Applied Catalysis A, General (v.395, #1-2)

Contents (iii-vii).

A comparison of Au/Co/Al2O3 and Au/Co/SiO2 catalysts in the Fischer–Tropsch reaction by Kalala Jalama; Neil J. Coville; Haifeng Xiong; Diane Hildebrandt; David Glasser; Stuart Taylor; Albert Carley; Jim A. Anderson; Graham J. Hutchings (1-9).
Display Omitted► Au showed similar effects on the silica- and alumina-supported Co catalysts. ► Adding Au improves Co reduction and catalyst activity for the FT reaction. ► The 5%Au/10%Co/Al2O3 had an activity 6 times higher than the undoped catalyst.The effect of Au addition on the structure of Co/Al2O3 and Co/SiO2 systems and their performance in the Fischer–Tropsch synthesis (FT) reaction has been investigated. In particular, the effect of the addition of Au (0–5%) to 10% Co/Al2O3 and 10% Co/SiO2 catalysts has been evaluated. An improvement in Co reduction was observed by adding Au to the supported Co/Al2O3 and Co/SiO2 catalysts. For both the silica and alumina-supported catalysts the catalyst activity increased significantly after the addition of Au up to 1.5 wt.%. Further increases in Au led to small increases in catalyst activity. The effect of adding Au to the supported Co catalysts was found to be similar to the effect of adding noble metals (Ru, Re and Pt); the Au also improved the catalyst reducibility and activity in the FT reaction. The most significant effect of Au addition on the catalyst activity was found for 5%Au/10%Co/Al2O3 where the maximum conversion was more than six times higher when compared to the activity of the undoped catalyst (10%Co/Al2O3).
Keywords: Gold; Alumina-supported cobalt catalyst; Silica-supported cobalt catalyst; Fischer–Tropsch synthesis;

Design of nano-sized FeO x and Au/FeO x catalysts supported on CeO2 for total oxidation of VOC by R. Bonelli; S. Albonetti; V. Morandi; L. Ortolani; P.M. Riccobene; S. Scirè; S. Zacchini (10-18).
Display Omitted► Preparation of iron and gold/iron CeO2 supported catalysts using metallic carbonyl clusters. ► Strong interaction between Au and oxide species, both of Fe and ceria, was achieved. ► The enhanced oxygen mobility favors methanol catalytic combustion.The total oxidation of methanol and toluene, chosen as representative VOCs, was investigated over CeO2-supported Au/FeO x catalysts prepared utilizing the bimetallic carbonyl cluster salt [NEt4][AuFe4(CO)16]. Characterization data showed that the catalysts prepared by the reported method exhibit highly and homogeneously dispersed iron oxide species on the ceria support together with small gold nanoparticles, whose size increases on increasing the amount of gold/iron. Addition of iron oxide species did not substantially increase the methanol combustion activity of ceria, whereas the presence of the mixed gold and FeO x species has been found to strongly enhance the activity towards the total oxidation of methanol. In the case of the toluene combustion the addition of FeO x or FeO x /Au species caused a significant decrease in the activity of the bare CeO2. The above catalytic behavior was rationalized on the basis of different interactions occurring among gold, iron oxide and cerium oxide, which synergically affects both the reactivity of the surface oxygen and the capacity of the support to adsorb the organic reactant.
Keywords: Catalytic combustion; Gold/iron-oxide catalysts; Cluster-derived catalysts;

Au–Pd/C catalysts for glyoxal and glucose selective oxidations by Sophie Hermans; Aurore Deffernez; Michel Devillers (19-27).
Display Omitted▶ Au–Pd/C catalysts were prepared by adsorption at optimized pH. ▶ The Au–Pd/C materials were highly active in selective glyoxal or glucose oxidation. ▶ A clear synergetic effect between the two metals was evidenced. ▶ Au plays a promoter role for Pd even in the form of big particles.A series of Au–Pd/C catalysts were prepared on an activated carbon named SX PLUS (SX+) by fixing the pH of impregnation in aqueous phase at an optimal value for maximizing the interactions between metals and surface. This bimetallic association leads to highly active catalysts in the oxidation of glyoxal into glyoxalic acid and of glucose into gluconic acid, with the activity correlated to high surface Pd/C ratios measured by XPS and the presence of small metallic Pd particles, even if gold was present as big crystallites. A cooperative effect between the two metals was evidenced on the yield in carboxylic acids in both reactions, which is believed to arise from an interface between the two metals even if they are mostly present as separated phases. The incorporation of Au on Pd rather than the opposite and the concomitant activation of both metals influence positively the catalytic performance. The use of NaBH4 as activating agent allowed the most active Au–Pd/C catalyst to be obtained, with similar performances to the best bimetallic Bi–Pd/C catalyst so far but without any metal leaching.
Keywords: Carbon; Palladium; Gold; Adsorption; Oxidation;

Display Omitted► Synthesis of sulfamic acid-functionalized magnetic Fe3O4 nanoparticles (SA-MNPs). ► High catalytic activity of SA-MNPs in synthesis of α-amino nitriles. ► Generality of the method, high yields and short reaction times. ► Recyclability and reusability of SA-MNPs without loss of its catalytic activity.Grafting of chlorosulfuric acid on the amino-functionalized Fe3O4 nanoparticles afforded sulfamic acid-functionalized magnetic Fe3O4 nanoparticles (SA-MNPs) as a novel organic–inorganic hybrid heterogeneous catalyst, which was characterized by XRD, FT-IR, TGA, TEM, and elemental analysis. The catalytic activity of SA-MNPs was probed through one-pot synthesis of α-amino nitriles via three-component couplings of aldehydes (or ketones), amines and trimethylsilyl cyanide in water, at room temperature. The heterogeneous catalyst could be recovered easily and reused many times without significant loss of its catalytic activity.
Keywords: Magnetic nanoparticles; Sulfamic acid; Heterogeneous catalysis; α-Amino nitriles;

Display Omitted▶ The silver supported onto HAp-encapsulated-γ-Fe2O3 is an ideal biomaterial as magnetically recoverable catalyst. ▶ Chemoselective oxidation of primary amines. ▶ Clean, green and low-cost methodology in the oxidation of primary amines to N-monoalkylated hydroxylamines.A novel magnetically recoverable silver nano-catalyst was fabricated by the adsorption–reduction of Ag (I) ions on the surface of hydroxyapatite encapsulated iron oxide nanoparticles. The magnetic catalyst could be easily separated by the application of an external magnetic field. The samples have been characterized by VSM, X-ray diffraction (XRD) and scanning and transmission electron microscopy (SEM and TEM), which reveal the superparamagnetic nano-nature of the particles. From these studies we can infer that the particles are mostly spherical in shape and have an average size of 10 nm. The catalytic ability of the Ag nanoparticles supported on the magnetic nanocarier was found to be excellent and they cleanly oxidize primary amines to N-monoalkylated hydroxylamines.
Keywords: Magnetically recoverable silver nano-catalyst; N-monoalkylated hydroxylamines; Hydroxyapatite encapsulated iron oxide nanoparticles; Oxidation of primary amines; Green chemistry;

Kinetics and mechanism for dye degradation with ionic Pd-substituted ceria by Parag A. Deshpande; Disha Jain; Giridhar Madras (39-48).
Display Omitted► Ionically substituted Pd in CeO2 was used for dye degradation. ► The effects of various parameters on dye degradation were studied. ► A mechanism consistent with the structure of the catalyst was proposed. ►Elementary surface processes were proposed and rate expressions were obtained.The degradation of the dye, Orange G, was carried out in the presence of H2O2 and Pd-substituted/impregnated CeO2. The effects of pH, initial dye concentration, initial H2O2 concentration, temperature, catalyst loading, and Pd content in the catalyst on the degradation of the dye were investigated. Eight to twelve percent degradation of the dye was obtained in 1 h when the reaction was carried out in the presence of CeO2 or H2O2 or Pd-substituted/impregnated CeO2 while 17% and 97% degradation was obtained when H2O2 was used with Pd-impregnated CeO2 and Pd-substituted CeO2, respectively. This difference clearly indicated that the ionic substitution of Pd played a key role in the degradation of the dye. A mechanism for the reaction was proposed based upon the catalyst structure and the electron transfer processes that take place in the metal ion substituted system in a reducible oxide. The reaction was found to follow first order kinetics and the influence of all the parameters on the degradation kinetics was compared using the rate constants.
Keywords: Advanced oxidation processes; Ionic substitution; Electron transfer; Dye degradation; Reaction mechanism; Kinetics;

Display Omitted► Efficient method for synthesis of ɛ-caprolactone using KHSO4 as an oxidising agent. ► Oxidation under phase transfer catalysis conditions. ► KHSO4 a commercially available, safe, stable and inexpensive compound. ► Relatively short reaction time, mild reaction conditions. ► ɛ-Caprolactone is obtained in high yields and with 100% selectivity.A new method for the synthesis of ɛ-caprolactone based on the Baeyer–Villiger oxidation of cyclohexanone was developed. In the proposed reaction, potassium peroxomonosulphate was used as an oxidising agent under phase transfer catalysis conditions. The effects of the reaction parameters, including the type of phase transfer catalyst, the concentration of the oxidising agent, the type of organic solvent and temperature, were investigated. When dichloromethane was used as an organic solvent and an adequate amount of water was added to the reaction mixture, the highest yield and selectivity for ɛ-caprolactone were achieved at 40 °C.
Keywords: Baeyer–Villiger oxidation; Phase transfer catalysis; KHSO5; ɛ-Caprolactone;

Synthesis, characterization and catalytic performance of metal-containing mesoporous carbons for styrene production by Cleanio L. Lima; Othon S. Campos; Alcemira C. Oliveira; Francisco F. de Sousa; Josué M. Filho; Pedro L. Neto; Adriana N. Correia; Gabriel Q. Sabadia; Izabel M. Nogueira; Gardenia S. Pinheiro; Alcineia C. Oliveira (53-63).
Display Omitted► TEM image showed highly ordered carbons with a high graphitisation degree. ► Increased surface area. ► Pt nanoparticles were attached inside MWCNT structure. ► Highly active in oxydehydrogenation of ethylbenzene.Metal-containing ordered carbons were synthesised and characterised by TEM, SEM, XRD, textural properties and Raman spectroscopy. The solids were evaluated in the ethylbenzene oxydehydrogention for styrene production. XRD and Raman studies showed highly ordered carbons with a high graphitisation degree and increased surface area when Pt nanoparticles were attached inside MWCNT structure, whereas Ni produced larger, inner nanoparticles with a lower organisation degree due to additional carbon growth on the top nickel particles. However, poorly graphitised carbon structures were obtained by incorporating Fe and Cu nanoparticles, which were deposited on the carbon surface. Studies of stability in the ethylbenzene dehydrogenation were done based on the physicochemical properties of the solids revealed that the stability of the metal-containing carbons was significantly improved through modification with Pt.
Keywords: Characterizations; Metal-containing carbon; Nanoparticles; Ethylbenzene; Styrene;

Display Omitted► The PdZn catalyst can be used to process near stoichiometric H2O/CH3OH feed. ► Pd–Zn alloy formed gradually under methanol steam reforming conditions. ► Carbon removal with air oxidation at 400–600 °C regenerates the catalyst. ► No special measures are required for the catalyst storage or activation. ► This catalyst can be applied to structured surfaces for H2 fuel cell applications.Performance, surface properties and structural transformation of a PdZn/Ceria catalyst were studied near stoichiometric H2O/CH3OH systematically over a range of aging conditions. Products CO and CO2 were found to lead to formation of carbonaceous compounds that negatively affect catalyst activity. Progressive formation of PdZn alloy and accumulation of carbonaceous compounds resulted in gradual improvements in reforming (H2 or CO2) selectivity but with slow deactivation with time. Air purge during reactor startup and shutdown or oxidation at 400–600 °C was found effective to recover the lost catalyst activity. With over 2000 h durability demonstrated at 400 °C, this catalyst is particularly suitable for washcoating on various metal surfaces to make compact reformers for fuel cell applications.
Keywords: Pd–Zn catalyst; Methanol steam reforming; Hydrogen production; Catalyst durability; Coking;

Heterogeneous oxidation catalysts formed in situ from molybdenum tetracarbonyl complexes and tert-butyl hydroperoxide by Patrícia Neves; Tatiana R. Amarante; Ana C. Gomes; Ana C. Coelho; Sandra Gago; Martyn Pillinger; Isabel S. Gonçalves; Carlos M. Silva; Anabela A. Valente (71-77).
Display Omitted► Efficient microwave-assisted synthesis of tetracarbonyl-pyrazolylpyridine complexes. ► Oxidative decarbonylation gives molybdenum oxide/pyrazolylpyridine catalysts. ► High selectivities in the epoxidation of olefins and the sulfoxidation of sulfides. ► The heterogeneous catalysts are stable and water-tolerant.The tetracarbonyl complexes cis-[Mo(CO)4{2-[3(5)-pyrazolyl]pyridine}] (1) and cis-[Mo(CO)4{ethyl[3-(2-pyridyl)-1-pyrazolyl]acetate}] (2) were obtained in excellent yields by microwave-assisted heating of a mixture of Mo(CO)6 and the organic ligand in toluene at 110 °C for 30 min. Complexes 1 and 2 are air stable, storable catalyst precursors for the epoxidation of olefins by tert-butyl hydroperoxide (TBHP). In situ oxidative decarbonylation of 1 gives the tetranuclear compound [Mo4O12{2-[3(5)-pyrazolyl]pyridine}4] (3). Elemental analysis and infrared data indicate that the oxidation of 2 gives an octameric species with the molecular formula [Mo8O24{ethyl[3-(2-pyridyl)-1-pyrazolyl]acetate}4] (4). The molybdenum oxide/pyrazolylpyridine compounds 3 and 4, which can be readily prepared in very good yields from the parent carbonyls upon reaction with TBHP in n-decane/CH2Cl2 at room temperature, are active and stable heterogeneous catalysts for the epoxidation of cis-cyclooctene (Cy) by TBHP, giving 1,2-epoxycyclooctane as the only product. The highest activity is found for 4: ca. 90% epoxide yield after 6 h reaction at 55 °C. Further experiments confirmed that 2 is an effective catalyst precursor for (i) the epoxidation of Cy by aqueous TBHP, giving the corresponding epoxide as the only product, (ii) the selective epoxidation of R-(+)-limonene by TBHP (in n-decane), and (iii) the selective oxidation of methyl phenyl sulfide to the corresponding sulfoxide by aqueous TBHP or H2O2 at 35 °C.
Keywords: Molybdenum; Heterogeneous catalysis; Pyrazolylpyridine ligands; Oxidative decarbonylation; Epoxidation; Sulfoxidation;

Transition metal-containing mixed oxides catalysts derived from LDH precursors for short-chain hydrocarbons oxidation by Serghei Tanasoi; Gheorghiţa Mitran; Nathalie Tanchoux; Thomas Cacciaguerra; François Fajula; Ioan Săndulescu; Didier Tichit; Ioan-Cezar Marcu (78-86).
Display Omitted► Transition metal-containing layered double hydroxides as catalyst precursors. ► Catalysts for short-chain hydrocarbons’ combustion and propane oxidehydrogenation. ► CuMgAlO catalyst is highly stable and active for the combustion. ► CoMgAlO catalyst gives the best propene yield during propane oxidehydrogenation.MMgAlO mixed oxide catalysts (M = Mn, Fe, Co, Ni, Cu, Zn, Ag and Pd) obtained from layered double hydroxide (LDH) precursors calcined at 1023 K were used in the complete oxidation of methane and the oxidative dehydrogenation of propane. The catalysts were characterized by XRD, N2 adsorption, EDX and H2-TPR experiments. In the catalytic complete oxidation of methane, the Pd-based catalyst has been proved the most active, but the less stable catalyst. Other mixed oxides containing transition metals have been tested and their catalytic activity followed the order: MgAlO ≈ FeMgAlO < NiMgAlO < ZnMgAlO < MnMgAlO < CoMgAlO < AgMgAlO < CuMgAlO. Total conversion was achieved at 858 K with CuMgAlO the most active and highly stable catalyst also able to perform the complete oxidation of ethane, propane and propene. It has been shown that highly reducible metal oxide species play an important role in the catalytic combustion of methane.In the oxidative dehydrogenation of propane in the temperature range from 723 K to 873 K the propene selectivity passed through a maximum for the Mn- and Fe-containing catalysts and decreased continuously for the other transition metal-containing catalysts to the benefit of CO x for CuMgAlO and of cracking products for CoMgAlO, NiMgAlO and ZnMgAlO. Considering the propene yield, the catalysts can be ranked in the following order: CoMgAlO > MnMgAlO > NiMgAlO > ZnMgAlO > FeMgAlO > CuMgAlO. No straight correlation between the H2-TPR reducibility and the catalytic performances of the samples was found in the oxidative dehydrogenation of propane into propene. The effects of the contact time and of the propane-to-oxygen molar ratio on the catalytic performances of the most active CoMgAlO, MnMgAlO and NiMgAlO mixed oxides have been investigated.
Keywords: Mixed oxides; Layered double hydroxides; Methane; Propane; Combustion; Oxidative dehydrogenation;

Display Omitted► Structure and properties of dolomite are changed significantly upon synthesis steps. ► This method increases strong basic site amount without changing their chemical nature. ► Water treatment develops more surface area and porosity as well as larger pore size. ► Greater basic site number and more accessible to reagent cause activity improvement.By means of a controlled hydration–dehydration process, the relatively low activity of calcined dolomite was modified into an active solid catalyst for the biodiesel production. This technique involves water treatment of the oxide phase under mild conditions followed by thermal decomposition at an elevated temperature. The results from various characterization techniques and the transesterification of palm olein showed that a structural transformation had taken place during the synthesis and structure–activity relation. Upon the calcination of dolomite, MgO grows on the surface of MgCa(CO3)2, which is progressively transformed into CaCO3 followed by the decomposition of calcite to CaO. The transformation of oxide to hydroxide phase and the reverse occurred simultaneously during the hydration–dehydration step with changes in the chemical and textural properties of the sample. The effectiveness of the hydration interaction appears to be due to a change in pore-size distribution, which is created by particle expansion in the formation of the hydroxide structure and the formation of more porosity and surface area during the dehydration and re-crystallization of oxide structure. Confirmed by TPD, in the hydration–dehydration step, the number of strong basic sites significantly increased while the chemical nature of these sites did not changed. The catalytic performance in transesterification is directly proportional to the number of strong surface base sites. This study provides an understanding regarding how this hydration–dehydration process influences the properties and activity of dolomite.
Keywords: Dolomite; Water; Hydration; Biodiesel; Heterogeneous catalyst;

New reaction pathways and kinetic parameter estimation for methanol dehydration over modified ZSM-5 catalysts by Kyoung-Su Ha; Yun-Jo Lee; Jong Wook Bae; Ye Won Kim; Min Hee Woo; Hyo-Sik Kim; Myung-June Park; Ki-Won Jun (95-106).
Display Omitted► Kinetic mechanisms on the alkali metal modified ZSM-5 catalysts. ► Simultaneous adsorption and activation of two methanol molecules. ► Presence of the methyl carboxonium ion. ► The kinetic parameters and the heats of adsorption were successfully estimated.Kinetics of the methanol (MeOH) dehydration has been investigated using two kinds of alkali metal-modified ZSM-5 (mZSM-5) catalysts, which were developed for the purpose of preparing dimethyl ether (DME) from water-containing MeOH. Two intrinsic kinetic mechanisms have been suggested and rigorous reaction rate equations were derived based on a series of reaction experiments in the presence and in the absence of water. In addition to the kinetic parameters, the heats of adsorption of MeOH and water were successfully estimated. The values are in good agreement with those obtained from the previously reported experimental results. According to the reaction pathways of our concern, two adsorbed MeOH molecules on the mZSM-5 simultaneously react with acidic sites to produce the intermediate molecule, which then undergoes the rate-determining step that the intermediate molecule rearranges itself to split into the smaller intermediates for the next step with or without the abstraction of water. In addition, the existence of the crucial intermediate closely related to the rate-determining step was also confirmed through FT-IR spectroscopy.
Keywords: Methanol; Dimethyl ether; Kinetics; Mechanism; Parameter estimation;

Modeling of adiabatic moving-bed reactor for dehydrogenation of isobutane to isobutene by Saeed Sahebdelfar; Parisa Moghimpour Bijani; Maryam Saeedizad; Farnaz Tahriri Zangeneh; Kamran Ganji (107-113).
Display Omitted► First-order kinetic expressions can express the trend of parameters in reactors. ► Slopes of adiabatic operating lines are underestimates due to side reactions. ► The dehydrogenation products leaving each reactor are close to equilibrium. ► Catalyst activity loss during a cycle before regeneration is large (ca. 75%).The dehydrogenation of isobutane to isobutene in adiabatic radial-flow moving-bed reactors was studied. First order rate expressions were considered for the primary reaction and deactivation kinetics incorporating the reversibility of dehydrogenation reaction. Kinetic data from a fixed-bed lab-scale reactor were used for modeling of the commercial size moving-bed reactor. The model was solved numerically by dividing the reactor into differential isothermal moving-bed reactors. The conversion of isobutane to isobutene was found to be equilibrium limited in commercial-sized reactors. The model predicted the trends of conversion, temperature, and catalyst activity with conversion levels somewhat lower than observed values which was attributed to the side-reactions.
Keywords: Isobutane dehydrogenation; Pt–Sn catalyst; Moving-bed reactor; Kinetics; Catalyst deactivation;

Display Omitted► The catalyst calcined at 800 °C exhibits the best catalytic performance. ► Initial activity, stability, Pt dispersion, Pt–Al interaction strength and CaO particle size present a sigmoidal curve tendency. ► The efficiency of CaO promotion effect depends on Ca–Al interaction strength and free CaO particle size. ► A complex with high Ca–Al interaction strength is formed at 900 °C in low CaO content catalysts.The cyclohexane dehydrogenation on CaO modified Pt/γ-Al2O3 was investigated with the aim of understanding the influences of calcination temperature of CaO modified γ-Al2O3 support (Ca/Al) on the efficiency of CaO promotion. The results showed that the catalyst calcined at 600 °C exhibited the worst, while the one calcined at 800 °C showed the best catalytic performance during the variation of Ca/Al calcination temperature from 500 to 900 °C. The catalyst pretreated at 800 °C exhibited an excellent hydrogen productivity of up to 4.45 L/(gcat  h) and high stability during 80 h continuous investigation of cyclohexane dehydrogenation in the absence of co-feed hydrogen at 300 °C and 8000 h−1 space velocity. That was attributed to weaker Pt–Al interaction and higher dispersed Pt, deriving from larger CaO particles. According to XRD spectra of model catalysts and CO2-TPD of Ca–Pt/Al catalysts, the efficiency of CaO promotion depended on the Ca–Al interaction strength and particle size instead of quantity of free CaO particles. The main calcium compound was free CaO in catalysts with low CaO content and low calcination temperature (below 800 °C). Complex CaO with high Ca–Al interaction strength and less CaO properties are formed in Ca900–Pt/Al catalyst.
Keywords: CaO promotion effect; Calcination temperature; Pt/γ-Al2O3 catalyst; CaO particle size; Ca–Al interaction;

H2-SCR of NO on Pt–MnO x catalysts: Reaction path via NH3 formation by Se Min Park; Mi-Young Kim; Eun Seok Kim; Hyun-Sik Han; Gon Seo (120-128).
Display Omitted► Prepared Pt–MnO x catalysts are active in the formation of NH3 from NO x and H2. ► They effectively reduce NO x by using supplied H2 or produced NH3. ► Manganese oxide and platinum show a synergistic effect in H2-SCR of NO x .Pt–MnO x catalysts without any alkali or transition metals were prepared and their performance in the selective catalytic reduction (SCR) of NO by H2 was examined. Their physicochemical properties were investigated using X-ray diffraction (XRD), extended X-ray adsorption fine structure (EXAFS), and X-ray photoelectron spectroscopy (XPS). The adsorption and removal of NO during H2-SCR were monitored by an in situ FT-IR spectrophotometer. The co-presence of MnO and MnO2 on Pt–MnO x was confirmed by EXAFS and XPS. NO was adsorbed on them as nitrate and nitrite, which were subsequently transformed to NH x species by the introduction of H2. The NH x species adsorbed on the acid sites of manganese oxide were active in the reduction of NO, although a direct reduction by H2 was also possible. The conversion of NO over the Pt(2.0)–MnO x catalyst was maximized to 64% at around 100 °C and fell with further increases in temperature. The N2 yield over the Pt(2.0)–MnO x catalyst was 30% at the same condition, indicating that about a half of NO was converted to N2. On the contrary, the Pt(2.0)/SiO2 catalyst exhibited very low N2 yield, 10%, because N2O was highly produced. The reaction between the hydrogen atoms activated on the platinum and the activated NO on the manganese oxide was considered essential for H2-SCR, and NH3 that formed as an intermediate effectively participated to the selective reduction.
Keywords: Manganese oxide; Platinum impregnation; H2-SCR; NO; NH3 formation;

Effect of NiO content in mesoporous NiO–Al2O3 catalysts for high pressure partial oxidation of methane to syngas by Yasukazu Kobayashi; Junpei Horiguchi; Seishiro Kobayashi; Yuichiro Yamazaki; Kohji Omata; Daisuke Nagao; Mikio Konno; Muneyoshi Yamada (129-137).
Display Omitted► Mesoporous NiO–Al2O3 catalyst shows high activity of oxidative reforming of methane at 650 °C and 1 MPa. ► The order of catalyst tolerance against oxidation of the nickel active species on them was: NiO(75)–Al2O3  > NiO(40)–Al2O3  > NiO(90)–Al2O3  > NiO(11)–Al2O3. ► NiO(40)–Al2O3 showed the stable activity without carbon deposition after 24 h reaction because of its moderate Ni particle size and Ni dispersion.The effect of NiO content in mesoporous NiO–Al2O3 catalysts on stability of the catalytic activity was investigated for partial oxidation of methane to syngas under the reaction conditions at 650 °C and 1 MPa over the contact time range from 0.1 to 5 ms. Mesoporous/porous NiO–Al2O3 catalysts with a high BET surface area were prepared with NiO content of 3.7–75 wt%. From XRD patterns and TPR profiles observed in these catalysts before H2 pretreatment, the presence of strong interactions between NiO and Al2O3 was indicated, which gave relatively small NiO particles in the catalysts. As results of activity tests conducted by changing the contact time from 5 ms to lower until the catalyst lost its oxidation activity, the order of the catalyst tolerance against oxidation of nickel active species on them was: NiO(75)–Al2O3  > NiO(40)–Al2O3  > NiO(90)–Al2O3  > NiO(11)–Al2O3. As results of long runs and TG–DTA analysis, NiO(40)–Al2O3 showed the stable activity without any carbon deposition after 24 h reaction. This is because the Ni particle size and dispersion are 5.9–7.1 nm and 10.8%, respectively, which are considered to be suitable to prevent both carbon deposition and oxidation of nickel species during reaction, while NiO(75)–Al2O3 with Ni particle size of 11.7–15.9 nm gave high carbon deposition after a long run. The Ni particle size of 10 nm was a borderline for carbon deposition under reaction conditions at 1 MPa.
Keywords: Partial oxidation; Syngas formation; Oxidative reforming of methane; NiO–Al2O3 catalyst; Short contact time reaction; Mesoporous;

Effects of glycols on Fischer–Tropsch synthesis activity and coordination structure of Co species in Co/SiO2: Mechanism for enhanced dispersion of Co0 nanoparticles by Naoto Koizumi; Shigenobu Suzuki; Satoshi Niiyama; Yukiya Ibi; Takayoshi Shindo; Muneyoshi Yamada (138-145).
Display Omitted► Impregnation of aqueous solution of Co nitrate and glycol enhanced FTS activity. ► Calcination temperature had an impact on activity enhancement induced by glycols. ► Smaller Co3O4 species were formed after calcination in the presence of glycols. ► Specific interactions between Co and glycol derivatives were observed during calcination.Co/SiO2 catalysts with higher dispersion of Co0 as well as high reducibility of Co were prepared by impregnation using an aqueous solution containing Co nitrate and a glycol under different glycol/Co2+ molar ratios. Glycols with different structures, i.e., straight chain and branched ones, were used for preparation of the catalysts to help understand the fundamental role of the glycols. The CO conversion was enhanced in the presence of these glycols. The highest conversion was around 60% under 503 K and 1.1 MPa regardless of the structures of the glycols, whereas the optimum glycol/Co2+ molar ratio for the highest conversion shifted toward higher values with decreasing molecular weight of the glycols. On the other hand, these conversions fell on one curve irrespective of the structures of the glycols when plotted against the C/Co2+ atomic ratios of the impregnation solutions, indicating that the C/Co2+ ratio was one of crucial factors for activity enhancement induced by the glycols. Furthermore, XRD and Co K-edge EXAFS measurements revealed that Co3O4 species with smaller sizes was formed after calcination in the presence of the glycols. Size of Co3O4 species fell on one curve when plotted against the C/Co2+ atomic ratios, which was consistent well with activity data. FT-IR measurements also provided evidence that Co species interacted with triethylene glycol (TEG) derivatives during calcination in the range of 400–470 K. In analogy to the polymerizable complex method, it was considered that this interaction included polymer complex-like species, in which Co species was immobilized in network of cross-linked structures formed by ester polymerization of TEG and dicarboxylic acid derived from TEG, resulting in the formation of smaller Co3O4 species after calcination, and the smaller Co0 nanoparticles after H2 reduction, i.e., enhanced FTS activity.
Keywords: Fischer–Tropsch synthesis; Co/SiO2; Glycols;