Catalyses zeolite

Figure C2.12.10. Different manifestations of shape-selectivity in zeolite catalysis. Reactant selectivity (top), product selectivity (middle) and transition state selectivity (bottom).

Kuhl G H 1999 Modification of zeolites Catalysis and Zeolites, Fundamentals and Applications ed J Weitkamp and L Puppe (Berlin Springer) pp 81-197... 

S. Bhatia, Zeolite Catalysis Principles and Applications, GRG Press, Boca Raton, El., 1990. 

Compensation-type behavior is quite general and has been extensively studied, especially in transition-metal catalysis [8a], sulfide catalysis [8b], and zeolite catalysis [7]. 

In the next section, we present a short discussion of compensation-type behavior in zeolite catalysis. 

As a further illustration of the compensation effect, we use solid-acid-catalyzed hydrocarbon activation by microporous zeolites. A classical issue in zeolite catalysis is the relationship between overall rate of a catalytic reaction and the match of shape and size between adsorbate and zeolite micropore. 

M. Tielen, M. Geelen, P.A. Jacobs, 1985, Proc. Inter. Symp. On Zeolite Catalysis, May 13-16, (1985) Siofok, Hungary, Acta Physicaet Chemica Szegediensis, Szeged,. 

Nowadays synthesis of mesoporous materials with zeolite character has been suggested to overcome the problems of week catalytic activity and poor hydrothermal stability of highly silicious materials. So different approaches for the synthesis of this new generation of bimodal porous materials have been described in the literature like dealumination [4] or desilication [5], use of various carbon forms as templates like carbon black, carbon aerosols, mesoporous carbon or carbon replicas [6] have been applied. These mesoporous zeolites potentially improve the efficiency of zeolitic catalysis via increase in external surface area, accessibility of large molecules due to the mesoporosity and hydrothermal stability due to zeolitic crystalline walls. During past few years various research groups emphasized the importance of the synthesis of siliceous materials with micro- and mesoporosity [7-9]. Microwave synthesis had... 

Bernhardt L. Trout, Car-Parrinello Methods in Chemical Engineering Their Scope and Potential R. A. van Santeen and X. Rozanska, Theory of Zeolite Catalysis... 

The major effect of new advanced techniques on catalyst structure is found in zeolite catalysis. NMR techniques, especially MASNMR, have helped to explain aluminum distribution in zeolites and to increase our understanding of critical parameters in zeolite synthesis and crystallization. MASNMR, combined with TEM, STEM, XPS, and diagnostic catalytic reaction probes, has advanced our knowledge of the critical relationship between the structure and reactivity patterns of zeolites in the chemical fuels industry. Throughout the symposium upon which this book is based, many correlations were evident between theoretical quantum mechanical calculations and the structures elucidated by these techniques. 

The frameworks of zeolites are formed by fully connected Si04 and A104 tetrahedra linked by shared oxygen atoms as shown in Figure 4.1 (top) for a Faujasite-type zeolite. Faujasite is a zeolitic mineral, which can be found in nature. Synthetic Faujasite-type zeolites are of particular importance in zeolite catalysis as we will see below. 

Jaenicke, S., Chuah, G.K. and Fow, K.L., Dynamic kinetic resolution combining enzyme and zeolite catalysis. Stud. Surf. Sci. Catal. 2007, 172, 313. 

Bhatia, S. (1990) Zeolite Catalysis Principles And Applications, CRC Press. 

Unique Aspects of Mechanisms and Requirements for Zeolite Catalysis in Refining and Petrochemicals... 

Hsia Chen, C.S. and Bridget, R. (1995) Shape-selective oligomerization of alkenes to near-linear hydrocarbons by zeolite catalysis. J. Catal., 161, 587-593. 

Maxwell, I.E. (1987) Zeolite catalysis in hydroprocessing technology. Catal. Today, 1, 385 13. 

The third and last part of the book (Chapters 12-16) deals with zeolite catalysis. Chapter 12 gives an overview of the various reactions which have been catalyzed by zeolites, serving to set the reader up for in-depth discussions on individual topics in Chapters 13-16. The main focus is on reactions of hydrocarbons catalyzed by zeolites, with some sections on oxidation catalysis. The literature review is drawn from both the patent and open literature and is presented primarily in table format. Brief notes about commonly used zeolites are provided prior to each table for each reaction type. Zeolite catalysis mechanisms are postulated in Chapter 13. The discussion includes the governing principles of performance parameters like adsorption, diffusion, acidity and how these parameters fundamentally influence zeolite catalysis. Brief descriptions of the elementary steps of hydrocarbon conversion over zeolites are also given. The intent is not to have an extensive review of the field of zeolite catalysis, but to select a sufficiently large subset of published literature through which key points can be made about reaction mechanisms and zeolitic requirements. 

Catalysis of 12-membered zeolites, H-mordenlte (HM), HY, and HL was studied In the alkylation of biphenyl. The para-selectlvltles were up to 70% for Isopropylblphenyl (IPBP), and 80% for dllsopropylblphenyl (DIBP) In HM catalyzed Isopropylatlon. Catalysis of HY and HL zeolites was nonselectlve. These differences depend on differences In pore structure of zeolites. Catalysis of HM to give the least bulky Isomer Is controlled shape-selectlvely by sterlc restriction of the transition state and by the entrance of IPBP Isomers. Alkylation with HY and HL Is controlled by the electron density of reactant molecule and by the stability of product molecules because these zeolites have enough space for the transition state to allow all IPBP and DIBP isomers. Dealuminatlon of HM decreased coke deposition to enhance shape selective alkylation of biphenyl. 

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