Carbon dioxide valorization and its conversion towards intermediates and fuel are considered helpful strategies for de-fossilizing several sectors that could contribute to mitigating the effect of greenhouse gas emissions on global warming. In this regard, zeolites are extensively investigated as key materials for promoting carbon dioxide capture and conversion. In this chapter, after a brief discussion about the carbon capture strategies when zeolites are employed, the most important features of these materials are discussed with a focus on the heterogeneous thermo-catalytic conversion of CO2 towards oxygenates or hydrocarbons via modified Fischer–Tropsch and methanol-mediated routes. Overall, this chapter provides an outlook on the role of zeolites in the Carbon Capture Sequestration and Utilization (CCSU) pathway.
Zeolites and related materials are an important class of environmental catalysts, both from a research (academic) perspective and from the application side. We discuss here two main industrially relevant areas: (i) zeolitic technologies for the reduction of polluting emissions, which include VOC removal, nitrogen removal (NOx and N2O), catalytic elimination of methane emissions (in a low concentration), and water treatment; and (ii) zeolitic technologies to enhance circularity, specifically CO2 reuse. The focus is on the analysis of pros/cons, particularly from an industrial viewpoint, rather than presenting a detailed state-of-the-art perspective.
The beneficial role of the small and homogeneous micropore size of conventional zeolites in specific applications becomes a major limitation when their physico-chemical properties are to be exploited as catalysts in reactions involving bulky reactants or intermediates. To overcome these limitations, multiple procedures have been developed over recent decades aimed at improving the accessibility of the active sites of zeolites. This improved accessibility not only results in higher activity, but also higher stability and lower deactivation rates. This chapter focuses on providing updates on the most groundbreaking advances in the synthesis of zeolites with improved accessibility over the last ten years and how these improvements impact their catalytic performance. Bottom-up and top-down approaches for the synthesis of nanosized zeolites and zeolites with hierarchical porosities are revisited and updated. In addition, new breakthroughs such as 2D zeolites and dendritic zeolites, and the use of eco-friendly synthesis routes, will be addressed. In summary, this chapter collects selected strategies to efficiently improve the uniformity of secondary mesopores, tailor the crystal morphology and size, increase the synthesis mass yields, simplify synthesis protocols or use cheaper and more sustainable reagents.
Zeotype aluminophosphates have tetrahedrally-connected framework structures similar to those of zeolites, but that only contain rings with even numbers of framework cations that show strict alternation of Al and P. While some of the topology types that these aluminophosphates exhibit are also known in aluminosilicate form, there are many that still act as a challenge for zeolite synthesis. These aluminophosphate zeotypes are chemically distinct from zeolites due to their greater ionicity. Substitution of framework P by Si (SAPOs) and Al by Mg2+ and divalent and trivalent first row transition metal cations (MAPOs) introduces catalytic acidic and redox properties. SAPOs and M(ii)APOs possess solid acidity, the most important example of which is in SAPO-34 (topology type CHA), which finds application on a large scale in the methanol-to-olefins (MTO) reaction. Here the steady state catalyst is a hybrid organic–inorganic material where protonated aromatic molecules in cha cages act as reactive scaffolds for the selective generation and delivery of light olefins from methanol or dimethylether. There are promising developments for this MTO activity in the tandem catalysis of C1 reactions. Cu-exchanged SAPO-34 is an active catalyst for ammonia SCR of NO in automobile exhaust catalysis, but suffers from long-term low temperature hydrolysis, while Co and MnAPOs are catalysts for heterogeneous selective oxidation reactions. Finally, there is considerable interest in the water adsorption behaviour of aluminophophate zeotypes, where stepped isotherms suggest applications in the sustainable provision of fresh water and energy efficient chillers.
Zeolites, as a class of representative microporous materials, have attracted significant attention for their uniform and ordered pore structures, excellent hydrothermal stability, and diverse active sites. They are widely applied in heterogeneous catalysis, adsorption, separation, and ion exchange. Due to the inherent diffusion limitations present in micropores, the preparation of novel extra-large pore zeolites and hierarchical zeolitic materials is critical to speed up intrapore diffusion and then enhance the catalytic performance. In addition, limited zeolite topologies are insufficient to satisfy the demands of the diverse catalytic field. Preparing novel topologies to enrich the zeolite database and providing excellent candidate catalysts for heterogeneous catalysis are crucial. In this chapter, we focus on the preparation of zeolites with extra-large pores, micro–mesoporous hierarchical structures, and novel topologies by hydrothermal synthesis and post-treatment strategies. We attempt to extract relevant insights from case studies to provide guidance for the design of novel zeolite materials in the future.
This chapter provides a brief introduction to computational chemistry in the context of zeolite research, emphasizing the capabilities and limitations of modern theoretical models for investigating their reactivity and chemical properties under operando conditions. A brief overview of the computational chemistry toolbox is given, followed by a discussion of state-of-the-art applications in zeolite chemistry and catalysis. This chapter also highlights the increasing impact of data-driven techniques, such as machine-learning potentials, in advancing computational methods in zeolite studies.
After decades of intense research, zeolites have gained a primary role in the economic landscape, with several important industrial applications deriving from their distinctive properties, for example as water softeners in detergents, adsorbents in separation and purification technologies, and heterogeneous catalysts in chemical, petrochemical, and refining processes. Today, there is a growing awareness of the unsustainability of the model based on fossil sources, whose massive use leads to the accumulation of greenhouse gases in the atmosphere. Achieving carbon neutrality is the industry’s primary goal, which is highly dependent on the availability of advanced materials. In this regard, zeolites have already proven to be capable of increasing the sustainability of chemical, petrochemical and refining processes. New applications require new advanced materials whose preparation is favored by the deep knowledge of the phenomena that govern their formation. In the case of zeolites, this is an interesting field of materials science, the development pathway of which started in the mid-eighteenth century, when they were discovered as minerals. Here, the fundamental stages of the history of zeolites are retraced, and this very interesting journey can help us better understand the great potential, but also the limits, of this fascinating family of materials.
Biomass transformation to value-added chemicals and fuels is an important topic facilitating a decrease of the use of fossil resources and promoting sustainability. The main emphasis of this work was to elucidate the effect of textural properties and acidity of zeolites and their mesoporous hierarchical counterparts in catalytic biomass transformation. Transformation of lignocellulosic material via pyrolysis and further deoxygenation to aromatics were summarized. In addition, synthesis of aromatics from biobased feedstock via the Diels–Alder condensation of furanic compounds with alcohols and alkenes as well as in the reaction between glycerol and alcohols over zeolite catalysts was discussed. The Prins cyclisation of bioderived molecules for production of pharmaceuticals is also an interesting example showing that reactivity can be correlated with the pore size of zeolites and kinetic diameter of the product. The prominent effect of zeolite pore sizes was also demonstrated in dehydration of cellulose and its monomeric sugars to value-added products, such as lactic and levulinic acids. For bifunctional catalysis using metal modified zeolites, like in upgrading by hydrodeoxygenation of bio-oil produced via pyrolysis of biomass, the property–performance relationship was emphasized, especially the pore size and acidity.
Crystalline microporous aluminosilicates, zeolites, are attractive catalysts and adsorbents in industrial and fundamental research fields. Their Brønsted and Lewis acidities are one of the most important features of their application. Moreover, zeolites can be modified with various metal incorporations from the perspective of new functions. Herein, we discuss the properties of zeolites modified with various metal species with different loading states (incorporated into framework and non-framework positions). The structural and compositional features of their active sites and parent zeolites, and the catalytic and adsorptive properties of metal-modified zeolites are summarized based on their application fields.
Zeolites, known for their crystallinity and porosity, exhibit versatile acid functionalities, making them valuable industrial catalysts. This chapter discusses the acidity of zeolites, including Brønsted and Lewis acids, and their variations. It focuses on the principal methodologies for adjusting zeolite acidity, including isomorphous substitution, steaming, and the impact of extraframework species. The engineering of acid site accessibility and its applications in catalysis, adsorption, and environmental remediation are also discussed. Future perspectives and viewpoints are briefly mentioned.
This chapter unveils the fascinating structural complexity of zeolites, whose highly organized, porous frameworks are the key to their diverse industrial applications. By delving into the intricate arrangement of their building units, this chapter explores how these elements combine to form unique zeolite structures, influencing their chemical composition, pore sizes, and framework connectivity. Understanding these structural features is essential for designing zeolites with tailored properties, particularly for catalysis, ion exchange, adsorption and new applications related to their particular structural features. While X-ray diffraction (XRD) provides a broader picture of the overall crystalline structure, this chapter emphasizes the critical role of local structural analysis. Advanced techniques like Transmission Electron Microscopy (TEM) and Nuclear Magnetic Resonance (NMR) uncover defects, atomic environments, connectivity and intergrowths, offering deep insights that are crucial for optimizing zeolite performances. By combining global and local perspectives, this chapter highlights how detailed structural knowledge drives innovation in zeolite design and application.
The first zeolites discovered were natural zeolites, more than 250 years ago. The current estimated world mine production of natural zeolites ranges between 3–4 Mt per year. This chapter provides an overview about the complex world of natural zeolites, with a journey through their crystal-chemistry, occurrence in Nature, principal properties (i.e., cation exchange capacity and molecular sieve ability, behaviour at non-ambient conditions), and their principal applications (i.e., in water and wastewater treatment, agronomy and environmental soil remediation, building industry).
Zeolites are the most important industrial catalysts, facilitating large-scale commercial processes in oil refining, petrochemistry and synthesis of fine chemicals while promoting environmental protection. However, many challenges still remain in zeolite chemistry and applications. This chapter addresses the main factors hindering the development of novel and more sustainable synthesis approaches and the preparation of new zeolites, as well as their detailed characterization and large-scale application.
In this chapter we explore how zeolites are essential for the production of fuels and key petrochemical building blocks, such as ethylbenzene and cumene, and illuminate their significance in Fluid Catalytic Cracking (FCC) and light olefin upgrading. The versatility of zeolites extends to methanol conversion processes, specifically in Methanol to Gasoline (MTG) and Methanol to Olefins (MTO), demonstrating their adaptability in transforming methanol into valuable hydrocarbons. We also briefly touch on other current applications of zeolites, such as in producing specialty chemicals such as pyridine and picolines. Beyond current applications, this chapter considers emerging trends that highlight the growing importance of zeolites in the transition towards a more sustainable future. This includes their use in the conversion of renewable fuels and waste plastics into valuable hydrocarbons, where processes such as Catalytic Fast Pyrolysis (CFP) utilize zeolites like ZSM-5 to transform biomass and waste plastics into useful fuels and chemicals. We show that ongoing research focused on optimizing zeolite properties, including morphology, acidity, pore structure, and stability is essential to adapt them to meet emerging challenges. We aim to provide a clear view of how zeolites continue to evolve and contribute to improved efficiency and sustainability in important chemical processes.
This chapter is dedicated to demonstrating how both the hydrothermal synthesis of crystalline zeolites with precise atomic compositions and the knowledge of their physics-chemical characteristics allow designing selective materials, useful as powerful tools for biomedical applications. The adsorption of proteins and enzymes, dyes, and drugs and the preparation of scaffolds for in vitro testing of new food and cosmetic formulations are discussed according to the configuration, the composition, and the morphology of prepared materials. Finally, the study of the chemical, molecular, and supramolecular interactions between interesting biological species, drugs, cells, and synthetic materials was used to produce advanced materials and active scaffolds.
