ChBE Seminar Series: Lloyd M. Robeson (Ph.D. '67)
Tuesday, March 10, 2015
11:00 a.m.-12:15 p.m.
Room 2108, Chemical and Nuclear Engineering Building
Professor Ganesh Sriram
Membrane Separation of Gases: The Analysis of the Upper Bound Relationship for Polymers
Lloyd M. Robeson (Ph.D. '67)
Member, National Academy of Engineering
Member, Clark School Innovation Hall of Fame
Air Products and Chemicals, retired (2007)
Adjunct Professor, Lehigh University
Membrane separation of gases has emerged from a novelty several decades ago to a widely employed commercial process. Understanding the limits (and structure/property relationships) of polymeric materials to optimize the separation characteristics (separation factor, permeate flux) has been an important research area. Specific limits of membrane separation transport properties were defined by an empirical upper bound relationship and later predicted by theory. The upper bound plot of αij (αij = Pi/Pj where Pi is the more permeable gas of the gas pair i and j) versus Pi (log-log plot) defined a line above which virtually no data points exist. This relationship holds for all gas pairs chosen from He, H2, O2, N2, CO2 and CH4. This seminar will detail an analysis of the polymer transport properties of permeability, diffusivity and solubility relationships (as P = DS; the solution-diffusion model). The analysis of a large database of P, D and S values has revealed the fundamental features of upper bound polymers. Some of these conclusions were unexpected and demonstrated that some generalizations widely noted in the literature were incorrect. The structure/property characteristics of upper bound polymers will be discussed along with the present "state-of-the-art" approaches optimizing the transport properties to achieve the desired membrane separation performance for polymers.