet; Ahmed Abassi; Robenson Cherizol; Trong-On Do (pp. 60-66).
Display Omitted► One-pot solvothermal synthesis of the uniform binary Cu-Ce-O x nanosystem. ► Their catalytic activity for CO higher than that of the conventional catalysts. ► Their high activity due to mutual and synergistic effect between two nanodomains Cu and Ce.One-pot solvothermal method has been developed for the synthesis of high-surface area Cu-Ce-O x binary nanocatalysts with various Cu contents in the presence of oleylamine as capping agent. The obtained binary nanocatalysts were characterized by different techniques including XRD, H2-TPR, TEM, BET and XPS. The influence of Cu contents on their catalytic performance for the CO oxidation was also studied. Our results revealed that the Cu-Ce-O x binary nanocatalysts show the better catalytic activity compared to those of the conventional Cu-Ce-O x, bare nano-CeO2 and nano-CuO catalysts. This is ascribed to mutual interaction and synergistic effect between copper oxide species and cerium oxide. Among the obtained nanocatalysts, the Cu-Ce-O x nanocatalyst with 5.6wt% Cu (noted as 5.6-Cu-Ce-O x) exhibits the best catalytic activity; the 50% CO conversion can be reached at 55°C. H2-TPR profiles show two reduction peaks at low and high temperatures for these catalysts, which could be attributed to the reduction of highly dispersed CuO on the CeO2 surface and the bulk-like CuO species, respectively. Using the one-pot solvothermal synthesis developed in this study, 6–8wt% Cu content is needed for the high catalytic activity for the CO oxidation at low temperature.
Keywords: Binary Cu-Ce-O; x; nanocatalyst; Nanostructure; Porous materials; Mutual interaction; CO oxidation
2-(1-(Arylimino)ethyl)-8-arylimino-5,6,7-trihydroquinolylcobalt dichloride: Synthesis and polyethylene wax formation by Wen-Hua Sun; Shaoliang Kong; Wenbin Chai; Takeshi Shiono; Carl Redshaw; Xinquan Hu; Cunyue Guo; Xiang Hao (pp. 67-73).
Display Omitted► New tridentate cobalt dichloride pre-catalysts exhibits high activity to polymerize ethylene. ► Highly thermal-stable cobalt(II) pre-catalysts in ethylene polymerization. ► Single-site active species of cobalt pre-catalysts. ► Cobalt pre-catalysts showed higher activities than their iron analogs did. ► Polyethylene waxes with narrow polydispersity.A series of 2-(1-(arylimino)ethyl)-8-arylimino-5,6,7-trihydroquinolylcobalt dichloride (aryl=2,6-R1-4-R2C6H2) pre-catalysts were synthesized and structurally characterized by FT-IR and elemental analyses. The molecular structures ofCo1 (R1=Me, R2=H),Co2 (R1=Et, R2=H) andCo5 (R1=Et, R2=Me) were determined by single-crystal X-ray diffraction analysis, and confirmedCo1 as a distorted trigonal bipyramidal geometry at the metal, whilst inCo2 andCo5 the metal is square-pyramidal. Upon treatment with either MAO or MMAO, all cobalt pre-catalysts exhibited highest activities at 60°C for ethylene polymerization. The resultant polyethylenes, under optimization reaction parameters, possessed low molecular weight (waxes) and narrow polydispersity.
Keywords: 2,8-Bis(imino)5,6,7-trihydroquinolylcobalt dichloride; Cobalt pre-catalyst; Thermal-stable pre-catalyst; Single-site active species; Polyethylene wax
Inactivation path during the copper (II) catalyzed synthesis of Questiomycin A from oxidation of 2-aminophenol by Cătălina Olmazu; Mihaela Puiu; Irina Babaligea; Adina Răducan; Dumitru Oancea (pp. 74-80).
Display Omitted► The catalytic oxidation of OAP to APX was achieved in the presence of simple copper salts. ► Low yields in APX and operational inactivation of the catalyst were observed. ► The inactivation path can be assigned to formation of a stable copper(II)–OAP complex. ► A 11-step kinetic model able to describe the inactivation of copper(II) catalyst was proposed.The catalytic oxidation of 2-aminophenol (OAP) to 2-amino-3H–phenoxazin-3-one (APX, Questiomycin A) was the object of numerous studies partly due to antimicrobial properties of Questiomycin A and mostly because it can be used as a model for the synthesis of the naturally occurring antineoplastic agent Actinomycin D. Several copper complexes were used as dioxygen and/or substrates activators in order to mimic the activity of phenoxazinone synthase, but the reported assays failed to provide reasonable mechanistic features in media compatible with natural conditions. The main purposes of our work were to use simple copper salts to perform oxidation of OAP in oxygenated aqueous solutions and to develop a reaction scheme able to explain the low yields in APX along with the operational inactivation of the catalyst. A 11-step kinetic model able to describe the inactivation of copper(II) catalyst during oxidation of OAP to APX in oxygenated solutions was developed, and the rate constants for both catalytic and non-catalytic branch were estimated either experimentally or using a computing program for detailed kinetic simulation. It was demonstrated that the inactivation path can be assigned to formation of the stable bis( o-iminosemiquinonato)copper(II) complex, a compound reported as a moderate antimicrobial agent.
Keywords: 2-Aminophenol; Oxidation; Questiomycin A; Kinetic modelling; Copper(II) complex
Fabrication of catalytically active AgAu bimetallic nanoparticles by physical mixture of small Au clusters with Ag ions by Haijun Zhang; Naoki Toshima (pp. 81-88).
Display Omitted► Highly active and durable AgAu bimetallic nanoparticles were prepared. ► About one third of the bimetallic nanoparticles could have a Ag-core/Au-shell structure. ► Mixture of Au nanoparticles and AgClO4 provided the small nanoparticles ( d<2.0nm). ► This is the first example of small AgAu bimetallic nanoparticles by physical mixture. ► The nanoparticles had twice catalytic activity of Au nanoparticles with same size.Catalytically highly active PVP-protected AgAu bimetallic nanoparticles (BNPs) less than 2nm in diameter were fabricated by simultaneous physical mixture of aqueous dispersions of Au clusters with Ag+ ions. The prepared AgAu BNPs, the dispersion of which was stably kept for more than 2 months under ambient conditions, were characterized by UV–vis, ICP, HR-TEM, and EDS in HR-STEM. The prepared BNP colloidal catalysts possessed a high activity for aerobic glucose oxidation. The highest activity of 3.77mol-glucoses−1mol-metal−1 was observed for the BNPs prepared with Ag/Au atomic ratio of 2/8, which was more than two times higher than that of Au nanoparticles with nearly the same particle sizes.
Keywords: AgAu; Bimetallic nanoparticles; Aerobic glucose oxidation; Gold catalyst; Physical mixtures
Photocatalytic synthesis of silver dendrites using electrostatic hybrid films of porphyrin–polyoxometalate by Iftikhar Ahmed; Xiaoxia Wang; Nadia Boualili; Hualong Xu; Rana Farha; Michel Goldmann; Laurent Ruhlmann (pp. 89-99).
Display Omitted► Porphyrin–polyoxometalate systems are formed by layer-by-layer method and are used for phototocatalysis. ► Photocatalytic reduction of Ag(I) (used as model system) is studied under visible illumination. ► Giant silver dendrites are obtained. ► The study entails aqueous heterogeneous catalysis where it is easy to recover catalyst.Films based on electrostatic interactions between tetracationic porphyrin, 5,10,15,20-(4-trimethylammoniophenyl) porphyrin tetra( p-toluenesulfonate), [H2TPhN(Me)3P]4+ and Dawson type polyoxometalate α2-[Fe(P2W17O61)]7− (POM) are formed by the so called layer-by-layer self-assembly method. Successive deposition of layers has been monitored by UV–visible absorption spectroscopy. Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) have been used to explore the morphology and composition, respectively. Electrochemistry and permeability studies have been carried out by cyclic voltammetry.The photocatalytic properties of these films have been also studied for the reduction of silver ions. Indeed, in these systems, porphyrins can be excited by visible light which play the role of photosensitizers able to give electrons to POM known to be good catalysts. Giant silver dendrites have been obtained.
Keywords: Porphyrin; Polyoxometalate; Photocatalysis; Dendrites; Nanoparticles; Silver; Layers-by-layers
Synthesis of nano-crystalline La1– xSr xCoO3 –δ perovskite oxides by EDTA–citrate complexing process and its catalytic activity for soot oxidation by D. Hari Prasad; S.Y. Park; E.-O. Oh; H. Ji; H.-R. Kim; K.-J. Yoon; J.-W. Son; J.-H. Lee (pp. 100-106).
Display Omitted► Soot oxidation over LSC catalysts prepared by EDTA–citrate process was investigated. ► Sr 3d spectra revealed a higher surface component of Sr for LSC64. ► O 1s spectra disclosed more number of surface oxygen species (MO) for LSC64. ► LSC64 showed higher catalytic activity than the other samples.In the present study, La1– xSr xCoO3– δ ( x=0.2, 0.3, 0.4, 0.5) perovskite nano-particles have been successfully prepared by EDTA–citrate complexing process and the catalytic performance was examined for the soot oxidation activity. The physio-chemical properties of these materials were characterized by means of X-ray diffraction (XRD), thermogravimetry–differential thermal (TG–DTA) analysis, BET surface area and X-ray photoelectron spectroscopy (XPS) analysis, scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) analysis. TG–DTA analysis suggested that, in the temperature range of 350–500°C, the pyrolysis of metal/nitrate/citrate/EDTA complexes takes place and the single phase La1– xSr xCoO3– δ perovskite oxides can be formed at 900°C and the phase formation has been confirmed by XRD analysis. The surface composition of the samples derived from XPS analysis indicated an impoverishment of lanthanum content at the surface with the increase of strontium content. For La0.6Sr0.4CoO3– δ sample, Sr-enriched perovskite surface has been observed along with the more number of surface oxides (M(Sr, La, Co)O) resulting in higher catalytic activity for soot oxidation than the others.
Keywords: La; 1–; x; Sr; x; CoO; 3–; δ; perovskite oxides; EDTA–citrate complexing process; Soot oxidation
Efficient route for oxazolidinone synthesis using heterogeneous biopolymer catalysts from unactivated alkyl aziridine and CO2 under mild conditions by Amal Cherian Kathalikkattil; Jose Tharun; Roshith Roshan; Han-Geul Soek; Dae-Won Park (pp. 107-114).
Display Omitted► Covalent functionalization of alkyl pyridinium halides to chitosan (CS-RPX). ► CS-RPX catalyst for efficient oxazolidinone synthesis. ► Synergism offered by hydroxyl, amino and anion of catalyst unit for cycloaddition. ► Recycled the catalyst up to five consecutive cycles.Biopolymers made of polysaccharide chains are emerging as promising materials for designing efficient, cheap, environmental friendly and recyclable heterogeneous catalysts. In this study, we synthesized a series of covalently functionalized chitosan-alkyl pyridinium halides (CS-RPX, R=ethyl, propyl, butyl, hexyl and X=Cl, Br) and evaluated their potential application as catalysts for the chemical transformation of CO2 to 4-methyl-2-oxazolidinone using 2-methylaziridine under mild reaction conditions. The catalysts were characterized using different physicochemical methods, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), thermo gravimetric analysis (TGA), elemental analysis (EA) and field emission scanning electron microscopy (FE-SEM).1H NMR, GC–MS, EA and FT-IR were used to confirm successful oxazolidinone formation. Cycloaddition was found to proceed through the synergistic effect of the hydroxyl and amine groups of chitosan together with the anion. The catalyst was reused five times after the cycloaddition reaction, with a loss of 2–6% in conversion and 1–3% in selectivity per cycle. The effect of different reaction parameters, such as catalyst amount, time, temperature and CO2 pressure were studied to determine the reaction conditions that resulted in the highest conversion and selectivity.
Keywords: Chitosan; Pyridinium ionic liquids; Carbondioxide; 2-Methylaziridine, 4-Methyloxazolidin-2-one
The role of shape selectivity in catalytic fast pyrolysis of lignin with zeolite catalysts by Yanqing Yu; Xiangyu Li; Lu Su; Ying Zhang; Yujue Wang; Huizhong Zhang (pp. 115-123).
Display Omitted► The molecular dimensions of lignin pyrolysis products were calculated. ► The effective pore size of four zeolites at 650°C were evaluated. ► The pore size of zeolite is substantially enlarged at high temperatures of CFP. ► Shape selectivity dictates the conversion of lignin-derived oxygenates in CFP.Catalytic fast pyrolysis (CFP) of lignin with four different zeolite catalysts was investigated to determine the role of shape selectivity of zeolites in CFP. These zeolites included ZSM-5, mordenite, beta, and Y zeolites, which have various crystallographically determined static pore sizes between 5.6 and 7.6Å. The molecular dimensions of pyrolysis products, including lignin-derived oxygenates and aromatics, were calculated using quantum chemical computations. The effective pore sizes of the four zeolites at 650°C were then determined by analyzing the molecular size and conversion behavior of the pyrolysis products in CFP. Results suggest that thermal distortion of the zeolite pore structure under high-temperature conditions of CFP effectively enlarge the crystallographically determined pore sizes of the zeolites by 2.5–3.4Å. Therefore, many lignin-derived oxygenates with a molecular size considerably larger than the static pore size were able to enter the pores of the zeolites and become effectively converted in our CFP tests. Bulkier monolignols derived from syringyl lignin, however, could not be effectively converted by ZSM-5 and mordenite zeolites due to size exclusion or pore blockage. Among the four zeolites, ZSM-5 produced the highest aromatic yield, followed in order by beta, mordenite, and Y zeolites. Beta and Y zeolites were the most effective catalysts for deoxygenating lignin-derived oxygenates. This analysis indicates that for CFP of softwood, ZSM-5 is the optimal catalyst because it can achieve satisfactory deoxygenation and aromatic production simultaneously, whereas for hardwood feedstock, beta zeolite may be used to convert bulky oxygenates derived from syringyl lignin.
Keywords: Pyrolysis; Biomass; Biofuel; Zeolite; Shape selectivity
Glycerol dehydration over calcium phosphate catalysts: Effect of acidic–basic features on catalytic performance by Dušan Stošić; Simona Bennici; Sergey Sirotin; Christophe Calais; Jean-Luc Couturier; Jean-Luc Dubois; Arnaud Travert; Aline Auroux (pp. 124-134).
Display Omitted► Calcium phosphates (Ca/P=1.39–1.77) were tested in glycerol dehydration reaction. ► Hydroxyapatite impregnated with WO3 was also investigated. ► Acidic–basic properties of catalysts were correlated with catalytic activity. ► Reducing the number of basic sites increases the production of acrolein. ► Reducing of number and strength of acid centers increases the acetol yield.This work focuses on investigation of calcium phosphate compounds with different Ca/P ratios (1.39–1.77). Additionally, hydroxyapatite impregnated with tungsten oxide was also investigated. The structural, textural, and surface properties of these materials have been fully characterized using appropriate techniques (low-temperature adsorption–desorption of nitrogen, X-ray diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and temperature-programmed reduction (TPR)). Adsorption microcalorimetry of NH3 or SO2 was used to estimate the population, strength and strength distribution of acid and basic sites. The nature of acidic sites was determined through the adsorption/desorption of pyridine, followed by infrared spectroscopy. Catalytic performance of the catalysts was tested in the gas phase dehydration of glycerol with the intention of finding correlations between catalytic activity and surface acid–base features. Results show that Ca/P ratio, beside the already known influence on acidic/basic features, also influences red-ox properties of these materials. The investigation performed here proved that, in order to get acrolein – with high selectivity – which is formed on acid sites, it is not only necessary to provide acidity, but also to hinder basic sites. Our results also show that reducing of number and strength of acid centers increases the yield of other desired product, acetol.
Keywords: Calcium phosphate catalysts; Acid–base properties; Glycerol conversion; Acrolein; Acetol
Catalytic oxidation of n-octane over cobalt substituted ceria (Ce0.90Co0.10O2− δ) catalysts by Mahadevaiah Narayanappa; Venkata D.B.C. Dasireddy; Holger B. Friedrich (pp. 135-143).
Display Omitted► Ce0.90Co0.10O2− δ catalyst is prepared by a single step solution combustion method. ► Ce0.90Co0.10O2− δ is a good catalyst for the oxidation of n-octane. ► Catalyst shows good activity and selectivity to oxygenates, octenes and aromatics. ► C8 aromatics like ethyl benzene and styrene formed through C1 to C6 cyclisation. ► No deactivation of the catalyst seen even after long start-up/shut-down operations.Catalytic oxidative activation of octane was carried out in the presence of Co substituted ceria catalysts of the type Ce1− xCo xO2− δ (Ce0.90Co0.10O2− δ). The catalysts were synthesized by the solution combustion method and the surface characteristics were determined by BET, powder XRD, structural refinement and XPS. The synthesized catalyst crystallizes with a fluorite structure, the crystallinity was confirmed by bright-field images of TEM. Hydrogen uptake studies show a strong reduction peak at 425°C and it proves substitution of cobalt ions inside the matrix of the lattice system. X-ray photoelectron spectroscopy (XPS) clarified that even though under reduction conditions, the cerium ions were slightly oxidized because of the sequence of standard reduction potentials of both cerium and cobalt ions. The catalytic activity of the catalyst was investigated between the temperature range from 350 to 550°C, in a continuous flow fixed bed reactor at GHSV 4000h−1 with varying n-octane to oxygen molar ratios from 1:0.5 to 1:2.5. Results show that the conversion and selectivity of products (alkenes, oxygenates, aromatics, carbon oxides and cracked products) from the n-octane varies consequently with n-octane to oxygen molar ratio. The product selectivity at iso-conversion for C8 products, aromatics, oxygenates and octenes was determined. The catalyst shows higher activity with respect to an increase in the n-octane to oxygen molar ratio and reaction temperature.
Keywords: Cobalt substituted ceria; Ce–Co ionic catalysts; n; -Octane; 1-Octene; Styrene; Oxidative dehydrogenation
Hydrodeoxygenation of lignin model compounds over a copper chromite catalyst by Keenan L. Deutsch; Brent H. Shanks (pp. 144-150).
Display Omitted► Reaction networks were determined for lignin model compounds conversion over copper. ► Demethoxylation was found to be a leading deoxygenation reaction. ► Hydroxyl/methoxy groups were found to activate the aromatic ring hydrogenation. ► Methyl groups stabilized the aromatic group against hydrogenation.The hydrodeoxygenation of benzyl alcohol, phenol, anisole, o-cresol, catechol, guaiacol, and vanillyl alcohol were carried out from 150 to 275°C at 50bar H2 with a CuCr2O4·CuO catalyst in a decalin solvent. The hydroxymethyl group of benzyl alcohol was found to be highly reactive towards hydrogenolysis to form toluene. Demethoxylation of anisole to form benzene was found to be the primary reaction pathway in contrast to demethylation and transalkylation reactions, which are more prevalent for conventional hydrotreating catalysts. The hydroxyl group of phenol strongly activated the aromatic ring towards hydrogenation forming cyclohexanol which was subsequently dehydrated and hydrogenated to form cyclohexane. Reaction networks of increasing complexity were devised for the major functional groups and integrated to describe the most complex molecule studied, vanillyl alcohol.
Keywords: Hydrogenolysis; Hydrodeoxygenation; Copper catalyst; Lignin; Bio-oil upgrading; Copper chromite
Effect of catalyst preparation conditions on the performance of eggshell cobalt/SiO2 catalysts for Fischer–Tropsch synthesis by Syed Ali Gardezi; John T. Wolan; Babu Joseph (pp. 151-163).
Display Omitted► An eggshell Co/SiO2 Fischer–Tropsch catalyst has been synthesized. ► Eggshell thickness modified using Thiele modulus calculations. ► Metal crystallite distribution within active shell is modified using solvent and calcination atmosphere. ► Eggshell catalyst gave maximum selectivity in middle distillate (Diesel and Jet Fuel) range. ► The solvent and calcination environment affect metal support interaction and activity of the catalyst.In this article, we examine the impact of solvent and calcination conditions, during catalyst preparation, on the performance of eggshell catalysts. Eggshell profile of silica supported cobalt catalysts provides a means to control selectivity in Fischer–Tropsch synthesis reactions. Solvents such as water and alcohol attach to the silanol groups on the silica gel surface and compete with metal salts during ion exchange and adsorption. The solution properties impact the metal dispersion and interaction with the metal support. The calcination conditions (static versus dynamic, oxidizing versus reducing atmosphere) also have an impact on metal dispersion and support interaction. Ethanol proved to be a better solvent for enhancing the dispersion due to its surface wetting pattern while direct reduction in dynamic hydrogen provided gradual decomposition of the cobalt precursor thus reducing agglomeration. The use of water as a solvent and a static air environment during calcination led to lower dispersion. Nitrogen physisorption experiments showed that under favorable conditions, synthesized eggshell catalyst retains most of the original support surface area. Surface elemental composition using XPS indicate that the effect of solvent was stronger than the calcination environment in determining catalyst dispersion. This result was also confirmed by hydrogen chemisorption studies. TPR results suggested that back reaction of calcination product (especially H2O) and the agglomeration were competing phenomena in a static oxidizing environment. However, hydrogen chemisorption indicated that metal agglomeration was far more significant than the back reaction in static air atmosphere. Catalyst activity and selectivity were tested in a fixed bed (FBR) reactor fitted with GC and FTIR analyzers. The eggshell catalyst demonstrated high activity as expected; however, selectivity of CO2 in our fixed bed catalytic reactor was higher than usual. The distribution of liquid hydrocarbon was in the narrow range of diesel and aviation fuel.
Keywords: Silica gel; Eggshell catalyst; Calcination; Fixed bed reactor; Cobalt catalyst; Selectivity; Fischer–Tropsch synthesis; Renewable fuels
A Ru-Sn-Co/AlO(OH) as a highly efficient catalyst for hydrogenation of dimethyl adipate to 1,6-hexanodiol in aqueous phase by Hong-Bin Jiang; Hai-Jun Jiang; Ke Su; De-Ming Zhu; Xue-Li Zheng; Hai-Yan Fu; Hua Chen; Rui-Xiang Li (pp. 164-170).
Display Omitted► The selectivity to 1,6-hexanodiol of 95% was obtained with a conversion of 98%. ► The addition of cobalt could stabilize Sn(IV). ► The addition of Sn and Co could promote the reduction of ruthenium oxide. ► The cooperation between Sn(IV) and hydrogen bond played an important role.A Ru-Sn-Co/AlO(OH) catalyst was prepared by co-impregnation, calcination, and hydrothermal reduction. The catalyst was well characterized by BET, XRD, SEM-EDX, XPS, H2-TPR, and Mössbauer spectroscopy, and then it was applied in the hydrogenation of dimethyl adipate to 1,6-hexanodiol in aqueous phase. It was found that the addition of cobalt could stabilize Sn(IV) and the cooperation between tin and cobalt could promote the reduction of ruthenium oxide. The γ-Al2O3 in the catalyst Ru-Sn-Co/γ-Al2O3 was transformed to AlO(OH) by the hydrothermal reduction. It was suggested that the stabilized Sn(IV) and the interaction between the hydroxyl group on the surface of AlO(OH) and the solvent water played a key role to improve the conversion of dimethyl adipate and the selectivity to 1,6-hexanodiol. The conversion of dimethyl adipate and the selectivity to 1,6-hexanodiol were up to 98% and 95%, respectively, under 5MPa of H2 and 493K for 10h.
Keywords: Ruthenium; Tin; Cobalt; Dimethyl adipate; 1,6-hexanediol; Hydrogenation
Kinetics and mechanism of hydrothermally prepared copper oxide nanorod catalyzed decomposition of ammonium nitrate by Anuj A. Vargeese; Krishnamurthi Muralidharan (pp. 171-177).
Display Omitted► Monoclinic CuO nanorods with aspect ratio ∼5 were hydrothermally synthesized. ► Catalytic decomposition of ammonium nitrate in presence of CuO nanorods were studied. ► Kinetic parameters for the catalytic and noncatalytic decomposition were computed. ► Advanced model-free and model-fitting methods used to compute kinetic parameters. ► Possible removal of NH3 by surface reactions changes the decomposition pathway.One of the key aspects in the development of materials science is the synthesis of particles with specific size and morphology for catalytic applications. Nowadays, nanostructured materials with specific morphology are gaining great importance in the field of catalysis. Thin, one-dimensional, monodispersed CuO nanorods with a significantly higher aspect ratio of 5, were successfully prepared by the hydrothermal method with subsequent ultrasonication. The formation of pure monoclinic CuO nanorods was confirmed by powder XRD and SAED. The CuO nanorod growth mechanism is investigated by using TEM and further characterized by FTIR, UV–visible spectroscopy and thermogravimetry. The catalytic decomposition of ammonium nitrate, an environmental friendly rocket propellant oxidizer, over the synthesized CuO nanorods was investigated. The thermal kinetic constants for the catalytic and noncatalytic decomposition of ammonium nitrate samples were computed by using model free (differential and non-linear integral) and model fitting approaches. The catalytic influence was evident even with 1% catalyst concentration. The model fitting method suggested contracting cylinder mechanism as the effective mechanism for all the investigated samples. Apparently, the CuO nanorods provide Lewis acid and/or active metal sites, facilitating the removal of ammonium nitrate decomposition inhibition species such as NH3 and thereby enhance the rate of decomposition.
Keywords: CuO nanorods; Ammonium nitrate; Reaction kinetics; Catalyzed decomposition; Surface reactions
Conversion of methanol into light olefins over ZSM-5 zeolite: Strategy to enhance propene selectivity by Francesca Lønstad Bleken; Sachin Chavan; Unni Olsbye; Marilyne Boltz; Fabien Ocampo; Benoit Louis (pp. 178-185).
Display Omitted► Design of ZSM-5 zeolites with tailored acidity. ► Development of stable and very active MTO catalysts. ► Optimal propene to ethene ratios (>5) obtained over a zeolite prepared via the fluoride route. ► Superior selectivity to propylene ascribed to low density of strong acid sites.Four ZSM-5 zeolite materials with varying crystal size, acid site density and morphology were prepared, characterized by BET, XRD, SEM, FT-IR, H/D exchange and n-hexane cracking experiments and tested as catalysts for the Methanol to Olefins (MTO) reaction at 350°C, WHSV=1.8g/gh under atmospheric pressure.Optimal propene to ethene ratios (>5) were obtained over a material prepared via the fluoride route. Its superior selectivity was tentatively ascribed to its low density of strong acid sites in combination with a long diffusion pathway and few crystal defects.
Keywords: Propene; MTO; ZSM-5 zeolite; Light olefins; Fluoride route
Slurry-phase hydrocracking of vacuum residue with a disposable red mud catalyst by Chinh Nguyen-Huy; Hyukmin Kweon; Hanna Kim; Do Kyoung Kim; Do-Woan Kim; Seung Hoon Oh; Eun Woo Shin (pp. 186-192).
Display Omitted► Red mud was used as a catalyst in slurry-phase hydrocracking of vacuum residue. ► The conversion of feedstock to distillate was thermally controlled. ► Coke formation and cracking reaction were suppressed in the presence of catalyst. ► Pyrrhotite (Fe( x−1)S x) was formed during reaction due to presence of sulfur in feed. ► Red mud was possibly self-activated during the reaction.In this study, red mud (RM) was used as a catalyst in slurry-phase hydrocracking of vacuum residue (VR) in batch system. Without RM, thermal cracking occurred and a lighter fraction and higher conversion was achieved than in the presence of catalyst. However, the catalytic cracking obviously inhibited both the coke formation and residue cracking reaction. We investigated the influence of reaction temperature, reaction time and RM concentration on VR conversion. Reaction temperature and time significantly improved the yield of naphtha, diesel and vacuum gas oil; unfortunately, they also increased the gas fraction, which is an undesirable product. Catalyst concentration negligibly affected the VR conversion while vacuum gas oil fraction in product distribution increased with catalyst concentration, indicating that the cracking reaction was suppressed in the presence of catalyst. Through the characterization of fresh and spent catalysts by diverse techniques, it has been determined that the crystalline iron oxide of RM transforms into pyrrhotite (Fe( x−1)S x), an active phase for the hydrocracking reaction, due to presence of sulfur in VR. Our results show that RM is possibly self-activated during the reaction and the pretreatment step can be eliminated.
Keywords: Red mud; Vacuum residue; Slurry-phase; Hydrocracking
The effect of fabrication method of hierarchical 3D TiO2 nanorod spheres on photocatalytic pollutants degradation by Hongwei Bai; Zhaoyang Liu; Siew Siang Lee; Darren Delai Sun (pp. 193-199).
Display Omitted► Hierarchical 3D TiO2 nanorod spheres were fabricated by hydrothermal and calcination method. ► Effect of fabrication method on property and activity of 3D TiO2 nanorod spheres were investigated. ► Well crystallized and monodisperse TiO2-C possesses larger surface area and light absorption. ► TiO2-C exhibited better photocatalytic activity than TiO2-H in degrading AO 7 and RhB. ► Calcination is promising for production of TiO2 nanorod spheres for pollutants degradation.The effect of fabrication method on the properties of hierarchical 3D TiO2 nanostructures was investigated by employing and developing both hydrothermal method and calcination method to synthesize hierarchical 3D TiO2 nanorod spheres in this study. A comprehensive comparison in terms of morphologies, crystallization, specific surface areas, light absorption capabilities, and photoluminescence spectrum was conducted between 3D TiO2 nanorod spheres synthesized via hydrothermal method and that synthesized via calcination method. A better photocatalytic activity was demonstrated over the TiO2 nanorod spheres synthesized through calcination method. This was ascribed to the better crystallization and monodispersion of the hierarchical 3D TiO2 nanorod spheres resulted from the calcination method; thus rendering it with more superior characteristics such as larger specific surface area, enhanced light absorption capability and faster transfer of electrons which suppress the recombination of photogenerated electrons and holes. This study is thus significant not only in promoting the development of hierarchical 3D TiO2 nanorod spheres via different methods, but also in revealing the effect of fabrication method on the photocatalytic activity of hierarchical 3D TiO2 nanorod spheres. The calcination method is proposed to be a facile and promising method for scale-up production of the hierarchical 3D TiO2 nanorod spheres with high photocatalytic activity for efficient pollutants degradation.
Keywords: 3D TiO; 2; nanorod spheres; Calcination; Hierarchical; Hydrothermal; Photocatalytic activity
Catalytic performance of Ru nanoparticles supported on different mesoporous silicas for preferential oxidation of CO in H2-rich atmosphere by Li Wang; Jiuling Chen; Archana Patel; Victor Rudolph; Zhonghua Zhu (pp. 200-209).
TEM image of Ru/MCM-41.Display Omitted► Ru catalysts supported on mesoporous silicas, MCM-41, MCM-48, SBA-15 and KIT-6. ► Preferential oxidation of CO in a H2-rich atmosphere (PROX). ► Ru/KIT-6 presents the highest surface activity.Ru catalysts supported on different mesoporous silicas, MCM-41, MCM-48, SBA-15 and KIT-6, were applied to the preferential oxidation of CO in a H2-rich atmosphere (PROX). The properties of mesoporous support and the supported Ru catalysts were investigated using N2 physisorption, FTIR, TEM, CO chemisorption, H2-TPR and XPS. The performance of Ru catalysts in PROX highly relates to the Ru dispersion, support pore structure, Ru reducibility and the interaction between Ru and support. Ru/KIT-6 presents the highest surface activity (TOF values), owing to the easiest reducibility of Ru. Nevertheless, its poor Ru dispersion results in a low number of surface active sites, leading to the low CO conversion value over Ru/KIT-6. Ru/MCM-41 can achieve full CO conversion and the high CO2 selectivity in the reaction temperature range of 115–180°C owing to the high Ru dispersion from the strong interaction between Ru and MCM-41.
Keywords: PROX; CO; 2; selectivity; Ru dispersion; Mesoporous silica