Author Topic: Practical electrolysis chamber construction  (Read 5333 times)

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Bandil

  • Guest
Practical electrolysis chamber construction
« on: May 17, 2003, 05:15:00 PM »
Hi!

Swim was pondering on some construction ideas for membrane separated electrolysis chambers.

One ide was to take two ½ L durable plastic containers(with an open top), that where formed like a perfect square. Then cut a hole in one of the sides of each container. The holes should be identical. Then a suitable exchange membrane would be glued  to cover one of the holes on cover it completely. Then the other container would be glued onto to the membrane to cover the hole. Then one would have a to compartment dived cell. Now for some performance questions:

1) The binding glue:
What kind of glue would be appropriate for this kind of work? I could imagine that regular epoxy glue would have a hard time in this kind of harsh environmet. Maybe cyanoacrylate would be more usable? It definately would make it alot easier using glue than using some kind of "press together mechanism".

2) The membrane.
If this system is built, the membrane cannot be replaced without rebuilding the whole lot. If a good "professional" cation-exchange membrane is purchased, how long will it last? For a single reduction, a couple of times or indefinately? I really have no idea on how long lasting such membranes are.

3) The plastic containers
What type of plastic should be used? There are often some evil solvents in contact with these, so it's essential to pick some good plastic. Maybe it should even be teflon coated metal in order to be really inert?

Thanks!

Regards
Bandil


hCiLdOdUeDn

  • Guest
Glass is the best choice.
« Reply #1 on: May 17, 2003, 06:47:00 PM »
I have found out that plastic containers usually arent chemically inert enough to perform organic electroylsis reactions especially from the heat of the reaction. I would use glass beakers or containers. I have also looked into electrolysis for reduction and found some useful patent #s on Google.

Here are the recent U.S. patents on Ion-exchange membranes:

6,359,019: Graft polymeric membranes and ion-exchange membranes formed therefrom
6,350,925: Perhaloethyl aromatic compounds and perhaloethenyl aromatic compounds therefrom
6,344,326: Microfluidic method for nucleic acid purification and processing
6,338,913: Double-membrane microcell electrochemical devices and assemblies, and method of making and using the same
6,337,120: Gasket for layer-built fuel cells and method for making the same
6,330,471: Iontophoresis electrode device
6,328,885: Current-efficient suppressors
6,328,875: Electrolytic apparatus, methods for purification of aqueous solutions and synthesis of chemicals
6,322,914: Method and apparatus for distributing water in an array of fuel cell stacks
6,322,690: Chemical method
6,315,886: Electrolytic apparatus and methods for purification of aqueous solutions
6,313,285: Purification of plasmid DNA
6,312,578: Method for extracting amine compounds from a liquid medium
6,300,381: Acid-base polymer blends and their application in membrane processes
6,284,124: Electrodeionization apparatus and method
6,274,020: Electrodialysis membrane and gasket stack system
6,268,532: Sulfonated perfluorovinyl functional monomers
6,265,224: Sample processing method using ion exchange resin
6,258,861: .alpha.,.beta.,.beta.-trifluorostyrene-based composite membranes
6,254,762: Process and electrolytic cell for producing hydrogen peroxide
6,248,469: Composite solid polymer electrolyte membranes
6,242,261: Assessment of ion availability in heterogeneous media using ion-exchange membranes
6,242,123: Solid polyelectrolyte membrane for fuel cells, and method for producing it
6,241,980: Sample processing method using ion exchange resin
6,235,186: Apparatus for producing electrolytic water
6,225,368: Water based grafting
6,221,923: Cross-linking of modified engineering thermoplastics
6,203,687: Method for shutting down an electrolysis cell with a membrane and an oxygen-reducing cathode
6,194,474: Acid-base polymer blends and their application in membrane processes
6,187,468: Electrodes for fuel cells
6,187,201: System for producing ultra-pure water
6,171,719: Electrode plate structures for high-pressure electrochemical cell devices
6,130,175: Integral multi-layered ion-exchange composite membranes
6,120,673: Method and device for regenerating tin-plating solutions
6,109,852: Soft actuators and artificial muscles
6,103,414: Blend membranes based on sulfonated poly(phenylene oxide) for polymer electrochemical cells
6,103,195: Micro-volume spin columns for sample preparation
6,103,075: Linear electrochemical conductor element
6,090,258: Ion-exchange spacer and processes for the preparation thereof
6,080,820: (Fluorovinyl ether)-grafted high-surface-area polyolefins and preparation thereof
6,080,298: Method for electrolysing a brine
6,077,434: Current-efficient suppressors and method of use
6,074,827: Microfluidic method for nucleic acid purification and processing
6,074,812: Method for desalting and dewatering of silver halide emulsions by electrodialysis
6,059,857: Ultrapurification of organic solvents
6,051,124: Zeta-potential determining apparatus
6,045,938: Linear electro chemical conductor element, process for its manufacture and apparatus for its use
6,045,684: Process and apparatus for the production of an aqueous solution of hydrogen peroxide
6,039,852: Bipolar plate for filter press electrolyzers

ClearLight

  • Guest
Does electrochemical even work?
« Reply #2 on: May 17, 2003, 08:40:00 PM »
does it even work? anyone had any practical effective xp w/ this?


Organ_Morgan

  • Guest
Why not concentric vessels?
« Reply #3 on: May 17, 2003, 08:42:00 PM »
Mount one cell within the other. Unglazed terracotta pots are reputed to work but their electrical resistance must be  high.

An idea is to construct the inner vessel by wrapping a cylindrical frame with goretex. This will give maximum membrane area (well almost) for the volume of electrolyte. This and circular geometry should create low electrical resistance: less heating and less voltage drop across the membrane.

Thinking about using clothing goretex put through a hot wash cycle with loads of detergent to remove the water repellent impregnation. The nylon laminate increases the strength of the membrane but not sure how this will react with whatever electrolyte (any ideas?). Goretex itself is expanded PTFE and chemically resistant, pore size around 20.

Making an SCE reference electrode looks fiddly but possible. For the counter electrode, I've been thinking about a graphite electrode mounted centrally in the inner cell. Several working electrodes could be mounted around the outside of the outer cell. Depending on the metal, the outer cell itself could form the working electrode. Wouldn't be too hard to find/make a suitable copper/lead/silver pot.

Any thoughts on this?

Organ_Morgan

  • Guest
Does it work?
« Reply #4 on: May 17, 2003, 09:01:00 PM »
All this sheep gut condoms with Mongolian silver dollar electrodes and a car battery sounds like pure BS to me. No one seems to have been successful with the kitchen electrochemistry recipes: I think this is more because the recipes are wrong or not detailed enough rather than 'it can't be done'.

There are loads of references to successful electrochemical reductive amination etc.

There seem to be many critical variables such as electrode composition, preparation and size, electrolyte composition, temperature, voltage and current and cell construction.

Proper setups do work, Frankenstein experiments do not.
:)

hCiLdOdUeDn

  • Guest
membrane possibilities
« Reply #5 on: May 17, 2003, 09:06:00 PM »
In the industry, they use DuPont's Nafion, a thin porous plastic-like sheet to allow ion exchange and create current. This is obviously not easily obtainable (or cheap). Could porous plaster (plaster of paris) be molded and allow ion exchange? Other ideas are cork, cotton balls stuffed in a tube between the cathode and anode compartments, or salt bridges.

Organ_Morgan

  • Guest
Membranes
« Reply #6 on: May 17, 2003, 09:16:00 PM »
Plaster of paris gets pretty soft and crumbly when wet. Why not just go with the plant pot method?

How reactive is cork? Might be good for the plug in the bottom of a reference electrode assembly.

hCiLdOdUeDn

  • Guest
Organ Morgan you are correct
« Reply #7 on: May 17, 2003, 09:18:00 PM »
Electrochemistry really does need to be exact. Current, voltage, temperature, anode and cathode choice selection DOES matter. You can't just stick two nails in a solution and hook it up to a car battery overnight to perform a succesful oxidation, it just wont work. You need a good adjustable power supply, watching the temperature carefully, and many other variables.

Promising Idea for MDP2NP->MDA synth, using NaNO3 salt bridge for electrolysis.
Electrochemical Cell For Reduction
Although I have seen many references to the use of electrochemical cells, the construction of them I have yet to see thoroughly described or for that matter where they can be purchased. This doesn't mean they are impractical, because for clandestine chemistry where the most reliable reduction reagents are watched like a hawk, electrochemical reductions could be the next breakthrough.

The cells are basically a container divided by some material which will allow charged ions to pass and therefore allow electricity to flow. The membrane also halts the flow (or reduces it considerably) of the material being reduced. This is necessary because if the membrane wasn't there, the reduced product could travel to the other electrode and become oxidized. The membranes are made of such materials as sintered glass, cellophane, porous ceramic plates etc.

This procedure was written for the analogous nitrostyrene which would lead to amphetamine. It should work equally well for MDA[46].

207g (1 mole) of the nitrostyrene is dissolved with a solvent prepared by mixing one liter of ethanol with 500ml of acetic acid and 500ml of 12N sulfuric acid. The solution is placed in the cathode compartment of a divided electrolytic cell containing a mercury, copper or metal of similar nature as the cathode electrode. The anode can be made of lead. 3N sulfuric acid is placed in the anode compartment. Current is passed equaling ~0.2 amperes/cm2 of cathode surface. The temperature is kept between 30-40°C during the electrolysis until at least 8 Faradays of electricity have passed through the solution.

The number of square centimeters of your cathode surface (count both sides if both sides are in contact with the solution) times 0.2 is the amount of current you need flowing through your cell. 1 Faraday is equal to 96485.309 coulombs/mole of electrons and 1 Ampere is equal to 1 coulomb/second. The amount of time in hours the reaction should be run is then 771882.5 divided by the number of Amperes divided by 3600. If you have a total cathode electrode area of 40 cm2 then you need 8 Amperes running through your cell for 26.8 hours.

Remove the ethanol and ethyl acetate present through distillation (quit distilling when the temperature approaches 100°C). Basify the remaining solution with 25% NaOH and extract the MDA from the solution with 3 portions of ether (or toluene or methylene chloride). Wash the extract with several portions of calcium carbonate solution, water and then dry with magnesium sulfate. Filter out the drying agent. Pass HCl gas through the solution until no more precipitate is formed. Filter the crystals and wash with ether and allow to dry.


Salt-bridge cell idea for reduction of MDP2NP to MDA

Rhodium

  • Guest
Salt bridge amperage
« Reply #8 on: May 17, 2003, 09:23:00 PM »
How much current can you push through a simple salt bridge? Wouldn't that have a too high resistance?

hCiLdOdUeDn

  • Guest
Plenty
« Reply #9 on: May 17, 2003, 09:43:00 PM »
Saturated salt solutions, or even slightly saturated salt solutions, are very strong conductors of electricity. So resistance is pretty low.

Rhodium

  • Guest
...how much is that in kilo-ohm?
« Reply #10 on: May 17, 2003, 09:48:00 PM »
Good conductors compared to what? Could you give an approximate figure in kohm instead?

Organ_Morgan

  • Guest
Salt bridge
« Reply #11 on: May 17, 2003, 09:49:00 PM »
That's a setup to measure the overvoltage of zinc against a hydrogen cathode isn't it? In that case, the current flow would be negligable and the resistance of a salt bridge unimportant.

If you want to push the reaction the other way, resistance might be too high.

Is hydrogen overvoltage the main criteria for electrode choice?

Organ_Morgan

  • Guest
salt water conductivity
« Reply #12 on: May 17, 2003, 09:54:00 PM »
I remember from somewhere that a 2M, strong electrolyte solution has 10% of the conductivity of metal.

Organikum

  • Guest
membranes for electro
« Reply #13 on: May 18, 2003, 01:32:00 AM »
Many of the usual plasticfoils can be used as cell dividers. One patent named PVC for example another PP. Depends on temperatures and electrolyte used. A clay pot perhaps in very hot conditions and also there fritted glass or glassfibre filters are preferable.
Design: the two boxes not glued together but hold together by springloaded screws  and a teflon (filled PTFE) seal holds the membrane.

Tip: many plasticfoils show no membrane qualities at first sight - but if you stretch them a little bit they work perfect. Try it!

Bwiti

  • Guest
putty epoxy..
« Reply #14 on: May 18, 2003, 08:11:00 AM »
Chemically, epoxy putty is some mean stuff. I've tested concentrated H2SO4, glacial acetic, etc. on it, and it refuses to break down. If you want to fix an anode/cathode in a glass cookie jar, then I highly recommend putty epoxy. Peace! 8)


roger2003

  • Guest
membranes
« Reply #15 on: May 18, 2003, 11:56:00 AM »
the electrochemical reduction of nitroalkenes in Ber. 124, 2303 (1991) was carried out with  membranes from glas frites  (G4)

Post 421272

(Vitus_Verdegast: "electrochemical reduction of nitroalkenes", Chemistry Discourse)
:

ClearLight

  • Guest
hmmm no experimenters?
« Reply #16 on: May 18, 2003, 08:02:00 PM »
I have the entire 8 vol set of electrochemistry sitting on my bookshelf... that's about 8 projects away from being cracked open..

  So i wondered who actually sucesssfully used this method? Since one of my more respected biochem buddies had no joy /w palladium electrodes and H2 reduction.. and he is a Membrane Filtration Specialist w/ all the stuff on hand!


jimwig

  • Guest
lets see now. Nafion is expensive.
« Reply #17 on: May 20, 2003, 01:38:00 AM »
lets see now. 

Nafion is expensive. but so is everything.
AND i have given up on synthesizing any of the complexed sulfonates that are called cation/anion etc.
couldn't i just pee in a cup and stick it in the blender on frappe? lots of foam should do it.

then you must construct a membrane and apply the IONx to it
i like the bridge idea.
conditions may have to rather exact but then if this were sand castles everyone would want to play. and the sharks couldn't feed properly.

Prince_Charles

  • Guest
glass frit separator
« Reply #18 on: May 20, 2003, 01:24:00 PM »
roger2003: Do you have any more information on their setup, glass frit isn't mentioned in VV's post?

Chemcast G4 is a zirconia-aluminia glass (alkali and thermal resistant).

Is glass frit the same as sintered glass?


roger2003

  • Guest
All about glas frites you can read (also in...
« Reply #19 on: May 20, 2003, 02:10:00 PM »
All about glas frites you can read (also in english) here:

http://www.robu.net/



One method for the setup is an u - tube (google and find)