Water-Separation Membrane Efficiently Converts CO2 into Methanol

An efficient and multipurpose chemical, methanol is used as fuel for producing an unlimited number of products. By contrast, carbon dioxide (CO₂) is a greenhouse gas that is regarded as an undesirable byproduct resulting from several industrial processes.

CO₂ can be beneficially used by changing CO₂ to methanol. Chemical engineers from Rensselaer Polytechnic Institute have now developed a highly effective separation membrane that can be used to convert CO₂ to methanol more efficiently. The researchers have demonstrated this method in a study recently published in the Science journal.

According to the scientists, this latest innovation can potentially enhance many industrial processes that rely on chemical reactions in which water is formed as a byproduct. For instance, the chemical reaction that causes the conversion of CO₂ into methanol also generates water, which significantly limits the continuous reaction.

The research team at Rensselaer Polytechnic Institute has set out to identify a new technique that would allow them to filter the water while the reaction is taking place, and still permit them to retain other important gas molecules.

The scientists ultimately developed a membrane composed of zeolite crystals and sodium ions. This membrane can rapidly and carefully enter into the water through tiny pores—referred to as water-conduction nanochannels—but without losing any essential gas molecules.

The sodium can actually regulate, or tune, gas permeation. 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.

Miao Yu, Endowed Chair Professor, Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute

Yu is also a member of the Center for Biotechnology and Interdisciplinary Studies (CBIS) at Rensselaer Polytechnic Institute, which headed the study.

Earlier, this kind of membrane was sensitive to defects, and as a result, other gas molecules were able to escape easily, added Yu. Now, Yu’s research team has devised a novel technique to improve crystal assembly that effectively prevents those defects.

The researchers discovered that when water is effectively eliminated from the process, the chemical reaction takes place very rapidly, added Yu.

When we can remove the water, the equilibrium shifts, which means more CO₂ will be converted and more methanol will be produced.

Huazheng Li, Study First Author and Postdoctoral Researcher, Rensselaer Polytechnic Institute

“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,” stated 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 researchers are currently working to create a scalable process and also establish a startup company that would enable this membrane to be used on a commercial scale to generate highly pure methanol.

According to Yu, this unique membrane could even be used to enhance many other reactions.

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, Endowed Chair Professor, Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute