Reactivity of t-butyl hydroperoxide and t-butyl peroxide towards reactor materials measured by a microcalorimetric method at 30 °C.

To investigate the oxidation of isobutane to t-butyl hydroperoxide (TBHP) for the first time as a two-phase process in a micro reactor in a broad range of flow rates (isobutane flow rate: 15 to 188 µl/min, oxygen: 0.1 to 1.5 ml/min), temperatures (75 to 150 °C) and pressures (25 to 100 bar), a study has been performed to select the most appropriate construction materials for the experimental facility, especially for the microreactor but also for fittings, sealings, sensors, pumps, tubes, the sampling unit etc. TBHP, as most hydroperoxides, is quite reactive and reacts with most metals, polymers, acids and bases. Therefore, the most suitable materials had to be determined to minimize losses of TBHP in the initiator pump and in the reaction mixture of the sample at ambient temperature. As TBHP ¬¬decom¬poses very slowly under such conditions, a microcalorimetric method (TAM) has been used to measure the heat production of TBHP in contact with selected materials at 30 °C. Among those materials various metals e.g. copper, gold, silver, zinc, aluminum, titanium, tantalum, normal steel, hastelloy C276, hastelloy C-2000, V4A steel as well as semiconductors like silicon and silicon carbide have been tested. Furthermore, several polymers like nitrile butyl rubber, PEEK, silicone, Chemraz® and PTFE have been studied. Moreover, the role of metals and metal ions as catalysts for the decomposition of TBHP and DTBP is discussed. The experiments showed that silver and copper are the most reactive metals of the investigated substances and silicon the most suitable coating material for the reactor. The most stable polymers were found to be PEEK, Tedlar, Chemraz® and PTFE.