Solid acid catalysts based on H3PW12O40 heteropoly acid: Acid and catalytic properties at a gas–solid interface

Alsalme, Ali; Wiper, Paul V.; Khimyak, Yaroslav Z.; Kozhevnikova, Elena F.; Kozhevnikov, Ivan V.

doi:10.1016/j.jcat.2010.09.014

Cited by 144 publications

(137 citation statements)

References 26 publications

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“…Before analysis, the samples were evacuated in situ at 250 • C for 3 h. Powder X-ray diffraction (XRD) of catalysts was measured on a PANalytical Xpert diffractometer using a monochromatic CuK˛ radiation ( = 1.542Å) in a 2Â range of 20-80 • . DRIFTS (diffuse reflectance infrared Fourier transform spectra) of adsorbed pyridine were taken on a Nicolet Nexus FTIR spectrometer as described elsewhere [22]. Catalyst samples were ground with KBr (10 wt% in KBr) and pre-treated at 150 • C/10 −5 bar for 1 h. The samples were then exposed to pyridine vapour at room temperature for 1 h, followed by pumping out at 150 • C/10 −5 bar for 1 h to remove physisorbed pyridine.…”

Section: Catalyst Characterisationmentioning

confidence: 99%

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Ketonisation of carboxylic acids over Zn-Cr oxide in the gas phase

Bayahia

Kozhevnikova

Kozhevnikov

2015

Applied Catalysis B: Environmental

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Section: Catalyst Characterisationmentioning

confidence: 99%

“…The DRIFT spectra were recorded at room temperature (4 cm −1 resolution). Differential heats of ammonia adsorption on the catalysts were measured at 150 • C by a pulse method in a flow system using a Setaram TG-DSC 111 differential scanning calorimeter as described previously [22].…”

Section: Catalyst Characterisationmentioning

confidence: 99%

Ketonisation of carboxylic acids over Zn-Cr oxide in the gas phase

Bayahia

Kozhevnikova

Kozhevnikov

2015

Applied Catalysis B: Environmental

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“…Despite the mild reaction conditions of this industrial process, its low conversion and selectivity requires significant advances to improve both atom and energy efficiency. A wide range of alternative catalysts have been explored including alloys, [14] clays, [18,19] zeolites, [20,21] sulphated zirconia, [16,22], Al-incorporated MCM-41 [23] and heteropolyacids (HPAs); [24][25][26][27][28] with strong solid acids conferring improved conversion and selectivity. [21,22,24,27,29] HPAs are polyoxometalate inorganic cages which possess high Brönsted acid strengths (approaching the superacidic region) and tunable redox activity depending on the particular constituent elements.…”

Section: Introductionmentioning

confidence: 99%

Support enhanced α-pinene isomerization over HPW/SBA-15

Frattini

Isaacs

Parlett

et al. 2017

Applied Catalysis B: Environmental

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Corresponding Author: a.f.lee@aston.ac.uk; +44(0)121 2044036 2 GRAPHICAL ABSTRACT Highlights  Mesoporous SBA-15 facilitates dispersion of low dimensional polyoxometallate clusters  HPW/SBA-15 is highly active for α-pinene isomerization under mild conditions  Selectivity to mono-versus polycyclic products is controlled by polyoxometallate acidity Abstract 3 A family of mesoporous SBA-15 supported H3PW12O40 (HPW) catalysts were synthesized by wetimpregnation and compared with fumed silica analogues for the solventless isomerization of α-pinene under mild conditions. Structural and acidic properties of supported HPW materials were characterized by powder XRD, HRTEM, XPS, TGA, N2 porosimetry, DRIFTS, and ammonia and propylamine chemisorption and TPD. The high area, mesoporous SBA-15 architecture facilitates the formation of highly dispersed (isolated or low dimensional) HPW clusters and concomitant high acid site densities (up to 0.54 mmol.g -1 ) relative to fumed silica wherein large HPW crystallites are formed even at low HPW loadings. α-Pinene exhibits a volcano dependence on HPW loading over the SBA-15 support due to competition between the number and accessibility of acid sites to the non-polar reactant, with the superior acid site accessibility for HPW/SBA-15 conferring a 10-fold rate enhancement with respect to HPW/fumed silica and pure HPW. Monocyclic limonene and terpinolene products are favoured over polycyclic camphene and β-pinene by weaker polyoxometallate analogues over SBA-15.

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“…Therefore, any enhancement of Pd activity would not cause a significant increase in benzene conversion. Silica-supported HSiW catalysts were prepared by the impregnation of Aerosil 300 silica by an aqueous HSiW solution, which was then dried at 150 • C/10 −3 kPa for 1.5 h [30,31]. The integrity of the HSiW Keggin structure on the silica surface in fresh and spent catalysts was confirmed by infrared spectroscopy ( Figure S1 in the Supporting Material).…”

Section: Chemicals and Catalystsmentioning

confidence: 99%

Selective Alkylation of Benzene by Propane over Bifunctional Pd-Acid Catalysts

et al. 2017

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Abstract:The alkylation of benzene by propane to yield isopropylbenzene (iPrPh) was studied using bifunctional Pd-acid catalysts, such as Pd-heteropoly acid and Pd-zeolite, in a fixed bed reactor at 300 • C and 1 bar pressure. Keggin-type tungstosilicic acid H 4 SiW 12 O 40 (HSiW) and zeolite HZSM-5 were used as the acid components in these catalysts. The reaction occurred most efficiently over 2%Pd/25%HSiW/SiO 2 , giving iPrPh with up to 88% selectivity. The Pd-HSiW catalyst was more selective than the Pd-HZSM-5; the latter gave only 11-18% iPrPh selectivity. The reaction proceeded via a bifunctional mechanism including the dehydrogenation of propane to form propene on Pd sites, followed by the alkylation of benzene with the propene on acid sites. The effect of Pd loading in Pd-HSiW and Pd-HZSM-5 catalysts indicated that the first step reached quasi-equilibrium at 1.5-2% Pd loading and the second step became rate limiting. The addition of gold to Pd-HSiW enhanced the activity of this catalyst, although the Au-HSiW without Pd was inert.

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Solid acid catalysts based on H3PW12O40 heteropoly acid: Acid and catalytic properties at a gas–solid interface

Cited by 144 publications

References 26 publications

Ketonisation of carboxylic acids over Zn-Cr oxide in the gas phase

Ketonisation of carboxylic acids over Zn-Cr oxide in the gas phase

Support enhanced α-pinene isomerization over HPW/SBA-15

Selective Alkylation of Benzene by Propane over Bifunctional Pd-Acid Catalysts

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