Determination of phenol in phenol tars from the cumene-to-phenol process streams with 13C-NMR spectroscopy

Abstract

¹³ C-NMR spectroscopy has been employed for the determination of phenol in phenol tars originating from the process of phenol industrial synthesis. Relaxation times T₁ of ¹³C nuclei in phenol and in dioxane (used as a standard for quantitation) have been measured in order to establish appropriate conditions for the acquisition of quantitative spectra. The results of ¹³C-NMR analyses are compared with the results obtained with ¹H-NMR, infrared spectroscopy, ultraviolet spectroscopy, gas chromatography and bromometric titration. The accuracy and repeatability of the determinations have been tested on samples with added weighed amounts of phenol. A great advantage of the ¹³C-NMR method is that three results from each spectrum are obtained, which may be averaged, while those involving large errors can be rejected. The scatter of the relative errors for single results has been tested and evaluated at the level ±0.8%.