Polysaccharide alkaline degradation products as a source of organic

Ind. Eng. Chem. Prod. Res. Dev. 1084, 23,70-73

70

resistant to displacement by water, adhesion loss can involve polymer degradation (e.g., by base hydrolysis in the cathodic polarization experiment). Registry No. (Isophorone diisocyanate).(2-ethyl-l,3-hexanediol) (copolymer), 38887-18-2; (1,4-butanediol diglycidyl eth-

Fowkes. F. M. In "Adheslon and Adsorption of Polymers", Lee, L. H., Ed.; Plenum: New York. 1980; p 42. Fowkes, F. M.; Sun, C. Y.; Josiln, S. T. I n "Corrosion Control by Organic Coatings", LeMheiser, H., Ed.; National Association of Corrosion Englneers: Houston, TX, 1981; p 1. Hammond, J. S.; Holubka, J. W.; DeVries, J. E.; Dickle, R. A. J . Coat. Techno/. 1079, 51(655), 45. Hammond, J. S.; Holubka, J. W.; DeVreis, J. E.; Dickle, R. A. Corros. Sci. er)~(2-ethyl-1,3-hexanediol)~(4-methyl-l,2-~clohex~i~~xy~c 1981, 21, 239. acid anhydride) (copolymer),88211-77-2;Epon 282,25068-38-6; Holubka, J. W.; Hammond, J. S.; DeVries, J. E.; Dickie, R. A. J . Coat. Tech1,I-butanediol,110-63-4. no/. 1080, 52(670), 63. LeMhelser. H.; Kendlg, M. W. Corras. NACE 1078, 32, 69. Literature Cited LeMheiser, H. Croat. Chem. Acta. 1080, 53, 197. Clerk, D. T.; " a s , H. R. J . Potym. Sci. Potym. Chem. Ed. 1078, 16, Leidheiser. H. Ind. Eng. Chem. Prod. Res. D e v . 1078, 17, 54. 791. Mayne, J. E. 0. I n "Corrosion", 2nd ed.,Shrelr, L. L., Ed.; Newnes-ButterdeVrles, J. E.; Holubka, J. W.; Dickie, R. A. Ind. Eng. Chem. Prod'. Res. worths: London, 1976; p 15:24. D e v . 1089, 22, 256. ScofieM, J. H. J . Electron Spectros. 1076, 8 , 129. Dickie. R. A.; Smith, A. G. C E M E C H 1080, 10, 31. Smith, A. G.; Dickie, R. A. Ind. Eng. Chem. Prod. Res. Dev. 1078, 17. 42. Dickle. R. A.; Hammond, J. S.; Holubka, J. W. Ind. Eng. Chem. Prod. Res. Wagner, C. D. Anal. Chem. 1077, 49, 1282. D e v . 1081, 2 0 , 3 3 9 . Walker, P. Off. Dig. 1065. 3 7 , 1561. Dickle, R. A. I n "Adhesion Aspects of Polymeric Coatings", Mkbl, K. L., Ed.; Wiggle, R. R.; Smith, A. G.; Petrocelli, J. V. J . Paint Techno/. 1088, 40(519). Plenum: New York, 1983 p 319. 174. Fadiey, C. S. W.D. Thesis, University of California, Berkley, CA, 1970 (LBL Report UCRL-19535 1970). Received for review May 23, 1983 Fowkes, F. M.; Mostafa, M. A. Ind. Eng. Chem. Prod. Res. D e v . 1078, 17, 2. Accepted August 23, 1983

Polysaccharide Alkaline Degradation Products as a Source of Organic Chemicals Marten Relntjes' and Geoffrey K. Coopert Conhlbutbn No. 237 from the Research Center of I T Rayonier Inc., SheRon, Washlngton 98584

Saccharinic or deoxyaldonic acids are found in alkaline pulping llquors and in the hot caustic extract produced in the pulp purification step in the manufacture of chemical celiulose. The latter resource is not used now for either its fuel value or its chemical content. The structure of saccharinic acids suggests utilization in many applications where gluconic acid Is now used including sequestration of metal ions, metal cleaning, scale removal, industrial detergents and concrete admixtures. A mixture of saccharinic and related hydroxy acids can be readily separated from the hot caustic extract. Treatment with amlnes leads to the correspondlng amides which can be converted to anionic and nonionic surfactants by reaction with chlorosulfonic acid or ethylene oxide.

COOH

Introduction

In 1838, Eugene Peligot reported that a very reactive acid is formed in the reaction of barium hydroxide or calcium hydroxide with glucose. This observation probably was the beginning of research covering one of the most perplexing reaction sequences in carbohydrate chemistry. In due course it was found that treatment of hexoses with alkali yielded principally lactic acid plus a series of sixcarbon, deoxyaldonic acids isomeric with the starting sugars. A slightly erroneous analysis of the first crystalline lactone (a-D-glucosaccharin) of a deoxyaldonic acid produced by the hexose-alkali reaction led Peligot (1879) to the conclusion that this substance was simply an isomer of sucrose (sacchrose) and he named it saccharin. Even though the confusion was soon recognized (Scheibler, 1880), the name was retained and expanded to include saccharinic acid for the corresponding free acid. Three structurally isomeric forms have been established for the six-carbon saccharinic acids. They are the saccharinic or 2-methylpentonic acids (I), the isosaccharinic acids (111, and the or 3-deoxy-2-hydroxymethylpentonic metasaccharinic or 3-deoxyhexonic acids (111). t ARC0

Bioengineering Center, Dublin, CA. 0196-4321/84/1223-0070$01 S O / O

COOH

COOH

CH3

i

OH

:c I

I CHOH I

I

c:

I

CHOH I

y

CHOH

CHzOH OH

YHZ

I

CHOH I

CHzOH

CHZOH

CHOH I CHOH I CH20H

Saccharinic Acid

lsosaccharinic Acid

Metasaccharinic Acid

2

m I II Saccharinic acids are formed in alkaline pulping and alkaline pulp purification processes. Potential availability from pulp mills is huge. The acidic material in kraft black liquor has been reported as 30-39% of the total organic material present (Green, 1956). Hagglund (1924) gave a yield of 18% hydroxy acids and lactones based on wood, of which 5% was lactic acid. The amount of isosaccharinic acid formed during the cooking of pine on a laboratory scale was reported to be 6.7% based on wood (Malinen and Sjbtrom, 1975). Assuming an average yield of 36% (based on black liquor solids) of hydroxy acids, the potential at a 500 tpd kraft pulp mill is 180 tpd. On an annual US. kraft capacity basis this amounts to about 14000000 tons per year. The recovery of kraft black liquor for its inorganic chemical and fuel value is, of course, an integral step in 0 1984 American Chemical Society

Ind. Eng. Chem. Prod. Res. Dev., Vol. 23,No. 1, 1984 71

Table I. Typical Composition of Hot Caustic Extract (% of Solids as Sodium Salts) chloride 3.3 formate 17.0 acetate 3.4 glucoisosaccharinate 27.0 other hydroxy acids 38.0 “complex” acids (insol. at pH 1) 11.3

the operation of a kraft mill. An unused or very much underutilized source for saccharinic acids is hot caustic extract. Hot caustic extraction is a pulp purification step in the manufacture of chemical cellulose or dissolving pulp. In contrast to cold caustic purification which relies on physical effects such as swelling and solubilization to remove short chain noncellulosic carbohydrates, hot alkali extraction utilizes primarily chemical reactions on the entire carbohydrate component for purification. The treatment is carried out at low caustic concentrations ( t y p i d y 0.3-370 NaOH solution concentration) and pulp consistencies of 10-20% at temperatures of 70-140 “C.A yield loss of about 3% per 1%increase in a-cellulose (long-chain cellulose) content is experienced; the process can be adjusted to give any desired yield and degree of purification to a maximum of about 96% a-cellulose content at 70-75% yield in the hot caustic extraction stage. Hot caustic extract at cooker pot strength has a solids content of about 3% and can be a problem at this stage because it is so dilute. Also, it may or may not contain chlorinated compounds depending on whether the hot caustic extraction was a primary stage or whether it followed a primary chlorination. It has a high pH of about 10-12 and even when concentrated, it can only be burned in recovery furnaces if it does not contain chlorine. A typical composition is shown in Table I. The combined saccharinic acid and other hydroxy acid fraction constitutes about 65% of the hot caustic extract. At an average yield of 80% cellulose across the stage, the potential availability from a 500 tpd sulfite dissolving pulp mill is about 80 tpd. With a total U.S.sulfite dissolving pulp capacity of 1500 000 tpy, the saccharinic acid potential from this resource is 250000 tpy. Manufacturing costs for the crude saccharinic acid mixture have been estimated to be 27$/lb. This includes 46/lb of solids to concentrate the dilute hot caustic extract in a six-effect evaporator from 2.5% to 60% solids using steam generated from oil. Gluconic acid, which is the most nearly similar material, sells for 50$/lb of solids as a 50% solution. Thus, the manufacture of even the crude saccharinic acid mixture for uses described in the discussion section of this paper would be profitable. The total variable cost for disposal of the hot caustic extract via a secondary treatment system is approximately l$/lb of solids for a typical northwest mill. The mechanism by which saccharinic acids are formed in the reaction of alkali with sugars has been elucidated over a period of many years. Saccharinic acid formation by recombination of sugar fragments was discussed by Kiliani and Kleemann (1884) and Windaus (1905) around the turn of the century. Nef (1907, 1910) suggested an isomerization of sugar enediols and epoxy compounds to an a-dicarbonyl compound which would undergo a benzilic acid type of rearrangement to a saccharinic acid. There appears to have been general agreement on the formation of an a-dicarbonyl compound, but Evans et al. (1926) suggested that the initial isomerization proceeded via unsaturated oxide compounds. bbell(1944) developed an acceptable course for the initial isomerization, based on consecutive electron-displacement reactions.

An experimental demonstration that the reaction sequence involves carbon-oxygen cleavage at the &carbon atom with respect to the carbonyl group was provided by Nicolet (1931). He observed that the products from the action of alkali on 2-hydroxy-3-methoxy-3-phenylpropiophenone (IV) were 2,3-diphenyllactic acid (V) and methanol. This conversion is completely analogous to the c=

0

CHZ

I

I C5H5

‘gH5

C6H5

‘gH5

C6H5

2-hydroxy-3methoxy-3phenylpropiophenone

2,3-diphenyllactic acid

P formation of a saccharinic acid from a reducing sugar. The @-alkoxycarbonyl mechanism explains why the predominant product in the hot caustic extract is isosaccharinic acid. This is based on work by Corbett and Kenner (1953) and Kenner and Richards (1954) in which it was shown that the position of substitution on a sugar unit determined which acid would be formed and the 40-substitution resulted in the formation of isosaccharinic acid. Evidence for the formation of the dicarbonyl intermediate was obtained by Blears et al. (1957). Whistler and BeMiller (1960) reported the isolation of the dicarbonyl compound, 4-deoxy-3-oxo-~-glycero-2-hexulose (VI) at Ip

CHZOH

I C=O

I C=O I

7%

HCOH

I CH20H

E t about the same time that Anet (1960) reported on the isolation of two additional dicarbonyl compounds. The formation of isosaccharinic acid in the hot caustic extraction of cellulose involves formation of the appropriate enediol via a Lobry de Bruyn-Alberda van Ekenstein transformation (VII VIII); p-elimination of an CHO

I ti- C

- OH

I HO-C-H

I -OR

H-C

7

-

CHOH

II C-

OH

I HO-C-H

I

CH20H

c =o

C -OH

I HO-C-H

I

7

H-C-OR

I

-

CHpOH I

I

H-C-OH

I

H-C

I -OH

I

CH2OH

1:4-glucan

PII

CH2OH

H -C

2 7

-OR

H -C

I I1 C-OH

1 H-C-OR

I -OH

H-C-OH

I

I

CH2OH

CH20H

1,2-enediol

2,3-enedlol

-

-

m

alkoxy1 group (VIII IX, R = cellulose); rearrangement to an a-dicarbonyl intermediate (IX X); and a benzilic acid type rearrangement to isosaccharinic acid (X XI).

-

CH20H

i

H - C:-OR

I

----

CHOH

HCH

I

CHOH

I

I

CHpOH

CH20H

I

CHOH

I CH20H

2,3-enediol

m

Ix

x

I CHOH

I CHpOH

isosaccharinic acid

XI

72

Ind. Eng. Chem. Prod. Res. Dev., Vol. 23, No. 1, 1984

A detailed discussion of saccharinic acids has been presented by Sowden (1957), and the alkaline degradation of polysaccharides has been reviewed by Whistler and BeMiller (1958). While isosaccharinic acid is formed in the classical “peeling reaction” (Kenner, 1955; Meller, 1960,1965), other low molecular weight acids in the hot caustic extract are formed in various types of fragmentation reactions (Machell and Richards, 1960). The presence of pyruvic, glycolic, lactic, and 3,4-dihydroxybutyric acids has been indicated by a number of researchers (MacLeod and Schroeder, 1982).

Table 11. Hydrophobic Surface Wetting Test for Surfactancy

Discussion In order to do anything with the hot caustic extract other than simply discharge it via a waste treatment system, it has to be concentrated. Once this is done, the material becomes useful to kraft mills for its sodium and fuel value in the case of a primary hot caustic extract. If the hot caustic extraction follows a primary chlorination, the concentrated material remains a problem and has few, if any, uses. Even the crude, nonchlorine containing product does not appear to have much use in any application besides its sodium and fuel value. Potential uses for the saccharinic and related acids are based on their structural similarity to other sugar acids. Such uses are related to their metal complexing abilities and include: general sequestration of metal ions, metal cleaning and refining, scale removal, industrial detergents, paint stripping, dyeing, concrete admixture (set retarder), and agricultural micronutrients. Various separation schemes can be considered to isolate the hydroxy acid fraction from the crude mixture. Separation schemes include: solvent extraction, ion exchange, electrodialysis, and ultrafiltration. For example, ultrafiltration has been recommended to remove color from bleach plant effluents. Ultrafiltration of hot caustic extract followed by reverse osmosis would provide a concentrate containing essentially only the hydroxy acid fraction. Most of the high molecular weight material is also readily removed by acidifying the concentrated hot caustic extract. Removal of water from an acidified, filtered solution leaves a syrup which upon extraction with isopropyl alcohol results in the isolation of all lactonizable material in the lactone form. This is convenient because reaction of the lactone mixture with a primary amine results in quantitative conversion to the corresponding mixture of amides. Reaction of lauryl or stearyl amine with the mixture yielded the corresponding amides which upon sulfation with chlorosulfonic acid gave water soluble anionic surfactants (XII XIV). Surfactancy was measured

Table 111. Hydrophobic Surface Wetting Test for Surfactancy

-

0 II O=C-NHR

CH20H

H-C-OH

I

XII

CH20H

L

CIS03H

1

NaOH

O = C -NHR Na03S0, I a R =lauryl b R

=

Na03SOCH2

/? y 2

steaiyl

H

- C - OSOBNa I

CH20S03Na

droplet area, mmz

sample

22 25 25 38

H2 0 saturated NaCl 2 N NaOH lauryl saccharinamide (sulfate Na salt) stearyl saccharinamide (sulfate Na salt) commercial detergent (control)

mol of ethylene oxide/mol of amide

sample

A

32 50

droplet area, mmz (0.1% surfactant)

2 5 10 20 30 40

B C

D E F commercial detergent water

100 90 85 80 50 50 120 20

by hydrophobic surface wetting. Results are shown in Table 11. Chemically more stable than the sulfated saccharinamides are the nonionic hydroxyethylated derivatives. The degree of control over molecular properties conferred by varying the ethyleneoxy content, which is commerically so useful in the case of nonylphenol/ethylene oxide adducts for example, is also available in the saccharinamide case as exemplified by hydroxyethylation of the lauryl amide (XV XVI). Results of the surfactancy tests of

-

HpC HO -C

I

- OH

H2C-

I

- C -NHR

I !

7%

HO(CH2CH20)x - C HpC

I :

- CH2

\

H-C-OH

/

>

I H2C-

(OCH2CH2)wOH

-C

OH

- NHR

YHZ H

- C - (OCH2CH2)yOH I H2C - (OCH2CH2),0H

R = lauryl

mzI products with varying ethyleneoxy content are shown in Table 111.

Conclusion It has been shown that useful and valuable products can be obtained from a process stream that is presently discarded and is costly in its disposal via a waste treatment system. Products prepared from the hot caustic extract of dissolving grade cellulose have both utility and constitute new compositions of matter for which patents have been applied. Experimental Section Recovery of Lactone Mixture. Hot caustic extract liquor from dissolving sulfite pulp production was evaporated to 20.6% T.S. A quantity of 3 L (3360 g) of the dark brown solution was acidified with concentrated aqueous hydrochloric acid/water (1:l)to a pH of 2.0. The precipitate was filtered off and the water removed under vacuum with a rotary evaporator (temperature,