Nitrogen Mixtures

(1936), 17, 161-4 (1937); IIe Congr. mondial petrole, 2, Sect. 2, Phvs., chim., raflnage, 163-7 (1937), (in French); Compt. rend., 203, 620-2 (1936), ...
2 downloads 0 Views 668KB Size
Download PDF
September, 1941

INDUSTRIAL AND ENGINEERING CHEMISTRY

Acknowledgment The authors wish to express their thanks to the Solvents Corporation and to the Purdue Research Foundation for financing this research as Fellowship 52.

Literature Cited

1143

(3) Scott, E. W., and Treon, J. F., IND.ENG.CHEM., ANAL.ED., 12, 189 (1940). (4) Urbanski, Thaddee, and Slon, MaFian, Roczniki Chem., 16, 466 (1936), 17, 161-4 (1937); IIe Congr. mondial petrole, 2, Sect. 2, Phvs., chim., raflnage, 163-7 (1937), (in French); Compt. rend., 203, 620-2 (1936), 204, 870-1 (1937); Chimie et industrie, 37,No.5,948 (1937); Przeglad Chem., 2,42-3 (1938).

(1) . . Hass, H. B., Hodpe, E. B.. and Vanderbilt. B. M.. IND.ENQ.

CHEM.,28,339 (1936). (2) H a m H. B., H o b , E. B., and Vanderbilt, €3. M., U.S. Patent 1,967,667 (July 24, 1934).

BASF~D upon a thesis submitted b y J. Dorsky to the faculty of P u r d u e University in partial fulfillment of the requirements for t h e degree of doctor of philosophy, June, 1940.

The Absorption of Olefins from Ethylene-Nitrogen and PropyleneNitrogen Mixtures E. R. GILLILAND AND J. E. SEEBOLD Massachusetts Institute of Technology, Cambridge, Mass. The similarities in physical properties of the olefinic and of the paraffinic constituents of cracked petroleum refinery gases renders their separation difficult and expensive. The high reactivity of the unsaturated molecular structure of the olefins suggests the possibility of exploiting the chemical dissimilarities of the components to effect a less expensive recovery. T o this end, a tower 3 inches in diameter and 10 feet high, packed with 3/s-inch Raschig rings, was constructed to study the absorption of the lower olefins in acid solutions of cuprous chloride. The operation of this tower at temperatures of 15" to 30' C. (59" to 86" F.)and pressures of 50 to 250 pounds per square inch, using

I

N RECENT years the development of the synthetic chemical branch of the petroleum industry has brought with it a recognized need for a simpler and more effective method of separating the chemically unsaturated constit,uents from cracked refinery gases. While the unsaturated components can in some cases be successfully subjected to chemical reaction while mixed with inactive gases, it is generally profitable, and frequently imperative from a technical point of view, first to isolate the olefin itself in a concentrated form, then to proceed further with the synthetic operations, and thus gain the advantages of using a pure raw material at the beginning. The reduction in operating pressures, equipment sizes, and yield losses, and the improvement of final product quality will ordinarily justify economically the preliminary extraction of the active constituents from the crude gases. Present methods of separation include, in the main, highpressure distillation a t low temperatures and absorption in organic solvents. These methods of recovery involve considerable capital investment, as well as operating expense, largely because their effectiveness resides in the relatively small differences in the physical properties of the olefinic and aliphatic

ethylene-nitrogen and propylene-nitrogen gas mixtures containing about 30 per cent olefin, successfully demonstrated the effectiveness of cuprous salt solutions for olefin extraction. Eighty per cent of the ethylene entering the experimental absorber was extracted at moderate operating conditions. The height of the absorber equivalent to one transfer unit (H. T. U.) was about 3 feet a t liquid rates approximating 5000 pounds per hour per square foot of tower cross section. Liquid film resistance to the diffusion of a complex, coppercontaining addition ion controls the absorption rate, diffusion and rapid chemical reaction occurring simultaneously in the liquid film.

constituents of the various gaseous mixtures available. The rapid growth in the importance of the light unsaturated hydrocarbons as raw materials for a host of industrial organic syntheses, resulting in such diversified products as alcohol, ethers, esters, oxides, acids, and halides, greatly increases the desirability of reducing the initial cost of processing the crude gas. The highly reactive nature of the unsaturated structure of the olefins occurring in the gases suggests the application of some chemical reaction to bring about the desired recovery. The success of such a chemical recovery process depends upon locating an agent which will (a) react with the olefins rapidly and to a significant degree under moderate, easily obtainable conditions, preferably differing in the extent of reaction with different olefins, ( b ) liberate the chemically unaltered olefin under other moderate and readily established conditions, and ( c ) will itself be easily regenerated in its original form to be recycled through the process. The choice of materials which approach these conditions is rather limited. Ethylene, for example, will react with many common substances to form various ethylene derivatives, but these deriva-

1144

INDUSTRIAL AND ENGINEERING CHEMISTRY

Vol. 33, No. 9

$ 1 FIGURE 1.

DIAGRAM OF

ABSORP~ION APPARATUS

1. 2. 3.

4:6.

7. 8 . Thermometers 9. Caustic scrubbers 10. Gas samplin cocks 11. Gas accurnuktor compressor 12.

13. Liquid-recirculation pump 14. Liquid precooler 15. Compressed-gas cooler 16. Compressor by-pass control valve 17. Gas-supply control valve 18. Rich-liquid throttling valve 19. Lean-gas throttling valve 20. Liquid-supply safety valve 21. Sight glass 22. Direct-ourrent motors 23. Cooling-water recirculating pump 24. Liquid Sam ling valves 2 5 . Steam suppt’y 26. Cooling water 27. Drain t o sewer 28. Entrainment traps 29. Pressure-equalizing line 30. Gas orifices 31. Liquid-pump check valves 32. Pressure gage 33. Gas-remixing line

tives rarely decompose easily with the regeneration of ethylene. Some of the derivatives which decompose easily either require the addition of another reagent, such as an acid, or do not regenerate the original active substance along with the ethylene, or both. A general review of the many reactions in which the various olefins take part led to the choice of the cuprous salts for the present study. The activity of cuprous salts, both in the dry form and in solution, toward such unsaturated gases as carbon monoxide, acetylene, and ethylene has been known for many years. Tropsch and RIattox (15) found that one mole of ethylene, under pressure, reacts with one mole of dry cuprous chloride to form a metastable addition compound (CuCl.C2H4). They also observed that the dry salts are partially effective in removing ethylene from gaseous mixtures. Chavastelon (,$) obtained an addition compound from the reaction of two moles of dry cuprous chloride and one mole of acetylene (Cu2C12.CSHI), and reports equilibrium pressures substantially lower than those for the ethylene compound. Morgan (9, 13) obtained equilibrium data which agree with those of Tropsch and Mattox. Fitzhugh ( 7 , 9 )found that ethylene reacts with dry cuprous bromide in the same molecular proportion (CuBr.C2H4)except that the addition compound in this case is less stable than the cuprous chloride compound and manifests higher equilibrium pressures. The authors (9) observed that propylene reacts with dry cuprous chloride in equimolecular proportion, and that isobutylene also reacts with cuprous chloride. All of these addition compounds decompose with decrease in pressure and/or increase in temperature to liberate the olefin and the free cuprous halide. Although certain other differences exist, the equilibrium pressures of the three cuprous chloride-olefin compounds studied (CuC1.C2H4, CuC1.C3He, and CuCl.iso-C4Hs), a h e n in contact with the pure gaseous olefins, are practically the same a t the same temperature. The reaction seems, therefore, to be characteristic of the cuprous atom and the unsaturated linkage of the olefins.

The dry salts, although advantageous from the standpoint of corrosion, seem to be less practical than Iiquid absorbents. The partial pressure of an olefin over its dry addition compound is determined, for all practical purposes, by temperature alone and is not affected by the degree of saturation of the solid adsorbent. Accordingly, the usuaI method of effecting substantially complete removal of a solute from a gaseous phase by bringing the discharge gas into contact with the least saturated absorbent in countercurrent flow cannot be applied. A high degree of olefin recovery using the dry salts can be obtained only through the use of high pressures at fairly low temperatures. The recovery of oIefins by the dry cuprous salts also presents certain mechanical and thermal difficulties. I n view of these considerations, attention was directed toward the possible use of solutions of cuprous salts to avoid the difficulties encountered with the solid salts. The solubility of ethylene in hydrochloric acid solutions of cuprous chloride was measured and reported by Berthelot ( I ) in 1901. Later, Manchot and Brandt (12) measured the solubility of ethylene a t various pressures in several acid and ammoniacal solutions of cuprous salts. Several patents (11, 16) have been granted relative to olefin recovery processes using ammoniacal solutions, although these processes apparently have not been commercially successful, probably as a consequence of the fact that most ethylene-contaming gases, obtained by cracking, also contain small amounts of acetylene which forms an explosive cuprous acetylide in alkaline solutions. Cuprous acetylide does not form in strong acid solutions. Although beyond this general information little may be learned directly from the literature of the reaction of light olefins and acid cuprous solutions, other available information is of interest in developing a working picture of the mechanics of the absorption process. For example, an addition reaction similar to that occurring in the case of the solid salts apparently occurs with the sparingly soluble cuprous chloride when in pure water solution, since the data of blanchot and Brandt (12) show that the solubilities of both ethylene and

September, 1941

INDUSTRIAL AND ENGINEERING CHEMISTRY

cuprous chloride increase when the two are simultaneously placed in contact with water. Although the solubility of the addition compound is low, the incremental increases in the two solubilities are in equimolar proportion. The data of Manchot and Brandt ( l a ) , as well as those of Green (IO), show also that the addition of hydrochloric acid to the solution increases the solubility of both ethylene and cuprous chloride, but the increase in the molecular quantity of dissolved cuprous chloride is greater than that of the ethylene and reduces the molecular ratio of ethylene to cuprous chloride well below 1. Bodlander and Storbeck (9) explain the increased solubility of cuprous chloride in hydrochloric acid by the following reactions:

+ c1- =CuClacuc12- + c1- =* CuCla-CUCl

(1) (2)

These authors found that below acid concentrations of 0.4 normal the dissolved copper probably exists almost entirely in the form of the anion CuClS-, while a t higher concentrations of acid this anion adds a chloride ion and becomes CuCls--. Assuming thaf the ratio of the concentration of the CuC18-ion to that of the CuCl2- ion is proportional t o the chloride ion concentration, and using the data of Chang and Cha (3) on the solubility of cuprous chloride in concentrated hydrochloric acid solutions, Green (IO) computed that, above acid concentrations of 4 normal, practically all of the copper exists in the form of the CuCla-- ion. Therefore, since the olefin addition compound formed in water solution is relatively insoluble, the greater absorption of olefins in more concentrated acid solutions apparently involves the reaction of the olefin with a complex chlorine-containing ion, possibly involving the displacement of some of the chlorine from the ion. The data of Green (IO)also show that the molal ratio of the ethylene addition ion to olefin-free copper-containing ion in hydrochloric acid solutions, assuming that one mole of ethylene exists in combination with one atom of copper, is directly proportional to the partial pressure of ethylene over the solution and inversely proportional to a fractional power of the acid concentration. The addition of ammonium chloride to the hydrochloric acid solutions of cuprous chloride further increases the solubility of cuprous chloride and ethylene. D'Angelo and Rote (6) measured the solubility of ethylene and propylene a t near atmospheric pressures in such solutions containing three gram moles of ammonium chloride per liter and a t several cuprous chloride and hydrochloric acid concentrations. They found that over a range of acid concentrations from 0.7 to 6 normal, the solubility of ethylene could be expressed by the relation, M = K j where M = moles of olefin per atom of olefin-free copper, assuming one mole of olefin exists in combination with one mole of copper f = fugacity of ethylene over solution K = a constant at a given acid and ammonium chloride concentration, and a given temperature The relative solubility, M , decreases as the total chloride concentration is increased. The later work of Park (14) showed further that with comparable solutions under higher ole& pressures, the olefin solubilities obtained agree closely with those predicted from the data of D'Angelo and Rote (6). Based on the foregoing information, an experimental study of the absorption of olefins in cuprous solutions was undertaken. Of the solutions considered by D'Angelo and Rote, one was chosen which showed the maximum solubility of ethylene, and which was free of crystallized solid matter a t 15" C. The rate of absorption of ethylene by this solution

1145

was then studied in a small high-pressure laboratory-scale unit. Later Fulton (8), working on the same equipment in conjunction with the authors, measured the rate of absorption of propylene in a similar solution.

Experimental Procedure The apparatus used is shown in Figure 1: The equipment consisted essentially of a 3-inch Everdur (copper-silicon-manganese alloy, resistant to the absorbing solution in the absence of oxygen) absorption tower (1) packed t o a height of 10 feet with S/s-inch acid-resisting Raschig rings. This tower was su plied with absorbing liquid by means of a small reciprocating {quid pump (13) constructed of Everdur, and with olefincontaining gas by means of a reciprocating compressor (12), capable of operating up t o a pressure of 250 pounds per square inch. A second tower (3), operating at near-atmospheric pressure, was constructed of copper and functioned as a flash chamber and stripper for the rich liquid discharged from the absorption tower under pressure. The apparatus was provided with gas (11) and liquid (7) accumulators, and was constructed t o recycle all materials and t o function in continuous operation. The recycling process, which consisted of recycling the liquid absorbent and remixed gases, simplified the operation of the equipment by reducing t o a minimum the quantity of gas and liquid needed. Orifices were provided for the measurement of gas and liquid flow. The gas and liquid supplied t o and discharged from the absorption tower were analyzed, and the purity of the olefin recovered was determined. The parts of the system in contact with the solution under pressure were constructed of Everdur. It was therefore necessary to machine from Everdur all valves, pumps, and fittings in contact with the solution. The low-pressure parts of the e uipment in copper or contact with the liquid were constructed either glass. By scrubbing the gas free of acid vapor or mist, it was possible to use steel in the construction of that portion of the apparatus not in contact with the solution. It was imperative that oxygen be kept out of the system at all times. The corrosive character of the solution and the operation under pressure made the use of automatic control devices on an experimental scale difficult, so that only manual controls were employed. After the system was set in operation, however, its operation was surprisingly steady, only occasional adjustment of the liquid level in the bottom of the tower being necessary t o maintain constant conditions. In all cases the equipment was allowed to reach a steady state of operation as evidenced by the constancy of all indicators, by gas and liquid analyses, and finally by satisfactory material balances over the absorption tower. The low-pressure limit of the equipment was determined by the extent of the inaccuracies introduced in the measurement of low flow rates and low pressures on the meters and gages built into the apparatus. Errors in these measurements became excessive below 3 or 4 atmospheres absolute pressure. The lower temperature limit was fixed at the point where crystallization occurred in the solution, plugging the lean liquid precooler. The up er limit of temperature was set by the rapidly decreasing solubi&y of the olefin at the upper end of the tem erature range. The absorber was operated at pressures ranging fProm 50 t o 250 pounds per square inch and at temperatures ranging from about 15" to 30" C. (59' t o 86" F.). Since a fairly high ratio of liquid t o gas must be maintained, it was necessary to operate at relatively high liquid rates in order t o maintain a gas rate of practical magnitude. Data were taken under varying conditions of operation, using mixtures of ethylene and nitrogen containing about 20 to 40 per cent of ethylene. Fulton (8) obtained data on mixtures of propylene and nitrogen with the same equipment.

07

The composition of the cuprous solutions used were: For Ethylene Absorption

For Propylene Absorption Gram moles per Ziter

NHkC1 HC1 CUCl

3.0 2.52 1.90

3.0 2.27 1.89

Results and Discussion The results of the investigation are summarized in Table I, which shows the conditions of pressure and temperature

INDUSTRIAL AND ENGINEERING CHEMISTRY

1146

Vol. 33, No. 9

TABLEI. SUMMARIZED DATAAND CALCULATED RESULTS

R u n No.

Absorption Pressure, Atm. Abs.

Gas Compn. % Olefin b y Vbl.

Av. Absorption g - E Temp., C . absorber

absorber

Li uid Compn., Molee 81efin/Mole c'cl

Inert Gas Rate, Lb. Molesa

Liquid Rate, Lb. Moles CuCP

(H.T.U.)l, Feet

(H.T.U.)*, Feet

Recovery,

2.66 4.16 3.82 2.93 5.17 3.84 6.18 3.94 2.72 2.63 2.74 4.02 4 51 4.34 2.66 3.90 2.83 2.20 2.26

9.26 7.98 7.32 8.41 8.63 7.60 7.09 8.12 7.32 7.30 7.10 6.89 6.70 6.90 8.34 7.78 11.34 7.78 IO. io

0.10 0.11 0.10 0.12 0.10 0.12 0.08 0.10 0.10 0.11 0.11 0.09 0.09 0.10 0.13 0.09 0.09 0.08 0.11

3.6 2.4 2.8 4.1 3.3 3.1 2.6 2.1 3.1 3.4 3.4 2.4 2.3 2.6 3.6 2.6 3.6 2.4 4.2

70 55 65 73 50 80 29 57 35 35 50 76 57 43 69 24 58 35

3.02 3.14 2.66 3.91 3.68 2.82

11.8 12.5 11.5 9.6 9.9 9.1

4.0 5.9 4.7 3.8 4.5 4.7

39 39 39 24 31 32

%

Ethylene 6

7

9 10

11

12 20 21 23 24 26 26 34 35 36 38 40 43 44

7.52 11.0 14.7 7.25 7.25 14.75 7.29 10.5 6.98 6.87 6.98 18.3 14.75 9.94 7.69 3.72 3.61 6.99 3.61

23.1 21.9 23.2 15.6 16.3 17.0 21.5 23.1 31.1 31.3 22.9 23.5 22.9 24.0 20.7 23.0 25.0 26.5 26.6

30.6 32.6 31.9 30.5 28.5 35.2 25.3 31.0 30.4 30.5 30.0 28.6 30.2 29.5 30.8 28.6 32.7 34.8 33.7

8.6 15.7 19.2 12.2 23.3 23.3 18.4 24.8

0.0041 0.0069 0.0072 0.0075 0.0063 0.0096 0.0065 0.0102 0.0093 0.0089 0.0075 0.0076 0.0096 0.0088 0.0089 0.0063 0.0027 0,0072 0.0080

15.0 18.0 14.5 14.5 14.5 14.5

26.2 26.0 25.5 26.3 23.1 23.1

26.5 25.5 25.3 22.7 22.0 15.7

18.0 17.4 17.1 18.3 16.4 11.2

0.0039 0,0040 0.0050 0.0059 0.0043 0.0076

11.6 18.0 14.0 10.6 16.6 9.7 19.4 16.3 22.0 22.2

17.7

0.091 0.149 0.170 0.118 0.121 0.224 0.092 0.132 0.065 0.062 0.088 0.181 0.176 0.122 0.103 0.053 0.048 0.090 0.046

37

Propylene F1 F2 F3 F4 F5

F6 a

0.0396 0,0377 0.0358 0.0346 0.0355 0.0253

.. ~. ..

.. ..

..

Per hour per square foot of column cross section

under which the absorption was effected; the temperature rise during absorption amounted to about 2" C. (3.6" F.). Under moderate operating conditions the experimental absorber removed as much as 80 per cent of the olefin from the rich gas supplied to the tower. While this value is not important in analyzing the performance of the absorber, it is qualitatively indicative of the effectiveness of acid cuprous solutions in the extraction of olefins from chemically saturated gases. The results obtained are expressed as the height of the absorber which is eauivalent t o one transfer unit (H.T.U.). Two values of the 'height equivalent to one transfer unit are shown in Table I, and both were computed on the liquid film basis. The (H.T.U.)I is computed on the assumption that the free olefin molecule difluses into the main body of the absorbing solution before its reaction with a soluble coppercontaining ion takes place. The (H.T.U.)2 is computed on the assumption of an instantaneous reaction at the phase interface between the olefin molecule diffusing into the interface from the gaseous phase and a soluble copper-containing ion diffusing outward from the body of the solution t o the interface, whereupon the olefin then diffuses into the abeorbing solution in combination with the copper-containing ion. This latter explanation offers the better basis for correlating the data, although the actual absorption process undoubtedly involves a combination of both effects. The simplified diffusion equation expressing the interphase transfer by free olefin diffusion through the liquid film is: ( L / S ) d X = ( R L u (c, ) ~ - ce)dh

(1)

Introducing CO, the total copper concentration, and rearranging, (H.T.U.)l is defined as follows (6):

Js,

."

C$

-

c.

Similarly, for the diffusion of the complex olefin-containing ion,

xi

-

x,

where Xi and X , are the concentrations of the complex addition ion a t the phase interface and in the main body of the solution, respectively. The H.T.U. values were calculated by the graphical evaluation of Equations 2 and 3. The mechanics of the absorption process may be explained on the basis of the calculated values of these two types of H.T.U. Table I shows that the values of (H.T.U.), are roughly 0.1 foot while those of (H.T.U.)2 are about 3 feet. The extremely low values of (H.T.U.)l as compared to those values generally observed for other absorption processes show that a much greater quantity of olefin was transferred than could be expected with the degree of interphase contact available in the absorber and under the concentration gradients available for free olefin diffusion through the liquid film. Therefore it must be concluded that a more soluble particle than the free olefin molecule also diffuses through the film. The values of (H.T.U.)2 are computed on the assumption that reaction occurs instantaneously a t the phase interface and that the resulting olefin-containing ion diffuses through the liquid film into the main body of the liquid. These values are seen to be more reasonable than those based on free olefin diffusion, although they are somewhat higher than might be expected. The rather high values probably result from a combination of three factors: First, the absorption tower was operated a t a high liquid rate for the size of packing used (3/8-in~hRaschig rings), the liquid rate approximating 5000 pounds per hour per square foot of tower cross section. Under this condition the interstices in the packing would be well filled with liquid and the interfacial area would be expected to be less than at lower liquid rates; high values of H.T.U. would result. Secondly, in the calculation of (H.T.U.)2 the reaction was assumed to occur instantaneously a t the phase interface. The free olefin must, no doubt, penetrate the liquid film to some finite depth before reaction takes place. That is, neither of the two diffusion processes occurs

INDUSTRIAL AND ENGINEERING CHEMISTRY

September, 1941

to the entire exclusion of the other; the two take place simultaneously, with the chemical addition reaction probably occurring throughout the entire thickness of the relatively stagnant liquid film. These combined effects would result in calculated values for (H.T.U.), somewhat greater than usual. While the actual magnitude of this effect is not accurately known, batch reaction rate experiments conducted in connection with the present work indicate that the reaction rate in the liquid phase between the olefin and the active copper-containing ion is rapid in comparison to the absorption rate observed in the absorption tower. Thirdly, the resistance of the gas film, which has been neglected in the computations, would, if accounted for, also decrease the calculated values of (H.T.U.)2. Since the consideration of these factors in the correlation greatly complicates the analysis of the problem, it is believed that for practical design purposes the simplified treatment presented is of greater utility. ,100 .080

,060

.040

.030

K

..010 .0030

O

.0032

Z I /T.OOM

Q

,0036 E

FIGURE 2. OLEFINSOLUBILITIES

In the design of commercial equipment it is necessary to have solubility data on the particular solution to be used. The olefin solubilities in the solutions used in this work are given in Figure 2. These results were taken from the data of D’Angelo and Rote (6) and are for solutions of the same compositions as were used in the absorption experiments. Regarding the accuracy to be expected of the data in Table I, material balances checking within 5 per cent were considered to be within the precision of the measurements of flow. The method of liquid analysis was checked, and an accuracy within 3 per cent is expected. The gas analyses involved the standard bromine water absorption of the olefin. The analyses of the gas entering the absorber are more critical in determining the values of H.T.U. than those of the gas leaving. Approximate computations show that the former can be expected to be accurate within 1 or 2 per cent of the values reported; the accuracies are greater for the larger values. A few runs in which errors of this magnitude could not be tolerated as a result of “pinching” or close approach to equilibrium a t the bottom of the absorber were not considered. The ratio of the average slopes of the operating and equilibrium lines on the usual absorption diagram, L/K’G, remained practically the same throughout the work at a value of about 1. I n the commercial use of this absorption process the consideration of corrosion would be of significant importance. The experimental unit resisted corrosion remarkably well. As D, result of the experimental nature of the equipment, much more oxygen gained admittance than would be ex-

1141

pected on a commercial scale, no facilities being provided for the removal of oxygen once it had entered the system. Such oxygen-removing equipment could readily be installed on a plant scale. The only corrosion difficulty in the experimental equipment of real importance from this standpoint occurred in the falling-film stripper. The heating surface of the stripper was constructed of ‘/le-inch copper tubing, which failed a t the point where the steam supplied to the stripper impinged on the metal. Pitting occurred from the inside after about two months of intermittent operation, and it became necessary to replace a section of the copper tubing.

Nomenclature Co = concentration of total copper in main body of solution

concentration of free olefin at phase interface concentration of free olefin in main body of solution = fugacity G = inert gas rate = height equivalent to one transfer unit, feet H.T.U. (H.T.U.), = H.T.U. based on diffusion of free olefin (H.T.U.)t = H.T.U. based on diffusion of complex olefin-containing ion packed height of tower, feet = absorption coefficient based on free olefin diffusion = absorption coefficient based on diffusion of complex ’ olefin-containing ion solubility constant, moles olefin per atom olefin-free copper per atmosphere = X/(1 - X ) f average slope of equilibrium line li uid rate, atoms total copper per hour saubility of olefin, moles olefin per atom olefin-free copper cross-sectional area of absorption tower concentration of olefin in liquid phase, moles per atom total copper concentration of olefin at ahase interface. moles aer atom total copper concentration of olefin in main body of liquid phase, moles per atom total copper

ca

=

f””

=

Literature Cited Berthelot, Ann. chim. phys., 23,32-9 (1901). Bodlander and Storbeck, 2..anorg. Chem., 31, 1-45 (1902). Chang and Cha, J. Chinese Chem. SOC.,2, 298 (1934). Chavastelon, Compt. rend., 126, 1810 (1898). ENQ.CHEM.,27,255 (1935). Chilton and Colburn, IND. D’Angelo and Rote, Mass. Inst. Tech., Chem. Eng. Thesis. 1938. Fitshugh, Ibid., 1937. Fulton, Ibid., 1938. Gilliland, Seebold, Fitshugh, and Morgan, J. A m . Chem. SOC., 61, 1960 (1939). Green, Mass. Inst. Tech., Chem. Eng. Thesis, 1938. Imperial Chemical Industries Ltd., French Patent 797.490 (April 27, 1936). Manchot and Brandt, Ann., 370,286-96 (1909). Morgan, Mass. Inst. Tech., Chem. Eng. Thesis, 1936. Park, Ibid., 1939. Troosoh and Mattox. J. A m . Chem. SOC..57. 1102-3 (1935) Waits (to Imperial Chem. Ind. Ltd.), U. S: Patent,’1,977,659 (Oct. 23, 1935); British Patent 393,317 (June 2, 1933).