[bigcanuknaz]

Hello:

This is my 1st visit to this forum.  Thanks for your help.

We are growers of organic tomatoes.  We can't use most synthetic chemicals for cleaning our greenhouse.  3 we can use are Hydrogen Peroxide, Acetic Acid(synthetic or non-synthetic) and Peracetic Acid.

Being organic growers, we like to do things as naturally as possible.  Rather than go through the cost, and suffer the synthetic production of Peracetic Acid by someone else, I thought I would explore making it ourselves.

I understand 100 moles of Acetic + 100 moles of H2O2 will make 37 moles of Peracetic plus leftover Acetic, H2O2 and water.

I have calculated this to be about 3 - 227kg drums of 80% Acetic Acid + 4 205kg drums of 35% H2O2 to make the Peracetic acid solution.

I understand some of the safety precautions I need to take.

Acetic acid is an dangerous acid. (especially at 80%)
H2O2 we have used for a number of years, and at 35% is a dangerous oxidizer
Peracetic acid in addition to being an acid, continuously liberates oxygen, so can't be in a closed container, or it will explode (because of pressure buildup).

Now we need to use peracetic acid at quite a low concentration.  I understand that the reaction from acetic + H2O2 to peracetic goes (better, faster??) with sulfuric acid as a catalyst.  But we can't use sulfuric acid.  Without sulfuric acid, would it be better to allow this reaction to take place as concentrated as possible?

I understand the reaction takes about 10 days using sulfuric acid.  How long will it take without sulfuric acid, or instead of 37% peracetic acid what will be the end percent without sulfuric acid.  If this is so long, or low, as to make it uneconomical, then is there any natural acid I can use as a substitute?

naz

[bigcanuknaz]

Hi:

I just had a thought.  How much sulfuric acid do we need?  Would there be some natural way of making sulfuric acid?  Say make some natural SO2 and bubble it up through some water.  Would this make a strong enuf sulfuric acid solution to use as a catalyst?

naz

[bigcanuknaz]

Hmmm...

Read a few more questions and answers here.   Am i in the right place?   Would there be a better place for me to post this question?

naz

[bigcanuknaz]

This should be in the chemical engineering forum, I think.  Sorry.

Would a moderator switch it to there, please?  If you think another forum would be better, switch it to the better one.

(please let me know if you switch it somewhere else.   nhansen .at. cogeco .dot. ca)

Thank you,

naz

[Borek]

I will move it tomorrow morning, for now let it sit in the organic chemistry. Could be Eugene (our engineering guru) will have something to tell - just be patient, he comes here only once a week or even fortnight. But I am afraid your question can be a little bit too specific.

I must admit from the first moment idea that peracetic acid is OK while other synthetic cleaning agents are NOK seems a little bit absurd to me - but that's irrelevant to your question.

[nj_bartel]

I must admit from the first moment idea that peracetic acid is OK while other synthetic cleaning agents are NOK seems a little bit absurd to me - but that's irrelevant to your question.

Yes

[bigcanuknaz]

I must admit from the first moment idea that peracetic acid is OK while other synthetic cleaning agents are NOK seems a little bit absurd to me - but that's irrelevant to your question.

Well, the organic rules do acknowledge that it is synthetic.  But the rule is basically:

1.  use only natural, unless you have to do it, and natural is not available.

2.  Then use what is least disruptive.

Peracetic acid is just vinegar which is organic, and oxygenated water which is pretty basic, and disassociates into just water and oxygen.  It has been cleared under organic rules as a "necessary evil"

We are using it for equipment cleaning.  If food equipment is not clean, then we get all kinds of food safety issues.   The goal of organic is to make food safer (and of course to protect the environment).  There is no way organic rules would require us to be unsafe.  If any of you have a more "organic" way of cleaning equipment, I am all ears.

naz

[eugenedakin]

Hi bigcanuknaz,

Sorry for the delay in my response.

The bad news: peroxide (as H₂O₂) is quite dangerous. I have worked with this material before, and upon contact with organic materials - such as small traces of oil or some other material - the mixture of oil and peroxide can spontaneously start on fire (no matches are needed).

I highly recommend purchasing the stabilized peracetic acid and not making it yourself. Small amounts of contamination can easily cause hydrogen peroxide to degrade and quickly start to degrade.

Sorry, the health and safety aspects of this reaction is so sensitive, that it is difficult to keep this material in a stable form once you have successfully created peracetic acid.

For the small amounts that you use, it is really not worth the problems (reactions, purity, heat, economics, toxicity, transportation, storage requirements, etc.). Please do not make this yourself. The 35% material is a diluted down version of the hydrogen material used to power rockets (yes, this used to be rocket fuel). As with any biocide, this material is highly regulated by almost all governments. Sorry for the bad news.

Once again my apologies for the delay in responding.

Best wishes,

Eugene

[bigcanuknaz]

Thanks Eugene:

We currently use about 10 drums per year of the 35% H2O2 material as a disinfectant, and as a general greenhouse cleaner.  Yes, we are aware of how powerful an oxidizer it it.  We take all the proper health and safety precautions and training.  It works quite well in our irrigation system, as an end of day cleaner, where we inject it, and leave it overnight so we don't get a buildup of organic contaminants in our irrigation emitters.  We inject straight from the drum, so this is reasonably safe.

It works as a general sanitizer between crops, but needs to be used at a higher concentration, and is very short lived, as it oxidizes very quickly.  Here we are diluting in manually into a spray tank at about 600ppm.  We are looking forward to using the peracetic acid, because it will work for a longer period, and provide better cleaning.

I suspected the making of peracetic acid would be delicate.  I presumed we would have to use distilled water, and possibly use continuous dosing of the various reagents.

We will probably use around US$5000 of peracetic acid per year, so for us, this is not a small amount.  But what you are saying, is that if the cost of the acetic acid and H2O2 is $1000, then making it is not worth the $4000/year savings.

Just to go over your problems and discuss really where we would be lacking:

1.  reactions- yes, this is where my understanding is most limited, and where I was seeking advice.

2.  purity - Here I think we could be alright, using pure reagents and water.  We were going to use 80% acetic, 35% H2O2, and distilled water.  Again the problem is the sulphuric acid, but it looks like we could add the required small amount as a catalyst, without breaking the organic rules.  The purchased peracetic we bought has 0.6% sulphuric acid in it.  (Already ahead of you there.  We bought it for this year.)

3.  heat - This is where I thought we might need to dose the reagents slowly into the mixing vessel, versus batch mix them.  Not sure if we could batch mix at a lower concentration, and if the reaction would take place at a lower concentration.

4.  economics. - because of the handling and transportation issues, peracetic is at least 5x the cost of the reagents.

5.  transportation -  That is the beauty of making it ourselves on site.  We don't need to transport peracetic.  and H2O2 and Acetic transport just fine.

6.  Storage - I am aware that peracetic continuously liberates oxygen, and needs to be stored vented.  That is why we would only mix up what we were going to use right away.  We could even make it at the final concentration (or at least very diluted) if the reaction would take place at these levels.  We only use it at 200ppm.

I am also aware of the regulation on the H2O2, as it is, as I understand, a precursor for a lot of illegal drug manufacturing.  Yes, we have to inventory and keep track of the H2O2 that we use.

Again, thanks for your help.  If you have any further ideas let us know.

naz