Author Topic: Question concerning dehydrogenation  (Read 1616 times)

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jim

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Question concerning dehydrogenation
« on: October 22, 2001, 07:58:00 AM »
Does anybody have any reference to dehydrogenations ( more specifically dehydrogenations of saturated aromatics)  being carried out in a vapor?  Perhaps over a hot nickel, Pt, or Pd screen mesh, or maybe even aluma?

Any information gleened from helped would be immediately devulged upon verification.  Please help me out here...

Osmium

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Re: Question concerning dehydrogenation
« Reply #1 on: October 22, 2001, 01:34:00 PM »
In principle the same catalysts that allow you to hydrogenate aromatics should also allow you to dehydrogenate them. It´s an equilibrium (well, sorta)

jim

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Re: Question concerning dehydrogenation
« Reply #2 on: October 22, 2001, 04:09:00 PM »
I know that, but I have NO references concerning vapor phase dehydrogenation and I was hoping that maybe someone else does.  -Thank you for the response however.

terbium

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Re: Question concerning dehydrogenation
« Reply #3 on: October 23, 2001, 05:54:00 AM »
From Vogel, 1957 revision of 3rd edition:

Dehydrogenation of Hydroaromatic Compounds ... The principal dehydrogenating agents are (i) sulphur, (ii) selenium, and (iii) catalytic metals ... Paladium and platinum catalysts. These catalysts are generally employed with a charcoal or asbestos carrier. The dehydrogenation can be conducted in the vapour phase by distilling the compound through a tube containing the catalyst heated to 300-350°C, but the liquid phase method is generally more convenient. Charcoal or asbestos are employed containing 10-30% of the metal. It has been established that the best results are obtained by conducting the process in an actively boiling medium (e.g. mesitylene, b.p 165°; p-cymene, b.p. 177°; naphthalene, b.p. 218°; and alpha-methylnaphthalene, b.p. 242°) and to provide for elemination of the hydrogen as it is formed (e.g., by sweeping the system with a stream of carbon dioxide).

...

Dehydrogenation of Tetralin
For small scale dehydrogenations, the apparatus shown in Fig VI,35,1 may be used (the figure is of a small, what I would call a sublimation device. A cold finger condenser inserted into a larger glass tube. The sublimer has been modified by the adition of two small glass tubes to the outer tube, one near the level of the tip of the cold finger and the other farther up for sweeping with inert gas.). Place 2.5 g of purified tetralin and 0.25 g of palladised charcoal in the apparatus and heat to boiling for 4 hours in a slow current of CO2. Maphthalene m.p. 81° collects on the condenser in almost quantitative yield ... If the current of inert gas is omitted, the reaction is complete after about 22 hours.

jim

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Re: Question concerning dehydrogenation
« Reply #4 on: October 23, 2001, 04:04:00 PM »
Thank you

Vibrating_Lights

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Re: Question concerning dehydrogenation
« Reply #5 on: October 24, 2001, 05:03:00 AM »

lugh

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Re: Question concerning dehydrogenation
« Reply #6 on: October 24, 2001, 06:22:00 AM »
Some references concerning aromatics from saturated hydrocarbons via dehydrogenation: 

JACS 71, 2955,2959,2962 (1949)
JCS 1146 (1937)
JCS 1157 (1940)
JACS 72, 1993 (1950)
JACS 70, 2209 (1948)
JACS 62,1708 (1940)
JCS 1134 (1940)
JACS 63, 741 (1941)
JACS 67, 84 (1945)
JACS 62, 2220 (1940)
JACS 60, 624 (1938)
JACS 67, 1357 (1945)
JACS 68, 571 (571)
JACS 62, 983 (1940)
JACS 70, 145 (1948)
JACS 70, 381 (1948)
JACS 63, 1320 (1941)
JACS 65, 1097 (1943)
JACS 68, 258 (1946)
JACS 57, 2192 (1935)
JACS 59, 2351 (1937)
JACS 69, 1388 (1947)
JCS 266 (1937)
JCS 510 (1937)
JCS 1950 (1934)
Ind Eng Chem 38, 829 (1946)
Ind Eng Chem 41, 563 (1949)
Ind Eng Chem 40, 1751 (1948)
JCSI 68, 225-8 (1949)

a critical review by Plattner can be found in Newer Methods of Preparitive Organic Chemistry p 21 (1948)

PolytheneSam

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Re: Question concerning dehydrogenation
« Reply #7 on: October 25, 2001, 01:39:00 AM »

Post 205716

(PolytheneSam: "Re: Acetaldehyde synthesis", Methods Discourse)


http://www.geocities.com/dritte123/PSPF.html

lugh

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Re: Question concerning dehydrogenation
« Reply #8 on: October 25, 2001, 03:43:00 AM »
Some other references on catalytic dehydrogenation of secondary alcohols into ketones are:

JACS 61, 3359 (1939)
JACS 68, 1385 (1946)
JACS 62, 2874 (1940)
JACS 70, 4247 (1948)
Bul Soc Chim France (5e) 8, 3359 (1939)
JOC 13, 455 (1948)
JOC 11, 788 (1946)

lugh

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Re: Question concerning dehydrogenation
« Reply #9 on: October 26, 2001, 03:24:00 PM »
Catalytic dehydrogenation of primary alcohols in the vapor phase has be studied in detail in Catalytic Oxidation of Organic Compounds in the Vapor Phase by Marek and Hahn pp 37-99 (1932)
Some other references on dehydrogenation of primary alcohols to obtain aldehydes:
JACS 55, 2992 (1933)
JACS 51, 1246 (1929)
JACS 62, 2874 (1929)
JCS 282 (1943)
JCS S25 (1950)
JCS 3361 (1950)
JOC 8, 160 (1943)
JOC 14, 1103 (1949)
JOC 14, 790 (1949)
JOC 3, 242 (1938)
JOC 10, 501 (1945)
JOC 10, 492 (1945)
Or Syn Coll Vol II 142 (1943)
Ind Eng Chem 42, 768 (1950)
Ind Eng Chem, Anal Ed 16, 441 (1944)
Bull Soc Chim Fr (3) 11, 300 (1894)
Bull Soc Chim Fr (4) 3, 119 (1908)