STABILITY OF
PURE HYDROCARBONS TO LIGHT Pure hydrocarbons exposed to the carbon arc light in oxygen developed peroxides, acids, and aldehydes. Color and haze formed only in the presence of sulfur or n-propyl disulfide. I n nitrogen or hydrogen, reaction of sulfur with saturated hydrocarbons occurred, resulting in color formation and evolution of hydrogen sulfide. Unsaturated hydrocarbons similarly exposed formed color, hydrogen sulfide, and mercaptans. n-Propyl disulfide reacted with the hydrocarbons in nitrogen or hydrogen to form mercaptans but caused color formation only in 2,2,4-trimethylpentane and cyclohexane. The changes observed affected only a small proportion of the hydrocarbons since no change in bromine number or refractive index occurred. The results were similar to those obtained with gasolines.
Photochemical Formation of Color, Haze, and Reaction Products J. C. MORRELL, W. L. BENEDICT, A N D GUSTAV EGLOFF Universal Oil Products Company, Riverside, 111.
unsaturates, two distillations were made immediately before use. The distillates were condensed under nitrogen. This procedure was necessary because unsaturates form peroxides rapidly if left in contact with air. The original properties of the pure hydrocarbons and those to which sulfur and n-propyldisulfide (typical of sulfur compounds added or formed in the sodium plumbite treatment of gasoline) were added are shown in Table I. The refractive indices were taken a t room temperature in diffused sunlight and corrected to 20" C. These conditions were considered accurate enough to determine whether this property changed during exposure. The values for exposed and unexposed samples were taken a t the same time. The hydrocarbons were exposed to the carbon arc lamp for one hour in atmospheres of oxygen, nitrogen, and hydrogen. In addition to the pure hydrocarbons, samples to which elementary sulfur (0.01 to 0.10 per cent) was added and other samples to which n-propyl disulfide was added in amounts equivalent to 0.10 per cent sulfur, were exposed. The results of the tests are shown in Table 11. The results show that with one exception the pure hydrocarbons developed neither color nor haze in the presence of oxygen, nitrogen, or hydrogen. The exception was benzene. Apparently pure hydrocarbons in general do not cause color and haze formation. Benzene became colored but formed no haze upon exposure to light in oxygen, nitrogen, or hydrogen. The benzene (Baker's c. P. thiophene-free) was refluxed for 3 hours with zinc followed by repeated shakings with 95 per cent sulfuric acid until the acid layer no longer became discolored. It was then allowed to settle, was separated, and was washed twice with water, then with sodium hydroxide solution, and again with water. After drying with calcium chloride, it was shaken with metallic mercury until no further blackening of the mercury occurred and then distilled. The benzene &ally used boiled a t a constant temperature of 79.4Oat 747mm. or80.5" C. corrected to 760 mm. pressure. The test for thiophene
T
HE effects of light on cracked and straightrun gasolines with and without added sulfur compounds were discussed in previous papers ( 1 , 4) . The present investigation was made to study the effect of light on the various types of hydrocarbons which are present in gasolines and to ascertain whether they are affected in the same manner by light. Hence, most of the previous work was repeated employing hydrocarbons instead of gasoline.
Apparatus, Materials, and Procedure The carbon arc lamp used as the source of light has been described (2). The hydrocarbons in quartz bottles were exposed to the light for one hour in atmospheres of oxygen, nitrogen, and hydrogen. The air was displaced from the samples by bubbling in gas for one hour prior to exposure in the same manner as in the former work with gasolines (4). After exposure the Saybolt color, peroxide number ( 5 ) , acid number ( I ) , bromine number (S), and refractive index were determined. Qualitative tests were made for hydrogen sulfide, mercaptans, elementary sulfur, sulfur dioxide and trioxide (4),and aldehydes (1). The hydrocarbons used were n-heptane, 2,2,4-trimethylpentane, 2-octene, diisobutylene, cyclohexane, cyclohexene, benzene, toluene, cyclopentadiene, pinene, and limonene. The hydrocarbons were obtained in as pure a state as possible and were furt.her purified by distillation. In the case of 448
APRIL, 1936
INDUSTRIAL AND ENGINEERING CHEMISTRY
with isatin and sulfuric acid was negative. Special care was taken to prevent contamination of the hydrocarbon after purification. In addition to exposure in quartz bottles a sample was exposed in a glass-stoppered bottle of Corex glass. The color drop in this case was from 30+ to 26' Saybolt. Therefore, benzene of the purity obtained by the method of treatment used appears to become discolored upon exposure to light. No explanation for the color instability of the benzene has been found. Peroxides, acids, and aldehydes were formed in the hydrocarbons upon exposure to light and oxygen. The olefin, cycloolefin, diolefin, and terpene hydrocarbons contained more of these oxidation products than the paraffins, cycloparaffins, or aromatic hydrocarbons. Benzene showed the least tendency to peroxidize, but toluene formed peroxides to about the same extent as the paraffin and cyclo paraffin hydrocarbons showing the effect of the alkyl group.
Effect of Sulfur In the presence of elementary sulfur, all of the hydrocarbons became discolored upon exposure to light in oxygen, nitrogen, or hydrogen. In oxygen all hydrocarbons containing sulfur except 2-octene, cyclopentadiene, and d-limonene also developed haze. I n atmospheres of nitrogen or hydrogen, all the hydrocarbons were clear after one-hour exposure. All of the hydrocarbons containing sulfur become hazy within 30 seconds after exposure to light, even in the presence of nitrogen. Samples containing 0.10 per cent formed a dense yellow-white cloud. The haze formed in all of the samples was temporary and gradually became less intense, disappearing entirely from samples containing 0.01 per cent sulfur within 2 minutes of further exposure, and within 10 to 25 minutes in those containing 0.10 per cent sulfur. Samples exposed in oxygen later developed a second haze which persisted until the end of the test; 2-octene, cyclopentadiene, and d-limonene were the exceptions. After exposure of hydrocarbons containing 0.10 per cent sulfur, there was a deposit of
449
sulfur on the sides of the quartz cylinders. With 0.01 per cent sulfur the deposit was slight, and in cases where the elementary sulfur reacted completely no deposit was observed. Hydrocarbons containing sulfur when exposed in oxygen tended to have lower peroxide numbers and higher acid numbers than the pure hydrocarbons upon similar exposure. These samples contained sulfur dioxide and trioxide. Even in nitrogen or hydrogen, reaction occurred between the hydrocarbons and sulfur upon exposure to light. The olefin and cycloolefin hydrocarbons contained hydrogen sulfide and mercaptans. The paraffin, cycloparaffin, and aromatic hydrocarbons contained hydrogen sulfide but no mercaptans. Instead a product was formed which reacted with mercuric acetate, indicating the formation of sulfides.
Effect of n-Propyl Disulfide %-Propyl disulfide caused the formation of color and haze in the paraffin, cycloparaffin, and aromatic hydrocarbons upon exposure to light and oxygen. Diisobutylene also became colored and hazy, but the straight-chain and cyclic olefins, 2-octene and cyclohexene, remained clear and colorless. In nitrogen or hydrogen the disulfide caused color but no haze formation in 2,2,4-trimethylpentane and cyclohexane but had no effect on the color stability of the other hydrocarbons. In oxygen the paraffin, cycloparaffin, and aromatic hydrocarbons containing the disulfide had lower peroxide numbers and higher acid numbers than the correspondingly exposed pure hydrocarbons. The disulfide had no effect on peroxide formation in the unsaturated hydrocarbons studied. In all cases the hydrocarbons to which the disulfide was added contained sulfur dioxide and trioxide after exposure to light and oxygen. In nitrogen or hydrogen, n-propyl disulfide reacted with the hydrocarbons to gire mercaptans. That the formation of mercaptans was a result of reaction between the disulfide and the hydrocarbons rather than a reduction of the disulfide
TABLEI. ORIGINAL PROPERTIES OF HYDROCARBONS Hydrocarbon n-Heptane
2,2,4-Trimethylpentane
2-Ootene
Diinobutylene
Cyclohexane
Cyclohexene
Beneene
Toluene
Cyalopentadiene Pinene &Limonene
Compound Added Per cent None Sulfur 0 . 0 1 Sulfur' 0 . 1 0 n-Pro6yl disulfide None Sulfur 0 . 0 1 Sulfur: 0 . IO n-Propyl disulfide None Sulfur, 0.01 Sulfur 0 . 1 0 n-Pro6yl disulfide None Sulfur 0.01 Sulfur' 0 . 1 0 n-Pro6yl disulfide None Sulfur 0 01 Sulfur: 0: 10 n-Propyl disulfide None Sulfur, 0.01 Sulfur 0 , l O n-Proiyl disulfide None Sulfur, 0 . 0 1 Sulfur, 0.10 %-Propyldisulfide None Sulfur 0 . 0 1 Sulfur' 0 . 1 0 n-Prodyl disulfide Xone None None
Color Sayboll 30 30+ 30+ 30 30 30 30+ 30+ 30 30 30 30+ 30+ 30+ 30+ 30 30+ 30+ 30 30 30 30 30 30 30+ 30 30+ 30+ 30
+ + ++ ++ + + ++
++ ++ +
+
30+
30+ 30+ 30430+ 28
Peroxide No.
Acid
No.
Bromine No.
Refractive Index
0.00
0.0
0
1.3875 1.3879 1.3879 1.3881 1.3916 1,3918 1.3916 1.3916 1.4157 1.4158 1.4158 1.4158 1.4109 1.4109 1.4108 1.4108 1.4267 1.4265 1.4265 1.4265 1.4461 1.4465 1.4465 1.4465 1.5009 1.5009 1.5012 1.5008 1.4957 1.4956 1.4956 1.4956 1.4465 1.4680 1.4718
Boiling Point
c. 0.00 0.00 0.00 0.00
0.00 0.00
0.00 0 22 0.41 0.22 0.34 0 45 0.22 0.22 0.11 0 00 0.00 0.00 0.00
0.93 0.34 0.34 0.34 0.00 0.00 0.00 0.00 0.00 0 00 0 00 0.00
0.054 0,054 0 11
0.0
0
0.0 0.0
0 0 0 0 0 0
0.0
0.0 0.0
0.0 0.2 0.2 0.1 0.1 0.1 0.1 0.1 0.0
0.0 0.0 0.0 0.0 0.1 0.3 0.1 0.3
138 138 138 138 142 139 142 139 0 0 0
0 200 200 200 202
0.0 0.0 0.0 0.0 0.0
0
0.0
0 0 0
0.0 0 0 0.3
0.1
...
0 0 0 0
... ... ...
97.1-97.3
Pressure M m . HQ 744
Boiling Point Cor. t o 760 Mm. O
c.
98.5-98. I3
98.9
753
122-124
747
122.9-124.9
101-103
752
101.7-103.7
80.1
753
80.7
82.3
752
83.1
79.4
747
80.5
110.4
754
110.9
41-42 157-158 176.2-177.2
750 750 752
...
99.4
... ...
VOL. 28, NO. 4
INDUSTRIAL AND ENGINEERING CHEMlSTRY
450
TABLE11. EFFECT OF LIGHTON HYDROCARBONS Hydrocarbon n-Heptane
Compound Added Per cent None None None Elementary, 0.01 Elementary, 0.-10 n-Propyl disulfide (equiv. to 0.10d)
2,2,4-Trimethylpentane
None None None Elementary 8, 0.01
Atmosphere Oz
Nz
H2 Oz NZ Hz OZ Nz Hz Or Nz Hz
OZ Nz Hz 0 2
NZ
H* Elementary 8 , 0.10 n-Propyl disulfide (equiv. to 0.10 S) 2-Octene
None None None Elementary S, 0.01
0 2
N2 H2 On Na Hn OZ
NZ
HZ 0 2
NZ
HZ Elementary S, 0.10
Diisobutylene
03 NZ H2
n-Propyl disulfide (equiv. t o 0.10S)
0 2
None None None Elementary 5 , 0.01
Op N2 Hn On Nz
Elementary 5, 0.10
0:
n-Propyl disulfide (equiv. toO.lOS)
On
None None None
0 2
Nz Hz
HZ
Cyclohexane
NZ Hn Nz
Hz Nz
Hn
Color O Saybolt 30f clear 30f clear 30f clear 17 hazy 16 clear 17 clear 17 hazy 19 clear 19 clear 16 . hazy 304- clear 30f clear 30f clear 30f clear 30f clear -16 cloudy 15 clear 15 clear 17 hazy 19 clear 19 clear cloudy -2 clear -2 clear 30-t clear 30f clear 30f clear 30+ clear 28 clear 29 clear 20 clear 20 clear 18 clear 30f clear 30+ clear 30f clear 30f clear 30+ clear 304- clear 21 hazy 26 clear 26 clear 17 haay 22 clear 22 clear 18 hazy 30+ d e a r 30f d e a r 30+ clear 30f clear 30f clear
Peroxide No.
by hydrogen was shown by the fact that as much mercaptan was formed in the presence of nitrogen as in hydrogen. In the case of 2-octene, for example, the mercaptan sulfur after exposure in nitrogen was 0.022 per cent, and in hydrogen 0.019 per cent. Diisobutylene and n-propyl disulfide gave 0.014 per cent mercaptan sulfur in nitrogen and 0.017 per cent in hydrogen.
Thermal Effects Exposure of the hydrocarbons to the carbon arc lamp was accompanied by a rise in temperature to about 58" C. except in the case of cyclopentadiene which was kept cooled by a coil immersed in the liquid in order to prevent vaporization. The final temperature in this case was 30" C. In order to show that the effects observed in the preceding tests were photochemical the pure hydrocarbons and those containing added sulfur compounds were heated in the dark in atmospheres of oxygen and hydrogen from room temperature to 58" C. over a period of one hour. They were then examined in the same manner as those exposed to the arc light. The results showed no change in the properties of the hydrocarbons and no evidence of reaction under these conditions except in cyclohexene, and even in this case the peroxide number only was slightly affected (from 0.5 to 1.0 peroxide number increase). Therefore, the effects observed in the preceding tests appear to be due to photochemical reactions.
1.82 0 011 0,011 2.12 0.022 0.011 0.172 0.00 0.00
0.83 0.011 0.031 1.52 0.011 0.011 0.27 0.00 0.00 0.054 0.00 0.00
0.41 0.054 0.11
25.7 0.40 0.71 12.26 0.71 0.91 2.02 0.22 0.51 27.75 0.50 0.50 13.15 0.54 0.45 5.20 0.44 0.44 2.32 0.164 0.22 12.2 0.22 0.22 0.87 0,042 0,011
Acid No. Trace 0.0 0.0 0.9 0.0 0.0 0.1 0.0 0.0 1.9 0.0 0.0 0.1 0.0 0.0 1.5 0.0 0.0 0.25 0.0 0.0 3.9 0.0 0.0 0.7 0.2 0.15 0.6 0.15 0.2 0.3 0.2 0.2 0.7 0.1 0.1 0.75 0.1 0.1 1.0 0.1 0.15 0.7 0.2 0.15 1.2 0.0 0.0 0.1 0.0
0.0
Refractive Index Bromine Cor. to No. 20' C. 0 0 0
0 0
0
0 0 0
0 0 B 0
0 0 0 0 0 0 0 0
0 0
0.
141 140 141 141 141 135 139 139 135 134 132 136 142 142 143 139 142 142 142 144 138 143 138 145 0 0 0
1.3875 1.3877 1.3875 1.3877 1.3877 1.3877 1.3878 1.3879 1.3879 1.3881 1.3881 1.3882 1.3916 1.3916 1.3916 1.3918 1.3916 1.3916 1.3916 1.3916 1.3916 1.3916 1.3916 1.3918 1.4157 1.4158 1.4156 1.4157 1.4157 1.4169 1.4158 1.4168 1.4159 1.4158 1.4159 1.4157 1.4109 1.4110 1.4110 1.4108 1.4108 1.4109 1.4109 1,4109 1.4110 1.4110 1,4110 1.4109 1.4267 1.4267 1.4207
Hz3 Neg. Neg. Neg. Neg.
Pos.
Pos. Neg. Pos.
Pos. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Pos. Pos. Neg. Pos. Pos. Neg. Neg. Nep. Neg. Neg. Neg. Neg. Pos. Poa. Neg. Pos. Pos. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Pos. Pos. Neg. Pos. Pos. Neg. Neg. Neg. Neg. Neg. Neg.
Mercaptans Neg. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Neg. POS. Pos. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Nep. Neg. Pos. Pos. Neg. Nea. Neg. Neg.
Pos. Pos.
Trace Pos.
Pos. Trace Pos. Pos. Neg. Neg. Neg. Neg. Pos. Pos. Neg. Pos. Pos. Neg. Poa. Pos. Neg. Neg. Neg.
Sulfur
SOz
Neg. Neg. Neg. Pos. Neg. Neg. Pos. Neg. Neg. Pos. Neg. Neg. Neg. Neg. Nee. Pos. Neg. Neg. Poa. Pos. Pos. Neg. Pos. Neg. Pos. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Nee. Neg. Pos. Pos. Neg. Neg. Trace Neg. Pos. Pos. Poa. Neg. Pos. Neg. Neg. Pos. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Trace Pos. Neg. Neg. Neg. Neg. Pos. Pos. Pos. Neg. Pos. Neg. Neg. Pos. Neg. Nee. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Neg.
Neg. Neg. Neg. Neg. Poa. Pos. Pos. Poa. Pos. Neg. Neg. Neg. Neg. Neg. Neg. Poa. Pos. Po%
90s Neg. Neg. Neg. Pos. Neg. Neg. Pos. Neg. Neg. Pos. Neg. Neg. Neg. Neg. Neg. Pos. Neg. Neg. Pos. Ne& Neg. Pos. Neg. Neg. Neg. Nee. Neg. Pos. Nee. Neg. Pos. Neg. Neg. Pos. Neg. Neg, Neg. Neg. Neg. Pos. Nag. Neg. Pos. Neg. Neg. Pos. Neg. Neg. Neg. Neg. Neg.
Behavior of Pure Hydrocarbons and Gasolines From the preceding data and within the limits of the hydrocarbons tested (with the exception of benzene), we may conclude that hydrocarbons are not responsible for color depreciation of gasolines exposed to light and oxygen. In general, hydrocarbons themselves, including the otherwise unstable dienes, do not form color or haze and hence are not responsible for color instability of gasolines. Previous work showed (2, 3, 4) that gasolines from which elementary sulfur and disulfides had been removed were color-stable in light and oxygen. The unsaturated hydrocarbons, being more susceptible to photochemical oxidation than the saturated or aromatic hydrocarbons, are probably responsible for the major part of the oxidation products found in gasolines exposed to light in the presence of oxygen. Gum determinations (A. S. T. M. method D381-34T) after exposure to light and oxygen showed no gum formation in 2-octene, whereas cyclopentadiene contained 182 mg., pinene 32 mg., and limonene 166 mg. of air-jet gum. None of these hydrocarbons contained gum before exposure except cyclopentadiene which gave 64 mg. This property was no doubt due to polymerization of the cyclopentadiene during evaporation in the gum test. These results show that the diene type hydrocarbons form gum readily in light and oxygen. For this reason their presence in gasolines is objectionable. The presence of small amounts of unsaturates in the straight-run gasolines previously studied
INDUSTRIAL AND ENGINEERING CHEMISTRY
APRIL, 1936
TABLE I1 (Continued) Hydrocarbon Cyclohexane (Cont'd)
Compound -4dded P e r cent Elementary S, 0 01
Atmosphere 0 2
N2 H 2
Elementary S, 0 10 n-Propyl disulfide (equiv. t o 0.10S ) Gyolohexene
None None None Elementary S,0 01
0 2
Nz Hz 0 2
N Z
Hi 0 2
NZ H2
Oa
N2
H2
Elementary S,0.10
0 2
N2
H2 n-Propyl disulfide (equir. t o 0.10 S)
On
None
0 2 x 2
Nz
H 2
Benzene
Hz Elementary 6, 0.01
0 2
N2
H2 Elementary 8, 0.10
0 2
N2 H 2
n-Propyl disul6de :equio. to 0.10S)
0 2
N2 H2
Toluene
None None None Elementary S, 0 01
0 2 N 2
H2 0 2
N2 H2
Elementary S, 0 . 1 0
0 2
N2
H2
Cyclopentadiene Pinene d-Limonene
n-Propyl disul6de to 0.10 S )
0 2
None s, 0.01 None S,O.Ol None s, 0.01
0 2 0 2
Nz H2 0 2
0 2 0 2
0 2
Color Sagbolt 6 hazy 15 clear 14 clear 7 hazy 16 clear 15 clear 17 hazy 23 clear 23 clear 3 0 4 clear 30+ clear 30+ clear 18 hazy 28 clear 25 clear 18 hazy 20 clear 19 clear 30+ clear 30+ clear 30+ clear 26 clear 20 clear 21 clear 17 hazy 10 clear 10 clear 15 hazy 15 clear 14 clear 18 hazy 22 clear 19 clear 30+ clear 30+ clear 30+ clear 14 hazy 7 clear 5 clear 12 clear 12 clear 11 clear 10 hazy 301- clear 30+ clear 30+ clear 28 clear
--
%+ 2;; 28 25
clear clear
(4) may account for the development in the presence of light and oxygen of considerably higher peroxide numbers than the pure saturated and aromatic hydrocarbons. Elementary sulfur had a deleterious effect on the color stability of all types of hydrocarbons studied; hence its presence in gasoline may be expected to reduce the color stability in light. Experience supports this conclusion. Under nitrogen or hydrogen, straight-run gasolines containing added sulfur were shown to form hydrogen sulfide. The formation of mercaptans may be accounted for by the presence of unsaturates in the gasoline which was found to be characteristic of this type of hydrocarbon. n-Propyl disulfide depreciated the color stability in light and oxygen of the paraffin, cycloparaffin, and aromatic hydrocarbons, and the branched-chain olefin, diisobutylene. The presence of these hydrocarbons in gasolines containing disulfides would account for the resultant color instability. n-Propyl disulfide affected the color stability of unsaturated hydrocarbons less than saturated or aromatic hydrocarbons. Similarly it had less harmful effect on the color stability of cracked than straight-run gasolines. The reactions in atmospheres of nitrogen and hydrogen between n-propyl disulfide and all the types of pure hydrocarbons studied which resulted in mercaptan formation were also shown to occur in straight-run, cracked, and blended gasolines (4). The behavior of n-propyl disulfide in the pure hydrocarbons was similar to that in gasolines.
Peroxide No.
Acid No.
0.022 0.00 0.00 0.022 0.00 0.00 0.20 0.00 0.00 14.0 0.61
0.65 0.0 0.0 0.10 0.0 0.0 1.1 0.0 0.0 0.5
14.3 0.51
0.7 0.25
3.32 0.38
0.4 0.1 0.3 0.85
...
...
...
17.5 0.83 0.51 0.20 0.011 0.022 0.033 0.00 0.011 0,033 0.011 0,011 0.043 0.011 0.00 1.32 0.00 0.11 0.165 0.00 0.00 0.11 0.00 0.00 2.02 0.11 0.00 8.85 9.02 18.8 16.8 24.6 22.8
... .
.
I
...
...
0.3 0 1 0.0 0.0 0.35 0.0 0.0 0.3 0.0 0.0 0.9 0.0 0.0 0.15 0.0 0.0 0.8 0.0 0.0 0.3
0.0 0.0 3.40 0.0 0.0 0.9 1.0 0.35 0.50
...
...
Refractive Index Bromine Cor. t o No. 20" C. 0 0 0. 0
0 0 0 0
0 200 199 201 196 202 199 200 201 200 200 202 202 0
0 0 0 0 0 0 0
0 0 0 0
0 0 0 0
0
0 0 0 0 0 0 0
...
... , . . , , ,
...
...
1.4262 1.4261 1.4263 1.4263 1.4262 1.4263 1.4265 1.4264 1.4264 1.4461 1.4463 1.4463 1.4461 1.4462 1.4462 1 .4465 1.4465 1.4464 1.4465 1.4464 1,4464 1 5009 1.5009 1.5009 1.5009 1.5009 1.5009 1.5012 1.5009 1.5008 1.5006 1.5008 1.6008 1.4957 1.4956 1.4956 1.4956 1.4956 1.4955 1.4956 1.4956 1.4956 1.4956 1.4956 1.4956 1.4479 1.4479 1.4680 1.4678 1.4718 1.4718
45 1
HIS Neg. Pos. PO%
Neg. Nag. Neg. Nag. Neg. Neg. Neg. Neg. Neg. Neg. POS. POS. POS.
Pos. Pos. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Pos. Pos. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Trace Pos. Pos. Trace PO&
Poa. Neg. Neg. Neg. Keg. Neg. Neg. Neg. Neg. Nea.
Mercaptans Neg. Neg. Neg. Neg. Neg. Neg. Neg. Pos. Pos. Neg. Neg. Neg. Pos. Pos. Pos. Poa. Pos. POS. Pos. Poa. Pos. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Trace Pos. Poa. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Neg. POS. Pas. Nee. Neg. Neg. Nee. Neg. Neg.
Sulfur Pos. P08.
Pos. Pos. Pas. PO&
501
so3
Pos. Neg. Neg. Pos. Neg. Neg Poe. Neg. Neg. Neg. Neg. Neg.
POS. Ne& Neg. Poa. Neg. Neg. Pos. Neg. Neg. Neg. Neg. Neg. Pos. Neg. Neg. Pos. Neg. Neg. Pos. Neg. Neg. Neg. Neg. Neg.
Neg. Neg. Neg. Nee. Neg. Neg. Neg. POS. Trace Neg. Neg. Neg. Pas. Poa. Pos. Neg. Pas. Neg. Neg. POS. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Pas. POS. Pos. Neg. Pos. Neg. Poa. POS. Poa. Neg. Poa. Neg. Neg. POS. Neg. Neg. Neg. Neg. Nag. Neg. Neg. Neg. Neg. Neg. Pos. Pos. Pos. Neg. Pos. Neg. Pos. Pos. POS. Neg. Poa. Neg. Neg. Poa. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Ne& Neg. Neg. Neg. Neg. Neg. Neg. Neg. Neg.
PO&
Neg. Neg.
Pos.
Neg. Neg. Pos. Neg. Neg. Neg. Neg. Neg. Pos. Neg. Neg. Pos. Neg. Neg. PO&
Neg. Nee. Neg. Neg. Neg. Neg. Nee. Nee.
Summary and Conclusions 1. The chemical and physical properties of hydrocarbons as indicated by the bromine number and refractive index were unchanged by exposure to light either in the presence or absence of sulfur or n-propyl disulfide. The hydrocarbons could be recovered in as pure state as the original by distillation. We may conclude, therefore, that the reactions resulting in the formation of color, haze, peroxides, etc., affect only a small amount of the hydrocarbons. 2. The changes observed did not take place in the absence of light under the same conditions of temperature and time in the arc lamp. The reactions occurring in the arc lamp test were therefore photochemical. 3. The pure hydrocarbons formed no color or haze upon exposure to light, with the exception of benzene which became colored in oxygen, nitrogen, or hydrogen. 4. Peroxides, aldehydes, and acids formed upon exposure of the hydrocarbons to light and oxygen. The olefin, cycloblefin, diolefin, and terpene hydrocarbons oxidized more readily than the paraffin, cycloparaffin, or aromatic hydrocarbons, 5. Sulfur caused color formation in all the hydrocarbons exposed to the light, and in oxygen also caused haze formation except in 2--octene, cyclopentadiene, and d-limonene. 6. Hydrocarbons containing sulfur tended to have lower peroxide numbers and higher acid numbers after exposure to oxygen than in the absence of sulfur.
INDUSTRIAL AND ENGINEERING CHEMISTRY
452
7. Sulfur contained in the hydrocarbons was partially or wholly oxidized to sulfur dioxide and trioxide upon exposure in oxygen. 8. In nitrogen or hydrogen, hydrocarbons reacted with sulfur in the light. Paraffin, cycloparaffin, and aromatic hydrocarbons formed hydrogen sulfide and sulfides. Olefin and cycloolefin hydrocarbons formed hydrogen sulfide and mercaptans. 9. Addition of n-propyl disulfide resulted in color and haze formation in all of the hydrocarbons except 2-octene and cyclohexene upon exposure to light and oxygen. In nitrogen or hydrogen the disulfide caused color formation in none of the hydrocarbons except 2,2,4-trimethylpentane and cyclohexane. 10. Saturated and aromatic hydrocarbons containing n-propyl disulfide developed less peroxides when exposed to light and oxygen than the pure hydrocarbons similarly exposed. The disulfide had no effect on the peroxide numbers of unsaturated hydrocarbons. 11. In nitrogen or hydrogen all hydrocarbons to which n-propyl disulfide was added contained mercaptans due to reaction between hydrocarbons and the disulfide. 12. Comparison of the work with pure hydrocarbons and with straight-run, cracked, and blended gasolines, with and without added sulfur or n-propyl disulfide, shows that the behavior of the gasolines was such as would be expected of
VOL. 28, NO. 4
mixtures of various types of hydrocarbons. In general, pure hydrocarbons or gasolines from which sulfur and disulfides had been removed were color-stable in light. The response tos ulfur of paraffin, cycloparaffin, and aromatic hydrocarbons was similar to straight-run gasolines except that the straightrun gasoline had higher peroxide numbers in oxygen and formed mercaptans in nitrogen or hydrogen. These differences might be accounted for by the presence of unsaturates in the straight-run gasoline. The response of unsaturated hydrocarbons to sulfur was like that of cracked gasoline. The behavior of hydrocarbons containing n-propyl disulfide was similar to gasolines. The disulfide had less deleterious effect on color stability of unsaturated hydrocarbons and cracked gasoline than it did on the stability of saturated or aromatic hydrocarbons or straight-run gasoline.
Literature Cited (1) Dryer, Lowry, Morrell, and Egloff, IND. ENO. CHEM.,26, 885 (1934).
(2) Egloff, Morrell, Benedict, and Wirth, Ibid., 27, 323 (1935). (3) Francis, Ibid., 18, 821 (1926). (4) Morrell, Benedict, and Egloff, Ibid., 28, 122 (1936). (5) Yule and Wilson, Ibid., 23, 1254 (1931).
RECEIVED October 5, 1936. Presented before the Division of Petroleum Chemistry at the 90th Meeting of the American Chemical Society, Saa Francisco, Calif , August 19 to 23, 1935.
4
,
2s
88
30
SUCROSE SOLUTIONS Influence of Pressure on Boiling Point Elevation Y
85
90
13.55 19.95
OR the purpose of more closely controlling sugar-boiling operations, boiling point elevations are widely used in estimating the degree of supersaturation. It is therefore obvious that accurate data on the boiling points of suorose solutions of various concentrations are essential. From this standpoint it is unfortunate that the boiling points of sucrose solutions as reported by various investigators have differed so greatly that considerable doubt has existed as to what values might be safely accepted. An investigation of this subject was accordingly undertaken with the object of finding answers to each of the following questions: 1. What values may be accepted as accurately representing the boiling point elevations of sucrose solutions of various concentrations?
2. To what extent, if any, are such boiling point elevations affected by the absolute pressure under which boiling takes place in vacuum pans?
In the course of this investigation a number of Iaboratory determinations were made on the boiling points of pure sucrose solutions of various concentrations a t an atmospheric pressure of 760 mm. of mercury. The results are plotted in Figure 1. The fact that boiling point elevations taken from this graph do not differ greatly from those reported by Claasen ( 2 ) is evident from Table I which compares the present determinations (reported as C. and H. data) with those of Claasen as well as with those reported by other investigators. From such results it is evident that Claasen’s values are checked closely, not only by the present determinations made a t atmospheric pressure but also by those reported by Inter-
