Determination of lanthanum oxide,cerium oxide and silicon dioxide in rare earth selective catalytic reduction (SCR) denitration catalysts by alkali fusion-inductively coupled plasma atomic emission spectrometry
YU Yahui1,2,3, MU Baowei4, CUI Kailu1,2,3, ZHANG Huizhen1,2,3, WANG Sumei*1,2,3
1. National Key Laboratory of Baiyunobo Rare Earth Resource Researches and Comprehensive Utilization,Baotou 014030,China; 2. Baotou Research Institute of Rare Earths,Baotou 014030,China; 3. Ruike National Engineering Research Centre of Rare Earth Metallurgy and Functional Materials,Baotou 014030,China; 4. Department of Chemistry,Baotou Teachers' College,Baotou 014010,China
Abstract：Rare earth selective catalytic reduction (SCR) denitration catalysts have been widely used in denitration system. The chemical composition proportion is one of important bases for the performance judgment. Therefore, it is very necessary to develop a method for the determination of lanthanum oxide, cerium oxide and silicon dioxide in rare earth SCR denitration catalysts. These catalyst products contain tungsten and titanium with high temperature resistance and high hardness, which are hardly decomposed by the conventional acid dissolution method. In this study, the sample was melted with sodium hydroxide and sodium peroxide. The orthogonal condition experiments of L16 (45) were carried out on the flux dosage, melting temperature, melting time and the amount of hydrochloric acid for leaching. The optimal conditions for sample pretreatment were obtained as follows: 1.5 g of sodium hydroxide and 3.0 g of sodium peroxide were used as the flux, the melting temperature was 850 ℃, the melting time was 15 min, and the dosage of hydrochloric acid for leaching was 25 mL. La 333.749 nm, Ce 446.021 nm and Si 251.611 nm were selected as the analytical lines. When the mass concentration of Na+ in sample solution was not more than 2.0 mg/mL, the recoveries of elements were between 95.3% and 100%. Therefore, the solution was diluted for 10 times in experiments, and the concentration of Na+ in the solution was about 1.5 mg/mL. The influence of coexisting elements on the measurement results could be negligible. Finally, the method for the determination of lanthanum oxide, cerium oxide and silicon dioxide in rare earth SCR denitration catalysts by inductively coupled plasma atomic emission spectrometry (ICP-AES) was established. The linear correlation coefficients of calibration curves for lanthanum oxide, cerium oxide and silicon dioxide were all 0.999 9. The limits of detection for lanthanum oxide, cerium oxide and silicon dioxide were 0.009 0 μg/mL, 0.008 7 μg/mL, and 0.069 μg/mL, respectively. The limits of quantification for lanthanum oxide, cerium oxide and silicon dioxide were 0.024%, 0.023%, and 0.18%, respectively. The contents of lanthanum oxide, cerium oxide and silicon dioxide in rare earth SCR denitration catalysts were determined according to the experimental method. The relative standard deviations (RSD, n=11) of determination results were between 0.007% and 0.74%, and the recoveries were between 99.4% and 100%. The contents of lanthanum oxide, cerium oxide and silicon dioxide in rare earth SCR denitration catalysts were determined according to the experimental method and X-ray fluorescence spectroscopy (XRF), and the found results were consistent.
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