Carbonylation of Dimethyl Ether with CO on Solid 12-Tungstophosphoric Acid: In Situ Magic Angle Spinning NMR Monitoring of the Reaction Kinetics
The Journal of Physical Chemistry C
, E-ISSN: 1932-7455
Kazantsev Maxim S.
Luzgin Mikhail V.
Stepanov Alexander G.
Boreskov Institute of Catalysis SB RAS
Knowledge of the elementary steps of the reaction on the surface of a heterogeneous catalyst is crucial for understanding the reaction mechanism. This valuable information could be provided by in situ monitoring of the reaction with solid-state NMR spectroscopy. In this paper, the kinetics of the dimethyl ether (DME) carbonylation on 12-tungstophosphoric acid has been followed with high temperature H-1 magic angle spinning (MAS) NMR. The equilibrium of the initial ether activation toward the intermediate surface methoxy species has been examined with C-13 MAS NMR as well. The energy profile of DME carbonylation with CO to the Keggin acetate on H3PW12O40 has been established. The apparent activation energy of the carbonylation, 95 +/- 10 kJ mol(-1), represents a sum (within experimental error) of the standard enthalpy of the methoxy group formation, 57 +/- 4 kJ mol(-1), and the activation barrier of the rate-determining step of the process, the interaction between methoxy group and carbon monoxide, 50 +/- 4 kJ mol(-1).