Editorial for the Special Issue “Research Advances in Zeolites and Zeolite-Based Catalysts”

Zeolites are crystalline aluminosilicates that have been widely used as heterogeneous catalysts in industrial processes, particularly in oil refining and petrochemistry [1,2]; more recently, they have been used in fine chemistry applications, both as catalysts and catalyst supports [3,4]. Their use in adsorption and purification processes has also been reported [5,6]. This broad spectrum of potential uses is possible due to a unique combination of properties like high thermal and mechanical stability, well-defined pore architecture, and intrinsic acidity [7]. The Special Issue “Research Advances in Zeolites and Zeolite-Based Catalysts” includes two review papers and three original research articles that highlight recent synthesis/modification strategies and the application of zeolite materials.

In Contribution 1, Clara Mongelli and coworkers investigated the performance of several Ni–Cu-loaded zeolites in one-pot synthesis of sustainable aviation fuel (SAF). Particularly the formulation, 12.8% Ni-3.2%Cu/ZSM-5 exhibited the highest conversion of brown grease (BG) and selectivity into SAF-like hydrocarbons. The contribution of this study highlighted the superior catalytic performance of ZSM-5 support when compared to others like SAPO-11, SAPO-34, and ZSM-22, offering valuable insights for catalysts design in the production of sustainable aviation fuels from fats, oils, and greases.

In Contribution 2, Cristopher K. Russell et al. confronted the catalytic behavior of HZSM-5 with Ga/HZSM-5 in propylene aromatization and highlighted the important role of operation condition, namely hydrogen partial pressure, on the reaction mechanism and the obtained products. The results obtained in this study showed that the presence of Ga enhanced the aromatic selectivity, especially at lower hydrogen pressure (1.9 kPa), through catalytic dehydrogenation that led to aromatization. On the other hand, for higher hydrogen pressure (50 kPa), the effect is less notorious as the dehydrogenation equilibrium shifts into paraffinic products.

In Contribution 3, Shan Jiang and coworkers investigated the performance of Pt₃Mn/SiO₂ + ZSM-5 bifunctional catalysts to convert ethane into high-demand aromatic molecules—benzene, toluene, and xylene (BTX)—through the dehydroaromatization (EDA) reaction. The authors studied the effect of several parameters on product distribution: catalyst composition, hydrogen partial pressure, and reaction temperature. The obtained result showed that the catalyst composition ZSM-5/Pt₃Mn = 1/1 ratio gave the highest BTX formation and ethane conversion rates. When the reaction temperature increases from 550 to 650 °C, both ethane conversion and benzene selectivity increase; but raising the hydrogen partial pressure reduces EDA reaction rate and BTX selectivity.

Contribution 4 is a comprehensive review by Ze-Long Guan and coworkers concerning the synthesis, characterization, and application of hierarchical porous materials in CO₂ reduction reactions (CO₂RRs). The authors described the main procedures for creating hierarchical porous materials with diverse chemical compositions. Basic methods like surfactant templating, replication, or sol–gel are described. Chemical technology strategies are illustrated by emulsion templating, phase separation, zeolitization, and self-assembly methods. Physical–chemical methods are also surveyed with the use of supercritical fluids, freeze drying, and selective leaching techniques. The applications of hierarchical materials prepared using the above strategies are illustrated in CO₂ reduction reactions, emphasizing the role of mesopores for promoting the efficient diffusion of CO₂ molecules towards the inner surface of the catalyst as well as the distribution of active sites inside the micropores.

Finally, in Contribution 5, Wentao Zhao and collaborators thoroughly review the recent progresses on the synthesis and applications of zeolites produced from industrial solid wastes. The authors systematically cover the present state and trends concerning some typical industrial solid wastes such as coal fly ash, metallurgical slags, waste glass or waste catalyst. The synthesis methodologies to transform waste into zeolites are surveyed as well as the impact of several parameters on synthesis like temperature and Si/Al ratio, among others. A selection of applications, illustrated with several examples—from degradation of volatile organic compounds to wastewater treatment or denitrification—is presented. This work conveys the message that the synthesis of zeolites from industrial wastes contributes to energy conservation and emission reduction while partially solving disposal issues; however, synthesis procedures still need optimization.

Taken together, the contributions in this Special Issue provide some key messages on zeolite and zeolite-based material synthesis, modifications, and use in important catalytic processes. The performances of conventional zeolites still have room for innovation; moreover, hierarchical zeolites have great potential, which should be explored in the near future. Finally, the synthesis of zeolites from industrial wastes provides an excellent opportunity to produce technological materials from potentially valuable resources, with a focus on building a circular economy.

I am deeply grateful to all the authors who contributed to this Special Issue. I sincerely hope that the original research papers and review articles featured may inspire further research on zeolites and zeolite-based catalysts. I also would like to extend my gratitude to MDPI Editorial team for the opportunity to serve as Guest Editor, with my special thanks to the Assistant Editor, Maeve Yue, for her dedicated efforts and collaboration. Finally, I would like to express my appreciation to all the reviewers for their essential and thoughtful evaluations that enriched the quality of this Special Issue.