Alasmari, Amal 
ORCID: 0000-0002-2331-1317, Al-Faze, Rawan, Kozhevnikova, Elena F ORCID: 0000-0001-8242-7945 and Kozhevnikov, Ivan V ORCID: 0000-0003-2453-5256
(2023)
Solid acid catalysts comprising heteropoly acids supported on SiO2, TiO2 and ZrO2: A microcalorimetric investigation of catalyst acidity and new insight into the mechanism of alcohol dehydration over HPA.
Catalysis Communications, 180.
p. 106710.
ISSN 1566-7367, 1873-3905
Abstract
Keggin-type heteropoly acids (HPAs) have strong Brønsted acidity and are widely used as acid catalysts. The aim of this work is the systematic characterisation of the acid strength of HPA catalysts comprising H<inf>3</inf>PW<inf>12</inf>O<inf>40</inf> and H<inf>4</inf>SiW<inf>12</inf>O<inf>40</inf> supported on SiO<inf>2</inf>, TiO<inf>2</inf> and ZrO<inf>2</inf> with 10–100% HPA loading and testing their activity in dehydration of alcohols to gain new mechanistic insight regarding the role of bulk-type and surface-type HPA catalysis in this reaction. The HPA catalysts were prepared by impregnation from an aqueous solution and characterised using BET, XRD, TGA, DRIFTS and ICP–OES. The acid strength of HPA catalysts was determined by NH<inf>3</inf> adsorption microcalorimetry and found to decrease in the order HPA/SiO<inf>2</inf> > HPA/TiO<inf>2</inf> > HPA/ZrO<inf>2</inf>. For each type of HPA catalyst, the acid strength increased with increasing HPA loading. This can be attributed to HPA-support interaction reducing the strength of HPA proton sites at low HPA loadings. The activity of HPA catalysts was tested in the gas-phase dehydration of MeOH and i-PrOH in a fixed-bed reactor. Evidence was obtained that alcohol dehydration over HPA catalysts in a steady-state flow system occurs via the surface-type rather than bulk-type catalysis as suggested hitherto. This follows from a strong correlation between the reaction rate and the number of surface proton sites in HPA catalysts.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | Heteropoly acid, Acid strength, Effect of support, Alcohol dehydration |
| Divisions: | Faculty of Science and Engineering > School of Physical Sciences |
| Depositing User: | Symplectic Admin |
| Date Deposited: | 30 Jun 2023 08:22 |
| Last Modified: | 04 Jun 2025 21:11 |
| DOI: | 10.1016/j.catcom.2023.106710 |
| Open Access URL: | https://doi.org/10.1016/j.catcom.2023.106710 |
| Related Websites: | |
| URI: | https://livrepository.liverpool.ac.uk/id/eprint/3171380 |
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