Where M, is methanol in the gas phase; M.S is an active
intermediate consisting of the unique zeolite surface species
bounded with the adsorbed methanol; W is water; D is dimethylether
in gas phase and W.S, represents adsorbed water on
free catalyst acidic sites.
With regard to the data presented in Table1, it is evident
that the values for equilibrium constants of water absorption
are low. This may indicate that in the reaction temperature,
water is rapidly released from the zeolite acidic sites. Thus, the
reaction mechanism may be simplified as follows,