Abstract
For the industrial production of chemicals a safe process design is required to avoid harm to people and environment. It becomes tremendous important if one or more of the following points are characteristic for the synthesis: high heat release, explosive atmosphere, presence of toxic and/or of thermal unstable substances. One substance group, known for being unstable, is the group of organic peroxides. They are potential high energetic substances. Many syntheses of organic peroxides are carried out in semi-batch mode to control the heat release in a good manner. With the aim to increase process control, the advantages of continuous reaction mode, combined with micro reaction technology, are used for the synthesis of one specific organic peroxide in this work.
This approach is not only characterised by shorter residence time, good heat transfer, but also by smaller quantities of managed chemicals, and, therefore, by a lower hazard potential. Often yield and selectivity can be improved additionally.
For the study a peroxyester, namely tert-Butyl peroxy-2-ethylhexanoate (TBPEH), with known thermal hazard potential was chosen. The two phase liquid/liquid reaction was carried out in three types of reactors. A small scale tubular reactor, stressed by ultrasound, and two different micro structured reactors were used. One of them had a meandering and the other a split-and-recombine channel structure. Synthesis temperature was also varied.
From preliminary studies it was known that the side reaction of the involved carboxylic acid chloride to the corresponding acid can become more important in continuous mode compared to semi-batch mode. The effect of reactor type and temperature on selectivity and therefore yield of TBPEH was analysed and compared.
In result the reaction could be carried out in a safe manner. The high heat-exchanging efficiency of the used reactors and the short residence time allowed synthesis temperature near the onset temperature of decomposition of TBPEH. In relation to the results of the capillary tube and of the reactor with meandering channel structure (MR), the results for the split-and-recombine reactor (SAR) showed the best trend line. Further studies have to underline the result. Compared to the traditional reaction path (the semi-batch mode), a higher space time yield could be achieved. This promising information is accompanied by the fact of low reaction volumes. In consequence the productivity is low without a numbering up of reaction channels or a scaling up of it. The nowadays existing philosophy of producing a specific quantity of product by a company, followed by the transport to the costumer may change. Just organic peroxides, used in small quantities, e.g. as initiators for polymerisation processes or as resin hardeners, provide the opportunity for an on-demand-production.
