In a 2012 paper (Moliner et al.), a team from the Universidad Politécnica de Valencia and Haldor Topsoe reported the synthesis of a Cu-exchanged SSZ-39 zeolite that showed an excellent catalytic activity for the selective catalytic reduction of NO_x. The material also exhibited extraordinary hydrothermal stability.

This material is a three-directional small pore zeolite containing large cavities with D6R, which can stabilize Cu²⁺ species, avoiding dealumination effects and copper migration during catalytic tests. Cu–SSZ-39 performs extremely well for the NH₃-SCR of NO_x, better than CHA structure, and shows an extraordinary hydrothermal stability. These preliminary results would suggest that Cu–SSZ-39 can be a very attractive catalyst for NO_x SCR converters in the automotive industry.

—Moliner et al. (2012)

In a paper published earlier this year in the ACS journal Industrial & Engineering Chemistry Research, Shantz and his team presented a thorough study of SSZ-39 formation. (Ransom et al. 2017)

The Tulane team will now test the ability of SSZ-39 in vehicles’ selective catalytic reduction (SCR), the system in cars that reduces harmful emissions.

Specifically, the Tulane team will test SSZ-39’s efficiency in reducing nitrogen oxides, which contribute to the production of acid rain. The focus of this program is to help better understand the properties of SSZ-39, with the goal of demonstrating whether SSZ-39 could be a commercially viable SCR catalyst.

The grant project is certainly relevant in the context of energy and the environment. This focused project will validate the ability of SSZ-39 to eliminate nitrogen oxides from automotive emissions systems by converting them to molecular nitrogen, the main component of the air we breathe. I am delighted that we will be able to work with scientists from SACHEM on this problem.

—Prof. Shantz

According to Shantz, one of the challenges for SCR catalysts are their ability to handle temperature increases from typical operating conditions. If the system typically operates between 300-400 degrees Celsius, materials are needed that can handle higher temperatures for short periods of time. The inability of current materials to be able to handle these high-temperature excursions is a limitation of the current technology.

The zeolite SSZ-39 material is something that could be potentially implemented in the next three years. What we are trying to do in the lab is to identify what this material can and cannot do: is it a good enough material catalytically? Will it be able to handle the temperature excursions better than the current state of the art?

Improvements in SCR technology will result in emissions systems in diesel trucks that will be able to operate longer, and emission systems will be replaced with less frequency. It goes without saying decreased nitrogen oxide emissions are beneficial to the environment.

—Prof. Shantz

The Shantz Lab in the Chemical and Biomolecular Engineering Department at Tulane is focused on the development of new materials that will be relevant in energy generation, storage and conversion.

Resources

• Manuel Moliner, Cristina Franch, Eduardo Palomares, Marie Grill and Avelino Corma (2012) “Cu–SSZ-39, an active and hydrothermally stable catalyst for the selective catalytic reduction of NO_x” doi: 10.1039/C2CC33992G

• Ransom, R., Coote, J., Moulton, R., Gao, F., Shantz, D. F. (2017) “Synthesis and Growth Kinetics of Zeolite SSZ-39” Ind. Eng. Chem. Res. 56(15), 4350-4356 doi: 10.1021/acs.iecr.7b00629