New zeolite membrane strips water from methanol

"In industry, there are so many reactions limited by water. This is the only membrane that can work highly efficiently under the harsh reaction conditions."Miao Yu, Rensselaer Polytechnic Institute

Methanol is a versatile and efficient chemical used in the production of countless products. Carbon dioxide (CO₂), on the other hand, is a greenhouse gas that is the unwanted by-product of many industrial processes.

Converting CO₂ to methanol is one way to put CO₂ to good use. In a paper in Science, researchers from Rensselaer Polytechnic Institute demonstrated how to make the conversion process from CO₂ to methanol more efficient by using a highly effective separation membrane they developed. This breakthrough, the researchers said, could improve a number of industry processes that depend on chemical reactions where water is a by-product.

The chemical reaction responsible for transforming CO₂ into methanol also produces water, which severely restricts the continued reaction. The Rensselaer team set out to find a way to filter out the water as the reaction is happening, without losing other essential gas molecules.

Their approach involved assembling a membrane made up of sodium ions and zeolite crystals that was able to carefully and quickly permeate water through small pores – known as water-conduction nanochannels – without losing gas molecules.

"The sodium can actually regulate, or tune, gas permeation," said Miao Yu, a professor of chemical and biological engineering and a member of the Center for Biotechnology and Interdisciplinary Studies (CBIS) at Rensselaer, who led the research. "It's like the sodium ions are standing at the gate and only allow water to go through. When the inert gas comes in, the ions will block the gas."

In the past, Yu said, this type of membrane was susceptible to defects that would allow other gas molecules to leak out. But his team developed a new strategy to optimize the assembly of the crystals, which eliminated those defects.

When water was effectively removed from the process by the membrane, Yu said, the team found that the chemical reaction was able to happen very quickly. "When we can remove the water, the equilibrium shifts, which means more CO₂ will be converted and more methanol will be produced," explained Huazheng Li, a postdoctoral researcher at Rensselaer and first author of the paper.

"This research is a prime example of the significant contributions Professor Yu and his team are making to address interdisciplinary challenges in the area of water, energy and the environment," said Deepak Vashishth, director of CBIS. "Development and deployment of such tailored membranes by Professor Yu's group promise to be highly effective and practical." The team is now working to develop a scalable process and a start-up company that would allow this membrane to be used commercially to produce high purity methanol.

According to Yu, the membrane could also be used to improve a number of other reactions. "In industry, there are so many reactions limited by water," he said. "This is the only membrane that can work highly efficiently under the harsh reaction conditions."

This story is adapted from material from Rensselaer Polytechnic Institute, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.