Applied Catalysis A, General (v.372, #1)
Editorial Board (CO2).
Investigation of the hydrogenation reactivity of some organic substrates using an electrocatalytic method by Márcio Vilar; Jadson L. Oliveira; Marcelo Navarro (1-7).
The hydrogenation of some organic substrates was investigated through an electrocatalytic method. Nickel deposit morphologies (catalyst surface) were also investigated, taking into account different cathode matrix materials (Cu, Ni, Fe, Fe/Ni (alloy 64:36)). Ni deposit/Ni cathode matrix ensemble exhibited slightly better activity, likely due the nanostructure of the nickel deposit. Hydrogenation reactivity order observed: α,β-unsaturated ketones > benzaldehydes > acetophenones.The hydrogenation reactivity of some classes of organic substrates (α,β-unsaturated ketones, benzaldehydes and acetophenones) was investigated using an electrocatalytic method (undivided cell, nickel sacrificial anode and water/methanol solvent). During the process a nickel deposit is produced on the cathode surface, at the same time that hydrogen is generated by water reduction. Nickel deposit morphologies (catalyst surface) were investigated, taking into account different cathode matrix materials (Cu, Ni, Fe, Fe/Ni (alloy 64:36)). The electrocatalytic method was evaluated by electrochemical efficiency of the hydrogenation process ((hydrogenation theoretical charge/experimental charge) × product yield). It was observed that Ni deposit/Ni cathode matrix ensemble exhibits slightly better catalytic activity, likely due the nanostructure of the nickel deposit. Moreover, the reactivity order determined through the electrochemical efficiencies (α,β-unsaturated ketones > benzaldehydes > acetophenones) is the same as that found in the literature.
Keywords: Electrocatalytic hydrogenation; Nickel sacrificial anode; Nickel catalyst; Olefins; Ketones; Aldehydes;
Continuous gas-phase isopropylation of toluene and cumene using highly acidic Supported Ionic Liquid Phase (SILP) catalysts by J. Joni; M. Haumann; P. Wasserscheid (8-15).
Continuous gas-phase Friedel-Crafts isopropylation of toluene and cumene has been investigated using novel acidic Supported Ionic Liquid Phase (SILP) materials as catalysts. Detailed kinetic studies in a multi-stage tubular reactor revealed that reactant's water content and the aromatic-to-alkene ratio are the most relevant influencing factors for the catalyst stability and selectivity in these reactions.Continuous gas-phase Friedel-Crafts isopropylation of toluene and cumene has been investigated using acidic Supported Ionic Liquid Phase (SILP) materials as the catalyst. Detailed kinetic studies in a multi-stage tubular reactor revealed that reactant's water content and the aromatic-to-alkene ratio are the most relevant influencing factors for the catalyst stability and selectivity in these reactions. Based on this insight, our process optimization led to the first highly stable, highly active and selective SILP-type acidic catalyst system for gas-phase aromatic alkylation. We anticipate that this concept offers great potential for more sustainable Friedel-Crafts alkylation processes.
Keywords: Friedel-Crafts alkylation; Acid catalysis; Continuous process; Supported Ionic Liquid Phase (SILP); Porous material;
Development of  fullerene supported on silica catalysts for the photo-oxidation of alkenes by George D. Panagiotou; Manolis D. Tzirakis; John Vakros; Loukia Loukatzikou; Michael Orfanopoulos; Christos Kordulis; Alexis Lycourghiotis (16-25).
Incipient wetness impregnation is an efficient method for supporting various amounts of C60 onto the silica surface. The immobilization of C60 on SiO2 increases considerably its catalytic activity for the photo-oxidation of alkenes. The easy separation of these catalysts from the reaction mixture and the retained activity in subsequent catalytic cycles make these catalysts suitable for fine chemicals small-scale synthesis.Simple or successive incipient wetness impregnation followed by heating at 180 °C is proved an efficient preparation method for dispersing effectively onto the silica surface various amounts of C60 in the range 1–4% (w/w). BET, XRD, DRS, TGA, microelectrophoresis and photoluminescence have been used to characterize the photocatalysts prepared. A high dispersion was obtained for the quite stable supported C60 phase, comprised mainly from relatively small or medium size C60 clusters/aggregates. The photocatalytic activity was assessed in the singlet oxygen oxidation of alkenes by examining the photo-oxygenation of 2-methyl-2-heptene as a probe reaction. The catalytic tests were carried out at 0–5 °C in CH3CN, under oxygen atmosphere and using a 300 W xenon lamp as the light source. The heterogeneous catalysts obtained were proved to be active in the photocatalytic oxidation of olefins via a 1O2 ene reaction. The catalysts exhibited significant conversion, turnover number and turnover frequency values, substantially higher than those achieved over the unsupported C60. The conversion increases with the amount of the supported C60 up to a value equal to 3% (w/w) and then it decreases whereas turnover number and turnover frequency decreases monotonically as the amount of the supported C60 increases. The easy separation of these solid catalysts from the reaction mixture, the high activity and stability as well as the retained activity in subsequent catalytic cycles, make these supported catalysts suitable for a small-scale synthesis of fine chemicals.
Keywords: C60; Photocatalysis; Singlet oxygen; Photo-oxidation; DRS; Supported catalysts; Supported C60; Photoluminescence; TGA; Ene reaction; SiO2;
Model reactions as probe of the acid–base properties of aluminas: Nature and strength of active sites. Correlation with physicochemical characterization by Sonia Carre; Benoit Tapin; Ngi Suor Gnep; Renaud Revel; Patrick Magnoux (26-33).
Acetonylacetone conversion was carried out over various transition aluminas in order to estimate simultaneously their acid–base properties. The formations of 2,5-dimethylfuran (DMF) and of 2-methyl-3-cyclopenten-1-one (MCP) were associated to acid and basic sites, respectively. The combination of model reactions and CO2 and DMP adsorption allows us to propose a description of the nature and the strength of the various aluminas surface.Acetonylacetone conversion at 250 and 350 °C was carried out over various transition aluminas (η- to θ-Al2O3) in order to estimate simultaneously their acid–base properties. The formation of 2,5-dimethylfuran (DMF) was associated to the presence of acid site, and the formation of 2-methyl-3-cyclopenten-1-one (MCP) associated to basic site. First, from carbon dioxide adsorption measurement, hydroxyl basic group was found to be the active site for MCP formation and 2,6-dimethylpyridine (DMP) adsorption measurement shows that Brønsted acid site is active site for DMF formation. Secondly, from catalytic results, we show that θ-Al2O3 possesses a basic/acid ratio (MCP/DMF = 16) higher than the other aluminas (MCP/DMF < 10), and from comparison with cyclopentanol/cyclohexanone mixture transformation (acid alcohol dehydration and acid–base hydrogen transfer between alcohol and ketone), we also show that acetonylacetone cyclization are a more difficult reaction. Finally, the combination of model reactions and CO2 and DMP adsorption allows us to propose a description of the nature and the strength of the various aluminas surface.
Keywords: Aluminas; Acid–base properties; Acetonylacetone cyclization; FTIR; Microcalorimetry;
Hydrogenation of phenylacetylene and 3-phenylpropyne using Rh(diene) complexes under homogeneous and heterogeneous conditions by Eliška Leitmannová; Jan Svoboda; Jan Sedláček; Jiří Vohlídal; Petr Kačer; Libor Červený (34-39).
Phenylacetylene and 3-phenylpropyne were hydrogenated using [Rh(diene)Cl]2 complexes in their immobilized forms and compared with hydrogenation in homogeneous arrangement.Hydrogenation of phenylacetylene (PA) and 3-phenylpropyne (PP) was carried out using [Rh(diene)Cl]2 complexes (diene is hexadiene (HD), cycloocta-1,5-diene (COD), norborna-2,5-diene (NBD)) in their immobilized forms and compared with hydrogenation in homogeneous arrangement. Immobilization brings significant increase of the catalytic activity and product selectivity in the step-wise hydrogenation to corresponding vinyl-resp. allyl-benzenes. Diene-ligand effect was apparent in PA hydrogenation; the product selectivity decreased in order Rh(HD) > Rh(NBD) > Rh(COD) and catalytic activity decreased in order Rh(HD) > Rh(COD) > Rh(NBD).
Keywords: Phenylacetylene; Rh(diene)complex; Selective hydrogenation;
Catalytic reduction of nitrate in water: Promoted palladium catalysts supported in resin by C. Neyertz; F.A. Marchesini; A. Boix; E. Miró; C.A. Querini (40-47).
Nitrate can be eliminated from drinking water by catalytic reduction. Nevertheless, the development of active and selective catalysts for this reaction has not been easy. We found that depending upon the preparation procedure very different catalytic behavior was found, as shown in the figure. The retention capacity of nitrate by ion exchange as well as its conversion depends not only on the metal content, but also in the preparation procedure.The reactive properties of Pd–Cu and Pd–In catalysts over weak anionic exchange resin as support was investigated in the catalytic nitrate reduction. Pd–Cu/resin catalysts were prepared upon different copper fixation procedures (ion exchange method and controlled surface reaction). The samples were tested in a batch reactor with H2 bubbling and constant pH. The fresh and reacted catalysts were characterized by TEM, EPMA, XRD and XPS. The results demonstrated a higher activity of the Pd–Cu/resin catalyst prepared upon controlled surface reaction due to a high concentration of binary sites in the external surface. On the other hand, the XRD and TEM analyses indicated that sinterization occurs during reaction, leading to an increase in the average particle size.In the same way, a Pd–In/resin was investigated showing more activity and less selectivity than the Pd–Cu/resin sample.
Keywords: Nitrate catalytic reduction; Pd–Cu catalysts; Pd–In catalysts; Resin; Water treatment;
Highly dispersed sol–gel synthesized Cu–ZrO2 materials as catalysts for oxidative steam reforming of methanol by Serena Esposito; Maria Turco; Giovanni Bagnasco; Claudia Cammarano; Pasquale Pernice; Antonio Aronne (48-57).
A novel one-pot sol–gel route allows to obtain Cu–ZrO2 with high surface areas (140–180 m2 g−1) and extraordinary dispersion of metallic Cu after reduction with H2. Cu(II) dissolved into ZrO2 stabilizes the tetragonal form. Not pre-reduced Cu–ZrO2 shows OSRM activity similar to that of Cu–ZrO2 pre-reduced at 300 °C. Zirconia contributes to the catalytic activity producing mainly (CH3)2O and CH2O. (For interpretation of the references to color in this artwork, the reader is referred to the web version of the article.)New nanodispersed Cu–ZrO2 systems (containing 0 and 8.3 mol% Cu) were synthesized by sol–gel method. Homogeneous gels were prepared starting from Zr propoxide and Cu(NO3)2·2.5H2O. The materials were characterized by XRD, TG/DTA, N2 adsorption, TPR techniques and N2O surface oxidation. In the Cu-containing material part of Cu2+ ions were incorporated into the zirconia lattice and strongly influenced the crystallisation behaviour of zirconia matrix. After treatment at 450–600 °C, the materials contained ZrO2 nanocrystals of the tetragonal polymorph. The samples heat treated up to 450 °C showed high surface areas in the range 140–180 m2/g. Copper oxide species with different reducibility were detected by TPR measurements. The H2 reduction treatments gave rise to metallic copper with very high dispersion. The catalysts showed high activity for the oxidative steam reforming of methanol. A noticeable activity was observed also with the not pre-reduced catalyst, although a previous reduction in H2 led to a higher selectivity and H2 production.
Keywords: Sol–gel; Cu–ZrO2 catalysts; ZrO2 catalyst; Cu dispersion; Oxidative steam reforming of methanol;
Synthesis, characterization and catalytic behavior of AlTf/UVM-7 as new green catalysts for the glycols etherification reactions by Natalia Candu; Simona M. Coman; Vasile I. Parvulescu; Jamal El Haskouri; Pedro Amoros; Daniel Beltran (58-66).
AlTf–UVM-7 materials are used as green catalysts for the etherification of ethylene glycol and propylene glycol with n-octanol to the corresponding non-ionic surfactants structures with a peaked distribution.Bimodal porous Al–UVM-7 system materials with different Si-to-Al ratios were prepared using the Atrane route. These were converted in strong acid heterogeneous AlTf-based catalysts after the treatment with methanolic solutions of triflic acid. The materials so obtained were used as catalysts for the conversion of ethylene glycol (EG) and propylene glycol (PG) with octanol under solvent-free conditions. The process is selective to short ethoxylated structures resulting in the corresponding monoethers. While the conversion of EG and PG was very high (>94%) irrespective of the support characteristics, 1-octanol was transformed only in low degree (3–35%), and its conversion depends on both the Si/Al molar ratio and the catalyst texture (Al–UVM-7 or AlTf–UVM-7). Recyclable experiments showed the catalysts are stable and the reuse occurred without changes in the chemical composition.
Keywords: Aluminum triflates; Mesoporous materials; Glycols; Etherification; Non-ionic surfactants;
Catalytic olefin epoxidation with cationic molybdenum(VI) cis-dioxo complexes and ionic liquids by Sandra Gago; Salete S. Balula; Sónia Figueiredo; André D. Lopes; Anabela A. Valente; Martyn Pillinger; Isabel S. Gonçalves (67-72).
The complexes [MoO2Cl(HC(bim)3)]Y (Y = Cl (1), BF4 (2) and PF6 (3)) have been prepared by reaction of MoO2Cl2(THF)2 (for 1) or [MoO2Cl(THF)3]Y (for 2 and 3) with the tridentate ligand HC(bim)3 = tris(benzimidazolyl)methane, and characterized by IR and Raman spectroscopy, and 1H NMR. The turnover frequencies for the epoxidation of cis-cyclooctene at 55 °C with tert-butyl hydroperoxide (TBHP, in decane) as the oxidant and complexes 1–3 as catalysts are in the range of 70–200 mol molMo −1 h−1. 1,2-Epoxycyclooctane is always the only reaction product for reaction times up to 24 h. With the aim of facilitating the recyclability of the complexes, the ionic liquids (ILs) [BMIM]Y and [BMPy]Y (BMIM = 1-n-butyl-3-methylimidazolium, BMPy = 1-n-butyl-3-methylpyridinium; Y = BF4 or PF6) were applied as ionic solvents. The catalytic performance for cyclooctene epoxidation depends strongly on the catalyst solubility in the IL. Of the 12 catalyst/IL mixtures examined, the systems 1/[BMIM]PF6 and 1/[BMPy]PF6 exhibit the most favorable reaction rates allied with good recyclability. The 1/[BMIM]PF6 system was further applied using different oxidants (aqueous TBHP, aqueous H2O2 and urea–hydrogen peroxide adduct) and olefins (norbornene, cyclohexene, styrene, α-pinene).The complexes mentioned in the title can be used as quite active catalysts for the oxidation of olefins to epoxides using tert-butyl hydroperoxide as the oxidant. No diol formation was observed with the substrates cis-cyclooctene, cyclohexene and norbornene. Hexafluorophosphate ionic liquids were used successfully with [MoO2Cl(HC(bim)3)]Cl to allow catalyst/solvent recycling and reuse.
Keywords: Dioxomolybdenum(VI); Tripodal ligands; Benzimidazole; Olefin epoxidation; Ionic liquids;
Heterogenized copper catalysts for the amination of arylhalide: Synthesis, characterization and catalytic applications by Nandkumar M. Patil; Sunil P. Gupte; Raghunath V. Chaudhari (73-81).
This research investigated the synthesis, characterization and catalytic activity of heterogenized copper complexes for the selective amination of aryl halides. Amination reactions using homogeneous copper catalyst systems are not generally selective and it is also difficult to recover the catalyst from the homogeneous system for recycling. To overcome these difficulties, our efforts were directed towards the development of cheaper heterogeneous catalyst systems, which can be easily recovered and recycled. Heterogenized analogs of the homogenous Cu complexes were prepared using two methods: (a) encapsulation of copper complexes in zeolite-Y and (b) tethering of copper complexes on various supports like zeolite-Y, silica, charcoal, or clay. The encapsulated and tethered copper catalysts on zeolite-Y were characterized using EPR, Diffused reflectance UV–vis, XRD, IAS, ICPES, SEM, and TEM. The results confirmed that the copper complexes were truly heterogenized in zeolite-Y support. Encapsulated and tethered copper complexes were tested for amination of aryl iodide. The effects of various reaction parameters were examined using tethered Cu(Phen)(PPh3)Br-PTA-Y catalyst to determine optimum conditions. A recycle study of encapsulated and tethered Cu catalyst was carried out to test their robustness for possible commercial exploitation.A heterogenized copper catalyst for selective amination to diphenylamine has been described. The Na–Y encapsulated copper complex catalyst for amination of aryl iodide showed shape-selective formation of diphenylamine. The catalyst could be recycled five times with a cumulative TON of ∼200.
Keywords: C–N coupling; Heterogeneous catalysis; Amination; Mesoporous materials; Copper;
Mesoporous silicas containing carboxylic acid: Preparation, thermal degradation, and catalytic performance by Sadanobu Sumiya; Yuka Kubota; Yasunori Oumi; Masahiro Sadakane; Tsuneji Sano (82-89).
Carboxylic acid-containing products were generated in the mesopores of SBA-15 and MCM-41 during the calcination and thermal degradation of the triblock copolymer, (PEO)20(PPO)70(PEO)20, and cetyltrimethylammonium bromide (CTAB) as templates. The acidity sensitively depended on both the calcination temperature and the atmosphere.The calcination and thermal degradation behaviors of surfactants in mesoporous silicas SBA-15 and MCM-41 were investigated by FT-IR, 13C CP/MAS NMR, TG/DTA, and GPC. It was found that carboxylic acid-containing products were generated as active components in the mesopores of SBA-15 and MCM-41 from the triblock copolymer (PEO)20(PPO)70(PEO)20 and cetyltrimethylammonium bromide (CTAB), respectively; the latter materials were used as templates. The carboxylic acid-containing mesoporous silica obtained showed a catalytic activity for hydrolysis of sucrose. The acidity was evaluated by means of NaOH titration. The acidity sensitively depended on both the calcination temperature and the atmosphere; the maximum appeared at 150 °C in air for SBA-15 where the highest activity was observed. However, the product in MCM-41 showed a lower catalytic activity than that in SBA-15. The SBA-15 product was easily leached from the mesopores of SBA-15 into the solution, but the degree of leaching for MCM-41 was considerably smaller than that for SBA-15.
Keywords: Carboxylic acid; Degradation; Surfactant; SBA-15; MCM-41; Sucrose hydrolysis;
Generation of protonic acid sites from pentane on the surfaces of Pt/SO4 2−-ZrO2 and Zn/H-ZSM5 evidenced by IR study of adsorbed pyridine by Sugeng Triwahyono; Aishah Abdul Jalil; Malik Musthofa (90-93).
The protonic acid sites from pentane are generated through the dissociation of a pentane molecule into a hydrogen atom and a pentyl radical, followed by spillover of the hydrogen atom onto the support and migration to reach Lewis acid site where each hydrogen atom donates an electron to a Lewis acid site and becomes a proton.Pyridinium ion was formed from pyridine, which had been bound to Lewis acid sites on Pt/SO4 2−-ZrO2 and Zn/H-ZSM5 by contact with pentane vapor. Protonic acid sites were generated on these surfaces by contact with pentane. The protonic acid sites generated in the presence of pentane were eliminated when pentane was removed from gas phase. The generation of the protonic acid sites occurred above 350 K for Pt/SO4 2−-ZrO2 and above room temperature for Zn/H-ZSM5.
Keywords: Protonic acid site; Pentane; Pt/SO4 2− -ZrO2; Zn/H-ZSM5;
Organotin compounds immobilized on mesoporous silicas as heterogeneous catalysts for direct synthesis of dimethyl carbonate from methanol and carbon dioxide by Binbin Fan; Hongyu Li; Weibin Fan; Jilong Zhang; Ruifeng Li (94-102).
A highly active and stable heterogeneous organotin catalyst for synthesis of dimethyl carbonate (DMC) from CH3OH and CO2 has been prepared by grafting (MeO)2ClSi(CH2)3SnCl3 on SBA-15 and successively substituting Cl− by CH3O−. The structures of mesoporous silicas, the methods used for removing surfactants, the types of dehydration agents and the reaction conditions had strong influences on the catalytic performance.Organotin compounds of (MeO)2ClSi(CH2)3SnCl3 have been grafted on a series of mesosporous silicas, as proved by XRD, N2 adsorption/desorption experiments and FTIR, diffuse reflectance UV–vis and 13C CP/MAS NMR spectroscopies. A further substitution of Cl− bonded to Sn4+ by CH3O− led to the formation of a series of active heterogeneous catalysts for the direct synthesis of dimethyl carbonate from methanol and CO2. The catalytic properties of these catalysts depended on the structure, crystal size and surface properties of mesoporous silicas. SBA-15 as a host was superior to SBA-16 and large-pore Ia3d. In addition, the methods used for removing surfactants occluded in mesoporous silicas had strong influences on the catalytic performance as a result of significantly affecting the surface areas and the concentrations of surface hydroxyl groups of the mesoporous silicas. The extraction of surfactants by an ethanol–HCl solution should be available. An increase in the reaction time, reaction temperature, methanol amount and CO2 pressure significantly increased the dimethyl carbonate yield before reaching thermodynamic equilibrium. The dimethyl carbonate yield could also be increased by adding dehydration agents to the reaction system. 2,2-Dimethoxypropane gave a much higher dimethyl carbonate yield than 3A molecular sieve and tetramethyl orthorsilicate. The prepared organotin/mesoporous silica catalysts were highly stable, as corroborated by the findings that the dimethyl carbonate yield obtained over the SBA-15-immoilized organotin compound did not decrease within six repeated runs with regeneration under the same reaction conditions and that the tetrahedral coordination state of Sn species was maintained after reaction.
Keywords: Dimethyl carbonate; Organotin; Mesoporous silica; Graft; SBA-15;
Kinetics study of hydrogen adsorption over Pt/MoO3 by Sugeng Triwahyono; Aishah Abdul Jalil; Sharifah Najiha Timmiati; Nurun Najwa Ruslan; Hideshi Hattori (103-107).
The hydrogen adsorption on Pt/MoO3 involves the dissociation of hydrogen molecules to hydrogen atoms, spillover of the dissociated hydrogen onto the surface of MoO3, surface diffusion of the spiltover hydrogen over the bulk surface of MoO3 and formation of H x MoO3. The rate controlling step is surface diffusion of spiltover hydrogen atom with the activation energy of 83.1 kJ/mol.The rate controlling step and the energy barrier involved in the hydrogen adsorption over Pt/MoO3 were studied. Rates of hydrogen adsorption on Pt/MoO3 were measured at the adsorption temperature range of 323–573 K and at the initial hydrogen pressure of 6.7 kPa. The rate of hydrogen uptake was very high for the initial few minutes for adsorption at and above 473 K, and reached equilibrium within 2 h. At and below 423 K, the hydrogen uptake still continued and did not reach equilibrium after 10 h. The hydrogen uptake exceeded the H/Pt ratio of unity for adsorption at and above 423 K, indicating that hydrogen adsorption involves hydrogen atom spillover and surface diffusion of the spiltover hydrogen atom over the bulk surface of MoO3 followed by formation of H x MoO3. The hydrogen uptake was scarcely appreciable for Pt-free MoO3. The rate controlling step of the hydrogen adsorption on Pt/MoO3 was the surface diffusion of the spiltover hydrogen with the activation energy of 83.1 kJ/mol. The isosteric heats of hydrogen adsorption on Pt/MoO3 were 18.1–16.9 kJ/mol for the hydrogen uptake range 2.4–2.8 × 1019 H-atom/g-cat. Similarities and differences in hydrogen adsorption on Pt/SO4 2−–ZrO2, Pt/WO3–ZrO2 and Pt/MoO3 catalysts are discussed.
Keywords: Pt/MoO3; Hydrogen adsorption; H x MoO3; Surface diffusion; Heat adsorption;
n-Pentane hydroisomerization on Pt-promoted acid zeolites by Carmen M. López; Virginia Sazo; Pedro Pérez; Luis V. García (108-113).
Hydroisomerization of n-pentane over platinum promoted acid zeolites was studied. The effect of structure and strength acid sites of the support was investigated on the reaction carried out under atmospheric pressure at 300 °C. In order to accomplish the above purpose, some zeolitic catalytic systems were studied, which have the same structure but different acidity and with similar acidity but different structure.Hydroisomerization of n-pentane over platinum promoted acid zeolites was studied. The effect of structure and strength of acid sites of the support was investigated on the reaction carried out under atmospheric pressure at 300 °C. In order to accomplish the above purpose, some zeolitic catalytic systems were studied, which have the same structure but different acidity and with similar acidity but different structure.
Keywords: n-Pentane; Hydroisomerization; Supported-metal catalysts; Zeolites;