Andrey G. Popov

In situ FTIR spectroscopy was established as a standalone method for quantifying mass transport in zeolites. By monitoring two independent IR markers, global isooctane uptake (δ(CH) bands) and Brønsted acid site accessibility (3610 cm ^–1 band), the method reveals a 5 to 11 times difference between overall uptake and true micropore diffusion, demonstrating its ability to distinguish surface adsorption from intracrystalline transport. While overall diffusion is slowest for ZSM-11, its micropore diffusion is comparable to that of ZSM-5 samples. This suggests that the straight intersecting channel system of the MEL framework facilitates intracrystalline transport, although this advantage is masked by slower surface adsorption in the overall uptake. A slight difference between TS-1 and ZSM-5 is attributed to a combination of pore geometry and weaker Lewis acidity of titanium-containing frameworks. In situ FTIR offers a direct, chemically specific means to assess diffusion contributions, providing a valuable tool for optimizing mass transport in zeolite-based catalysts.

Modification of MFI-type zeolites with tin involves impregnating the zeolite with an SnCl₂ solution in excess NaCl, calcination (to fix the tin oxide), and water washing (to remove excess NaCl). Loading platinum on the tin-modified support results in a highly active (5–10 mol of C₃H₆ per mol of Pt per second), selective (96–98% towards propylene), and stable catalyst for dehydrogenation of propane. Due to the high dispersion of tin, which serves as an anchor for platinum, the average Pt particle size is 1.2 nm. The dispersion of tin is facilitated not only by the molecular dilution of its precursor with sodium chloride but also by the redispersion of tin across the surface due to the formation of volatile SnCl₄ during calcination.

Two series of zeolites, vis., the MEL and MFI types, with different Si/Al molar ratios were synthesized by a steam-assisted crystallization method, specifically dry gel conversion (DGC). Their physicochemical properties were characterized by low-temperature nitrogen adsorption, scanning electron microscopy, and X-ray fluorescence analysis. The acidic properties were examined by IR spectroscopy of adsorbed pyridine and 2,6-di-tert-butylpyridine as well as by ammonia temperature-programmed desorption. The DGC-synthesized zeolites were distinguished by high crystallinity, small crystal size, and well-developed surface. All the samples exhibited high activity and deactivation resistance in the oligomerization of a butane–butylene fraction. A comparative assessment of the catalytic performance the MEL and MFI samples demonstrated that the structural difference between the MEL and MFI types barely affects their deactivation resistance. Therefore, MEL zeolite is a valid alternative to the MFI type in the development of oligomerization catalysts.

Synthesis of MOF-5 at room temperature was optimized. The phase-pure crystalline structure with high hydrogen capacity was prepared at room temperature and atmospheric pressure. The MOF-5 pressing and subsequent fractionation singificantly improves its operation properties. An adsorption apparatus was designed and assembled to study the adsorption properties of the synthesized materials under the conditions close to the real one. Experiments on studying the adsorption properties of MOF-5 under the conditions of cryogenic hydrogen adsorption showed that the samples adsorbed up 3.3 wt % H₂ at a 30 atm pressure and –196°С.

MEL-type zeolite was synthesized by a novel steam-assisted crystallization method. This zeolite was characterized by X-ray diffraction, low-temperature nitrogen adsorption/desorption, scanning electron microscopy, and X-ray fluorescence analysis. IR spectroscopy of probe molecules (pyridine and 2,6-di-tert-butylpyridine) was used to characterize the acidic properties of this sample. The MEL zeolite synthesized by steam-assisted crystallization consisted of aggregated nanocrystals up to 300 nm in size and exhibited a high phase purity, a large micropore volume (0.13 cm³/g), and high concentrations of both Brønsted and Lewis acid sites. When tested in oligomerization of a butane–butylene fraction and hydroconversion of n-hexadecane, this MEL zeolite proved to be comparable to MFI-type zeolites in terms of catalytic performance.