Recent developments in (bio)ethanol conversion to fuels and chemicals over heterogeneous catalysts

Bioethanol is one of the most important bio-resources produced from biomass fermentation and is an environmentally friendly alternative to fossil-based fuels as it is regarded as renewable and clean. Bioethanol and its derivatives are used as feedstocks in petrochemical processes as well as fuel and fuel additives in motor vehicles to compensate for the depletion of fossil fuels. This review chronicles the recent developments in the catalytic conversion of ethanol to diethyl ether, ethylene, propylene, long-chain hydrocarbons, and other important products. Various heterogeneous catalysts, such as zeolites, metal oxides, heteropolyacids, mesoporous materials, and metal-organic frameworks, have been used in the ethanol conversion processes and are discussed extensively. The significance of various reaction parameters such as pressure, temperature, water content in the ethanol feed, and the effect of catalyst modification based on various kinds of literature are critically evaluated. Further, coke formation and coke product analysis using various analytical and spectroscopic techniques during the ethanol conversion are briefly discussed. The review concludes by providing insights into possible research paths pertaining to catalyst design aimed at enhancing the catalytic conversion of (bio)ethanol.

Two-Dimensional Zeolite Materials: Structural and Acidity Properties

Zeolites are generally defined as three-dimensional (3D) crystalline microporous aluminosilicates in which silicon (Si⁴⁺) and aluminum (Al³⁺) are coordinated tetrahedrally with oxygen to form large negative lattices and consequent Brønsted acidity. Two-dimensional (2D) zeolite nanosheets with single-unit-cell or near single-unit-cell thickness (~2-3 nm) represent an emerging type of zeolite material. The extremely thin slices of crystals in 2D zeolites produce high external surface areas (up to 50% of total surface area compared to ~2% in micron-sized 3D zeolite) and expose most of their active sites on external surfaces, enabling beneficial effects for the adsorption and reaction performance for processing bulky molecules. This review summarizes the structural properties of 2D layered precursors and 2D zeolite derivatives, as well as the acidity properties of 2D zeolite derivative structures, especially in connection to their 3D conventional zeolite analogues' structural and compositional properties. The timeline of the synthesis and recognition of 2D zeolites, as well as the structure and composition properties of each 2D zeolite, are discussed initially. The qualitative and quantitative measurements on the acid site type, strength, and accessibility of 2D zeolites are then presented. Future research and development directions to advance understanding of 2D zeolite materials are also discussed.

2D Oxide Nanomaterials to Address the Energy Transition and Catalysis

2D oxide nanomaterials constitute a broad range of materials, with a wide array of current and potential applications, particularly in the fields of energy storage and catalysis for sustainable energy production. Despite the many similarities in structure, composition, and synthetic methods and uses, the current literature on layered oxides is diverse and disconnected. A number of reviews can be found in the literature, but they are mostly focused on one of the particular subclasses of 2D oxides. This review attempts to bridge the knowledge gap between individual layered oxide types by summarizing recent developments in all important 2D oxide systems including supported ultrathin oxide films, layered clays and double hydroxides, layered perovskites, and novel 2D-zeolite-based materials. Particular attention is paid to the underlying similarities and differences between the various materials, and the subsequent challenges faced by each research community. The potential of layered oxides toward future applications is critically evaluated, especially in the areas of electrocatalysis and photocatalysis, biomass conversion, and fine chemical synthesis. Attention is also paid to corresponding novel 3D materials that can be obtained via sophisticated engineering of 2D oxides.

Effect of different seed sources on the hydrothermal crystallization of MCM-22 zeolite catalysts

Ball-milled MCM-22 and dried mother liquor seeds proved to be effective in the synthesis of the MCM-22P lamellar precursor with a low Si/Al ratio. Crystallization times were reduced from 25 to 2–4 days with a considerable decrease in crystallite sizes.

Layer like porous materials with hierarchical structure

Many chemical compositions produce layered solids consisting of extended sheets with thickness not greater than a few nanometers. The layers are weakly bonded together in a crystal and can be modified into various nanoarchitectures including porous hierarchical structures. Several classes of 2-dimensional (2D) materials have been extensively studied and developed because of their potential usefulness as catalysts and sorbents. They are discussed in this review with focus on clays, layered transition metal oxides, silicates, layered double hydroxides, metal(iv) phosphates and phosphonates, especially zirconium, and zeolites. Pillaring and delamination are the primary methods for structural modification and pore tailoring. The reported approaches are described and compared for the different classes of materials. The methods of characterization include identification by X-ray diffraction and microscopy, pore size analysis and activity assessment by IR spectroscopy and catalytic testing. The discovery of layered zeolites was a fundamental breakthrough that created unprecedented opportunities because of (i) inherent strong acid sites that make them very active catalytically, (ii) porosity through the layers and (iii) bridging of 2D and 3D structures. Approximately 16 different types of layered zeolite structures and modifications have been identified as distinct forms. It is also expected that many among the over 200 recognized zeolite frameworks can produce layered precursors. Additional advances enabled by 2D zeolites include synthesis of layered materials by design, hierarchical structures obtained by direct synthesis and top-down preparation of layered materials from 3D frameworks.

Synthesis of titanosilicate pillared MFI zeolite as an efficient photocatalyst

Adsorption assisted photocatalysis over pillared lamellar zeolite.

Synthesis of the RTH-type layer: the first small-pore, two dimensional layered zeolite precursor

There are several distinct two-dimensional zeolite building layers that can condense through different stacking arrangements of the layers to form various three-dimensional framework materials. All known building layers are dense layers in that they do not contain 8-membered ring (MR) or larger pores perpendicular to the two-dimensional layers. Herein, we report a new material (CIT-10) that consists of a two-dimensional layer (termed "rth" layer) that contains an 8 MR perpendicular to the layer. Calcination of CIT-10 forms pure-silica RTH (SSZ-50). CIT-10 can be pillared to form a new framework material with a three-dimensional pore system of 8 and 10 MRs, denoted CIT-11, that can be calcined to form a new microporous material, denoted CIT-12.

One-pot synthesis of MWW zeolite nanosheets using a rationally designed organic structure-directing agent

A new material MIT-1 comprised of delaminated MWW zeolite nanosheets is synthesized in one-pot using a rationally designed organic structure-directing agent.

A new material MIT-1 comprised of delaminated MWW zeolite nanosheets is made in a one-pot synthesis using a rationally designed organic structure-directing agent (OSDA). The OSDA consists of a hydrophilic head segment that resembles the OSDA used to synthesize the zeolite precursor MCM-22(P), a hydrophobic tail segment that resembles the swelling agent used to swell MCM-22(P), and a di-quaternary ammonium linker that connects both segments. MIT-1 features high crystallinity and surface areas exceeding 500 m² g^–1, and can be synthesized over a wide synthesis window that includes Si/Al ratios ranging from 13 to 67. Characterization data reveal high mesoporosity and acid strength with no detectable amorphous silica phases. Compared to MCM-22 and MCM-56, MIT-1 shows a three-fold increase in catalytic activity for the Friedel–Crafts alkylation of benzene with benzyl alcohol.

Nb and Zr modified MWW zeolites – characterisation and catalytic activity

Hydrogen forms of MCM-22 and delaminated MCM-56 zeolites were modified with niobium and zirconium species.