Quantitating corrosive naphthenic acids in crude oil

A process for quantitating iron-reactive naphthenic acids in liquid hydrocarbons, comprising:

• (a) providing a sample of a feed stock that comprises liquid-phase hydrocarbons and naphthenic acids;
• (b) mixing the sample with a metal or metal alloy comprising iron at a temperature that facilitates a reaction between carboxylic acid functional groups on at least a portion of the naphthenic acids and the iron to produce a modified sample comprising iron naphthenates;
• (c) mixing the modified sample with a ligand to produce a stabilized modified sample comprising stabilized iron naphthenates;
• (d) analyzing a portion of the stabilized modified sample by ionization mass spectrometry to produce a mass spectrum that distinguishes free naphthenic acids that are not bound to iron from iron-reactive naphthenic acids comprising stabilized iron naphthenates by mass-to-charge ratio;
• (e) calculating from the mass spectrum the percentage of total naphthenic acids that are iron-reactive naphthenic acids;
• (f) obtaining a total acid number for the sample, and multiplying the total acid number by the percentage of total naphthenic acids that are iron-reactive naphthenic acids to produce a corrected total acid number for the sample, wherein a value for the corrected total acid number that meets or exceeds an predetermined action threshold value results in a least one of:
• 1) mixing the feed stock with a second feed stock that comprises a TAN or corrected TAN that is below the action threshold value, wherein the feed stock is mixed with the second feed stock at a ratio that is sufficient to decrease the corrected total acid number of the mixture to less than the action threshold value and produce a decreased acidity feed stock that is upgraded in a commercial refinery to produce at least one transportation fuel, wherein the second feed stock;
• 2) adding a chemical additive to the feed stock to produce a treated feed stock that is upgraded in a commercial refinery to produce at least one transportation fuel, wherein the treated feed stock comprises a concentration of the additive that is sufficient to prevent the corrosion of metal surfaces in the commercial refinery that are contacted with the treated feed stock;
• 3) rejecting the feed stock for upgrading in a commercial refinery and selecting an alternative feed stock for upgrading in a commercial refinery to produce at least one transportation fuel, wherein the alternative feed stock comprises a corrected total acid number that is less than the action threshold value;
• 4) catalytically transforming the feed stock in a manner sufficient to decrease the quantity of corrosive naphthenic acids in the feed stock and decrease the corrected total acid number to less than the action threshold value and produce a de-acidified feed stock that is upgraded in a commercial refinery to produce at least one transportation fuel;
• 5) purchasing the feed stock at a price that is discounted relative to a current market price for an alternative feed stock that comprises a corrected total acid number that is less than the action threshold value, and upgrading the feed stock in a commercial refinery to produce at least one transportation fuel, wherein the corrected TAN value is utilized to schedule a rate of periodic maintenance for the commercial refinery.