HU192878B - Process for production of di-n-prophyl-amin - Google Patents

Abstract

Di-n-propyl-amine is prepd. from propio-nitrile by catalytic hydrogenation with hydrogen contg. gas in inert solvents at a pressure of 1-6 MPa at 80-270 deg.C on catalysts contg. 5-50 wt.% nickel, while keeping the ratio of propionitrile gas to liq. in the range of 1.8-3.0 normal cubic metre per kg. The flow rate of the hydrogenation reaction is 0.4-0.8 litre propionitrile per litre catalyst per hr., the propionitrile contains 50-1000 mg per kg cycloalkane-diols, aromatic diols or mono- or di-esters of these with carboxylic acids with 1-4 carbons.

Description

The present invention relates to an improved process for the preparation of di-n-propylamine by selective catalytic hydrogenation of propiononitrile in a continuous process.

It is known that di-n-propylamine can be prepared by catalytic amination of n-propanol or by catalytic hydrogenation reduction of propiononitrile. In the latter case, the process can also be carried out by starting from acrylonitrile, firstly producing propiononitrile by saturating the carbon-carbon double bond and then using the resulting propiononitrile and the gas mixture used to hydrogenate the acrylonitrile. as starting materials for the manufacture of n-propylamine. In addition to di-n-propylamine, mono- and tri-n-propylamine are formed in each case. The known processes differ greatly in the selectivity of the preparation of di-n-propylamine.

No. 78,805. According to a Romanian patent, the hydrogenation of acrylonitrile is carried out in the presence of a nickel catalyst suspended in vegetable oils, and the resulting propionitrile is further hydrogenated. The process is carried out in a continuous operation apparatus. In the final product, di-n-propylamine is formed with only 30% selectivity.

No. 74-47,304. According to the Japanese patent application, propiononitrile is hydrogenated in the presence of a nickel and palladium containing catalyst. A batch autoclave is recommended for carrying out the procedure. By this method, di-n-propylamine can be prepared with 61% selectivity.

No. 179,522. According to the Hungarian patent, di-n-propylamine can be prepared from propiononitrile with 92% selectivity. The essence of the process is that the propiononitrile, which can also be used in the form of a reaction mixture formed when the acrylonitrile is hydrogenated, is hydrogenated on a catalyst bed of two different nickel containing catalysts. The process is performed in continuous operation.

A common disadvantage of the described processes is that the di-n-propylamine is formed in a state contaminated with inadequate selectivity and, at most, at least 8% by-products. Therefore, the purification of the final product requires the use of expensive purification equipment which, due to the distillation steps, also requires a significant energy input.

It is also known that the hydrogenation of propiononitrile is a very rapid and exothermic reaction that can easily lead to an undesired temperature rise. · Overheating of the reaction mixture results in an increase in the reaction yield of tri-n-propylamine and other byproducts, thus impairing reaction selectivity. Meanwhile, further snow development is occurring and the management and control of the reaction is more difficult.

In order to reduce the difficulties caused by the development of heat, no. According to the Hungarian patent, the hydrogenation of propiononitrile is carried out on catalyst beds filled with two catalysts of different activity, so that part of the reaction heat generated between the two catalyst beds can be removed in a refrigerator. However, this measure only allows to a limited extent to prevent harmful temperature rise and consequent decrease in selectivity. Because of external disturbances (eg temperature change in the preheater, pump delivery disturbances, etc.), the first low activity - from the catalyst bed - is transferred to the second, high activity, catalyst bed, where it is fully reactive, and a quantity of reaction heat is released which causes a significant rise in temperature and leads to secondary reactions. The reaction becomes completely out of control, the catalyst is pulverized, and the reactor structural material is permanently damaged. Occasionally extremely high temperatures (600-700 ° C) present an immediate risk of explosion and fire.

It is an object of the present invention to provide an improved process for the preparation of di-n-propylamine by hydrogenation of propiononitrile in the presence of a nickel catalyst which is well controllable under operating conditions and provides the desired di-n-propylamine with high selectivity with the simultaneous suppression of the formation of -propylamine.

It has been found that when a small amount of dihydroxybenzene, a monoether of dihydroxybenzene with C 1 -C 4 alcohols, a C 5 -C 7 cycloalkanediol or a mixture thereof is added to the reaction mixture, the additive inhibits tri-n-propylamine and other formation of secondary reaction products, consequently increasing the selectivity of the formation of di-n-propylamine. By suppressing secondary reactions, overheating of the reaction mixture and consequent malfunctions can also be eliminated. As a further benefit, we have found a significant increase in the lifetime of the nickel-containing catalyst used.

The present invention relates to an improved process for the preparation of di-n-propylamine in the presence of a propiononitrile inert solvent at a pressure of 1 to 6 MPa at 80 to 270 ° C, 1.8 to 3.0 Nm ³ / kg of propiononitrile gas / by maintaining a liquid ratio by catalytic hydrogenation of hydrogen containing gas on a supported catalyst containing 5-50% nickel. According to the invention, propiononitrile is based on the weight of the material stream

In the presence of 50-1000 mg / kg of dihydroxybenzene, dihydroxybenzene ether with C 1-4 alcohol and / or C 5-7 cycloalkanediol, relative to propiononitrile

192873 is hydrogenated at 0.4-0.8 1/1 x hour space speeds.

Throughout the specification and the I-series, the terms "cycloalkane diol" and "dihydroxybenzene" are understood to include the corresponding oxo tautomers (di- ketones). Among the ethers of dihydroxybenzene, methyl ethers such as methoxyphenols are particularly preferred. Particularly preferred additives are hydroquinone, p-methoxyphenol or 1,2-, 1,3- or 1,4-cyclohexanediol. The concentration of the additive is preferably from 100 to 500 mg / kg.

Propiononitrile is hydrogenated according to the invention as follows:

Propiononitrile is preferably diluted with cyclohexane, n-hexane or a hydrocarbon solvent containing predominantly these compounds, which is inert (i.e., inert to the reaction). Propiononitrile is usually diluted 1: 2 to 1: 5 by weight with the solvent used. If starting from propiononitrile derived from the hydrogenation of acrylonitrile, it is also possible to mix the solvent with the acrylonitrile and introduce it into the reactor together with the propiononitrile from the hydrogenation of the acrylonitrile. The catalyst used is preferably a catalyst containing from 5 to 50% by weight, preferably 8 to 20% by weight, of nickel on an alumina or aluminosilicate support. The hydrogenation may be carried out using pure hydrogen gas or a gas mixture, preferably containing at least 50 volumes of hydrogen, mixed with an inert gas such as nitrogen or argon. The hydrogenation may be carried out using the gas mixture used in the hydrogenation of the acrylonitrile saturator in accordance with known methods.

The mixture of propiononitrile, solvent and additive, and hydrogenation gas 40 are passed through the catalyst bed under the operating conditions described above. The flow of material from the reactor is cooled and the liquid is separated from the gas. The gas is then blown off or partially or completely recycled to the reaction and the liquid is distilled off into its components. The monopropylamine is recycled to the reactor for further reaction and the separated solvent is used to dilute propiononitrile (or, if acrylonitrile is obtained, acrylonitrile).

The process according to the invention provides di-n-propylamine in a yield of 97-98% relative to the theoretical value and with the same selectivity. The amount of tri-n-propylamine formed can be reduced below 1.5%. The catalyst life is significantly increased; sometimes exceeding 2500 hours.

The process according to the invention provides the following main advantages over the known methods:

di-n-propylamine is obtained with excellent (97-98%) selectivity;

reducing the amount of by-products, thus reducing cleaning costs; the space velocity can be increased from 0.4-0.5 1/1 x hours so far to 0.4-0.8 1/1 x hours;

- the catalyst life can be increased from 1000 to 1500 hours to 2500 hours or more due to milder reaction conditions.

The invention is illustrated in detail by the following non-limiting Examples.

Example 1

Propiononitrile was diluted with 82% (w / w) n-hexane hydrocarbon distillate (1: 2) and added

250 mg / kg of p-methoxyphenol, followed by 2.4Nm ^{3 of} gas / kg of propiononitrile B in a ratio of 75% (v / v) hydrogen ammonia synthesis gas, and the reaction mixture was pressurized with 4 MPa at 140 ° C for 0.7 hours. It was passed through a reactor filled with alumina supported catalyst containing 15% by weight of nickel at 1/1 x hour. The hydrogenation of the propiononitrile was complete by conversion. No mono-n-propylamine was formed during the reaction; the product was only 98% by weight with di-n-propylamine

It contained 1.4% by weight of tri-η-propylamine. During the experiment, a catalyst lifetime of 2600 hours was measured.

The above procedure was repeated except that p-methoxyphenol was not smelled on the propiononitrile. The product contained 8% by weight of tri-n-propylamine and 91% by weight of di-n-propylamine.

Example 2

Propiononitrile was diluted 1: 3 by weight with hydrocarbon distillate containing 90% by weight cyclohexane 45, a 1: 1 mixture of hydroquinone and 1,4-cyclohexanediol was added at 350 mg / kg and mixed with 2.6 Nm ^{3 of} gas / kg of propiononitrile. 50% by volume with a mixture of 65 volumes of hydrogen and 35 volumes of nitrogen, which was separated from the separator by acrylonitrile saturation hydrogenation. The reaction mixture was passed through a reactor filled with alumina support containing 10% by weight of nickel at a pressure of 4 MPa, 130 ° C, at a rate of 0.55 to 55 L / L for 1 hour. The hydrogenation of the propiononitrile was complete by conversion. The formation of mono-n-propyl60-amine was suppressed by recirculation, but no recirculation of tri-n-propylamine was required. The product was 97.8 wt.% Di-n-propylamine and 1.8 wt. containing propylamine. During the experiment, a catalyst lifetime of 65 2500 hours was measured.

The above procedure was repeated except that no propiononitrile was added. The product formed contained 15% by weight of tri-n-propylamine with 80% by weight of di-n-propylamine and 5% by weight of other by-products. The yield for di-n-propylamine was only 70%. In the experiment, we dived for 800 hours of catalyst life.

Example 3

Acrylonitrile was diluted 1: 2 by weight with hydrocarbon distillate containing 90% by weight cyclohexane and then added with hydroquinone (350 mg / kg) and 75% by volume hydrogen and 25% nitrogen by volume with 2.6 Nm ³ gas / kg acrylonitrile. ammonia synthesis gas was stirred. The acrylonitrile was hydrogenated in a known manner and, after condensation and cooling, the reaction mixture was introduced into the nitrile hydrogenation reactor. The hydrogenation of propiononitrile was carried out under the conditions described in Example 2. The product obtained

It contained 97.8% by weight of di-n-propylamine and 1.8% by weight of tri-n-propylamine.

Claims (3)

PATENT CLAIMS A process for the preparation of di-n-propylamine in the presence of a propiononitrile inert solvent at a pressure of from 1 to 6 MPa at 80 to 270 ° C at a ratio of 1.8 to 3.0 Nm ³ / kg propiononitrile gas / fluid volume. with 5 to 50 weight% nickel on a supported catalyst by catalytic hydrogenation with hydrogen containing gas, characterized in that the propiononitrile is present in an amount of from 50 to 1000 mg / kg of additive, namely dihydroxybenzene, dihydroxybenzene. ethers with carbon atoms and / or In the presence of C 5-7 cycloalkane diol - 0.4-0.8 1/1 based on propiononitrile Hydrogenate at 20 x hour space speed. 2. A process according to claim 1 wherein the additive is present in an amount of 100 to 500 mg / kg. The process according to claim 1 or 2, wherein the additive is p-methoxyphenol, hydroquinone and / or 1,4-cyclohexanediol.