Catalysis Club of Chicago

Member-North American Catalysis Society

Advanced Zeolite Catalysis Technologies for Emission Control Applications

Monday, March 11, 2019

The Great Escape 
Irving Park Road
Schiller Park, IL 60176

Dr. Bjorn Moden
Research Manager
Zeolyst International
280 Cedar Grove Road
Conshohocken, PA 19428, USA

Zeolyst Web Site

Abstract: Over the past decade, zeolites have found increasing commercial use in a variety of emission control technologies.  In this presentation, I will give an overview of some of these technologies as well as highlight a few specific zeolite examples.  Selective catalytic reduction with urea (urea-SCR) is one of these automotive applications, where microporous materials containing either Fe or Cu cations catalyze conversion of nitrogen oxides (NOx) from diesel exhaust with ammonia to form harmless nitrogen and water.  Early adoption of zeolite-based on-road urea-SCR in Japan and the US to meet stringent regulations in 2009 and 2010, respectively, was followed by introduction in Europe in 2014.  Over the next few years, tightening regulations in e.g. China, India and Brazil will likely lead to zeolite-based SCR catalysts being used in these countries as well.  Among Cu-based materials, the development of small-pore high-silica Cu-chabazite and Cu-SAPO-34, both with CHA framework, were major breakthroughs achieving high thermal stability up to 900 oC as well as high SCR activity.  For SCR applications where milder aging conditions are encountered, organic-free zeolites with lower SiO2/Al2O3 ratio (SAR) can offer benefits relative to the high silica zeolite materials while still having sufficient stability.  In this presentation, I will cover examples based on organic-free Beta (BEA) and organic-free low-silica chabazite (CHA) and compare them with their counterparts that are synthesized using organic structure directing agents.  For Fe-exchanged organic-free BEA with 10 SAR, the SCR activity at low exhaust temperatures is superior relative to a traditional Fe-exchanged 25 SAR BEA both in the fresh form and after steaming at 750 oC.  This improvement is attributed to both the higher Fe-exchange capacity and the increased fraction of isolated active Fe-sites at 10 SAR relative to that for 25 SAR BEA.  Cu-exchanged organic-free CHA with 5.5 SAR is not stable in steam at 750 oC but collapses during the aging.  In order to solve this stability issue, we investigated adding additional cations to the material.  When Ca is added to the low SAR Cu-CHA, the resulting Cu,Ca-CHA retains its stability following aging at 750-800 oC.  After these steam treatments the Cu,Ca-CHA materials have comparable low-temperature SCR activity to high SAR Cu-CHA, and the selectivity at high temperatures is higher for Cu,Ca-CHA relative to high SAR Cu-CHA allowing for lower urea consumption at a given NOx conversion.  In addition to the SCR performance, the N2O formation is lower for the low SAR CHA, providing an additional benefit in countries that have begun or will introduce green-house gas regulations. 

Bio: Bjorn Moden is a Research Manager at Zeolyst International at the PQ Corporation R&D center in Conshohocken, PA.   His team is responsible for development of new zeolite products for various areas including emission control and custom zeolite applications.  Bjorn received his Ph. D. in Chemical Engineering from University of California, Berkeley under the direction of Enrique Iglesia in 2006 and his undergraduate degree in Chemical Engineering from the Royal Institute of Technology (KTH), Stockholm in 2000.  Over the past decade, Bjorn has been active in various roles in the Catalysis Club of Philadelphia (secretary, sponsorship director, chair-elect, chair, past chair) and the North-East Corridor Zeolite Association (NECZA; poster chair, chair).  He is currently the secretary for the organizing committee of the 2020 International Conference on Catalysis.