The in situ analysis of catalysed gas phase reactions offers not only an accurate characterisation of the reactions, but also the possibility to validate numerical simulations. The latter allows optimizing operational performance and reducing industrial costs as well as predicting possible risks at scaled up reactors. Nuclear Magnetic Resonance (NMR) can be used as a non-invasive method for the in situ analysis of velocity, diffusion, temperature, and concentration of species in heterogeneously catalysed systems. The possibility of monitoring the crucial reaction parameters online and simultaneously in opaque reactors turns NMR into a powerful toolkit for the operando analysis of reactions. To determine each parameter, optimised NMR techniques are required. This contribution shows practical and methodological examples of NMR methods in the fields of in reaction engineering with emphasis on methanation reaction. The talk includes NMR Velocimetry (MRV) of methane gases in foam catalyst carriers followed by an analysis of diffusion and dispersion of gas in monolithic structures. Furthermore, NMR spectroscopic imaging (MRSI), and NMR Thermometry will be discussed in order to show how the temperature profile of catalyst bed can be determined in highly exothermic reactions such as methanation or Fischer-Tropsch reaction. Finally, the analysis of tortuosity, NMR relaxation times and diffusion in micro- and macrospores illustrates to which extent NMR can characterise heterogeneous catalysts coated on foams or pellets. The obtained results may directly improve numerical micro- or macroscale simulations.