Susana Valencia

Bio: Susana Valencia is an academic researcher from Polytechnic University of Valencia. The author has contributed to research in topics: Zeolite & Catalysis. The author has an hindex of 42, co-authored 126 publications receiving 8049 citations. Previous affiliations of Susana Valencia include University of Amsterdam & Spanish National Research Council.

Sn-zeolite beta as a heterogeneous chemoselective catalyst for Baeyer – Villiger oxidations

Abstract: The Baeyer-Villiger oxidation, first reported more than 100 years ago, has evolved into a versatile reaction widely used to convert ketones-readily available building blocks in organic chemistry-into more complex and valuable esters and lactones Catalytic versions of the Baeyer-Villiger oxidation are particularly attractive for practical applications, because catalytic transformations simplify processing conditions while minimizing reactant use as well as waste production Further benefits are expected from replacing peracids, the traditionally used oxidant, by cheaper and less polluting hydrogen peroxide Dissolved platinum complexes and solid acids, such as zeolites or sulphonated resins, efficiently activate ketone oxidation by hydrogen peroxide But these catalysts lack sufficient selectivity for the desired product if the starting material contains functional groups other than the ketone group; they perform especially poorly in the presence of carbon-carbon double bonds Here we show that upon incorporation of 16 weight per cent tin into its framework, zeolite beta acts as an efficient and stable heterogeneous catalyst for the Baeyer-Villiger oxidation of saturated as well as unsaturated ketones by hydrogen peroxide, with the desired lactones forming more than 98% of the reaction products We ascribe this high selectivity to direct activation of the ketone group, whereas other catalysts first activate hydrogen peroxide, which can then interact with the ketone group as well as other functional groups

Supramolecular self-assembled molecules as organic directing agent for synthesis of zeolites

Abstract: Solid materials with uniform micropores, such as zeolites, can act as selective catalysts and adsorbents for molecular mixtures by separating those molecules small enough to enter their pores while leaving the larger molecules behind1,2. Zeolite A is a microporous material with a high void volume. Despite its widespread industrial use in, for example, molecular separations and in detergency3,4, its capability as a petroleum-refining material is limited owing to its poor acid-catalytic activity and hydrothermal stability, and its low hydrophobicity. These characteristics are ultimately a consequence of the low framework Si/Al ratio (normally around one) and the resulting high cationic fraction within the pores and cavities1,2. Researchers have modified the properties of type-A zeolites by increasing the Si/Al compositions up to a ratio of three5,6,7,8,9. Here we describe the synthesis of zeolite A structures exhibiting high Si/Al ratios up to infinity (pure silica). We synthesize these materials, named ITQ-29, using a supramolecular organic structure-directing agent obtained by the self-assembly, through π–π type interactions, of two identical organic cationic moieties. The highly hydrophobic pure-silica zeolite A can be used for hydrocarbon separations that avoid oligomerization reactions, whereas materials with high Si/Al ratios give excellent shape-selective cracking additives for increasing propylene yield in fluid catalytic cracking operations. We have also extended the use of our supramolecular structure-directing agents to the synthesis of a range of other zeolites.

Direct Synthesis and Characterization of Hydrophobic Aluminum-Free Ti−Beta Zeolite

Abstract: Incorporation of Ti into the framework of aluminium-free zeolite Beta has been achieved in F- medium and has produced hydrophobic selective oxidation catalysts. The Ti−Beta(F) materials have been characterized by X ray diffraction, infrared, Raman, ultraviolet, XANES, EXAFS, 29Si MAS NMR, and 1H→29Si CP MAS NMR spectroscopies, adsorption microcalorimetry, and catalytic testing. At near neutral pH the incorporation of Ti into the framework appears to present an upper limit of ca. 2.3 Ti/uc, beyond which anatase is detected in the calcined materials. However, at higher pH (ca. 11) larger amounts of Ti can be incorporated without anatase formation. After calcination, Ti incorporation in the framework is characterized by an increase in the unit cell volume, the appearance of one Raman band and three infrared bands in the region near 960 cm-1 and the presence of a strong absorption band in the 205−220 nm ultraviolet spectrum. By 29Si MAS NMR, 1H→29Si CP MAS NMR, and infrared spectroscopies it is concluded that...

Fast parallel algorithms for short-range molecular dynamics

Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Synthesis of transportation fuels from biomass: chemistry, catalysts, and engineering.

Abstract: 1.0. Introduction 4044 2.0. Biomass Chemistry and Growth Rates 4047 2.1. Lignocellulose and Starch-Based Plants 4047 2.2. Triglyceride-Producing Plants 4049 2.3. Algae 4050 2.4. Terpenes and Rubber-Producing Plants 4052 3.0. Biomass Gasification 4052 3.1. Gasification Chemistry 4052 3.2. Gasification Reactors 4054 3.3. Supercritical Gasification 4054 3.4. Solar Gasification 4055 3.5. Gas Conditioning 4055 4.0. Syn-Gas Utilization 4056 4.1. Hydrogen Production by Water−Gas Shift Reaction 4056

Carbon Dioxide Capture in Metal–Organic Frameworks

Abstract: Kenji Sumida, David L. Rogow, Jarad A. Mason, Thomas M. McDonald, Eric D. Bloch, Zoey R. Herm, Tae-Hyun Bae, Jeffrey R. Long

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

Abstract: 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