Oil Stock w/high pH

[oprogue]

I have some oil that is testing out at 7g NaOH/L + the base/L amount; I've been fortunate to only have to use 3.5 g NaOH/L as a base amount in the past, but this current oil needs a total of 10.5 g NaOH/L and it seems to have one heck of a high jell point after processing. This particular grease came from a chicken restaurant, a mixture of chicken fryer and french fry fryer oils. Could the high chicken fat content be behind the high jell point?

I will try pre-washing (no water) with 20% glycerin prior to reacting in an attempt to adjust the pH ... I'm curious as to whether any testing of the glycerin has been done before using it using this method of glycerin addition?

... are there any other possible solutions to this delemia?

... acid/base two step process perhaps?

... pretreat with NaOH/methanol without heating, the retest the pH of the oil and adjust?

Thanks in advance.

[quantum_tdi]

Two problems you're running into there.

The original base of 3.5g/l will net you an incomplete reaction (bad information off of the Journey to Forever site). Are you saying you use 3.5g + titration? The suggested amount is 5g or more + titration for NaOH, 8-9g + titration for KOH depending on purity.

Then you're using beat down oil with either a partial hydrogenated mix of oils or as you guessed a very high chicken fat content. The oil may also be burned, increasing its FFA content. Pretreatment with glycerine does seem to help flock out some of the crap that contributes to poor reactions and may lower the FFA as well. The use of acid/base process introduces quite a bit more work and monitoring, but it will allow you to use very high titrating oil with success.

At the level you're working, you might do a two-step base process (look up 80/20 method).

Are you testing the feedstock for water content?

What kind of wash methods are you using?

Have you done a 3/27 test to see if you have remaining unreacted oil in your finished product?

[oprogue]

With the orginal attempt:

The 80/20 method resulted in a glob - the mass would assume the shape of the container, but wouldn't flow.

The feedstock oil had no measureable water content, water was negligible to non exsistant even with an ATR spectrograph.

Bubble wash and/or two week settling process when possible ... but this stuff wouldn't process to be washed ... and the same for the 3/27 test.

Currently:

Pre-treatment with glycerin lowered the NaOH addition to 3 g NaOH/L oil; oil even began to clear the test batch within the first couple of hours. I'll be density, cloud and gel testing tomorrow.

Acid/Base batch processed well with the exception of soap layer and relatively huge glycerin layer (using the upper limits, as previous post noted, of NaOH). I will be running two additional test batches tomorrow that will be acid/base reacted and will report back results this weekend.

The FATTA method, while it works, raises some questions for clarification:

2 mL of phenolphthalein is an enormous amount of indicator (a few drops should do, other wise the weak acid of the indicator will affect the reaction), is this a standard amount determined by trial and error?

... and only 0.5 of the acid value is FFA?

"Add an amount of concentrated sulfuric acid equal to 0.05g for every gram of FFA" is that 0.05 g of acid for every gram of oil (the addition is by weight, not by volume)?

Thanks again in advance,

Ralph.

[quantum_tdi]

Mmmm... specrograph. It sounds like you'll be able to do some very tightly controlled experiments with this. OK, here are a bunch of thoughts that are not all necessarily related. I tried to put them in some sort of order that makes sense, but read each paragraph on its own if it gets to be too much.

You may solve your glop problem by investing in KOH. The use of KOH also allows composting of the glycerine if you're recovering the methanol.

I'm also wondering if you're letting the first layer of 80% settle enough to remove the glycerine before doing the final 20% reaction in the second step of the 80/20 method. Again, agitation with NaOH rather than KOH may be the other reason for glop at that point.

In regard to acid/base: the FATTA method still assumes a base of 3.5g/l for NaOH (See Tony from West Oz's posting on the same FATTA thread suggesting 5g/l). They may do this to avoid what you ran into- soap production. The use of KOH will help to eliminate the problem of solids and glop.

Agreed on the indicator- only 2-3 drops are needed in the standard titration. Use Murphy's (murph titration) or the collaborative biodiesel tutorial one here

Ironically they have you calculating acid value by using KOH and not NaOH which suggests that first post is just a conglomeration of cut-and-paste, not a well thought out posting. The original reference to the thread they cut from would be helpful because I wager there are some postings correcting some of the problems with the original formulas.

Pretreatment with glycerine will inevitably lead to glycerine in your feedstock. It won't all drop out. That may be where some of your extra is coming from after processing.

[oprogue]

The ATR is useful for general inferances of composition, a simple Spec20 or a UV-Vis would be more revealing (especially the later ... working on that one now ... there's an interface for the TI83/84 calculators that could be used in making field determinations of oil quality).

Interesting development with the sample of gloop today ... I was lecturing on rates of reaction, blah blah blah and was questioned by one of my students on reacting the jar of gloop at the end of class (he was trying to abate going to his last class of the day and I was the excuse). So I permitted him to shake like mad and apply heat (mild liquification occurs after a few moments but this particular batch remained a pretty thick consistancey). He ask what did I think would liquify it and I mentioned the glycerin fortification ... he said why not do it ... excellent moment of inquiry so I said "let's see". My train of thinking was either it'd work or I'd merely let it settle and pour off the glycerin. Keep in mind this was the intial 80% MeOH/NaOH mixture; waaalaaa ... the student shook it maybe twice and it was a very fluid liquid again. Before I left I did a quick inspection of the reactions for the day and it had seperated out quite well, touch of soap (but a well defined layer) and considerable amount of glycerin. Because I suspect (as you've indicated) there is a loss of ester/transesterifiable material, I intend to treat the remaining soap with some sulfuric acid over night, test and process as usual just to see what the end result is.

KOH is an alternative we considered except it precludes the ability to make bar soap (which our Occupational Career Services class is looking forward to) ... guess they could always consider liquid soap ... I would like to purify some KOH from ash just to see if I can generate enough of it. Meanwhile NaOH is just so cheap and convenient.

The thought of the 80/20 and KOH vs. NaOH maybe be a valid assumption ... I've seen batches clabber up instantly an NaOH addition and only get thicker with agitation. Heat seemed to be the only thing that was initally effective at combatting it, a pump simply couldn't handle the high viscosity and would stop. Whether it's the lack of quality control or poor technique (or a combination of both) is also of consideration as well. I think these particular experimenteers may have put double the NaOH in this particular batch ... while I've make gloop also with it, nothing like the sample in question.

The base amount of NaOH does vary from formula to formula. I often wonder the trial and error and as to how much the ease of degradation/comtamination of NaOH plays in this. I've played this by intution following titration. If it seemed to dictate 1-2 gram additions of NaOH I would usually just use something between 4 and 4.5; higher amounts I tried to keep all additions below 6-7 g NaOH/L oil ... and haven't really had any issues (nothing that a touch of anti-gel and some pump diesel wouldn't take care of ... just didn't want to fool with the batch anymore) till now with the 10.5 g NaOH/L oil.

I don't think (least not at first thought ... some say I shouldn't think at all, especially ex #1) the use of titrant really matters when your taking into consideration the normality/concentration of the standard. The variance between the two comes out in the wash of consistency of the method. I would like to see the unit analysis for the calculation though ... it might shed some light on the whole process.


I processed a 1L acid/base test batch today (I treated with 2 mL Sulfuric/1lL oil for 2+ hours @ 50C and then 5g NaOH/L oil *the oil tested at 6 g NaOH/L but I conservatively held back 1 g) for another 2 hours also at 50C). The batch had begun to seperate out before I left today ... anxious again to see how it turns out.

We have some planned physical testing of the oils to look for similarities this coming week, I hope to process 3 - 6 L of oil test batches this coming week of the high FFA stuff to compare last week's data with. I'm trying to keep things rudamentry so anything I do can be replicated by the averate person/student at home.

Other experiences with high FFA are most welcome ... questions and comments as well ... I'm hoping to gain some insight from the thread ... someone give me some more food for thought.

Thanks again in advance,

Ralph.

[quantum_tdi]

Hey, have you hooked up with the biodiesel in schools list? There is a yahoo group dedicated especially to education about biodiesel. One of the locals here (Chicagoland actually) is Barry Latham and he's really pushing science ed with it. He was at our recent GirlMark class and even had a great column for doing waterless wash (which I still don't believe in, but it is coming along in technology).

I'll PM you with his email address. He can get you hooked up with biodiesel in schools list. I know they've been trying to get more discussion going recently and share techniques.

[oprogue]

Awesome! I think that information needs to trickle back here eventually ... the inclusion of all involved with accelerate the skill/abilities of all involved.

Thanks again!

[quantum_tdi]

What part of NC are you in? GirlMark is doing another couple of classes out there soon-

www.girlmark.com/tour

[quantum_tdi]

One other thing- what % methanol are you driving the reaction with?

[oprogue]

I'm in western NC just south of Asheville, and work on the Reservation next to the TN/GA lines.

I use a minimum of 20-22% MeOH, but in making test batches I have used as much as 33% MeOH (I don't want the MeOH to be the limiting reactant but rather the oil/NaOH).