固相萃取-气相色谱法测定合成气制烯烃产物中的含氧化合物

采用C18固相萃取技术对合成气制烯烃(SGTO)的产物进行预处理,将产物分离为含氧化合物与烃类,采用气相色谱-质谱法(GC-MS)考察分离效果并鉴定产物中的含氧化合物,使用氢焰离子化检测(FID)定量实际样品中的含氧化合物,使用其正构2-酮、正构醇的响应因子作为同碳数酮、醇的FID响应因子。优化C18小柱洗脱条件,使用标准样品比较预处理前后的方法回收率。醇类标准品回收率为88%~98%,酮类标准品回收率为64%~87%。在197~4785 mg/L范围内,标准品具有较好的线性关系,相关系数均大于0.99。定性并定量测定了SGTO产物中的67种含氧化合物,发现正构醇、正构2-酮为SGTO产物中的主要含氧化合物,同时存在少量其他异构体。该方法操作简单、快速、样品需求量小,并能够在10 min内完成样品的预处理。分析结果为SGTO工艺催化剂、动力学深入研究提供了必要的基础数据。

Determination of oxygenates in syngas-to-olefin products by solid phase extraction combined with gas chromatography-mass spectrometry

The syngas-to-olefin (SGTO) products mainly consist of hydrocarbons along with small amounts of oxygenates as the byproducts. A C18 solid-phase extraction (SPE) column was used for oxygenates enrichment in SGTO products. As the hydrophobic compounds, the hydrocarbons had stronger interaction with a C18 SPE column than oxygenates. Under the optimized elution conditions, the oxygenates were first eluted from the C18 SPE column with 60% (v/v) methanol solution. The fraction of oxygenates was then analyzed with gas chromatography-mass spectrometry (GC-MS) for qualification and gas chromatography-hydrogen flame ionization detection (GC-FID) for quantification. The FID response factors of n-alkanol and n-ketone were used for alkanols and ketones quantitative calculation and the method recoveries were 88%-98% and 64%-87% respectively. In the range of 197-4785 mg/L, good linear relationships of the FID responses with the corresponding mass concentrations of the standard samples were obtained with the linear regression coefficients greater than 0.99. Sixty-seven oxygenates were analyzed qualitatively and quantitatively. The results showed that the fraction of the oxygenates mainly consists of alkanols and ketones. The total content of the oxygenates in SGTO products was 6.2%. The enrichment method only requires a very small amount of sample and the total process can be completed within 10 min. The analysis results of SGTO product studies can provide the necessary basic data for SGTO catalysts and dynamics studies.