Improved Processes to Remove Naphthenic Acids

1. W.A. Goddard and Y. Tang Improved Processes to Remove Naphthenic Acids Materials and Processes Simulation Center (MSC) Power, Environmental & Energy Research Center (PEER) California Institute of Technology (Caltech)

2. Content • Objective • Backgrounds and Challenges • Our Approaches • Current achievements • Working Plans • Summary

3. Statement 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.

4. NA 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, 3rd Intern. Symp. on Oilfield Scale, Aberdeen, Scotland, January 29-31, 2002

5. Challenges 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

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

7. Our 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.

8. Our Approaches - Experimentally • To develop high active, selective low temperatureNA 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.

9. Tasks to Be Performed Low-T Decarboxylation Catalyst Development. Experimental Reaction Mechanism Study – Time Resolved Multiple Cold Trap (TRMCT). Theoretical Reaction Mechanism Study – Computational Simulation. NA Adsorption on Solid Phase – Modeling. NA Adsorption – Experimental Measurements. Process Designs for Efficiently Removing NA.

10. Preliminaryresults

11. Classifications 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 numberis 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.

12. Acidity of NA – pKa calculations The ionization constant (pKa) in aqueous solutions is calculated from the following thermodynamic cycle: 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.

13. Calculated Acidities of NA The acidity of the saturated NA is structure independent.

14. Distribution Coefficients of NA - logP 3 Theoretical calculations by using clogP program.

15. Model NA Compounds FLUKA Cyclopentyl (methylene) n-monocarbonic acid (n=0,1,...) (average Molecular Weight ~245 g/mol) trans-4-Pentylcyclohexane- carboxylic acid (PCA) 4-Heptylbenzoic acid (HB) Deoxycholic acid (DA) 5-beta-Cholanic acid (CA)

16. Catalytic Decarboxylation Reactions 1. Metal Insertion Mechanism 2. Free radical Mechanism Cu(II)/Cu(I) -CO2 R-COOH R-COO- R-COO• or (R-COO+)? R• + (R+)?

17. Cleavage of C-O bonds by Metal Complexes A Homogeneous catalytic process by Marui et al. Yield: 55% in toluene 95% in dioxane HO-C-C-NH2 or RO-C-C-NH2 or R-C(OH)-C-NH2were used to extract NA. They could also be used as metal ligand or bound to resin.

18. Coal Decarboxylation Decarboxylation Oxidation Coal Polycarboxylic acid Polyaromatics + CO2 Catalyst Naphthenalene Conversion (%) Silver (I) oxide 71 Copper (II) chromite 54 Copper (I) oxide 83

19. Our Strategies – Heterogeneous Catalysis 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.

20. Schedule and Milestone

21. Deliverables • 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

22. Anticipate 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.

23. Summary 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.