Magnetic Fe3O4@MgAl–LDH composite grafted with cobalt phthalocyanine as an ef...Pawan Kumar
Magnetically separable layered double hydroxide MgAl–LDH@Fe3O4 composite supported cobalt
phthalocyanine catalyst was synthesized and used for the aerobic oxidation of mercaptans to corresponding
disulfides under alkali free conditions. The catalyst exhibited excellent activity for the oxidation of
mercaptans using molecular oxygen as an oxidant which can be effectively recovered by using an external
magnetic field. In addition, the covalent immobilization of cobalt phthalocyanine to MgAl–LDH@Fe3O4
support prevents the leaching of the catalyst and improves its activity and stability
Formulation and operation of a Nickel based methanation catalystSakib Shahriar
The objective of this experiment was to get a firsthand experience of the preparation of a catalyst for methanation reaction and to evaluate the performance of the catalyst in a fixed bed tubular reactor. In the first part of the experiment a nickel-based catalyst was synthesized. The catalyst will have nickel as the active component and alumina as the support. the catalyst precursor was prepared by co-precipitation from a solution of nitrate salts of nickel and aluminum. The precipitate was filtered out, washed, dried and calcined to obtain the catalyst. In the second part, the catalyst was activated and performance analysis was done alone with loaded in a fixed bed reactor. The percentage conversion of CO to CH4 was 96.38% and the selectivity of CH4 production to CO2 production was 3.348.
Studies on Nitration of Phenol over Solid Acid Catalyst | Crimson PublishersDanesBlake
Phenol was selectively nitrated in liquid phase to produce ortho-nitrophenol using dilute nitric acid (30%) at room temperature in presence of hydrochloric acid treated γ-alumina. Initially Al(NO3) and NH4HCO3 were reacted to prepare Al (OH)3 which on successive calcinations at 550 ᴼC for 5h produce γ-alumina. The γ-alumina was characterized by BET, XRD, SEM and NH3-TPD analysis. The XRD profile confirmed the crystalline structure of the solid acid catalyst γ-alumina. The NH3-TPD analysis showed the development of lewis acidity on the surface of hydrochloric acid treated γ-alumina. The effects of various parameters such as concentration of reactants, types of catalyst, weight of the catalyst, solvent, temperature and time of reaction have been studied. The kinetics of the reaction was also investigated.
Studies on Nitration of Phenol over Solid Acid Catalyst by Lipika Das, Koushi...crimsonpublisherspps
Phenol was selectively nitrated in liquid phase to produce ortho-nitrophenol using dilute nitric acid (30%) at room temperature in presence of hydrochloric acid treated γ-alumina. Initially Al (NO3) and NH4HCO3 were reacted to prepare Al (OH)3 which on successive calcinations at 550 0C for 5h produce γ-alumina. The γ-alumina was characterized by BET, XRD, SEM and NH3-TPD analysis. The XRD profile confirmed the crystalline structure of the solid acid catalyst γ-alumina. The NH3-TPD analysis showed the development of lewis acidity on the surface of hydrochloric acid treated γ-alumina. The effects of various parameters such as concentration of reactants, types of catalyst, weight of the catalyst, solvent, temperature and time of reaction have been studied. The kinetics of the reaction was also investigated
https://crimsonpublishers.com/pps/fulltext/PPS.000505.php
For more open access journals in Crimson Publishers
Please click on link: https://crimsonpublishers.com
For More Articles on Prime research material
Please click on: https://crimsonpublishers.com/pps/
Nitrogen-doped graphene-supported copper complex: a novel photocatalyst for C...Pawan Kumar
A copper(II) complex grafted to nitrogen-doped graphene (GrN700–CuC) was synthesized and then
demonstrated as an efficient photocatalyst for CO2 reduction into methanol under visible light irradiation
using a DMF/water mixture. The chemical and microstructural features of GrN700–CuC nanosheets were
studied by FTIR, XPS, XRD and HRTEM analyses. Owing to its truly heterogeneous nature, GrN700–CuC
could be easily recovered after the photocatalytic reaction and showed efficient recyclability for
subsequent runs.
Magnetic Fe3O4@MgAl–LDH composite grafted with cobalt phthalocyanine as an ef...Pawan Kumar
Magnetically separable layered double hydroxide MgAl–LDH@Fe3O4 composite supported cobalt
phthalocyanine catalyst was synthesized and used for the aerobic oxidation of mercaptans to corresponding
disulfides under alkali free conditions. The catalyst exhibited excellent activity for the oxidation of
mercaptans using molecular oxygen as an oxidant which can be effectively recovered by using an external
magnetic field. In addition, the covalent immobilization of cobalt phthalocyanine to MgAl–LDH@Fe3O4
support prevents the leaching of the catalyst and improves its activity and stability
Formulation and operation of a Nickel based methanation catalystSakib Shahriar
The objective of this experiment was to get a firsthand experience of the preparation of a catalyst for methanation reaction and to evaluate the performance of the catalyst in a fixed bed tubular reactor. In the first part of the experiment a nickel-based catalyst was synthesized. The catalyst will have nickel as the active component and alumina as the support. the catalyst precursor was prepared by co-precipitation from a solution of nitrate salts of nickel and aluminum. The precipitate was filtered out, washed, dried and calcined to obtain the catalyst. In the second part, the catalyst was activated and performance analysis was done alone with loaded in a fixed bed reactor. The percentage conversion of CO to CH4 was 96.38% and the selectivity of CH4 production to CO2 production was 3.348.
Studies on Nitration of Phenol over Solid Acid Catalyst | Crimson PublishersDanesBlake
Phenol was selectively nitrated in liquid phase to produce ortho-nitrophenol using dilute nitric acid (30%) at room temperature in presence of hydrochloric acid treated γ-alumina. Initially Al(NO3) and NH4HCO3 were reacted to prepare Al (OH)3 which on successive calcinations at 550 ᴼC for 5h produce γ-alumina. The γ-alumina was characterized by BET, XRD, SEM and NH3-TPD analysis. The XRD profile confirmed the crystalline structure of the solid acid catalyst γ-alumina. The NH3-TPD analysis showed the development of lewis acidity on the surface of hydrochloric acid treated γ-alumina. The effects of various parameters such as concentration of reactants, types of catalyst, weight of the catalyst, solvent, temperature and time of reaction have been studied. The kinetics of the reaction was also investigated.
Studies on Nitration of Phenol over Solid Acid Catalyst by Lipika Das, Koushi...crimsonpublisherspps
Phenol was selectively nitrated in liquid phase to produce ortho-nitrophenol using dilute nitric acid (30%) at room temperature in presence of hydrochloric acid treated γ-alumina. Initially Al (NO3) and NH4HCO3 were reacted to prepare Al (OH)3 which on successive calcinations at 550 0C for 5h produce γ-alumina. The γ-alumina was characterized by BET, XRD, SEM and NH3-TPD analysis. The XRD profile confirmed the crystalline structure of the solid acid catalyst γ-alumina. The NH3-TPD analysis showed the development of lewis acidity on the surface of hydrochloric acid treated γ-alumina. The effects of various parameters such as concentration of reactants, types of catalyst, weight of the catalyst, solvent, temperature and time of reaction have been studied. The kinetics of the reaction was also investigated
https://crimsonpublishers.com/pps/fulltext/PPS.000505.php
For more open access journals in Crimson Publishers
Please click on link: https://crimsonpublishers.com
For More Articles on Prime research material
Please click on: https://crimsonpublishers.com/pps/
Nitrogen-doped graphene-supported copper complex: a novel photocatalyst for C...Pawan Kumar
A copper(II) complex grafted to nitrogen-doped graphene (GrN700–CuC) was synthesized and then
demonstrated as an efficient photocatalyst for CO2 reduction into methanol under visible light irradiation
using a DMF/water mixture. The chemical and microstructural features of GrN700–CuC nanosheets were
studied by FTIR, XPS, XRD and HRTEM analyses. Owing to its truly heterogeneous nature, GrN700–CuC
could be easily recovered after the photocatalytic reaction and showed efficient recyclability for
subsequent runs.
Nitrogen-doped graphene-supported copper complex: a novel photocatalyst for C...Pawan Kumar
A copper(II) complex grafted to nitrogen-doped graphene (GrN700–CuC) was synthesized and then
demonstrated as an efficient photocatalyst for CO2 reduction into methanol under visible light irradiation
using a DMF/water mixture. The chemical and microstructural features of GrN700–CuC nanosheets were
studied by FTIR, XPS, XRD and HRTEM analyses. Owing to its truly heterogeneous nature, GrN700–CuC
could be easily recovered after the photocatalytic reaction and showed efficient recyclability for
subsequent runs.
Maiyalagan,Performance of carbon nanofiber supported pd ni catalysts for elec...kutty79
Carbon nanofibers (CNF) supported Pd–Ni nanoparticles have been prepared by chemical reduction
with NaBH4 as a reducing agent. The Pd–Ni/CNF catalysts were characterized by X-ray diffraction
(XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electrochemical
voltammetry analysis. TEM showed that the Pd–Ni particles were quite uniformly distributed on the
surface of the carbon nanofiber with an average particle size of 4.0 nm. The electro-catalytic activity of
the Pd–Ni/CNF for oxidation of ethanol was examined by cyclic voltammetry (CV). The onset potential
was 200mV lower and the peak current density four times higher for ethanol oxidation for Pd–Ni/CNF
compared to that for Pd/C. The effect of an increase in temperature from 20 to 60 ◦C had a great effect on
increasing the ethanol oxidation activity
Visible light assisted reduction of nitrobenzenes using Fe(bpy)3+2/rGOnanocom...Pawan Kumar
Visible-light-induced photocatalytic reduction of aromatic nitrobenzenes to the corresponding anilinesat room temperature using reduced graphene oxide (rGO) immobilized iron(II) bipyridine complex asphotocatalyst is described. The rGO-immobilized iron catalyst exhibited superior catalytic activity thanhomogeneous iron(II) bipyridine complex and much higher than metal free rGO photocatalysts. Theheterogeneous photocatalyst was found to be robust and could easily be recovered and reused for severalruns without any significant loss in photocatalytic activity.
V mn-mcm-41 catalyst for the vapor phase oxidation of o-xylenesunitha81
The role of V and Mn incorporated mesoporous molecular sieves was
investigated for the vapor phase oxidation of o-xylene. Mesoporous monometallic
V-MCM-41 (Si/V = 25, 50, 75 and 100), Mn-MCM-41 (Si/Mn = 50) and bimetallic
V-Mn-MCM-41 (Si/(V ? Mn) = 100) molecular sieves were synthesized by
a direct hydrothermal (DHT) process and characterized by various techniques such
as X-ray diffraction, DRUV-Vis spectroscopy, EPR, and transmission electron
microscopy (TEM). From the DRUV-Vis and EPR spectral study, it was found that
most of the V species are present as vanadyl ions (VO2?) in the as-synthesized
catalysts and as highly dispersed V5? ions in tetrahedral coordination in the calcined
catalysts. The activity of the catalysts was measured and compared with each other
for the gas phase oxidation of o-xylene in the presence of atmospheric air as an
oxidant at 573 K. Among the various catalysts, V-MCM-41 with Si/V = 50
exhibited high activity towards production of phthalic anhydride under the experimental
condition. The correlation between the phthalic anhydride selectivity and
the physico-chemical characteristics of the catalyst was found. It is concluded that
V5? species present in the MCM-41 silica matrix are the active sites responsible for
the selective formation of phthalic anhydride during the vapor phase oxidation of
o-xylene.
International Journal of Engineering Research and DevelopmentIJERD Editor
Electrical, Electronics and Computer Engineering,
Information Engineering and Technology,
Mechanical, Industrial and Manufacturing Engineering,
Automation and Mechatronics Engineering,
Material and Chemical Engineering,
Civil and Architecture Engineering,
Biotechnology and Bio Engineering,
Environmental Engineering,
Petroleum and Mining Engineering,
Marine and Agriculture engineering,
Aerospace Engineering.
Octahedral rhenium K4[Re6S8(CN)6] and Cu(OH)2cluster modifiedTiO2for the phot...Pawan Kumar
tOctahedral hexacyano rhenium K4[Re6S8(CN)6] cluster complexes were grafted onto photoactive Cu(OH)2cluster modified TiO2{Cu(OH)2/TiO2} support. The rhenium and copper cluster modified TiO2photocata-lyst combines the advantages of heterogeneous catalyst (facile recovery, recycling ability of the catalyst)with the reactivity, selectivity of the soluble molecular catalyst. The synthesized heterogeneous cata-lyst was found to be highly efficient photoredox catalyst for the reduction of CO2under visible lightirradiation. Methanol was found to be the major liquid product with the formation of hydrogen as a byproduct as determined with GC-FID and GC-TCD, respectively. The methanol yield after 24 h irradiationwas found to be 149 mol/0.1 g cat. for Re-cluster@Cu(OH)2/TiO2photocatalyst that is much higher than35 mol/0.1 g cat. for Cu(OH)2/TiO2and 75 mol/0.1 g cat. for equimolar rhenium cluster in the presenceof triethanolamine (TEOA) as a sacrificial donor. The quantum yields (MeOH) of Re-cluster@Cu(OH)2/TiO2and Cu(OH)2/TiO2were found to be 0.018 and 0.004 mol einstein−1, respectively. These values are muchhigher than those reported for other heterogeneous catalysts for six electron transfer reaction
Nitrogen-doped graphene-supported copper complex: a novel photocatalyst for C...Pawan Kumar
A copper(II) complex grafted to nitrogen-doped graphene (GrN700–CuC) was synthesized and then
demonstrated as an efficient photocatalyst for CO2 reduction into methanol under visible light irradiation
using a DMF/water mixture. The chemical and microstructural features of GrN700–CuC nanosheets were
studied by FTIR, XPS, XRD and HRTEM analyses. Owing to its truly heterogeneous nature, GrN700–CuC
could be easily recovered after the photocatalytic reaction and showed efficient recyclability for
subsequent runs.
Maiyalagan,Performance of carbon nanofiber supported pd ni catalysts for elec...kutty79
Carbon nanofibers (CNF) supported Pd–Ni nanoparticles have been prepared by chemical reduction
with NaBH4 as a reducing agent. The Pd–Ni/CNF catalysts were characterized by X-ray diffraction
(XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electrochemical
voltammetry analysis. TEM showed that the Pd–Ni particles were quite uniformly distributed on the
surface of the carbon nanofiber with an average particle size of 4.0 nm. The electro-catalytic activity of
the Pd–Ni/CNF for oxidation of ethanol was examined by cyclic voltammetry (CV). The onset potential
was 200mV lower and the peak current density four times higher for ethanol oxidation for Pd–Ni/CNF
compared to that for Pd/C. The effect of an increase in temperature from 20 to 60 ◦C had a great effect on
increasing the ethanol oxidation activity
Visible light assisted reduction of nitrobenzenes using Fe(bpy)3+2/rGOnanocom...Pawan Kumar
Visible-light-induced photocatalytic reduction of aromatic nitrobenzenes to the corresponding anilinesat room temperature using reduced graphene oxide (rGO) immobilized iron(II) bipyridine complex asphotocatalyst is described. The rGO-immobilized iron catalyst exhibited superior catalytic activity thanhomogeneous iron(II) bipyridine complex and much higher than metal free rGO photocatalysts. Theheterogeneous photocatalyst was found to be robust and could easily be recovered and reused for severalruns without any significant loss in photocatalytic activity.
V mn-mcm-41 catalyst for the vapor phase oxidation of o-xylenesunitha81
The role of V and Mn incorporated mesoporous molecular sieves was
investigated for the vapor phase oxidation of o-xylene. Mesoporous monometallic
V-MCM-41 (Si/V = 25, 50, 75 and 100), Mn-MCM-41 (Si/Mn = 50) and bimetallic
V-Mn-MCM-41 (Si/(V ? Mn) = 100) molecular sieves were synthesized by
a direct hydrothermal (DHT) process and characterized by various techniques such
as X-ray diffraction, DRUV-Vis spectroscopy, EPR, and transmission electron
microscopy (TEM). From the DRUV-Vis and EPR spectral study, it was found that
most of the V species are present as vanadyl ions (VO2?) in the as-synthesized
catalysts and as highly dispersed V5? ions in tetrahedral coordination in the calcined
catalysts. The activity of the catalysts was measured and compared with each other
for the gas phase oxidation of o-xylene in the presence of atmospheric air as an
oxidant at 573 K. Among the various catalysts, V-MCM-41 with Si/V = 50
exhibited high activity towards production of phthalic anhydride under the experimental
condition. The correlation between the phthalic anhydride selectivity and
the physico-chemical characteristics of the catalyst was found. It is concluded that
V5? species present in the MCM-41 silica matrix are the active sites responsible for
the selective formation of phthalic anhydride during the vapor phase oxidation of
o-xylene.
International Journal of Engineering Research and DevelopmentIJERD Editor
Electrical, Electronics and Computer Engineering,
Information Engineering and Technology,
Mechanical, Industrial and Manufacturing Engineering,
Automation and Mechatronics Engineering,
Material and Chemical Engineering,
Civil and Architecture Engineering,
Biotechnology and Bio Engineering,
Environmental Engineering,
Petroleum and Mining Engineering,
Marine and Agriculture engineering,
Aerospace Engineering.
Octahedral rhenium K4[Re6S8(CN)6] and Cu(OH)2cluster modifiedTiO2for the phot...Pawan Kumar
tOctahedral hexacyano rhenium K4[Re6S8(CN)6] cluster complexes were grafted onto photoactive Cu(OH)2cluster modified TiO2{Cu(OH)2/TiO2} support. The rhenium and copper cluster modified TiO2photocata-lyst combines the advantages of heterogeneous catalyst (facile recovery, recycling ability of the catalyst)with the reactivity, selectivity of the soluble molecular catalyst. The synthesized heterogeneous cata-lyst was found to be highly efficient photoredox catalyst for the reduction of CO2under visible lightirradiation. Methanol was found to be the major liquid product with the formation of hydrogen as a byproduct as determined with GC-FID and GC-TCD, respectively. The methanol yield after 24 h irradiationwas found to be 149 mol/0.1 g cat. for Re-cluster@Cu(OH)2/TiO2photocatalyst that is much higher than35 mol/0.1 g cat. for Cu(OH)2/TiO2and 75 mol/0.1 g cat. for equimolar rhenium cluster in the presenceof triethanolamine (TEOA) as a sacrificial donor. The quantum yields (MeOH) of Re-cluster@Cu(OH)2/TiO2and Cu(OH)2/TiO2were found to be 0.018 and 0.004 mol einstein−1, respectively. These values are muchhigher than those reported for other heterogeneous catalysts for six electron transfer reaction
Reduced graphene oxide–CuO nanocomposites for photocatalyticconversion of CO2...Pawan Kumar
Reduced graphene oxide (rGO)–copper oxide nanocomposites are prepared by covalent grafting of CuOnanorods on the rGO skeleton. Chemical and structural features of rGO–CuO nanocomposites are probedby FTIR, XPS, XRD and HRTEM analyses. Photocatalytic potential of rGO–CuO nanocomposites is exploredfor reduction of CO2into the methanol under the visible light irradiation. The breadth of CuO nanorods andthe oxidation state of Cu in the rGO–CuO/Cu2O nanocomposites are systematically varied to investigatetheir photocatalytic activities. The pristine CuO nanorods exhibited very low photocatalytic activity owingto fast recombination of charge carriers and yielded 175 mol g−1methanol, whereas rGO–Cu2O andrGO–CuO exhibited significantly improved photocatalytic activities and yielded five (862 mol g−1) andseven (1228 mol g−1) folds methanol, respectively. The superior photocatalytic activity of CuO in therGO–CuO nanocomposites was attributed to slow recombination of charge carriers and efficient transferof photo-generated electrons through the rGO skeleton. This study further excludes the use of scavengingdonor.
Reduced graphene oxide–CuO nanocomposites for photocatalyticconversion of CO2...Pawan Kumar
tReduced graphene oxide (rGO)–copper oxide nanocomposites are prepared by covalent grafting of CuOnanorods on the rGO skeleton. Chemical and structural features of rGO–CuO nanocomposites are probedby FTIR, XPS, XRD and HRTEM analyses. Photocatalytic potential of rGO–CuO nanocomposites is exploredfor reduction of CO2into the methanol under the visible light irradiation. The breadth of CuO nanorods andthe oxidation state of Cu in the rGO–CuO/Cu2O nanocomposites are systematically varied to investigatetheir photocatalytic activities. The pristine CuO nanorods exhibited very low photocatalytic activity owingto fast recombination of charge carriers and yielded 175 mol g−1methanol, whereas rGO–Cu2O andrGO–CuO exhibited significantly improved photocatalytic activities and yielded five (862 mol g−1) andseven (1228 mol g−1) folds methanol, respectively. The superior photocatalytic activity of CuO in therGO–CuO nanocomposites was attributed to slow recombination of charge carriers and efficient transferof photo-generated electrons through the rGO skeleton. This study further excludes the use of scavengingdonor.
Production of Renewable Fuels by the Photocatalytic Reduction of CO2 using Ma...Pawan Kumar
The photo-reductive performance of natural ilmenite was boosted and the production of renewable fuels from the reduction of CO2 was enhanced by doping the natural mineral with magnesium. The doping was achieved by high energy ball milling in the presence of MgO and Mg(NO3)2. The photo-reduction of CO2 in aqueous solution led to the evolution of H2, CH4, C2H4, and C2H6, and the insertion of Mg in the structure of ilmenite enabled increases of up to 1245% in the fuel production yield, reaching total production of 210.9 µmol h-1 gcat-1. Displacements of the conduction band to more negative potentials were evidenced for the samples doped with magnesium. Indirect effects such as increases in the valence band maximum, and the introduction of intermediate energy levels were also evidenced through the measurement of the crystallite size and the determination of the band structure of the materials. Mott-Schottky analyses of the samples showed the n-type nature of the semiconductor materials and enabled the estimation of the density of charge carriers, which strongly influenced the photocatalytic performance. The strong potential of the application of natural ilmenite in gas phase artificial photosynthesis was proved by the evaluation of CO2 reduction in gas conditions, which allowed the enhancement in the selectivity and significantly increased the production of CH4 as compared to aqueous solution, reaching an important yield of CH4 of 16.1 µmol h-1 gcat-1.
Performance of carbon nanofiber supported pd–ni catalysts for electro oxidati...suresh899
Carbon nanofibers (CNF) supported Pd–Ni nanoparticles have been prepared by chemical reduction
with NaBH4 as a reducing agent. The Pd–Ni/CNF catalysts were characterized by X-ray diffraction
(XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electrochemical
voltammetry analysis. TEM showed that the Pd–Ni particles were quite uniformly distributed on the
surface of the carbon nanofiber with an average particle size of 4.0 nm. The electro-catalytic activity of
the Pd–Ni/CNF for oxidation of ethanol was examined by cyclic voltammetry (CV). The onset potential
was 200mV lower and the peak current density four times higher for ethanol oxidation for Pd–Ni/CNF
compared to that for Pd/C. The effect of an increase in temperature from 20 to 60 ◦C had a great effect on
increasing the ethanol oxidation activity.
Performance of carbon nanofiber supported pd–ni catalysts for electro oxidati...sunilove
Carbon nanofibers (CNF) supported Pd–Ni nanoparticles have been prepared by chemical reduction
with NaBH4 as a reducing agent. The Pd–Ni/CNF catalysts were characterized by X-ray diffraction
(XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electrochemical
voltammetry analysis. TEM showed that the Pd–Ni particles were quite uniformly distributed on the
surface of the carbon nanofiber with an average particle size of 4.0 nm. The electro-catalytic activity of
the Pd–Ni/CNF for oxidation of ethanol was examined by cyclic voltammetry (CV). The onset potential
was 200mV lower and the peak current density four times higher for ethanol oxidation for Pd–Ni/CNF
compared to that for Pd/C. The effect of an increase in temperature from 20 to 60 ◦C had a great effect on
increasing the ethanol oxidation activity.
Metal-organic hybrid: Photoreduction of CO2 using graphitic carbon nitride su...Pawan Kumar
A novel heteroleptic iridium complex supported on graphitic carbon nitride was synthesized and used for photoreduction of carbon dioxide under visible light irradiation. The methanol yield obtained after 24 h irradiation was 9934 μmol g−1cat (TON 1241 with respect to Ir) by using triethylamine (TEA) as a sacrificial donor, which was significantly higher as compared to the semiconductor carbon nitride 145 μmol g−1cat under identical conditions. The presence of triethylamine was found to be vital for the higher methanol yield. After the reaction, the photocatalyst could easily be recovered and reused for subsequent six runs without significant loss in photo activity.
Metal-organic hybrid: Photoreduction of CO2 using graphitic carbon nitride su...Pawan Kumar
A novel heteroleptic iridium complex supported on graphitic carbon nitride was synthesized and used
for photoreduction of carbon dioxide under visible light irradiation. The methanol yield obtained after
24 h irradiation was 9934 mmol g1cat (TON 1241 with respect to Ir) by using triethylamine (TEA) as a
sacrificial donor, which was significantly higher as compared to the semiconductor carbon nitride
145 mmol g1cat under identical conditions. The presence of triethylamine was found to be vital for the
higher methanol yield. After the reaction, the photocatalyst could easily be recovered and reused for
subsequent six runs without significant loss in photo activity.
Metal-organic hybrid: Photoreduction of CO2 using graphitic carbon nitride su...Pawan Kumar
A novel heteroleptic iridium complex supported on graphitic carbon nitride was synthesized and used
for photoreduction of carbon dioxide under visible light irradiation. The methanol yield obtained after
24 h irradiation was 9934 mmol g1cat (TON 1241 with respect to Ir) by using triethylamine (TEA) as a
sacrificial donor, which was significantly higher as compared to the semiconductor carbon nitride
145 mmol g1cat under identical conditions. The presence of triethylamine was found to be vital for the
higher methanol yield. After the reaction, the photocatalyst could easily be recovered and reused for
subsequent six runs without significant loss in photo activity.
Metal-organic hybrid: Photoreduction of CO2 using graphitic carbon nitride su...
Sdarticle (2)
1. Tetrahedron 62 (2006) 2922–2926
Palladium supported on hydrotalcite as a catalyst
for the Suzuki cross-coupling reaction
Jose´ R. Ruiz,* Ce´sar Jime´nez-Sanchidria´n* and Manuel Mora
Departamento de Quı´mica Orga´nica, Universidad de Co´rdoba, Campus de Rabanales, Edificio Marie Curie,
Ctra. Nnal. IV-A km. 396, 14014 Co´rdoba, Spain
Received 22 November 2005; revised 19 December 2005; accepted 4 January 2006
Available online 20 January 2006
Abstract—The efficiency of various palladium salts as catalysts in the Suzuki cross-coupling reaction, and the influence of the base and
temperature used on its conversion, were studied. The use of PdCl2 supported on hydrotalcite as catalyst in the presence of potassium
carbonate as base was found to provide the best results. Reaction temperatures above 90 8C ensured conversion levels on a par with those for
many homogeneous catalysts.
q 2006 Elsevier Ltd. All rights reserved.
1. Introduction
The palladium-catalysed Suzuki cross-coupling reaction has
for some time been one of the most powerful tools for the
formation of carbon–carbon bonds in organic synthesis.1–3
In most cases, the reaction involves a homogeneous
palladium catalyst and a ligand of variable nature such as
a phosphine.2,4–6 Recently, however, some cross-coupling
processes have used palladium supported on various types
of supports such as sepiolites,7,8 silica,9 zeolites and zeolitic
materials,10–12 layered double hydroxides,13,14 carbon15,16
and organic complexes bound to inorganic solids.17–21
These heterogeneous catalysts are being increasingly used
to circumvent some shortcomings of homogeneous catalysts
such as the need to remove the catalyst after the reaction, its
poor reusability and potential environmental pollution
problems. Also, palladium ligands and precursors are
expensive, which severely restricts their industrial use.
Hydrotalcite is a naturally occurring mineral of the layered
double hydroxide family that constitutes a major class of
anionic clay materials. Hydrotalcite is structurally related to
brucite [Mg(OH)2]: magnesium cations are at the centres of
octahedra the vertices of which are occupied by hydroxyl
groups to form stacks. In hydrotalcite, some Mg2C ions are
replaced by aluminium cations, which introduces a charge
deficiency in the layers. In order to ensure electroneutrality
in the overall structure, the positive charge is countered by
carbonate ions present in a disorderly manner in the
interlayer spacing, which also contains crystallization
water (Fig. 1).22 Hydrotalcite has been extensively used
by our research group in organic processes such as the
epoxidation of limonene,23,24 the Meerwein–Ponndorf–
Verley reduction25–27 and the a-arylation of diethyl
malonate.28
In this work, we prepared various catalysts consisting of
Pd2C supported on hydrotalcite by using various precursor
salts and employed them in the Suzuki cross-coupling
reaction in the presence of various inorganic bases (see
Scheme 1). We studied the influence of the aryl halide and
temperature used. All catalysts and the hydrotalcite
0040–4020/$ - see front matter q 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2006.01.004
Mg–Al–(OH)x
layers
Hydrogen
bonds
Water and carbonate ions
Hydrogen
Oxygen
Carbon
Magnesium or Aluminium
Figure 1. Structure of hydrotalcite.
Keywords: Suzuki cross-coupling; Hydrotalcite; Palladium; Boronic acid.
* Corresponding authors. Tel.: C34 957 216 638; fax: C34 957 212 066;
e-mail: qo1ruarj@uco.es
2. J. R. Ruiz et al. / Tetrahedron 62 (2006) 2922–2926 2923
precursor were characterized in terms of structure and
surface properties by using various instrumental techniques.
2. Results and discussion
2.1. Characterization of catalysts
Based on the elemental analysis, the hydrotalcite and the
palladium catalysts that were supported on it had an Mg/Al
ratio of 2:1 and a Pd2C content of 1%.
The XRD analysis of solid HT (Fig. 2) revealed a high
crystallinity. As can be seen from the XRD pattern, the solid
had a typical structure of stacked layers similar to those
previously found by Reichle et al.29 in hydrotalcites.
Therefore, using the hydrotalcite as a support for our Pd
catalysts caused no structural change in the mineral as the
catalysts deposited on its outer surface only (XRD patterns
for the catalysts not shown). Some anions from the
palladium salt may have been exchanged with the carbonate
ions in the interlayer spacing. Such an exchange would have
altered the interlayer distance, which is defined by the lattice
parameter c (viz. three times the distance between two
adjacent layers). Based on the position of the strongest line,
corresponding to the crystallographic indices (003), the
lattice distance, d003, was calculated and used to determine c
(cZ3$d003, Table 1). The c values thus obtained differed,
which suggests that some carbonate ions were replaced by
the anions of the palladium salt; however, the difference was
so small that it had no practical consequences—particularly
in catalytic terms.
Table 1 also shows the specific surface area of the
hydrotalcite and catalysts. As can be seen, it increased
slightly upon deposition of the metal.
2.2. Suzuki reaction
The Suzuki cross-coupling reaction is known to require a
base in order to abstract the proton during the reductive
elimination of the organopalladium intermediate leading to
the end-product.1 The bases most frequently used in this
process are carbonates or acetates of alkaline metals such as
sodium or potassium, as well as some organic amines. The
best choice in each case must be determined on an
individual basis. To this end, we used our hydrotalcite-supported
Pd catalysts in the Suzuki reaction between
phenylboronic acid and bromobenzene in the presence of
various inorganic bases. The sole reaction product obtained
in all cases was biphenyl.
Table 2 shows the conversion results and Figure 3 the
temporal variation of the conversion for the three studied
catalysts in the presence of K2CO3 as the base. All reactions
exhibited a linear relationship between the natural logarithm
of the bromobenzene concentration and the reaction time,
which suggests that the reaction is first-order in such a
concentration:
Ln ðc0=cÞZkt
where c0 and c are the bromobenzene concentrations at
times zero and t, respectively, k the rate constant and t time.
B(OH)2 + Br
Pd-LDH
Base
Scheme 1. Suzuki cross-coupling reaction studied.
Figure 2. XRD patterns for HT.
Table 1. Specific surface area and lattice parameter c for the catalysts
Catalyst c (A)a SBET (m2/g)b
HT 23.1844 75.7
HT–PdCl2 23.1075 86.5
HT–Pd(AcO)2 23.2647 86.2
HT–PdCl4 23.2227 87.3
a Lattice parameter.
b Specific surface area.
Table 2. Conversion obtained in the Suzuki cross-coupling reactiona
Catalyst Base Conversion (%)b k (hK1)c
HT–PdCl2 K2CO3 47.2 0.312
Rb2CO3 2.1 0.003
CsF 2.2 0.003
K3PO4 7.1 0.009
HT–Pd(AcO)2 K2CO3 27.21 0.171
Rb2CO3 1.3 0.004
CsF 2.5 0.005
K3PO4 10.64 0.047
HT–PdCl4 K2CO3 25.6 0.137
Rb2CO3 3.9 0.006
CsF 1.0 0.003
K3PO4 8.24 0.024
Blank-1d K2CO3 0 —
Blank-2e — 0 —
a Reactions conditions: 1.98 mmol PhBr; 3 mmol PhB(OH)2; 3.96 mmol
K2CO3; 0.24 g (0.04 mol%); 5 mL toluene, TZ55 8C.
b Conversion to biphenyl (reaction time: 3 h).
c Rate constant.
d Blank without catalyst.
e Blank without base.
45 HT-Pd-1
0 50 100 150 200
Time (min)
Conversion (% Biphenyl)
30
15
0
HT-Pd-2
HT-Pd-3
Figure 3. Temporal variation of the biphenyl conversion in the Suzuki
cross-coupling reaction.
3. 2924 J. R. Ruiz et al. / Tetrahedron 62 (2006) 2922–2926
As can be seen from Table 2, K2CO3 was the base providing
the best conversion and catalytic activity results, well ahead
of K3PO4. The other bases studied exhibited very poor
conversion. Also, catalyst PdCl2, in the presence of K2CO3,
was that providing the best results; it was therefore adopted
for further testing, which included examining the influence
of the reaction temperature and aryl halide, as well as
catalyst leaching and reuse tests.
The influence of temperature on the conversion and rate of
the Suzuki reaction between bromobenzene and phenyl-boronic
acid using catalyst Pd–HT-1 in the presence of
K2CO3 was examined at 55, 75, 90 and 110 8C. Table 3
shows the biphenyl conversion and rate constant obtained as
described above. As expected, raising the temperature
substantially increased the conversion, which exceeded
90% after only 3 h of reaction at 90 8C. These results are
quite good; in fact, they are as good as or even better than
those obtained with other heterogeneous catalysts and many
homogeneous ones. The activation energy for the process as
calculated from an Arrhenius plot was 47 kJ/mol.
We then studied the influence of the phenyl halide on the
coupling reaction, using the previous catalyst (HT–PdCl2)
and base (K2CO3). One of the major shortcomings of this
process is its inefficiency with aryl chlorides or fluorides as
substrates. This has aroused much interest in developing
efficient catalysts (particularly aryl chlorides, which are
more readily available and inexpensive than aryl bromides).
Most catalysts for the Suzuki reaction are of the
homogeneous type, and not all provide acceptable conver-sion.
4,30–33 We used both chlorobenzene and fluorobenzene
and found the reaction to develop as summarized in Table 4.
As can be seen, chlorobenzene provided good results: the
conversion amounted to 28% after only 3 h of reaction at
quite a low temperature (558C). Fluorobenzene gave
poorer, but still promising, results; in fact, aryl fluorides
started to be used in this process only 2 years ago34,35 as
the C–F bond is the strongest of all C–halogen bonds and its
cleavage had been achieved in only a few cases and never
with heterogeneous palladium catalysts.
The heterogeneous character of the Pd2C catalyst was
determined in a leaching test on the reaction between
bromobenzene and phenylboronic acid at 55 8C using solid
HT–PdCl2 as the catalyst and K2CO3 as the base. After
30 min, the reaction was stopped—the biphenyl conversion
at the time was 23.1%—to remove the catalyst and base by
filtration. The remaining solution was supplied with K2CO3
and the reaction allowed to proceed at 55 8C for a further
24 h. The biphenyl conversion thus obtained was identical,
so the catalytic action of Pd2C was of the heterogeneous
type. Also, we have made experiments without bromoben-zene,
and the conversion to biphenyl is negligible, so we
rule out the homocoupling of the boronic acid.
Finally, we studied the reusability of the catalyst, again by
using the reaction between bromobenzene and phenyl-boronic
acid at 55 8C in the presence of HT–PdCl2 as the
catalyst and K2CO3 as the base. Figure 4 shows the results
obtained after three catalytic cycles; as can be clearly seen,
the catalyst lost some activity after each reuse. Therefore,
reusing the catalyst entails its prior reactivation. This is also
the case with other heterogeneous catalysts used in the
Suzuki reaction.
3. Conclusions
100
75
50
25
The results obtained in this work show that the deposition of
palladium salts on hydrotalcite is an effective method for
preparing solids that are active catalysts in the Suzuki cross-coupling
reaction—particularly those obtained by deposit-ing
PdCl2. The biphenyl conversion in the reaction between
bromobenzene and phenylboronic acid was found to depend
on the particular base used, of which K2CO3 proved the best
among those tested. These catalysts are also active in the
reduction of chloro- and fluorobenzenes, where few
catalysts—particularly of the heterogeneous type—are
effective. The temperature is one other crucial variable
here. The activation energy for the process was calculated to
Table 3. Conversion obtained in the Suzuki cross-coupling reaction at a
variable temperaturea
T (8C) Conversion (%)b k (hK1)c
55 47.2 0.312
75 72.4 1.795
90 90.6 2.873
110 95.3 4.168
a Reactions conditions: 1.98 mmol PhBr; 3 mmol PhB(OH)2; 3.96 mmol
K2CO3; 0.24 g HT–Pd-1 1 (0.04 mol%); 5 mL toluene.
b Conversion to biphenyl (reaction time: 3 h).
c Rate constant.
Table 4. Influence of the phenyl halide used in the Suzuki cross-coupling
reactiona
Phenylhalide Conversion (%)b k (hK1)c
Ph-F 14.9 0.090
Ph-Cl 28.1 0.191
Ph-Br 47.2 0.312
a Reactions conditions: 1.98 mmol PhX; 3 mmol PhB(OH)2; 3.96 mmol
K2CO3; 0.24 g HT–Pd-1 1 (0.04 mol%); 5 mL toluene, TZ55 8C.
b Conversion to biphenyl (reaction time: 3 h).
c Rate constant.
Cycle of reuse
Conversion (% of biphenyl)
0
Figure 4. Influence of catalyst reuse on the biphenyl conversion in the
Suzuki cross-coupling reaction.
4. J. R. Ruiz et al. / Tetrahedron 62 (2006) 2922–2926 2925
be 47 kJ/mol. Finally, testing revealed the catalytic process
to be completely heterogeneous in nature.
4. Experimental
The hydrotalcite used was prepared by mixing two solutions
of Mg(NO3)2$6H2O and Al(NO3)3$9H2O in a 2:1 ratio,
using a coprecipitation method described elsewhere.36 In a
typical synthetic run, a solution containing 0.3 mol of
Mg(NO3)2$6H2O and 0.15 mol of Al(NO3)3$9H2O in
250 mL of de-ionized water was used. The solution was
slowly dropped over 500 mL of an Na2CO3 solution at
pH 10 at 60 8C under vigorous stirring. During precipitation,
the pH was kept constant by adding appropriate volumes of
1 M NaOH. The suspension obtained was kept at 80 8C for
24 h, after which it was filtered and washed with 2 L of de-ionized
water. Any residual nitrate ions in the hydrotalcite
structure were removed by exchange with carbonate ions.
For this purpose, 2.5 g of the LDH was dispersed in 125 mL
of de-ionized water, the dispersion being supplied with
250 mg of Na2CO3 and refluxed for 2 h. Then, the solid was
separated by centrifugation and the water discarded. The
hydrotalcite obtained following exchange with carbonate
ions was designated HT.
The hydrotalcite was used as a support for the palladium
catalysts, which were obtained by impregnation, a method
previously used by our group to prepare Pd catalysts
supported on various materials such as silica and aluminium
orthophosphate.37,38 The catalysts used in this work were
obtain as follows: the amounts of PdCl2, Pd(AcO)2 and
Na2PdCl4 required to obtain a final Pd content of 1% in the
catalyst were dissolved in N,N-dimethylformamide and
supplied with 2 g of hydrotalcite in a flask. The mixture was
kept at room temperature in a rotavapor for 24 h, after which
the solvent was evaporated at a low pressure to obtain the
three supported palladium catalysts, which were designated
HT–PdCl2, HT–Pd(AcO)2 and HT–PdCl4 according to
whether they were obtained from the chloride, acetate or
tetrachloropalladate, respectively, as precursor.
The catalysts and the hydrotalcite support were charac-terized
by using various instrumental techniques including
X-ray diffraction and nitrogen adsorption.
Acknowledgements
The authors gratefully acknowledge funding from Spain’s
Ministerio de Ciencia y Tecnologı´a, Plan Nacional de
Investigacio´n, Desarrollo e Innovacio´n Tecnolo´gica, Fon-dos
Feder and Consejerı´a de Educacio´n y Ciencia de la
Junta de Andalucı´a.
References and notes
1. Miyaura, N.; Suzuki, A. Chem. Rev. 1995, 95, 2457–2483.
2. Suzuki, A. J. Organomet. Chem. 1999, 576, 147–168.
3. Kotha, S.; Lahiri, K.; Kashinath, D. Tetrahedron 2002, 58,
9633–9695.
4. Cioffi, C. L.; Spencer, W. T.; Richards, J. J.; Herr, R. J. J. Org.
Chem. 2004, 69, 2210–2212.
5. Feuerstein, M.; Doucet, H.; Santelli, M. Tetrahedron Lett.
2001, 42, 5659–5662.
6. Baillie, C.; Chen, W.; Xiao, J. Tetrahedron Lett. 2001, 42,
9085–9088.
7. Corma, A.; Garcı´a, H.; Leyva, A.; Primo, A. Appl. Catal., A:
Gen. 2004, 257, 77–83.
8. Shimizu, K.; Maruyama, R.; Komai, S.; Kodama, T.;
Kitayama, Y. J. Catal. 2004, 227, 202–209.
9. Shimizu, K.; Koizumi, S.; Hatamachi, T.; Yoshida, H.;
Komai, S.; Kodama, T.; Kitayama, Y. J. Catal. 2004, 228,
141–151.
10. Kosslick, H.; Monnich, I.; Paetzold, E.; Fuhrmann, H.;
Fricke, R.; Muller, D.; Oehme, G. Microporous Mesoporous
Mater. 2001, 44–45, 537–545.
11. Corma, A.; Garcı´a, H.; Leyva, A. Appl. Catal., A: Gen. 2002,
236, 179–185.
12. Artok, L.; Bulut, H. Tetrahedron Lett. 2004, 45, 3881–3884.
13. Choudary, B. M.; Roy, M.; Roy, S.; Kantam, M. L. J. Mol.
Catal. A: Chem. 2005, 241, 215–218.
14. Choudary, B. M.; Madhi, S.; Chowdari, N. S.; Kantam, M. L.;
Sreedhar, B. J. Am. Chem. Soc. 2002, 124, 14127–14136.
15. Dyer, U. C.; Shapland, P. D.; Tiffin, P. D. Tetrahedron Lett.
2004, 42, 1765–1767.
16. Gruber, M.; Chouzier, S.; Koehler, K.; Djakovitch, L. Appl.
Catal., A: Gen. 2004, 265, 161–169.
17. Paul, S.; Clark, J. H. J. Mol. Catal. A: Chem. 2004, 215,
107–111.
18. Baleizao, C.; Corma, A.; Garcı´a, H.; Leyva, A. J. Org. Chem.
2004, 69, 439–446.
19. Phan, N. T. S.; Brown, D. H.; Styring, P. Tetrahedron Lett.
2004, 45, 7915–7919.
20. Blanco, B.; Brissart, M.; Moreno-Man˜as, M.; Pleixats, R.;
Medhi, A.; Reye´, C.; Bouquillon, S.; Henin, F.; Muzart, J.
Appl. Catal., A: Gen. 2006, 297, 117–124.
21. Alonso, F.; Beletskaya, I. P.; Yus, M. Tetrahedron 2003, 61,
11771–11835.
22. Carlino, S. Chem. Br. 1997, 33, 59–65.
23. Aramendia, M. A.; Borau, V.; Jime´nez, C.; Luque, J. M.;
Marinas, J. M.; Romero, F. J.; Ruiz, J. R.; Urbano, F. J. Stud.
Surf. Sci. Catal. 2000, 130, 1667–1672.
24. Aramendia, M. A.; Borau, V.; Jime´nez, C.; Luque, J. M.;
Marinas, J. M.; Ruiz, J. R.; Urbano, F. J. Appl. Catal., A: Gen.
2001, 216, 257–265.
25. Aramendia, M. A.; Borau, V.; Jime´nez, C.; Marinas, J. M.;
Ruiz, J. R.; Urbano, F. J. J. Chem. Soc., Perkin Trans. 2 2002,
1122–1125.
26. Aramendia, M. A.; Borau, V.; Jime´nez, C.; Marinas, J. M.;
Ruiz, J. R.; Urbano, F. J. Appl. Catal., A: Gen. 2003, 249, 1–9.
27. Aramendia, M. A.; Borau, V.; Jime´nez, C.; Marinas, J. M.;
Ruiz, J. R.; Urbano, F. J. Appl. Catal., A: Gen. 2003, 255,
301–308.
28. Aramendia, M. A.; Borau, V.; Jime´nez, C.; Marinas, J. M.;
Ruiz, J. R.; Urbano, F. J. Tetrahedron Lett. 2002, 43,
2847–2849.
29. Reichle, W. T.; Kang, S. Y.; Everhardt, D. S. J. Catal. 1986,
101, 352–359.
30. Littke, A. F.; Fu, G. C. Angew. Chem., Int. Ed. 1998, 37,
3387–3388.
5. 2926 J. R. Ruiz et al. / Tetrahedron 62 (2006) 2922–2926
31. Bedford, R. B.; Blake, M. E.; Butts, C. P.; Holder, D. J. Chem.
Soc., Chem. Commun. 2003, 466–467.
32. Mukherjee, A.; Sarkar, A. Tetrahedron Lett. 2004, 45,
9525–9528.
33. Kostas, I. D.; Andreadaki, F. J.; Kovala-Demertzi, D.;
Prentjas, C.; Demertzis, M. A. Tetrahedron Lett. 2005, 46,
1967–1970.
34. Widdowson, D. A.; Wilhelm, R. J. Chem. Soc., Chem.
Commun. 2003, 578–579.
35. Kim, Y. M.; Yu, S. J. Am. Chem. Soc. 2003, 125, 1696–1697.
36. Aramendı´a, M. A.; Avile´s, Y.; Borau, V.; Luque, J. M.;
Marinas, J. M.; Ruiz, J. R.; Urbano, F. J. J. Mater. Chem. 1999,
9, 1603–1607.
37. Aramendia, M. A.; Borau, V.; Jime´nez, C.; Marinas, J. M.;
Romero, F. J.; Ruiz, J. R. React. Kinet. Catal. Lett. 1995, 55,
341–347.
38. Aramendı´a, M. A.; Borau, V.; Jime´nez, C.; Marinas, J. M.;
Sempere, M. E.; Urbano, F. J. Appl. Catal. 1990, 63, 375–383.