I-VDUSTRIAL A S D ENGINEERING CHEMISTRY
306
Attention should be called to the considerable amount of water absorbed by some of the waxes. Even the hydrocarbons, paraffin, ceresin, and “Superla” wax, absorb measurable amounts, while certain of the natural waxes which contain fatty acids and esters, which as a rule have a greater affinity for water, absorb from 0.5 to 6.0 per cent. Shellac,
VOl. 19, X O . 2
which is widely used as an insulating material in electrical apparatus, absorbs 4.3 to 5.1 per cent of water under the conditions of these experiments and loses its insulating properties to a greater extent than any of the other naturally occurring waxes, resins, or bitumens which have been tested.
Oxidation and Hydrolysis of Light Wood Oil’.’ By P. 0. Powers with A. Lowy and W. A. Hamor UNIVERSITY OF PITTSBURGH, PITTSBURGH, PA.
A n investigation has been made of the methods for and the method of distillation, IGHT wood oil is obconverting light wood oil, a by-product in the disbut also to the method of tained from three printillation of hardwood, into possibly useful products. storage before shipment of cipal sources in the inSamples of the oils from various plants have been exthe sample. dustrial distillation of hardamined and the effects of treatment with oxidizing The low-boiling fractiors wood: (1) the distillate on agents and alkalies have been studied. Among the distilled over slightly colored. steaming the settled tar, (2) oxidizing agents tried, nitric acid has been found to The odor of the first 10 per the refined pyroligneous acid give the best results, and research attention has been cent of the distillate was pleasin the copper stills, and (3) accorded to effect of conditions on the yield of organic ant, but thencefrom it became the weak methanol distillate acids. Of the alkalies, lime has been shown to afford strong and pungent. The from the lime lee still. The satisfactory results and these products have been exfractions on distillation oils from these sources are amined. Hydrolysis gave the best results and a method ranged from pale yellow to s o m e t i m e s separated but for the treatment of the oil by this method has been deep red and darkened to more often collected together. devisedd e e p b r o w n o n standing. The oil is usually a-darkSome f r a c t i o n s darkened c o 1o r e d , flammable liquid with an exceedingly disagreeable odor. Its vapors irritate much more readily than others, but in general the higher the eyes and throat. Practically all the wood oil produced boiling fractions were much more deeply colored. The wood oil possessed a sharp characteristic odor, which is consumed as fuel, although the higher fractions have found some uses. For this reason the work of the authors was was especially evident in the fraction from 65” to 150’ C. confined to the fractions boiling below 195” C. A large num- The vapors had a lachrymatory action. Neither nitrogen. sulfur, nor halogen was found in the ber of various types of organic compounds have been isolated oil when elementary tests were applied. Group tests showed from certain wood oils and tars.3 the presence of aldehydes, ketones, esters, acids, furfurDistillation aldehyde, phenols, and unsaturated compounds. Samples of light wood oil were obtained from wooddistilling plants at Smethport, Betula, and Seargent in Pennsylvania, and Wells, Michigan. Most of the investigational work was done with the sample from Betula. An estimate of the wood used a t this plant showed the following distribution as to varieties: maple, 55 per cent; beech, 35 per cent; birch, 5 per cent; ash, 3 per cent; and oak, 2 per cent. Samples of the oils were distilled from a 3-liter flask through a Clark and Rahr’s column. The following fractions were obtained:
L
FRACTIONSSMETHPORT BETULA SEARGENT WELLS
c.
Per cent
70
2.0 33.2
Residue
33.6
O
-
- 160 - 195
66.4
P w cent 22.3 52.6 74.9 25.1
P e r cent 1.0 57.0 77.0 23.0
Per cent 14.5 47.0 65.0 35.0 PERCENTAGE
Distillation curves for such oils are given in Figure 1. It will be noticed that the boiling range of these oils varied considerably. .This was due not only to the wood used 1
Received September 29, 1926.
* The research described in this paper was carried out while Dr. Powers was the junior incumbent of the Multiple Industrial Fellowship sustained in Mellon Institute by the National Wood Chemical Association (1923-51, to which organization the authors are grateful for this support and also for the release of the work for publication. The present contribution is an abstract of a thesis presented by Dr. Powers t o the Graduate School of the University of Pittsburgh in partial fulfilment of the requirements for the degree of Ph.D. * Bunbury, “The Destructive Distillation of Wood,” p. 106 (1923).
Figure I-Boiling
DISTILLED
Range of Light Wood 011
Oxidation of the Oil
Preliminary experimentation showed that wood oil gave a good yield of organic acids when treated with oxidizing agents. After several experiments with chlorine, bromine, bleaching powder, and chromic and nitric acids, it was found that nitric acid gave the best results. The oxidation with nitric acid was then investigated in more detail. METHOD-The fraction to 195’ c. of the Betula oil was used in Seventy per cent nitric acid was diluted with water
all this work.
ILVDUSTRIAL A S D ENGINEERING C H E - I S T R Y
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Table I-Nitric
? ;"
EXPT.
PURPOSE
Acid O x i d a t i o n of L i g h t Wood Oil (below 195' C . )
NITRIC ACID
TIME
RESIDUALhTITRIC OIL ACID ( B Y VOL.) USED
ORGANIC ACIDS Total
CONCLUSIONS
Volatile
%
R
%
39
87 99
38.6 28.7 36.0 39.5
26.6 25.3 19.3 24.3
6 per cent nitric acid gave the best results. Stronger nitric acid caused side reactions
55 34
46 36
23.1 34.4
16.4 2i.5
Vanadium pentoxide the oxidation
16
19
64
29.8
16.6
16
44
86
28.5
21.3
Air did not oxidize the fraction of light wood oil even in the presence of nitric acid
6 12 18 26 32
25
5 5 52 84 91
16.9 17.7 29.7 42.1 44.3
24.1
Nitric acid hydrolyzed the esters of light wood oil Nitric acid oxidized light wood oil to organic acids and other products
16
78
64
10.8
7.4
yo
Grams 92 92 92 92
Grams
70
1 2 3 4
70 70
io
70
6 9 16 20
16 16 16 16
52 24 38 43
Use of vanadium pentoxide
5 6
92 92
35 70
9 16
8 8
Air and nitric acid
7
92
70
16
Air, nitric acid, and vanadium pent- 8
92
70
9
9
92
70
9
10
92
35
9
E5ect of nitric acid concentration
307
Hours
...
catalyzed
oxide ~
~~
~~~~
~
Effect of time and temperature; first 2 runs a t i o o C., last 3 a t 80' C.
Oxidation of the hydrolyzed oil with nitric acid
to the desired concentration and the strength determined. The acid and oil were placed in a round-bottom flask equipped with a n agitator and a reflux condenser. The flask was placed in a water bath and heated, the temperature being raised until the contents of the flask began t o boil. The temperature was held a t this point for 4 hours, and then gradually raised about 10 degrees and the heating continued. Care had to be exercised throughout the operation, because a t times the reaction became very vigorous.
The batch was then cooled and a sample titrated with standard sodium hydroxide, employing thymol blue as indicator. By this indicator the amount of nitric acid not used and the amount, of organic acids formed could be determined from the two end points.
Oxidation without hydrolysis
the concentration employed. The organic acids are reported as percentage by weight of the original oil and calculated as acetic acid. Six per cent nitric acid was found to be of sufficient strength to oxidize wood oil, and no advantage was observable in using higher percentages. With 20 per cent acid the yield of organic acids was much the same, but nearly three times the amount of nitric acid was consumed. Vanadium pentoxide catalyzed the reaction and apparently accelerated the oxidation to acids rather than to side reactions, since the best yields of organic acids based on nitric acid used were obtained with its use. Only half the time was required when the catalyst was employed. The use of air blown through the reaction mixture did not increase the yield of acids. On the other hand, the lowboiling fractions JT-ere largely removed by this treatment. At 70" C. nitric acid hydrolyzed the esters in the oil. The nitric acid is very slowly destroyed; at 80" C. the nitric acid is destroyed and the oil is oxidized. On treating an oil from which the esters had been removed by treatment with alkali, the yield of organic acids mas considerably decreased. LIGHT
W O O D - 01L (0.8Liters of fraction t o I95 * Cj
WATER (0.6 Liters)
REFLUXED SIX HOURS A N D
The oil layer was separated and washed with water, and its volume was measured. The water layer and the mash water were combined; the free nitric acid was neutralized with sodium hydroxide solution, and the volatile acids distilled, adding more water as necessary to complete their distillation. The oil left after oxidation was very viscous, from dark brown to black in color, and had a disagreeable odor. It could only be distilled with great difficulty and at 180" C. left a thick pitch. It was apparent from the boiling range and amount of oil recovered that a large portion of the oil was affected by the oxidation. About half of the oil was converted into water-soluble products and only half of the waterinsoluble part boiled within the range of the original oil. Table I shows the results of ten experiments, in which the fraction to 195" C. from Betula was used. This fraction had a specific gravity of 0.9194 (22'/4O C.) and the weight used is reported. I n the column headed "nitric acid" are given the weight of 100 per cent nitric acid used and also
(0.10Kyj
DISTILLED
tyrN WATER
RE3lDUAL
m METHANOL
I
METHANOL
CALCIUM ACETATE (plus excess 7ime) I
SULFURIC ACID
FILTRATION CALCIUM ACETATE SOLUTION
t ACETATE OF LIME: (0.2 7 Kg. 6Oper cent)
F i g u r e +Flow
S h e e t of H o t Hydrolysis w i t h
Lime
I
ISDCSTRIAL A S D ENGINEERISG CHEMISTRY
308
Hydrolysis of Oil
The use of alkali was suggested by the work of Fraps4 and was also deduced from the results of Experiment 9, Table I. After preliminary trials with calcium and sodium hydroxides, it was found that better results were obtained a t elevated temperature. It was decided to use lime since this substance is employed in the wood-distillation industry. METHOD-Hydrolysis was effected by placing the oil and an equal volume of water in a flask with a slight excess of lime. The amount of lime was determined by the saponification of a sample of the oil with standard alkali. The flask was provided with a reflux condenser and mechanical agitation, and the mixture was stirred vigorously and refluxed six hours. The oil and methanol were then steam-distilled from the resulting emulsion; the oil was separated and the methanol washed from it with water. The residue in the still was neutralized with sulfuric acid, water added as necessary, filtered hot, and washed with hot water. The solution was then evaporated and the lime salts dried.
The residual oil was light yellow and much improved in odor. The weak methanol was carefully redistilled through a column and evaluated on its specific gravity as determined by a Westphal balance. The calcium salts were ground and weighed and a sample analyzed by distillation with phosphoric acid.5 Figure 2 gives a comparison of the boiling range of the oil before and after hydrolysis. The curve shows that the oil above 165" C. is not greatly affected by the hydrolysis. Figure 3 outlines the treatment of a fraction of Betula oil, with the percentages of residual oil, methanol, and calcium acetate recovered. The experiments reported in Table I1 were conducted on different fractions of oils from various sources according to the method outlined above. The yields of residual oil, methanol, and calcium acetate are presented in each case. The lime salts formed varied in composition with the fraction of the oil from which they were obtained. The salt from the 55-70" C. fraction was almost entirely calcium acetate. The salt from the 70-160" C. fraction contained only 77 per cent as calcium acetate and was entirely free Am. Chem. J . , 25, 26 (1901). Griffin, "Technical Methods of Analysis," p. 32 (1921).
6
VOl. 19, KO. 2
from tar. It contained some calcium acetate, but was chiefly propionate and butyrate. The salt from the 160195" C. fraction contained only 56 per cent as calcium acetate and consisted of salts of higher acids. Table 11-Hydrolysis
of L i g h t Wood Oil
WOOD RESIDUAL 827, 80% ACETATESOURCEBOILINGRANGE OIL OIL METHAXOL O F LIME O F OIL OF ORIGINAL OIL Lilers 0.60 0.90 1.10 1.00 3.80 8.80 5.20 0.70 0.50 1.20 0.40 0.70 0.50 1.60 a
Per cent 58 34 61 68 47 60 31 56 64 59 44 68 89 67
Per centa 16.1 29.6 12.3 2.7 39.5 12.5 0.6 6 9 6.3 6.6 33.0
1A.i
G.9"
Kg./liter 0.27 0.50 0.22 0.05 0.35 0.19 0.06 0.16 0.07 0.12 0.36 0.14 0.07 0.21
c. Betula Betula Betula Betula Betula Betula Betula Seargent Seargent Seargent Wells Wells Wells Wells
55-195 55-66 66-145 145-195 55-70 70-160 160-193 55-160 160-195 55-195 55-70 70-160 160-195 55-195
Per cent by volume of original oil
The methanol obtained contained appreciable amounts of methyl ketones, some acetone, but chiefly methylethylketone. The methanol was systematically investigated for higher alcohols, but no traces of any alcohol except methanol could be found. Evidently the oil contains considerable amounts of methyl esters. The results of the experiments on hydrolysis show that methanol and lime salts can be obtained by refluxing fractions of wood oil with milk of lime. The amounts of these products vary considerably with the source of the oil. The oil recovered from this treatment is much improved in odor and color. The lime salts vary in composition with the fraction from which they are obtained. Hydrolysis of t h e Oil R e m a i n i n g a f t e r NaHSOt Extraction
Aldehydes and methyl ketones are removed from wood oil by shaking with a strong sodium bisulfite solution. About 40 per cent of the volume of the oil was removed by this treatment. The remaining oil was hydrolyzed with lime in the usual manner. The yield of calcium salts was somewhat lower than was usually obtained.
Evaluation of Turbine Oils' By T. H. Rogers a n d C . E. Miller STANDARD OIL COMPANY (INDIANA), WHITING,IND.
T
HE oxidation and evaluation of turbine oils becomes
a problem of increasing importance with the growing use of steam turbines as prime movers. Two years ago Funk2 presented the problem from the standpoint of the user, stating that further improvement in turbine design, affecting the stability of the oil, could not be expected, and that improvement in quality of turbine oils was therefore a problem for the refiners. However, the first step toward such development has hardly been accomplished, inasmuch as no method of evaluating the quality of turbine oil has been generally accepted. Emulsion tests are worth while for determining the initial quality of an oil, but, aside from indicating the care used in refining, they are not a measure of the stability of an oil in service. Turbine oils in service are maintained at elevated temperatures (varying from about 115' to 170" F. in different in1 Received August 28. 1926. Presented before the Division of Petroleum Chemistry at the 72nd Meeting of the American Chemical Society, Philadelphia, P a , September 5 to 11, 1926. 2 THIS JOURNAL, 16, 1080 (1924).
stallations) in the presence of air. The undesirable changes which take place in the oil are formation of insoluble material and, in the presence of water, very persistent emulsions. These changes are undoubtedly due to oxidation, as it has been found that in the absence of oxygen mineral oils are perfectly stable. From laboratory experiments it has been found that with oils of turbine grade oxidation is characterized by gradual formation of asphaltenes, free acids, and saponifiable material, the latter probably being lactones or anhydrides. Asphaltenes are very slightly soluble in turbine oils a t ordinary temperatures and are strong emulsifying agents of the water-in-oil type. The acids apparently are emulsifying agents of the opposite type, but this effect is very mild. Acids are particularIy harmful because they form soaps by action on the metal surfaces, particularly iron and copper. These heavy metal soaps, like asphaltenes, are slightly soluble in the oil at elevated temperatures, and deposition of both materials takes place in cooling coils or settling tanks when the temperature of the oil is lowered. These soaps are, of course, powerful emulsifying agents, and are of the same
