Chemical composition monitoring in a batch distillation process using Raman spectroscopy

Raman spectroscopy was used to monitor the batch distillation of an ethanol/water mixture in a sieve-plate column. The chemical composition of the top product was determined as a function of process time. Four different experimental runs with systematically varied heating and reflux strategies were studied. The results show that the reflux ratio influences the process timing as well as the product quality, whereas the heating strategy impacts the timing only. In the second part of this work, we demonstrate that the Raman technique can also be applied to hydrocarbon systems that are relevant in the oil and gas industries. For this purpose, hexane isomers and their mixtures were studied. The results show that, even though they exhibit very similar structure, the individual compounds can be identified and, moreover, quantified in a mixture. In conclusion, Raman spectroscopy is a useful and versatile tool for monitoring practical distillation processes.