The catalyst bed consists of 100 mg of catalyst material diluted by 200 mg of nonporous silica beads (150 -250 µm) and was reduced in situ at 400 °C under pure H2 for 12 h. The packing is held in place by 1 g of silica beads upstream and 0.6 g downstream and silica wool in between the layers. The total packing length sums up to 12 cm, with a catalyst bed length of 2 cm. The catalyst bed is placed in an isothermal zone, monitored by measuring the axial temperature profile. The pressure in the setup was regulated by two high precision back pressure regulators (LF1 Equilibar). The analytics consisted of a mass spectrometer (MS, MKS Cirrus 3XD), calibrated to the mass-tocharge ratios 2 (H2), 4 (He), 15 (CH4), 18 (H2O), 20 (Ne), 26 (C2), 28 (CO), 40 (Ar) and 43 (C3). Ethane and Ethylene were pooled together, as we were unable to distinguish them in the MS. The same applies to C3+, with the major contributors C3H8 and C4H10.