Chemical Processing - March 2008 - (Page 32)

ices nn a gr a o rb inem m be used for zeolite-polymeric membranes,” he explains. His group aims to marry the performance of the zeolite and the cost of the polymer. “You can’t get performance of zeolite with the cost of polymer — but you can get close,” Koros notes. How near depends on selectivity, which is very significant to process efficiency, he says. “You might be able to get as close as a factor of two.” Mixed-matrix membranes still must overcome “very serious obstacles,” he admits. The biggest is building new membranes around old technology. “Do that and thermal separation problems arise.” The mixed-matrix product represents a practical platform, Koros emphasizes. It can be implemented relatively quickly and provides, at lower cost, many of the advantages of pure inorganic membranes, he says. However, it’ll be three to five more years before commercial production of zeolite-polymeric membranes begins, he predicts. Some companies certainly see the potential. Chevron, for instance, has been working with Koros since the mid1990s on membranes for natural gas purification and other uses, notes Steve Miller, senior consulting scientist with Chevron Energy Technology Co., Richmond, Calif. “The membranes we have been investigating have been primarily composites of zeolites or carbon molecular sieves within a polymer matrix, where the zeolite or sieve enhances the separation properties of the membrane beyond that of the polymer alone.” While Miller didn’t reveal when commercialization will begin, he says this is “a promising approach for enhancing the performance of polymer membranes.” It can help make membrane separation more competitive with alternative technologies for some separations, he believes. (Polymer membranes are advancing in their own right, too. For example, as CP reported in November (www. ChemicalProcessing.com/industrynews/2007/042.html), polymer membranes with hour-glass-shaped pores reportedly provide significantly better performance for gas separation than do conventional membranes. The first industrial trial should occur within five years in Korea for CO2 removal from power-plant stack gas.) Bold action needed Now squarely on the commercialization path is collaborative research by Noble and Falconer. With support from Shell for the past four to five years, they’ve investigated SAPO-34 zeolite membranes to remove carbon dioxide from natural gas. “We have been able to improve productivity — a technical term for permeance, the flux across the membrane divided by the driving force, which is the delta P [pressure] — by a factor of 10, while maintaining the selectivity at or near 100,” Noble says, noting that selectivity here means the ratio of CO2 permeance to methane permeance. “That means less membrane is needed,” he adds. And, because of that finding, “Shell has indicated that they’re pursuing commercialization.” Like Koros’ best guess for zeolite polymerics, Noble reckons it will be three to five years before industrial availability. “This would be the first commercial production and application of a gas-separation zeolite membrane,” he believes. “[It] will make a big splash,” Noble hopes, because current polymeric gas-separation membranes are mature technology. For real progress, he says, “it’s going to have to be the introduction of new materials where the traditional polymeric membranes don’t work… [And] if this becomes commercial, then that gets people’s attention — and that means that economics and science are viable.” However, getting gas-separation membranes to market will require cost-effective technology as well as industrial boldness, Koros suggests. He predicts “tremendous” growth in use of gas-separation membranes if membranes’ selectivity can be enhanced “especially in high-gas-volume areas of natural-gas sweetening and low-purity nitrogen production.” The key, he believes, will be “having people willing to take enough of a step, to say, ‘We’re going to try to ‘use membranes.’” CP www.chemicalprocessing.com 32 • March 2008 http://www.westernstates.com http://www.chemicalprocessing.com

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Chemical Processing - March 2008 Contents From the Editor ChemicalProcessing.com Field Notes In Process Energy Saver Compliance Advisor Distillation is Bubbling Feel Secure About Vulnerability Assessments The Door Opens For Membranes Achieve Effective Heat Exchanger Control Epoxy Maker Finds the Right Glue for Its Business Process Puzzler Plant InSites Equipment & Services Product Spotlight/Classifieds Ad Index End Point

Chemical Processing - March 2008

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