Continuous preparation method of pyridine N-oxides

Abstract

The invention discloses a continuous preparation method of pyridine N-oxides. The method comprises the steps that a catalyst TS-1 molecular sieve and distilled water are added into a slurry reactor, the temperature is increased to 70-90 DEG C, the pressure is adjusted to be 0-1.5 MPa, then, a pyridine compound and hydrogen peroxide are added, and the air speed of the pyridine compound is adjusted to be 1-10 h<-1>, and the air speed of the hydrogen peroxide is adjusted to be 2-20 h<-1>; the molar ratio of the pyridine compound to the hydrogen peroxide is 1:1-1.1; the pyridine compound and the hydrogen peroxide are subjected to an oxidation reaction to generate a crude N-pyridine oxide, distillation separation and drying are performed to obtain the pyridine N-oxides, and the deactivated catalyst TS-1 molecular sieve is activated and continues to be adopted as a catalyst for use. According to the method, the titanium silicalite molecular sieve is adopted as the catalyst, the catalyst is high in repeated utilization ratio, the catalysis effect is good, the service life is long, the pyridine conversion rate and the pyridine N-oxide selectivity is high, and the effective utilization rate of the hydrogen peroxide is high; the slurry reactor is adopted as the reactor, operation is easy, postprocessing is simple, continuous production can be achieved, and the method is suitable for large-scale industrial production.

Description

technical field [0001] The invention relates to a preparation method of N-pyridine oxide, in particular to a continuous preparation method of N-pyridine oxide, especially a continuous preparation method of pyridine oxide and collidine oxide. Background technique [0002] N-pyridine oxide and its derivatives belong to nitrogen heterocyclic compounds, and their properties are very different from those of unoxidized parent compounds, and they are obviously different in electrophilic substitution and nucleophilic substitution reactions. Since the oxygen atom has an important influence on the reaction and can be removed by reduction after the reaction, it is often used as a positioning group for substitution, rearrangement and other reactions. A series of pyridine compounds can be synthesized through the platform and pathway of pyridine oxidation reactants. Most of them have the special structure of pyridine heterocycle, so they exhibit many unique chemical properties and physio...

AI Technical Summary

Problems solved by technology

[0005] In the glacial acetic acid method, glacial acetic acid is used as a catalyst, hydrogen peroxide is used as an oxidant to oxidize pyridine, and then it is extracted with chloroform, dried and distilled under reduced pressure. This method has obvious defects: long reaction time and large demand for hydrogen peroxide , the process is complex; N-pyridine oxide has a high solubility in water, the chloroform extraction effect is not good, and the product loss is serious

[0006] In addition, there are other oxidation methods. For example, Chinese patent CN102757384 introduces a method using ozone as an oxidizing agent. This method is to add a titanium-silicon molecular sieve catalyst, pyridine, solvent, ozone and diluent gas in an autoclave. Separation, low cost and other advantages, but the conversion rate is low, the ozone utilization rate is low, and it is difficult for industrial production

Chinese patent CN102060760 introduces a phosphorus-tungsten-silicon composite catalyst to oxidize pyridine under the hydrogen peroxide system. This method has simple catalyst preparation, good catalytic effect, and high product yield, but the amount of catalyst added is large, and the tank reaction treatment is relatively complicated. , the catalytic efficiency is low, the product purity is low, and the utilization rate of hydrogen peroxide is low