ASTM D4926-20

4.1 This test method is for estimating the relative amount of gamma alumina in calcined catalyst or catalyst carrier samples, assuming that the X-ray powder diffraction peak occurring at about 67 °2θ is attributable to gamma alumina. Gamma alumina is defined as a transition alumina formed after heating in the range from 500 to 550 °C, and may include forms described in the literature as eta, chi, and gamma aluminas. Delta alumina has a diffraction peak in the same region, but is formed above 850 °C, a temperature to which most catalysts of this type are not heated. There are other possible components which may cause some interference, such as alpha-quartz and zeolite Y, as well as aluminum-containing spinels formed at elevated temperatures. If the presence of interfering material is suspected, the diffraction pattern should be examined in greater detail. More significant interference may be caused by the presence of large amounts of heavy metals or rare earths, which exhibit strong X-ray absorption and scattering. Comparisons between similar materials, therefore, may be more appropriate than those between widely varying materials.

1.1 This test method covers the determination of gamma alumina and related transition aluminas in catalysts and catalyst carriers containing silica and alumina by X-ray powder diffraction, using the diffracted intensity of the peak occurring at about 67 °2θ when copper Kα radiation is employed.

1.2 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.3 This 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.

1.4 This 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.