Combined Alkali-Organoammonium Structure Direction of High-Charge-Density Heteroatom-Containing Aluminophosphate Molecular Sieves.

The charge density mismatch concept was applied to the synthesis of high-charge-density silicoaluminophosphate SAPO-69 (OFF) and SAPO-79 (ERI) and zincoaluminophosphate PST-16 (CGS), PST-17 (BPH), PST-19 (SBS), and ZnAPO-88 (MER) molecular sieves. Combined alkali-organoammonium structure direction in these systems is thus enabled. Structure direction is treated from the perspective of stabilizing an ionic framework, the relationships between reaction charge density (OH- /H3 PO4 ), alkali and organoammonium content, and ionicity of tetrahedral framework atoms in successful structure direction are presented.

A Complex Zeolite Containing Multiple Ring Sizes in a Single Channel: One-Dimensional Zeolite UZM-55.

Zeolites are porous aluminosilicate materials utilized in a variety of sorption, separation, and catalytic applications. The oil refining industry in particular has seen a number of significant advances due to the introduction of new technologies enabled by new zeolites. Of particular importance are zeolites with 10- or 12-membered ring pores, resulting in pore shapes and sizes appropriate for the interaction with small hydrocarbon molecules. Here, the synthesis of a new zeolite UZM-55 is reported and the idealized structure thereof is presented. The most complex structure solved to date, UZM-55 possesses a large triclinic unit cell containing 52 T-sites. The material uniquely contains both 10- and 12-membered ring pores in a single, undulating one-dimensional channel, the first example in a zeolitic material of multiple delimiting rings in a single channel. This discovery opens new opportunities in shape-selective adsorption and catalysis. Demonstrated here is the unique adsorption behavior of UZM-55, shown both experimentally and computationally to adsorb one nonane molecule per unit cell in a linear conformation.

Sorbate Transport in Carbon Molecular Sieve Membranes and FAU/EMT Intergrowth by Diffusion NMR.

In this paper we present and discuss selected results of our recent studies of sorbate self-diffusion in microporous materials. The main focus is given to transport properties of carbon molecular sieve (CMS) membranes as well as of the intergrowth of FAU-type and EMT-type zeolites. CMS membranes show promise for applications in separations of mixtures of small gas molecules, while FAU/EMT intergrowth can be used as an active and selective cracking catalyst. For both types of applications diffusion of guest molecules in the micropore networks of these materials is expected to play an important role. Diffusion studies were performed by a pulsed field gradient (PFG) NMR technique that combines advantages of high field (17.6 T) NMR and high magnetic field gradients (up to 30 T/m). This technique has been recently introduced at the University of Florida in collaboration with the National Magnet Lab. In addition to a more conventional proton PFG NMR, also carbon-13 PFG NMR was used.