Chemical Reactions of Cracked Residues
CRUDE-TOPPISG SELECTIVE CRACXING AND FOR MI NU UNIT, 18,000 BARBELS m a DAYCAPACITY
I
HANS TROPSCH,1 CHARLES L. THOMAS, little is known of the chemical N THE cracking of petroJ. c. MOMELL, AND GUSTAV EGLOFF reactions of these constituents. leurn to produce gasoline, two main by-products are It seems likely that this is UnivenaJ Oil Products Company, Riverside, 111. obtained-namely, gas and responsible to a large extent for cracked residue. Considerable the fact that these residues are progress has been made towards the utilization of the cracked still used empirically for fuels, road oils, and coke sources. With more knowledge of the chemistry of cracked residues gas, but the supply of cracked residue is greater than the demand. In 1937 the U. S. production of cracked residue i t seems likely that uses may be found which will lead to was 235,550,000 barrels (29). more valuable products. In a general way it is known that At present the commonest use of cracked residue is for cracked residues contain products formed by the polymerizafuel oil (19, %O). Large quantities are also coked (4, 10, 11, tion and condensation of some of the hydrocarbon decom18, 81,2487, 31). Many cracking plants are equipped to do position products as well as sulfur, nitrogen, and oxygen this without removing the cracked residue from the system. compounds (19). In some cases there is evidence that If cracked residue is mixed with noncoking or semicoking the compounds are chiefly aromatic and hydroaromatic in coals and processed in the Knowles oven, a hard, dense structure (85). The amount of aromatic hydrocarbons presmetallurgical coke is produced (9). Cracked residues can be ent will vary with the conditions employed in the cracking used as road oils or be converted into asphalt by steam or by operation. The residue produced by cracking a t 700" C. has air blowing or by a combination of the two ( 1 , S , 8,18,26, %8, been shown to be chiefly aromatic (7). 30). A number of proposa!s have been made for utilizing Description of Cracked Residue residues further. These include hydrogenation (15,16), solvent extraction, and high-vacuum distillation to make more In general, the process of petroleum cracking consists in exposing the petroleum toelevated temperatures (475-60OoC.) valuable oils, including lubricating oils (S, 6, fD,16,22). The utility of these proposals has already been reviewed (8). and usually elevated pressures (3-75 atmospheres) for a The constituents of cracked residues are unknown, and controlled length of time. In this operation there is a tendency to produce coke in those parts oi the equipment exposed 1 Deaessed October 8. 1935. 1112
., ,
SEPTEMBER, 1949
___
.
__,_.
INDUSTRIAL AND ENGINEERING CHEMISTRY
1113
to the elevated temperature so that eventually the unit must PARTIALLY REACTED NATURAL RESIDUE. If oil containing natural residue is passed through the heated section of a be shut down to remove this coke. This difficulty is partly eliminated by discharging the vapors from the hot portion of cracking plant, the natural residue can react by cracking, condensation, polymerization, and dehydrogenation to give the cracking unit into a flash chamber where a certain amount products which differ from the natural residue but still boil of high-boiling material is condensed while the rest of the vapors are fractionated into gas, gasoline, and recycle stock. in the range that is separated as residue. The removal of this high-boiling material gives a clean reThis type of residue is not characterized as easily as natucycle stock and thus helps to eliminate the coke deposition. ral and synthetic residues. As a very rough characterizaThe high-boiling material removed is cracked residue (23). The method of separating this FRACTIONATING C O L U M N residue is illustrated in the flow diagram of a cracking plant in Figure 1. REACTION C H A There are a t least three general types of residues-namely, natural or asphaltic residue, LICtIT 01 L synthetic or aromatic residue, and partially HEATER FURNACE DISTILLATE reacted natural residue. NATURALOR ASPHALTICRESIDUE. Most ,”‘,FE,” CRUDC C H A P G E petroleums contain more or less high-boiling hydrocarbons, together with a certain amount of asphaltic material usually called “asphaltines.” These may be separated from the crude petroleum merely b y distillation. I n the cracking unit, that portion which is not decomposed to lower boiling hydrocarbons in one pass through the hot zone drops out in the flash pot as a cracked residue. FIGURE 1. FLOW DIAGRAM OF A CRACKING PLANT This type of residue is characterized by being fairly instable thermally and b y givtion it is more aromatic than natural residue and less aroing a light, highly porous coke upon destructive distillation. matic than synthetic residue. SYNTHETIC OR AROMATIC RESIDUE,’ If a clean distillate, Usually crude oils or reduced crudes are charged to the such as kerosene or gas oil containing no high-boiling material cracking units. For this reason the average cracked residue which would separate in the flash pot, is cracked, a certain will contain all of the above types of residue. The ratio will amount of high-boiling material is formed by condensation depend upon the type of charging stock used and the treatduring the cracking operation. This material is black and ment to which it is subjected. After the types of residues viscous so that superficially it resembles the natural residue. have been mixed, there is no analytical method for determining the ratio of the types of residue present (cf. 6 ) .
The oil from cracked residues reacts with chlorine by substitution but with such ease that it resembles addition to a double bond. The oil reacts with sulfuryl chloride to produce chlorine substitution. Under conditions described, the oil can be sulfonated to give compounds which act as hard water soaps. The oil can be nitrated to give a derivative easily separated from unnitrated material. The oil reacts with aluminum chloride etherate to give a product thought to contain an ethoxyl group. The oil can be carried through a series of chlorination and alkylation steps in much the same manner used for pure compounds. None of these observations offers an immediate market for cracked residue but they do offer leads which may be helpful in developing useful products from cracked residue.
It is more stable thermally than the natural residue and, when heated, forms a coke that is hard and dense. Many of its characteristics lead one t o believe that it is fairly aromatic in character.
Proximate Composition of Cracked Residues Although the ultimate composition of cracked residues cannot be determined in terms of the chemical compounds present, certain groups or types can be readily determined. COKE,CARBENES,AND CARBOIDS. Certain cokelike materials are present which are determined by the amount of insoluble material left from a n extraction with hot benzene. I n some cases this material is actually coke although in most cases it is hydrocarbon material containing very little hydrogen. The material exists as a suspension in the original residue and may be seen readily by looking a t a smear of the residue under the microscope. The amount of this material is a function of the treatment given the oil during cracking. Usually it is less than one per cent. Any ash present in the original oil is also found as coke by the test outlined above. ASPHALTINES OR ASPHALT. The addition of forty volumes of pentane t o one volume of cracked residue gives a precipitate of an amorphous brown to black solid. This solid is classed as asphaltines, and it contains carbon, hydrogen, sulfur, oxygen, and sometimes nitrogen. The asphaltines are probably present in the cracked residue as colloids. The presence of asphaltines in cracked residue is very important from the fuel oil point of view since the asphaltines act as pour-point depressors. Thus a cracked residue can be separated into an asphaltine fraction and an oil fraction with both fractions having a higher pour point than the original residue. The asphaltines seem t o act as protective colloids which prevent the crystallization of the wax ( 1 7 ) . Usually the asphaltine content of the cracked residue is less than 25 per cent.
INDUSTRIAL AND ENGINEERING CHEMISTRY
1114
VOL. 31, NO. 9
TABLEI. PROPERTIES OF CRACKED RESIDUES Stock charged to cracking unit Density a t 15.6O C. A. P.I. gravity a t 60' F. (15.6' C . ) Vacuum Engler distn., ' F. (" C.): Initial b. p. 5% over
Kevin, Mont., Mid-continent Mich. StraightN. Mex. Calif. Topped Crude Topped Crude Run Gasoline Topped Crude Topped Crude 1.053 1.027 0.999 1.019 1.053 2.9 6.2 10.1 7.4 2.9 495(257) 462 239) 200 (93 486 (252) 588 (309) 550 {288) 450 232j 558 (292) 612 (322 480 [249) 615 (324 600 (316) 754 (4011 591 (311 770 (410) 750 (399) 870 {466) 860 (460) 718 (3811 895 (479), 890 (477) 1001 (538) 1020 (549)
;% (%]
50% 70%
-
% ' bottoms and aoke
24.0 360 U F 210 122 98.9 50 113 156 L__ 3.13
Av. mol. weight Viscosity= Temp., O F. Temp., O C. Seconds
sulfur xold test, ',F. ' C.) bensene-inso$. pentane-insol. F 0 U = Universal viscometer;
....
7
=
0.14 7.67 Furol viscometer.
I?!:$
i::
-
30.0 350 F 122 50 122 0.82 25(-4) 0.09
...
OIL AND WAX. The major component of cracked residue is a mixture of oil and wax. These form 75-95 per cent of the cracked residue. The oil may be high-boiling compounds present in the original stock, high-boiling condensation products formed by the cracking operation, or a mixture of the two. I n all cases the character of the oil fraction is a function of the type of charging stock t o the cracking unit and the I n any event the oil cracking conditions used in the unit. has a low gravity (high density) for its viscosity and a low viscosity index, indicating that the oil is naphthenic or partially aromatic in character. According t o present theory the wax which usually accompanies the oil in cracked residues is thought to be highboiling paraffin hydrocarbons which have escaped change in the cracking unit and which have been removed in the flashing operation. The wax constituents vary from a soft petrolatum product to a hard white wax melting up to 70" C.
Qualitative Reactions of Oil from Cracked Residue AIR. At 200-450" C. air is absorbed, with the formation first of asphalt and finally of coke ( I ) . At room temperature in the presence of a cobalt siccative, air is absorbed with the formation of a weak film. The product seems t o be more of a resin than an asphalt. CHLORINE reacts until 30-40 grams have reacted with 100 grams of residue. The main reaction seems t o be substitution, since slightly more chlorine is evolved as hydrogen chloride than is retained by the residue. SULFURIC ACID. A black sludge is precipitated which probably contains the asphaltines present in the oil. Continued treatment gives sulfonic acids which can be separated and in some cases used to form soaps. A small amount of sulfur dioxide is formed a t room temperature (cf. 14). PHOSPHORIC ACID is similar t o sulfuric acid in forming the sludge. The nature of the products has not been further investigated. SULFURYL CHLORIDE seems to react according to the equation: RH SOzClz ----f RCI SO2 HC1
+
+
+
Although the nature of R is not known, the reaction is in agreement with what might be expected from the observation made with chlorine. SODIUM. No appreciable reaction occurs. ETHYLMAGNESIUM BROMIDE. No appreciable reaction occurs. ETHYLSULFATE. Upon warming, some reaction takes place. The nature of the product has not been determined.
... ...
--20.1 265
U F 100 122 37.8 50 479 25.8
L y -
0.16
5( - 15) 0.53 2.68
38.0 345 U F 210 122 98.9 50 154 263
45.0 340 U F 210 122 98.9 50 309 1110 0.94 60(15.6) 0.20 21.10
- -....
....
0.24 13.5
Okla. Topped Crude 1.020 7.2 463 (239) 623 (328)
Okla. Crude 1.002 9.7 459 237) 557 1292
910 (488
... ...
50.0 ~~. 410 U 210 98.9 244 0.70 65(18) 0.40 11.05
875 (468) 30.0
___ am
U 210 98.9 159
...
35U.7) 0.5 14.0
ANHYDROUS ALUMINUXCHLORIDE. A black sludge forms which coats the aluminum chloride particles. The reaction is rather violent and is capable of consuming large amounts of aluminum chloride. ANHYDROUS STANNIC CHLORIDEAND TITANIUM TETRACHLORIDE behave like aluminum chloride. NITRIC ACID. By controlling the conditions cracked residue and oils can be nitrated b y a mixture of nitric and sulfuric acid. The nitro,product is a brown to yellow oil which is soluble in acetone. (The original residue is practically insoluble in acetone.) The solid paraffin originally present remains unnitrated and insoluble in the acetone. The oil portion of cracked residues gives similar reactions to asphalt ( I ) . This would seem to indicate that the same type of hydrocarbons is present in both instances, but in the case of asphalt the processes of polymerization and condensation have proceeded further to give products of higher molecular weight. I n general, there are certain constituents in cracked residue that are very reactive chemically. Although some of the reaction is undoubtedly by substitution, suggesting aromatic hydrocarbons, the reactions go very easily; this suggests olefinic hydrocarbons reacting a t the double bond.
Experiments on Cracked Residue The hydrocarbon material in cracked residues is already in the lubricating oil boiling ranges and is sufficiently viscous so that many of the inspection tests applied t o lubricating oils can be applied to cracked residues and its fractions. Also there are approximations between viscosity and hydrocarbon types which permit the types of chemical changes taking place during reaction to be followed. For these reasons viscosity was the principal analytical method used in following these changes. The residue described in the last column of Table I was employed in these experiments. The first step was t o remove the asphaltines. This was done in a vacuum batch still taking 58.4 per cent overhead, but was not entirely satisfactory since considerable thermal reactions took place during the long time necessary for distillation. A 612-gram portion of the vacuum distillate was dissolved in 6 liters of 50-50 ethyl ether-methanol, and the mixture was cooled t o -20" C. to separate wax. A few of the properties of the oil and wax are given in Table 11. It can be seen from the difference in aniline points and molecular weights given in Table I1 that a considerable separation in hydrocarbon types has been effected by the ethyl ether-methanol treatment. Even so the improvement in viscosity index is surprisingly small.
INDUSTRIAL AND ENGINEERING CHEMISTRY
SEPTEMBER, 1939
Both the oil and the wax produced above are of rather low Viscosity. The possibility of increasing the viscosity through the reaction,
+ Clp + CsHs AlCla
RH RCl
----f
+
RCI HCl CaHrR + HCI
where RH represents the hydrocarbon oil, was next considered. To carry out this scheme, 263 grams of the batch distillate were dissolved in 250 cc. of carbon tetrachloride, and the mixture wsfi chlorinated in an ice bath until E t.otal of 75 grams of chlorine had been used. Considerable hydrogen chloride was evolved. The carbon tetrachloride was removed by heating to a maximum temperature of 125' C . at reduced pressure. The cooled chlorinated product (a dark brown oil, smelling slightly of hydrogen chloride) was dissolved in 350 cc. of benzene, and 35 grams of anhydrous aluminum chloride were added with stirring. The mixture became warm enough to reflux the benzene, and hydrogen chloride was evolved. when the reaction subsided, the mixture was heated on a water bath until no more hydrogen chloride was evolved (3 hours). Upon cooling, the aluminum chloride lower layer became so viscous that the benzene solution could be separated by decantation. The benzene was removed at reduced pressure; the yield was 188 grams or 41.4 per cent of the original residne. I n the following table the properties of the product are compared with the original vacuum batch distillate: Batch Dist.
Ssybolt Universal viscosity, sac.: 100' $5. (37.80 C.) 2100 F. (98.90 C.) Pour point, ' F. (* C.) TIi8008it~index
Product
116 41
609
8
48
60 (10)
60
20 (-6.7)
The treatment raises the viscosity and viscosity index and lowers the pour point. The final product was black, and the color was not improved by sulfuric acid and/or clay treatment. This result is merely a11 indication that lubricating oils might be made in this way with the proper conditions. Even so the treatment is rather expensive. Several tests have been made by means of the same procedure on the entire cracked residue. The chlorination was
1115
TABLE 11. PROPERTIBS OB OIL m u WAX FROX CRACKED RESIDVEBY BATCHmSTILLATON AT REnucEn PRESSURE Oil war Produot % of "ripinn1 residue Mol. weigbi SeybuU U n i v ~ i s s l visoosity,
Original Residue
from Diat.
from Dist.
58.4
..
33.9 260
24.5 340
..
116
142
41 8
106 66
159
1M)
390
Bstoh Diet.
*eo.:
loOD F. (87.8' C.)
F. (54.4' C.) 210- F.,(98.9' C.) Viscosity index Pour point, OF. (" C.) Aniline mint. e c . 130'
..
..
.. 35(1.7) ..
85
43 9
40
7
SO(10)
..
..
..
23
79
TABLE111. COMPARISON OF BATCH-DISTILLED A m VACUUMFLASHED OILS
Batch Dist.
r
e of origi"e.1 residue
58.4
aybolt Univeissl viscaaity, ma.: 100" F. (37.8-C.1 116 210: F.,(98.9"C.) 41 Viscosity index 8 Pour oint, F. c.) 50(10) h . P . ~ . ~ r a r . i t g s t B O ' F . ( l 5 . b ~ C . ) ., Density at 15.6' C. ..
--vacuurn-Flruhed1
2
~
62.5
71.8
480 57
868 66.4
(14
40
SO(26.7) 25(-3.91 13.1 12.3 0.929 0.984
oarried out in both beneene and carbon tetrachloride solution using 28-30 grams of chlorine for each 100 grams of residue. During the chlorination the asphaltines precipitated from t,he solution. The material that was not precipitated from t,he benzene solutiou was treated with anhydrous aluminum chloride. After removal of the benzene the product was a soft solid that was not studied further. This result emphasizes tlre desirability of removing the asplialtines before t,reating the cracked residue oils.
Vacuum-Flashed Oils It seemed desirable to study oils from cracked residue whicli liad not undergone the thermal reaction encountered in batch distillation a t reduced pressure. Vacuum flashing was used. The operation consisted in cliarging the residue into a small heated chamher at reduced pressure and continuousIy removing the unvaporiied portion fyom the bottom of the vessel. I n this type of operation the tlieiial reaction is reduced, but there is a small amount of asphaltiiies carried over by entrainment (Table HI). The vacuum-flashed material has quite different properties from those of the batch distillate. Further, fiasheddistillate 2 is different from 1. This gives an excellent example of the ability of small amounts of asphaltines to lower the pour point, in this case from 80" to 25" F. The asphaltincs were entrained during distillation. The bottoms from bobh flash distillations were viscous tars whcu warm and solid when cold. The vacuum-flashed distillates were used in making the following tests: EXPERIMXXT A. Three hundred
TWO-COIL SELECTIVE CB~CKENG UNITWITH A CAPACITY OF 4000 BARRELS PER DAY, FOR CRACKED RSBIDUIIX PRoUUCTloN
grams of distillate 1 were dissolved in 325 CD. of drv benzene. and 63 grams of chlorinebere passed through in 3 hours. The mixture %%.as stirred
INDUSTRIAL AND ENGINEERING CHEMISTRY
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VOL. 31, NO. 9
to remove tho remaming "pep er sludge." The oil solution then had a bri \t golden yellow color. Chlorine was adde3 until 40 grams had been nassed in. This Droduct was aeain filtered thmugh clay t o remdve a small am&t of sludge formed during chlorination. Kinety cubic centimeters of benzene and 10 grams of anhydrous aluminum chloride were added to the solution, and the mixture was reftoxed 3 hours; 5 grams more of anhydrous aluminum cbloride were added, and the reffuxing waa continued for 6 hours. The Droduct was 61tered through clay 5nd the pkntane removed. EXPERIMENT F. Five hundred grams of distillate 2 were dissolved in 1 liter of pentane, and the solution was treated with 37 cc. of 63 per cent sulfuric acid. Of the total sludge formed, 20 grams were easily collected. The sludge was a soft black pitch a t room tem era ture; it was insoluble in water, insoliibye i, aqueous potassium hydroxide, and slightly soluble in alcoholic potassium hydroxide. After the above sludge was removed, the oil-pentme solution was treated with 32 cc. of 87 per cent sulfuric acid. In this caSe a semifluid, black sludge is formed which smells of sulfur dioxide. The sludgeisinsoluble in water but partly soluble in sodium carbonate or sudium hydroxide. Acidification of the alkaline solution of sludge recipitated a black oil. CRACKED RssrnarM U i t a w - o ~ F.AND FLASH C~MBER This sludge was pa& asphaltine products and nartlv sulfuric acid reaction nraduets with hvdrooe&bons in the oil. and ke t i n an ice bath during chlorination. The chlorine was Removal oi the pepper sludge in a clay filtration gave a stoppez and 30 grams oi anhydrous aluminum chloride were bright orange-colored product. This solution vas treated with added. There was no reaction in ice and very little a t room 25 cc. of 96 Der cent suliuric acid containing 1.25 m a m of boric tom erature. The mixture was heated in a Rater bath until no furtier hydrogen chloride was evolved. The benzene was removed by heating in vacuo. The properties of tho products are given in Table 1V. EXPEHrMEsT B. Test A was repeated, using half as much kydroxide gave a brown solution that had all the characteristics nf thr an.rallarl hnril wster e n ~ n s benzene, chlorine, and aluminum chloride. EXPERIMENT C. Three hundred grams of distillate 1 were dissolved in 500 ce. of pentane and chlorinated witil 84 grams ui chlorine had passed in. Eighty-five grams of naphthalene were added to the product and, upon its complete solution, 20 grams of anhydrow aluminum chloride. The mixture was stirred and refluxed for 7 hours. The pentane wm removed by distillation and excess na hthalene by steam distillation. The product w,v&s 2 Iiorirs and then itirred and refluxed ior 3 hours. After being a soit dark-eofored solid. EXPEBIMENT D. One hundred and sixty grams of potassium pennanganatc and 20 grams of anhydrous sudium carbonate m r e dissolved in 2.5 liters of water. Two hundred grams of distillate 1 R~ereadded, and the mixture was agitated violently a t room temperature and then a t 50" C. until the permanganate color disappeared. Eight grams of oily acidic material were obtained by acidifying t.lie aqueous solution and extracting with 1.0 gram of baric acid. This tGeatment removed the asnhalt; ether. EXPERlUIEljT E. Thrce hundred grams of flashed distillate 2 were dissolved in 500 ce. of pentane and treated with 20 cc. of 63 per cent sulfuric acid. After the sludge \vas removed, the precipitate rvith tl'ie~aluminumchloride. This was partly overoil solution was treated with 20 cc. of 96 per cent suifurie acid containing 1.0 gram oi boric acid. After most of the sludge was removed, the oil solution was filtered through a small clay filter c
TABLE IV. PRODUCTS FROM VACUUM-FLASEED DISTILLATES S~~boIt~,U~ivemd Visoomty, seo. Erpt.
NO.
100' F. 210' F. (37.8' C.1 (98.8' C.1
Product
B C D
Original raidue Vaouum-fla?hed dist. 1 No. I chlorinated end treated with benzene and AlCl, Same 88 A with half as much Clr, A!Cir. and benaene No. 1 oxidized with KMnO. aateriinsol. product S o . 1 obiorinated and treareh with naphthalene AICL
2
Vaeuum-Bashed,dist.
1
A
+
+
E No. 2 treated with I(sSO6 CIS benaene AlCb F No. 2 treated with 63,87: axxi 96% K+O. G No. 2 treated w i t h 100% phosphoric acid K No. 2 treated pith H&O. and AICla 1CnHd20oompler
>6000
480 Too high 3778 1326 Too h u h 868 2275 415 502
455
A. P. I.
Viscosity
Index
159 57 332 127
6000 868 476 366 412 610 832 2387 2723
-
210’ F. (98.9’ C.) 159 66.4 58 53 56 64 76 120 118
formed, the mixture was stirred and refluxed until no more hydrogen chloride was evolved (7 hours). The sludge was removed, the product clay-treated, and the pentane removed. EXPERIMENT I. Twelve hundred grams of distillate 2 were dissolved in 2000 cc. of pentane and treated with 60 cc. of 63 per cent sulfuric acid, and the sludge was removed. The solution was then treated with 60 cc. of 96 per cent sulfuric acid containing 3 grams of boric acid, the sludge removed, and the solution filtered through clay. At this point two samples, I, and I b , each corresponding to one sixth of the total oil, were separated from the main body of oil. The remaining solution was diluted to one gallon and chlorinated (in ice) until 20 grams of chlorine had passed in. At this point hydrogen chloride was just beginning to be evolved. One fourth of the solution was removed (Ic). This should contain 5 grams of chlorine. The chlorination was continued on the remainder (3 quarts) until 15 grams of chlorine had assed in, and a second quart of solution was removed ( I d ) . T i i s should contain the reaction products equivalent to 10 grams of chlorine. The two quarts of solution remaining were treated with 20 grams of chlorine, and the third quart was removed (Ie). This should contain the reaction products equivalent to 20 grams of chlorine. The remaining quart of solution was treated with 20 grams of chlorine (If). This should contain reaction products equivalent to 40 grams of chlorine. Samples I,, Id, and I, were greenish black in color and opaque. Sample I was reddish brown and transparent, but became opaque upon standing overnight. All chlorinated samples lose hydrogen chloride slowly upon standing. Samples It,, I,, Id, I,, and If were treated in the same manner. Ninety cubic centimeters of benzene were added, followed by 10 grams of anhydrous aluminum chloride, stirred for 1 hour a t room temperature, and warmed so that the pentane refluxed while the stirring was continued for 2 additional hours. Five grams of anhydrous aluminum chloride were added, and stirring and refluxing continued until no more hydrogen chloride was evolved (1-4 hours). Sample I, was given no treatment besides the acid treatment and a light clay treat. The properties of these products are given in Table V. EXPERIMENT J. A procedure was followed t o duplicate sample I,, but the benzene was omitted in the alkylation step.
Discussion of Results Experiments A to H in Table IV were of an exploratory nature and serve t o indicate some of the reactions of the residue and the effect of these reactions on the properties of the oil. From these experiments the mild chlorination followed by alkylation with aluminum chloride and benzene seemed interesting. For this reason the experiments in Table V were made t o find the optimum amount of chlorine. They have shown that the major factor in raising the viscosity index is the sulfuric acid treatment. The chlorination and alkylation with benzene serve to increase the viscosity. The optimum amount of chlorine is about 10 per cent of the original flashed distillate (experiment I,). The benzene enters into the reaction since a n entirely different product is obtained without it (cf. experiments I, and J). Experiment H also gave a n interesting product by the use of the aluminum chloride-ether complex. The drop in A. P. 1. gravity leads us t o the opinion that the ether has entered into the reaction and the product retains some of the oxygen from
A. P.I . Gravity Viscosity at 60’ F. Index (15.6’ C.) 9.4
