Sciencemadness Discussion Board - Parr Shaker Hydrogenator

Parr Shaker Hydrogenator

Ozonelabs - 20-2-2009 at 08:15

Hello everyone.

At Ozonelabs, having recently sourced pure, pressurised Hydrogen as well as an appropriately priced Hydrogenation catalyst we are searching for a Shaking Parr Hydrogenator.

Should anyone happen to have one that is in full working order for sale please do personal message us!

We seem to recall having seen (perhaps by Sauron) these offered on this board in the past...

Thankyou in advance for any replies.

Ozonelabs

chemrox - 20-2-2009 at 08:19

I got the one Sauron posted about and am delighted with it. The vendor is no longer in business; a victim of the 'free market economy.' I have Pd/C and nothing else but am going to use Rainy Ni some day (a Rainy day?) soon.

Sauron - 20-2-2009 at 11:45

Actually the vendor IS still in business, just under another name, This is the 4th name change in the decade I have been doing business with these people. The proprietor is Larry Turner in Muskeegon, MI. Used to be Turner Technologies, then WestShore Tech, then Surplus Labs, now Waters Edge. AFAIK same location.

As chemrox knows I had a dispute with one of their staffers, and quit doing business with them. That was shortly after chemrox bought that Parr shaker. I goy own Parr shaker from someone else but my Parr autoclave from Larry Turner and a whole lot of other stuff.

They terminated the woman who gave me a problem. But I have not bought from them since.

stoichiometric_steve - 20-2-2009 at 13:21

i need one, too!

chemrox - 20-2-2009 at 18:23

Maybe you should give him another shot. It can take awhile to get rid of a bad apple. I had a guy hassling all my other employees (when I had an environmental shop). Reminds me of one of the mods here. I got rid of him but it took ahwile to get wise to it all and I tried to rehabilitate him for both our sakes. Could you offfer a little more detail on how to get hold of the guy? Is it "Waters Edge" now? The old phone # died... I learned that.

Sauron - 20-2-2009 at 20:17

Try Waters Edge Surplus in Google.

http://watersedgesurplus.com/index.aspx

I am still on their spam list but I always delete it so I do not have the details, sorry. I no longer have warehouse and transshipping facility in USA as my friend closed his business. So I won't be buying much in US I'm afraid, as it would have to be shipped piecemeal and that is too costly.

Anyway all my funds are going into the fume hood purchase this year.

Once I get past that, we will see.

A moment of googling got me:

CONTACT US

Waters Edge Surplus
P.O. Box 626
Grand Haven Mi 49417

Phone: 231-955-0038

sales@watersedgesurplus.com
buying@watersedgesurplus.com

http://watersedgesurplus.com/index.aspx

Another reliable lab equpment supplier is Mike Hnatow of HiTechTrader

Http://www.hitechtrader.com

However, their Parr shakers tend to be pricey. At least compared to the ones that chemrox and I have obtained in the past.

If you want a bargain, monitor labx and ebay and look for something in the $500 range.

If you need one now, look at Mike's site, they are in the $2000 and up category.

I got a bargain on mine but then changed the motor out for 220V, added a mantle, pressure bottle and some hardware, and now have maybe $3000 tied up, the motor from Parr, a GE, was costly. If you are in USA you will not have to do this but you always have to get little bits and pieces. I have yet to ever see one of these come with the bottle, and treyc are usually missing the shield.

The larger model is the best, but rarely turns up. What I have is limited to 500 ml with a working capacity 2/3 of that.

[Edited on 21-2-2009 by Sauron]

Sauron - 21-2-2009 at 03:49

Slightly off topic, but it's an auction for a Parr temperature controller and allegedly a 4521 reactor.

However it is obvious from the photo that the "reactor" is merely the baseplace and mantle for a 4522 2 liter reactor. No stirrer, no motor, no autoclave, and the seller wants an opening bid of $6100! He has stuck a flask on top to try to pass this off as an ordinary mantle. But ever see an ordinary mantle and controller priced used for $6000+?

I have dealt with this seller and less said about him the better.

While I would like to have the mantle, it is worth about 1/10th of asking price. I already have the controller.

It is always best to know more than the seller does and it is a mistake to educate him.

[Edited on 21-2-2009 by Sauron]

[Edited on 21-2-2009 by Sauron]

381680-0.jpg - 61kB

stoichiometric_steve - 21-2-2009 at 04:14

i can get a new 700ml one complete with stirrer heater etc. for about 3500 EUR.

Quote:

Originally posted by Sauron
Slightly off topic, but it's an auction for a Parr temperature controller and allegedly a 4521 reactor.

However it is obvious from the photo that the "reactor" is merely the baseplace and mantle for a 4522 2 liter reactor. No stirrer, no motor, no autoclave, and the seller wants an opening bid of $6100! He has stuck a flask on top to try to pass this off as an ordinary mantle. But ever see an ordinary mantle and controller priced used for $6000+?

I have dealt with this seller and less said about him the better.

While I would like to have the mantle, it is worth about 1/10th of asking price. I already have the controller.

It is always best to know more than the seller does and it is a mistake to educate him.

[Edited on 21-2-2009 by Sauron]

[Edited on 21-2-2009 by Sauron]

Sauron - 21-2-2009 at 04:20

I have a complete 1000 ml Parr 4521 and controller and paid $2000 for it.

The money is in the pressure vessel, all else is ancillary.

[Edited on 21-2-2009 by Sauron]

stoichiometric_steve - 21-2-2009 at 04:32

sell it to me, you dont use it for the right things anyways!

Sauron - 21-2-2009 at 05:01

Well, if I ever were to sell it I will give you first shot at it. But I have plans for it.

zed - 28-3-2009 at 03:35

Ummm. There was a Parr unit at auction on e-bay a few months ago, and it was located near me. I was tempted, but I passed on it. I could have obtained it for less than $100 U.S., but balked. I have better stuff laying around, if I ever get the notion, and to my way of thinking, the classic "shaker" design is clunky and less than efficient.

For those of you that don't have a unit, I recently came across some simple plans for quickly assembling a usable machine at very low cost. Hopefully, the following link will take you there.

http://springerlink.metapress.com/content/l38433856746r7u2/f...

[Edited on 28-3-2009 by zed]

[Edited on 28-3-2009 by zed]

[Edited on 28-3-2009 by zed]

Sauron - 28-3-2009 at 10:58

That document has been available on Rhodium for many years.

zed - 28-3-2009 at 18:45

Yup! It has indeed, you are correct, yet somehow I missed it on Rhodium. I accessed the document via the UC Berkeley, Chemistry Library, online.

Sauron - 28-3-2009 at 21:38

That unit is designed for 250 ml Parr bottles, which have a working capacity of max 150 ml. While scaling the design up to 500 ml is not too difficult, I found that trying to do same for the 2.2 L Parr bottle was not practical.

Besides, you still need the hydrogen storage, gauging and delivery subsystem as it would not be prudent to connect this apparatus directly to the regulator of a H2 tank.All in all an autoclave is better. The performance envelope of the glass shaker bottles, in terms of psig and temp, is quite limiting.

zed - 29-3-2009 at 07:26

All true. The Pressure Reactor is far superior. And, it isn't limited to low pressure, low temperature hydrogenation. It can do almost anything, is very durable, and used units aren't prohibitively expensive.

As I recall, it can even be used to manufacture LiAlH4. Not a commonly required reagent, but sometimes you need it and nothing else will do. What the Parr unit can't reduce, the LiAlH4 can.

Sauron - 29-3-2009 at 11:41

Making LAH is easy if you can obtain or make LiH

With LiH and anhydrous AlCl3, LAH is easy and does not require an autoclave.

If you mean use the Parr to make the lithium hydride then you are probably right.

The downside of used SS pressure reactors is possible catalyst poisoning. If so then only fix is a new vessel, head and all wetted partts and that is expensive.

I have a 1 liter Parr stirred reactor and its controller as well as a 3911 shaker 500 ml setup. They are both useful.

Magpie - 29-3-2009 at 12:17

Sauron says:

Quote:

Besides, you still need the hydrogen storage, gauging and delivery subsystem as it would not be prudent to connect this apparatus directly to the regulator of a H2 tank.

I'm curious as to what exactly you mean here? Do you mean that you need some type of backflow prevention like a check valve or surge vessel? Please explain.

chemrox - 29-3-2009 at 21:55

go to the Parr web site and dl the manual. Parr 3911 medium pressure shakers have a built in tank. A H2 tank fills that through the plumbing and a regulator. I was fortunate enough to get a controller, heating mantle and H2 regulator with mine.

Sauron - 29-3-2009 at 22:48

Chemrox and I apparently have people at a disadvantage because we both own Parr shakers.

http://www.parrinst.com/default.cfm?Page_ID=241

To access manuals and sales literature you have to register with Parr and login.

Yes they have a built in tank 1 liter with valves and gauges in and out and the connecting hoses to go to the inlet of the pressure bottle and to the main H2 tank.

With the outlet valbe of the secondary tank closed you charge the tank with H2 to not more than 100 psig then you close input valve. You now have a liter of H2 @100 psi and you can calculate if that is enough for your reaction. If so you can shut the regulator on main tank and disconnect the hose and remove tank to its normal location as a safety measure.

For details on how to conduct the reduction see Parr manuals and also Org.Syn. original writeup by Roger Adams, the prototype shaker he designed is very little different from the commercial Parr model based on it.

If you only do smaller scale reductions you can replace the 1 L tank with a 200 ml one, limit is still 100 psig. Limit of the glass bottles is 40-60 psig depending on sisze and temperature.

Optional accessories

Heating mantle
Controller for mantle, displays output of t/c
Cooling jacket - some reductions are exothermic
Thermouple

[Edited on 30-3-2009 by Sauron]

Magpie - 30-3-2009 at 15:38

Yes, I see the equipment layout for the Parr shaker hydrogenator. But for the UC Berkeley knock-off it seems that all that would be required is a H2 cylinder and a regulator w/valve and gauges. Of course connecting tubing and a teed vent valve would also be needed, as shown in the UC Berkeley literature.

Sauron - 30-3-2009 at 21:20

Most catalytic hydrogenations involve some risk of fire and explosion because of the pyrophoricity of the various catalysts.

Part of the acculturation of a chemistry student is to teach the proper manipulation of the catalyst.

Look at what is on or at the bench:\

A pressurized cylinder of flammable H2
Flammable solvent and substrate
Highly pyrophoric catalyst.

It always has seemed to me, in the 35-40 years since I first read Roger Adams' writeup on this apparatus in Org.Syn., that the smaller lower pressure tank was there to allow the main H2 tank to be gotten well out of the hazard zone. A 1 L tank at <100 psi would be dramatic enough is things went wrong. A full sized cylinder at 3000 psi would be a catastrophe.

Bypassing the subsystem is not a prudent idea.

What UC Berkeley knockoff? The stirred unit described in the paperposted by zed is from Cal State San Bernardino. Not even Northern California!

[Edited on 31-3-2009 by Sauron]

Magpie - 30-3-2009 at 21:58

Although my experience with catalytic hydrogenation is very limited I can appreciate the hazards. I was simply amazed to see some Pd/C soaked in H2 burst into flame when exposed to the atmosphere.

Yes, I had my California institutions confused. I just scrolled up to one of zed's posts. I do know where San Berdo is as I was stationed nearby compliments of the USAF.

To address this hazard you can locate the 3000 psi H2 tank anywhere that you want, say in the next room behind a concrete block wall. It's just a matter of running a long enough tube to reach the Parr bottle. It looks like the Parr shaker is using a PE tube; if so, that would be easy enough.

I do see that by having its own local supply tank the shaker becomes quite portable, however.

Sauron - 30-3-2009 at 23:44

Remember, for small runs, the 200 ml tank is even safer.

The shaker is larger and heavier than it looks. The motor is quite heavy and altogether it is a pain in the ass to move from one bench to another. Even more so from one room to another. I would recommend a wheeled cart for such jobs. I would say, operate it on the cart, but IMO inside the hood is the best place.

H2 tanks are often actually 5000 psi and special regulators are beeded if you need to deliver H2 to an autoclave (not a shaker) at 1000-1500 psi - in comparison to the low pressure delivery to charge the smaller tanks of the shaker.

The sequence of opening and closing the regulator and valves ought to be pretty obvious. When filling the small tank you set the regulator to no more than 100 psig and open inlet valve while outlet valve is closed. When inlet valve reads the desired pressure, never more than 100 psig, close inlet valve and close regulator.

Prior to working with H2 you really need to test the enrire system end to end for leaks using N2 or Ar. Do not use compressed air as you will want to purge O2.

I attach the original Adams peper from Org.Syn. which describes the complete procedure on an apparatus very akin to the Parr and from which the Parr was developed with Adams' involvement.

[Edited on 31-3-2009 by Sauron]

Attachment: Adams.pdf (157kB)
This file has been downloaded 1110 times

zed - 31-3-2009 at 01:38

Actually, I was referring to LiAlH4 synthesis via Heat/Pressure/Li+Al+2H2+THF.

I've always thought it is wasteful to use 4 moles of LiH to produce 1 mole of LiAlH4.

But, I digress. The subject is Parr shakers. Easy to build they are.

Not my cup of tea, but I have had several friends that built their own. Not much to it really, and the finished units worked quite well.

Overall, I'd prefer to entrain my H2 by stirring. And, I saw an interesting stirrer patent yesterday. I don't know if the units are commercially available. Heck, I don't know if they are likely to work. Have any of you seen such devices? http://patapsco.nist.gov/TS/220/sharedpatent/pdf/6585405.pdf

[Edited on 31-3-2009 by zed]

madcease - 31-3-2009 at 01:58

I think the Parr Shaker type apparatus is much better than the stirring type correct me if im wrong but when using some catalysts it tends to be very pyrophoric such as Rayney Nickel which if stirred the catalyst has a tendency to sit on side walls without being in solution whereas the shaker is always saturated and gives no chance to ignite.

Very interesting patent Zed. I have another type of apparatus that can be built very easily like the previous UC Berkeley, Chemistry Library stirred apparatus you found which used to be on Rhodium. Just have to find it ill post the link once done so.

Sauron - 31-3-2009 at 03:03

Hmm, I have no refs for direct combination of Li, Al, and 2 H2. How much heat and pressure? I am constrained to 1900 psi and something <400 C. with the equipment I have at hand.

Merck, Brauer, etc give only the prep from 4 LiH + AlCl3 in Et2O which may consume LiH but requires neither autoclave nor H2.

It's academic for me as I have a lot of LAH and when I want more, I order it.

LiH is no joy to prepare if you have to. Even to use the commercial LiH in prep of LAH requires grinding, best done under N2 in a special ball mill in anhydrous Et2O - whiclso sounds like great fun for all.

[Edited on 31-3-2009 by Sauron]

Attachment: ja01197a061.pdf (180kB)
This file has been downloaded 2679 times

Sauron - 31-3-2009 at 03:24

There is only one y in Raney.

My personal approach to separation of pyrophoric catalysts from solutions after reduction is to do the filtration and transfer in an inert atmosphere glove box with an airlock and tus avoiding any exposure of the catalyst to air.

All else is russian roulette.

Magpie, re direct attachment of main high pressure H2 cyclinder to reaction bottle, that is still onjectionable even if you run a long gas line. Why? Think of the reaction bottle, particularly the H2-rich catalyst, as a match, the H2 line as a very fast fuze and the H2 tank as a bomb.

At the bare minimum a flash arrester needs to be interposed. And even then I like a small secondary tank at low pressure better. The Parr tanks are brass. 100 psig is a little more than 6 arm. and a liter of H2 # 6 atm isn't much.

zed - 31-3-2009 at 03:25

I'll see if I can dig up a reference. I'm pretty sure I know what book it is in, it's just a question of finding the book. Surrounded by books. Not as many as I used to have, but still too many. Like, maybe 10,000 or so.

madcease - 31-3-2009 at 04:02

Is there a reason why Parr Inst sell mainly the shaker type and not stirred type?
Seems as if shaker is the way to go instead of a stirred apparatus.

Sauron - 31-3-2009 at 04:52

Parr makes a very wide range of pressure reactors, mostly stirred, medium and high pressure autoclaves. The shaker type hydrogenator is really a very minor product of theirs

They also make stirred low pressure glass reactors, calorimeters and a variety of other instruments and equipment.

Do a google on "parr pressure reactors" to get to their home page. If you register and create a password to go with your email address you can access their brochures and manuals, exploded drawings, parts lists etc.

They are not cheap!! but sometimes you can find a bargain on labx or a generic auction site like ebay.

Zed, according to Ullmann's, the LiH + AlCl3 method is the only industrially employed method of making LAH.

They do mention two other methods, hot used:

2 LiH + 2Al + 3 H2 -> 2 LiAlH4

at unspecified and unreferenced elevated temp and pressure. This probably what you were thinking of.

and by metathesis:

NaAlH4 + LiCl -> LiAlH4 + NaCl

The requisite sodium aluminum hydride can be produced from Na, Al and 2 H2 at 100-200 C and 1450-2900 psi according to a series of patents held by the Ethyl Corporation. Best done in hydrocarbon solvent and in presence of trimethylaluminum catalyst, what fun. My Parr tops out at 1900 psi.

It can also be prepared from

4 NaH + AlCl3 -> NaAlH4 + 3 NaCl

E. C. Ashby: "The Chemistry of Complex Aluminohydrides," Adv. Inorg. Chem. Radiochem. 8 (1966) 283 – 335.

Sodium hydride is easier to come by and cheaper than lithium hydride but just as much of a pain to prepare.

Attachment: US4045545.pdf (231kB)
This file has been downloaded 601 times

[Edited on 31-3-2009 by Sauron]

Magpie - 31-3-2009 at 09:33

Quote:

Think of the reaction bottle, particularly the H2-rich catalyst, as a match, the H2 line as a very fast fuze and the H2 tank as a bomb.

Sauron, I think it is more reasonable to think of the H2 rich catalyst as a bunsen burner with the line just a conduit to the high pressure supply. Without O2 the H2 does nothing.

Sauron - 31-3-2009 at 13:53

But your Bunsen is in a bucket of petrol and there's air and vapor all round,

You can do it your way, just remind me not to visit when you are hydrogenating.

Anyway, here is the improved Ethyl Corp. patent describing lower pressure (700-1500 psig) two stage preparation (140 and 80 C) of NaAlH4 from Na, Al, and 2 H2.

Remember, sodium aluminum hydride metathesizes with LiCl to LiAlH4. So if you have an ordinary autoclave like mine and can get or make Na metal, Al powder and H2 cylinder you can make your own LAH in a 2 step procedure with only LiCl.

BTW despite the broad claims in the above patents, Ethyl Corp does not make LAH this or any other way, and while they make NaAlH4 on a modest scale, there is no demand for it in bulk. From this I surmise that the direct combination of the elements is not so practicable for LAH directly, as the "omefficient" prep from 4 LiH and AlCl3 remains the only manufacuring process in use after 65 years.

LiCl can of course be electrolyzed and Li metal recovered and hydrogenated back to LiH or used in another manner so the "wastefulness" of the process has perhaps been overstated for purposes of patent prosecution.

Attachment: US4512966.pdf (210kB)
This file has been downloaded 605 times

[Edited on 31-3-2009 by Sauron]

zed - 31-3-2009 at 16:25

Indeed that was the procedure I found.

From "Advanced Inorganic Chemistry" pg 339, 4th Edition, 1980, By Cotton and Wilkinson.

" However, for AlH4 the sodium salt can be obtained by direct interaction:

Na + Al + 2H2 -------------------------------------------------> NaAlH4"
150C/2000 p.s.i./24h/ in THF

The NaAlH4 may be used directly(some actually prefer it to LiAlH4 due to ease of post reaction workup)......or it may be precipitated by the addition of Toluene.

The NaAlH4 may then be efficiently converted to the Lithium salt.

NaAlH4 + LiCl ---------------------------------------->NaCl (solid ppt) + LiAlH4
Et2O

Nice thing about obtaining a Parr high pressure reactor. Once you have one, most things are do-able.

Thank you for the Patent links, Sauron. I did not have those.
************************************************

As a side note.....My understanding is that at lower temperatures the Parr reactor can withstand higher pressures.

Parr vessels are often rated as 1900psi at 350C. At 150C they can withstand somewhat more pressure. I believe Parr provides a table or graph somewhere that describes that pressure/temperature relationship.

*Wow, just read that Ashby Patent. Pretty Nice. Much better than the method I was familiar with.

[Edited on 1-4-2009 by zed]

[Edited on 1-4-2009 by zed]

[Edited on 1-4-2009 by zed]

[Edited on 1-4-2009 by zed]

Sauron - 31-3-2009 at 20:28

Now read the Nelson followup patent.

-- toluene preferred solvent
-- triethylaluminum catalyst (pyrophoric liquid, formerly used in military flamethrower M3 and ignites as soon as it hits air)
-- 14o C first stage, 80 C second stage
-- 1000 psig H2 pressure

First stage forms Na3AlH6, second stage NaAlH4.

Reason why ethers shunned is that NaAlH4 is unstable in ethers, and the ethers are hard to completely remove from solid. At least per patent. This does not appear to be a problem with LAH production from LiH and AlCl3 in ether.

This does appear to do the trick. A one pot two stage prep from the elements in toluene, then an easy metathesis in eyjer. The trialkyl aluminum is a minor hassle, practice your airless technique and handle under inert atmosphere. Syringe, transfer line, usual drill. The solvent with triethylaluminum inside is reusable. That helps.

zed - 31-3-2009 at 21:41

Actually, somewhere in Ashby's patents, it suggests that the catalyst can be formed in-situ. I like that idea.

Overall, the procedures look pretty good.

I have no current use for any of the products, but it is nice to know they can be manufactured if need be.

Nelson's patent suggests about 2lbs of NaAlH4 were produced per 1 gallon of reactor capacity. In a 400 gallon reactor, about 750lbs of product was produced.

So by extrapolation, in a single run, in a 1 liter Parr reactor about 1/2 Lb of NaAlH4 could be produced.

THAT is practical.

Thank you again for sharing your research with us.

Sauron - 31-3-2009 at 21:59

De nada, it was interesting to find out.

I have no doubt that Li, Al, and H2 will combine under conditions were the Li is a melt dispersed as sand in toluene and the H2 is under pressure. It's just a question of how much pressure, and how long the reaction time. On a bench scale I don't mind if it takes 24 hrs. Throughput is a process engineer's problem and not that of a synthesist. Li metal is easy to buy, I have maybe 500 g wire in oil. It's a lot cheaper than LiH and need not be wet-milled in Et2O under N2.

BUT on the other hand I have maybe 12 Kg Na and it is a LOT cheaper. So there is little point in swimming upstream.

Zed, while the ealier patent (Ashby) does mention making catalyst in situ. he was referring to sodium alkyl or similar monovalent metal alkyls. Unfortunately things are not that simple for trialkyl aluminums and the patents are quite specific about triethylamuminum being the catalyst of choice.

It is commercially available as a 25% wt solution in toluene, this is almost certainly not an accident.

What happens when you react alkyl halide (say ethyl bromide) with Al is that you get a mixture of ethylaluminum dibromide and diethylaluminum bromide. These cannot readily be separated. However the ethylaluminum dibromide can be reduced with Na metal to the diethylaluminum bromide and this then purified and converted to triethylaluminum in decent overall yield.

Better is to incorporate the reducing agent into the aluminum as an alloy, thus 30% Mg 70% Al alloy turnings are reacted with EtBr and the resulting Et2ALBr reduced with Na to Et3Al. See Brauer above. Also here is the original 1940 paper from JOC.

[Edited on 1-4-2009 by Sauron]

Attachment: jo01208a004.pdf (221kB)
This file has been downloaded 1405 times

Sauron - 1-4-2009 at 12:44

Sorry, here are the pages from Brauer describing prep of diethylaluminum bromide and triethylaluminum from Al/Mg "magnalium" 70/30 alloy turnings (Dow Chemical).

Attachment: Pages from brauer_ocr.pdf (91kB)
This file has been downloaded 768 times

madcease - 2-4-2009 at 02:06

If one is to build one of these pressure shakers/stirrers, should there be a pressure relief valve attached to the apparatus like a pressure cooker which if for some reason pressures go over 50-60PSI then the relief valve will open causing no breakage of glass.

Sauron - 2-4-2009 at 03:05

Such devices are common for high pressure steel autoclaves but are not used on shaken or stirred glass hydrogenators which are by nature of the vessels limited to 30-60 psig depending on size of the bottle.

The 250 ml and 500 ml Parr bottles max 60 psi

The 1 L and 2 L machine made Parr bottles 40 psi I think

The costlier hand blown 2 L Parr bottle and the steel 2 L Parr bottle 60 psi.

We are only talkin 4 atmospheres here. As H2 is taken up pressure drops so normally the highest pressure is at the onset. Sometimes there is an exotherm, and external cooling jackers are abailable. Sometimes heating is necessary and thermocouple monitored PID controller mantles are also available.

Sauron - 2-4-2009 at 19:38

Since this thread is about Parr shakers, rather than making LAH, I have started a new thread about making LAH so please let's allow this older thread to return to topic. Thanks.

zed - 1-5-2009 at 00:18

Ah, back to Parr Shakers! I don't disparage them. They have their place. But, under some conditions, an ordinary filter flask, equipt with a magnetic stir bar, driven by a modern stir plate, is superior.

In the past, for hydrogenations, such setups, achieved results approximately equivalent to those achieved with shaker units.

Magnetic de-coupling of the stir-bar, at higher speeds, limited reaction rates. At high rpm, the turbulence created in the stirred solution, would overwhelm the magnetic bond between the the stir-bar, and the drive magnets in the stir plate.

This old problem, caused my charming young Granddaughter, Munchkinkiss, to design a simple little experiment using alternative stir bars. She figured....Stronger magnets=Stronger coupling.

So, she got herself some stronger magnets to use as stir bars. And, low and behold, by using modern, super-strong Neodymium Alloy Magnets as Stir-bars, formerly undreamed of turbulence can be achieved. They don't break loose easily!

Ordinary stir-bar stirring? Dust-devil.

Stirring with Neodymium Magnet? Full-force Hurricane. Lots of gas entrainment.
I've never seen a Parr shaker that could equal it.

Neodymium Alloy magnets, which are usually only nickel plated, may need extra coating to render them sufficiently inert to corrosive reagents, and of course, they demagnetize at high temperatures.

If your hydrogenation can be achieved at relatively normal temperatures, Neodymium stir-bars may be the way to go.

A Parr shaker retails for 3-4 Thousand dollars, while you can purchase a parcel of ten 1/4 inch by 1 inch Neodymium magnets, for about $16.00 including postage. Link two, end on end, and create a 1/4 inch by 2 inch magnet, that will produce good turbulence and gas entrainment, in a 2000 ml filter flask containing 1000 mls of liquid.
Stable at a fairly high RPM too.

If you still have doubts, observe the even greater turbulence and gas entrainment, achieved by a Neodymium Cylinder magnet, 1/2 inch by 2 inchs, spinning at high RPM. Your doubts will be erased.

A parcel of four, 1/2 inch by 2 inch N48 Neodymium Cylinder Magnets retails for about $30.00 including postage.

[Edited on 1-5-2009 by zed]

Sauron - 1-5-2009 at 00:55

No one in their right mind buys Parr anything new except spares. Parr shakers go for a song on the used market. I payd $300 for my 3911\\In fact I have less than $2K ib my 1 L Parr stirred heated SS autoclave which is somewhere in mid 5 figures new and rated for 1900 psig @ 350 C

The temp controller for mantle for Parr shaker vessels is restricted to 80 C. Some hydrogenations do call for heating and some are qute exothermic. Those thick walled filter flasks were never designed as pressure vessels, and never designed to be heated. They were designed for aspirator reduced pressure of substantilly less than 1 atm negative pressure, typically more like 50-100 torr.

The Parr glass vessels are rated, depending on size and type, to between 30 psig and 60 psig @ 80 C. In fact they are indicidually tested to 10 atm (150 psi) at the factory.

Ace pressure vessels are rated to 50 psi.

In neiter case dothey warranty due to the nature of glass.

zed - 1-5-2009 at 15:37

An interesting premise. Since I've had filter flasks quite hot, at 200C to 300C, under fairly high vacuum, and never had a mishap, my experience has been that they are pretty durable.

That however, was in the past. What currently manufactured glassware is capable of, may be a different matter.

At any rate, I wasn't suggesting significant pressure. Nor was I suggesting the use of heat.

Most of my personal experience has been with small scale "Brown" type hydrogenations.

Basically STP condition hydrogenations, using very active catalyst, in Erlenmeyer type flasks or Filter flasks.

In that environment, greater magnetic coupling, via Neodymium Alloy stir-bars, allows for more vigorous stirring, and highly improved gas entrainment.

Still to be addressed, is the question, "How much internal pressure can a modern filter flask withstand?" This would be nice to know!

Currently, I have no idea. But, I'm going to research it.

Hopefully, someone somewhere knows, and I won't have to burst a bunch of filter flasks to find out.

Glassware is so expensive now.

jimwig - 1-5-2009 at 16:05

they appear to be gone

Sauron - 1-5-2009 at 16:17

Zed, I have no headache with the use of a filter flask for a 1 atm hydrogenation at room temperature.

That would for example be fine for removing Z-protecting groups from amino acids or peptides with H2 and Pd black- an old method but a good one.

zed - 1-5-2009 at 23:49

I'll try to find out more about pressure and temperature capability. Naturally, I wouldn't suggest trying to push the limits if the filter flasks can't take it.

It would be nice if they can take a little pressure. The shape of the Erlenmeyer flask is very advantageous for the entrainment of gas via stir bar.

It is unfortunate that the shape may have less than optimal strength for containing
pressurized gas.

Of course, stainless steel vessels can also be used for stir-bar hydrogenations, and stainless can take more pressure.

But to date, I've haven't seen spin bars create really good gas entrainment in high-pressure vessels. The inch thick stainless steel bottoms, prevent the strong magnetic coupling required. Too much distance between the drive magnets and the spin bar.

Sauron - 2-5-2009 at 00:03

Dedicated autoclaves are generally either packed-gland direct drive stirred, or magnetically coupled at the top (lid) - mine is packed gland sealed, belt driven continuously variable speed, I forget the top end, it's on the Parr sire. Of course this is not a dedicated hydrogenation apparatus. I's more versatile than that. Still, there's a gas inlet.

benzylchloride1 - 18-8-2010 at 15:49

I recently purchased an older Parr model 3911 pressure reactor from a surplus store for $17.00. It came with everything besides the glass reaction bottle and a hydrogen cylinder. It appears to be in excellent condition, but required some cleaning. Now I just have to rent a hydrogen cylinder, purchase tubing, regulator and pressure bottle

entropy51 - 18-8-2010 at 16:21

Quote: Originally posted by benzylchloride1

I recently purchased an older Parr model 3911 pressure reactor from a surplus store for $17.00. It came with everything besides the glass reaction bottle and a hydrogen cylinder. It appears to be in excellent condition, but required some cleaning. Now I just have to rent a hydrogen cylinder, purchase tubing, regulator and pressure bottle

Nice find! Now you have catalyst-induced hydrogen fires like the rest of us.

Magpie - 18-8-2010 at 19:06

Yes, a very nice find. Anything new from Parr is very expensive. What is a surplus store that has such equipment?

benzylchloride1 - 18-8-2010 at 20:02

I purchased it from a university surplus store along with a Lindberg bench top furnace. I could spend a lot of money in the surplus store since there is a large number of other potentially useful items such as hot plates, FTIRs, to name a few items.

zed - 18-8-2010 at 20:34

I found an illustration of a "Brown-Type" Hydrogenator in in Vogel's Practical Organic Chemistry Edition 5. Included are instructions. Page 91 onwards. The Original J. Org. Chem., and J. of the Am. Chem. Soc., articles.... Are pretty hard to access on line.

Brown uses NaBH4 as his hydrogen source, but any type material that releases H2 via contact with water or acid ....will do.

According to Brown, his technique is aided by the unusually active catalyst, created by the reaction of NaBH4 on Chloroplatinic Acid.

[Edited on 19-8-2010 by zed]