TEMPERATURE-SWITCHED MAS NMR - A NEW METHOD FOR TIME-RESOLVED IN-SITUSTUDIES OF REACTION STEPS IN HETEROGENEOUS CATALYSIS

The temperature of zeolite samples containing adsorbed methanol molecu les was switched from room temperature to 500-600 K within 30-40 s by means of a laser beam. The catalytic reaction was monitored by C-13 MA S NMR and H-1 MAS NMR, the latter in steps of one second. A two-dimens ional Fourier-transformation of the difference between the time-depend ent and the equilibrium state of the system gives a good representatio n of reaction steps. For the methanol conversion it was found that the primarily formed C-3/C-4 alkanes are still involved in further reacti ons, whereas methane is an inert product under these conditions.