Continuous nitration of alcohols in a Freon flow†
The first ever installation for continuous nitration in a liquefied gas mobile phase was developed. The installation was used to convert 2-ethylhexan-1-ol, diethylene glycol, and glycerol into their corresponding nitro esters. The starting compounds were treated with a 10% excess of dinitrogen pentoxide in liquefied 1,1,1,2-tetrafluoroethane (TFE) medium. The flow reactions proceeded at room temperature and ≤10 bar pressure with excellent conversion and selectivity. An important feature of the developed procedure is TFE recycling which prevents its release into the atmosphere. The proposed approach for nitro esters flow production outperforms the known batch-type analogs in terms of having a far better specific productivity (by two orders of magnitude), reduced fire and explosion risks, and less pronounced negative impact on the environment. The enumerated advantages along with equipment availability lay the foundation for the development of a highly efficient nitration technology, which is characterized by reduced amounts of waste by employing a TFE medium.