Improved Processes to Improved Processes to Remove Naphthenic AcidsRemove Naphthenic Acids

Materials and Processes Simulation Center (MSC) Materials and Processes Simulation Center (MSC) Power, Environmental & Energy Research Center (PEER)Power, Environmental & Energy Research Center (PEER)

California Institute of Technology (Caltech)California Institute of Technology (Caltech)

W.A. Goddard and Y. Tang

ContentContent

1. Objective

2. Backgrounds and Challenges

3. Our Approaches

4. Current achievements

5. Working Plans

6. Summary

Statement of Project ObjectivesStatement of Project Objectives

To conduct an integrated computational modeling and novel experimental research to develop cost-effective methods for removing naphthenic acid from crude oil.

1. To develop a catalytic system to cleanly decarboxylate simple aliphatic and aromatic acids under low temperature conditions.

2. To remove naphthenic acid via solid liquid separations.

NA Corrosions & RemovalsNA Corrosions & Removals

NA Corrosion is an old enemy of the petroleum industry 1. Attempts to remove NA using neutralization and dilution

blending are not entirely satisfactory 2. Other techniques, such as extraction, clay filtration and

resin filtration, have been studied. Catalytic converting NA to non-corrosive oil components

is a promising approach.

1 W. A. Derungs, “Naphthenic Acid Corrosion – An Old Enemy of the Petroleum Industry”, Corrosion, 12(2), 41 (1956)2 A. Goldszal, paper SPE 74661, presented at the Society of Petroleum Engineers, 3 rd Intern. Symp. on Oilfield Scale, Aberdeen, Scotland, January 29-31, 2002

Challenges on NA Removal TechniquesChallenges on NA Removal Techniques

Conventional Methods - neutralization and dilution blending

Problems: No completed removals

By-products

Wastewater problems

Other Attempts – extraction, clay filtration or resin filtration

Problems: Have not fully optimized

Catalyzed Decarboxylation – promising approaches

Requirements: Lower Temperature

Lower costs

Our ApproachOur Approach

An strong integration of our advanced computational approach and novel catalyst development technologies.

Our Approaches - TheoreticallyOur Approaches - Theoretically

Quantum Mechanical Density Functional Theory (DFT)

Computational Modeling

To select NA model by evaluating the acidity (pKa) and octane/water distribution coefficient (logP).

To study decarboxylation reaction mechanisms with key transition states located and thermodynamic properties taking into account.

To provide the theoretical guidance on catalyst selections and designs.

To investigate the adsorption of NA on metal and/or alloy solid surfaces.

To help develop and optimize a process of effectively removing NA.

Our Approaches - ExperimentallyOur Approaches - Experimentally

To develop high active, selective low temperature NA removal catalyst based on the reported work and the computational results.

To formulate and synthesize both heterogeneous and homogeneous catalysts.

To conduct decarboxylation experiment combined with Time Resolved Multiple Cold Trap analyzer to obtain information on decarboxylation mechanism and reaction kinetics.

To characterize catalysts’ surface and electronic features to provide reference for catalyst design.

To perform adsorption measurement and core flood tests of dilute NA solution on designed resin and clay adsorbents.

Tasks to Be PerformedTasks to Be Performed

1. Low-T Decarboxylation Catalyst Development.

2. Experimental Reaction Mechanism Study – Time Resolved Multiple Cold Trap (TRMCT).

3. Theoretical Reaction Mechanism Study – Computational Simulation.

4. NA Adsorption on Solid Phase – Modeling.

5. NA Adsorption – Experimental Measurements.

6. Process Designs for Efficiently Removing NA.

Preliminary results

Classifications of Naphthenic AcidsClassifications of Naphthenic Acids

Naphthenic acid (NA) represents a collective group of organic acids presenting in crude oils, which includes:

Saturates = saturated rings + an alkyl group + COOH (60-80 %)

Aromatics = aromatic rings + an alkyl group + COOH (10-20%)

Heterocyclics = S, N substituted rings + an alkyl group + COOH ( ~10%)

The Z number is the commonly used classification for saturates

CnH2n+ZO2

where Z specifies a homologous series.

Double Bond Equivalent has also been used

DBE = 1 + ½ [Ni (Vi –2)]

where Ni is the number of atoms of element i, Vi is the valence of atom i.

Acidity of NA – pKa calculationsAcidity of NA – pKa calculations

The ionization constant (pKa) in aqueous solutions

is calculated from the following thermodynamic cycle:

AH(g) A-(g) + H+(g)

AH(aq) A-(aq) + H+(aq)

A

B C D

E

A and E are the free Gibbs Energies in gas-phase and in solution.

B, C, and D are the solvation energies of acid (AH), deprotonated compound (A-) and proton (H+), respectively.

Calculated Acidities of NACalculated Acidities of NA

The acidity of the saturated NA is structure independent.

Distribution Coefficients of NA - logPDistribution Coefficients of NA - logP

Chemical Name CAS Number Chemical Formula Exp. logP Calc.logP 3

Benzoic Acid

1-Napthoic Acid

2-Naphthoic Acid

Antheracene-9-Carboxylic Acid

Cyclohexanecarboxylic Acid

Phenol

1-Naphthol

2-Naphthol

Anthranol

Cyclopentanol

Cyclohexanol

Decahydro-2-Naphthol

Thiophenol

1-Naphthalenethiol

2-Naphthalenethiol

Cyclopentanethiol

Cyclohexanethiol

000065-85-0

000086-55-5

000093-09-4

000723-62-6

000098-89-5

000108-95-2

000090-15-3

000135-19-3

000529-86-2

000096-41-3

000108-93-0

000825-51-4

000108-98-5

000529-36-2

000091-60-1

001679-07-8

001569-69-3

C7H6O2

C11H8O2

C11H8O2

C15H10O2

C7H12O2

C6H6O

C10H8O

C10H8O

C14H10O

C5H10O

C6H12O

C10H18O

C6H6S

C10H8S

C10H8S

C5H10S

C6H12S

1.87

3.10

3.28

3.85

1.96

1.46

2.85

2.70

3.86

0.71

1.23

2.66

2.52

3.86

3.86

2.55

3.05

1.82

2.94

3.00

4.21

1.64

1.39

2.71

2.73

3.77

0.69

1.39

2.71

2.19

2.99

3.05

2.13

2.64

3 Theoretical calculations by using clogP program.

Model NA CompoundsModel NA Compounds

FLUKA Cyclopentyl (methylene) n-monocarbonic acid (n=0,1,...)

(average Molecular Weight ~245 g/mol)

Deoxycholic acid (DA)

trans-4-Pentylcyclohexane-carboxylic acid (PCA)

5-beta-Cholanic acid (CA)

4-Heptylbenzoic acid (HB)

Catalytic Decarboxylation ReactionsCatalytic Decarboxylation Reactions

1. Metal Insertion Mechanism

O

R OR' + M

acyl fission:

sp2-sp3 C-O

activation

alkyl fission:

sp3-sp3 C-O

activation

O

R MO

O

R O

M

R'R'

2. Free radical Mechanism

R-COOH R-COO- R-COO• or (R-COO+)? R• + (R+)?

Cu(II)/Cu(I) -CO2

Cleavage of C-O bonds by Metal ComplexesCleavage of C-O bonds by Metal Complexes

A Homogeneous catalytic process by Marui et al.

Yield: 55% in toluene

95% in dioxane

Ru3(CO)12+HCOONH4

N

O

O

N

OH+160 Co, 40 hrs

HO-C-C-NH2 or RO-C-C-NH2 or R-C(OH)-C-NH2 were used to extract NA. They could also be used as metal ligand or bound to resin.

Coal DecarboxylationCoal Decarboxylation

Coal Polycarboxylic acid Polyaromatics + CO2

Oxidation Decarboxylation

COOHN

O

CO2+200 Co, 12h

Catalyst

Catalyst Naphthenalene Conversion (%)

Silver (I) oxide 71

Copper (II) chromite 54

Copper (I) oxide 83

Main experimental work – to develop a heterogeneous catalytic reaction system, such as supported metal catalysts, for the C-O bond cleavage under mild conditions.

Active metal choices – Transition metals such as Cu, Ni, Fe or Ag for cost-efficiency, with comparison to rare metals such as Ru, Rh and Pd.

Support choices - Al2O3, SiO2, TiO2, active carbon, zeolite,

particularly the influence of specific surface areas and surface acidities.

Solvent effects – the difference between the aqueous phase and the oil phase.

Our Strategies – Heterogeneous Catalysis

Schedule and MilestoneSchedule and Milestone

Year One Year Two Year Three

1 2 3 4 1 2 3 4 1 2 3 4TASK 1: Low Temperature Decarboxylation Catalyst Development

TASK 2: Decarboxylation Reaction Study by Time Resolved MCT

TASK 3: Computational Modeling of Carboxylic Acid Decarboxylation

TASK 4: Modeling Efforts: Nap. Acid Adsorption on Solid Phase

TASK 5: Nap. Acid Adsorption Measurement on Solid Surfaces

TASK 6: Develop and optimize a process for efficiently removing NA from crude oil.

DeliverablesDeliverables

Design concepts of novel low temperature NA removal catalyst

Physical NA removal approach with designed polymer resins or clays

Comprehensive understanding on catalytic decarboxylation process via experimental and computational investigation

Anticipate BenefitsAnticipate Benefits

1. A fundamental understanding of the NA chemistry.

2. Enhance refining processes for heavy crude oils.

3. Novel heterogeneous catalyst designs.

4. Potential breakthroughs in the upstream arena.

SummarySummary

A joint effort from both theoretical and experimental aspects is assembled aiming at providing a fundamental understanding of naphthenic acid chemistry and improving the refinery products and performance.

If successful, the impact is very large, particular toward heavy, sour crude oil. The new technology will improve significantly petroleum-refining process for heavy crude.