UOP, a Honeywell company, produces test methods used by the petroleum industry to evaluate the performance of catalysts. UOP 979 is a test method to measure the total chloride content in fresh, regenerated and spent alumina- supported catalysts by wavelength dispersive XRF. The method covers the range of chloride content from 0.01 to 3.0 wt %.This study was produced in collaboration with UOP, a Honeywell company.
This study was performed using the wavelength dispersive optics of the Zetium XRF spectrometer. It was configured with a 1 kW Rh anode SST R tube with Malvern Panalytical’s proprietary CHI-BLUE chemical resistant window coating, X-Y sample handler and state-of-the-art SuperQ software, featuring an advanced Fundamental Parameters algorithm. Zetium is engineered for excellence in terms of analytical accuracy, precision and operator performance.
Sample preparation and analysis parameters
Samples were prepared as loose powdered material in 45 mm diameter liquid cups using a 3.5 µm Mylar support film. All analyses were performed in a helium environment. The chloride analysis was performed using a curved Ge crystal for improved performance. The Cl Kα peak was used for the analysis with single background position. The specific measurement conditions are shown in Table 1.
Table 1: Measurement conditions used in this study
Calibration and results
The calibration was performed using 6 fresh alumina-based catalyst standards with chloride concentrations between 0.01 and 2.9 wt %. The calibration standards were provided by UOP as part of the collaboration in this evaluation. The calibration is shown in Figure 1.
Figure 1. Cl calibration curve
The accuracy of the Cl calibration is indicated by the RMS in Table 2.
Table 2. Concentration range and accuracy
Repeatability and site precision
The precision of the method was determined according to UOP method 999 regarding precision statements:
“The nested design was carried out for determining the total chloride content by two analysts on two separate days, performing two analyses each day for a total of 8 analyses. Using a stepwise analysis of variance procedure, the within- day estimated standard deviations (esd) were calculated at the concentration means listed in Table 3. Two analyses performed in one laboratory by the same analyst on the same day should not differ by more than the repeatability allowable differences shown in Table 3 with 95% confidence.
Two analyses performed in one laboratory by different analysts on different days should not differ by more than the site precision allowable differences shown in Table 3 with 95% confidence. The data in Table 3 represent short-term estimates of the repeatability of the method. When the test is run routinely, use of a control standard and a control chart is recommended to generate an estimate of long-term repeatability.”
The data presented in Table 3 are well within the requirements of UOP 999.
Table 3: Repeatability and site precision in wt % according to UOP method 999
The data collected in this study clearly demonstrate that the Zetium XRF spectrometer is more than capable of producing high-quality analyses of chloride in alumina-based catalysts that meet and exceed the requirements of UOP method 979.