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April 4, 1961 B. H. NICOLAISEN ETA 2,978,296 "Y HYDRO HALIC

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April 4, 1961 B. H. NICOLAISEN ETA 2,978,296 April 4, 1961 B. H. NICOLAISEN ETA 2,978,296 MANUFACTURE OF HYDRAZINE DIHYDROHALIDES Filed Sept. 22, 1958 "y HYDRO HALIC ACD EVA PORATOR CONCENTRATE AQUEOUS HYDRAZINE HYDRAZINE DHYDRO HAL DE MONOHYDROHAE SLURRY 8 MOTHER L COR HYDRAZINE MOTHER COR REACTOR SEPARAOR HYDRO HAC AC HYDRAZINE DHYDROHALDE Bernard H. Nicolaisen Richord C. Harsh mon INVENTORS BY 6ela 1-2-Co 9-11-e-le?-2. 42. AORNEY United States Patent Office Patented Apr.2,978,296 4, 1961. 1 2 when no heat is being applied which might cause hy drogen halide losses. For a better understanding of this 2,978,296 See the attached schematic diagram. ---- More particularly, the hydrazine monohydrohalide MANUESSEESRAZINE 5 liquor is evaporated to a concentration of about 25 to 60 - percent and aqueous hydrogen halide is added to pro Bernard H. Nicolaisen, Tonawanda, and Richard C. vide a molar ratio of acid to hydrazine of 2.05:1 to Harshman, Kenmore, N.Y., assignors to Olin. Mathie- 2.5:1. The dihydrohalide liquor is cooled to crystallize son Chemical Corporation, a corporation of Virginia Solid dihydrohalide at a temperature of about 20° to 40 Filed Sept. 22, 1958, Ser. No. 762,315 10 C. and the crystals are separated. The liquor is re . cycled and fortified by the addition of hydrazine and 5 Claims. (CI. 23-87) hydrohalogen acid in proportion to reconstitute the . monohydrohalide liquor which is then evaporated as de . - . scribed. This invention relates to improvements in the manu- 15 . In starting the cyclic process of the present invention, facture of hydrazine dihydrohalides. as applied to the production of hydrazine dihydrochlo Hydrazine, dihydrochloride finds use in copper and ride, a preferred way of proceeding is to react hydrazine brass cleaning compositions, as a chlorine scavenger in hydrate with sufficient hydrochloric acid to provide 1 hydrogen chloride gas, and as a chemical intermediate in, mode of hydrogen chloride per mole of hydrazine. Wa for example, the preparation of 3,6-dihydroxypyridazine 20 ter is then evaporated from the solution and, while cool as described in J. Am. Chem. Soc., 73, 1873-4 (1951). ing the resulting hydrazine monohydrochloride concen Hydrazine dihydrofluoride and hydrazine dihydrobro- trate, additional hydrochloric acid is added to provide mide are useful in soldering flux compositions. from about 2.05 to 2.5 moles of hydrogen chloride per Solid hydrazine dihydrohalides are stable except at ele- mole of hydrazine. The excess of hydrogen chloride vated temperatures where they dissociate into the hy- 25 depresses the solubility of the desired hydrazine dihydro drazine monohydrohalide and hydrogen halide. In wa- chloride salt. Cooling is continued, preferably to about ter, they are quite soluble, though less so than the mono- 25 C. A slurry of hydrazine dihydrochloride forms hydrohalides. They are largely dissociated into hydro- and it is filtered. Since the mother liquor has substan gen halide and monohydrohalide in aqueous solution. tially the composition of the precipitating crystals, ex For these reasons, hydrazine dihydrochloride, for exam- 30 cept for water and excess hydrogen chloride, it is not ple, cannot be prepared satisfactorily by simply mixing essential that it be washed. On the other hand, it is a solution of hydrazine with a solution of hydrochloric advantageous to wash the crystals with, for instance, acid and concentrating by evaporation...'. When this is at- methanol to avoid caking problems. Water can be used tempted, hydrogen chloride is lost and hydrazine mono- to Wash too, but care must be taken not to use too much. hydrochloride or a mixture of mono and dihydrochloride 35 Then, the washings, if any, are combined with the mother is obtained as a solid product. The preparation of the liquor containing hydrazine dihydrochloride in solution dihydrohalides in an anhydrous way does not offer an and fresh hydrazine hydrate and hydrochloric acid are economically feasible method of avoiding these difficul- added to form a solution of hydrazine monohydrochlo ties due to the high cost of anhydrous hydrazine and hy- ride. Thereafter, the solution is distilled, recovering drogen halides. ... ." " . ... : 40 methanol if it was used in a washing step, and further It has now been found that the problems posed in the concentrated by the removal of water. production of hydrazine dihydrohalides by their solu- The evaporation may be carried out at atmospheric bility in water and their tendency at elevated tempera- or under reduced pressure. It is advantageously discon tures to lose hydrogen halide and revert to the more tinued before the concentration of the solution is such stable hydrazine monohydrohalide can be overcome. 45 that hydrazine monohydrochloride would separate at the This is accomplished by the cyclic process of the pres- hydrazine dihydrochloride precipitation temperature. ent invention which involves, the steps of reacting hy- The evaporation is, preferably, continued until the solu drazine or hydrazine hydrate and aqueous hydrogen hal- ition contains approximately 55 percent by weight hy ide to produce aqueous hydrazine monohydrohalide, re- drazine monohydrochloride. At lower concentrations moving water from the aqueous hydrazine monohydro-50 less hydrazine dihydrochloride will be formed in the halide thermally to produce a hydrazine monohydrohalide. crystalline state in the subsequent crystallization. At concentrate, cooling the hydrazine monohydrohalide cons concentrations less than 25 percent by weight hydrazine ... centrate and adding aqueous hydrogen halide to produce monohydrochloride, uneconomically small amounts of - a slurry of hydrazine dihydrohalide crystals and a mother crystals will beformed in each cycle. With more than liquor, separating the hydrazine, dihydrohalide crystals 55 about 60 percent by weight solids, toothick a slurry of ind the mother liquor, and adding sufficient hydrazine crystals of hydrazine dihydrochloride could be formed aqueous hydrogen halide to the mother liquor to n the crystallization step and the desired product might produce aqueous hydrazine monohydrohalide. Thus, the be contaminated with hydrazine monohydrochloride. method of the present invention contemplates thermal For these reasons, the preferred concentration of hy. removal of the water when the salt present in solution is 60 drazine monohydrochlorides following the evaporation "" ' ' '.' . " ' '. ...' ... 'o' halide. step is about 50 to 60 percent by weight. - Upon cooling of the hydrazine monohydrochloride - concentrate, additional hydrochloric acid is added to pre cipitate hydrazine dihydrochloride crystals. The cool-l. 2,978,296 3 4 ing and addition of hydrochloric acid may be concurrent dihydrochloride crystallized out and was removed by provided only that the cooling is sufficient to prevent filtration. It amounted to 1724 pounds of dry salt, loss of acid. Advantageously excess hydrochloric acid The resulting filtrate was recycled with additional hy is added to depress the solubility of the hydrazine dihydro drazine hydrate and hydrochloric acid to form additional chloride. The molar ratio of HCl to hydrazine can be hydrazine dihydrochloride. from about 2.05:1 to 2.5:1, but from about 2.05:1 to Example III 2.25:1 is preferred in order to obtain the maximum effect A 250 gallon, jacketed, agitated, nickel reactor was on depression of solubility of the salt. This, in turn, charged with 1000 pounds of water and 308 pounds of gives the maximum recovery of hydrazine dihydrochloride 70 percent aqueous hydrofluoric acid. The hydrofluoric per cycle. O acid was added under a nitrogen atmosphere to minimize Using aqueous hydrazine and aqueous hydrochloric possible corrosion of the reactor. Aqueous hydrazine acid as pure as are commercially available, substantially. (540 pounds of 64 percent NH4 solution) was added all of the hydrazine and hydrochloric acid are eventually slowly with cooling and agitation. The rate of addition recovered in the form of hydrazine dihydrochloride with was controlled to maintain the temperature below 50° C. out appreciable losses. Using less pure reactants, it 5 Water (248 pounds) was then evaporated from the solu is desirable after several cycles to extend the evaporation tion and the solution was cooled to 25° C. and an addi step and recover solid hydrazine monohydrochloride by tional 370 pounds of 70 percent aqueous hydrofluoric crystallization, discarding the impure mother liquor and acid was added with cooling and agitation, at such a re-dissolving the hydrazine monohydrochloride for re rate as to maintain the temperature below 25 C. After cycle. - 20 Hydrazine may be introduced into the system as an all of the hydrofluoric acid had been added, the slurry hydrous hydrazine, but it is more advantageous economi was cooled to 19 C. and the crystals were separated by cally to use hydrazine hydrate or commercially available centrifugation. The wet crystals from the centrifuge (652 compositions approximating such proportions. Even more pounds wet weight) were dried without washing and dilute solutions of hydrazine may be charged but this 25 yielded 601 pounds of product. The mother liquor (1325 increases the load on the evaporator. Thus, hydrazine hy pounds) was again charged to the same reactor and first drate of commerce is the preferred starting material for 110 pounds of 70 percent hydrofluoric acid and then 418. this reactant. pounds of 64 percent hydrazine solution were added. Concentrated acids are preferably used, although more Agitation and cooling was maintained during additions
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