DE1043320B - Process for the production of acrylic acid amides substituted on nitrogen - Google Patents

Description

It is known that N-substituted amides are more saturated Carboxylic acids by reacting carboxylic acids with primary or secondary amines in the liquid State at elevated temperature. One such process is for the production of a, /? - unsaturated Carboxamides are not very suitable because the amines are already at normal temperature add to the unsaturated double bond of the acids and so the reaction leads to mixtures which, in addition to the desired acid amide, a number of others Connections included.

N-substituted acrylic acid amides have therefore hitherto been prepared in such a way that from / j-Halopropionic acid amides with alkali or splits off organic bases, such as pyridine, hydrogen halide (cf. USA patents 2 288 197, 2,593,888) or by having acetoxypropionic acid amide heated to a higher temperature (see the USA. patent 2,494,583). Other known methods consist in making alcohol from / I-alkoxypropionic acid amides split off or / J-N-alkylaminopropionic acid alkylamides converted into the unsaturated acrylic acid alkylamides by thermal treatment (See U.S. Patent 2,683,741). All of these known methods are cumbersome and have the Disadvantage that the preparation of the starting materials is time consuming and additional reactions are required power.

It has now been found that acrylic acids and primary or secondary aliphatic or aromatic amines without the formation of large amounts of undesired by-products in good yield N-substituted acrylic acid amides are obtained by putting the starting materials together in the gas state at temperatures above about 150 ° C via phosphoric acid or phosphate containing, dehydrating Acting catalysts conducts.

In addition to acrylic acid itself, methacrylic acid is also suitable as a starting material.

Suitable amines are all primary and secondary aliphatic and aromatic amines. Particularly suitable primary amines are e.g. B. methylamine, ethylamine n- and isopropylamine, n-butylamine, isobutylamine, 2-ethylhexylamine and aniline. Examples of secondary amines may be mentioned Dimethylamine, diethylamine, dipropylamine, dibutylamine, methylethylamine, ethylbutylamine, methylaniline and ethylaniline.

The reaction takes place above about 150 ° C, the upper temperature limit only by the Decomposition temperature of the amine to be converted is determined. Pedal at too low temperatures Side reactions, especially addition reactions and resin formation, cause the catalyst to stop early procedure

for the production of am nitrogen
substituted acrylic acid amides

Applicant:

Aniline & Soda Factory in Baden

Corporation,

Ludwigshafen / Rhine

Dr. Otto Leichtle and Dr. Fritz Nicolai,

Ludwigshafen / Rhine,
have been named as inventors

to make something useless. In general, it is advisable to work between 200 and 300 ° C., the most advantageous being Temperature depends on the type of amine and can easily be determined for the individual amines is.

Possible catalysts for the process are free phosphoric acid and all kinds of phosphates, for example alkali, alkaline earth, ammonium, beryllium, aluminum, titanium and especially boron phosphate. Also salts of organic bases with phosphoric acids and optionally mixtures of Phosphates and free phosphoric acid are suitable. The phosphoric acid and / or its salts can serve as catalysts both alone and on supports. As a carrier you can, for. B. silica gel, Use pumice stone and coke.

The reaction is usually carried out at normal pressure, but the use of reduced pressure is often associated with advantages, especially when working with higher pressure boiling amines, since then the reaction temperature can be reduced and the risk of a Polymerization of the available unsaturated amide is reduced.

The simplest is the process in an externally heated, suitably made of stainless steel or ceramic materials, lead through the vertical pipe that is completely or with the catalyst is partially filled or in which the catalyst is firmly arranged in layers. Main can do the procedure but also carry out in such a way that the catalyst by the vaporous starting materials kept moving. The Rea-

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tion participants can be inert gases, can, and one should have expected that such as nitrogen, hydrogen or carbon oxides, than with increasing temperatures, as they are according to the invention also evaporated inert solvents, e.g. B. Carbon for the implementation of acrylic acid with amines in the Hydrogen, or even water mixed in, can be considered, this formation of the steam state the. As a result, the catalyst can not only make 5 higher molecular weight, non-cleavable polymers more lightweight be moved, but achieved by weighing.

the dilution generally spares the substances π · · ι ι
in the implementation, especially the easily polymerized

acrylic acid. An externally electrically heated pipe made of corrosive

The reactants are generally in ion-resistant steel 100 cm in length and 50 mm

equimolar amounts are used. If desired, the diameter is filled with one made of boron phosphate

can one or the other participant also in the existing catalyst with a particle size of

Be used in excess. The acid in less than 5 to 7 mm. The upper end of the pipe is each with one

apply excess amount, e.g. B. in the 1.05 evaporator for the acrylic acid and the amine so

up to 1 times the stoichiometrically calculated amount is bound to that which emerges from the evaporators

mostly functional. Vapors up to just above the catalytic converter

To carry out the process, the filling is brought out separately and only then is the amine and acrylic acid mixed in vapor form and mixed. The reaction tube is heated to approximately, if necessary, to the reaction temperature pre-260 ° C. while passing a stream of nitrogen through it, warms the reaction space so that both parts are up and down and the one vaporizer is 100 cm ^{3 per hour in the desired proportions} Acrylic acid dissolved in benzene, while within or just above the catalysts, 100 cm ^{3 of} one per hour are encountered at the same time in the others. The Austre- zolic solution of diethylamine from the reaction chamber enters. The reaction products tend to form quantities of the two solutions on cooling, usually two layers. The lower layer contains the water of acrylic acid and water of reaction which is saturated with acid amide in equal parts by volume. The diethylamine solution in the equivalent amounts of the upper reaction layer consists of the acrylic acid amide and participants were contained. Each 100 cm ^{3 of} benzene solution contains, if appropriate, the 50 g of acrylic acid or 50 g of diethylamine used in the reaction. keep.

The N-substituted 30 die can be removed from the reaction tube at the lower end by distillation.

Acrylic acid amide, optionally after the addition of less reaction vapors, are stored in a cooler

Amounts of a poorly volatile acid, e.g. B. Liquefied phosphorus and collected in a separator. the end

acid or p-toluenesulfonic acid, in pure form, 1.08 kg diethylamine, 1.08 kg 99.5% acrylic acid

keep. An addition of polymerization retarders and 1.50 kg of benzene make 3647 g of one of two

z. B. of thiodiphenylamine, in the distillation, the 35 layers of existing reaction mixture are obtained,

usually under reduced pressure, the upper layer of 2945 g consists of acrylic acid

is beneficial. The distillation residue can be diethylamide and benzene. It results in the distillation

if desired, alone or together with fresh 1191 g of acrylic acid diethylamide. By distilling the

Starting materials passed over the catalyst again and the lower aqueous layer gives a further 171 g

will. 40 Acrylic acid diethylamide and small amounts of diethyl

It is from US Pat. No. 2,615,918 aminopropionic acid.

known that acrylic acid amide is obtained if one by fine distillation of the combined acrylic acid

Ammonia on a solution of acrylic anhydride diethylamide distillates are 1311 g of pure amide from

obtained in an inert organic solvent at temp. Kp. ₇ = 84 ° C,
Temperatures from 0 to about 25 ° C can act. This ⁴ ^

However, the method has significant disadvantages insofar as Example 2
only half of the acrylic acid contained in the anhydride can be converted into acrylic acid amide and the pre-acrylic acid anhydride described in Example 1 is used for a technical process direction and is available in sufficient quantities under the conditions specified there. ^{50 conditions 100 cm 3} an hour for one vaporizer. in which aminopropionic 100 cm ^{3 of} a solution prepared from 450 g of n-butylamine and 345 g of benzene acid amide at temperatures between 100 and 300 ° C is passed.

thermally cleaves to acrylic acid amides, this is invented

process according to the invention insofar as this is superior, there is the reaction product, the two layers

starting from the easily accessible acrylic acid, in th, from 1547 g. From the benzene layer

one process stage leads directly to the amide, while one obtains by distillation under reduced

According to its essence, the known process is pressure 588 g of acrylic acid-N-butylamide with a b.p. _2O = 137

is two-stage by first adding acrylic acid esters at 60 to 140 ° C, a yield of 75% of theory

Ammonia or amines correspond to the aminopropionic acid.

amides have to be converted in order to then remove the residues from the distillation residue and from the water storage compound to split. It was surprising to find that the layer, 240 g, became 150 g by distillation that the reaction of acrylic acid with amines in the case of higher-boiling products obtained after the processing in the vapor state smooth and in good evaporation and renewed throughput by the Kata wading In addition to the corresponding acrylic acid amide lysator tube, a further 42 g of acrylic acid-N-buitylamide are carried out, because already give when working in the liquid state.

at the lower temperatures, under which essentially the evaporators are carried out every 100 cm ³

borrowed an addition takes place, higher molecular weight poly from 308 g ethylamine and 507 g benzene and from 500 g

Kidney are formed, the thermally not cleaved 7 ° 99.5% acrylic acid and 449 g of benzene produced

To solutions, a reaction mixture which forms two layers and consists of 1293 g of a benzene and 295 g of an aqueous layer.

By working up both layers 455 g of acrylic acid N-ethylamide with a b.p. ₂₁ = 120 to 130 ° C. are obtained, which corresponds to a yield of 66.5% of theory.

Example 3

1 1 of a catalyst consisting of silica gel impregnated with orthophosphoric acid and before its use was dried at 300 ° C and contains 10 percent by weight orthophosphoric acid in a vertical, externally electrically heated pipe made of corrosion-resistant steel of 100 cm Length and 5 mm diameter filled. The tube is heated to 250 ° C at a pressure of 100 torr and nitrogen passed through from top to bottom in an amount of 5 liters per hour. Simultaneously a mixture of 288 g per hour is fed to the top of the pipe through two separate feed lines Acrylic acid and 452 g of benzene in vapor form and a vaporous mixture of 372 g of aniline and 379 g Benzene too. The introduction of these vapor mixtures takes place in such a way that the mixtures are only mixed occurs immediately above the catalyst surface. The vapors emerging from the pipe below are liquefied and collected in a template.

The liquid reaction mixture obtained every hour is recovered after the has been distilled off Benzene 475 g. Distillation under reduced pressure turns this into 420 g of acrylic anilide, boiling range 170 to 200 ° C at 30 Torr, which crystallize after cooling, won. The yield is % of theory.

Claims (3)

Patent claims: 1. A process for the preparation of acrylic acid amides substituted on the nitrogen, characterized in that that one acrylic acid or methacrylic acid and primary or secondary aliphatic or aromatic amines in the gas state at temperatures above about 150 ° C together Phosphoric acid-containing or phosphate-containing, dehydrating catalysts conducts. 2. The method according to claim 1, characterized in that the reaction is carried out in the presence inert gases or vaporized inert liquids. 3. The method according to claim 1 and 2, characterized in that the reaction under reduced Printing. Considered publications:
British Patent No. 723,006;
U.S. Patent Nos. 2,683,741, 2,615,918;
Organic Synthesis, Vol. 1, 1932, p. 4. © »678/41« 11.58 ·