TAN vs NAT 1

[MaNaTMoS]

Hello,

In several articles I have been reading, the subject was the difference between total acid number (TAN), determined by ASTM standard method, and naphthenic acid number (NAN), determined by mysterious (to me) "naphthenic acid titration test - NAT". What kind of test is it? Can it be found in some of the present standard test methods?

The articles were dealing with naphthenic acid contribution to total acidity of crude oil(s) where, of course, TAN is always greater than NAN.

Is someone familiar with these methods/tests?

Regards,
MaNaTMoS

 

[25362]

Googleing around I found a laboratory offering services to measure the naphthenic acidity:

http://www.geomarkresearch.com/pdf Proposals/gTAN Proposal.pdf

which claims doing the measuring based on "Determination of NA in crude oils using non aqueous ion exchange solid phase extraction (SFE)" that appeared in Anal. Chem. 73:703-707 by Meridith, Watson, et al. (1999).

I'm unable to reach a technical library, but I hope you could. I'll be grateful if you'd be so kind as to let me know of your findings.

 

[MaNaTMoS]

Thanks, 25362

Concerning the naphthenic acid analysis and theory, I've manage to find the following (according to several sources, all available online - "CorrosionSource", "SetLaboratories", "AaChE" etc.):

1) The ASTM procedures for Total Acid Number (TAN) - also called neut number - were not developed for crude oils. There were used for determining the oxidation of petroleum products and lubricants. ASTM D974 is a colorimetric titration method and has a reproducibility of 15%. ASTM D664 is a potentiometric titration method with reproducibility of 20 to 44%, depending on the end point (buffer or inflection), type of oil (used or fresh), and titration mode (automatic or manual). Inorganic acids, esters, phenolic compounds, sulfur compounds, lactones, resins, salts, and additives such as inhibitors and detergents interfere with both methods. In addition, these ASTM methods do not differentiate between naphthenic acids, phenols, carbon dioxide, hydrogen sulfide, mercaptans, and other acidic compounds present in the oil.
2) In the UOP procedures, sulfur compounds are removed before analysis of acid number. UOP 565 is a by potentiometric method and UOP 587 is a colorimetric method.
3) In the chromatographic method or Mobil method, naphthenic acid are expressed by weight percent. The acids are extracted by liquid chromatography and then analyzed by IR spectroscopy. Unfortunately, the instrument is calibrated with standard naphthenic acid, which might not have the same composition and molecular weight as the sample. Thus, the weight percent can be used for comparison purpose only.
4) Another variation of the chromatographic method is the Naphthenic Acid Number (NAN) or Naphthenic Acid Titration (NAT) whereby the sample is extracted by chromatography and then titrated per ASTM D664.

I'll try to do some more by asking expert from another location; he'll be available soon, I hope.

 

[MaNaTMoS]

BTW, friend, you smoke too much!

)

 

[25362]

You're right. I'll stop ... using the emoticon !

 

[MaNaTMoS]

Very good, my friend; as a first step, I'm giving you a big shiny star for the right decision.

I'm a passionate tobacco guy also, but I'm affraid 100 millions of stars wouldn't help me to quit smoking. Maybe I should try with drugs?

Wish you good health,
MaNaTMoS
)

 

[25362]

Think about the pleasures of pneumonia, and may be it will somehow help.

 

[visangio]

Daer MaNaTMos,
as explained by other people TAn is a standard ASTM test.
NAN is a proprietary method e therefore you will not find too much about it.
It has been developped to better identify which areas of a crude atmospheric or vacuum disttilation can be subject to corrosion by naphtenic acids.
In the literature you often find that there is a potential risk when TAN exceeds a level of 0.5 - 1.0.
However, when porcessing naphtenic crudes, it is necessary to have better tools in order to define a strategy to avoid this very dangerous corrosion.
If you want more detailed information, please write to me and I will be glad to give to you.
Best regards,
Vincenzo Sangiorgio -

http://www.gewater.com

Vincenzo Sangiorgio

http://www.gewater.com