Patented Aug. 12, 1952 2,606,878

UNITED STATES PATENT OFFICE 2,606,878 DOUBLE-CALCINATION PROCESS OF PRE PARING AN ALUMNA-PLATINUM-HALO. GEN CATALYST Wladimir Haensel, Hinsdale, Ill., assignor to Uni versal Oil Products Company, Chicago, Ill., a corporation of Delaware No Brawing. Application June 28, 1949, Serial No. 10,903 6 (Cairns. (C. 252-442) 2 This application is a continuation-in-part of ent invention relates to a method of preparing a my c0pending application Serial No. 788,672 filed catalyst which comprises adding a basic pre November 28, 1947, now U. S. Patent No. cipitant to aluminum chloride to form alumina, 2,479,109. Washing to remove soluble impurities, calcining . This invention relates to the manufacture of at a temperature of from about 800° to about ;Catalysts and particularly to the manufacture of 1400 F., commingling therewith a platinum con platinum containing catalysts. In another em taining solution in an amount to form a final bodiment the present invention relates to the use catalyst containing from about 0.01% to about of these catalysts in the conversion of hydro 1% by weight of platinum, thereafter com carbons and particularly in the reforming of mingling hydrogen fluoride solution in an gasoline. amount to form a final catalyst containing from Platinum-containing catalysts and various about 0.1% to about 3% by weight of fluorine, methods of manufacturing the same heretofore and heating the composite at a temperature of have been Suggested. These catalysts have been from about 700 to about 1100°F. . . . of limited commercial acceptance because of the 5 In still another embodiment the present inven high cost thereof. The present invention is tion relates to the use of catalysts prepared in based on the discovery that exceptionally good the manner herein set forth for the conversion catalysts may be prepared by specific methods of of hydrocarbons including the reforming of preparation to be hereinafter described in detail. gasoline to improve its antiknock characteristics. in One embodiment the present invention re 20 It has been found that exceptionally good cat lates to a method of preparing a catalyst which alysts are prepared in accordance with the novel comprises commingling platinum with alumina, features of the present invention. While these thereafter cornpositing a halogen, and heating catalysts may contain larger concentrations of the composite. platinum, which may range up to about 10% by In another embodiment the present invention 25 Weight or more of the alumina, it has been found relates to a method of preparing a catalyst which that exceptionally good catalysts may be pre comprises forming a mixture of alumina and pared to contain as low as from about 0.01% to platinum, thereafter compositing therewith about 1% by Weight of platinum. Catalysts of halogen in an amount of from about 0.2 to about these low platinum concentrations are particu 8% by weight, and heating the composite, 30 larly preferred in the present invention because In a Specific embodiment the present invention of the considerably lower cost of the catalyst. It relates to a method of preparing a catalyst which is well known that platinum is very expensive comprises precipitating alumina from aluminum and any Satisfactory method of reducing the chloride, commingling a platinum-containing amount of platinum required in catalysts con Solution therewith, thereafter combining hydro siderably reduces the cost of the catalyst and gen fluoride therewith in an amount of fluorine thus enhances the attractiveness of the catalyst of from about 0.1% to about 3% by weight of for use in commercial processes. The platinum Said alumina, and thereafter heating the com generally comprises a major portion of the cost of posite to a temperature of from about 700° to the catalyst and, therefore, by reducing the about 100°F. 40 amount of platinum required to one half, for In another specific embodiment the present example, reduces the cost of the catalyst sub invention relates to a method of preparing a Stantially by one half. Further, for eXarple, catalyst which comprises adding a basic pre When the amount of platinum is reduced to about cipitant to aluminum chloride to form alumina, 0.1% by Weight as against 5% by weight, or more, adding hydrogen sulfide to a chloroplatinic acid 45 as heretofore required, it is readily apparent solution and commingling the resultant Solution that the cost of the catalyst is reduced by at least With alumina, drying the mixture and calcining 50 times. at a temperature of from about 700 to about However, in order to obtain improved results 1100 F., thereafter commingling hydrogen fluo With these low platinum concentrations, it is ride solution in an amount to form a final cat 50 necessary that a particular type of supporting alyst containing from about 0.1% to about 3% by Component must be composited with the plat Weight of fluorine, and subsequently heating the inum. It has been found that alumina shows composite at a temperature of from about 700° unexpected advantages for use as a supporting ito about 1100 F. component for the low platinum concentrations, In still another specific embodiment the pres 55 apparently due to some peculiar association of 2,606,878 3 4. the alumina, with the platinum, either as a chem during subsequent heating is minimized. The ical combination or as a physical association. It amount of acetic acid, when employed, will gen has been found that the specific combination of erally be within the range of from about 0.05 alumina and low platinum concentration is not to about 0.5 no of acetic acid per no of alumina. only a very active catalyst, but also has a long Alumina prepared in the above manner, after catalyst life; that is, the catalyst retains its high washing and filtration is generally recovered as activity for long periods of service. After these a wet cake. In one embodiment of the invention long periods of service, the catalyst may show a the wet cake, either with or without being made drop in activity and it has further been found into a slurry with Water, is commingled with a that the particular combination of alumina and 10 Suitable platinum containing Solution in order platinum renders the catalyst susceptible to to composite the platinum With the alumina. ready regeneration. Chloroplatinic acid solution is preferred because To further improve these catalysts, it is an of its ready availability. However, any suitable essential feature of the present invention that platinum solution may be used, including solu the final catalyst contains halogen in a specific 5 tions of tetraamino platino chloride, ammonium concentration. It has been found that the pres platino-nitrite, dinitro-diamino-platinum, etc. ence of halogen within a specific range enhances These compounds are soluble in cold aqueous the activity of the catalyst. It is believed that Solutions and, therefore, are readily usable. the halogen enters into a chemical combination Other platinum compounds are soluble in hot or loose complex with the alumina, and/or plat 20 water and therefore can be used by heating the inum, and thiereby serves to improve the final Solution and using the hot solution to obtain the catalyst. desired commingling with the alumina. Stil While any of the halogen ions will serve to other platinum compounds may be insoluble in effect improved results, the fluoride ions are pre Water but are Soluble in other solvents such as ferred. Next in order are the chloride ions, while 2 5 ketones, ethers, etc. and, when these compounds the bromide and iodide ions are generally less are used, it Will be necessary to employ a suit preferred. It is understood that, while all of able solvent. these halogenS will serve to effect an improve The platinum preferably is added in a manner ment, they are not necessarily equivalent. to obtain a uniform distribution throughout the The catalyst of the present invention may be alumina. When the platinum is added to the wet prepared in any suitable manner, a particularly alumina, a particularly preferred method is to preferred method is to prepare alumina by add form a separate Solution of chloroplatinic acid in ing a suitable reagent, such as ammonium hy water and introduce hydrogen sulfide into this droxide, ammonium carbonate, etc. to a salt of solution at room temperature, until the chloro aluminum, such as aluminum chloride, aluminum platinic acid solution reaches a constant colora Sulfate, aluminum nitrate, etc. in an amount to tion; that is, Will not change color upon the addi form aluminum hydroxide which upon drying is tion of more hydrogen Sulfide. The chloro converted to alumina and, in the interest of sim platinic acid solution is normally light yellow plicity, the aluminum hydroxide is referred to and, upon addition of hydrogen sulfide gas, turns as alumina in the present specification and claims 40 to a dark brown color. Apparently the chloro in order that the percentages are based on alumi platinic acid and hydrogen sulfide react to form na, free of combined water. It has been found one or more complex chemical compounds. In that aluminum chloride is generally preferred another method of preparation the chloro as the aluminum salt, not only for convenience platinic acid may be added to the slurry of alu in subsequent washing and filtering procedures, mina gel, and hydrogen sulfide then is added to but also because it appears to give best resultS. the mixture. Another suitable method is to react sodium alu In some cases, satisfactory catalyst may be pro minate with aluminum chloride or other suitable duced by commingling the chloroplatinic acid aluminum salt in order to prepare the alumina. Solution. With the slurry of alumina gel, and then After the alumina has been formed, it is gen- it drying and heating in the manner hereinafter erally washed to remove soluble inpurities. set forth. In this method, hydrogen sulfide is Usual washing procedures comprise washing with not used. However, experiments have shown that water, either in combination. With filtration or as the hydrogen sulfide addition is preferable be separate steps. It has been found that filtra cause it tends to further fix the platinum in the tion of the alumina is improved when the Wash 5 5 form of an insoluble compound on the alumina, water includes a small amount of ammonium hy so that the platinum compound Will not migrate droxide. The washing should be of sufficient during the Subsequent heating of the catalyst. severity to substantially completely remove all In another enbodiment of the invention the soluble impurities because it has been found that alumina may be formed into particles and cal the presence of impurities may have a deleterious 60 cined prior to commingling the platinum solu effect on the activity of the catalyst. A particul tion therewith. In this embodiment of the in larly preferred method is to utilize pure alumi wention the Wet filter cake is dried at a tempera num chloride in the preparation of the alumina, ture of from about 200 to 500 F. or more for a and likewise to use purified water and other re period of from about 2 to 24 hours or more. The agents in preparing the catalyst so as not to in dried material is then ground and, when par troduce impurities into the catalyst from these ticles of irregular size and shape are desired, the ground material may be calcined at a tempera SOCeS.In some cases, it may be desired to commingle ture of from about 800 to about 1400 F. for a an organic acid and particularly acetic acid period of from about 2 to 12 hours or more. When which has been found to have a favorable effect O particles of uniform size and shape are desired, on the catalyst. The acetic acid apparently a suitable lubricant Such as stearic acid, rosin, hy serves to peptize the alumina and thereby to ren drogenated coconut oil, graphite, etc. is added der it in a better condition for compositing with and the alumina is formed into pills in any suit the platinum, and also partly to fix the platinum able pelleting apparatus. Particularly satisfac on the alumina, so that migration of the platinum 75 tory pills comprise those of a size ranging from 2,606,878 5 6 about s' x 5' to 4'x4' or thereabouts. Pills platinium mixture or it may be added after the of uniform size and shape may also be formed by alumina-platinuin mixture has been calcined extrusion methods. - and formed into particles of either uniform or In this embodiment of the invention the irregular size and shape. In the former instance, platinum solution is preferably commingled with the final composite of alumina-platinum and the alumina in the presence of ammonium hy halogen is dried, ground and calcined, or dried, droxide as it has been found that uniform dis ground, pilled and calcined in the manner here tribution of the platinum throughout the inbefore set forth. In the latter instance, the alumina is obtained. The ammonium hydroxide alumina-platinum-halogen composite is dried may be commingled with the platinum solution and calcined as herein set forth. and then added to the alumina, or the platinum After the alumina, platinum and halogen have Solution or ammonium hydroxide solution may been composited, the catalyst is dried at a tem be first added to the alumina, and then the other perature of from about 200 to 500° or more for material added. In this embodiment, a particu a period of from about 2 to 24 hours or more and larly Satisfactory method of commingling the then preferably is calcined at a temperature of platinum solution. With the alumina is to Sus from about 700 to about 1100°F. for a period of pend the alumina, pills in the platinum from about 2 to 12 hours or more. The calcina annonium hydroxide solution and then to heat tion is preferably effected in the presence of air the mixture to evaporate the volatile material. or other oxygen containing gas. In another em In another embodiment the pills may be dipped 20 bodiment of the invention the calcination may in the Solution, while still in another embodiment comprise a two stage method in which it is first the solution may be percolated through the conducted in the presence of hydrogen and then alumina pills. followed by calcination in air, or the reverse pro After the platinuin has been composited with Cedure may be employed. In Some cases the re the alumina, the halogen is then added to the 25 duction with hydrogen or hydrogen containing catalyst. The halogen may be added in any suit gas may be effected with a lower temperature able manner but should be added in a form which Within the range of from about 300° to about Will readily react with the alumina, and also one 600° E. that will not leave undesired deposits in the in SOne cases the lubricant Will be removed catalysts. A preferred method of adding the 30 during the high temperature heating. In other halogen is in the form of an acid, such as hy Cases as, for example, when graphite is used as drogen fluoride, hydrogen chloride, hydrogen the lubricant, the separate high temperature bromide and/or hydrogen iodide. Hydrogen heating step may be omitted, and the effective fluoride is preferably added as an aqueous solu heat treatment of the catalyst may be obtained tion for ease in handling and for control of the 35 in the plant before or during processing of the Specific amount to be added. Another satis hydrocarbons. factory Source to be used for adding the halogen Although the catalyst of the present invention is the volatile Saits, such as ammonium fluoride, will have a long life, it may be necessary to re annonium chloride, etc. The ammonium ions generate the catalyst after "long periods of Will be reinoved during the Subsequent heating 40 service. The regeneration may be effected by of the catalyst and, therefore, will not leave un treatment with air or other oxygen-containing desirable deposits in the catalyst. In still an gas to burn carbonaceous deposits therefrom. other method, the halogen may be added as In general, it is preferred to control the regener fluorine, chlorine, bromine, or iodine, but, in view ation temperature not to exceed about 1100° F. of the fact that fluorine and bromine normally 4. 5 In Some cases it may be desirable to follow the exist as gases, it is generally preferable to utilize burning operation with treatment with hydro them in the form of a solution for ease in gen-containing gas at temperatures of from handling. In Some cases, the inclusion of certain about 700° to about 1100°F. . . . components will not be harmful but may be The improved catalyst of the present inven beneficial, and in these cases the halogen may tion may be employed in any process for which be added in the form of salts such as potassium platinum is a catalyst. The improved catalysts fluoride, Sodium fluoride, thorium fluoride, are particularly satisfactory for reforming oper Sodium chloride, potassium chloride, etc. ations in which a saturated gasoline, such as The concentration of halogen in the finished straight run gasoline, natural gasoline, etc., is catalyst Will be within the range of from about 55 Subjected to conversion to produce a reformed 0.1% to about 8% by weight of the alumina on a gasoline of improved anti-knock properties. The dry basis. The fluoride appears to be more active Saturated gasoline generally comprises a mixture and therefore will be used within the range of of naphthenic and paraffinic hydrocarbons and from amout 0.1% to about 3% by weight of the the reforming operation effects dehydrogenation alumina on a dry basis. The chloride will be 60 of the naphthenic hydrocarbons to aromatics, used within the range of from about 0.2% to cyclization of the paraffinic hydrocarbons to aro about 8% and preferably from about 0.5% to matics, as Well as to effect a controlled type of about 5% by weight of the alumina on a dry cracking which is selective both in quality and in basis. In One embodiment, halogen may con quantity. In addition, other reactions may occur prise a mixture of halogens such as a mixture of 65 Such as isomerization, hydrogen transfer, etc. fluorine and chlorine. The total amount of The controlled or selective cracking is desirable halogens being within the range herein specified. because it further increases the octane number It has been found that halogen concentrations of the reformed gasoline, produces a gasoline of below these lower limits do not give the desired higher volatility and converts higher boiling. improvement and, on the other hand, concen 70 fractions to lower boiling fractions within the trations of halogen above the upper limits ad range of gasoline. However, this cracking must versely affect the Selectivity of the catalyst, thus be controlled because excessive cracking produces catalyzing side reactions to an extent greater excessive normally gaseous products and also ex than desired. cessive carbonaceous deposits on and deactivation The halogen may be added to the wet alumina 75 of the catalyst. The improved catalysts of the 2,606,878 7 8 present invention are particularly desirable for hourly space velocity from about 0.5 to 5. The reforning operations because the catalyst effects Weight hourly Space Velocity is defined as the the desired aromatization and controlled crack Weight of oil per hour per weight of catalyst in ing under Selected conditions of operation. the reaction Zone. It is understood that the gasoline may com In one embodiment of the process, Sufficient prise a full boiling range gasoline or any Se hydrogen Will be produced in the reforning re lected fraction thereof, and reference to gasoline action to furnish the hydrogen required in the in the present specification and claims shall mean proceSS and, therefore, it may be unnecessary the full boiling gasoline or any selected fraction to either introduce hydrogen from an extraneous thereof. 10 Source Or to recycle hydrogen. Within the process. The catalyst of the present invention may also However, it usually Will be preferred to introduce find utility in treatment of higher boiling Saturat hydrogen from an extraneous source, generally ed fractions Such as kerosene, gas oil, etc. In at the beginning of the operation, and to recycle maily cases it...is desirable to produce from kero hydrogen within the process in order to be Sene a highly aromatic product useful as a 5 assured of a sufficient hydrogen atmosphere in solvent, and the present invention is readily the reaction Zone. In Some cases the gas to be applicable for this purpose. The gasoline, kero recycled Will contain hydrogen Sulfide, introduced Sene, etc. fractions comprise a mixture of differ With the charge or liberated from the products, ent hydrocarbons and, in accordance with the in and it is Within the Scope of the present inven vention, the full boiling range fraction or any 20 tion to treat the hydrogen containing gas to Selected fraction thereof may be subjected to the remove hydrogen sulfide or other impurities be desired conversion. When a selected fraction is fore recycling the hydrogen within the process. SO treated, it may be blended, all or in part, with The process of the present invention may be the other fraction or fractions. effected in any Suitable equipment. A particular The catalyst of the present invention alay ly suitable process comprises the well known prove particularly useful for destructive hydro fixed bed System in which the catalyst is disposed genation or hydrocracking reactions in which in a reaction Zone and the hydrocarbons to be hydrocarbons and particularly oil heavier than treated are passed therethrough in either up gasoline is Subjected to conversion to produce Ward or downward foW. The products are frac lower boiling products and particularly gasoline. 30 tionated to Separate hydrogen and to recover For cracking reactions, it is prefered that the the desired products. As hereinbefore set forth, halogen content of the catalyst be within the the hydrogen may be recycled for further use in upper limits of the range hereinbefore set forth the process. Other suitable units in which the because these higher halogen- catalysts are more process may be effected include the fiuidized type active for effecting decomposition reactions. process in which the hydrocarbons and catalysts The catalyst of the present invention may also are maintained in a state of turbulence under be useful for effecting hydrogenation reactions hindered. Setting conditions in a reaction zone, including the hydrogenation of unsaturated the compact moving bed type in which the cata aliphatic hydrocarbons, such as mono-olefins, di lyst and hydrocarbons are passed either concur olefins, etc., to form the corresponding Saturated 40 reitly or countercurrently to each other, the hydrocarbons, hydrogenation of unsaturated Suspensoid-type of operation in which the catalyst cyclic hydrocarbons, hydrogenation of unsaturat is carried into the reaction Zone as a slurry in ed alcohols, ketones, acids, etc. Other reactions the hydrocarbon oil, and the fluidized fixed bed in which these catalysts may find utility in type of proceSS in which the reaction is effected clude oxidation as, for example, oxidation of in Substantially the same manner as described in olefins to form the corresponding oxide, such as the fluidized type process except that the catalyst the oxidation of ethylene to ethylene oxide, pro does not leave the reaction zone. pylene oxide, etc., oxidation of alcohols, ketones, The following example is introduced to fur etc. These and other oxidation reactions are ther illustrate the novelty and utility of the well known in the art, and it is within the scope ; present invention, but not with the intention of of the present invention to effect these reactions unduly limiting the same. in the presence of the novel catalysts. In re Eacample actions involving hydrogenation, oxidation or condensation, it is prefered that the halogen con 581 grams of annonium hydroxide diluted to tent of the catalyst be within the lower linits of 2000 ml. in Water were added to 724 grams of the ranges hereinbefore specified in order to aluminum chloride hexahydrate in 3000 m. of minimize side reactions. distilled Water. The resultant aluminum hydrox As hereinbefore set forth, selected processing ide was washed and filtered 6 times with Water conditions are required depending upon the pai containing a small amount of ammonium hydrox ticular reaction desired. For reforning of 60 ide and Was then washed and filtered With Water. straight run gasoline the temperature employed After the last wash, the aluminum hydroxide should be within the range of from about 600 Was slurried in sufficient water to make a thick to about 1000 i., the pressure within the range slurry. A separate solution of chloroplatinic of from about 50 to about 1000 pounds per square acid-hydrogen sulfide was formed and this co inch, and the weight hourly spaced velocity within loidal solution was added to the slurry of alu the range of from about 0.5 to about 10. For minum hydroxide in an amount to form a final dehydrogenation of normal butane the tempera catalyst containing 0.3% by weight of platinum. ture Should be within the range of from about The mixture was dried at a temperature of about 800° to about 1025 F., the pressure from about 340 F. for 9 hours, ground and calcined at a atmospheric to about 50 pounds per Square inch 70 temperature of 932 F. for 3 hours. Hydrogen and the gaseous hourly space velocity from about fluoride Solution was then added to the calcined 200 to about 5000. For hydrogenation reactions material in an amount to form a final catalyst the temperature may range from atmospheric containing 0.75% by weight of fluorine. The to about 500 F., the pressure from about Composite Was then dried on a Water bath, stero i00 to about 3000 pounds or more, and the weight 73 tex was added as a lubricant, the composite was 2,606,878 9 10 pilled, and the pills were calcined at a temperature and heating the resultant composite at a tem of 932 F. for a period of 3 hours to burn out the perature of from about 700° to about 1100° F. Sterotex and to calcine the catalyst. 4. A method of preparing a catalyst which com The catalyst prepared in the above manner was prises precipitating alumina, from aluminum used for the reforming of a Mid-Continent naph 5 chloride, commingling a chloroplatinic acid-hy tha, having an initial boiling point of 180° F., an drogen sulfide solution with the alumina in an end boiling point of 400 F. and an A. S. T. M. amount to form a final catalyst containing from motor method octane number of 35. The reform about 0.01% to about 1% by Weight of platinum, ing was effected at a catalyst temperature of about heating the composite at a temperature of from 850 F., a pressure of 500 pounds per square inch, 10 about 700° to about 1100 F., thereafter commin a space velocity of 2, and a hydrogen to hydro gling aqueous hydrogen fluoride with the alumina, carbon ratio of 3 to 1. The run was continued in an amount to form a final catalyst containing for 3 days, and the volume percent of reformed from about 0.1% to about 3% of fluorine by weight gaSoline for the 3 days averaged 93.1% and the of the alumina on a dry basis, and heating the A. S. T. M. motor method octane number for the resultant composite to a temperature of from 3 days averaged 78.5. The percent of aromatics about 700 to about 1100°F. in the reformed gasoline averaged about 44%. 5. A method of preparing a catalyst which com I claim as my invention: prises calcining precipitated alumina, at a tem 1. A method of manufacturing a catalyst which perature of from about 800° to about 1200° F., comprises commingling a Solution of a platinum 20 commingling a chloroplatinic acid-ammonium compound with alumina in an amount to form a hydroxide Solution with the calcined alumina, in final catalyst containing from about 0.01% to an amount to form a final catalyst containing about 10% by Weight of platinum, heating the from about 0.01% to about 1% by weight of plati resultant mixture at a temperature of from about num, thereafter commingling aqueous hydrogen 700 to about 1100°F., subsequently commingling 25 fluoride with the alumina, in an amount to form With the alumina, a halogen-containing Solution a final catalyst containing from about 0.1% to in an amount to combine from about 0.1% to about 3% of fluorine by Weight of the alumina about 8% by weight of halogen with the alumina, On a dry basis, and heating the resultant com on a dry basis, and calcining the resultant com posite at a temperature of from about 700° to posite at a temperature of from about 700° to 30 about 1100°F. about 1100 F. 6. A method of preparing a catalyst which com 2. A method of manufacturing a catalyst which prises commingling a chloroplatinic acid-hydro comprises commingling ammonium hydroxide and gen sulfide solution with precipitated alumina in a platinum-containing solution with calcined par an amount to form a final catalyst containing ticles of precipitated alumina, said solution being from about 0.01% to about 1% by weight of plati in an amount to form a final catalyst containing num, heating the composite at a temperature of from about 0.01% to about 10% by Weight of from about 700 to about 1100°F., thereafter com platinum, Subsequently commingling with the mingling aqueous hydrogen fluoride with the alu alumina, a halogen-containing Solution in an mina in an amount to form a final catalyst con amount to combine from about 0.1% to about 8% 40 taining from about 0.1% to about 3% of fluorine by weight of halogen with the alumina, on a dry by weight of the alumina on a dry basis, and basis, and calcining the resultant composite at a heating the resultant composite to a temperature temperature of from about 700° to about 1100° F. of from about 700° to about 100° F. 3. A method of preparing a catalyst which com VLADIMIR HAENSEL. prises precipitating alumina from aluminum 45 chloride, calcining the alumina at a temperature of from about 800 to about 1200°F, commingling REFERENCES CITED a chloroplatinic acid-ammonium hydroxide solu The following references are of record in the tion with the calcined alumina in an amount to file of this patent: form a final catalyst containing from about 0.01% 50 UNITED STATES PATENTS to about 1% by Weight of platinum, thereafter Number Name Date commingling aqueous hydrogen fluoride with the 2,005,412 Connolly et al. ------June 18, 1945 alumina in an amount to form a final catalyst 2,479,109 Haensel ------Aug. 16, 1949 containing from about 0.1% to about 3% of fluo 2,479,110 Haensel ------Aug. 16, 1949 rine by weight of the alumina on a dry basis, 55