March 22, 1960

2,929,680 United States Patent Office Patented Mar. 22, 1960 2 lithium perchlorate drops on hot crushing rolls 8 main tained at a temperature in excess of 180° C. The per 2,929,680 chlorate is then reduced in size in a pug mill 9. The ground product is sized on screen 10, oversize being re PREPARATION OF LITHUMPERCHLORATE 5 turned to the crusher, the undersize to the reactor and David R. Stern, Fullerton, Calif., assignor to American the product being recovered as desired. Poiash & Clemaical Corporation, a corporation of Del The exhaust gas is passed through a lithium hydroxide 328 Scrubber 5, which selectively removes carbon dioxide as lithium carbonate, which is removed through line 12 Application June 28, 1957, Serial No. 668,769 O to a centrifuge 14. Wet solids from the centrifuge are 5 Claims. (Cl. 23-85) dried in flash drier 16 and returned as make-up lithium carbonate. The liquid stream from the centrifuge con tains a small amount of carbonate and this stream is sent to the lithium hydroxide dissolver 17 or a portion This invention relates to a process for the preparation 5 of anhydrous lithium perchlorate. can be removed to prevent impurities from accumulating. Lithium perchlorate is in increasing demand as a solid The lithium hydroxide stream is fed by pump 18 to the oxidizer in rocket propellants. It has a high available filter 9 and thence to the absorber 11. Oxygen content, is relatively stable, melting at 250 C., Typical examples illustrating the practice of this inven has a high density, and yields a rather high specific impulse tion are as follows: since its flame temperature is high and the average molec 20 ular weight of its combustion products are low. Example------Batch ContinuousIII Miellor cites three methods of preparing lithium per chlorate. They may be represented chemically as follows: Ii-CO3 (lbs.)------348 348 NH4ClO4 (lbs.)------105 05 LiOH--HClO4.2H2O-LiClO3HO (1) Mol Ratio (NHClOf Li;CO)------2.0 2.0 (70-72% acid) Reaction Time (min.)------90 58 Reactor Temperature (° C.)-- - 220-240 200-230 LiCO3-2(HClO4.2H2O)-2LiClO4-5HO--CO (2) Product (lbs.)------963 1008 NH3 Recovered (lbs.). ------32 LiCl--HClO4.2H2O-->LiClO)--HCl--2:EH2O (3) Rate of Conversion (percentimin 1.00 1. ?25 These methods have the disadvantage that they require Product Purity (percent).------99.7 99.4 expensive and difficult to handle perchloric acid. More 30 Yield (percent)------96.0 00.0 over, since they are carried out in the presence of water, the stable trihydrate of lithium perchlorate is formed. Chemical analyses of the products from the above are The hydrated water must be removed by difficult drying given below: techniques since the trihydrate is so soluble that it will Product, Example : neit in its own water of crystallization before dehydrating. Compound- Wit. Percent i propose to prepare lithium perchlorate in a molten LiClO4 ------99.68 state by the following reaction: Nii CIO? 4 ------0.14 iliaCO3--2NH4ClO >2LiClO4-2NH-CO-HO (4) LigCO3 ------Ni if one compares this system with those of Equations 4. Cl —------0.12 1, 2 and 3, it will be seen that one theoretically could evaporate per mole of lithium perchlorate six, five and 99.94 four times as much water. If Reactions 1, 2 or 3 are roduct, Example II: carried out in an aqueous medium, the quantity of water Compound may be ten to fifteen times as much, while the present LiClO4. ------99.4 process is carried on under anhydrous conditions. The NH4CIO4 ------0.42 process of Equation 4 has several advantages over earlier Li2COa ------Ni methods as follows: C ------0.14 (1) Uses readily available chemical raw materials in their industrial available form, i.e., LiOHHO and 99.96 NHClO. 50 Although I have illustrated the process with the perchlo (2) Considerable less water evaporation required since rate, it will be obvious to those skilled in the art that am reaction takes place in a completely anhydrous medium monium nitrate can be substituted for ammonium per and lithium carbonate is practically insoluble. chlorate and the same process equipment employed. A (3) No vacuum or extreme drying times are required. typical example illustrating this process with the nitrate (4) Process readily conducted on a continuous basis. 35 is presented below: (5) Any closed plant cycle requires an impurity blow Example IiII down stream. The chemical efficiency of this process Batch will be high since the blow down takes place with a stream LigCO3 (lbs-) –------536 which contains very little lithium. Any plant using an NH4NO3 (lbs.) ------1161 aqueous stream cycle containing LiClO4 loses considerable 0. Mol ratio (NH4NO3/Li2CO3) ------2.0 lithii in since lithium perchlorate is extremely soluble. Reaction time (min.) ------90 (6) Technical LiOH and Li2CO3 and NHCl O4 con Reactor temperature (C.) ------237 tains organics which can give an off color product. React Product (lbs.) ------1000 ing these materials at elevated temperatures oxidizes the NH3 recovered (1bs.) ------organics to carbon dioxide giving a white product. 65 Rate of conversion (percent/min.) ------1.0 A flow sheet and material balance for the process are Product purity (percent) ------99.9 given in Figure 1. Yield (percent) ------98.0 Solid NHClO, and LiCOs are mixed in a screw feeder. I claim: This mixture drops into a heel of molten LiClO4 main 1. A process for the preparation of lithium perchlorate tained at 250-275 C. in a reactor 7. Reaction takes 70 comprising: heating lithium perchlorate sufficiently to place liberating NH, CO, and water vapor. The molten render it molten; passing ammonium perchlorate and ?.929,680 3 4. lithium carbonate into said molten lithium perchlorate and comprising: heating lithium perchlorate to between about allowing said materials to react whereby to produce ad 250 and 275 C. whereby to render it molten; passing ditional lithium perchlorate. ammonium perchlorate and lithium carbonate into said 2. A process for the preparation of lithium perchlorate molten lithium perchlorate; allowing said materials to comprising: heating lithium perchlorate to a temperature react whereby to form additional lithium perchlorate; and 'of at least about 250° C. whereby to render it molten; maintaining said lithium perchlorate at an elevated tem passing ammonium perchlorate and lithium carbonate perature for a time sufficient to drive off substantially all into said molten lithium perchlorate and allowing said ammonia gas, carbon dioxide and water vapor produced materials to react whereby to produce additional lithium by said reaction. perchlorate. O 3. A process for the preparation of lithium perchlorate References Cited in the file of this patent comprising: heating lithium perchlorate to a temperature between about 250 and 275 C. whereby to render UNITED STATES PATENTS it molten; passing ammonium perchlorate and lithium car 1,276,499 Dantsizen ------Aug. 20, 1918 bonate into said molten lithium perchlorate; and allowing 5 1,738,930 Smith ------Dec. 10, 1929 said materials to react whereby to produce additional 1,824,101 Smith ------Sept. 22, 1931 lithium perchlorate. 2,413,644 Nicholson ------Dec. 31, 1946 4. The process of claim 3 wherein the carbon dioxide 2,489,574 i Hampel ------Nov. 12, 1949 also produced is recovered and thereafter reacted with OTHER REFERENCES lithium hydroxide whereby to form additional lithium 20 carbonate which in turn is recycled in said process. Ind. and Eng. Chem. (Anal. Ed.), vol. 17, No. 8, page 5. A process for the preparation of lithium perchlorate 474 (August 1945).