Quantifying how the <i>cis</i>/<i>trans</i> ratio of <i>N</i>,<i>N</i>-dimethyl-3,5-dimethylpiperidinium hydroxide impacts the growth kinetics, composition and local structure of SSZ-39

This work integrates experiments and computational methods to quantify how the <i>cis</i>/<i>trans</i> ratio of the OSDA used in SSZ-39 synthesis impacts the crystallization kinetics, material properties, and final product composition. The crystallization kinetics increase by 30% when increasing the <i>trans</i> isomer content from 14% to 80%. Per prior work, in all cases based on the synthesis gel composition and product yield aluminum is the limiting reagent, and the absence of any amorphous material detected in the time resolved PXRD studies leads us to conclude that FAU dissolution is the rate limiting step in the formation of SSZ-39 in this synthesis protocol. The TGA and NMR results suggest that the <i>trans</i> isomer of OSDA is selectively incorporated into the product. The NMR binding studies, and corresponding DFT-based results show that the <i>trans</i> isomer binds to FAU more strongly than the <i>cis</i> isomer, providing one possible explanation for this enhancement in kinetics and preferential uptake of the <i>trans</i> isomer. The EDS analysis indicates that the Si/Al ratios are between 7.7 and 8.6 at low and high <i>trans</i> OSDA content, indicating zeolite composition is mildly sensitive to the <i>trans</i> isomer content. EDS results show this decrease in aluminum content leads to a corresponding decrease in sodium uptake. DFT-based calculations confirm OSDA-sodium interactions cannot explain any decrease in sodium uptake, reinforcing lower aluminum content as the cause of lower sodium uptake. Preliminary cobalt titration experiments show a surprisingly low cobalt uptake but also show a clear dependence of the cobalt uptake on the solution pH.