US1819233A - Preparation of pentosans - Google Patents

Description

Patented Au 18, 1931 UNITED STATES PATENT OFFICE ELTON R. DARLING, OF DANVILLE, ILLINOIS, ASSIGNOR TO CORNSTALK PRODUCTS COMPANY, INC., OF NEW YORK, N. Y., A CORPORATION OF DELAWARE PREPARATION-OF PENTOSANS il'o Drawing. Application filed April 10,

The present invention relates to an im- )roved process producing highly purified )entosans of the xylan type.

One of the objects of the invention is to xtract from farm wastes, such as cornstalks, orncobs, etc., xylan type of pentosans in lighly purified form suitable for commerial utilization.

Another object of the invention is to treat he said farm wastes with bleaching agents .nd sodium hydroxide solutions alternately 11 order to remove therefrom lignins and aentosans other than of the xylan type, so hat 'the treated material can afterward be ubjected to suitable extraction methods to ecover the desirable purified xylans.

Other objects of the invention will apear from'the description and claims hereobelow.

It has been noticed that the pentosans obained from wood pulp by treatment thereof t high temperature and long digestive time ifi'er quite markedly in their properties rom pentosans obtained from the mild alali treatment of farm wastes and plants aving an annual growth such as bagasse, Jrghum stalks and the like. It appears that he high temperature employed in the treatient of wood for the manufacture of wood ulp depolymerizes the pentosans in the 'ood, yielding pentosans of lower molecular 'eight than those which are obtainable by iilder treatment from cornstalks, and the ke,

When the pentosans have a comparative igher molecular weight, their colloidal roperties are more strongly enhanced and ieir adhesiveness is much superior to that f the lower grade of depolymerized xylan btained from wood. It has also been found lat the. purer forms of pentosans, and parcularly xylan, when in pure condition, g ve etter yields of xylose and corresponding entoses on hydrolysis.

Predicating the research work on the bove considerations, the present invention ventuated.

It was found that cornstalks as well as )rncobs could be converted by a comparavely simple method into a raw material 1930. Serial No. 443,258.

yielding a large amount of pentosans of the xylan type of a purity sutficient for the commercial manufacture of xylose.

The process comprises in essence the treatment of corncobs and/or cornstalks in comminuted condition with bleaching agents and alkaline solutions alternately so as to remove selectively the lignin and some of the similar compounds therefrom whereby, on subsequent treatment with strong, cold' alkalies, a pure xylan can be extracted therefrom.

In order to practice the invention, the following procedure may be followed with satisfactory results, although it is to be understood that the exact proportions given are merely illustrative and not limiting.

Corncobs and/or cornstalks are ground or shredded, in any suitable grinding or shredding device, to a finely divided powder, say from to 80 mesh. This powder is then softened in hot water, which is. afterwards drained off and the still wet powder is placed in a solution of a hypochlorite of a strength equivalent substantially to 2% chlorine. The mixture of powdered material and hypochlorite solution is'agitated for about one hour, at the end of which time the material" appears somewhat lighter in color, while the solution has assumed a brown color, The material is then separated from the solution by filtration and washed to remove the residual hypochlorite, whereupon the material is suspended in a very .weak solution of sodium hydroxide containing a proximately 0.2% of sodium hydroxide 2 grams per liter of solution). This strength of sodium hydroxide solution is low enough to prevent any action whatever upon the pentosans contained in the product, whilst the removal of the chlorine compounds, formed from the hypochlorite and some of thelignin, is effected.

The length of time that the material is allowed to remain in contact with this dilute alkali is from 4 to 6 hours, the treatment being carried out at ordinary room temperature. The alkaline solution, at the end of this time, will be brown in color.

The suspended material is filtered from the alkaline solution and thoroughly washed when it assumes a light brown appearance. It is thereupon again suspended in water containing suflicient hypochlorite to be equivalent to 2% of chlorine and is allowed to remain suspended in the said solution for a period of one hour; this again yielding a brown solution, from which the material is filtered oil and washed, being thereafter again suspended in a sodium hydroxide solution of 0.2% strength as already stated.

Upon removal from the causticsoda solution, after contact therewith from 4 to 6 hours, the product will be still lighter in color. The material is then washed and suspended in water containing sufiicient hypochlorite to be equivalent to 1% of chlorine, contact being maintained for one hour and the product assuming a very light brown color. The material is then removed and once more is subjected to the dilute alkaline treatment. At this stage the alkaline solution is only faintly colored, while the product is almost white.

The product is removed from the alkaline solution, washed and again treated with 1% solution of chlorine in the form of hypochlorite; this treatment bringing the product to a final white. The resultant product is filtered from the solution of the hypo: chlorite, thoroughly washed, and then is subjected to extraction in the cold with a 5-6% sodium hydroxide solution. On maintaining the material in the cold sodium hydroxide solution for a few hours, the pentosans therein contained, and particularly the xylan, will dissolve in the sodium hydroxide to rorm sodium-xylan or sodium xylanate. The caustic soda solution of the xylan is filtered from the cellulosic debris and either acidified or treated with alcohol in order to precipitate the xylan, in the first case in the free state, and in the second case as a sodium-xylan complex.

The product obtained is a very superior form 0 xylan being very adhesive, readily hydrolyzed and forming a valuable colloid material for numerous purposes.

The process is simple and easy to carry out as no heat is required at any time, the reagents used are inexpensive, and but little care need be exercised in the operation of the process.

The essential features lie in the mild treatment with dilute hypochlorites and very dilute alkalies u'sed alternately, whereby the li eous components of the raw material are ractionated from the same without deleteriously aflecting the desired pentosans.

The invention can be carried out in any type of apparatus such as wooden tanks when the dilute solutions are employed, although enamelled steel equipment is preferable if the color of the product is a consideration.

The calcium hypochlorite described may, of course, be replaced by an equivalent quan tity of sodium hypochlorite, the choice of materials bein merely predicated upon thecobs which comprises subjecting the same, 1n

comminuted condition, to alternate treatments of dilute hypochlorite solutions and very dilute sodium hydroxide solution with intervening washing operations, whereby the ligneous component of the said raw material is selectively removed therefrom, and thereafter extracting the therein contained pentosans by means of a cold solution of sodium hydroxide conta' substantially 60 grams of sodium hydroxi e per liter.

2. The process of recovering substantially pure pentosans from cornstalks and/ or corncobs which comprises subjecting the same, in comminuted condition, to alternate treatments of dilute calcium hypochlorite solutions and very dilute sodiumhydroxide solution with intervening washing operations, whereby the ligneous component of the said raw material is selectively removed therefrom, and thereafter extracting the therein contained pentosans by means of a cold solution of sodium hydroxide containing sub- Tfantially 60 grams of sodium hydroxide per 'ter.

3. The process of recovering substantially pure pentosans from cornstalks and/ or corncobs which comprises subjecting the same, in comminuted condition, to alternate treatments with dilute calcium h hlorite solutions and 0.2% sodium hy oxide solutions with intervening washing operations, whereby the ligneous component of the said raw material is selectively removed therefrom,

' and thereafter extracting the therein contained pentosans by means of a cold solution of sodium hydroxide containing substan- {ially 60 grams of sodium hydroxide per iter.

4. The process of recovering substantially pure pentosans from cornstalks and/or corncobs which comprises subjecting the same, in comminuted condition, to alternate treatments of dilute calcium hypochlorite solutions of successively diminishing strength, and 0.2% sodium hydroxide solution, with intervening washing operations, whereby the ligneous component of the said raw material is selectively removed therefrom and thereafter extracting the therein-contained pentosans by means of a cold solution of sodium hydroxide containing substantially 60 grams of sodium hydroxide per liter.

' 5. In the process of recovering pentosans from corncob meal by alkaline extraction the step which comprises conditioning said meal by successive immersion into progressively more dilute solutions of hypochlorites alternated with dilute sodium hydroxide solutions so as to remove selectively ligneous and non-pentosan material other than cellulose.

6. The process as defined in claim 4 wherein the hypochlorite is calcium hypochlorite.

7. The process as defined in claim 4 wherein the sodium hydroxide used for conditionin contains substantially 2 grams of sodium ydroxide per liter. s

In witness whereof, I have hereunto subscribed my name.

ELTQN R. DARLING.