Chapter 2 Zeolites and molecular sieves: An historical perspective

Abstract

Molecular sieves are porous solids with pores of the size of molecular dimensions, 0.3–2.0 nm in diameter. Examples include zeolites, carbons, glasses, and oxides. Some are crystalline with a uniform pore size delineated by their crystal structure, e.g., zeolites. Others are amorphous, e.g., carbon molecular sieves. Most current commercial molecular sieves are zeolites. The pore size distribution for representative commercial adsorbent types contrasts the singular pore size of zeolites 5A and X or Y, with the broader distribution and larger mean pore diameter of the amorphous activated carbon and alumina adsorbents. The carbon molecular sieve has a mean pore diameter intermediate between that of 5A and X or Y zeolite but has a significantly broadened pore size distribution.