TWO-STAGE METHOD FOR PREPARING N-METHYLANILINE Russian patent published in 2005 - IPC

FIELD: organic chemistry, chemical technology.

SUBSTANCE: invention relates to the improved method for preparing N-methylaniline from nitrobenzene, methanol and hydrogen in gaseous phase on a copper-containing catalyst comprising zinc and chrome compounds. The process is carried for two stages in two in-line connected contact reactors and nitrobenzene and methanol or their mixture are fed into each reactor: nitrobenzene is fed into the first reactor and methanol - into the second reactor using in layers charging the catalyst in the first contact reactor and forming "frontal layer" wherein temperature must not exceed 350°C and volume is 10-50% of the total volume of catalyst used in this contact reactor. The preferable mole ratio nitrobenzene : methanol : hydrogen = 1:3:15, respectively. The separate feeding of reagents is possible. For example, all nitrobenzene is fed into the first contact reactor and feeding methanol is carried out into the first and the second contact reactors in the mole ratio 1:2 or 2:1, or all nitrobenzene is fed into the first contact reactor and methanol is fed into the second contact reactor in the amount 1.5 mole per a mole of nitrobenzene. As a rule, 50-70% of all nitrobenzene used is fed into the first contact reactor and 30-50% is fed into the second reactor. In both contact reactor a copper-containing catalyst of the following composition is used mainly, wt.-%: copper oxide, 37-40; chrome oxide 18-20; zinc oxide, 20, and aluminum oxide, the balance, or in both contact reactors a copper-containing catalyst of the following composition is used, wt.-%: copper oxide, 21.4-26.4; chrome oxide, 3.4-5.8; aluminum oxide, 3.3-22.3; binary copper and zinc chromite of empirical formula: Zn_xCu_yCr₂O₄ wherein x = 0.8-10; y = 0.4-0.9, 54.5-71.9. Usually, aluminum oxide granules impregnated with copper, chrome and zinc salts in the ratio of active components = 2:1:1, respectively, are used in upper part of the first contact reactor.

EFFECT: improved preparing method.

8 cl, 8 ex