with ethyl ether for 1 hour. The ethyl ether was then evaporated by placing the flask in a beaker of ~ a t e at r 60’ C., and the acetic acid added. It was not necessary to filter off the nitrocellulose or other materials in ball propellants insoluble in ethyl ether. Lead stearate, which is found in some ball propellants, did not interfere. The method was applicable to the determination of diethyl, dibutyl, and dioctyl phthalates. It was not satisfactory for dimethyl phthalate, probably because of partial hydrolysis, nor for diphenyl phthalate because of a peculiar side reaction. When diphenyl phthalate was treated with the hydroxylamine-sodium hydroxide reagent, the solution turned pink, and on heating in the oven, yellow. Apparently the diphenyl phthalate partially dccornposed in the alcoholic sodium hydroxide solution into phthalic anhydride and phenol, which then reacted with each other to form phenolphthalein (sodium derivative). The reaction of phthalic anhydride and phenol to form phenolphthalein is a well known synthcsis ( 2 ) . The presence of the hydroxylamine was not necessary for the formation of the pink color. The curves obtained by carrying diethyl, dibutyl, and dioctyl phthalates through the extraction procedure were fairly close to the curves obtained for pure phthalates. However, it is rec-
ommended that the working curves be prepared by the use of the extraction procedure. The curves followed Beer’s law. The method was not applicable to propellants containing other esters such as triacetin. RESULTS
(2) Conant, J. €%., “Chemistry of Organic Compounds,” p. 515, Macmillan, Sew York Q X X. - __ _ York, , I1933. (3) Gcddu, R. F., LeBlanc, N. F., Wright, M., A N A L . CHEM. 27. 27, 1251 (1955). (\ 4 ,) Hall. R. T.. Shaefer. W. E.. “Detertermination of’ Esters,‘’ in ’“Organic
c.
Analysis,” by Mitchell, J., Kolthoff, I. M., Proskaurr, E. S.,Weissberger, .I\., Vol. 11, pp. 38, 57, Interscience, Kew York, 1954. 15) Hill U. T.. I N D .EXG.CHEM..AXAL. ED.18,317 (1946). (6) Zbid., 19,932 (1947). (7) Kight, W. E., Report of Phthalatr Committee, Joint Army-Na~--AirForce Panel, on Arialytical Chemistry of Solid Propellants, November 1957. (8) NaoGm, P., L‘Nitroglycerine and Nitroglycerine Explosives,” p. 121, Rilhams & Wilkins, Baltimore, 1928. (9) Norwitz, G., Anal. Chim. Acta 19, \
Various synthetic samples v ere prepared by adding nitroglycerin, ethyl centralite, dinitrotoluene, diphenylamine, 2-nitrodiphenylamineJ and lead stearate to aliquots of the standard phthalate solutions (Table V). The results obtained for dibutyl phthalate in a 0.2-gram sample of a ball propellant containing nitrocellulose, nitroglycerin, ethyl centralite, dinitrotoluene, and diphenylamine (4.95% as determined by difference) were: 4.90, 4.75, 4.70, 4.90, 4.75, 4.85, and 4.90; average 4.82%; standard deviation, 0.086%. ACKNOWLEDGMENT
The author is indebted to Samuel Sitelman of this laboratory for his suggestions. LITERATURE CITED
(1) Butts, P. G., Meikle, W. J., Shovers, J., Kouba, D. L., Becker, W. W., ANAL. CHEM.20,947 (1948).
,
216 (1958). 0) Sandhoff, A. G., Kight, W. E., Report of Phthalate Committee, Joint
Army-Navy-Air Force Panel, on Analytical Chemistry of Solid Propellants, June 1956. 1 ) Stalcup, H., Fauth, M. I., Watts, J. O., Williams, R. W., ANAL. CHEM.
29, 1482 (1957). (12) Stalcup, H., McCollum, F., Whitman, C. L., Zbid., 29, 1479 (1957). (13) Swann, M. H., Zbid., 29, 1352 (1957). (14) Thompson, A . R., Australian J. S a . Research 3A, 128 (1950). (15) Thorpe, J. F., Whiteley, M. .4.,
“Tho;,pe’s Dictionary of Applied Chemistry, Vol. IV, p. 512, Longmane, Green, London, 1940.
RECEIVEDfor review April 10, 1959. Accepted August 24, 1959.
Rapid Methods for the Analysis of Petroleum Cokes ANNE L. CONRAD and JEAN K. EVANS Research Department, The Standard Oil Co. (Ohio), Cleveland, Ohio
b Rapid methods for the determination of volatile, ash, and metal contents of petroleum cokes have been developed using the induction furnace. By carefully controlling the burning conditions, volatile and ash results can be obtained in approximately 1 hour, as compared to the 8 hours required for the ASTM D 271 procedures. Average deviations of 0.4 and 0.01% have been obtained for volatile and ash contents, respectively, between the proposed rapid procedure and the ASTM method. Subsequent color development of several metals can be performed on the fused ash solution.
T
processing of raw petroleum coke and possibly other bituminous materials requires strict control of volatile, ash, and metal contents. Sampling difficulties inherent with these HE
solid materials necessitate more frequent sampling and thus extensive analytical measurements. The need for more rapid procedures exists wherever strict controls are required. ASTM D 271 Sections 10(b) and 13(b) ( 2 ) illustrate the standard method which originated many years ago. This method is applicable but time-consuming, as it requires controlled heating to remove the volatile matter, followed b y several hours of muffle furnace heating to reduce the sample to an ashed residue. Individual metal contents are determined colorimetrically on the acid solution of the ash. Although a few refinements such as the description by Hensel (4) of a n automatic unit for determining volatile matter in coke have appeared, the original ASTM method remains essentially unchanged. It requires 8 hours of elapsed time before the ash is available for metal determinations.
By the proposed method, volatile and ash contents comparable to those obtained b y the AST51 procedure are available in 1 hour and subsequent colorimetric metal determinations can be made. The use of an induction furnace (6) with rapid and controlled heat input eliminates the tedious ashing procedure. Several available models of induction furnaces (with controlled units which will maintain any predetermined maximum temperature) used with a n optical pyrometer to determine temperatures are satisfactory and will handle samples as large as 1 gram. This sample size is required to obtain measurable amounts of ash and metals. Crucibles of either T’ycor (Leco Model 534-215) or platinum (5-ml. standard form, 2.0 em. deep, American Platinum Co.) are suitable, but platinum is preferred if metals such as silicon are to be determined. Either type of VOL. 31, NO. 12, DECEMBER 1959
2015
I. Volatile and Ash Contents of Coke (ASTM D 271 us. induction furnace method)
Table -___
ASThI lab 1 8.9 8.7 10.0 8.1 8.4 8.3 9.7 9.4 11.7
5
% Volatiles ASTM
lab 2 9.3 9.3 9.0 8.4 7.7 10.0 9.6 9.8 12.3
9.3 10.2 20.7O Single determination. Table II.
Sample Vanadium, wt. yo Rapid induction Average A4STM Iron, wt. Yo Rapid induction Average ASTM Nickel, wt. yo Rapid induction Average -4STM Silicon, wt. yo Rapid induction Average ASTM
70
Induction lab 3 8.8 9.2 10.0 8.3 8.0 8.9 9.6 8.8 11.3, 11.2 1 1 . 3 , 11.4 9.2 20.8
ASTM lab 2 0.18 0.18 0.19 0.13 0.21 0.22 0.16 0.15 0.13
0.15
0.16
Ash
Induction lab 3 0.20 0.16 0.19 0.13 0.20 0.20 0.15 0.147, 0.148 0.143, 0.146 0.16
Metals Content in Petroleum Coke
(Rapid induction furnace us. ASTM ashing) 1 3 3 4
5
0.044 0.048
0.043 0.048
0.045 0.046
0.017 0.016
0.021 0.021
0.021 0.020
0.011 0.012
0.018 0,014
0.036 0.036
0.025 0.024
0,019 0.018
0.019 0.020
0.018 0.018
0.011 0.011
0,014 0.013
0.004
0.007
0.006
0.016 0.016
0,003
...
...
crucible may be brought to constant weight by heating for 3 minutes in the induction furnace at the maximum temperature required for ashing. The removal of volatile constituents from coke must be carefully controlled. The ASTM procedure requires that the sample be lowered slowly into the hot furnace to prevent spattering. By the induction furnace method, spattering is prevented by controiling the initial temperature at 750" C. and gradually increasing it to 950" C., using a n optical pyrometer. During heating a stream of nitrogen passes over the sample and through the combustion tube. The rate at which temperatures may be raised from 750" to 950" C. depends upon the volatile content of the sample. For cokes containing a high percentage of volatile matter (20%), spattering is considerable if the sample is heated too rapidly. For cokes containing only 5 to 10% volatile matter more rapid heating is permitted. The appearance of the sample is frequently indicative of the practical heating rate. I n any case, the T'ariac control permits constant adjustment of the heating rate and no difficulties are observed in obtaining the smooth evolution of volatile matter. After the furnace temperature has reached 950" C., it is maintained for exactly 6 minutes, still under nitrogen atmosphere. The sample is then removed from the furnace, cooled in a desiccator, and weighed. The loss in 2016
ASTM lab 1 0.18 0.18 0.20 0.13 0.21 0.22 0.16 0.16 0.16
ANALYTICAL CHEMISTRY
...
0.004
weight is calculated as per cent volatile matter. The volatile-free sample is returned to the furnace and burned a t 950" C. under a stream of oxygen. Fifteen or 20 minutes are usually sufficient to burn off all of the carbon. The crucible with the ash residue is removed from the furnace, cooled in a desiccator, and weighed. The ash is usually retained and dissolved or fused for metal determinations by colorimetric procedures. Iron is determined by the o-phenanthroline procedures (3, 9) , nickel by dimethylglyoxime (9, IO), vanadium by diphenylbenzidine (IO), and silicon by molybdenum blue ( I , 6). Only volumes must be reduced to maintain the same sample to reagent ratios. Similar combustion methods are applicable to the determination of sulfur (6, 7 ) and carbon (j),where evolved gases are collected in suitable absorbers and titrated. The simultaneous determination of these elements with the volatile and ash determinations is not practical. Incomplete oxidation occurs during the evolution of volatile matter under nitrogen, and concentrations are too high for using a 1-gram sample. Accurate results on both sulfur and carbon can be obtained b y burning individual aliquots of the sample for each determination. PROCEDURE
Volatiles Determination.
Using an
induction furnace (Leco Model 521A) with a variable, controlled heating transformer and a Vycor combustion tube (Leco Model 534-201) with a high-temperature ring seal (Leco Model 521-113), connect the oxygen and nitrogen gases t o a purifying train (Leco Model 519). With a n optical pyrometer, accurately determine the milliampere readings on the furnace required to maintain temperatures of 750" and 950" C. These readings should be established with an empty crucible plus the quartz-enclosed crucible (Leco Model 534-214) in the furnace, as results obtained using a Vycor crucible will be slightly different from those obtained with a platinum crucible. Bring the crucible to constant weight by holding it at 950" C. in the furnace for 3 minutes. Cool the crucible in a desiccator, and weigh. Grind and dry the coke sample, following the ASTM D 271 procedure Sections 6(a) and 6(b); desiccate until used. Weigh 1 gram of dried sample into the crucible, insert this crucible uncovered into the quartz-enclosed carbon crucible, and place in the furnace for heating. Turn on the purified nitrogen stream a t the rate of 0.5 liter per minute and connect the gas exhaust system. Turn on the high voltage, controlling the temperature a t 750" C. Gradually increase the voltage input a t such a rate that no spattering occurs (5 to 6 minutes) until a temperature of 950" C. is reached. Hold the temperature a t 950' C. for exactly 6 minutes. Turn off the high voltage and nitrogen, remove the crucible, cool it in a desiccator, and weigh. Calculate the loss in weight as the % volatiles. Ash Determination. Position t h e IH-10-548C oxygen jet in the t o p of the combustion tube and connect i t to the oxygen gas purifying train. Return t h e uncovered crucible containing the volatile-free coke t o t h e furnace set a t 950' C., and turn on the high voltage. When the quartzenclosed carbon crucible is glowing, turn on the oxygen a t the rate of 0.15 liter per minute. Hold t h e furnace temperature a t 950" C. until all the carbon is burned (15 to 20 minutes). Turn off the high voltage and oxygen, remove the crucible from the furnace, cool it in a desiccator, and weigh. Calculate the increment in weight over that of the empty crucible as per cent ash. Metals Determination. Fuse the entire ash content in t h e platinum crucible with 1 gram of fusion mixture consisting of 2 parts of C.P. sodium carbonate and 1 part of C.P. boric acid. Cool the fusion mixture and add 4 mi. of triple distilled water. Heat until a clear solution is obtained. Place t h e cooled crucible in a 20-ml. beaker, acidify t h e solution, and transfer i t to the 20-ml. beaker. Heat gently until all the carbonate is removed. Transfer the solution to a 25-ml. volumetric flask and make up to volume. IRON. Transfer a n aliquot containing between 0.005 and 0.04 mg. of iron
(usually 1 ml.) to a 25-ml. volumetric flask. Add 0.25 ml. of 10% hydroxylamine hydrochloride, dilute to 10 ml., and adjust the p H to 3 to 5 with 1 to 1 ammonium hydroxide. Add 1.25 ml. of ammonium acetate buffer and 1.26 nil. of O.lyc o-phenanthroline. Adjust to volume and wait 20 minutes before reading the absorbance a t 508 mp in 5cm. cells. NICKEL. Transfer a n aliquot containing 0.0025 to 0.04 mg. of nickel (usually 1 nil.) to a 25-ml. volumetric flask. Dilute to approximately 10 nil. and add 2.5 ml. of ammonium citrate solution and 1.0 ml. of 0.05s iodine solution. Shake the flask well after each addition. Add concentrated ammonium hydroxide until the solution is decolorized, plus 1.5 nil. in excess. Add 1.5 ml. of 0.2y0alcoholic dimethylglyoxime, swirl, and make up to \rolume. After 20 minutes read the absorbance a t 540 m,p in 5-cm. cells. VANADIUM.Transfer a n aliquot containing 0.002 to 0.03 nig. of vanadium (usually 1 nil.) to a 10-nil. volumetric flask. Add 2 to 3 drops of bromine water and a few drops of ammonium hydroxide until the bromine color disappears. .idd 1 to 1 hydrochloric acid dropn-ise until the color reappears and 1 drop in excess. Dilute to approximately 5 nil. and boil until the volume is reduced t’o approximately 2 ml. Cool and add 6 nil. of phosphoric acid, mix, and cool. Add 2.5 nil. of the diphenjlbenzidine solution, dilute to volume, mix, and after 10 i 1 minutes, read the absorbance a t 575 mp in 1-cm. cells. SILICOS.Transfer a n aliquot containing 0.001 t o 0.015 mg. of silicon to a 25-mI. volumetric flask. Add 0.25 nil. of 1 to 3 sulfuric acid, dilute to approximately 10 ml., and add 2.5 ml. of .5y0 ammonium molybdate. After 5
minutes, add 5.0 nil. of 1 to 3 sulfuric acid. Invert for mixing and add 0.25 nil. of 1% stannous chloride. Dilute to volume and after 5 minutes read the absorbance a t 5G5 mp in l-cnl. cells. Prepare a blank similarly for all metal determinations. RESULTS
A series of production samples was taken from a petroleum coker unit. These samples were uniformly ground, mixed, and dried to a moisture-free basis, following the ASTM procedure. The resulting samples were divided and sent to three separate laboratories, two of which followed the ASTM procedure. The third laboratory followed the proposed rapid induction method. Comparative results on volatile and ash contents are shown in Table I. The volatile content as obtained by the rapid method varied from the ASTbf results in approximately the same order of magnitude as did the results from the two laboratories following the ASTM procedure. hlaximum deviation was lyo,whereas average deviation from the A S T N results was =t0.44%. Similarly, ash content (Table I), as determined by the rapid procedure gave an average deviation of *O.Ol% from the average of the two ASTM results. Precision as shown on some samples may be as high as 0.003%. Table I1 s h o m the results obtained for iron, nickel, vanadium, and silicon content from five of these samples. Only average results are shown for those laboratories following the ASTAI ashing procedure. Although not enough data
are presented for calculating standard deviations, the results show good agreement. Average differences on all metals were less than =k00.002’70‘,. ACKNOWLEDGMENT
The authors are indebted to all the laboratories which contributed to the cooperative work, as well as to the Standard Oil Co. (Ohio) for permission to publish this work. LITERATURE CITED
(1) Am. SOC. Testing Materials, Phil-
adelphia, Pa., “Methods for Chemical Analysis of Metals,” Designation E
107-56T. (2) Am. SOC. Testing Materials, Phil-
adelphia, Pa., “Standards on Coal and Coke,” Designation D 271-48. (3) Fortune, W. B., Mellon, M. G., IND. EKG.CHEM.,ANAL.ED.10,60 (1938). (4) Hensel, R. P., Jones, S. A,, ANAL. CHEM.30,402 (1958). (5) Laboratory Equipment Corp., ‘‘Induction Furnace Series IH-1OC for Carbon Analysis,” July 1952. (6) Laboratory Equipment Corp., “Instruction Manual for Operation of Leco 521A and 521s Induction Furnaces for Determining Ash and Sulfur in Coal and Coke,” April 1957. (7) Laboratory Equipment Corp., “Instructions for the Analysis of Sulfur in Hydrocarbons by the Leco a i g h Frequency Combustion Procedure,” May 1958.
(8) Luke, C. L., ANAL. CHEM.25, 148 (\ -19RR’I. - - - I .
(9) Milner, 0. I., Glass, J. R., Kirchner, J. P., Yurick, A. N., Zbid., 24, 1729 (1952). (10) Wrightson, F. M., Zbid., 21, 1543 (1949).
RECEIVEDfor review June 11, 1959. Accepted September 10, 1959.
Determination of Dissolved Gases in Petroleum Fractions b Y Gas Chromatography JAMES A. PETROCELLI and DEAN H. LICHTENFELS
Gulf Research & Development Co., Pittsburgh, Pa. b A gas chromatographic procedure has been developed for the determination of dissolved gases, especially oxygen and nitrogen, in petroleum fractions. The essential feature of this method involves the use of a precolumn or trapping column in series with a Molecular Sieve column. The hydrocarbons are retained in the precolumn and the oxygen and nitrogen are resolved in the Molecular Sieve column. This method is applicable for determining these dissolved gases in petroleum fractions up through the lubricating oil
range. It also has been applied experimentally to other similar analytical problems.
M
of the methods for determining dissolved gases in petroleum fractions are based on heating the sample under a vacuum and measuring the volume of the liberated gas in a suitable apparatus. Various methods of this type are discussed by Markham and Kobe (7). Polarography has been successfully applied t o the determination of dissolved oxygen in various media OST
(1, 2, 6, 8). Hall (6) employed a polarogrP,phic procedure for the determination of dissolved oxygen in petroleum fractions. Elsey (4) recently reported the use of a gas chromatographic technique for determining dissolved oxygen in lubricating oil. Although these methods have been satisfactory, it was believed that a gas chromatographic procedure for dissolved gases, in particular oxygen and nitrogen in petroleum fractions, would be a n improvement. The essential feature of the determinaVOL. 31, NO. 12, DECEMBER 1959
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