Catalytic activity of FeZSM-5 zeolites in benzene hydroxylation by N2O: The role of geometry characterized by fractal dimensions

The fractal dimensions of FeZSM-5 zeolites were used to characterize the change in their geometry depending on different post-synthesis treatments. The fractal dimension values were estimated from the Dubinin-Astakhov isotherms of nitrogen adsorption and related to the activity of these zeolites in the benzene hydroxylation to phenol by nitrous oxide. The zeolites had two different iron contents (350 and 5800 ppm) and a Si/Al ratio of 42. The catalysts were activated by steaming (823 K) and/or calcinations in He (1323 K). The FeZSM-5 activated by steaming exhibited fractal dimensions lower than the samples activated by calcinations. The steamed samples also had activities in the benzene hydroxylation per Fe(II) site (TOF values) somewhat higher as compared to the zeolites activated by calcinations. This indicates the importance of the zeolite geometry for the reaction of bulky benzene molecule within a confined space. (c) 2005 Elsevier B.V. All rights reserved

Data for: Effects of structural properties of fillers on performances of Matrimid 5218 mixed matrix membranes

All the data, related to the structural properties of the filler materials as well as the performances of the Matrimid® MMMs, which were used in the statisical investigations are provided

Data for: Effects of structural properties of fillers on performances of Matrimid 5218 mixed matrix membranes

All the data, related to the structural properties of the filler materials as well as the performances of the Matrimid® MMMs, which were used in the statisical investigations are provided,THIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV

Relation of water adsorption capacities of zeolites with their structural properties

An investigation was carried out to determine the extent of relations between various structural properties of zeolite frameworks and their experimental water adsorption capacities. For this aim, average water capacity values were determined for different zeolite frameworks by utilizing water adsorption capacities reported in the literature for related materials. It was observed that the theoretical surface areas and volumes available for water adsorption in zeolites as well as the fractal dimensions of these materials exhibited some correlation with their experimental adsorption capacities. The results might give an indication of the potential for development of different zeolite frameworks, regarding their water adsorption capacities. Analogue materials of known zeolite framework structures, with different chemical compositions, which may allow for relatively high water adsorption capacities, may be prepared for such an improvement. The investigations may also be informative for the development of new zeolite-like adsorbents with relatively high capacities

Tailoring the reaction mixture composition for preparing zeolite coatings on aluminum supports in alkaline environments

Various alkaline reaction mixture compositions were tested for determining their suitability to be used in the direct crystallization of zeolites on aluminum supports. No organic materials, such as templates, complexing agents, and corrosion inhibitors were included in the reaction mixtures. It was observed that aluminum supports remained quite stable in alkaline synthesis mixtures when suitable reaction mixture compositions with relatively high silica content were used. These favorable compositions might be recognized from their sodium silicate/(sodium hydroxide + sodium aluminate) mass ratios, as depicted in this study. Coatings were prepared on aluminum by using some of these compositions. It was determined that aluminum hydroxide phases commonly forming on the support could be eliminated to a great extent and consequently, crystalline coatings of zeolites P and Y were obtained on aluminum surfaces. The coatings exhibited trivial mass loss in the mechanical stability tests applied

Adsorption kinetics of zeolite coatings directly crystallized on metal supports for heat pump applications (adsorption kinetics of zeolite coatings)

A series of theoretical studies had previously indicated that the utilization of zeolite coatings directly crystallized on metal surfaces might improve the performance of adsorption heat pumps significantly. In this study, for the first time, kinetic measurements were performed to determine the rate of adsorption of zeolite coatings, which is the relevant parameter for increasing the power density of heat pump applications. The zeolite coatings investigated were prepared by using the substrate heating method. A scale-up of the substrate heating system was made in order to be able to grow zeolite coatings on 5 x 5 cm(2) stainless steel plates, instead of the 1 x 1 cm(2) plates, conventionally used in synthesis experiments. Two different reactors were constructed in which zeolite A and X coatings, with mass equivalent thicknesses of about 38 mu m and 230 mu m, respectively, could be obtained. The zeolite X coating, which had a quite open nature, exhibited quite favorable overall adsorption kinetics when compared to a reference sample, a paper-like polymer structure containing zeolite laminated on a metal layer