This project will apply a unique capability in the EMSL at PNNL for heterogeneous catalysis R&D employing steady-state isotopic transient kinetic analysis (SSITKA) techniques with mass spectroscopic detection that is coupled with in-situ transmission fourier transform infrared (FTIR) spectroscopy. The apparatus provides an in situ probe of adsorbed reactants/intermediates/ products on catalyst surfaces, as well as measuring gas phase concentrations to elucidate reaction mechanisms and kinetic parameters. The resulting data will be interpreted and applied to develop microkinetic models for catalytic reactions of importance to the US's future energy, environment, and economic security. This instrument was developed primarily with PNNL LDRD funding and capital equipment was procured with PNNL GRE funds. The instrument does provide unique capabilities for catalysis research that greatly complements existing EMSL resources, and has been a valuable resource to EMSL users. As such, it has been always located in EMSL and has greatly benefited from being available to EMSL collaborative users. Still, because of difficulty in operating the instrument and a lack of available EMSL support for an operator during its collaborative EMSL use, it is still primarily used by the Resource Owner's (C.H.F. Peden) group. This "Resource Owner" EMSL user proposal documents some of the science being done on this instrument.