Acidic Cs{sup +}, NH{sub 4}{sup +}, and K{sup +} salts of 12-tungstophosphoric acid as solid catalysts for isobutane/2-butene alkylation
- Universidad Politecnica de Valencia (Spain)
The cesium, ammonium, and potassium salts of 12-tungstophosphoric acid (HPW) have been prepared with different stoichiometries (1{le}x{le}3) and their catalytic behavior measured for the liquid phase alkylation of isobutane with 2-butene at 80{degrees}C. The salts with a cation content of 2.5 {le}x{le}3, and that of Cs{sup +} with x=2, showed a much higher surface area than the parent acid, which is partially due to the formation of micropores. The micropores presented a fairly homogeneous distribution, with an average diameter in the range of 6-11 {Angstrom}, depending on the type of cation and cation content. The activity of the heteropoly acid and their monovalent type B salts for isobutane alkylation could be correlated with the surface acidity of the solids. Thus, the initial (1 min TOS) olefin conversion went through a maximum for the NH{sub 4}{sup +} and K{sup +} salts with a cation content of x = 2.5, and in the range of 2{le}x{le}2.5 in the case of the Cs{sup +} compounds. (NH{sub 4}){sup 2.5}PW showed a very high initial cracking activity (ca. 72 wt% C{sub 5}-C{sub 7} in C{sub 5+}), suggesting the presence of surface acid sites of a higher acid strength in the ammonium salt, as compared to the caesium and potassium salts with similar composition. In all cases the desired trimethylpentanes (TMPs) were the predominant compounds in the C{sub 8} fraction formed in the initial reaction stages. The deactivation rate also depended on the nature of the cation exchanged in the heteropoly salts. 57 refs., 7 figs., 4 tabs.
- OSTI ID:
- 468693
- Journal Information:
- Journal of Catalysis, Vol. 164, Issue 2; Other Information: PBD: Dec 1996
- Country of Publication:
- United States
- Language:
- English
Similar Records
Characterization of sorbed intermediates and implications for the mechanism of chain growth in the conversion of methanol and ethanol to hydrocarbons over 12-tungstophosphoric acid using infrared photoacoustic spectroscopy
High-pressure oligomerization of propene over heteropoly acids