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

Ordered mesoporous materials in catalysis

Lewis Acids: From Conventional Homogeneous to Green Homogeneous and Heterogeneous Catalysis

This review provides an overview of different aspects of inclusion chemistry in ordered mesoporous host materials such as MCM-41 or MCM-48 (Mobil codes). A rich field of inclusion chemistry has been explored in this context, including sorption, ion exchange, imbibition followed by reduction, grafting of reactive metal alkoxides, halides etc., grafting of silane coupling agents (sometimes followed by subsequent reactions), grafting of reactive metal complexes, and polymerization in the channels. Finally, co-condensation of reactive species during the mesopore synthesis is a method to incorporate functionality into the walls of the channel system. Important applications of these modified and functionalized systems are heterogeneous catalysis and photocatalysis involving bulky grafted catalysts and/or the conversion of large substrates. Other potential applications include ion exchange and separations, removal of heavy metals, chromatography, stabilization of quantum wires, stabilization of dyes, and polymer...

Inclusion Chemistry in Periodic Mesoporous Hosts

Oil is nowadays the main energy source and this prevalent position most probably will continue in the next decades. This situation is largely due to the degree of maturity that has been achieved in oil refining and petrochemistry as a consequence of the large effort in research and innovation. The remarkable efficiency of oil refining is largely based on the use of zeolites as catalysts. The use of zeolites as catalysts in refining and petrochemistry has been considered as one of the major accomplishments in the chemistry of the XXth century. In this tutorial review, the introductory part describes the main features of zeolites in connection with their use as solid acids. The main body of the review describes important refining processes in which zeolites are used including light naphtha isomerization, olefin alkylation, reforming, cracking and hydrocracking. The final section contains our view on future developments in the field such as the increase in the quality of the transportation fuels and the coprocessing of increasing percentage of biofuels together with oil streams. This review is intended to provide the rudiments of zeolite science applied to refining catalysis.

Zeolites as catalysts in oil refining

Owing to its large molecular size, alkylation of 2,4-di-tert-butylphenol with cinnamyl alcohol does not take plAcc using HY zeolite (pore opening 7.4 A) as catalyst even after controlled steaming treatment to increase its mesoporosity; by contrast, novel mesoporous aluminosilicate MCM-41 catalyses this reaction giving rise to 6,8-di-tert-butyl-2-phenyl-2,3-dihydro[4H]benzopyran (arising from intramolecular cyclization of the primary cinnamylphenol) together with 4-tert-butylphenol and small amounts of 6-tert-butyl-2-phenyl-2,3-dihydro[4H]benzopyran.

Mesoporous aluminosilicate MCM-41 as a convenient acid catalyst for Friedel–Crafts alkylation of a bulky aromatic compound with cinnamyl alcohol

The photophysical properties of 2,4,6-triphenylpyrylium (TPP+) and three para-substituted tritylium ions encapsulated within Y, β, and MCM-41 have been studied. It was found that TPP+ adsorbed within MCM-41 or silica only emits fluorescence (λmax 470 nm), whereas when this cation is incorporated within HY and LaY, simultaneous emission of fluorescence and room-temperature phosphorescence (λmax 560 nm) was observed. The fluorescence decay consists of two consecutive first-order processes and is dominated by the fast (0.2−0.7 ns) component. In addition to the prompt fluorescence, delayed emission observable 40 μs after excitation was also detected for the three TPP+ samples. Weak fluorescence was observed for the series of tritylium ions embedded within zeolites. The characteristic T−T absorption spectrum of the TPP+ triplet excited state has been detected using time-resolved diffuse reflectance. Depending on the zeolite, shifts in the reflectance maximum and changes in the extinction coefficient of the lon...

Intrazeolite Photochemistry. 13. Photophysical Properties of Bulky 2,4,6-Triphenylpyrylium and Tritylium Cations within Large- and Extra-Large-Pore Zeolites

A series of substituted triarylmethylium cations, including malachite green, tris(4-methoxyphenyl)methylium, and bis(4-methoxyphenyl)phenylmethylium cations, has been prepared adsorbed on tridirectional large pore zeolites Y and β in their H+ or La3+ form, as well as within the novel mesoporous aluminosilicate MCM-41, by ship-in-a-bottle synthesis from the corresponding benzaldehyde and N,N-dimethylaniline or anisole. The resulting composites exhibit diffuse reflectance and IR spectra characteristic of these trityl dyes. The cation content was determined by thermogravimetry−differential scanning calorimetry. Preparation of these triarylmethylium cations exclusively on the external surface of ZSM-5, a medium pore zeolite whose internal voids are too small to accommodate these cations, is also possible. Therefore, the methodology based in the diffusion of smaller precursors does not guarantee itself the intrazeolite location of the synthesized guests. In this work, we have experimentally determined that the...

Triarylmethylium cations encapsulated within zeolite supercages

A series of vapor-phase adsorptions of C60 on NaY zeolite have been carried out under reduced pressure (1 Torr) in the range of temperatures between 400 and 700 °C to determine whether C60-fullerene (0.79 nm diameter) can be incorporated within the internal voids of faujasites (tridirectional large-pore zeolite containing supercavities of 1.3 nm diameter tetrahedrally connected through 0.74 nm windows). After the incorporation procedure, the samples were submitted to exhaustive solid−liquid extraction using toluene as solvent. The optimum adsorption temperature was found to be around 650 °C. Analogous treatment using silica−alumina instead of NaY did not lead to significant retention of C60. The samples were characterized by X-ray powder diffraction, combustion chemical analysis, and thermogravimetry-differential scanning calorimetry as well as by diffuse reflectance, Fourier transform infrared, and magic angle spinning 13C NMR spectroscopies. None of these techniques provides direct evidence of the locat...

On the Incorporation of Buckminsterfullerene C60 in the Supercages of Zeolite Y

Acid Zeolites as Electron Acceptors. Generation of Xanthylium, Dibenzotropylium, and Fluorenylium Cations from Their Corresponding Hydrides through an Electron-Transfer Mechanism

María Luz Cano

Papers

Mesoporous aluminosilicate MCM-41 as a convenient acid catalyst for Friedel–Crafts alkylation of a bulky aromatic compound with cinnamyl alcohol

Intrazeolite Photochemistry. 13. Photophysical Properties of Bulky 2,4,6-Triphenylpyrylium and Tritylium Cations within Large- and Extra-Large-Pore Zeolites

Triarylmethylium cations encapsulated within zeolite supercages

On the Incorporation of Buckminsterfullerene C60 in the Supercages of Zeolite Y

Acid Zeolites as Electron Acceptors. Generation of Xanthylium, Dibenzotropylium, and Fluorenylium Cations from Their Corresponding Hydrides through an Electron-Transfer Mechanism