Application of Microporous Solids as Catalysts

Lercher, Johannes A.; Jentys, Andreas

doi:10.1002/9783527618286.ch18h

Cited by 11 publications

(8 citation statements)

References 225 publications

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“…Zeolites and related molecular sieves are the key element in a wide variety of catalytic and sorptive processes in the petroleum and petrochemical industries. − The materials combine a well-defined crystalline structure that includes regular void spaces (pores and cavities) with well-defined functional groups generated by the controlled substitution of elements into silicate or aluminumphosphate lattices. , When the formal charge at the metal cation is lower than the average charge of the metal cations, a localized charge is generated that needs to be balanced by a proton, metal, or organic cation. , For hydrocarbon catalysis, protons are the main functional groups controlling catalytic activity …”

Section: Introductionmentioning

confidence: 99%

Surface Processes during Sorption of Aromatic Molecules on Medium Pore Zeolites

2004

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The elementary steps of sorption and transport of benzene, toluene, and o- and p-xylene from the gas phase to hydroxy groups of zeolite H/ZSM-5 on the outer surface (SiOH groups) and in the pores (SiOHAl groups) were studied using pressure modulations followed by fast time-resolved IR spectroscopy. Sorption on these acid sites occurs via a common physisorbed state on the outer surface. The equilibration of the molecules in this state is fast compared to the sorption rates on SiOH and SiOHAl groups. The relative rates of equilibration of functional groups with the aromatic molecules suggest that the aromatic molecules move freely on the surface of the outer surface before reversibly binding to OH groups, entering the micropores or desorbing. Molecules able to enter into the pores (benzene, toluene, p-xylene) adsorb faster on SiOHAl groups than on SiOH groups. If the access of the molecules into the pores is sterically constrained (o-xylene), the rate of adsorption on the remaining accessible SiOH groups is strongly enhanced.

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Section: Introductionmentioning

confidence: 99%

Surface Processes during Sorption of Aromatic Molecules on Medium Pore Zeolites

2004

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“…The inhomogeneous distribution of Al within zeolites has been noted in numerous occasions and depends on the type of zeolite framework, Si/Al ratio, crystal size and synthesis parameters 5 leading to distinct Al distributions that are characterized by either short-range (T-site distribution) or long-range (zoning or extra-framework) lengthscales. The unit cell of the industrially important zeolite ZSM-5 (refs 6 , 7 , 8 ) has 12 distinct crystallographic T-sites 9 10 11 . Using techniques, such as X-ray diffraction, the distribution of Al atoms over specific T-sites is difficult to determine due to low scattering contrast between Si and Al.…”

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confidence: 99%

Determining the location and nearest neighbours of aluminium in zeolites with atom probe tomography

et al. 2015

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Zeolite catalysis is determined by a combination of pore architecture and Brønsted acidity. As Brønsted acid sites are formed by the substitution of AlO4 for SiO4 tetrahedra, it is of utmost importance to have information on the number as well as the location and neighbouring sites of framework aluminium. Unfortunately, such detailed information has not yet been obtained, mainly due to the lack of suitable characterization methods. Here we report, using the powerful atomic-scale analysis technique known as atom probe tomography, the quantitative spatial distribution of individual aluminium atoms, including their three-dimensional extent of segregation. Using a nearest-neighbour statistical analysis, we precisely determine the short-range distribution of aluminium over the different T-sites and determine the most probable Al–Al neighbouring distance within parent and steamed ZSM-5 crystals, as well as assess the long-range redistribution of aluminium upon zeolite steaming.

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“…This also includes the synthesis of fine and specialty chemicals [1,[5][6][7]. It is in these applications that liquid solvents are frequently used to contact reactants with a solid catalyst.…”

Section: Introductionmentioning

confidence: 99%

Novel Process Options for Application of Zeolites in Supercritical Fluids and Ionic Liquids

Gläser¹

2007

Chem Eng & Technol

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Supercritical fluids and ionic liquids offer attractive opportunities for modifying and applying zeolites as adsorbents and catalysts. After a brief introduction to the most important properties of these solvents, examples of zeolite applications in supercritical fluids and ionic liquids from the recent literature are discussed. Particular emphasis is put on the influence of reaction media on the processes occurring in the zeolitic pore systems, e.g., during shape-selective conversions in zeolite catalysts. The present potential and future challenges for the application of zeolites in supercritical fluids and ionic liquids are identified. Most attractive process options arise from a combined use of both ionic liquids and supercritical fluids in integrated reaction schemes.

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Application of Microporous Solids as Catalysts

Cited by 11 publications

References 225 publications

Surface Processes during Sorption of Aromatic Molecules on Medium Pore Zeolites

Surface Processes during Sorption of Aromatic Molecules on Medium Pore Zeolites

Determining the location and nearest neighbours of aluminium in zeolites with atom probe tomography

Novel Process Options for Application of Zeolites in Supercritical Fluids and Ionic Liquids

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