Alkali nitro-phenolate continuous prodn. for high yield - using chloro nitrophenol and aq. sodium or potassium hydroxide in tubular short reactor with low frequency pulsation, for economy and energy redn.

摘要

Prodn. involves reacting Cl-substd. nitro-aromatics (II) with 5-20% aq. NaOH or KOH soln. in 1:(2-25) molar excess at elevated temp. and pressure in fluid phase. The reactants are fed to a tubular reactor with mantle for heat exchange medium. The reaction mixt. is discharged through a discharge unit regulating the reactor pressure and then worked up. The reaction mixt. is low frequency lengthwise pulsed with a frequency of 0.5-50 Hz with approx. the same amplitude over the entire range of action. It is mixed intensively by these pulses superimposed on the feedstream. The system pressure is greater than the sum of the partial pressures of all components in the reactor. The reactor is kept isothermally at 120-190 deg.C by a circulating medium in the liquid/vapour phase transition. ADVANTAGE - Safer than usual and the quality of alkali nitro phenolate (I) is improved. In an example, a 6.5 m high, jacketed, vertical tubular reactor with an operating vol. of 12 l was kept at 189-191 deg.C with superheated water. It was filled with 10% NaOH soln. preheated to 120-130 deg.C and supplied with 43.75 l/h (48.5 kg/h) of the same soln. at the top, using a high pressure membrane dosing pump, and the pressure was kept at 9.0 MPa. When the reactor was full, 7.7 l/h (9.6 kg/h) (II) melt, preheated to 120-130 deg.C, were also supplied to the top, using a second high pressure membrane dosing pump. In addn., undamped lengthwise pulses with a frequency of 0.5 Hz were applied to both ends of the reactor with synchronised high pressure membrane pumps. The reaction mixt. was discharged and worked up, giving Na 4-nitrophenolate in 97.5% yield. This was free from by-prods. and decomposition prods.