Patented Aug. 3, 1943 2,325,589

UNITED STATES2,325,589 PATENT OFFICE ACETALDEHYDE-FORMALDEHYDE con DENSATTION PRODUCT Edward A. Bried, Elsmere, Del, assignor to Her cules Powder Company, Wilmington, Del, a corporation of Delaware No Drawing. Application March 8, 1941, Serial No. 382,341 5 Claims. (C. 260-615) - This invention relates to a method of prepar ing pentaerythritol and dipentaerythritol and the concentration of dipentaerythritol is as more particularly to a method which yields a highway. as 35% to 46% is readily obtained in this higher proportion of dipentaerythritol than The process may be carried out by forming heretofore. an initial reaction mixture of acetaldehyde, It is known to prepare a mixture of penta formaldehyde, fixed alkali, and up to 15 mols erythritol and dipentaerythritol by the conden of free water per mol of acetaldehyde. This sation of acetaldehyde with formaldehyde in mixture is allowed to react by maintenance at the presence of a fixed alkali. See article of a temperature not above 25 C. for a substantial Friederich et, al., Ber. 63, 2681 (1930). HOW 0. period, say 24 hours, whereupon the reaction ever the proportion of dipentaerythritol in the mixture is treated to recover the pentaerythritol product has not been desirably high. Thus, in and dipentaerythritol therein. Where calcium Friederich et. al. the product contained as a hydroxide is used as the fixed alkali, this recov maximum 15% of dipentaerythritol and this fig ery may conveniently be effected by acidifying ure was for the product after purification with with less than the theoretical quantity of sul hot alcohol which increases the concentration 'furic acid and completing the neutralization of dipentaerythritol due to the preferential sol With Oxalic acid, filtering off the precipitated vent action of alcohol on pentaerythritol. calcium salts, and recovering the crude penta Therefore, the crude product of Friederich et al. erythritol-dipentaerythritol mixture high in contained a considerably lower percentage of di dipentaerythritol from the filtrate. This crude pentaerythritol. mixture may be resolved in any known manner Since dipentaerythritol has become commer into relatively pure pentaerythritol and dipen cially important because of the desirable prop taerythritol if desired. erties of its resinous esters, a method of improv The molar ratio of formaldehyde to acetalde ing the direct yield of dipentaerythritol in the 2 5 hyde employed may vary from 1 to 1 to 8 to 1. manufacture of pentaerythritol is desirable. It I prefer to use a 3 to 1 molar ratio because this is known that in the preparation of pentaery gives highest yields of product and highest per thritol Some dipentaerythritol is frequently also centages of dipentaerythritol in the product. produced. See, U. S. 2,186,272; 2,004,010; 2,206, The formaldehyde is conveniently employed 379; also Br. 440,891 which shows Washing and 30 in the form of the commercially available aque scouring the crude pentaerythritol product and . ous solution known as formalin which contains filtering to separate pentaerythritol from an im about 35% by weight of actual formaldehyde. purity alleged to be dipentaerythritol. How Since this solution presents three mols of water ever, the yield of dipentaerythritol is too low in per mol of actual formaldehyde, it cannot be the known processes. 35 used for formaldehyde-acetaldehyde mol ratios . It is the object of the present invention to above 5 to 1, without introducing more than 15 produce dipentaerythritol in high concentration mols of water per mol of acetaldehyde. Accord in admixture with pentaerythritol, without any ingly, in order to use mol ratios. of formaldehyde intermediate concentrating step to remove pen to acetaldehyde which are higher than 5 to 1, I. taerythritol from the mixture, in other words di 40 find it necessary either to use a more concen rectly. trated formaldehyde solution or to add the cal Another object is to provide a method where cium oxide to the reaction mixture which re by a higher yield of dipentaerythritol is ob duces the amount of free water by combining tained in the crude directly-obtained product. therewith. Either of these expedients or both Another object is to provide. a method which 45 may be resorted to in order to have present not enables positive control of the yield of dipen over 15 mols of water per mol of acetaldehyde, taerythritol. when using a formaldehyde-acetaldehyde ratio Still other objects will appear hereinafter. above 5 to 1. I have discovered that higher concentration Preferably, the initial reaction mixture con of dipentaerythritol in the crude directly-ob 50 tains as a minimum 9 mols of water per mol tained product may be had by carrying out the of acetaldehyde. Presence of less water than condensation of the formaldehyde with the acet this results in a diminished yield. aldehyde in the presence of a limited amount of As the fixed alkali I may use either the alkali water, namely not more than 15 mols of water metal hydroxides such as sodium, potassium or per mol of acetaldehyde. A product in which 55 lithium hydroxides, or the alkaline earth metal

4. 2 2,325,589 hydroxides Such as calcium, barium or strontium quantities with stirring while preventing the tem hydroxides. I prefer to use calcium hydroxide perature from rising above 20° C. The mixture which may be in the form of a paste or slurry was stirred for 24 hours and kept from rising formed by slaking calcium oxide with an excess above 20° C. throughout. It was then acidified of water. Preferably the fixed alkali is added 5 with less than the theoretical quantity of Sull gradually to the pre-mixed acetaldehyde and furic acid and the balance with oxalic acid. The formalin, with control of temperature so as to precipitate of calcium salts was removed by fil prevent its rising above 25 C. and preferably tration. The filtrate was then concentrated in above 20° C. vacuum and exhaustively worked for crystalline The amount of alkaliis preferably in the neigh 0 material in the usual way (as for example by the borhood of one-half mol per mol of acetaldehyde, method of Organic Synthesis, Vol. IV, page 53 though larger amounts may be used. (1925.) In a preferred embodiment, therefore, I use a The entire crystalline mixture of pentaerythri 3 to 1 formaldehyde-acetaldehyde molar ratio, tol and dipentaerythritol as thus obtained add no water other than that in the formalin amounted to 100 parts by weight and analyzed and a slight excess used to slake the calcium 36% dipentaerythritol. This figure was for the Oxide, keep the temperature from rising above directly obtained crystals without purification or 20° C. during the introduction of the calcium hy treatment in any manner, prior to analysis, which droxide and from rising about 25 C. during the would change the relative amounts of pen subsequent reaction, and use one-half mol of cal taerythritol and dipentaerythritol in the mixture. cium hydroxide per mol of acetaldehyde. . . A run in which all conditions were identical If desired, there may be present in the reac with Example 1 except that 53.8 mols of water tion mixture a Cannizzaro catalyst such as Raney per mol of acetaldehyde (conventional propor nickel as is disclosed in the copending application tions) instead of 14.3i mols were present gave of R. F. Cox, Serial No. 343,176, filed June 29, 124 parts by weight of a product analyzing only 1940. However, such a catalyst is preferably not 19.0% dipentaerythritol, used because its presence acts as an inhibitor for The use of a ratio of formaldehyde to acetalde formation of dipentaerythritol. hyde other than 3:1 gives a lower yield of product Below are given several specific examples illus and a lower proportion of dipentaerythritol in the trative of the invention. product. The following is an example of such In these examples the percentage of dipen use of a ratio of 4:1. taerythritol in the product was determined by Ecample 2 the dibenzal method as follows: Transfer about 1. g. of the product, dried two Relative molar amount, mols hours at 110. C., and accurately weighed, to a 3 5 Acetaldehyde ------125 ml. Erlenmeyer flask, and dissolve in 10 ml. Formaldehyde (actual) ------4. of water by heating. Cool and add 10 ml of Calcium hydroxide ------0.5 methanol, 3 ml. of benzaldehyde and 2 ml. of Water------12.2 Concentrated HCl. Stopper, shake well, and let The ingredients were reacted exactly as in Ex stand overnight. 40 ample 1. The directly-obtained product con Transfer the precipitated dibenzal of pent tained 21.5% of dipentaerythritol. The yield of aerythritol to a weighed glass filter crucible and product was 46.5% based on the acetaldehyde. filter by Suction. Then wash with 100 ml, , of a From the foregoing it will be seen that the 1:1 mixture of methanol and water in 5-10 ml. process of the present invention, by operating in portions, stirring the precipitate well with each 45 a concentrated aqueous solution, together with portion. Air dry the precipitate and then dry temperature control, and preferably also by using it in an oven at 110° C. for three hours. Cool and a 3:1 formaldehyde-acetaldehyde ratio, brings Weigh. The dried dibenzal should melt not lower about a surprisingly high yeld of dipentaerythri than 155 C. Calculation: Add 0.05 g. (the tol which is becoming increasingly important as amount of the dibenzal remaining in solution and 50 a raw material in the organic chemical field. lost in Washing) to the weight of the pen Moreover, by carrying out the reaction at a lower taerythritol dibenzal. Use this as the wt. of di temperature, I obtain a product of lighter color benzal in the following equation: and decrease the extent of purification required to obtain white crystals. Per cent dipentaerythritol 55 It will be understood that the details and ex Wt. of sample-(0.4359) (wt. of dibenzal) amples hereinbefore set forth are illustrative Wt. of sample X 100 only and that the invention as broadly described Eacample 1 and claimed is in no way limited thereby. What I claim and desire to protect by Letters Patent is: PSis Relative molar 60 1. A process of preparing pentaerythritol and weight amounts dipentaerythritol which consists in commingling 88 parts by weight of acetaldehyde and 514 parts Acetaldehyde (C.P.)------88 1 mol. by weight of about 35% by weight aqueous form Formalin (35% HCHO).------514 (SRES 65 aldehyde at a temperature not above 20° C., Calcium oxide saked in water------{ 2. ESE). slowly introducing a slurry of 74 parts by weight J Total free water present in reaction of calcium hydroxide in about 182 parts by mixture= 14.31 mols. weight of water while preventing the tempera ture from rising above 20° C., maintaining the The acetaldehyde and formalin were admixed 70 mixture at not above 20° C. for several hours, at a temperature of not over 20° C. The slurry acidifying the reaction mixture with less than of calcium hydroxide formed by slaking the cal the theoretical amount of sulfuric acid and com cium oxide in the 200 parts of water, and which pleting neutralization with oxalic acid, filtering, comprised 74 parts of calcium hydroxide and 182 and recovering pentaerythritol and dipentaery. parts of water, was then added slowly in small 75 thritol from the filtrate. 2,825,589 3 2. A process of preparing directly a mixture of dehyde in the molar ratio of about 3 mols of pentaerythritol and dipentaerythritol containing formaldehyde to each mol of acetaldehyde, in the a high concentration of dipentaerythritol which presence of about A mol of calcium hydroxide comprises condensing acetaldehyde with formal and from about 9 mols to about 15 molls of water dehyde in the molar ratio of about 3 mols of per mol of acetaldehyde, while maintaining the formaldehyde to each mol of acetaldehyde, in the reaction temperature at below about 25 C. presence of a fixed alkali and from about 9 mols 5. A process of preparing directly a mixture of to about 15 mols of water per mol of acetalde pentaerythritol and dipentaerythritol containing hyde, while maintaining the reaction tempera a high concentration of dipentaerythritol which ture at below about 25 C. O comprises commingling acetaldehyde with form 3. A process of preparing directly a mixture of aldehyde in the molar ratio of about 3 mols of pentaerythritol and dipentaerythritol containing formaldehyde to each mol of acetaldehyde at a a high concentration of dipentaerythritol which temperature not above about 25 C., then slowly Comprises condensing acetaldehyde with formal introducing about a mol of a fixed alkaliper mol dehyde in the molar ratio of about 3 mols of 5 of acetaldehyde, the amount of water present in formaldehyde to each mol of acetaldehyde, in the the reaction mixture being within the range of presence of about 4 mol of a fixed alkali and about 9 mols to about 15 mols per mol of acet from about 9 mols to about 15 mols of water per aldehyde, maintaining the reaction mixture at mol of acetaldehyde, while maintaining the reac below about 25 C. until substantially complete tion temperature at below about 25 C. 20 reaction is effected, acidifying the reaction mix 4. A process of preparing directly a mixture of ture and recovering a mixture of pentaerythritol pentaerythritol and dipentaerythritol containing and dipentaerythritol containing a high concen a high concentration of depentaerythritol which tration of dipentaerythritol. comprises condensing acetaldehyde with formal EDWARD A, BRED.