Method for preparing chloroaniline by catalysis hydrogenation

Abstract

The invention discloses a method for preparing chloroaniline by catalysis hydrogenation, comprising the following steps: by using chloronitrobenzene as material, alcoholic solution as solvent, and Ni-B amorphous alloys as a catalyst and a dechlorination inhibitor, introducing H2 for catalytic hydrogenation-reduction reaction to obtain the chloroaniline. The Ni-B amorphous alloy in the invention is a catalyst and has relatively high reactivity and selectivity, the selectivity of chloroaniline is greater than 99%, and the production rate of chloroaniline is high; and the function of inhibiting dechlorination of amines is obvious, and the amount of dechlorination is less than 0.5%.

Description

technical field [0001] The invention belongs to the preparation technology of chloroaniline, in particular to a method for preparing chloroaniline by catalytic hydrogenation. Background technique [0002] Chloroaniline is an important organic intermediate widely used in the synthesis of fine chemical products such as dyes, medicines, pesticides, and spices. Chloroaniline is generally prepared by reduction of chloronitrobenzene, and catalytic hydrogenation, as an efficient and clean method, is widely favored by people. However, hydrogenolysis of the C–Cl bond easily occurs during catalytic hydrogenation to generate aniline. Therefore, improving the catalytic selectivity has become the most concerned issue. The most common method for selective hydrogenation is the addition of dechlorination inhibitors to the catalyst system. There are many inhibitors reported about nickel-based catalysts, but the dechlorination inhibitors reported around RaneyNi have more or less shortcomin...

AI Technical Summary

Problems solved by technology

There are many inhibitors reported about nickel-based catalysts, but the dechlorination inhibitors reported around RaneyNi have more or less shortcomings. The shortcomings can be summarized as follows: one is that the inhibitory effect is not obvious. Better inhibitory effect requires more inhibitors, such as general amine compounds, calcium hydroxide or magnesium hydroxide (U.S.Pat.NO.3067253, J.Pat.NO 73-49728), in the catalysis, it Insufficient inhibitory ability, in order to obtain a better inhibitory dechlorination effect, it is necessary to increase its amount or reduce the catalytic reaction temperature, which is not suitable for industrial production; the second is to reduce the activity of the catalyst, such as sulfur-containing compounds, mainly There are thiourea, sulfoxide or sulfone (U.S.Pat.NO.5126485), etc. This type of compound mainly uses S to seal the active site on the catalyst. Because S has a strong binding ability with the catalyst, the active site of the catalyst is reduced, causing the catalyst to be active. The third is that in the catalytic reaction, the inhibitor itself will participate in the reaction, and it is necessary to continuously add inhibitors, such as dicyandiamide, cyanamide, etc. (U.S.Pat.NO.3989756). Saturated bonds will be hydrogenated into their saturated compounds in the catalytic reaction, making the inhibitor ineffective; fourth, it is difficult to separate the inhibitor from the product, mainly because the boiling point of the inhibitor is quite close to that of the product and reactant, and it is difficult to separate the inhibitor

Fifth, the inhibitory effect is not ideal, such as phosphorus derivatives phosphorus derivatives such as (EtO) 3 P etc. (G..B.Pat.NO.1498722), the dechlorination rate can still reach 2-8%.

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