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Standard Test Method for Determination of Relative Crystallinity of Zeolite Beta by X-Ray Diffraction
NORMA vydaná dňa 1.10.2020
Označenie normy: ASTM D8352-20
Dátum vydania normy: 1.10.2020
Kód tovaru: NS-1013202
Počet strán: 5
Približná hmotnosť: 15 g (0.03 libier)
Krajina: Americká technická norma
Kategória: Technické normy ASTM
crystallinity, X-ray diffraction, zeolite Beta,
|Significance and Use|
4.1Zeolite Beta is a siliceous zeolite that can be crystallized with SiO2/Al2O3 ratio greater than 20. Zeolite Beta, upon modification to the H-cation form in a post-crystallization step, has been used in catalytic NOx reduction, isomerization of waxes, alkylation of aromatics, hydrocarbon adsorption from exhaust gas emission, etc.
4.2This X-ray procedure is designed to allow a reporting of the relative degree of crystallinity upon manufacture of zeolite Beta. The relative crystallinity of zeolite Beta number has proven useful in technology, research, and specifications.
4.3The Integrated Peak Area Method (Procedure A) is preferred over the Peak Height Method (Procedure B) since it calculates XRD intensity as a sum from several peaks rather than utilizing just one peak. Drastic changes in intensity of individual peaks in the XRD pattern of zeolite Beta can result from changes in distribution of electron density within the unit cell of the zeolite Beta. The electron density distribution is dependent upon the following factors:
4.3.1Extent of filling of pores with guest molecules and the nature of these guest molecules.
4.3.2Type of cations and extent of their presence (these cations may also affect the absorption of X rays by the zeolite Beta sample).
4.3.3In this XRD method, the guest molecule H2O completes the filling of the pores. Other guest molecule types may also be present, including one of numerous amines, diamines, and quaternary ammonium cations that can function as a template for crystallization of the zeolite Beta structure.
4.3.4Because of the factors mentioned in that could vary the intensities of the XRD peaks in zeolite Beta, this XRD method will provide the best determination of relative crystallinity when the reference zeolite Beta and sample zeolite Beta have a similar history of preparation and composition.
4.4If crystalline phases other than zeolite Beta are present in the sample, their diffraction peaks may overlap with some of the zeolite Beta peaks selected for the Integrated Peak Area Method (Procedure A). If there is reason to suspect the presence of such components, then the Peak Height Method (Procedure B) should be chosen for analysis, provided that there is no interference with the 22.5 2? peak that is used for the calculation.
1.1This test method covers a procedure for determination of the relative crystallinity of zeolite Beta containing samples using selected peaks from the X-ray diffraction (XRD) pattern of the zeolite.
1.2The test method provides a number that is the ratio of intensity of a portion of the XRD pattern of the sample zeolite Beta to intensity of the corresponding portion of the pattern of a reference zeolite Beta. The intensity ratio, expressed as a percentage, is then labeled percent XRD relative crystallinity of zeolite Beta. This type of comparison is commonly used in zeolite technology and is often referred to as percent crystallinity.
1.3This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.4This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
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