NAMS 2002 Workshop - ICOM 2008

Facilitated Transport Membranes – 6
Friday July 18, 12:15 PM-12:45 PM, Wai’anae
Selectivity and Stability of Facilitated Transport Membranes Containing
Silver Nanoparticles for Propylene Separation
L. Pollo (Speaker), Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
A. Habert, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
C. Borges, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil -
cristiano@peq.coppe.ufrj.br
Propylene is the key building block for the production of important petrochemical
products, such as polypropylene, acrylonitrile, propylene oxide, cumene, phenol,
isopropylic alcohol and many others. The worldwide demand for propylene has
been increasing at 5.7% a year since 1990, with a forecast of 84 million tons for
2010. To obtain propylene many successive stages of distillation are necessary,
the separation of propane and propylene being the most difficult and expensive.
With close molecular sizes and relative volatility, distillation towers must run at
high rates of reflux extreme pressure and temperature conditions, with a high
energy cost.
Polymeric membranes have long been used in the separation of mixtures, like
oxygen from air, carbon dioxide from methane, and the dehumidification of air
amongst others. Nevertheless, conventional polymeric membranes are not
competitive for the separation of olefin/paraffin mixtures, due to an unfavorable
tradeoff of selectivity and permeability. Similar physicochemical properties and
molecular size of these compounds are indeed limitations for membrane
separation based on sorption/diffusion mechanism. One alternative that has been
sought is a simultaneous increase of permeability and selectivity by incorporating
in the membrane matrix specific agents that interact reversibly with propylene but
not with propane. In this way, propylene permeation occurs by facilitated
transport mechanism.
Our research group has been investigating silver salts as propylene carriers,
obtaining very good results. However, silver salts have a low chemical stability
resulting in the loss of transport activity over long periods of time. In order to
overcome this problem, this work investigates the use of metallic silver
nanoparticles in polyurethane composite membranes. Metallic nanoparticles
have attracted much attention due to their unique physicochemical properties.
The silver nanoparticles were photogenerated in situ in the polyurethane matrix
using UV light radiation and AgCF3SO3 salt as precursor. The composite
membrane was prepared by coating a commercial microfiltration membrane of
nylon. It was observed an improved stability of silver nanoparticles, which may