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April 7, 1942. D. J. OER E. A. 2,278,550 PREPARATION OF ALKALI METAL ALKOXIDES Filed June 21, 1939 REACTION ------ REGENERATION OFMX FROM M-represents an alkali metal N-represents a number from 2 to 3 R-represents an alkyl group X-represents the anion of a weak acid Donald D. Lee Donald J. Loder NVENTOR BY 232 az - ATTORNEY Patented Apr. 7, 1942 2,278,550 UNITED STATES PATENT OFFICE 2,278,550 PREPARATION OF ALKALI METAL ALKOXDES Donald J. Loder and Donald D. Lee, Wilmington, Del, assignors to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware Application June 21, 1939, Serial No. 280,308 16 Claims. (CI. 260-632) The invention relates to improvements in the and R is an alkyl, or aralkyl radical which may be manufacture of metal alkoxides and more particu Saturated, unsaturated, substituted or unsub larly to the preparation of alkali metal alkoxides stituted. by the interaction of alcohols with alkali metal In Reactions 1 and 2, an alkali metal salt of a salts of weak acids. weak acid is digested with an alcohol at an ap Alkali metal alkoxides have been prepared by propriate temperature, the digestion being Con. direct reaction of the alkali metal as such with tinued until equilibrium has been substantially an alcohol. or by action of an alkali metal hy reached. The equilibrium mixture is filtered for. droxide. upon an alcohol. The higher cost of the the separation of any undissolved (MX or M3X) first of these methods has limited somewhat the O salt and the resulting solution (or filtrate) is industrial use of the alkoxide thus prepared and found to contain an alkali metal alkoxide, or much effort has been expended in endeavors to aralkoxide, (MOR) hereinafter called 'al make the second more commercially practicable. koxides,' as well as small amounts of the In spite of a number of improvements, the latter (M2X and M3X) salts which have not reacted and process has not been given full commercial ac 5 traces of the corresponding alkali metal acid ceptance due to problems resulting from the in salts (MHX and MaHX). Substantially all of complete character of the reaction. the (M2X, MaX, MHX, and MgHOK) salts can be An object of the present invention is to provide precipitated from the solution by concentra improved processes for the preparation of alkali tion, which may be effected by simple distillation metal alkoxides, which processes have eliminated of a portion of the alcohol present therein. many of the difficulties inherent in the processes Specific examples of Reactions 1 and 2 for the known prior to the invention. Another object preparation of potassium methoxide, sodium is to provide a process for the preparation of the methoxide and sodium glycolyloxide proceed in alkali metal alkoxides by the reaction of an al accord with the following equations: kali metal salt of a weak acid with an alcohol. Yet another object is to provide a process for the 25 1a. KaCO3--CH3OH=KOCH3--KHCO3 preparation of alkali metal alkoxides by the 1b. NA2S--CH3OH=NaOCH3-NaHS interaction of alkali metal salts of weak acids 2a. Na3PO4--CH2OHCHOH= with alcohols, which reaction gives, together NaOCH2CH2OH.--NazHPO with the alkali metal alkoxides, a salt which is 30 The reactions described can be forced to the relatively insoluble in and readily separable from right, in accord with the known laws of mass the alcohol. Still another object is to provide a action, by removal of the alkali metal alkoxide process wherein alkali metal alkoxides are pre (MOR), or the acid salt (MHX or MaHX). By pared by interacting alkali metal salts of weak this means it is possible to obtain concentrations acids with alcohols, which reaction gives, together 35 of the “alkoxides' in excess of those resulting with the alkali metal alkoxide, a gaseous reac from equilibrium conditions such as are indi tion product. A further object is to provide a cated by the equations. This effect may, for ex process for the interaction of an alkali metal Salt ample, be realized by continuously extracting a of a weak acid with an alcohol in which the salt solid alkali metal salt with an alcohol at the ap is soluble and thereby producing the correspond 40 propriate temperature. The extract, containing ing alkali metal alkoxide. Other objects and ad the 'alkoxide,' alkali metal salt and alkali metal vantages of the invention will hereinafter ap acid salt, is concentrated by distilling of a por pear. tion of the alcohol whereupon the alkali metal The above and other objects may be realized acid salt precipitates and is removed by filtra by dissolving an alkali metal salt of a weak acid tion. (For continuous operation of the process in an alcohol until a saturated Solution is ob this precipitate may be returned to the extrac tained, and when equilibrium has been Substan , tion stage.) During the concentration step it tially established between the solid and liquid has been found that the Small amount of alkali phases and the reaction is substantially com metal acid salt present reacts with an equivalent plete, filtering the resulting mixture, separating 50 amount of the "alkoxides' to produce the normal from the filtrate the undissolved alkali metal salts alkali metal salt (Max or MX) and the alcohol, and recovering the alkali metal alkoxide from which reaction is the reverse of Reactions 1 and 2. the filtered solution. The reaction may be con The distilled alcohol may, if desired, be returned ducted in accord with the following equations: to the extraction stage. This cyclical process is 55 continued until the concentration of the 'al 1. Max+ROH=MOR--MHX koxides' in the extract has reached the desired 2. Mix--ROH=MOR+MHX figure, preferably the concentration of a solu M is an alkali metal ion, x-, x=, or x= (see tion Saturated at room temperature or a tempera equations below for use of X-) are the anions ture which is most suitable for handling the solu of weak acids which may or may not be volatil, 60 tion during subsequent operations, or the extract 2 2,278,550 may be distilled to completely remove the alcohol, excess of atmospheric ranging generally from 10 leaving the solid 'alkoxides.' The attached mm. mercury pressure to 5 atmospheres or more, drawing, in the form of a flow sheet, illustrates although the reaction is preferably conducted at the flow of materials with especial reference to a 1 atmosphere pressure. The temperatures of the continuous process. The alkali metal acid salt, 5 reactions are determined in large measure by which is filtered out may be reused as such, if the particular alkali metal salt and alcohol to desired, while in the case of the carbonates, the be reacted. Generally, however, it may be stated acid carbonate may be calcined to produce the that the following temperatures are best suited corresponding normal carbonate, water, and for the reactions designated: carbon dioxide. O The equilibria of Reactions 1 and 2 are shifted Temperature range Reaction Preferred by the removal of the salt formed from the zone o of the reaction. Another class of reactions cov 0-100C------------------------------------ ld 5-25 0-100'0------------------------------------ 1b. 65-70 ered by the present invention will now be dis 50-200 C. 20 00-150 cussed wherein the equilibrium is forced to the 100-200 C. 3y 170-200 right by the removal from the reaction mixture 100-200 C- - - - 4 - 190-210 of a gaseous product. These reactions may be 100-30°C. 45 20-125 designated by the following chemical formulas: 100-20 C---------------------------------- 5. 195-205 3. MX--ROH=MOR-HX f 20 Reactions 3a, 4a, 4b, and 5a are preferably car 4. MsCO-2ROH=2MOR--H2O --COa t ried out at the boiling point of the mixture, the M, X, and R have the same designations as they preferred temperature being from 0 to 10 C. have in Equations 1 and 2. above the normal boiling point of the particular In accord with the Equations 3 and 4 a solid alcohol used. alkali metal salt of a weak acid, which salt will 25 In addition to potassium carbonate, already hydrolyze to give a volatile acid, under reaction designated as suitable for Reaction la, lithium conditions, is mixed with an alcohol and heated carbonate (Li2CO3), rubidium carbonate to the boiling point of the mixture, whereupon (Rb2CO3), and caesium carbonate (Cs2CO3) may the acid, formed by the reaction of the salt with be employed, to prepare "alkoxides' by reaction the alcohol, distills of leaving unreacted alkali 30 of the salts with methanol, ethanol, propenol, metal salts and "alkoxides." In lieu of a salt ethylene glycol, propylene glycol, and benzyl al of a weak acid giving a volatile acid, a salt may cohol. be used which gives an acid that is substantially In Reaction lb, lithium sulfde (LiaS), potas insoluble in the reaction medium. When con sium sulfide (KS), rubidium sulfide (Rb28) and 35 caesium sulfide (Ce2S) may be used in lieu of ducted in this manner it is difficult to separate sodium sulfide and these sulfides may be reacted the acid formed from the metal alkoxide and, with the alcohols designated above for Reaction accordingly, this process is most useful when 1d. the mixture of metal alkoxide and acid can be In Reaction 2a, lithium phosphate (IPO), employed for catalyzing the same reaction or at potassium phosphate (KPO4), rubidium phos least for reactions in which the acid has no 40 phate (RbpO4) and caesium phosphate (CsPO4) undesirable effect. The solution is concentrated may be used as well as sodium phosphate to by distillation with simultaneous removal of part react with the glycols, or all of the alkali metal salt by filtration.