ABSTRACT
This chapter explores the type of transport as a separation method for gases and suggests that whether the system exhibits facilitated transport. It explains the combinations of diffusion and reaction responsible for facilitated transport and emphasizes the membranes used for this type of separation. The chapter discusses the origins of membrane instability, because this instability has inhibited commercial applications of this technology and also discusses four facilitated membrane separations. First, a membrane for separating hydrogen sulfide from flue gas illustrates both the early hope for facilitated transport in liquid membranes and the reasons why this hope has faded. Second, separations of olefins from alkanes exemplify facilitated transport in more stable systems. Third, membrane separations of ammonia from nitrogen and hydrogen show how highly selective transport is not always facilitated transport. Finally, membranes for air separations show the challenges and the pitfalls of this enticing but elusive mechanism of membrane separation.
