Feasibility of simultaneous measurement of xylene isomers and other hydrocarbons in p-xylene production processes using near-infrared spectroscopy

The feasibility of simultaneous measurement of important components such as o-xylene, m-xylene, p-xylene, ethylbenzene, toluene, aliphatic hydrocarbons, and total C-9-C-10 aromatic hydrocarbons in the p-xylene production process is investigated, Mixtures of those components were prepared to simulate concentration levels in actual p-xylene processes, and near-infrared (NIR) spectra were collected from mixtures over the spectral range of 1100 to 2500 nm. Even with the very similar spectral features of xylene isomers and other aromatic compounds, the concentrations of each of the components in the mixtures are accurately predicted by using a partial least-squares (PLS) algorithm and show excellent correlation with conventional gas chromatographic analysis. The results clearly demonstrate the possibility of using NIR spectroscopy for monitoring the major components in an actual p-xylene production process for process control and optimization.