TEMPERATURE-PROGRAMMED OXIDATIVE COUPLING OF METHANE OVER A LI-NI-CO-O CATALYST MONITORED IN-SITU BY AC ELECTRICAL PARAMETERS COUPLED TO MULTIPLE-ION MONITORING OF THE PRODUCT SPECIES

By using the multiple ion-monitoring facility of a quadrupole mass spe ctrometer, the on-line analysis of species has been studied for temper ature programmed methane coupling over a non-stoichiometric mixed oxid e Li0.9Ni0.5Co0.5O2-delta catalyst between 400-800 degrees C. The effe cts of water vapour, methane and oxygen were also separately studied. The a.c. electrical characteristics of the catalyst pellet between 100 Hz and 1 MHz were simultaneously monitored in-situ. Catalytic changes are immediately reflected in changes in the a.c. characteristics. Fre quency dependent a.c. losses due to surface dipole effects dominate du ring phases of strong chemisorption and reaction, whilst reversion to thermally activated behaviour occurs during regions of reduced chemica l activity. Lattice oxygen is able to act as a source of oxygen and re act with methane. The oxidative coupling of methane showed stable beha viour for 3h at 750 degrees C.