DE2545695A1 - Reductive methylation of amines - with cobalt or nickel catalyst pre-used for hydrogenation or amination - Google Patents

Abstract

Prodn. of methylamines comprises subjecting prim or sec. mono- or polyamines to reductive N-methylation with HCHO and H2 on a fixed bed of catalyst contg. Co or Ni in reduced form. The catalyst is first used in a conventional hydrogenation (pref. of nitrile to amine) or amination (pref. of alcohol with NH3 in presence of H2) process. N-Methyl tert mono- and polyamines are used as absorbents for removing acid components from synthesis gas, as catalysts for the prepn. of polyurethanes, epoxy resins and polyamides, as detergent additives for oils and fuels, as selective solvents, and as textile assistants. Carrying out prior hydrogenation or amination with the catalyst reduces catalyst consumption during reductive methylation.

Description

Process for the preparation of metbylamines

The invention relates to a process for the production of metbylamines Durable hydrogenating N-methylation of mono- or cross-valent primary or secondary Amines with formaldehyde and hydrogen on a fixed catalyst, the Cobalt or nickel in a reduced form debells.

Mono- or monovalent tertiary amines containing one or two methyl groups Carry on the nitrogen atom are valuable substances that are used on a technical scale for various purposes can be used, e.g. for the purification of synthesis gas from acidic components or as catalysts for the production of polyurethanes, Sposidbarzen and polyamides.

They are represented by hydrogenating N-methylation: The hydrogenating N-methylation is generally thermoset for various reasons by means of permanently arranged contacts (fixed bed catalysts) in vertically standing zglindriseben reactors.

The well-known procedures have one disadvantage: the lifespan of the Contact is too short; it soon disintegrates into fine-grained parts, which are found in the empty spaces set the corrugation in the reactor and cause a pressure drop, so that a Change of contact becomes necessary. Part of the broken contact becomes with washed out of the liquid reaction mixture and also clears blockages in downstream robots and valves.

The service life of the contact can depend on the specific contact consumption The amount of contact consumed åe 100 kg is expressed in kilograms Amine indicates; In general, the contact consumption takes care of more than 1 kg to be amine per 100 kg. The bobe of contact consumption makes the process expensive and it sets itself the task of diminishing ibn.

It has been found that the process described at the outset can be used with Carry out a considerably reduced contact consumption (to 0.2 to 0.5 kg per 100 kg) can, if the catalyst after reduction with hydrogen for a usual Hydrogenation or amination is used and only then is used for the hydrogenating N-methylation is used.

It is particularly favorable if you first have an alipbatiscbes cycloalipbatiscbes or aromatisobic nitrile with hydrogen, preferably in the presence of ammonia byrated to the corresponding amine.

It is also beneficial if you first have a (e.g., aliphatiscben or cycloaliphatic) alcohol with ammonia in the presence of hydrogen for the corresponding Amine converts.

The hydrogenating N-meubylation of the amines is expedient at 40 to 200, preferably 80 to 11,000 and at pressures between 1 and 500, preferably 20 to 100 bar carried out.

The pre-reaction according to the invention, d.b. Hydrogenation or amination, happens under the process conditions typical for these reactions. You can generally equated approximately with the aforementioned process conditions will.

The process of hydrogenating N-methylation itself can be divided into two Stages are carried out, whereby one in the first stage Amine and formaldehyde converts and the reaction mixture obtained in a second stage hydrogenated It is, however, advantageously possible to react the amine with Formaldehyde and hydrogen at the same time.

The process has been used with success in the N-methylation of aliphatic or cycloaliphatic mono- or polyvalent primary or secondary Amines. These amines generally have 1 to 30 carbon atoms. As examples may be mentioned: methylamine, ethylamine, cyclohexylamine, octylamine, stearylamine, ethylenediamine, Heaametbylenediamine (1,6), 1,4-butanediol bis (3-aminopropyl) ether, nonadecanediamine isomer mixtures, Diethylenetriamine, dibesamethylenetriamine, polyalkylene-polyamine, piperazine, N- (3-aminopropyl) -piperazine, N-methyl-piperazine, hexamethyleneimine, piperidine, ethanolamine, diethanolamine, N- (3-aminopropyl) -ethylenediamine, aromatic amines such as aniline, toluylenediamine, napbtylamine, etc.

Formaldehyde can z03. as aqueous, aqueous-alcoholic or as a solution be used in aliphatic alcohols, especially n- or isobutanol. It It is particularly advantageous to use a formaldehyde solution in n-butanol or isobutanol to be used with 25 to 50% formaldehyde content.

The implementation is stoichiometric; however, an excess of the one or the other reactant has a great influence on the course of the reaction 0 per molar equivalent reactive hydrogen bonded to nitrogen becomes 1 mole of formaldehyde consumed; expediently the proposed molar ratio is about 1 ç 0.8 to 1 ¢ 1.20 In individual cases, however, only partial methylation can be aimed for and be achieved. Any surpluses can be recovered or returned will. As catalysts, the known z.3. at Houben-Weyl, Metboden der Organic Chemistry, 4th ed. Volume 11/1, pages 641 to 643 described hydrogenation catalysts containing cobalt or nickel as an effective component can be used.

Full metal contacts or metal on substrates such as pumice, aluminum oxide, Use silica, clay, etc. The contacts can also contain additives such as iron, Copper, manganese, molybdenum, chromium, aluminum, silver, alkali and alkaline earth metals or their compounds, vanadium, tungsten, boron or its oxygen compounds, also precious metals, phosphoric acid, etc.

contain.

The tertiary amines which can be prepared by the process according to the invention, which carry one or two methyl groups per nitrogen atom are suitable for the purposes mentioned at the beginning.

Some of these compounds can also be used as mineral oil and fuel additives (Detergents), selective solvents, detergents, etc. can be used.

Certain amines are used for synthesis gas scrubbing.

Example of the preparation of N-pentamethyl-d iäthylenetriamine A vertical Upright cylindrical high pressure pipe made of V2A rod, which has a capacity of 100 1 and has a height to diameter ratio of 40 o 1, 125 kg becomes one Roben contacts made of cobalt oxide, formed into strands 2 mm in diameter and 6 mm in length is shaped, filled.

The contact becomes 60 at a temperature rising to 3000C Reduced with hydrogen for hours.

To "form" the contact, ethylamine is used according to the equation 02H5 OH + 02H5E2 + H20: 26 kg of ethanol and 50 kg of ammonia per hour are introduced into the reactor head, the reaction is carried out at a pressure of 200 bar and 200 ° C and the amount of reaction product corresponding to the feed is passed into the distillation plant from a pressure separator attached to the bottom. At the same time, three times the amount withdrawn from the system is returned to the inlet of the reactor in the form of a circuit.

The response is sustained continuously for 18 days and in this time 11 tons of ethylamine were produced.

According to the invention, N-pentamethyl-diethylenetriamine (I) is now obtained according to the equation H2N - (CH2) 2-NH72-H + 5 CH2O + 5 H2 (I) + 2.5 H20 produced. For this purpose, 10.3 kg of diethylenetriamine, 37.5 kg of 40 percent aqueous formaldehyde solution containing 0.2 phosphoric acid and 1.1 kg of hydrogen are fed to the reactor head separately every hour.

A temperature of 80 to 10500 and a pressure of 200 bar are maintained 0 hourly the pressure separator 48.8 kg of reaction mixture, the 35.5% (I), 63% water and 1.4 ffi methanol, removed and into the Headed distillation plant. In each case 150 kg of reaction mixture are produced at the same time cooled to dissipate the heat of reaction and fed back into the reactor in a circle.

By distillation, 7.0 kg of (I) with a boiling point (at 10 mbar) from 850C; the water content according to Fischer is 0.1 1>, the purity according to GC analysis 99.1. Furthermore, 0.3 kg of distillation residues (polyamines) educated. The calculated yield of (I) is 98%.

The reaction will be sustained for a long time maintain consistent operating conditions; after that is the efficiency the catalyst filling is exhausted.

A total of 42 tons of distilled amine were produced, resulting in a contact consumption of 0.3 kg / 100 kg amine is calculated.

$ 1 comparison attempt Proceed as described above, but without "boring" the contact. Rather, immediately after the reduction raw contact with hydrogen sets the N-methylation reaction in motion. The maximum possible hourly production of (I) is 16.0 kg with a purity according to GO analysis of 95%. At the same time, a distillation residue is in a Quantity of 0.9 kg formed hourly. The calculated yield of distilled Value product is 92.4.

As early as the 10th of the operating period, the yield was 89 ff sunk.

On the 14th day the reactor had to be shut down because the pressure drop was too high will. It turns out that about 20% of the contact disintegrates into a fine-grained mass is.

A total of 5.0 t of distilled amine (I) were provided in 14 days, the specific contact consumption is 2.5 kg per 100 kg of amine.

Claims (3)

Claims Process for the production of methylamines by hydrogenating agents N-methylation of mono- or polyvalent primary or secondary amines with formaldehyde and hydrogen on a fixed catalyst containing cobalt or nickel in reduced form, characterized in that the catalyst is removed from the Reduction initially used for a usual hydrogenation or amination and then used for the hydrogenating N-methylation. 2. Verabren according to claim 1, characterized gekennzeicbnet that the Catalyst initially used for the hydrogenation of a nitrile to an amine0 3. Procedure according to claim 1, characterized by the fact that the catalyst is first applied for the reaction of an alcohol with ammonia in the presence of hydrogen to the corresponding Amine used.