The carbonylation of methanol over Rh{single bond}Y zeolite catalyst in the presence of methyl iodide was studied at 423 to 473 K under atmospheric pressure. The catalytic activity of Rh{single bond}Y was much superior to other supported rhodium chloride catalysts such as RhCl3/Al2O3, RhCl3/SiO2{single bond}Al2O3, RhCl3/SiO2, and Rh-cation exchanged resin. Methyl acetate was the main product of this carbonylation, although the yield of acetic acid increased with contact time and the partial pressure of methyl iodide. The rate of methyl acetate formation increased with the content of Rh on the zeolite up to 0.6 wt%. For Rh{single bond}Y with more than 0.6 wt% of Rh, however, the rate decreased with the process time, and it was observed that the rhoidum species fell off from the catalyst support system and the most zeolite framework was broken. During the first stage of the reaction, an induction period was observed which could be eliminated by calcining in nitrogen or helium at 473 K. However, the catalytic activity of Rh{single bond}Y was reduced by calcination at 573 K. When Rh{single bond}Y was calcined in hydrogen at 573 K, the catalyst had no activity. Therefore, it was concluded that the precursor of the active rhodium site was a trivalent rhodium which was firmly anchored on the zeolite by an ion exchange process, and that water molecules adsorbed in the zeolite prevented the formation of the active Rh site. The active Rh sites on Y zeolite were stable up to 473 K, but over 483 K was inactivated with an irreversible change. © 1979 Academic Press, Inc. All rights reserved.
