Method for preparing N,N-dimethyl cyclohexylamine

Abstract

The invention discloses a method for preparing N,N-dimethyl cyclohexylamine. The method comprises the following steps: adding wet Raney nickel into a reactor, removing air in the reactor with nitrogen, pumping dimethylamine into the reactor, introducing hydrogen, starting stirring, conducting heating to 45-90 DEG C, dropwise adding a mixed solution of cyclohexanone and a cocatalyst sulfur-containing organic matter into the reactor, and conducting reacting to obtain N,N-dimethyl cyclohexylamine. Compared with a traditional noble metal catalyst, the non-noble metal catalyst Raney nickel and the sulfur-containing organic matter are adopted as the cocatalyst, so that the production cost is greatly reduced, and the yield of the N,N-dimethyl cyclohexylamine can reach 96% at most.

Description

technical field [0001] The invention belongs to the technical field of synthetic chemical engineering, and in particular relates to a method for preparing N,N-dimethylcyclohexylamine. Background technique [0002] N,N-Dimethylcyclohexylamine is a low-viscosity, moderately active amine catalyst, mainly used as a catalyst for rigid polyurethane foam. Catalyst, in addition to being used for rigid foam, is also used as auxiliary catalyst for molding soft foam and semi-rigid foam. The current industrialized preparation methods of N,N-dimethylcyclohexylamine include cyclohexanone method, cyclohexylamine method and N,N-dimethylaniline hydrogenation method. [0003] CN1092061 discloses a method for preparing N,N-dimethylcyclohexylamine using cyclohexanone and 40% dimethylamine aqueous solution as raw materials and palladium carbon as a catalyst. , react for 3 to 8 hours, and the reaction liquid is separated and rectified to obtain the finished product, with a yield of 98%. The dis...

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[0003] CN1092061 discloses a method for preparing N,N-dimethylcyclohexylamine using cyclohexanone and 40% dimethylamine aqueous solution as raw materials and palladium carbon as a catalyst. , react for 3-8 hours, and the reaction solution obtains the finished product through liquid separation and rectification, and the yield is 98%. The disadvantage of this method is that the precious metal palladium is used as the catalyst, and the price of palladium is high. The palladium is easy to lose in the reaction process, and the production cost is relatively high.

[0004] CN101208319A discloses a cyclohexanone and dimethylamine as raw materials, amine: ketone molar ratio of 1.2, palladium carbon as a catalyst, under 14bar hydrogen pressure and 120°C, react for 6h, the conversion rate of cyclohexanone is 94%, N, The selectivity of N-dimethylcyclohexylamine is 98%. This method also uses noble metal palladium as a catalyst, and the production cost is relatively high.

[0005] CN104892429A discloses a method for preparing N,N-dimethylcyclohexylamine using cyclohexanone, ammonia, hydrogen and formaldehyde as raw materials. The catalyst adopts a supported nickel-based catalyst doped with copper and chromium, and the carrier is γ-oxidized Aluminum, silica and molecular sieve, the loading of nickel is 0.1%~50%, the reaction is carried out in two series fixed bed reactors, the reaction pressure is 6MPa, the reaction temperature of the first stage is 120°C, and the reaction temperature of the second stage is 130°C , The yield of N,N-dimethylcyclohexylamine is 84.2%, and the yield of N-methyldicyclohexylamine is 10.3%. The disadvantage of this method is that the yield of the main product is low, and the total yield of the two products is only 94.5%. , large investment in equipment

[0006] CN111333520A discloses a method for preparing N,N-dimethylcyclohexylamine using cyclohexylamine, solvent and formaldehyde aqueous solution as raw materials and palladium carbon as a catalyst. Add formaldehyde aqueous solution, formaldehyde is added dropwise for 6 hours, and the yield of N,N-dimethylcyclohexylamine is greater than 99%. This method also uses noble metal palladium as a catalyst, and the production cost is relatively high

[0008] (1) The existing mainstream N,N-dimethylcyclohexylamine industrialization process, cyclohexanone and cyclohexylamine processes both use precious metal palladium as a catalyst. In recent years, the price of palladium has risen sharply, greatly increasing the N,N- The production cost of dimethylcyclohexylamine, and simply using Raney nickel as a catalyst, the yield of N,N-dimethylcyclohexylamine is very low, mainly generating by-product cyclohexanol

[0009] (2) The method of preparing N,N-dimethylcyclohexylamine using a non-precious metal catalyst, using a supported catalyst and a fixed-bed reactor, has low yield, large equipment investment, high requirements for catalyst stability, and poor service life Catalysts are difficult to industrialize