Feb. 6, 1968 FP, SOFPCHAK 3,367,736 PROCESS FOR PRODUCTION OF ANTIMONY TRICHLORIDE

INVENTOR PETER SO PCHAK ???d-re????BY ATTOP??? 3,367,736 United States Patent Office Patented Feb. 6, 1968 2 3,367,736 feeding solid antimony to said suspension, discharging PROCESS FOR PRODUCTION OF liquid antimony trichloride from said suspension, and ANTyINY TRELOR)E regulating the feed of antimony metal and the discharge Peter Sopchak, Ciay, N.Y., assignor to Alied Chemical of liquid antimony trichloride to maintain the concentra Corporation, New York, N.Y., a corporation of New tion of solid antimony in said suspension within the range York of 25-65% by weight preferably 50-60% by weight. It Filed ydy 29, 1965, Ser. No. 475,756 is most important that the temperature of the suspension 4 Cainns. (C. 23-98) be held below 215° C. preferably below about 200° C. For some unexpected reason the chlorination rate at or ABSTRACT OF THE DSCLOSURE near about 220 C. was reduced approximately 6-fold with, of course, proportional reduction in capacity of the This specification discloses an improved process for the reactor and thus these higher temperatures should be production of antimony trichloride whereby antimony avoided. Another important operating condition in the metal is substantially all suspended by agitation in anti process of the present invention is the slurry concentra mony trichloride at a concentration of 25-65 percent by 5 tion. At a slurry concentration in excess of 65 weight per weight at a temperature of 90-215 C., and passing chlo cent there is a loss of slurry fluidity and the operation rine gas into the suspension to react with the antimony. is unsatisfactory. Slurry concentrations below 25 weight Antimony trichloride is removed from the reaction, and percent are undesirable because of loss in capacity. The additional chlorine and antimony metal are added at rates optimum concentration is 55-60 weight percent of anti to maintain the concentration of antimony as described 20 mony metal suspended in liquid antimony trichloride. above. This process is continuous and produces antimony The accompanying drawing diagrammatically illustrates trichloride essentially free of antimony pentachloride the present invention. more economically than known processes. Antimony metal of relatively high purity is commer cially available generally in the form of cakes weighing Conventional preparation of antimony trichloride is by about 50 or more pounds. Two typical analyses of com fixed bed reactor in which is disposed a stationary bed mercial antimony metal are as follows: of antimony metal and chlorine gas is passed in contact with the antimony to produce antimony trichloride. Be cause of the relatively low thermal conductivity of anti 30 Grade A RIMAM mony and its compounds along with the poor heat trans Percent, Sb (by diff.).------99.650 99.830 fer characteristics of fixed bed systems, very high re Percent Pb------.270 Trace action interface temperatures develop which cause fusion Percent As. - .033 05 Percent Fee 020 .072 and caking of the antimony bed. Frequent rodding is re Percent C .003 .008 quired to seal chlorine breakthrough channels in an effort 35 Percent Sn- .000 ------Percent Zn ?????? Trace ------to maintain product quality. Thus the difficulties in pro Percent S-...--- Trace 024 duction of antimony trichloride by conventional methods Percent Ni------.007 are poor quality product or low capacity resulting from inherently inefficient operating conditions. Antimony tri chloride of good quality contains a minimum of 99.0% 40 SbCl with premium quality containing more than 99.6% Relative to antimony trichloride, arsenic and sulfur antimony trichloride and in addition should contain not chlorides are volatile constituents and, in the process of more than a negligible amount of antimony pentachloride the present invention, can leave the system via vents sepa in an amount of less than 0.06%. One of the difficulties rately or be combined with the product. Iron, lead and in the preparation of antimony trichloride from antimony remaining trace metal chlorides, on the other hand, are metal is keeping down the antimony pentachloride im high melting, nonvolatile impurities. Depending upon the purities to a negligible amount. use in which the antimony trichloride product may be An object of the present invention is to provide an effi employed, these impurities may be allowed to remain as cient economical process for producing high quality anti contaminants in the product or provision for their elimini mony trichloride containing no more than a negligible 50 nation may be incorporated in the process as for example amount of antimony pentachloride as an impurity. by intermittent purging. Another object of the present invention is to provide a Antimony cakes each weighing approximately 50 continuous process for producing high purity antimony pounds and shaped like truncated pyramids with base di trichloride free of antimony pentachloride at high capacity mensions of iO/3' x 10%' and a height (truncated) of with substantially quantitative yields. Other objects and 55 3' entering crusher 1 are crushed therein from cake size advantages of the present invention will be apparent from to particle size passing a V8 inch screen. The size of the the following description and accompanying drawing. particles of antimony feed is not critical but should be of In accordance with the present invention antimony a size which can be readily maintained in suspension in metal is converted to a product having an assay above the liquid antimony trichloride. Merely as illustrative 99.60% antimony trichloride with virtually no penta 60 crushed antimony having the following granulation was chloride present, at high throughput rates by maintaining found satisfactory. a suspension of antimony metal particles in liquid anti U.S. mesh: Percent retained mony trichloride at a temperature of 90° to 215 C. 8 ------O preferably within the range of about 190-200 C., said 20 ------31 suspension having a concentration of solid antimony par 65 60 ------34 ticles in liquid antimony trichloride within the range of 100 ------16 25-65 weight percent preferably 50-60 weight percent Pan ------19 solid antimony based on the total weight of the suspen The crushed antimony metal is fed through line 2 into sion, passing gaseous chlorine through said suspension of surge bin 3. solid antimony in liquid antimony trichloride to effect Start-up of the reaction system first involves removal conversion of the solid antimony to antimony trichloride, of water vapor and oxygen from the process apparatus 3,367,736 3. ? by purging with nitrogen. Reactor 4 equipped with jacket Non-condensable gases including those such as arsenic 5 and provided with agitator 6 is charged with cominer and sulfur chlorides may be vented from the top of re cial antimony trichloride flake which is melted (-73.4° actor 4 through line 11 and any antimony trichloride C. M.P.) in situ using steam passing through jacket 5. vapor which may be carried over is condensed in con After a melt temperature of 90-100° C. is achieved, agi 5 denser 12 and drops back through line 1 to reactor 4. tation is started and crushed antimony metal added via Line 13 connects lines 9 and ii. line 7. Initial start-up charges of antimony and antimony The antirrhony trichloride overflowing from reactor 4 trichloride are precalculated to develop the overflow op through line 9 enters evaporator vessel E4 equipped with erating volume with desired antinhony concentration in a heating jacket, not shown in the drawing, for the pur the reactor. For example, to obtain 1000 ml. of 60 weight pose of vaporizing the antimony trichloride thereby ef percent suspension at 200 C., total charge consists of fecting further purification of the product. Non-volatile 2290 grams of antimony and 1530 grains of antimony tri impurities such as iron and lead chiorides would collect chloride. During the charging period the temperature is in evaporator 14 and could be discharged through line maintained above 90° C. Upon completion of antimony g5. If these minor amounts of inpurity are not important addition, heating is discontinued and reaction (chlorine 15 to product quality then evaporator vessel 14 may be sparging) initiated. Reactor 4 temperature is allowed to omitted. Vapors of antimony trichloride at a temperature increase as a result of reaction heat from approximately of about 223° C. pass upwardly from evaporator i4 90 until a desired level e.g. 200° C. is reached after through line 6 thence through product condenser 7 which cooling water is introduced in jacket 5 to the reac wherein the vapors are cooled and liquefied and the liquid for wall to maintain the specific temperature. The reac 2) condensate then passed down through line i8 into re tion may be illustrated by the following equation: ceiver 19. If desired the liquid product may be transferred to a conventional flaking machine and the resultant anti mony trichloride flaked product bagged for Sale or liquid 60 Wt. 9, Shi (s): 40. Wit. 9, SbCls (1) -> antinomy trichloride may be discharged from receiver E9 Sb(s) +gCl,,(g) 190-210°C. for captive use in the plant. The capacity of the plant for a given size unit is de SbCls (1) termined in large measure by the amount of antimony trichloride produced per unit volume of slurry in the re During normal operation chlorine feed is continuously in actor. When the antimony trichloride is operated in ac troduced through line 8. Antimony is fed into the System 3) cordance with the present invention, rates in excess of 2.5 through line 7 to maintain the concentration of antimony and approaching 3.0 pounds of antimony trichloride per in suspension within the desired range of 25-65 weight hour per gallon of reactor slurry were achieved. percent preferably within the range of 50-60 weight per The following examples iliustrate the present inventicia. cent. Antimony need not be fed continuously but may be fed intermittently to maintain the concentration within EXA, 1. the prescribed range. Agitation should be sufficient to maintain all the antimony particles suspended and in a Conimercial Grade A antimony cakes, each weighing state of high activity. Complete uniformity of suspen approximately 50 pounds were manually hainnered to 3 sion is not necessary. In practice rotation of the agitator inches and under and this material was sent to a Braunl at 350–450 r. p.m. was found to give satisfactory results. Chipmunk Jaw Crusher (Model No. Wi) 64, 3 HP), and Intense agitation while not affecting the reaction rate reduced to 34 inch and under. The % inch and under gives no beneficial result. Too low an agitator speed re was fed to a 2 HP, BICO pulverizer (radded with nitro Sults in partial to complete settling of the antimony from gen to prevent oxidation of the fine particles on the hot the slurry thereby reducing available reaction surface grinding surfaces) and was reduced to minus 8 plus 20 Which causes premature chlorine breakthrough. Con 45 mesh. tinuous removal of liquid SbCl essentially free of Sb, The antimony metal feed analyzed as follows: from the agitated reactor slurry is accomplished through takeoff tube 9. The liquid antimony trichloride may be Percent

caused to flow through inclined or elevated settling tube Sb (by diff.) ——~—-——----~------–-——–--- 99.83 9 by means of the density difference between reactor slurry and exiting SbCl. In this manner, any particles of antimony which may be carried with the liquid anti mony trichloride will drop back by gravity to the body of suspension in reactor 4. To further prevent any pos sibility of antimony metal being entrained in the liquid antimony trichloride discharging from the reactor vessel, a low withdrawal velocity of the order of less than 0.5 In a reactor having a working volume of 1,000 ml. feet/min. preferably less than 0.1 feet/min. may be em (0.264 gallon) and equipped with a paddle type stirrer ployed. The reaction temperature rises due to the exo as illustrated in the drawing, was maintained a body of thermic heat of reaction resulting from the formation of 60 liquid antimony trichloride having suspended therein par antimony trichloride. Control of the temperature is main ticles of antimony metal in which the antinhony metal was tained by passing cool water through jacket 5. 56 weight percent in the slurry of Sbcla. The agitator was Monitoring of product quality during regular orera rotated at 450 r.p.m. and the reaction temperature inai:- tion may be carried out by melt point and visual (color) tained at 200° C. During the operation chlorine was in observation of samples. Color of acceptable product in troduced at the rate of 0.36 pound per hour. Chlorine was the solid state is white. A yellow to brown discoloration, 65 fed at the maximum rate to obtain a reactor capacity at except for Some other obvious source of contamination the highest level without Cl gas breakthrough, as evi (iron, decomposed organic compounds), indicates pres denced by formation of yellow SbCl5 va cors andi discolora ence of pentachloride which causes low melt points. Prod tion of K indicator paper in the reactor space. Antimony uct with a melt point below 71° C. was also considered 70 metal was fed into the reactor to maintain the concen unacceptable. Melt point determination consisted of cool tration of antimony in the slurry at about 56%. Liquid ing liquid product in the Erlenmeyer flask equipped with antimony trichloride was withdrawn from the reactor at a thermometer and recording temperature after partial a rate to maintain a substantially constant volume. The solidification Was observed (subcooling occurred before reactor capacity (rate of production of antimony tricillo crystallization started). 75 ride) in terms of pounds SbO3/hour/gallon was 2.92 asad 3,367,786 5 6 the product was of high purity as shown by the following tating said suspension at a rate sufficient to maintain sub analysis: stantially all the antimony particles in suspension at a SbCl3 ------percent - 99.8 temperature within the range of 90° to 215 C., said SbCls ------do---- nil suspension having a concentration within the range of AS ------do---- <-001 5 25-26 weight percent solid antimony based on the total Fe ------9. p. II).-- 8 weight of the suspension, passing gaseous chlorine through insol. in HCl ------percent-– 1 ND said suspension of antimony in liquid antimony trichlo Freezepoint ------C 73.1 ride to effect conversion of the solid antimony to anti Color ------White mony trichloride, feeding solid antimony to said suspen O sion, discharging liquid antimony trichloride from Said 1Not detected Suspension, and regulating the feed of antimony metal and EXAMPLE 2. the discharge of liquid antimony trichloride to maintain In a second comparable operation the temperature in the concentration of solid antimony in said suspension the reactor was maintained at 140° C. and the agitator within the range of 25-65 percent by weight of the sus speed reduced to 350 r.p.m. The results were substantially pension. the same i.e. a reactor capacity of 2.9 pounds SbCls per 2. A process for production of antimony trichloride hour per gallon was obtained and the antimony trichlo which comprises maintaining a suspension of antimony ride product was of high purity similar to that of Ex metal particles in liquid antimony trichloride while agi ample 1. tating said suspension at a rate sufficient to maintain sub EXAMPLE 3 20 stantially all the antimony particles in suspension at a temperature of about 190–200° C., said suspension hav A third operation conducted substantially as Example 1 ing a concentration within the range of 50-60 weight except that a temperature of 210 C. in the reactor was percent solid antimony based on the total weight of the maintained. The results were substantially the same as suspension, passing gaseous chlorine through said sus in Example 1. 25 pension of antimony in liquid antimony trichloride to EXAMPLE 4 effect conversion of the solid antimony to antimony tri For purposes of comparison an operation was conduct chloride, feeding solid antimony to said suspension, dis ed as in Example 1 except that a temperature of 220° C. charging liquid antimony trichloride from said suspension, was maintained in the reactor. To avoid chlorine gas and regulating the feed of antimony metal and the dis breakthrough it was necessary to reduce the chlorine rate 30 charge of liquid antimony trichloride to maintain the to 0.06 pound Cl2 per hour. As a result the reactor concentration of solid antimony in said suspension within capacity was quite low namely 0.49 pound SbCls/hour/ the range of 50-60% by weight of the suspension. gallon. 3. A process as claimed in claim 1 wherein the liquid EXAMPLE 5 antimony trichloride discharged from the suspension is heated to convert the antimony trichloride to vapor, the In another comparative operation similar to Example 1 antimony trichloride vapor separated from non-volatile the percent of antimony suspended in the antimony tri impurities and the antimony trichloride vapor cooled, chloride was increased to approaching 65% and the speed condensed and recovered as liquid or solid antimony tri of the agitator was 350 rp.m. As a result there was a chloride. reduction in the maximum chlorine rate to 0.26 pound/ 40 hour and a reduced reactor capacity of 2.11 pounds 4. A process as claimed in claim 1 wherein impurities SbCl3/hour/gallon. more volatile than antimony trichloride are vented from Although certain preferred embodiments of the inven the suspension of antimony metal in liquid antimony tri tion have been disclosed for purpose of illustration, it chloride undergoing reaction. will be evident that various changes and modifications may be made therein without departing from the scope References Cited and spirit of the invention. UNITED STATES PATENTS I claim: 1,384,918 7/1921 Ralston ------23-98 1. A process for production of antimony trichloride which comprises maintaining a suspension of antimony 50 MILTON WEISSMAN, Primary Examiner. metal particles in liquid antimony trichloride while agi OSCAR R, VERTIZ, EDWARD STERN, Examiners.