SARA test? 1

[shahyar]

In SARA test;
S stand for Saturates. What does it mean? Alkanese?(CnH2n+2)
A stand for Aromatics .(I know them)
R stand for Resins. What is their formula?
A stand for Asphatenes.(I know them)

Thanks

 

[25362]

It all depends on what you are analysing and the technique used.

For example, when speaking of hydrocarbon fractions in bitumens, generally regarded as colloidal systems in which the micelles are dispersed in a lower molecular weight medium called maltenes: saturates are obtained as a n-heptane eluate, cyclics or aromatics as a toluene eluate, resins as a toluene/ethanol (or methanol) eluate, while asphaltenes compose the fraction precipitated by n-heptane. These four fractions aren't pure chemical compounds with definite chemical compositions.

Saturates, solid or viscous liquids, include straight chain and branch chain alkanes and isoalkanes, and cycloparaffins (called naphthenes in the petroleum industry) with single or multiple rings (sometimes fused and bridged). They may also contain alkyl aromatics with long alkyl chains. Molecular weight typical range: 500-800. Thus the general paraffinic formula C_nH<sub>2n+2/sub] mentioned by shahyar doesn't apply.

Resins are of a strong polar nature. Beside carbon and hydrogen they may contain small amounts of sulfur, nitrogen and oxygen. They are generally less aromatic but more aliphatic and contain more oxygen than asphaltenes. They are adhesive, dark brown, solid and semi-solid. Typical MW range: 900-1300.

Cyclics (aromatics) are viscous liquids composed largely of C and H but may contain some S,N,O. MW range: 550-850.

Asphaltenes are brown or black amorphous solids, mainly aromatic materials with S,N,O. Their MW: 200-5000.

Bitumen micelles are considered to be asphaltenes with an adsorbed sheath of high MW resins extending outwards into the less aromatic dispersion medium. The stable micelle precipitates when a solvent such as n-heptane is added.</sub>

 

[shahyar]

Thanks, excellent.
25362, can you add something about their "water solubilities"?
Can I say:
(More soluble) Asphaltenes > Resins > Aromatics > saturates (less soluble)

Thanks Again

 

[25362]

Shayar, thanks for the star and sorry for the delay. Nothing I can say definitely about water solubilities. Those are low in general, and depend on molecular weight, polarity, hydrogen bonding, van der Waals forces, temperature, acidity, etc. Let's not forget that not only these fractions each have many chemical components, but they differ from crude to crude.

Based on general rules, and at sufficiently high temperatures, I'd say that your assumption may be right. Can you enlarge on the importance you attach to water solubility and why ?

 

[shahyar]

Thank you 25362. Actually I am not "oil guy", I am "water guy" in oil industry. I wanted to know if I can predict total dissolved oil in water based on SARA test of oil. Apparently it is not possible. I understood just about 0.05 to 0.1 % of oils dissolve in water,almost independent of their SARA test analysis.
Sorry for delay, here was long weekend.