Ind. Eng. Chem. Process Des. Dev. 1982, 21, 334-337
334
Table 111. Estimated Energy Requirements feed, wt % EtOH 6.39
8.0
reference Black (1980) Scheller (1978)
distillation process Btu/lb EtOH 4423 9186
optimized but are close to the results obtained from run I of Table 11. These energy requirements could be reduced by optimization of the extraction, by optimizing heat recovery in the distillations, and by increasing alcohol content in the feed to the predistillation. Note that the results in Table I11 are only estimates. Firmer results would require a detailed simulation of the gasoline recovery distillation column and calculation of the heat recovery obtainable. Conclusions The extraction of ethanol from water with gasoline to form a gasohol with 10 wt % ethanol was achieved experimentally. The feed to the extraction column needs to be about 90 wt % ethanol. Recovery of the gasoline in the raffinate stream and recycle of the raffinate would be required. Behavior of the gasoline extraction can be qualitatively predicted with theoretical calculations done with single component equilibrium data. Acknowledgment Discussions with Dr. George Quinn and Professors Michael Ladisch and George Tsao were most helpful. We wish to thank Amoco Oil for the donation of naphtha and the Laboratory of Renewable Resources Engineering at Purdue University and the State of Indiana for partial support.
Btu/lb gasohol . -
extraction, Btu/lb gasohol
ratio: extrldist
442.3 918.6
300 290
0.68 0.32
.
I
Chambers, R. S.;Heredeen, R. A.; Joyce, J. J.; Penner, P. S. Science 1979, 206, 789. Doronin, V. N.; Zhavoronkov, N. M.; Nikolaev, A. M.; Professy Zhidkosfoni Ekstrakti. Tr. Nauchn - Tekn. Soveshch, Leningrad, 1963, 1961, 32. (Chem. Abstr. 1964,6 0 , 3743e). Fanta, G. F.; Burr, R. C.; Orton, W. L.; Doane, W. M. Science 1980. 210, 646. Gelbeln, A. P. Chem. Eng. News 1980,58(35) 2. Gregor, H. P.; Jeffries, T. W. Government Report Announcement Index (U.S.) 1979, 79(18) 215. Report Order No. NTIS-PB-295645. Hartine, F. F. Science 1979,206, 41. King, C. J., "SeDaration Process", 2nd ed.;McGraw-Hill: New York, 1980; chapter 6. Ladisch, M. R.; Dyck, K. Science 1979,205, 898. Leeper, S.A. M.S. Thesis, Purdue Unhrersky, West Lafayette, IN, 1960. Mertslin, R. V.; Nikurashina, N. I. Russ J. Phys. Chem. 1981, 35, 1293. Mevers. R. T. Chem. €no. News 1980.58117). 4. NakaGchi, G. M.;~Keller,j.L., "Ethanol Fuel'Mddification for Highway Vehicle Use", DOE Final Report, Contract #EY-764-04-3683, Modific., A003, (DOE ALO, EY-764-04-3683-31) July, 1979. Othmer, D. F. Chem. Eng. News 1980,58(36), 4. Othmer, D. F., Ratcliffe, R. L. Ind. Eng. Chem. 1943. 35, 798. Othmer, D. F., Trueger, E. Trans. AIChE 1941,37, 597. Roddy, J. W. Ind. Eng. Chem. Process Des. Dev. 1981,20, 104. Scheibel, E. G. Chem. Eng. Prog. 1948a,44, 681. Scheibel, E. G. Chem. Eng. Prog. 1948b,44, 771. Scheibel. E. G. Ind. Eng. Chem. 1950,42, 1497. Schelier, W. A.; Mohr, 8. J. CHEMTrCH 1977, 7, 816. Scheller, W. A. "Energy Requirements for Grain Alcohol Production", presented at the 176th National Meetlng of the American Chemical Society, Miami Beach, FL, Sept 10-15, 1978. Smith, B. D. "Design of Equiilbrium Stage Processes"; McGraw-Hill: New York, 1963; Chapter 7. Vorob'eva, A. I.; Karapet'yants, N. Kh. Russ. J. Phys. Chem. 1966, 40, 1819. Washburn, E. R.; Beguin. A. E.; Beckord, 0. C. J. Am. Chem. SOC. 1939, 61, 1694. Wymore. C. E. Ind. Eng. Chem. Prod. Res. Dev. 1962, 1, 173. '
Literature Cited Arora, S. Chem. Eng. News 1980,58(29) 4. Black, C. Chem. Eng. Prog. 1980, 76(9) 78.
Received f o r review April 10, 1981 Accepted October 26, 1981
Extraction of Strong Mineral Acids by Organic Acid-Base Couples Aharon Eyal and Avraham Banlel' Casali Institute of Applied Chemistty, The Hebrew University of Jerusalem, Jerusalem, Israel 9 1904
A new method is described for the separation of strong mineral acids from other species present in aqueous solutions, by liquid-liquid extraction. An extracted acid c a n be recovered by backwashing of the extractant phase with water at concentrations approaching those in the original solutions. Even higher concentrations may be obtained
using common ion effects or temperature effects. Extractants consist of a strong organic acid and an amine dissolved in a carrier solvent. Both the organic acid and the amine are water insoluble, in free and in salt form. Extractant characteristics to satisfy the requirements of a given process are obtained through the selection of the acid and of the amine that form the extracting couple and adjustment of their molar ratio. Processes achievable include the separation and recovery of acids from mixtures of acids (e.g., recovery of H2S04,H2SiF,, and H3P04 from "wet process" phosphoric acid) and conversions by reaction in acid media (e.g. conversion of KCI to KNO, by HNO, with the recovery of concentrated HCI).
Introduction Long chain aliphatic amines form stable salta with strong mineral acids. They are therefore useful in the extraction of acids from aqueous solutions. They are also selective, which makes them suitable for the separation of strong mineral acids, present in aqueous solutions, from each other. (Bertocci and Rolandi, 1961; Grinstead and Davis, 1968). The order of selectivity is generally illustrated by the sequence: HCIOI > HN03 > HC1> HBr > H2S04> H3POk However, the extraction is practically irreversible. Reversibility may be obtained in specific systems-for 0196-4305/82/1121-0334$01.25/0
example by hydrolyzing with water at higher temperatures-but the strong acids are recovered only at low concentrations. The only published industrial process based on amine-salt hydrolysis relates to an organic acid-citric acid (Baniel, 1972), which due to its structure must have an unusually high AST contribution to free energy. Reversible extraction at fairly high acidity levels is possible with salts of amines with strong mineral acids as extractants. When only one mineral acid is present in a system the salt of that same acid with an amine is an 0 1982 American Chemical Society
Ind. Eng. Chem. Process Des. Dev., Vol. 21, No. 2, 1982
335
Table I. Selectivity in Extracting a Strong Mineral Acid (HA) from a Mixture with Another Acid (HB) equilibrium aqueous phase extractants used a
HA
HI3
HA concn, M
HNO, HNO, %SO, H,SiF, HCl HNO, H,SiF,
HCl HC1 H3PO4 HW, H3PO4 HCl H3PO4 Hm4 HC1
1.2 1.35 0.15 0.3 3.4 1.4 0.3 0.4 2.7
%SO,
HNO,
HB concn, M 5.3 6.75 5.3 5.3 3.8 9.2 5.3 5.3 5.8
equilibrium HA:AB molar ratio
distribution
aqueous phase solvent phase coefficient 1:4.42 1:5.0 1 : 35.3 1:17.7 1:1.12 1:6.57 1:17.7 1:13.2 1:2.15
1:l 1:l.l 1:4.76 1:2.13 1:0.14 1:1.54 1:2.94 1:2.56 1:0.18
4.4 4.5 7.4 8.3 8.0 4.3 6.0 5.2 11.9
a The extractants used were: (a) a solution containing 0.2 mequiv/mL HDNNS and 0.2 mequiv/mL TCA in Norpar 1 2 t o which 5 mL of a 80:20 solution of l-dodecanol-xylene was added t o ensure homogeneity; ( b ) a solution containing 0.25 mequiv/mL HDNNS and 0.25 mequiv/mL TLA in white spirits; ( c ) a solution containing 0.25 mequiv/mL HDNNS and 0.25 mequiv/mL Primene JM-T in white spirits; ( d ) a solution containing 0.375 mequiv/mL HDNNS and 0.25 mequiv/mL Primene Primene JM-T. (HA: HB)(solv)/(HA:HBj(aq).
effective extractant above a certain minimum acidity (Shmidt and Mezhov, 1965). However, when separations between two or more acids are involved it is virtually impossible to maintain a constant extractant composition. Separations based on these extractants were proposed but apparently are not applied in industry. The extractants described in this communication consist of a hydrocarbon solution of an amine and of a strong organic acid (Baniel, 1980). The amine by itself and the organic acid by itself, either in free or in salt form, should be oil soluble and water insoluble so as to ensure their virtually complete retention in the oil phase when this is equilibrated with aqueous solutions containing strong mineral acids. Grinstead et al. (1969) proposed similar acid-base systems for extraction of neutral inorganic salts. They considered their use to be “restricted” to aqueous systems, where the “pH is within a few units of neutrality”. Here it is shown that such extractants are capable of extracting strong mineral acids from aqueous solutions and releasing these acids to water or aqueous media of low acidity without any change in their composition. Differently put, they act as reversible extractants. Experimental Methods The solvent phase was prepared by mixing the desired amine, organic acid, and carrier solvent at desired proportions. The following amines were used: (1)tricaprylyl amine (TCA) (Alamine 336 General Mills); (2) trilauryl amine (TLA) (Alamine 304 General Mills); (3) Primene JM-T (Rohm and Haas), a mixture of primary aliphatic amines (C18-C22,neutral equivalent, 336) in which the nitrogen atom is bonded directly to a tertiary carbon atom. The following organic acids were used: (1)a-bromolauric acid (ABL) which was prepared in our laboratory by bromination of lauric acid; (2) dinonylnaphthalene sulfonic acid (HDNNS) (Synex DN-052 of King Industries); (3) didodecylnaphthalene sulfonic acid (HDDNS) (Synex DD-052 of King Industries); (4) bis(2-ethylhexyl)hydrogen phosphate (DEHPA) (Pfaltz and Bauer). The following carrier solvents were used: (1)xylene; (2) Norpar 12 (C10X13, normal paraffins, Exxon); (3) aromatic free white spirits (bp 180-220 “C). Experiments were performed by the following steps: (1) Solvent and aqueous solution were equilibrated by hand agitation in a separatory funnel for 5 min and were then separated. (2) The aqueous phase was analyzed. (3) Acids extracted in the first operation were back-extracted into water by equilibrating the solvent with several successive portions of H20 until no further extraction was perceived by pH measurement. (4)The acids content of the com-
bined aqueous washings was analyzed. Experimental Observations Reversibility of Extraction. Five milliliters of 0.4 N solution of TLA in xylene was mixed with 5.5 mL of a 0.4 N solution of HDNNS, obtained by adjusting Synex DN-052 from King Industries with the addition of xylene. The homogeneous solvent phase obtained was equilibrated (with gentle agitation) with 2 mL of 1 N HNO,. After settling and separation the aqueous phase was 0.64 N in HNO,. The solvent phase was then washed. The combined aqueous washings contained practically the full 0.72 mequiv of the extracted HN03. The solvent phase was again equilibrated with 2 mL of 1 N HNO, and washed. The same results were obtained. It is thus obvious that the combination of TLA-HDNNS in equivalent ratio of 1:l.l acted with respect to HNO, as a reversible extractant. For comparison, 5 mL of 0.4 N TLA in xylene underwent a similar test. It was found that 2 mequiv of TLA extracted 2 mequiv HNO,, irreversibly under the conditions of the experiment. Reversibility was established by similar tests with solvents containing one of three amines (TLA, TCA, Primene JM-T), one of four acids (ABL, DEHPA, HDNNS, HDDNS), and one of two carrier solvents (xylene, white spirits) in different proportions (from amine:acid = 2:l to amine:acid = 1:2) in contact with aqueous phases containing one of the four mineral acids (HC1, HNO,, H3P04, H2S04)in several concentration levels (up to 10 mol/L). Loading and Selectivity. These acid-amine couple solvents show selectivity in extracting strong mineral acids from mixtures of acids. Examples showing selectivity to HNO, in mixture with HCl and selectivity to H2S04,HC1, and H2SiF, in mixtures with H3P04are summarized in Table I. The amine-acid couples retain selectivities which characterize the amines they contain. The reversibility secured by the adjunction of a strong organic acid is thus essentially additional to the basic characteristics of amine extractants. The loading of acid per mole of amine in the extractant and the selectivity coefficient, however, are new parameters reflecting the character of the amine and its ability to interact with the organic acid. This is illustrated in the tests comparing two solvents containing the same organic acid, same carrier solvent, and same amine to organic acid ratio, but different amines. Results are summarized in Tables I1 and 111. In a similar way these parameters reflect the character of the organic acid and its ability to interact with the amine, as illustrated in Table IV, comparing similar solvents containing different organic acids. Amine to acid molar ratio constitutes an additional
338
Ind. Eng. Chem. Process Des. Dev., Vol. 21, No. 2, 1982
Table 11. Loading of Solvents, Containing 0.25 N HDNNS and 0.25 N Amine, in Strong Mineral Acids equilib concn of mineral amine acid in loading, aq phase, M %
mineral acid
amine in extractant
HZSO,
Primene JM-T TLA
WO,
1.95 1.95
Primene JM-T TLA
3 6
9.5 9.5
H,SO, H,PO, concn, concn, M M
0.37 a
5.34
Primene JM-T:HD"S molar ratio 1:l
1:l.l 1:1.25 1:1.5
32 74
Table 111. Selectivity of Solvents Containing 0.25 N HDNNS and 0.25 N Amine in Extracting Sulfuric Acid from a Mixture with Phosphoric Acid aqueous phase in equilibrium
Table VI. Selectivities of Solvents Containing Different HDNNS to Primene JM-T Molar Ratios in Extracting HNO, from an Aqueous Solution (7.9 M H ', 0.7 M K+, 5.9 M Cl-, and 2.7 M NO; organic phase loading in equilibrium in mol/mol of amine H+
K'
c1-
NO;
0.59 0.61 0.68 0.60
0.003 0.003 0.01 0.01
0.31 0.34
