H5CoW12O40 supported on nano silica from rice husk ash: A green bifunctional catalyst for the reaction of alcohols with cyclic and acyclic 1,3-dicarbonyl compounds

Rafiee, Ezzat; Khodayari, Maryam; Kahrizi, Masoud; Tayebee, Reza

doi:10.1016/j.molcata.2012.03.005

Cited by 22 publications

(9 citation statements)

References 44 publications

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“…These characteristic peaks are also observed in the FT‐IR spectrum of CoW. In addition, the strong absorption peaks of 948–935 cm −1 , WO t (terminal oxygen); 881–875 cm −1 , W―O c ―W (corner sharing oxygen) and 773–752 cm −1 , W―O e ―W (edge sharing oxygen) are the characteristic peaks of CoW 12 O 40 6− . XRF is also applied to investigate the content of Co and W, and the results are shown in Table .…”

Section: Resultsmentioning

confidence: 91%

Effect of anion of polyoxometalate based organic-inorganic hybrid material on intumescent flame retardant polypropylene

2016

Polym. Adv. Technol.

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In this work, 12‐tungestocobaltic acid based organic–inorganic hybrid material, [Bmim]6CoW12O40 (CoW) was synthesized and applied as a synergist in polypropylene (PP)/intumescent flame retardant (IFR) composites. The flame retardant properties were investigated by the limiting oxygen index (LOI), UL‐94 vertical burning test, thermal gravimetric analyzer (TGA), cone calorimeter and scanning electron microscopy (SEM) etc. The results showed that the PP composites with 16 wt% IFR and 1 wt% CoW achieves the UL‐94 V‐0 rating and gets a LOI value 28.0. However, only add no less than 25 wt% single IFR, can the PP composites obtain the UL‐94 V‐0 rating, which suggests that CoW has good synergistic effects on flame retardancy of PP/IFR composites. In addition, the SEM and cone calorimeter tests indicated the CoW improves the quality of char layer. The rate of char formation has been enhanced also because of the existence of CoW. It is the combination of a better char quality and a high rate of char formation promoted by CoW that results in the excellent flame retardancy of PP/IFR composites. Copyright © 2016 John Wiley & Sons, Ltd.

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Section: Resultsmentioning

confidence: 91%

Effect of anion of polyoxometalate based organic-inorganic hybrid material on intumescent flame retardant polypropylene

2016

Polym. Adv. Technol.

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“…The intact structure of the POM in the composite material was also confirmed using FT‐IR vibrational spectroscopy. As shown in Figure (b), the FT‐IR spectrum of Co‐POM@MIL‐101 is the sum of the characteristic bands of the free components: Co‐POM (Figure a) with characteristic peaks in the region 700–1200 cm −1 assigned to W═O, WOW and CoO bonds and MIL‐101 (Figure c) with characteristic vibrational bands of (OCO) groups of the framework around 1550 and 1400 cm −1 and of C═O vibrations at 1708 and 1658 cm −1 …”

Section: Resultsmentioning

confidence: 99%

Dodecatungstocobaltate heteropolyanion encapsulation into MIL‐101(Cr) metal–organic framework scaffold provides a highly efficient heterogeneous catalyst for methanolysis of epoxides

Marandi

Tangestaninejad

Mirkhani

et al. 2017

Applied Organom Chemis

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A heterogeneous catalyst was synthesized by encapsulation of a Keggin‐type heteropolytungstate, potassium dodecatungstocobaltate trihydrate, K5[CoW12O40]·(Co‐POM), into chromium(III) terephthalate (MIL‐101). Encapsulation was achieved via a ‘build bottle around ship’ strategy in aqueous media, following a hydrothermal method. The structure of the resulting crystalline solid was characterized using X‐ray diffraction, correlated with Fourier transform infrared and UV–visible spectroscopy. The metal content was analysed using optical emission spectroscopy. Transmission electron microscopy was used to measure particle size and N2 adsorption in a Brunauer–Emmett–Teller instrument to characterize the specific surface area. The catalytic activity was investigated using methanolysis of epoxides under mild conditions as a test reaction. The turnover frequency of the heterogeneous Co‐POM@MIL‐101 catalyst was more than 20 times higher than that of the homogeneous Co‐POM catalyst. The Co‐POM@MIL‐101 catalyst was reused several times with negligible leaching of Co‐POM and with no considerable loss of its initial efficiency. The simplicity of preparation, extraordinary stability and high reactivity make Co‐POM@MIL‐101 an exceptional catalytic matrix that is easily separable from reaction media.

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“…tert-Butanol was also reacted with dimedone to provide the corresponding β-keto enol ether in 50% yield (entry 6), while some previous approaches did not apply this alcohol or gave negative results for similar reactions. [34][35][36]39,40 same experimental conditions. The results in Fig.…”

Section: Catalytic Reactionmentioning

confidence: 99%

“…All products were identified by comparing of their spectral data, 1 H-NMR 13 C-NMR, with those of the authentic samples. 31,[33][34][35][36] …”

Section: Catalytic Reactionmentioning

confidence: 99%

H3PW12O40 encapsulation by nanoporous metal organic framework HKUST-1: Synthesis, characterization, activity and stability

Rafiee

Nobakht

2016

ACSi

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Hybrid composite material was obtained through encapsulation of H 3 PW 12 O 40 (PW) into HKUST-1 (Cu 3 (BTC) 2 , BTC = 1,3,5-benzenetricarboxylic acid), in molar composition of 5 Cu(NO 3 ) 2 · 3H 2 O /2.8 BTC/ 0.3 PW/ 0.6 CTAB by adding solutions of PW and copper salts to mixture of BTC and surfactant. The catalyst was characterized by various techniques including powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), laser particle size analyzer, Brunauer Emmett-Teller (BET). The acidity of the catalyst was measured by a potentiometric titration with n-butylamine and PW/HKUST-1 presented very strong acidic sites with Ei > 100 mV. This nano catalyst was successfully used for the synthesis of various β-keto enol ethers at 45 °C with 51-98% yield after 5-75 min. The catalyst was easily recycled and reused at least four times without significant loss of its activity (94% yield after forth run). The presence of the PW in PW/HKUST-1 and reused PW/HKUST-1 structure, eliminating any doubt about collapse of the HKUST-1 after catalytic reaction and can be followed by FT-IR, XRD and SEM techniques. Brönsted and Lewis acidity of the PW/HKUST-1 catalyst was distinguished by studying the FT-IR and determined by chemisorption of pyridine. The strength and dispersion of the protons on PW/HKUST-1 was considerably high and active surface protons became more available for reactant.

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H5CoW12O40 supported on nano silica from rice husk ash: A green bifunctional catalyst for the reaction of alcohols with cyclic and acyclic 1,3-dicarbonyl compounds

Cited by 22 publications

References 44 publications

Effect of anion of polyoxometalate based organic-inorganic hybrid material on intumescent flame retardant polypropylene

Effect of anion of polyoxometalate based organic-inorganic hybrid material on intumescent flame retardant polypropylene

Dodecatungstocobaltate heteropolyanion encapsulation into MIL‐101(Cr) metal–organic framework scaffold provides a highly efficient heterogeneous catalyst for methanolysis of epoxides

H3PW12O40 encapsulation by nanoporous metal organic framework HKUST-1: Synthesis, characterization, activity and stability

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