US2842591A - Process of treating sugar beet molasses to recover barium saccharate and glutamic acid - Google Patents

Description

James L. Shelton, San Jose, Calif., assignor to International Minerals & Chemical Corporation, a corporation of New York No Drawing. Application November 15, 1955 Serial No. 547,039

Claims. (Cl. 260-527) This invention relates to the processing of sugar beet molasses, and more particularly, to the removal of sugar values from sugar beet molasses in such a manner that the nitrogenous volues contained in the molasses are preserved.

Precipitation of sugar values in sugar beet molasses as barium saccharate, acidulation of the barium saccharate to free the sugar and recover the same by crystallization is a well known commercial process. The conditions of precipitation, the weight ratio of barium oxide to sugar contained in the molasses, the temperature of the molasses during precipitation and the processing of the waste Water are usually all adjusted and designed to recover the highest possible economic yield of crystal sugar per unit weight of molasses treated. Nitrogenous values originally contained in the beet molasses are recovered by subsequently hydrolyzing the barium process filtrate to convert the glutamine and/ or pyrrolidone-carboxylic acid content to glutamic acid. Hydrolysis is accomplished either through the use of strong alkalis, such as caustic soda, or strong acids, such as hydrochloric acid. Glutamic acid may be crystallized from the hydrolyzate at its isoelectric point.

It is an object of the present invention to provide a process for recovering sugar values from sugar beet molasses while simultaneously hydrolyzing substantially all glutamic acid values present so that no additional hydrolysis is necessary subsequent to removal of sugar from the molasses.

It is a further object of the invention to employ barium oxide or its hydrate, barium hydroxide, in a dual role, namely, as a precipitant for the sugar values and as the hydrolyzing agent for the nitrogenous values contained in the beet molasses.

Another object of this invention is to provide a process for recovering sugar from sugar beet molasses while simultaneously substantially completely converting glutamic acid precursors to glutamic acid in a manner to avoid destruction of glutamic acid values and to afford emcient recovery of barium for reuse.

in accordance with this invention, sugar beet molasses is treated with a barium oxide compound, that is, barium oxide or barium hydroxide, in an aqueous medium at a temperature of at least 50 C. until reaction between the barium and sugar and hydrolysis of glutamic acid precursor compounds are substantially complete. Barium oxide or the barium oxide equivalent of barium hydroxide must be present in. an amount of at least 60% of-the weight of the sugar in the molasses. Glutamic acid may be recovered from the hydrolyzate by conventional means following separation of the barium saccharate formed. Barium saccharate may be recovered from the reaction mixture by any convenient means as by filtration, and treated according to conventional procedures to recover the sugar and the barium. Conveniently, the barium saccharate cake is slurried in water and the slurry carbonated'by passing carbon dioxide through the slurry nited States Patent "ice until substantially all barium is in the form of barium carbonate. The latter is insoluble and may be filtered from the reaction mixture. Mother liquor remaining which contains dissolved sugar may be treated to crystallize the sugar therefrom. Barium carbonate thus recovered may be calcined to produce barium oxide and the latter used for treating a fresh quantity of molasses.

Sugar beet molasses ordinarily has a solids content of the order of between about 83% and about 87% by weight. In accordance with this invention, it is desirable that the molasses be diluted with water or an aqueous solution containing barium oxide to produce a more workable consistency and to insure intimate contact with the barium oxide compound to be added.- The molasses, therefore, is admixed with sufiicient water to reduce its solids content to less than about 70% by Weight. In general, it is impractical to reduce the solids content of the molasses to below about 40% by weight due to handling difiiculties and the expense of later removing the excess water.

Barium oxide or barium hydroxide is utilized in this invention in an amount equivalent to at least about 60% by weight barium oxide based on the weight of sugar in the molasses. Preferably, the barium oxide compound is present in an amount equivalent to between about 65% and about 85% barium oxide based on the weight of sugar in molasses, this quantity of barium oxide compound permitting completion of the reaction in shorter periods of time and at lower temperatures. More than 85% barium oxide may be used, but there is little, if any,

advantage in doing so.

Addition of the barium oxide compound to the dilute molasses is desirably effected by slurrying the barium oxide compound in sufficient water to facilitate handling and to insure intimate contact of the barium oxide compound with the sugar in the molasses. While solid barium oxide or barium hydroxide may be utilized, there is difficulty in obtaining intimate contact between the solid barium oxide compound and the molasses under these conditions and this method is less desirable. Preferably, the barium oxide compound will be admixed with between about two and about four times its weight of water and the resulting slurry added to the dilute molasses. Excessive Water is undesirable because the excess will ultimately have to be removed, thereby adding to' the cost of the overall process. For convenience and ease of handling it is desirable to maintain the barium oxide slurry at a temperature of at least 65 C.

The term barium oxide compound as used in the specification and claims refers to barium oxide or barium hydroxide. All reference to quantities or percentages of barium oxide compound refer to barium oxide itself or the barium oxide equivalent of barium hydroxide.

The process of this invention is carried out at a temperature above about 50 C., and preferably, at a temperature between about 60 C. and about 85 C. Temperatures below about 50 C. are avoided as resulting in such slow hydrolysis rates of glutamic acid precursor compounds as to be impractical. Best reaction rates are Obtained at temperatures between about 60 C. and about 85 C. By operating within this preferred range, substantially complete hydrolysis of the glutamic acid precursor compounds and substantially complete precipitation of the sugar content of the molasses may be obtained in a relatively short period of time, this is, within a few hours, if the quantity of reagents and other reaction conditions are properly correlated.

Correlation of amounts of reagents and reaction conditions must be effected if the most efficient recovery of sugar and glutamic acid values is to be obtained. However, any of the variables may be varied over a fairly J) wide range. Utilizing'a barium oxide compound in an amount of about 80% of the weight of the sugar in molasses and maintaining a temperature of 80 C. substantially complete precipitation of sugar and substantially complete hydrolysis of glutamic acid precursor compounds may be obtained in about two hours. Utilizing lower tempratures and the same amount of barium oxide compound, substantially the same results may be obtained in longer reaction time. Similar results may be obtained by utilizing barium oxide compound at the 60% level and utilizing a lower temperature, say about 70 C. for a longer holding time. Ordinarily the reaction between barium oxide and sugar and the simultaneous hydrolysis of glutamic acid precursor compounds to glutamic acid is substantially complete in between about one-half hour and about five hours. The reaction is preferably continued for between about one hour and about three hours.

Barium saccharate produced by reaction of the barium oxide compound and sugar present in the molasses is removed from the reaction product mixture by any convenient means, for example by filtration. Barium saccharate cake is preferably washed with a dilute barium oxide or barium hydroxide solution to remove any residual liquor from the cake. The wash solution preferably contains between about 1% and about 3% barium oxide, by weight, and more preferably about 2% barium oxide, by weight. Wash solution recovered from the washing of the barium saccharate cake is, in accordance with a preferred embodiment of this invention, used to dilute fresh molasses and replaces fresh water for this purpose. Dilution of fresh molasses with this wash solution also permits a savings in barium oxide and increases recoveries of glutamic acid values under certain conditions. For example, with a one-half hour reaction time at 80 C. and utilizing 60% barium oxide based on the weight of sugar, highest recoveries of glutamic acid values are obtained by recycling 83% of the barium saccharate wash solution, and at 50 C. under the same conditions, best recoveries are obtained using 100% recycle of wash solution.

Optionally, barium saccharate wash solution may b mixed with any amount of fresh water prior to dilution of molasses but preferably about 83% of the wash solution will be recycled and utilized for diluting fresh molasses. The most complete hydrolysis of glutamic acid values is obtained by reacting a molasses diluted being fresh water), and reacted with about 80% barium oxide based on the sugar for about two hours at about 80 C. For the optimum recoveries of both sugar and glutamic acid in accordance with the invention, a dilute molasses is reacted with about 70% barium oxide based on the sugar in the molasses at about 65 C. for about one hour, the molasses having been diluted with a solution consisting of about 83% of a barium saccharate wash solution obtained in a prior run of the process. Under these conditions sugar precipitation is about 94% with a purity of 95% and glutamic acid value recovery is about 96%.

The mother liquor remaining following the removal of the barium saccharate precipitate is termed barium filtrate and contains substantially all of the glutamic acid values. Recovery of the glutamic acid from the barium filtrate in accordance with this invention involves first removing barium ions from the solution by treatment with sodium carbonate, or potassium carbonate, or by passing a carbon dioxide-containing gas through the filtrate until the pH is adjusted to between about 8 and about 10, preferably between about 8.5 and about 9.5. The addition of a small quantity of water-soluble alkali metal compound, such as sodium hydroxide, potassium hydroxide, sodium carbonate, potassium car onate or the like, to the filtrate prior to carbonation, that is between about 0.4% and about 3% water-soluble alkali metal compound based on the weight of filtrate, improves the carbonation reaction. In the presence of this small amount of alkali metal compound substantially more barium is precipitated as barium carbonate than is otherwise possible. Carbonation in the presence of sodium hydroxide is continued until the pH is adjusted to the above mentioned values. Barium carbonate, which precipitates during the carbonation reaction, may be removed by any convenient means, for example by filtration. The filtrate remaining following the removal of barium carbonate contains substantially all of the glutamic acid values. In order to recover the glutamic acid from the solution, it is concentrated to at least about solids and preferably to about solids. Following concentration, the filtrate is next treated in a manner depending upon whether glutamic acid is to be recovered immediately or whether the concentrated filtrate is to be stored prior to recovery. Storing the concentrated filtrate without further treatment results in the destruction of substantial quantities of glutamic acid present. However, concentrated filtrate may be stored for long periods of time without loss of glutamic acid if the pH of the concentrated filtrate is first adjusted to between about pH 6 and about pH 8, preferably to about pH 7. Adjustment of the pH may be made by the addition of a suitable inorganic acid, such as hydrochloric acid.

If the concentrated filtrate is to be processed immediately for the recovery of glutamic acid therefrom, an inorganic acid, such as hydrochloric acid, is added to adjust the pH to between about 5 and about 6, preferably to about pH 5.4. The adjusted filtrate is then further concentrated with the result that inorganic salts precipitate. Following removal of the precipitate the mother liquor is adjusted to about pH 3.2 by the further addition of hydrochloric acid, and glutamic acid is crystallized from the adjusted solution in accordance with conventional procedures.

The following examples represent specific embodiments of the invention. All parts and percentages are by weight unless otherwise indicated.

Example I Beet molasses having a solids content of about 85% and containing about 100 parts of sugar was diluted with fresh water in an amount equal to of the weight of the molasses and the mixture heated to C. To the heated mixture was added 80 parts of barium oxide in the form of a suspension in 236 parts of water at 80 C. The admixture was maintained at 80 C. for about two hours and then filtered to remove the barium saccharate which had formed. In order to remove entrained liquor from the barium saccharate cake, the latter was washed with about 300 pounds of an aqueous barium oxide solution containing about 2% barium oxide at a temperature of 80 C. One hundred seventy pounds of dried barium saccharate cake was obtained, this quantity corresponding to 96.9% of the sugar in the molasses. Analysis of the mother liquor remaining following removal of the barium saccharate cake showed that 98.2% of the glutamic acid precursor compounds present in the molasses had been hydrolyzed to glutamic acid.

Sodium carbonate in an amount of about .5 by weight was added to the glutamic acid-containing mother liquor and carbon dioxide gas was passed through the mother liquor until the pH amounted to about 8.6. During the carbonation reaction barium carbonate precipitated. Following removal of the precipitate by filtration, the barium carbonate cake was washed with hot water and freed of mother liquor. Filtrate and wash water were concentrated to about 60% dry solids and adjusted to about pH 7.0 by the addition of sulficient hydrochloric acid. The adjusted filtrate was stored for 349 days and then analyzed for glutamic acid. It was found that the glutamic acid content of the filtrate was substantially unaffected during the storage.

Following the procedure above, but omitting adjustment of the filtrate obtained following removal of barium carbonate precipitate and concentration, the unadjusted filtrate which had a pH of about 8.6 was stored for 349 days and then analyzed for glutamic acid. It was found that during the storage period the glutamic acid content of the filtrate had been diminished by 14%,

Glutamic acid was recovered from both of the above filtrates in accordance with the conventional procedures by adjusting the pH of the filtrates to about 3.2 with hydrochloric acid and crystallizing glutamic acid from the solution.

Example 11 Beet molasses having a solids content of about 85 and containing 100 parts of sugar was diluted with about 150 parts of wash solution from a previous barium saccharate filtration. About 150 parts of wash solution containing about 2% barium oxide by weight was utilized. After heating the diluted molasses to 80% C. a slurry of barium oxide in 150 parts of additional wash solution from the previous filtration was added, the slurry containing 73 parts of fresh barium oxide and 5.8 parts of barium oxide already in the wash liquors. The total barium oxide added amounted to 80% of the sugar in the molasses plus recycled wash solution. After holding the mixture at 80% C. for two hours, it was filtered and the barium saccharate cake washed with 300 parts of a barium oxide solution at 80 C., the solution containing about 2% barium oxide by weight. Barium saccharate cake was obtained in an amount indicating that the precipitation of sugar was about 97% complete. Glutamic acid precursor compounds in the molasses were found to have been 98% hydrolyzed. Glutamic acid was recovered from the barium saccharate filtrate by passing carbon dioxide gas through the filtrate until the pH was adjusted to about 8.6, separating the barium carbonate precipitate by filtration, concentrating the filtrate to 60% solids, adjusting the pH of the concentrated liquor to about 5.4 by the addition of hydrochloric acid, concentrating again and separating inorganic salts from the concentrated liquor, adjusting the remaining liquor to pH 3.2 by the further addition of hydrochloric acid, and crystallizing glutamic acid from the adjusted liquor.

Example III Beet molasses containing about 100 parts of sugar was diluted with fresh water in an amount of about 75% of the weight of molasses and heated to 80 C. A 50% sodium hydroxide solution in the amount of 11 parts was added to the diluted molasses and then 70 parts of barium oxideslurried in 225 parts of water was added, the slurry having a temperature of 80 C. The admixture was maintained at 80 C. for two hours and then filtered to remove the barium saccharate solids. Following washing of the filter cake with 300 parts of a 2% barium oxide solution at 80 0., there was obtained 170 pounds of dry barium saccharate showing that sugar precipitation was 96.3% complete. Glutamic acid values in the barium saccharate filtrate andwash water amounted to 98.1% of those in the molasses. The glutamic acid values in the filtrate were recovered in the same manner as in Example H. The presence of sodium hydroxide during carbonation resulted in the precipitation of barium during the carbonation reaction in an amount of about 30% in excess of the amount of barium precipitated in Example II where there was no added'sodium hydroxide;

Having now fully described and illustrated the character of the instant invention, what is desired to be secured by Letters Patent is: I

l. A process which comprises treating sugar beet molasses with at least. about 60% by weight of barium oxide, based on the weight of sugar in the molasses, in an aqueous medium having a dry substance content between about 40 and about 70% by weight, exclusive of the barium oxide, at a temperature between about and about 85 C. for a period or" about one-half to about five hours, varying inversely with the temperature, whereby the sugar is precipitated as barium saccharate and the glutamic acid precursor compounds in said molasses are substantially completely hydrolyzed to glutamic acid, separating the precipitated barium saccharate, and recovering glutamic acid from the barium saccharate mother liquor.

2. A process as in claim 1 wherein said molasses is treated with between about and about 85% of barium oxide.

3. A process which comprises treating sugar beet molasses with at least about 60% by weight of barium oxide, based on the weight of sugar in the molasses, at a temperature between about 60 and about 85 C. for a period of about one-half to about five hours, varying inversely with the temperature, in an aqueous medium having a dry substance content between about 40 and about by weight, exclusive of the barium oxide and containing recycled barium saccharate cake wash liquor obtained in a subsequent step of the process, whereby the sugar is precipitated as barium saccharate and the glutarnic acid precursor compounds in said molasses are substantially completely hydrolyzed to glutamic acid, separating the barium saccharate precipitate from the reaction product mixture, washing said precipitate with a dilute aqueous barium oxide solution, recycling between about and about 100% of the resulting wash liquor to the treatment of additional molasses, and recovering glutamic acid from the barium saccharate mother liquor.

4. A process which comprises treating sugar beet molasses with at least about 60% by weight of barium oxide, based on the weight of sugar in the molasses, at a temperature between about 60 and about C. for a period of about one-half to about five hours, varying inversely with the temperature, in an aqueous medium having a dry substance content between about 40 and about 70% by weight, exclusive of the barium oxide, and containing recycled barium saccharate cake wash liquor obtained in a subsequent step of the process, whereby the sugar is precipitated as barium saccharate and the glutamic acid precursor compounds in said molasses are substantially completely hydrolyzed to glutamic acid, separating the barium saccharate precipitate from the reaction product mixture, washing said precipitate with a dilute aqueous barium oxide solution, recycling between about 80 and about of the resulting wash liquor to the treatment of additional molasses, adding between about 0.4 and about 3% of an alkali-metal hydroxide to the barium saccharate mother liquor, passing a carbon dioxide-containing gas through said mother liquor until the pH is lowered to between about 8 and about 10, whereby barium is precipitated substantially completely therefrom, separating the precipitate of barium carbonate, and recovering glutamic acid from the barium carbonate mother liquor.

5. A process which comprises treating sugar beet molasses with at least about 60% by weight of barium oxide, based on the weight of sugar in the molasses, at a temperature between about 60 and about 85 C. for a period of about one-half to about five hours, varying inversely with the temperature, in an aqueous medium having a dry substance content between about 40 and about 70% by weight, exclusive of the barium oxide,

and containing recycled barium saccharate cake wash liquor obtained in a subsequent step of the process, whereby the sugar is precipitated as barium saccharate and the glutamic acid precursor compounds in said molasses are substantially completely hydrolyzed to glutamic acid, separating the barium saccharate precipitate from the reaction product mixture, washing said precipitate with a dilute aqueous barium oxide solution, recycling between about 80 and about 100% of the resulting wash liquor to the treatment of additional molasses, adding between about 0.4 and about 3% of an alkali-metal hydroxide to the barium saccharate mother liquor, passing a carbon dioxide-containing gas through said mother liquor until the pH is lowered to between about 8 and about 10, whereby barium is precipitated substantially completely therefrom, separating the precipitate of barium carbonate, and acidifying the barium carbonate mother liquor to about pH 7, whereby the glutamic acid values therein are rendered stable during prolongedastorage.

References Cited in the file of this patent UNITED STATES PATENTS 1,686,440 Dahlberg Oct. 2, 1928 .8 Royal Apr. 10, 1945 Bennett Dec. 26, 1950 OTHER REFERENCES Fort et al.: Aconitic Acid Content and Composition of Louisiana Blackstrap Molasses, 3 pages (reprinted from October 1952 issue of Sugar).

Kowkabany et al.: Agricultural and Food Chemistry, 10 vol. 1, No. l (1953), p. 84-7.

Montgomery et al.: Ind. and Eng. Chemistry, vol. 4-5 (1953), p. 1137..

Claims (1)

1. A PROCESS WHICH COMPRISES TREATING SUGAR BEET MOLASSES WITH AT LEAST ABOUT 60% BY WEIGHT OF BARIUM OXIDE, BASED ON THE WEIGHT OF SUGAR IN THE MOLASSES, IN AN AQUEOUS MEDIUM HAVING A DRY SUBSTANCE CONTENT-BETWEEN ABOUT 40 AND ABOUT 70% BY WEIGHT, EXCLUSIVE OF THE BARIUM OXIDE, AT A TEMPERATURE BETWEEN ABOUT 60 AND ABOUT 85*C. FOR A PERIOD OF ABOUT ONE-HALF TO ABOUT FIVE HOURS, VARYING INVERSELY WITH THE TEMPERATURE, WHEREBY THE SUGAR IS PRECIPITATED AS BARIUM SACCHARATE AND THE GLUTAMIC ACID PRECURSOR COMPOUNDS IN SAID MOLASSES ARE SUBSTANTIALLY COMPLETELY HYDROLYZED TO GLUTAMIC ACID, SEPARATING THE PRECIPITATED BARIUM SACCHARATE, AND RECOVERING GLUTAMIC ACID FROM THE BARIUM SACCHARATE MOTHER LIQUOR.