Detection and Characterization of Organic Gases during Coal Carbonization Using VUV-SPI-TOFMS

Abstract

A VUV-SPI-TOFMS system was developed for the continuous analysis of pyrolysis gases generated during coal carbonization and aromatic molecules were detected using high-resolution quantitative techniques. Although IR spectroscopy is suitable for detecting low-molecular-weight gases present in dry distillation gas, such as CH₄ and CO₂, it is not sensitive to aromatic hydrocarbon gases. On the other hand, the VUV-SPI-TOFMS technique is applicable for the quantification of low-concentration gases at the ppb concentration level, including aromatic hydrocarbons, generated during coal carbonization, which entails continuous heating from room temperature to 800°C. Benzene and toluene were predominantly detected at 540–590°C in the dry distillation gas of bituminous coal having relatively low oxygen concentration, whereas gases containing OH groups, such as phenol and cresol, are predominantly generated from sub-bituminous coal and lignite with high oxygen concentrations. Solid ¹³C NMR spectra obtained for each natural coal sample exhibited substantial proportions of oxygen bound to aromatic carbons (aromatic–O) in young coals. The temperature range at which cyclohexane was generated was found to be lower than that of aromatic molecules, indicating that coals releasing it may exhibit a structure that is more susceptible to thermal decomposition.