Oxalic Acid from Sulfite Waste
T. J. SICEWES AND
H. IC. BENSON University of Washington, Seattle, Wash.
Courtesy, Rayonier, Inc.
INTHISPULPMILL THE WASTE LIQUORIs MADE INTO RAYLIGBINDER AND SOILSTABILIZER
I
N THE decomposition of complex organic substances by the application of heat alone or by suitable chemical trea.tment, oxalic acid is frequently found as a minor product associated with carbon monoxide, carbon dioxide, and water. The latter compounds frequently arise, in part, as end products in the partial decomposition of the oxalic acid. This acid may appear as a major product under certain conditions, such as the fusion of sawdust with sodium and potassium hydroxides a t 220" C. I n this process the yield of oxalic acid was sufficiently high to have made this the principal commercial method before the introduction of the sodium formate process. Again, by the oxidation of wood in the form of sawdust or wood flour with nitric acid, oxalic acid can be obtained in good yield. Considerable work has been done on the preparation of oxalic acid by the treatment of cellulosic materials with nitric acid. A comparatively small amount of work has been carried out on the nitric acid oxidation of isolated lignin and sulfite waste liquor. A patent granted to Reed (3) in 1917 provides for the treatment of the residue obtained by evaporation of sulfite waste liquor to dryness with three times its weight of concentrated nitric acid a t 95" C. until oxidation is complete. From the resulting mixture the nitric acid is evaporated off, and the remaining solution is further concentrated until crystals of oxalic acid separate out. Heuser, Roesch, and Gunkel (1) treated isolated lignin with concentrated nitric acid a t 50" to 60" C. for 2 hours, after which the reaction maw was permitted to stand overnight. Crystals of oxalic acid were obtained by filtration of the resulting solution in 20 per cent yield, based on the weight of lignin taken. They also investigated the effect of various catalysts as well as the effect of dilute nitric acid and nitricsulfuric acid mixtures on the lignin oxidation. Of the published work on the nitric acid oxidation of lignin-containing substances, that of the previously cited investigators was most closely related to the present problem. This paper deals with the nitric acid oxidation of the following sulfite waste liquor products for the formation of oxalic acid: (a) a sulfite waste liquor before concentrating by evapo-
Oxalic acid may be obtained in yields of over 28 per cent by treatment of evaporated sulfite waste liquor with concentrated nitpic acid; smaller yields are obtained by treatment of precipitated calcium lignosulfonate. Dilute nitric acid gives much smaller yields of oxalic acid than the concentrated acid, whereas fuming nitric acid is essentially equivalent to the concentrated acid. The use of vanadium pentoxide as catalyst does not appreciably affect the yield of oxalic acid.
ration, ( b ) the solids obtained by highly concentrating the liquor, (c) "Raylig," a commercially concentrated product, and (d) a precipitated calcium lignosulfonate,
Materials Used The sulfite waste liquor was of hemlock origin and was kindly furnished by the Soundview Pulp Company of Everett, Wash. It was collected from the digesters before the blowing operations and was found to contain 88.5 per cent moisture plus volatile matter at 105" C. All of the laboratory-evaporated product referred to in this paper was derived from this liquor. The precipitated calcium lignosulfonate was prepared from the above liquor by a modified Howard process (2) described later. "Raylig," a sulfite waste liquor concentrated by waste stack gas, was donated by Rayonier Incorporated of Shelton, Wash. Supplied as a solid, i t contains 6.87 per cent moisture and 12.66 per cent calcium oxide; as a liquid it contains approximately 46 per cent total solids. All inorganic chemicals were of technical grade, with the exception of the nitric acids which were of reagent quality.
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INDUSTRIAL AND ENGINEERING CHEMISTRY
The technical chemicals were used without further purification, with the exception of the calcium chloride which was filtered after dissolving to rid it of insoluble matter.
Method of Analysis of Reaction Liquor Two methods were used for the determination of the oxalic acid. The first was approximate and was employed when it was desirable t o determine the amount of oxalic acid crystals that could be isolated at the completion of any run. It consisted of removing the spent liquor by decantation, washing the crystals with several small portions of nitric acid, drying, and weighing. To determine the purity of the oxalic acid, it was dissolved in dilute sulfuric acid and diluted t o 1 liter with water, and aliquot portions were titrated with 0.1 N potassium permanganate. By this method it was found that approximately 1 per cent of calcium sulfate separated at the same time. The second method was more quantitative, accounting for the dissolved as well as the crystalline oxalic acid. I t consisted of diluting the reaction liquor containing the crystals to 1 liter, followed by neutralizing a 50-ml. aliquot portion until it was slightly alkaline t o litmus, and then acidifying it slightly with acetic acid. A solution of calcium chloride was added to the cold solution until complete precipitation took place. The precipitate was filtered off, washed thoroughly with water, dissolved in dilute sulfuric acid, heated to 90’ C., and titrated with 0.1 N potassium permanganate solution. In this last method it is important to dilute the reaction liquor before precipitating the calcium oxalate; otherwise certain undecomposed lignin material will precipitate also. This lignin residue is difficult to separate from the calcium oxalate. Attempts to find a selective solvent for either the lignin residue or the calcium oxalate proved unsuccessful. Only if the lignin were completely decom osed would this lignin material be entirely absent; com lete iecomposition was not found in any of the runs tested. Digculty with lignin residues obtained by similar treatment of isolated lignin was experienced by Heuser, Roesch, and Gunkel (1). They further found that direct titration of the oxalate in the reaction liquor was subject $0 large error due to the nitrous acid present. The latter compound could be destroyed by treatment of the solution with phenylene diamine.
Nitric Acid Oxidation of Original Liquor The most apparent method of oxidation of sulfite waste liquor is by the direct treatment of the original liquor without concentration by evaporation or precipitation methods. Samples of the liquor were refluxed with varying amounts of concentrated nitric acid for 0.75, 1.5, and 2.0 hours, respectively, with and without the addition of small amounts of vanadium pentoxide as catalyst. In no case could oxalic acid be found in the resulting solution. I n the presence of vanadium pentoxide, Sellers (4) and Webber (6) found that oxalic acid is rapidly destroyed by nitric acid solutions at temperatures around 100” C. I n the absence of the catalyst it is probable that any small amount of oxalic acid, if formed, mould be decomposed a t this temperature. The effect of adding varying amounts of concentrated nitric acid to the liquor and permitting it to stand a t room temperature for several days before testing for oxalic acid again proved unsuccessful. The mild initial exothermic nature of the reaction with the original liquor as compared with the concentrated liquor (discussed later) accounts for the much smaller decomposition and absence of oxalic acid. Nitric Acid Oxidation of Evaporated Liquor The preparation of the concentrated liquor from the original sulfite waste liquor was carried out by evaporation on a steam bath until the final weight of the sirupy hot liquor was one seventh of its original weight. Upon cooling, the liquor became brittle, after which it was powdered and used in the following work. By the nitric acid oxidation of this evaporated product, good yields of oxalic acid were obtained. The evaporated product (5 grams) was treated with 10 ml. of nitric acid (100 per cent) during 15 minutes. The reaction was allowed to proceed under its own heat, reaching a maximum temperature of about 96” C.; when cool, 11 ml. of concen-
VOL. 31, NO. 9
trated nitric acid (70 per cent) were added directly with 0.1 per cent of vanadium pentoxide. The reaction mixture was allowed to stand 3 days, after which the oxalic acid crystals were determined by the approximate first method given under method of analysis. The yields of oxalic acid (dihydrate) based on the weight of solids in the evaporated product varied from 24.5 to 28.4 per cent. Using the same procedure as before with only concentrated nitric acid (70 per cent) and without the addition of any catalyst gave yields of over 28 per cent. Thus, this latter treatment was more effective and simpler than the previous one.
Nitric Acid Oxidation of “Raylig” and Precipitated Calcium Lignosulfonate The solid “Raylig” containing 6.87 per cent moisture when treated according to the simplified procedure used for the evaporated product was found to give yields of about 28 per cent of oxalic acid (dihydrate). “Raylig” containing 46 per cent solids yielded only small amounts of oxalic acid under the same conditions. The large amount of water in this latter product dilutes the nitric acid sufficiently to diminish greatly its oxidizing action on the liquor. This was exactly the same case with the original liquor when treated under these same conditions. Calcium lignosulfonate was prepared essentially according to the Howard patent ( 2 ) . Calcium oxide was added to the liquor until a purple color had developed. At this point the calcium sulfite was precipitated and filtered off, and more calcium oxide was added to the filtrate until a light brown sludge separated out. This was centrifuged, filtered, and found to contain 21.10 per cent total solids. Runs treating this material in the same manner as the total solids from the liquor evaporation did not yield any crystals of oxalic acid. A portion of this precipitated calcium lignosulfonate was evaporated to dryness a t 105” C. This product gave yields of about 21 per cent of oxalic acid (dihydrate) when treated according to the previously described method. All further treatment of the precipitated product was carried out with this dry material.
Comparison of Dilute with Concentrated Nitric Acid on Sulfite Waste Liquor Solids The three types of solids (evaporated liquor, precipitated calcium lignosulfonate, and “Raylig”) were treated with concentrated (70 per cent) and dilute (10 per cent) nitric acid to determine the comparative yields. The treatment with the concentrated acid consisted of adding 20 ml. of the 70 per cent acid in small portions to 5 grams of each of the previously mentioned solids. The mixtures were allowed to stand over night, and the resulting solution was diluted to 1 liter and analyzed according to the second method given under method
WITH DILUTE AND CowTABLE I. RESULTSOF TREATMENT CENTRATED NITRICACID ON SOLIDS
Max. Weight Nitric Acid Temp. Grams M1. = c. Concentrated Nitric Acid (70 Per Cent) 20 90 Evap. total solids 4 20 90 CaIcium lignosulfonate6 ? 20 90 Ray1ig”c Dilute Nitric Acid (10 Per Cent) Evap. total solids 5 40 galcium lignosulfonateb 5 40 5 40 Ray1ig”c 0 Dihydrate. b Dried a t 105’ C. C Containing 6.87 per cent moisture. Material
.. .. ..
Oxalic Acid Yielda
% 28.6 21.0 27.3 8.02
0.45
6.00
SEPTEMBER, 1939
INDUSTRIAL AND ENGINEERING CHEMISTRY
of analysis. I n the dilute acid trckatment, 5 grams of each of the solids were treated with 40 ml. of 10 per cent nitric acid in the same manner as the concentrated acid Sreatment. A comparison of the results from the two treatments is given in Table I. These results show that a much greater yield is obtained by the use of concentrated than of dilute acid which is consistent with the low yields obtained by the action of concentrated nitric acid on evaporated liquors containing relatively high water contents. The initial reaction with the concentrated acid is much more violent and markedly exothermic as compared with the dilute acid. The smaller yields with the latter acid are due to the less complete decomposition of the lignin materials. When fuming nitric acid (specific gravity 1.56) was substituted for the concentrated acid, the yield of oxalic a.cid was not appreciably increased.
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Experiments with and without the addition of catalyst (0.1 per cent vanadium pentoxide) indicated that no significant increase in yield could be effected by its addition.
Acknowledgment The writers express their thanks to E. C. Sherrard of the U. S. Forest Products Laboratory, Madison, Wis., for suggesting the problem, and to T. F. Doumani for assistance in the study.
Literature Cited (1) Heuser, E., Roesch, H., and Gunkel, L., Cellulosechem., 2, 13 (1921). ( 2 ) Howard, G., Canadian Patent 304,644(Oct. 7,1930). (3) Reed, H., U.S. Patent 1,217,218(Feb. 27,1917). (4) Sellers, J., thesis, Univ. Ill., 1929. ( 5 ) Webber, H.A , , Iowa Eng. Expt. Sta., Bull. 118,31(1934).
Effect of Pressure on Viscosity in Relation to Lubrication J
J. W. GIVENS Shell Development Company, Emeryville, Calif.
A n analysis has been made of data on the temperature rises in three oils while a partial bearing was being lubricated at high loadings. Using the pressure coefficients of viscosity of these oils, an operating variable was calculated that accounted for the observed temperature rises and that should be useful in studying lubrication. Differences in the frictional characteristics of these oils that might be ascribed to oiliness could be accounted for by known properties of the oils. The use of the term “oiliness” to account for such differences admits ignorance of the properties of liquids, and the need for this term will disappear proportionately as more exact information becomes available.
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N BOTH the hydrodynamic and dimensional theories of
fluid lubrication, the viscosity of the lubricant has been shown to be of paramount importance. Evidently it is not the viscosity as ordinarily measured but the viscosity existing a t the working surfaces that is required for a mathematical treatment of the problem. The variation of viscosity with temperature has long been recognized and taken into account. There has, however, been some difficulty in getting the actual operating temperatures. The effect that the change of viscosity with pressure might have in lubrication has only recently been considered. We may expect a t the outset that owing to the small change of viscosity with pressure, the effect will be appreciable only
in experiments made a t very high loadings but again not a t loadings sufficiently high to cause boundary lubrication to occur. It will be recalled that under conditions of boundary lubrication viscosity plays no part. This paper gives calculations made on data recently published by Everett (3) that were obtained in such a way that the foregoing conditions are fulfilled. The results of these calculations obtained throw further light on the mechanism of lubrication in general, and in particular they demonstrate that one more effect previously ascribed to oiliness can be accounted for by known properties of the lubricants.
Data and Calculations Everett (3) described lubrication experiments made with a machine described by Bradford and co-workers ( I , 2 ) . I n these experiments the rubbing surfaces consisted of a large steel journal running against a small brass block accurately fitted to the shaft and carefully run in. The block subtended 8’ of arc on the journal and could tilt so that a wedge-shaped film could be formed. Lubrication was provided by a stream of oil flowing over the journal. The temperatures of the incoming and outgoing oil were measured by thermocouples. The temperature rises were measured a t various loads for an eastern, a mid-continent, and a western oil. The three oils had viscosities of about 215 Saybolt Universal seconds at 130’ F. and a t atmospheric pressure. Data were also given (3) relating viscosity to pressure for these oils over a range from atmospheric to 54,000 pounds per square inch. It was observed that the viscosity of the western oil increased most rapidly with pressure and that of the eastern oil least rapidly. It was pointed out that this result correlated with the observation that on the testing machine the western oil showed the greatest temperature rise for a given load, and the eastern oil the least.
