Here, n C2H2,out and n C2H2,in are molar flow rates of acetylene leaving and entering the reactor, respectively. The values of X C2H2 are in the range [0,1]. The values of zero and one correspond, respectively, to inactive materials and reaction conditions, and to 100% (or full) acetylene conversion. The selectivity towards the formation of ethylene (S C2H4 ) was evaluated as