“…The type of hysteresis observed in the present case, in which the activity is higher with decreasing temperature than with increasing temperature is considered as a ''normal or regular'' hysteresis [49]. Hysteresis phenomena have been attributed to several factors, for example thermal inertia of the catalyst multiple steady states due either to reaction exotherm or surface or inhibition due to adsorption/desorption phenomena [49], change of the state of the catalyst (oxidised/reduced) [50,51]. Evidence, however, has grown that for strongly exothermic reactions, mass and heat transfer limitations may play a dominant role [52,53].…”