It is possible to say that zeolites are the most widely used catalysts in industry They are crystalline microporous materials which have become extremely successful as catalysts for oil refining, petrochemistry, and organic synthesis in the production of fine and speciality chemicals, particularly when dealing with molecules having kinetic diameters below 10 A The reason for their success in catalysis is related to the following specific features of these materials:1 (1) They have very high surface area and adsorption capacity (2) The adsorption properties of the zeolites can be controlled, and they can be varied from hydrophobic to hydrophilic type materials (3) Active sites, such as acid sites for instance, can be generated in the framework and their strength and concentration can be tailored for a particular application (4) The sizes of their channels and cavities are in the range typical for many molecules of interest (5-12 A), and the strong electric fields2 existing in those micropores together with an electronic confinement of the guest molecules3 are responsible for a preactivation of the reactants (5) Their intricate channel structure allows the zeolites to present different types of shape selectivity, ie, product, reactant, and transition state, which can be used to direct a given catalytic reaction toward the desired product avoiding undesired side reactions (6) All of these properties of zeolites, which are of paramount importance in catalysis and make them attractive choices for the types of processes listed above, are ultimately dependent on the thermal and hydrothermal stability of these materials In the case of zeolites, they can be activated to produce very stable materials not just resistant to heat and steam but also to chemical attacks Avelino Corma Canos was born in Moncofar, Spain, in 1951 He studied chemistry at the Universidad de Valencia (1967−1973) and received his PhD at the Universidad Complutense de Madrid in 1976 He became director of the Instituto de Tecnologia Quimica (UPV-CSIC) at the Universidad Politecnica de Valencia in 1990 His current research field is zeolites as catalysts, covering aspects of synthesis, characterization and reactivity in acid−base and redox catalysis A Corma has written about 250 articles on these subjects in international journals, three books, and a number of reviews and book chapters He is a member of the Editorial Board of Zeolites, Catalysis Review Science and Engineering, Catalysis Letters, Applied Catalysis, Journal of Molecular Catalysis, Research Trends, CaTTech, and Journal of the Chemical Society, Chemical Communications A Corma is coauthor of 20 patents, five of them being for commercial applications He has been awarded with the Dupont Award on new materials (1995), and the Spanish National Award “Leonardo Torres Quevedo” on Technology Research (1996) 2373 Chem Rev 1997, 97, 2373−2419

From Microporous to Mesoporous Molecular-Sieve Materials and Their Use in Catalysis

This review paper deals with proven and potential applications of mesoporous molecular sieves in catalysis. In addition to introduction and conclusion, the text is divided into two parts, respectively, dedicated to the design of solid catalysts and catalyst supports and to some relevant examples of catalytic processes.

/pdf/perspectives-in-catalytic-applications-of-mesostructured-4jgvbmynn3.pdf

Perspectives in catalytic applications of mesostructured materials

https://www.cell.com/trends/biotechnology/pdf/S0167-7799(00)01481-5.pdf

Synthetic spider silk: a modular fiber

Non-silica periodic mesostructured materials: recent progress

Modification of mesoporous silicas by incorporation of heteroelements in the framework

1. Summary The influence of surfactant/silica molar ratio(Sur/Si) in M41S syntheses was studied in the simple synthesis system consisting of tetraethylorthosilicate(TEOS), water, and the cetyltrimethylammonium(CTMA) cation at 100°C. As the Sur/Si increased from 0.5 to 2, the siliceous products obtained were identified and could be classified into four separate groups: MCM-4 1(hexagonal), MCM-48(cubic), thermally unstable M4 1 S, and a molecular species, the organic octamer [(CTMA)SiO2, 5]8. One of the thermally unstable structures has been identified as a lamellar phase. These results are consistent with micellar phase transformations that occur at various surfactant concentrations and reinforce the concept that micelle structures serve as templating agents for the formation of M41S type materials.

Development of a formation mechanism for M41S materials

The use of cationic surfactants as structure directing agents has resulted in the discovery of M41S, the first, ordered mesoporous molecular sieves. Herein we describe the ability of the surfactant molecules to interact with silicate counterions resulting in the formation of organosilicate-surfactant composite arrays which exhibit hexagonal, cubic or lamellar structure.

Designed Synthesis of Mesoporous Molecular Sieve Systems Using Surfactant-Directing Agents

Publisher Summary The chapter explores the ability of alkyltrimethylammonium surfactants of the type C n H 2n+I (CH 3 ) 3 NBr to serve as structure directing agents, or templates, for the formation of microporous or mesoporous molecular sieves frameworks At equivalent gel compositions and reaction conditions, it was observed that the alkyl chain length of the surfactant molecule dictated the nature of the silicate product obtained as indicated by the X-ray diffraction patterns Over the entire range of synthesis temperatures examined (100–200°C) the shortest alkyl chain length surfactant (n=6), produced amorphous or microporous zeolitic materials, such as ZSM-5 The zeolite contained the intact surfactant cation consistent with a commonly observed molecular templating effect At 100°C as the surfactant chain length was increased (n=8, 10, 12, 14, and 16), the formation of mesoporous molecular sieves (MCM-41) was observed In these cases, a combination of surfactant chain length and reaction conditions favor surfactant aggregation (micelles), and hence, the formation and utilization of supramolecular templates

J.S. Beck

Papers

Development of a formation mechanism for M41S materials

Designed Synthesis of Mesoporous Molecular Sieve Systems Using Surfactant-Directing Agents

Molecular Or Supramolecular Templating: Defining The Role of Surfactant Chemistry In the Formation of M41S and Zeolitic Molecular Sieves