Shape-selective zeolites

Haag W O, Lago R M and Weisz P B 1982 Transport and reactivity of hydrocarbon molecules in a shape-selective zeolite Faraday Disouss. Chem. Soo. 72 317-30... 

ZSM-5 is Mobil Oil s proprietary shape-selective zeolite that has a different pore structure from that of Y-zeolite. The pore size of ZSM-5 is smaller than that of Y-zeolite (5.1°A to 5.6°A versus 8°A to 9 A). In addition, the pore arrangement of ZSM-5 is different from Y-zeolite, as shown in Figure 3-16. The shape selectivity of ZSM-5 allows... 

At the low-molecular-weight end of the spectrum, a process newly commercialized by Mobil for converting methanol into gasoline has significantly expanded opportunities in C-1 chemistry— the upgrading of one-carbon molectrles to mrrlticarbon products. The process involves the use of ZSM-5, a shape-selective zeolite catalyst. (See "Zeolite and Shape-Selective Catalysts" in Chapter 9.)... 

Shape-selective zeolites can also be used to discriminate among potential products of a chemical reaction, a property called product shape selectivity. In this case, the product produced is the one capable of escaping from the zeolite pore structure. This is the basis of the selective conversion of methanol to gasoline over... 

Zeolite chemistry is an excellent example of how a three-dimensional surface can alter the course of chemical reactions, selecting for one product out of a host of potential candidates. In addition to the many commercial applications that they have found, shape-selective zeolites have provided the basis for a rich new area of catalytic science and technology, one expected to spawn yet more materials, knowledge, and applications. 

The catalyst used for the conversion of methanol to gasoline is based on a new class of shape-selective zeolites (105-108), known as ZSM-5 zeolites, with structures distinctly different from other well-known zeolites. Apparently, the pore dimensions of the ZSM-5 zeolites are intermediate between those of wide-pore faujasites (ca. 10 A) and very narrow-pore zeolites such as Zeolite A and erionite (ca. 5 A) (109). The available structural data indicate a lattice of interconnecting pores all having approximately the same diameter (101). Hydrocarbon formation... 

Csicsery, S.M. (1986). Catalysis by shape selective zeolites - science and technology. Pure Appl. Chem. 58, 841-856... 

The first mode of the high resolution C-NMR of adsorbed molecules was recently reviewed Q-3) and the NMR parameters were thoroughly discussed. In this work we emphasize the study of the state of adsorbed molecules, their mobility on the surface, the identification of the surface active sites in presence of adsorbed molecules and finally the study of catalytic transformations. As an illustration we report the study of 1- and 2-butene molecules adsorbed on zeolites and on mixed tin-antimony oxides (4>3). Another application of this technique consists in the in-situ identification of products when a complex reaction such as the conversion of methanol, of ethanol (6 7) or of ethylene (8) is run on a highly acidic and shape-selective zeolite. When the conversion of methanol-ethylene mixtures (9) is considered, isotopic labeling proves to be a powerful technique to discriminate between the possible reaction pathways of ethylene. 

There are several means to maximize the yield in the desired monoalkylation product high aromatic/alkylation agent ratio, association of a transalkylation unit to the alkylation unit, and use of a shape selective zeolite as catalyst. 

Thomas, J.M., Millward, G.R., and Ramdas, S. (1981) New methods for the strucmral characterization of shape-selective zeolites. Faraday Discuss. 

P., and Romano, U. (2003) A priori selection of shape-selective zeolite catalysts for the synthesis of 2,6-dimethylnaphthalene. J. Catal., 217, 298-309. 

P.B. (1982) Transport and reactivity of hydrocarbon molecules in shape selective zeolites. J. Chem. Soc., Farad. Disc., 72, 317. 

The use of a shape-selective zeolite, such as Mobil s ZSM-5, has attracted the refiner s interest because this zeolite... 

ZSM-5 is a Mobil-proprietary, shape-selective zeolite which is used commercially in synthetic fuels (methanol-to-gasoline), petrochemicals (xylene isomerization, toluene disproportionation, benzene alkylation) and in petroleum refining (lube and... 

A different product distribution is obtained by shape-selective zeolites.85,86 Since the diffusion coefficient of p-xylene with its preferred shape into the zeolite... 

Continuous Catalytic Conversion of Acetylene to Higher Hydrocarbons over a Metal Modified Shape Selective Zeolite Catalyst... 

Acetaldehyde decomposition, reaction pathway control, 14-15 Acetylene, continuous catalytic conversion over metal-modified shape-selective zeolite catalyst, 355-370 Acid-catalyzed shape selectivity in zeolites primary shape selectivity, 209-211 secondary shape selectivity, 211-213 Acid molecular sieves, reactions of m-diisopropylbenzene, 222-230 Activation of C-H, C-C, and C-0 bonds of oxygenates on Rh(l 11) bond-activation sequences, 350-353 divergence of alcohol and aldehyde decarbonylation pathways, 347-351 experimental procedure, 347 Additives, selectivity, 7,8r Adsorption of benzene on NaX and NaY zeolites, homogeneous, See Homogeneous adsorption of benzene on NaX and NaY zeolites... 

The discovery of a new family of shape selective zeolites by Mobil (239) has now extended the range of pore sizes and thus the accessible range of configurational diffusion. To date the majority of studies have been carried out... 

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