(304g) Comparative Study of SSZ-39 Formation, Growth Kinetics, and Material Properties Made with Different Organic Structure Directing Agents.

The small-pore SSZ-39 zeolite has proven to be a promising catalyst for selective catalytic reduction (SCR) of NOx emissions due to its exceptional activity and hydrothermal stability. Recent studies have shown that the distribution of OSDA (organic structure directing agent) isomers in the zeolite synthesis gel can affect the aluminum siting and distribution within the SSZ-39 framework. Prior work from our lab and others have shown that the trans isomer of this OSDA leads to an enhancement in the crystallization kinetics as compared to the cis isomer.

In this talk we present a comparative study of the growth kinetics, zeolite composition and other properties of SSZ-39 materials made using three different OSDA – N,N-dimethyl-3-5-dimethylpiperidinium hydroxide, N,N-diethyl-2-6-dimethylpiperidinium hydroxide and tetraphosphonium hydroxide. A comprehensive comparative analysis of SSZ-39 materials synthesized using both quaternary ammonium compounds and phosphonium OSDAs is performed. Particular attention is paid to elucidating the influence of OSDA isomer identity on growth kinetics, synthesis yields and their dependence on synthesis conditions. Synchrotron diffraction coupled with Rietveld analysis is used to determine the copper locations and their variation with changing Cu/Al ratios. Aluminum arrangement will be examined using cobalt titration to probe isolated and paired aluminum species, while NO binding studies will provide insights into copper speciation.

In addition to our comparative synthesis study, we will also present preliminary results for the low temperature SCR of NO. Prior work from our lab has investigated the role of the copper ion exchange on low temperature SCR. Here by contrast we will compare how SSZ-39 samples made with different OSDAs loaded with copper in the same manner behave for this reaction.