Selective gas phase tert-butylation of 4-hydroxyanisole over mesoporous PWA/Al-MCM-41 molecular sieves

Rajasekar, K.; Ameen, K. Balkis; Pandurangan, A.

doi:10.1016/j.catcom.2008.08.009

Cited by 13 publications

(5 citation statements)

References 22 publications

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“…Thus, IR spectra can be used to explain the acidic properties of the bulk. In the IR spectrum shown in Figure , the bands due to a pyridinium cation − at 1540 and 1636 cm –1 , as well as very weak ones due to hydrogen-bonded pyridine , at 1446 and 1598 cm –1 , were observed. Thus, it is thought that the first layer of H 4 SiW 12 O 40 does not decompose.…”

Section: Resultsmentioning

confidence: 96%

Changes in Surface Acidity of Silica-Supported Dodecatungstosilicic Acid in Relation to the Loading Amount

et al. 2011

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Changes in surface acidity of H4SiW12O40/SiO2 in relation to the loading amount were investigated by using temperature-programmed desorption (TPD) of benzonitrile (BN), BN infrared (BN-IR) spectroscopy, and test reactions, including skeletal isomerization of n-butane and double-bond shift of 1-butene. From BN-TPD profiles and BN-IR spectra, H4SiW12O40/SiO2 had medium strength Brønsted (Mid-B site) and strong Brønsted acid sites (Strong-B site) on its outermost surface, whereas there was no evidence for Lewis acid sites regardless of the loading amount. The number of Strong-B sites correlated with the catalytic activity for the skeletal isomerization of n-butane and was a maximum when the loading amount was 50 wt %. On the other hand, the number of Mid-B sites was a maximum for 30 wt % H4SiW12O40/SiO2, which had the highest activity for the double-bond shift reaction of 1-butene. Mid-B sites of H4SiW12O40/SiO2 were present in the starting H4SiW12O40, whereas the Strong-B sites formed when H4SiW12O40 was supported on SiO2. There were no Strong-B sites on H4SiW12O40/SiO2 with low loadings, including 5 and 10 wt %. Thus, it was concluded that the direct interaction of H4SiW12O40 with the surface of SiO2 caused the Strong-B sites to form in the second-layer of H4SiW12O40 exposed on the surface.

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Section: Resultsmentioning

confidence: 96%

Changes in Surface Acidity of Silica-Supported Dodecatungstosilicic Acid in Relation to the Loading Amount

et al. 2011

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“…Peaks in the region of 550-650 °C in the PW sample indicated the presence of strong acid sites (Fig. 6, B), 42,43 while the peaks in the region of 250-550 °C for the PW-TPSP and 30PW-Si/TPSP samples (Fig. 6, C and D) indicated the presence of strong acid sites at lower temperature.…”

Section: Catalysis Science and Technology Papermentioning

confidence: 96%

Highly efficient triphenyl(3-sulfopropyl)phosphonium functionalized phosphotungstic acid on silica as a solid acid catalyst for selective mono-allylation of acetals

Kamble

Shinde

Rode

2015

Catal. Sci. Technol.

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Silica supported phosphotungstic acid functionalized with triphenylĲ3-sulfopropyl)phosphonium (PW-Si/ TPSP) was developed as a solid acid catalyst for C-C bond formation via Hosomi-Sakurai allylation of acetals. Functionalization of PW as well as its binding to silica was confirmed by solid state 31 P-NMR and 29 Si-NMR, respectively. Among the various catalysts prepared, the 30% PW loaded (30PW-Si/TPSP) catalyst gave an excellent yield of homoallyl ethers (HAEs) via selective mono-allylation of acetals with allyltrimethylsilane. A plausible reaction pathway has also been proposed in which the strong Brønsted acid sites of 30PW-Si/TPSP play an important role in activating the acetals to form the corresponding oxonium cations. The versatility of our catalyst was demonstrated for the allylation of a wide variety of acetals while its stability was established in five successful recycling runs.

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“…The band at 1545 cm –1 (pyridinium ion) was assigned to Brönsted acid sites, whereas bands at 1610 and 1450 cm –1 (pyridine coordinated to Lewis acid sites) were assigned to Lewis acid sites. The band at 1490 cm –1 (hydrogen bonded pyridine) is common to both types of acidic sites. , The surface of MCM-41 contained only Lewis acid sites, but as PWA was dispersed on MCM-41, both Brönsted as well as Lewis acid sites were observed. The acidity increased gradually with increasing PWA loading, as revealed by the acidity measurement (NH 3 -TPD) shown in Figure .…”

Section: Resultsmentioning

confidence: 98%

“…The band at 1490 cm −1 (hydrogen bonded pyridine) is common to both types of acidic sites. 16,17 The surface of MCM-41 contained only Lewis acid sites, but as The concentration of acid sites (in terms of NH 3 desorbed) of parent MCM-41 increased from 0 to 0.9 μmol S −1 with an increase in PWA loading from 0 to 30% (Table 1).…”

Section: Methodsmentioning

confidence: 99%

“…On the other hand, bulk PWA showed lowest activity as compared to the supported PWA catalysts despite its strong Bronsted acidity. The very low surface area (<10 m 2 /g) of bulk PWA causes limited availability of acidic sites on the surface, 17 hence lower activity for acid catalyzed hydroxyalkylation of phenol and phthalic anhydride. When the bulk PWA was dispersed on MCM-41, a number of active sites on the surface increased considerably leading to higher activity of supported PWA catalysts as compared to bulk PWA.…”

Section: Catalytic Activitymentioning

confidence: 99%

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MCM-41 Supported Phosphotungstic Acid for the Hydroxyalkylation of Phenol to Phenolphthalein

Jha

Garade

Mirajkar

et al. 2012

Ind. Eng. Chem. Res.

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A novel application of phosphotungstic acid, H3PW12O40 (PWA) supported on MCM-41 molecular sieve as a solid acid catalyst has been demonstrated for the synthesis of phenolphthalein by hydroxyalkylation of phenol and phthalic anhydride. PWA/MCM-41 (20%) showed the highest activity as compared to that of parent PWA and MCM-41 individually, due to the excellent dispersion of PWA on MCM-41 leading to the redistribution of Bronsted and Lewis acid sites on MCM-41. The effect of PWA loading on phthalic anhydride conversion and phenolphthalein selectivity was also studied. All these prepared catalysts were characterized by XRD, N2 adsorption–desorption isotherm, pyridine-FTIR, and NH3-TPD. The effect of various reaction parameters, namely, mole ratios, catalyst concentration, temperature, reaction time, and percentage of PWA present in the catalysts on conversion and selectivity of products has been also investigated. The utility of 20% PWA/MCM-41 catalyst was established by its efficient activity for hydroxyalkylation of phenol and p-cresol with formaldehyde to the corresponding dihydroxydiarylmethane products.

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Selective gas phase tert-butylation of 4-hydroxyanisole over mesoporous PWA/Al-MCM-41 molecular sieves

Cited by 13 publications

References 22 publications

Changes in Surface Acidity of Silica-Supported Dodecatungstosilicic Acid in Relation to the Loading Amount

Changes in Surface Acidity of Silica-Supported Dodecatungstosilicic Acid in Relation to the Loading Amount

Highly efficient triphenyl(3-sulfopropyl)phosphonium functionalized phosphotungstic acid on silica as a solid acid catalyst for selective mono-allylation of acetals

MCM-41 Supported Phosphotungstic Acid for the Hydroxyalkylation of Phenol to Phenolphthalein

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