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GC × GC oil detection application:Determination of aromatic hydrocarbon content in coal based Fischer Tropsch synthetic lubricant base oil

Determination of aromatics in coal based Fischer Tropsch synthetic lube base oil

Gai Qingqing, zhujiaqing, AI Jun, zhaoshuai, shenqiaoling, liucongyun

(Beijing Institute of low carbon and clean energy, Beijing, one02209)

Fischer Tropsch synthesis is a key technology in the process of indirect coal liquefaction. It is a process that takes syngas (co+h2) as raw material and converts it into liquid hydrocarbon fuel and other chemicals on catalyst [one]. Compared with traditional petroleum based products, Fischer Tropsch synthetic oil (wax) products have the characteristics of low content of sulfur, nitrogen and aromatics and high content of alkanes, which meet the environmental protection requirements of clean oil products and are the raw materials for the production of high-quality and high-end lube base oil [2]. The lubricant base oil produced by Fischer Tropsch synthetic wax has high viscosity index and low evaporation loss. It can be used as a lubricant base oil with ultra-high viscosity index for all kinds of engine oil, gear oil, hydraulic oil, compressor oil, grease, etc. Compared with the main lube base oil products I and II in the current market, these products have better viscosity temperature characteristics and can play a greater role in energy saving and emission reduction, and prolonging the service life of machinery.

The base oil of Fischer Tropsch synthetic lubricating oil is mainly alkanes with low aromatic content. The existing method standards nb/sh/t 0966 and gb/t oneone08one both use UV spectrophotometry to determine the aromatic content. Due to the interaction between the molecules of liquid samples, Doppler broadening and pressure broadening, the spectral fine structure of liquid samples becomes blurred or even disappears. The method error for determining the aromatic content is large.

Comprehensive two-dimensional gas chromatography (GC × GC) is a multi-dimensional chromatographic separation technology rising in recent years. It connects two capillary chromatographic columns with different polarity through a modulator to form a two-dimensional gas chromatographic system to analyze the sample components. Compared with conventional one-dimensional gas chromatography, full two-dimensional gas chromatography is widely used in the analysis of petroleum fractions because of its high resolution, large peak capacity, good sensitivity and strong spectral distribution regularity [3]. It is a powerful tool for the separation and identification of volatile components in complex samples, especially for the group separation of compounds with different polarity. Due to the high viscosity and distillation range of lube base oil, there are few reports on the composition analysis of Fischer Tropsch synthesis base oil by full two-dimensional gas chromatography.

In this paper, full two-dimensional gas chromatography and mass spectrometry (GC × A method for the determination of aromatics in Fischer Tropsch synthetic lube base oil was established by GC-MS).firstAromatics are extracted and adsorbed on the extraction head by headspace solid-phase microextraction, and then thermally analyzed and injected at the gas chromatography injection port, separated by full two-dimensional chromatography, detected by mass spectrometer and quantified by internal standard method. Using the best solid phase microextraction conditions and chromatographic separation conditions, GC × Samples a and B of Fischer Tropsch synthetic lube base oils obtained under different hydroisomerization conditions were analyzed by GC-MS. According to the results of mass spectrometry, the group separation bands are obtained. As it is a reversed-phase two-dimensional system, the polarity of the compounds is getting stronger from top to bottom. The chromatographic bands are alkanes and aromatics respectively,Most of them are alkanes, with a small amount of aromatics,See Figure one

Fig. one full two-dimensional chromatographic three-dimensional diagram of Fischer Tropsch synthetic lube base oil

Fig. one 3D surface plot of GC × GC for Fischer-Tropsch synthetic lube base oil

由图one可知,由于两个样品的加氢异构条件不同,其组成也有明显的差别,主要是芳烃含量的差异。在定性分析中,自动识别信噪比大于one0的色谱峰,通过自动解卷积和NIST 20one4质谱库比对检索,筛选相似度大于750的组分,确认样品中芳烃组分。A样品中检测到极少量的芳烃,分别是二甲苯和三甲苯,内标法定量芳烃的总量为0.one26 mg/L;B样品中检测到二十多种芳烃组分,均为单环芳烃,内标法定量芳烃的总量为one0.65one mg/L。A、B样品中芳烃含量的差别反映到样品的外观上,A样品无色透明,B样品呈现黄色。这些结果也表明During the hydroisomerization of sample B, obvious aromatization side reaction occurred, and more aromatics were generated. Therefore, GC × The combination of GC and MS can not only quickly and accurately analyze the composition and content of aromatics in the base oil of Fischer Tropsch synthetic lubricating oil, but also provide a reliable quality detection means for the optimization operation and advanced control of lubricating oil production, and provide a reference for accurately obtaining the composition information of lubricating oil base oil at the molecular level.

reference

[one] Xiong H F,Motchelaho M A,Moyo M, et al. Effect of Group I alkali metal promoters on Fe/CNT catalysts in Fischer–Tropsch synthesis[J].  Fuel, 20one5,one50:687-696.

[2] 张雅琳,张占全,王燕,等. 费托合成油和石油基加工产品对比分析[J],化工进展,20one8,37(one0)378one-3786

[3]刘明星,刘泽龙,李颖,等. 固相萃取法/全二维气相色谱-飞行时间质谱测定柴油及其加氢产品中的含硫化合物[J]. 石油炼制与化工, 2020, 5one(4):96-one03.

Author:gaiqingqing, Beijing Institute of low carbon and clean energy


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