Publikationsrepositorium - Helmholtz-Zentrum Dresden-Rossendorf

Tertiary butyl hydroperoxide (TBHP), as an intermediate for the production of propylene oxide according to the Oxirane process, is currently produced at industrial scale by the partial oxidation of liquid isobutane using bubble columns or bubble tray reactors. In this process, liquid isobutane reacts with oxygen at temperatures of 120 to 140 °C and pressures of 25 to 37 bars at high residence times of up to 12 hours. The conversion is limited to 35 to 50 % in order to obtain a TBHP selectivity of 50 to 60 % minimizing the formation of by-products, which are caused by the decom-position of the TBHP due to the complex reaction mechanism. Besides safety aspects, the high reaction enthalpy of the oxidation as well as heat and mass transport problems are further issues of this process. In the frame of the Helmholtz-Energy-Alliance project “Energy efficient chemical multiphase processes“, this reaction has been investigated for the first time as a Taylor-Flow process in a broad range of flow rates, temperatures and pressures in a micro reactor with the aim to enhance the space-time yield of the process. The advantages of micro reactors are the high surface – volume ratio for an efficient heat transfer and the improved, nearly inherent, safety. This permits to investigate yet unexplored process windows, for instance within the explosive region of a reaction mixture.
The reaction has been studied varying the molar ratio of the starting pro¬ducts, temperature, pressure, and initiator concentration using two different initiators, namely TBHP and di-t-butyl peroxide (DTBP). For all experiments the selectivity of the reaction products and the conversion of the reaction have been studied. The reaction course has been followed by sampling and analyzing the reaction by GC/MS where a new analytical method has been developed. The use of TBHP as initiator increases the selectivity of the reaction for the target product TBHP. The beneficial effect on the TBHP selectivity compared to DTBP might be explained on the basis of the suitable thermochemical properties of TBHP. TBHP seems to give a better selectivity since at high temperatures as they are necessary for the initiator effect of DTBP the formation of propanone already becomes important which favours the decomposition of TBHP.