HU187285B - Process for producing nitrils - Google Patents

Abstract

FIELD OF THE INVENTION The present invention relates to an improved process for the preparation of C2-C22 carbon atoms with carboxylic acids and ammonia having an appropriate carbon number at atmospheric or elevated pressure and at temperatures of from 300 to 450 ° C, preferably from 380 to 420 ° C in an amount of 0.2 to 5% by weight of the periodic table II. up to two of the metals in its column by its reaction with a water-soluble salt or oxide and reacting in the presence of a dehydrating catalyst activated prior to starting the reaction. In accordance with the present invention, ammonium gas is blown to the acid at 1-15, preferably 4-8 molar, molar ratios of the liquid and boiling-point carboxylic acid used as starting material, and the resulting steam mixture is heated to the reaction temperature relative to the initial carboxylic acid. 0.2-1.0 hrs1 are passed through the catalyst at room velocity. -1-

Description

The present invention relates to a process for the preparation of C ₂ -C ₂₂ nitriles from the corresponding carboxylic acids by reacting the latter with ammonia in the presence of a promoted dehydrating catalyst. The process of the present invention achieves a high degree of conversion or yield, and the final product can be obtained without isolation of the products of the intermediate reactions.

It is known (Fodor, "Organic Chemistry", Volume II, p. 1086) that nitriles can be prepared from carboxylic acids according to the following general reaction equation:

RCOOH + NH ₃ - + RCN + 2 H ₂ O

The first step in the reaction is the formation of an ammonium salt which, depending on the reaction conditions, is converted to the acid amide in the presence of a dehydrating catalyst in the presence of a water cleavage catalyst. An additional water molecule is cleaved from the acid amide to form the corresponding nitrile. These reactions can be represented by the following equations.

RCOOH + NH ₃ t ± rcoonh ₄

RCOONH ₄ ? ± R'CONH ₂ + H ₂ O

RCONH ₂ RCN + H ₂ O

RC0NH ₂ - RCN + RCOOH + NH,

It is also known that bauxite, alumina, silica gel or aluminum phosphate can be used as dehydrating catalysts.

It will be appreciated by those skilled in the art that a process for the preparation of a nitrile which does not require the separation of several intermediates formed in the above reaction equations without the need for separate operations or the conversion of the starting intermediates to the target product in a single reaction step.

For the continuous production of nitriles from fatty acids, see Ind. Engng. Chem., 42, 202-213 (1950) describes a process in which fatty acids and ammonia are pre-reacted in a bell-plate with a reboiler and a reflux condenser after preheating under intensive boiling for amide production. The amide and low nitrile vapors leaving the column head are then passed through a separate reactor over a dehydrating catalyst at 400 ° C. The disadvantage of the process is that two reaction steps are required to produce the target product, i.e., in the first step, an amide is produced, and in the second step, the nitride is made from the amide.

German Patent No. 1,206,883 uses bismuth phosphorus molybdate catalyst on a silica gel support for nitriles. The yield of the process for acetonitrile is about 50% starting from ethanol and only 20.8% starting from acetic acid.

Nitriles are prepared in three steps starting from C ₈ -C ₂₂ fatty acids and ammonia according to the process described in U.S. Patent 2,808,426. The total reaction time is 2-4 hours. In the first step, the liquid starting carboxylic acids are reacted with ammonia at 160-180 ° C for 45-120 minutes to give the corresponding amides. The amides thus obtained in the second stage of operation are maintained at a temperature of about 300 ° C for 45-90 minutes, and then in a third step at 330-350 ° C over a dehydrating catalyst with a residence time of 2-20 seconds. The conversion rate for the amide is about 70%.

The process described in U.S. Patent No. 3,299,117 also converts fatty acids into nitriles in three steps. In the first step, working at 5 kg / cm ² and 180 ° C, a mixture of 13.5% fatty acid, 50% fatty acid amide and 36.4 nitrile is formed. In the second step, this mixture is further reacted at 1.2 kg / cm ² and 300 ° C to give a product mixture containing 11.8% amide and 85.6% nitrile with 2.6% residual fatty acid content. In the third step, the reaction is carried out at atmospheric pressure and 320 ° C to give a mixture containing 0.5% fatty acid, 4.1% amide and 95.4% nitrile. The reactor for the first and second steps is filled with a Raschig ring, a Berlin saddle or a Helixpack, while the reactor for the third step is filled with a dehydrating catalyst.

A two-step process using premixing with ammonia is described in Czechoslovak Patent No. 169,169. The process has the disadvantages mentioned above. No. 156,577. A process for the preparation of acetonitrile using cadmium and zinc compounds for promotional purposes is known from our Hungarian patent specification. The main disadvantage of the process is the relatively low productivity.

Thus, it can be seen that, in the prior art, the production of higher nitriles is usually carried out in several reaction steps to ensure efficient removal of water formed as a byproduct of the reactions and has a relatively modest conversion rate or yield.

Thus, one skilled in the art would recognize that a process for the preparation of C ₂ -C ₂₂ nitriles, in which the corresponding carboxylic acids, independently of their carbon number, can be converted into nitriles at high conversion rates, essentially dimerization, amide and residual fatty acids, and other polymers formation of by-products: without.

-2187.285 retains its activity for a long time.

The invention is further illustrated by the following embodiments.

It has now been found that nitriles can be prepared as described above by blowing ammonia gas in an amount of 1 to 15, preferably 4 to 8 molar, relative to the acid in the liquid carboxylic acid used as starting material or at a temperature close to its boiling point. elevated pressures from 300 to 450 ° C temperature, the starting carboxylic acid is from 0.2 to 1 hour ^"1 space velocity of the surface in an amount from 0.2 to 5% by weight of the Periodic Table II. of at least two of the metals in columns 1 to 5 are passed through a dehydrating catalyst, preferably alumina, promoted by its water-soluble salt or oxide and activated by heat treatment.

SUMMARY OF THE INVENTION The present invention relates to a process for the preparation of C ₂ -C ₂₂ nitriles at appropriate atmospheric or elevated carboxylic acids and ammonia, and at a temperature of from 300 to 450 ° C, preferably from 350 to 420 ° C, at 0.2-5% by weight. up to a maximum of two of the metals of column 1 are reacted in the presence of a water-soluble salt or oxide and activated prior to the reaction by heat treatment in the presence of a dehydrating catalyst. According to the present invention, the liquid carboxylic acid used as starting material is blown with ammonia gas at a rate of 1 to 15, preferably 4 to 8 molar, in a liquid carboxylic acid which is preheated to a temperature close to its boiling point, and the resulting vapor mixture is 0.2 to 1.0 hour ” ¹ through the catalyst.

In the practice of the process of the present invention, one of the catalysts mentioned in the prior art, preferably alumina, is used as the dehydrating catalyst. In practice, a water soluble magnesium or barium salt, or a mixture thereof, is utilized for the promotion. Organic salts such as nitrates may be used as water soluble salts. The salts form the corresponding metal oxides upon heat treatment of the catalyst. Addition of the salts can be carried out by impregnation, but of course the catalyst is prepared from the corresponding ratio was Mg ⁺⁺ and / or Ba combined with water-soluble isolation aluminiumsókból containing ⁺ weight. Activation of the dehydrating catalyst is suitably carried out in a nitrogen atmosphere, from 100 ° C to 400 ° C, by slow heating at 50 ° C every 2 hours.

The starting carboxylic acid is conveniently heated to its boiling point and thus introduced into the ammonia gas. The conventional evaporator unit may be equipped with ammonia injection nozzles. No reaction occurs when ammonia is purged. The conversion to nitrile between the fatty acids and ammonia takes place in a reactor in a reactor over the promoted catalyst in a yield of over 90%. The catalyst used

Example I

A 1.5% alumina catalyst containing 1.5% barium oxide was charged to the reactor and activated by a slow increase of 50 ° C in nitrogen atmosphere every 2 hours, followed by a 1: 4 molar mixture of acetic acid and ammonia at 380 ° C and atmospheric pressure. , calculated from the acetic acid 0.50 h ^"1 space velocity. Feeding acetic acid and ammonia to the reactor is accomplished by heating the acetic acid to 80 ° C and introducing ammonia gas into the preheater. After purging, ammonia is saturated with acetic acid vapor and enters the catalyst-containing reactor where the raw materials are converted to nitrile.

The product leaving the reactor contained 99.2% acetonitrile with 0.7% acetamide and 0.1% residual acetic acid.

Example 2

1.0% by weight of barium nitrate and 1.5% by weight of magnesium nitrate were impregnated onto the surface of the alumina support and, after drying, the catalyst thus obtained was charged to a 2 liter reactor. The reactor temperature was adjusted to 400 ° C by bubbling nitrogen gas at 50 ° C every two hours, and then heated at 400 ° C for a further 5 hours to activate the catalyst, and then feed the reactants. The evaporator unit at a temperature of 300 ° C (which is 33% stearic acid, 20% linoleic acid, 12% myristic acid, 31% palmitic acid, 4% caprylic acid) was added to 1.7 liters per hour _i0 C ₂ -C 2 -C molten fatty acid mixture, and the same place through nozzles ammonia gas was introduced at a rate of 1 m ² / hr. The fatty acid-saturated ammonia gas is introduced into the reactor, where it is converted to the nitrile. The product leaving the reactor was found to contain 98.7% nitrile, 0.8% acid amide and 0.5% fatty acid.

Example 3

A promoted alumina catalyst containing 2.0% by weight of magnesium oxide was prepared by one of the known methods and then charged to a 10 liter reactor. The reactor 'slow heating to a temperature of 400 Al "2 hours, the catalyst was heated to 50 C, then through the evaporator system is started at 300 ° C for 25 m ^J / hr of ammonia 32

187,285 transformation. The product leaving the reactor contained 98.9% nitrile, 0.6% acid amide and 0.4% fatty acid.

niagase and 40 liters / hour of melted stearic acid at about 80 ° C to the reactor to convert the raw materials to nitrile. The product leaving the reactor contained 99.2 stearyl nitrile, 0.36% stearyl amide, 0.44% unconverted stearic acid.

Example 4 10

A 98: 1: 1 mixture of gamma-alumina, zinc oxide, and magnesium oxide was tabletted and the tablets were charged to the reactor. The reaction temperature was raised at 50 ° C every 2 hours to 400 ° C under nitrogen purge. and then maintained at this temperature for a further 5 hours to activate the catalyst. Then start feeding the reactants.

The tallow fatty acid consisting of 4% myristic acid, 29% palmitic acid, 25% 20 stearic acid, 36% oleic acid and 6% other fatty acids was melted and transferred to a evaporator unit heated to 300 ° C using a metering pump at 15 L / h. At the same jets, ammonia gas of 1.3 m ³ / h was passed and ammonia saturated with tallow fatty acid vapors was introduced into the reactor, where nitrile

Claims (1)

A patent claim A method suitable C ₂ -C ₂₂ carbon atoms for preparing nitriles having carbon numbers of carboxylic acids and ammonia at atmospheric or elevated pressure and at 300-450 ° C, preferably 380-420 ° C in the amount of 0.2-5% by weight of the Periodic Table II. up to two of the metals in Column 1 are reacted with water soluble salt or oxide and activated prior to the reaction by heat treatment in the presence of a dehydrating catalyst, characterized in that ammonia gas was blown through and the resulting steam mixture was passed through the catalyst at a reaction rate of 0.2 to 1.0 hour relative to the starting carboxylic acid at the reaction temperature.