THERMAL EFFECTS DURING THE OXIDATIVE COUPLING OF METHANE OVER MN NA2WO4/SIO2 AND MN/NA2WO4/MGO CATALYSTS/

The exothermic reactions that occur during the oxidative coupling of m ethane over Mn/Na2WO4/SiO2 and Mn/Na2WO4/MgO catalysts result in relat ively narrow hot spots that may produce temperature increases as large as 150 degrees C. Under integral conditions, the temperature of the h ot spots is related to the CH4/O-2 ratio and the activity of the catal yst. Although the Mn/ Na2WO4/SiO2 catalyst was stable for up to 97 h o n stream, the Mn/Na2WO4/MgO catalyst gradually deactivated. This deact ivation was manifested by motion of the hot spot toward the exit of th e catalyst bed. The loss of activity is attributed mainly to the decre ase in Mn concentration at the surface of the catalyst. (C) 1998 Elsev ier Science B.V.