Ind. Eng. Chem. Process Des. Dev. 1986, 25, 767-771
more simple but in fact it is more sensitive to disturbances in the intermediate component feed composition. Any light component that drops out of the bottom of the first column of the LOF system must appear as impurity in the toluene product. In the SSS structure, the light component that enters the stripper tends to be stripped out. Notice that the simulation results are consistent with the theoretical predictions. The MRI values of the two configurations indicated essentially equal controllability, which was seen in the simulations. The MIC and Niederlinski index predicted the system to be integral controllable, which it was. The TLC curves predicted that the toluene and xylene product purities would be slightly better controlled in the SSS configuration, and this was observed in the simulations. The TLC curves predicted that the benzene product purity would be better controlled over the low-frequency range in the LOF configuration but would be better controlled over the high-frequency range in the SSS configuration. These results can be seen in the simulation results. Thus, the simulations confirmed the reliability of the various indexes and measures of performance. Conclusion The complex, interacting, multivariable SSS configuration was successfully controlled by using four conventional P I controllers. The sidedraw rate had to be manipulated to maintain energy efficiency and rangeability. The load response of the SSS system was as good as, if not better than, the response of the conventional LOF system. The recycle and coupling nature of the SSS system contributed positively to disturbance attenuation. Nomenclature d = disturbance (intermediate feed composition ZF(2)) G = open-loop plant transfer function matrix F = feed flow rate, lb mol/h LOF = light-out-first configuration LS = liquid draw rate from main column to stripper, lb mol/h
MIC = Morari index of integral controllability MRI = Morari resiliency index QB = main column reboiler heat-transfer rate, Btu/h
787
QBl = first LOF column reboiler heat-transfer rate, Btu/h QB2 = second LOF column reboiler heat-transfer rate, Btu/h QBS = stripper reboiler heat-transfer rate, Btu/h R = reflux flow rate, lb mol/h R1 = first LOF column reflux flow rate, lb mol/h RGA = relative gain array RR2 = reflux ratio in second LOF column S S S = sidestream stripper configuration AT = temperature difference, O F XB(J) = bottoms composition (mole fraction of component J)
XBP(J) = second LOF column bottoms composition (mole fraction of component J) XD(J) = distillate composition (mole fraction of component J)
XDl(J) = first LOF column distillate composition (mole fraction of component J) XD2(J) = second LOF column distillate composition (mole fraction of component J) XS(J) = sidestream product composition (mole fraction of component J) y, = jth output variable Greek Symbols u = minimum singular value o = frequency, rad/min Registry No. Benzene, 71-43-2;toluene, 108-88-3;o-xylene, 95-47-6. Literature Cited Alatiqi, I. M., Ph.D. Thesis Lehigh University, 1985. Alatlqi, I. M., Luyben, W. L. Ind. Eng. Chem. ProcessDes. D e v . 1985, 2 4 ,
500. Doukas, N., Luyben, W. L. Inst. Techno/. 1978, 2 5 , 43. Elaahi, A., Luyben, W. L. Ind. Eng. Chem. Process Des. Dev. 1985, 24, 368. GrosdMier, P., Morari, M., HoR, 8. R. Ind. Eng. Chem. Fundam. 1985, 2 4 , 221. Lenhoff, A. M., Morari, M. Chem. Eng. Sci. 1982. 37, 245. Ogunnaike, B. A. et ai. AIChE J. 1983, 29, 4. 632. Tyreus, B. D., Luyben, W. L. Ind. Eng. Chem. Process Des. L b v . 1975, 14, 391. Yu, C. C . , Luyben, W. L. Ind. Eng. Chem. Process Des. D e v . 1986, 25, 498.
Received for review July 18, 1985 Revised manuscript received December 23, 1985 Accepted January 22,1986
Thermolytic Reactions of Isomeric Ethylphenols with Solvent Dodecane Pelrheng Zhou and Bllly L. Qynes" School of Chemical Engineering, Oklahoma State Universiv, Stillwater, Oklahoma 74078
Low-conversion thermolyses of p - and m-ethylphenols (PEP and MEP) in dodecane under N, or H, atmosphere were conducted, and the results are compared with those of o-ethylphenol (OEP). Overall reactivities, as well as those for dehydroxylation and dealkylation, fall in the order of ortho > para > meta. This is the reverse of their reactivity order in catalytic dehydroxygenation. OEP, PEP, and MEP also inhibit dodecane cracking, while the latter accelerates their conversion. This promotion effect is suppressed in the presence of molecular hydrogen. The same mechanism is believed to apply to these three isomers: molecular dissociatian followed by radical reactions but with insignificant chain lengths. The variations in their reactivities and product patterns are attributed to different isomeric configurations.
Phenols are the most abundant organic oxygen-containing compounds in coal-derived liquids. For a better
* To whom correspondence should be sent. 0196-4305/86/1125-0767$01.50/0
understanding of their thermal behavior during coal oil processing, ethylphenol was chosen as representative of the alkyl-substituted, single-ring phenols with a single OH group, existing in coal oils. The reaction characteristics 0 1986 American Chemical Society
768
Ind. Eng. Chem. Process Des. Dev., Vol. 25, No. 3, 1986
of the three isomeric ethylphenols under thermal treatment conditions in the environment of N2 or H2 were studied in our laboratory. The thermolytic reactions, kinetics, and mechanisms of o-ethylphenol (OEP) and the carrier solvent dodecane have been reported in two previous papers (Zhou and Crynes, 1985a,b). A free-radical chain reaction mechanism was suggested for dodecane thermolysis, and molecular decomposition in combination with radical reactions was proposed for OEP thermolytic conversion. The mutual influences of dodecane and OEP during thermal treatment were also discussed. The thermolysis behaviors of the other two isomers, p - and m-ethylphenols (PEP and MEP), are presented here, in comparison with that of the ortho isomer. The reaction characteristics of the solvent dodecane, in the presence of the isomeric ethylphenols, are also described.
Experimental Section p-Ethylphenol (Eastman Kodak, reagent grade, 99% minimum purity), m-ethylphenol (Aldrich Chemical, 99+ % purity), and dodecane (Fisher Scientific, purified grade) were used as received, since our analysis showed a purity in excess of 99.5 wt % for each of the chemicals we obtained. PEP or MEP, with an initial concentration around 6 mol % , was thermolyzed in an autoclave reactor (Autoclave Engineers, 0.001-m3capacity) under an atmosphere of N2 or H2 (Union Carbide, prepurified specialty gas grade H2and ultra-high-purity grade N2). Dodecane was employed as a carrier solvent to provide a hydrocarbon environment at an ethylphenol concentration characteristic of the single-ring phenols in coal liquids. The reactor system with devices designed for rapid feed injection and periodic sampling, the analytical instrumentation (GC and GC/MS), and the experimental and analytical procedures have been described elsewhere (Zhou and Crynes, 1985b). For comparison purpose, the same set of conditions (623 K, 9.2 MPa) as used in OEP thermolysis was employed for PEP and MEP cracking. The conditions were mild to achieve low conversions in order to examine the primary reactions, which have never been recorded in the literature. Results and Discussion For the reasons discussed previously (Zhou and Crynes, 1985a), our thermolysis experiments of PEP and MEP are believed to be free of heat- and mass-transfer limitations, and their reactions proceed in the kinetic regime. A glass liner was used for all experiments, and surface effects of the metal walls were negligible. The experimental runs had material balances better than 95 wt YO,not including the cracked gas which was mixed with a relatively large amount of N2 or H2. The kinetic constants were calculated with an average deviation of 24%. I. Thermal Reactivities and Reaction Kinetics. At the conditions used in the present study, low conversions were obtained for ethylphenol thermolyses. Under a N2 atmosphere for a reaction period of 24 X 103s, thermolytic conversions for 0-,p-, and m-ethylphenols were 8.2, 3.0, and 1.9 mol 5% ,respectively, demonstrating a relative order of thermal reactivity of ortho > para > meta. Just like the case of OEP cracking (Zhou and Crynes, 1985b),a global first-order rate equation most satisfactorily fits PEP and MEP conversion data, in either N2 or H2. Pseudo-first-order rate coefficients for the disappearance of the three isomeric ethylphenols are summarized in Table I. . As expected from the conversion data, OEP has the highest rate constant, MEP the lowest, and PEP intermediate. Activation energy data are not available for PEP
Table I. Pseudo-First-Order Rate Coefficients for the Thermolyses of Isomeric Ethylphenols (623 K, 9.2 MPa) rate coeff reactant environment k, s-l x lo6 correlation coeff N2 1.6 0.9360 OEP H2 1.6 0.9763 OEP N2 4.1 0.9466 OEP in dodecane OEP in dodecane H2 1.7 0.9317-0.9915 PEP in dodecane N2 1.3 0.9906 MEP in dodecane N2 0.7 0.9804 HZ 0.3 0.9558 MEP in dodecane
and MEP, since the reaction temperature was not changed. With cresols, the ease of dehydroxylation was found to be in the order ortho > para > meta (Gonikberg and Li, 1960). In the case of ethylphenols, at least the overall conversion follows this same order. Besides energy considerations, a speculation can be made based on the ortho-para directing property of the OH group (Pauling, 1960). The strong resonance effect of this group may cause the ortho and para substituents to react easier; the ortho isomer, with the side chain closer to the OH functional group, may be most reactive. The relative order of thermal reactivities for isomeric ethylphenols is exactly the reverse of the order of catalytic reactivities reported for phenols, that is, meta > para > ortho (Odebumni and Ollis, 1983a). The latter is attributed to the steric hindrance to catalytic hydrodeoxygenation (HDO), especially in ortho-substituted phenols (Weisser and Landa, 1973; Rollman, 1977; Weigold, 1982; Odebumni and Ollis, 1983b). Being difficult to eliminate in catalytic hydrotreatment, ortho-substituted phenols turn out to be relatively facile. This fact suggests an appropriate combination of thermal and catalytic processes for the ortho-substituted phenols to be efficiently removed. Certain alkyl-substituted phenol radicals may also be sterically hindered toward bimolecular reactions, and their lives may be as long as several weeks (Porter and Land, 1961). This implies that not only hydrogen abstraction from ethylphenol molecules but also the radical decomposition is not easily achieved with these substituted phenol-derived radicals during thermolysis. This suggests that under thermal treatment conditions, the reaction chain, if it exists, may be restricted in length and molecular dissociation is relatively important, as proposed for OEP thermolysis mechanism (Zhou and Crynes, 1985b). A similar mechanism is believed to apply to PEP and MEP thermolysis. 11. Product Distribution. The product distribution patterns are shown in Figures 1-4. Hydrocarbon products are not included. Heavier phenols, 2,4-xylenol and 2- and 4-propylphenols, were detected in both the feed and products. Binuclear compounds were not found in the products. When Figures 1-3 are compared, for these three isomers, under nitrogen atmosphere, the thermolytic product patterns are similar, but the complexity in product composition (number of chemical species) decreases in the order ortho > para > meta, in parallel with the order of their thermal reactivities. Thermolytic product yields for these ethylphenols are listed in Table 11. Since the conversion and, hence, the product concentrations are very low for MEP thermolysis, the relative error of the MEP product data is larger. Somewhat different product distributions were obtained for the three isomers. Under N2 environment, and in the dodecane solvent, OEP gave mainly aromatic hydrocarbons and smaller phenols with minor isomerization. PEP underwent substantial isomerization and dehydroxygenation.
Ind. Eng. Chem. Process Des. Dev., Val. 25, No. 3, 1986 769
,
I I I -- 1 ' I
I
I
I
--7
I
T M0
0
1
XYLENOLS + HC'S
4
-c! 2- 20 rl x
2
L z U
10 U
n a
0
P n.
12.0 REACTION
0 0
6.0
12,o REACTION TINE
18.0
24.0
~ ~ 1 0 - 3
5,9,
n w. E
A
0-CRESOL
I
1
l
5.7L
0
i
1
MEP PHENOL 0-COMPDS + H C ' S
0
PHENOL
3E
(s) 10-3
Figure 3. Product distribution of o-ethylphenol thermolysis in dodecane under nitrogen environment (623 K, 9.2 MPa).
Figure 1. Product distribution of m-ethylphenol thermolysis in dodecane under nitrogen environment (623 K, 9.2 MPa).
0
24,o
TIME,
b
HVY
T
7
OEP
f ,
XYLENOLS + HC'S
MEP H V Y 0-CONPDS + HC'S
n.
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b
/'
/
0
6.0
12,o
18.0
29,o
REACTION T I N E (SlX10'3
Figure 4. Product distribution of m-ethylphenol thermolysis in dodecane under hydrogen environment (623 K, 9.2 MPa).
0
0
6.0
12.0
18.0
24,o
REACTION T I N E (Slx10-3
Figure 2. Product distribution of p-ethylphenol thermolysis in dodecane under nitrogen environment (623 K, 9.2 MPa).
Considerable amounts of heavier phenols were formed from OEP and PEP. MEP not'only was the most difficult to react but also produced the largest yield of heavy compounds and few lower molecular weight products. OEP and MEP made some cresols, obviously via breaking of the C-C bond in the side chain, and isomerization between the cresols was also possible. PEP essentially produced no cresols, and the little 0-cresol is best explained as a product from OEP which was formed from isomerization of PEP. MEP underwent no isomerization, substantially.
Table 11. Products from Thermolyses of Isomeric Ethylphenols i n Dodecane (623 K, 9.2 MPa, 24.0 X lo3 8 ) moles per 100 mol converted for reactant PEP environment conversion, mol % light arenes phenol o-cresol p-, m-cresols OEP PEP MEP heavy oxygen compds with some heavy hydrocarbons " N D = not detected.
N2 1.9 17 7 6 9 ND 3 58
Hz 1.0 56 23 NDa ND ND ND
22
Nz 3.0 25 3.9 1.3 ND 34 4.4 32
OEP N2 8.2 30.0 10.5 5.5 2.9
H2 3.1 25.8 22.4 6.8 ND
4.1 12.2 2.2 5.1 42.7 27.8
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Ind. Eng. Chem. Process Des. Dev., Vol. 25, No. 3, 1986
Table 111. Pseudo-First-Order Rate Coefficients for Solvent, Dodecane, Thermolysis (623 K, 9.2 MPa) rate coeff k , s-l X reactant environment io7 correlation coeff N2 4.7 0.9887 dodecane 0.9829 H2 3.8 dodecane N2 2.5 0.7515 dodecane with OEP HZ 1.2 0.8907-0.9803 dodecane with OEP 0.9757 NZ 1.8 dodecane with PEP N2 1.9 0.9517 dodecane with MEP H2 1.1 0.8945 dodecane with MEP
From the product yield data in Table 11, an order for the relative ease of dehydroxylation and dealkylation is ortho > para > meta, which is in accordance with the order of overall reactivities. 111. Effect of Molecular Hydrogen. Hydrogen effect on OEP thermolysis with dodecane was observed and discussed previously (Zhou and Crynes, 1985b). On MEP thermolysis, this effect is also obvious from the data in Figures 1 and 4, as well as in Tables I and 11. In the hydrogen atmosphere, a significant amount of hydrogen dissolved in the reaction liquid (Zhou and Crynes, 1985a) and participated in the reactions. A role of radical capping is suggested for the hydrogen function. As a result, the promotion effect of the solvent dodecane was cancelled, and the overall MEP conversion and its rate coefficient were reduced, most probably down to the values of MEP thermolysis without the presence of the solvent, as observed in the case of OEP. Hydrogen reduced the MEP rate constant, under otherwise identical conditions, to an extent of about 60%,just the same as in the case of OEP (Table I). One may reasonably expect the same effect of molecular hydrogen on P E P cracking, also. Generally, hydrogen reduced the yield of heavy products considerably, which indicates that the coupling reactions of the radicals were significantly inhibited. This is consistent with the proposed mechanism of radical capping by dissolved hydrogen. Hydrogen also increased the formation of phenol. As inferred from OEP thermolysis experiments, phenol yield was much higher when OEP was thermolyzed without solvent than with. This is interpreted as the result of the coupling reactions between phenol and hydrocarbon radicals, the latter being provided by dodecane cracking. The participation of hydrogen, by way of capping and stabilizing corresponding radicals, terminates the reaction chain of dodecane, inhibits the coupling reactions, and thus recovers more or less the phenol yield to the level of pure OEP thermolysis. This mechanism is believed to apply to PEP and MEP cracking, too. No definite information regarding the hydrogen influence on dehydroxylation could be achieved, since the yields of the arenes were somewhat complicated by their distribution between the gas and liquid phases in the reaction system. Anyhow, the formation of cresols was not favored by the hydrogen atmosphere, while OEP isomerization seemed to be favored. IV. Solvent Behavior. In the presence of these ethylphenols, the global, first-order rate of dodecane conversion was appreciably reduced, compared with that of pure dodecane cracking. This is demonstrated in Table 111. A common inhibition effect of the ethylphenols on dodecane cracking in the environment of N2is obvious. OEP may be somehwat stronger in this aspect due to its higher reactivity. This inhibition effect can be explained by the scavenging role of the oxygen-containing radicals on dodecane-derived radicals because of the coupling reactions between them. This leads to the increased yields of heavier
Table IV. Product Yields of Dodecane Thermolysis with and without Ethylphenols (623 K, 9.2 MPa, 24.0 X IO3 a ) moles Der 100 mol converted with pure OEP PEP environment N2 Hz conversion, mol % 1.3 1.0 IC, 21.5 15.9 C6= 14.2 14.2 c6 10.1 9.9 c'i= 8.9 11.4 c7 5.8 7.3 CS= 9.7 9.0 c6 5.9 7.3 Cg= 6.5 6.8 CQ 4.7 6.0 GO' 3.8 3.7 G O 1.6 1.5 c11=
Cl, 'C,, a
N2 0.5 18 16 12
H2
Nz
0.3 0.5 17 10 13 16 14 7 14 16 25b 9 6 10 13 14 8 3 6 8 9 6 3 9 5 2 NA" 3 NA NA 1 0.2 NA 2 2.7c 0.5' 4 NA NA 16.2 14.6 NA NA NA
N2
0.8 6 20 9 10 7 9 9 13 9 6 1 3 2
H2 0.2 14 16 7 7 6 9 6 6 6 2 0.5
NA NA NA NA
NA = not available. *Including C7=. Including Cll=.
products when ethylphenol is thermolyzed with dodecane under N2 Hydrogen further reduces the dodecane reaction rate by capping the hydrocarbon radicals and, in doing so, lowers the yield of heavy products. The mutual influence between OEP and dodecane during cocracking and the mechanism proposed (Zhou and Crynes, 198513) also hold for PEP and MEP. We thus believe that PEP-and MEP also thermolyze by a molecular decomposition mechanism followed by some radical reactions, but the radical chain length is short and negligible. While cocracking, the ethylphenol and dodecane essentially behave according to their own mechanisms, but considerable interactions between the ethylphenol-derived and dodecane-derived radicals take place. These interactions are fully responsible for the differences between the pure-compound thermolysis and cocracking. Since the radical reaction chain is relatively unimportant for the thermolysis of ethylphenols, therefore, hydrogen does not significantly affect their overall conversion while thermolyzed alone, except for some reduction in the yield of coupling products. Hydrocarbon products from dodecane cracking are shown in Table IV. These data are subject to greater errors owing to the small conversions. However, the results agree in general trends, and a decreasing yield with increasing molecular weight of the components is clear. This implies that no significant change in the dodecane thermolysis mechanism occurred when it was thermolyzed in the presence of the ethylphenols, except for a reduction in reaction rate.
Conclusions The relative ease of overall thermolytic conversion, as well as dehydroxylation and dealkylation, of the three isomeric ethylphenols is in the order of ortho > para > meta, which is exactly the reverse of their reactivity order in catalytic HDO. In a mixture with solvent dodecane, PEP and MEP inhibit dodecane thermolysis in the same manner as OEP does, whereas their thermolyses are most probably accelerated by the coexistence of dodecane cracking. This acceleration is suppressed by molecular hydrogen. During thermolysis in dodecane, PEP mainly undergoes isomerization and dehydroxylation and also produces considerable amounts of heavier components. MEP gives heavier compounds as major products but minor amounts of lower molecular weight products. In contrast, OEP generates light aromatic hydrocarbons and lower phenols, as well as heavier phenols.
771
Ind. Eng. Chem. Process Des. Dev. 1988, 25, 771-776
We believe that the same mechanism used to adequately interpret data of OEP thermolysis works for PEP and as The ethylphenols react through a combination of molecular dissociation and radical reactions that follow. The radical chain length is short. Acknowledgment -
This study was performed under the financial sponsorship of the University Center for Energy Research and the Of Engineering Of Oklahoma State University. Some analytical services were provided by the Water Quality Research Laboratory of the Same institution.
L i t e r a t u r e Cited Gonlkberg, M. G.; Li, G.-N. Izv. Akad. Nauk SSSR, Ser. Khim. 1960, 498; Chem. Abstr. 1960, 5 4 , 22439. Wbumni, E, 0,; Ollis, D. F. J . &tal. 1983a, 80, 56. Oliis, D. F. J . Catel. 1063b, 80, 76. Odebumni, E. 0.; Pauiing, L. "The Nature of the Chemical Bond", 3rd ed.;Cornell University Press: New York. 1960. Porter,-G.; Land, E. J: "Preprints, The Fifth International Symposium on Free Radicals": Gordon and Breach: New York, July 6-7, 1961. Rollman, L. D. J . Catal. 1977, 4 6 , 243. Weigoid, H. Fuel 1962, $ 1 , 1021. Weisser, 0.;Landa, S. "Sulphide Catalysts, Their Properties and Applications"; Pergamon Press: Elmsform, New York, 1973; p 157. Zhou, P.; Crynes, B. L. Ind. Eng. Chem. Process Des. D e v . 19858, in press. Zhou, p.; Crynes, B. L. Ind. E W . Chem. Process Des. DeV. 1985b, In Dress. r --
Received f o r review May 14, 1985 Accepted January 24, 1986
Registry No. H2,1333-74-0; p-ethylphenol, 123-07-9; methylphenol, 620-17-7; dodecane, 112-40-3.
Purification of Industrial Acrylamide by Ion Exchange Pllar GurmBn, Inmaculada Ortlz, and Angel Irablen' Departmento de Qdmica TGcnica, Facultad de Clenclas, Universidad del Pa% Vasco, Apdo. 644, Bllbao, Spain
In the manufacture of acrylamide by hydration of acrylonitrile with Raney copper as the catalyst, the reaction product is contaminated by a partial solubilization of copper. The solubility depends on the amount of acrylonitrile and acrylamide, but it is always smaller than 500 ppm. Complex formation between acrylonitrile, acrylamide, and copper(I1) has been studied, and equilibrium parameters are given. Ion exchange seems to be a useful operation in order to purify the reaction product. Equilibrium behavior of strong cationic and complexing (iminodicetate and amidoxime groups) resins is shown in this paper. The acrylonitrile influence in the ion-xchange equilibria has been explained by the formation of complexes between acrylonitrile and copper(I1) and acrylamide and copper(II), which show exchange possibilities. Ion-exchange equilibrium parameters are given for the systems copper(II)/acrylonitrile-copper( 11) complex and different commercial resins.
Ion exchange finds application in chemical processing, analytical chemistry, hydrometallurgy, and environmental pollution control as a technique for sorbing, concentrating, or separating soluble metallic species (Kennedy, 1980). This technique has not been exploited as widely as it could be, because ion-exchange sorption is a complex phenomenon. This makes it difficult to predict quantitative sorption behavior in complex or multicomponent systems (Kunin, 1958; Helfferich, 1962; Dorfner, 1972; Marinsky and Marcus, 1973). In the last 2 decades, there has been a renaissance in inorganic chemistry inspired by the understanding of structure and bonding in the broad class of coordination complexes of transition metals. Simultaneously there has been a surge of interest in the chemistry of catalysis by certain transition-metal complexes and by surfaces of many of the same metals, so that homogeneously catalyzed reactions and heterogeneously catalyzed reactions in the liquid phase play important roles in chemical processing (Gates et al., 1979). Some industrial processes like the Wacker process (Smidt et al., 1959) for the ethylene oxidation to acetaldehyde, the oxidation of olefins to ketone or aldehydes (Stern, 1967), or the synthesis of vinyl acetate from ethylene and acetic acid (Moiseev et al., 1974) homogeneously catalyzed by PdC12 and CuC12 do not present
* Author
problems for the separation of the final products by distillation. In the development of heterogeneous catalytic processes in the liquid phase on a solid catalyst, one of the common problems is the partial solubility of the catalyst in the liquid phase, leading to the contamination of the final products. Manufacture of products like acrylamide does not offer great difficulties from the point of view of the chemical reactions involved in the industrial processes, but the isolation of pure acrylamide, crystalline solid, which is assuming increasing industrial importance as a chemical intermediate and monomer, is a complex operation. Most practical methods of isolating acrylamide involve neutralization in water to give a water-insoluble salt. The salt is then removed by filtration and the filtrate is concentrated and/or cooled to recover crystals of acrylamide (Kirk and Othmer, 1969). In these cases, separation operations like filtration are not able to guess the product specifications. The manufacture of acrylamide by hydration of acrylonitrile in the presence of Raney copper as the catalyst Kirk and Othmer, 1969) is one of the industrial processes leading to a copper contamination of the product in the range of 10-500 ppm depending on the reaction variables and catalyst. CHz=CH-C_N
to whom correspondence should be addressed. 0196-4305/86/1125-0771$01.50/0
.
Raney copper "20
0 1986 American Chemical Society
CH,=CH-C
