Catalysis on Zeolites and Zeolite-like Materials, 3rd Edition

The scientific and practical interest in catalysts based on zeolites and zeolite-like materials continues to be strong; therefore, this Special Issue of Catalysts, “Catalysis on Zeolites and Zeolite-Like Materials, 3rd Edition,” continues the successful publication of the preceding two volumes. These materials have regular pore systems with cavities and channels in molecular dimensions, granting them unique properties such as high thermal stability, intrinsic acidity, and well-defined, shape-selective pore structures. A growing number of researchers are investigating the key catalytic properties of zeolites and related materials, and they are additionally being used commercially in an expanding range of fields. Ongoing research on the synthesis of novel structures and on the modification of existing zeolite-based and zeolite-type catalysts continues to advance, opening up new possibilities for innovative and environmentally friendly chemical processes. Beyond their traditional use in the petrochemical industry, zeolites are gaining importance in sustainable catalysis, and are beginning to play a key role in conversion of biomass or biomass-derived compounds into green fuels and other basic chemicals. In addition, the zeolites are often combined with photo(electro)catalytic components to further increase catalytic efficiency.

In this context, the reviews by Contributions 1 and 2 presented in this Special Issue are of particular interest. Contribution 1 demonstrates the potential of zeolite-supported TiO₂ for environmental applications, and highlights a sustainable approach for removing pollutants from the environment. The combination of the regular pore structure, high surface area, and adsorption capacity of various zeolites with the photocatalytic properties of TiO₂ gives rise to synergistic effects. These effects enable the effective degradation of a wide range of organic pollutants and hazardous substances found in wastewater. Contribution 2 discusses the mechanisms of photocatalytic and photothermal catalytic substances. It summarizes recent progress in zeolite-based catalysts for treatment of environmental pollutants through photocatalytic or photothermal catalytic processes. In addition, Contribution 3 describes the synthesis of the core–shell-structured microspheres composed of SiO₂@Fe(III)-based metal–organic frameworks. These materials enable efficient Fenton-like degradation of dyes, achieving degradation efficiencies of up to 96%. These catalysts can also be easily recovered by filtration and washing, and maintain high catalytic activity over six consecutive cycles in photo-Fenton wastewater purification processes. In Contribution 4, the conversion of glucose to levulinic acid, catalyzed by synergistic Cr/HZSM-5 in a GVL/H₂O biphasic system, was investigated. The study focuses on the effects of the solvent GVL (γ-valerolactone) using kinetic analysis. It shows that the presence of GVL reduces the activation energy for the conversion of glucose to levulinic acid, thereby improving the glucose dehydration process.

The review by Contribution 5 presents the recent progress in and strategies for designing zeolite-based catalysts for the hydroformylation of olefins. The catalytic properties are defined by the characteristics of the zeolite channels, the method used to deposit the active metal, the size of metal particles, and the microenvironment around them. Notably, exceptionally high activity in the hydroformylation of styrene was achieved with an MFI-type zeolite-based catalyst. This system also showed the highest reported n-regioselectivity in the hydroformylation of linear α-olefins among phosphorous-free catalytic systems—values close to 100%. For propylene hydroformylation, the best performance was obtained using a Rh-loaded MEL zeolite-based catalyst.

In Contribution 6, the hierarchical structuring of BEA-type zeolite was investigated using two different approaches. In addition, niobium pentoxide at different loadings was impregnated into the hierarchical materials. Both treatments increased the SiO₂/Al₂O₃ ratio and produced crystals with domains of approximately equal size. The hierarchical methods produced secondary mesopores and reduced the micropore volume of the treated zeolites. These structural changes had different effects on the dehydration of ethanol and propanol. Contribution 7 reports on a multifunctional Na-promoted FeCo-modified H-ZSM-5 zeolite catalyst for CO₂ hydrogenation to light aromatics via a modified Fischer–Tropsch synthesis pathway. This study systematically varies the Si/Al ratio of acidic zeolite and investigates its crucial role in influencing selectivity toward light aromatics. The results provide guidance for the rational design of bifunctional catalysts with targeted, shape-selective functions. In Contribution 8, the dimethyl ether-to-olefin (DTO) reaction was studied on ferrierite zeolites loaded with different amounts of phosphorus. The goal was to maximize the n-butene yield by optimizing the amount of phosphorus loading. Multiple regression analysis of the data obtained revealed that the ratio of strong-to-weak acid sites and the total pore volume correlate strongly with the n-butene yield. Based on these correlations, the DTO reaction mechanism was discussed using the dual-cycle reaction model. Finally, Contribution 9 describes the use of different synthesized FER zeolites as catalysts for n-butene skeletal isomerization. FER-type zeolites were successfully prepared either with pyrrolidine as an organic template or without pyrrolidine, using Na-form or H-form seeds. The seed-derived FER samples showed similar topological and morphological properties compared to the pyrrolidine-derived sample, as well as similar total acid densities. The study demonstrates that combining pyrrolidine-containing seeds with an optimal aluminum distribution in the FER framework enhances the performance in the zeolite in terms of the skeletal isomerization of n-butene.