Boron Trifluoride Treatment of Cracked Gasolines H. BEUTHER
AND
R. G. GOLDTHWAIT
Gulf Research & Development Co., P.O. Drawer 2 0 3 8 , Piftsburgh 30, Pa.
Anhydrous boron trifluoride treatment of cracked gasolines has been found to improve their storage stability and engine cleanliness characteristics. This process consists of continuously contacting boron trifluoride with the unstable gasoline, settling to remove a small amount of insoluble sludge! water washing to remove dissolved boron trifluoride, and redistilling to remove soluble polymers. Treatment preferably is carried out a t room temperature and a t contact times of 1 to 10 minutes. Stable naphthas were produced when highly unstable, high sulfur, heavy fluid catalytically cracked naphthas were treated with 0.1% boron trifluoride and an unstable, high sulfur, heavy thermally cracked naphtha was treated with 0.05y0 boron trifluoride.
T
REATMENT of cracked gasolines to improve storage stability has been practiced commercially for a number of years. Most frequently sulfuric acid, caustic, and clay have been employed with varying degrees of effectiveness, depending on the nature of the charge stock and the degree of stability required. Each of these processes, however, has certain disadvantages or limitations. For example, sulfuric acid treatment results in high yield losses, corrosion, and sludge disposal problems. ClaJ. treatment requires low space velocities and correspondingly large equipment sizes to treat adequately some of the unstable gasolines currently being produced, while caustic treatment appears to be limited in the degree of improvement R hich can be obtained. I n an effort to overcome these disadvantages and to develop a process which would be effective, inexpensive, and simple, a boron trifluoride treatment has been thoroughly investigated. Boron trifluoride ( 1 ) is a polymerization catalyst which is gaseous a t atmospheric temperature and pressure, highly soluble in gasoline, and not corrosive to most materials of construction unless appreciable quantities of water are present. The treatment consists of continuously contacting boron trifluoride with the unstable gasoline in a relatively simple reactor, followed by fiettliiig to remove the small amount of insoluble sludge which is produced, water washing to remove residual boron trifluoride, and redistilling to remove soluble polymers. The operation preferably is carried out a t room temperature, atmospheric pressure, and contact times of 1 to 10 minutes. Stable naphthas were produced by treating unstable, high sulfur, heavy catalytically cracked fluid naphthas (415 * to 430" F. end point) with 0.1% boron trifluoride and b y treating an unstable, high sulfur, heavy thermally cracked naphtha (450 F. end point) with 0.05y0 boron trifluoride. The treated naphthas \%erestable on the basis of storage tests at 100" F., accelerated storage tests a t 150"F., and conventional laboratory tests. Engine cleanliness characteristics, as indicated by General Motors Sludge Numbers, Method B ( 2 ) , were also improved. The improvement in stability and engine cleanliness characteristics brought about by boron trifluoride treatment also was shown by a comparison of blends of untreated and boron trifluoride-treated naphthas with other refinery gasolines. Yield losses from boron trifluoride treatment and redistillation were 5 to 7% by volume compared with approximately 5 % for redistillation of the untreated naphtha t o the same end point (approximately 408" F.). Preliminary economic studies have shown that the boron tri-
fluoride treatment costs approximately the same as the sulfuric acid or the cla~7treatments. Evaluation of Product Quality A4ccurateevaluation of product quality is a relatively difficult consideration in gasoline treatment programs. I n this work, copper dish gum determination and oxidation stability were used to obtain a preliminary measure of stability; however, these tests may be misleading, particularly when testing individual high boiling fractions. Selected samples of treated naphtha, which appeared to be stable on the basis of the laboratory tests and which had been produced a t favorable operating conditioris, were tested further by accelerated storage at 150" F. and storage at 100" F. The accelerated test a t 150" F. was similar to a method described by Walters and coworkers ( 3 ) . Samples of 100 ml. of naphtha are stored in 8-ounce stoppered glass bottles placed in a bath a t 150" F. for approximately 10 days. Every 2 days a bottle is removed to determine the existent gum (ASTM D 381-50) content and the air is replaced in the reiiiaiiiing bottles. In the storage test at 100" F., I-quart samples are stored in sealed 1/2-gallon brown bottles for periods of 6 months or more. At 2-month intervals, representative samples are removed for determination of the existent gum content and to replenish the air supply. T h e results from both tests are expressed b y plots of existent gum content as a function of time. The storage times can be extrapolated to lower temperatures by a correlation TR E ATE0 NAPHTHA PRODUCT
O
764
NAPHTHA CHARGE
t
WHEN SLUDGE
'FLOW
IS RECYCLED
HEAVY NAPHTHA AND POLYMERS
Y
Figure 1.
Schematic flow diagram for pilot plant boron trifluoride treatment
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 47, No. 4
GASOLINE PROCESSING I
9g
"O
100
d
3
50
..
ow a
3 0.32 BFs RATE,% BY WT.
Figure 2. Effect of boron trifluoride rate on treatment of heavy fluid gasoline, sample C
presented by Walters and coworkers ( 3 ) . Extrapolated storage times at 80" F. are presented as secondary abscissas for the gumtime plots which are included in this paper. Storage for 100 hours at 150 F. is equivalent to about 18 months at 80 O F., and storage for 100 days a t 100 O F. is equivalent to about 16 months a t 80" F. I n this work, treated naphthas were considered to be satisfactory if they contained less than 10 mg. per 100 ml. of gum after approximately 100 hours a t 150" F. or 100 days at 100" F. These criteria are relatively conservative since the treated naphthas are blended with more stable, low boiling gasolines in the manufacture of finished refinery gasolines. GM Sludge Number was used as an indication of engine cleanliness of the treated naphthas. O
i 3
LUO 0
EF3 RATE ,% BY WT.
Figure 3. Effect of boron trifluoride rate on treatment of heavy fluid gasoline, sample C
eo0
I50 100 50
0 700 800
50 0 400
300 200 100
Treatment and Apparatus
P
Three different refinery heavy fluid naphthas and one refinery heavy thermal naphtha were used as charge stocks to the pilot plant for boron trifluoride treatment. The samples were obtained in carefully cleaned, nitrogen-purged drums and were inhibited with 10 pounds of antioxidant (phenylenediamene type) per 1000 barrels. The inhibitor was removed a t the laboratory prior to treatment by washing with 3.5y0 hydrochloric acid solution, followed by neutralization with a 1% caustic solution, and water washing. I n all handling steps extreme care was taken t o prevent contacting the naphtha with air. After inhibitor removal, the naphtha was stored at a temperature of 35" F. for no longer than a week prior to its use. This method of handling was effective in maintaining a given sample of naphtha refinery fresh. Naphthas which were 6 to 8 months old showed no increase in gum content or deterioration in stability; however, none of the naphthas were used later than 3 or 4 months after original refinery sampling. No special handling of the gasoline is required prior to boron trifluoride treatment. During the early part of the experimental program the naphtha was dried over calcium chloride prior to charging to the pilot plant; however, investigation showed that this step was not necessary and, if all traces of water were removed, t h e treatment results were poorer. Figure 1 shows a flow diagram for pilot plant boron trifluoride treatment. Most runs were carried out in a continuous, mechanically-agitated reactor; however, the use of a series of mixing orifices was also effective. The untreated naphtha was pumped t o a reactor using a small piston pump, and the boron
April 1955
0
BF3 RATE ,% BY WT.
Figure 4. Effect of boron trifluoride rate on treatment of heavy thermal gasoline
trifluoride, which is readily soluble in the naphtha, was pressured into the reactor from a small bomb (100-ml. capacity) using an orifice meter t o measure the flow rate. The boron trifluoride bomb was weighed before and after each run to determine the amount of reagent actually used. The effluent from the reactor passed to a settler in which the sludge (0.1 to 0.3% by weight) readily separated. After separation of the sludge, the naphtha was bubbled through a water scrubber to remove traces of dissolved boron trifluoride. No further treatment or neutralization other than the water washing is necessary to remove boron trifluoride completely. The treated naphthas were then stored under refrigeration until they were distilled. After treatment, the naphtha was distilled in a batch still of approximately 18 theoretical plates to remove soluble polymers and to obtain an end point of approximately 405 a F. During the distillation, the pot temperature was limited t o 300' F. by reduc-
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
765
ENGINEERING, DESIGN, AND 'PROCESS DEVELOPMENT
58
s4
z?8
13
3% z*
BO
&i
ae
*ti
4
f
$ai 8
ao 0.12
9
0.20
I
am
$
0.10
-!
L
O M
o
0.02
0.04
aoe
o.oa
ai0
O.IP
O M
BF3 RATE,% BY WT.
Figure 5. Effect of boron trifluoride rate on treatment of heavy thermal gasoline
ing the pressure in several steps to 5 to 10 mm. of mercury absolute to avoid possible deterioration of the naphtha. While this temperature limitation of the pot may be unduly cautious, it was practiced to eliminate distillation conditions as a variable. There was no evidence that boron trifluoride forms thermally unstable compounds as does sulfuric acid. Yield losses on distillation were usually 5 to 7% by volume for heavy fluid naphtha; however, a yield loss of 570 was obtained when rerunning the untreated charge stock to the same end point as the treated naphthas. The corresponding losses for heavy thermal naphtha were slightly higher as the charge stock had a higher end point. The treated naphthas were inhibited with 10 pounds of antioxidant (aminophenol type) per 1000 barrels. Effect of Operating Variables
'
The amount of boron trifluoride used in gasoline treating operations is by far the most important of all operating variables. Since boron trifluoride is a relatively expensive reagent (about 60 cents per pound), the amount of boron trifluoride used is important both from the economic and a product quality standpoint. The effect of boron trifluoride amount on the quality and yield of the treated product is shown in Figures 2 and 3 when charging a heavy fluid naphtha and in Figures 4 and 5 when charging a heavy thermal naphtha. Values a t 0% boron trifluoride are for the untreated charge stock redistilled to the same end point as the treated products. All operations were carried out a t room temperature and contact times of 1 to 10 minutefi. An increase in boron trifluoride rate from 0 to 0.1% by weight for heavy fluid naphtha resulted in the greatest improvement in determinations of copper dish gum and GM Sludge Number, while further increases to 0.3% brought about relatively little additional improvement. For heavy thermal naphtha an increase in boron trifluoride from 0 to 0.05% effected the greatest improvement. Oxidation stability improvement was fairly uniform with increase in reagent rate. An increase in boron trifluoride rate also brought about small decreases in naphtha yield and sulfur content and an increase in sludge yield. Octane numbers are not affected by treating. Table I presents the effect of charge stock on treated product inspections for three samples of heavy fluid and one sample of heavy thermal naphtha. The treatment rates produced stable naphthas as indicated by storage tests a t 100' and 150" F., as well as by laboratory inspections. Table I was developed from plots similar to Figures 2 to 5. These data show that only 0.05% boron trifluoride produced a stable product from heavy thermal
166
naphtha, while 0.1% boron trifluoride is required to produce stable products from the three heavy fluid naphthas. In general, the heavy fluid naphthas responded well to treatment, although a few differences are evident. The charge stock with the lowest GM Sludge Number produced the treated product with the lowest GM Sludge Number, and the stock with the highest sulfur content had the poorest copper dish gum determination. The reason for variations in oxidation stability values is not apparent; however, this test has definite limitations in comparing the quality of different gasolines. The naphthas used as charge stocks for the boron trifluoride treatment were the poorest in engine cleanliness and stability that could be obtained from the refineries. The poorest gasolines in these respects are those produced from high sulfur charge stocks. Figure 6 shows the effect of sulfur in the gasoline on stability and gum contents for untreated full range fluid distillates from pilot plant cracking of a large number of charge stocks. The heavy fluid distillates used in the treating program varied in sulfur content from 0.296 to 0.439% by weight and corresponded to full range fluid gasolines of about 0.25 t o 0.30% sulfur. The heavy thermal distillate had a sulfur content of 0.254%. The effect of contact time on boron trifluoride treatment showed that variations in the range of 1 to 10 minutes had a negligible effect on product quality.
40
30
PO 10 Oo
0.05
0.10 0.15 o.eo 0.2s 0.30 GASOLINE SULFUR CONTENT,% BY WT.
b
1.0
APPROXIMATE
SULFUR CONTENT OF FLUID CHARGE,'/.
Figure 6.
1
a35
1
9.0
3.0
BY WT.
Effect o f sulfur content on stability of full range fluid gasoline Catalyst
SR Filtrol
Reactor temp., ' F. Conversion, % by vol. Inhibifor, lb./lOOO bbl.
925
60 10
Pilot plant runs at a contact time of 1 and 1.5 minutes were made to compare a series of orifices as a simple less expensive reactor with the mechanical agitator normally used. The orifice reactor consisted of four l/lE-inch diameter mixing orifices inserted in a 2-foot length of 1-inch pipe., Even though the flow was not in the turbulent range and the contact time was low, there were no significant differences in the treatment effectiveness. These experiments show the simplicity of boron trifluoride treatment commercially. Analyses of representative samples of insoluble sludge showed a boron trifluoride content of 30 to 3570, mostly in the form of complexes. Since boron trifluoride could not be recovered simply, treatment was carried out on heavy fluid gasoline employing a sludge recycle to determine if the catalytic
INDUSTRIAL AND E N G I N E E R I N G CHEMISTRY
Vol. 47, No. 4
.
GASOLINE PROCESSING Table 1.
Effect of Charge Stock Properties on Quality of BF8 Treated Naphthas
.
Charge stock Sample Charge stock inspections, inhibited with 10 lb./1000 bbl. Sulfur, Lamp, 9% Copper dish gum, mg./100 ml. Oxidation stability, min. GM sludge number ASTM distillation. O F. Over point End point 10%
A
Heavy Fluid Naphtha
B
0,296 292 > 1440
0.254
0.312 485 661 147.6
0.439 472 199 149.5
281 430 307 348 399
259 422 287 339 391 0.1
250 414 284 330 378
41 175 52
33 350 70
47 2130 73
10 280
125 155
128 155
>25qa
100.0
... ... a
Heavy TliernLal Saphtha
C
8:)s
213 174.7 160
450 201 301 396 0.05
79
>189"
Value on run from treating with 0 . 0 6 % BFa.
,4
EXISTENT OUM UNTREhTEO
s
I
I
'I
-1'
,
$
'
0
quality or treatment efficiency could be improved. I n the runs made at 300" F., the pressure was increased to 50 pounds per square inch gage to maintain the naphtha in the liquid phase. The results showed that treatment at higher than room temperature produced no significant improvement in naphtha quality. There was a small improvement in the GM Sludge Numbers, the copper dish gum determinations were slightly poorer, and the oxidation stability data were inconsistent.
3
"i
.
S I
a 0
6 0 n
160
E:
-
- - -
TREATED
~
U 140
P Figure 7. Effect of cut point on properties of boron trifluoride-treated and untreated heavy fluid naphthas
: 2
leo
100 L1
00
activity remaining in the sludge could be utilized to reduce boron trifluoride consumption. Since the sludge yield from single pass treatment is only about 0.2% of charge, a very long recycle run would be required to establish the equilibrium conditions necessary to predict commercial results accurately. The experimental work, however, only determined if the sludge was active; it did not represent equilibrium conditions. During the pilot plant operation, the sludge recycle rate was gradually increased to approximately 15y0of the gasoline charge. After 45 hours of operation, the naphtha produced from recycle treatment with addition of 0.05% fresh boron trifluoride was equally as stable as that from single pass treatment with 0.1% boron trifluoride. The sludge product is an active treatment agent, but the data do not necessarily show the results that might be expected From recycling an equilibrium sludge. Sludge recycle may reduce boron trifluoride costs; however, sludge activity may vary widely depending on the amount of boron trifluoride charged and the amount required by the gasoline being treated. Pilot plant boron trifluoride treatment runs mere made at higher reactor temperatures (150" to 300" F.) to determine if naphtha
April 1955
65
70
75
80
05
SO
SO
100
Y I E L D , % BY VOL. OF UNTREATED CHARGE
Figure 8. Effect of cut point on properties of boron-treated and untreated heavy fluid naphthas
Various methods of pretreating the charge stock prior to boron trifluoride treatment were investigated to improve the effectiveness and to reduce the required amount of boron trifluoride. The raw cracked naphthas were given pretreatments of caustic washing, saturation with water, thorough drying, and addition of inhibitor. These pretreatments were either detrimental or had no effect. It is necessary to have traces of water present in naphtha to obtain effective treating. A number of methods for aftertreatment of boron trifluoridetreated naphthas prior to redistillation were investigated to improve naphtha quality, and in particular t o eliminate the redis-
INDUSTRIAL AND ENGINEERING CHEMISTRY
767
ENGINEERING, DESIGN, AND PROCESS DEVELOPMENT tillation step. These were caustic washing, ammonium hydroxide washing, filtering, and percolating through clay. None of these methods improved the quality of either the undistilled or redistilled naphtha over that of normal water washing.
ated storage at 150" F. of several of the blends of treated and untreated distillates are shown in Figure 9, These data show that the addition of the heavy naphtha fractions generally resulted in a lowering of stability as measured by the accelerated storage test, existent gum, oxidation stability, and copper dish gum determination for both untreated and boron trifluoridetreated naphthas. The lowering in quality does not occur sharply but is gradual; therefore, there is not any great advantage in severe undercutting of the treated gasolines for stability improvement. However, undercutting of high boiling cracked distillates improves engine cleanliness.
Evaluation of Blends of Boron Trifluoride-Treated Naphthas with Other Reflnery Gasolines Blends were made of boron trifluoride-treated naphthas with untreated refinery gasolines to determine if the improvements in stability shown by the treated naphthas alone would also be evident in blends with other refinery gasolines. A refinery base stock consisting of light straight-run, thermally cracked, and light fluid gasolines was blended with boron trifluoride-treated naphthas in the ratio of 8 parts of base to 1 part of boron trifluoride-treated heavy fluid and 1 part of boron trifluoride-treated
STORAGE TIME AT I?IO'F.,HR. I 0
1
IO
I
eo
EXTRAPOLATED STORAGE TIME
1
30 40 AT 80-F .,MONTHS
Figure 9. Effect of cut point on accelerated storage tests (150' F.) for boron trifluoride-treated and untreated heavy fluid naphthas
The amount of heavy ends removed by distillation has a marked effect on the stability of the naphtha whether it be treated or untreated. For the boron trifluoride treated naphthas which have been only water washed, there exists a small amount of heavy polymers from the treating operation which must be removed by distillation. T o determine the amount of heavy ends which it was necessary to remove to obtain good stability, a heavy fluid naphtha which had been treated with 0.11% boron trifluoride was batch distilled under vacuum to obtain heavy fractions vaTying from 360' to 430" F. vapor temperature cut point. A series of naphthas of varying end points was blended aliquotly from these fractions. A similar distillation and series of blends were made on the untreated heavy fluid naphtha charge stock for comparison. The resulting inspection data are plotted as functions of yield in Figures 7 and 8. Results from acceler-
i
I
E! W
i
Rerun
Treated
Table 111.
i0
STORAGE T I M E AT
BO*F., MONTHS
*
Properties of Residue Products from BF3 Treating of a High Sulfur Heavy Fluid Naphtha
98 .'8
0.072 9 1 2.1 711 49.2
Storage time a t 10 mg./100 ml. gum content 150' F., hr. 56 >233 100° F., days 30 > 188 a Corrected for treating loss Heavy fluid treated witd 0.1% BFa; heavy thermal treated with 0.06% BFs.
768
io
io
EXTRAPOLATED
Figure 10. Storage tests a t 100" and 150' F. for heavy fluid naphthas treated by various methods
BFs
0.077 16.0 3.8 247 65.6
40
MONTHS
w L
%
40 18 2 20 1oa 1oa Untreated
98.7
30 STORAGE TIME AT 80.F.,
$
VOl.
Treating method Yield, % by vol. of blend containing untreated stocks Insoections. inhibited with 10 lb./1000 bbl
nu I
I
PO
I-
Table II. Comparison of Refinery Blends Containing Treated Heavy Thermal and Fluid Naphthas Composition Straight run Light fluid Light thermal Polyform Treated heavy fluid Treated heavy thermal
STORAGE AT ISO* F . ,
: : A EXTRAPOLATEDIO 5 =-
Average yield, % by vol. of naphtha charge Gravity, A P I Viscosity, S.U.S 100" F. 130" F.
-_
2100 F
Water'and sedimenL,'% Sulfl-. Carbon residue, Conradson, %
Insoluble Sludgea
Rerun Bottoms
0 . 0 2 , wt. %
6 18.8
11.4
...
522 82.9
...
7.54
72.0 50.8
...
0.1 (on 10% 26.77 bottoms)
BFs content, 30 to 3.576 by weight.
INDUSTRIAL A N D E N G I N E E R I N G CHEMISTRY
Vol. 47,No. 4
GASOLINE PROCESSING Table IV.
Comparison of Treating Methods for Heavy Fluid Naphtha, Sample C Tmated 10 lb./bbl. H2S01 Clay" ~~~~
Treating Method Yield of treated and rerun naphtha, by vol. of charge Insoections of treated and rerun naphtha ,ed with 10 lb./1000 bbl.
content 150' F., hr. 100' F., days Operating conditions Temperature, O F. ' Space velocity, bbl./hr./ton Pressure, lb./sq. inch gage
Untreated Rerun Charge charge
0 44 472 76 3 199 149 6
... ...
BFa
94.9
94.8
93.0
0 35 130 9 5 136 131.9
0.33 47 2.8 290 73
0.29 22 1.0 260 88
126 26 155 Estimated. 50
170 >240
~~
~
0.4% Caustic
93.5
95.56
0.34 77 5.8 323 41.9
0.31 33 6.2 259 120.7
155 120
140
...
450 1 4 31
heavy thermal naphthas. This ratio mas the approximate production from one of our refineries when these samples were taken several years ago. A comparable blend was made using untreated heavy fluid and thermal distillates which had been dietilled to obtain the same cut point as the treated naphthas. The blend containing the treated naphthas showed a considerable improvement in stability determined by both the 100" and 150" F. storage tests over the blend containing the untreated naphthas, even though the treated distillates comprised only 20% of the blend. Gum values do not show up as significantly as do storage tests, GM Sludge h-umbers, and oxidation stabilities. This typical refinery blend containing the treated naphthas could be stored for more than 20 months a t 80" F. before 10 mg. of gum would be present in the gasoline. Inspection data for these blends are given in Table 11. Evaluation of Residues from Boron Trifluoride Treatment
Two residue products are produced from boron trifluoride treating. These are insoluble sludge, amounting to about 0.2oj, of the naphtha charge, and a heavy naphtha fraction from redistillation of the treated product, which amounts to about 5 to 7% of the charge. The insoluble sludge, which contains 30 to 35% boron trifluoride largely in the form of low activity complexes, is separated from the treated naphtha by settling. The active boron trifluoride can be removed readily from the sludge by caustic washing and the washed product can be blended into No. G fuel oil. The sludge can be burned directly because of its relatively low viscosity. Approximately 8 barrels are produced per day from a 5000-barrel-per-day treating unit. The bottoms fraction from redistillation consists of heavy ends of gasoline and soluble polymers. Since this fraction is in the furnace oil boiling range, it can be used as viscosity cutting oil for No. 6 fuel oil. Inspection data on representative samples of the two hydrocarbon residue products are presented in Table 111.
April 1955
0.1%
Comparison of Boron Trifluoride Treatment with Other Methods
Pilot plant treatment operations were carried out using boron trifluoride complexes but none was found which produced stable naphthas a t a reagent cost as low as anhydrous boron trifluoride. Treating with boron trifluoride dihydrate did not produce stable naphthas, while boron trifluoride etherate required a relatively large boron trifluoride equivalent to produce a stable naphtha. A comparison of product yield and quality data from treating a high sulfur heavy fluid naphtha with 0.1% boron trifluoride with corresponding data from treating the same naphtha with other commonly used processes is presented in Table IV. Storage stability data a t 100" and 150" F. are plotted in Figure 10. These competitive processes are caustic treatment a t a rate of 0.4% (NaOH basis) of a 35y0 solution, sulfuric acid treatment a t a dosage of 10 pounds per barrel, the vapor-phase clay treatment at a space velocity of 1.4 barrels per hour per ton. These operations were carried out at a minimum reagent dosage or severity necessary to produce stable naphthas. I n conclusion, a simple but effective treatment has been developed for improving storage stability and engine cleanliness characteristics of cracked gasoline5 by the use of small quantities of boron trifluoride. This process is competitive commercially with other present-day processes and has advantages of extreme simplicity, lack of corrosiveness, and effectiveness in treatment. Literature Cited Booth, H. S., and Martin, D. R., "Boron Trifluoride and Its Derivatives," Wiles, New York. (2) Coordinating Research Council, 30 Rockefeller Plaza, New York, Report, "Laboratory Bench Tests of Sulfur in Alotor Gasoline Field Test Fuels," February 1950. (3) "alters, E. L., Yabroff, D. L., l l i n o r , H. B., and Sipple, H. E., (1)
Anal. Chem., 19, 987-91 (1947). RECEIVED for review September 20, 1054.
INDUSTRIAL AND ENGINEERING CHEMISTRY
ACCEPTED February 8, 1955.
769
