Periodic operation of a catalytic nitric oxide converter

Abstract

Rifects of transient operation on the performance of a tubular heterogeneous catalytic reactor were studied both experimentally and theoretically. The reaction system considered was the reduction of nitric oxide by hydrogen over Girdler G-SO catalyst.

Mathematical simulations of the reaction system included both equilibrium and non-equilibrium modes of adsorption-desorption on the catalytic surface. Numerical solutions of pertinent system equations by both quasilinearization and orthogonal collocation techniques agreed with experimental results by predicting a significant increase in NH₃ production as well as very small changes in total NO conversion for transient relative to steady-state operation.

For transient runs, NO and H₂ entrance concentrations were varied sinusoidally with average concentrations equal to those used for steady-state experiments. When transient results were compared with those from steady-state operation, a definite increase in NH₃ relative to N₂ production was observed. No significant changes in total NO conversion were measured for transient operation.

The packed, tubular reactor was operated isothermally at approximately 400°C with a constant total flow rate. For steady-state runs the reactor feed concentrations were set at 5 mole percent of both NO and H₂ in helium. Nitric oxide conversions and product selectivity were determined By absorptionin a Mg(Cℓ0₄)₂ trap as well as chromatographic analysis.