Acetic acid +NaOH = Methane?

[birkATO]

Has anyone ever heard of a reaction that uses Acetic acid, or Sodium Acetate using Sondium Hydroxide to produce Methane gas? I am talking on a production scale, not lab scale.

 

[Zoobie]

I have never heard of this but I wonder what the point of this is would be. Is this for making methane in locations where natural gas is not at all accessible? Where would you want to use this...geographically speaking? How much methane are we talking about? What would you use the methane for? Acetic acid is usually made from methane (natural gas) via syngas production followed by methanol carbonylation. This means that in most of the developed world the economics of this reaction for producing methane are awful. If the methane is to be used as fuel for anywhere in the world than the economics are awful.

I don't mean to sound negative...I am curious more than anything else.

 

[vpl]

So zoobie, what you're saying is that this process would involve taking methane, converting it to acetic acid, then converting it back to methane?

What would the benefits be to doing this?

Patricia Lougheed

Please see FAQ731-376 for tips on how to make the best use of the Eng-Tips Forums.

 

[Ashereng]

Patricia,

I am not sure of birkATO's situation, and this is pure speculation but I am guessing:

1) doesn't have methane gas available, but does have access to acetic acid and caustic?
2) can't handle gas (no pipe), but can handle liquids (has rail)?
3) just curious?

 

[Zoobie]

vpl,

That is exactly what I'm saying. Methane is used to make petrochemicals. Petrochemicals are not used to make methane.....think of it like taking some ashphalt, diesel, kerosene, and gasoline mxing them up to make crude oil. What purpose would this serve.

 

[Zoobie]

Ashereng,

I believe your comments are in line with my questions as well.

I was going to write a bit more but deleted it....I was starting to rant a bit.

Oh just one...you need between $3 and $4 dollars worth of acetic acid to make $1 worth of methane (I am not familiar with the reaction so I am assuming that you get 2 mols of methane for each one of AA. If you get only one then double the number). Then add in caustic and all the other operating costs.

Maybe if get a response from birkATO we can satisfy our curiousity.

 

[Ashereng]

Zoobie, vpl,

I think we are all thinking the same thing.

The one other thought I had is that should methane be a key ingredient to a high margin product, then cost of the acetic acid and caustic would be justified.

I too am waiting for birkATO's response.

 

[Zoobie]

Ashereng,

The cost would be 'partially' justified. There are cheaper ways of making methane from liquids or solids.....just get some cows or pigs .

 

[Ashereng]

Zoobie,

I agree.

To add to the cows or pigs option, another common source of methan is garbage dumps. They have to put methan vents in them anyways, so some entrepreneur can pipe it to a plant. Oh, that and beans! Tee Hee Hee ;-)

 

[Zoobie]

Ashereng,

My wife thinks that I am a pretty good source of methane too. During my peak production rates I'm sure she would love to send me off to wherever this plant is.

 

[birkATO]

I am a consultant. One of our clients has access to acetic acid as a waste stream and wanted to know if that reaction would be possible. The only way I know to make methane out of Acetic acid is using microbes. I just though I would run in through here to see if anyone has ever heard of a process I don't know about. Thanks for the input.

 

[Ashereng]

Zoobie,

Laughing Out Loud!!!

 

[vpl]

birkATO

Just a thought, maybe your client should consider diluting and bottling up the waste acetic acid, maybe with a bit of perfume? Those are the main ingredients in nail polish remover, something I buy frequently!

In a more serious vein, it would be a better solution to find ways to use the acetic acid or to sell to another company than to try to turn it back into methane.

Patricia Lougheed

Please see FAQ731-376 for tips on how to make the best use of the Eng-Tips Forums.

 

[moltenmetal]

That'd be vinegar, Patricia, not nail polish remover. Nail polish remover is principally acetone, not acetic acid. But I sincerely doubt you'd want to put this particular stream on yer fish 'n chips!

 

[Zoobie]

birkATO,

I presume you have never heard of any such reaction either. If you consider your first year chemistry course (if you are a degreed Chem Engg), then the only thing that makes sense is that you will neutralize the acid. I presume the AA is in an aqueous solution. If you add caustic you get sodium acetate. As far as I know, adding more caustic will only raise the pH further. If high pH will destroy the acetate anion then that would be a very interesting piece of information.

Is there a reference for this suggested reaction? Or is this someone's wild idea?

 

[zdas04]

Generating electricity off of land-fill gas is becoming a big, mainstream business. One guy told me he was running gas turbines on "methane, keytones, and baby diapers", but he may have been exaggerating.

David

 

[kenvlach]

Bunch of cynics didn't figure out that birkATO's client may have heard of the process involving sodium hydride (not sodium hydroxide):

NaH + CH₃COOH --> CH₄ + NaCOOH

[Δ]G_Rxn = -184.7 kJ/mol per my CRC Handbook values.

It's been investigated for methane generation for fuel cell vehicles, but I think not feasible due to NaH cost & NaCOOH byproduct.
Also, the reaction is rapid & requires anhydrous acetic; NaH reacts with water & you end up with sodium acetate as mentioned by Zoobie.
But NaH may be worth considering as a good storage means for H-fueled vehicles.

 

[Ashereng]

Bunch of cynics didn't figure out that birkATO's client may have heard of the process involving sodium hydride (not sodium hydroxide):

Yup. Guilty.

Actually, I don't have the capability to tell if your reaction would work either... so... I'll leave it to my more learned colleagues to comment.

 

[Zoobie]

Well I might agree to being a cynic...which tends to be a function of time of day and coffee intake (or rather lack thereof). As responders to posts in this forum we have to rely on the information in the original query. I have seen many threads get derailed because the starting point was not accurate or someone presumed something right from the start.

birkATO, what is the waste stream composed of? If it is an aqueous solution then you will be faced with azeotropic distillation to get to anyhydrous AA.

Well it is almost supper time and I tend to get cynical before dinner so I better sign off.