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Applied Catalysis A, General (v.338, #1-2)
Mild oxidation of tetrahydrothiophene to sulfolane over V-, Mo- and W-containing layered double hydroxides by Alina-Livia Maciuca; Emil Dumitriu; François Fajula; Vasile Hulea (pp. 1-8).
Layered double hydroxides (LDH) with Mg2+ and Al3+ cations in the brucite-like layer and W-, V- and Mo-oxospecies in the interlayer gallery were prepared, characterized and tested as catalysts for the sulfolane synthesis by mild sulfoxidation of tetrahydrothiophene with H2O2. In the temperature range of 20–30°C, the best performances were obtained with WO42−-containing LDH catalysts.▪A series of layered double hydroxides (LDH) with Mg2+ and Al3+ cations in the brucite-like layer and W-, V- and Mo-oxospecies in the interlayer gallery were prepared, characterized and tested as catalysts for the sulfolane synthesis by mild sulfoxidation of tetrahydrothiophene (THT) with H2O2. The structural and textural properties of solids and the nature of the metal species were investigated by X-ray diffraction (XRD), N2 adsorption, thermogravimetric analysis (TGA), diffuse reflectance ultraviolet spectroscopy (DRUV), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The catalytic activity was evaluated in the liquid-phase THT oxidation with dilute H2O2 in various organic solvents and temperature range of 20–30°C. The best performances in terms of catalytic activity and stability were obtained with WO42−-containing LDH catalyst.
Keywords: Tetrahydrothiophene; Sulfolane; Hydrogen peroxide; Layered double hydroxide; Tungstate; Vanadate; Molybdate
Mild oxidation of tetrahydrothiophene to sulfolane over V-, Mo- and W-containing layered double hydroxides by Alina-Livia Maciuca; Emil Dumitriu; François Fajula; Vasile Hulea (pp. 1-8).
Layered double hydroxides (LDH) with Mg2+ and Al3+ cations in the brucite-like layer and W-, V- and Mo-oxospecies in the interlayer gallery were prepared, characterized and tested as catalysts for the sulfolane synthesis by mild sulfoxidation of tetrahydrothiophene with H2O2. In the temperature range of 20–30°C, the best performances were obtained with WO42−-containing LDH catalysts.▪A series of layered double hydroxides (LDH) with Mg2+ and Al3+ cations in the brucite-like layer and W-, V- and Mo-oxospecies in the interlayer gallery were prepared, characterized and tested as catalysts for the sulfolane synthesis by mild sulfoxidation of tetrahydrothiophene (THT) with H2O2. The structural and textural properties of solids and the nature of the metal species were investigated by X-ray diffraction (XRD), N2 adsorption, thermogravimetric analysis (TGA), diffuse reflectance ultraviolet spectroscopy (DRUV), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The catalytic activity was evaluated in the liquid-phase THT oxidation with dilute H2O2 in various organic solvents and temperature range of 20–30°C. The best performances in terms of catalytic activity and stability were obtained with WO42−-containing LDH catalyst.
Keywords: Tetrahydrothiophene; Sulfolane; Hydrogen peroxide; Layered double hydroxide; Tungstate; Vanadate; Molybdate
Niobium to alcohol mol ratio control of the concurring esterification and etherification reactions promoted by NbCl5 and Al2O3 catalysts under microwave irradiation by Sandro L. Barbosa; Gabriela R. Hurtado; Stanlei I. Klein; Valdemar L. Junior; Miguel J. Dabdoub; Carlos F. Guimarães (pp. 9-13).
Alcohols and acids can be switched to produce ethers or esters by varying the alcohol to catalyst mol ratio, in a new etherification and esterification method using NbCl5/Al2O3 catalyst under “solvent free” conditions and promoted by MW (microwave) irradiation. A “two sites” mechanism for the reaction is proposed, in an attempt to clarify the tendency of the catalyst to be dependent on the alcohol alone during the esterification process.Alcohols and acids can be switched to produce ethers or esters by varying the alcohol to catalyst mol ratio, in a new etherification and esterification method using NbCl5/Al2O3 catalyst under “solvent free” conditions and promoted by MW irradiation. A “two sites” mechanism for the reaction is proposed, in an attempt to clarify the tendency of the catalyst to be dependent on the alcohol alone during the esterification process. Dependency of product distribution to the NbCl5 to alcohol mole ratio for the esterification of benzyl alcohol with glacial acetic acid. Reaction conditions: 5min MW irradiation at 360W; acetic acid, 2.8000mmol; benzyl alcohol, 1.0000mmol; 0.1000g of Al2O3. Determined by1H NMR.▪
Keywords: Esterification; Etherification; Solid phase catalysis; Microwave; Solvent free
Niobium to alcohol mol ratio control of the concurring esterification and etherification reactions promoted by NbCl5 and Al2O3 catalysts under microwave irradiation by Sandro L. Barbosa; Gabriela R. Hurtado; Stanlei I. Klein; Valdemar L. Junior; Miguel J. Dabdoub; Carlos F. Guimarães (pp. 9-13).
Alcohols and acids can be switched to produce ethers or esters by varying the alcohol to catalyst mol ratio, in a new etherification and esterification method using NbCl5/Al2O3 catalyst under “solvent free” conditions and promoted by MW (microwave) irradiation. A “two sites” mechanism for the reaction is proposed, in an attempt to clarify the tendency of the catalyst to be dependent on the alcohol alone during the esterification process.Alcohols and acids can be switched to produce ethers or esters by varying the alcohol to catalyst mol ratio, in a new etherification and esterification method using NbCl5/Al2O3 catalyst under “solvent free” conditions and promoted by MW irradiation. A “two sites” mechanism for the reaction is proposed, in an attempt to clarify the tendency of the catalyst to be dependent on the alcohol alone during the esterification process. Dependency of product distribution to the NbCl5 to alcohol mole ratio for the esterification of benzyl alcohol with glacial acetic acid. Reaction conditions: 5min MW irradiation at 360W; acetic acid, 2.8000mmol; benzyl alcohol, 1.0000mmol; 0.1000g of Al2O3. Determined by1H NMR.▪
Keywords: Esterification; Etherification; Solid phase catalysis; Microwave; Solvent free
Aerobic oxidation of alkyl arenes and alcohols using cobalt(II) phthalocyanine as a catalyst in 1-butyl-3-methyl-imidazolium bromide by Ahmad Shaabani; Elham Farhangi; Abbas Rahmati (pp. 14-19).
The aerobic oxidation of alkyl arenes and alcohols to the corresponding carbonyl compounds has been achieved using a catalyst and oxygen (0.1atm) in an ionic liquid. Excellent yields were obtained under mild, easily obtainable conditions. Among the various metallophthalocyanine catalysts and ionic liquids examined, the best results were obtained with cobalt(II) phthalocyanine in 1-butyl-3-methylimidazolium bromide ([bmim]Br). These materials can be recycled and reused for several times without any significant loss of catalytic activity.
Keywords: Aerobic oxidation; Cobalt(II) phthalocyanine; 1-Butyl-3-methylimidazolium bromide; Alkyl arene; Alcohol
Aerobic oxidation of alkyl arenes and alcohols using cobalt(II) phthalocyanine as a catalyst in 1-butyl-3-methyl-imidazolium bromide by Ahmad Shaabani; Elham Farhangi; Abbas Rahmati (pp. 14-19).
The aerobic oxidation of alkyl arenes and alcohols to the corresponding carbonyl compounds has been achieved using a catalyst and oxygen (0.1atm) in an ionic liquid. Excellent yields were obtained under mild, easily obtainable conditions. Among the various metallophthalocyanine catalysts and ionic liquids examined, the best results were obtained with cobalt(II) phthalocyanine in 1-butyl-3-methylimidazolium bromide ([bmim]Br). These materials can be recycled and reused for several times without any significant loss of catalytic activity.
Keywords: Aerobic oxidation; Cobalt(II) phthalocyanine; 1-Butyl-3-methylimidazolium bromide; Alkyl arene; Alcohol
Catalytic applications of ordered mesoporous magnesium oxide synthesized by mesoporous carbon by Amit Dubey; Braj Gopal Mishra; Divya Sachdev (pp. 20-26).
In an attempt to introduce the intrinsic basicity properties, ordered mesoporous magnesium oxide (MgO) is synthesized using mesoporous carbon (CMK-8) as the host material for its effective use for base catalysis. The catalytic activity studies for various base catalyzed condensation reactions studied showed very high activity and selectivity. The knowledge obtained was extended for aldol condensation reaction between glyceraldehydes acetonide and acetone. Very high activity and selectivity of the desired product was observed compared to the other mixed oxides reported in the literature. ▪In an attempt to introduce the intrinsic basicity properties, we synthesized ordered mesoporous magnesium oxide (MgO) using mesoporous carbon (CMK-8) as the host material for more effective use for base catalysis. The catalytic activity studies for various base catalyzed condensation reactions showed very high activity and selectivity. The knowledge obtained was extended for the aldol condensation reaction between glyceraldehydes acetonide and acetone. Very high activity and selectivity of the desired product was observed compared to the values for other mixed oxides reported in the literature.
Keywords: Mesoporous materials; Catalysts; Ordered mesoporous MgO
RETRACTED: Catalytic applications of ordered mesoporous magnesium oxide synthesized by mesoporous carbon by Amit Dubey; Braj Gopal Mishra; Divya Sachdev (pp. 20-26).
This article has been retracted at the request of the Editors. Please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy).Reason: This article copies material published in the paperOrdered mesoporous magnesium oxide with high thermal stability synthesized by exotemplating using CMK-3 carbon, J. Am. Chem. Soc., 127 (2005) 10961097, doi:10.1021/ja043605u. The authors of the present article have completely copied one figure (Fig. 3) and partially copied one figure (Fig. 1: right panel), which were previously published as Fig. 2 and Fig. 1: top curve (respectively) in the article referenced above, and presented them as original data. As such, this article represents a severe abuse of the scientific publishing system and a clear violation of publishing ethics, and therefore must be retracted.
Pt/TiO2 (rutile) catalysts for sulfuric acid decomposition in sulfur-based thermochemical water-splitting cycles by L.M. Petkovic; D.M. Ginosar; H.W. Rollins; K.C. Burch; P.J. Pinhero; H.H. Farrell (pp. 27-36).
Splitting of water into hydrogen and oxygen can be accomplished by thermochemical cycles at lower temperatures than by direct thermal decomposition. Sulfur-based thermochemical cycles employ a high temperature sulfuric acid decomposition reaction as the oxygen producing reaction. This work reports activity and post-operation analyses of 1wt% Pt/TiO2 (rutile) catalysts for decomposing concentrated sulfuric acid at 1123K.▪Thermochemical cycles consist of a series of chemical reactions to produce hydrogen from water at lower temperatures than by direct thermal decomposition. All the sulfur-based cycles for water splitting employ the sulfuric acid decomposition reaction. This work reports the studies performed on 1wt% Pt/TiO2 (rutile) catalysts submitted to flowing concentrated sulfuric acid at 1123K and atmospheric pressure for different times on stream between 0 and 548h. Catalyst activity showed an initial decrease that lasted for about 66h, followed by a slight recovery of activity between 66 and 102h TOS, and a period of slower deactivation after 102h TOS. Catalyst sulfation did not seem to be detrimental to catalyst activity. The activity profile suggested that a complex dynamic situation, involving platinum sintering, volatilization, and oxidation, along with TiO2 morphological changes, affected catalyst activity in a non-monotonic way.
Keywords: Sulfuric acid decomposition catalysts; Thermochemical water splitting; Sulfur–iodine cycle; Platinum titania catalysts
Pt/TiO2 (rutile) catalysts for sulfuric acid decomposition in sulfur-based thermochemical water-splitting cycles by L.M. Petkovic; D.M. Ginosar; H.W. Rollins; K.C. Burch; P.J. Pinhero; H.H. Farrell (pp. 27-36).
Splitting of water into hydrogen and oxygen can be accomplished by thermochemical cycles at lower temperatures than by direct thermal decomposition. Sulfur-based thermochemical cycles employ a high temperature sulfuric acid decomposition reaction as the oxygen producing reaction. This work reports activity and post-operation analyses of 1wt% Pt/TiO2 (rutile) catalysts for decomposing concentrated sulfuric acid at 1123K.▪Thermochemical cycles consist of a series of chemical reactions to produce hydrogen from water at lower temperatures than by direct thermal decomposition. All the sulfur-based cycles for water splitting employ the sulfuric acid decomposition reaction. This work reports the studies performed on 1wt% Pt/TiO2 (rutile) catalysts submitted to flowing concentrated sulfuric acid at 1123K and atmospheric pressure for different times on stream between 0 and 548h. Catalyst activity showed an initial decrease that lasted for about 66h, followed by a slight recovery of activity between 66 and 102h TOS, and a period of slower deactivation after 102h TOS. Catalyst sulfation did not seem to be detrimental to catalyst activity. The activity profile suggested that a complex dynamic situation, involving platinum sintering, volatilization, and oxidation, along with TiO2 morphological changes, affected catalyst activity in a non-monotonic way.
Keywords: Sulfuric acid decomposition catalysts; Thermochemical water splitting; Sulfur–iodine cycle; Platinum titania catalysts
NiMCM-36 and NiMCM-22 catalysts for the ethylene oligomerization: Effect of zeolite texture and nickel cations/acid sites ratio by Michael Lallemand; Oana Alice Rusu; Emil Dumitriu; Annie Finiels; François Fajula; Vasile Hulea (pp. 37-43).
Nickel ion-exchanged MCM-36 and MCM-22 zeolites were prepared, characterized, and tested in the ethylene oligomerization reaction performed in slurry semi-batch mode ( T=70–150°C, p=4MPa). NiMCM-36 catalysts, with large accessibility in the mesoporous structure and mild acidity, showed an excellent activity (46g of oligomers/gcatalysth) and selectivity in this reaction.▪Nickel ion-exchanged MCM-36 and MCM-22 zeolites were prepared, characterized, and tested in the ethylene oligomerization reaction performed in slurry semi-batch mode ( T=70–150°C, p=4MPa). The behavior of catalysts was evaluated in relation to their texture and nickel cations/acid sites ratio. NiMCM-36 catalysts, with large accessibility in the mesoporous structure and mild acidity, showed an excellent activity (46g of oligomers/gcatalysth) and selectivity (100% olefins with even number of carbon atoms) in ethylene oligomerization, while lower catalytic activity and selectivity were observed over NiMCM-22 possessing microporous structure and high acid sites concentration.
Keywords: NiMCM-36; NiMCM-22; Acidity; Ethylene; Oligomerization
NiMCM-36 and NiMCM-22 catalysts for the ethylene oligomerization: Effect of zeolite texture and nickel cations/acid sites ratio by Michael Lallemand; Oana Alice Rusu; Emil Dumitriu; Annie Finiels; François Fajula; Vasile Hulea (pp. 37-43).
Nickel ion-exchanged MCM-36 and MCM-22 zeolites were prepared, characterized, and tested in the ethylene oligomerization reaction performed in slurry semi-batch mode ( T=70–150°C, p=4MPa). NiMCM-36 catalysts, with large accessibility in the mesoporous structure and mild acidity, showed an excellent activity (46g of oligomers/gcatalysth) and selectivity in this reaction.▪Nickel ion-exchanged MCM-36 and MCM-22 zeolites were prepared, characterized, and tested in the ethylene oligomerization reaction performed in slurry semi-batch mode ( T=70–150°C, p=4MPa). The behavior of catalysts was evaluated in relation to their texture and nickel cations/acid sites ratio. NiMCM-36 catalysts, with large accessibility in the mesoporous structure and mild acidity, showed an excellent activity (46g of oligomers/gcatalysth) and selectivity (100% olefins with even number of carbon atoms) in ethylene oligomerization, while lower catalytic activity and selectivity were observed over NiMCM-22 possessing microporous structure and high acid sites concentration.
Keywords: NiMCM-36; NiMCM-22; Acidity; Ethylene; Oligomerization
Cobalt-containing mesoporous silicas—Preparation, characterization and catalytic activity in toluene hydrogenation by Ágnes Szegedi; Margarita Popova; Vesselina Mavrodinova; Christo Minchev (pp. 44-51).
Cobalt impregnated mesoporous silica materials, MCM-41 with conventional and spherical morphology and SBA-15, were synthesized with hydrothermal and sol–gel methods. It was found that the cobalt–support interaction depends mainly on the presence of accessible terminal SiOH groups in the pore wall of the support. Mild oxidative salt decomposition had favorable effect on the reducibility of the cobalt oxide species. In case of spherical MCM-41 and SBA-15 materials the strong metal–support interaction resulted in low reducibility, hindering the formation of metallic cobalt active in toluene hydrogenation.▪The effect of post synthesis modification was studied on cobalt impregnated mesoporous materials having different textural properties. The supports were SBA-15 and MCM-41 with conventional and spherical morphology. The modified materials were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), temperature-programmed reduction (TPR), FT-IR spectroscopy of adsorbed probe molecules (pyridine and CO) and toluene hydrogenation as a catalytic test reaction. It was found that the amount of surface silanol groups of the mesoporous supports and the variation of the pretreatment procedure have a notable influence on the nature of the cobalt oxide species formed upon the precursor decomposition. Formation of Co3O4, CoO and Co2+ species in different ratio, depending on the mesoporous support, was established. The strength of interaction with the support determines the dispersion, reducibility and the catalytic activity in toluene hydrogenation.
Keywords: Mesoporous materials; CoMCM-41; CoSBA-15; Toluene hydrogenation
Cobalt-containing mesoporous silicas—Preparation, characterization and catalytic activity in toluene hydrogenation by Ágnes Szegedi; Margarita Popova; Vesselina Mavrodinova; Christo Minchev (pp. 44-51).
Cobalt impregnated mesoporous silica materials, MCM-41 with conventional and spherical morphology and SBA-15, were synthesized with hydrothermal and sol–gel methods. It was found that the cobalt–support interaction depends mainly on the presence of accessible terminal SiOH groups in the pore wall of the support. Mild oxidative salt decomposition had favorable effect on the reducibility of the cobalt oxide species. In case of spherical MCM-41 and SBA-15 materials the strong metal–support interaction resulted in low reducibility, hindering the formation of metallic cobalt active in toluene hydrogenation.▪The effect of post synthesis modification was studied on cobalt impregnated mesoporous materials having different textural properties. The supports were SBA-15 and MCM-41 with conventional and spherical morphology. The modified materials were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), temperature-programmed reduction (TPR), FT-IR spectroscopy of adsorbed probe molecules (pyridine and CO) and toluene hydrogenation as a catalytic test reaction. It was found that the amount of surface silanol groups of the mesoporous supports and the variation of the pretreatment procedure have a notable influence on the nature of the cobalt oxide species formed upon the precursor decomposition. Formation of Co3O4, CoO and Co2+ species in different ratio, depending on the mesoporous support, was established. The strength of interaction with the support determines the dispersion, reducibility and the catalytic activity in toluene hydrogenation.
Keywords: Mesoporous materials; CoMCM-41; CoSBA-15; Toluene hydrogenation
Recoverable rhodium nanoparticles: Synthesis, characterization and catalytic performance in hydrogenation reactions by Marcos J. Jacinto; Pedro K. Kiyohara; Sueli H. Masunaga; Renato F. Jardim; Liane M. Rossi (pp. 52-57).
We here report the first Rh(0) nanoparticle-based magnetically separable catalyst with extraordinary recovery and recycling properties. Rh(0) nanoparticles were immobilized in magnetic supports to be efficiently recovered from the reaction medium by applying an external magnetic field and reused in successive catalytic reactions. The separation method is significantly simple thereby, overcoming traditional time- and solvent-consuming purification procedures. ▪We here report the first magnetically recoverable Rh(0) nanoparticle-supported catalyst with extraordinary recovery and recycling properties. Magnetic separation has been suggested as a very promising technique to improve recovery of metal-based catalysts in liquid-phase batch reactions. The separation method is significantly simple, as it does not require filtration, decantation, centrifugation, or any other separation technique thereby, overcoming traditional time- and solvent-consuming procedures. Our new magnetically separable catalytic system, comprised of Rh nanoparticles immobilized on silica-coated magnetite nanoparticles, is highly active and could be reused for up to 20 times for hydrogenation of cyclohexene (180,000mol/molRh) and benzene (11,550mol/molRh) under mild conditions.
Keywords: Rhodium nanoparticle; Catalyst recovery; Benzene hydrogenation
Recoverable rhodium nanoparticles: Synthesis, characterization and catalytic performance in hydrogenation reactions by Marcos J. Jacinto; Pedro K. Kiyohara; Sueli H. Masunaga; Renato F. Jardim; Liane M. Rossi (pp. 52-57).
We here report the first Rh(0) nanoparticle-based magnetically separable catalyst with extraordinary recovery and recycling properties. Rh(0) nanoparticles were immobilized in magnetic supports to be efficiently recovered from the reaction medium by applying an external magnetic field and reused in successive catalytic reactions. The separation method is significantly simple thereby, overcoming traditional time- and solvent-consuming purification procedures. ▪We here report the first magnetically recoverable Rh(0) nanoparticle-supported catalyst with extraordinary recovery and recycling properties. Magnetic separation has been suggested as a very promising technique to improve recovery of metal-based catalysts in liquid-phase batch reactions. The separation method is significantly simple, as it does not require filtration, decantation, centrifugation, or any other separation technique thereby, overcoming traditional time- and solvent-consuming procedures. Our new magnetically separable catalytic system, comprised of Rh nanoparticles immobilized on silica-coated magnetite nanoparticles, is highly active and could be reused for up to 20 times for hydrogenation of cyclohexene (180,000mol/molRh) and benzene (11,550mol/molRh) under mild conditions.
Keywords: Rhodium nanoparticle; Catalyst recovery; Benzene hydrogenation
Supercritical deposition of Pt on SnO2-coated Al2O3 foams: Phase behaviour and catalytic performance by G. Incera Garrido; F.C. Patcas; G. Upper; M. Türk; S. Yilmaz; B. Kraushaar-Czarnetzki (pp. 58-65).
The deposition of platinum from an organometallic platinum complex dissolved in supercritical CO2 solution produced Pt/SnO2 catalysts having a narrow particle size distribution around 3nm. These catalysts had a much higher activity in the low-temperature oxidation of carbon monoxide than a Pt/SnO2 catalyst prepared by conventional wet deposition. The thermodynamics of the system Pt(COD)Me2/scCO2 were studied to determine the conditions for an optimal Pt deposition.▪Deposition and reduction of an organometallic platinum complex from a supercritical Pt(COD)Me2/CO2 solution was carried out to produce Pt/SnO2 catalysts supported on Al2O3 foams for CO oxidation at moderate temperatures. The phase behaviour of the complex in supercritical carbon dioxide was investigated to find the optimum pressure and temperature conditions for the deposition. For the Pt(COD)Me2/CO2 mixture, the melting point decreased with increasing pressure from 378K at 0.1MPa to 360K at 25.6MPa. Additional investigations showed that the solubility of Pt(COD)Me2 in CO2 increases from 5.9×10−4mol/mol at 11.2MPa and 313K to 3.4×10−3mol/mol at 29.6MPa and 353K. The supercritical deposition yielded catalysts with highly dispersed platinum nanoparticles of approx. 3nm having a narrow size distribution and thus, a superior activity towards oxidation of carbon monoxide in comparison to a catalyst prepared by the conventional aqueous impregnation of Pt.
Keywords: Supercritical fluid; Platinum; Nanoparticle; CO oxidation; Ceramic foam
Supercritical deposition of Pt on SnO2-coated Al2O3 foams: Phase behaviour and catalytic performance by G. Incera Garrido; F.C. Patcas; G. Upper; M. Türk; S. Yilmaz; B. Kraushaar-Czarnetzki (pp. 58-65).
The deposition of platinum from an organometallic platinum complex dissolved in supercritical CO2 solution produced Pt/SnO2 catalysts having a narrow particle size distribution around 3nm. These catalysts had a much higher activity in the low-temperature oxidation of carbon monoxide than a Pt/SnO2 catalyst prepared by conventional wet deposition. The thermodynamics of the system Pt(COD)Me2/scCO2 were studied to determine the conditions for an optimal Pt deposition.▪Deposition and reduction of an organometallic platinum complex from a supercritical Pt(COD)Me2/CO2 solution was carried out to produce Pt/SnO2 catalysts supported on Al2O3 foams for CO oxidation at moderate temperatures. The phase behaviour of the complex in supercritical carbon dioxide was investigated to find the optimum pressure and temperature conditions for the deposition. For the Pt(COD)Me2/CO2 mixture, the melting point decreased with increasing pressure from 378K at 0.1MPa to 360K at 25.6MPa. Additional investigations showed that the solubility of Pt(COD)Me2 in CO2 increases from 5.9×10−4mol/mol at 11.2MPa and 313K to 3.4×10−3mol/mol at 29.6MPa and 353K. The supercritical deposition yielded catalysts with highly dispersed platinum nanoparticles of approx. 3nm having a narrow size distribution and thus, a superior activity towards oxidation of carbon monoxide in comparison to a catalyst prepared by the conventional aqueous impregnation of Pt.
Keywords: Supercritical fluid; Platinum; Nanoparticle; CO oxidation; Ceramic foam
Single stage water gas shift conversion over Pt/TiO2—Problem of catalyst deactivation by K.G. Azzam; I.V. Babich; K. Seshan; L. Lefferts (pp. 66-71).
Pt/TiO2 is an active and selective catalyst for single stage water gas shift reaction. However, the catalyst deactivated with time on stream. Detailed studies of fresh, used, and reactivated Pt/TiO2 catalysts were carried out using kinetic (steady state and transient) and in situ IR spectroscopic methods in order to understand the mechanism of deactivation. The loss of Pt surface area was the cause of Pt/TiO2 deactivation, exclusively. Pt sintering occurred mainly due to the presence of traces of formaldehyde formed under WGS reaction conditions by reaction of H2 and CO. Details concerning the deactivation behavior are discussed.Deactivation of Pt/TiO2 WGS catalyst is caused by Pt sintering in the presence of traces of formaldehyde formed under WGS reaction conditions by reaction of H2 and CO.▪
Keywords: WGS; Bifunctional; Catalysts; Platinum; Titania; Stability; Deactivation; SMSI; Sintering
Single stage water gas shift conversion over Pt/TiO2—Problem of catalyst deactivation by K.G. Azzam; I.V. Babich; K. Seshan; L. Lefferts (pp. 66-71).
Pt/TiO2 is an active and selective catalyst for single stage water gas shift reaction. However, the catalyst deactivated with time on stream. Detailed studies of fresh, used, and reactivated Pt/TiO2 catalysts were carried out using kinetic (steady state and transient) and in situ IR spectroscopic methods in order to understand the mechanism of deactivation. The loss of Pt surface area was the cause of Pt/TiO2 deactivation, exclusively. Pt sintering occurred mainly due to the presence of traces of formaldehyde formed under WGS reaction conditions by reaction of H2 and CO. Details concerning the deactivation behavior are discussed.Deactivation of Pt/TiO2 WGS catalyst is caused by Pt sintering in the presence of traces of formaldehyde formed under WGS reaction conditions by reaction of H2 and CO.▪
Keywords: WGS; Bifunctional; Catalysts; Platinum; Titania; Stability; Deactivation; SMSI; Sintering
Tetramethylguanidine covalently bonded onto silica gel surface as an efficient and reusable catalyst for transesterification of vegetable oil by Elaine A. Faria; Hugo F. Ramalho; Jéssica S. Marques; Paulo A.Z. Suarez; Alexandre G.S. Prado (pp. 72-78).
A solid base catalyst was obtained through attachment of tetramethylguanidine onto silica gel surface. Infrared spectroscopy,13C and29Si nuclear magnetic resonance data are in agreement with the proposed structure. SEM images showed that the catalyst presented high homogeneous spherical particles of 1μm with surface area of 216.14±34m2g−1. The obtained material was used as catalyst in the transesterification of soybean oil for biodiesel production. The catalytic efficiency was followed and the biodiesel conversion presented a yield of 86.73±2.2% at 3h of reaction. The catalyst was recovered and reused nine times, maintaining about 62% of its catalytic efficiency.A solid base catalyst was obtained through attachment of tetramethylguanidine onto silica gel surface, which was used for transesterification of soybean oil to produce biodiesel. The catalytic efficiency presented a yield of 86.73% at 3h of reaction. The catalyst was recovered and reused 9 times, maintaining about 62% of its catalytic efficiency.▪
Keywords: Transesterification; Biodiesel; Vegetable oils; Tetramethylguanidine
Tetramethylguanidine covalently bonded onto silica gel surface as an efficient and reusable catalyst for transesterification of vegetable oil by Elaine A. Faria; Hugo F. Ramalho; Jéssica S. Marques; Paulo A.Z. Suarez; Alexandre G.S. Prado (pp. 72-78).
A solid base catalyst was obtained through attachment of tetramethylguanidine onto silica gel surface. Infrared spectroscopy,13C and29Si nuclear magnetic resonance data are in agreement with the proposed structure. SEM images showed that the catalyst presented high homogeneous spherical particles of 1μm with surface area of 216.14±34m2g−1. The obtained material was used as catalyst in the transesterification of soybean oil for biodiesel production. The catalytic efficiency was followed and the biodiesel conversion presented a yield of 86.73±2.2% at 3h of reaction. The catalyst was recovered and reused nine times, maintaining about 62% of its catalytic efficiency.A solid base catalyst was obtained through attachment of tetramethylguanidine onto silica gel surface, which was used for transesterification of soybean oil to produce biodiesel. The catalytic efficiency presented a yield of 86.73% at 3h of reaction. The catalyst was recovered and reused 9 times, maintaining about 62% of its catalytic efficiency.▪
Keywords: Transesterification; Biodiesel; Vegetable oils; Tetramethylguanidine
Ultraviolet photoemission study of lithium nickel oxide: A contact of valence-band structure and selective oxidation by T. Miyazaki; D. Yoshimura; K. Okudaira (pp. 79-82).
We present a study of ultraviolet photoemission spectroscopy (UPS) and constant-initial-state spectroscopy (CIS) of lithium nickel oxide using synchrotron radiation. The top valence-band structure of Li0.1Ni1.9O2 and LiNiO2 has been applied to the investigation of selectivity for oxidative coupling of methane. It is suggested that lattice oxygen species are separable into two bands, and the proportion of the two O2p and Ni3d states was related to the function of the selective oxidation.We have examined the oxidative function and valence electronic structure of LiNiO2 as a selective oxidation model catalyst, because the surface lattice oxygen is converting methane to ethane and ethylene. The ultraviolet photoemission spectroscopy (UPS) and the constant-initial-state spectroscopy (CIS) were applied to identify the contribution of each element to the valence band of LiNiO2. As the UPS was surface sensitive technique and effective for the top valence-band structures which determined the activities of the selective oxidation, it should be carefully investigated for the surface electronic structure. Also, the treatment of sample by the argon sputtering was done in order to imitate dynamic redox surface and remove the surface impurity. It was confirmed that the surface oxygen was separable into two states at Eb<15eV below the Fermi energy. For comparison of Li0.1Ni1.9O2 and LiNiO2, it was suggested that the lattice oxygen species of the lower binding energy mainly formed in hexagonal LiNiO2. The selectivity of the oxidative reaction for methane should be decided by the formation of two oxygen states and its proportion of the density of states.▪
Keywords: Lithium nickel oxides; Ultraviolet photoemission spectroscopy; Valence-band structure; Oxidative coupling of methane; Selective oxidation
Ultraviolet photoemission study of lithium nickel oxide: A contact of valence-band structure and selective oxidation by T. Miyazaki; D. Yoshimura; K. Okudaira (pp. 79-82).
We present a study of ultraviolet photoemission spectroscopy (UPS) and constant-initial-state spectroscopy (CIS) of lithium nickel oxide using synchrotron radiation. The top valence-band structure of Li0.1Ni1.9O2 and LiNiO2 has been applied to the investigation of selectivity for oxidative coupling of methane. It is suggested that lattice oxygen species are separable into two bands, and the proportion of the two O2p and Ni3d states was related to the function of the selective oxidation.We have examined the oxidative function and valence electronic structure of LiNiO2 as a selective oxidation model catalyst, because the surface lattice oxygen is converting methane to ethane and ethylene. The ultraviolet photoemission spectroscopy (UPS) and the constant-initial-state spectroscopy (CIS) were applied to identify the contribution of each element to the valence band of LiNiO2. As the UPS was surface sensitive technique and effective for the top valence-band structures which determined the activities of the selective oxidation, it should be carefully investigated for the surface electronic structure. Also, the treatment of sample by the argon sputtering was done in order to imitate dynamic redox surface and remove the surface impurity. It was confirmed that the surface oxygen was separable into two states at Eb<15eV below the Fermi energy. For comparison of Li0.1Ni1.9O2 and LiNiO2, it was suggested that the lattice oxygen species of the lower binding energy mainly formed in hexagonal LiNiO2. The selectivity of the oxidative reaction for methane should be decided by the formation of two oxygen states and its proportion of the density of states.▪
Keywords: Lithium nickel oxides; Ultraviolet photoemission spectroscopy; Valence-band structure; Oxidative coupling of methane; Selective oxidation
Catalytic oxidation of toluene with molecular oxygen over manganese tetraphenylporphyrin supported on chitosan by Guan Huang; Jin Luo; Cao Cheng Deng; Yong An Guo; Shu Kai Zhao; Hong Zhou; Shan Wei (pp. 83-86).
Catalysis by simple manganese tetraphenylporphyrin [Mn TPP] supported on chitosan [CTS] for liquid phase aerobic oxidation of toluene has been investigated. The toluene conversion depends on the reaction temperature, the air pressure and the amount of catalyst, but the selectivity for aldehyde and alcohol is little affected by these three parameters. Using the Mn TPP/CTS containing 2mg of Mn TPP as a catalyst, the aerobic oxidation of toluene under the optimum conditions of 195°C and 0.6MPa produced benzaldehyde and benzyl alcohol at 96% selectivity with 5.9% conversion of toluene. The catalyst can be reused once. Chitosan played an important role in the catalytic oxidation of toluene.Chitosan-supported manganese tetraphenylporphyrin was used as catalyst for the aerobic oxidation of toluene. The supported catalyst gave 5.9% toluene conversion and about 96% selectivity for aldehyde and alcohol, and a catalyst turnover number of 3.70×105. The supported catalyst can be efficiently reused once and showed better performance than the unsupported catalyst for toluene oxidation.▪
Keywords: Chitosan; Manganese tetraphenylporphyrin; Toluene oxidation; Air
Catalytic oxidation of toluene with molecular oxygen over manganese tetraphenylporphyrin supported on chitosan by Guan Huang; Jin Luo; Cao Cheng Deng; Yong An Guo; Shu Kai Zhao; Hong Zhou; Shan Wei (pp. 83-86).
Catalysis by simple manganese tetraphenylporphyrin [Mn TPP] supported on chitosan [CTS] for liquid phase aerobic oxidation of toluene has been investigated. The toluene conversion depends on the reaction temperature, the air pressure and the amount of catalyst, but the selectivity for aldehyde and alcohol is little affected by these three parameters. Using the Mn TPP/CTS containing 2mg of Mn TPP as a catalyst, the aerobic oxidation of toluene under the optimum conditions of 195°C and 0.6MPa produced benzaldehyde and benzyl alcohol at 96% selectivity with 5.9% conversion of toluene. The catalyst can be reused once. Chitosan played an important role in the catalytic oxidation of toluene.Chitosan-supported manganese tetraphenylporphyrin was used as catalyst for the aerobic oxidation of toluene. The supported catalyst gave 5.9% toluene conversion and about 96% selectivity for aldehyde and alcohol, and a catalyst turnover number of 3.70×105. The supported catalyst can be efficiently reused once and showed better performance than the unsupported catalyst for toluene oxidation.▪
Keywords: Chitosan; Manganese tetraphenylporphyrin; Toluene oxidation; Air
Influence of calcination on the microstructures and photocatalytic activity of potassium oxalate-doped TiO2 powders by Cheewita Suwanchawalit; Sumpun Wongnawa (pp. 87-99).
The uncalcined potassium oxalate-doped TiO2 has high adsorptivity power for dye solution at high concentration. Decolorization efficiencies were investigated for both the uncalcined and the calcined samples. The used uncalcined samples can be regenerated by H2O2 with UV irradiation and can be reused to decolorize dye solution again without loss of decolorizing efficiency.▪Potassium oxalate-doped TiO2 powders were prepared by the base-catalyzed sol–gel process with TiCl4 as a precursor and hexamethylenetetramine as basic agent. The influence of calcination on the structure and photocatalytic activity of the as-prepared TiO2 samples was investigated. The physical properties of the pre- and post-calcined materials were studied by X-ray diffraction spectroscopy, scanning electron microscopy, specific surface area, Fourier-transformed infrared spectroscopy, photoluminescence spectroscopy, and diffuse reflectance ultraviolet-visible spectroscopy. The photocatalytic activity of the products was evaluated by decolorizing methylene blue solutions and comparing them with a commercial TiO2 powder (Degussa P25). The optimum calcination temperature of 800°C yielded samples with enhanced photocatalytic activity comparable to Degussa P25. On the other hand, the non-calcined TiO2 sample (amorphous phase with small amount of anatase phase) produced a better decolorization efficiency than did commercial P25, due to its excellent adsorptive properties with high concentrations of methylene blue solutions. More significantly, the dye adsorbed onto the surface of the non-calcined TiO2 sample could be removed by treating with hydrogen peroxide solution under UV irradiation. The regenerated TiO2 samples could be reused in the subsequent decolorization of methylene blue solution without a decline in decolorization efficiency compared with freshly prepared TiO2 samples, with even slightly better efficiency.
Keywords: Titanium dioxide; Amorphous titanium dioxide; Sol–gel process; Calcinations; Methylene blue; Dye decolorization
Influence of calcination on the microstructures and photocatalytic activity of potassium oxalate-doped TiO2 powders by Cheewita Suwanchawalit; Sumpun Wongnawa (pp. 87-99).
The uncalcined potassium oxalate-doped TiO2 has high adsorptivity power for dye solution at high concentration. Decolorization efficiencies were investigated for both the uncalcined and the calcined samples. The used uncalcined samples can be regenerated by H2O2 with UV irradiation and can be reused to decolorize dye solution again without loss of decolorizing efficiency.▪Potassium oxalate-doped TiO2 powders were prepared by the base-catalyzed sol–gel process with TiCl4 as a precursor and hexamethylenetetramine as basic agent. The influence of calcination on the structure and photocatalytic activity of the as-prepared TiO2 samples was investigated. The physical properties of the pre- and post-calcined materials were studied by X-ray diffraction spectroscopy, scanning electron microscopy, specific surface area, Fourier-transformed infrared spectroscopy, photoluminescence spectroscopy, and diffuse reflectance ultraviolet-visible spectroscopy. The photocatalytic activity of the products was evaluated by decolorizing methylene blue solutions and comparing them with a commercial TiO2 powder (Degussa P25). The optimum calcination temperature of 800°C yielded samples with enhanced photocatalytic activity comparable to Degussa P25. On the other hand, the non-calcined TiO2 sample (amorphous phase with small amount of anatase phase) produced a better decolorization efficiency than did commercial P25, due to its excellent adsorptive properties with high concentrations of methylene blue solutions. More significantly, the dye adsorbed onto the surface of the non-calcined TiO2 sample could be removed by treating with hydrogen peroxide solution under UV irradiation. The regenerated TiO2 samples could be reused in the subsequent decolorization of methylene blue solution without a decline in decolorization efficiency compared with freshly prepared TiO2 samples, with even slightly better efficiency.
Keywords: Titanium dioxide; Amorphous titanium dioxide; Sol–gel process; Calcinations; Methylene blue; Dye decolorization
Aromatization and isomerization of 1-hexene over alkali-treated HZSM-5 zeolites: Improved reaction stability by Yuning Li; Shenglin Liu; Zekai Zhang; Sujuan Xie; Xiangxue Zhu; Longya Xu (pp. 100-113).
A series of HZSM-5 zeolites with micro-mesopore hierarchical porosity were prepared by adjusting the conditions employed in the post-synthesis of alkali treatment, and were found to be highly effective in improving the reaction stability of aromatization and isomerization of 1-hexene. The alkali-treatment conditions for the ZSM-5 zeolite were optimized, and the roles of the introduced mesopores in the improved catalytic performance were studied.▪The HZSM-5 zeolites with micro-mesopore hierarchical porosity have been prepared by the post-synthesis of alkali treatment, and tested in the aromatization and isomerization reactions of 1-hexene in a continuous flow fixed bed. Effects of several variables upon the controlled formation of mesopores have been thoroughly investigated. The results showed that new mesopores could be created and enlarged on ZSM-5 zeolite by increasing the NaOH concentration, temperature and treatment time employed in the alkali treatment, among which the NaOH concentration was the most effective variable in the studied extent. However, excessive high NaOH concentration induced the collapse of zeolite framework, while high temperature and long treatment time induced the backward deposition of amorphous Si onto the zeolite, which would decrease the amount of formed mesopores. When the properly alkali-treated HZSM-5 zeolites were used as catalysts, the reaction activity of 1-hexene was enhanced, and the stabilities of aromatization and isomerization reactions were improved while that of the cracking reaction was deteriorated. These variations of reaction stabilities were associated with the introduction of mesopores over the zeolites, which shortened the diffusion pathlength of the feed/products and reduced the channel blockage.
Keywords: HZSM-5 zeolite; Alkali treatment; Aromatization; Isomerization; 1-Hexene
Aromatization and isomerization of 1-hexene over alkali-treated HZSM-5 zeolites: Improved reaction stability by Yuning Li; Shenglin Liu; Zekai Zhang; Sujuan Xie; Xiangxue Zhu; Longya Xu (pp. 100-113).
A series of HZSM-5 zeolites with micro-mesopore hierarchical porosity were prepared by adjusting the conditions employed in the post-synthesis of alkali treatment, and were found to be highly effective in improving the reaction stability of aromatization and isomerization of 1-hexene. The alkali-treatment conditions for the ZSM-5 zeolite were optimized, and the roles of the introduced mesopores in the improved catalytic performance were studied.▪The HZSM-5 zeolites with micro-mesopore hierarchical porosity have been prepared by the post-synthesis of alkali treatment, and tested in the aromatization and isomerization reactions of 1-hexene in a continuous flow fixed bed. Effects of several variables upon the controlled formation of mesopores have been thoroughly investigated. The results showed that new mesopores could be created and enlarged on ZSM-5 zeolite by increasing the NaOH concentration, temperature and treatment time employed in the alkali treatment, among which the NaOH concentration was the most effective variable in the studied extent. However, excessive high NaOH concentration induced the collapse of zeolite framework, while high temperature and long treatment time induced the backward deposition of amorphous Si onto the zeolite, which would decrease the amount of formed mesopores. When the properly alkali-treated HZSM-5 zeolites were used as catalysts, the reaction activity of 1-hexene was enhanced, and the stabilities of aromatization and isomerization reactions were improved while that of the cracking reaction was deteriorated. These variations of reaction stabilities were associated with the introduction of mesopores over the zeolites, which shortened the diffusion pathlength of the feed/products and reduced the channel blockage.
Keywords: HZSM-5 zeolite; Alkali treatment; Aromatization; Isomerization; 1-Hexene
A new Langmuir–Hinshelwood mechanism for the methanol to dimethylether dehydration reaction over clinoptilolite-zeolite catalyst by Sayed Javid Royaee; Cavus Falamaki; Morteza Sohrabi; Sayed Siamak Ashraf Talesh (pp. 114-120).
The kinetic behavior of a modified clinoptilolite zeolite for the methanol to dimethylether dehydration reaction has been investigated using a differential fixed bed reactor. It was observed that at high partial pressures, MeOH plays an inhibition role. A novel Langmuir–Hinshelwood type reaction mechanism has been developed that predicts the latter effect. The modified clinoptilolite zeolite subject of this study might be of high industrial interest because of the relative lower activation energy (ca. 60kJmol−1) compared to other reported zeolitic and non-zeolitic catalysts.▪The kinetic behavior of a modified clinoptilolite zeolite for the methanol to dimethylether dehydration reaction has been investigated using a differential fixed bed reactor. It was observed that at high partial pressures, MeOH plays an inhibition role. A novel Langmuir–Hinshelwood type reaction mechanism has been developed that predicts the latter effect.
Keywords: Clinoptilolite; Methanol dehydration; Dimethylether; Langmuir–Hinshelwood
A new Langmuir–Hinshelwood mechanism for the methanol to dimethylether dehydration reaction over clinoptilolite-zeolite catalyst by Sayed Javid Royaee; Cavus Falamaki; Morteza Sohrabi; Sayed Siamak Ashraf Talesh (pp. 114-120).
The kinetic behavior of a modified clinoptilolite zeolite for the methanol to dimethylether dehydration reaction has been investigated using a differential fixed bed reactor. It was observed that at high partial pressures, MeOH plays an inhibition role. A novel Langmuir–Hinshelwood type reaction mechanism has been developed that predicts the latter effect. The modified clinoptilolite zeolite subject of this study might be of high industrial interest because of the relative lower activation energy (ca. 60kJmol−1) compared to other reported zeolitic and non-zeolitic catalysts.▪The kinetic behavior of a modified clinoptilolite zeolite for the methanol to dimethylether dehydration reaction has been investigated using a differential fixed bed reactor. It was observed that at high partial pressures, MeOH plays an inhibition role. A novel Langmuir–Hinshelwood type reaction mechanism has been developed that predicts the latter effect.
Keywords: Clinoptilolite; Methanol dehydration; Dimethylether; Langmuir–Hinshelwood
Hantzsch pyridine synthesis using hydrotalcites or hydrotalcite-like materials as solid base catalysts by Churchil A. Antonyraj; S. Kannan (pp. 121-129).
Multicomponent one-pot synthesis of Hantzsch dihyropyridine (DHP) was achieved by the condensation of benzaldehyde, ethyl acetoacetate and ammonium acetate at room temperature using environmentally friendly as-synthesised medicinally acceptable hydrotalcites (HT) and hydrotalcite-like (HT-like) materials as solid base catalysts. The multifunctional activity of these materials is again proved by this important reaction. Among the catalysts screened, MgAl2-HT (Mg/Al atomic ratio=2.0) showed maximum yield (61% in 6.5h using acetonitrile as solvent). We propose that the high activity of this catalyst may be attributed to cooperative contribution of acid–base bifunctional sites. The versatility of these materials was checked by employing various aldehydes (acyclic, cyclic and aromatic) which showed reasonable yields of DHPs over MgAl2-HT. To our knowledge, this is the first report wherein HT and HT-like materials performed as catalysts for this multicomponent reaction and also the first case of employing a solid base catalyst for DHP synthesis.Multicomponent one-pot synthesis of Hantzsch dihyropyridine (DHP) was achieved at room temperature for the first time using environmentally friendly as-synthesised hydrotalcites (HT) and hydrotalcite-like (HT-like) materials as solid base catalysts.▪
Keywords: Hydrotalcites; Hydrotalcite-like materials; Layered double hydroxides; Dihydropyridines (DHP); Hantzsch reaction
Hantzsch pyridine synthesis using hydrotalcites or hydrotalcite-like materials as solid base catalysts by Churchil A. Antonyraj; S. Kannan (pp. 121-129).
Multicomponent one-pot synthesis of Hantzsch dihyropyridine (DHP) was achieved by the condensation of benzaldehyde, ethyl acetoacetate and ammonium acetate at room temperature using environmentally friendly as-synthesised medicinally acceptable hydrotalcites (HT) and hydrotalcite-like (HT-like) materials as solid base catalysts. The multifunctional activity of these materials is again proved by this important reaction. Among the catalysts screened, MgAl2-HT (Mg/Al atomic ratio=2.0) showed maximum yield (61% in 6.5h using acetonitrile as solvent). We propose that the high activity of this catalyst may be attributed to cooperative contribution of acid–base bifunctional sites. The versatility of these materials was checked by employing various aldehydes (acyclic, cyclic and aromatic) which showed reasonable yields of DHPs over MgAl2-HT. To our knowledge, this is the first report wherein HT and HT-like materials performed as catalysts for this multicomponent reaction and also the first case of employing a solid base catalyst for DHP synthesis.Multicomponent one-pot synthesis of Hantzsch dihyropyridine (DHP) was achieved at room temperature for the first time using environmentally friendly as-synthesised hydrotalcites (HT) and hydrotalcite-like (HT-like) materials as solid base catalysts.▪
Keywords: Hydrotalcites; Hydrotalcite-like materials; Layered double hydroxides; Dihydropyridines (DHP); Hantzsch reaction
Sonocatalysis and zeolites: An efficient route to prepare N-alkylimidazoles by V. Calvino-Casilda; R.M. Martín-Aranda; A.J. López-Peinado; M. Bejblová; J. Čejka (pp. 130-135).
The kinetic of imidazole alkylation with 1-bromobutane (sonochemical vs. thermal activations) over zeolites (H-ZSM-5, Mordenite, H-Beta and H-Y) is reported. Acidity and channel size of zeolites affect activity and selectivity of imidazole alkylation. Mordenite and NH4Y zeolites produce N-alkylimidazoles in high yields (>80%) and 100% selectivity under mild conditions, ultrasound activation at 333K in only 1h. ▪The synthesis of N-substituted imidazoles via alkylation of imidazole with 1-bromobutane using sonochemical and thermal activations over zeolites (H-ZSM-5, Mordenite, H-Beta and H-Y) is reported. The effect of the acidity and channel size of zeolites on the activity and selectivity of imidazole alkylation was investigated in a liquid phase. The N-alkylimidazoles are important intermediates in the synthesis of pharmaceuticals with antiviral properties. N-alkylimidazoles were obtained in high yields (>80%) as main product (100% selectivity) under mild conditions, ultrasound (US) activation at 333K in only 1h, when Mordenite and NH4Y zeolites were used as catalysts.
Keywords: N; -alkylimidazoles; Acid zeolites; Sonocatalysis; Green chemistry; Kinetic aspects
Sonocatalysis and zeolites: An efficient route to prepare N-alkylimidazoles by V. Calvino-Casilda; R.M. Martín-Aranda; A.J. López-Peinado; M. Bejblová; J. Čejka (pp. 130-135).
The kinetic of imidazole alkylation with 1-bromobutane (sonochemical vs. thermal activations) over zeolites (H-ZSM-5, Mordenite, H-Beta and H-Y) is reported. Acidity and channel size of zeolites affect activity and selectivity of imidazole alkylation. Mordenite and NH4Y zeolites produce N-alkylimidazoles in high yields (>80%) and 100% selectivity under mild conditions, ultrasound activation at 333K in only 1h. ▪The synthesis of N-substituted imidazoles via alkylation of imidazole with 1-bromobutane using sonochemical and thermal activations over zeolites (H-ZSM-5, Mordenite, H-Beta and H-Y) is reported. The effect of the acidity and channel size of zeolites on the activity and selectivity of imidazole alkylation was investigated in a liquid phase. The N-alkylimidazoles are important intermediates in the synthesis of pharmaceuticals with antiviral properties. N-alkylimidazoles were obtained in high yields (>80%) as main product (100% selectivity) under mild conditions, ultrasound (US) activation at 333K in only 1h, when Mordenite and NH4Y zeolites were used as catalysts.
Keywords: N; -alkylimidazoles; Acid zeolites; Sonocatalysis; Green chemistry; Kinetic aspects
Large-scale synthesis of carbon nanofibers on Ni–Fe–Al hydrotalcite derived catalysts by Zhixin Yu; De Chen; Magnus Rønning; Torbjørn Vrålstad; Esther Ochoa-Fernández; Anders Holmen (pp. 136-146).
Ni2+–Fe2+–Al3+ hydrotalcite catalysts have been prepared by coprecipitation from Fe2+. Pure hydrotalcite structures can only be prepared at low Fe2+ concentrations, while mixed oxide phases with spinel structure will form at high Fe2+ concentrations. Pure hydrotalcite structures are very important for small particle size, narrow size distribution and large surface area of the resulting catalysts.▪A series of Ni2+–Fe2+–Al3+ hydrotalcite (HT) catalysts with varying compositions have been prepared by coprecipitation from Fe2+. The structure and properties of the catalysts were carefully characterized by various methods such as XRD, EXAFS, TGA, TPR, N2 adsorption/desorption, XPS and H2 chemisorption. It was shown that pure HT structures can only be prepared at low Fe2+ concentrations, while mixed oxide phases with spinel structure will form simultaneously at high Fe2+ concentrations. Pure HT structures are very important for small particle size, narrow size distribution and large surface area of the resulting catalysts. XPS study demonstrated Fe enrichment on the catalyst surfaces, which might have partly contributed to the low hydrogen chemisorption capacity for the Fe-containing catalysts.
Keywords: Ni–Fe–Al; Hydrotalcite; Preparation; Characterization; Surface enrichment
Large-scale synthesis of carbon nanofibers on Ni–Fe–Al hydrotalcite derived catalysts by Zhixin Yu; De Chen; Magnus Rønning; Torbjørn Vrålstad; Esther Ochoa-Fernández; Anders Holmen (pp. 136-146).
Ni2+–Fe2+–Al3+ hydrotalcite catalysts have been prepared by coprecipitation from Fe2+. Pure hydrotalcite structures can only be prepared at low Fe2+ concentrations, while mixed oxide phases with spinel structure will form at high Fe2+ concentrations. Pure hydrotalcite structures are very important for small particle size, narrow size distribution and large surface area of the resulting catalysts.▪A series of Ni2+–Fe2+–Al3+ hydrotalcite (HT) catalysts with varying compositions have been prepared by coprecipitation from Fe2+. The structure and properties of the catalysts were carefully characterized by various methods such as XRD, EXAFS, TGA, TPR, N2 adsorption/desorption, XPS and H2 chemisorption. It was shown that pure HT structures can only be prepared at low Fe2+ concentrations, while mixed oxide phases with spinel structure will form simultaneously at high Fe2+ concentrations. Pure HT structures are very important for small particle size, narrow size distribution and large surface area of the resulting catalysts. XPS study demonstrated Fe enrichment on the catalyst surfaces, which might have partly contributed to the low hydrogen chemisorption capacity for the Fe-containing catalysts.
Keywords: Ni–Fe–Al; Hydrotalcite; Preparation; Characterization; Surface enrichment
Large-scale synthesis of carbon nanofibers on Ni-Fe-Al hydrotalcite derived catalysts by Zhixin Yu; De Chen; Magnus Rønning; Bård Tøtdal; Torbjørn Vrålstad; Esther Ochoa-Fernández; Anders Holmen (pp. 147-158).
Carbon nanofibers (CNFs) were synthesized on hydrotalcite derived Ni-Fe/Al2O3 catalysts to achieve optimization of quality and productivity. Only Fe catalyst could produce CNFs from CO, and only Ni catalyst could produce CNFs from C2H4. In C2H4/CO mixture all catalysts could produce CNFs from C2H4 decomposition. Post-synthesis XPS and EXAFS characterization demonstrated that the bimetallic surfaces are restructured during CNF growth.▪Carbon nanofibers (CNFs) were synthesized on a series of hydrotalcite (HT) derived Ni-Fe/Al2O3 catalysts in order to achieve optimization of quality and productivity. It was found that only the Fe catalyst is active in CO disproportionation and only the Ni catalyst is active in ethylene decomposition, whereas all catalysts are active in ethylene decomposition when the reactants are a mixture of C2H4/CO. The catalysts were characterized after CNF growth by XPS and EXAFS in order to understand the catalyst structural changes during CNF synthesis. The structure and properties of the as-synthesized CNFs were characterized by SEM, TEM, TPO and XRD to correlate the CNF structure and crystallinity with the catalyst composition and the nature of the gas precursors. Based on the experimental results a reaction mechanism was proposed. Moreover, it was demonstrated that Ni-Fe/Al2O3 catalysts derived from HT precursors are promising for controlled large-scale synthesis of CNFs.
Keywords: Ni-Fe/Al; 2; O; 3; Hydrotalcite; CNF synthesis; Large scale
Large-scale synthesis of carbon nanofibers on Ni-Fe-Al hydrotalcite derived catalysts by Zhixin Yu; De Chen; Magnus Rønning; Bård Tøtdal; Torbjørn Vrålstad; Esther Ochoa-Fernández; Anders Holmen (pp. 147-158).
Carbon nanofibers (CNFs) were synthesized on hydrotalcite derived Ni-Fe/Al2O3 catalysts to achieve optimization of quality and productivity. Only Fe catalyst could produce CNFs from CO, and only Ni catalyst could produce CNFs from C2H4. In C2H4/CO mixture all catalysts could produce CNFs from C2H4 decomposition. Post-synthesis XPS and EXAFS characterization demonstrated that the bimetallic surfaces are restructured during CNF growth.▪Carbon nanofibers (CNFs) were synthesized on a series of hydrotalcite (HT) derived Ni-Fe/Al2O3 catalysts in order to achieve optimization of quality and productivity. It was found that only the Fe catalyst is active in CO disproportionation and only the Ni catalyst is active in ethylene decomposition, whereas all catalysts are active in ethylene decomposition when the reactants are a mixture of C2H4/CO. The catalysts were characterized after CNF growth by XPS and EXAFS in order to understand the catalyst structural changes during CNF synthesis. The structure and properties of the as-synthesized CNFs were characterized by SEM, TEM, TPO and XRD to correlate the CNF structure and crystallinity with the catalyst composition and the nature of the gas precursors. Based on the experimental results a reaction mechanism was proposed. Moreover, it was demonstrated that Ni-Fe/Al2O3 catalysts derived from HT precursors are promising for controlled large-scale synthesis of CNFs.
Keywords: Ni-Fe/Al; 2; O; 3; Hydrotalcite; CNF synthesis; Large scale