Preparation and acidity studies of silica-alumina catalysts

✍ Scribed by Sinhamahapatra, Pratap K. ;Sharma, Devendra K. ;Mehrotra, Raghunath P.

• Publisher: Blackwell Publishing
• Year: 1978
• Tongue: English
• Weight: 297 KB
• Volume: 28
• Category: Article
• ISSN: 0142-0356
• DOI: 10.1002/jctb.5700281108

✦ Synopsis

The surface acidic strength distribution in a series of silica-alumina catalysts prepared by coprecipitation and stepwise precipitation techniques has been measured by the butylamine adsorption method. The amount of silica in the finished catalysts ranged from 86.0 to 96.9 %. A linear relationship between the pH of the final gel (i.e. pH values of the solution in equilibrium with the gel material before washing) and X[=A1~03/ (SiOz+Alz03)] was observed up to a certain level of pH; for coprecipitated catalysts it was 6.0 whereas for those precipitated stepwise the limit of pH was 7.0. Coprecipitated silica-aluminas were more enriched with weak acid sites or Bronsted sites (pKa = +6.8) and their concentration reached a maximum at about 87% silica.

Stepwise precipitated silica-aluminas, on the other hand, have a greater population of strong acid sites, thus making them useful for cracking reactions. ' *