PROCESS FOR THE PRODUCTION OF FURFURAL

Abstract

The present invention refers to a method of producing furfural and optionally further basic chemicals from biomass material comprising treatment of the biomass material at elevated pressures and temperatures, to the condensates and solid product obtained by the method of the invention, as well as to their use.

Claims

1. A method of producing furfural, comprising the steps of: (i) providing biomass material in a reaction vessel, (ii) adjusting the pressure in the reaction vessel to an elevated pressure p.sub.1 and the temperature in the reaction vessel to an elevated temperature T.sub.1, (iii) maintaining the pressure p.sub.1 and/or the temperature T.sub.1 for a predetermined time span t.sub.1, (iv) adjusting the pressure in the reaction vessel to an elevated pressure p.sub.2 and/or the temperature in the reaction vessel to an elevated temperature T.sub.2, (v) optionally maintaining the pressure p.sub.2 and/or the temperature T.sub.2 for a predetermined time span t.sub.2, (vi) opening the reaction vessel, and (vii) optionally separating solid products from the reaction mixture present in the reaction vessel, wherein the pressure p.sub.1 is higher than the pressure p.sub.2, and wherein a furfural containing vapor stream is withdrawn during steps (iii), (iv), (v) and/or (vi) and collected in the form of condensates.

2. The method according to claim 1, wherein the biomass material derives from lignocellulosic material and/or algae.

3. The method according to claim 2, wherein the lignocellulosic material is wood, straw, sawdust, corn cobs, corn husks, corn stover, grass, cotton hulls, switchgrass, Arundo Donax, waste paper, sugar cane bagasse, sorghum, sorghum stalk residue, palm fruit bunches, or mixtures thereof.

4. The method according to claim 1, wherein the pressure p.sub.1 is >1 bar, such as in the range of from 2-50 bar, preferably from 10-30 bar, more preferably from 15-25 bar, most preferably from 19-21 bar.

5. The method according to claim 1, wherein the predetermined time span t.sub.1 is 0-1,800 s, preferably 1-1,800 s, preferably 1-1,000 s, more preferably 100-700 s and most preferably 500-700 s.

6. The method according to claim 1, wherein adjusting the pressure in the reaction vessel to p.sub.1 is performed with a rate of 1-15 bar/min, preferably 2-7 bar/min.

7. The method according to claim 1, wherein the temperature T.sub.1 ranges from 150° C. to 280° C., preferably from 180° C. to 230° C.

8. The method according to claim 1, wherein the temperature T.sub.2 ranges from 100° C. to 250° C., preferably from 150° C. to 200° C.

9. The method according to claim 1, wherein step (i) further comprises providing a catalyst in the reaction vessel.

10. The method according to claim 9, wherein the catalyst is selected from acidic compounds such as sulfuric acid, hydrochloric acid, phosphoric acid, organic acids such as acetic acid or formic acid, and mixtures thereof, and/or from halide salts such as metal chlorides.

11. The method according to claim 9, wherein the catalyst is present in a concentration of up to 5 mol/kg dry biomass materials, preferably 0.01-5 mol/kg, more preferably 0.1-2 mol/kg dry biomass material.

12. The method according to claim 1, wherein step (ii) comprises introducing pressurized steam in the reaction vessel.

13. The method according to claim 12, wherein no additional internal or external heating of the reactor, such as introduction of pressurized steam into the reaction vessel, is performed in step (iii).

14. The method according to claim 1, wherein the pressure p.sub.2 is in the range of from >1 to 50 bar, preferably from 2-30 bar, more preferably from 5-15 bar, most preferably about 9 bar.

15. The method according to claim 1, wherein the predetermined time span t.sub.2 is 0-800 s, preferably 10-500 s, more preferably 50-250 s and most preferably about 100 s.

16. The method according to claim 1, wherein adjusting the pressure in the reaction vessel to p.sub.2 is performed with a rate of 1-15 bar/min, preferably 5-10 bar/min.

17. The method according to claim 1, wherein the steps (ii)-(v) are repeated several times, preferably 1-10 times, prior to opening of the reaction vessel in step (vi).

18. The method according to claim 1, wherein opening of the reaction vessel in step (vi) is controlled to depressurize the reaction vessel with a rate of 10-100 bar/min, preferably 40-70 bar/min.

19. The method according to claim 1, wherein solid products present in the reaction vessel after step (vi) have a concentration of pentose in the range of 0-2 wt. %, preferably 0-0.5 wt. %, with regard to the dry solid product.

20. The method according to claim 1, wherein solid products present in the reaction vessel after step (vi) have a rest moisture of about 30-95 wt.-%, preferably 35-45 wt.-%, most preferably about 40 wt.-%.

21. The method according to claim 1, wherein the biomass material has a rest moisture of about 30-80 wt.-%, preferably 30-40 wt.-%, most preferably about 35 wt.-%.

22. The method according to claim 1, wherein the method is performed in the presence of oxygen or oxygen donors, particularly at a concentration of 0.01-0.50 mol, preferably 0.05-0.30 mol O.sub.2 or O.sub.2 equivalents per kg of dried biomass material.

23. Condensate obtainable according to the method of claim 1.

24. Use of the condensate according to claim 23 for the production of basic chemicals such as aldehydes, ketones, organic acids, or alcohols, in particular of furfural, acetic acid, methanol and/or acetone.

25. Solid product obtainable according to the method of claim 1.

26. Solid product according to claim 25, having a concentration of pentose in the range of 0-2 wt.-%, preferably of 0-0.5 wt. %, with regard to the dry solid product.

27. Solid product according to claim 25, having a rest moisture of about 30-95 wt.-%, preferably 35-45 wt.-%, most preferably about 40 wt.-%.

28. Use of the solid product according to claim 25 for the production of basic chemicals and/or fuels.

29. Use of the solid product according to claim 25 for the preparation of pellets.

30. Pellets containing the solid product according to claim 25.

31. Use of the solid product according to claim 25 or pellets comprising said solid product in combustion processes.

Description

EXAMPLE 1

[0045] An empty reaction vessel (about 12 m.sup.3) was loaded with about 1200 kg of sawdust mainly deriving from spruce. The residual moisture in the sawdust was determined to be about 33 wt.-%.

[0046] The reactor was sealed and pressurized steam was introduced for about 350 s through the inlet until a pressure of about 20 bar was reached. Then, the steam inlet valve was closed and the internal pressure of the reaction vessel was allowed to further increase to the predetermined pressure p.sub.1 of 21 bar which was reached after about 150 seconds. Then, a pressure-regulating valve was partially opened in order to maintain the predetermined pressure p.sub.1 for about 500 s. Furfural containing vapour emerging from the reaction vessel was condensed and collected. Afterwards, the pressure-regulating valve was completely opened to adjust the pressure of the reaction vessel to p.sub.2=9 bar in a time of about 100 s. Again, furfural containing vapour emerging from the reactor was condensed and collected. Finally, the outlet valve of the reaction vessel was opened and thereby emerging furfural containing vapour from the reactor was condensed and collected. The reactor was discharged into a flash tank wherein solid products from the reaction mixture were collected. A respective pressure/time profile is shown in FIG. 1.

[0047] The solid products, having a moisture content of about 38%, were post-dried to a moisture content of about 5% and used for the manufacturing of brown pellets. Post-drying effluent, containing small amounts of furfural, was condensed and collected. The unified condensates are subjected to chemicals separation and purification.

[0048] The total amount of condensate collected throughout the above process was roughly 50 wt.-% of the final solid products (on dry weight basis) and contained about 24 g of furfural per litre of condensate. The condensate was used for subsequent furfural separation and purification.

EXAMPLES 2-4

[0049] Examples 2-4 according to the invention were performed according to example 1, except that: [0050] the time t.sub.1 was 700 s (Example 2); [0051] the pressure p.sub.1 was 19 bar (Example 3); [0052] the pressure p.sub.1 was 19 bar and the time t.sub.1 was 700 s (Example 4);

COMPARATIVE EXAMPLE 5

[0053] Comparative example 5 was performed according to example 1, except that—after a pressure of 21 bar was reached—no maintaining step was performed (t.sub.1=0 s), but the pressure in the reaction vessel was directly adjusted to 9 bar.

[0054] The total amount of condensate collected throughout the comparative process was roughly 50 wt.-% of the final solids (on dry weight basis) and contained about 10 g of furfural per litre of condensate.

Analysis

[0055] The carbohydrate composition of the initial biomass material as well as of the post-dried final solid products obtained according to Examples 1-5 was analyzed using ion chromatography with pulsed amperometric detection (IC-PAD). The results are displayed in table 1.

TABLE-US-00001 TABLE 1 IC-PAD analysis of the biomass and final solid product carbohydrate composition. The specific carbohydrate contents are expressed with regard to the total carbohydrate content set as 100 wt.-%. arabinose galactose glucose xylose mannose Example p.sub.1 t.sub.1 p.sub.2 (wt.-%) (wt.-%) (wt.-%) (wt.-%) (wt.-%) biomass — — — 1.5 2.8 70.8 7.9 16.9 material 1 21 500 9.0 0.1 1.0 89.5 2.9 6.5 2 21 700 9.0 <0.1 0.8 92.5 2.3 4.4 3 19 500 9.0 0.2 1.6 84.3 3.8 10.2 4 19 700 9.0 0.1 1.0 89.3 2.9 6.6 5 21 0 9.0 0.6 2.6 74.6 6.6 15.6

[0056] Both, the experimental yield of furfural obtained and the IC-PAD analysis of the remaining solid product clearly show that the method according to the invention provides an improved conversion of pentose sugars such as arabinose and xylose comprised in the biomass starting material to furfural when compared to state of the art methods lacking a step of maintaining the pressure in the reaction vessel constant for a predetermined time span.