Bifunctional catalytic isomerization of decane over MTT-type aluminosilicate zeolite crystals with siliceous rim

Micrometer-size MTT-type zeolite crystals with aluminum depiction in the outer layer were synthesized. The compositional variation in individual crystals was obtained by altering the chemical composition of the gel during crystal growth of MTT-type zeolite. Chemical composition of Al-27 MAS NMR and XPS, respectively. The zeolite with siliceous rim was converted the bulk and the surface of the crystals was determined using 27 into a bifunctional catalyst by neutralizing the cation-exchange capacity with protons and plating with a trace amount of platinum metal. The MTT zeolite with siliceous crystal termination was catalytically much less active than the isostructural ZSM-23 zeolite with homogeneous chemical composition. The catalytic activity reflects the aluminum content on the surface of the crystals determined by XPS, rather than the bulk composition. The reaction mechanism and the reaction kinetics were analyzed using a microkinetic model developed previously for the structurally related TON-type zeolite. The catalytic data are in favor of the pore mouth catalysis model of skeletal isomerization of long n-alkanes on 10-membered ring tubular pore zeolites. (c) 2006 Elsevier Inc. All rights reserved

Skeletal isomerization of octadecane on bifunctional ZSM-23 zeolite catalyst

Octadecane was isomerized over three different Pt/H-ZSM-23 samples. The distributions of methylheptadecane and dimethylheptadecane skeletal isomers obtained on the Pt/ZSM-23 samples were very similar. Positional isomer distributions are fingerprints of the zeolite framework structure. The independence of skeletal isomer distributions from Al-gradients and particle size constitutes a strong argument in favor of pore-mouth catalysis

Catalytic activation of OKO zeolite with intersecting pores of 10- and 12-membered rings using atomic layer deposition of aluminium

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Catalytic activation of OKO zeolite with intersecting pores of 10- and 12-membered rings using atomic layer deposition of aluminium

Tetrahedral framework aluminium was introduced in all-silica zeolite -COK-14 using Atomic Layer Deposition (ALD) involving alternating exposure to trimethylaluminium and water vapour. The modification causes permanent conversion of the originally interrupted framework of -COK-14 to a fully connected OKO type framework, and generates catalytic activity in the acid catalysed hydrocarbon conversion reaction

Mechanistic Aspects of n-Paraffins Hydrocracking: Influence of Zeolite Morphology and Acidity of Pd(Pt)/ZSM-5 Catalysts: Influence of zeolite morphology and acidity of Pd(Pt)/ZSM-5 catalysts

The influence of zeolite domain size, acidity, and metal type on n-decane and n-nonadecane hydroconversion was investigated for bifunctional Pd(Pt)/ZSM-5 zeolite (bulk, desilicated, thin and thick nanosheets). Decreasing the size of zeolitic domains to a few nanometers results in lower overall activity, higher skeletal isomerization yield, and an imbalance between metal and acid functions. These changes are attributed to a lower pore occupancy of olefinic intermediates due to the substantially larger external surface of nanosheets and higher desorption rates. Well-balanced bifunctional behavior and higher activity of nanosheet ZSM-5 can be achieved by strengthening the metal function or lowering the acidity. The influence on the isomerized and cracked product fractions is also discussed. Hydroconversion of n-nonadecane gave low yields of skeletal isomers over all Pd-loaded ZSM-5 catalysts and led to significant over-cracking due to the long intracrystalline residence times of the long hydrocarbon reactant