PNNL

Abstract

A novel apparatus for gas-phase heterogeneous catalysis kinetics is described. The apparatus enables fast isotopic transient kinetic analysis (ITKA) to be performed in which both the gaseous and adsorbed species inside the catalytic reactor are monitored simultaneously with rapid-scan transmission FTIR, and its gaseous effluent can be monitored by mass spectroscopy during rapidly switching of reagent gas streams. This enables a more powerful version of the well-known steady-state isotopic kinetic analysis (SSITKA) technique in which the vibrational spectra of the gas phase and adsorbed species are also probed: FTIR-SSITKA. Unique reactor characteristics include tungsten construction, liquid nitrogen cooling or heating (~200-700 K), fast reactor disassembly and reassembly, and catalyst loading in a common volume. The FTIR data acquisition rate of this apparatus (3 Hz) is 10-fold faster than previously reported instruments. A 95% signal decay time of ~3 seconds for gas switching was measured. Very good temperature reproducibility and uniformity (