separation of Pd/C catalyst from Celite?

joe_aldehyde · huxleys associate

hypothetically speaking, how does one recover filtered catalyst from the celite/catalyst cake after filtration?

sony · Tue Jul 12, 2005 7:46 pm

Unless you dissolve your Pd in aqua regia, it doesnt look like you can completeley separate the catalyst from the celite.

If you pack the celite more tightly you can carefully remove the upper part which contains only a part of the Celite allong with most Pd/C this can be used in a new reaction.

64bandil · Busy Bee

Reused Celite and Pd/C mixtures works quite well... I usually reuse the whole lot.

anime · Wed Jul 13, 2005 4:31 am

java · Consumer

There is an article on the regenaration of the Pd catalyst in the hive archives............. as to how many times, as long as yhou can see that Hydrogen is beintaken up , that is a good sign , once exhausted it's usually poisoned .................java

the alchemist · Wed Jul 13, 2005 8:11 am

Just scrape the top layer of celite and reuse, i presume. How wmany times can you use the same Pd catalyst bandil? To think that people just quench this valuable resource into some NaOH solution after use... Sad

anime · Wed Jul 13, 2005 12:09 pm

64bandil · Busy Bee

I've reused Pd/C up to five times without loss of yield. Never tried to go above that - but im sure its possible with some catalyst cleaning.

joe_aldehyde · huxleys associate

about putting the catalyst in NaOH: does that really help at all? i've never seen any reference to that in OC books.

anime · Wed Jul 13, 2005 8:00 pm

yes, its generally used to reactivate the reaction.
Look at US3214385.

This was originally posted at the hive by Aurelius. Post No. 439554. First post thread is #434889
------
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.

Act quickly or not at all.
----------------

the alchemist · Wed Jul 13, 2005 8:38 pm

Hmmm... That is very interesting. I was taught by someone that putting the catalyst into a bottle of dilute aqueous NaOH soln deactivates the catalyst. You could even see the catalyst zip around the surface of the soln before dying out and settling to the bottom of the bottle.

spicybrown · Thu Jul 14, 2005 9:43 am

Regarding the celite, it's an inert material, you don't need to separate it at all. Just like bandil says, reuse the whole thing, the celite won't do anything or go anywhere, and then hey.. you filter it again!

-SpicyBrown

joe_aldehyde · huxleys associate

i'm SO dumb... Wink

speaking about inert material