ANALYTICAL EDITION
June, 1945
other straight-run Cq streams in the refinery to the extent of about 0.4 mole %. ACKNOWLEDGMENTS
The authors wish to express their gratitude to K. E. Train of this laboratory who performed the isothermal distillations of the reference standards, and to Edward Gelus for his advice and aid in the concentration by distillation of the neopentane samples and also in the interpretation of the isothermal distillation curves. The authors are-further indebted to the Shell Oil Company for granting permission to publish this work.
351 LITERATURE CITED
(1) hston, J . C.. and Messerly, G. H., J . A m . Chern. Soc., 58, 2355
(1936).
(2) Avery, W. H., J . Optical SOC.A m . , 31, 633 (1941). (3) Brattain, R. R., Rasmussen, R. S., and Cravath, .4. M.,J. A p p l i e d Phys., 14, 418 (1943). (4) Echols, L. s., and Gelus, E. (to be published). ( 5 ) Ellis. C. E., “Chemistry of Petroleum Products”, pp. 17, 32,
New York, Chemical Catalog Co., 1934.
(6) Rossini, F. D., Petroleum Engr., 14, No. 5, 41 (1943). (7) Smoker, E.H.. Trans. A m . Inst. Chem. Engrs., 34, 165 (1938).
PRESENTED before the Division of Petroleum Chemistry at t h e 108th XIeetIng of the A?IERXCASCHEUICAL S O C I E T Y , New York, N. Y
Determination of Aluminum Chloride and Hydrochloric A c i d in Hydrocarbon Streams W A L T E R G R E E N A N D S. R. BAKER Wilrhire Oil Co., Inc., Norwalk, Calif.
THE
analytical method presented here does not depend on a new principle, since Craig (1) published a similar method in 1911 for the determination of free acid or aluminum oxide in alum and Scott modified this method to some extent ( 3 , 4). Martin published a method for the determination of aluminum in ore which makes use of the reaction between aluminum salts and potassium fluoride. Other methods of analysis are discussed by Willard and Diehl ( 6 ) . The method of Malaprade ( 8 ) probably could be adapted to the analysis of aluminum chloride and hydrogen chloride mixtures but requires the use of a potentiometer. The advantage would be that iron would not interfere. The author’s method is a new application of the use of potassium fluoride, inasmuch as hydrogen chloride or alumina is determined in addition to the aluminum chloride and iron chlorides. The method does not distinguish between the iron and aluminum cliloridcs. However, in the present application, iron chlorides are not present in sufficient quantities to cause serious errors in the result8. The method used in this 1aborat.ory is rapid and accurate and depends upon the fact that when a neutral solution of potassium fluoride is added to an aqueous solution containing aluminum chloride and hydrochloric acid, the aluminum chloride is decomposed into two stable compounds, neutral to phenolphthalein. The following reaction is believed to take place:
AlCla
+ 6KF + XHCl
= AlFJ.3KF
SAMPLING PROCEDURE
The following sampling procedure is designed for sampling butane streams containing aluminum chloride and hydrogen chloride. Construct a sampling arrangement similar to that shown in Figures 1 and 2, so that a sample may be taken from a circulating, steam-trace line. Do not attempt to warm up the sampling
LEAD FILL
+ 3KC1 + XHCl
The free hydrochloric acid may then be accurately titrated with potassium hydroxide. I n the absence of potassium fluoride, potassium hydroxide reacts with both the aluminum chloride and the hydrochloric acid. The aluminum chloride is found as the difference between the potassium hydroxide r e q u k d in a titration withnut and a titration with potassium fluoride. APPARATUS A N D REAGENTS
Three gas-washing bottles. Wet test meter or dry ice trap, depending upon boiling range of hydrocarbon stream. Wide-mouthed DeRar flask. All reagents were of reagent grade. 0.5 X potassium hydroxide, 0.5 N hydrochloric acid, and 1% ’ phenolphthalein indicator solution. POTASSIUM FIXORIDE SOLUTIOS.Dissolve 200 grams oi potassium fluoride in 400 ml. of carbon dioxide-free distilled water, which has been neutralized with hydrochloric acid or potassium hydroxide, using phenolphthalein as indicator. This solution should be kept in a paraffin-coated bottle.
Figure 1. Detail of Sample Valve Assembly
352
INDUSTRIAL AND ENGINEERING CHEMISTRY
connection during sampling, as this may cause volatilization of the sample before it reaches the valve. With the needle valve closed, screw the sample connection in place and attach to its exit three gas-washing bottles followed by a wet test meter. Place 100 ml. of distilled water in each bottle. Open the master valves, so that the flow will be partially diverted to pass through the sample line shown, and t,hen carefully open the needle valve sufficiently to allow a moderate rate of flow. Pass between 1.416 and 2.832 X 10' cc. (0.5 and 1 cu. feet) of gas through the meter, close the needle valve, and disconnect the absorbers from the sample connection. Close the master valves, open the bleeder valve to drop the pressure, and remove the sample connection. Wash the aluminum chloride from the needle valve and entry tube into a beaker and combine the Xvashings with the contents of the pas-washing bottles.
total hydrogen chloride, made up of hydrogen chloride from aluminum chloride and any originally free hydrogen chloride if it has been present. CALCULATIONS
Aliquot -4,titration of free hydrogen chloride 1. 311. of KOH X N - ml. of HC1 X N = ml. of N KOH equivalent to free HC1
.a
$1
B U T A M FLUSH LINE
SAMPLE VALV€
2.
Gram moles of HC1 =
3.
Gram moles of butane =
4.
Mole % HCl in butane (neglecting 41C1,) = gram moles of HC1 X 100 gram moles of HC1 gram moles of butane
cu. ft.
x
(PB - P,) 460 T
+
x
0.851
5 . Pounds of 1k1203per barrel of butane a t 60' F. = - ml. of KOH X iV) X (460 T ) (0.0702) (ml. of HC1 X cu. ft. x F x (Pa - P,)
+
.Aliquot B, titration of both .11C1, and free HCI Pounds of .i1C13per barrel of butane a t 60" F. = [(ml. of KOH X N) - C] X (460 T ) X 0.183 cu. ft. x ( P B - P,) x F
+
S
= normality of reagent used. P B = barometric pressure, mm. of mercury. P , = vapor pressure of water a t T o F. T = temperature of water in meter, O F. C = ml. of N potassium hydroxide equivalent to free hydrochloric acid from B 1. F = fraction of total sample taken for analysis. It should be the same for A and B.
Carbon dioxide-free water should be used with the phenolphthalein indicator. If iron is present in more than traces, a separate determination should be made and deducted from aluminum chloride content found. REPRODUCIBILITY
Duplicate determinations should agree within =t 1.0%, providing the iron content is negligible or corrections are made for it. Table I indicates the accuracy obtainable. The work was done on synthetic samples, but plant samples have been found to give equally good results (Table 11).
BL EED€f? VAL YE
Figure
ml. of KOH X N - ml. of HCl X N 1000 x F
2.
+
METHOD OF ANALYSIS
Dilute the above washings to a definite volume and take aliquots. To one aliquot, A, add 10 ml. of 0.5 *V hydrochloric acid and 10 ml. of potassium fluoride solution. Stir vigorously and titrate with 0.5 N potassium hydroxide, using phenolphthalein as indicator until a pink end point, permanent for one minute, is reached. The difference between the potassium hydroxide titration and the hydrochloric acid added will be due to free hydrochloric acid or alumina. If the potassium hydroxide titration minus the hydrochloric acid titration is positive, the sample contains free acid mid no alumina. If this difference is negative, t,he reverse is true. To another aliquot, U , add phenolphthalein and titrate with 0.5 LV potassium hydroxide until a pink end point, permanent for one minute, is reached. This titration will sho\T the
+.
Vol. 17, No. 6
Sample L i n e Flow Diagram
DISCUSSION Table
I.
Analysis of Samples" of Known Composition of A l u m i n u m Chloride and Hydrochloric A c i d by Proposed M e t h o d
KF
HC1 Difference AlClj HCI Solution AlCls Present Present Added Found Found AlCls HC1 Gram Gam Gram Ml. Gram Gram Gram - 0.0013 -0,0014 0 2224 0.1811 10.0 0.1825 0,2237 0.0000 -0,0017 0,1808 0 0224 10.0 0.1825 0.0224 0,0030 .... 0 . 0 0.2207 0.0 0.0 0.2237 -0.0003 -0.0003 0.0221 0.0180 10.0 0,0183 0.0224 0.0005 0.0003 0.0186 0.2232 10.0 0.0183 0.2237 .... -0.0004 0.0 0.0220 0.0 0.0 0.0224 .... +o. 0001 0.0 0.0225 10.0 0.0 0.0224 0,2000 - 0.0003 -0.0007 0 0221 10.0 0.200i 0,0224 -0.0003 -0.0004 0.0180 0 0220 10.0 0.0183 0.0224 a Made u p f r o m stock solutions of aluminum chloride and hydrochloric Aluminum chloride content of stock so!utions determined grariacid. metrically by precipitation with 8-hydroxgquinol1ne reagent.
+
I!.
Analysis of Plant Samples" of Butane Streams for Aluminum Chloride and Hydrochloric A c i d Hydroxyquinoline Point of Snmplinx Proposed Method Nethod Lb. AlCla/ Lb. Ah08/ Mole Q Lb. AlCli bbl. butane bbl. butane HC1 bbl. buta? E 2.31 8.40 2.42 0.0 Reactor 0.0 10.00 1.22 2:68 0 . 0 0 . 0 2.17 AlClr saturator 5.09 0.19 0.0 4.94 AlCla column bottoms .. 0.0 3.04 0.0 85.8 0.0 0.0 HCI column overhend .. 10.5 0 . 0 0 . 0 HC1 charge 4 Samples taken f r o m butane isomerization unit, operated by Wilshire Oil Co. Table
Large errors may result from incorrect sampling, since either excessive heating or cooling of the sample lines will result in deposit of aluminum chloride. Hot butane should be used for flushing sample lines, since the solubility of aluminum chloride is very low in cold butane. Large pressure drops in the sampling lines should be avoided, as they will cause the butane to vaporize and deposit aluminum chloride especially if the stream is saturated. The sample lines leading from the main lines should be maintained a t a temperature only slightly higher than that of the main lines t o avoid separation of aluminum chloride from a saturated stream. This can usually be accomplished by use of steam tracing and insulation. ACKNOWLEDGMENTS
The authors wish to acknowledge the helpful suggestions of
lh. Iverson and other members of the Universal Oil Products Company in the design of the sampling system used. LITERATURE CITED
(1) Craig, T. J. I., J . SOC.Chem. Ind., 30, 185 (1911). (2) Malaprade, Congr. chim. ind., 18, 115 (1938). (3) Scott, W. W., J. ISD. ENG.CHEM.,7, 1059 (1915). (4) Scott, W. W., "Standard Methods of Chemical Analysis", Vol. I, p. 1617, New York, D. Van Nostrand Co., 1939. (5) Willard, H. H., and Diehl, H., "Advanced Quantitative Analysis", p. 153,New York, D. Van Nostrand Co., 1943.
