DD297398A5 - PROCESS FOR PREPARING N, N-DIMETHYLCYCLOHEXYLAMINE IN THE GAS PHASE AND CATALYST FOR CARRYING OUT THE METHOD - Google Patents

Abstract

The invention relates to a process for the preparation of N, N-dimethylcyclohexylamine in the gas phase and to a catalyst which is used in carrying out the process. Characterized in that the gas phase hydrogenation at pressures up to 10 bar, preferably at atmospheric pressure, and at temperatures between 150C and 180C, preferably at 160C and 175C, takes place, and the N, N-dimethylaniline at rates between 0.05 and 0.1 kg l h 1 is reacted, and the catalyst of palladium on g alumina carrier with basic proportions and palladium in amounts between 0.1 and 5 * preferably 0.2 and 1 * based on the total mass of the catalyst, and basic proportions of the alumina carrier as oxides and / or carbonates of the alkaline earth metals, in particular of calcium, in amounts of from 0.1 to 3 *, in particular 0.2 to 2 *, calculated as sodium carbonate, is attained, according to a technologically simple and efficient process by catalytic gas phase hydrogenation of dimethylaniline Full implementation of N, N-dimethylaniline N, N-dimethylcyclohexylamine can be produced, the cyclohexylamine only a mini have by-product content. {N, N-dimethylcyclohexylamine; gas-phase hydrogenation; continuous, low pressure; elevated temperatures; Catalyst palladium on g alumina carrier with basic proportions}

Description

Field of application of the invention

The invention relates to a process for the preparation of N.N-dimethylcyclaohexylamine in the gas phase and to a catalyst which is used in carrying out the process.

This Ν, Ν-dimethylcyclohexylamine is used in the chemical industry as an important catalyst for polyurethane systems and required as a starting material for the production of various chemicals and pharmaceuticals Phai.

Characteristic of the known state of the art

According to a known preparation process according to DE-PS 851189 is by continuous vapor phase hydrogenation of N ₁ N-dimethvlanilin (DMANL) at about 80 to lOObar and 180 to 19O ⁰ C colorless NN-dimethylcyclohexylamine (DMCHA) with a purity of η röhr than 99% receive. Nickel catalysts are used to carry out the process. Of particular disadvantage are the increased pressure and the low conversion rate of only 0.025 kg Γ 'h ~ \ relative to DMANL.

Object of the invention

The aim of the invention is to produce N, N-dimethylcyclohexylamine by a technically simple and efficient process by catalytic gas-phase hydrogenation of Ν, Ν-dimethylaniline with complete conversion of the dimethylaniline. It should be used an easily prepared catalyst.

Explanation of the essence of the invention The egg-finding is to achieve the objective of the object, N, N-dimethylcyclohexylamine by gas phase hydrogenation

in the low pressure range, if possible at atmospheric pressure to produce with little technical effort, the Ν, Ν-Dimethylcyciohexylamin has only a minimal content of by-products and wherein the catalyst used allows the production in the low pressure range and has a long service life.

According to the invention the object is achieved in that the gas phase hydrogenation at pressures up to 10bar, preferably at Normal pressure, and at temperatures between 150 ⁰ C and 180 ^c C, preferably at 16O ⁰ C and 175 ° C, by passing the Gas mixture over a fixed catalyst from top to bottom takes place and the Ν, Ν-dimethylaniline with Speeds between 0.05 and 0.1 kg Γ 'h " ^{1 is} implemented. According to the invention, the object is also solved by using such a catalyst, which consists of palladium Y-alumina carrier with basic proportions exists and palladium as hydrogenation-active Bastandteil in quantities between

0.1 and 5 wt .-%, preferably 0.2 and 1 wt .-%, based on the total mass of the catalyst, and basic proportions of

Alumina support as oxides and / or carbonates of alkaline earth metals, in particular of calcium, in amounts of 0.1 to

6 wt .-%, in particular 1 to 4Gew .-%, calculated as calcium oxide and that of the alkali metals, in particular of sodium, in

Amounts of 0.1 to 3w .-%, in particular 0.2 to ', 5Gew .-%, calculated as sodium carbonate. It was completely surprising that with particular advantage in the vacuum range up to 10 bar, preferably at normal pressure

arranged hydrogenation catalysts of palladium on alumina carrier with basecliun additives are unexpectedly well suited to catalyze the continuous reaction of DMANL with excess hydrogen in the gas phase to DMCHA completely and with a minimum content of by-products at elevated temperature.

In contrast, other hydrogenation catalysts, such as a mixture of cobalt oxide and calcium carbonate in solid

arranged form not suitable under otherwise identical hydrogenation conditions.

The amount of excess hydrogen is 5 times to B0 times, preferably 10 to 40 times, theoretically

required amount. The excess hydrogen can be performed in a known per se width as a circulating gas, wherein according to the consumption, the required amount of fresh hydrogen is added continuously to the cycle gas.

The turnover rate for DMANL is 0.05 to 0.1 kg per liter of catalyst volume and hour. As a carrier will

γ-alumina with a surface area greater than 10OmVg, preferably greater than 15OmVg, as an intimate mixture with basic

Shares used. The carriers, after intimate mixing of γ-alumina with the basic additives, become strands in a known manner, Cylinders odor balls deformed, wherein the strand shape is preferred. For the preparation of the complete hydrogenation catalysts is

in a known manner, the palladium of acidic, especially nitric acid solution applied by soaking the moldings on this fine and uniform, and then dried at about 100 ⁰ C. The hydrogenation catalysts are directly usable without preactivation and have a service life of at least 2000 hours.

The continuous gas phase hydrogenation process according to the invention allows boi in a simplified technical embodiment Press up to 10 bar, preferably at atmospheric pressure with the complete and highly selective production of DMCHA from DMANL with

increased turnover speed. Another advantage is that the hydrogenation of available raw materials i η technically simple manner can be produced. Also advantageous is the long service life of the hydrogenation catalyst.

The invention will be explained with the following exemplary embodiments: Embodiment 1

Above 11 of a fixed strand-shaped catalyst of 3mm diameter containing 0.5Gew .-% palladium on γ-alumina carrier with proportions of 2.5Gew .-% calcium oxide and 1.2Gew .-% sodium carbonate and previously by uniform impregnation of the carrier with Palladium nitrate solution and subsequent drying at about 100 ° C was obtained, hourly 60g gaseous DMANL together with 500 NL hydrogen continuously from top to bottom at atmospheric pressure and 17O ⁰ C out. It will contain a colorless DMCHA with a purity of about 98%.

Embodiment 2 The procedure is as in Example 1, but using a catalyst with 0.8% palladium on γ-Alumlniumoxidträger

at levels of 3.5 wt .-% calcium oxide and 0,6Gew .-% of sodium carbonate, 90g through which gaseous hourly DMANL and 1500 NL of hydrogen at atmospheric pressure and are routed 172 ⁰ C, one obtains colorless DMCHA over with a purity

Embodiment 3

It works with a catalyst according to Example 1, via soft hourly at 5 bar and 170 ⁰ C 70 g of gaseous DMANL together with 1100 NL hydrogen are passed from top to bottom. This gives a colorless DMCHA with a purity of over 98%.

Comparative example The procedure is as in Example 1, but uses a strand-shaped catalyst of 20Gew .-% cobalt oxide and 60Gew .-% Calcium carbonate of 3mm diameter, so is a colored synthesis mixture with a maximum of 25 wt .-% DMCHA content

receive.

Claims (2)

1. A process for the preparation of NN-dimethylcyclohexylamine in the gas phase by catalytic gas phase hydrogenation of Ν, Ν-dimethylaniline, characterized in that the gas phase hydrogenation at pressures up to 1Obar, preferably at atmospheric pressure, and at temperatures between 150 ^c C and 180 ⁰ C, preferably 160 ⁰ C and 175 ° C, by passing the mixture of Ν, Ν-dimethylaniline and hydrogen over a fixed catalyst from top to bottom and the Ν, Ν-dimethylaniline with rates between 0.05 and 0.1 kg Γ ¹ h ~ ^{1 is} implemented. 2. Catalyst for carrying out the process, characterized in that the catalyst consisting of palladium on y-alumina carrier with basic proportions, palladium in amounts of between 0.1 and 5 wt .-%, preferably 0.2 and 1 wt .-% , based on the total mass of the catalyst, and basic proportions of the y-alumina carrier as oxides and / or carbonates of the alkaline earth metals, in particular of the calcium, in amounts of 0.1 to 6 wt .-%, preferably 1 to 4Gew .-%, calculated as Calcium oxide and that of the alkali metals, in particular of sodium, in amounts of from 0.1 to 3% by weight, in particular from 0.2 to 1.5% by weight, calculated as sodium carbonate.