Isobutyric acid or its lower alkyl ester cpds. continuous prodn. - by Koch process from propylene, carbon mon:oxide and water using short dwell time

摘要

Prodn. of isobutyric acid (IA) or its lower alkyl esters (IB) by the Koch's synthesis involves the one-stage reaction of C3H6, CO and H2O or a lower alcohol, opt. (partly) replaced by their adducts, in the presence of HF as catalyst. The novel feature is that the starting materials are reacted continuously, with high remixing, at 80-160 deg.C, the dwell time of the liquid phase being under 20 min., so that the content of C3H6 or the isopropyl formate used as adduct in the reacting mixt. is under 1 wt.% w.r.t. the liquid phase. The water or alcohol (MeOH) content is kept below 5 (below 2) mole-%. The total pressure is 50-150 bar, temp. 100-140 deg.C and dwell time of the liquid phase 2-10 min. The amt. of HF used is 5-15 mole/mole C3H6. The water or alcohol and C3H6 are supplied continuously in (0.9-1.1):1 molar ratio and the CO and C3H6 are mixed in the gas phase. Reaction is carried out in a gas-liquid reactor with dispersed gas phase. (I) can be dehydrogenated to methacrylic acid or its esters, which are starting materials for valuable plastics. High yields and selectivity are attained and the oligomer problem is minimised, whilst the throughput is high and the dwell time short.