US1433654A - Process of recovering sucrose from solutions - Google Patents

Description

re atta STATES rarer reins;

ALEXANDER S. EAIVIAGE, 033 DETROIT, MICHIGAN, ASSIGNOR TO INTERNATIONAL COLOR & CHEMICAL COMPANY, INCORPORATED, F DETROIT, IJIICHIGAN, A. COR- PORATION OF NEW YORK.

PROCESS OF RECOVERING SUCBOSE FROM SOLUTIONS.

No Drawing.

To all whom it may concern Be it known that I, ALEXANDER RAM- AGE, a citizen of the United States, residing at Detroit, in the county of Wayne and State of Michigan, have invented certain new and,

useful Improvements in Processes of Recovering Sucrose from Solutions, of which the following is a specification.

This invention is a novel process for the separation and recovery of sucrose from impure solutions, and particularly from cane molasses, whether derived from the refining of raw sugar or directly from the cane syrups. According to the invention the su crose is precipitated as lead sucrate by direct reaction with lead hydroxid in excess, and the mixed precipitate thus obtained is treated in such manner as to yield on the one hand a sucrose solution wholly free from lead, and on the other hand a lead hydroxid suitable for use in a continuation of the process. The process is therefore essentially cyclical in character, in that the lead compounds are quantitatively regenerated.

As is well known cane molasses contains considerable proportions of reducing sugars commonly termed glucose. 1 have found that glucose cannot be quantitatively precipitated by lead oxid or hydroxid as lead glucosate, except at temperatures below about 5 C. At temperatures higher than this I find that the glucose is decomposed by lead hydroxid into soluble lead products, amounting at 20 C. to about 2030%, and at 100 C. practically all of the glucose disappears. The products formed also change according to the temperatureused. If the temperature has been kept below 60 the principal products appear to be lead salts ofsaccharic lactone and glucinic lactone, these salts decomposing rapidly upon standing to thecorresponding lead salts of saccharic and glucinic acids. These lead salts are largely precipitated on 1012 hou s standing.

At temperatures between 60100 C. the

principal products formed on standing are the lead salts of saccharic and lactic acids. If the precipitate produced by addition of the lead hydroxid to a glucose solutionis washed, and then carbonated at about 60 C., it is still further decomposed leaving insoluble lead salts of its oxidation products. The decomposition proceeds to such extent Application filed March 18, 1920. Serial Ito. 3%,939.

that usually only from 1020% of the original'glucose can be recovered in the solution after carbonation.

Furthermore the lead precipitate left from carbonation presents the peculiarity of forming in the filter presses a very firm caxe, contalning about 25% of water, which however upon rubbing quickly turns to a thin paste. On heating to 150 C. this product start-s to decompose, and at about 200 C. its lead content is reduced to finely divided spongy lead which catches fire in presence of air. The proportion of organic matter contained in this lead precipitate is approx mately 10-12%.

The molasses from refining raw sugars generally contains around 2024;% glucose and 1822% sucrose, together with some acid products derived from fermentation. The final molasses from sugar cane, when fresh, usually contains about 30-34% sucrose with 18-20% glucose. 1

JVhile my invention is not limited to the employment of any specific proportions of lead hydroxid, I find it to be good practice to use lead hydroxid in the proportion of approximately LS times by weight of the glucose present, plus 2.5 to 3 times the sucrose content. In addition allowance may also be made for any free acids which may be present.

Following is a specific illustration of my process, it being understood, however, that the invention is not limited to the employment of the precise proportions mentioned by way of illustration, or to the exact operating conditions hereinafter detailed.

2600 pounds of cane molasses containing about 20% of glucose and 22% of sucrose is diluted with 25% of water and thoroughly agitated with. a paste containing 2'700280O pounds of lead hydroxid (PbO l l The agitation is continued until the mass acquires a semi-solid consistence, after which it may be allowed to stand for a few hours in order to complete the reaction. This precipitation may be carried out at normal or higher temperates, up to about 70 C. At the conclusion of the reaction sufficient cold water is added to transform the mass into a pulp which is then pumped to the'filter presses.

where suiiicient milk of lime is added to render the solution. alkaline. and carbon dioxid is passed through, preferably at about 60 6., until all of the lead is precipitated. The resulting lead precipitate is filtered ofii and returned to the process, being preferably combined with the lead precipitate derived from the carbonation to be described below. The lead precipitate from the molasses, after thorough washing with cold water, consist-s essentially of lead sucrate, more or less lead glucosate according to the temperature of precipitation, some excess of lead hydroxid, and any precipitatablenonsugars. This suspended in a liquid bath, preferably a dilute syrup from a previous operation, and is carbonated therein, preferably at about (1, the passage of the carbon dioxid being continued just so long as the polarization of the liquid increases, that is to say, so long as sucrose and glucose continue to be set free. At the completion of this operation the precipitate filtered out, yielding a filtrate which consists essentially of a sucrose solution. containing some glucose, and containing also some soluble lead compounds of the oxidation products of glucose; and a precipitate which, as regards itsinetallic salt contents, is essentially a basic carbonate of lead, corresponding more or less closely according to the operating conditions to the formula 2PbCO PbO H together with insoluable lead compounds of sacchario and glucinic acids, and other insoluble organic compounds containing lead. The basic'carbonate under ordinary conditions may comprise some 60-'Z0% by weight of the dried precipitate.

The sucrosebearing solution obtained as above is agitated with sutlicient lime to pre cipitate the whole of its lead content, and is heated to about 70 C. for one-halt hour, then carbonated to faint alkalinity and filtered. The filtrate is then concentrated, and is preferably again limed and carbonated as is the practice in the treatment of best juice; and is carefully tested for lead. The lead-free solution may advantageously be treated at this point with animal charcoal or other decolorizing carbon, which would of course serve to remove any traces of lead which might escape the previous precipi tating step. From this solution the sucrose can be directly recovered inmerchantable form by the usual crystallization methods.

The lead bearing precipitate from the cal bonating step is re-conv'erted into the hydroxid for re-use 'inth'e process. This is preferably done as follows: w l

The basic carbonate from several batch operations asabove described is distributed. to a series of wooden tanks each provided the amount theoretically essee;c

with an agitator, each tank receiving ap proximately 3000 pounds dry weight of the precipitate. To the precipitate in the first tank l add an excess of caustic soda above required to convert the carbonate component into hydroxid. In practice l find it desirable to introduce the caustic soda in the form of a 510% solution, and in quantity equivalent to a 30-50% excess above the theoretical proportions above mentioned. The reaction proceeds more rapidly at temperaturesabove normal and in practical prefer to agitate the mass at a temperature of about 70-80 C. for a period ot' amiroximately one hour. At the end of this time-the solid contents of the tank con substantially or lead hydroxich and may be separated from the solution, washed, and utilized directly in a repetition of the molasses-treating step of the process, precisely as described above.

The solution (Dililfill'lS'EOCl'lUlll carbonate, to ether with "approximately 10% of the lead content of the first tank, in the form of sodium plumbite usually with some excess of uncombined caustic soda and the whole of the organic non-sugars. This solution is brought into presence of the basic carbonate in the second tank, and is agitatedtherewith in the cold. flhereby the sodium plumbite is devomp'osed. its lead content being precipitated in the term of lead hydroxid. Any excess of caustic soda contained in the solution;together with that liberated by the decomposition oi the plumbite, reacts upon the basic lead carbonate in the second tank I to convert the same into hydroxid. The solution resulting from this treatment should consist es e ntially of sodiun 'carbonate and organic substances, but as a matter of precaution, it may be introduced into presence oi? the basic carbonate, in the third tank in series, and 'tated therewith, in order to remove any traces of caustic soda or plumbite which" may be present; or the solution containingitrce alkali and lead may be carbonated it desired. thereby converting its lead and caustic alkali contents into basic lead carbonatefand sodium, carbonate respectively. This solution is then withdrawn, and may be causticized with lime in the usual manner, yielding caustic soda, which returns to. the cycle at the appropriate point, and .l-ime mud containing the organic matters. 1 I

The contents of the second tank, Which .by the above treatment have been partially convertedinto hydroxid, are then treated with caustic soda in excess precisely as above described with reterence to the contents of the first tank in series; and the resulting hydroXid used inthe sucrose precipitation. It will be understood of course that in computing the excess of caustic soda to be used in the treatment of the second tank, due all0wance must be made for the conversion of carbonate to hydroxid which has already occurred through the action of the mother liquor. It the liquor from the first tank has been carbonated instead of being utilized in the second tank, the resulting basic carbon.- ate of lead is at once filtered off and returned to the process, while the carbonate.

of soda containing the organic non-sugars is causticized with lime as above.

In carbonating the sucrate precipitate in order to set free the sucrose, it is desirable to avoid continuing the passage of the car bon dioxid after the polarization value of the liquid. has ceased to rise, since under these conditions organic matters other than sucrose which may have been carried down by the precipitated mass pass again into the sucrose solution. It is desirable that such organic matters should be retained by the precipitate at this stage since they are dissolved therefrom in the subsequent treatment with caustic soda, and pass ultimately into the lime mud resulting from the recausticizing step of the process.

All of the plant washings, whether from the treatment of beet or cane sugar products, should be examined for lead; and in case it is found to be present in material quantities, these washings should be subjected to carbonation preferably at about 70 6., to

separate the precipitate and recover the lead. The same caution applies also to the mother liquors from the lead sucrate precipitation.

I claim 1. A cyclical process of recovering sucrose from crude solutionsfthereof containing also glucose, comprising adding to such solutions lead hydroxid in sufficient excess to precipitate the sucrose together with nonsucrose substances; separating the precipitate from the mother liquor and liberating the sucrose content of the precipitate by limited carbonation; thereby forming a sucrose-bearingsolution containing soluble lead compounds and a residual precipitate containing non-sucrose substances; separat ing the sucrose-bearing solution from the residual precipitate and eliminating lead from thesucrose-bearing solution by means of lime; treating the residual precipitate containing non-sucrose substances with an alkali hydroxid in excess thereby dissolving nonsucrose material, and converting the bulk of the lead-content of the said precipitate into hydroxid; separating the resulting lead hydroxid from the alkaline solution containing non-sucrose material; and introduc bearing solution from the residual precipi tate and eliminating lead from the sucrosebearing solution by means of lime; treating the residual precipitate containing non-sucrose substances with an alkali hydroxid in excess, thereby disolving non-sucrose material. and converting the bulk of the lead-content of the said precipitate into hydroxid; separting the resulting lead .hydroxid from the alkaline solution containing non-sucrosematerial; introducing said lead hydroxid in excess into a further quantity of the crude sucrose-bearing solution in a succeeding cycleof the process; and recovering the excess of alkali hydroxid, together with its content of dissolved lead from the alkaline solution containing non..-sucrose material, by reacting thereon with an excess of the lead-bearing precipitate resulting from the carbonation.

In testimony whereof, I atfix my signature.

ALEXANDER S. RAMAGE.