CATALYTIC CONTRIBUTION OF REACTOR WALL MATERIALS ON OXIDATIVE COUPLING OF METHANE

Gas-phase oxidative coupling of methane (OCM) was investigated with em pty tubular-how reactors made of various materials (quartz, ceramic an d stainless steel tubes). When the temperature is higher than 680 degr ees C, the CH4 conversions in three kinds of empty reactors are measur able, and the gas-phase OCM becomes noticeable at 750 degrees C or hig her. High temperature is beneficial to the activation of CH4 and the d ehydrogenation of C2H6 to C2H4. Residence time of reactants in the hea ted volume plays an important role in the gas-phase OCM. Experiments i ndicated that the gas-phase OCM can be minimized by increasing reactan t gas velocity or filling the free volume of the reactor with inert ma terials. Reactor surface also has an effect on the reaction and may pa rticipate in some surface reactions. Based on the kinetic results and the SEM investigation on the surfaces of reactors, a gas-phase reactio n mechanism of OCM is proposed.