The synthesis of peroxycarboxylic esters, as one subgroup of organic peroxides, is characterized by a high thermal hazard potential regarding process safety. In case of failure in the production process, e.g., if the heat of reaction cannot be removed sufficiently fast, decomposition reactions can be triggered, and as a result, remarkable amounts of heat and gas can be released and can cause a high extent of damage. Multifarious technical and organizational measures are necessary to ensure the safe industrial production of peroxides. With the introduction of microreaction technology plenty of possibilities have been opened to carry out highly exothermic reactions in smaller volumes and with more efficient heat removal. In this paper we report the application of three different microstructured reactors, representing different mixing strategies, to synthesize two peroxymonocarboxylic esters, namely tert-butyl peroxypivalate and tert-butyl peroxy-2- thylhexanoate. The following reactor types were considered: an orifice microreactor, a split and recombine microreactor and a capillary tube reactor in combination with ultrasonication. The efficiency of the two Phase liquid/liquid reaction is expressed in comparison of conversion and selectivity. With microreaction technology a remarkable increase in space-time-yield, ranging from 12,500 kg·m−3·h−1 to 414,000 kg·m−3·h−1, is achieved.
A major item of thermal process safety, concerning the industrial realisation of exothermic reactions, is the determination of a temperature, where a reaction can be carried out without risk for humans, environment, and of economic loss. The so-called limit temperature Texo is a safety parameter for the reaction process and should not be mixed up with the Self Accelerating Decomposition Temperature (SADT). The last one refers to a temperature value for safe transportation including specific conditions like transport time and type of containment.
In Germany a technical guide (Identification and Control of Exothermic Chemical Reactions, TRAS 410, 2012) specifies three approaches for determining Texo. In this work, all these approaches were applied to specify Texo for the synthesis of three tert-Butyl peroxycarboxylic esters. Peroxycarboxylic esters are a subdivision of organic peroxides, known for their high hazardous potential.
Results differed partly significant. Anyhow, all of the used techniques and evaluation methods led to Texo values, which were on the safe side – taken the Texo value estimated by the heat release criterion as reference. This method is considered by the authors as a very accurate one.