Issue Date: April 5, 2004
NEW TURF FOR NANOFILTRATION
Membrane Extraction Technology (MET), a start-up company launched by the technology transfer office of Imperial College London in 1996, is a six-person shop that still leases laboratory space from the college. Its idea of establishing organic solvent nanofiltration (OSN) as a staple in fine chemicals and pharmaceutical manufacturing is starting to show some promise, however, and MET is getting the technology into the hands of some major companies for trial runs.
Launched with a $243,000 investment from British chemical major ICI, MET initially worked on filtration systems for the removal of chemical waste from aqueous streams in large refining and chemical operations. More recently, the firm has worked to expand the application of OSN to include catalyst recovery, organic materials recovery, solvent exchange, and product purification in fine chemicals and pharmaceutical manufacturing.
Having worked with some big names in bulk chemicals--ICI, Degussa, Atofina, Rohm and Haas, and Solutia--MET's list of interested potential customers now includes Johnson Matthey, Lonza, and three major pharmaceutical companies, according to Lina Christopoulou, commercial development manager. The firm, which doubled its revenues last year, hopes that some of these companies will scale up what until now have been investigative nanofiltration operations, Christopoulou says.
MET employs a combination of chemistry and engineering in the design of OSN processes for batch chemical manufacturing. It uses a polyimide membrane, manufactured by Grace Davison, that is stable in solvents such as toluene, xylene, ethyl acetate, methanol, ethanol, and hexane at temperatures up to 60 °C. Membranes are available with molecular weight cut-offs--the molecular weight at which membranes reject 90% of solute molecules--of between 200 and 400 daltons.
The company was born in the laboratory of Andrew Livingston, a chemical engineering professor at Imperial College. In the mid-1990s, Livingston, now MET's managing director, was working with nonporous extraction membranes for use in separating organic compounds from aqueous streams exiting chemical plants.
Livingston says he was developing commercial applications for new materials, honing his expertise in process design. "We were taking breaking technology and developing it through laboratory work--which often meant doing some equipment and process development--and taking it right through to commercial applications, dealing with thousands of tons of material," he says.
AT THE SAME TIME, Grace Davison was developing solvent nanofiltration membranes for lubricant oil dewaxing and other refining applications. That work culminated in a large-scale nanofiltration plant at the ExxonMobil refinery in Beaumont, Texas. Livingston says his group was familiar with the work under way at Grace Davison and envisioned broader applications for the technology.
The need for efficiency improvements in pharmaceutical and fine chemicals manufacture made for a perfect target market, Livingston says. "A lot of the cost and waste in fine chemicals and pharma processes come in the separations you do after the reactions," he says. "People use technologies like chromatography and absorption to try and take out fragments of catalysts from the reaction. These technologies can be very expensive, generate waste, and reduce yield."
While similar uses for nanofiltration were under investigation at other academic laboratories, Livingston says MET's background in engineering gave it a leg up. "We develop the process equipment in conjunction with the process," he says.
In 2002, MET landed a commercial agreement with Grace Davison in which it received rights to develop processes and market membranes for fine chemicals and pharmaceutical applications. Along the way it also received venture-capital injections from outside investors such as Nikko Capital.
MET's course was set in part by a graduate student, Dinesh Nair, who was working on catalyst recovery with nanofiltration membranes for his Ph.D. at Imperial. "The technology lends itself to complex separations such as solvent exchanges," Nair says. "It is also applicable to impurity removal, such as the removal of dimers from target monomers in a pharmaceutical batch process."
MET claims its methods are generally less destructive than traditional catalyst removal techniques. "There are methods for removing catalysts that will work, but you end up destroying the catalyst and probably losing some of your valuable product along the way," Nair says. Chromatography and distillation are harder to scale up to commercial application than nanofiltration membranes, he claims, and they also result in product loss. In addition, membrane processes require less energy than most alternatives, Nair says.
THE TECHNOLOGY has no real size limitations, according to Livingston. "It's not an issue, because the plant that Grace is running at the Beaumont refinery can handle 11,000 tons a day of solvent," he says. "The scale at which it's proven itself in refining is huge."
Nevertheless, MET has been concentrating on small-scale processes for prospective customers. It recently introduced a standardized benchtop reverse-osmosis and nanofiltration apparatus, METcell, which is suitable for small-scale testing, using both aqueous and nonaqueous solvents.
Companies that have tested MET's technology say they recognize its benefits and are looking for fits in their existing operations. John F. McGarrity, director of outsourcing R&D at Lonza, says he has been trying MET's technology in a number of applications revolving around the removal and reclamation of organometallic catalysts.
Where the technology pans out, the company may decide to pursue commercial-scale applications, most likely in tandem with other technologies, according to McGarrity. "This wouldn't displace our filtering technology," he says. "It would be added to processes in order to recycle catalysts and make the process simpler and more economical."
Simon Collard, development director for platinum group metal refining and products at Johnson Matthey, has been vetting MET's OSN membrane for pharmaceutical and fine chemicals catalyst recovery. He says it is useful in dealing with dilute metal streams. "Being able to concentrate metal or selectively remove impurities such as organic compounds allows us to remove metal in a form in which it is more readily refined," Collard says. He notes that OSN provides an alternative to traditional incineration techniques where residue is burned in order to concentrate metal.
Johnson Matthey has its own technology, AquaCat, for catalyst recovery based on supercritical water oxidation. "The big benefit of AquaCat is that organic components are rapidly decomposed into substances like carbon dioxide and nitrogen," Collard says. "That is a very complete oxidation with emissions well below all detectable measurements." Ultimately, he sees OSN as "another tool in the kit that might be used in conjunction with AquaCat or other technologies."
Meanwhile, MET is preparing to leave the nest. Christopoulou says the firm is looking at available space at science parks in and around London and hopes to be established off-campus later this year.
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