Researchers optimize filtration media for bio applications

By Bryan Sims | October 21, 2011

After 10 years of investigation, researchers at the University of Minnesota are reporting that significant progress is being made in the development of a highly efficient molecular sieve that could drive down capital and operating expenditures during the production of advanced biofuels and biobased chemicals. The research was published in the latest issue of the journal Science.

According to Michael Tsapatsis, chemical engineering and materials science professor at UM leading the project, the research specifically involves the development of suspended, ultra-thin zeolite nanosheets that enable higher throughput of alcohols, such as ethanol or butanol, and subsequent dehydration of water that occur during the separation process at the backend of biorefining. Tsapatsis described the membrane as having zeolite crystals with molecular-sized pores pitted in a strategic formation that act as a sieve for separating out alcohols and dehydrating water.

“We’ve already demonstrated that these membranes can remove water or can remove alcohol from these mixtures, depending on what course material is chosen,” Tsapatsis told Biorefining Magazine, adding that work is primarily focused on a hydrophobic filtration membrane to enable for higher throughput of alcohols.

While zeolite membranes aren’t new to the biorefining industry, having typically been used as absorbents and catalysts for many years, Tsapatsis said prevailing challenges have been trying to find more cost- and energy-efficient methods for extending the life of zeolitic-based membranes for purifying alcohol product during biorefining applications as alternatives to traditional techniques such as distillation.

“There are membranes used today in some biorefining applications, but zeolite membranes are quite costly,” Tsapatsis said. “Membranes are typically sold by square meter, which can translate into $10,000 per square meter…that’s quite expensive. We don’t increase the cost of the membrane, we increase the flux; meaning we increase the productivity per square meter of the membrane and that will have not only energy savings, but capital savings as well.”

Tsapatsis added that the zeolitic molecular sieve that’s being developed by his team at UM could potentially be integrated in biorefining process for improving upon existing separation techniques like distillation and absorption in a type of hybrid application.

“What our technology will improve in the membrane separation is, it’s going to be done more efficiently,” Tsapatsis said.

The team has filed a provisional patent and Tsapatsis said he hopes to commercialize the technology. The research is being funded by the U.S. DOE, Carbon Sequestration Program, the Catalysis Center for Energy Innovation (An Energy Frontier Center), the National Science Foundation and a variety of UM partners.

To view the full paper published in Science, visit