Reactor systems Spectroscopic cells

In this paper we will first describe a fast-response infrared reactor system which is capable of operating at high temperatures and pressures. We will discuss the reactor cell, the feed system which allows concentration step changes or cycling, and the modifications necessary for converting a commercial infrared spectrophotometer to a high-speed instrument. This modified infrared spectroscopic reactor system was then used to study the dynamics of CO adsorption and desorption over a Pt-alumina catalyst at 723 K (450°C). The measured step responses were analyzed using a transient model which accounts for the kinetics of CO adsorption and desorption, extra- and intrapellet diffusion resistances, surface accumulation of CO, and the dynamics of the infrared cell. Finally, we will briefly discuss some of the transient response (i.e., step and cycled) characteristics of the catalyst under reaction conditions (i.e.,... 

Fig. 7 Schematic IR reactor system enables time-resolved kinetic and IR spectroscopic data measurements (a) IR cell (b) total set...

The transition metal ion-containing films were prepared carefully by ion-exchange as described elsewhere (10-16). These films were mounted in appropriate stainless steel or pyrex glass reactors/spectroscopic cells. Both reactors, described in detail elsewhere, had infrared (KBr) or uv-vis (quartz) transmitting windows for spectroscopic studies. They were equipped with vacuum valves for evacuation and gas admission, a heating system and a temperature monitor. 

The cell design has already been reported [3], It is installed in a continuous flow system built directly on the FT-IR spectrometer (Nicolet Magna 750) to minimize the dead volume. Tlie cell can be considered as a gas flow reactor with a dead volume less than 0.2 cm. Those capabilities permit reactivity experiments, combined with rapid IR spectroscopic measurements of surface species to be made in a mamier which has not been possible in standard IR cell. The GC collection was perfonned with a Delsi cliromatograph on line. Gases were also analysed by FT-IR in a short spacial cell, also directly comiected to tlie IR cell-reactor, with a Nicolet 5SX spectrometer. NOx reduction was measured as the ratio C% = (NO°- (NO + NO )) 100/NO°... 

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