Further development of selective physisorption for measuring catalyst surface area

Abstract

Platinum supported on silica is used as a model supported catalyst for the purpose of demonstrating that the selective physisorption method yields the fractional catalyst surface area of supported catalysts, including metal compounds catalysts for which the method is primarily intended. The selective physisorption results with nitrous oxide as adsorbate are compared with hydrogen chemisorption results for this purpose. Experimental and theoretical refinements of the method developed earlier in our laboratory are presented that allow rather accurate determination of the catalyst surface area. The refinements also make the method effective even when the catalyst covers a small portion of the total surface area. Because of the nature of physisorption, the method should be applicable to any supported catalyst including metal compounds catalysts, provided a suitable adsorbate is used. Adsorbates other than nitrous oxide and carbon dioxide which are suitable for selective physisorption, are suggested.

Catalyst characterization

“…With respect to macroporous catalysts, Lee and co-workers (1128) reported further development of the method of selective physisorption for measuring catalyst surface area. The purpose of the method is to determine the individual surface areas of both catalyst and support.…”

“…Initial demonstration of the method involved using the thermal desorption of C02 from K2C03/carbon black and Ag/Al203 to determine the fractional surface coverage of each component. In the latest demonstration (1128), N20 was used as the sorbate for determining fractional surface areas of Pt on Si02. Further theoretical and experimental refinements to the method were made in order to make it effective for this case (i.e., where catalyst only covers a small fraction of the surface area).…”