Study On The Determination Method Of Sulfur Content In Low Sulfur Petroleum Products

The gas produced by the combustion of sulfide in petroleum products is the main substance that forms acid rain,which not only pollutes the environment,but also endangers human health.With the upgrading of national standards for petroleum products,especially fuel oil,the sulfur content in petroleum products is also declining.At present,the sulfur content in gasoline and diesel products is close to the detection limit of existing analysis methods,and the accuracy of the test method is tested.Therefore,to establish an analysis method that can be used to detect lower sulfur content and improve the accuracy of test results is an urgently needed and practical task at this stage.This article compares and analyzes many sulfur content detection methods which commonly used,including using tube furnace method,micro-coulometric method,ultraviolet fluorescence method and single-wavelength X-ray fluorescence spectroscopy method,and then establishes analytical methods for methodological validation and compares the advantages and disadvantages of the methods and the scope of application:(1)The tube furnace method is suitable for petroleum products with sulfur content greater than 0.1%(m/m).However,the detection limit is high,and there are many human factors so that the error is large.(2)The lower limit of quantification of the micro-coulometric method can reach 1 mg/kg,and the instrument equilibration time is longer,and other substances present in the sample that react with iodine will cause the results to deviate.(3)The lower limit of quantification of X-ray fluorescence spectroscopy can reach 2 mg/kg.The accuracy is higher when the sample is close to the standard substance matrix,and the inconsistency of the matrix has a greater impact on the results.(4)The lower limit of quantification of the ultraviolet fluorescence method can reach 1 mg/kg,and the detection result may be greatly affected by the influence of chlorine,nitrogen and other elements in the sample matrix.In view of the problems in the above sulfur content testing methods,after comprehensively considering the advantages and disadvantages of each method,this paper proposes to improve based on the tube furnace method,and establishes a tube furnace combustion-ion chromatography method to determine sulfur content in petroleum products.The linear relationship is good in the range of 0.010~5.000 mg/L.And take peak area of sulfate ion as the Y-axis and the concentration as X-axis.The standard curve equation is Y=0.27991X-0.00482(r=0.9998),and the detection limit is 0.0036 mg/L with good precision and reproducibility(RSD<5%),and the spike recovery rate is between 95.0% and 103.0%.It can achieve the same result as the current national standard arbitration method-ultraviolet fluorescence method test.In order to improve the applicability of the method,the sample-loaded porcelain boat,combustion tube and temperature control program of the tube furnace were improved,and an improved tube furnace combustion-ion chromatography method was established.After the improvement,the sample burns more fully,the sample load can be increased,the measurement result is accurate,and the operation is more convenient.The method has a good linear relationship in the range of 0.004 to 2.560 mg/L,and the standard curve equation is Y=0.28847X-0.0025(r=0.9998),and the detection limit is 0.0025 mg/L.The precision and repeatability meet the requirements,and the recovery rate is between 96.51%~101.89%,which meets the requirements of the analysis method.The operation is simpler and more practical.The tube furnace combustion-ion chromatography method established in this paper and the improved tube furnace combustion-ion chromatography method can better detect the sulfur content in low-sulfur petroleum products,which can make up for the shortcomings of the existing analytical methods and be applied as a supplement to the national standard method.