I
F. H. OTEY, J. W. SLOAN, C. A. WILHAM, and C. L. MEHLTRETTER Northern Regional Research Laboratory, Peoria, Illinois
Erythritol and Ethylene Glycol from Dialdehyde Starch The process described here may be the key to increased industrial use of corn
D I A L D E H m E STARCH produced by periodic acid oxidation of starch has recently become available as a n industrial chemical (7). T h e peculiar polymeric dialdehyde structure of this product, which is composed of alternately linked residues of erythrose and glyoxal, indicates the possibility of its reductive hydrolysis to the tetrol, erythritol, and ethylene glycol in attractive yields.
I
H
n
H
I l H-C-C-C-C-H I l OH
OH
1 3 H .
H
l l
H
OH
n
1 1
+
H
H
OH
OH
OH
I H-C-C-H I
I 1
Earlier attempts to develop a practical process for preparing these polyols (6, 7) from dialdehyde starch utilized Raney nickel catalyst and gave analytical yields of erythritol of 60 to 7070. This work describes the effect of adding catalyst supports to nickel on the course of reductive hydrolysis of dialdehyde starch, under appropriate conditions of pH, time, and temperature. Both kieselguhr and activated carbon when mixed with nickel catalyst were found to improve the yields of erythritol and ethylene glycol to over 90% of theory and allowed the use of dialdehyde starch in 25% concentration. At least 86Y0 of theory of the erythritol was isolated in crystalline form and 8 3 7 ~of the ethylene glycol was recovered by distillation. Presumably the reaction proceeds by hydrogenation of the aldehyde group of dialdehyde starch followed by hydrolysis of the resulting polymeric triol to
erythritol and glycolic aldehyde with concomitant reduction of the latter to ethylene glycol. Experimental Forty grams of
dialdehyde
starch
(95% dialdehyde content; moisture, 11.3%) (5) was suspended in 70 ml. of
water, producing a p H of 3.3. T h e n 8 grams of a nickel catalyst supported on kieselguhr (Girdler G-49A) was added, increasing the p H to 7.5. T h e suspension was then transferred with 30 ml. of water to a high-pressure vessel. Hydrogen was introduced to a pressure of 2000 p.s.i., agitation was started,
Erythritol is now an expensive chemical, selling for about $200 per pound in small lots. A suitable raw material, dialdehyde starch, has recently become commercially available a t a cost of about $1.00 per pound. It is likely that price will b e reduced to $0.30 to 0.40 per pound wilh multimillion pound production. Using the conditions outlined here, a production cost of about $0.75 per pound seems reasonable for erythritol.
I 15
I 20
I 25
I
30
I 35
40
Concentration of Dialdehyde Starch, Wt.
%
Best yields of erythritol were obtained a t concentrations of dialdehyde starch of 15 to 25 wt. % VOL. 53, NO. 4
0
APRIL 1961
267
Table I. Yields of Erythritol Are Affected b y Changing Temperature and Catalyst Dialdehyde starch concentration,
2.570,; Reaction time, 5.5 Hours
Yields, % Ethylene ~
Catalysta Concn., %
Temp., O C
Catalyst
160 l8OC
Girdler G-49A Girdler G-49A Girdler G-49A Girdler G-49A Girdler 6.-498 Raney M i W-4 Raney Mil W-4 Girdler G-49A Girdler G-49A Girdler G-498
180 180 180 180
180 200 200 230
glpol
..
91 89 94, 85d 95 94 66 91 91, 8Cid 76 84
11 22
Based on weight of dialdehyde starch. By analysis. yield. e Ethanol wet. f 22% Darco G-60 added.
and the reaction mixture was heated a t 200° C. for 5.5 hours. T h e reactor was then cooled, vented, and opened; after which the catalyst was separated by filtration. A small aliquot of the resulting colorless solution was diluted with water to a known volume and was chromatographed on Whatman h-0. 1 filter paper with a biitanol-pyridinewater (6 : 4: 3) mixture. Poly01 spots were located by spraying guide strips with ammoniacal silver nitrate. Erythritol was then quantitatively eluted from the paper ( Z ) , and the eluate was analyzed by the chromotropic acid method (4). T h e reaction mixture contained 91Yc of the calculated quantity of erythritol. Products were isolated by evaporating the remaining original solution in vacuo to a sirup and then cooling to crystallize the erythritol. T h e colorless crystals were filtered, washed with ethanol, and dried to yield 21.2 grams of erythritol (m.p. 114-117' C . ) , which is 86y0 of the calculated quantity. T h e slightly contaminated erythritol was recrystallized from ethanol to obtain a pure product of melting point 121' C. which was characterized as its tetrabenzoate.
Erythritol6
22 22 22 22 22 33e 33e 22
.. 84 91 91
.. .. .. .. ..
Iicaction time 2.5 hours.
Isolated
Ethylene glycol was recovered in 837, yield by combining the filtrate a n d ethanol wash: concentrating in vacua, and distilling a t a bath temperature of about 100' C. and 2-mm. pressure. When evaporation losses during concentration and distillation were accounted for by chromotropic acid analysis of solid carbon dioxide trapped condensates, the total ethylene glycol yield exceeded 90% of theory. All results were calculated to percentage of erythritol theoretically obtainable from dialdehyde starch after correcting for the 5% of unoxidized glucose residues in the oxidized starch and the 4% of nonreducing end groups in starch. Data from a number of trials indicated that about 60 grams of erythritol and 32 grams of ethylene glycol of the above-described purities may be obtained from 100 grams of the dry dialdehyde starch. Discussion Table I shows that high yields of erythritol and ethylene glycol occur in the reaction temperature range of 160' to 200' C. using a supported nickel catalyst. Raney nickel alone is not a
Table II. Effect of Alkali Solubilization and Acid-Forming Salts on Yield of Erythritol Dialdehyde
Starch Conen., Vit. yo
Reductiona Time, Temp., Hr.
O
c.
15 15 15
4.0
15 20 20 36
1.0 1.0
100 200 200 200 200 200 200
4.0
200
4.0
200
15
4.0 4.0
Acid-Forming Salt, 2.8% Concn.
ErythritolC Yield, %
No
MgClz. 6HzO
99, 77d
No Yes Yese Yes Yes Yes Yes
MgC12.6H20 None None MgClz. 6HzO MgCIz. BBzO MgC12.6HnO MgCln. 6H20
90 78
Alkali Solubiliaedb
268
INDUSTRIAL AND ENGINEERING CHEMISTRY
Literature Cited (1) Chem. Eng. News 38, 64 (Mar. 7, 1960) ; Chem. Week 86, 38 (Jan. 2, 1960). (2) Dimler, R . J., Schaefer. W.C., Wise, C. S . , Rist,' C. E., Anal. Chem. 24, 141 1
(1952). (3) Hartstra, L.; Bakker, L., Van Western, H. A. (to Shell Development C o . ) , U. S. Patent 2,518,235 (Aug. 8, 1950). (4) Lambert. M., Neish, A. C., Can. J . Research 26B, 8 3 (1950).
(5) Pfeifer, V. F., Sohns, V. E., Conway, H. F., Lancaster, E. B., Dabic, S., Griffin, E. L., Jr., IND.ENG.CHEM.52, 201 (1960). (6) Sloan, .J. W., Wulff, I. A. (to Secretary of Agriculture), U. S. Patent 2,795,447 (June 18, 1957). (7) Sloan, J. W., Hofreiter, B. T., MehlZbzd., 2,783,tretter, c. L., Wolff, I. 283 (Feb. 26, 1957). (8) Whistler, R. L., Chans, P. K., Richards, G. N.: J. A m , Chcm. SOC.81, 3133 (1959). A\.,
57 91, 7 3 d 81 81
70
Girdler G-49A catalyst was used. Neutralized with hydrochloric acid after solubilization i n 0.05-9' sodium hydroxide. By analysis. Isolated yield. e Kot neutralized after alkali solubilization. a
suitable catalyst; hoivever, when mixed with activated carbon its catalytic action is comparable to that of commercial nickel supported on kieselguhr. T h e exact function of these supporting agents is not known, but it is believed they maintain a more uniform p H range in the reaction mixture a t elevated Temperatures. A comparison of erythritol yields obtained by varying the concentration of dialdehyde starch under constant conditions of temperature, pH, and time is shown in the figure. Optimum results are achieved u p to cmcentrations of about 2576 of dialdehyde starch. T h e use of a n acid-forming salt, such as magnesium chloride (3), to create higher acidity during the reaction and presumably to effect a more rapid hydrolysis and reduction of the dialdehyde starch, did not appreciably alter the reaction results (Table 11). Solubilization of dialdehyde starch in 0.05N sodium hydroxide (7) prior to reductive hydrolysis produced lower yields of erythritol. TVhen the solubilized material was hydrogenated in the presence of magnesium chloride, the reaction rate increased and a high yield of erythritol was realized, but only if the concentration of dialdehyde starch did not exceed 157,. I n these cases as soon as the maximum temperature was reached, hydrogen uptake was nearly complete. Higher concentrations of alkali were avoided to present extensive degradation of the oxystarch to lower molecular weight fragments (8).
RECEIVED for review September 26, 1960 ACCEPTEDDecember 30, 1960 The Northern Laboratory is part of the Northern Utilization Research and Development Division, Agricultural Research Service, U. S. Department of Agriculture. Trade names are given as part of the exact experimental conditions and not as a n endorsement by the U . S . Department of Agriculture of the products named over those of other manufacturers.
