US2243471A - Manufacture of nitric acid esters - Google Patents

Description

May 27, 1941. J. F. OLIN MANUFACTURE OF NITRIC ACID ESTER S Filed Nov. l5, 1938 Q kw? QE O .xkmeow I INVENIOR: JOHNF.OL1N W QM A TTORNE Y Patented May 27, 1941 MANJJFACTURE F NITRIC ACID ESTERS John F. Olin, Grosse Ile, Mich assi'g nor to 'lhe Sharples Solvents Corporation; Philadelphia, Pa.

Application November 15, 1938;,Se1'ia1-No.'240,513

Claims.

pered by the lack of a process for producing suchmaterials on a commercial scale at a reasonable price. Under prior art practice the yields of nitrated products, with very few exceptions, are low and the operations are dangerous.

Two procedures for the preparation of nitrates frommethyl, ethyl, propyl, butyl and amyl alcohols have been described. One method, which has been used to prepare nitrates from monohydric. alcohols containing not more than three carbon atoms, consists essentially in the distillation of a mixture of nitric acid and alcohol in thepresence of urea. readily; volatilized and may be distilled from the. reactionzone to prevent accumulation of the ester the: nitrating vessel which might otherwise result'in explosions.- Since the presence of even small amounts of nitrous'acid tends.

to initiate a vigorous auto-oxidation of explosive violence, urea is added to decompose nitrous acid as formed. in accordance with the. following equation:

CCKNHZ)2+2HNO2=CO2+2N2+3H2O By the above process the methyl and ethyl nitrates maybe prepared with fairly good results, but the method is not suitable for the nitration of alcohols containing four or more carbon atoms. In the case of the nitration of propyl or butyl alcohol or alcohols of higher carbon content than butyl alcohol, higher temperatures are required to obtain the esterification reaction than when the lower alcohols are nitrated. Higher temperatures are also required for distillation of theiesters from the nitration mixture in the case of? higher alcohols than in the caseof the lower alcohols. As the result of these two facts,.

attemptsto nitrate propyl and higher alcohols have resulted in the oxidation of the alcohol to produce the corresponding aldehydathis oxidation reaction occurring incident to nitration of thealcoholand therefore preventing the success.-

The nitration of aliphatic alcohols to.

The nitrate formed is.

ful practice of. the nitration process. In such cases the. oxidation of the alcohol can be to some. extent prevented'by the addition of urea to theireaction mixturabuteven when this precaution is taken the yield of the desired nitrate is still very low. In the coursezof the oxidation reaction occurring when attempts are made to nitrate the higher alcohols, the nitric acid intended for esterification" is. reduced to nitrous acid. Theoxidation of the alcohol is therefore a deleterious reaction both from the standpoint of producing undesired b-y-products and from the standpoint of reducing the esterifying acid. Even withthelowest alcohols the-yield is rarely in excess :of 75% (SystematicOrganic Chemistry, Cumming, Hop-per and Wheeler, page 254) A process. of nitrating isoamyl alcohol which has beensuccessf-ul from a laboratory viewpoint involves the addition of isoamyl alcohol or a mixture of the alcohol with concentrated sulfuric acid to anices-cold bathof nitric and concentrated sulfuric acid inthe volume ratio of 1:3. This processhas not achieved commercial success because of the diificulties of recovering unused nitric. acid and of reconcentrating the sulfuric acid; A. more. serious defect of this method lies in: the frequentexplosions occurring unless the alcohol is verypure.

Neither of the-above processes givessatisfactory resultsinthe nitration of monohydrio alcoholsother than-primary alcohols and no satisfactory methodhas-been heretofore-devised for the preparation of secondary alkyl nitrates. The yields. obtained by treating asecondary or tertiaryaliphatic alcohol by. either of the methods ment-.with.35% to 60% nitric acid. Concentrations. belowgave very low-grade esters while the -useof acid having a-nitric acid content in excess of resulted in substantialoxidation with consequent-decreasein yield. The present inventionrests upona procedure by which the objectionable-featuresof prior art processes are avoided bypassing the reactants to the reaction chamber in a continuousmanner and continuously passing; the reaction mixture from the reaction chamber, thismixture-being separated object has been to afford a satisfactory method of producing nitrates of propyl and higher alcohols. The practice of the features of the invention is particularly useful in producing alkyl nitrates by esterifying alcohols containing from 3' to 8 carbon atoms, inclusive, with nitric acid.

It may be logically inferred. that the esterification of an aliphatic alcohol proceeds through the formation of an oxonium derivative of very low vapor pressure. From that intermediate compound, the ester is formed by loss of water, but in the presence of concentratednitric acid, the oxonium derivative is oxidized to. form undesired by-products. These reactions may be represented as follows:

1. CHHOH+HONO2=C5H11OH.HONO2 Amyl alcohol Nitric Oxonium derivative 2. C5H OH.HONOz=C5H ONO2+H2O Oxonium derivative Amyl nitrate W ater 3. C5HnOH.HONO2=C4HaCHOI-HNO2 Oxonium derivative Valeralde- Nitrous hyde acid In the above equations the reactions represented by Equations 1 and 2 are the desirable reactions, while the reaction represented by Equation 3 is the undesirable reaction, since it results in the formation of undesired valeraldehyde and reduction of the nitric acid which might otherwise be converted into amyl nitrate.

When concentrated nitric acid is used in the practice of the process of nitration as indicated by Equations 1 to 3 above, the reactions of Equations 1 and 3 predominate; and the desired reaction of Equation 2 is depressed.

When concentrated nitric acid is used, the concentrated nitric acid also causes auto-oxidation of the alkyl nitrate formed in accordance with Equation 2 above, with the result that thecontents of the reaction vessel frequently explode.

On the other hand, when very dilute nitric acid is employed in this reaction, the reaction is extremely slow and the yields of the desired products are small.

The operator, desiring to produce amyl nitrate, for example, is on the horns of a dilemmawhen attempting to operate in accordance with the prior art procedure for producing methyl and ethyl nitrates. If he initiates the reaction with the use of a concentrated nitric acid, the initial reaction involves undesired production of valeraldehyde and reduction of the nitric acid as indicated in Equation 3. If, on the other hand, he initiates the reaction by the use of nitric acid of the concentration found most suitable for the accomplishment of the reactions of Equations 1 and 2, water formed incident to the esterification reaction as indicated in Equation 2 rapidly dilutes the reaction mixture and reduces the nitric acid to a concentration at which itwill not eificiently perform its nitrating function.

Reasoning from the above premises, the apauto-oxidation of the alkyl nitrate formed in accordance with Equation 2.

reaction vessel I3 at this time.

In accordance with the present invention, autooxidation in the esterification vessel is prevented by removing the alkyl nitrate from the esterification vessel promptly after the formation thereof. This is accomplished by passing the reactants continuously through the reaction apparatus, nitric acid, the alcohol to be esterified and an amount of urea sufficient to inhibit auto-oxidation bein continuously passed to the reaction vessel and a mixture of alkyl nitrate, alcohol, nitric acid and water being continuously discharged from the 'esterification vessel. By proceeding in this manner, the concentration of nitric acid in the esterification vessel may be maintained substantially constant, since the water of esterification is removed from that vessel at the same rate at which it is formed incident to the esterification. The reaction mixture is thereafter separated into its constituents by extraction and distillation steps to be described hereinafter.

Since there is usually a tendency toward formation of nitrous acid in the reaction mass which will initiate oxidation if permitted to accumulate, it is preferred that a small proportion of urea be added to the vessel in which the present process is practiced. As a general rule the proportion of urea added is less than that employed in the process of the prior art, but as a precaution agains decreased yields, inferior grade ester, and explosion it is always well to follow the practice of adding at least a small amount of urea.

In its preferred embodiment the invention may be advantageously practiced in the apparatus shown diagrammatically in the accompanying drawing wherein I0, H and I2 designate storage tanks which may contain nitric acid of the desired concentration, an alcohol and 50% urea solution respectively, and each of these tanks is connected by a valved pipe to reaction vessel I3, which is provided with an agitator and a heating coil.

In the practice of the invention, nitric acid is first passed into the reaction vessel I3 to a level slightly below the level of the takeoff line which connects that vessel with the mixer I4. A small quantity of urea is also preferably passed to the The nitric acid is then heated to the desired temperature at which it is reacted with the alcohol to be esterifled. Quantities of alcohol from tank II and an excess of nitric acid from tank III are then run continuously into the esterification vessel I3. Since the temperature in the reaction vessel I3 is at the point best facilitating the reaction, the alcohol and nitric acid will react promptly upon contact with each other in that vessel. The reaction mixture, containing the desired alkyl nitrate, unreacted nitric acid, water of esterification, urea and alcohol, passes continuouslyfrom the esterification vessel I3 to a mixer I4, which is provided with a mechanical agitator.

The rate of withdrawal of the reaction mixture fromthe esteriflcation vessel I3 tothe mixer.

I4 is substantially the same as the rate of passage of nitric acid and alcohol from containers l and H to the esterification vessel. A solvent for the ester content of the reaction mixture is continuously passed from tank l5 to mixer It in such proportion as to selectively dissolve the ester and alcohol in the mixer hi to the substantial exclusion of nitric acid and water. The solvent added in mixer I l may be any good, inert, oil solvent, such as benzene, toluene, hexane, heptane, ether or a chlorinated hydrocarbon solvent such as carbon tetrachloride. In case the ester formed is heavier than the nitric acid solution contained in the mixture passed to the mixer M, it is preferable to employ a solvent of highspecific gravity, such as carbon tetra chloride, in order to facilitate subsequent separation of the solution of ester and alcohol in the solvent from the nitric acid of the reaction mixture. In cases in which, on the other hand, the ester formed is lighter than the nitric acid solution passed to the mixer l4, it is preferred to employ a. solvent of lower specific gravity than that of the nitric acid solution, such as benzene, toluene, hexane, heptane or ether. i5 is preferably provided with a coil, through which a cooling liquid is circulated in order to prevent volatilization in case a high volatile solvent, such as other, is employed.

The mixture of nitric acid solution and solution of ester and alcohol in the solvent is next passed to a decanter IS, in which the major part of the nitric acid solution is removed from the solution of ester and alcohol in the solvent from tank I 5. The nitric acid solution may be passed to receiver IT for subsequent fractionation to remove organic constituents and reconcentration. The solution of ester and alcohol in the solvent is passed from decanter It to a mixer 18. It is to be noted at this point that, if thenitric acid solution is of lower specific gravity than the ester solution (oil layer) decanted from decanter IS, the decanter connections will be reversed, the lighter efiluent (nitric acid solution) being passed to receiver ll and the heavier effluent to receiver I53.

Water from tank 59 is mixed with the oil layer passing to tank 38 from decanter l6, and the mixture so produced is passed continuously to a decanter is, where the aqueous layer is removed and sent to the receiver :7. The oil layer from decanter 99 (which may be the lighter or heavier layer, depending upon the specific gravity of the ester produced and the specific gravity of the solvent used) is passed continuously to a mixer 28, where it is treated with an aqueous alkaline solution, such as a sodium carbonate solution, which removes the last traces of free acid. This alkaline solution is passed from tank 22 to the mixer 2d and the mixture produced in the mixer 28 is then passed to a decanter 2 l, which effects removal from the oily solution of the alkaline aqueous liquid produced in mixer 2d. The aqueous alkaline solution is passed to receiver 23 the oil layer from decanter 2i is passed to a mixer where it is again mixed with water from container is The mixture from mixer 24 is passed to a decanter 25, from which the aqueone layer is passed to receiver 23, while the oil layer is passed to stripping apparatus to be described hereinafter.

The material collected in the receiver 23, like the material collected in receiver H, is subjected to a stripping operation to remove unused alcohol, and this unused alcohol may be returned The mixer small.

to the tank II. The oil layer from decanter 25 is next passed to a stripping column 26, which is maintained at such a temperature that the solvent passes overhead and is condensed in condenser 21 and returned to the tank i5. A residue consisting of unused alcohol and the nitric acid ester collects in the still 28, and this residue is pumped into column 28, which is operated at such a temperature as to pass the alcohol overhead in the form of a binary constant boiling mixture containing a part of the alkyl nitrate. This overhead fraction is condensed in condenser 39. A part of the condensate is refluxed to column 29 and another part may be returned to tank I l as illustrated.

After separation of the alcohol content of this mixture from the desired nitrate, this alcohol may be returned to storage tank I l. Alkyl nitrate is pumped from the still 3i into a column 32, where further purification of this ester is obtained, followed by condensation in the condenser 3:3. The ester so obtained from condenser 34 is sufficiently pure to be used commercially. In cases in which relatively high boiling esters are produced, it is preferable to maintain the columns 26, 2e and 32 under sub-atmospheric pressure in order to avoid decomposition of these esters, which might occur in case the temperatures necessary to effect distillation at atmospheric pressure were employed.

The use of concentrated acid, that is, nitric acid containing substantially more than 70% HNOa, is possible under very closely controlled conditions, but should be avoided in most nitration reactions of the present type. The term dilute nitric acid as used in this disclosure and in the claims appended hereto is to be understood as referring to an acid containing HNOs not substantially in excess of 70%. It has been noted that extremely dilute acids generally give slow reactions and poor conversions and although some of the benefits of this invention may be obtained with acid of low concentration it is usual ly found that better results are obtained when using nitric acid having an HNG3 content in excess of i. e., in which the total water content of the esterification vessel does not bear a ratio to the total I-INO3 content of greater than 70:30. While acids having a concentration between about 30% and 65% give highly satisfactory results as compared with prior processes, the preferred range is to concentration of nitric acid since a reagent within the latter limits has been found generally suitable to the nitration of alcoholsesterified in accordance with the present invention. The acid added continuously to the esterification vessel should be of somewhat higher concentration than the concentration of acid which it is desired to maintain in that vessel, since acid continuously added to the vessel will be diluted to the desired con centration by the water of esterification formed in that vessel. A fairly good general rule is that lower acid concentrations should be used in connection with alcohols having a greater number of substituents on the carbinol group, e. that lower acid concentrations should be used in esteriiying secondary alcohols than primary alcohols.

The use of urea is recommended to oxidation. The process here described represents a striking improvement over the prior art by depressing side reactions to the very minimum and the amount of urearequired is therefore very The low cost of this reagent in the amounts used in the preferred embodiment of this invention is fully justified by the additional safety and improved yield obtained thereby. In connection with the nitration of primary alcohols, such as butanol-l, very little of the oxidation inhibitor is normally used, while more liighly substituted carbinols generally require appreciable amounts of this reagent.

Example 1--Preparation normal propyl nitrate.--Reaction vessel I3 is charged with 60% nitric acid and a 50% solution of urea in water is added from tank l2 in an amount constituting of the weight of nitric acid in the esterification vessel I3. Steam is then passed into the heating coil of the vessel 13 until the contents are raised to a temperature between 80 and 85 C. The agitator in the vessel i3 is then started and further quantities of 70% nitric acid from tank I0 and normal propyl alcohol from tank II are run in, in approm'mate Volume ratio of 1.3 to 1. As the reaction proceeds, further quantities of urea solution in amounts necessary to inhibit oxidation are added. Simultaneously with the addition of acid, alcohol and urea liquid overflows from esterification vessel l3 into mixer l4, and the mixture in mixer I4 is reduced to a temperature of 25 C. An amount of normal hexane equal in volume to the volume of alcohol passed from tank I I to vessel I3, is continuously supplied to the mixer Hi. The mixture passing from mixer I4 is decanted in decanter l6 and the oil layer from decanter I5 is further washed and decanted, as indicated in the above description. The Washed ester from decanter 25 is then passed into column 26, where the hexane containing traces of propyl alcohol and propyl nitrate is passed overhead and returned to storage tank [5. The bottoms from still 28 are then pumped into column 29, and the small amount of propyl a1- cohol remaining in the crude mixture is passed overhead, together with some propyl nitrate, and returned to storage tank II. The crude ester is then rectified by pumping it from still 3| into column 32 and obtaining relatively pure propyl nitrate boiling between 108 and 111 C. The ester produced in this manner has a specific gravity of 1.045.

In the case of the preparation of this ester, it is to be observed that, because of the solubility of propyl alcohol in the diluted nitric acid and in the aqueous wash water passed to receivers l1 and 23, only a relatively small quantity of propyl alcohol was recovered in the subsequent distillation operations performed in columns 26 and 29. However, upon distillating the diluted acid from receiver l1 and the diluted alkaline washes from receiver 23, substantially all of the propyl alcohol not accounted for as propyl rfitrate may be recovered.

Example Z-Jllixed amyl nitrates-In the manufacture of this material, 50% nitric acid is charged into vessel 13 to approximately a point one-third below the takeoff. Upon heating to 90 C., esterification is caused to take place by the continuous addition of amyl alcohol and 65% nitric acid; the latter being used in 50% excess, or such excess as is required to maintain the free acid at 40-50%. Benzene may be used as a solvent instead of hexane, if desired, and theabsolute .pressure inthe fractionation columns 26, 29 and 32 is preferably reduced to 200 mm. The process is otherwise identical with that described in Example 1. The mixed amyl nitrate material obtained by conducting the process in this manner in the esterificatio-n with the mixture of amyl alcohol, commercially known as Pentasol, has a specific gravity at a temperature of C. of 0.988, and boils between 142 and 154.2" C. This mixture is a colorless liquid and has a pleasant odor.

From the above discussion, the manner in which the objects of the invention have been attained will be apparent. By conducting the reaction continuously, and removing the reaction mixture from the esterification vessel as formed, conditions in the esterification vessel are maintained substantially constant, and may be maintained at the point found most suitable for esterification of the particular alcohol being reacted with nitric acid. By operating in this manner, the disadvantage inherent in operating in accordance With prior art procedure of progressive dilution of the nitric acid is avoided. In View of this fact, it is not necessary to initiate the practice of the process by the use of acid of higher concentration than that most satisfactory for the preparation of the desired ester, and all of the disadvantages of the prior art discussed above are thus obviated.

While specific apparatus has been described in the foregoing description of the invention, 1 wish it understood that the invention is in no way limited to such specific apparatus, but that, it may be practiced in any apparatus suitable for the performance of the above-described process steps. Thus, for example, the esterification vessel 13 does not necessarily have to be a reaction vessel of the type illustrated, but maybe any suitable column, coil, or other contacting device, in which nitric acid of the desired strength is brought into contact with alcohol, and from which the reaction mixture is continuously discharged to apparatus for the performance of a series of steps in which the reaction mixture is separated into its constituents, as described.

Still further modifications will be obvious to those skilled in the art and I do not therefore wish to be limited except by the scope of the subjoined claims.

I claim:

1. The process of preparing an aliphatic nitrate which comprises continuously passing nitric acid of between forty-five and fifty-five percent concentration and an aliphatic alcohol together through a reaction zone, continuously removing the reaction mixture from said reaction zone during the feed of nitric acid and alcohol thereto, and thereafter separating the desired aliphatic nitrate from the reaction mixture so produced by solvent extraction.

2. The process of preparing an aliphatic nitrate which comprises continuously passing nitric acid and an aliphatic alcohol together through a reaction zone, continuously removing the reaction mixture from said reaction zone during the feed of nitric acid and alcohol thereto, and thereafter separating the desired aliphatic nitrate from the reaction mixture so produced by a process in volving extraction of the reaction mixture with a solvent for said aliphatic nitrate.

3. The process of preparing an aliphatic nitrate which comprises continuously passing nitric acid and an aliphatic alcohol together through a reaction zone, continuously removing the reaction mixture from said reaction zone during the feed of nitric acid and alcohol thereto, and thereafter separating the desired aliphatic nitrate from the reaction mixture so produced by a process involving extraction of the reaction mixture with a solvent chosen from the class consisting of chlorinated hydrocarbons, benzene, toluene, hexane, heptane and {ether.

4. 'Thejprocess-of preparing an aliphatic nitrate-whieh comprises continuously'passing nitric acid and an aliphatic alcohol together through a reaction zone, continuously removing the reaction mixture from said reaction zone during the feed of nitric acid and alcohol thereto, and thereafter separating the desired aliphatic nitrate from the reaction mixture so produced by a process involving extraction-of the'reactionmixture with a solvent for said aliphatic nitrate and subsequent washing with water of the material dissolvedin the extraction solvent.

5. The process of preparing an aliphatic'nitrate which comprises continuously passing nitric acid and an aliphatic alcohol together through a reaction zone, continuously removing the reaction ixture from said reaction zone during the feed of nitric acid and alcohol thereto, and thereafter separating the desired aliphatic nitrate from. the reaction mixture so produced by a process involving extraction of the reaction mixture with a solvent for said aliphatic nitrate, washing with water the material dissolved in the extraction solvent and subsequently neutralizing the waterwashe'dmix-ture by washing with abase.

6. The process of preparing an aliphaticnitrate which comprises continuously passing nitric acid and an aliphatic alcohol together through areaction zone, continuously removing the reaction mixture from said reaction zone during the feed of nitricacid and alcohol thereto, and thereafter separating the desired aliphatic nitrate from. the reaction mixture so produced by a process involving extraction of the reaction mixture with a solvent for said aliphatic nitrate, washing with water the material dissolved in the extraction solvent, neutralizing the water-washed mixture by washing with a base and thereafter again washing the solvent-extracted, water-washed and neutralized mixture with water.

7. The process of preparing an aliphatic nitrate which comprises continuously passing nitric acid and an aliphatic alcohol together through a reaction zone, continuousl removing the reaction mixture from said reaction zone during the feed of nitric acid and alcohol thereto, and thereafter separating the desired aliphatic nitrate from the reaction mixture so produced by a process involving extraction of the reaction mixture with a solvent for said aliphatic nitrate and subsequent distillation of the extracted organic constituents of the reaction mixture to separate solvent and alcohol therefrom.

8. The process of preparing an aliphatic nitrate which comprises continuously passing nitric acid and an aliphatic alcohol together through a reaction zone, continuously removing the reaction mixture from said reaction zone during the feed of nitric acid and alcohol thereto, and thereafter separating the desired aliphatic nitrate from the reaction mixture so produced by a process involving extraction of the reaction mixture with a solvent for said aliphatic nitrate, washing with Water the material dissolved in the extraction solvent and subsequent distillation of the extracted organic constituents of the reaction mixture to separate solvent and alcohol therefrom.

9. The process of preparing an aliphatic nitrate which comprises continuously passing nitric acid and an aliphatic alcohol together through a reaction zone, continuously removing the reaction mixture from said reaction zone during the feed of nitric acid and alcohol thereto, and thereafter separating the desired aliphatic nitrate from the reaction mixture so produced by a process involving extraction of the reaction mixture with a solvent for said aliphatic nitrate, washing with water the material dissolved in the extraction solvent, neutralizing the water-washed mixture and subsequent distillation of the extracted organic constituents of the reaction mixture to separatesolvent and alcohol therefrom.

10. The process of preparing an aliphatic nitrate which comprises continuously passing nitric acid and an aliphatic alcohol together through "a reaction zone, continuously removing the reaction mixture from said reaction zone during the feed of nitric acid and alcohol thereto, and thereafter separating the desired aliphaticnitrate fromthe reaction mixture so producedbyva process involving extraction of the reaction mixture with a solvent for said aliphatic'nitrate and subsequent distillation of the extracted organic constituents of the reaction mixture to separate solvent and alcohol therefrom and returning to the reaction zone alcoholrecovered in said distillation step.

11. The process of preparing an aliphatic nitrate which comprises continuously passing nitrio acid and an aliphatic alcohol together through a reaction zone,'continuously removing the reaction mixture from said reaction zone during the feed of nitric acid and alcohol thereto, and thereafter separating the desired aliphatic nitrate from the reaction mixture so produced bya process involving extraction of the reaction mixture with a solvent for said aliphatic nitrate and subsequent distillation of the extracted organic constituents of the reaction mixture to separate solvent and alcohol therefrom and returning to the solvent extraction step of the process solvent recovered in said distillation step.

12. The process of preparing an aliphatic nitrate which comprises continuously passing nitric acid and an aliphatic alcohol together through a reaction zone, continuously removing the reaction mixture from said reaction zone at approximately the rate of feed 01' reactants to said reaction zone during the feed of nitric acid and alcohol thereto, and thereafter separating the desired aliphatic nitrate from the reaction mixture so produced by solvent extraction 13. The process of preparing an aliphatic nitrate which comprises continuously passing nitric acid and an aliphatic alcohol together through a reaction zone, continuously removing the reaction mixture from said reaction zone during the feed of nitric acid and alcohol thereto, and thereafter separating the desired aliphatic nitrate from the reaction mixture so produced by solvent extraction, the amount and concentration of acid continuously introduced into the reaction zone being so co-related to the rate of Withdrawal of reactants from said zone as to maintain the degree of concentration of aci in said zone substantially constant.

14. The process of preparing an aliphatic nitrate which comprises continuously passing nitric acid and an aliphatic alcohol containing between three and eight carbon atoms inclusive in its aliphatic radical together through a reaction zone, continuously removing the reaction mixture from said reaction zone during the feed of nitric acid and alcohol thereto, and thereafter separating the desired aliphatic nitrate from: the reaction mixture so produced by solvent extraction.

15. The process of preparing an aliphatic nitrate which comprises continuously passing nitric acid and an aliphatic alcohol containing between three and eight carbon atoms in its aliphatic radical together through a reaction zone, continuously removing the reaction mixture from said reaction zone during the feed of nitric acid and alcohol thereto, and thereafter separating the desired aliphatic nitrate from the reaction mixture so produced by a process involving extraction of the reaction mixture with a solvent for said aliphatic nitrate, Washing with water the material dissolved in the extraction solvent and subsequent distillation of the extracted organic constituents of the reaction mixture to separate solvent and alcohol therefrom.

16. The process of preparing amyl nitrate, which comprises continuously passing nitric acid and amyl alcohol together through a reaction zone, continuously removing the reaction mixture from said reaction zone during the feed of nitric acid and amyl alcohol thereto, and thereafter separating the desired amyl nitrate from the reaction mixture so produced by solvent extraction.

17. The process of preparing amyl nitrate, which comprises continuously passing nitric acid and amyl alcohol together through a reaction zone, continuously removing the reaction mixture from said reaction zone during the feed of nitric acid and amyl alcohol thereto, and thereafter separating the desired amyl nitrate from the reaction mixture so produced by a process involving extraction of the reaction mixture with trate which comprises continuously passing nitric acid and a monohydrie aliphatic alcohol containing between three and eight carbon atoms inclusive in its aliphatic radical together through a reaction zone, continuously removing the reaction mixture from said reaction zone during the feed of nitric acid and alcohol thereto, and thereafter separating the desired aliphatic nitrate from the reaction mixture so produced by solvent extraction.

19. A process as defined in claim 18, in which the extraction of the aliphatic nitrate from the reaction mixture is accomplished by treatment with a solvent chosen from the class consisting of chlorinated hydrocarbons, benzene, toluene, hexane, heptane and ether.

20. The process of extracting an aliphatic nitrate from a mixture containing said aliphatic nitrate, water, urea, nitric acid, and an aliphatic alcohol which comprises extracting said reaction mixture with a solvent chosen from the class consisting of chlorinated hydrocarbons, benzene, toluene, hexane, heptane and ether,

JOHN F. OLIN.

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