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Production of higher ketones by the dehydrogenation of secondary alcohols over copper-chromium and nickel-chromium catalysts
PRODUCTION OF H I G H E R KETONES BY THE D E H Y D R O G E N A T I O N OF SECONDARY ALCOHOLS OVER C O P P E R - C H R O M I U M AND NICKEL-CHROMIUM CATALYSTS* A. N . ~BASHKIROV, V. V. K A M Z O L K I N a n d M. M. 1)OTARIN A. V. Topchiev Institute of Petroleum-Chemical Synthesis, U.S.S.R. Academy of Sciences
(Received 29 July 1963)
THE possibility of obtaining higher aliphatic ketones by the liquid-phase dehydrogenation of the corresponding secondary alcohols, obtained in their turn by the oxidation of paraffinic hydrocarbons in the presence of boric acid [2], has been shown previously [1]. In this work the catalyst was Raney nickel. It appeared to be desirable to investigate also the possibility of dehydrogenating the alcohols over certain catalysts widely used in industrial hydrogenation processes.
rnmole/g
3"0
•
•
2
0
3
~-- 1
2"0
2"0
1"0,
3"0
/
~
~
2
~
4
1
1"0
6 Hours
?-~"3 ~ ' ~ z ~ " l
0
2
FIG. 1
4
8
8 Hours
FIG. 2
FIG. 1. Influence of the temperature on the dehydrogenation of secondary alcohols over a copper-chromium catalyst: • - - c a r b o n y l compounds; O--alcohols; ~_.~--unsaturated compounds. 1 - 2 0 0 ° ; 2--220 °. FIG. 2. Influence of the pressure on the dehydrogenation of secondary alcohols over a copper-chromium catalyst at 220°: • - - c a r b o n y l compounds; ©--alcohols; / \ - - u n s a t . urated compounds. 1--760 m m Hg; 2--360 m m Hg; 3--240 m m Hg. * Neftekhimiya 4, No. 2, 298-301, 1964. 73
74
A.N. BASHKIROVet
al.
In the present work are given the results of the liquid-phase dehydrogenation of secondary aliphatic alcohols and of cyclododecanol over copper-chromium and nickel-chromium catalysts. The experimental procedure, the analyses of the reaction products, and the nature of the initial alcohols have been given in the previous paper [1]. In addition to analysing the dehydrogenizate obtained, in some experiments we measured the amount of hydrogen liberated in the reaction. The influence of the temperature, the pressure, the reaction time, and other factors on the dehydrogenation of higher secondary alcohols over copper-chromium catalysts was studied. It was found that a rise in the temperature increased the velocity of dehydrogenation and the degree of conversion of the initial alcohols (Fig. 1). At 220 ° it was possible to obtain a yield of ketones of ~75~o molar. A further rise in the temperature did n o t substantially affect the yield of ketones. Performing the reaction under reduced pressure somewhat raised the velocity of the process but did not increase the limiting degree of conversion (Fig. 2). A reduction in the amount of catalyst from 10% by weight to 5% by weight did not affect t h e velocity and degree of conversion of the initial alcohol. The catalyst can be used repeatedly without any appreciable loss in activity. Volume of H2,Nl 2 0"5
I
0
1
2 Hours
]FIG. 3. Dehydrogenation of cyclododeeanol over an unredueed copper-chromium catalyst: 1--200°; 2-220°; 3-200 °, reduced catalyst. We studied the dehydrogenation of cyclododecanol, obtained by the oxidation of cyclododecane in the presence of boric acid [3], in addition to that of the aliphatic alcohols. The cyclododecanol subjected to dehydrogenation (hydroxyl No. 268.8, carbonyl No. 27.7) contained about 10% molar of cyclododecanone. Figure 3 gives the kinetic curves for the dehydrogenation of this alcohol (from the hydrogen liberated). The dehydrogenizate obtained at 220 ° was characterized by a hydroxyl No. of 20-0, a carbonyl No. of 245.0, and an iodine No. of 0.64, which correspond to a degree of conversion of the alcohol of 92.5% molar and a yield of ketone of 91"0~o molar, calculated on the initial alcohol.
Production of higher ketones
75
The results show that the catalyst gains in activity during the reaction (curves 1 and 2, Fig. 3), while at a higher temperature the reaction takes place faster. The hypothesis has been put forward that this phenomenon of the "evolution" of the catalyst m a y be connected with its reduction b y the hydrogen liberated in the dehydrogenation process. In view of this, in some experiments the catalyst was subjected to reduction with hydrogen at 200 ° and a space velocity of 1000 hr -1 for 2 hours. The results of the dehydrogenation of cyclododecanol over a previously reduced catalyst showed that its activity did not increase during the reaction (curves 1 and 3, Fig. 3) and the rate of dehydrogenation was approximately one third of the maximum rate of dehydrogenation over an nnreduced catalyst. A similar investigation was carried out on the dehydrogenation of secondary aliphatie alcohols and cyclododecanol over a nickel-chromium catalyst. An investigation of the influence of the temperature on the dehydrogenation of the secondary alcohols at atmospheric pressure in the temperature range between 185 and 220 ° showed that the nickel-chromium catalyst does not possess appreciable activity at a temperature below 185 °. During the first 2 hours, there was practically no evolution of hydrogen or increase in the carbonyl numbers. At higher temperatures, the formation of ketones and the consumption of the alcohols took place at a considerable rate and at 220 ° the dehydrogenation process was practically complete in 2 hours. The shape of the kinetic curves was similar to those for the dehydrogenation of alcohols over the copper-chromium catalyst. The yield of ketones was 77.4% molar. Carrying out the process at reduced pressure did not lead to an increase in the yield of carbonyl compounds. In the dehydrogenation of cyclododecanol (at 220 °, reaction time 1.25 hour), a yield of ketones of 93.6% molar at a degree of conversion of the initial alcohol of 97-2% molar was obtained. In dehydrogenation over the nickel-chromium catalyst (200 ° ) there was an increase in the activity of the catalyst during the reaction similar to that found in the dehydrogenation of alcohols over the copper-chromium catalyst. SUMMARY
1. The higher ketones of the paraffinic and naphthenic series can be obtained b y dehydrogenating the corresponding secondary alcohols in the liquid phase over copper-chromium and nickel-chromium catalysts. 2. Under optimum conditions, the degree of conversion of the initial alcohols amounts to 90-95% molar; in the dehydrogenation of the higher aliphatic alcohols the yield of ketones reaches ~ 75 °/o molar and in the dehydrogenation of eyelododecanol more than 90% molar. 3. Dehydrogenation over the catalysts studied takes place at a higher temperature than over R a n e y nickel. Tra~slated by B. J. HAZZA~D
76
A . N . BASHKn¢OVe t a [ .
REFERENCES 1. A. N. BASHKIROV, V. V. KAMZOLKIN, M. M. POTARIN and G. D. KOLOVERTNOV, Dokl. Akad. Nauk SSSR 131, 1067, 1960 2. A. N. BASHKIROV, Khim. n a u k a i prom., No. 1, 273, 1956 3. A. N. BASHKIROV, V. V. KAMZOLKIN, K. M. SOKOVA, T. P. ANDREYEVA, V. V. KORNEVA and L. I. ZAKHARKIN, l~eftekhimiya 1, No. 4, 527, 1961
(Received 29 July 1963)
THE possibility of obtaining higher aliphatic ketones by the liquid-phase dehydrogenation of the corresponding secondary alcohols, obtained in their turn by the oxidation of paraffinic hydrocarbons in the presence of boric acid [2], has been shown previously [1]. In this work the catalyst was Raney nickel. It appeared to be desirable to investigate also the possibility of dehydrogenating the alcohols over certain catalysts widely used in industrial hydrogenation processes.
rnmole/g
3"0
•
•
2
0
3
~-- 1
2"0
2"0
1"0,
3"0
/
~
~
2
~
4
1
1"0
6 Hours
?-~"3 ~ ' ~ z ~ " l
0
2
FIG. 1
4
8
8 Hours
FIG. 2
FIG. 1. Influence of the temperature on the dehydrogenation of secondary alcohols over a copper-chromium catalyst: • - - c a r b o n y l compounds; O--alcohols; ~_.~--unsaturated compounds. 1 - 2 0 0 ° ; 2--220 °. FIG. 2. Influence of the pressure on the dehydrogenation of secondary alcohols over a copper-chromium catalyst at 220°: • - - c a r b o n y l compounds; ©--alcohols; / \ - - u n s a t . urated compounds. 1--760 m m Hg; 2--360 m m Hg; 3--240 m m Hg. * Neftekhimiya 4, No. 2, 298-301, 1964. 73
74
A.N. BASHKIROVet
al.
In the present work are given the results of the liquid-phase dehydrogenation of secondary aliphatic alcohols and of cyclododecanol over copper-chromium and nickel-chromium catalysts. The experimental procedure, the analyses of the reaction products, and the nature of the initial alcohols have been given in the previous paper [1]. In addition to analysing the dehydrogenizate obtained, in some experiments we measured the amount of hydrogen liberated in the reaction. The influence of the temperature, the pressure, the reaction time, and other factors on the dehydrogenation of higher secondary alcohols over copper-chromium catalysts was studied. It was found that a rise in the temperature increased the velocity of dehydrogenation and the degree of conversion of the initial alcohols (Fig. 1). At 220 ° it was possible to obtain a yield of ketones of ~75~o molar. A further rise in the temperature did n o t substantially affect the yield of ketones. Performing the reaction under reduced pressure somewhat raised the velocity of the process but did not increase the limiting degree of conversion (Fig. 2). A reduction in the amount of catalyst from 10% by weight to 5% by weight did not affect t h e velocity and degree of conversion of the initial alcohol. The catalyst can be used repeatedly without any appreciable loss in activity. Volume of H2,Nl 2 0"5
I
0
1
2 Hours
]FIG. 3. Dehydrogenation of cyclododeeanol over an unredueed copper-chromium catalyst: 1--200°; 2-220°; 3-200 °, reduced catalyst. We studied the dehydrogenation of cyclododecanol, obtained by the oxidation of cyclododecane in the presence of boric acid [3], in addition to that of the aliphatic alcohols. The cyclododecanol subjected to dehydrogenation (hydroxyl No. 268.8, carbonyl No. 27.7) contained about 10% molar of cyclododecanone. Figure 3 gives the kinetic curves for the dehydrogenation of this alcohol (from the hydrogen liberated). The dehydrogenizate obtained at 220 ° was characterized by a hydroxyl No. of 20-0, a carbonyl No. of 245.0, and an iodine No. of 0.64, which correspond to a degree of conversion of the alcohol of 92.5% molar and a yield of ketone of 91"0~o molar, calculated on the initial alcohol.
Production of higher ketones
75
The results show that the catalyst gains in activity during the reaction (curves 1 and 2, Fig. 3), while at a higher temperature the reaction takes place faster. The hypothesis has been put forward that this phenomenon of the "evolution" of the catalyst m a y be connected with its reduction b y the hydrogen liberated in the dehydrogenation process. In view of this, in some experiments the catalyst was subjected to reduction with hydrogen at 200 ° and a space velocity of 1000 hr -1 for 2 hours. The results of the dehydrogenation of cyclododecanol over a previously reduced catalyst showed that its activity did not increase during the reaction (curves 1 and 3, Fig. 3) and the rate of dehydrogenation was approximately one third of the maximum rate of dehydrogenation over an nnreduced catalyst. A similar investigation was carried out on the dehydrogenation of secondary aliphatie alcohols and cyclododecanol over a nickel-chromium catalyst. An investigation of the influence of the temperature on the dehydrogenation of the secondary alcohols at atmospheric pressure in the temperature range between 185 and 220 ° showed that the nickel-chromium catalyst does not possess appreciable activity at a temperature below 185 °. During the first 2 hours, there was practically no evolution of hydrogen or increase in the carbonyl numbers. At higher temperatures, the formation of ketones and the consumption of the alcohols took place at a considerable rate and at 220 ° the dehydrogenation process was practically complete in 2 hours. The shape of the kinetic curves was similar to those for the dehydrogenation of alcohols over the copper-chromium catalyst. The yield of ketones was 77.4% molar. Carrying out the process at reduced pressure did not lead to an increase in the yield of carbonyl compounds. In the dehydrogenation of cyclododecanol (at 220 °, reaction time 1.25 hour), a yield of ketones of 93.6% molar at a degree of conversion of the initial alcohol of 97-2% molar was obtained. In dehydrogenation over the nickel-chromium catalyst (200 ° ) there was an increase in the activity of the catalyst during the reaction similar to that found in the dehydrogenation of alcohols over the copper-chromium catalyst. SUMMARY
1. The higher ketones of the paraffinic and naphthenic series can be obtained b y dehydrogenating the corresponding secondary alcohols in the liquid phase over copper-chromium and nickel-chromium catalysts. 2. Under optimum conditions, the degree of conversion of the initial alcohols amounts to 90-95% molar; in the dehydrogenation of the higher aliphatic alcohols the yield of ketones reaches ~ 75 °/o molar and in the dehydrogenation of eyelododecanol more than 90% molar. 3. Dehydrogenation over the catalysts studied takes place at a higher temperature than over R a n e y nickel. Tra~slated by B. J. HAZZA~D
76
A . N . BASHKn¢OVe t a [ .
REFERENCES 1. A. N. BASHKIROV, V. V. KAMZOLKIN, M. M. POTARIN and G. D. KOLOVERTNOV, Dokl. Akad. Nauk SSSR 131, 1067, 1960 2. A. N. BASHKIROV, Khim. n a u k a i prom., No. 1, 273, 1956 3. A. N. BASHKIROV, V. V. KAMZOLKIN, K. M. SOKOVA, T. P. ANDREYEVA, V. V. KORNEVA and L. I. ZAKHARKIN, l~eftekhimiya 1, No. 4, 527, 1961