Determination of Chloride in Bauxite-Supported Anhydrous Aluminum Chloride Catalysts W. A. LA LANDE, JR., HEINZ HEINEMANN, AND W. S. W. McCARTER Porocel Corporation, 260 South Broad St., Philadelphia, Penna.
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denser. The 500-ml. absorption flask shown is convenient, although other types of absorption vessels may be used. Approximately 20 grams of a representative sample are rapidly transferred to a 30-ml. weighing bottle and weighed to the nearest milligram. The contents of the weighing bottle are added to the flask through a wide glass tube, flared at the top, and extending a few centimeters below the bottom of the neck of the flask. The addition tube is withdrawn, the flask is clamped in position, 200 ml. of 18 X sulfuric acid are added rapidly, and the condenser and absorption vessel (containing 200 ml. of water) are quickly fitted into place.
UMEROUS patents describe the use of catalysts made
by impregnating bauxite and other granular adsorbents with anhydrous aluminum chloride. The growing largescale application of this type of catalyst makes necessary a dependable method of analysis for control during manufacture and for assaying shipments and spent material. The purpose of this paper is twofold: to describe satisfactory practical procedures for the determination of the chloride content of the catalyst, and to discuss the experience gained from several thousand analyses. For a routine determination of the aluminum chloride content of the catalyst the total chloride may be calculated to aluminum chloride. The total chloride is derived not only from anhydrous aluminum chloride, but also from partially hydrated aluminum chloride, probably basic aluminum chloride, small amounts of hydrogen chloride and ferric chloride, and possibly traces of other metallic chlorides produced by the action of aluminum chloride, hydrogen chloride, and water on the carrier during the impregnation. Of all the methods investigated, extraction with water and distillation with concentrated sulfuric acid, followed by the volumetric or gravimetric estimation of chloride in the extract or distillate, gave the most reproducible results after the procedures were carefully standardized. Both methods give lorn results, since it is impossible to wash the bauxite free of chloride in the extraction procedure, and impractical to ensure complete volatilization of hydrogen chloride by the hot concentrated sulfuric acid because of the coarse mesh size of the sample and the amounts of sample and sulfuric acid i t is feasible to employ in the analysis.
TABLEI. COJIP~RISON OF EXTRACTION AXD DISTILLATIO\ METHODS Aluminum Chloride Distillation Method Extraction Method Difference 1 2 Av. ( a ) 1 2 Av. ( b ) ( a ) - ( b )
Samplesa Unimpregnated bauxite 1 2 3 4 5
%
%
%
%
%
%
0.00 5.67 6.28 11.06 12.38 12.78 14.52
0.00
...
0.00
0.00 5.83 6,l5
...
5 83 5.99 5.77 6.28 6.20 6.28 11.14 11.54 11.22 12.33 12.49 12.27 12,74 12.22 12.70 14 49 13.97 14.46 6 14.54 7 14.53 14.67 14,40 16.68 8 16.48 16.56 16.79 16.61 9 16.56 16.58 16.63 15.67 14.74 15.70 10 15.63 16.19 15.86 16.12 11 16.26 12 18.26 17.83 18.25 18.27 18.04 18.10 13 17.98 17.48 4 Samples 1 to 9, inclusive. were 4/10 mesh; were 6/14 mesh.
5.80 6 18 11.60 11.57 12.1s 12.34 12.57 12.40 14.11 14.24 14.58 14.63 16.50 16.52 16.37 16.16 14.75 14.75 15.80 15.74 17.84 17.84 17.49 17.49 samples 10 to 13,
/
r
FIGURE 1.
7
\
*4PPARATUS FOR
D~STILLATION SIETHOD
%
The mixture is then heated carefully, TTith occasional shaking, to control foaming. The distillation is continued for 5 minutes following the first appearance (usually after 20 to 25 minutes) of an oily condensate (sulfuric acid) in the upper part of the condenser. During the period of heating approximately 100 ml. of distillate collect in the receiver. The condenser is then removed from the flask and washed down into the absorpt.ion vessel with two 25-m1. portions of water. The contents of the absorption vessel are washed into a 1-liter volumetric flask and the volume is adjusted to the mark. A 25-ml. aliquot is transferred t o a 250-ml. Erlenmeyer flask, 1.5 ml. of concentrated nitric acid, 25 ml. of 0.1 N silver nitrate, and 1 ml. of saturated ferric alum solution are added, and the mixture is titrated with 0.1 N ammonium thiocyanate according to the directions of Kolthoff (1). EXTRACTION METHOD. Approximately 50 grams of sample are weighed into a 60-ml. low-form weighing bottle. The weighing bottle is then opened under 300 ml. of cold distilled water in a 800-ml. tall-form beaker (or the sample may be rapidly poured into the water). The bottle and stopper are removed from the mixture, which is then heated to the boiling point with,mechanical stirring a t a rate which keeps the granules in suspension. The boiling is maintained for exactly 1 minute. The mixture is then allowed to settle for 1 minu$e and the supernatant liquid (bearing some finely divided bauxite in suspension) is decanted into a 1-liter volumetric flask. Three hundred milliliters of water are added to the residue in the beaker and the
0:03 0.10 -0.43 -0.01 0.34 0.38 -0.04 0.18 0.24 0.92 0.39 0.42 0.55 inclusive,
Analytical Procedures The two recommended methods are given in detail in t h e following sections. Typical results are s h o m in Table I. The analyses were made on commercial preparations of Isocel, a catalyst containing 15 to 20 per cent of aluminum chloride on low-iron bauxite, and on samples taken from the impregnators a t intermediate stages of manufacture. DI~TILLATIos METHOD. The apparatus illustrated in Figure 1 is constructed from a 500-ml. Kjeldahl flask and a suitable con-
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INDUSTRIAL AND ENGINEERING CHEMISTRY
386
heating, stirring, boiling, and decantation are repeated. The residue in the beaker is washed into a mortar and the lumps are crushed to a coarse powder. The material is tben washed back quantitatively into the beaker, the volume adjusted to approximately 200 ml., and the extraction procedure again repeated. The contents of the volumetric flask are refrigerated to room temperature, and made up to 1000 ml. The chloride content is determined as described under the distillation method.
Vol. 15, No. 6
ously lo^ results (due to variation in the amount of chloride retained by the bauxite) are encountered when samples substantially larger than 20 grams are used. EXTRBCTION METHOD.The amount of chloride found by this method varies with the number of extractions and the state of subdivision of the sample. Higher values are obtained by extracting a finely ground sample, but serious errors are introduced if the sample is ground prior to the The data in Table I show that the distillation method first extraction; however, after one or more extractions the usually gives higher results than the extraction method, granules may be reduced to powder without loss of chloride. irrespective of the chloride content. The difference between There is no detectable loss of hydrogen chloride during the the results obtained by the two methods is greater for the boilings. The volumes of water recommended for the expreparations of finer mesh size. The mean variation between tractions are optimum; larger amounts are unnecessary and duplicate determinations on each of a series of 13 samples inconvenient, while the use of smaller portions results in was 0.12 for the distillation method and 0.14 for the exlower values for the chloride content. The data in Table traction method. I11 show that tlvo extractions followed by crushing and a third extraction give higher values than one to three extracTABLE 11. CHLORIDE CONTENT IN RELATION TO SIZEOF S A M P L ~ tions without crushing, or one extraction with subsequent (Distillation method) crushing and one re-extraction. The extracted residues Aluminum Chloride were shown by the distillation analysis to contain residual 10-gram sample 20-gram sample 50-gram sample Sample No. chloride equivalent to 8 to 9 per cent of the total chloride % % % 21 12.18 11.48 content-i. e., 1.0 to 1.6 per cent of aluminum chloride for 10.12 22 16.03 15.55 14.37 samples containing 13.5 to 19.5 per cent of (total) aluminum chloride (Table 111). Although the distillation method and the extraction method Discussion as applied directly to the sample give low results, the total DISTILLATION METHOD. I n determining the conditions chloride content can be calculated from the sum of the for the distillation method it was necessary to consider the values obtained by the standard extraction of the original size of the sample, the amount of acid used for the digestion, sample and the standard distillation procedure applied to the the mesh size of the sample, and the means for detecting ground residue from the extraction. The following comwhen the evolution of hydrogen chloride could be considered pilation compares the results obtained by the standard methods and the combination procedure. The numbers in complete. It was found that reproducible results could be obtained parentheses indicate the percentage of chloride detected by the different techniques. JJ7hile a combination of the by heating the mixture for 5 minutes following the first appearance of a few drops of oily distillate (sulfuric acid) two methods will indicate the total chloride content of the in the upper part of the condenser. At this point the supercatalyst, it is too time-consuming to be recommended for natant liquid in the flask is chloride-free, but the granules routine plant control procedure: of catalyst remaining undisintegrated contain chloride which can be detected after proPer Cent Aluminum Chloride Sample 14 Sample 15 Sample 16 Sample 17 longed soaking in water. The chloride can be Standard extraction PIUS entirely expelled from the unground catalyst distillation of extracted by using 20 ml. of 18 11: sulfuric acid for each residue 17.84 (100) 13.52 (100) 16.37 (100) 19.49 (100) 18.26 (93.5) 12.49 (92.3) 15.67 (96.4) 16.68 (93.5) gram of sample and continuing the digestion ~ ~ r 16.58 ~(92.7) ~ 12.42 (91.9) ~ ;14.75 (90.6) 17.84 (91.5) until the bauxite is completely decomposed. This procedure is impractical for a routine SOLUBLEIRONCONTENTOF CATALYST.The data in analysis, since a 20-gram sample would require 400 ml. of sulfuric acid and several hours’ digestion a t fuming temperTable IV show that 12 to 15 per cent of the iron content of ature. It follows that higher results should be obtained by the carrier is converted into soluble form (probably ferrous decreasing the size of the sample without changing the and ferric chlorides) by the action of the aluminum chloride and hydrogen chloride during impregnation. The iron conamount of sulfuric acid used for the decomposition. The tributed by the aluminum chloride may be neglected, since data in Table I1 show the average values obtained for the chloride content by varying the size of the analytical sample the chemical used in the manufacture of these samples conwhile otherwise following the recommended procedure. tained only 0.1 per cent iron (as Fe203). The bauxite used Experience indicates, however, that samples smaller than as carrier contained not more than 2.5 per cent Fe203 (volatile-free basis). The samples m-ere processed by the extraction 20 grams should not be used because of excessive variation due to sampling difficulties; lack of reproducibility and serimethod and the extract and extracted residue were analyzed for iron. The iron values are calculated on the basis of the “as received” catalyst TABLE 111. VARI.4TIOX O F CHLORIDE CONTENT WITH VARIOUS EXTRACTION PROCEDURES sample. Treatment SAMPLING.T h e sample Extrac- ExtracAluminum Chloride Content tions tions Sample 14” Sample l 5 a Sample l B a Sample 174 taken in t h e p l a n t for before after Original Extracted b Original Extracted b Original Extractedb Original Extracted b analysis should be as large KO. crushing crushing sample residue sample residue sample residue sample residue % 70 % % % % % % and as representative as 1 2 1 16.58 1.26 12.42 1.10 14.75 1.52 17.84 1.65 possible. It is delivered to 2 3 16.39 1.09 12.19 0.95 ,,. ... the laboratory in a tightly3 2 16.20 1.35 11.87 1.10 ... ... .. 4 1 i 16.17 1.48 12.00 1.23 . . . . . . . . stoppered glass container and Samples 14 and 15 were 4/8 mesh, samples 16 and 17 were 6/14 mesh. b Determined b y distillation methdd. subdivided with a 16 to 1 splitter contained in a r
~~;;~;:~
I
ANALYTICAL EDITION
June 15, 1943
O F I R O N IN THE EXTR.4CTION LfETHOD TABLE IT. DISTRIBUTION OF ANALYSIS
% F e as Fen08 (a)
Sample 18 19
20
In
extract 0.24 0.24
0.35
Total Fe as % Fen02
(b)
I n extracted residue 1.74 1.66 2.06
( a ) -k ( b ) 1.98 1.90 2.40
Direct analysis of catalyst 1 87 1 90 2.23
“dry box”. The sinall fraction i5 transferred to a glass container for analysis. The analytical sample is taken by inserting a test tube (holding 20 or 50 grams under the sampling conditions) into the bottle to the bottom, thereby removing a reasonably representative portion of the material for transfer t o the weighing bottle.
Summary Decomposition of the catalyst with sulfuric acid and removal of the liberated hydrochloric acid by distillation, ivith
387
subsequent argentiometric estimation of chloride, give reproducible results representing 92 to 96 per cent of the total chloride content. Reproducible but l o x results for the chloride content of bauxite-supported aluminum chloride catalysts may be obtained by mater-extracting the catalysts by a standardized procedure. The method indicates 90 to 93 per cent of the total chloride content of the sample. The total chloride content of the catalyst may be determined by a combination of the tn-0 methods: standard extraction of the original sample plus standard distillation of the ground residue from the extraction. Either the extraction or the distillation method is proposed as a satisfactory routine procedure. The combination method may be used when i t is essential to know the absolute chloride content. (1)
Literature Cited Kolthoff and Furman, “Volumetric Analysis”, Vol. 2, 244, New York, John Wiley & Sons, 1929.
pp. 218,
Determination of Iron In the Presence of Chromium and Titanium with the Jones Reductor F. S. GRIMALDI, R. E. STEVENS, A N D M .K. CARRON Geological Survey, U. S. Department of t h e Interior, Washington, D. C.
Sulfuric acid solutions of titanous and chromous sulfates, obtained by passage through the Jones reductor, are oxidized by aeration for from 5 to 10 minutes in the presence of a trace of copper sulfate as a catalyst. Ferrous sulfate is essentially unosidized
T
HE Jones (6) reductor was originally proposed as a
rapid and convenient device for the reduction of ferric to ferrous salts, prior to titration with a standardized solution of an oxidizing agent. The solution to be reduced is preferably a sulfuric acid solution, because side reactions that may occur in the presence of hydrochloric acid are thereby avoided in the ensuing titration. Although the Jones reductor is convenient, several elements other than iron are also reduced by zinc, and various methods have been proposed to eliminate the effect of these interfering elements. Previous studies have dealt mainly with the interference of titanium. The stability to air-oxidation of ferrous sulfate in sulfuric acid solution was studied by Baskerville and Stevenson (Z), who showed that practically no oxidation of the ferrous sulfate occurred after 3 hours of aeration. They observed also that the presence of cobalt, chromium, copper, and titanium salts had no effect upon the air-oxidation of the ferrous sulfate. Thornton and Roseman (8) studied the preferential oxidation by air of titanous sulfate in the presence of ferrous sulfate. Their results were good, but they suggest that “the procedure is most apt t o succeed when the iron is equal to, or preponderates over, the titanium’’. Gooch and Nexton ( 4 ) used bismuth trioxide for the
and is titrated with permanganate after aeration. Best results are obtained by using 0.0003 millimole of copper sulfate in about 300 ml. of solution. Larger quantities of copper sulfate lead to slightly low results when both chromium and titanium are present.
preferential oxidation of the titanium. Their method requires the removal of the excess of bismuth trioxide before the estimation of iron. Brandt (5)used titanium trichloride as the reducing agent for ferric ion, the excess titanium trichloride being destroyed by copper sulfate. In this procedure the cupric ion is reduced to metal by the titanium trichloride and the precipitated copper is filtered off before titrating the iron. That simple air-oxidation of a titanous solution is not dependable is shown by hlcSabb and Skolnik ( 7 ) . Their results corroborate the experience of Margaret D. Foster of this laboratory, who found that in a solution containing titanous salt equivalent to 0.04 gram of titanium dioxide less than three fourths of the titanium was reoxidized to the quadrivalent state after 10 hours of aeration; a solution containing 0.09 gram of titanium dioxide &-asless than nine-tenths converted in the same time. Axt and Leroy ( 1 ) increased the rate of oxidation by using a perforated plate for supplying the air. McSabband Skolnik ( 7 ) found that the addition of 50 ml. of saturated mercuric chloride solution greatly increased the rate of oxidation of titanous sulfate by aeration. The method described below is based on the discovery by Zintl and Wattenberg (10) that copper in solution catalyzes air-oxidation of titanous ion. This method is applicable for all proportions of iron, titanium, and chromium. Molybdenum and vanadium should be absent.
