The Experts below are selected from a list of 3795 Experts worldwide ranked by ideXlab platform
Ramesh Chandra - One of the best experts on this subject based on the ideXlab platform.
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Phosphotungstic Acid an efficient catalyst for the aqueous phase synthesis of bis 4 hydroxycoumarin 3 yl methanes
Catalysis Letters, 2010Co-Authors: Prashant Singh, Pradeep Kumar, Anju Katyal, Rashmi Kalra, Sujata K Dass, Satya Prakash, Ramesh ChandraAbstract:In this present work, we report that Phosphotungstic Acid provides a simple, efficient and environmentally benign route is a two-component one-pot domino Knoevenagel-type condensation/Michael reaction between 4-coumarin derivative and an aldehyde in water as a solvent in shorter duration with high yields.
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Phosphotungstic Acid an efficient catalyst for the aqueous phase synthesis of bis 4 hydroxycoumarin 3 yl methanes
Catalysis Letters, 2010Co-Authors: Prashant Singh, Pradeep Kumar, Anju Katyal, Rashmi Kalra, Sujata K Dass, Satya Prakash, Ramesh ChandraAbstract:In this present work, we report that Phosphotungstic Acid provides a simple, efficient and environmentally benign route is a two-component one-pot domino Knoevenagel-type condensation/Michael reaction between 4-coumarin derivative and an aldehyde in water as a solvent in shorter duration with high yields. Open image in new window
Hari C Bajaj - One of the best experts on this subject based on the ideXlab platform.
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Phosphotungstic Acid as an efficient catalyst for allylation of isatins and n tert butyloxycarbonylamido sulfones under solvent free conditions
ChemInform, 2015Co-Authors: Debashis Ghosh, S Saravanan, Naveen Gupta, Sayed H R Abdi, Noorul H Khan, Rukhsana I Kureshy, Hari C BajajAbstract:An efficient procedure for the allylation of less-reactive isatins and N-protected amido sulfones is developed using Phosphotungstic Acid as catalyst.
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magnetic fe3o4 nanoparticle supported Phosphotungstic Acid as a recyclable catalyst for the kabachnik fields reaction of isatins imines and aldehydes under solvent free conditions
ChemInform, 2015Co-Authors: Mohd Nazish, S Saravanan, Sayed H R Abdi, Noorul H Khan, Rukhsana I Kureshy, Prathibha Kumari, Hari C BajajAbstract:Phosphotungstic Acid supported on nanoparticles of Fe3O4—SiO2 is an efficient catalyst for the solvent-free hydrophosphonylation of aldehydes (I) and isatins (VIII) leading to corresponding α-hydroxyphosphonates (III) and (IX), respectively.
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magnetic fe3o4 nanoparticle supported Phosphotungstic Acid as a recyclable catalyst for the kabachnik fields reaction of isatins imines and aldehydes under solvent free conditions
ChemPlusChem, 2014Co-Authors: Mohd Nazish, S Saravanan, Sayed H R Abdi, Noorul H Khan, Rukhsana I Kureshy, Prathibha Kumari, Hari C BajajAbstract:Magnetic-nanoparticle-supported Phosphotungstic Acid has been used to efficiently catalyze the hydrophosphonylation reaction of isatins, imines, and aldehydes using dimethyl and diethyl phosphite as a nucleophile to give the corresponding α-hydroxy and α-amino phosphonates in excellent yields for a wide range of substrates. The reaction conditions were simple, green, and efficient. The catalyst was recycled up to five times with retention of its activity. Based on the NMR spectroscopy studies, a probable catalytic cycle was proposed.
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Phosphotungstic Acid as an efficient catalyst for allylation of isatins and n tert butyloxycarbonylamido sulfones under solvent free conditions
Asian Journal of Organic Chemistry, 2014Co-Authors: Debashis Ghosh, S Saravanan, Naveen Gupta, Sayed H R Abdi, Noorul H Khan, Rukhsana I Kureshy, Hari C BajajAbstract:The present work demon- strates the use of Phosphotungstic Acid (H3PW12O40·H2O) as an efficient catalyst for the allylation of isatin de- rivatives as well as N-tert-butyloxycar- bonyl (Boc)-a-amido sulfones with al- lyltributyltin as an allylating agent under solvent-free conditions at room temperature. Excellent allylation product yields of up to 99 % for the isatins substrates and good to excel- lent yields of up to 98 % for the N- Boc a-amido sulfones were obtained. The present allylation protocol is scal- able as demonstrated by allylation of N-methylisatin at 1 g scale. Based on 1 H, 13 C, and 31 P NMR studies a catalyt- ic cycle was proposed for allylation of isatins as well as N-Boc amido sul- fones. The allylation products N-Boc homoallyl amines were successfully epoxidized to get multifunctional compounds, which are valuable inter- mediates for natural products and bio- active compounds.
Yan Xiang - One of the best experts on this subject based on the ideXlab platform.
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a poly vinyl alcohol based composite membrane with immobilized Phosphotungstic Acid molecules for direct methanol fuel cells
Electrochimica Acta, 2017Co-Authors: Haining Wang, Yan XiangAbstract:Abstract Phosphotungstic Acid (H3PW12O40, HPW) molecules were anchored onto carbon nanotubes (CNTs) by electrostatic self-assembly using poly(diallyldimethylammonium chloride) (PDDA); subsequent incorporation of these particles into poly(vinyl alcohol) (PVA) afforded a methanol-blocking membrane for direct methanol fuel cell (DMFC) application. The prepared membrane exhibited a significantly higher proton conductivity of 9.4 mS cm−1 at 60 °C and satisfactory proton conductivity stability over a 120-h test than a PVA membrane. Moreover, the composite membrane showed a decrease in the methanol permeability by ∼40% compared to a PVA membrane (6.10 × 10−7 cm2 s−1) and much better proton-to-methanol selectivity because of a higher dimensional stability after the incorporation of CNTs. A single DMFC based on the prepared membrane exhibited a maximum power density of 16 mW cm−2 at 60 °C. Thus, CNT-PDDA-HPW/PVA membranes have a great potential as an alternative proton exchange membrane for DMFC application.
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novel methanol blocking proton exchange membrane achieved via self anchoring Phosphotungstic Acid into chitosan membrane with submicro pores
Journal of Membrane Science, 2016Co-Authors: Haining Wang, Dawei Liang, Yan XiangAbstract:Abstract A novel chitosan/Phosphotungstic Acid composite proton exchange membrane was prepared by self-anchoring Phosphotungstic Acid into chitosan membrane with submicro-pores ( smp CTS/HPW). The smp CTS/HPW membrane exhibits enhanced proton conductivity and excellent methanol-blocking performance. The proton conductivity of the composite membrane is significantly affected by the content of HPW which could be modulated by introducing soft template P123 into the membrane to obtain varied porosity. The highest proton conductivity ( σ ) of the composite membrane, 2.9×10 −2 S cm −1 at 80 °C, was achieved with soft template P123 content of 40%. Moreover, the smp CTS/HPW membrane showed very stable proton conductivity under deionized water condition due to HPW molecules self-anchored in the CTS matrix. The methanol permeability ( P ) of 40%- smp CTS/HPW membrane was 4.7×10 −7 cm 2 s −1 , which was 60% lower than that of Nafion 212 membrane. The highest selectivity factor ( σ / P ), 2.27×10 4 S cm −3 s, was obtained on 40%- smp CTS/HPW membrane. A direct methanol fuel cell (DMFC) based on the 40%- smp CTS/HPW membrane achieved a peak power density of 16 mW/cm 2 at 80 °C. This study indicates the promising potential of smp CTS/HPW membrane as alternative proton exchange membrane for DMFCs application.
Yuanbiao Huang - One of the best experts on this subject based on the ideXlab platform.
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Phosphotungstic Acid encapsulated in the mesocages of amine functionalized metal organic frameworks for catalytic oxidative desulfurization
Dalton Transactions, 2014Co-Authors: Xusheng Wang, Yuanbiao HuangAbstract:Highly dispersed Keggin-type Phosphotungstic Acid (H3PW12O40, PTA) encapsulated in the mesocages of amine-functionalized metal–organic frameworks MIL-101(Cr)-NH2 has been prepared by an anion-exchange method. PTA anions (PW12O403−) are stabilized in the mesocages via the electrostatic interaction with amino groups of the MIL-101(Cr)-NH2. The obtained catalyst (denoted PTA@MIL-101(Cr)-NH2) exhibits high catalytic activity in the extractive and catalytic oxidative desulfurization (ECODS) system under mild conditions. Moreover, it can be easily recovered and recycled several times without leaching and loss of activity.
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Phosphotungstic Acid encapsulated in the mesocages of amine functionalized metal organic frameworks for catalytic oxidative desulfurization
Dalton Transactions, 2014Co-Authors: Xusheng Wang, Yuanbiao Huang, Zujin Lin, Rong CaoAbstract:Highly dispersed Keggin-type Phosphotungstic Acid (H3PW12O40, PTA) encapsulated in the mesocages of amine-functionalized metal–organic frameworks MIL-101(Cr)-NH2 has been prepared by an anion-exchange method. PTA anions (PW12O403−) are stabilized in the mesocages via the electrostatic interaction with amino groups of the MIL-101(Cr)-NH2. The obtained catalyst (denoted PTA@MIL-101(Cr)-NH2) exhibits high catalytic activity in the extractive and catalytic oxidative desulfurization (ECODS) system under mild conditions. Moreover, it can be easily recovered and recycled several times without leaching and loss of activity.
San Ping Jiang - One of the best experts on this subject based on the ideXlab platform.
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a novel Phosphotungstic Acid impregnated meso nafion multilayer membrane for proton exchange membrane fuel cells
Journal of Membrane Science, 2013Co-Authors: Qing Hong Fang, San Ping JiangAbstract:Abstract A novel mesoporous Nafion (meso-Nafion) based multilayer membrane impregnated with Phosphotungstic Acid (HPW) is developed for the operation of proton exchange membrane fuel cells (PEMFCs) at elevated high temperature and low humidity conditions. Very different to the pristine Nafion membrane, the HPW-impregnated meso-Nafion multilayer membrane possesses a much higher conductivity under both high and low humidity conditions. For example, the proton conductivity is 0.072 S cm−1 at 80 °C under 40% RH, which is ∼4 times better than 0.015 S cm−1 measured on pristine Nafion 1135 membrane under identical conditions. Moreover, the new multilayer structure effectively alleviates the leaching problem of impregnated HPW. The fuel cells assembled with the multilayer membrane show good performances and much low degradation when operated at reduced humidity and elevated temperatures of 120 °C, as compared to the cells with pristine Nafion membranes. The results indicate that the multilayer membrane can significantly widen the application range of PEMFCs under low relative humidity (RH) and elevated high temperatures.
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characterization of high temperature proton exchange membranes based on Phosphotungstic Acid functionalized mesoporous silica nanocomposites for fuel cells
Journal of Physical Chemistry C, 2011Co-Authors: Jie Zeng, San Ping JiangAbstract:The synthesis and characteristics of high-temperature proton-exchange membranes based on mesoporous silica nanocomposite functionalized with Phosphotungstic Acid (HPW) were investigated in detail for applications in proton-exchange membrane fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs). The HPW–meso-silica nanocomposites were characterized by small-angle X-ray scattering (SAXS), FTIR spectroscopy, Raman spectroscopy, TGA, N2 absorption isotherm, water uptake, TEM, conductivity, and fuel cell performance. The spectroscopy results indicate interactions between the Keggin anions of HPW and meso-silica and the possible formation of (≡SiOH2+)(H2PW12O40–) species. The results show that the proton conductivity of the HPW–meso-silica nanocomposites depends strongly on the content of HPW. The threshold for the proton conductivity of the nanocomposite is ∼10 wt %. The best proton conductivity is 0.07 S cm–1 at 25 °C under 100% relative humidity (RH) with an activation energy of ∼14 kJ mol–1, obtained o...
