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Feb. 26, 1957 I 1. w. GROTE 2,783,124 METHOD OF MAKING DIHYDROXY ‘ALUMINUM CARBONATE COMPOUNDS‘ ' Filed Oct. 21, 19755 ‘ Ohn.O.inOnonn00»ON6'0d0-O-n0 . 2,783,124 States Patent 'icc Patented Feb. 26, 1957 2 present invention are preferably the aluminum alkoxides, such as aluminum isopropylate (tri-isopropoxide), but 2,783,124 other aluminum tri-alkoxides may be used in which the alkoxide groups are C2-C4 groups. These aluminum al METHOD OF MAKING DEHYDROXY ALUMINUM coholates are hydrolyzable in an alkaline aqueous medi~ CARBQNATE CDMPOUNDS um to form aluminum hydroxide or other aluminum lrvine W. Grote, Chattanooga, Tenn., assignor to The group containing at least two hydroxyl radicals, the other Chattanooga Medicine Company, Chattanooga, Tenn, valency of the aluminum being satis?ed by, possibly, an a corporation of Tennessee alkoxide radical. 10 The reaction involved in the case of the aluminum Application October 21, 1955, Serial No. 542,023 alcoholates is represented by the following equation: 11 Claims. (Cl. 23-14) (1) ‘ (ZHzO) . A1(OR)3 + M11003 ---> (H0)2A1o COzM+3ROH wherein R is a C2-C4 alkyl group and M is a monovalent This invention relates to a method of preparing di 15 radical of the class consisting of alkali metal and am hydroxy aluminum carbonate compounds, and more par monium radicals. It is probable, as before stated, that ticularly to a method of making dihydroxy aluminum the reaction involves an intermediate formation of di sodium, potassium, or ammonium carbonates. These are hydroxy aluminum alcoholate. This reaction is prefera true compounds having the generic structural formula bly carried out in the presence of equi-molar proportions hereinafter given. The compounds so obtained may be of the reactants, although the bicarbonate may be in used in forming lakes in dyeing processes. In particular, slight excess. The disadvantage of using any appreciable however, the dihydroxy aluminum sodium carbonate is excess of bicarbonate is that it tends to be absorbed or useful as an antacid, as more particularly described and occluded in the precipitate of the dihydroxy aluminum claimed in my copending application ?led of even date carbonate compound and must then be washed out in herewith. Serial No. 541,938, ?led October 21, 1955. 25 order to obtain the pure compound. Actually, only the It has heretofore been proposed, as in the Lowig Ger one reaction product, namely, the dihydroxy aluminum man Patent No. 19,784 of 1882, to prepare a carbonated alkali metal or ammonium carbonate, is formed, regard sodium aluminate or carbonated potassium aluminate by les of the excess of the bicarbonate used, thus con?rming the reaction between sodium aluminate and sodium bi the fact previously stated that this reaction leads to a carbonate or the corresponding potassium salts. Accord single true compound. The bicarbonate compound, ing to that patent, the reaction that takes place under being on the alkaline side itself, if present in at least equi the conditions speci?ed therein is exempli?ed by the fol molar proportions, maintains a ‘pH of at least 7, a condi lowing equation: tion that is favorable to the formation of the desired end product. 35 Another suitable source of the cationic aluminum The German patent explains that ‘the caustic alkali in _ group is aluminum hydroxide, itself, which is available an atmosphere charged with carbonic acid immediately in the form of a gel, dried or semi-dried, or compressed, is reconverted to bicarbonate and consequently is merely or in other water-reactive form. Any form of altuninum the carrier of the carbonic acid to the alkali aluminate. hydroxide can be used that is capable of providing the di The method of the present invention differs from that 40 or tri-hydroxy aluminum group in a reactive state when of the German patent in starting with an aluminum com dispersed in an aqueous medium at a pH of at least 7. pound in which the aluminum is cationic and in yielding The reaction between aluminum hydroxide and sodium a ?nal product that differs in structure from Lowig’s prod bicarbonate is shown by the following equation: not in respect to the location of the sodium atom. Fur thermore, the aluminum compound used as my starting 45 material is preferably a relatively water insoluble com The potassium and ammonium carbonates react in the pound capable upon hydrolysis in a basic medium of fur same manner as shown for sodium carbonate in-the above nishing aluminum groups containing at least 2 hydroxyl equation. Instead of starting with aluminum hydroxide, radicals, or of furnishing aluminum hydroxide,,Al(OI-l)3. it is possible, although not so satisfactory, to start with Aluminum alkoxides, or alcoholates, and aluminum hy 50 an aluminum acylate, such as aluminum acetate, basic droxide gels are examples of preferred starting materials aluminum acetate, aluminum aceto-tartrate, and the like, meeting these requirements. The other reactant is an or an inorganic aluminum salt, such as aluminum borate, alkali metal or ammonium bicarbonate. The reaction is bromate, bromide, chloride, and the like, and use such carried out in an aqueous medium under basic conditions an excess of the bicarbonate as not only to neutralize such that cationic aluminum groups associated with two 55 the acidic component of the aluminum compound select or more hydroxyl radicals are available for reaction with ed as the starting material but also to effect the formation the alkali metal or ammonium bicarbonate to give the of the intermediate di- or tri-hydroxy aluminum group desired end product, namely, a dihydroxy aluminum for further reaction with the bicarbonate to form the di alkali metal carbonate, or dihydroxy aluminum am hydroxy aluminum alkali metal or ammonium carbonate. monium carbonate. The principal objection to starting with the aluminum It is therefore an important object of this invention to acylates or inorganic aluminum salts is that a pure di provide a new method for the preparation of these di hydroxy aluminum alkali metal or ammonium carbonate hydroxy aluminum alkali metal or ammonium carbonate compound is more difficult to obtain. Furthermore, un compounds by reacting an aluminum compound of the less the conditions are such as to bring about the inter type referred to with the corresponding bicarbonate com 65 mediate formationv of the di- or tri-hydroxy aluminum pound, in the presence of water. ' group previously referred to, other water insoluble prod Other and further important objects of this invention ' ucts than the desired dihydroxy aluminum alkali metai will become apparent from the ‘following description and or ammonium carbonate are likely to be formed. It is appended claims. The drawing is a chart ‘of the speci?c therefore much simpler and greatly to be preferred to titration curve for dihydroxy aluminum sodium 70 start with an aluminum alcoholate or aluminum hy carbonate. - ‘ droxide as the source of the cationic aluminum group. The aluminum compounds used in the, method of my The aluminum compound and the bicarbonate that are 2,783,124 selected may be admixed dry and added to the water, corded with time. In this determination, the Fisher or they may be added separately, or they may be dissolved titrimeter was used with calomel and glass electrodes for separately and the solutions admixed. In reactions in pH determinations. The eye control was set using a volving the preferred starting materials, such as the alumi buffer solution of pH 3 made by mixing 0.1 molar citric num alcoholates and aluminum hydroxide, the bicar acid solution with 0.2 molar disodium phosphate solution bonate is preferably dissolved in water ?rst, and the in the proportion of 15.89 ml. to 4.11 ml. according to aluminum compound added to the resulting solution of Mcllvaines’ standard butler solution directions. The pH the bicarbonate. In reactions which are not extremely readings at 23 ° C. were as follows: fast or which require additional heat and/or agitation to proceed at a reasonable rate, there may not be too much 10 Time in minutes 1 l 2 1 advantage in having one or both of the reactants in solu tion before being brought into contact, since one of the 1.61 1.40 main advantages of putting the bicarbonate into solution 2.32 2. 00 3.10 2. 05 first is that this procedure tends to avoid precipitation of 3.30 3.12 the bicarbonate by occlusion or adsorption along with ................ .. 3.30 3 30 x30 the insoluble reaction product. In a preferred procedure, 3.30 3.51 the bicarbonate is dissolved in Water and the aluminum 3.30 3. 33 3. 30 32 alcoholate, in a. substantially pure form, is stirred there 3 30 :s. 31 into. A gelatinous precipitate forms very rapidly, but with time or continued stirring, is converted into a more 20 1 Specimens 1 and 2 were specimens 01' dihydroxy aluminum sodium granular and, therefore, a more easily ?ltered precipitate, carbonate prepared in accordance with the method of Example T, which may be readily separated from the aqueous rc It will be seen from the foregoing that under the condi inalnder ol‘ the reaction system. tions of the neutralization determination above set forth, The following examples show speci?c embodiments: the pH value rises to a pH of at least 3 within ?ve minutes 25 EXAMPLE I of the beginning of the test period and shortly thereafter reaches and stays at a pH of about 3.30 for the balance Sodium bicarbonate (168 gms, 2 moles) was dissolved of the thirty minute test period. in 1400 cc. of water in a 2 liter stainless steel beaker. Dihydroxy aluminum sodium carbonate, prepared as The solution temperature was adjusted to between 45 above described, is substantially amorphous, or at least and 50° C.