People often call the Industrial Revolution the start of a new age of civilization, but the chemical revolution of the past century has had equally profound effects.
From the first commercial, industrial synthesis of indigo in 1897, chemicals that changed the world and the way we live have been produced mostly in batch reactors — great big tanks where chemicals are mixed at precise temperatures to produce just the right molecule. The ever-increasing cost of raw materials, transportation, and energy are combining to drive industrial chemical production to become more sustainable.
Advances in machining and fabrication are enabling these changes in the way chemicals are made — with the Spinning Tube-in-Tube (STT) reactor being a prime example. One expert says such technology could help lower the cost of producing such things as biofuel and pharmaceuticals.
James T. Ciszewski, director of the Danville, Va.-based Institute for Sustainable Chemistry at the Institute for Advanced Learning and Research, part of Virginia Tech’s Outreach and International Affairs, began using the STT reactor about eight years ago as a Postdoctoral Fellow at the U.S. Environmental Protection Agency’s research center in Cincinnati.
The technology is both more efficient and more effective than traditional large batch reactors, he said. "It works especially well with bimolecular reactions, which are essential steps in making everything from plastics to pharmaceuticals. Any reaction where the rate is dependent on collisional frequency should occur faster in the STT."
The continuous-flow reactor consists of a spinning tube (rotor) inside a fixed tube (stator). The gap between the two can be as small as 100 microns, about the width of a human hair. Crank the rotor up to 10,000 revolutions per minute, start the reactant feeds, optimize the temperature, and out comes a stream of product. Sustainable or "green" chemistry interests Ciszewski, as the STT produces far less waste than traditional chemistry while greatly increasing yields compared with current industrial processes.
The federal government's green expectations for the technology are spelled out in an EPA Science in Action article.
"When a pharmaceutical company uses a thousand-gallon reactor, most of what’s inside of it is solvent. Lots of that becomes waste that can’t always be recycled," Ciszewski said. The STT is also much better at maintaining the proper temperature during reactions, he said. This minimizes conversion of starting materials into waste that must be separated from the desired product, then trashed.
"The compact design of the STT and similar technologies will shrink the size of chemical plants and fundamentally change the industry. What is now done in large batches in large plants can soon be done in a much, much smaller arena," he said. "Imagine a mobile biodiesel plant that can move between clusters of farms at harvest time, able to directly produce fuel for the farmers' use from that year's excess harvest, and then moving on to do the same in the next township. This model minimizes transportation and storage costs and increases energy independence in a really meaningful way."
The small STT reactor enables the institute's scientists to test processes before companies decide to invest in the technology. Ciszewski said the technology will scale up in a linear fashion, compared with batch chemistry. That means a larger version of the STT will yield the same reliable results in greater quantities, reducing the time a company would need to go from research to production. Ciszewski said he foresees the institute becoming both a development center and a showcase for multiple innovative technologies for chemistry and materials science, where potential clients can share best practices and find the right fit for their particular processes.
Research at the Institute for Advanced Learning and Research includes sustainable chemistry, materials science, and plant biology as it relates to agriculture and horticulture. Virginia Tech students have earned doctoral and master’s degrees through their work at the institute.
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