ENGINEERING, DESIGN, AND PROCESS DEVELOPMENT A simplified graphical method of determining catalytic reaction mechanisms is used in the above application. T h e rate equation indicates t h a t the reaction rate changes exponentially with temperature and linearly with hydrogen concentration. T h e effect of increased propylene concentration is t o increase the reaction rate a t low propylene concentrations and decrease i t at moderate and high concentrations. Propane reduces the reaction rate. Acknowledgment
The authors are indebted to R. D. Williams for setting up and calibrating the conductivity cell. Nomenclature
A l3
activation energy, cal./gram-mole effective entropy of activation effective enthalpy of adsorption reaction rate constant adsorption-equilibrium constant total molal flow rate, gram-moles/sec. partial pressure, atm. gas constant left side of rate equation as written in Equation 1 reaction rate, gram-moles/(hr.) (gram unreduced catalyst) effective entropy of adsorption = temperature, O K. = catalyst weight, grams = mole fraction in gas phase
= = AH = F = K = A’ = p .= R = R’ = T = AS =
2’ 20
y ay =
YHi
- UHo
= total pressure, atm. = sL2 = effectiveness factor
?r
e
Subscripts H = hydrogen U = propylene S = propane i = reactor inlet conditions o = reactor outlet conditions References (1)
Baron, S., Ph.D. dissertation, Dept. of Chemical Engineering, Columbia University, 1950; Potter, C.. and Baron, S., Chem. Eny. Progi., 47, 473 (1951).
Vol, I. Physical Adsorption,” Princeton, Princeton Vniversity Press,
(2) Brunauer, S., “Adsorption of Gases arid Yapors.
1943. (3) Daynes, H. A,, “Gas Analysis,” London, Cambridge University Press, 1933. (4) Emmet, P. H., and Gray, J. A,, J . Am. Chem. Soc., 66, 133843 (1944). (5) Farkas, A., and Farkas, L., Tians. Faraday Soc., 33, 678-90 (1937). (6) Goldfeld, Y . €I., and Koboaev, N.I., J . P h y s . Chem. ( C S S R ) , 15, 257-74 (1943). ( 7 ) Grassi, V., IZ Ahovo cimento, 11, 147-63 (1916). (8) Gieenhalgh, R. K., and Polanyi, h l . , Trans. Faraday Soc., 35, 520-42 (1939). (9) Holmes, J. W., and Taylor, E. H., J . Am. Chem. Soc., 63, 291115 (1941). (10) Hougen, 0. A., and Watson, K. XI., “Chemical Process Principles,” Pt. 111, New York, John Wiley & Sons, 1948. (11) Hougen, 0. A,, and Watson, K. A I . , IND.ENG.CHEM.,35, 52941 (1943). (12) Kistiakowsky, G. B., and Nickle, 9.B., J . Chem. Phys., 10, 78-9 (1942). (13) Kistiakowsky, G. B., Ruhoff, J. R., Smith, H. A, and Vaughan, ‘iv. E., J . A m . Chem. Soc., 57, 8 7 6 8 2 (1935). (14) Pease, R. N., Ibid., 45, 1196-1210 (1923). (15) Ibid., PP. 2235-42. (16) Schuster, C., Z . Elektrochem., 38, 614-18 (1932). (17) Taylor, E. H., J . Am. Chem. Soc., 63, 2 9 0 6 1 1 (1941). (18) Taylor, H. S., and Burns, R. M., Ibid , 43, 1273-87 (1921). (19) Taylor, H. S., and Joris, G. G., Bull. Soc. C h i m . Belg., 45, 24152 (1937). (20) Toyama, O., Rev. P h y s . Chem. Japan, 14, 86-100 (1940). (21) Tschernitz, J., Bornstein, S., Beckmann, R. B., and Hougen, 0. A., Trans. Am. Inst. Chem. Engrs., 42, 883-905 (1946). (22) Twigg, G. H., Trans. Faraday Sac., 35, 9 3 4 4 5 (1939). (23) Wilke, C. R., and Hougen, 0. A , Trans. .4m. Inst. Chem. Engis., 41, 445-51 (1945). (24) Williams. R. D.. oersonal communication (1950). (25j Wynkoop, R., Ph:D. dissertation, Dept. of ’Chemical Engineering, Princeton University, 1948. (26) Wynkoop, R., and Wilhelm, R. H., Chem. Eng. Proyr., 46, 30010 (1950). (27) Yang, K. H., and Hougen, 0. il.,Ibid., 46, 148-57 (1950). \-
I
RECEIVED for review July 15, 1953. - 4 c C e ~ T ~December o 15, 1953. Prevented at the 4th Annual Megtin~-in-hiiriiatur~ of the North Jersey Section of t h e AHERICAP CHEMICAL SOCIETY, Jan. 28, 1952. Contribution 33 from the Chemical Engineering Laboratories, Engineering Center, Coliirnbia University, h-ew York, N . Y.
Effect of Initiation Temperature on Continuous Emulsion Polymerization M. FELDON
AND
R. F. MCCANN
Governrnenf laboratories, University o f Akron, Akron, Ohio
P
ROPER initiation of the charge entering a continuous
polymerization system can increase favorably the polymer output of such a system. A significant factor t h a t influences initiation in a continuous polymerization system is temperature. T h e average polymerization rate a t 41 O F. t o 60% conversion in the pilot plant continuous emulsion polymerization unit at the Government Laboratories, consisting of twelve 20-gallon reactors connected in series, was increased appreciably in several instances b y initiating the reactions at temperatures above 41 ’ F. T h e initiation was accomplished b y adding the peroxide (or the reducing agent) to the otherwise complete charge, which had been adjusted t o a temperature of about VO” F., by passing through a heat exchanger at a point in a holdup or displacement line several feet from the first reactor. The completed charge in the holdup line was maintained a t the initiation temperature
March 1954
for a few minutes and then cooled by means of a heat exchanger to 41” F. before i t entered the first reactor. T h e charge was maintained at the initiation temperature for only about 0.3% of the total displacement time; however, 5 to 10% of the total conversion occurred during this brief interval. “High” temperature initiation was applied successfully t o charges prepared in accordance with low-sugar redox formulas specifying about 1.0 part of dextrose per 100 parts of monomers (6) and to peroxideamine formulas ( 1 ) . However. initiation at temperatures u p t o 60” F. in the first reactor of t h e 12-stage continuous unit, as contrasted t o the similar initiation in the holdup line, decreased the polymerization rate ( 8 ) . This unexpected result was subsequently confirmed b y polymerizations at the Port Neches, Tex., copolymer plant operated by the B. F. Goodrich Co., when a reduction in temperature of the latex in the first reactor
INDUSTRIAL AND ENGINEERING CHEMISTRY
465
80
-
70
-
SITE
60 -
8
50-
z 0 $
40-
W
minutes prior to gradual cooling (over an interval of 1.2 minutes) to 41 ' F. and continued polymerization in the stirred 20-gallon reactors a t 41' F. for 15 hours. Samples of the lat'ex ere removed after polymerization for 2.3 and 4.7 minutes, and 1.25, 5.0, 10.0, and 15.0 hours to determine the extent of conversion of nionomer to polymer. Since the reactor cooling system wa.q arranged to circulate brine through the jackets of the first three reactors in series, it was necessary, when initiating above 41 F. in the first reactor, to preheat the uninitiated charge. This procedure cornplicatcd the initiation conditions. T h e equipment and general procedure have beeu descritmi previously ( 6 , 7); the charge \vas prepared according to t'he i'olloning formula:
z
ou
30
-
20
-
10I
0
L
2 '
3
4 '
'
REACTOR NUMBER 6 7 8
5 '
'
'
'
10
9
IO
'
'
11 t
12 '
But,adiene Styrene Xodifier Emulsifier Potassium phosphate Tetrasodium ethylenediamine tetraacetate Diisopropylbenzene monohydroperoxide Tetraethylenepeiitamine Water
Parts by JTTeipht 71.5 28.5 0.20 4.6 0.60 0,0033' 0.20 0.10 200
ENGINEERING, DESIGN, AND PROCESS DEVELOPMENT
Table II.
Effect of hitiation Temperature on Polymer Properties Initiation Temp. in Holdup Line, ' F. __ 41 62 23.4 1
Conversion % Combined ityrene, 5% Gel % Dilkte solution viscosity liooney viscosity, htL-4 Raw Compounded Mill shrinkage, % hlill processing index Extrusion index
50 52 22.1 1 1.96 . 37 51 38 4.5 13.8
55 56 23.2 1
1.76
60 63 24.2 3 2.18 64 67 42 4.4 13.0
28 39 43 54 33 37 4.1 4.5 11.6 13.8 Stress-Strain Properties a t 77' F. 1290 1300 1120 300% Modulus, Ib./sq. inch 1200 Tensile strength, Ib./sq. inch 3720 3960 4150 4210 620 Elongation, 5% 610 690 660 Optimum cure, min. 32 42 59 03 Special Physical Properties
Rebound, 70 At 770 F. At 2120 F. Hysteresis temp. rise, Flex life X 10-3 Quality index Gehman values, ' C. Tio Tiw
F.
56 72 46 7.0 3.9
-36 -43
58 73 42 4.0 2.6 -39 -46
59 72 43 7.5 4.7 -39 -43
58 72 48 10 5.2 -39 -46
70 61 23.8 2 2.06 63 65 40 4.1 12.5 1170 3880 610 47
59 72 49 7.0 3.5
-39 -46
80 63 23..i 0 *.07 62 67 45 5.8
12.5 1110 3980 630 52
59 72 48. 6.0 3 1 -39 -47
Test Conditions Dilute solution viscosity hlooney viscosity Compounding recipe
T h e chemical and physical properties of these polymers reveal no correlation wit,h initiation temperature (Table 11). All of the polymers were essentially gel free, and the stress-strain and other properties of the vulcanixates with polymers of similar conversion and viscosity were equivalent and independent of the initiation temperature. This result could have been anticipated, since only a relat,ively small proportion of the total amount of polymer was actually made at the initiation temperature. Conclusion
Initiation of a peroxide-amine charge at temperatures above 41 O F. in the first reactor of a 12-stage continuous overflow
Literature Cited (1) Feldon, M., et al., Government Laboratories, University of Akron, private communication to Office of Synthetic Rubber, RFC, 1949. ( 2 ) Garvey, B. S., Jr., Whitlock, M. H., and Freese, J. A., I N D .ENG.CHEW.,34,1309 (1942).
Gehman, S. D., Woodford, D. E., and Wilkinson, S. C., Jr., Ibid., 39, 110s (1947). (4) Kiesskalt, S.,Schaich, W., Brunotte, A , , and Winnacker, K. ( t o Mien Property Custodian), U. S . Patent 2,302,445 (Nov. 17, 1942); I. G. Farbenindustrie, Brit. Patent 522,789 (June 27, 1940), French Patent 840,631 (April 28, 1939), and Ger. Patent 695,177 (July 15,1940). (,Laundrie, i) R. W.,and R'lcCann, R. F.,ISD. ENG.CHEM..41, 1568 (1949). ( 0 ) Laundrie, R. W., el a!., Government Laboratories, University of Akron, private conrmunications to Office of Synthetic Rubber, RFC, 1949 and 1950. ( 7 ) Laundrie, R. W., et al., ISD. EA-G.CHEM.,42, 1439, 2355 (1950). (8) AIcCmn, R. >'., et al., Government Laboratories, University o f Akron, private communication to Office of Synthet,ic Rubber, RFC, 1950. (9) Pryor, B. c., Harrington, E. m7., and Druesedow, D., IND.ENG. C H E M . , 1311 ~ ~ , (1953). (10) Sohade, J. W., and Labbe, B. G., Government Laboratories, University of Akron, private communication to Office of Synthetic Rubber, RFC, 1946.
0 . 2 3 % Solution in benzene' 4-Min. reading; large rotor; 212' F. 100 Polymer 40 E P C black, 5 zinc oxide, 2 sulfur, 3 .41tax, 1.J stearic h i d ; cure temp. 292' F. Uill processing index Method of Schade and Labbe (10) Extrusion index Procedure of Garvey et 52. ( 2 ) Stress-strain tests OSR specification procedure Jan. 1, 1949; vulcanizates nearest the optimum cure as judged from 300% modnlu? Hysteresis temperature rise Goodrich Flexometer; 143' Ib./sq. inch load, 0.176-inch stroke; 1800 r.p.m.: 30-min. test a t 212' 'F,; samples a t optimum cure Flex life De l l a t t i a Flexometer. pierced specimens; reported as number of flexures produce 0.8-inch crack growth a t 312 cycles/min. and 212' F.; samples a t optimum cure Quality index Ratio of flexures of test sample to flexures of GR-S-1000 at equal hysteresis temperature rise Goodyear-Healy pendulum. angle of inertia 15O; specimens Rebound rnred for 30 min. beyond ihe optiiniim Gehman low-teinperalure test .4s described ( 3 ): specimens cured for 30 min. beyond the optimum
tb
system, follow~edby polymerization a t 41 O F. in the remaining 11 reactors, decreased the reaction rate compared t o t h a t obtained at a n initiation temperature of 41 O F. On the other hand, initiation at high temperatures in the holdup pipe for a few minutes prior to continued polymerization at 41" F. for 15 hours resulted in significantly increased rates of conversion and polymers with properties t h a t were equivalent to those of stock made entirely a t 41" F. to the same conversion and viscosity levels. Thus, the use of "high" initiation temperatures in the holdup line appears to be a commercially feasible method of increasing the capacity of continuous emulsion polymerization systems.
(3)
RECEIVED for review September 17, 1933 ACCEPTEDDecember 7, 1953. This work was performed as part of the research project sponsored b y the Reconstruction Finance Corp., Office of Synthetic Rubber, in connection with the Government Synthetic Rubber Program.
END OF ENGINEERING, DESIGN, AND PROCESS DEVELOPMENT SECTION
March 1954
INDUSTRIAL AND ENGINEERING CHEMISTRY
467
