Method for continuously preparing nitrile from amide

Abstract

The invention discloses a method for continuously preparing nitrile from amide, which comprises the following steps: preparing a molecular sieve-loaded lead catalyst from a lead salt and a molecular sieve by an impregnation method, and filling a fixed bed reactor with the molecular sieve-loaded lead catalyst; feeding an amide or an amide solution into the fixed bed reactor from the top of the fixed bed for catalytic dehydration, and leading out an obtained reaction product from the bottom of the fixed bed; and separating the reaction product to obtain a crude nitrile product corresponding to amide. A fixed bed continuous production process is adopted, the reaction process is simple, the production efficiency is high, product aftertreatment is simple, and industrial production is easy to achieve.

Description

technical field [0001] The invention belongs to the field of chemical industry, in particular to a method for continuously preparing nitriles from amides. Background technique [0002] Nitrile is an important chemical raw material and synthetic intermediate, widely used in the manufacture of medicines, synthetic fibers and plastics. For example, adiponitrile is the raw material for the preparation of nylon 66. Acrylonitrile is the monomer used to produce polyacrylonitrile. It is copolymerized with other monomers and can be used to produce synthetic rubber and engineering plastics. Benzonitrile is mainly used as an intermediate for advanced coatings such as benzomelamine, and is also an intermediate for the synthesis of pesticides, aliphatic amines, and benzoic acid, and can be used as a solvent for nitrile rubber, resins, polymers, and coatings. Phenylacetonitrile is used to produce phenylacetic acid, phenylethylamine, diphenylacetonitrile, β-phenylethanol, phenylacetaldehy...

AI Technical Summary

Problems solved by technology

[0004] The traditional method for the dehydration of amides to prepare nitriles is to use stoichiometric acidic reagents (such as P 4 o 10 , POCl 3 , SOCl 2 、TiCl 4 etc.) and alkaline reagents (such as NaBH 4 ) as a dehydrating agent to promote the dehydration of amides. These methods will produce a large amount of acidic or alkaline by-products, which will corrode equipment and cause high environmental pressure; on this basis, scholars have developed a series of new catalysts, including hydrosilane dehydration systems, high-temperature catalytic system, palladium catalyzed dehydration nitrilation system, etc., in which various transition metals or nitrites catalyze the activation of Si-H bonds of hydrosilicides to form electrophilic silicon hydrogen species. These reaction intermediates can promote the dehydration of primary amides to form nitriles, However, during the reaction process, hydrogen and silyl ether are produced, which increases the difficulty of separation; in the absence of a dehydrating agent, the dehydration of amide to generate nitrile requires a higher reaction temperature (>160 ° C), Campbell et al. (Campbell J, McdougaldG , Mcnab H, et al.Synthesis, 2007, 20:3179-3184) reported the dehydration performance of amides and oximes catalyzed by dehydrating agent 3A molecular sieve and tungsten trioxide under fast vacuum pyrolysis conditions, and the reaction did not produce other by-products , but the reaction temperature is high (above 300°C), only suitable for thermally stable amides

Sueoka et al. (Sueoka S, Mitsudome T, Mizugaki T, et al. Chem Commun, 2010, 46:8243-8245) reported that a material supporting monomeric vanadium oxide on hydrotalcite can be used for heterogeneous amide dehydration Catalyst, under the catalysis of 20mol% load, amide is refluxed in mesitylene and dehydrated into nitrile, which is difficult to achieve continuous production

[0005] If the above-mentioned amide dehydration reaction in the absence of a dehydrating agent is assumed to be carried out at room temperature, the reaction will not be able to proceed effectively

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