Separating gases using a rigid polymer sieve
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Gas separation is crucial for many industrial processes
including obtaining nitrogen or oxygen from air and purifying natural gas or
hydrogen. Currently, the most energy efficient method for separating gases
involves polymer membranes, however, most polymers either let gases pass
through slowly (i.e. have low permeability) or are not selective towards one
gas over another. Gas separation would be cheaper and use less energy if
polymer membranes could be made both highly permeable and selective. A team
from the University's School of Chemistry reports in the journalScience a new polymer that efficiently separates
gas mixtures based on the different sizes of the gas molecules. The polymer's
molecular structure is very contorted so that it cannot fill space efficiently,
therefore leaving gaps for small gas molecules to move through quickly.
However, the transport of larger gas molecules is hindered by the polymer's
extreme rigidity so that it acts as an efficient molecular sieve.
The
Cardiff's team's collaborators at the Institute on Membrane Technology,
ITM-CNR, Italy, confirmed that membranes prepared from the polymer are both
highly permeable to gases and demonstrate remarkable selectivity for smaller
gases such as hydrogen or oxygen over larger gases such as nitrogen or methane.
Professor
Neil McKeown, a member of the School of Chemistry's team behind the research
said: "The preparation of this highly rigid and contorted polymer required
us to develop a new polymerisation reaction. In fact we used some very old
chemistry -- the formation of Tröger's base, which is a compound that was first
prepared 125 years ago. This simple chemistry allows us to prepare highly rigid
ladder polymers of high molecular mass from readily available starting
materials. In addition to making polymers for efficient gas separation
membranes, we anticipate that this new process will be useful for preparing
polymers for a variety of different applications."
Cardiff
University has applied for a patent covering this new polymerisation process.
Source: Cardiff University
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Posted by Unknown
on Saturday, January 19, 2013.
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