Advances in the synthesis of Lewis acid zeolites have been bolstered by the synthesis of nano-zeolites to overcome diffusion limitations. Key challenges remain for the synthesis of Lewis acid nano-zeolites since current methods tend to result in a low tin incorporation efficiency (25%) and a low material yield (∼25%). In this work, insights on how to overcome these limitations are investigated through synthesizing nano-zeolite MFI with different tin precursors (n-Sn-MFI) and different ratios of water to silica and/or structure directing agent (SDA) to silica. The crystallization process is monitored using dynamic light scattering, and it is determined that the tin precursor has a minor impact on the final particle size, but the water and SDA concentrations did affect the final particle size. Compared to the standard synthesis (SiO2/SDA/H2O of 1:0.4:23), reducing the amount of SDA/SiO2 to 0.2:1 results in a larger particle size but increases the yield and tin incorporation efficiency. Reducing the amount of water (H2O/SiO2 of 19 and SDA/Si of 0.2) improves the tin incorporation efficiency over the standard case and results in small particles while achieving a yield of up to 78%. The resulting materials are characterized using several standard techniques to demonstrate that the materials are of high quality. The materials are tested for catalytic activity in the alcohol ring opening reaction of epoxide as a probe reaction and are found to have comparable activity. The rate of conversion of 1,2-epoxyhexane can be increased through synthesizing small crystals in high yield through decreasing the SDA/SiO2 ratio to 0.2:1 and reducing the H2O/SiO2 ratio to 19:1. Overall, the work demonstrates that the synthesis conditions can be tuned to increase the tin incorporation efficiency and increase the yield of the Lewis acid nano-zeolites while producing a highly active catalyst.

Sn-Beta is a promising catalyst for numerous reactions involved in biomass upgrading and fine chemical production, but it is complex with multiple types of active sites. The activity for Sn-Beta can be calculated on a per-site basis using site quantification experiments that involve adding a Lewis basic probe molecule, but it is not clear which types of sites are being titrated. Our work connects site quantification experiments with spectroscopic measurements to explain differences in the catalytic activity of materials crystallized for different amounts of time. For alcohol ring opening of epoxides, experiments reveal that Sn-Beta crystallized for 10 days (Sn-Beta-200-10d) is more active than Sn-Beta crystallized for 40 days (Sn-Beta-200-40d). These materials are investigated using site quantification experiments with three probestriethylamine, pyridine, or 2,6-lutidineto reveal the different fractions and types of sites. As the probe:Sn ratio is increased, these experiments result in two distinct slopes, indicating two distinct activities: high and low activity. The difference in activity between Sn-Beta-200-10d and Sn-Beta-200-40d can be attributed to the reduced fraction of high-activity sites. Although the two slopes have typically been assigned to open defect Sn sites for high activity and closed Sn sites for low activity, 15N NMR measurements of materials dosed with 15N-labeled pyridine contradict this assignment. Indeed, at low concentrations, pyridine adsorbs on both open defect and closed Sn sites whereas the low activity corresponds to pyridine binding to SnOH groups in addition to closed Sn sites. Overall, the identification of appropriate site quantification experiment parameters and the combination of these titrations with NMR techniques allows for the establishment of a synthesis–structure–activity relationship that has the potential to improve the performance of Sn-Beta.