A series of BEA-type zeolites with SiO2/Al2O3 ratios of about 50 were synthesized by steam-assisted (SAC) and hydrothermal crystallization (HTC) in fluoride and alkaline media. Their physicochemical properties were characterized by low-temperature nitrogen adsorption, XRD, SEM, XRF, and NH3-TPD. The catalytic performance was investigated in liquid-phase toluene disproportionation. The SAC-synthesized samples were distinguished by a higher concentration of acid sites. The BEAs prepared by SAC in alkaline media exhibited a higher activity in toluene disproportionation. The samples synthesized in fluoride media, both by steam-assisted and hydrothermal crystallization, proved to be comparable in activity.

The paper is devoted to characterization of BEA and MFI zeolite samples synthesized in alkaline and fluoride media. Using a number of synthesized and commercial samples, enzyme adsorption isotherms were recorded, specifically for Aspergillus oryzae β-galactosidase. The highest adsorption capacity (32–33 mg/g) was achieved on fine-crystalline (0.2–0.6 μm) MFI samples. The fine-crystalline BEA samples (0.3–1 and ˂0.1 μm) exhibited maximal adsorption capacities of 18 and 26 mg/g, respectively. The coarse-crystalline BEA and MFI zeolites prepared by fluoride synthesis reached a markedly lower enzyme adsorption capacity, not exceeding 6 mg/g. The NMR spectroscopy data indicate that the low adsorption capacity of the zeolites synthesized in fluoride media was not only owing to their crystal size but also to the low content of hydroxyl groups on their surface.

This study investigated the physicochemical properties of BEA zeolites with SiO 2 /Al 2 O 3 ratios of 50 to 250 synthesized in fluoride and alkaline media and tested their catalytic activity in alkylation of benzene with propylene under liquid phase conditions. The samples similar in SiO 2 /Al 2 O 3 ratio synthesized by the fluoride route exhibited a larger crystal size and fewer crystal defects. Regardless of the synthesis medium, the samples with SiO 2 /Al 2 O 3 = 50 proved to be more active and stable in alkylation of benzene with propylene than the samples with lower aluminum content in the zeolite framework. The samples prepared by the fluoride route achieved higher cumene selectivity. This can be explained by their lower external surface area than that in the zeolites prepared in alkaline media, where side reactions produce large molecules of di- and triisopropylbenzenes.