Patented May 18, 1948 244,602

UNITED STATES PATENT OFFICE 2441,602 RECOVERY OF PRODUCTS FROM PENTA ERYTHRTOL PROCESS WASTELIQUORS John E. Snow, Hasbrouck Heights, Robert H. Barth, Ridgewood, and Ralph J. Boesel, Gar field, N.J., assignors to Heyden Chemical Cor poration, New York, N. Y., a corporation of Delaware No Drawing. Application November 23, 1943, Serial No. 584 9 Claims. (C. 260-637) 2 This invention involves a new process for the to treat it further to obtain useful products. It recovery of useful products, such as pentaeryth is generally discarded as Waste material. ritol and by-products, from the waste or end It is an object of the present invention to pro liquors produced in processes for the preparation vide a process for the recovery of pentaerythritol of pentaerythritol and poly-pentaerythritols. and other products from the aforementioned type In the manufacture of pentaerythritol by the of syrupy end liquors from which major portions Condensation of acetaldehyde and formaldehyde, of the pentaerythritol and Substantially all the in addition to the pentaerythrito itself, smaller polypentaerythritols have theretofore been re announts of related hydroxylated substances are moved. Further objects and advantages of the also obtained. One of these, which is obtained in lo invention will be apparent to those skilled in the a considerable amount, is dipentaerythritol. An art to which the invention pertains. other related hydroxylated substance obtained in The process of the present invention involves Somewhat Smaller amounts, is white and crystal the discovery that substantially all the penta line, melts at 230-240° C., and has a hydroxyl erythritol can be recovered from such end liquors content of 33%. This substance, which is re 6 as follows: The end liquors are concentrated to ferred to as pleopentaerythritol, is probably a between 50 and 90 per cent solids content and mixture of dipentaerythritol, tripentaerythritol, mixed with from 1 to 6 parts of a water-Soluble and possibly additional related alcohols. aliphatic alcohol such as ethanol, isopropanol or Dipentaerythrito, tripentaerythritol and pleo n-propanol. The resulting mixture is heated to pentaerythritol may be grouped together under 20 about 75 to 90° C. and will contain the penta the generic term "polypentaerythritols,” by which erythritol and large amounts of Syrupy by-prod term is meant those compounds having higher lucts dissolved in the Water-soluble alcohol. The molecular Weights than pentaerythritol which alcohol will not dissolve very much of the alkali are formed either actually or theoretically by metal formate or alkaline-earth-metal formate. etherifying one or more of the hydroxyl groups 26. The formate salts are removed by filtering or set of pentaerythritol with other pentaerythritol ting in a separator of the salt-box type. Water residues. / is substantially removed from the aqueous alco In the process for producing pentaerythritol hol solution and the dissolved materials, namely, and pentaerythritol polymers, described in the pentaerythritol and a slight amount of alkali pending application Serial No. 484,478, filed April 30 metal or alkaline-earth-metal formate, are crys 24, 1943, by John P. Remensnyder, Philip I. Bow tallized out by chilling. man and Robert H. Barth, the main bulk of the The following is a more detailed, general de desired products are removed from the reaction Scription of the process. The reaction end liq liquor by concentration and crystallization. lors are concentrated by evaporation in vacuum However, about 10 per cent of the solid products as and mixed with a lower aliphatic alcohol such as present in the liquor, together with syrupy prod ethyl, isopropyl or n-propyl alcohols. This mix lucts and alkali formates, such as sodium for ture is refluxed to dissolve the polyhydric alco nate or potassium formate, or alkaline-earth hol, and filtered hot. The formate salt present formates Such as calcium formate, remain to be is insoluble in the alcoholic Solution and is filtered separated, the character of the formate depend to off. The pentaerythritol and syrupy by-products ing on the specific alkali used in the process. remain in solution. The resulting filtrate is then Processes in operation commercially for the dehydrated, either by distilling off the water and recovery of products from these end liquors aliphatic alcohol as a binary azeotrope or by the simply involve a concentration of these liquors use of benzene or toluene, which form ternary and fractional crystallization of the mixtures to 4s azeotropes with alcohols and water, in a suitable Separate the alkali formates or alkaline-earth apparatus. The anhydrous alcoholic solution that formates from the pentaerythritol. Several con remains is cooled for several hours and filtered. centration steps are necessary, and generally only The solid product which is thus removed is a mix about 4 to 5 per cent of the pentaerythritol (based ture of pentaerythritol and a small amount of On the pentaerythritol in the Original reaction so metal formate salt. The alcohol is removed from mixture, which is approximately 40 per cent of this dehydrated filtrate by distillation under re the pentaerythritol present in the end liquor) is duced pressure, and a light-Colored syrup re removed, together with 40 to 60 per cent of the mains. formate salts. The remaining liquor is verythick This syrup amounts to 2 to 10 per cent of the and syrupy, and it has heretofore been impossible 55 yield of pentaerythritol or polymers of penta 2,441,602 3 4. erythritol, and is water-soluble, possessing glycer parts of filtered liquor obtained from a penta ol-like properties. It is very useful as a glycerol erythritol charge made by using potassium hy substitute. droxide as a condensing agent were concentrated The following examples illustrate the scope of to 663 parts. Fifty (50) parts of this were mixed the process: as described in Example I, with 150 parts of iso Eacample I.-The mother liquor obtained from propanol, and from this were obtained 41.3 parts the crystallization of technical pentaerythritol is of 97.6% potassium formate. Twenty-five (25) processed as follows: parts of the above slurry were treated as in Ex Five hundred (500) parts of this filtrate were ample I, with 150 parts of isopropanol, and there concentrated in vacuum to 235 parts by renoval 10 was obtained from this 18.6 grams of potassium of water. To the resulting slurry 705 parts of formate which assayed 98.2%. isopropanol were added, and this mixture was Eacample VI.-Five hundred (500) parts o stirred, heated and refluxed for 25 minutes. The mother liquor obtained from the crystallization sodium formate, which was insoluble in the alco of mono, d, and tripentaerythritol, made accord holic solution, was filtered of hot and washed 5 ing to the process described in application Serial twice with 35 parts of fresh alcohol. The sodium No. 484,478, were concentrated under vacuum to formate (145 parts) was dried and assayed 98.4%. 231.6 parts and mixed with 694.8 parts of iso To the alcoholic filtrate, which contained the propanol containing 1.6% water, in the usual pentaerythritol, syrup and some sodium formate, way. The Solid sodium formate which separated were added 50 parts of benzene. The alcoholic 20 was removed and dried. It weighed 152.5 parts, solution was dehydrated by fractionation of the and was 99.2% pure. Ninety (90) per cent of ternary benzene-isopropanol-water azeotrope in the isopropanol was removed by boiling, which an apparatus which allowed the return of the removed 90% of the water present originally. benzene-isopropanol layer to the column while Approximately 21.6 parts of crude pentaerythri the water-isopropanolayer was drawn off. After tol containing 20.4% sodium formate crystalized dehydration and removal of the benzene were from the alcoholic residue at 10° C., which con complete, the anhydrous alcoholic solution of tained 4.6% water. The filtrate upon evaporation syrup, pentaerythritol and sodium formate was yielded 21.5 parts of syrup containing 6.3% so cooled to and maintained at 5' C. for 24 hours. dium formate. During this time the pentaerythritol and most of 30 Having thus described our invention, what we the sodium formate crystallized. This mixture claim as new and desire to secure by Letters Pat was filtered of and amounted to 23 parts (73.8% ent is: pentaerythritol). The alcoholic Solution was then 1. A process for the recovery of pentaerythritol evaporated in vacuum and the residual Syrup and other products from an end liquor which con (9.6 parts) remained in the still pot. 35 sists of a reaction liquor obtained from the con Eacample II-A similar quantity of pentaeryth densation of formaldehyde and acetaldehyde in ritol liquor was evaporated as described in Ex the presence of an alkaline condensing agent, ample I, and mixed with 705 parts of n-propanol. from which liquor the major proportions of pen This mixture was heated and refluxed for 30 taerythritol and polypentaerythritols have been minutes. The sodium formate (145 parts) was 40 removed but which liquor still contains water, filtered off and washed with fresh propanol. Fif metal formate, pentaerythritol and substantial ty (50) parts of benzene were added, and the proportions of Syrupy organic byproducts, which solution was dehydrated as described in Example comprises removing the major proportion of the I, except that a pressure of 500 mm. of mercury water from said end liquor by evaporation, there was used to keep the temperature below 70° C. 45 after diluting and heating the resulting dried On cooling, 18.8 parts of a mixture of 85% penta product with such a quantity of a water-soluble erythritol and 15% sodium formate was obtained monohydric alcohol selected from the group con after filtering and drying. Upon evaporation of sisting of ethanol, n-propanol and isopropanol. the filtrate 12.2 parts of syrup were obtained. that a substantial portion of the organic materials Eacample III-A similar quantity of penta 50 is dissolved and a substantial portion of the metal erythritol liquor as described in Example I was formate is not dissolved, separating the undis evaporated and mixed with 705 parts of n-propa solved metal formate from the hot solution by nol. The filtrate from the sodium formate filtra filtration, removing the major proportion of the tion was dehydrated by fractionation of the bi residual water from the resulting solution with a nary azeotrope Of n-propanol and water. This 55 portion of the alcohol by azeotropic distillation, was done under reduced pressure (500 mm. of and Subsequently allowing the solution to cool mercury) to keep the boiling point around 70° C. and removing the crystallized metal formate and and thereby prevent color-formation in the syr pentaerythritol therefrom. upy residue. After removal of the alcohol there 2. A process for the recovery of pentaerythritol was obtained 10.5 parts of residue after separa 60 and other products from an end liquor which con tion of 18.8 parts of 70% pentaerythritol by cool sists of a reaction liquor obtained from the con ing and filtration, densation of formaldehyde and acetaldehyde in Eacample IV-A similar quantity of pentaeryth the presence of an alkaline condensing agent, ritol liquor as described in Example I was evap from which liquor a portion of the metal formate Orated and mixed with 705 parts of ethanol. This 65 and the major proportions of pentaerythritol and was filtered after heating and refluxing 30 min polypentaerythritols have been removed but which utes, and yielded 141.2 parts of 98.9% sodium liquor still contains water, metal formate, penta formate. The filtrate was dehydrated as de erythritol and Substantial proportions of syrupy scribed in Example I, using the benzene-ethanol organic byproducts, which comprises removing Water ternary azeotrope. Upon cooling to and 70 the major proportion of the water from said end maintaining the mixture at 5 C., 18.2 parts of liquor by evaporation, thereafter diluting and 50% pentaerythritol were obtained, and after heating the resulting dried product with such a evaporation of the alcohol from the filtrate there quantity of a water-soluble monohydric alcohol were obtained 27.2 parts of syrupy residue. selected from the group consisting of ethanol, Eacample W.-Ten hundred sixty-three (1063) 75 n-propanol and isopropanol that a substantial 2,441,802 5 6 portion of the organic materials is dissolved and the major portions of pentaerythritol and polya a substantial portion of the metal formate is not pentaerythritols by crystallization, thereafter con dissolved, separating the undissolved metal for centrating the end liquor, which still contains mate from the hot solution by filtration, removing water, metal formate, pentaerythritol and sub the major proportion of the residual water from stantial proportions of syrupy organic byproducts, the resulting solution with a portion of the alcohol diluting and heating the resulting concentrated by azeotropic distillation, and subsequently allow end liquor with such a quantity of a water-soluble ing the solution to cool and removing the crystal alphatic alcohol selected from the group consist lized metal formate and pentaerythritol there ing of ethanol, n-propanol and isopropanoi that from. O a substantial portion of the organic materials is 3. A process for the recovery of pentaerythritol, dissolved and a substantial portion of the metal metal formate and other products from an end formate is not dissolved, separating the undise liquor obtained from the condensation of form solved metal formate from the solution, remov aldehyde and acetaldehyde in the presence of a ing the major portion of the residual water from metal hydroxide condensing agent, from which the resulting solution by azeotropic distillation liquor the major proportions of pentaerythritol with the alcohol, and subsequently allowing the and polypentaerythritois have been removed but solution to cool and removing the crystalized which liquor still contains water, metal formate, metal formate and pentaerythritol therefrom. pentaerythritol and substantial proportions of 7. A process for the recovery of pentaerythritol, syrupy organic byproducts, which comprises cons Sodium formate and other products from an end centrating said end liquor to a high solids content, liquor obtained from the condensation of form thereafter diluting and heating the resulting aldehyde and acetaldehyde in the presence of so concentrated product with from approximately 1 dium hydroxide, from which liquor the major pro to approximately 6 times its weight of a water portions of pentaerythritol and polypentaeryth soluble monohydric aliphatic alcohol selected 25 ritols have been removed but which liquor still from the group consisting of ethanol, n-propanol contains water, sodium formate, pentaerythritol and isopropanol, separating the undissolved metal and substantial proportions of syrupy organic by formate from the hot solution by filtration, there products, which comprises concentrating said end after removing the major portion of the residual liquor to a high solids content, thereafter dilut water from the resulting solution with a portion O ing and heating the resulting concentrated prod of the alcohol by azeotropic distillation, and Sub uct with from approximately 1 to approximately sequently allowing the Solution to COol and re 6 times its weight of isopropanol, separating the moving the crystallized metal formate and penta undissolved sodium formate from the hot solu erythritol therefron, tion by filtration, thereafter adding benzene and 4. A process as defined in claim 3 in which the 35 removing the major proportion of the residual major portion of the residual water is removed water from the resulting solution by distillation from the solution from which the undissolved as an isopropanol-Water-benzene ternary azeo metal formate has been separated by distillation trope, and Subsequently allowing the solution to of the water from the solution with a portion of cool and removing the crystallized sodium formate the alcohol as a ternary azeotropic mixture with 40 and pentaerythrito therefrom. an aromatic hydrocarbon Selected from the group 8. A process for the recovery of pentaerythrito, consisting of benzene and toluene, Sodium formate and other products from an end 5. A process for the recovery of pentaerythritol, liquor obtained from the condensation of form Sodium formate and other products from an end aldehyde and acetaldehyde in the presence of so liquor obtained from the condensation of form 45 dium hydroxide, from which liquor the major pro aldehyde and acetaldehyde in the presence of portions of pentaerythritol and polypentaeryth sodium hydroxide, from which liquor the major ritols have been removed but which liquor still proportions of pentaerythritol and polypenta contains water, sodium formate, pentaerythrito erythritols have been removed but which liquor and Substantial proportions of syrupy organic by still contains Water, sodium formate, pentaeryth 50 products, which comprises concentrating said end ritol and substantial proportions of Syrupy or liquor to a high solids content, thereafter diluting ganic byproducts, which comprises concentrating and heating the resulting concentrated product said end liquor to a high solids content, thereafter With from approximately 1 to approximately 6 diluting and heating the resulting Concentrated times its weight of n-propanol, separating the product with from approximately 1 to approxim 55 undissolved sodium formate from the hot solu mately 6 times its weight of a Water-soluble mono tion by filtration, thereafter adding benzene and hydric aliphatic alcohol selected from the group removing the major proportion of the residual consisting of ethanol, n-propanol and isopropanol, Water from the resulting solution by distillation separating the undissolved sodium formate from as an n-propanol-Water-benzene ternary azeo the hot solution by filtration, thereafter adding trope, and subsequently allowing the solution to an aromatic hydrocarbon selected from the group O cool and removing the crystallized sodium formate consisting of benzene and toluene, which forms and pentaerythritol therefrom. a ternary azeotropic mixture with the alcohol and 9. A process for the recovery of pentaerythritol, water, and removing the major proportion of the Sodium formate and other products from an end residual water from the resulting solution by dis 35 liquor obtained from the condensation of form tillation as such ternary azeotrope, and Subse aldehyde and acetaldehyde in the presence of so quently allowing the solution to cool and remov dium hydroxide, from which liquor the major pro ing the crystallized sodium formate and penta portions of pentaerythritol and polypentaeryth erythritol therefrom. ritols have been removed but which liquor still 6. In a process for the production of penta contains water, sodium formate, pentaerythritol erythritol by the condensation of formaldehyde O and substantial proportions of syrupy organic by and acetaldehyde in the presence of an alkaline products, which comprises concentrating said end condensing agent, the improvement in the process liquor to a high solids content, thereafter diluting of recovering the pentaerythritol which comprises and heating the resulting concentrated product concentrating the reaction mixture and removing 75 with from approximately 1 to approximately 6 2,441,802 8 times its weight of n-propanol, separating the REFERENCES C TED undissolved sodium formate from the hot solu The following references are of record in th tion by filtration, thereafter renoving the major file of this patent: proportion of the residual water from the result ing solution by distillation as a n-propanol-wa 5 UNITED STATES PATENTS ter binary azeotrope, and subsequently allowing Number Name Date the solution to cool and removing the crystallized 2,135,063 Walker et al. ------Nov. 1, 1938 sodium formate and pentaerythritol therefrom. 2,270,839 Wyler ------Jan. 20, 1942 2,360,186 Wyler ------Oct. 10, 1944 JOHN E. SNOW. OTHER REFERENCES ROBERTH.BARTH, Ebert, "Ber. der Deut. Chem. Gesell," vol. 64B, RALPH. J. BOESE, pages 14-119 (1931).