Tests for absence of intraparticle diffusion effects in branched-pore systems

Abstract

Tests which have been recommended for detecting the presence or absence of mass transport in continuous-pore systems are considered for their applicability in branched-pore systems. When diffusion effects are absent in the primary pore system, three of the tests—the Weisz—Prater—Bischoff criterion, Hudgins' approach, and the Stewart—Villadsen criteria—can be used to show the presence or absence of these effects in the secondary system. In addition, two upper bounds are derived for the quotient of the secondary system Thiele modulus devided by the primary system modulus. These bounds can also be used for showing the absence of mass transport effects in the secondary pore system whenever the primary pore system is unaffected. Application of this latter development to porous materials suggests that if the primary pore system is unaffected by mass transport, then the secondary system is also unaffected, except under abnormal circumstances.