关键词: 汽油, 含氧化合物, 中心切割, 气相色谱

Abstract:

A gas chromatographic system equipped with back-flush and heart-cutting (microfluidic deans switch) parts and three connected columns is established for determination of trace level light oxygenates in gasoline products. The oxygenate in gasoline comprising heavy hydrocarbons can directly be analyzed by pressure changes of carrier gas, and the hydrocarbon components in the sample do not interfere with the determination results. Through the pressure changes of carrier gas, the components with the boiling points lower than n-undecane can be eluted from a 2 meters long pre-column into a 30 meters long non-polar column, meanwhile the heavy fractions are back-flushed to the vent port to leave the system. The components coming into the 30 m long column are separated by switching solenoid valve of heart-cutting parts, only the separated components with boiling point lower than 2-hexanone can be eluted from the non-polar column and enter into a 10 meters long polar OxyPLOT column to separate the light oxygenates and hydrocarbons, and then the effluents are detected by flame ionization detector and quantitatively determined with external standard method. Light oxygenate contents such as C1-C4 alcohols, C2-C5 aldehydes, C3-C6 ketones, methyl tert-butyl ether, ethyl tert-butyl ether and methyl tert-amyl ether in gasoline can be analyzed. The detection limit for single component is between 0.5-2.0 μg/g, the adding standard recovery rate for different components is 80%-120%, and the RSD (relative standard deviation ) is in the range of 2%-5%. The results of analysis of products from catalytic cracking and catalytic pyrolysis process show that the main oxygenates in these products are ketones with little amount of alcohols, aldehydes, and ethers.

Key words: gasoline, oxygenates, heart-cutting, gas chromatography