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when is neutralization of glycerin necessary for applications (compost/soap/etc)
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Hi, I'm really new to this stuff and have a few questions regarding glycerine byproduct neutralization. I'm looking at what alternatives are available for recycling the glycerin byproduct from biodiesel synthesis. I understand that in making soap or composting the methanol must be removed, but I'm not clear on if any neutralization is done as well. Neutralization will result in separation of byproduct (from KOH catalyzed biod) into FFA's,glycerin/methanol layer, and catalyst/phosphorus layer, right? Can the FFA's be reused to produce more biodiesel? For small scale biod. production when would one want to do the neutralization? Is that only to refine the glycerin enough to sell??? Again, I'm very new to this stuff. Thanks...
 
Location: MA | Registered: January 09, 2009Reply With QuoteReport This Post
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JeanG,

A few options:

1. You can make soap directly from the byproduct AFTER demething. Since about 50% of what's left is glycerol, you'll have a very sticky/gummy bar of soap if you don't combine with steric acid or something else to firm up the bar.

2. You can neutralize (I use 31+% HCL) and separate into glycerine and FFA parts. I use the glycerine to prewash my finished biodiesel...it REALLY improves the quality of washing. The FFA can be used to make soap. I don't know if it will make biodiesel unless you use an acid/base process....my guess is yes. You could use a portion of the glycerine (about 15% for 'standard' soap and something like 25% to get a more clear bar of soap) to make soap with the FFA that you have recently separated.

Note: You should change your profile to indicate where you're from....so that we know.

Good luck!

Steve


2007 Dodge Ram, 2x-2006 VW Jettas - 34,000 B100 miles by 2009.
 
Location: Bay Area, California | Registered: October 05, 2007Reply With QuoteReport This Post
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Hi JeanG and AwesomeNet,

AwesomeNet,

Thank you for clarifying my perplexed thoughts on glyceine soap making, in that you neutralize the soaps into FFA and Salt then use the FFA to make pure soap. Is there any threads that you know of that give recipes for doing so? Any feedback would be much appreciated!

JeanG,

I feel that you could face a few problems if you attempted to make biodiesel out of pure FFA. The esterification of FFA and Methanol with an acid catalyst produces 1 mol of water per mol of biodiesel. Once too much water is formed, it will inhibit the reaction. (this was true in a few of my small scale reactions in which the water content caused the reaction to gel up). If you want any more details on why this occurs let me know.

Thanks all,

~Ryan J.


Chemical & Energy Engineering -- The Pennsylvania State University
 
Registered: May 22, 2008Reply With QuoteReport This Post
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My understaning of veg oil is that it is 3 fatty acids bound to a glycerin molecule. Why then will FFAs and glycerin not rebind together (with heat)? I am sure there is a reason, otherwise everyone would be doing it, but I would really like to understand that reason.

Many thanks
Ed
 
Registered: March 20, 2011Reply With QuoteReport This Post
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