The Study Of Sulfur Compounds And Alkyl Benzenes In Petroleum Products

In this paper, qualitative and quantitative investigations about sulfur compounds and alkyl benzenes in petroleum products were developed. The detection methods used were gas chromatography with flame photometric detector (GC-FPD) and gas chromatography mass spectrometry (GC-MS), respectively.In the study of determination of sulfur compounds in light hydrocarbon and its products, gas chromatography with a flame photometric detector was applied. The experimental conditions were examined and some types of standard curves were studied in detail. The determination limits of 2-propyl mercaptan, 1-propyl mercapan and methyl thioether are 0.56, 0.21 and 0.37μg/ml, respectively.. The proposed method was applied to the determination of sulfur compounds in light hydrocarbon and its products and the results obtained are satisfactory. The proposed method is suitable for the quantitative analysis for plenty of similar samples, especially for petroleum and chemical industry products and the experimental instrument used is conventional. However, because the kinds of standard curves are relative to the sulfur compounds, the different kinds of standard curves should be applied for the different sulfur compounds.In the study of identification of sulfur compounds in industrial mixed alkanes, GC-MS was applied. By treating samples with AgNO3 and KOH, organic sulfur compounds were separated and enriched effectively from industrial mixed alkanes, which were in favor of the analysis by GC-MS. When the mercaptan or thioether reacts chemically with silver nitrate the silver alkyl sulfide precipitates. The mercaptan can react chemically with potassium hydroxide or sodium hydroxide to produce sodium mercaptan. The thiophene does react with both silver nitrate and alkalis. When potassium hydroxide was added into industrial mixed alkane, the mercaptan can be extracted into the aqueous phase, and thioether and thiophene remain in industrial mixed alkane. When the silver nitrate was added into the sample, the mercaptan and thioether precipitate and the thiophene remains in the sample. The mercaptan, thioether and thiophene can be isolated from each other. The silver alkyl sulfide can be solved into ammonia, and the thioether compounds can be extracted into hexane. The mercaptan in aqueous phase can be extracted into hexane by acidifying the aqueous phase with acetic acid. This treating method can be applied directly in the qualitative analysis of sulfur compounds in a series of products of light hydrocarbon, mixed hexane, industrial pentane, industrial octane, cyclopentane and so on. In the study of identification method of structure of mixed alkyl benzenes, GC-MS was considered and chosen finally. The results indicated that both reproducibility and separating degree of this method were satisfactory. By this method, the average molecular weight of mixed alkyl benzenes can be obtained easily. In the future, this method can be used in the identification of composition of crude alkyl benzenes and provide credible reference to improve the quality of alkyl benzene sulfonates in the industrial manufacture.