A one-stage process involving CH4 catalytic oxidative coupling over Li/MgO at approximately 730-degrees-C to C2 hydrocarbons and thermal decomposition of the formed C2H6 to C2H4 at approximately 850-degrees-C in the postcatalytic zone (PCZ) was studied in a multisectional stainless steel tubular reactor of a scaled-up laboratory unit. Alternative forms of the process with admission of C2H6 or C3H8 to PCZ were also examined. Product distribution along the catalyst bed and along the PCZ in the large steel tubular reactor was determined and, on this ground, a verification of a one-stage concept provided. A one-stage process was shown to be generally acceptable. It was confirmed, however, that severe operating conditions applied in PCZ for securing effective C2H6 dehydrogenation increased C2H4 decomposition to H-2 and a coke deposit, CO2 reduction to CO (by reactions with H-2, a coke, and hydrocarbons), and some other surface-sensitive transformations. Under applied operating conditions, the C2H4/C2H6 ratio was increased from 1.52 (standard coupling) to 4.89 (one-stage process), whereas the total C2 yield decreased from 15.4 % to 13.5 %, respectively.