ASTM D5758-01 (R2021) pdf free download.Standard Test Method for Determination of Relative Crystallinity of Zeolite ZSM-5 by X-Ray Diffraction.
1.1 This test method covers a procedure for determination of the relative crystallinity of zeolite ZSM-5 using selected peaks from the X-ray diffraction pattern of the zeolite.
1.2 The test method provides a number that is the ratio of intensity of a portion of the XRD pattern of the sample ZSM-5 to intensity of the corresponding portion of the pattern of a reference ZSM-5. The intensity ratio, expressed as a percentage. is then labeled percent XRD relative crystallinity/ ZSM-5. This type of comparison is commonly used in zeolite technology and is often referred to as percent cryslallinity.
3. Summary of Test Method
3.1 XRD patterns of the sample ZSM-5 and the reference ZSM-5 arc obtained undcr the same conditions. From these patterns, there is a choice from two procedures for calculation of relative crystallinity/ZSM-5.
3. 1.1 Procedure A (Integrated Peak Area Method)—A comparison is made of the sums of intensities (sample versus reference) of the strong peaks, having maxima between about 23.1 and 24.3° 20.
3. 1 .2 Procedure B (Peak Height Meihod)—A comparison is made of the absolute peak heights (sample versus reference) of the 24.3° 20 peak.
4. Significance and Use
4.1 ZSM-5 is a siliceous zeolite that can he crystallized with Si02/Al2O3 ratio in the range of 20 to greater than 1000. ZSM-5, upon modification to the H-cation form (HZSM-5) in a post-crystallization step. has been used since the 1970s as a shape selective, acid-site catalyst for petroleum refining and petrochemicals production. including such processes as alkylation. isomerization. fluid cracking catalysis (FCC), and methanol-to-gasoline. The most siliceous member of the ZSM-5 family, sometimes called silicalite, is hydrophobic and it is used for selective sorption of organic molecules from water-containing systems.
4.2 This X-ray procedure is designed to allow a reporting of the relative degree of crystallization upon manufacture of ZSM-5. The relative crystallinity/ZSM-5 number has proven useful in technology, research, and specifications.
4.3 The 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 ZSM-5 can result from changes in distribution of electron density within the unit cell of the ZSM-5 zeolite. The electron density distribution is dependent upon the following factors:
4.3.1 Extent of filling of pores with guest molecules and the nature of these guest molecules.ASTM D5758 pdf download.