Full Composition Analysis Of Fischer-Tropsch Synthesis Oil Using Extraction/Gas Chromatography

Fischer-Tropsch (F-T) synthesis is a technology by which syngas CO and H2 turn into complex products that are mainly composed of hydrocarbon materials in the presence of catalyst. Fischer-Tropsch synthesis products can be divided into gas phase, aqueous phase, oil phase and wax phase products according to their phase state. Oil phase products (namely F-T synthesis oil) are often processed and refined to become alternatives to gasoline and diesel. They can be used in petrochemical industry, and therefore have very important economic value and research significance. At present, the study of Fischer-Tropsch synthesis technology in our country is still in the initial stage. We have many blind and unknown spots towards the reaction mechanism and process development. The composition and distribution of the products are very important to the understanding and mastering of the two aspects. Therefore, composition analysis and distribution pattern of the F-T products are the main targets in this assertation.In this dissertation, catalyzed low-temperature F-T synthesis oil which is provided by Yanzhou Mining Company is determined as the research object and a detailed qualitative and quantitative analysis is conducted over the composition and distribution of the product. The technical routine, which is pretreatment first and analysis later, is determined on the basis of previous studies.First, pretreatment of F-T synthesis oil is done by means of distillation, column chromatography and extraction methods respectively. The separation efficiency of the three methods is observed and compared. Results show that extraction method is a proper way for pretreatment here. DMSO is used as an extractant for extracting F-T synthesis oil. According to different polarity and solubility, components are separated. Oxygen containing compounds are enriched in the extraction phase while hydrocarbons concentrated in the raffinate phase.Second, the extraction conditions are optimized. Since the DMSO is little in the raffinate phase, the interference of DMSO on other components can be neglected. But there are large amounts of DMSO in the extraction phase, which will impose a great impact on the subsequent analysis. So DMSO needs to be removed before further analysis. Water is used to remove DMSO since they have good mutual solubility. Good removal efficiency can be obtained at volume ratio 1:1 by optimization experiment. Then the raffinate phase and extraction phase (DMSO removed) are analyzed by gas chromatography-mass spectrometry (GC-MS).146 hydrocarbons and 86 oxygenates are identified qualitatively in total. It is found that these components have their specific product features and distribution characteristicsThird, n-alkanes and n-alcohols of F-T synthesis oil are quantitatively analyzed by means of external standard method. The results show that alkane and alcohol standard samples each have a good linear relationship over a relatively wide concentration range with the correlation coefficients greater than 0.99. The concentrations of n-alkanes and n-alcohols obtained are in consistent with previous reports, meaning that the results are convincing. And the method has high precision, high accuracy and good repeatability, which meets the requirement of quantitative analysis.