Ethanol conversion over cesium-doped mono- and bi-cationic aluminum and gallium H3PW12O40 salts

• Mono- and bi-cationic heteropoly salts of H3PW12O40 containing Ga, Al and Cs atoms were synthesised.
• Review of heteropoly salts physicochemical properties.
• Activity in ethanol conversion enhanced by the introduction of Ga and Cs atoms into H3PW12O40.

The objective of this study was synthesis, characterization, and catalytic testing of mono-cationic (GaPW12O40, AlPW12O40) and bi-cationic (CsGa0.5H0.5PW12O40, CsAl0.5H0.5PW12O40) salts of tungstophosphoric acid. These heteropoly salts are characterized by Brönsted acidity derived from protons generated by dissociation of water molecules coordinated to the metal atoms. Catalytic activity of the studied salts was evaluated based on ethanol conversion and compared with the well-known parent heteropolyacid H3PW12O40. The reaction products, ethylene and diethyl ether, were monitored simultaneously by FTIR spectroscopy and chromatographic analysis. The infra-red studies indicated that ethylene is formed not only from ethanol but also by diethyl ether decomposition. Cs-doped bi-cationic catalysts exhibited higher activity for ethylene and ether formation than the mono-cationic salts. The following order of catalytic activity was established: H3PW12O40 > CsGa0.5H0.5PW12O40 ∼ CsAl0.5H0.5PW12O40 > GaPW12O40 > AlPW12O40. It is in agreement with the order of their acid strength determined by microcalorimetry and specific surface areas of the studied catalysts.

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