(129e) On-Line Sampling and Gas-Chromatographic Method for a Micro-Scale Gas-Liquid Oxidation Reactor

The development and application of a novel 5-cc micro reactor system for gas-liquid hydrocarbon oxidation kinetic studies under commercial conditions is described. A unique system feature is that it contains a novel automated method for direct sampling and analysis of the liquid phase. This is accomplished by use of a custom designed liquid-injection sample valve that is integrated into the reactor body and directly connected to an on-line GC system.

The sampling concept was demonstrated using a test vessel whose geometry mimicked a 5 cc stirred micro reactor. Two modes of liquid sampling were evaluated: (1) flashing of the liquid sample into a calibrated loop of a 6-port Valco® gas sampling valve; and (2) flashing of the liquid sample directly into the injection port of a HP 5890 Series II gas chromatograph. The test samples consisted of an aqueous mixture of ca. 1 % each of C1 to C4 alcohols, and a crude reaction product obtained from a commercial-scale cyclohexane oxidation reactor.

The results showed that the ability to fill the sampling loop following conventional practice was dependent upon the pressure developed by the flashing liquid. This effect was not observed for the direct injection method developed here since the total GC area counts were reproducible within 0.1 %. Details on the valve design, test results, and its application to the oxidation of para-xylene to terephthalic acid will be described.