US1795166A - Process for the saccharification of wood - Google Patents

Description

Patented Mar. 3, 1931 UNITED STATES PATENT OFFICE EDUARD FARBER, GREGOIRE MINKOFF, AND THOMAS W. M. POND, OF GENEVA, SWIT- ZERLAND, ASSIGNORS TO THE INTERNATIONAL SUGAR AND ALCOHOL COMPANY LIMITED, OF LONDON, ENGLAND, A BRITISH COMPANY PROCESS FOR THE SACCHARIFICATION OF WOOD No Drawing. Application filed June 16, 1927, Serial No. 199,397, and in Germany July 7, 1926.

.ture with a highly concentrated mineral acid i. e. converted into soluble compounds, and these substances have been converted into sugar by heating them with a very dilute acid under pressure.

According to one known process saw dust was treated with an excess of, for example, 40% hydrochloric acid in the proportion of about 100 parts of wood to 700-1000 parts of hydrochloric acid. The treatment was effected in a battery of diffusers in which the saw dust remainedin contact with the highly concentrated hydrochloric acid until the saccharification was completed. Thereupon the wood sugar solution was separated from the insoluble residue by displacement with 40% hydrochloric acid.

In another known process hydrochloric acid gas was used in addition to the highly concentrated hydrochloric acid whereby the quantity of liquid hydrochloric acid employed was considerably reduced. The saw dust was saccharified by moistening 100 parts thereof with 70100 parts of 40% hydrochloric acid and then the mass was enriched with about 20 parts hydrochloric acid gas. By this method the saw dust was first intimately mixed with strong hydrochloric acid and some hydrochloric acid gas (first stage of the process). The saccharification of the moist mixture was eifected, preferably in thin layers, whilst the addition of the main quantity of hydrochloric acid gas was effected in a second stage, of the process when the saccharification had been completed; then, after driving off the main quantity of hydrochloric acid in a third stage, the resultant wood sugar was dissolved out.

By the present invention these known processes are improved in many respects. The use of 40% hydrochloric acid is retained to a certain extent and the process is carried out with less hydrochloric acid gas, with smaller apparatus and in two stages. This is rendered possible by combining the last portionof the saccharification with the separation of the sugar solution from the solid residue. The separation and washing are effected simultaneously by means of hydrochloric acid of which the concentration is less than that of the hydrochloric used originally, the amount thereof depending upon the manner in which the previous work was carried out.

Differently stated, according to the new process such quantities of primarily applied highly concentrated hydrochloric acid together with hydrochloric acid gas are employed as sufiice to chemically change only a portion of the cellulose present. The weaker hydrochloric acid subsequently applied dissolves and hydrolizes then only the remaining unchanged cellulose. The second step in the acid reaction has here quite another purpose than in known processes and accordingly the working conditions are also quite different. Also the weaker hydrochloric acid applied in the second step must still be a fairly concentrated hydrochloric acid (over 35%). Its reaction also takes place without the addition of heat or increase of pressure.

parts of saw dust and 40-00 parts of 40% hydrochloric acid and 15 parts of hydrochloric acid gas. With these proportions the wood mass n'ioistencd with the acid absorbs the hydrochloric acid gas from a stream of gas diluted with air so that the important advantage is obtained of being able to use'dilutod hydrogen chloride. After the wood acid mixture has absorbed the given quantity of hydrochloric acid gas it is conducted directly into a diffusion battery where without agitation it is allowed to stand for a time. By reason of the use of a small quantity of hydrochloric acid gas the saccharification cannot be completed freely. If now however fairly concentrated liquid hydrochloric acid acts thereon the breaking up is completed. This part of the saccharification is carried out as stated simultaneously with the removal of the sugar solution in the diffusion battery.

The more hydrochloric acid that is used in the first stage the more dilute may be the acids used at the conclusion in the diffusion battery.

111 the improved method of carrying out the diffusion operation, an increase in concentration of the acid last admitted takes place in the battery from the material rich in hydrochloric acid which is introduced into the diffusers so that the saccharification can be completed.

Method of emecution.0n 100 parts sawdust parts highly concentrated (i. e. 40%) hydrochloric acid and 15 parts hydrochloric acid gas are allowed to react. After some hours a third of the cellulose of the wood has entered into solution and split up into sugar. The portion of cellulose remaining in the wood is now completely converted into sugar by means of 38% hydrochloric acid, the latter serving at the same time to separate the sugar from the solid residue. The temperature may be between 15 and 25 C. Increased pressure need not be applied.

In comparison with the difiusion operation refered to in the introduction of this specification with wood which has not been previously treated and without the addition of hydrochloric acid gas, the present invention presents the advantage that a smaller diffusion battery serves for the same output or that with a battery of the same size a larger output may be obtained. As a portion of the actual saccharification takes place during the preliminary treatment a much shorter duration of diffusion battery treatment is now required; in fact according to the new. process 10-12 diffusers can'be'recharged and emptied within 24 hours whereas the output was previously limited to 4-6 diffusers. A further advantage is obtained from the economy in hydrochloric acid because, as has been stated above, it is possible besides 40% hydrochloric acid to'use also hydrochloric acid of lower concentration and diluted hydrochloric acid gas, which are both produced in the manufacture of 40% hydrochloric acid.

What we claim is 1. A process of converting wood into sugar consisting in first treating about 100 parts of sawdust with about 50 parts of 40% hydrochloric acid and about 15 parts of hydrochloric acid gas, and then completing the conversion by transferring to a diffusion battery, allowing to stand without agitation, then adding hydrochloric acid of about 38% con- Y centration, and simultaneously withdrawing the sugar solution.

2. A process of converting wood into sugar consisting in first treating about 100 parts of sawdust with about 50 parts of 40% hydrochloric acid and about 15 parts of hydrochloric acid gas, and at ordinary pressure, and then completing the conversion by transferring to a diffusion battery, allowing to stand without agitation, then adding hydrochloric acid of about 38% concentration, and simultaneously withdrawing the sugar solution.

3. A process of converting wood into sugar consisting in first treating about 100 parts of sawdust with about 50 parts of 40% hydrochloric acid and about 15 parts of hydrochloric acid gas, and at a temperature ranging between 15 C. and 25 (1, and then co1npleting the conversion by transferring to a diffusion battery, allowing to stand without agitation, then adding hydrochloric acid of about 38% concentration, and simultaneously withdrawing the sugar solution.

4. A process of converting wood into sugar consisting in first treating about 100 parts of sawdust with about 50 parts of 40% hydrochloric'acid and about 15 parts of hydrochloric acid gas, and at ordinary pressure and a temperature ranging between 15. C. and 25 0., and then completing the conversion by transferring to a diffusion battery, allowing to stand without agitation, then adding hydrochloric acid of about 38% concentration, and simultaneously withdrawing the sugar solution.

5. A process of converting wood into sugar consisting in first treating the wood with concentrated hydrochloric acid and hydrochloric acid gas in quantities insufficient to effect the complete conversion into sugar, and then transferring to a difiusion battery, allowing to stand without agitation, then completing the conversion by treatment with hydrochloric acid of concentration less than that of the first mentioned acid but over 35% concentration, and simultaneously withdrawing the sugar solution.

6. A process of converting wood into sugar, consisting in first treating the wood with hydrochloric acid of about 40% concentration and hydrochloric acid gas in quantities insufficient to effect the complete conversion into sugar,and then transferring to a diffusion battery, allowing to stand without agitation,then completing the conversion by treatment with hydrochloric acid of less than 40% concentration but greater than 35% concentration, and simultaneously withdrawing the sugar solution.

7. A process of converting wood into sugar, consisting in first treating the wood with hydrochloric acid of about 40% concentration and hydrochloric acid gas in quantities insufficient to effect the complete conversion into sugar, and then transferring to a diffusion battery, allowing to stand without agitation, then completing the conversion by treatment at ordinary pressure with. hydrochloric acid of less than 40% concentration but greater than 35% concentration, and simultaneouslv withdrawing the sugar solution. 0

8. A process of converting wood into sugar, consisting in first treating the wood with hydrochloric acid of about 40% concentration and hydrochloric acid gas in quantities insuificient to efiect the complete conversion into sugar, and then transferring to a diifusion battery, allowing to stand without agitation, then completing the conversion by treatment at a temperature ranging between 15 C. and 25 C. with hydrochloric acid of less than 40% concentration but greater than 35% concentration, and simultaneously withdrawing the sugar solution.

9. A process of converting wood into sugar, consisting in first treating the wood with hydrochloric acid of about 40% concentration and hydrochloric acid gas in quantities insufiicient to effect the complete conversion into sugar, and then transferring to a difli'usion battery, allowing to stand without agitation, then completing the conversion by treatment at ordmary pressure and a temperature ranging beteen 15 C. and 25 C. with hydrochloric acid of less than 40% concentration but greater than 35% concentration, and simultaneously withdrawing the sugar solution.

In testimony whereof we have signed our names to this specification.

EDUARD FARBER. GREGOIRE MINKOFF. THOMAS POND.