Acidity Studies of Silica-Alumina Catalysts

Abstract

The protonic acid content of some acid-type solid catalysts was determined by base exchange with 0.1 N ammonium acetate solution followed by pH measurement. This procedure also permitted evaluation of the relative acid strengths of the catalysts. Measurements were made on silica-alumina catalysts of various compositions after heat treatments ranging from 100 to 900°and were compared with data from non-aqueous butylamine titrations and propylene polymerization tests. Polymerization activity correlated better with protonic acid content than with total acids determined by butylamine titration for the entire composition range from pure silica to pure alumina. The results are consistent with the view that protons on the catalyst surface are necessary for acid catalysis such as heat treatment at 900°was regained by rehydration.

The Acidity of Bound Wood Acid: A New Method for Determining the Acidity of Insoluble Acids

“…One portion was used for the acetate exchange (Holm, Bailey and Clark 1959;Subramanian, Somasekharan and Johns 1983) äs follows.…”

“…For example, in the presence of nitric acidtreated wood, the gelation timeS of urea-formaldehyde resin formulations were found to be correlated with the concentration of bound wood acid (Subramanian, Somasekharan and Johns 1983). Several methods for determining the strength of insoluble acids exist (De Marco and Smith 1946;Tamele 1950;Milliken, Mills and Oblad 1950;Walling 1950;Johnson 1955;Benesi 1956;Holm, Bailey and Clark 1959;Hirschler 1963;Garcia de la Banda and Tezanos 1963;Hair and Hertl 1970;Kutsuna andKamamori 1981, Hanocq Van Damme andFuks 1983). Several methods for determining the strength of insoluble acids exist (De Marco and Smith 1946;Tamele 1950;Milliken, Mills and Oblad 1950;Walling 1950;Johnson 1955;Benesi 1956;Holm, Bailey and Clark 1959;Hirschler 1963;Garcia de la Banda and Tezanos 1963;Hair and Hertl 1970;Kutsuna andKamamori 1981, Hanocq Van Damme andFuks 1983).…”

Nature and Estimation of Functional Groups on Solid Surfaces

“…In many cases, the substance may be attacked by aqueous alkali; this is the case with silica or with alumina. Instead of adsorption from more or less alkaline solutions, ion exchange adsorption from ammonium acetate [467,468] or calcium acetate [469], has also been used with titration of the liberated acetic acid against bromphenol blue. It has been held against this method that Lewis acids may form Bronsted acids in aqueous media by polarization of adsorbed water molecules.…”

Oligomerization

“…It has also been found that lower acid strength sites are in fact more effective for oligomerization than higher acid strength sites [60]. It has also been found that lower acid strength sites are in fact more effective for oligomerization than higher acid strength sites [60].…”