Carboxylic Cation Exchange Resin in Water Conditioning
Eng~;rn ig
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development
I
HYDROGEN CYCLE FRANCIS X. McGARVEY AND JOSEPH THOMPSON R O H M & H A A S CO., P H I L A D E L P H I A , P A .
*
This study indicates t h a t considerable economy and improved operation may be obtained when the carboxylictype exchanger is used either as a deallializer or as a component in a deionization system. Treatment of beverage process waters by carboxylic-type exchangers should be particularly successful in regions where temporary hardness is a major constituent i n the water supply.
Although the exchange characteristics of carboxylic cation exchange resins have been reported previously, an application study of this resin i n water conditioningislacking. The carboxylic cation exchange resin, Amberlite IRC-50, was selected for this study. The capacity and ion exchange characteristics of this resin have been determined as a function of influent concentration of flow rate, ratio of alkalinity to mineral acidity, and ratio of sodium to calcium. Although i t exhibits high regeneration efficiency, increased leakage will occur if the bed is not regenerated fully. Regeneration efficiency is much higher than t h a t found for sulfonic acid cation exchange resins and the effects of calcium sulfate precipitation are lacking. Carboxylic cation exchange resins are most applicable for waters containing high ratios of alkalinity and hardness.
A
LTHOUGH the application of carboxylic cation exchange
resins to recovery and concentration problems has received considerable attention (6), meager data are available on the use of such materials in the water-conditioning field. The use of the German carboxylic cation exchanger, Wofatite C, in water oonditioning has been described briefly by Myers (6). However, except for some preliminary data on the use of the resins for the dealkalization of bicarbonate water, the report indicates that the
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F L O W R A T E G A L PER CUBIC F O O T PER M I N U T E INFLUENT ON CENT RATION, P.P.M. AS GCO,
Figure 1. Capacity of Amberlite IRC-50 for Calcium
Figure 2.
Bicarbonate
74 1
Capacity of Amberlite IRC-50 as a Function of Flow Rate
142
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 43, No. 3
41
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F L O W F U N C T I O N , GRAMS/MIN./CUBIC
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ALKALINITY RATIO,
Capacity of Amberlite IRC-50 for Calcium Bicarbonate Solutions
Figure 4.
As a function of flow function
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Capacity of Amberlite IRC-50 for Sodium Ions As a function of alkalinity
application had been developed on only a limited basis. Kunin and Barry ( 3 ) have studied the exchange characteristics of a carboxylic exchange resin, Amberlite IItC-50, and have indicated that such a material exhibits unusual exchange properties. I n particular, a considerably greater degree of selectivity of divalent over monovalent ions was found for the carboxylic-type exchanger than for the well known sulfonic acid exchangers. The equilibria and column data indicated that an estrenicly high acid regeneration efficiency is associated with the carboxylic group. The following study was undertaken for the purpose of investigating more fully the usefulness of a carboxylic acid cation exchange resin in water conditioning, ivhen operat,ing in the hydrogen cycle. I n particular, deallcalization and deionization applications were investigated.
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911 st,udieswere conducted with the carboxylic resin, Amberlit'e IRC-50, and the sulfonic reains, Aniberlites IR-105 and IR-120. The carboxylic resin had an effective size of 0.43 mm. and a uniformity coefficient of 1.72. Initially, the resin was placed in the hydrogen form with a n excess of 1 S hydrochloric acid, followed by a copious rinse with distilled n-ater. The solutions used t o exhaust the resins were of three general types: h pure calcium bicarbonate solution was prepared by passing a 0.01 N calcium chloride solution through a bed of mixture of equal volumes of the carbonate and bicarbonate salts of Amberlite IRA-400. The effluent from this bed was 0.005 AT with respect t o calcium bicarbonate ( p H 8.0 t o 8.5) and free of chlorides. f-
Figure 5.
Capacity and Leakage of Amberlite IRC-50 for Alkalinity
A s a function of alkalinity retia of calcium birarbonatecalcium chloride solutions
INDUSTRIAL AND ENGINEERING CHEMISTRY
March 1951
743
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CATION RATIO
MONOVALENT CATIONS
CATION
RATIO
TOTAL CATIONS
Figure 6.
MONOVALENT OATIONS T0TP.L CATIONS
Capacity of Amberlite IRC-50 for Natural Waters
Solutions containing various amounts of calcium bicarbonate, calcium chloride, and sodium chloride were prepared in varying proportions by mixing sodium bicarbonate and calcium chloride in the proper amounts. In solutions where calcium bicarbonate alkalinity was desired, the calcium hydroxide was dissolved and dr ice was used to introduce carbon dioxide t o the solution. AXer mixing with air, satisfactory solutions were obtained. Natural water was obtained from the Delaware River a t Philadelphia Calcium studies were conducted in glass tubes 1 inch in diameter according to the procedure described in the literature ( 3 , 4 ) . Sodium and calcium concentrations were analyzed by the zinc uranyl acetate and oxalate methods, respectively. Standard soap titrations were used in certain experiments. Alkalinity titrations were performed in the standard manner with methyl orange as the indicator (1).
grains per cubic foot per minute). Figure 3 describes the results of such a correlation using the data presented in Figures 1 and 2. WITH SODIUMCARBONATE AND BICARBONATE. Although the sodium ion does not show a great affinity for the carboxylir acid group, sufficient capacity was found to warrant a study of the capacity and leakage characteristics of this system. The data in Figure 4 indicate the capacity t o be a function of the ratio of alkalinity t o total anion. A distinction, however, must be made between carbonate and bicarbonate ion, owing to the pH sensitivity of Amberlite IRC-50. WITH MIXEDINFLUENTS. The effect of the presence of mineral acidity on the capacity of Amberlite IRC-50 for the dealkalization of calcium bicarbonate solutions is described in Figure 5 .
RESULTS O F STUDIES
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FVITH CALCIUM BICARBONATE. The capacity of the carboxylic resin for calcium bicarbonate was determined as a function of concentrations, pH, and flow rate. The data are presented in Figures 1 and 2, respectively. The capacities have been based upon an end point of 10% leakage, which corresponds closely to a true breakthrough for these runs. An examination of these runs indicates that the capacity is dependent upon both rate and concentration. In order to correlate such data in a simple manner, a mass flow rate should be used instead of a space velocity unit. This unit is useful in correlating data in which both concentration and flow rates are variables. The new unit is the product of concentration and flow rate, and has dimensions expressed as milliequivalents per milliliter of resin per minute (or
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Figure 7.
Characteristics of Effluent of Amberlite IRC-50
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 43, No. 3
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0.0020 N Ca Clz
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1.2
Characteristics of Effluent of Amberlite IRC-50 41
31 20 40 60 80 I 0 The end points for these runs are based arbitrarily on a 25% D E G R E E OF REGENERATION - P E R C E N T alkalinity leakage, so that the data may be shown over a complete Figure 9. Effluent pH of Amberlite IRC-50 range of alkalinity ratios. The effects of ratio of monovalent t o total cation as well as As a function of degree of r e g e n e r a t i o n in sodiumh y d r o g e n cycle ratio of alkalinity t o total anion for mixtures of sodium and calcium salts are illustrated in Figure 6, in which capacity has been expressed as a function of both alkalinity and monovalent cation shown as a function of extent of regeneration and ionic strength ratio. A description of the effluent characteristics of two of the of the rinse solution. Figure 10 describes the result of studies on above runs is shown in Figures 7 and 8. the calcium form of the resin. The tendency t o hardness leakagc REGENERATION OF RESIN. I n these studies the use of‘ 110 to due t o exchange in the lower portion of a partially regenerated bed 120% of the theoretical amount of acid was sufficient to obtain has been investigated and the results are plotted in Figure 11. complete regeneration. Capacity losses due to precipitation of Although the calcium form shows less tendency to hydrolyze than calcium sulfate were negligible when sulfuric acid n a s used as the the sodium form, small amounts of calcium left on the bottom of regenerant. A 1% solution of sulfuric acid was used on ail runs the bed will tend to pass into the solution when the beds are in to minimize the mechanical blocking of the column by precipitaservice. Deionized water will do this t o some extent by direct tion. Although Dreciuitation was observed occasionally even with 1% sulfuric acid, the calcium sulfate was easily rinsed from the bed without the acSUPPLIES ( 2 ) TABLE I. WATER h . 4 L Y S I S O F TYPICAL companying loss in capacity Water Type frequently found under similar h B C D conditions with sulfonic acid Indianapolis, Baton Rouge, Los Anpeles, Philadelphia, La. Calif. Pa. Ind. cation exchangers. Constituent, l’.P.AI. as CaCOs although the regeneration 274 34 3 316 Total hardness 44 183 202 311 Methyl orange alkalinity was found t o be effective, the 40 20 193 39 Sulfates a n d chlorides (theoretical 190 40 beginning of any run was char20 39 mineral acidity) 50 100 214 35 Sodium a n d potassium acterized by a trace of acid that 0.60 0.27 0 99 0 10 Ratio of monovalent to total cation 0 52 0.49 0.91 0.89 Ratio of a1kalinit.y to total anion may be due to the slight ability 0 0 60 0 Carbonate alkalinity ... of the resin to split neutral 0 42 ... ... Carbonate-methyl orange alkalinity 0 0 0 0 Free C O S salts. In order to avoid this, and to establish the best regenOF OPERATIONAL ECOXOMICS BETWEEN CARBOXYIJC AND SULFONI c TABLE11. COMPARISON eration level for good performACID CATIONEXCHANGERS ance, a study was made of the effluent characteristics of beds which were only partly regenerated. The resin beds were 24 1300 3.7 2.9 2 Alkalinity break A IRC-50 regenerated with acid, followed 2-3 Alkalinity break IR-10.5 9 488 2.5 2.1 by a long rinse with deionized B IRC-50 4 0 340 0.7 2 . 0 2 2-3 Alkalinity water until the p H became con1110 2.5 2.3 12 d IR-105 1.6 2 Hardness leakage (25%) 1.25 stant. Solutions of 0.001 and C IRC-50 8.2 785 2-3 10% reduction in min276 2.5 11.0 6.0 IR-105 0.01 A; sodium chloride were era1 acidity passed through the beds and IRC-50 6.0 1720 0.75 0.43 3 Alkalinity a n d hardness leakage (25%) D the effluent pH waa recorded IR-105 7.0 1430 1.75 3-4 Mineral acidity end 2.5 Doint when constancy was obtained. Cost of sulfuric acid. 1 cent per lb. (1% sulfuric acid used as regenerant). In Figure 9, the pH of the effluent for beds of sodium resin is
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March 1951
INDUSTRIAL AND ENGINEERING CHEMISTRY
745
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Figure 10.
- PERCENT
Effluent pH of Amberlite IRC-50
As a function of degree of regeneration of caleiumhydrogen cycle
Figure 11.
hydrolysis, but much larger quantities of calcium will be found in the efluent when salts are present. Countercurrent regeneration techniques may be helpful in the elimination of leakage due t o incomplete regeneration. DISCUSSION
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-
Effluent Hardness of Amberlite
IRC-50
A s a function of degree of regeneration in caloiumsodium-hydrogen cycle
and chemical costs for the two resins for each of the water types. * An analysis of the results shown in Table I1 indicates that a carboxylic resin is b y far more economical than a sulfonic exchanger for dealkalizing waters high in bicarbonates (Type A). Dual beds of sulfonic acid exchangers operated in the softening and acid cycle followed by blending will approach the efficiency of a carboxylic exchanger, but when control equipment and initial expenses are considered as well as the extra labor costs for operating the dual system, the capital investment for such a system is excessive compared to that required for a carboxylic cation exchanger system. Operations on a Type B water are equally effective with both resins. T h e low capacity of the carboxylic exchanger is offset by its increased regeneration efficiency. Because the sulfonic acid resin has a high capacity for this type of water, it is doubtful that the use of carboxylic resin can be justified, except in special cases where these waters may be considered aggressive to phenolic-type exchangers owing t o high p H or high temperatures. Where blending is not desired, the carboxylic resin will have the advantage of not producing free mineral acids.
The results obtained in this study are of definite interest t o the water conditioning field, in t h a t they indicate the performance that may be expected when a monofunctional resin such as Amberlite IRC-50 is used under conditions approaching those found with natural waters. The excellent performance experienced with solutions containing large amounts of calcium and magnesium bicarbonate indicates t h a t Amberlite IRC-50 may be most useful in treating midwestern waters. Flow rate and concentration sensitivity may be severe limitations, but these deficiencies are outweighed by the high efficiency of regeneration and high capacity. I n order to illustrate the usefulness of a carboxylic exchanger, four typical waters were selected for a comparison of the dealkalization treatments using Amberlite IRC-50 in one case and Amberlite IR-105, a standard sulfonic acid cation exchanger, in t h e other. The compositions of these waters are shown in Table I. With the exception of water D, all the values in Tables I, 11, and I11 are calculated values based on the experiments reported above. T h e comuarison has been made for dealkalization and softening. No attempt is made TABLE111. COMPARISON OF n E I O N I Z A T I O N PERFORMANCE ON PHIL.4DELPHIA WATER WITH AND WITHOUT PRETREATMENT t o show the economics involved Capacity as CaCOs Regeneration Costs, Cents/ Total costs in split stream dealkalization Combi- Kilograins/Cu. Foot: Gal./Cu. Foot Lb. HzS04/Cu. F o o t 1000 Gal. cents/lood with Amberlite IR-105, benation IRC-50 Sulfonic IRC-60 Sulfonic IRC-50 Sulfonic IRC-50 Sulfonic Gal. cause this would introduce 1~c-50 12 8.0 6200 2220 4.15 2.5 0.66 1.12 1.78 variables c o n c e r n i n g d u a l 12 6200 5950 4.15 5.0 0.66 0.85 1.51 21.5 equipment which would make IR-120 IR-105 ... 6.5 ... 1330 ... 2.5 ... 1.88 1.88 a direct comparison difficult. IR-120 . ., 8.4 ... 1720 ... 5.0 ... 2.90 2.90 Table I1 gives the performance
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INDUSTRIAL AND ENGINEERING CHEMISTRY
Although the treatment of Type C waters appears attractive, the amount of hardness present is considerably in excess of the amount of bicarbonate alkalinity, so that leakage of the order of 90 to 100 p.p.m. hardness may be expected. Such waters are not favorable for carboxylic resins. Treatment of Type D water with a carboxylic resin exchange is ineffective because of the alkalinity leakage (see Figure 8). Holvever, a high capacity for calcium ion is obtained, due t o exchange with sodium form of the resin. This effective softening, plus partial dealkalization of the water, may be a considerable aid to the conventional deionization system. In Table 111, an estimate is given to illustrate the costs to be found when a dual system of Amberlite IRC-50 and Amberlites IR-105 and IR-120 is used for deionization. The usefulness of a carboxylic exchanger in water conditioning depends to a great extent upon the composition of the vater to be treated. Because a carboxylic exchanger is m-eakly acidic, it can be used to advantage only with alkaline waters, in particular with waters high in calcium and magnesium bicarbonates Under
EngFnyring Process development
Vol. 43, No. 3
these conditions, a high capacity and high regeneration efficiency will be realized. ACKNOWLEDGMENT
The authors wish t o acknowledge the laborat,ory assistance of Edward Keyser, Diana Edmonds, and Ruth Klaas during the course of this st,udy. LITERATURE CITED
(1) Xm. Public H e a l t h Assoc.. New Y o r k , " S t a n d a r d Methods for the E x a m i n a t i o n of W a t e r a n d Sewage," 8th e d . , 1936. ( 2 ) Collins, T Y . D . , ' L a m a r , TI'. L., a n d L o h r , E . W., U. S. Geologirai Survey. W a t e r S u p p l y P a p e r 658 (1932). (3) Kunin, R., a n d B a r r y , R., IND.ENG.CHEM.,41,1269 (1949). (4) K u n i n , R., a n d M c G a r v e y , F., Ibid., 41,1266 (1949). (R) Myers, F. S., U. S. D e p t . C o m m e r c e , FIdT Rept. PB 42,802 (1946). (6) W i n t e r s , J. C., a n d K u n i n , R., IND. Exa. C H E ~ 41, ~ , ,469 ( 1 9 4 9 ) . RECEIVED May 18, 1950. Presented before Division of Water, Sewage, a n d Sanitation Chemistry a t the 117th XIeeting of t h e A ~ I E R I C A C S HE~~ICAL SOCIETI, Detroit, LIich.
lower Paraffin Hydrocarbons CATALYTIC CONVERSION BY BORON FLUORIDE WITH HYDROGEN FLUORIDE E. C. HUGHES AND S. M. DARLING THE STANDARD OIL CO. (OHIO), CLEVELAND, OHIO
T h e thermal reforming of lower paraffin hydrocarbons such as naphthas gives higher knock-rating gasoline, but with resulting loss of gas. This work was undertaken in an effort to find a new method without this objectionable feature. I t is important to be able to isomerize butane and pentane for purposes of aviation gasoline manufacture. This work was undertaken to provide means for so doing. It was shown that boron fluoride with hydrogen fluoride behaves as a typical Friedel-Crafts catalyst in bringing about conversions of hydrocarbons. From a scientific standpoint, this worlr adds one more type of compound to the known list of Friedel-Crafts catalysts. Practically i t will provide an alternative method for isomerizing lighter hydrocarbons. The ability to recover the reagent by distillation w-ill provide some advantages over the presently used aluminum halide system.
B
OROK fluoride has been employed as a Friedel-Crafts
catalyst for a vide variety of reactions (S, 6). Hydrogen fluoride serves as a promotor for boron fluoride, similar to the action of hydrogen halides upon aluminum halides, even though hydrogen fluoride, being a liquid a t convenient temperatures and pressures, may be present in excess as a separate liquid phase. The system hydrogen fluoride-boron fluoride has the unique advantage of being highly volatile, thus permitting recovery of the catalyst from its inactive hydrocarbon complexes by distillation. A considerable patent literature has appeared on the use of this halide system (9, 11-15, 15, 18, 23, SO). The present work is a study of the reactions of propane, butane, pentane, and heptane in the presence of hydrogen fluoride-boron fluoride. Although the work was largely exploratory in character, the data obtained suggest some ideas regarding the theory of halide catalysis.
APPARATUS
Under the conditions used in thip work, the catalyst system consisted of a liquid hydrogen fluoride phase and a gaseous boron fluoride phase. The solubility of the catalyst in the paraffin hydrocarbons is very small-for example, one measurement showed that a dearomatized Pennsylvania kerosene dissolved 0.451 weight % of hydrogen fluoride plus 0.225 weight % boron fluoride at 26" C. and a pressure of 150 pounds per square inch gage. T h r use of the catalyst,, therefore, required intimate mixing of the two liquid phases, hydrogen fluoride and hydrocarbon, with the gas phase, boron fluoride. The low viscosities of the liquids made mixing and settling relatively easy. The apparatus employed consisted of a Monel-lined pressure bomb with a %inch inside diameter and a capacity of 2.8 liters. The bomb was equipped with three turbinelike stirrers which rotated imide a peripheral group of stationary Alone1 baffles. The bomb contained t v o siphon tubes, one extending t o the bottom t,o provide complete drainage, the other est,ending only partway int,o the bomb, leaving a space of 730 mi. below it,. The short siphon tube permitted the separation of the lighter hydrocarbon phase from the heavier catalyst phase, leaving t'he latter for subsequent use in cycle operations. The liquid catalyst phase was extremely corrosive to steel, alt,hough either component alone can be handled in it,. The alloys Monel, Inconel, and Hastelloy B resisted corrosion, the resistance improving in the order given. Copper and brass were used successfully under some conditions, and polgtetrafluoroethylene was the only plastic found to be suitable. The presence of hydrocarbon, water, or oxygen accelerated the rate of corrosion. Most of the work done here was carried out in hIonel vessels and copper transfer linea. EXPERIMENTAL PROCEDURE
Before each experiment the apparatus was thoroughly dried and flushed with tank nitrogen. The hydrogen fluoride and hydrocarbon charges were forced into the reactor from pressure vessels which could be weighed to measure the charges. The desired partial pressure of boron fluoride was maintained from a small cylinder, which also could be weighed to measure boron fluoride consumption. The reactor &-as immersed in a water bath for
