ETHERIFICATION OF CARBOHYDRATES USING SUPERHEATED STEAM

Abstract

A method for the etherification of a carbohydrate is provided, by subjecting the carbohydrate to superheated steam under alkaline conditions in the presence of an etherification agent to obtain a carbohydrate ether.

Claims

1. A method for the etherification of a carbohydrate, comprising subjecting the carbohydrate to superheated steam under alkaline conditions in the presence of an etherification agent to obtain a carbohydrate ether.

2. The method according to claim 1, wherein the etherification is carried out in the absence of a solvent.

3. The method according to claim 1, wherein alkaline conditions are achieved by subjecting the carbohydrate to a pretreatment with an alkaline agent prior to the etherification.

4. The method according to claim 3, wherein the alkaline agent is a hydroxide, a carbonate or an organic base.

5. The method according to claim 3, wherein the ratio between the carbohydrate and the alkaline agent is 0.01-3 mol alkaline agent/mol carbohydrate monomer.

6. The method according to claim 1, wherein the superheated steam has relative humidity of between 10 and 95 wt. %.

7. The method according to claim 1, wherein the superheated steam has a temperature of 50-300° C.

8. The method according to claim 1, wherein the etherification agent comprises an epoxide functional group or a carbon substituted with a leaving group selected from a group consisting of iodide, bromide, chloride, triflate, tosylate, mesylate or carbonate.

9. The method according to claim 1, wherein the carbohydrate is starch.

10. The method according to claim 9, wherein the starch is granular.

Description

EXAMPLES

[0041] As an exemplary carbohydrate, an amylopectin-rich potato starch was used (Eliane™ 100, Avebe).

[0042] The carbohydrate was pretreated to result in an either acidic or alkaline carbohydrate, by stirring 1 kg carbohydrate (dry weight) for 15 hours in a Lödige powder mixer at 950 rpm after addition of 24.7 g of NaOH, or 85.2 g NaH.sub.2PO.sub.4 or 90.2 g adipic acid

[0043] The alkaline and acidic carbohydrates were used in the processes according to the invention using superheated steam, and in comparative processes using a slurry reaction or an oven reaction. It was found that the obtained DS under the same conditions was considerably higher, and/or the reaction time to attain the same DS was considerably shorter, when using superheated steam, than when using slurry- or oven conditions.

[0044] In the below, the DS has been determined by HPLC/ELSD on the basis of the assumption that the response factor for all components is more or less equal. This is applicable for measurements with an evaporating light scattering detector (ELSD). There are no reference standards for the exact components to be measured, so that the below reference standards were used. These reference standards were used in a conventional fashion:

[0045] Solutions of the used reference standards were prepared in a series of known concentrations, and the detector response of the reference standard was evaluated at each concentration. The detector response was thus usable as a measure for concentration, so that the detector response of the investigated samples allowed for knowing their concentration. The DS of the product was calculated after hydrolysis with 2M trifluoroacetic acid, for 1 hour at 100° C. while stirring. After the pH of the hydrolysate was set to 6, the reference standard was added. The solution was diluted with methanol to obtain a concentration of 50% methanol. The amount of etherified glucose was measured with HPLC-ELSD, in relation to the reference standard.

[0046] The used reference standards were n-dodecyl β-D-maltoside for the calculation of the DS for glucose-EHGE, and octyl β-D-glucopyranoside for the DS of glucose-GNE.

Example 1: Superheated Steam Reactions

[0047] The procedures are done in duplicate.

Alkaline Eliane™ 100 and 2-ethylhexyl glycidyl ether

[0048] To 13 g (as is, moisture content 13.7 wt. %) alkaline amylopectin-rich potato starch (0.1 mol NaOH/mol anhydro-glucose), EHGE (0.2 mol/mol anhydro-glucose) is introduced and then homogenized. The mixture is transferred into the superheated steam reactor (SHS) for 2 hours. The SHS conditions are 150° C. and 3.3 atm. (RH 70%).

Acidic Eliane™ 100 and 2-ethylhexyl glycidyl ether

[0049] To 13 g (as is, moisture content 13.7 wt. %) phosphate loaded amylopectin-rich potato starch (0.1 mol NaH.sub.2PO.sub.4/mol anhydro-glucose), EHGE (0.2 mol/mol anhydro-glucose) is introduced and then homogenized. The mixture is transferred into the SITS for 2 hours. The SHS conditions are 150° C. and 3.3 atm. (RH 70%).

Acidic Eliane™ 100 and 2-ethylhexyl glycidyl ether

[0050] To 13 g (as is, moisture content 13.7 wt. %) adipic acid loaded amylopectin-rich potato starch (0.1 mol adipic acid/mol anhydro-glucose), EHGE (0.2 mol/mol anhydro-glucose) is introduced and then homogenized. The mixture is left overnight at room temperature. The mixture is transferred into the SITS for 2 hours. The SITS conditions are 150° C. and 3.3 atm. (RH 70%).

[0051] The three above described procedures are repeated with glycidyl 4-nonyl-phenylether.

TABLE-US-00001 TABLE 1 Overview products SHS reaction, 2 hours reaction time. Average DS Starch Epoxide (2 hrs) Alkaline starch ethylhexyl 0.05 glycidyl ether glycidyl 4-nonyl- 0.007 phenylether Phosphate starch ethylhexyl ND glycidyl ether glycidyl 4-nonyl- ND phenylether Adipic acid starch ethylhexyl ND glycidyl ether glycidyl 4-nonyl- ND phenylether ND = not detected

Example 2: Slurry Reactions (Comparative)

[0052] Alkaline Eliane™ 100 and 2-ethylhexyl glycidyl ether

[0053] To 431 g water, 160 g sodium sulfate and 400 g (as is, moisture content 14.6 wt. %) amylopectin-rich potato starch was added. The suspension is stirred and sodium hydroxide (7.5 g/kg starch) as 4 wt. % solution was added. EHGE (0.2 mol/mol anhydro-glucose) was introduced and the temperature was raised to 50° C. The reaction was allowed to proceed 24 hours. The slurry was neutralized with 3 M sulfuric acid to pH 5.5. The sample was filtered, washed with water and dried.

[0054] The yield was 500 g product, moisture content 31.2 wt. %, DS 0.001.

Acidic Eliane™ 100 and glycidyl 4-nonyl-phenylether. To 431 g water, 160 g sodium sulfate and 400 g (as is, moisture content 14.6 wt. %) amylopectin-rich potato starch was added. The suspension is stirred and sodium hydroxide (7.5 g/kg starch) as 4.4 wt. % solution were added. GNE (0.2 mol/mol anhydro-glucose) is introduced and the temperature was raised to 50° C. The reaction was allowed to proceed for 24 hours. The slurry was neutralized with 3 M sulfuric acid to pH 5.5. The sample was filtered, washed with water and dried.

[0055] The yield was 550 g product, moisture content 37.1 wt. %, DS 0 (not detected).

Example 3: Oven Reactions (Comparative)

[0056] Alkaline Eliane™ 100 and 2-ethylhexyl glycidyl ether

[0057] To 175 g (as is, moisture content 13.7 wt. %) alkaline amylopectin-rich potato starch (0.1 mol NaOH/mol anhydo-glucose), 30 mL water was added and the resulting mixture was homogenized. Subsequently, EHGE (0.2 mol/mol anhydro-glucose) was introduced and the resulting mixture was homogenized. The mixture was transferred to a covered pot and left in an oven at 85° C. for 2, 4 or 24 hours, after which the DS was determined. The relative humidity in the oven is 100 wt. %.

Acidic Eliane™ 100 and 2-ethylhexyl glycidyl ether

[0058] To 175 g (as is, moisture content 14.0 wt. %) phosphate loaded amylopectin (0.1 mol NaH.sub.2PO.sub.4/mol anhydro-glucose), 30 mL water was added and the resulting mixture was homogenized. Subsequently, EHGE (0.2 mol/mol anhydro-glucose) was introduced and the resulting mixture was homogenized. The mixture was transferred to a covered pot and left in an oven at 85° C. for 2, 4 or 24 hours, after which the DS was determined. The relative humidity in the oven is 100 wt. %.

Acidic Eliane™ 100 and 2-ethylhexyl glycidyl ether

[0059] To 175 g (as is, moisture content 14.2 wt. %) adipic acid loaded amylopectin (0.1 mol adipic acid/mol anhydro-glucose), 30 mL water was added and the resulting mixture was homogenized. Subsequently, EHGE (0.2 mol/mol anhydro-glucose) was introduced and the resulting mixture was homogenized. The mixture was transferred to a covered pot and left in an oven at 85° C. for 2, 4 or 24 hours, after which the DS was determined. The relative humidity in the oven is 100 wt. %.

[0060] The three above described procedures were repeated with glycidyl 4-nonyl-phenylether.

TABLE-US-00002 TABLE 2 Overview products oven reaction. Starch Epoxide DS (2 hrs) DS (4 hrs) DS (24 hrs) Alkaline starch ethylhexyl 0.002 0.005 0.05 glycidyl ether glycidyl 4- 0.001 0.001 0.004 nonyl- phenylether Phosphate ethylhexyl ND ND ND starch glycidyl ether glycidyl 4- ND ND ND nonyl- phenylether Adipic acid ethylhexyl ND ND ND starch glycidyl ether glycidyl 4- ND ND ND nonyl- phenylether ND = not detected