Applied Catalysis A, General (v.402, #1-2)
Editorial Board (CO2).
Cellulose reactivity and glycosidic bond cleavage in aqueous phase by catalytic and non catalytic transformations by Amandine Cabiac; Emmanuelle Guillon; Flora Chambon; Catherine Pinel; Franck Rataboul; Nadine Essayem (1-10).
Display Omitted► Lignocellulosic biomass valorisation. ► Cellulose hydrolysis. ► Aqueous phase. ► Heterogeneous acid catalysis. ► Modest yields in glucose. ► Heterogeneous metal/acid catalysis. ► Valuable bioproducts.A key challenge for the next decades is to develop effective, safe, environmental friendly and economic technologies to convert lignocellulosic biomass into target molecules. The catalytic transformation of cellulose in aqueous phase is a promising way to obtain valuable products.This short review highlights different aspects related to this process from cellulose nature to its reactivity in various operating conditions. Focus will be made on recent advances dealing with use of heterogeneous catalysis for cellulose transformation.
Keywords: Cellulose; Biomass; Bioproduct; Heterogeneous catalysis;
Silica bonded n-propyl-4-aza-1-azoniabicyclo[2.2.2]octane chloride (SB-DABCO): A highly efficient, reusable and new heterogeneous catalyst for the synthesis of 4H-benzo[b]pyran derivatives by Alireza Hasaninejad; Mohsen Shekouhy; Nooshin Golzar; Abdolkarim Zare; Mohammad Mahdi Doroodmand (11-22).
Display Omitted► Introducing a new catalyst for organic transformations. ► Introducing an efficient new method for synthesis of 2-amino-4H-benzo[b]pyrans. ► Superiority of the catalyst in comparison with the reported catalysts. ► Generality and simplicity of the method, high yields and short reaction times. ► Environmental compatibility, non-toxicity, low cost and recoverability of the catalyst.The reaction of 3-chloropropyl silica with diazabicyclo[2.2.2]octane in dry acetone affords silica bonded n-propyl-4-aza-1-azoniabicyclo[2.2.2]octane chloride (SB-DABCO) as a new basic catalyst. The catalyst is used for the efficient synthesis of 4H-benzo[b]pyran derivatives via one-pot three-component reaction of cyclic ketones/1,3-diketones with aromatic aldehydes and alkylmalonates.
Keywords: Silica bonded n-propyl-4-aza-1-azoniabicyclo[2.2.2]octane chloride (SB-DABCO); 4H-Benzo[b]pyran; Silica supported catalyst; Alkylmalonate; 5,5-dimethylcyclohexane-1,3-dione;
Preparation of nitrogen doped K2Nb4O11 with high photocatalytic activity for degradation of organic pollutants by Yongfu Qiu; Lei Wang; Chi-fai Leung; Guijian Liu; Shihe Yang; Tai-Chu Lau (23-30).
Display Omitted► A new photocatalyst, K2Nb4O11-N, has been prepared and fully characterized. ► The activity of K2Nb4O11-N for OG, BPA and PCP photodegradation has been evaluated. ► A mechanism for the photodegradation of OG, BPA and PCP by K2Nb4O11-N is proposed.Nitrogen doped K2Nb4O11 (K2Nb4O11-N) has been prepared by solid state reaction between K2Nb4O11 and urea at 400 °C. K2Nb4O11-N has been characterized by XRD, SEM, XPS and UV/vis diffuse reflectance. The photodegradation of various organic pollutants in water by this material, including Orange G (OG), bisphenol A (BPA) and pentachlorophenol (PCP) have been studied at λ > 330 nm and >399 nm. The results show that the photocatalytic activity of K2Nb4O11-N at >399 nm is higher than those of K2Nb4O11 and Degussa TiO2 P25, indicating the activating effect of nitrogen doping. A mechanism for the photodegradation of organic substrates by K2Nb4O11-N is proposed.
Keywords: Photodegradation; Niobate; Nitrogen-doped; Organic pollutants;
Application of different pore diameter SBA-15 supports for heavy gas oil hydrotreatment using FeW catalyst by Philip E. Boahene; Kapil K. Soni; Ajay K. Dalai; John Adjaye (31-40).
.Display Omitted► Pore diameter plays a vital role in the hydrotreating of heavier petroleum fractions. ► Catalyst with pore diameter ∼10 nm showed the highest hydrotreating activity. ► DRIFTS studies show that the catalyst with pore diameter of 10 nm has the highest number of coordinatively unsaturated sites (CUS).This work focuses on utilizing mesoporous SBA-15 materials of different pore diameters as potential hydrotreating catalyst supports for heavy gas oil (HGO). Hexane was used as swelling agent for the preparation of variable pore diameter SBA-15 materials. Four kinds of SBA-15 supported FeW catalysts with different pore diameters in the range of 5–20 nm were prepared and designated as Cats-A to D. The aqueous co-impregnation technique was employed for preparation of the catalysts. The supports were characterized by several techniques including X-ray powder diffraction (XRD) and N2 adsorption–desorption isotherms. The SBA-15 supported FeW catalysts were characterized by ICP-MS, BET surface area analysis, powder XRD, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and CO chemisorption. Results from XRD profiles, TEM images, and N2 adsorption–desorption isotherms confirmed the presence of highly ordered two-dimensional hexagonal structure with cylindrical arrays of pores. The structural integrity of the samples was preserved even after loading of 2 wt.% Fe and 15 wt.% W. Hydrotreating experiments were conducted using bitumen derived heavy gas oil under industrial conditions of temperature, pressure, LHSV, and gas to oil ratio of 375–400 °C, 8.8 MPa, 1 h−1, and 600 mL/mL, respectively. The SBA-15 supported catalyst with pore diameter of 10 nm (Cat-B) was the best among the supports studied for FeW catalysts, probably due to sufficient mass transfer of reactant liquids and gases through the catalyst's pores while still maintaining a high surface area necessary for metal dispersion.
Keywords: SBA-15; Pore diameter; FeW catalyst; Heavy gas oil; HDN; HDS; Hydrotreating;
Surface temperature profiles in CH4 CPO over honeycomb supported Rh catalyst probed with in situ optical pyrometer by Alessandro Donazzi; Dario Livio; Alessandra Beretta; Gianpiero Groppi; Pio Forzatti (41-49).
Display Omitted► Operando technique for short contact time catalytic reactions with strong T gradients. ► Spatially resolved surface temperature profiles probed by in situ optical technique. ► 45° angled optical fibers allow an accurate measurement of the surface temperature.The rigorous estimation of the temperature of the surface of a working catalyst is an issue of fundamental and practical relevance, especially in the case of high temperature reactions. In the present article, the potentialities and complexities of an optical technique, consisting of an optical fiber connected to an infrared pyrometer, are explored with respect to the catalytic partial oxidation of CH4 performed over Rh honeycomb catalysts. The case of a 400 cpsi cordierite honeycomb support is analyzed. The effects of different geometrical configurations of the fiber probe are measured and the associated optical artifacts are analyzed. By comparing the experimental results with a predictive numerical model, it is confirmed that the expected surface temperatures are closely captured with a 45° angled optical fiber specifically calibrated and that the use of a thermocouple, sliding from the front face, reveals the temperature of the gas phase. This latter can be dramatically different from that of the solid phase at the reactor inlet, where heat and mass transfer control the kinetics. The application of a non contact infrared device to measure the solid surface temperature is therefore essential, provided that its application is minimally intrusive both with respect of the catalytic volume and of the reactor set-up.
Keywords: Optical fiber; IR pyrometer; Spatial profiles; Catalytic partial oxidation; Methane; Rhodium; High temperature catalysis;
Effect of the support, Al2O3 or SiO2, on the catalytic behaviour of Cr–ZnO promoted Pt catalysts in the selective hydrogenation of cinnamaldehyde by E.V. Ramos-Fernández; J. Ruiz-Martínez; J.C. Serrano-Ruiz; J. Silvestre-Albero; A. Sepúlveda-Escribano; F. Rodríguez-Reinoso (50-58).
Display Omitted► Cr–ZnO supported on SiO2 and Al2O3 as catalyst promoter. ► Catalysts for liquid phase hydrogenation of cinnamaldehyde. ► Higher promoter dispersion was achieved on the silica-supported sample. ► High selectivity was found in silica-supported sample. ► Diffusional problems were found in alumina-supported sample.The effect of the support, Al2O3 or SiO2, on the catalytic behaviour of Cr–ZnO promoted Pt catalysts has been studied in the liquid phase hydrogenation of cinnamaldehyde. A model Pt/Cr–ZnO catalyst has been used as a reference. H2PtCl6 in aqueous solution has been used as platinum precursor for the synthesis of catalysts. They have been calcined at 773 K and reduced at two different temperatures, 473 and 623 K, before the determination of their catalytic behaviour. It has been shown that the support greatly affects the properties and characteristic behaviour of the final catalysts. A higher promoter dispersion was achieved on the silica-supported sample, which favoured a high selectivity towards the unsaturated alcohol.
Keywords: Cinnamaldehyde hydrogenation; Support effects; Cr–ZnO; Pt catalysts;
Desilication of MOR zeolite: Conventional versus microwave assisted heating by V. Paixão; R. Monteiro; M. Andrade; A. Fernandes; J. Rocha; A.P. Carvalho; A. Martins (59-68).
.Display Omitted► Textural and catalytic properties depend on the method of heating.► Samples heated by both methods develop mesoporosity.► Microwave irradiation causes a partial enlargement of the micropores.► Microwave treated samples present catalytic properties closer to the parent material.MOR zeolites were modified via desilication treatments with NaOH, under conventional and microwave heating. The samples were characterized by powder X-ray diffraction, 27Al and 29Si NMR spectroscopy, TEM and N2 adsorption at −196 °C. The acidity of the samples and the space available inside the pores were evaluated through a catalytic model reaction, the isomerization of m-xylene, for which the profiles of the coke thermal decomposition were also analyzed. Powder X-ray diffraction and 29Si and 27Al MNR results show that in comparison with conventional heating, microwave irradiation (a less time consuming process) leads to identical amount of Si extraction from the zeolite framework. With this treatment, in addition to the customary mesopores development promoted by conventional heating, a partial conversion of the zeolite microporosity into larger micropores, is observed. The microwave irradiated and conventionally heated samples show different catalytic behavior in the m-xylene isomerization model reaction. It was observed that, by controlling the experimental conditions, it is possible to obtain samples with catalytic properties closer to the parent material, which is also confirmed by the respective coke analysis.
Keywords: Mesoporous mordenite; Desilication; Microwave; m-Xylene transformation; Coke analysis;
Kinetics of acetic acid synthesis from ethanol over a Cu/SiO2 catalyst by Bodil Voss; Niels Christian Schjødt; Jan-Dierk Grunwaldt; Simon Ivar Andersen; John M. Woodley (69-79).
Display Omitted► Cu/SiO2 is a selective catalyst for the dehydrogenation of ethanol to acetic acid. ► An empirical kinetic model was derived based on 71 data sets. ► A suggested hydroxyl oxidation pathway is consistent with the kinetic model. ► The activity of the catalyst was maintained for more than 800 h.The dehydrogenation of ethanol via acetaldehyde for the synthesis of acetic acid over a Cu based catalyst in a new process is reported. Specifically, we have studied a Cu on SiO2 catalyst which has shown very high selectivity to acetic acid via acetaldehyde compared to competing condensation routes. The dehydrogenation experiments were carried out in a flow through lab scale tubular reactor. Based on 71 data sets a power law kinetic expression has been derived for the description of the dehydrogenation of acetaldehyde to acetic acid. The apparent reaction order was 0.89 with respect to water and 0.45 with respect to acetaldehyde, and the apparent activation energy was 33.8 kJ/mol. The proposed oxidation of acetaldehyde with hydroxyl in the elementary rate determining step is consistent with these both. Density Functional Theory (DFT) calculations show the preference of water cleavage at the Cu step sites. In light of this, an observed intrinsic activity difference between whole catalyst pellets and crushed pellets may be explained by the Cu crystal size and growth rate being functions of the catalyst particle size and time.
Keywords: Ethanol dehydrogenation; Acetic acid; Cu crystal; Kinetics; Step sites;
Methods to improve the photocatalytic activity of immobilized ZnO/Bi2O3 composite by Chunzhi Li; Junying Zhang; Jing’an Yang; Tianmin Wang; Xiao Lv; Zilong Tang (80-86).
Display Omitted► ZnO film/Bi2O3 microgrid showed higher solar-light photocatalytic activity. ► Ag modification improved photocatalytic activity of the ZnO/Bi2O3 heterojunction. ► The proposed ZnO/Ag and Bi2O3/Ag band structures were given to discuss the mechanisms.In this paper, the photocatalytic activity of the immobilized ZnO/Bi2O3 composite was effectively improved by a special composite technology and surface modification method. The ZnO thin film was coated by a connected Bi2O3 microgrid via a microsphere lithography strategy to form ZnO film/Bi2O3 microgrid heterojunction, which showed higher photocatalytic activity than the pure ZnO film, Bi2O3 film and ZnO film/Bi2O3 film composite under xenon lamp irradiation. The annealing temperature was determined to have a great effect on the photocatalytic activity of ZnO film/Bi2O3 microgrid heterojunction, and the optimum calcining temperature was determined to be 300 °C. Ag particles were deposited on the surface of the samples to further improve the photocatalytic performance. The relationship of the energetic positions of Ag with ZnO or Bi2O3 deduces the separation of photo-generated electrons and holes.
Keywords: Photocatalysis; Heterojunction; Microgrid; Ag deposition;
Mesoporous sulfated zirconia mediated acetalization reactions by Apurba Sinhamahapatra; Narottom Sutradhar; Malay Ghosh; Hari C. Bajaj; Asit B. Panda (87-93).
Display Omitted► Synthesis of mesoporous sulfated zirconia (m-SZ) with high specific surface area. ► Strong and high amount of acid sites are present. ► Highly active towards acetalization reactions. ► 97% yield of dimethyl ketal of cyclohexanone was obtained using methanol in 45 min. ► m-SZ is easily recoverable from reaction system and can reuse for at least 5 times.A novel, convenient, one step synthetic procedure for the synthesis of mesoporous sulfated zirconia (m-SZ) using zirconium carbonate complex and its use as solid acid catalyst for the acetalization of different carbonyl compound is reported. The high specific BET surface area (234 m2 g−1) of m-SZ is achieved after the removal of the surfactant (cetyltrymethylammonium bromide, CTAB) through calcination at 550 °C for 6 h. Microscopic analysis indicated the presence of spherical particles with worm like pores. DRIFT (diffuse reflectance FTIR) of pyridine adsorbed m-SZ and NH3-TPD (temperature programmed desorption) analysis suggested the presence of appreciable amount of Brönsted acid sites. The synthesized m-SZ showed high catalytic activity towards protection of carbonyl compounds through acetal/ketal formation. For the open ketal (from cyclohexanone and methanol) 97% conversion with 100% selectivity was obtained in 1 h at room temperature under solvent free condition. The catalyst can be easily recycled after separation from the reaction system without considerable loss in catalytic activity.
Keywords: Acetalization reaction; Solid acid catalyst; Mesoporous sulfated zirconia;
Selective production of lactobionic acid by aerobic oxidation of lactose over gold crystallites supported on mesoporous silica by Luis-Felipe Gutierrez; Safia Hamoudi; Khaled Belkacemi (94-103).
Display Omitted► Highly active gold crystallites successfully dispersed on mesoporous silica (SiO2-meso). ► SiO2-meso presents a wormhole-like framework with interconnected 3D-mesopores. ► 0.7% Au/SiO2-meso is very active for lactose partial oxidation to lactobionic acid (LBA). ► 0.7% Au/SiO2-meso is 100% selective towards LBA production.Partial oxidation of lactose over Au-based catalyst system using nanostructured silica materials with improved activity, selectivity and stability was investigated as a novel chemo-catalytic approach for selective synthesis of lactobionic acid (LBA) for therapeutic, pharmaceutical and food grad applications.Highly active gold crystallites dispersed on mesoporous silica (SiO2-meso) using bis-[3-(triethoxysilyl) propyl] tetrasulfide (BTSPT), a silane coupling agent to immobilize gold, were successfully formulated, and their catalytic activity was evaluated in an agitated semi-batch reactor. The catalysts were characterized by N2 physisorption, XRD, XPS and TEM. The influence of the reaction conditions, i.e., temperature, pH value, metal loading and catalyst/lactose ratio on lactose conversion were investigated. After 100 min of reaction, the catalyst containing 0.7% Au showed the highest catalytic activity (100% lactose conversion) and a 100% selectivity towards LBA, when it was used at a catalyst/lactose ratio of 0.2 under alkaline (pH 9.0) and mild reaction temperature (65 °C).
Keywords: Lactobionic acid; Lactose; Oxidation; Gold clusters; Mesoporous silica;
Activity and selectivity of colloidal platinum nanocatalysts for aqueous phase cyclohexenone hydrogenation by Nathan E. Musselwhite; Sarah B. Wagner; Kimberly A. Manbeck; Lindsay M. Carl; Kyle M. Gross; Anderson L. Marsh (104-109).
Display Omitted► The use of larger sized nanoparticles results in higher selectivity to cyclohexanone. ► Larger sized nanoparticles also display higher turnover frequencies. ► Spectroscopic evidence links these observed trends to catalyst surface structure and adsorbate orientation.The effect of varying the particle size of poly(vinylpyrrolidone)-capped colloidal platinum nanocatalysts, synthesized in the 1–10 nm size range, on the activity and selectivity during the aqueous-phase hydrogenation of cyclohexenone was investigated. For all particle sizes utilized, products observed during the reaction in order of increasing selectivity were cyclohexenol, cyclohexanol, and cyclohexanone. Selectivity for the unsaturated alcohol (cyclohexenol) was found to be highest for the smallest-sized nanocatalyst, whereas selectivity for the saturated ketone (cyclohexanone) was found to be highest for the largest-sized nanocatalyst. Activities for cyclohexenone hydrogenation were observed to increase with increasing particle size, yet apparent activation energies were determined to be similar for 2.9–7.1 nm nanocatalysts, likely indicating that the same surface reaction is kinetically favored on these nanocatalyst surfaces. Attenuated total reflectance infrared (ATR-IR) spectroscopic measurements on adsorbed cyclohexenone suggest the η 1(C＝O) form is more prevalent on the smaller sized nanocatalysts, while the η 2(C＝C) and η 4(C＝O, C＝C) forms are more preferred on the larger sized nanocatalyst. The findings presented herein provide further evidence that structure sensitivity in ketone hydrogenation reactions is linked with catalyst surface structure and adsorbate orientation.
Keywords: Ketone; Chemoselective hydrogenation; Colloidal platinum; Nanocatalyst;
Mild alkane C–H and O–H oxidations catalysed by mixed-N,S copper, iron and vanadium systems by Ricardo R. Fernandes; Jamal Lasri; M. Fátima C. Guedes da Silva; José A.L. da Silva; João J.R. Fraústo da Silva; Armando J.L. Pombeiro (110-120).
Display Omitted► Syntheses of bis-pyridyl dithioether copper, iron and vanadium complexes. ► Application of the metal complexes in mild alkane C–H and O–H oxidations. ► High catalytic activity in the presence of certain acid additives. ► Effects of type and amount of acid promoter, oxidant and catalyst are reported. ► Solvent-free microwave-assisted oxidation of primary and secondary alcohols.Reactions of 1,6-bis(2′-pyridyl)-2,5-dithiahexane (Py2S2) with different sources of Cu(II), Fe(II) and V(III) afford the corresponding novel complexes [CuCl(Py2S2)]Cl (1), [CuCl(Py2S2)](CuCl2) (1′), [Cu(OTf)2(Py2S2)] (2), [Cu(Py2S2)(H2O)2](OTf)2 (2′), [FeCl2(Py2S2)] (3), [Fe(Py2S2)(CH3CN)2][SbF6]2 (4) and [VCl2(Py2S2)]Cl (5), bearing Py2S2 as a tetradentate ligand. All the compounds were characterised by IR, ESI–MS, elemental analyses and, in the cases of 1′, 2′ and 4, the molecular structures were also elucidated by single X-ray crystal diffraction analysis. Complexes 1–5 were evaluated as catalysts or catalyst precursors for the mild peroxidative oxidation of cyclohexane in acetonitrile typically at 25 °C and in the solvent-free oxidation of primary and secondary alcohols under microwave (MW) irradiation. The influences of the type and amount of acid promoter, amounts of oxidant and catalyst, time and temperature, on the product yields and TONs, are investigated.The iron(II) complexes 3 and 4 are the most active catalysts in the oxidation of cyclohexane with H2O2 in a slightly acidic medium, leading to maximum overall yields (based on the alkane) of 38 and 28%, and turnover numbers (TON) up to 950 and 1450, respectively.Additionally, the Cu and Fe complexes (1–4) proved to be useful catalysts in various MW-assisted alcohol oxidations at 80 °C with t-BuOOH. The oxidation of 1-phenylethanol catalysed by the Fe complex 3 in the presence of pyrazine-2-carboxylic acid (co-catalyst) is very fast, giving the acetophenone product (TOF = 4470 h−1) in good yield (75%) just after 5 min of reaction time.
Keywords: N,S-ligands; Peroxidative oxidations; Acid additives; C–H bond activation; O–H bond activation;
The role of alkali modifiers (Li, Na, K, Cs) in activity of 2%Pd/Al2O3 catalysts for 2-ethyl-9,10-anthraquione hydrogenation by R. Kosydar; A. Drelinkiewicz; E. Lalik; J. Gurgul (121-131).
Display Omitted► Hydrogenation of 2-ethylanthraquinone on alkali-doped Pd/Al2O3 catalyst. ► A role of alkali promoters in activity and selectivity. ► Keto–enol (hydroquinone–oxoanthrone) tautomerization.Present research concentrates on the role of alkali modifiers (Li, Na, K, Cs) in activity of 2%Pd/Al2O3 catalyst for 2-ethyl-9,10-anthraquinone (eAQ) hydrogenation. The catalysts with various content of alkali modifier (Me/Pd molar ratio ranges from 0.5 up to 4, Me-alkali metal) were prepared by impregnation of pre-reduced 2%Pd/Al2O3 catalyst with appropriate alkali metal carbonates. The XPS, EDS and TEM measurements show that alkali promoters are introduced into alumina matrix. The microcalorimertic experiments of CO adsorption prove the interaction of CO with catalysts leading to stronger bonding of carbon monoxide by alkali doped catalysts. The presence of alkali promoters in Pd/Al2O3 catalyst plays an essential role in the whole eAQ hydrogenation process. The nature of alkali promoter and its content (Me/Pd atomic ratio) in catalyst are of importance. As the alkalinity of promoter increases going from Li to Cs all the effects caused by their presence become stronger. In the presence of alkali doped catalysts the content of 2-ethyloxoanthrone (OXO, isomer of 2-ethyl-9,10-anthrahydroquinone) formed is higher than that on un-doped 2%Pd/Al2O3. On the other hand, reactions in the “deep hydrogenation” stage comprising the formation of 2-ethyl-5,6,7,8-tetrahydro-9,10-anthraquinone (H4eAQ) and the transformation of OXO to 2-ethylanthrone and other degradation products are remarkably inhibited. In particular, the formation of 2-ethylanthrone via hydrogenolysis of OXO isomer is strongly suppressed. The Cs-doped catalyst exhibits the highest activity to OXO among all the catalysts tested whereas the ability of Cs-doped catalysts to the formation of anthrone is most effectively inhibited. The role of alkali modifiers is considered to be associated with stronger interactions between the catalyst and quinone reagents, and in particular OXO isomer. Moreover, in the reagent adsorption the centres of support nearby the palladium particles may also participate by affecting the mode of reagents adsorption.
Keywords: 2-Ethylanthraquinone; Palladium catalysts; Hydrogenation; Alkali modifier;
Immobilization of a Rh complex derived from the Wilkinson's catalyst on activated carbon and carbon nanotubes by M. Pérez-Cadenas; L.J. Lemus-Yegres; M.C. Román-Martínez; C. Salinas-Martínez de Lecea (132-138).
Display Omitted► Activated carbon and carbon nanotubes are suitable supports for the Wilkinson's catalyst. ► The immobilized Wilkinson's complex is active in hydrogenation and reusable. ► The catalyst prepared with carbon nanotubes is more active than the homogeneous complex. ► The positive effect of the support is explained by a confinement effect.A Rh complex, derived from the Wilkinson's catalyst [RhCl(PPh3)3], has been immobilized on activated carbon and carbon nanotubes through a linear organic molecule (6-amino-1-hexanol), covalently bonded to the support. This molecule acts as a linker in order to keep the complex apart of the support surface and to mimic its environment in homogeneous phase. The catalysts have been tested in the hydrogenation of cyclohexene. The hybrid catalyst prepared with the activated carbon is as active as the homogeneous Wilkinson's catalyst, while the catalyst prepared with nanotubes is noticeably more active. Negligible leaching is observed and the catalysts are recyclable. The positive effect of the support has been attributed to the confinement of the active species inside the pores, and thus, the structure and the pore size of the support have an outstanding role in the catalytic behaviour of the hybrid catalyst. The structure of the carbon nanotubes leads to hybrid catalysts with a noticeably enhanced catalytic activity.
Keywords: Hybrid catalysts; Activated carbon; Carbon nanotubes; Wilkinson's catalyst; Hydrogenation;
Methanol dehydration into dimethylether over ZSM-5 type zeolites: Raise in the operational temperature range by Guillaume Laugel; Xavier Nitsch; Fabien Ocampo; Benoit Louis (139-145).
Display Omitted► Efficient methanol conversion (73%) into dimethylether was achieved (selectivity >99%). ► The operational temperature range of the reaction was enhanced up to 400 °C under air flow. ► Synthesis of ZSM-5 in fluoride medium led to maintain a selectivity in DME > 90% at 400 °C. ► Long-term experiments were performed under air and no loss in activity was observed at 400 °C.Zeolites having different pore topologies were tested in the dehydration of methanol into dimethylether (DME) under inert and oxidative atmosphere. The experiments were carried out under air to inhibit the Methanol-To-Hydrocarbons (MTH) reaction, which tends to decrease the selectivity in DME. In addition, the presence of air led to broadening the operational temperature range (OTR) up to 400 °C, while maintaining the DME selectivity above 90% during 50 h on stream. Among the solid acid catalysts, the ZSM-5 zeolites exhibited the higher catalytic activity, with a degree of methanol conversion close to 75%. Furthermore, H-[F]ZSM-5 zeolite, prepared via a fluoride-mediated route, remains the more stable and selective toward DME at 400 °C.
Keywords: Methanol dehydration; Dimethylether; ZSM-5 zeolite; Operational temperature range;
Influence of the structural and surface characteristics of activated carbon on the catalytic decomposition of hydrogen peroxide by A. Rey; J.A. Zazo; J.A. Casas; A. Bahamonde; J.J. Rodriguez (146-155).
Display Omitted► AC structural order and surface oxygen groups affect the H2O2 decomposition. ► A lower ordering of the carbon structure leads to a higher decomposition rate. ► At similar structural ordering the reaction rate decreases due to the oxygen groups. ► These effects have been modelled by means of TPO, TPD and XPS analyses.Hydrogen peroxide decomposition has been studied with three activated carbons before and after different modifications upon HCl lixiviation, oxidation with HNO3 and heat treatment in inert atmosphere. The surface of activated carbon promotes H2O2 decomposition to an extent depending on related-structural features and the amount and nature of surface oxygen groups. A lower ordering of the carbon structure with less developed graphene layers leads to a higher decomposition rate due to a higher surface concentration of unpaired electron active sites. In activated carbons with a similar structural ordering, the presence of acidic surface oxygen groups inhibits the decomposition of hydrogen peroxide. Taking into account these two phenomena, empirical equations based on the most reactive carbon fraction by TPO, defects aliphatic carbon fraction, assessed by XPS, and the content of surface oxygen groups, determined by TPD, have been developed for describing the hydrogen peroxide decomposition ability of activated carbons.
Keywords: Hydrogen peroxide decomposition; Activated carbon; Structure; Surface oxygen groups; Hydroxyl radical;
Isolation of titania nanoparticles in monolithic ultraporous alumina: Effect of nanoparticle aggregation on anatase phase stability and photocatalytic activity by M. Bouslama; M.C. Amamra; O. Brinza; S. Tieng; K. Chhor; M. Abderrabba; J.-L. Vignes; A. Kanaev (156-161).
Display Omitted► Titania nanoparticles were built in alumina matrices. ► Aggregation of the nanoparticles was shown to be prohibited. ► Nanocrystals in these alumina matrices retained their thermal stability. ► The non-aggregated titania nanoparticles show high photocatalytic activity.We report on the preparation of a new photocatalyst by impregnation of size-selected TiO2 nanoparticles into monolithic ultraporous alumina of θ and α polymorphs. The alumina matrix is prepared by selective surface oxidation of liquid Hg-alloys in a humid atmosphere at room temperature with subsequent annealing at 1100–1300 °C. An additional treatment with trimethylethoxysilane was used to mechanically reinforce the ultraporous structure. Monodispersed titanium-oxo-alkoxy nanoparticles were generated in a sol–gel reactor with rapid micromixing, then deposited by liquid colloid impregnation and thermally treated above 350 °C to form anatase TiO2. High-resolution TEM images show evidence of non-aggregated 5-nm nanoparticles in θ-alumina matrix at a mass loading of 26 wt.%, which conserve their anatase crystalline structure after the thermal treatment at temperatures as high as 1000 °C. The rutile phase appears only at T ≥ 1100 °C when particle size increases to ∼17 nm due to the aggregation. The photocatalytic activity (ethylene decomposition) of the non-aggregated nanoparticles is conserved over a wide temperature range, and it decreases as soon as the aggregation takes place.
Keywords: TiO2 nanoparticles; Ultraporous alumina; Aggregation state; Anatase polymorph stability; Photocatalytic activity;
Augmented photocatalytic activity of palladium incorporated ZnO nanoparticles in the disinfection of Escherichia coli microorganism from water by A. Khalil; M.A. Gondal; M.A. Dastageer (162-167).
Display Omitted► Nano palladium doped ZnO using incipient wetness impregnation method was synthesized. ► This photo-catalyst was applied for the efficient removal of E. coli from water. ► Significant improvement in the rate constant of the bacterial decay process was observed. ► The grain size of palladium doped ZnO measured with FESEM and HRTEM was in the 15–30 nm range.Palladium incorporated ZnO nanoparticles were synthesized using incipient wetness impregnation method in different concentrations of Pd incorporated in ZnO nanoparticles and their effects as a photocatalyst under UV laser radiations in the removal of Escherichia coli microorganism from water were studied. A significant improvement in the rate constant of the bacterial decay process was observed and discussed on the basis of the blue shifted band gap energy of nano-ZnO due to the incorporation of palladium. The morphological study of Pd incorporated ZnO nanoparticles was carried out using Field Emission Scanning Electron Microscope and High Resolution Tunneling Electron Microscope and the grain size of the synthesized material was found to be in the 15–30 nm range. The photoluminescence spectra and the absorption spectra showed a blue shift in the band gap energy of Pd incorporated ZnO nanoparticles, which positively contributed to the enhanced photocatalytic activity.
Keywords: Near resonance laser photocatalysis; Pd incorporated ZnO nanoparticles; Nano-materials and their applications; Waste water treatment; Escherichia coli;
Doping effects of Ni–MgO on the structure and performance of carbon nanotube-supported Pt catalysts for preferential oxidation of CO in a H2 stream by Hongwei Yang; Chao Wang; Bodong Li; Haiqiang Lin; Ken-ichi Tanaka; Youzhu Yuan (168-175).
Display Omitted► Pt–Ni alloy adjoined by Ni–MgO solid solution is formed on CNT surface. ► Pt–Ni–Mg/CNT catalyst can completely remove CO in a H2 stream at 333–453 K. ► CO-PROX reaction can be performed in a H2 stream containing CO2 and H2O vapor. ► Particle size of Pt–Ni alloy influences the CO-PROX performance. ► Deactivated catalyst is recoverable by heat treatment and reduction at higher temperature.The preferential oxidation of CO (CO-PROX) in a H2-rich stream is performed on a series of supported Pt catalysts doped with Ni–MgO. The characterizations of the catalysts by means of in situ X-ray diffraction, high resolution transmission electron microscopy, and scanning transmission electron microscopy–energy dispersive spectroscopy reveal that the nanocomposites of Pt–Ni alloys that intimately adjoined Ni–MgO solid solution are present on the surfaces of carbon nanotube (CNT). However, the Pt–Ni alloying is hardly detected when the same compositions are supported on other carriers like active carbon, graphite, TiO2, SiO2 and Al2O3 followed by identical treatment. The CNT-supported Pt0.3Ni1.0Mg2.4 (Pt0.3Ni1.0Mg2.5/CNT, the data at subscript stand for the Pt/Ni/Mg atomic ratio) catalyst with overall metal loading of 15 wt% affords 100% CO conversion and 50% O2 selectivity in H2 at temperatures ranging from 333 to 453 K, whereas the CNT-supported Pt catalyst and the other carriers-supported Pt0.3Ni1.0Mg2.4 ones perform very low or insufficient activities under the same reaction conditions. Further, the Pt0.3Ni1.0Mg2.4/CNT catalyst with a mean Pt–Ni particle size about 7.3 nm shows negligible drop in CO-PROX performance at 373 K for longer than 40 h on the streams either with or without H2O vapor and CO2. The deactivation of the catalyst is largely due to the accumulation of H2O/OH− species and carbonates, which can be removed by calcination and reduction to get the regeneration of the CO-PROX performance as a result. The high performance of the catalysts is ascribed to the interaction between Pt and Ni with the formation of Pt–Ni alloy which is strongly interacted with Ni–MgO solid solution.
Keywords: Ni–MgO; Carbon nanotube; Pt catalyst; Pt–Ni alloy; Preferential oxidation of CO;
Role of catalyst support over PdO–NiO catalysts on catalyst activity and stability for oxy-CO2 reforming of methane by U. Oemar; K. Hidajat; S. Kawi (176-187).
Display Omitted► Effect of catalyst supports over PdO–NiO catalysts for oxy-CO2 reforming of methane. ► PdO–NiO/Y2O3 catalyst shows formation of metal-support compound. ► Formation of metal-support compound results in small metal size. ► Small metal size of PdO–NiO/Y2O3 catalyst is required for high catalytic activity. ► Surface β-oxygen species on PdO–NiO/Y2O3 catalyst can promote cracking of C–H bond in CH4 to CO and H2.PdO–NiO catalysts over several commercial metal oxides were synthesized using incipient wet impregnation method. The activities of PdO–NiO catalysts for syngas production via oxy-CO2 reforming of methane were investigated at temperatures ranging from 500 °C to 800 °C in a fixed-bed continuous-flow reactor. The PdO–NiO/Y2O3 and PdO–NiO/Al2O3 catalysts show very high CH4 and CO2 conversions due to the formation of metal-support compound on these catalysts. On the PdO–NiO/Y2O3 catalyst, Pd interacts with Y2O3 support to form Pd x O y Y z compound while Ni interacts with Al2O3 support to form NiAl2O4 spinel compound on the PdO–NiO/Al2O3 catalyst. However, the amount of deposited carbon on the spent PdO–NiO/Y2O3 catalyst is much lower than the one on the PdO–NiO/Al2O3 catalyst due to the presence of surface β-oxygen species and ability of Y2O3 to form oxycarbonate species, resulting in stable catalytic performance without noticeable deactivation during reaction. The surface β-oxygen species are found to promote cracking of C–H bond in CH4 while the oxycarbonate species can oxidize the deposited carbon, respectively, hence leading to the stability of the PdO–NiO/Y2O3 catalyst.
Keywords: PdO–NiO catalyst; Oxy-CO2 reforming of methane; Formation of metal-support compound; Y2O3; Spinel catalyst; Syngas production; Hydrogen production; CO2 utilization; CO2 conversion;
Selective synthesis of 1-butanol from ethanol over strontium phosphate hydroxyapatite catalysts by Shuhei Ogo; Ayumu Onda; Kazumichi Yanagisawa (188-195).
Display Omitted► We examined the catalytic conversion of ethanol over substituted hydroxyapatites. ► Strontium phosphate hydroxyapatite (Sr–P) showed high 1-butanol selectivity. ► The Sr–P catalyzes the aldol condensation of acetaldehyde. ► The Sr–P inhibited the coking in the hydrogen transfer reaction of 2-butene-1-ol.We previously reported the ability of strontium hydroxyapatite to catalyze the conversion of ethanol into 1-butanol with higher selectivity than that reported for calcium hydroxyapatite catalysts. In the present study, we investigated the catalytic conversions of ethanol over substituted hydroxyapatites, such as Sr10(PO4)6(OH)2, Ca10(VO4)6(OH)2, Sr10(VO4)6(OH)2, and Ca10(PO4)6(OH)2, and their solid solutions, such as Ca10 − z Sr z (PO4)6(OH)2, Ca10(PO4)6 − x (VO4)6 − x (OH)2, and Sr10(PO4)6 − x (VO4)6 − x (OH)2, were investigated. The strontium phosphate hydroxyapatite [Sr10(PO4)6(OH)2: Sr–P] exhibited the highest 1-butanol selectivity among the tested catalysts in the region of the ethanol conversions between 1 and 24%. The reaction mechanism of 1-butanol formation over the Sr–P hydroxyapatite catalyst includes the dehydrogenation of ethanol into acetaldehyde, the aldol condensation of acetaldehyde into crotonaldehyde, and the hydrogenations of crotonaldehyde, 2-buten-1-ol, and/or butyraldehyde into 1-butanol. The Sr–P hydroxyapatite catalyst showed high selectivity into crotonaldehyde in the aldol condensation of acetaldehyde and inhibited the coking in the hydrogen transfer reaction of 2-buten-1-ol into 1-butanol, which might be reasons why the Sr–P hydroxyapatite catalyst showed the high 1-butanol selectivity in the catalytic conversion of ethanol.
Keywords: Strontium phosphate hydroxyapatite; Ethanol; 1-Butanol;
Vapor-phase isomerization of endo-tetrahydrodicyclopentadiene to its exo isomer over zeolite catalysts by Cong-ming Sun; Gang Li (196-200).
Display Omitted▶ H-USY is an efficient catalyst for vapor-phase isomerization of endo- to exo-THDCPD. ▶ The conditions for isomerization in vapor phase are milder than those in liquid phase. ▶Exo-THDCPD with purity of ≥98 wt% can be directly obtained from the reactor outlet.Vapor-phase isomerization of endo-tetrahydrodicyclopentadiene (endo-THDCPD) to exo-THDCPD over zeolite catalysts (HY, H-USY, Hβ, HZSM-5 and HMOR) was studied as a green synthesis route for exo-THDCPD. The HY and H-USY catalysts showed catalytic activity while the Hβ, HZSM-5 and HMOR catalysts did not. Higher yield of exo-THDCPD was obtained over the H-USY catalyst than that over the HY catalyst, attributing to the presence of strong acid sites and mesopores in the H-USY catalyst. The yield of exo-THDCPD obtained via vapor-phase isomerization was better than that reported via liquid-phase isomerization. In addition to the properties of the catalyst itself, the vapor-phase isomerization process of endo-THDCPD was also affected by the reaction temperature, the concentration of endo-THDCPD, the contact time and the time on stream. Under the optimized conditions, high purity (>98 wt%) exo-THDCPD was directly obtained without any separation processes. Although deactivation of the catalyst with the time on stream was observed, the activity could be recovered easily via regeneration in air.
Keywords: Tetrahydrodicyclopentadiene; Vapor-phase isomerization; Ultra-stable Y zeolite; JP-10;
Methylamine and dimethylamine photocatalytic degradation—Adsorption isotherms and kinetics by Sihem Helali; Eric Puzenat; Nathalie Perol; Mohamed-J. Safi; Chantal Guillard (201-207).
Display Omitted► Same area density (molecule nm−2) of adsorbed MA and DMA are obtained. ► The higher reactivity of MA than DMA is due to the higher reactivity of the cationic form. ► The breaking of C–N bond is the main initial step in the degradation of DMA. ► For MA and DMA, the coverage rates of the TiO2 in dark and under UV were different.The photocatalytic degradation of two nitrogenous organic compounds, methylamine CH3NH2 and dimethylamine (CH3)2NH, used in pharmaceutical and chemical industries was investigated in the presence of UV-irradiated TiO2 aqueous suspensions. Different parameters were studied: adsorption under dark and UV-A conditions, photolysis, kinetics of degradation, and chemical pathway of methylamine (MA) and dimethylamine (DMA) degradation. The percentage of covered OH in the dark was equal for different concentrations of MA and DMA. The adsorption isotherms of these two amine compounds MA and DMA follow the Langmuir model. The photocatalytic oxidation kinetics of MA and DMA are described by the Langmuir–Hinshelwood model with a first order kinetics for concentrations below 0.5 mmol L−1, and then reach a plateau.For both MA and DMA, the coverage rates of the TiO2 surface in the dark and under illuminated conditions were different. The nitrogen atoms were decomposed mainly to ammonium (NH4 +). Nitrite (NO2 −) was also formed but was rapidly oxidized to nitrate (NO3 −). MA was detected as an intermediate product during the degradation of DMA. Formic acid (HCOOH), and two other products not identified were detected. These non-identified products do not correspond to formamide. Total Organic Carbon (TOC) analysis shows the presence of final slightly mineralised intermediate compounds.
Keywords: Adsorption; Dimethylamine; Methylamine; Photocatalytic degradation; TiO2;
Methanol to hydrocarbons over zeolites with MWW topology: Effect of zeolite texture and acidity by Antoine Lacarriere; Francis Luck; Dariusz Świerczyński; François Fajula; Vasile Hulea (208-217).
Display Omitted► MCM-36 zeolite was studied for the first time in the conversion of methanol to hydrocarbons. ► This catalyst produced selectively aliphatic hydrocarbons and exhibited a high resistance to the deactivation. ► Under similar conditions MCM-22 produced higher amount of aromatics and coke. ► These performances were related to the textural and acidic properties of catalysts.MCM-36 and MCM-22 zeolites derived from the same precursor with MWW topology were compared for the conversion of methanol to hydrocarbons (MTH) at 450 °C. MCM-36 was found to be a very attractive catalyst, showing a selective formation of C3+ aliphatic hydrocarbons (about 90% at WHSV = 2 h−1) and a high resistance to the deactivation. Under similar conditions MCM-22 produced higher amount of aromatics and coke. This behavior was mainly related to the textural and acidic properties of catalysts. The dual meso-/microporosity of MCM-36 facilitates the diffusion of bulkier species produced by different reactions in the MTH process which results in lower deactivation rate of this zeolite compared to the purely microporous MCM-22 catalyst. Moreover, the density of the acid sites in MCM-36 (three times lower than that of the MCM-22 sample) is unfavorable to secondary reactions like aromatization and hydrogen transfer which are responsible for the formation of aromatics and coke precursors.
Keywords: Methanol; Hydrocarbons; MCM-36; MCM-22;
A simple visible spectrum deconvolution technique to prevent the artefact induced by the hypsochromic shift from masking the concentration of methylene blue in photodegradation experiments by Gregorio Marbán; Tan T. Vu; Teresa Valdés-Solís (218-223).
Display Omitted► Methylene blue concentration is evaluated by means of visible spectroscopy. ► During reaction the formation of intermediates masks this evaluation. ► Here a novel deconvolution method is presented to avoid this artefact. ► Methylene blue concentrations are higher when ignoring the artefact.This paper analyzes the experimental evaluation of methylene blue concentration applied during photocatalytic experiments. In most studies a satisfactory evaluation of the concentration of methylene blue by means of visible spectroscopy is masked by the presence of intermediates during the reaction, resulting in an overestimation of the amount of methylene blue present. The deconvolution technique described in the present study solves this problem by estimating the contribution by intermediates to the visible spectrum. In the photodegradation of methylene blue by Degussa P25 TiO2 particles the main intermediate detected in the visible spectral region was azure A, produced from the gradual demethylation of azure B. The methylene blue concentrations obtained if the artefact is not taken into account give lower values for the kinetic rate constants of photocatalytic degradation than those provided by this novel deconvolution technique.
Keywords: Methylene blue; Photocatalysis; TiO2; Visible spectroscopy; Artefact; Deconvolution;