The estimated self-diffusion coefficients of methanol with an aliphatic ester or aromatic aldehyde promoter present are shown in figs. 5 and 6. Methanol diffuses faster than any of the promoters; aliphatic ester and aromatic aldehyde promoters substantially reduce its diffusion coefficient by an average of 70 % and 41 %, respectively. Methanol diffusion is reduced in the straight pores (b direction) more than in the sinusoidal (a direction).