固相萃取-气相色谱法测定甲醇制烯烃副产汽油及甲醇制汽油产物中的含氧化合物

采用纯硅胶柱固相萃取技术对甲醇制烯烃副产汽油或甲醇制汽油产物进行预处理,将产物中的含氧化合物与烃类进行色谱分离,采用质谱鉴定产物中的含氧化合物。使用标准溶液优化纯硅胶小柱的洗脱条件,比较预处理方法的回收率,考察预处理方法的重复性。结果表明,标准溶液的各含氧化合物组分回收率为87.7%~95.3%。采用气相色谱-火焰离子化检测器(GC-FID)通过内标法对实际样品中除甲醇和乙醇外的含氧化合物进行定量分析,使用丁酮、叔戊醇、戊酮和己酮的响应因子作为同碳数醛、酮、醇的FID响应因子,定量甲醇制烯烃副产汽油和甲醇制汽油产物中的含氧化合物。对于甲醇和乙醇,采用GC-MS分析提取特征离子用外标法定量。结果表明,甲醇制烯烃副产汽油和甲醇制汽油产物中的含氧化合物以酮类、醛类为主,并有少量的醇类。

Determination of oxygenates in methanol-to-olefin gasoline byproducts and methanol-to-gasoline product with solid phase extraction-gas chromatography

Silica solid phase extraction (SPE) column was used for sample pretreatment to enrich the target analytes and simplify background. Due to its high efficiency, reliability and simplicity, the technique has been widely used in many fields. The byproduct gasoline of methanol-to-olefin (MTO) and the product of methanol-to-gasoline (MTG) mainly consist of hydrocarbons along with small amounts of oxygenates. Trace amounts of oxygenates are hard to identify because of their complex hydrocarbon components. With the SPE technique, the samples were separated into two major classes, oxygenates and hydrocarbons. Oxygenates were then determined with gas chromatography-mass spectrometry (GC-MS). The elution conditions of the silica solid phase extraction column were optimized with the standard sample. Under the optimized elution conditions, the hydrocarbons were first eluted from the SPE column with 5 mL dichloromethane, the oxygenates were then eluted with 3 mL acetonitrile. The recoveries of standard samples were tested before and after pretreatment. The standard recoveries were 87.7%-95.3%. The oxygenates except methanol and ethanol were then quantified by gas chromatography-flame ionization detection (GC-FID) and internal standard method. Methanol and ethanol were then quantified by extracting characteristic ion chromatograms and external standard method. The results show that the oxygenates of MTO byproduct gasoline and MTG product mainly consist of ketones and aldehydes. The method improves the sensitivities of the target compounds and reduces the interference of the background.