Author Topic: Pd/C preparations and varying activity!  (Read 10290 times)

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ClearLight

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Pd/C preparations and varying activity!
« on: May 22, 2003, 09:50:00 PM »
In Rylander's book ( thx orgk!) he describes a paper which discuss the variations in degree of activity of preparations of Pd/C catalyst's all using the same base materials.

  If anyone has library access, the following journal article is the reference for this statement.

 J. Org. Chem. 18, 227 (1953) j.g young, w.h. hartung and H.H. Daniels


   This should be a very interesting read if someone would be kind enough to post it..



roger2003

  • Guest
special preparation
« Reply #2 on: May 23, 2003, 03:53:00 AM »
A special preparation for a one step (low pressure) reduction of 1-phenyl-2-nitropropene LT/:Edit: to amphetamine (1-phenyl-2-aminopropane)End Edit:

Patent US3458576


Barium

  • Guest
Oh yes!
« Reply #3 on: May 23, 2003, 05:03:00 AM »
Roger I could kiss you!! Thank you for finding that patent  ;D


roger2003

  • Guest
Pd/C reactivation
« Reply #4 on: June 12, 2003, 07:11:00 AM »
And a reactivation method for Pd/C

Patent US3214385

:

LaBTop

  • Guest
Good idea.
« Reply #5 on: June 12, 2003, 08:36:00 AM »
Basicly: Treat spent catalyst (5%Pd/C) with dilute (5-10%) NaOH or KOH aqueous solution, then washing the catalyst with water, drying the catalyst, and expose the catalyst to air.

Have seen this mentioned several times before here, f.ex. by PolytheneSam?
Still good idea. LT/


LaBTop

  • Guest
Quite old,
« Reply #6 on: June 12, 2003, 09:18:00 AM »
that pdf file which Rhodium digged up so fast, it has something to remind however:

""Aside from theoretical considerations, the results of this study serve to em-
phasize the importance of accuracy and precision in catalytic hydrogenation ex-
periments, and indeed, add impetus to the statement of Homer Adkins (3):
“It may not be amiss, however, to suggest that the author of a paper upon
catalytic hydrogenation should state exactly how he prepared his catalyst ; how
much of it and the hydrogen acceptor be used; a t what pressure of hydrogen, at
what temperature, and for how long the reaction was carried out; and how much
of each product was actually isolated in a pure state.”  ""

The last link from roger is a 20 years younger one, and there are many recent studies written on this same subject, see the Catalysts Degussa site,

http://www.sivento.de/catalysts/

  or the Johnson Matthey Catalysts website, or mine around at Espaceweb. LT/


Barium

  • Guest
Reactivation
« Reply #7 on: June 12, 2003, 09:30:00 AM »
Perhaps simple treatment with 2 or 3N sulfuric acid with slight heating (50-60°C) will reactivate Pd or Pt catalyst after amine production too? I've heard that this will be sufficient unless the crystal structure has been changed due to too high temperatures during reaction. Then metal recovery by aqua regia treatment must be done and the catalyst prepared again.


Aurelius

  • Guest
US Patent 3214385 butyrolactone catalyst recovery
« Reply #8 on: June 12, 2003, 11:07:00 AM »
US Patent 3214385

Reactivation of Spent Pd/C Hydrogenation Catalyst


Abstract:

Catalyst having been used in the manner of this patent can be regenerated using washes with dilute alkali metal hydroxide solution, washing the catalyst with water until the washing have pH of 7.5-10.0, drying the catalyst, and then exposing the catalyst to an oxygen containing gas.  This procedure increases the number of times the catalyst may be used without substantial reduction in catalytic activity.


Example 1:

A: (Initial Reaction)

100 parts succinic anhydride, 450 parts ethyl acetate and 8 parts of 4.5% Pd/C were charged to a stainless steel, rocking autoclave.  The temperature was brought to 40*C and the agitation started.  Hydrogen was introduced to the autoclave to a pressure of 1200 psig.  The hydrogenation reacted for one hour and the temperature was allowed to rise to 75*C.  The reaction mix was then cooled, filtered through a medium-porosity sintered glass filter to remove the catalyst and then distilled at atmospheric pressure to remove the ethyl acetate and water.  The residue was vacuum distilled at to give 79 parts of a fraction boiling at 91-92*C/17mmHg.  This corresponds to a 90% of butyrolactone.

B: (Recycling the Catalyst)

The catalyst on the filter was washed with 40 parts of ethyl acetate at RT to remove crude product.  After drying for 10 minutes with the aid of suction, the catalyst was slurried with 2x40 part portions of 5% aq. NaOH solution at RT, being filtered after each portion.  The catalyst was then slurried for 4 minutes with 2x40 parts of water, between each of which the catalyst was filtered off.  The wet catalyst was then dried with filtered air for 10minutes during which time heat was evolved.  The catalyst thus obtained was recycled to the autoclave and the hydrogenation above was carried out with the recycled catalyst.


Notes:

The catalyst gave yields of 84-91% of theory in all reactions.  (The 84% was achieved after 18 uses of the same catalyst having been run successive reaction/cleaning cycles.)  In some cases alcoholic (ethanol or methanol) NaOH or KOH solution were used for the catalyst recovery with no change in activity when compared with aqueous NaOH or KOH washings. 

In a 4-reaction cycle the yields were as follows, respectively, 94, 72, 36, 92% yields.  The first used fresh catalyst and was not recycled until after the third reaction showing the effectiveness of said recovery procedure.



Aurelius

  • Guest
US Patent 3458576 reduction of phenylnitropropene
« Reply #9 on: June 12, 2003, 11:35:00 AM »
US Patent 3458576

Reduction of Arylnitropropenes


Abstract:

Phenylnitropropenes are hydrogenated under mild conditions, e.g. at a temperature under 100*C and a pressure of less than 75psig., in the presence of a slurry of a catalyst in the hydrogenation solvent which has been treated at 45*C for about 4 minutes prior to the hydrogenation.  Pd, Pt, and mixtures of these metals with non-pyrophoric nickel are the catalyst used.


Treatment of the Catalyst:

The catalyst is first slurried in the hydrogenation solvent, e.g. methanol.  The actual time and temperature conditions employed may be varied to some extent  depending on the boiling point of the solvent and the particular catalyst used.  The amount of time required for the heating is indirectly proportional to the amount of heat applied.  For the preparation of catalysts for the reduction of the title compounds, it has been found that the best time and temperature are 3-5 minutes and 40-50*C, respectively.  After the heat treatment, the solvent mass is cooled with a water bath.  The mixture is added to the hydrogenation vessel shortly after its preparation for use.

Example 1:

The materials employed are as follows: 12.5 parts 1-phenyl-2-nitropropene, 53 parts absolute ethanol, 1 part glacial acetic acid, 2.5 parts of 5% Pd/C and enough H2 to maintain a pressure of 64 psig for the duration of the reaction.  Temperature ranged from 46-67*C. 9.02g of amphetamine sulfate was recovered from the reaction mixture after isolated using standard acid/base procedures.  This corresponds with a yield of 64%.

Notes:

A minimum of 0.01 parts of noble metal catalyst must be applied to the non-pyrophoric nickel catalyst for the benefit of this treatment to work.  Pd/C is the preferred catalyst.    For unexplained reasons, pure nickel catalysts are unable to receive benefit from this treatment.  It is apparent though that the mixtures act much differently than the separate pure catalyst.  Operating hydrogenation pressures after treatment range from below 60 to over 500psig.  The optimum pressure being 75psig.  Operating temperatures after treatment range from 25-100*C.  The temperature found to be optimum changes as per solvent used.  Methanol is best employed at a temperature of 25-50*C while ethanol is best used from 45-80*C.  In most cases, 1.5-2hours times was enough for hydrogenation completion.


Aurelius

  • Guest
US patents 3113138 287628 2772292
« Reply #10 on: June 12, 2003, 12:12:00 PM »
Low yielding or otherwise not advantageous patents for butyrolactone

US Patent 3113138
82-94% butyrolactone from succinic anhydride
94% butyrolactone from maleic anhydride
(just a primary reference from the procedure given below)

Uses the procedure found in

Post 439554

(Aurelius: "US Patent 3214385 butyrolactone catalyst recovery", Methods Discourse)


US Patent 287628
20% butyrolactone from succinic anhydride

US Patent 2772292
74% butyrolactone from succinic anhydride
(uses 2000+psi and 250*C+)


Barium

  • Guest
US Patent 3458576 tried for 2,4-DMA
« Reply #11 on: July 19, 2003, 05:04:00 AM »
Low-pressure catalytic hydrogenations of nitroalkenes to aminoalkanes have always interested me. Unfortunately it has always been next to impossible according to the litterature unless massive amounts of catalyts are used.

Patent US3458576

changed this with a great step in the right direction. The authors still use a huge amount of catalyst. But I guess I can live with that.

The method described was tried with 1-(2,4-dimethoxyphenyl)-2-nitropropene but gave only 23% amine. I suspected the low amount of acetic acid used in the patent could be the reason so I tried it again this time with 5 mol eq. acetic acid. This time I got 58% amine. In the trial I used 20% w/w 5% Pd/C pre-treated with 4 bar H2 at 65°C for 6 minutes, for 8g of the nitroalkene in 50ml EtOH. The hydrogenation temperature was then 65-75°C and the pressure was kept between 4-5 bar for 4 hours.


roger2003

  • Guest
Pd/C
« Reply #12 on: July 19, 2003, 10:42:00 AM »
Old Germans use al lot of Pd/C. In the patent

Patent DE968545



they use 50g Pd/C to convert 60g Ephedrine/Hcl in Meth.
But it works

;)


ragnaroekk

  • Guest
thats not right - no Pd/C was used
« Reply #13 on: July 19, 2003, 05:52:00 PM »

Old Germans use al lot of Pd/C. In the patent

Patent DE968545

they use 50g Pd/C to convert 60g Ephedrine/Hcl in Meth.
But it works




In this patent they use palladium sponge what is not Pd/C at all. Thats plain palladium black in spongeous form AFAIK. The amount palladium is enormous here!  I believe the patent belonging to this kind which are made for a company planning to manufacture a compound to proof to own a procedure and so not having to pay license fees. How they really do it in the factory - nobody knows.
But yes, it should work. If a benzylic alcohol can be reduded with palladium this should work.

Don´t mind roger, UF made the same mistake when he transfered this patent in one of his books.  ;)  He also forgot to reference it.....




roger2003

  • Guest
You are right
« Reply #14 on: July 20, 2003, 02:06:00 AM »
You are right

"Palladiummohr" means fine powdered palladium black

http://www.seilnacht.tuttlingen.com/Lexikon/46Palla.html


java

  • Guest
Re: The method described was tried withÊ...
« Reply #15 on: August 03, 2003, 03:56:00 PM »

The method described was tried with 1-(2,4-dimethoxyphenyl)-2-nitropropene but gave only 23% amine. I suspected the low amount of acetic acid used in the patent could be the reason so I tried it again this time with 5 mol eq. acetic acid. This time I got 58% amine. In the trial I used 20% w/w 5% Pd/C pre-treated with 4 bar H2 at 65°C for 6 minutes, for 8g of the nitroalkene in 50ml EtOH. The hydrogenation temperature was then 65-75°C and the pressure was kept between 4-5 bar for 4 hours




Barium, will this method work with nitromethane in the conversion to methylamine?  The pre-treatment of the catalyst in the acetic acid is for what,... to modify the catalyst ?  Is the reaction necessary to heat up since I've herd that most nitrate reductions are exothermic?

In using a Parr Hydrogenator the hydrogenation is fast and efficient, hence so why would it take so many hours to hydrogenate ?  Is the hydrogenation of nitrates that difficult for the hydrogen to replace the Oxygen and make H2O and methylamine. I'm willing to try it but want to read all the information and possible hazards noted by those that have tried the procedure.

I missed your post so I started a thread on the search for the answers with someone that has had hands on or is familiar with the literature with the process.....java

Post 451095

(java: "A question about methylamine synthesis", Chemistry Discourse)




Barium

  • Guest
Methylamine
« Reply #16 on: August 04, 2003, 07:16:00 AM »
Hi Java, the reaction conditions I used to make 2,4-dimethoxyamphetamine from the nitropropene is not necessary if you want to make methylamine from nitromethane. Beside from not being needed, those conditions would be outright dangerous.

Nitrometane is by far easier to reduce than the nitropropene I used so both lower temperature and a lower catalyst loading would be needed in order not to get a very violent exotherm. I would use about 5% w/w 5%Pd/C (5g catalyst/100g nitromethane) while keeping the reaction temperature at between 40-60°C and the pressure at 3-5 bar.

The pre-treatment I used is jsut a way to "activate" the catalyst. What happens is probably that the catalyst is saturated with hydrogen. Why it gives this effect I don't know.

The Parr-system is outdated nowdays both in terms of safety and efficiency. The bottles used doesn't have the correct shape for work under pressure and the mixing by shaking is not particulary efficient to transfer gaseous hydrogen to the catalyst surface. The reactor should have the form of a cylinder with a rounded bottom (like a gas cylinder). Parr uses flasks with flat bottoms as well as a neck - not good. High efficiency mixing is done with stirring not by shaking. This gives the highest surface area of the gaseous hydrogen which is of utmost importance for a good and steady reaction rate.


java

  • Guest
Re: About the hydrogenation of nitrates
« Reply #17 on: August 04, 2003, 12:22:00 PM »
Barium: thanks for the direction as I plan to put a cooling jacket on my parr borosilicate bottle  with a thermocuple to monitor the temp . So I can run it in methanol while observing the catalyst ratio your provided , also assuming the pre treatment of the catalyst is not necessary. . While the reaction  is exothermic  I will cool it down  with the water circulating jacket, such that at the end I will have methyl amine in methanol. I could then gas it or add Hcl and remove the methanol to get methylamine Hcl salts , correct me if I'm wrong......java

P.S. thanks again for your help as there is much misinformation about this procedure from the impossible to the extreme danger, but then none had hands on experience to give first hand reports.


roger2003

  • Guest
Pd/C
« Reply #18 on: August 05, 2003, 04:51:00 AM »
Poisioning and deactivation of palladium catalysts:

Journal of Molecular Catalysis A: Chemical 173 (2001)275-286

http://www2.sivento.de/sivento/uploads_all/text/Poisoning_and_deactivation.pdf




Barium

  • Guest
Nitromethane reduction
« Reply #19 on: August 06, 2003, 05:45:00 AM »
I plan to put a cooling jacket on my parr borosilicate bottle  with a thermocuple to monitor the temp . So I can run it in methanol while observing the catalyst ratio your provided , also assuming the pre treatment of the catalyst is not necessary. . While the reaction  is exothermic  I will cool it down  with the water circulating jacket, such that at the end I will have methyl amine in methanol. I could then gas it or add Hcl and remove the methanol to get methylamine Hcl salts

Do small batches first until you get the hang of how this reduction works. Then you can increase the batch size stepwise. What cooling area does your jacket provide? Remember that glass is a poor heat conductor so any strong exotherm might become a runaway reaction if you can't cool it down quick and efficient.

If you run a hydrogenation and the temperature and pressure starts to rise rapidly, the first thing to do is to cut the hydrogen supply and stop the stirring/shaking. This kills the reaction since no more hydrogen is delivered.

Don't start with a 100g batch. Start with a 10g batch and work your way up.