Study of By-product from Cyclohexane Oxidation by Multiple Mass Spectrometry Technologies

A method for analyzing by product from cyclohexane oxidation by multiple mass spectrometry technologies was established. The by product was distilled to light fraction (distillation range <300 ℃) and heavy fraction (distillation range >300 ℃) by vacuum distillation. The qualitative and quasi-quantitative analysis for the light fraction of the by product were carried out by comprehensive two-dimensional gas chromatography-time of fight mass spectrometry (GC×GC-TOF MS). 54 kinds of oxygen compounds, which composed of ketones, ethers, alcohols, esters, aldehydes, phenols and hydrocarbons are identified. The carbon number distribution of the light fraction is 5-14. The compounds, with the carbon number of 12, account for more than 70% of the light fraction. As the carbon number of 2-cyclohexylidene-cyclohexanone, 2-(1-cyclohexenyl) cyclohexanone and oxydicyclohexane, which are the major compounds of the light fraction, were all 12. The compounds with the carbon number of 6 have the second highest content.The composition of the heavy fraction is more complex than the light fraction. It was characterized by Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS). The main components of the heavy fraction are O.2-O.5 compounds. The carbon number distribution of these oxygen compounds range widely, which are from 10 to 40. The compounds with the carbon number of 18 and 24 have higher content. The fact that compounds with multiples of 6 carbon atoms have higher content both in light and heavy fraction, illustrates that the structure of cyclohexane is reserved during the oxidation procedure. As for the compounds in the heavy fraction, their carbon numbers increase with the rising of oxygen numbers, while the distribution of double bond equivalents (DBE) remains the same. The structures of hexatomic ring, C[CDS1]C, C[CDS1]O and C—O of alcohols or ethers were predicted in the heavy fraction, which was verified by Fourier transform infrared spectroscopy (FTIR). The detailed composition information is helpful for the reproduction and reprocessing of the by product from cyclohexane oxidation. It can provide a new method for analyzing and researching of the complex system containing oxygen compounds.