rev drone [Image] posted 07-23-1999 02:58 PM
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LabTop,
Just to clarify what system we're looking at, let's take
a typical situation. Actually, I already posted it, but
let's look at it again, shall we? The SRV/KRV variation
of the Wacker.
At the end, in the solutioner we have:
EtOH
ketone
isomerized starting material
red tarry gunk
CuCl2
PdCl2
There is also some PdCl2 precipitated out of the solution
in the vessel. This is the situation we're looking at.
At this point, there is no "sludge", per se. The solution
is already less dense than DCM, and again the solvent
here is EtOH, which is miscible with DCM. "the Pd salt as
the only heavier part in it." Don't forget that the
densities of CuCl2, ketone, and isomerized starting
material are *all* denser than MeOH, in fact they are all
denser than H2O, and in the case of the inorganic
compounds, denser than DCM.
I really think precpitation is sounding better and
better. Dimethylgyoxime chelates the Pd2+ species, and
crashes out. This is filtered, and the filtrate added to
a ammonium hydroxide solution, boil. Now add HCl, and you
will precipitate out Pd(NH3)2Cl2, or palladium yellow.
This is kinda where it get's stuck...
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-the good reverend drone
LaBTop [Image] posted 07-24-1999 06:16 AM
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Are these Pd salts perhaps attrackted by a magnet?
If not, why not decant the mix,red tarry gunk GONE. Then
dissolve all the decants in DCM, and centrifuge.
Now you decant again, and you have a LAYERED mix of 2
solids: CuCl2 and PdCl2.
That looks simple to me to seperate...
The decanted fluids is another story, to be continued.
Eeh, do'nt forget I do'nt know the SRV/KRV, give me a url
please. [Image] LT/
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LaBTop [Image] posted 07-24-1999 11:42 AM
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Some new info on use of hexane to get rid of the tar from
MethylMan:
http://hive.lycaeum.org/ubb_board/Forum1/HTML/002102.html
[Image] LT/
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EMOTIONSwill always beFREE!
rev drone [Image] posted 07-24-1999 12:30 PM
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Pd salts aren't ferromagnetic, but that certainly is good
thinking. How would you remove the red tarry gunk? To
clarify myself, the gunk is dissolved in the EtOH.
I think we're having a communication problem. Let me
re-state what the situation is. At the end of the
reaction, one is left with an ethanolic solution of the
following:
* ketone (the actual final product of the reaction)
* isomerized starting material (a byproduct of the
reaction)
* red tarry gunk (a polymerized byproduct, fairly soluble
in organic solvents)
* CuCl2 (the cocatalyst)
* PdCl2 (the catalyst)
Everything I just lised is DISSOLVED in EtOH; they're all
in there, floating around together in solution. There is
a small amount of precipitated PdCl2. This is easily
enough filtered out, but it does not represent the bulk
of PdCl2 present; most of that is still dissolved in
EtOH.
Regarding all this "decanting", I think you must mean
something else.
quote:
-----------------------------------------------
decant \De*cant"\, v. t. [imp. & p. p.
Decanted; p. pr. & vb. n. Decanting.] [F.
d['e]canter (cf. It. decantare), prop., to pour
off from the edge of a vessel; pref. d['e]-(L.
de) + OF. cant (It. canto) edge, border, end.
See Cant an edge.] To pour off gently, as
liquor, so as not to disturb the sediment; or
to pour from one vessel into another; as, to
decant wine.
-----------------------------------------------
The red tarry gunk *CANNOT* be simply separated off by
decantation. As for your "Decants", I can only assume you
mean either 1)the sendiments left over after pouring, 2)
the liquid that was poured off. Either way, I don't
understand what you're doing.
Now I have to admit I'm skeptical. I have a hard time
believing that a home-made centrifuge, using a bicycle
tire, is going to be powerful enough to cause the two
inorganic salts in question to precipitate out in even
layers. Typical commercial centrifuges run in the range
of 10,000 to 100,000 rpm. If you're doing this on a small
scale, you're still talking about at least a kilogram of
solution being spun around at rather high velocities. If
you're taking about an industrial-scale batch (like one
of your 25 kg "sample batches"), you're talking about
using a centrifuge rotating possibly HUNDREDS of liters
of solution at 10,000 rpm. Your little sister's bicycle
wheel PROBOBLY won't work here. Then again, I guess I've
never seen what kind of bicycle your sister rides.
Now what I meant of course was a system THEORETICALLY
similar to the SRV/KRV procedure, which can be found at
http://rhodium.lycaeum.org/chemistry/mdp2p.srv.txt
. The
practical oxidation of safrole is a nice system to
analyze, but all of this is of course only academic
musings.
There are numerous chelating procedures in the
literature, though the one that stands out the most is
with dimethylglyoxime. The question is, once you've
formed a nicely-cheltated metal cmplex, how do you remove
the ligands to return to PdCl2?
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-the good reverend drone
rev drone [Image] posted 07-24-1999 12:40 PM
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I guess what I'm saying is, its very easy to recover
palladium using DMG, ETDA, 2,4-pentadione, etc., but then
one is left with an insoluble palladium chelate, like
PdDMG, but not PdCl2. MY question is, would treating the
chelated precipitate with HCl lead to PdCl2 again? If its
that easy, we 're set.
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-the good reverend drone
Osmium [Image] posted 07-26-1999 05:05 AM
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IMHO it would be best to quench the SRV with water,
extract the organics with hexane (which hopefully does
not dissolve anything inorganic), and collect the aq.
solution. Once you have enough of it (like several liters
containing 20g Pd or so), you can start your recycling.
Reducing agent which doesn't reduce the copper, followed
by some aqua regia or HCl/Cl2 or HBr/Br2 to make PdCl2
again. Or any other of the procedures mentioned above.
LaBTop [Image] posted 07-26-1999 11:58 AM
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I support the advise of Osmium, plus:
Palladium can be recovered by heating the spent catalyst
to redness in order to remove organic impurities.
The palladium is then dissolved out with aqua regia and
the solution evaporated; the residue is dissolved in hot
water and hydrochloric acid to form palladium chloride.
Vogel,first edition, 1948, page 670, Section IV,120,the
Rosenmund reduction of acid chlorides.
That's a simple answer to a simple question.
BTW, my sister rides a Norton Commander, a collectors
item.She's a wild woman, looks abit like, eeeh, Cher, but
then red. [Image] LT/
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LaBTop [Image] posted 07-26-1999 12:00 PM
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I support the advise of Osmium, plus:
Palladium can be recovered by heating the spent catalyst
to redness in order to remove organic impurities.
The palladium is then dissolved out with aqua regia and
the solution evaporated; the residue is dissolved in hot
water and hydrochloric acid to form palladium chloride.
Vogel,first edition, 1948, page 670, Section IV,120,the
Rosenmund reduction of acid chlorides.
That's a simple answer to a simple question.
BTW, my sister rides a Norton Commander, a collectors
item.She's a wild woman, looks a bit like, eeeh, Cher,
but then red. [Image] LT/
PS: why do I think your not satisfied with this.....?
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LaBTop [Image] posted 07-26-1999 12:01 PM
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I support the advise of Osmium, plus:
Palladium can be recovered by heating the spent catalyst
to redness in order to remove organic impurities.
The palladium is then dissolved out with aqua regia and
the solution evaporated; the residue is dissolved in hot
water and hydrochloric acid to form palladium chloride.
Vogel,first edition, 1948, page 670, Section IV,120,the
Rosenmund reduction of acid chlorides.
That's a simple answer to a simple question.
BTW, my sister rides a Norton Commander, a collectors
item.She's a wild woman, looks a bit like, eeeh, Cher,
but then red. [Image] LT/
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EMOTIONSwill always beFREE!
rev drone [Image] posted 07-26-1999 01:49 PM
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LabTop,
Sounds like your little sister would DEFINATELY not want
that to happen to her bike. [Image] Well, I guess you
think I'm not satisfied for several reasons: 1) Because
palladium chloride has a surprising tendancy to be
readily soluble in a lot of non-polar solvents, and so a
simple extraction like that is questionable (many Pd
complexes favor non-polar solvents; a fact that is
utilized in cases of Pd recovery where large amouns of
organic products aren't involved), 2) Because the
purification of palladium by reducing and regenerating
PdCl2 sounds like more work than it has to be 3) because
I can be a pernicious little jerk when it comes to this
stuff (I can't rest until I've examined something like
this backwards and forwards and from every possible
angle.)
Extracting with hexanes would nice, but I'm not so sure
it'll work. Oh yes, hexanes will extract the ketone, but
I'm not convinced that it wouldn't leave the palladium
salts alone. DCM, a rather non-polar solvent, when used
in this fashion, does an EXCELLENT job extracting both
product AND catalyst together. Now hexanes are definately
more non-polar, and this may do the trick -- I guess
someone will have to try it out (if I hear any rumors in
the near future, I'll keep y'all posted.) I'm definately
not ruling it out, mind you; this may be the way to go.
I'm just pointing out the fact this may not be the
solution.
As for the catalyst purification, yes heating palladium
to redness will destroy impurities, but I'd prefer to
avoid having to go back to the metallic form and
regenerating PdCl2 with aqua regia and HCl. Of course, if
all else fails, this would work, and it might not be so
bad if combined with the chelation step ( PdDMG is
precipitated, then reduced by roasting or by NaBH4 in
chloroform to the metallic form, yada, yada, yada.)
As I said before, Chelating Pd to extract it is still
pretty nice looking, though I have to admit I'm still not
100% certain as to the best means of making it back into
PdCl2. Thus far, I propose:
1. Precipitate Pd out of the solution with PdDMG
2. Dissolve PdDMG in excess NH4OH sol., boil, then add
HCl to crash out Pd species as easily-filtered palladium
yellow, Pd(NH3)Cl2
Now those extra amine ligands are a pain-in-the-ass, as
they are bonding to the palladium right where our
catalyst friend does its magical thing, but this may not
be too much of a problem. Those amines are very
loosely-bonded ligands.
Here's a question: if you carefully heated palladium
yellow, could it be selectively decomposed to PdCl2?
Rather than roast it all the way to Pd(0), could one just
heat it up enough to liberate the two ammonia
equivalents? According to the CRC, palladium yellow
decomposes at a fairly low temperature; is the product
from decomposition the stuff we want?
The problem is, there are tons of ref's on recovering Pd
as a metal, but few on keeping it as a salt. The result:
ton's of descriptions of recovering catalytically useless
salts and roasting them into Pd sponge.
Incidentally, in case anyone wanted to know, as everyone
already knows, Pd is oxidized by aqua regia, and PdCL2 is
obtainable that way, as well as by Cl2 gas at red heat,
but Pd can also be oxidized by nitric acid, yielding the
nitrate, Pd(NO3)2. This, when heated in H2O, decomposes
to yield Pd(OH)2 (a very active hydrogenation catalyst
indeed), which could be acidified to yield PdCl2.
Anyways, that's all I have to say 'bout that for now.
Please, if anyone out there knows the answer to my
question about the decomposition of Pd(NH3)2Cl2, pleeeez
say so.
Take care,
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-the good reverend drone
LaBTop [Image] posted 07-26-1999 06:42 PM
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Some ECONOMIC ruling of thumb:
When you have to consider the amount of labour, risk and
chemicals involved, would'nt it be a bit wiser to forget
the damned stuff, bill the EVENTUAL clients with a raise
in price, and buy from that your next batch of PdCl2 ? So
just filter it out?
And you still can liberate the pure Pd and use that in
numerous other (pressurized)hydrogenation
techniques...easier by the way...more yield by the way...
But I have the same problem: if it looks impossible,
that's the point when it gets really interesting, there's
allways a way, but at what costs and risks? [Image] LT/
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rev drone [Image] posted 07-26-1999 07:18 PM
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I did a search, and found that, yes indeed in
http://hive.lycaeum.org/ubb_board/Forum4/HTML/000402.html
everyman mentioned that extracting the ketone w/
petroleum ether was the preferred method, since it
extracts the ketone, while leaving the catalyst and red
tar behind. This is very good.
So, with this nugget of information, we know to add H2O,
then extract with pet. ether a few times. At that point,
The red gunk has (mostly) precipitated out, so a quick
filtration should get rid of most of the gunk remaining,
leaving a fairly clean solution of CuCl2 and PdCl2. The
PdCl2 can be extracted from there with DCM. For added
extraction power, tossing in a little more HCl ought to
persuade more of the PdCl2 to dissolve in the DCM layer.
For small-scale Wacker oxidations, it really doesn't pay
to get the palladium out. But for larger batches, at
$7/gram (bulk, and only if you're lucky), PdCl2 gets very
expensive.
Which reminds me of something. You seem to know a thing
or two about industrial production, so I figure you'd be
the one to ask. What industrial ketone synthesis would
you recommend? (Hypothetically speaking, of course.) It
seems it isn't a variation of the Wacker oxidation, so
which one is it?
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-the good reverend drone
LaBTop [Image] posted 07-26-1999 08:42 PM
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In my very past, I studied many ways of ketone synthesis,
and based on a few facts, mostly economical, only 2 made
it into the final:
[1]the one from I think UF with the bathtube safrole to
ketone, using PdCl2, and
[2]the performic acid one.
So with those recipees and a "bit" of money I went off to
the far east. There a perfume factory in financial
trouble was found, and after finding out they could not
get PdCl2 in sufficient quantities and on a steady
delivery basis, the choice was made for the performic
method. A lot of resistance had to be mastered about the
environmental aspects of the shitload of remaining
chemicals after the process, untill they found a way to
bring those to a waste-burning facility for a reasonable
price.
We made a setup from two 1000 liter reaction tanks,
rigged together with 3 big watercoolers/boilers and 2
watercooled tanks above that for the starting mix process
of the iso and the rest, so that that mixed together and
was controlled in a sight-glass by 2 valves. It then
flowed to the first 1000 liter water cooled tank and the
rate of flow controlled the reaction temp. A big mixer
inside provided enough vortexes.
After reaction ended, it was tapped in the second 1000
liter tank and 15 % H2SO4 was added etc etc.
That way they delivered every 4 weeks 1000 kg 65 to 85 %
raw MDP2P, which was transported to a seaport and brought
on board the ship under another name on the bill of
loading etc. etc.,then LOTS of trouble to get it in the
desired country where it was distillated to get 98% pure
MDP2P and you may guess what we did then... So,: the
Classical Performic Acid Method, very reliable, allways
ketone, only discrepancy in yields which were never
satisfactedly solved. [Image] LT/
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equarius [Image] posted 07-27-1999 09:52 PM
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Instead of recovering the Pd what about re-using the Pd
and solvent in solution as is. The goal being to create a
re-ussable catalytic reaction vessel.
This is pretty tricky because it would have to be
accomplished by extracting the oils without extracting
the Pd. A top dwelling extraction solvent would be much
preferred. Possible pet ether, ether, or toluene. Then
once extracted all one would do is add more CuCl2 and
Olefin, then wack away.
Obviuosly I don't have the chem knowledge, or even the
memory of what top dwells and what doesn't to make this
work.
Feasable??
jimwig [Image] posted 07-28-1999 04:19 PM
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Spitball-give Curtis Mayfield a credit line for writing
those words and music.
rev drone [Image] posted 07-31-1999 04:53 PM
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Equarius,
The problem is that there are still other byproducts in
there as well. Good thinking, but when this stuff is
over, there is some quite visible impurities that may
have an unpleasant effect on things. Remember this
mantra: garbage in, garbage out.
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-the good reverend drone
ymir [Image] posted 07-31-1999 06:44 PM
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It turns out that LabTop is probably correct about a
bicycle being able to be converted a centrifuge. A.
Gallenkamp and Co. Ltd., London marketed a hand
centrifuge in the past that worked similarly. The tubes
should pivot, and be balanced with .1 gram. One thing
about centrifugal seperations that should be noted is
that the tubes should be spun for at least five minutes,
and then allowed to slow down over a period of around ten
minutes, to prevent particles supernatent solution from
dispersing by swirling.
rev drone [Image] posted 07-31-1999 07:22 PM
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How on Earth are you going to practically make a
centrifuge from a bicycle tire that could separate even a
medium-sized batch of ketone? I'll stick to separation
technology.
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-the good reverend drone
ymir [Image] posted 07-31-1999 07:43 PM
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The same as any other engineer, by building one. I am
looking at a diagram of the aforementioned machine, it
got up to 3000 RPM. It's gear driven like a bicycle, so
his idea could be built by one with enough mechanical
aptitude. Obviously, not every member of the hive is able
to build their own equipment. Some are!
ymir [Image] posted 07-31-1999 09:13 PM
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A reference that explains how the early centrifuges used
in the sugar industry were built is to be found in
Metallurgical and Chemical Engineering, Vol. XI, No. 6,
p338-9. A basket design is published in Sugar, September
1919, p. 476. These designs are lower speed overhead
shaft drive units that need not be so precisely balanced.
rev drone [Image] posted 07-31-1999 09:22 PM
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I still am not sure as to what advantage a 3000 rpm
centrifuge would have over an extraction procedure, but
if an industrially useful one can be made, perhaps its
not entirely that impractical. I'm curious what these
schemes look like. What is your information source for
the A. Gallenkamp and Co. model centrifuge? I'll give
that other source a try as well.
Still though, why the interest in centrifuges over the
extraction/separation techniques?
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-the good reverend drone
Osmium [Image] posted 08-02-1999 04:06 AM
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I wouldn't want to be close when one of those home-made
bicycle-wheel centrifuges loaded with several liters of
spent solvents disintegrated. Good luck.
