FORMATION OF KETENES BY REACTION OF CARBOXYLIC-ACIDS OVER ALKALI METAL-EXCHANGED ZEOLITES

The formation of ketene from acetic acid by reaction over alkali metal-exchanged zeolites at ∼350°C and low partial pressure is reported. Acetone and carbon dioxide are also produced. The greatest proportion of ketene was produced by the large-pore, faujasite zeolites exchanged with the smallest cations (Li+ and Na+). The corresponding ketenes from propanoic acid and isobutanoic acid, but not n-butanoic acid, were also observed. It was possible to react the ketene in situ by addition of a further reactant to the acetic acid feed, provided the additional reactant did not react with the zeolite catalyst. For example, methanol and dimethylamine were readily acetylated but ethanol reacted to produce ethene and water. Reaction of acetic acid with dimethylamine over NaY at 300°C gave a 70% conversion of dimethylamine with 100% selectivity to dimethylacetamide. © 1991.