Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B21/00—Nitrogen; Compounds thereof
  • C01B21/082—Compounds containing nitrogen and non-metals and optionally metals
  • C01B21/16—Hydrazine; Salts thereof

Definitions

• This invention relates to an improved process for the manufacture of hydrazine and particularly to substantially anhydrous hydrazine, i e. a product containing at least about 95% hydrazine by weight.
• This application is a continuation in part of co-pending application Serial No. 156,046, filed February 14, 1950, and now abandoned.
• Hydrazine as ordinarily manufactured, is obtained in relatively dilute aqueous solution. Hydrazine and water form .a constant boiling mixture so that the dilute solutions obtained cannot be concentrated by ordinary fractional distillation to a hydrazine content greater than about 64% to 70%.
• a dehydrating agent such as sodium hydroxide, barium oxide, or calcium oxide.
• further distillation is carried out at reduced pressure. However, even with such precaution explosions occur.
• hydrazine In the absence of oxygen, hydrazine will, under suitable circumstances, decompose violently. Such explosions may be attributed to the presence of small amounts of impurities such as iron oxide, electric sparks, and the like which initiate the autodecomposition of the hydrazine.
• the distillate is composed of substantially anhydrous hydrazine and the hydrocarbon. Inasmuch as the liquid hydrocarbon is immiscible with the hydrazine, the distillate separates into two layers and the hydrocarbon layer may be decanted and returned for reuse in concentrating more hydrazine.
• the hydrazine solution may be distilled safely at atmospheric pressure due to the fact that in the presence of the hydrocarbon the hydrazine distills over at a lower temperature and the fact that the amount of such hydrocarbon vaporized with the hydrazine is sufiicient to prevent violent decomposition of the hydrazine, thereby greatly reducing the explosive hazard.
• Any hydrocarbon which is saturated and boils within the range of about 90 C. to 175 C. at atmospheric pressure is satisfactory for the purpose.
• Such hydrocarbons are exemplified by the paraflins, cyclo- 2,4,4-trimethylhexane;
• aqueous hydrazine solution in contact with a dehydrating agent and the hydrocarbon.
• Sodium hydroxide is the preferred dehydrating agent although barium hydroxide, calcium oxide and the like may be tane;
• n is an integer, and boiling within the range of about C. to C.
• Representativeexamples are normal heptane; normal octane; n-decane; Z-methylnonane; 2,7-dimethyloctane; 2,3,6-trimethylheptane; Z-methylheptane; 3-methylheptane; 4- methylheptane; cycloheptane; nonane; 2,4-dimethylheptane; Z-methyloctane; 2,5-dimethylheptane; 2,6-dimethylheptane; 4-ethylheptane; 3-methyloctane; 4-rnethyloctane; 2,2,4-trimethylpentane, 2,2,3,3-tetramethylbutane; 3-ethylpentane; 3-ethyl-2-methylpentane
• Suitable mixtures of saturated hydrocarbons obtained by fractionation of petroleum crude oils and boiling in the range between 143 C. and 175 C. are also available. It will be noted that such commercially available saturated hydrocarbons may contain minor amounts of unsaturated aromatics, which in such amounts are permissible. Unsaturated aromatic hydrocarbons, in general however, are not suited for the purpose due to their tendency to react with the hydrazine. Ordinarily such reaction involves hydrogenation of the aromatic with the conversion thereof to a saturated hydrocarbon with a resulting loss in yield of hydrazine. In situations where it is an economy to use a saturated hydrocarbon which is contaminated with substantial proportions of unsaturated compounds, at a sacrifice in the yield of substantially anhydrous hydrazine, such impure saturated hydrocarbons may, of course, be used.
• Hydrocarbons having a boiling point substantially above 175 C. are not satisfactory for the purpose due to their low vapor pressure and insuflicient amount distilled over to prevent decomposition of the hydrazine.
• Hydrocarbons having a boiling point substantially below about 90 C. are not in general suited for the purpose due to the impractically large amount of such hydrocarbon distilled over with a given amount of hydrazine.
• Minor amounts of such higher and lower boiling hydrocarbons may, of course, be included in a hydrocarbon mixture for the purpose, provided the resulting mixture boils within the range of about 90 C. to about 175 C.
• the amount of the saturated hydrocarbon distilled over with the hydrazine will, of course, vary with different hydrocarbons but the preferred hydrocarbons boiling in the range from 90 C. to 175 C. distill over in ample amount to prevent hazardous decomposition of the accompanying hydrazine.
• Table II shows for representative hydrocarbons in the first column, the approximate boiling temperature of the pure hydrocarbon; in the second colrunn, the average temperature attained during distillation of the hydrazine when distilling at atmospheric pressure a mixture of the aqueous hydrazine, sodium hydroxide and the hydrocarbon; in the third column, the minimum mole percent of the hydrocarbon in a mixture of the hydrocarbon vapor and hydrazine vapor effective to prevent mass decomposition of the hydrazine; and in the fourth column, the mole percent of hydrocarbon in the mixture of substantially anhydrous hydrazine and hydrocarbon vapors actually distilled over at atmospheric pressure.
• Table II shows that a vapor mixture containing 13% n-heptane and 87% hydrazine is not sensitive to mass decomposition from the action of electric sparks and the like, and further that such a vapor mixture containing greater than 13% n-heptane is likewise insensitive whereas lesser amounts are hazardous.
• the Table 11 further shows, for example, that the vapor distilled from a mixture of aqueous hydrazine, n-heptane, and sodium hydroxide (present in amount equimolar with the water) is composed of approximately 69% n-heptane and 31% substantially anhydrous hydrazine, all such percentages being calculated in mole percent.
• the ratio of n-heptane to hydrazine in the distillate is therefore advantageously greater than the permissible minimum ratio represented by the 13% content of n-heptane.
• the per- 4 missible minimum for decane is 9.6% but as will be noted the amount of decane actually distilled over, namely 15%, is ample to prevent such mass decomposition.
• the process is well suited for continuous operation.
• Such continuous operation may be accomplished for instance, by continuously feeding the dilute aqueous hydrazine, sodium hydroxide and hydrocarbon to the still while continuously removing sodium hydroxide monohydrate from the still and separately removing the hydrocarbon and hydrazine from the distillate receiver.
• the hydrocarbon from the distillate can be fed continuously back into the still and a portion of the sodium hydroxide monohydrate solution removed from the still can be enriched with sodium hydroxide to serve as the sodium hydroxide fed to the still with the aqueous hydrazine.
• the amount of sodium hydroxide monohydrate removed from the system depends upon the amount of water fed to the still in the aqueous hydrazine solution and such sodium hydroxide monohydrate may be dehydrated to recover sodium hydroxide, which anhydrous material can then be returned to the still and the cycle continued.
• the decomposition hazard therein can be advantageously reduced in accordance with this invention by including therewith some of the hydrocarbon.
• the substantially anhydrous hydrazine was sepairated from the hydrocarbon in the distillate by decantation and was found to represent 99% of the original hydrazine and had :a hydrazine concentration of 96.3 .v
• composition of the vapor distilled off in the foregoing example was such that electric sparks and the like could not bring about mass decomposition of the hydrazine vapor.
• the amount of hydrocarbon vapor was suflicient to prevent any hazard of fire or explosion even with the presence of small amounts of air. 7
• the hydrocarbon may be metered as a vapor into the still in sufiicient amount to prevent autodecomposition of the hydrazine vapor, but the use of the liquid in excess of the amount distilled over is preferred. In such operation some liquid hydrocarbon should be maintained in the still throughout the distillation.
• the step which comprises distilling said hydrazine in contact with a dehydrating agent and a saturated hydrocarbon whose boiling temperature at atmospheric pressure is within the range of about 90 C. to 175 C., said hydroc'ar-bon being present in an amount sufiicient to maintain the vapor of said hydrocarbon in intimate contact with the evolved hydrazine vapor throughout the distillation.
• the method of desensitizing hydrazine vapors which comprises maintaining the hydrazine vapor in intimate contact with saturated hydrocarbon vapor, condensing the vapors, and separating the hydrazine from the hydrocarbon condensate, said hydrocarbon having a boiling temperature at atmospheric pressure within the range of about 90 C. to 175 C.
• the step which comprises distilling said hydrazine in contact with a dehydrating agent and a saturated hydrocarhon whose boiling temperature at atmospheric-pressure is within the range of about C. to 175 C. while maintaining some of said hydrocarbon in the distilland throughout the distillation, said hydrocarbon being present in an amount sufficient to maintain the vapor of said hydrocarbon in intimate contact with the evolved hydrazine vapor throughout the distillation.
• step 4 which comprises distilling said hydrazine in contact with sodium hydroxide and a saturated hydrocarbon whose boiling temperature at atmospheric pressure is within the ran-geof about 90 C. to 175 C., said hydrocarbon being present in an amount suflicient to maintain the vapor of said hydrocarbon in intimate contact with the evolved hydrazine vapor throughout the distillation.
• the step which comprises distilling said hydrazine in contact with. sodium hydroxide and a "saturated hydrocarbon having a boiling temperature at atmospheric pressure within the range of about 90 C. to 175 C. while maintaining some of said hydrocarbon in the distilland throughout the distillation, said hydrocarbon being present in an amount suflicient to maintain the vapor of said hydrocarbon in intimate contact with the evolved bydrazine vapor throughout the distillation.
• aqueous hydrazine which comprise distilling a mixture of aqueous hydrazine, a dehydrating agent, and a saturated hydrocarbon having a boiling temperature at atmospheric pressure within the range of about 90 C. to 175 C. until substantially all the hydrazine has been removed from the -mixture while maintaining some of said hydrocarbon in the mixture throughout the distillation, collecting the distillate and mechanically separating the layer of hydrocarbon from the layer of hydrazine in saiddistillate, said hydrocarbon being present in an amount suificient to maintain the vapor of said hydrocarbon in intimate contact with the evolved hydrazine vapor throughout the distillation.
• the process of concentrating dilute aqueous hydrazinesolution which comprises intermix-ing an aqueous hydrazine solution with sodium hydroxide in the proportion of at least one mole of sodium hydroxide (for each mole of water to be removed and including therewith a saturated hydrocarbon having a boiling temperature within the range of about 90 C. to 175 C., distilling the mixture until substantially all of the hydrazine has been collected in the distillate while maintaining some out said hydrocarbon in the mixture throughout the distillation, and mechanically separating the substantially anhydrous hydrazine and the hydrocarbon in the distillate.
• the step which comprises distilling said hydrazine in contact with a dehydrating agent and a saturated hydrocarbon whose boiling temperature at atmospheric pressure is within the range of about 90 C. to C., said hydrocarbon being present in an amount sufiicient to maintain the vapor ,of said hydrocarbon in intimate contact with the evolved hydrazine vapor throughout the distillation.
• the method of desensitizi-ng hydrazine vapors which comprises maintaining the hydrazine vapor in intimate contact with saturated hydrocarbon vapor, condensing the vapors, and separating the hydrazine from the hydrocarbon condensate, said hydrocarbon having a boiling temperature at atmospheric pressure within the range of about 90 C. to 150 C.
• the step Which comprises distilling said hydrazine in .contact with sodium hydroxide and a saturated hydrocarbon having a boiling temperature at atmospheric pressure within the range of about 90 C. to 150 C. while maintaining some of said hydrocarbon in the distilland throughout the distillation, said hydrocarbon being present in an amount sufficient to maintain the vapor of said hydrocarbon in intimate contact with the evolved hydrazine vapor throughout the distillation.
• aqueous hydrazine which comprise distilling a mixture of aqueous hydrazine, a dehydrating agent, and -a saturated hydrocarbon having a Iboiling temperature at atmospheric pressure Within the range of about 90 C. to 150 C. until substantially all the hydrazine has been removed from the mixture While maintaining some of said hydrocarbon in the mixture throughout the distillation, collecting the distillate and mechanically separating the layer of hydrocarbon from the layer of hydrazine in said distillate, said hydrocarbon being present in an amount suflicient to maintain the vapor of said hydrocarbon in intimate contact with the evolved hydrazine vapor throughout the distillation.
• substantially anhydrous hydrazine the process of concentrating dilute aqueous hydraziine solution which comprises intewrmixing an aqueous hydrazine solution with sodium hydroxide in the proportion of at least one mole of sodium hydroxide for each mole of Water to be removed and including therewith a saturated hydrocarbon having a boiling temperature Within the range of about C.

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Cited By (5)

Citations (11)

• 0
  • BE BE528536D patent/BE528536A/xx unknown
• 1953
  • 1953-04-02 US US346513A patent/US2774725A/en not_active Expired - Lifetime

Patent Citations (11)

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