Author Topic: Acetic acid from vinegar... A better method  (Read 6840 times)

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abacus

  • Guest
Has anyone actually got anything from ketene?
« Reply #40 on: April 25, 2004, 03:32:00 PM »
SWIM has tried bubbling ketene into 500 ml GAA over the last 2 weeks.  Standard  ketene gas set up, bubbled gas for at least 10 hours, yield acetic anhydride mixture bp over 130 Deg less than 70g, total waste of  time IMHO.

Organikum

  • Guest
What is a "Standard ketene gas set up
« Reply #41 on: April 25, 2004, 06:23:00 PM »
What is a "Standard  ketene gas set up" ? Could you please elaborate?

thanks
ORG


Tdurden969

  • Guest
Interesting
« Reply #42 on: April 26, 2004, 05:32:00 AM »
Oxidation of Ethanol by Hydrogen Peroxide in a Modular Microreactor System

M. Krauta, A.Nagelb, K. Schuberta

a) Institute for Micro Process Engineering
Karlsruhe Research Center
Hermann-von-Helmholtz-Platz 1
76344 Eggenstein-Leopoldshafen
Germany

b) Bayer AG
Process Technology/Reaction Engineering
51386 Leverkusen
Germany

Klaus.Schubert@IMVT.FZK.DE
WWW.FZK.DE/IMVT

Prepared for presentation at the 2002 AIChE Spring National Meeting (IMRET 6 - 6th International Conference on Microreaction Technology), March 10-14, New Orleans, LA

Proposed topic: TBa05: Poster Session Microreactors as Tools in Chemical Research

Abstract

The iron(III)-catalyzed oxidation of ethanol by hydrogen peroxide to acetic acid is a highly exothermic reaction that was intensively studied by Hafke [1]. This makes it an ideal test reaction for microstructured reactors. Experiments were performed in a newly built test stand planned for a throughput of up to 10 kg/h, temperatures of up to 180 °C, and pressures of up to 10 bar.

We developed a modular microreactor system for this chemical reaction, which is parametrically sensitive and strongly exothermic. The modules consist of a micromixer and microreactors. The reactors are built as cross-flow devices. The reaction passage consists of 169 channels with cross-sections of 150 µm x 200 µm and lengths of 6 cm. The other passage, through which the reaction heat is removed, has 1960 channels with cross-sections of 150 µm x 200 µm and lengths of 1.8 cm each. The modules are flanged together, as a result of which a small dead volume is obtained between the modules. This prevents an uncontrollable temperature rise in this space. The complete microreactor system is built up by combining the micromixer and four reactor modules. The temperatures can be adjusted for each of the modules individually.

In a typical experiment, 1.2 l/h ethanol and 3.1 l/h hydrogen peroxide solution (30%) plus 50 ml/h of an acidic aqueous solution of Fe(NO3)3 serving as a catalyst were fed into the microreactor system. The temperatures in the four reactor modules were adjusted to 70 °C, 105 °C, 105 °C, and 20 °C respectively. The yield was 99.3% acetic acid with a complete conversion of both ethanol and hydrogen peroxide, thereby generating about 3.8 kW of heat. The steady state was achieved and the temperature was kept within narrow boundaries for each of the modules.

Thus, it has been shown that a highly exothermic fast liquid phase reaction can be performed isothermally in microstructured reactors.

References:

[1] C. Hafke, PhD thesis, Universität Stuttgart 1972.

http://www.aiche.org/conferences/techprogram/paperdetail.asp?PaperID=365&DSN=spring02




abacus

  • Guest
ketene via heating acetone
« Reply #43 on: April 26, 2004, 10:25:00 AM »
Org,

ketene was produced ad nauseum (as posted by others here before) by using a controlled red hot element in the vapour phase of refluxing acetone.

That is, 2 neck flask, one had the condenser with ice cold water running through it, the other heating element.

The heating element was from an electrical radiant heater, had a resistance of 55 Ohms and was voltage controlled via light dimmer so that it glowed red hot in the flask. 

The top of the condenser was attached to another condenser (with ice cold water running through it) leading down to another 2 neck flask serving as an acetone trap.  The 2nd neck of this trap flask was attached to a bubbler set up so that the gasses were bubbled through GAA and finally exhausted to a propane burner.

There was no doubt ketene was produced (nasty stuff indeed)as well as the by product methane (which was burnt off in the burner).

Used about 5L acetone and well over 10 hours in total.  used sodium acetate method to try to seperate GAA from the anhydride, over all yield very dissapointing in relation to how much effort was put in.

Resorted to making acetic anhydride from sodium acetate, bromine, and sulphur, which proved much much better, faster, easier and cheaper due to the fact SWIM blew up 3 expensive light dimmers in the process, not to mention slight fire issues.

Nothing like seeing a 2 foot flame of burning acetone vapours coming out the side neck of a flask.

Abacus

Organikum

  • Guest
Re: ketene was produced ad nauseum (as posted...
« Reply #44 on: April 26, 2004, 11:45:00 AM »

ketene was produced ad nauseum (as posted by others here before) by using a controlled red hot element in the vapour phase of refluxing acetone.


Now I understand. This method is known to be ineffective and hazardous. If one cannot get his hands on a original ketene-lamp this setup should be avoided. Also the setup as described by VOGEL 3rd Ed. doesnt work well. If one reads the text it shows up that the claimed yields refer to the original ketene-lamp and not to the inferior setup depicted in the book.
I know it doesnt help shit, but abacus you are not the first and will not be the last to fall for this.  :(

There are two proven working ways to accomplish the thermolysis of acetone to ketene in acceptable yields:
- the first is to use an about 70 cm long and about 2 cm inner diameter tube preferable made from porcelain/ceramics and filled with broken porcelain,
- the second is to use a coppertube of about 1 meter length and about 3 mm inner diameter - all details are described in the

Patent GB425973


Rapid cooling down to below 500°C after the actual "hot spot" is the key. The second method has higher throughput the first one is more resistant against polymerization.

The second method was done by myself, the first claimed functional by persons I trust in this. As both work it is a question of meterials available and personal taste. If one decides to go for the second setup I advise to read the named patent several times, to redo the calculations and to make sure to have really understood everything whats told there. Who reads it once and thinks he knows now how it is done WILL fail.

I myself prefer the coppertube as the small inner diameter prevents any flameback and provides more security when running the device overnight or even longer.


hope this helps
ORG




abacus

  • Guest
maybee
« Reply #45 on: April 26, 2004, 02:35:00 PM »
As I stated, there was NO doubt ketene was being produced

Also, if it wasn't working, how can you explain the constant flammmable gas that was the by-product? ie methane?????

Organikum

  • Guest
Sorry, I never told it doesnt work at all - I...
« Reply #46 on: April 26, 2004, 03:34:00 PM »
Sorry, I never told it doesnt work at all - I only told it is ineffective and hazardous - both is described in your first post.
- There was not very much ketene produced - just enough to get 70 gram AA in 10 hours what you told to be not satisfying at all.
- Flames out of the flask as described are to be called hazardous after my definition.

Please dont interpret things into my post I have not written.
Thanks.
ORG


Osmium

  • Guest
How come the yield was so low?
« Reply #47 on: April 26, 2004, 03:37:00 PM »
How come the yield was so low? Maybe the shit didn't get absorbed into the acetic acid and got burned with the methane?


Organikum

  • Guest
The only ketene lamp "design" which...
« Reply #48 on: April 26, 2004, 03:54:00 PM »
The only ketene lamp "design" which I can remember posted here is the one of HYPO which doesnt even include an condensor for recondensing the acetone which wasnt pyryolized - if this is the way it was done the yield is absolutely ok.
The original ketene-lamp was the work of life of a german chemist (Ott? - dunno now) and was never reached by others. I would love to see a picture or better drawing of this device. I have seen one from a russian ketene lamp which micht be a exact copy of the original but I am not sure on this.

The described tubes are much simpler and cheaper and give good results. The approach to homebuild a balanced system like the ketene-lamp is bound to fail if one doesnt have the plans and an glassblower by hand. This does by no way say it doesnt work at all - but the famous yield and throughput cant be reached.


abacus

  • Guest
ok
« Reply #49 on: April 27, 2004, 01:50:00 PM »
Osmium, the ketene dissolved in the GAA which caused the GAA solution to heat up, which was cooled periodically while dismantling to replace the used acetone with fresh acetone.

No traces of ketene gas seemed to pass through the GAA. This was tested by periodically stopping burning the flammable by product, methane, and carefully sniff tested (not really recommended) for traces of obnoxious ketene gas.

I did work, but as  Org has mentioned the set up used proved to be ineffective.  I dont know why, coz heaps of methane was produced, but in any case SWIM wont be trying that experiment again.

Tdurden969

  • Guest
>and carefully sniff tested (not really...
« Reply #50 on: April 27, 2004, 11:37:00 PM »
>and carefully sniff tested (not really recommended) for traces of obnoxious ketene gas.

Wow, do you understand just how poisonous that stuff is?


lugh

  • Guest
Hypo's design wasn't intended to produce ...
« Reply #51 on: April 29, 2004, 04:47:00 AM »
Hypo's design wasn't intended to produce liters of acetic anhydride, so abacus's results aren't very surprising. As far as pictures, the pages from Vogel's 3rd Edition concerning the keten lamp:



The commercial keten lamps for sale, primarily in Europe, are based on the design of H Stage, published in Chem Ztg 97 67 (1973)  :)  Hershburg's modifciations of Hurd's design:



Another design of possible interest from Ind Eng Chem 38 53-7 (1938) that has been used for liquid phase pyrolysis of acetone to produce keten:



8)


hypo

  • Guest
hypo's setup
« Reply #52 on: April 29, 2004, 09:33:00 AM »
i think i never could explain the setup correctly. that's what it looked like:

the 2nd condensor improved yield, because there wasn't that ugly middle
fraction. if one has the equipment for a ketene lamp, distillation should be easy.
i really don't see why 1l/week wouldn't be doable this way. if that is
too inefficient -> bummer. there's still the S2Cl2 methods.


Rhodium

  • Guest
Concentration of acetic acid and formic acid
« Reply #53 on: April 29, 2004, 05:53:00 PM »
Check out these patents:

Post 259042

(PolytheneSam: "concentrating carboxylic acids", Methods Discourse)


According to one of them it is possible to vacuum distill out the water from 80% acetic acid by the addition of a bunch of sodium acetate to the distillation flask...


Daphuk_up

  • Guest
quick question (as opposed to a slow one)
« Reply #54 on: May 03, 2004, 02:07:00 AM »
SWID recently mixed 300mL of 40% acetic acid and 650mL of 91% IPA.  With the stirrer on high, a large quantity of sodium chloride was added until there was an undissolved layer on the bottom of the erlyenmeyer.  There was no biphasic layers visible.  This was left (stoppered) in the fridge overnight.  The next day, there was still no layers visible.

Because of previous posts, SWID is somewhat confused.  Is there supposed to be a biphasic seperation or not?  How else could one isolate the AA/IPA mix?  Should SWID add more IPA or water to effect seperation?

Ok, 3 quick questions. ;D


lugh

  • Guest
Stage's Article
« Reply #55 on: June 20, 2004, 01:56:00 AM »
The article by H Stage, mentioned in

Post 503663

(lugh: "Hypo's design wasn't intended to produce ...", Chemicals & Equipment)
; Chem Ztg 97 67 (1973)



8)


Shane_Warne

  • Guest
ketene lamp yields
« Reply #56 on: June 20, 2004, 04:49:00 AM »
Org, why don't the ketene lamps perform adequately?

There are nichrome wires with insulating coatings.
Ceramic, glass.

With superfine wires, your going to have problems maintaining heat without insulation.

If the wires aren't arranged thoughtfully, I'd also invisage failure.

I found tables of various nichrome wire gauges and types, relating amperage across them to gain specific temperatures.

I'm sort of stuck choosing the gauge and type of nichrome (fine insulated or thicker uninsulated etc), and the electrical components required to adjust the temperature of the chosen wire.