Applied Catalysis A, General (v.321, #1)

Contents (iii-vi).

A novel core–shell like composite In2O3@CaIn2O4 for efficient degradation of Methylene Blue by visible light by Wen Ku Chang; K. Koteswara Rao; Hua Cing Kuo; Jen Fong Cai; Ming Show Wong (1-6).
A novel core–shell like composite In2O3@CaIn2O4 was observed at intermediate calcinations of solid-state reaction between CaCO3 and In2O3, and showed superior visible light induced photocatalytic degradation of Methylene Blue compared to single phase CaIn2O4. Selective charge separation and efficient charge transport at the interface are the reasons for the enhanced performance of this composite catalyst.▪In the process of preparing a visible light photocatalyst CaIn2O4, a novel core shell like composite In2O3@CaIn2O4 was observed at intermediate calcination temperatures, during the solid-state reaction between ball milled powders of CaCO3 and In2O3. The composition, crystallinity and photo absorption of the coupled phases obtained in the temperature range 873–1323 K, were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV–vis diffused reflectance spectroscopy. The coupled composite phases In2O3@CaIn2O4 showed superior visible light induced photocatalytic degradation of Methylene Blue (MB) compared to single phase CaIn2O4. Selective charge separation and efficient charge transport at the interface when illuminated are considered to be the possible reasons for the enhanced photocatalytic performance of this composite catalyst.
Keywords: Photocatalyst; Core shell; Photocatalytic degradation of Methylene Blue; Crystallinity;

Effect of the location of cobalt species on NO adsorption and NO x -SCR over Co–mordenite by Laura B. Gutierrez; Eduardo E. Miró; María A. Ulla (7-16).
Different cobalt-loading catalysts were treated with different procedures (heated on He, O2, H2 and H2O) in order to study the cobalt species location on NH4–mordenite using NO-TPD, H2-TPR, Raman and FTIR with NO as probe molecule. Cobalt position strongly depend on the pretreatments and on the presence of Co-oxide particles. ▪A thorough characterization of Co–mordenite was carried out using NO-TPD, H2-TPR, Raman, DRX and FTIR with NO as probe molecule. Different cobalt-loading catalysts (8.85, 5.70, 2.91, 2.45 and 1.15 wt.%) were prepared by ion exchange over NH4–mordenite and treated with different procedures (heated on He, O2 and H2). The effect of adding water to the reaction stream at 500 °C on the location of the cobalt species was also analyzed. All catalysts were evaluated for the SCR of NO x with methane as a test reaction both under dry and wet conditions. The NO adsorption capacity depended not only on the Co/Al ratio and pretreatments but also on the presence of Co oxides. In fact, for similar Co/Al ratios, Co2.91MOR showed a lower NO/Co ratio than Co2.45MOR due to the higher Co3O4 concentration in the former. These species probably blocked the main mordenite channels and/or produced the formation of some Co island on the zeolite surface, lowering the amount of surface Co. The main NO surface species detected were dinitrosyl and mononitrosyl. Their stability and relative amount depended on the cobalt species and the pretreatments. Heating in He or H2 induced the stabilization of part of the exchanged Co in less gas-accessible sites, whereas the calcination with O2 involved the mobilization of Co to more external sites. However, those effects were less significant for samples containing Co oxides suggesting that the spinel hinders the Co migration. During the wet reaction treatment, the cobalt mobilization to hidden positions occurred along with the formation of Co-oxides, which negatively affected both the catalytic activity and the NO adsorption capacity.
Keywords: NO-TPD; Co–NO interaction; Co–mordenite; Co species on the SCR;

Selective ring opening of decalin with Pt–Ir on Zr modified MCM-41 by K. Chandra Mouli; V. Sundaramurthy; A.K. Dalai; Zbigniew Ring (17-26).
Selective ring opening of decalin over the catalysts comprising of Ir in combination with Pt supported on mesoporous material, Zr–MCM-41 was studied in a trickle bed reactor. The Zr substituted MCM-41 (Si/Zr = 5) support was synthesized by hydrothermal method and characterized by BET surface area measurement, XRD, FTIR, TPD of ammonia. XRD showed hexagonal nature of MCM-41. TPD of ammonia and DRIFTS of ammonia adsorption spectra, respectively, showed moderate acidity and presence of Lewis and Brønsted acid sites. Zr–MCM-41 catalysts loaded with Ir and Pt in the range of 0–1.5 wt.% were prepared and characterized by DRIFT spectroscopy of CO adsorption, DRIFT of NH3 and TEM. The activity and selectivity of Ir/Pt-loaded Zr–MCM-41 were investigated in the ring opening of decalin in the temperature range of 300–400 °C at 5 MPa in the presence of hydrogen. Increase in Ir loading significantly increased the ring opening products yield and selectivity. Maximum conversion of 55 wt.% obtained at 400 °C. In the range of operating conditions studied, the optimum loading for better ring opening yield of 15 wt.% was 1.5 wt.% Ir and 0.75 wt.% Pt.Selective ring opening of decalin over Ir–Pt catalysts supported on mesoporous Zr–MCM-41 was studied in a trickle bed reactor. Increase in Ir loading significantly increased the ring opening products yield and selectivity. The optimum loading for better ring opening yield was 1.5 wt.% Ir and 0.75 wt.% Pt on Zr–MCM-41. ▪
Keywords: Zr–MCM-41; Ring opening; DRIFT; Platinum; Iridium; Decalin;

NiSO4/TiO2–ZrO2 for ethylene dimerization was prepared by the impregnation method. The surface area and acidity of TiO2–ZrO2 binary metal oxide increased remarkably compared with single metal oxide. NiSO4 supported on 50TiO2–50ZrO2 among TiO2–ZrO2 binary oxides exhibited the highest catalytic activity for ethylene dimerization. The catalytic activities of supported NiSO4 catalysts were correlated with the acidity of catalysts.▪A series of catalysts: NiSO4/TiO2–ZrO2, having different TiO2–ZrO2 compositions, for ethylene dimerization was prepared by the impregnation method using an aqueous solution of nickel sulfate. No diffraction line of nickel sulfate was observed up to 30 wt%, indicating good dispersion of nickel sulfate on the surface of the supported NiSO4 catalysts. The surface area and acidity of TiO2–ZrO2 binary metal oxide increased remarkably compared with the values for single metal oxides, TiO2 or ZrO2. The binary oxide TiO2–ZrO2 calcined above 600 °C resulted in the formation of a crystalline orthorhombic phase of ZrTiO4. Therefore, NiSO4/TiO2–ZrO2 calcined at 500 °C exhibited a maximum catalytic activity, and then the catalytic activity decreased with the calcination temperature. NiSO4 supported on 50TiO2-50ZrO2 (TiO2/ZrO2 ratio = 1) exhibited the highest catalytic activity for ethylene dimerization among TiO2–ZrO2 binary oxides. The catalytic activities of supported NiSO4 catalysts were correlated with the acidity of catalysts measured by the ammonia chemisorption method, regardless of the kind of support (TiO2, ZrO2, or TiO2–ZrO2).
Keywords: Ethylene dimerization; Effect of TiO2–ZrO2 composition; Acidic properties; ZrTiO4 phase;

One-pot catalytic synthesis of higher aliphatic ketones by Cristina Della Pina; Ermelinda Falletta; Michele Rossi; Michele Gargano; Potenzo Giannoccaro; Rosaria Ciriminna; Mario Pagliaro (35-39).
The catalytic synthesis of high molecular weight aliphatic ketones by reductive condensation of lower molecular weight ketones was achieved by using CO in the presence of a multifunctional catalyst containing copper dispersed on alumina. The useful combination of condensation, water gas shift and hydrogenation reactions in a one-pot reaction allowed high yields of methylisobutylketone from acetone.▪The catalytic synthesis of high molecular weight aliphatic ketones by reductive condensation of lower molecular weight ketones was achieved by using CO in the presence of a multifunctional catalyst containing copper dispersed on alumina. The useful combination of condensation, water gas shift and hydrogenation reactions in a one-pot reaction allowed high yields of methylisobutylketone from acetone.
Keywords: Heterogeneous catalysis; Ketones; Copper; Alumina; Methylisobutylketone; Carbon monoxide;

Comparison of oxidation properties of Nb and Sn in mesoporous molecular sieves by Izabela Nowak; Agnieszka Feliczak; Iveta Nekoksová; Jiří Čejka (40-48).
Mesoporous molecular sieves containing Nb and Sn were prepared and used for oxidation of cyclohexene, cyclohexanone and cyclohex-2-en-1-one; Nb oxidizes cyclohexene to epoxide, Sn cyclohexanone to lactone; while Nb oxidizes cyclohex-2-en-1-one preferentially the double bond of cyclohex-2-en-1-one with a much higher activity than Sn. ▪Oxidation properties of niobium and tin in mesoporous matrices were investigated in oxidation of cyclic ketones, cyclic olefins and cyclic keto-olefins with hydrogen peroxide as an oxidation agent. Mesoporous molecular sieves of MCM-41 and MCM-48 types were synthesized and niobium and tin were incorporated into the structure. X-ray diffraction and nitrogen sorption isotherms confirmed a high-quality of these mesoporous molecular sieves even after incorporation of Nb and/or Sn. It was shown that niobium selectively oxidizes double bond of the substrates to epoxide followed by further hydration and forms diols and keto-diols in the second step of the reaction. On the other hand, tin carries out Baeyer–Villiger oxidation of cyclic ketones to lactones without further consecutive reactions while Nb is inactive in this reaction. When substrate contains both C=C double bond and carbonyl group on the same ring, Nb oxidizes preferentially the double bond with a much higher activity than Sn.
Keywords: Mesoporous molecular sieves; Niobium; Tin; Synthesis; Oxidation properties; Cyclohexene; Cyclohexanone; Cyclohex-2-en-1-one;

Efficient biomimetic epoxidation of alkenes and hydroxylation of alkanes with sodium periodate catalyzed by zeolite-encapsulated Mn(III)-salophen, ZEMS, is reported. Alkyl aromatic and cycloalkanes were oxidized efficiently to their corresponding alcohols and ketones in the presence of this catalyst. ▪Efficient biomimetic epoxidation of alkenes and hydroxylation of alkanes with sodium periodate catalyzed by zeolite-encapsulated Mn(III)-salophen, ZEMS, is reported. This catalytic system shows a good activity in the epoxidation of linear alkenes. Alkyl aromatic and cycloalkanes were oxidized efficiently to their corresponding alcohols and ketones in the presence of this catalyst. This heterogenized catalyst, ZEMS, has been characterized by FT-IR, UV–vis spectroscopic techniques, SEM, thermal and elemental analysis.
Keywords: Zeolite; Manganese(III) salophen; Periodate; Epoxidation; Hydroxylation;

Influence of the preparation method on the activity of phosphate-containing CoMo/HMS catalysts in deep hydrodesulphurization by R. Nava; J. Morales; G. Alonso; C. Ornelas; B. Pawelec; J.L.G. Fierro (58-70).
Hexagonal mesoporous silica (HMS) containing a 1.5 wt.% P2O5 was selected as a substrate to deposit cobalt and molybdenum oxide precursors by sequential and co-impregnation methods. The sulphide catalysts were tested in DBT HDS and the series prepared by co-impregnation was substantially more active than that prepared by sequential impregnation. ▪Phosphate-containing hexagonal mesoporous silica (P/HMS) materials were used as supports of hydrotreating CoMo catalysts. Two series of catalysts were prepared by sequential and simultaneous impregnation of P/HMS substrates with cobalt and molybdenum salts solutions. Both bulk and surface structures of calcined and sulphided samples were determined by several techniques (SBET, XRD, UV–vis, TPD-NH3, TPR, FTIR of adsorbed NO and pyridine, HRTEM and XPS). The activity of P-containing CoMo catalysts was examined in hydrodesulphurization (HDS) of dibenzothiophene (DBT) and compared to that of a conventional commercial CoMo/Al2O3 catalyst. It was found that the dispersion of oxide and sulphide Co and Mo species depends on the presence of phosphate and also on the sequence of Co and Mo incorporation being co-impregnation more favourable than sequential impregnation. HRTEM analysis of sulphided samples (673 K) showed that larger stacking degree of MoS2 phase and better dispersion of Co and Mo species are achieved by co-impregnation. Activity tests revealed that sequential incorporation of Mo and Co is less effective for S-removal from DBT than co-impregnation. Contrary to sequential impregnation, the presence of P2O5 (up to 1.5 wt.%) on support surface enhanced S removal from DBT on the catalysts prepared by co-impregnation but the selectivity in this reaction was not influenced by phosphate and catalyst's preparation method. A close parallelism between active phase surface exposure and catalytic response was found.
Keywords: CoMo catalysts; Phosphorous; HMS support; HDS; DBT;

The highly crystalline octahedral molecular sieves containing cobalt (Co-todorokite), nickel (Ni-todorokite), and magnesium (Mg-todorokite) were prepared by the sequential method under optimum conditions. For the acrylonitrile hydration, the apparent activation energies of todorokite catalysts depend on the foreign metals. Some products were formed over Mg-todorokite. The only product formed over Co-todorokite and the Ni-todorokite was acrylamide. ▪An octahedral molecular sieve known as OMS-1 has todorokite structure composed of magnesium and manganese oxides, which was named as Mg-todorokite here. Octahedral molecular sieves containing cobalt (Co-todorokite) or nickel (Ni-todorokite) without magnesium were prepared by a sequential method under optimum conditions and compared with the Mg-todorokite by powder XRD, ICP, FESEM, and catalytic reactions. The compositions of Co-todorokite, Ni-todorokite, and Mg-todorokite are Co0.37MnO2.3(H2O)2.1, Ni0.24MnO2.0(H2O)2.1, and Mg0.22MnO2.0(H2O)2.2, respectively. The Co-todorokite and Ni-todorokite are comparable in crystallinity with the highly crystalline Mg-todorokite. The catalytic properties were examined for the hydration of acrylonitrile. The apparent activation energies depend on the foreign metals. The order is Co-todorokite < Ni-todorokite < Mg-todorokite. The four products of the Mg-todorokite catalysis are 3-hydroxy-propionitrile, and bis-2-cyano-ethylether, succinonitrile, and acrylamide. The acid treatments for Mg-todorokite suppress the formations of 3-hydroxy-propionitrile and bis-2-cyano-ethylether, which would be due to the weakening of the basicity with the removal of magnesium ions. The only product of the Co-todorokite and the Ni-todorokite catalysis is acrylamide because of not containing magnesium.
Keywords: Todorokite; Octahedral molecular sieves; Manganese oxides; Catalysts; Acrylonitrile hydration;

The catalyst prepared from dehydrated ethanol exhibited stable and the highest activity than the catalysts prepared from any other cobalt nitrate solution. It is considered that different structure properties of metallic cobalt, loosely constructed form clusters, in CoE catalyst, contributed to formation of more reactive adsorbed CO, and determining the highest catalytic activity in FTS reaction. ▪Silica-supported cobalt (20 wt%) catalysts were prepared by incipient-wetness impregnation of silica with different cobalt nitrate solutions. The catalyst prepared from dehydration ethanol solution exhibited stable and the highest activity, as well as significantly low methane selectivity. Cobalt crystalline size of the catalyst prepared from dehydrated ethanol was smaller than that of the catalyst prepared from aqueous solution, and existed two different size where the large particles showed low bulk density with cluster-like structure. But only larger clusters existed in the catalyst prepared from aqueous solution. The increased amount of active sites and more reactive adsorbed CO on the surface determined the highest activity of the catalyst prepared from dehydrated ethanol solution in liquid-phase Fischer-Tropsch synthesis (FTS) reaction.
Keywords: Fischer-Tropsch synthesis; Co/SiO2 catalyst; Ethanol solvent; Preparation method; Syngas;

The efficiency of electrochemical promotion to improve the catalytic performance of a Pt impregnated catalyst for the reduction of NO was investigated in a typical temperature range of exhaust gases. As the reaction temperature increased the promotional phenomena in the catalytic activity decreased. However, the presence of sodium promoters always induced a large increase in N2 selectivity.▪The aim of this work was to study the influence of the reaction temperature on the efficiency of the electrochemical promotion to improve the catalytic performance of a Pt impregnated catalyst for the reduction of nitrogen oxides under lean burn conditions. Open circuit catalytic and potential measurements were carried out in order to explain the potentiostatic behaviour of the electrochemical catalyst under different reactions temperatures. At low temperature (220 °C), the application of negative polarization increased the NO reduction rate by a factor of 1.4 (electrophilic behaviour). But as the reaction temperature was higher, the efficiency of electrochemical promotion to improve the catalytic activity decreased, even leading to a poisoning effect at 300 °C. This progressive suppression of the promotional effect was due to an increase with temperature of the oxygen coverage on the catalyst, which led to a C3H6 adsorption inhibition. Nevertheless, at all explored reaction temperatures, the presence of sodium promoter gave a large increase in N2 selectivity, even reaching 90%. These results demonstrated that electrochemical promotion is a suitable technique to improve the catalytic performance of Pt catalyst for the practical development of HC-SCR process to removal nitrogen oxides.
Keywords: Electrochemical promotion; NEMCA effect; Selective catalytic reduction; Platinum impregnated catalyst;

Catalytic activity of Pt-based intermetallics for the hydrogen production—Influence of ionic activator by Milica P. Marčeta Kaninski; Vladimir M. Nikolić; Tanja N. Potkonjak; Branislav R. Simonović; Nebojša I. Potkonjak (93-99).
Objective was to compare electrocatalytic efficiency of TiPt and MoPt2 cathodes for hydrogen production, also with influence of Mo–Co based ionic activator (i.a.). Figure reveals activation energies obtained from Arrhenius plots for TiPt-30.2 (a) and MoPt2-40.7 kJ mol−1 (b), respectively, with addition of i.a. 13.7 and 34.6 kJ mol−1. Results suggest to significant catalytic performance of MoPt2 specially if used with activator.▪In continuous search for advanced electrocatalytic materials for the hydrogen evolution reaction (HER), based on transition metal series, two types of intermetallic compounds, TiPt and MoPt2, were investigated as cathode materials. Additionally, ionic activator (i.a.), the mixture of Na-molybdate and tris(ethylenediamine)Co(III) chloride, was in situ added into electrolyte, 6 M aqueous potassium hydroxide solution. The objective was to qualitatively compare their electrocatalytic efficiency evaluated by quasi-potentiostatic and galvanostatic technique. Results are presented to show: the Tafel slope, the exchange current density, the overpotential needed for a fixed hydrogen production rate and the apparent energy of activation.Obtained kinetic parameters reveal advanced catalytic ability of the MoPt2 over the TiPt cathode towards HER. Also, important step forward was achieved by using ionic activator. The presence of Mo and Co species attached to the cathode surface was confirmed by XRF analysis. Thus, enhanced catalytic activity was assigned to the formation of Mo–Co-based electrodeposit. Results suggest to significant catalytic performance of the MoPt2 cathode specially if used with ionic activator in alkaline water electrolysis.
Keywords: Electrocatalysis; Hydrogen evolution; Pt-based intermetallics; Mo–Co-based ionic activator; In situ activation;