Comparative study of reactive flash distillation vs semibatch reactor technologies for the glycerol hydrochlorination with gaseous HCl

The present work provides a systematic comparison of solvent-free glycerol hydrochlorination with semibatch and reactive flash distillation technologies. All the experiments were performed at atmospheric pressure and constant flow rate of gaseous HCl in the temperature range of 70 to 120 °C. Both acetic acid and adipic acid were used as homogeneous catalysts, separately, at a concentration of 12% by moles of each. In addition, a series of noncatalytic experiments was investigated. A comparative analysis between reactive flash distillation and semibatch operation suggested that reactive flash distillation only increases the production rate of the desired product 1,3-dichloropropan-2-ol (αγ-DCP) for the highest temperature, i.e. 120 °C. Many aspects of the HCl liquid uptake were also exposed once water was allowed to leave the liquid phase, revealing that water also has a positive influence on the reaction rate because it promotes HCl solubility and hydrolysis. Such an important effect was not predicted by previous investigations, and it is hereby described for the first time. Additional semibatch experiments were conducted, in which different amounts of water and αγ-DCP were initially added. It was found that, water exerts competing effects in the glycerol hydrochlorination; addition of αγ-DCP showed an improvement of the reaction kinetics and decrease of HCl consumption. It is suggested that instead of using reactive distillation, a wiser choice to perform glycerol hydrochlorination would be to recycle large amounts of the product stream to achieve high conversion levels at milder temperatures and consuming less HCl gas.