Oil & Natural Gas Projects
Exploration and Production Technologies
Improved Processes to Remove Naphthenic Acids
This project was selected in response to DOE's Coal, Oil, and Gas Broad-Based
This work will use an integrated computational and experimental approach (for
both kinetics and catalyst synthesis) to: 1) obtain a fundamental mechanistic
understanding of the catalytic decarboxylation of model naphthenic acids and
2) develop an inorganic solid filter that is specific to extracting carboxylic
acids from dilute solutions under rapid flow conditions.
California Institute of Technology
Two types of decarboxylation catalysts were developed. Catalyst A promotes catalytic
decarboxylation, acid-base neutralization, and C-C cracking to some degree.
Catalyst B shows excellent decarboxylation activity for the naphthoic acid model
compound-acid conversion reached 93.9%.
Gaining a fundamental understanding of effective mechanisms of removing naphthenic
acid compounds from heavy crude oil will significantly help the U.S. petroleum
industry in improving refinery processing of heavy crude oils possessing high
contents of naphthenic acid.
Naphthenic acids, which are unfunctionalized aliphatic, alicylic, and aromatic
carboxylic acids, cause enormous refinery problems due to their corrosivity
toward mild steel. Naphthenic acids are unique components of most crude oils
and are especially prevalent in heavy and biodegraded oils. They have a higher
rate of chemical activity than other components of crude oil. Their reactivity
translates to metal corrosion in refineries and processing plants. In the upstream
phases of oil production and transportation to refineries, naphthenic acids
can react with other materials to form sludge and gum, thus plugging pipelines
and operating machinery.
The project accomplishments included these developments:
- More-oxidative metal oxide catalysts were developed that were effective
in catalytic decarboxylation of model acid compounds. Ag2O shows excellent
decarboxylation activity for naphthoic acid at 300° C; acid conversion
reached 93.9%. A laboratory-scale flow reaction line was developed for continuous
evaluation of catalytic activity. Kinetics were studied using IR adsorption,
Total Acid Number, and oil viscosity.
- The kinetic measurements were performed on two catalysts, which were typical
of the effective catalysts that were developed. The two catalysts were effective
for the removal of naphthenic acids for up to more than 10 hours. Treatment
capacities could reach 95 grams per gram of catalyst.
- Several clay minerals were selected for the adsorption of naphthenic acids.
Sepiolite and montmorillonite demonstrate higher adsorptive capacities in
comparison with other clays.
- Theoretical studies of the decarboxylation mechanism suggest that:
-The radical pathway will be predominant when transition metals such as Cu
(II), Mn (III) are involved. These cation species are able to generate an internal
electron-transfer due to the closed shell (from Cu (II), -3d9 to Cu (I), -3d10
electronic configurations) and half-closed shell (from Mn (III) -3d4 to Mn (II)
-3d5 electronic configurations).
-The concerted pathways could be a rationalized mechanism when base metals
are involved. In the concerted pathway, the nucleuphilic attack on the ß-carbon
is important as the initiative step.
-The hydroxyl group on the metal surface could assist in C-C bond breaking.
This result seems to suggest that a basic condition is essential for the initial
base-acid reaction, an acidic condition would be important for the further decarboxylation
Tasks to be performed in this project include:
- Task 1, which covers development of a low-temperature decarboxylation catalyst,
including new catalyst design; determination of kinetics and the reaction
mechanism of decarboxylation reactions under a specific catalyst system; ascertainment
of reaction mechanisms and kinetic parameters (activation energies); and synthesis
of new catalysts to remove naphthenic acids from crude oil via low-temperature
- Task 2, which calls for researchers to perform decarboxylation reaction
study by time-resolved multiple cold trap analyzer that including establishing
and validating a theoretical first-principles understanding of decarboxylation
reactions; collect data on adsorption energy on various materials, heat capacity,
enthalpy, and entropy terms; study the reaction pathways of catalyzed decarboxylation
reactions; correlate results with critical catalyst properties; develop more-detailed
complex models of the mechanism and rates for processes leading to decarboxylation;
quantify the changes of products with temperature catalyst, pressure changes,
and carboxylic acid feed compositional changes; optimize catalyst design and
process conditions for decarboxylation; and characterize the catalyst before
and after decarboxylation synthesis via x-ray techniques
- Task 3, which entails performing computational modeling of carboxylic acid
decarboxylation, including calculating the thermodynamic properties of various
key intermediates in decarboxylation reactions; determining pathways and rate
parameters for each reaction that plays an important role in decarboxylation;
and developing simplified reaction models, including rates and pathways that
can be used to fit the experimental data with a limited number of variables
- Task 4, in which researchers model efforts to model naphthenic acid adsorption
on solid phase that includes developing an improved Force Field (based on
the MS-Q FF formalism) as the basis for the study of naphthenic acid-filter
- Task 5, which calls for project participants to perform naphthenic acid
adsorption measurement on different solid surfaces, which includes validating
modeling results of the calculated relative affinity of acid to adsorb on
common solids such as polymer resins and clays; equilibrating a solution of
known starting naphthenic acid concentration with a known mass of solid surface;
calculating the amount of acid adsorbed onto the solid surfaces; determining
which solid phase will provide best selective adsorption features for future
potential filtration application; and running coreflood tests (flow oil through
a solid packing) to measure naphthenic acid retention in dynamic conditions.
- Task 6, in which researchers develop and optimize a process for efficiently
removing naphthenic acids from crude oil, based on the experimental and the
computational results, including evaluating the overall process and economic
calculations and making recommendations toward a new naphthenic removal process.
The project is nearing completion.
Project Start: September 30, 2002
Project End: September 30, 2005
Anticipated DOE Contribution: $799,566
Performer Contribution: $199,892 (20% of total)
NETL - Kathy Stirling (email@example.com or 918-699-2044)
California Institute of Technology - William Goddard (firstname.lastname@example.org or