Petroleum Coke Testing

Gazulla, María Fernanda, et al. Talanta Open 6 (2022): 100134.

Controlling trace metal concentrations in petroleum coke is crucial for its use as an anode material, as metal impurities can negatively impact electrode performance and the purity of final products. This study presents a novel microwave-assisted digestion method for determining trace levels of Si, Fe, V, Ni, Ca, Na, P, Al, Ti, Mg, K, Zn, Mo, Ba, and Co in both green and calcined petroleum cokes.

The optimized digestion conditions included mixing 9 g of HNO₃ and 3 g of HCl, heating the mixture to 260°C for 55 minutes with 0.5 g of the sample, achieving recoveries above 98% for all target elements. The method significantly reduced the sample preparation time to just 1.5 hours compared to the standard 8-hour method. Validation was performed using certified reference materials and alternative techniques, including wavelength dispersive X-ray fluorescence spectrometry (WD-XRF), confirming the accuracy of the results.

This microwave-assisted method offers several advantages over traditional techniques, including reduced environmental impact due to lower waste generation, improved efficiency, and reduced sample preparation time. Additionally, the method achieves low limits of quantification and minimal uncertainties, making it an ideal tool for monitoring trace metals in petroleum coke for quality control purposes.

Zhang, Wenhao, et al. Spectrochimica Acta Part B: Atomic Spectroscopy 177 (2021): 106076.

A novel laser-induced breakdown spectroscopy (LIBS) method has been proposed for the rapid determination of Vanadium (V), Iron (Fe), and Nickel (Ni) in petroleum coke. Unlike traditional methods, which require lengthy operation times and various reagents, LIBS offers significant advantages such as minimal sample preparation, faster measurements, and no reagent consumption, reducing both environmental impact and operational complexity.

The method involved wavelength feature selection for V, Fe, and Ni in the LIBS spectrum, followed by prediction of element concentrations using Support Vector Regression (SVR) modeling. The root-mean-square error of predictions (RMSEP) for V, Fe, and Ni was 36.4 mg/kg, 36.04 mg/kg, and 14.94 mg/kg, respectively. These results showed close agreement with the reproducibility of element measurements using the ASTM D6376–10 standard, specifically the wavelength dispersive X-ray fluorescence spectroscopy (WD-XFS) method, where the RMSEP for V and Ni were 32 mg/kg and 14 mg/kg.

This study demonstrated that LIBS is a promising alternative for the rapid, efficient, and accurate detection of trace elements in petroleum coke, making it suitable for industrial quality control and environmental monitoring in the petroleum coke sector.

Fernández-Ruiz, Ramón, et al. Spectrochimica Acta Part B: Atomic Spectroscopy 174 (2020): 105997.

The impact of particle size distribution on sulfur content in petroleum coke was explored using the Suspension Assisted Analysis (SAA) combined with Total-reflection X-ray Fluorescence (TXRF) for sulfur quantification. The study optimized the SAA-TXRF method by evaluating sulfur recoveries across three different particle size distributions of the same petroleum coke sample. It was found that smaller particle sizes led to higher sulfur recovery, indicating that sulfur signal intensity is significantly affected by the particle size and deposition morphology of the coke.

This effect was confirmed through comparison with CHNS elemental analysis and microwave-assisted digestion TXRF measurements. The sulfur signal was found to be influenced by a strong absorption effect and the distortion of the X-ray Standing Waves (XSW) field, which occurs between sulfur and internal standard elements such as Ti and Co. The sulfur recovery was up to 45.5% lower in SAA-TXRF than in CHNS analysis.

The results highlight the necessity of optimizing the particle dispersion for accurate sulfur measurement in petroleum coke using the SAA-TXRF method. The use of a high-power ultrasound probe proved crucial for achieving consistent and reliable results, underscoring the importance of precise sample preparation in elemental analysis for industrial applications.