Abstract

This paper reports the details of a high-pressure and -temperature <i>in situ</i> transmission infrared reactor cell and experimental approaches for investigation of the nature of adsorbates in CO hydrogenation and NOCO reaction on Rh/SiO₂ catalyst. The infrared cell used in this study allows easy assembling and reliable operation up to 773 K and 6.0 MPa. The structure and coverage of adsorbates during reaction are determined by an infrared spectrometer, and the composition of gaseous effluent from the infrared cell is monitored by a mass spectrometer. The steady-state ¹³CO step transient shows that gaseous CO rapidly exchanges with adsorbed CO, which is slowly converted to CH₄ during CO hydrogenation at 513 K and 0.1 MPa. The pulsing CO study reveals that linear CO is more reactive than bridged CO during methane and CO₂ formation, and bridged CO sites are blocked from CO disproportionation. Steady-state ¹³CO pulse transients show that the CO₂ response leads the CO response, and Rh-NCO and Si-NCO are not involved in the formation of CO₂ from CO during NO-CO reaction. The advantages and limitations of the <i>in situ</i> infrared and transient approaches for catalysis research will be discussed.

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