Plasma catalysis is the combination of plasma and catalysis to reach an efficient conversion of molecules for flexible operating parameters and flexible feed gases. By combining plasmas with conventional thermal catalysis, the temperature windows may be different and the process may be insensitive to catalyst poisoning. The understanding of plasma catalysis mechanisms, however, is an extremely difficult task due to the strong coupling between plasma, gas phase chemistry and surface. A multitude of reaction pathways may be enhanced or reduced by the presence of a plasma that provides excited species as reaction partners. We developed a robust setup to analyse those processes based on a parallel plate atmospheric pressure plasma jet that allows a plug flow design. The plasma chemistry is analysed by Fourier transform infrared absorption spectroscopy and mass spectrometry. The electrodes in contact with the plasma are temperature controlled and can easily be replaced to apply a catalyst on top of them. The basic characteristics of the setup are discussed as well as three examples for its application are given (i) the analysis of methane oxidation using the plug flow scheme, (ii) the plasma catalytic conversion of CO2, and (iii) the plasma catalytic conversion of methane in methane oxygen mixtures.