COPPER CHROMITE CATALYSTS FOR RED UCTIVE ALKYLATION FRED S. DOVELL AND H A R O L D G R E E N F I E L D 'Vaugatuck Chemical, Dzaiszon of' LTnited States Rubber Co., ,Vaugatuch, Conn.
Copper chromite has been investigated as a catalyst for the preparation of alkylaryl secondary amines b y the reductive alkylation of a primary aromatic amine with an aliphatic ketone in the presence of hydrogen. Copper chromite avoids the nuclear hydrogenation and hydrogenolysis o f carbon-nitrogen bonds obtained with nickel and with noble metal catalysts; however, a large amount of ketone is reduced to the corresponding alcohol. The desired selectivity-i.e., reductive alkylation rather than ketone reduction-is favored b y low pressure. Various commercial copper chromite catalysts have marked differences in activity and selectivity. Catalyst pretreatment and reuse can greatly affect activity and selectivity, and are, therefore, important factors in development work.
of this investigation has been to study the use of copper chromite as a catalyst for the preparation of alkylaryl secondary amines by the reductive alkylation of a primary aromatic amine \virh a n aliphatic ketone in the presence o f hydroeen ( J ) . FIE P U R P O S E
H H R
R
Cupric oxide-rype catalysts, such as copper chromiteperhaps better termed copper-chromium oxide ( 7 , 2: 8)--are useful for this reaction (,3, 7, 9.70). T h e other commonly used catalysts are nickel and the noble metals, platinum and palladium. Nickel results in excessive nuclear hydrogenation ( 3 ) . and the noble metals cause both nuclear hydrogenation (5) and forination of alkylamines (5. 9) b>- h>-drogenolysis of the carbon-nitrogen bond bettveen the alkyl group and the nitrogen H? -+ ArH atom in the secondary amine-i.e.: A r N H R RSH:. Copper oxide catalysts avoid these undesirable side reactions, but a large amount of ketone is reduced to the corresponding alcohol. The compositions of the copper chromite catalysts used are given in Table I. T h e active portion of the catalyst probably is black cupric oxide Lvhich loses its activity if reduced to the red cuprous state ( 7 , 2. 8 ) . T h e cupric oxide probably is stabilized toward reduction by rhe chromium oxide ; further stabiliza-
+
Table 1.
+
Copper Chromite Catalysts
Drsiqnatiori
cu0
:I Harshaw Cu-l402P 6: Harshaw Cu-1 l06P C Harshaw Cu-0401 P D Girdler G-22 E Girdlrr G-13 E Harshaw Cu-1800P G Harshaw Cu-0202P
40 40 41
Analjs7s. Tt't. 70 Cr.Oa
47 44
40 (min. j 51
10 11 Yes
50 (min.) 82
BaO
60
47 17
tion by rhe addition of barium or other alkaline earth metals has been found in certain cases ( 7 ) . T h e effect of several factors upon the desired selectivity of the reaction-i.e., reductive alkylation in preference 'io ketone reduction-and upon the rate of reaction-i.e., the combined rates of h>-drogen absorption for the reductive alkylation and ketone reduction--\vas investigated for the synthesis of .V-isopropylaniline (.I--IP.4) from aniline and acetone. T h e reductive alkylation of .V-phenyl-p-phenylenediaminewith acetone also \vas briefly investigated. Experimental
Reductive Alkylation of Aniline with Acetone. Each experiment \vas i u n in a 600-ml. stainless steel Magne-Dash autoclave ivith 46.6 grams (0.50 mole) of aniline (Eastman Kodak No. 25). 116 grams (2.0 moles) of acetone (Baker reagent grade). and 5.0 grams of a copper chromite catalyst. T h e reaction \vas alloived to proceed at the specified temperature and pressure until gas absorption stopped. T h e cooled reaction mixture was removed from the autoclave. and the catalyst filtered off onto Celite filter-aid (Johns-Nanville) and -\vashed cvith 2-propanol (Baker reagent grade). I n all cases the spent catalyst !vas black. indicating littlc or no rereduction to the relatively inactive cuprous or metallic forms. \Vhen the spent catalyst -\vas reused, it \vas accompanied by the Celite anti about 35 ml. of 2-propanol. Preactivation Lvith hydrogen \vas accomplished by treating 5.0 grams of copper chromite in 200 ml. of 2-propanol at 160' to 165' C. and 1100 p.s.i.g. for 1 hour in the Magne-Dash autoclave. 1-here -\vas a n indication of h>-drogen absorption during the heat-up a t about 120' C. and 970 p.s.i.g. T h e catalyst was filtered off on Celite and xvashed with 2-propanol. I t was added to the reductive alky-lation charge with the Celite and about 35 ml. of' 2-propanol. T h e reaction products \vere separated by distillation into a low-boiling fraction consisting mostly of '-propanol. a small amount of middle cut u p t o a pot temperature of 170Oto 18OoC., and the residue product. Each fraction -\vasanalyzed by vapor phase chromatography, and the low-boiling fraction also \vas titrated for amines. Analyses showed the presence of ?-proVOL. 1
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panol, water, aniline, and .V-isopropylaniline, ivith only traces of other products. There was no indication of nuclear hydrogenation. hydrogenolysis of the carbon-nitrogen bond of .Y-IPA, or of any reaction except reductive alkylation and ketone hydrogenation. T h e results with fresh and with once reused samples of several copper chromite catalysts at 160' to 165' C. and 900 to 1100 p.s.i.g. are shobvn in Table 11. The experiment Lvith fresh catalyst A \vas repeated in the presence of Celite and 2-propanol to estimate their effect with reused catalysts. There was no significant difference in rate of reaction. but the yield of .\-IPA increased from 38 to 48%. This factor was not
further investigated and does not affect the general conclusions regarding catalyst reuse. Reductive Alkylation of N-Phenyl-p-phenylenediamine with Acetone. Each experiment was run in the 600-ml. Magne-Dash autoclave with 92.0 grams (0.50 mole) of distilled ,Y-phenyl-p-phenylenediamine, 116 grams (2.0 moles) of acetone, and 4.6 grams of copper chromite catalyst A (Harshaw Cu-l402P). T h e catalyst was removed by filtration and the filtraie topped to a pot temperature of 170' C. a t 22 nim. T h e residue product then \vas analyzed for ,\'-isopropyl-.V'-phenylp-phenylenediamine by infrared spectroscopy: and for .V-phenyl p-phenylenediamine by colorimetric determination of i t reaction product Lvith salicylaldehyde in glacial acetic acid.
Table II.
Reductive Alkylation with Copper Chromite at 160' to 165' C. and 900-1 100 P.S.I.G.5 Yield S-IsopropylTime at 160-5'. Hr. aniline, M o l e yo Fresh Reused Copper Chromite Fresh Reused Catalyst catalyst cataly.4 catalyst catalysth .A 38 74
B 30 21 19 C 10 17 9 D E 12 75 F 24 46 G 32 37 a Each experiment was run in a 600-ml. .Vagne-Dash autoclave zoith 46.6grams (0.50 mole) of aniline. 116grams (2.0 moles) acetone, of and 5.0 grams of catalyst until gas absorption ceased. After one use; added with Celite jilter aid and about 35 ml. of 2popanol. Effect of Preactivation of Catalyst A with Hydrogen Time at Yield Pressure, Temp., Temp., .T-IPA, Catalyst Treatment P.S.I.G. C. Hr. .Mole %
Table 111.
None (fresh catalyst) Spent catalyst from 900-1100 above expt. Celite and 2-propanol added with fresh catalyst Preactivated with hydrogen None (fresh catalyst) Preactivated with 400-600 hydrogen
3
38 74
1'/4
48
11/4
160-165
29
I/2
160-165
41/2
70
2
53
Effect of Pressure on Reductive Alkylation with Catalyst A Time at Yield Temp., .T-I P A , Pressure, Temperature. P.S.Z.G. O Hr. .Ifole % 400-600 160-1 65 41/2 70
Table IV.
c.
900-1 100 1400-1 600
160-1 65 150-165
Table V.
Temp., a
c.
165 165 180-1 85
Pressure, P.S.I.G. 400-600 400-600 500-600
1'/4 -1/2
38 15
Time at Temp., Hr. 41/r 2 3
Moles Hn Absorbed Per mole Per mole AVT-phenylPPDa acetone 3.1 1.7 3.1
~~'-Phenyl-p-phenylenediamine.
c
Melting point of pure ~'-isopropyl-N'-phenyl-PPD is 79.5580' C.
N-Isopropyl-N'-phenyl-p-phenylenediamine.
l&EC
Effect of Catalyst Composition. T h e results obtained both with fresh and with reused catalyst (Table 11) d o not indicate any obvious relationship between catalyst composition and either selectivity or rate. There is a striking variation in the behavior of different catalysts. An old sample of Harshaw catalyst Cu-O102P, said by the manufacturer to be the same in composition and method of preparation as catalyst A , gave a 97 mole % yield? based on starting aniline, of .V-IPA in 5 R / 4 hours at 160' to 165' C. and 900 to 1100 p.s.i.g. Thus, this catalyst was far less active and much more selective than any other tested. T h e reason for this is not known. Effect of Catalyst Reuse. T h e effect of catalyst reuse is shown in Table 11. T h e two "best" catalysts, A and E? show a marked decrease in activity and a concurrent increase in desired selectivity when reused. However, this trend is not general. and the effect of reuse varies u i t h the specific catalyst used. This very pronounced effect of catal)-st reuse on selectivity as well as on activity could be very important in any development work with a copper chromite catalyst, particularly in a batch process. Effect of Catalyst Preactivation. T h e effect of preactivation of catalyst A with hydrogen is shown in Table 111. An experiment with reused catalyst is included for comparison. Pretreatment with hydrogen increases activity but decreases selectivity at both 400-600 and 900-1100 p.s.i.g. T h e preactivation treatment appeared to be accompanied by a small hydrogen absorption a t about 120' C. a t a pressure of about 1000 p.s.i.g. A similar absorption of hydrogen by such catalysts has been previously described (2). A copperchromium oxide catalyst also has been activated by refluxing in cyclohexanol, which was simultaneously partially converted into cyclohexanone ( 6 ) . Effect of Pressure. An increase in pressure increased the activity but decreased the selectivity of both a fresh catalyst
Copper Chromite-Catalyzed Alkylation of N-Phenyl-p-phen ylenediamine
a
180
Discussion
PRODUCT RESEARCH AND DEVELOPMENT
0.78 0.43 0.78
Yield, .Mole 7 0 Atl.'-tsopropylS'-phenvl.V;bhenylPPDb PPDa 93 70 92
0.1 28 0.2
M . P. of Crude Rest due Pioduct, a C.C 74.5-79 51-70 74-78
(‘Table 11.) and a preactivated catalyst (Table 111). Thus, formation of .\’-IPA is favored by low hydrogen pressure, bvhile rapid hydrogenation is favored by high pressure. T h e observed rate of hydrogen absorption is for the combined reductive alkylation and ketone hydrogenations. T h e large enhancement in selectivity at lower pressures probably is the most significant finding of this study. Effect of Ratio of Ketone to Amine. T h e yield of A‘-IPA \vas increased from 70 to SS%/,: and the rate of gas absorption !vas approximately doubled by raising the mole ratio of acetone to aniline from 4 : l to 8 : l a t 160’ to 165’ C. and 400-600 p.s.i.g. T h e same catalyst concentration was used in both experiments. This suggests that high conversions of the starting amine to the desired alkylated product can be achieved by using a large excess of ketone. .4lthough this may not be commercially feasible, it can be very useful in laboratory preparations. Synthesis of n‘-Isopropyl-4’-phenyl-p-phenylenediamine. A high yield of n’isopropyl-A’’-phenyl-fi-phenylenediarnine \vas obtained by the alkylation of .\’-phenyl-p-phenylenediamine with acetone using catalyst A (Table V). Stopping the reaction a t about 55y0of the total gas absorption resulted in a large recovery of unreacted :l’-phenyl-p-phenylenediamine ( 2 8 % ) , although the gas absorption was 170y0 of that theoreticall!- required for the alkylation reaction. This demon-
strates that the hydrogenation of acetone to 2-propanol takes place concurrently with the desired reductive alkylation. Acknowledgment
The authors are indebted to LVilliam T. Seville for the vapor phase chromatographic analyses. literature Cited
(1) Adkins, H., “Reactions of Hydrogen with Organic Compounds over Copper-Chromium Oxide and Nickel Catalysts.“ T h e University of IVisconsin Press, Madison, \Vis., 1937. (2) Adkins, H., Burgoyne, E. E., Schneider, H. J.. J . Am. Chew!. SOL.72, 2626 (1950). (3) Bramer: H. V., Davy, L. G., Clemens, M. L., .Jr. (to Eastinan Kodak), L.S. Patent 2,323,948 (July 13, 1943). (4) Emerson. \V, S., in “Organic Reactions,” Vol. IV, chap. 3. Wiley, X e w York, N. Y . , 1948. (5) Naugatuck Chemical Development Dept., Division of U. S. Rubber Go.?Naugatuck, Conn., unpublished work, 1958. (6) Nes. \V. R.. J . Org. Chem. 23, 899 (1958). (7) Ruggles, A. C. (to Eastman Kodak), U . S. Patent 2,494,059 (Jan. 10, 1950). (8) Stroupe, J. D., J . ,4772. Chem. Soc. 71, 569 (1949). (9) \Yard, S., Lamb, S. A , , Hodgson: M. A. E. (to ICI). Brix. Patent 712,100 (July 21, 1954); \Vard, S., Lamb, S. A. (to I C I ) , Brit. Patent 716,239 (Sept. 29, 1954). (10) IVard: S.. Lamb, S. .4., Hodgson, M. A. F,. (to ICI): Can. Patent 575,801 (May 12, 1959). RECEIVED for review May 8, 1962 .4CCEP’rED July 13, 1962
STABILITY OF THE URON RING IN WASH= WEAR FINISHING OF COTTON R I C H A R D L . A R C E N E A U X A N D J . D A V I D R E I D Southern Regzonal Research Laboralor), .Yeit’ Orleans, L a . Cotton fabric finished with N,N’-bis(methoxymethy1)uron has good wrinkle-resistance properties which are durable to repeated launderings and resistant to chlorine damage after repeated home-type and high temperature alkaline launderings. The stability of the uron ring in this agent is greater than that of N methyl-N’-methoxymethyluron and N,N’-dimethyluron. The latter is unstable under the acid conditions used in the application of cross-linking agents to cotton. An explanation for the cause of this difference is proposed. Properties of cotton fabric treated with pure N,N’-bis(methoxymethy1)uron and with a crude product are given.
research effort has been expended by various \\.orkers in the effort to modify dimethylolurea so that i t will be more satisfactory as a wash-xvear finishing agent, and particularly to improve resistance to chlorine damage after hypochlorite bleaching. A number of compounds derived from urea have been suggested, with the object of eliminating the amido hydrogens \vhich serve as sites for the formation of chloramide groups. Reasons for cloth degradation because of chloramide formation have been discussed recently (72). An obvious method of avoiding sites for chlorine retention would be to use the symmetrical dimethyloldimethylurea (I) to cross-link the cellulose. However, Einhorn (7) found that only monomethylol derivatives could be prepared from monoand disubstituted ureas. H e was unable to obtain a formaldehyde derivative of triethylurea under any condition. IYalker ( 7 5 ) suggests the formation of the tautomeric isoureas (II?111. IV), in which urea behaves like a n amino acid amide. to explain these facts, and concludes that useful resins are not GCH
formed when two or more urea hydrogen atoms have been replaced by alkyl groups. Another method of reducing the number of hydrogens available for reaction with chlorine would be to use tetramethylolurea (\’) as the cross-linking agent. However, although this compound has been claimed, there is no good evidence that it or even the trimethylolurea is stable in aqeous solution. Regardless of theory, the fact remains that the simple methyl01 derivatives of urea or methylurea are not practical for use in stable wash-wear finishes, and other methods have been sought to avoid chlorine damage. Research workers have used the cyclic ureas Lvith notable success to obtain cross-linking agents without hydrogen atoms on the nitrogens. Dimethylolethyleneurea (VI) has enjoyed great popularity. Other compounds in this series are the dimethyl01 derivatives of pyrimidinones, 4,5-dihydroxyethyleneurea? and the triazones. T h e resistance of these finishes to chlorine damage is predicated on blocking chloramide formaVOL. l
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