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Journal of Molecular Catalysis. A, Chemical (v.283, #1-2)
Esterification of mandelic acid catalyzed by heteropoly acid by Ezzat Rafiee; Mohammad Joshaghani; Fariba Tork; Akram Fakhri; Sara Eavani (pp. 1-4).
The efficacy of various supported heteropoly acids in synthesis of mandelates from mandelic acid and alcohols is investigated. Dodecatungestophosphoric acid (PW) supported on silica gives the best yield in short reaction times. The present procedure represents a clean, practical, simple, mild, time-saving, and eco-friendly method for synthesis of mandelates in short reaction times and excellent yields with 100% selectivity. The catalyst is found to be stable, highly efficient, reusable, and inexpensive during all runs.The efficacy of various supported heteropoly acids in synthesis of mandelates from mandelic acid and various alcohols is investigated.The results demonstrate that SiO2 can be regarded as the best support for HPAs in comparison to other supports. The present procedure represents a clean, practical, simple, mild, and time-saving method for synthesis of mandelates with excellent yields and 100% selectivity.▪
Keywords: Supported heteropoly acid; Mandelate; Heterogeneous catalyst; Esterification reaction
Esterification of mandelic acid catalyzed by heteropoly acid by Ezzat Rafiee; Mohammad Joshaghani; Fariba Tork; Akram Fakhri; Sara Eavani (pp. 1-4).
The efficacy of various supported heteropoly acids in synthesis of mandelates from mandelic acid and alcohols is investigated. Dodecatungestophosphoric acid (PW) supported on silica gives the best yield in short reaction times. The present procedure represents a clean, practical, simple, mild, time-saving, and eco-friendly method for synthesis of mandelates in short reaction times and excellent yields with 100% selectivity. The catalyst is found to be stable, highly efficient, reusable, and inexpensive during all runs.The efficacy of various supported heteropoly acids in synthesis of mandelates from mandelic acid and various alcohols is investigated.The results demonstrate that SiO2 can be regarded as the best support for HPAs in comparison to other supports. The present procedure represents a clean, practical, simple, mild, and time-saving method for synthesis of mandelates with excellent yields and 100% selectivity.▪
Keywords: Supported heteropoly acid; Mandelate; Heterogeneous catalyst; Esterification reaction
Vanadyl acetylacetonate anchored onto amine-functionalised clays and catalytic activity in the epoxidation of geraniol by Clara Pereira; Ana Rosa Silva; Ana Paula Carvalho; João Pires; Cristina Freire (pp. 5-14).
Vanadyl(IV) acetylacetonate was immobilised onto two clays, laponite and K10-montmorillonite, functionalised with (3-aminopropyl)triethoxysilane. To assess the effectiveness of the immobilisation procedure, the complex was also directly anchored onto the two unmodified clays. The [VO(acac)2]-based materials were tested in the geraniol epoxidation. All catalysts were recycled and reused for 4 cycles.▪The parent clays laponite (Lap) and K10-montmorillonite (K10) and those functionalised with (3-aminopropyl)triethoxysilane (APTES) were used as supports to immobilise vanadyl(IV) acetylacetonate ([VO(acac)2]). All the materials were characterised by elemental analysis, XRD, TG-DSC, nitrogen adsorption isotherms at −196°C and IR spectroscopy. The K10-based materials were also characterised by XPS.In the case of K10-based materials, higher vanadium content was obtained for the APTES-functionalised K10, showing that the clay functionalisation enhanced the complex anchorage. In Lap-based materials the opposite tendency was observed, with a higher vanadium loading being obtained for direct complex immobilisation onto the parent clay. This is probably due to clay particles aggregation (resultant from the delaminated nature of Lap) provoked by functionalisation with APTES. Furthermore, FTIR data pointed out that in the amine-functionalised clays, the VO(IV) complex was anchored by Schiff condensation between the carbonyl groups of the acetylacetonate ligand and the amine groups from the grafted APTES, whereas the direct immobilisation of the complex onto the parents clays took place mostly through covalent bonding between the metal centre and the clay surface hydroxyl groups.The [VO(acac)2]-based materials were tested in the epoxidation of geraniol using t-BuOOH as oxygen source and reused several times repeatedly. The [VO(acac)2]APTES@K10 material was the most efficient and stable catalyst upon reuse (5 cycles), among the four materials tested, with a substrate conversion and 2,3-epoxygeraniol regioselectivity comparable to the homogeneous phase reaction; the organofunctionalisation of K10 was also quite advantageous in the catalytic reaction since it passivated some active sites of the K10 support. In the case of Lap-based materials, the [VO(acac)2]@Lap was more catalytically efficient than [VO(acac)2]APTES@Lap.
Keywords: Oxovanadium(IV) acetylacetonate; Laponite; Montmorillonite; Organosilane functionalisation; Allylic epoxidation
Vanadyl acetylacetonate anchored onto amine-functionalised clays and catalytic activity in the epoxidation of geraniol by Clara Pereira; Ana Rosa Silva; Ana Paula Carvalho; João Pires; Cristina Freire (pp. 5-14).
Vanadyl(IV) acetylacetonate was immobilised onto two clays, laponite and K10-montmorillonite, functionalised with (3-aminopropyl)triethoxysilane. To assess the effectiveness of the immobilisation procedure, the complex was also directly anchored onto the two unmodified clays. The [VO(acac)2]-based materials were tested in the geraniol epoxidation. All catalysts were recycled and reused for 4 cycles.▪The parent clays laponite (Lap) and K10-montmorillonite (K10) and those functionalised with (3-aminopropyl)triethoxysilane (APTES) were used as supports to immobilise vanadyl(IV) acetylacetonate ([VO(acac)2]). All the materials were characterised by elemental analysis, XRD, TG-DSC, nitrogen adsorption isotherms at −196°C and IR spectroscopy. The K10-based materials were also characterised by XPS.In the case of K10-based materials, higher vanadium content was obtained for the APTES-functionalised K10, showing that the clay functionalisation enhanced the complex anchorage. In Lap-based materials the opposite tendency was observed, with a higher vanadium loading being obtained for direct complex immobilisation onto the parent clay. This is probably due to clay particles aggregation (resultant from the delaminated nature of Lap) provoked by functionalisation with APTES. Furthermore, FTIR data pointed out that in the amine-functionalised clays, the VO(IV) complex was anchored by Schiff condensation between the carbonyl groups of the acetylacetonate ligand and the amine groups from the grafted APTES, whereas the direct immobilisation of the complex onto the parents clays took place mostly through covalent bonding between the metal centre and the clay surface hydroxyl groups.The [VO(acac)2]-based materials were tested in the epoxidation of geraniol using t-BuOOH as oxygen source and reused several times repeatedly. The [VO(acac)2]APTES@K10 material was the most efficient and stable catalyst upon reuse (5 cycles), among the four materials tested, with a substrate conversion and 2,3-epoxygeraniol regioselectivity comparable to the homogeneous phase reaction; the organofunctionalisation of K10 was also quite advantageous in the catalytic reaction since it passivated some active sites of the K10 support. In the case of Lap-based materials, the [VO(acac)2]@Lap was more catalytically efficient than [VO(acac)2]APTES@Lap.
Keywords: Oxovanadium(IV) acetylacetonate; Laponite; Montmorillonite; Organosilane functionalisation; Allylic epoxidation
Asymmetric hydroformylation of olefins catalyzed by rhodium nanoparticles chirally stabilized with ( R)-BINAP ligand by Difei Han; Xiaohong Li; Huidong Zhang; Zhimin Liu; Gengshen Hu; Can Li (pp. 15-22).
Rhodium nanoparticles have been conveniently synthesized by one-pot chemical reduction of aqueous rhodium chloride (RhCl3·3H2O) dispersed in toluene solution in the presence of amphiphilic tetraoctylammonium bromide (TOAB) and chiral ( R)-BINAP at ambient conditions. The resulting highly dispersed rhodium nanoparticles show small and narrowly distributed core sizes (1.5–2.0nm). The chirally stabilized rhodium nanoparticles were also immobilized on silica by impregnation to give the corresponding supported catalysts.31P MAS NMR results and IR spectra of adsorbed CO confirm that chiral ( R)-BINAP ligands stabilize the nanoparticles by coordinative interaction between phosphine and rhodium, and produce chirally catalytic active sites on the rhodium nanocatalysts. Chirally stabilized catalysts exhibit high regioselectivity and chiral induction ability for the asymmetric hydroformylation of olefins. The supported rhodium nanocatalysts show the increased activities compared to the unsupported catalysts (e.g. from 12 to 22h−1 for the hydroformylation of styrene). One hundred percentage regioselectivity of branched aldehyde and up to 59% ee were obtained for the hydroformylation of vinyl acetate.The chirally stabilized rhodium nanoparticles and their supported catalysts exhibit high regioselectivity and chiral induction ability for the asymmetric hydroformylation of styrene and vinyl acetate.▪
Keywords: Rhodium nanoparticles; Enantioselective hydroformylation; Chiral stabilization; Coordination; Phosphorus ligands
Asymmetric hydroformylation of olefins catalyzed by rhodium nanoparticles chirally stabilized with ( R)-BINAP ligand by Difei Han; Xiaohong Li; Huidong Zhang; Zhimin Liu; Gengshen Hu; Can Li (pp. 15-22).
Rhodium nanoparticles have been conveniently synthesized by one-pot chemical reduction of aqueous rhodium chloride (RhCl3·3H2O) dispersed in toluene solution in the presence of amphiphilic tetraoctylammonium bromide (TOAB) and chiral ( R)-BINAP at ambient conditions. The resulting highly dispersed rhodium nanoparticles show small and narrowly distributed core sizes (1.5–2.0nm). The chirally stabilized rhodium nanoparticles were also immobilized on silica by impregnation to give the corresponding supported catalysts.31P MAS NMR results and IR spectra of adsorbed CO confirm that chiral ( R)-BINAP ligands stabilize the nanoparticles by coordinative interaction between phosphine and rhodium, and produce chirally catalytic active sites on the rhodium nanocatalysts. Chirally stabilized catalysts exhibit high regioselectivity and chiral induction ability for the asymmetric hydroformylation of olefins. The supported rhodium nanocatalysts show the increased activities compared to the unsupported catalysts (e.g. from 12 to 22h−1 for the hydroformylation of styrene). One hundred percentage regioselectivity of branched aldehyde and up to 59% ee were obtained for the hydroformylation of vinyl acetate.The chirally stabilized rhodium nanoparticles and their supported catalysts exhibit high regioselectivity and chiral induction ability for the asymmetric hydroformylation of styrene and vinyl acetate.▪
Keywords: Rhodium nanoparticles; Enantioselective hydroformylation; Chiral stabilization; Coordination; Phosphorus ligands
Influence of plasma spraying parameter on microstructure and photocatalytic properties of nanostructured TiO2–Fe3O4 coating by Qinghe Yu; Chungen Zhou; Xin Wang (pp. 23-28).
TiO2–Fe3O4 coatings on transparent glasses were prepared by atmospheric plasma spraying (APS). As-sprayed TiO2–Fe3O4 coatings consist of anatase TiO2, rutile TiO2, Fe3O4 and FeTiO3. The grain size, rate of porosity and fractions of the anatase and TiFeO3 phases in APS coatings were dependent on the process parameters. With an increase in plasma power, the content of anatase TiO2 and the rate of porosity in the coatings were decreased while the content of the resultant FeTiO3 phase and the grain size in the coating were increased. The coating condition of 500A has the best photocatalytic efficiency and 600A has the worst. The photocatalytic property of the APS TiO2–Fe3O4 coatings was primarily dependent on synergistic effect of the fractions of FeTiO3 and anatase phases.▪TiO2–Fe3O4 coatings on transparent glasses were prepared by atmospheric plasma spraying (APS). As-sprayed TiO2–Fe3O4 coatings consist of anatase TiO2, rutile TiO2, Fe3O4 and FeTiO3. The grain size, rate of porosity and fractions of the anatase and TiFeO3 phases in APS coatings were dependent on the process parameters. With an increase in plasma power, the content of anatase TiO2 and the rate of porosity in the coatings were decreased while the content of the resultant FeTiO3 phase and the grain size in the coating were increased. The coating condition of 500A has the best photocatalytic efficiency and 600A has the worst. The photocatalytic property of the APS TiO2–Fe3O4 coatings was primarily dependent on synergistic effect of the fractions of FeTiO3 and anatase phases.
Keywords: Plasma spraying; Photocatalytic property; TiO; 2; Fe; 3; O; 4
Influence of plasma spraying parameter on microstructure and photocatalytic properties of nanostructured TiO2–Fe3O4 coating by Qinghe Yu; Chungen Zhou; Xin Wang (pp. 23-28).
TiO2–Fe3O4 coatings on transparent glasses were prepared by atmospheric plasma spraying (APS). As-sprayed TiO2–Fe3O4 coatings consist of anatase TiO2, rutile TiO2, Fe3O4 and FeTiO3. The grain size, rate of porosity and fractions of the anatase and TiFeO3 phases in APS coatings were dependent on the process parameters. With an increase in plasma power, the content of anatase TiO2 and the rate of porosity in the coatings were decreased while the content of the resultant FeTiO3 phase and the grain size in the coating were increased. The coating condition of 500A has the best photocatalytic efficiency and 600A has the worst. The photocatalytic property of the APS TiO2–Fe3O4 coatings was primarily dependent on synergistic effect of the fractions of FeTiO3 and anatase phases.▪TiO2–Fe3O4 coatings on transparent glasses were prepared by atmospheric plasma spraying (APS). As-sprayed TiO2–Fe3O4 coatings consist of anatase TiO2, rutile TiO2, Fe3O4 and FeTiO3. The grain size, rate of porosity and fractions of the anatase and TiFeO3 phases in APS coatings were dependent on the process parameters. With an increase in plasma power, the content of anatase TiO2 and the rate of porosity in the coatings were decreased while the content of the resultant FeTiO3 phase and the grain size in the coating were increased. The coating condition of 500A has the best photocatalytic efficiency and 600A has the worst. The photocatalytic property of the APS TiO2–Fe3O4 coatings was primarily dependent on synergistic effect of the fractions of FeTiO3 and anatase phases.
Keywords: Plasma spraying; Photocatalytic property; TiO; 2; Fe; 3; O; 4
Potassium phthalimide -N-oxyl: An efficient catalyst for cyanosilylation of carbonyl compounds under mild conditions by Mohammad G. Dekamin; Shahrzad Javanshir; M. Reza Naimi-Jamal; Rahim Hekmatshoar; Javad Mokhtari (pp. 29-32).
Potassium phthalimide -N-oxyl was used as an effective, easy to handle and readily available Lewis basic organocatalyst for the facile addition of trimethylsilyl cyanide to various carbonyl compounds at room temperature under mild conditions to afford corresponding cyanohydrin trimethylsilyl ethers in high to quantitative yields. The high yields of products, high turnover numbers of the catalyst, compatibility of other functional groups, and simplicity in the operation are the advantages of this method.Potassium phthalimide -N-oxyl was used as an effective, easy to handle and readily available Lewis basic organocatalyst for the facile addition of trimethylsilyl cyanide to various carbonyl compounds under mild conditions. ▪
Keywords: Cyanohydrins; Carbonyl compounds; Potassium phthalimide-; N; -oxyl; Nucleophilic catalyst
Potassium phthalimide -N-oxyl: An efficient catalyst for cyanosilylation of carbonyl compounds under mild conditions by Mohammad G. Dekamin; Shahrzad Javanshir; M. Reza Naimi-Jamal; Rahim Hekmatshoar; Javad Mokhtari (pp. 29-32).
Potassium phthalimide -N-oxyl was used as an effective, easy to handle and readily available Lewis basic organocatalyst for the facile addition of trimethylsilyl cyanide to various carbonyl compounds at room temperature under mild conditions to afford corresponding cyanohydrin trimethylsilyl ethers in high to quantitative yields. The high yields of products, high turnover numbers of the catalyst, compatibility of other functional groups, and simplicity in the operation are the advantages of this method.Potassium phthalimide -N-oxyl was used as an effective, easy to handle and readily available Lewis basic organocatalyst for the facile addition of trimethylsilyl cyanide to various carbonyl compounds under mild conditions. ▪
Keywords: Cyanohydrins; Carbonyl compounds; Potassium phthalimide-; N; -oxyl; Nucleophilic catalyst
Promotional effects of Cu and K on precipitated iron-based catalysts for Fischer–Tropsch synthesis by Haijun Wan; Baoshan Wu; Chenghua Zhang; Hongwei Xiang; Yongwang Li (pp. 33-42).
The effects of Cu and K promoters on precipitated iron-based Fischer–Tropsch synthesis (FTS) catalysts were investigated by using N2 physical adsorption, temperature-programmed reduction/desorption (TPR/TPD) and Mössbauer effect spectroscopy (MES). The FTS performances of the catalysts were tested in a slurry-phase continuously stirred tank reactor (CSTR). The characterization results indicated that Cu promoter facilitates the high dispersion of Fe2O3, significantly promotes the reduction and H2 adsorption, but severely suppresses CO adsorption and the carburization. However, K promoter severely retards the reduction and suppresses the H2 adsorption, facilitates the CO adsorption and promotes the carburization. In the FTS reaction, it was found that Cu promoter decreases the FTS initial activity and water gas shift (WGS) reaction activity, promotes the oxidation of iron carbides to Fe3O4 and accelerates the deactivation of iron-based catalyst. However, K promoter improves the FTS activity and WGS reaction activity, suppresses the oxidation of iron carbide to Fe3O4 and significantly improves the stability of iron-based catalyst. As compared with individual promotion of Cu or K, the double promotions of Cu and K significantly improve the FTS and WGS activities and keep excellent stability. Due to weaker CO adsorption and stronger H2 adsorption than the catalysts without Cu, Cu promoted catalysts have higher selectivity to light hydrocarbons and methane and lower selectivity to heavy hydrocarbons. However, the opposite result is obtained on the catalyst incorporated with K promoter.The activity and stability of the catalysts. Reaction condition: 260°C, 1.5MPa, H2/CO=0.67 and GHSV=1000h−1. The addition of Cu promoter into iron-based catalyst decreases the catalyst activity and accelerates the deactivation of iron-based catalyst. The addition of K and the co-promotional effects of Cu and K not only increase the catalyst activity, but also improve the catalyst stability.▪
Keywords: Fischer–Tropsch synthesis; Iron-based catalyst; Cu promoter; K promoter
Promotional effects of Cu and K on precipitated iron-based catalysts for Fischer–Tropsch synthesis by Haijun Wan; Baoshan Wu; Chenghua Zhang; Hongwei Xiang; Yongwang Li (pp. 33-42).
The effects of Cu and K promoters on precipitated iron-based Fischer–Tropsch synthesis (FTS) catalysts were investigated by using N2 physical adsorption, temperature-programmed reduction/desorption (TPR/TPD) and Mössbauer effect spectroscopy (MES). The FTS performances of the catalysts were tested in a slurry-phase continuously stirred tank reactor (CSTR). The characterization results indicated that Cu promoter facilitates the high dispersion of Fe2O3, significantly promotes the reduction and H2 adsorption, but severely suppresses CO adsorption and the carburization. However, K promoter severely retards the reduction and suppresses the H2 adsorption, facilitates the CO adsorption and promotes the carburization. In the FTS reaction, it was found that Cu promoter decreases the FTS initial activity and water gas shift (WGS) reaction activity, promotes the oxidation of iron carbides to Fe3O4 and accelerates the deactivation of iron-based catalyst. However, K promoter improves the FTS activity and WGS reaction activity, suppresses the oxidation of iron carbide to Fe3O4 and significantly improves the stability of iron-based catalyst. As compared with individual promotion of Cu or K, the double promotions of Cu and K significantly improve the FTS and WGS activities and keep excellent stability. Due to weaker CO adsorption and stronger H2 adsorption than the catalysts without Cu, Cu promoted catalysts have higher selectivity to light hydrocarbons and methane and lower selectivity to heavy hydrocarbons. However, the opposite result is obtained on the catalyst incorporated with K promoter.The activity and stability of the catalysts. Reaction condition: 260°C, 1.5MPa, H2/CO=0.67 and GHSV=1000h−1. The addition of Cu promoter into iron-based catalyst decreases the catalyst activity and accelerates the deactivation of iron-based catalyst. The addition of K and the co-promotional effects of Cu and K not only increase the catalyst activity, but also improve the catalyst stability.▪
Keywords: Fischer–Tropsch synthesis; Iron-based catalyst; Cu promoter; K promoter
The CO adsorption on a Fe2O3–Ce0.5Zr0.5O2 catalyst studied by TPD, isotope exchange and FTIR spectroscopy by Vladimir Galvita; Liisa K. Rihko-Struckmann; Kai Sundmacher (pp. 43-51).
The interaction of carbon monoxide with Fe2O3–Ce0.5Zr0.5O2 was investigated by the adsorption investigation under isothermal CO/H2 exposure and temperature-programmed desorption (TPD), as well as by in-situ diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS), in order to understand the carbon monoxide formation during the cyclic water gas shift reaction. When the Fe2O3–Ce0.5Zr0.5O2 catalyst was exposed to a mixture of CO and H2, the majority of the surface species depicted by the DRIFT analysis were associated with carbonates. Investigations carried out using a H2O/He mixture showed that carbon oxides were produced during the interconversion of carbonate species on the catalyst surface with steam. The steady-state isotopic C18O experiments revealed that the Boudouard reaction occurred at temperatures higher than 350°C (see following figure). The carbon deposits which were formed on the catalyst surface during the reduction step through the Boudouard reaction, led to CO formation during the successive re-oxidation step.▪The interaction of carbon monoxide with Fe2O3–Ce0.5Zr0.5O2 was investigated by the adsorption investigation under isothermal CO/H2 exposure and temperature-programmed desorption (TPD), as well as by in-situ diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS), in order to understand the carbon monoxide formation during the cyclic water gas shift reaction. When the Fe2O3–Ce0.5Zr0.5O2 catalyst was exposed to a mixture of CO and H2, the majority of the surface species depicted by the DRIFT analysis were associated with carbonates. The carbonates were essentially stable in a He atmosphere at temperatures ranging from 60 to 450°C. An increase in the temperature leads to the conversion of the carbonates, where the oxygen comes from the catalyst lattice. Investigations carried out using a H2O/He mixture showed that carbon oxides were produced during the interconversion of carbonate species on the catalyst surface with steam. The main gas component produced during the TPD of an Fe2O3–Ce0.5Zr0.5O2 catalyst in the temperature interval of 60–500°C was carbon dioxide. The amount of carbon oxides produced decreased at elevated temperatures. The steady-state isotopic C18O experiments revealed that the Boudouard reaction occurred at temperatures higher than 350°C. The carbon deposits which were formed on the catalyst surface during the reduction step through the Boudouard reaction led to CO formation during the successive re-oxidation step.
Keywords: Cyclic water gas shift reaction; WGS; Fe; 2; O; 3; –Ce; 0.5; Zr; 0.5; O; 2; DRIFTS; TPD; Isotope exchange
The CO adsorption on a Fe2O3–Ce0.5Zr0.5O2 catalyst studied by TPD, isotope exchange and FTIR spectroscopy by Vladimir Galvita; Liisa K. Rihko-Struckmann; Kai Sundmacher (pp. 43-51).
The interaction of carbon monoxide with Fe2O3–Ce0.5Zr0.5O2 was investigated by the adsorption investigation under isothermal CO/H2 exposure and temperature-programmed desorption (TPD), as well as by in-situ diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS), in order to understand the carbon monoxide formation during the cyclic water gas shift reaction. When the Fe2O3–Ce0.5Zr0.5O2 catalyst was exposed to a mixture of CO and H2, the majority of the surface species depicted by the DRIFT analysis were associated with carbonates. Investigations carried out using a H2O/He mixture showed that carbon oxides were produced during the interconversion of carbonate species on the catalyst surface with steam. The steady-state isotopic C18O experiments revealed that the Boudouard reaction occurred at temperatures higher than 350°C (see following figure). The carbon deposits which were formed on the catalyst surface during the reduction step through the Boudouard reaction, led to CO formation during the successive re-oxidation step.▪The interaction of carbon monoxide with Fe2O3–Ce0.5Zr0.5O2 was investigated by the adsorption investigation under isothermal CO/H2 exposure and temperature-programmed desorption (TPD), as well as by in-situ diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS), in order to understand the carbon monoxide formation during the cyclic water gas shift reaction. When the Fe2O3–Ce0.5Zr0.5O2 catalyst was exposed to a mixture of CO and H2, the majority of the surface species depicted by the DRIFT analysis were associated with carbonates. The carbonates were essentially stable in a He atmosphere at temperatures ranging from 60 to 450°C. An increase in the temperature leads to the conversion of the carbonates, where the oxygen comes from the catalyst lattice. Investigations carried out using a H2O/He mixture showed that carbon oxides were produced during the interconversion of carbonate species on the catalyst surface with steam. The main gas component produced during the TPD of an Fe2O3–Ce0.5Zr0.5O2 catalyst in the temperature interval of 60–500°C was carbon dioxide. The amount of carbon oxides produced decreased at elevated temperatures. The steady-state isotopic C18O experiments revealed that the Boudouard reaction occurred at temperatures higher than 350°C. The carbon deposits which were formed on the catalyst surface during the reduction step through the Boudouard reaction led to CO formation during the successive re-oxidation step.
Keywords: Cyclic water gas shift reaction; WGS; Fe; 2; O; 3; –Ce; 0.5; Zr; 0.5; O; 2; DRIFTS; TPD; Isotope exchange
Oxidation of 2-chloroethyl ethyl sulfide using V-APMS by Stephanie R. Livingston; Dharmesh Kumar; Christopher C. Landry (pp. 52-59).
Vanadium-doped acid prepared mesoporous spheres (V-APMS) were prepared with vanadium loadings of 1–40wt% using a wet-impregnation method. The effects of vanadium loading on the support were studied using N2 physisorption and powder XRD. The pore volumes, surface areas, and pore diameters of the catalysts decreased as a function of vanadium loading and diffraction peaks corresponding to crystalline V2O5 were detected by XRD at an intermediate V loading, becoming more intense as the V content increased. These results indicate that at low V loadings, the vanadium oxide species were well-dispersed on the silica; however, at higher V loadings crystalline V2O5 was formed within the pores of the APMS. V-APMS was then studied as a heterogeneous catalyst for the oxidation of the chemical warfare agent stimulant 2-chloroethyl ethyl sulfide (CEES) using tert-butyl hydroperoxide (TBHP) as the oxidant. Kinetic studies at temperatures ranging from 0 to 50°C showed that materials with low V loadings were the most effective catalysts for the reaction. The mechanism of the oxidation reaction appeared to be different for catalysts that were composed of well-dispersed vanadium oxide species than for catalysts containing microcrystalline or crystalline V2O5. Finally, a possible reaction scheme for the oxidation of CEES by V-APMS is discussed.Vanadium-doped mesoporous silica was prepared by wet impregnation and characterized by XRD and N2 physisorption. The physical properties of the material were then correlated with results from the catalytic oxidation of 2-chloroethyl ethyl sulfide with peroxide. Isolated vanadium sites, obtained at low loadings, were important in producing the most active catalysts. Possible reaction schemes are discussed.▪
Keywords: Mesoporous silica; Vanadium; Oxidation; Mustard gas; Heterogeneous catalysis
Oxidation of 2-chloroethyl ethyl sulfide using V-APMS by Stephanie R. Livingston; Dharmesh Kumar; Christopher C. Landry (pp. 52-59).
Vanadium-doped acid prepared mesoporous spheres (V-APMS) were prepared with vanadium loadings of 1–40wt% using a wet-impregnation method. The effects of vanadium loading on the support were studied using N2 physisorption and powder XRD. The pore volumes, surface areas, and pore diameters of the catalysts decreased as a function of vanadium loading and diffraction peaks corresponding to crystalline V2O5 were detected by XRD at an intermediate V loading, becoming more intense as the V content increased. These results indicate that at low V loadings, the vanadium oxide species were well-dispersed on the silica; however, at higher V loadings crystalline V2O5 was formed within the pores of the APMS. V-APMS was then studied as a heterogeneous catalyst for the oxidation of the chemical warfare agent stimulant 2-chloroethyl ethyl sulfide (CEES) using tert-butyl hydroperoxide (TBHP) as the oxidant. Kinetic studies at temperatures ranging from 0 to 50°C showed that materials with low V loadings were the most effective catalysts for the reaction. The mechanism of the oxidation reaction appeared to be different for catalysts that were composed of well-dispersed vanadium oxide species than for catalysts containing microcrystalline or crystalline V2O5. Finally, a possible reaction scheme for the oxidation of CEES by V-APMS is discussed.Vanadium-doped mesoporous silica was prepared by wet impregnation and characterized by XRD and N2 physisorption. The physical properties of the material were then correlated with results from the catalytic oxidation of 2-chloroethyl ethyl sulfide with peroxide. Isolated vanadium sites, obtained at low loadings, were important in producing the most active catalysts. Possible reaction schemes are discussed.▪
Keywords: Mesoporous silica; Vanadium; Oxidation; Mustard gas; Heterogeneous catalysis
Studies on the reaction mechanism of the Fischer–Tropsch synthesis on iron and cobalt by J. Gaube; H.-F. Klein (pp. 60-68).
A novel mechanism of the Fischer–Tropsch synthesis is proposed based on the hypothesis that two incompatible mechanism are involved resting exclusively on methylene and on carbon monoxide insertion, respectively. This hypothesis is supported by various co-feeding experiments with alkenes, alcohols and diazomethane and contributes to a sound interpretation of the promoter effect of alkali on iron and of the distribution of branched hydrocarbons.▪A new mechanism of the Fischer–Tropsch synthesis is proposed based on the hypothesis that two incompatible mechanisms are involved resting exclusively on methylene and on carbon monoxide insertion, respectively. This hypothesis is reflected by the well known superposition of two Anderson–Schulz–Flory distributions. Experiments with co-feeding of ethene, 1-alkenes and diazomethane as a source of surface methylene and also the carbon number distribution of branched hydrocarbons strongly support the hypothesis of two independent mechanisms and the methylene insertion mechanism of one of them.Co-feeding of alcohols, the dependence of the ratio of the two mechanisms on the pressure of hydrogen and carbon monoxide and the promoter effect of alkali on iron catalysts also prove the hypothesis of the two mechanisms and point to the carbon monoxide insertion mechanism as the second mechanism that is characterized by the higher growth probability of the resulting Anderson–Schulz–Flory distribution.Furthermore new interpretations of the crucial steps of C–C linkage and chain termination are given. The insertion of methylene is interpreted by coupling of an alkylidene and a methylene surface species towards a coordinated olefin with the chance of chain growth termination by 1-alkene desorption. For the carbon monoxide insertion mechanism the termination of chain growth is assumed to occur by the formation of 1-alkenes and of alcohols via an alcoholate intermediate.The new mechanism gives without any exception a sound interpretation of a great variety of experiments and contributes also to the interpretation of the promoter effect of alkali and of the different performance of cobalt and iron catalysts.
Keywords: Fischer–Tropsch synthesis; Reaction mechanism; Iron catalyst; Cobalt catalysts
Studies on the reaction mechanism of the Fischer–Tropsch synthesis on iron and cobalt by J. Gaube; H.-F. Klein (pp. 60-68).
A novel mechanism of the Fischer–Tropsch synthesis is proposed based on the hypothesis that two incompatible mechanism are involved resting exclusively on methylene and on carbon monoxide insertion, respectively. This hypothesis is supported by various co-feeding experiments with alkenes, alcohols and diazomethane and contributes to a sound interpretation of the promoter effect of alkali on iron and of the distribution of branched hydrocarbons.▪A new mechanism of the Fischer–Tropsch synthesis is proposed based on the hypothesis that two incompatible mechanisms are involved resting exclusively on methylene and on carbon monoxide insertion, respectively. This hypothesis is reflected by the well known superposition of two Anderson–Schulz–Flory distributions. Experiments with co-feeding of ethene, 1-alkenes and diazomethane as a source of surface methylene and also the carbon number distribution of branched hydrocarbons strongly support the hypothesis of two independent mechanisms and the methylene insertion mechanism of one of them.Co-feeding of alcohols, the dependence of the ratio of the two mechanisms on the pressure of hydrogen and carbon monoxide and the promoter effect of alkali on iron catalysts also prove the hypothesis of the two mechanisms and point to the carbon monoxide insertion mechanism as the second mechanism that is characterized by the higher growth probability of the resulting Anderson–Schulz–Flory distribution.Furthermore new interpretations of the crucial steps of C–C linkage and chain termination are given. The insertion of methylene is interpreted by coupling of an alkylidene and a methylene surface species towards a coordinated olefin with the chance of chain growth termination by 1-alkene desorption. For the carbon monoxide insertion mechanism the termination of chain growth is assumed to occur by the formation of 1-alkenes and of alcohols via an alcoholate intermediate.The new mechanism gives without any exception a sound interpretation of a great variety of experiments and contributes also to the interpretation of the promoter effect of alkali and of the different performance of cobalt and iron catalysts.
Keywords: Fischer–Tropsch synthesis; Reaction mechanism; Iron catalyst; Cobalt catalysts
Direct synthesis of methanethiol from H2S-rich syngas over sulfided Mo-based catalysts by Aiping Chen; Qi Wang; Qiaoling Li; Yingjuan Hao; Weiping Fang; Yiquan Yang (pp. 69-76).
One-step synthesis of CH3SH from the reaction of H2S-rich syngas (H2S/CO/H2 mixtures) was investigated over the sulfided supported K–Mo catalysts. Compared to the CH3OH–H2S route for the synthesis of methanethiol, this method skips the step of the synthesis of CH3OH from syngas.▪The direct synthesis of methanethiol from H2S-rich syngas was investigated over sulfided Mo-based catalysts supported on SiO2. K-promoted Mo/SiO2 catalysts exhibited a high activity for the synthesis of CH3SH. The incorporation of cobalt into the K–Mo/SiO2 catalyst increased the catalytic activity, but slightly decreased the selectivity to methanethiol. The selected catalysts were characterized by using X-ray diffraction (XRD), CO temperature-programmed desorption (CO-TPD), electron spin resonance (ESR), and X-ray photoelectron spectroscopy (XPS) techniques. The results showed that the potassium interacts with Mo component and increases the active sites for the CH3SH synthesis by changing the concentration of Mo5+ species after sulfidation. A mechanism for the synthesis of CH3SH was proposed.
Keywords: Methanethiol synthesis; Hydrogen sulfide; Syngas; Mo-based catalysts; Potassium; Cobalt; Hydrogenation
Direct synthesis of methanethiol from H2S-rich syngas over sulfided Mo-based catalysts by Aiping Chen; Qi Wang; Qiaoling Li; Yingjuan Hao; Weiping Fang; Yiquan Yang (pp. 69-76).
One-step synthesis of CH3SH from the reaction of H2S-rich syngas (H2S/CO/H2 mixtures) was investigated over the sulfided supported K–Mo catalysts. Compared to the CH3OH–H2S route for the synthesis of methanethiol, this method skips the step of the synthesis of CH3OH from syngas.▪The direct synthesis of methanethiol from H2S-rich syngas was investigated over sulfided Mo-based catalysts supported on SiO2. K-promoted Mo/SiO2 catalysts exhibited a high activity for the synthesis of CH3SH. The incorporation of cobalt into the K–Mo/SiO2 catalyst increased the catalytic activity, but slightly decreased the selectivity to methanethiol. The selected catalysts were characterized by using X-ray diffraction (XRD), CO temperature-programmed desorption (CO-TPD), electron spin resonance (ESR), and X-ray photoelectron spectroscopy (XPS) techniques. The results showed that the potassium interacts with Mo component and increases the active sites for the CH3SH synthesis by changing the concentration of Mo5+ species after sulfidation. A mechanism for the synthesis of CH3SH was proposed.
Keywords: Methanethiol synthesis; Hydrogen sulfide; Syngas; Mo-based catalysts; Potassium; Cobalt; Hydrogenation
New tripodal iminophosphorane-based ethylene oligomerization catalysts by Laurence Beaufort; Federica Benvenuti; Lionel Delaude; Alfred F. Noels (pp. 77-82).
Seven transition-metal complexes based on new tripodal iminophosphorane ligands were investigated as initiators for the oligomerization of ethylene in the presence of aluminum co-catalysts using high-throughput techniques. Structural modifications, either at the metal center or within the tripodal ligand, did not markedly affect the catalytic activity but had a significant impact on the oligomer distribution.▪Seven transition-metal complexes of general formulaRC(CH2NPR′3)3)MX2 based on new tripodal iminophosphorane ligands were investigated as initiators for the oligomerization of ethylene in the presence of aluminum co-catalysts using high-throughput techniques. In all cases, ethylene consumption peaked at ca. 30°C and was not drastically affected by varying the nature of the metal (M=Ni, Fe, Pd, Cu), the aluminum co-catalyst (MMAO, Et2AlCl, or EtAlCl2) or the substituents of the tris(iminophosphorane) ligand (R=Me, Ph; R′=cyclopentyl, Ph). Structural modifications of the organometallic complexes, either at the metal center or within the tripodal ligand, however, had a significant impact on the oligomer distribution obtained. In particular, Pd-based catalyst (PhC(CH2NPPh3)3)PdCl2 displayed an excellent selectivity toward hexene formation.
Keywords: Cu complexes; Fe complexes; Ni complexes; Pd complexes; Tripodal ligand
New tripodal iminophosphorane-based ethylene oligomerization catalysts by Laurence Beaufort; Federica Benvenuti; Lionel Delaude; Alfred F. Noels (pp. 77-82).
Seven transition-metal complexes based on new tripodal iminophosphorane ligands were investigated as initiators for the oligomerization of ethylene in the presence of aluminum co-catalysts using high-throughput techniques. Structural modifications, either at the metal center or within the tripodal ligand, did not markedly affect the catalytic activity but had a significant impact on the oligomer distribution.▪Seven transition-metal complexes of general formulaRC(CH2NPR′3)3)MX2 based on new tripodal iminophosphorane ligands were investigated as initiators for the oligomerization of ethylene in the presence of aluminum co-catalysts using high-throughput techniques. In all cases, ethylene consumption peaked at ca. 30°C and was not drastically affected by varying the nature of the metal (M=Ni, Fe, Pd, Cu), the aluminum co-catalyst (MMAO, Et2AlCl, or EtAlCl2) or the substituents of the tris(iminophosphorane) ligand (R=Me, Ph; R′=cyclopentyl, Ph). Structural modifications of the organometallic complexes, either at the metal center or within the tripodal ligand, however, had a significant impact on the oligomer distribution obtained. In particular, Pd-based catalyst (PhC(CH2NPPh3)3)PdCl2 displayed an excellent selectivity toward hexene formation.
Keywords: Cu complexes; Fe complexes; Ni complexes; Pd complexes; Tripodal ligand
Mechanistic study on the oxidation of (phenylthio)acetic acids by oxo(salen)manganese(V) complexes and the reactivity–selectivity principle by Arunachalam Chellamani; Paramasivan Sengu (pp. 83-92).
The oxygenation of several ( para-substituted phenylthio)acetic acids with various substituted oxo(salen)manganese(V) complexes follows an overall second-order kinetics, first-order each in the oxidant and substrate. Substituent effect studies reveal the operation of a SET mechanism. This redox system falls under strong reactivity–selectivity principle.▪A systematic study on the kinetics and mechanism of oxidation of several ( para-substituted phenylthio)acetic acids with various substituted oxo(salen)manganese(V) complexes in acetonitrile at 20°C is presented. The kinetic data indicate that the reaction is second-order overall, first-order each in (phenylthio)acetic acid and oxo(salen)manganese(V) complex. Rate studies with substituted (phenylthio)acetic acids give an excellent Hammett correlation with σ+/ σ− constants and the ρ-values are in the range of −0.82 to −1.17 for different oxo(salen)manganese(V) complexes. The log k2 values observed in the oxidation of each (phenylthio)acetic acid by substituted oxo(salen)manganese(V) complexes correlate with 2 σ, giving ρ-values from 0.26 to 0.56. A mechanism involving single electron transfer from the sulfur center of the substrate to the oxo complex in the rate-controlling step is envisaged. Kinetic data were obtained over a temperature range of 15–35°C and the activation parameters evaluated. Correlation analyses show the presence of an inverse relationship between reactivity and selectivity in the reactions of various (phenylthio)acetic acids with a given oxo(salen)manganese(V) complex and also in various oxo(salen)manganese(V) complexes with a given (phenylthio)acetic acid. Mathematical treatment of the results shows the operation of a valid reactivity–selectivity principle in this redox system.
Keywords: (Phenylthio)acetic acids; Iodosylbenzene; (Salen)Mn; III; complexes; Catalyzed oxidation; Reaction mechanismAbbreviation; salen; N; ,; N; ′-ethylenebis(salicylideneaminato)
Mechanistic study on the oxidation of (phenylthio)acetic acids by oxo(salen)manganese(V) complexes and the reactivity–selectivity principle by Arunachalam Chellamani; Paramasivan Sengu (pp. 83-92).
The oxygenation of several ( para-substituted phenylthio)acetic acids with various substituted oxo(salen)manganese(V) complexes follows an overall second-order kinetics, first-order each in the oxidant and substrate. Substituent effect studies reveal the operation of a SET mechanism. This redox system falls under strong reactivity–selectivity principle.▪A systematic study on the kinetics and mechanism of oxidation of several ( para-substituted phenylthio)acetic acids with various substituted oxo(salen)manganese(V) complexes in acetonitrile at 20°C is presented. The kinetic data indicate that the reaction is second-order overall, first-order each in (phenylthio)acetic acid and oxo(salen)manganese(V) complex. Rate studies with substituted (phenylthio)acetic acids give an excellent Hammett correlation with σ+/ σ− constants and the ρ-values are in the range of −0.82 to −1.17 for different oxo(salen)manganese(V) complexes. The log k2 values observed in the oxidation of each (phenylthio)acetic acid by substituted oxo(salen)manganese(V) complexes correlate with 2 σ, giving ρ-values from 0.26 to 0.56. A mechanism involving single electron transfer from the sulfur center of the substrate to the oxo complex in the rate-controlling step is envisaged. Kinetic data were obtained over a temperature range of 15–35°C and the activation parameters evaluated. Correlation analyses show the presence of an inverse relationship between reactivity and selectivity in the reactions of various (phenylthio)acetic acids with a given oxo(salen)manganese(V) complex and also in various oxo(salen)manganese(V) complexes with a given (phenylthio)acetic acid. Mathematical treatment of the results shows the operation of a valid reactivity–selectivity principle in this redox system.
Keywords: (Phenylthio)acetic acids; Iodosylbenzene; (Salen)Mn; III; complexes; Catalyzed oxidation; Reaction mechanismAbbreviation; salen; N; ,; N; ′-ethylenebis(salicylideneaminato)
Kinetic study on photocatalytic degradation of reactive orange 5 solution with phosphotungstic acid by Zhong Junbo; Ma Di; Zhao Hong; Li Minjiao; Xie Bin; Li Jianzhang (pp. 93-98).
Figure shows plot of the reciprocal of the initial rater0−1 versus the reciprocal of the initial concentrationC0−1 for photocatalytic degradation of KGN. It is clear that a good fitting of the model to the experimental data may be observed thus confirming the L–H nature of the photocatalytic degradation reaction mechanism.▪Increasing environmental pollution caused by toxic dyes due to their hazardous nature is a matter of great concern. It has been generally agreed that reactive orange 5 (KGN) can be effectively degraded in aerated phosphotungstic acid (HPA) homogeneous reaction system using near-UV irradiation. The knowledge on the kinetics of the system possesses both practical and theoretical values. The results reveal that the photocatalytic degradation reaction of KGN with HPA in a homogenous solution can be described by Langmuir–Hinshelwood equation; the results manifest the reaction is first-order with lower concentration and is zero-order with higher concentration. As the initial concentration goes up, the order of the reaction is reduced from 1 to 0, the limiting rate constant and the adsorption constant in this case are 0.8098mgL−1min−1 and 4.359×10−2Lmg−1, respectively. The paper reveals that the optimal amount of photocatalyst in our experimental conditions for the degradation of KGN is 0.6gL−1. The effects of irradiation intensity and pH value on the degradation rate constant were also demonstrated, where special attention was paid on the nature of the photocatalyst itself.
Keywords: Abbreviations; KGN; reactive orange 5; HPA; phosphotungstic acid; L–H; Langmuir–Hinshelwood; POM; polyoxometalatePhosphotungstic acid; Photocatalytic degradation; Reactive orange; Kinetic; Wastewater treatment
RETRACTED: Kinetic study on photocatalytic degradation of reactive orange 5 solution with phosphotungstic acid by Zhong Junbo; Ma Di; Zhao Hong; Li Minjiao; Xie Bin; Li Jianzhang (pp. 93-98).
This article has been retracted at the request of the Editor-in-Chief and Authors. Please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy).Reason: The authors have plagiarized the Masters thesis of Min Zhu, Dalian Jiaotong University, 2004. They have also duplicated significant parts of a paper published in Central European Journal of Chemistry 6 (2008) 99–105, doi:10.2478/s11532-007-0064-2. One of the conditions of submission of a paper for publication is that authors declare explicitly that their work is original and has not appeared in a publication elsewhere. Re-use of any data should be appropriately cited. As such this article represents a severe abuse of the scientific publishing system. The scientific community takes a very strong view on this matter and we apologize to readers of the journal that this was not detected during the submission process. We thank Professor Xiuhua Zhu (Dalian Jiaotong University) for bringing the thesis plagiarism to our attention.
Immobilization of metalloporphyrins into nanotubes of natural halloysite toward selective catalysts for oxidation reactions by Guilherme Sippel Machado; Kelly Aparecida Dias de Freitas Castro; Fernando Wypych; Shirley Nakagaki (pp. 99-107).
The process of metalloporphyrin immobilization into the nanotubes/nanoscrolls of natural halloysite is described. Immobilization of 100% was attained with an anionic iron(III) porphyrin via a pressurized system. The catalytic activities of the new materials were evaluated in the oxidation of cyclo-octene, cyclohexane and n-heptane. The results obtained in the present study show that these novel immobilized catalysts are a promising system for selective oxidation reactions. ▪This paper describes the immobilization of anionic and cationic metalloporphyrins into the nanotubes/nanoscrolls of natural halloysite and investigates the catalytic activity of these novel materials in the oxidation of organic substrates. Two methods for metalloporphyrin immobilization were tested: immobilization under pressure and immobilization under stirring/reflux conditions. The best immobilization rate (100%) was obtained with the anionic iron(III) porphyrin immobilized via the pressurized system. A cationic iron(III) porphyrin was also immobilized into the support with relatively good yields, but no encouraging results were obtained for the immobilization of a neutral iron(III) porphyrin. The obtained materials were characterized by UV–vis and infrared spectroscopies, X-ray diffraction, and transmission electron microscopy. The catalytic activity of a fully immobilized iron(III) porphyrin was evaluated in the oxidation of cyclo-octene, cyclohexane and n-heptane, using iodosylbenzene as the oxygen donor. It has been shown that these novel immobilized catalysts are a promising system for selective oxidation reactions.
Keywords: Porphyrin; Halloysite; Supported catalyst; Catalysis; Oxidation
Immobilization of metalloporphyrins into nanotubes of natural halloysite toward selective catalysts for oxidation reactions by Guilherme Sippel Machado; Kelly Aparecida Dias de Freitas Castro; Fernando Wypych; Shirley Nakagaki (pp. 99-107).
The process of metalloporphyrin immobilization into the nanotubes/nanoscrolls of natural halloysite is described. Immobilization of 100% was attained with an anionic iron(III) porphyrin via a pressurized system. The catalytic activities of the new materials were evaluated in the oxidation of cyclo-octene, cyclohexane and n-heptane. The results obtained in the present study show that these novel immobilized catalysts are a promising system for selective oxidation reactions. ▪This paper describes the immobilization of anionic and cationic metalloporphyrins into the nanotubes/nanoscrolls of natural halloysite and investigates the catalytic activity of these novel materials in the oxidation of organic substrates. Two methods for metalloporphyrin immobilization were tested: immobilization under pressure and immobilization under stirring/reflux conditions. The best immobilization rate (100%) was obtained with the anionic iron(III) porphyrin immobilized via the pressurized system. A cationic iron(III) porphyrin was also immobilized into the support with relatively good yields, but no encouraging results were obtained for the immobilization of a neutral iron(III) porphyrin. The obtained materials were characterized by UV–vis and infrared spectroscopies, X-ray diffraction, and transmission electron microscopy. The catalytic activity of a fully immobilized iron(III) porphyrin was evaluated in the oxidation of cyclo-octene, cyclohexane and n-heptane, using iodosylbenzene as the oxygen donor. It has been shown that these novel immobilized catalysts are a promising system for selective oxidation reactions.
Keywords: Porphyrin; Halloysite; Supported catalyst; Catalysis; Oxidation
Ruthenium–indenylidene complexes in ring opening metathesis polymerization (ROMP) reactions by Pierre de Frémont; Hervé Clavier; Véronique Montembault; Laurent Fontaine; Steven P. Nolan (pp. 108-113).
A series of well-defined ruthenium-based indenylidene catalysts are tested in ring opening polymerization metathesis (ROMP) with cycloocta-1,5-diene. The reactivity of the catalysts is examined by the polymerization kinetics.▪The ring opening metathesis polymerization (ROMP) of cycloocta-1,5-diene (COD) is mediated by a series of six well-defined ruthenium-based indenylidene catalysts. The polymerization kinetics are monitored and compared with three generations of Grubbs’ catalyst. Moderate control over the polymerizations was observed for both benzylidene and indenylidene-based catalysts.
Keywords: Indenylidene; Ruthenium; Ring opening metathesis polymerization (ROMP)
Ruthenium–indenylidene complexes in ring opening metathesis polymerization (ROMP) reactions by Pierre de Frémont; Hervé Clavier; Véronique Montembault; Laurent Fontaine; Steven P. Nolan (pp. 108-113).
A series of well-defined ruthenium-based indenylidene catalysts are tested in ring opening polymerization metathesis (ROMP) with cycloocta-1,5-diene. The reactivity of the catalysts is examined by the polymerization kinetics.▪The ring opening metathesis polymerization (ROMP) of cycloocta-1,5-diene (COD) is mediated by a series of six well-defined ruthenium-based indenylidene catalysts. The polymerization kinetics are monitored and compared with three generations of Grubbs’ catalyst. Moderate control over the polymerizations was observed for both benzylidene and indenylidene-based catalysts.
Keywords: Indenylidene; Ruthenium; Ring opening metathesis polymerization (ROMP)
Carbon-bridged diphosphine ligands for chromium-catalysed ethylene tetramerisation and trimerisation reactions by Matthew J. Overett; Kevin Blann; Annette Bollmann; Raylene de Villiers; John T. Dixon; Esna Killian; Munaka C. Maumela; Hulisani Maumela; David S. McGuinness; David H. Morgan; Adam Rucklidge; Alexandra M.Z. Slawin (pp. 114-119).
The use of carbon-bridged diphosphine ligands in chromium-catalysed ethylene tri- and tetramerisation reactions was investigated. A catalyst with the bis(diphenylphosphino)benzene ligand was found to be among the most active selective oligomerisation catalysts yet reported. Various aspects of ligand design were found to independently affect the catalyst selectivity (1-octene:1-hexene ratio), including steric constraints around the catalytic centre, phosphine basicity, P–Cr–P bite angle and ligand bridge structure.▪The use of carbon-bridged diphosphine ligands in chromium-catalysed ethylene tri- and tetramerisation reactions has been investigated. Two- and three-carbon spacer ligands all showed activity for selective oligomerisation, with a structure–selectivity correlation between P–Cr–P bite angle and 1-octene:1-hexene ratio evident. Activated chromium complexes of single carbon spacer diphosphines were also shown to be effective tetramerisation catalysts, provided that the ligand is innocent under the conditions of catalyst activation. A catalyst with the bis(diphenylphosphino)benzene ligand was found to be exceptionally active, although the combined 1-hexene and 1-octene selectivity was lower than with the best diphosphinoamine (PNP) ligands. The yield losses to by-products can to an extent be minimised by the use of high reaction temperatures and pressures. Unlike with the PNP-based systems, attempts to activate the Cr/bis(diphenylphosphino)benzene catalyst in situ from a chromium salt and free ligand resulted in low activity and high polymer formation. The effect of different phosphine substitution on catalyst selectivity was explored. Steric constraints around the catalytic centre ( ortho-alkylphenyl phosphines) resulted in a shift towards 1-hexene formation, as with PNP catalysts. Additionally, the basicity of the phosphines appears to influence catalyst selectivity, with alkyl phosphines favouring trimerisation. An interplay between phosphine basicity and bridge structure is in evidence, however, as a catalyst containing a ligand with both basic phosphine atoms and a small bite angle was shown to be selective towards 1-octene.
Keywords: Chromium; Phosphine ligands; Ethylene trimerisation; Ethylene tetramerisation; Homogeneous catalysis
Carbon-bridged diphosphine ligands for chromium-catalysed ethylene tetramerisation and trimerisation reactions by Matthew J. Overett; Kevin Blann; Annette Bollmann; Raylene de Villiers; John T. Dixon; Esna Killian; Munaka C. Maumela; Hulisani Maumela; David S. McGuinness; David H. Morgan; Adam Rucklidge; Alexandra M.Z. Slawin (pp. 114-119).
The use of carbon-bridged diphosphine ligands in chromium-catalysed ethylene tri- and tetramerisation reactions was investigated. A catalyst with the bis(diphenylphosphino)benzene ligand was found to be among the most active selective oligomerisation catalysts yet reported. Various aspects of ligand design were found to independently affect the catalyst selectivity (1-octene:1-hexene ratio), including steric constraints around the catalytic centre, phosphine basicity, P–Cr–P bite angle and ligand bridge structure.▪The use of carbon-bridged diphosphine ligands in chromium-catalysed ethylene tri- and tetramerisation reactions has been investigated. Two- and three-carbon spacer ligands all showed activity for selective oligomerisation, with a structure–selectivity correlation between P–Cr–P bite angle and 1-octene:1-hexene ratio evident. Activated chromium complexes of single carbon spacer diphosphines were also shown to be effective tetramerisation catalysts, provided that the ligand is innocent under the conditions of catalyst activation. A catalyst with the bis(diphenylphosphino)benzene ligand was found to be exceptionally active, although the combined 1-hexene and 1-octene selectivity was lower than with the best diphosphinoamine (PNP) ligands. The yield losses to by-products can to an extent be minimised by the use of high reaction temperatures and pressures. Unlike with the PNP-based systems, attempts to activate the Cr/bis(diphenylphosphino)benzene catalyst in situ from a chromium salt and free ligand resulted in low activity and high polymer formation. The effect of different phosphine substitution on catalyst selectivity was explored. Steric constraints around the catalytic centre ( ortho-alkylphenyl phosphines) resulted in a shift towards 1-hexene formation, as with PNP catalysts. Additionally, the basicity of the phosphines appears to influence catalyst selectivity, with alkyl phosphines favouring trimerisation. An interplay between phosphine basicity and bridge structure is in evidence, however, as a catalyst containing a ligand with both basic phosphine atoms and a small bite angle was shown to be selective towards 1-octene.
Keywords: Chromium; Phosphine ligands; Ethylene trimerisation; Ethylene tetramerisation; Homogeneous catalysis
Host (nanocage of zeolite–Y)/guest (manganese(II), cobalt(II), nickel(II) and copper(II) complexes of 12-membered macrocyclic Schiff-base ligand derived from thiosemicarbazide and glyoxal) nanocomposite materials: Synthesis, characterization and catalytic oxidation of cyclohexene by Masoud Salavati-Niasari (pp. 120-128).
A series of Mn(II), Co(II), Ni(II) and Cu(II) complexes with 12-membered macrocyclic tetradentate ligand have been synthesized and characterized as homogeneous and encapsulated into the nanopores of zeolite–Y. The chelation of zeolite-exchanged metal(II) by N-containing ligand gives rise to a whole class of Host–Guest Nanocomposite Materials (HGNM) as heterogeneous liquid-phase oxidation, which exhibits similar catalytic performances than the homogeneous ones.▪A series of Mn(II), Co(II), Ni(II) and Cu(II) complexes with 12-membered macrocyclic tetradentate ligand; H6C6N6S2=1,2,5,6,8,11-hexaazacyclododeca-7,12-dithione-2,4,8,10-tetraene; have been synthesized and characterized as homogeneous and encapsulated into the nanopores of zeolite–Y. These catalytic systems show a good activity in the oxidation of cyclohexene to 2-cyclohexene-1-one, 2-cyclohexene-2-ol and 1-( tert-butylperoxy)-2-cyclohexene. The chelation of zeolite-exchanged metal(II) by N-containing ligand gives rise to a whole class of Host–Guest Nanocomposite Materials (HGNM) as heterogeneous liquid-phase oxidation, which exhibits similar catalytic performances than the homogeneous ones. The encapsulated complexes abbreviated here as [M(H4C6N6S2)]–NaY, catalyze the oxidation of cyclohexene using TBHP as oxidant in good yield. Cyclohexene catalyzed by [M(H4C6N6S2)]–NaY under optimized reaction conditions gave three reaction products namely, 2-cyclohexene-1-one, 2-cyclohexene-2-ol and 1-( tert-butylperoxy)-2-cyclohexene. In the presence of tert-butylhydroperoxide all catalysts gave 2-cyclohexene-1-one in major yield, though overall conversion has been found low (40–90%).
Keywords: Nanocomposite materials; 12-Membered macrocycle; Zeolite encapsulation; Oxidation of cyclohexene
Host (nanocage of zeolite–Y)/guest (manganese(II), cobalt(II), nickel(II) and copper(II) complexes of 12-membered macrocyclic Schiff-base ligand derived from thiosemicarbazide and glyoxal) nanocomposite materials: Synthesis, characterization and catalytic oxidation of cyclohexene by Masoud Salavati-Niasari (pp. 120-128).
A series of Mn(II), Co(II), Ni(II) and Cu(II) complexes with 12-membered macrocyclic tetradentate ligand have been synthesized and characterized as homogeneous and encapsulated into the nanopores of zeolite–Y. The chelation of zeolite-exchanged metal(II) by N-containing ligand gives rise to a whole class of Host–Guest Nanocomposite Materials (HGNM) as heterogeneous liquid-phase oxidation, which exhibits similar catalytic performances than the homogeneous ones.▪A series of Mn(II), Co(II), Ni(II) and Cu(II) complexes with 12-membered macrocyclic tetradentate ligand; H6C6N6S2=1,2,5,6,8,11-hexaazacyclododeca-7,12-dithione-2,4,8,10-tetraene; have been synthesized and characterized as homogeneous and encapsulated into the nanopores of zeolite–Y. These catalytic systems show a good activity in the oxidation of cyclohexene to 2-cyclohexene-1-one, 2-cyclohexene-2-ol and 1-( tert-butylperoxy)-2-cyclohexene. The chelation of zeolite-exchanged metal(II) by N-containing ligand gives rise to a whole class of Host–Guest Nanocomposite Materials (HGNM) as heterogeneous liquid-phase oxidation, which exhibits similar catalytic performances than the homogeneous ones. The encapsulated complexes abbreviated here as [M(H4C6N6S2)]–NaY, catalyze the oxidation of cyclohexene using TBHP as oxidant in good yield. Cyclohexene catalyzed by [M(H4C6N6S2)]–NaY under optimized reaction conditions gave three reaction products namely, 2-cyclohexene-1-one, 2-cyclohexene-2-ol and 1-( tert-butylperoxy)-2-cyclohexene. In the presence of tert-butylhydroperoxide all catalysts gave 2-cyclohexene-1-one in major yield, though overall conversion has been found low (40–90%).
Keywords: Nanocomposite materials; 12-Membered macrocycle; Zeolite encapsulation; Oxidation of cyclohexene
Oxidation of adamantane catalysed by imidazolylporphyrinatoiron(III) complexes and structural studies of 5-coordinating iron(III) porphyrin by Yuji Miyazaki; Akiharu Satake; Yoshiaki Kobuke (pp. 129-139).
Oxidation of adamantane with peroxyphenylacetic acid in the presence of chloro-5-(1-methyl-2-imidazolyl)-10,15,20-tri(pentafluorophenyl)porphyrinatoiron(III) (ImTPFPP–Fe(III)Cl) gave adamantanols in 76% yield, whereas the yield was only 26% in the case of chloro-5,10,15,20-tetra(pentafluorophenyl)porphyrinatoiron(III). The apparent effect of the appended imidazolyl group is discussed in terms of a 5-coordinated dimer of ImTPFPP–Fe(III)Cl, which was observed in the1H and19F NMR, and UV–vis spectra.▪Oxidation of adamantane with phenylperacetic acid was carried out in the presence of three imidazolyltriarylporphyrinatoiron(III) complexes having pentafluorophenyl, phenyl, and mesityl (2,4,6-trimethylphenyl) groups as meso-substituents and three corresponding tetraarylporphyrinatoiron(III) complexes. The yield of 1- and 2-adamantanols was 76% in the case of chloro-5-(1-methyl-2-imidazolyl)-10,15,20-tri(pentafluorophenyl)porphyrinatoiron(III) (ImTPFPP–Fe(III)Cl), whereas the yield was only 26% in the case of chloro-5,10,15,20-tetra(pentafluorophenyl)porphyrinatoiron(III) in the presence of 100eq. N-methylimidazole. The apparent effect of the appended imidazolyl group is discussed in terms of a 5-coordinated dimer of ImTPFPP–Fe(III)Cl, which was observed in the1H and19F NMR, and UV–vis spectra.
Keywords: Iron porphyrin; Oxidation; Peroxy acid; Imidazole coordination; Supramolecule
Oxidation of adamantane catalysed by imidazolylporphyrinatoiron(III) complexes and structural studies of 5-coordinating iron(III) porphyrin by Yuji Miyazaki; Akiharu Satake; Yoshiaki Kobuke (pp. 129-139).
Oxidation of adamantane with peroxyphenylacetic acid in the presence of chloro-5-(1-methyl-2-imidazolyl)-10,15,20-tri(pentafluorophenyl)porphyrinatoiron(III) (ImTPFPP–Fe(III)Cl) gave adamantanols in 76% yield, whereas the yield was only 26% in the case of chloro-5,10,15,20-tetra(pentafluorophenyl)porphyrinatoiron(III). The apparent effect of the appended imidazolyl group is discussed in terms of a 5-coordinated dimer of ImTPFPP–Fe(III)Cl, which was observed in the1H and19F NMR, and UV–vis spectra.▪Oxidation of adamantane with phenylperacetic acid was carried out in the presence of three imidazolyltriarylporphyrinatoiron(III) complexes having pentafluorophenyl, phenyl, and mesityl (2,4,6-trimethylphenyl) groups as meso-substituents and three corresponding tetraarylporphyrinatoiron(III) complexes. The yield of 1- and 2-adamantanols was 76% in the case of chloro-5-(1-methyl-2-imidazolyl)-10,15,20-tri(pentafluorophenyl)porphyrinatoiron(III) (ImTPFPP–Fe(III)Cl), whereas the yield was only 26% in the case of chloro-5,10,15,20-tetra(pentafluorophenyl)porphyrinatoiron(III) in the presence of 100eq. N-methylimidazole. The apparent effect of the appended imidazolyl group is discussed in terms of a 5-coordinated dimer of ImTPFPP–Fe(III)Cl, which was observed in the1H and19F NMR, and UV–vis spectra.
Keywords: Iron porphyrin; Oxidation; Peroxy acid; Imidazole coordination; Supramolecule
Heck-type reactions of allylic alcohols by Anna Maria Zawisza; Benjamin Ganchegui; Iván González; Sandrine Bouquillon; Anna Roglans; Françoise Hénin; Jacques Muzart (pp. 140-145).
Under microwave irradiation, the Pd-catalyzed 5- endo- trig cyclizations depicted on the scheme proceed not only more quickly than under thermal heating, but also with higher yields.▪Various conditions have been tested to obtain efficiently 2-methyl-1-indanone via the Pd-catalyzed 5- endo- trig cyclization of 1-( o-bromophenyl)-2-methylprop-2-en-1-ol. High yield (97%) was obtained at 120°C in DMF with Pd(OAc)2/cinchonine as the catalytic system and NaHCO3 as the base. Use of this procedure for the synthesis of other substituted indanones led to lower yields but replacing thermal heating by microwave heating improved greatly the results.
Keywords: Palladium; Catalysis; Heck reaction; Cyclization; Allylic alcohol; DMF; Cinchonine; Microwaves
Heck-type reactions of allylic alcohols by Anna Maria Zawisza; Benjamin Ganchegui; Iván González; Sandrine Bouquillon; Anna Roglans; Françoise Hénin; Jacques Muzart (pp. 140-145).
Under microwave irradiation, the Pd-catalyzed 5- endo- trig cyclizations depicted on the scheme proceed not only more quickly than under thermal heating, but also with higher yields.▪Various conditions have been tested to obtain efficiently 2-methyl-1-indanone via the Pd-catalyzed 5- endo- trig cyclization of 1-( o-bromophenyl)-2-methylprop-2-en-1-ol. High yield (97%) was obtained at 120°C in DMF with Pd(OAc)2/cinchonine as the catalytic system and NaHCO3 as the base. Use of this procedure for the synthesis of other substituted indanones led to lower yields but replacing thermal heating by microwave heating improved greatly the results.
Keywords: Palladium; Catalysis; Heck reaction; Cyclization; Allylic alcohol; DMF; Cinchonine; Microwaves
Heterogeneous selective oxidation of formaldehyde to formic acid on V/Ti oxide catalysts: The role of vanadia species by G.Ya. Popova; T.V. Andrushkevich; E.V. Semionova; Yu.A. Chesalov; L.S. Dovlitova; V.A. Rogov; V.N. Parmon (pp. 146-152).
The activity of supported V/Ti oxide catalysts is determined by the nature of vanadium oxide species. The monolayer vanadium–titania catalysts are highly active in the formaldehyde oxidation to formic acid. According to the TPR data, these vanadium species contain a more weakly bonded oxygen as compared to oxygen in bulk V2O5. The bulk V2O5 is highly selective, but low active in respect to the oxidation of formaldehyde to formic acid as compared with the supported V/Ti oxide catalysts. The presence of bulk amorphous or crystalline V2O5 in the V/Ti oxide catalysts leads to a partial blocking of the active sites and hence decreases the catalyst activity in the oxidation of formaldehyde to formic acid.▪The present work deals with the study of the role of vanadium species in the V/Ti-supported oxide catalysts for the oxidation of formaldehyde to formic acid. Two different series of catalysts were prepared, the first one consisting of catalysts of composition 20wt.% V2O5/80wt.% TiO2 calcined at 400 and 450°C (series 1), and the second one was prepared by washing of series 1 samples with nitric acid (series 2). All the samples were characterized by XRD, IR spectroscopy, temperature-programmed reduction with H2, and differential dissolution methods. In the catalysts of series 1, vanadium is represented by both monolayer species (monomeric and polymeric VO x) and V2O5 phase in crystalline or X-ray amorphous state, depending on the calcination temperature. Washing the samples of series 1 with nitric acid removes the V2O5 phase, and the samples of series 2 contain only monolayer vanadium species. The monolayer vanadia–titania catalysts are highly active in the formaldehyde oxidation to formic acid, while crystalline and amorphous V2O5 exhibit a low activity in that reaction. Moreover, the presence of the V2O5 phase blocks the catalyst active sites and thus decreases the catalyst activity. The monolayer vanadium species are easier to be reduced by H2 as compared to bulk V2O5.
Keywords: Supported vanadia catalysts; Formaldehyde oxidation; Vanadium species
Heterogeneous selective oxidation of formaldehyde to formic acid on V/Ti oxide catalysts: The role of vanadia species by G.Ya. Popova; T.V. Andrushkevich; E.V. Semionova; Yu.A. Chesalov; L.S. Dovlitova; V.A. Rogov; V.N. Parmon (pp. 146-152).
The activity of supported V/Ti oxide catalysts is determined by the nature of vanadium oxide species. The monolayer vanadium–titania catalysts are highly active in the formaldehyde oxidation to formic acid. According to the TPR data, these vanadium species contain a more weakly bonded oxygen as compared to oxygen in bulk V2O5. The bulk V2O5 is highly selective, but low active in respect to the oxidation of formaldehyde to formic acid as compared with the supported V/Ti oxide catalysts. The presence of bulk amorphous or crystalline V2O5 in the V/Ti oxide catalysts leads to a partial blocking of the active sites and hence decreases the catalyst activity in the oxidation of formaldehyde to formic acid.▪The present work deals with the study of the role of vanadium species in the V/Ti-supported oxide catalysts for the oxidation of formaldehyde to formic acid. Two different series of catalysts were prepared, the first one consisting of catalysts of composition 20wt.% V2O5/80wt.% TiO2 calcined at 400 and 450°C (series 1), and the second one was prepared by washing of series 1 samples with nitric acid (series 2). All the samples were characterized by XRD, IR spectroscopy, temperature-programmed reduction with H2, and differential dissolution methods. In the catalysts of series 1, vanadium is represented by both monolayer species (monomeric and polymeric VO x) and V2O5 phase in crystalline or X-ray amorphous state, depending on the calcination temperature. Washing the samples of series 1 with nitric acid removes the V2O5 phase, and the samples of series 2 contain only monolayer vanadium species. The monolayer vanadia–titania catalysts are highly active in the formaldehyde oxidation to formic acid, while crystalline and amorphous V2O5 exhibit a low activity in that reaction. Moreover, the presence of the V2O5 phase blocks the catalyst active sites and thus decreases the catalyst activity. The monolayer vanadium species are easier to be reduced by H2 as compared to bulk V2O5.
Keywords: Supported vanadia catalysts; Formaldehyde oxidation; Vanadium species
Hydrogen generation by direct decomposition of hydrocarbons over molten magnesium by K. Wang; W.S. Li; X.P. Zhou (pp. 153-157).
Hydrogen and carbon were prepared by hydrocarbon direct decomposition.CnHm⟶MoltenMgnC+m2H2Methane and higher hydrocarbons were directly decomposed to hydrogen and carbon over molten magnesium. Hydrogen and micrometer size carbon particles were formed as products. The catalyst losses activity because of the evaporation of metal Mg. The activity of the catalyst can be recovered by heating the upper cold section of the reactor to slide Mg back to the reactor bed. Mg2C3 was identified as reaction intermediate in the reaction. Compared to the reforming process, the hydrocarbon direct decomposition process produces CO-free hydrogen, does not emit CO2 to environment, generates useful carbon powder, and is also an energy-saving approach for hydrogen preparation. To form each molar of hydrogen by methane direct decomposition only consumes about 65.1% of the energy as that needed in the steam reforming of methane. The reaction is also proved to be useful in the decomposition of waste polyolefins, such as ploy olefin plastic and rubber.
Keywords: Hydrogen preparation; Molten metal catalyst; Hydrocarbon decomposition; Molten metal catalysis
Hydrogen generation by direct decomposition of hydrocarbons over molten magnesium by K. Wang; W.S. Li; X.P. Zhou (pp. 153-157).
Hydrogen and carbon were prepared by hydrocarbon direct decomposition.CnHm⟶MoltenMgnC+m2H2Methane and higher hydrocarbons were directly decomposed to hydrogen and carbon over molten magnesium. Hydrogen and micrometer size carbon particles were formed as products. The catalyst losses activity because of the evaporation of metal Mg. The activity of the catalyst can be recovered by heating the upper cold section of the reactor to slide Mg back to the reactor bed. Mg2C3 was identified as reaction intermediate in the reaction. Compared to the reforming process, the hydrocarbon direct decomposition process produces CO-free hydrogen, does not emit CO2 to environment, generates useful carbon powder, and is also an energy-saving approach for hydrogen preparation. To form each molar of hydrogen by methane direct decomposition only consumes about 65.1% of the energy as that needed in the steam reforming of methane. The reaction is also proved to be useful in the decomposition of waste polyolefins, such as ploy olefin plastic and rubber.
Keywords: Hydrogen preparation; Molten metal catalyst; Hydrocarbon decomposition; Molten metal catalysis
Characterization of Na+-β-zeolite supported Pd and PdAg bimetallic catalysts using EXAFS, TEM and flow reactor by Wei Huang; Raul F. Lobo; Jingguang G. Chen (pp. 158-165).
Flow reactor studies of the selective hydrogenation of acetylene in the presence of ethylene have been performed on Na+ exchanged β-zeolite supported Pd, Ag and PdAg catalysts, as an extension of our previous batch reactor studies [W. Huang, J.R. McCormick, R.F. Lobo, J.G. Chen, J. Catal. 246 (2007) 40–51]. Results from flow reactor studies show that the PdAg/Na+-β-zeolite bimetallic catalyst has lower activity than Pd/Na+-β-zeolite monometallic catalyst, while Ag/Na+-β-zeolite does not show any activity for acetylene hydrogenation. However, the selectivity for the PdAg bimetallic catalyst is much higher than that for either the Pd catalyst or Ag catalyst. The selectivity to byproduct (ethane) is greatly inhibited on the PdAg bimetallic catalyst as well. The results from the current flow reactor studies confirmed the pervious results from batch reactor studies [W. Huang, J.R. McCormick, R.F. Lobo, J.G. Chen, J. Catal. 246 (2007) 40–51]. In addition, we used transmission electron microscope (TEM), extended X-ray absorption fine structure (EXAFS), and FTIR of CO adsorption to confirm the formation of Pd–Ag bimetallic alloy in the PdAg/Na+-β-zeolite catalyst.Alloying Pd with Ag reduced the acetylene hydrogenation activity but increased the selectivity. The apparent activation energy of acetylene hydrogenation on Pd/Na+-β-zeolite and PdAg/Na+-β-zeolite were estimated to be 8kcal/mol and 15.2kcal/mol. The formation of PdAg bimetallic particles on the Na+-β-zeolite support was confirmed by TEM, EXAFS, and CO adsorption using FTIR spectroscopy.▪
Keywords: Selective hydrogenation; Acetylene; Ethylene; Pd; Pd–Ag; Bimetallic catalysts; Na; +; -β-zeolite; Flow reactor; EXAFS; CO adsorption; TEM
Characterization of Na+-β-zeolite supported Pd and PdAg bimetallic catalysts using EXAFS, TEM and flow reactor by Wei Huang; Raul F. Lobo; Jingguang G. Chen (pp. 158-165).
Flow reactor studies of the selective hydrogenation of acetylene in the presence of ethylene have been performed on Na+ exchanged β-zeolite supported Pd, Ag and PdAg catalysts, as an extension of our previous batch reactor studies [W. Huang, J.R. McCormick, R.F. Lobo, J.G. Chen, J. Catal. 246 (2007) 40–51]. Results from flow reactor studies show that the PdAg/Na+-β-zeolite bimetallic catalyst has lower activity than Pd/Na+-β-zeolite monometallic catalyst, while Ag/Na+-β-zeolite does not show any activity for acetylene hydrogenation. However, the selectivity for the PdAg bimetallic catalyst is much higher than that for either the Pd catalyst or Ag catalyst. The selectivity to byproduct (ethane) is greatly inhibited on the PdAg bimetallic catalyst as well. The results from the current flow reactor studies confirmed the pervious results from batch reactor studies [W. Huang, J.R. McCormick, R.F. Lobo, J.G. Chen, J. Catal. 246 (2007) 40–51]. In addition, we used transmission electron microscope (TEM), extended X-ray absorption fine structure (EXAFS), and FTIR of CO adsorption to confirm the formation of Pd–Ag bimetallic alloy in the PdAg/Na+-β-zeolite catalyst.Alloying Pd with Ag reduced the acetylene hydrogenation activity but increased the selectivity. The apparent activation energy of acetylene hydrogenation on Pd/Na+-β-zeolite and PdAg/Na+-β-zeolite were estimated to be 8kcal/mol and 15.2kcal/mol. The formation of PdAg bimetallic particles on the Na+-β-zeolite support was confirmed by TEM, EXAFS, and CO adsorption using FTIR spectroscopy.▪
Keywords: Selective hydrogenation; Acetylene; Ethylene; Pd; Pd–Ag; Bimetallic catalysts; Na; +; -β-zeolite; Flow reactor; EXAFS; CO adsorption; TEM
Water-soluble metal complexes and catalysts by Denys Baskakov; Wolfgang A. Herrmann (pp. 166-170).
Novel water-soluble ligands were prepared in high yields by condensation of various amino acids with tris(hydroxymethyl)phosphane. Rhodium complexes of these ligands, formed in situ, were tested in two-phase hydroformylation of propylene. Selectivity observed with these ligand systems is easily controlled by altering the pH of the reaction mixture.
Keywords: Two-phase hydroformylation; Rhodium catalysts; Amino acids
Water-soluble metal complexes and catalysts by Denys Baskakov; Wolfgang A. Herrmann (pp. 166-170).
Novel water-soluble ligands were prepared in high yields by condensation of various amino acids with tris(hydroxymethyl)phosphane. Rhodium complexes of these ligands, formed in situ, were tested in two-phase hydroformylation of propylene. Selectivity observed with these ligand systems is easily controlled by altering the pH of the reaction mixture.
Keywords: Two-phase hydroformylation; Rhodium catalysts; Amino acids