A bottle of freshly prepared levulinic acid from paper mill sludgePreparation of levulinic acid from hexose sugarsLevulinic acid is a major product of the controlled degradation of hexose sugars by acids. Because the supply of hexoses from cellulose-containing plant material is immense and replenishable, conversion of such materials into a single chemical product meets one of the requirements for a basic chemical raw material.
The reactive nature shown by the keto and carboxyl groups meets the second requirement. Although levulinic acid has been known since the 1870's, when many of its reactions were first established, it has never reached commercial use in any significant volume.
Hexoses are convertible to levulinic acids by essentially a process of dehydration and cleavage of a mole of formic acid. The theoretical yield from a hexose is 64.5%, but the literature as reviewed by Wiggings (
Advances in carbohydrate chem 4, 306-314 (1950)) shows that only about two thirds the theoretical yield can be attained; the balance proceeds to insoluble residues. Substantially the same yields from cellulose in Douglas fir sawdust were amply demonstrated by Frost and Kurth in 1951 (
Tappi 34, 80-86 (1951); C.A. 45, 4441).
Formation of levulinic acid from low-cost cellulosic products overcomes one of the major difficulties encountered in other processes.
The preparation of levulinic acid from carbohydrates by the action of mineral acids is known from G. J. Mulder (
J. Prakt. Chem. 21, 219 (1840) cited in
Patent US5189215
).
Early work on levulinic acid involved reacting different carbohydrate sources with mineral acids.
Levulinic acid has been produced by the action of acids on carbohydrates such as:
- glucose;
- galactose and sucrose
Wiggins, "
Utilization of Sucrose" (
Advance in Carbohydrate Chemistry, 4, 306-314 (1949))
Thomas, et al., "
Studies on Levulinic Acid. I. Its Preparation from Carbohydrates by Digestion with Hydrochloric Acid Under Pressure" (
J.S.C.I. Jun. 8, vol 53, 2324-2328 (1931));
- fructose, glucosamine, chitose, sorbose, deoxypentoses, and hexose
Patent US3258481
Patent US2206311
;
- cane sugar and starch
Patent US2270328
;
- disaccharide and polysaccharide unions
Wiggins, "
Utilization of Sucrose" (
Advance in Carbohydrate Chemistry, 4, 306-314 (1949)).
Here is the procedure from
Organic Syntheses coll vol 1 p 335:
http://www.orgsyn.org/orgsyn/buttons.asp?showprint=1&prep=cv7p0034
1. Procedure
To a solution of 500 g. (1.46 moles) of cane sugar (Note 1) in 1 l. of water in a 2-l. flask is added 250 cc. of concentrated hydrochloric acid (sp. gr. 1.16). The flask is heated on a steam bath for twenty-four hours, during which time considerable carbonization takes place. The black solid is filtered off with suction and washed with 300 cc. of water. The filtrate is placed in a large evaporating dish on a steam bath and allowed to evaporate overnight. The black solid residue obtained on the following morning is ground to a powder and placed in a folded filter paper of 34-cm. diameter. This is placed in a 25-cm. funnel fitted with a water-cooled 12-l. flask as described on p. 375. The solid is extracted with 500 cc. of ether for six to eight hours. The ether is distilled and the residue (Note 2) fractionated under reduced pressure. The fraction distilling at 150–160°/15 mm. or 135–140°/10 mm. forms a rather dark liquid which does not completely solidify on cooling.
On redistillation under reduced pressure a fraction boiling over a range of not more than 2° (e.g., 137–139°/10 mm.) is obtained with very little loss; this fraction solidifies almost completely at 30°. The yield is 72–76 g. (21–22 per cent of the theoretical amount).
2. Notes
1. Equally good results may be obtained with starch; the mixture however, must be warmed more slowly as it is apt to foam at the outset.
2. When larger quantities of levulinic acid are to be prepared it has been found by the checkers to be more convenient to fractionally distil the first filtrate under reduced pressure, without evaporating to dryness and extracting with ether. In this case a considerable quantity of tarry residue remains in the distilling flask. The yields are equally good.
A good yielding procedure is found in
Patent US5859263
, which prepares levulinic acid from starch in a reactive extrusion process with yields of about 48% which is about 70% of theoretical.
Reduction of levulinic acidReduction of levulinic acid first yields 4-hydroxyvaleric acid, which, as the free acid, lactonizes readily to
gamma-valerolactone (lactone of 4-hydroxyvaleric acid). The sodium salt of
gamma-hydroxyvaleric acid can be obtained, as described by Rhodium in:
Sodium 4-Hydroxyvalerate, a Novel GHB Analoghttps://www.thevespiary.org/rhodium/Rhodium/chemistry/4-methyl-ghb.html
Levulinic acid has been reduced to
gamma-valerolactone by means of:
- sodium in alcohol
J. Am. Chem. Soc. 48, 3163-65 (1926);
- sodium amalgam
J. Gen. Chem. USSR 9, 924-931 (1939); C.A. 34, 368;
- sodium borohydride
J. Am. Chem. Soc. 71, 122-125 (1949);
- lithium borohydride
J. Am. Chem. Soc. 71, 3245-46 (1949);
- aluminium amalgam
Bul. Sci. Fakultat Terkult. Kyushu Imp. Univ. Fukuova 11, 86-90 (1944); C.A. 43, 5367I hereby challenge everyone to beat this in OTC'ness..