N-METHYLANILINE ISOLATION PROCESS Russian patent published in 2001 - IPC

FIELD: industrial organic synthesis. SUBSTANCE: invention relates to isolation of N-methylaniline from catalysate obtained from vapor-phase N-hydroalkylation of aniline with methanol in presence of hydrogen at atmosphere pressure and elevated temperature. Catalysate, also containing methanol, aniline, water, N,N- dimethylaniline, and others, is subjected to rectification on three columns. Into the first column, catalysate is fed in the form of overheated vapor at 180-250 C in presence of promoter of purification of methanol and water from aniline and N-methylaniline, in particular hydrogen in concentration 1 to 7% in the column feed. First-column top product is a mixture of methanol, water, hydrogen, and small amounts of amines. Mixture is freed from hydrogen, cooled, and fed into the second rectification column, whose top fraction is methanol, which is returned into synthesis, and bottom fraction consists of water, subjected to thermal detoxification, and amines, which are separated and returned into synthesis block. First- column bottom product, containing N-methylaniline and small amounts of aniline and N,N-dimethylaniline (weight proportion from 0.5:1 to 7: 1), is fed into the third column operated under vacuum at top temperature 95-120 C and pressure difference between feeding tray and column top equal to 20 to 80 mm Hg. Desired product is tapped off as side distillate from the lower part of column. When concentration of recycled N,N-dimethylaniline in catalysate goes above 15 wt %, its excess is removed as side distillate from one of the trays disposed between feeding one and desired product takeoff tray. EFFECT: simplified process due to lower number of rectification columns and increased yield of commercial product in rectification stage. 2 cl, 11 ex