Adsorbent Pellets for Washing Biodiesel

Pure hogwash and wishful thinking. This totally ignores the reality. Contaminants in conventional trans esterification product may reach several volume percent. Adsorbents are economical ONLY at very low parts per million contaminant removal. The 'spent' adsorbent must be replaced (or regenerated somehow).

The ANSWER is to NOT MAKE contaminated bio-diesel. Use ESTERIFICATION employing a solid acidic ion-exchange catalyst and completely avoid the product contamination issue.

Alright go and tell all the people who are currently using adsorbents, to change immediately.

Ion-Exchange catalysts exchanges ions even as the name implies. So the FFA in the presence of an acid, say, sulphuric acid and methanol loses a Hydrogen atom that is replaced with methoxide unit producing water that inhibits the reaction and must be removed. except that here you are replacing the liquid acid with a solid acidic ion-exchange catalysts. So be specific give the name and chemical formula of the ion-exchange so that we can determine what it would be exchanging into the reaction mixture prior to the transesterification reaction

Now also tell me does the ion-exchange catalysts ever get "spent'? Does it not have to be regenerated even as the pellets have to be regenerated? Catalysts in general do get deactivated at some point in time of their use, correct? Then what?

I do hope that you will answer this time and not run off like you did last time when asked you to support your assertion with scientific argument.

Ion exchange catalysts are x-linked polystyrene beads which have vinyl benzene sulfonic acid copolymerized with the styrene. They can be used as acid catalysts in the same way as pTSA. Functioning as a catalyst, they "loan" their acid proton, but do not "spend" it. If it is a clean-running rxn, they can be filtered out and reused, or packed into an ion exchange bed and the rxn pumped thru it. If the rxn produces crud, then the beads get fouled and need to be cleaned. If the acid beads are used to scavenge amines or HO-, then they need to be regenerated back to the acid form. I have not tried acid beads as a biodiesel catalyst, but have worked with the beads before. Dow makes them, Dowex MSC-1H or something like that was the product I used to scavenge amines.

That is just the point I was trying to get Keith to ensnare himself in. This Keith seems to have a habit of writing things about which he does not bother to get comprehensive knowledge of.

The esterification reaction apparently entails the stripping of OH ion leading to the attachment of a methyl group to the free fatty acid and a replacement of the H ion used in the stripping of the OH ion. Hence, as per your supposition the resin would need to be periodically regenerated.

Besides, the oil for which the pellets were developed is the algal oil which has very small amount of free fatty acids, and again making his (Keith's) observation of the suitability of the pellets valid - by which he contradicts himself.

Moreover, the oil for which esterification is suitable is the Waste Vegetable Oil, WVO, and these have large quantities of food junk even after cleaning by reducing the viscosity on heating to enable sedimentation of the junk, followed by filtering; all of which will lead to the fouling of the resins.

Finally, by one of our recent posting, Domestic waste Vegetable Oil Recycle Chem Reactor, it is clear that such a reactor will significantly reduce the Free Fatty Acids content prior to the transesterification reaction; and the question then becomes why would resins consuming polymers of all sorts, the production of which generates waste of it own, be preferred over the use of seemingly inexhaustible natural minerals as are being used in the pellets? Moreover, because the ionic-charge of the Magnesium Silicate is derivative of the monoclinic crystalline structure instead of chemical structure, the regeneration is very simply and inexpensive.

In any event, thank you very much for enabling the elicitation to Keith about the prospective shortcomings of his suggestion.

Hate to be nit-picky, but there is a minor misconception of the esterification process. With free fatty acids and an acid catalyst, the acid proton from the catalyst protonates the carboxylic acid OH, making R-C=O-OH2+. This protonated acid OH leaving group is displaced by the methanol to make the methyl ester, giving off H2O, and regenerates a proton for the acid catalyst in the process. HO- ion is not stripped in this process. With these triglyceride oils, glycerin is a by-product of the transesterification process of converting cooking oil into B-100. It is often done with KOH or sodium methoxide under alkaline conditions.

I think we are saying the sae things but from different perspectives: Lets say, the H+ from the sulphuric acid proponates the [-OH] - happens to have negative polarity - unit of the carboxylic acid, as you have written it. Now if the displacement occurs at the carboxylic carbon... That is what I meant by stripping - and not free floating OH- ion, perhaps I should have said [-OH] unit

However, here is the question: how does your catalyst operate?

Consider the sequence: a proponation occurs, a displacement occurs, H+ is released. Now if this sequence is correct(?) then
Since the H+ in the catalyst will now "proponate" the carboxylic acid and stay bound to the OH until the H+ is released with the full reestablishment of the C-O bond of the carboxylic acid, would the regenerated H+ replace the OH now bound to the catalyst.

Simplistically speaking, a proton is a proton is a proton. The proton from the acid catalyst becomes water as the methanol displaces it (H2O). The OH proton from the methanol comes off as the ester is formed and regenerates the acid catalyst.

I have this sneaky feeling that something is not quite right: When you use sulphuric acid, the little water in the acid allows the acid to exist in ionized state or free proton state and at the interface between the [water-] acid and the fatty acid or oil, the free H+ ion can react and proponate the carboxylic acid, and get the reaction started..... get where I am going with this? Would the methanol -OH unit be more susceptible to reacting in this case? I would consider a mechanism research of this.

Don't forget we're running this in a copious excess of methanol which acts as a solvent as well as a reactant. Methanol can be rather nucleophilic in this case and displace the protonated acid. At elevated temperatures (~50C) it can form a rather homogeneous mixture. Methanol solvent is a totally different medium than H2O. This is an equilibrium rxn and removal of water and/or excess methanol help drive it.

I believe that you are speaking about the chemistry in general and I am speaking reaction mechanism.

So let me restate the mechanism I was proffering. H+ exists in water not really as free ion but rather as an hydroxonuim (? - spelling) ion which is effectively written as H₃O+. The expression shows that the water molecule is actually reconstructed to form three hydrogne bonds with the oxygen atom forced to give up one electon in some complex covalent bond. This then is the state in which most organic reactions are considered when H+ is talked about. The water molecule potonation is very specific.

Therefore in your reactor where the ion-exchange is being used given that there is no water and "free" ion to start the reaction, you have suggested that the H+ of the catalyst will be freely yeilded to the surrogate-solvent, methanol. In that situation I have proposed that the -OH unit of the methanol gets protonated resulting in an ion of the form CH₃(H₂O)+ and with the ion-charge preferentially centered on the C atom, exactly the situation when the carboxylic molecule gets protonated.

That said, now I suggest that this form of protonation of methanol will actually 'be equivalent in dynamics to "a scavenging of an OH- ion" ' and therefore require a regeneration of the catalyst. You obviously disagree, so I then suggested that a mechanism research is in order.

The removal of water drives the reaction to the right is not because of the reversibility of the reaction but rather because methanol binds stronger - hence preferentially - with water than with carboxylic acids, so the removal of water makes more methanol available. The reversibility of the reaction can also be altered with the use of catalysts that change the reaction mechanism - think about this last point, and come back.

Any idea what amount of these pellets would be required to process a 5000 gallon batch? Are the pellets easily reusable? Sorry if the questions are general, but most of the technical side of the discussion is over my head.

Actually, the user has those answers by virtue of how the pellets are made. each user is likely to make his/her own to her taste. We only propse the science and it is users to make their own.

The number/quantity of pellets you need will depend on the concentration of talc in your pellets, the porosity of the pellets, and the strength of electric field by which you polarize the talc in the pellet.

So at present this is not a commercial absorption product, just a do it yourself formula?

Once produced, would these pellets be reusable?

Yes. the regeneration is quite easy. The "inversion" electric field coupled while running water over it regenerates it.

My company sells the ion exchange resin beads. I do know know the mechanism but, my technical department could help. Just post your question at www.resintech.com

Thanks