DE1263738B - Process for the continuous production of saturated, higher molecular weight fatty acid nitriles - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

German mJTim patent office

EDITORIAL

Int. Cl .:

Number:
File number:
Filing date;
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C 07 c

German KL: 12 o-11

A40014IVb / 12o
April 19, 1962
March 21, 1968

The present invention relates to a process for the continuous production of saturated higher molecular weight fatty acid nitriles by stepwise reaction of the free acids or their esters with Ammonia in the presence of a dehydration catalyst to give the corresponding amide and its Conversion into the nitrile by further catalytic elimination of water in the presence of ammonia.

It is already from US Pat. No. 2,061,314 known, fatty acids at normal pressure in the liquid phase in a single stage initially into the amides and then convert it to the nitrile. This process carried out in a single reaction vessel is, however, has the disadvantage that at the higher temperatures used, the low-boiling Acids and amides evaporate, so that reflux condensers are used for their recovery Need to become. Apart from the fact that the operation of this cooler in large-scale processes represents an economic burden, they also easily clog as a result of the separation of acids and Amides in solid form. Methods have therefore been developed to overcome these difficulties which take place in two or three stages, with the fatty acid first heated in the liquid phase and added to the Amide reacted and then the amide is converted into the nitrile in the vapor phase. These procedures which work partly in liquid and partly in vapor phase and in the USA patents 2524 831, 2,546,521, 2,808,426 and 2,794,043 still have some significant disadvantages, the most important of which are mentioned below:

High temperatures are required for the evaporation, the generation of which results in high energy costs. In addition, large amounts of ammonia are used to lower the evaporation temperature required, requiring larger ammonia recovery plants. Since the distillation temperature is high, the catalyst chambers become unwanted by-products taken along, which contaminate the reaction product, so that this must be subjected to a second distillation. Finally, according to the previously known Process fatty acids with a molecular weight of over 300 no longer economically process as too much ammonia is required for evaporation.

The disadvantages just outlined, which burden the previously known processes for the production of nitriles, which run in the liquid and vapor phase, are now being used in over-process for the continuous production of
saturated, higher molecular weight fatty acid nitriles

Applicant:

Armor and Company, Chicago, JIl. (V. St. A.)

Representative:

Dipl.-Ing. R. H. Bahr and Dipl.-Phys. E. Betzier,

Patent Attorneys, 4690 Herne, Freiligrathstr. 19th

Named as inventor:

Ralph Harrison Potts, La Grange, JH. (V. St. A.)

Claimed priority:

V. St. v. America April 24, 1961 (104 952)

surprisingly overcome by the method according to the invention. This process for the continuous production of saturated, higher molecular weight fatty acid nitriles by stepwise reaction of the free acid or its ester with ammonia in the presence of a dehydration catalyst to give the corresponding amide and its conversion into nitral by further catalytic elimination of water in the presence of ammonia is characterized in that the reaction is carried out of the amide to the nitrile in the liquid phase at a temperature of about 280 to 320 ° C under a pressure of about 2 to 3 kg / cm ² .

The inventive method makes it possible to continuously take nitriles for the conversion to produce suitable temperatures and pressures of fatty acids in amides and of amides in nitriles, working continuously in the liquid phase.

According to the process according to the invention, the amides can be used at a comparatively low temperature and high pressure, while the conversion of the amides into the nitriles at comparatively low pressure and high temperature. Working in stages in the liquid phase has the advantage that the reaction proceeds practically quantitatively in a very short time, with a minimal Amount of ammonia is required. In addition, the measure essential to the invention that the Conversion of the amide into the nitrile is carried out in the last process stage in the liquid phase, the formation of undesirable by-products, which during

809 519/670

3 4

Working in the vapor phase in the catalyst chamber ammonia is in -den by the device 31 occur and partially pass into the nitrile, blown into the reactor. Here 80 to 90% of the prevented, so that an end product is obtained, the amide and practically all of the remaining fatty acid special is rekl. In addition, this enables it to be converted into the nitrile. The reactor 24 according to the invention Method of processing 5 letting product flows through line 25 and 32 Fatty acids with a molecular weight of more in the heater 33, in which it together with the dated than 300 in an economical way, since with the previous bottom of the reactor 34 withdrawn product, which Process in which the reaction of the amide is carried out through line 35, pump 36 and line the nitrile took place in the vapor phase, the conversion 37 is fed to the heater 33, is heated. That to fatty acid amides. with. such a high molecular temperature material is heated from the heater 33 by the lar weight was only low. Line 38 fed to the reactor 34, in which

In summary, it can be stated that a pressure of about 0.35 to the method according to the invention through the valve 39 maintains the technique around 1.05 kg / cm ² . The temperature nitrile production process is enriched, which in this reactor is 300 to 320 ° C. due to its only taking place in the liquid phase the relatively low temperature (170 to 180 ° C) reactor 34 withdrawn through lines 35 and 40 and high pressure (3.5 to 7 kg / cm ² ) and the conversion and in the separator 41 to remove the dissolved settlement of the amide in the nitrile at low pressure ammonia, which is withdrawn through line 42 (2 to 3 kg / cm ² ) and high temperature (280 to 20, is expanded to normal pressure. The crude nitrile 320 ° C) takes place with a minimal cost and , is taken through line 43 and then connected to Zeitauf wall. ßend through continuous high vacuum fast

Based on the schematic drawing, a distillation over alkaline materials, as is preferred Embodiment of the invention, for example calcium carbonate or sodium hydroxide, are explained according to the procedure. Through the 25 of the polymeric byproducts and the last Pump 10 is freeing fatty acid along with one of the traces of fatty acid.

Bottom of the reactor 12 withdrawn fatty acid and In the process described, the up-

Amide mixture via line 13 and pump 14 given fatty acid comparatively low temperature the heater 11 passed. In this heater, its temperature and a fairly high pressure for heating coils through the conversion of the major part of the fatty acid into the the steam are heated, the mixture is subjected to amide, whereby by working at heated to a temperature of 170 to 180 ° C, followed by considerable amounts of heat at a lower temperature the reactor 12 can be saved via the line 15 and a lot due to the high pressure fed and in finely divided form due to the faster reaction of the ammonia with the fat catalyst bed 16, which is made from an acid.

suitable dehydration catalyst, for example. The process of the invention is applicable to any

activated aluminum oxide, bauxite, aluminum - any, consisting mainly of amides phosphate, silica gel or the like. Reaction mixture of fatty acids with ammonia

In the heater 17, ammonia gas is superheated and usable. Tests have shown that, for example, in a ratio of about 1.5 moles of NH ₃ per mole, a fatty acid composed of 26.4% fatty acids and 62.8% amides can pass through the existing mixture via line 18 at a temperature of Direction 19 in the lower part of the reactor 12 at 280 ° C and a pressure of 4.2 kg / cm ² at a, in which it with the fatty acid amide trickling down to the reactor bed after 1 to the reactor bed with the granular supply of 1.541 ammonia Mixture IV 2 hours practically quantitative comes into contact with the corresponding. The rotational speed of the 45 nitrile has been converted. After 4 hours of the mixture through the heater 11, the amide and nitrile content is 20 times the rate at which the fresh fat reaction product determined to be 3.2 and 93.3%, acid is fed to the system. Was the same procedure at a higher level

The main amount of the supplied temperature (300 ° C.) is carried out in reactor 12, so it was th, 50 containing at least 8 carbon atoms, practically no acid is present after 1 hour. Fatty acid with elimination of water, which on After 4 hours the amide content was 0.7 and the upper end of the reactor through a tube over a nitrile content of 88.8%.

Relief valve 21 is removed, in the amide in order to- At one in a similar manner, but at one

changed. The pressure relief valve 21 was carried out at a temperature of 320 ° C., the internal pressure in the reactor was set at about 7 kg / cm ² and the fatty acid content disappeared after about 2 hours. The amide passes from the reactor 12 through the. After 4 hours the amide content was 2.6 and line 22 to the heater 23, in which it was 90.2% with the nitrile content.

the bottom part of the reactor 24 originating material, deviating from the above-described

which was applied through the line 25, the pump 26 and the search at which a pressure of 4.2 kg / cm ^{2 applied} line 27 is introduced into the heater 23, 60 was mixed at a pressure of 0.35 to will. In the heater 23, the temperature of 0.7 kg / cm ² and a temperature of 300 ° C. for the material is brought to 280 to 300 ° C., whereupon an ammonia feed of 1.541 per minute is added to the reactor 24 through line 28 . An analysis carried out after 2 hours is conducted, in which it was shown via a dehydration of the reaction product that no fatty acid catalyst bed 29 was again present with superheated 65, while the amide content 4.7 brought ammonia into contact in countercurrent and the nitrile content 89, 4%. After 4 hours it will. The pressure in the reactor 24 is adjusted by the excess, the amide content to 1.4 and the nitrile content to pressure valve 30 to about 2.8 kg / cm ² . That determined 96.3%.

A comparison of these results shows that the conversion into the nitriles is better at lower pressure runs. Possibly this phenomenon is at a much quicker and more effective distance of the water under these conditions.

Although the nitriles were prepared in three separate reactors according to the embodiment of the process according to the invention described above, the process can of course also be carried out in a smaller or larger number of reactors depending on the nature of the fatty acids or amides to be converted and the desired nature of the end product . For example, the method according to the invention can also take place in two stages. In this case, the first reactor is brought to a temperature between 250 and 300 ° C. while the pressure is kept at about 3.5 to 7 kg / cm ² . Superheated ammonia is introduced at the bottom of this reactor in a ratio of about 1 to 2 moles of ammonia to 1 mole of fatty acid used. Under these conditions, the fatty acid is converted into a mixture of amide and nitrile which is contaminated with unreacted fatty acid. This mixture is passed from the first to the second reactor where it is mixed with the bottoms of the second reactor. In the second reactor, the temperature is increased to 320 ° C. and the mixture is again brought into contact with superheated ammonia in a dehydration catalyst bed. The pressure in the second reactor is kept at 0.7 to 2.1 kg / cm ² by a pressure relief valve.

If only two reactors are used instead of three, it is expedient to reduce the residence time in to increase each reactor.

The following examples explain the process according to the invention in more detail.

example 1

This experiment was carried out in an apparatus which corresponded to that shown in the drawing. With a speed of 278kg / hour. (this corresponds to 1 mole per hour) tallow fatty acid with a molecular weight of 274 was fed to the first reactor. The temperature was 180 ° C. and the pressure was 5 kg / cm ² . In addition, 2 moles of ammonia were introduced into the reactor. The product withdrawn from the first reactor contained 15.8% free fatty acid, 39.2% amide and 45% nitrile. This mixture was fed to the second reactor 24, the temperature of which was kept at 300 ° C. while the pressure was 1.2 kg / cm ² . The rate of feeding ammonia into this reactor is 1 mole per hour. The reaction product withdrawn therefrom consisted of 4.4% fatty acid, 11% amide and 84.6% nitrile. It was then passed into a third reactor, the temperature of which was 310 ° C. at normal pressure and into which ammonia was passed at a rate of 0.5 mol per hour. The final product withdrawn from this reactor was composed of 95.4% nitrile, 3.6% amide and 1% fatty acid. This material was then distilled under reduced pressure to leave 3 to 4% of a pitch to obtain a distillate containing 0.25% fatty acid, 1.5% amide and 98% nitrile. The ammonia consumed in the entire process is 3.58 moles per mole of fatty acid used.

Example 2

The apparatus shown in the drawing was also used in this example. A hydrogenated tallow fatty acid at a temperature of 180 ° C. was fed at a rate of 282 kg (= 1.02 mol) per hour to the reactor 12, in which a pressure of 5 kg / cm ^{2 was} maintained. Ammonia was introduced into this reactor at a rate of 2.03 moles per hour. The product withdrawn therefrom was composed of 13.5% fatty acid, 50% amide and 36.4% nitrile and was introduced into the reactor 24, the temperature of which was 300 ° C. at a pressure of 1.2 kg / cm ² . At the same time, ammonia was introduced in an amount of 1 mol per hour. The product leaving this reactor consisted of 2.6% fatty acid, 11.8% amide and 85.6% nitrile and was fed to reactor 34, which was under normal pressure and the temperature of which was 300.degree. Ammonia was introduced into this reactor in an amount of 0.58 mol. The product obtained here consisted of 25.4% nitrile, 4.1% amide and 0.5% fatty acid. Distillation under reduced pressure gave a nitrile which still contained 0.8% fatty acid and 1.2% amide.

Claims (4)

Patent claims: 1. Process for the continuous production of saturated, higher molecular weight fatty acid nitriles by stepwise reaction of the free acids or their esters with ammonia in the presence of a dehydration catalyst to give the corresponding amide and its conversion into the nitrile by further catalytic dehydration in the presence of ammonia, characterized in that the reaction is carried out of the amide to the nitrile in the liquid phase at a temperature of about 280 to 320 ° C under a pressure of about 2 to 3 kg / cm ² . 2. The method according to claim 1, characterized in that the conversion of the fatty acid or its ester to the amide is carried out in the liquid phase at a temperature of about 170 to 180 ° C under a pressure of about 3.5 to 7 kg / cm ² . 3. The method according to claim 1, characterized in that the conversion of the amide into the nitrile in the presence of a dehydration catalyst and ammonia at a temperature of 300 to 320 ° C under a pressure of about 0.35 to 1.05 kg / cm ² performs. 4. The method according to claim 1 to 3, characterized in that from the liquid end product dissolved ammonia removed by decompression to normal pressure. Considered publications:
British Patent No. 793 020. 1 sheet of drawings 809 519/670 3. 68 © Bundesdruckerei Berlin