Heavy Oil Upgrading   |  Napthenic Acid Removal
NAPHTHENIC ACID REMOVAL FROM CRUDE OIL ----- UPGRADING THE QUALITY OF HEAVY OIL
Background
 It has been known that carboxylic acids are present in crude oil and contribute to the acidity of oil products. The existence of these compounds e.g. naphthenic acids in oil has been recognized as one of the major sources of corrosion that occurs in transportation pipelines and distillation units in refineries. Consequently, the oil products with high concentrations of naphthenic acid are labeled as poor oil quality and have a lower price in the market. The conventional method to remove naphthenic acid is based on a caustic wash. However, this treatment results in the formation of emulsion. Once it is formed, this emulsion is very difficult to be broken.
Goal of the project
The aims of the current project are to develop cost-effective methods to remove naphthenic acids from crude oil. Two objectives are targeted: (1) to develop a novel decarboxylation process through a catalytic reaction to convert these acids to non-corrosive components. (2) to remove naphthenic acids via a chemical adsorption process by using solid absorbent.
Approaches
Catalytic decarboxylation Use commercial available chemicals or self-prepared materials as catalysts to test their effectiveness with model compound first and then approach to the real oil. NA solid absorption Target naturally abundant, low cost materials such as clays to explore their probability for the selective adsorption of naphthenic acid from crude oil. Theoretical modeling Use sophisticated computational tools to investigate the possible reaction pathways and to obtain the fundamental understanding of the interaction among the reaction species.
Promising results
With the model acid reaction, e. g. C10H7COOH-->C10H8 + CO2. several metal oxide catalysts have been found to be very effective to the catalytic decarboxylation, which were verified by the formation of CO2.
A newly developed catalyst with an additive was able to reduce the total acid number (TAN) of a heavy Texaco Crude Oil from 4.38 to 0.60at 300° C for 4 hours.
Flow reaction test shows that one of the catalysts we developed can maintain its effectiveness for 12 hours at 250° C.
Several natural occurring clays showed promise as adsorption agents to the selective removal of acids. The adsorption capacity of one of the clays was as high as about 70 mg-NA/g-clay.

 

Sponsor: U. S. Department of Energy(DOE)
Co-sponsors: ChevronTexaco, ConocoPhillips


Publications:
Catalytic Decarboxylation for Naphthenic Acid Removal from Crude Oil - A Theroretical and Experimental Study, Aihua Zhang, Qisheng ma and Yongchun Tang, Prepr Pap-Am Soc, Div Pet Chem 2004, 49 (2) 218