Preparation of mesityl oxide and/or methyl isobutyl ketone

摘要

Mesityl oxide is prepared by continuously contacting an oxygenated hydrocarbon feed, which contains acetone, in the gas phase in a condensation zone with a catalyst consisting mainly of zinc oxide at a temperature of about 400 DEG to 800 DEG F., continuously withdrawing a product stream containing mesityl oxide from the condensation zone, cooling the product stream below 120 DEG F., separating a vaporous fraction containing substantial amounts of hydrogen, propylene and acetone and minor amounts of isopropanol, water, methylisobutyl ketone and mesityl oxide from a liquid fraction containing the remainder of the unreacted feed and reaction products, distilling this liquid fraction to recover a fraction rich in unreacted feed and a mesityl oxide-rich fraction, and recycling part of the vaporous fraction and unreacted-feed fraction to the condensation zone in such amounts that the recycled mesityl oxide does not exceed 0.5 mol. per cent of the total feed to the condensation zone. A preferred embodiment involves contacting the mesityl oxide-rich fraction with hydrogen in the presence of a hydrogenation catalyst, suitably nickel, to convert mesityl oxide to methyl isobutyl ketone, fractionating the effluent from the hydrogenation zone to separate methyl isobutyl carbinol, and recycling the methyl isobutyl carbinol and part of the vaporous fraction and unreacted feed fraction to the condensation zone under the same conditions with respect to molar percentage of mesityl oxide recycled. Products can be withdrawn at various stages of the process and can consist essentially of mesityl oxide, methyl isobutyl ketone or methyl isobutyl carbinol. The catalyst for the main reaction in the condensation zone is preferably 70-99% by weight of zinc oxide with 1-30% of a promoter which can be cerium, thorium or zirconium oxide. Preferred conditions in the condensation involve contacting acetone with the catalyst at a space velocity of 0.25 to 2 volumes of total feed per volume of catalyst per hour, in admixture with 0.01 to 1 mol. (or better, 0.01-0.04 mol.) of hydrogen per mol. of acetone at a temperature between 500 DEG and 800 DEG F. and pressure of 5 to 75 p.s.i.g. such that the conversion level of acetone to mesityl oxide is between 7 and 12%, wherein the vaporous fraction of the feed contains less than 0.3 mol. per cent of recycled mesityl oxide and the acetone-rich fraction not more than 0.2 mol. per cent of mesityl oxide.