RESEARCHERS FIND MATERIAL THEY SAY CAN MORE EFFICIENTLY CAPTURE CO2

Tamar Hallerman
GHG Monitor
09/28/12

Researchers from the United Kingdom and China have found a material that can selectively capture carbon and sulfur dioxide without most of the energy and environmental penalties associated amine capture technologies, they report in the most recent issue Nature Chemistry. The adsorbent, NOTT-300, is a metal organic framework (MOF) made from aluminum nitrate salt, relatively cheap organic materials and water that has high chemical and thermal stability, as well as good selectivity and uptake capacity for CO2 and SO2, according to the study. NOTT-300 is also non-toxic and carries less of an energy penalty than amine solvents because it does not require heat for regeneration, one of the study’s authors, Sihai Yang of the University of Nottingham, said in an interview this week. “NOTT-300 is ultra stable and can be recycled many times without the material decomposing,” Yang said. “It also contains zero amines in it, so it won’t cause any environmental impacts compared to the amine materials.” 

Used for decades by the oil and gas industry, amine solvents have long dominated the field of CO2 capture technologies. However, some researchers—particularly in Norway—have raised questions surrounding the materials’ impact on the environment and public health if emitted into the atmosphere and mixed with other chemicals. Amines are also highly corrosive and energy intensive because their aqueous solutions must be heated up after separation for regeneration. According to Yang, amines constitute an “easy on, difficult off” model for CO2 separation that is not very efficient. “Amine materials have been used for years because of their very high selectivity of CO2 molecules. So once the CO2 is on, it’s always on. However, it’s very difficult to take it off, that’s why people have to heat it up a hundred degrees to regenerate—it’s an ‘easy on, difficult off’ system,” he said. “But in the case of NOTT-300, it’s very easy to put the CO2 in, and also very easy to take the CO2 off by reducing the pressure with zero heating input. In other words, ‘easy on, easy off.”

NOTT-33 Uses Water for Solvent

Yang said NOTT-300 could be a particularly good alternative to amines because it is more environmentally and economically sustainable. “There are a number of other porous materials being developed for their carbon capture properties, but people try to put amines into the porous materials to improve the selectivity to the CO2 molecules. This has been a major research trend which is dominating this area of research, but in this case, we’re going the other way and using zero amines with the material, and it turned out that we also achieved a very high selectivity without the amine incorporation,” he said. Yang added that NOTT-300 is more efficient because it uses water as its only solvent and can be regenerated at ambient temperatures.

Yang said his team used a computer program to identify the promising MOF, and then tested the NOTT-300 on the U.K.’s ISIS neutron source and Diamond Light Source synchrotron facility to further understand how CO2 and SO2 bind to the material. “The material shows high uptake of CO2 and SO2. In the case of SO2, this is the highest reported for the class of materials to date. It is also selective for these gases, with other gases—such as hydrogen, methane, nitrogen, oxygen—showing no or very little adsorption into the pores,” said project lead Martin Schröder, who is also Dean of the Faculty of Science at The University of Nottingham, in a statement. Yang said that the research team is now working with two companies to scale up the MOF to see if it can be applicable for large-scale CO2 capture.