Peroxides in Gasoline I'Mects of Peroxide Formation in Crackcd Gasolines J. C. MORRELL, C. G. DRYER, C. D. LOWRY, JR., AND GUSTAVEGLOFF Universal Oil Products Company, Chicago, Ill.
T
N E d e t e r i u r a t i o n of been reported as an early step Peroxides are formed in controlled urrrount in c r a c k e d gasoline apin the drying of linseed oil by four represerztative cracked gasolirie.s, two trealed parently begins by Falirion (8) and other investigaarid two unlrmled. Tlie oxidized gasoline is liutoxidation of its unsaturated tors. P c r o x i d e s are also imanalyzed, and from par1 of it the perozides are components. 1x1 tests made in portant in the development OS remoced by percolution through fuller's earth. this l a b o r a t o r y ( 7 ) , gasoline rancidity in fats which, accord.stored a\r&y Sroni liglit showed in:: to Wheeler (25), is caused Comparison is then made .f tlie octarie number, marked deterioration only in the by an autoxidation of unsatugum content, arid indacliori period of the original, presence OS oxygen. The first rated glycerides. Motor detunaperoxidized, arid regenerated yasolines, with and e v i d e n c e of change is usually tion has been a t t r i b u t e d by without inhibitors. It is found lhal, as the the appearance OS substances C a l l e n d a r (5) and others to peroxides are increased, tlie copper-dish gum, having the characteristics of perf o r m a t i o n OS peroxidic conioxides. As the aging of g:iaipounds in tlie engine. Mourcu whether measured with or wilhout an inhibitor, line cont.inues, there is darkenand co-workers explain the acis increased, and octane number and induction ing in color, formation of gum, tion OS antioxidants by a peroxperiod are reduced. On. r e m t a l of peroxides, loss of antiknock value, ;uuldr.ide mechanism (18). there is lillle effect on the copper-dish gams crease in susceptibi1it.y to iiiThe structures of the peroxidic except when ari inhibitor is used, in which case liibitors. substances w-hich are formed by Brook? (8)reported the qiautoxidation OS cracked gasolincs the inhibitor reduces the copper-dish gum. The pearance OS p e r o x i d e s on air are not knou-n. Even the chemirutLcction period is ulso increased by peroxide oxidation of "unsaturated petroistry of peroxide formation Srom r e m o d , both zoitli and without a n inhibitor. To leum oils,'' and stated (8) that single unsaturated hydrocarbons attain a giceri induction period, more inhibitor their formation is the most inihas not been ent.irely elucidated. is necessary wlien peroxides are present than portant reaction in gum formaThe addition product of an olefin tion. Kogerman (ZI), Mardles and oxygen is most frequently when it is peroxideJree. Ari excessiue amount and Moss (i4),Story, Provine, Sormulated R2C-Cltz, where R of perozide negatives the irthihitiny influence. I1 1, and Bennett (Pi?), and Wligiier The rate of peroxide .fornialiort during the inducand Hyinan (S3) confirmed the 0--0 lion period of the yawline, with and without a n presence of peroxides in old gasomay be an alkyl or aryl radical, inhibitor, is ulso determined. line. Cassar ( 6 ) slioiwd t.liat or livdropen. Koeorman 112) peroxidized olefins increased tlie postulaFes the f&mation of tendency oE unstable cracked distillates to gnm Scmnation. peroxides Srom conjugated diolefin. by l,.i-addition to give The work of Yule and TVilsoii 1861 R&-CII=CI-I --CI1,. Milas (16, i7) and Staudinger (20) , , is of nnrt,icular importaoce because they dewlopcd a rapid qiiantit.ativc method I I (J for the determination OS peroxides in gasoline, showed the efiect OS a niimtier of reagents on these peroxides, and in- believe more active peroxides of different structure antecede dicated a relat,ionship between pcroxidc Sonnation and gum peroxides OS this type. Stephens (21) admits "a difference in energy content between the Sreslily formed peroxide mole content. Practical importance has been claimed for yeriixides in a culcs and the normal molecules of isolable product," but iiumiier of fields besides that of cracked gnroline. Notor finds "no reason Sor associating this with a structural differbenzenes which contain unsaturnted hydrocarbons are re- encc wliirli can tie rcprcsented by any present system of notaported by IIoffert and Claxton (9) to "resinify rapidly in t,ion." So peroxide of a siniple olefin has been isolated and s t o r a g e a n d give nositivelv identified. reactions indicating Tlie individual perthe presence of such oxides which ham substances as perbeen o b t a i n e d , oxides, aldehydes, usually oils, appear and acids unto be polymerized doubtedly formed substances, as they by oxidation." The have high molecular gum Sormed iii enrweiglits. Aldrhydes bureted wat,er gas have been reported has been found by in oxidized cracked Ward, Jordan, and gasolines, and some Fulweiler (24) to oS.the peroxides contain peroxidic f o u n d m a y come Persubstances. Srom them. These oxide formation has would be of a differ~I
498
INDUSTRIAL AND E N G I N E E R I N G CHEMISTRY
Vol 26, No. 5
oxidation, the bombs were filled with oxygen or air a t room temperature to the pressure indicated, closed, and heated without regulating the pressure attained. The results are shown in Figure 1. Each point on the curves represents a separate experiment. The curves show that at all pressures peroxide formation began a t a comparatively slow rate and then accelerated. The rate of peroxide formation increased as the oxygen concentration in the bomb was raised. In the runs a t 100 pounds per square inch (7.03 kg. per sq. cm.) oxygen pressure, the rate of peroxide formation continued to increase to the end of the test. When lower pressures of air or oxygen were used, there was a falling off of the rate after a time because of approaching exhaustion of the oxygen present. The ratio of oxygen to gasoline in the bombs even at high pressure was not great. EmpIoging the information from these curves, a series of samples of regularly increasing peroxide concentration was prepared. The properties of each gasoline were then determined, alone and with an inhibitor present. From a part of each sample, peroxides (and possibly other oxygenated compounds as well) were removed by passage at room temperature a t the rate of 15 cc. per minute through 50 to 150 grams of fuller’s earth, for a 1500-cc. sample of gasoline, the amount of earth used depending upon the amount of peroxide to be removed. Properties were then redetermined. The inhibitors used were catechol and hardwood tar distillate (13). They were added in sufficient amount to give induction periods in the original gasoline of about 240 minutes, which would assure satisfactory storage life. Catechol was selected, in spite of its unsuitability for commercial use, FIGURE1. RATESOF PEROXIDE FORMATION OF UNREFINED by reason of its high solubility in water, in order to relate PENNSYLVANIA GASOLINE this study to the extensive work which has been done on ent type from those arising from unsaturated hydrocarbons. pure compounds as inhibitors. The hardwood tar disWagner and Hyman (H)believe that peracids formed from tilIate, a commercial gasoline inhibitor, was used because of the bearing of peroxide studies on the practical application aldehydes are the essential catalysts in gum formation. I n this paper the term “peroxide” is used for all substances of inhibitors. determinable by the method of Yule and Wilson. The OF PEROXIDE REMOVAL FRON TREATED extent to which such substances are present in gasoline is of TABLEI. METHODS MIDCONTINENT GASOLINE great importance which is not lessened by the fact that their GUM structure is not definitely known. INDUCTION CuAirPEROXIDE No. COLOR PERIOD dish jet The general plan of the present investigation has been to Minutes IVQ./~OO cc subject representative cracked gasolines to controlled oxida- Original gasoline 94 2 255 20 0 tion and obtain series of gasoline samples containing per- Same C 0.025% wood47 1 .. 405 ... tar distillate inhibitor oxides in measured amount over a wide range of concentra- Gasoline after oxidationa 6.3 240 i 85 18 ti 202 .. 905 ... inhibited tion. From part of each sample, peroxides were removed. Same Treatment of oxidized gasoline: The properties of the original, peroxidised, and regenerated 58 0 120 15 0.4 Steam disti!latioa gasolines were compared, noting particularly gum content, L 66 355 .. 0.4 Same inhibited 4 49 21 120 0.4 Fuller’s earthb antiknock value, and susceptibility to inhibitors. 15 3 330 .. ... Same inhibited 12 191 75 li 0.2 Sodium carbonate0 When gasoline is exposed to oxidizing conditions, other 170 13 160 ... Same inhibjted products than peroxides are formed. These products are 222 52 45 BrbwD 0.7 Sulfur dioxided 117 52 90 .. ... Same inhibited being studied in work now in progress in this laboratory. 19 207 55 14 0.9 Ferrous sulfate’ 188 13 .. 105 ... Same inhibited. It is not certain that all the changes in the properties of 201 10 50 14 0.7 Stannous chloride/ gasoline which accompany the formation of peroxides are 14 115 297 .. ... Same inhibited due to them alone. Peroxide number has been used as a a Oxidised 150 minutes a t 100 lb. per sq. in. (7.03 kg. per sq. cin.) oxygen convenient measure of the extent of gasoline deterioration. pressure. b Percolated through column. Shaken with 10% solution. Peroxide numbers are significant, not alone because the by weight added i n three portions wlth half-hour d Approximately 0 1 formation of peroxides is important but because the con- agitation after each adgtjon, followed by wash with 10% NszCOa. e Agitated 1.5 hpurs with 20% by volume of saturated solut!on. centration of peroxides is an index to the entire complex series I Agitated 30 minutes with 5y0 by volume of saturated solution. of reactions which go on when cracked gasoline is in contact with oxygen. Peroxide concentration, determined by the method of Yule and Wilson, is expressed in their unit, “peroxide numUNREFINED PENNSYLVANIA GASOLINE ber” or gram equivalents of active oxygen per 1000 liters. An untreated Pennsylvania gasoline obtained by cracking The determination depends upon the quantitative oxidation a mixture of water-white distillate and gas oil was oxidized of ferrous to ferric ion by peroxide, followed by determination a t 100’ C. in the bombs described in an earlier paper (7) of the ferric ion by titration with titanous chloride in the under varied concentrations of oxygen, and the rates of presence of thiocyanate. The method is delicate and rapid peroxide formation were determined. I n carrying out the in operation and to the writers’ knowledge is the best avail0
May, 1931
1N D U S T R I A L
A N D E N GI N EE R IN G CH E M ISTR Y
able. Experiments with the potassium iodide method of Wheeler (M), which is widely used for fats and fatty oils, indicated that reaction is incomplete when it is applied to gasoline. If a small amount of sulfuric acid is added in making the test, the sensitiveness of the iodide method is increased, and it then gives values somewhat higher than the Yule and Wilson method. The English workers tried the potassiuni iodide method of Marks and Morrell (16) and found that, while less sensitive than the thiocyanate method, it gave much higher values when the peroxide concentration was considerable. Fuller's earth was selected for peroxide removal, after trial of a number of reagents, because in most cases it eliminated peroxides quickly and completely, and of the reagents tested it made the least change in other properties of the gasoline. It could be used without subsequent distillation, whereas other methods of peroxide removal, as shown in Table I, unless followed by distillation, impaired the color of the gasoline, increased gum, or failed to restore induction period and susceptibility to inhibitors.
TABLE
11.
499
SUMMARY O F CRACKING OPERATIOX O F UNTREATED
PENNSYLVANIA GASOLINE
Charging stock, blend of water, white distillate, and gas oil: Sp. gr. Gr.. A. P. I. A. S. T. M. 100-cc. distn : Initial b. p. % ' distilled over:
0.8118 42.8
c.
10
50 90 End point Cracking conditions: Pressure, lb,./in.* (kg./cm.2) Max. cracking temp., O C. ( O F . ,
166
F.) (330)
201 276 362 397
(394) (528) (684) (746)
400 518
(28.12) (965)
( 0
The properties of the original gasoline, of the oxidized samples, and of the gasolines from which peroxides had been removed are presented in Table 111. TABLE111. PEROXIDES I N UNTREATEDPEXNSYLVANIA GASOLINE
%:.g:i P. 1.
6.
T. M. 100-cc. distn Initial b. p. yo distilled over' 10 50 90 End point CONDITIONS O F OXIDATION GUM Air pressure PEROXIDECuAirTime in bomb No. dish jet .Win Lb./tn.2 (ke./crn.2) .Mg /loo cc
A.
PEROXIDE
No oxidation 28 ci.'i$) 32 25 (1.76) 45 Atmospheric 120 Atmospheric 60 25 (1.76) 80 50 (3.52)
is
0.7208 64.8 c. ( 0 F . ) 36 ( 96)
51 106 165 178
(123) (222)
OCTANEINDUCTION No. PERIOD Min
FORMATION
0 .ooa 0.18 0.40 0.84 1.60 3.00 6.70
31 86 177 105 135 165 213
0
0 2 0 2 10 28
76b 76 75 75 76 75 78
65 60 60 55 50 35 35
INHIBITION OF PEROXIDIZED GASOLINES
0.05% wood-tar distillate inhibitor
O . O l ~ ocatechol
0 . ooa
5 5 15 21 80 146 187
2 0 4 0 2 12 30
0 . ooa
6 6 9 5 28 116 190
0 0 2 0 2 6 28
0.18 0.40 0.84 1.60 3.00 6.70 0.18 0.40 0.84 1.60 3.00 6.70
PROPERTIES
AFTER PEROXIDE REMOVAL
PEROXIDE NUMBER From: To: n nn n .on. 0.18 0.00 0.00 0.40 0.84 0.00 0.16 1.60 3.00 0.20 1 .oo 6.70
R4 -~ 71 138 151 104 226 198
BY
280 285 250 245 205 125 90
..
220 235 190 185 190 140 80
..
.. .. .. ..
FULLER'S
EARTH
n
76 b
75
8 6 10 10 18 28
76 75 75 76 75 74
SO 80 80 60 65 50
INHIBITION AFTER PEROXIDE REMOVAL
TIME IN
FIGURE
7.
Muvures
PEROXIDE FomfATION DURING INDUCTION PERIOD OF UNTREATED PENYSYLVANIA GASOLINE
Copperdish gum determinations in this investigation were made in the apparatus designed by the Atlantic Refining Company (4). Air-jet gum was determined by method A of A. S. T. M. Committee D2 ( 1 ) . Octane numbers were by the C. F. R. Committee Research method. Induction periods were found by the procedure of Hunn, Fischer, and Blackwood (10) in the bombs which have been mentioned. A summary of the cracking operation by which the unrefined Pennsylvania gasoline was prepared is given in Table 11.
0.05% wood-tar diaiillate inhibitor 0.00 0.18 0.40 0.84 1.60 3.00 6.70
0.000 0.00 0.00 0.00 0.16 0.20 1.00
8 19 20 26 22 27 109
2 S
4 8 8 14 24
.. ..
.. .. ..
Original. b Octane ratings were determined on inhibited samples to avoid possibility of chsnge in properties between oxidation and determination of octane number, The inhibitor does not change octane number. a
Table I11 shows that, as the peroxide number was increased within the limits studied, the following changes occurred in the other properties of the gasoline: 1. The copper-dish gum increased.
The air-jet gum, initially zero, remained negligible until the peroxide number of 1.6 was passed and then increased. This differs from the report of Yule and Wilson ($6) who found gum formed on evaporation proportional to the amount of peroxides present. 3. The induction period was reduced. 4. The octane number droppd slightly. 2.
500
IN D U S TR I A L A N D E N G I N E E R I N G C H E MI S T R Y
When the wood-tar distillate inhibitor or catechol was added, the samples having peroxide numbers of 0.84 or below showed little gum in the copper-dish test. The induction period was raised by either inhibitor to a figure not greatly below that produced by the addition of the inhibitor to the 4
Vol. 26, No. 5
6.7 did the induction period with inhibitor fail by a small amount to return to its original value. It is interesting to note that this regenerated sample, which had a peroxide number of 1.0, gave the same induction period as the sample initially oxidized to about the same figure-0.84 peroxide number. The air-jet gum figures were slightly reduced by the inhibitor. The results indicate that a gasoline in which peroxides have developed to such an extent that i t cannot be satisfactorily inhibited but which has not otherwise deteriorated may be successfully inhibited if peroxides are first removed. REFINEDPEKNSYLVANIA GASOLINE Samples of a Pennsylvania cracked gasoline which had been refined with fuller's earth in the vapor phase were similarly oxidized a t 100 pounds per square inch (7.03 kg. per sq. cm.) oxygen pressure to give peroxide contents as nearly as possible equal to the peroxide contents of the untreated samples which have been discussed. The behavior of these samples toward inhibitors and the effects of peroxide removal were then determined as on the untreated gasoline. A summary of the cracking operation by which this gasoline was made is given in Table IV. TABLEIV. SUMMARY OF CRACKING OPERATIOSOF REFINED PENSSYLVANIA GASOLINE Charging stock, gas oil: Sp. gr. Gr., A . P. I. A. 9. T. R?. 100-cc. distn.: Initial b. p. % ' distilled over: 10 50 90
End Doint Cracking conditions: Pressure (reaction chamber), lb./in.Z (kgJcm.2) Max. cracking temp., C. (" F.)
FIGURE 3. PEROXIDE FORMATION DURING IXDUCTION PERIOD OF REFINEDPENNSYLVANIA GASOLINE original peroxide-free gasoline. Above this peroxide value, however, the inhibitors were much less effective in reducing copper-dish gum and gave much shorter induction periods. The inhibitors had little or no effect on air-jet gum. These results confirm the statement of Yule and Wilson that peroxides decrease the efficiency of a n inhibitor. I n this laboratory peroxide determination is a routine test made on every sample of gasoline which is to be inhibited, and satisfactory results are not expected if peroxides are present in considerable concentration. Except with the gasoline of 6.7 peroxide number, practically complete removal of peroxides was obtained by the passage through fuller's earth. By this treatment the original gasoline was somewhat increased in copper-dish gum and induction period, but air-jet gum was unchanged. Removal of peroxides from the oxidized samples produced practically no change in the copper-dish gum. The air-jet gum was slightly increased, but, where the peroxide content was low, the gum did not rise above a permissible figure. The induction periods of the oxidized samples were also restored except the sample having a peroxide number of 6.7 from which peroxides were not completely removed. I n the original gasoline or the samples with peroxide number of 1.6 or below, after they had been passed through fuller's earth, the wood-tar distillate inhibitor was more effective than before this treatment. The deleterious effects of the peroxides on inhibitor action had been completely eliminated. Only with the sample having an initial peroxide number of
0.8285 39.3 a c. ( 0 F.) 159 (318) 240 240 371 396
(464) (627) (699)
400 518
(28.12) (965)
(745)
The results on the refined gasoline which are given in Table V show, in general, the same trends as did the untreated samples. With increasing peroxide number there was an increase in gum, drop in octane rating, and lowering of induction period. I n samples oxidized to 0.4 peroxide number and above, susceptibility to inhibitor was much reduced, both in respect to lowering of copper-dish gum and increasing the induction period. Passage through fuller's earth removed the peroxides, with a marked reduction in copper-dish gum and regeneration of octane rating, but the treatment failed to restore the original induction period. The gasoline freed of peroxide responded well to the wood-tar distillate inhibitor, with the exception of those samples from which a high peroxide content had been removed. I n comparing the unrefined and refined Pennsylvania gasolines, a number of differences will be noted: 1. More vigorous oxidation is required with the treated than the untreated gasoline to form peroxides to a definite concentration. 2. Low peroxide concentrations have more effect in the refined than in the unrefined samples in reducing induction period. With a peroxide number of 0.4, for example, there was practically no change in the induction period of the unrefined gasoline, while at this number the refined sample had a markedly lower induction period. 3. The gum content, by both copper-dish and air-jet methods, was lower for a given peroxide number in the refined than in the unrefined samples. 4. The induction period with inhibitors was much more affected by a given peroxide content in the refined than in the unrefined gasoline, particularly when the concentration of peroxides was low. Increase in peroxide number from about 0.2 to 0.4 reduced the induction period of the refined gasoline by more than 33 per cent, while in the unrefined gasoline the same change caused a difference of only about 10 per cent.
INDUSTRI.4L
May, 1934
-4YD E N G I S E E R I N G C H E M I S T R Y
5. The inhibitors were a number of times more effective in the refined gasoline than in the unrefined, much more than in proportion to the induction periods of the two gasolines. 6. Removal of eroxides did not bring the induction period of the refined gasofine back t o its original value, although the removal was even more complete than in the case of the untreated gasoline. This may indicate that changes other than peroxide formstion have been produced by the severe Conditions of oxidation t o which the gasoline has been subjected. 7 . The samples of the refined gasoline from which peroxides had been removed showed less copper-dish gum than did the peroxidined samples. In the case of the unrefined gasoline, peroxide removal was not accompanied by a lowering of copperdish gum. While air-jet gum was slightly increased by passage of the untreated gasoline through fuller's earth, no increase, and in some cases a decrease, occurred in the case of the treated samples. By addition of inhibitor, the copper-dish gum in the treated samples was lowered t o a much greater extent than in the untreated gasolines. 8. While the inhibition of samples from which a low peroxide content had been removed was satisfactory, samples which had been reduced from a high peroxide content did not respond as well to the inhibitor as did the corresponding samples of untreated gasoline, perhaps because of the severity of the oxidation they had undergone.
TABLEV. PEROXIDES IN TREATED PEYNSYLVASIA GASOLISE s p . gr. Gr., O A. P.I. A . S. T. M. 100-cc. distn.: Initial b. p. Distilled over:
0.7256 63.5
c.
36
10 50 90
54 117 171 196
End point
TIMEOF
Gnnr .kirdish jet M g . / i O O CC.
PEROXIDE Cu-
OXIDATION^
No.
Min.
OCTANE
No.
P E R O X I D E FORllATION
No oxidation
0.OOb 0.24 0.40 0.87 1.40 3.60 7.60 10.00
35 45 52 65 88 107 111
8 21 57 56 84 83 106 111
0 0 0 0 0
4 8 10
74 73 72 i2 72 72 70 68
INHIBITION OF PEROXIDIZED GASOLINE5
0.006%, wood-tar
inhibitor
0 0 0 0 0 4 8 10
0.0015% catechol
O.OOb 0.24 0.40 0.87 1.40 3.60 7.60
10.00
4 6
25 52 58 66 113 90
4 4 10
..
.. .. ..
..
...
.. ..
like those which have been given for the Pennsylvania gasolines. While the gasolines varied in the severity of oxidation conditions needed to produce a given peroxide formation, they all showed the increase in guni, lessening of induction period, and loss of antiknock value and inhibitor susceptibility with increasing peroxide content which was evident in the Pennsylvania samples. From peroxidized samples of all of these gasolines, peroxides were satisfactorily removed with restoration of the properties of the gasoline to substantially their original values.
CALIFORXIA GASOLISES Two California gasolines from the same cracking stock, one untreated and the other after treatment with 4 pounds of 98 per cent sulfuric acid per barrel, proved quite different from the other gasolines studied in their behavior on oxidation. A summary of the cracking operation by which these gasolines were produced is given in Table 6-1. TABLE VI.
Charging stock, Lo8 Angeles-Kettleman Hills fuel oil: Sp. gr. Gr., A . P. I. Cracking conditions: Pressure (reaction chamber), Ib./in.z (kg./cm.*) Max. cracking temp., C. ( " F.)
TABLE VII.
0.24 0.40 0.87 1.40 3.60 7.60 10.00
0.006 GZrwood-
Ih-HIBITION
0.00 0.00 0.08 0.16 0.09 0.06 0.15
68 7 5 4
45
1 14
11
0 0 0 0 0 2 2 2
73 72 72 72 73 72 72 72
275 190 190 175 120 60 65
(I
.. .. .. . I
(14.76) (892)
Gull qirdish let Mg./iOO cc.
PMROXIDE Cu-
TIMEOF OXIDATION^ Min.
NO.
120 105 - .
c.
End Doint
GASOLINE
(0
P.)
42
(108)
65 124 184 207
(149) (256) (363) (405) . .
INDUCOCTANE TION No. PERIOD Min.
PEROXIDE FORMATION ~
K O oxidation
90
85 80 60 40 40
0.66b 1.58 10.20
10 120
495 481 443
INHIBITION OF PEROXIDIZED
wood-tar distillate O'?%bi tor
AFTER PEROXIDE REMOYAL
0.16 6 0 0.09 3 4 0.06 4 4 0.15 5 4 At 100 Ib. per aq. in. (7.03 kg. per sq. cm.) oxygen presaure.
210 478
0.7619 56.7
10 50 YO
0.01% catechol
1.40 3.60 7.60 10.00
0.9303 20.6
PEROXIDES IN WNTREATED CALIFORNIA
Sp. gr. Gr., A. P. 1. .I. S. T. M. 100-eo. distn.: Initial b. p. 70 distilled over:
PROPERTIES AFTER PEROXIDE REMOVAL BY FCLLER'S EARTH
PEROXIDE NEMBER From: To: 0.00 0.OOb
SUMMARY OF CRACKING OPERATIOXo x CALIFORNIA GASOLINES
The properties of these gasolines and a study of their behavior on oxidation is presented in Tables \TI and VIII. The untreated sample peroxidized normally, requiring more INDUCsevere oxidation conditions than the Pennsylvania untreated TION PERIOD sample but oxidizing more easily than the Midcontinent Min. untreated gasoline. However, the use of a large percentage of inhibitor failed t o give a material reduction in copper-dish 120 130 gum on either the original or peroxidized samples, nor did so 70 it have its usual power to increase induction period. Thor70 ough removal of peroxides by fuller's earth was not obtained, 60 .~ 40 and no great change in guni or induction period was brought 40 about by this treatment. Similar results have been obtained in experiments with other untreated California gasolines, 255 a number of which do not respond well to inhibitors, although 230 150 some can be satisfactorily inhibited. 140 145 100 60 55
, .
50 1
PROPERTIES
230 200 165 150
36 12 34
76 74 73
445 430 355
QABOLINES
0.66 1.58 10.20
262 359 304
2 4 18
0.66 1.58 10.20
323 409 240
8 4 30
.. *. .. .. ..
480
670 405
405 575 420
..
AFTER PEROXIDE R E M O Y A L BY FULLER'S
EARTH
PEROXIDE NUMBER From:
0.66 1.58 10.20
b Original.
To:
0.19 0.83 1.94
469 496 136
14 8 16
76 74 74
300 345 285
I N H I B I T I O N AFTER PEROXIDE REMOVAL
Similar studies were made of a "reformed" gasoline produced by cracking a West Texas straight-run gasoline, and of two Midcontinent gasolines cracked from the same stock, one unrefined and one acid-treated. I n general, the results were
0.05y0 wood-
tar distillate inhibitor
.. ..
0.66 0.19 210 6 1.58 0.83 109 8 10.20 1.94 126 14 .It 100 lb. per aq. in. (7.03 kg. per sq. cm.) oxygen pressure.
..
b
Original.
435 465 385
INDUSTRIAL AND ENGINEERING CHEMISTRY
502
TABLE VIII.
PEROXIDES I N
%:.g.’k P. I.
A. S. T.M. 100-cc.distn.: Initial b. p. % distilled over:
TREATED C.4LIFORNIA GASOLINE* contains but a small proportion of easily oxidizable material 0.7479 which is readily removed by acid, leaving a remarkably 57.7 ~.. . stable treated gasoline. Some unknown factor prevents the c. F.) 41 (105) inhibitor from exerting a significant action on the untreated gasoline. 62 (144) (0
-10 _ 60 90
133 (272) 185 (365) 205 (401) PEROXIDE GUM OCTANE No. Cu-dish Air-jet No.
End point
TIMEOF OXIDATIONb
Min.
M g . I l O 0 cc. PEROXIDE FORMATION
No oxidation
0.1oc
360 720
2.33 0.55
16 31 72
0 6
74
16
70
0
..
72
INHIBITION O F PEROXIDIZED GA0OLINEB
0.01% wood-tar distillate inhibitor 0.10 2.33 0.55 0.0025% catechol PROPERTIER
0.10 2.33 0.55 AFTER
PEROXIDE
INRIBITION
16 32 55
0 14
10 14 51
REMOVAL BY
PEROXIDE NUMBER From: To: 0.10 0.01 2.33 0.25 0.55 0.30 0.017 wpod-tar disOil ate inhibitor
Vol. 26. No. 5
. EFFECTS OF HIGHPEROXIDE NUMBERS To show the changes in gasoline properties produced by a still higher degree of peroxidation, samples of the same treated Pennsylvania gasoline (from a different drum) were subjected to more severe conditions of oxidation (Table IX) . TABLEIX. EFFECTSOF HIGH PEROXIDE CONTENTOF UNTREATED PENNSYLVANIA GASOLINE
.,
-
GUM
0
.. E.iRTR
2 4 5
PEROXIDA-OXIDE
~ I M EOF
74 73 70
AFTER PEROXIDE REMOVAL
o.
0.01 9 0 .. 2.33 0.25 13 2 .. 0.55 0.30 34 3 .. No induction periods are shown, a8 no sample showed a break in the oxygen absorption curve in 1600 minutes. b At 100 lb. per sq. in. (7.03kg. per sq. cm.) oxygen pressure. C Original.
The treated California gasoline showed a still different behavior. There was no break in the oxygen pressure curve in 1600 minutes, and so the effect of inhibitors on induction period could not be investigated. One sample of this gasoline was oxidized for 48 hours without a marked drop in pressure. It formed peroxides very slowly, and, instead of the peroxide
FIGURE 4. EFFECT OF PEROXIDE CONTENTON INDUCTION PERIOD OF REFINED PENNSYLVANIA GASOLINE
number increasing with time as in other gasolines, the peroxide concentration rose slightly and then fell. The gum content was low at the start, increased slowly, and was not much affected by inhibitors. Tests on other treated California gasolines have shown, however, that this peculiar behavior is not always found, and that some gasolines from this region are, and can be, reduced in gum and increased in induction period by inhibitors. It seems possible that the untreated California gasoline
WOOD-TAR DISTILLATE INHIBITOR ~
NO INHIBITOR
Cu-
~
~~~~
UN-
AirCuAir- OCTANEINHIB. jet diah jet No. ITBD Min , ---Ma. ver 100 cc. Min. _ . Oh 0.1 25 60 0 6 0 74 75 15 54 0.4 25 2 12 0 .. 74 12.8 24 30 107 34 70 135 10 20.8 19 45 165 142 24 67 16 60 17 63.3 399 415 82 61 99 75 102.0 16 142 156 46 1 218 58 At 100 Ib. per sq. in. (7.03 kg. per a q . c1n.j. b Original.
TI ON^
13 59 41
0.01% WOODTAR DIS
0.01%
4 14 FULLER’S
INDUCTION PERIOD
No. COLORdish
-
TILLATE INHIBITOR
Min. 285 150 60 45 30 30
As the peroxide content increased to a high figure: 1. The octane number dropped markedly. 2. The gasoline depreciated in color. ,
3. The gum content, both copper-dish and air-jet, increased
to high values.
4. The effectiveness of the inhibitor became negligible, both on gum content and length of the induction period.
PEROXIDE FOXMATION DURING INDUCTIONPERIOD To compare the rates of peroxide formation in uninhibited gasolines and in the same gasoline containing different concentrations of inhibitor, portions of the untreated and treated Pennsylvania gasoline were oxidized at 100 pounds per square inch (7.03 kg. per sq. cm.) oxygen pressure and 100’ C., alone and after addition of the wood-tar distillate inhibitor. Peroxide numbers were determined a t 10-minute intervals, a separate sample being oxidized for each point on the curve. The results are shown graphically in Figures 2 and 3. It is seen that: 1. During the fist part of the induction eriod of an uninhibited gasoline, there is a slow formation orperoxides. The development of peroxides goes on a t a gradually increasing rate, and &ally, near the “break” or end of the induction period, there is rapid peroxidation. 2. When an inhibitor is present, peroxides form for a time at a very slow rate, but peroxide formation is not entirely eliminated. They build up a t fist at a fairly uniform rate, then a t an increasing rate, probably as the inhibitor is becoming reduced in concentration, and finally at the break with great rapidity. Increase in the amount of inhibitor present reduces the rate of peroxide formation during the early part of the induction period and prolongs this period. 3. The rate of peroxide formation during the early part of the induction period, both when it is uninhibited and in the presence of an inhibitor, appears to be characteristic of each gasoline, and, while not unrelated t o the length of the induction period, is not proportional t o it. Thus the reformed gasoline with an induction period of 45 minutes forms peroxides before the break at a slower rate than the untreated Pennsylvania gasoline, although the latter has a longer induction periodnamely, 65 minutes. 4. The rate of peroxide formation during the early part of the induction period and the inhibitor susceptibility appear closely related. The writers do not find that, strictly speaking, “the response. . . .varies with the original induction period,” ns claimed by Rogers and Voorhees (19). The wood-tar dis-
INDUSTRIAL AND ENGINEERING CHElTISTRY
May, 1934
503
c o n c e n t r a t i o n increases, other changes occur-darkening in color, gum formation, loss in antiknock value and in s u s c e p t i b i l i t y t o i n hibitors. 2. Peroxides in low conc e n t r a t i o n can be removed from most cracked gasolines, with practically c o m p l e t e recovery of its initial properties. 3. Peroxides decrease the effectiveness of inhibitors but, unless present in high concentration, do not p r e v e n t their a c t i o n entirely. 4. T h e response of a cracked gasoline to inhibitors a p p e a r s to be closely related to the rate of peroxide formation during the induction period.
t i l l a t e i n h i b i t o r proved about twice as effective in t h e We st T e x a s reformed gasoline, which formed peroxides slowly, as in the untreated Pennsylvania sample, although the Pennsylvania gasoline h a d a s l i g h t l y longer i n i t i a l i n d u c t i o n period. The inhibitor was still more effective (much more than t h e i n d u c t i o n period could i n d i c a t e ) in the treated gasoline, which was the slowest of the three gasolines in rate of peroxide formation.
EFFECTOF INITIAL PEROXIDE CONTEXTO N INDUCTION PERIOD
It has been clearly shown that the presence of peroxides decreases t h e The c o n c l u s i o n s p r e susceptibility of g a s o l i n e sented in this paper were to inhibitors. To d e t e r obtained in work in which mine more accurately the peroxides in gasoline were i n f l u e n c e of initial perproduced, one might say, oxide concentration on in“synthetically” b y r a p i d h i b i t o r effectiveness, the o x i d a t i o n . It is known wood-tar distillate inhibit h a t p e r o x i d e s develop tor was added in several also in s t o r e d gasolines. concentrations to a series While it is probable that of samples of the treated m a n y of the conclusions Pennsylvania g a s o 1in e of which have b e e n d r a w n known peroxide content. LABORATORY EXPERIMEYTAL CONTINUOUS CRACKINGUNIT FOR PRODUCING THE GASOLINES TESTED are applicable to gasolines I n d u c t i o n D e r i o d s and in which p e r o x i d e s have c o p p e r - d i s h gums were then determined, with results shown in Table X and in formed under ordinary conditions of storage-, further work is necessa.ry and is being done in this laboratory to prove this Figure 4. point. TABLEX. EFFECT OF INITIALPEROXIDE CONTENTo r IKDUCTION P E R I O D OF TREATED PENNSYLVANIA G.4SOLINE LITERATURE CITED INHIBITED WITR WOOD-TAR DISTILLATE INHIBITOR 0.0570 0.1% Cu- InducCu- Induc-
N o INHIBITOR 0.0170 CuInducCu- InducPEBOXIDE dish tion dish tion NO. gum period gum period
M%/
100 cc.
Original 0.03 0.20 0.40 0.94 1.40 3.60 6.60 10.00 22.40
...
a
4 69 98 67 92 154 124 132
Min.
.+fO./
100 cc.
...
...
110 110 95 75 45 45 45 45
7 11 57 29 64 103 78 175
120
2
Min. ... 345 280 255 180 175 90 80 60 50
dish tion gum period
M O ./
100 cc.
Mzn.
..
... 840 725 720 540 515 330 265 200 105
2
7 6 16 12 23 75 63 96
dish
tion
g u m period .Mil./ 100 cc. X t n . ‘9
8 6 4 7 29 44 70 83
lie0
1200 1095 960 915 660 490 360 220
The results show that, while peroxides reduced the inhibited induction period, even when present in low concentrations, high concentration of peroxides did not entirely destroy the effectiveness of the inhibitor. As would be expected, the amount of inhibitor necessary to keep copperdish gum low increased as the peroxide number went up. COKCLUSIONS The followying general conclusions may be drawn from this study: 1. Peroxides are the first products which the authors have been able to detect when cracked gasoline deteriorates. They form at different rates in different gasolines, and in any one gasoline they build up with time at an increasing rate. As their
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Mardles and Moss, J. Inst. Petroleum Tech., 15, 657 (1929). Marks and Morrell, Analyst, 54, 504 (1929). Milas. Chenz. Rev., 10, 295 (1932). Milas, J. P h y s . Chem., 33, 1204 (1929). Moureu and Dufraisse, Chem. Rev., 3, 151 (1927). Rogers and Voorhees, IND.ENQ.CHEM., 25, 520 (1933). Staudinger and Lautenschlhger, Ann., 488, 1 (1931) : Staudinger, Ber., 58, 1075 (1925). Stephens, J. Phvs. Chsm., 37, 209 (1933). Story, Provine, and Bennett, IND. ENQ.CHEM.,21, 1079 (1929). Wagner and Hyman, J . Inst. Petroleum Tech., 15, 674 (1929). Ward, Jordan, and Fulweiler, IND. EXQ.CHEM.,24, 969 (1932). Wheeler, Oil and Soap, 9, 89 (1932). Yule and Wilson, IND.ENQ.CHEX.,23, 1254 (1931). RECEIVED November 10, 1933. Presented before the Division of Petroleum Chemistry a t the 85th hleeting of the American Chemical Society, Washington. D. C., March 26 t o 31, 1933.
