1. MIXED ACIDS REMOVAL FROM AQUEOUS SOLUTION
University of Jeddah, Department of Chemical Engineering, Jeddah, Saudi Arabia
University of Maine, Department of Chemical and Biological Engineering, Orono, Maine USA
MIXED ACIDS REMOVAL FROM AQUEOUS SOLUTION
Dr. Aymn Abdulrahman
September, 2016

2. Outline Introduction Motivation Objectives Material and Method
Procedure
Results and Conclusion
Future Works
Acknowledgment

3. Introduction Biomass-derived fuels such as ethanol,
Maine is a Forest state ( covers 90 % of the state)
Major wood components
Cellulose
Hemicelluloses
Lignin
Biomass-derived fuels such as ethanol,
renewable, widespread, cheap and sustainable
10% to 50% of transportation fuels could replaced between 2010 and 2050 in USA (B. Han, 2006)
High selling price of acids such as acetic acid is double that of ethanol

4. Overall Pulp and Biorefinery Flow Diagram
Wood Chips
Hot Water
Extractor
Kraft pulping process
Green Liquor
Wood chips
Pulp and paper
Solvent
Solvent+ HAc
Distillation
HAc
HAc Removal
Ethanol
Fermentation
Lignin Removal
water
Acid Hydrolysis
Sulfuric Acid
Sugar Concentration

5. Objectives
Liquid-liquid extraction to recover mixed acids (C2-C7 aliphatic acids) from two systems:
Clean system ( mixed acid in DI water )
Mixed acids from fermentation broth
Using CYANEX 923 as a solvent and compare to TOPO and TOA
Determining best extraction conditions
Develop an analytical method for organic phase
Solvent recyclability
Washing by 1 M NaOH solution

6. Carboxylic Acids and Ethanol

7. Lignocellulose Hydrolysis
7 acetyl groups per every 10 xyloses
USDA Agricultural Research Service

8. Pretreatment Processes
Solubilizes polymer sugars in the wood
Makes them accessible to enzymatic hydrolysis
Fermentable by the mixed culture of microbes

9. Acids Concentration

10. Lignin Removal Solid Lignin Soluble Lignin Filtration Centrifuging
Lower pH

11. L-L Extraction Methods
Liquid-Liquid Extraction
Clean System (acids in DI water)
Mixed acids from fermentation broth
Separations
Centrifuging
Distillation
Recycling

12. Extraction Flow Diagram
Acids After Fermentation
Solvent
Volatile solvent
Liquid-Liquid Extraction
Acids
Centrifuge
Solvent
Solvent + Acids
Centrifuge
Distillation
Pure Acids Recovery
Solvent Recycle
Aqueous Phase

13. Materials Solvent C2-C7 aliphatic acids
Trioctylphosphine oxide (TOPO) ( [CH3(CH2)7]3PO, mol wt )
Undecane ( C11H24, mol. wt )
Trioctylamine (TOA) ( [CH3(CH2)7]3N, mol wt )
Octanol ( CH3(CH2)7OH, mol wt )
CYANEX 923 a mixture of liquid phosphine oxide (mol wt. 348 )
C2-C7 aliphatic acids
Sulfuric acid ( H2SO4 ), Phosphoric acids or HCL

14. CYANEX 923 Advantages Completely miscible with all common hydrocarbon
Easy Handle it at low room temperatures
Direct use it (no dilution needed)

15. L-L Extraction Procedure
Aq. +
Cyanex
Analysis
Shaker for 30 min, 230 speed
Centrifuge
(3000 rpm, 30 minutes)

16. Two Phases Separation
Note: Phase separation after TOPO-undecane extraction at 70  C and pH=1

17. Distillation Fractional distillation column
Separate mixed acid from solvent

18. Analysis Aqueous phase
High Performance Liquid Chromatography (HPLC) (Bio-Rad Aminex HPX-87H Column)
Gas Chromatography (GC) with He as carrier gas and FID
Organic phase
pH meter

19. Extraction Conditions
Effect of concentrations of solvent in the organic solution
Effect of ratios of organic to aqueous phase
Effect of pH
Effect of temperature
Effect of agitation on extraction % (using CYANEX 923)
Effect of centrifuging on extraction % (using CYANEX 923)

20. Extraction % of Acetic Acid Using Different Solvents
Note: The solvent concentration for TOPO was 370 g/L TOPO/undecane, for TOA was 200 g/L TOA/octanol and a pure CYANEX 923, solvent : aqueous ratio [1:1] and pH 2

21. Extraction % of Mixed Acids Fermented Using CYANEX 923
Note: Using pure CYANEX 923, solvent : aqueous ratio [1:1], initial concentration of acids as following: 5.6 g/L of acetic acid, 1.6 g/L of propionic acid, 6.6 g/L of butyric acid, 1.1 g/L of valeric acid, 10.6 g/L of hexanoic acid and 0.1 g/L of heptanoic acid

22. Acetic Acid Recovered by Distillation
Solvent
HAc before Distillation
g/L
HAc after Distillation
HAc Recovering
[w/w] %
TOA
3.6
TOPO
5.6
0.2 89
CYANEX 923
5.1
0.3 84
Note: Green liquor extracts are used for TOA and TOPO, fermented broth is used for CYANEX 923, volume ratio was 1, pH is 2, 370 g/L TOPO/undecane, 200 g/L TOA/octanol and pure CYANEX 923

23. Several Modifying Methods for Distillation System to Improve Acids Recovering
Note1: slowly increasing heat and slow separation (Retention time 4 hr), no headspace in boiling flask, with vacuum, 2: fast increasing heat and fast separation (Retention time 15 min), with headspace (1/3 of boiling flask is empty) with vacuum, 3: Moderate rate of separation, using lamp-heated column, with vacuum, 4: Moderate rate of separation, insulated column, with vacuum 5: Moderate separation rate, insulated column, ice-cooled condenser with vacuum and 6: Organic mixture diluted with Undecane before distillation

24. Effect of High Boiling Temperature on Solvent’s Color
Note: Boiling temperature is the temperature at the bottom of the distillation column

25. Solvent Recyclability through Extraction and Distillation of Mixed Acids
Note: Initial total acids concentration is 31 g/L in aqueous solution for clean system, the extraction conditions were 1 pH, 1 ratio and at room temperature, using 400 g/L CYANEX/tridecane as solvent

26. Conclusion on Distillation
Not work for long chain acids
Due to an azeotrope formation
Need high temperature
May cause solvent degradation
No significant affect using vacuum system
Reduce solvent recyclability

27. Whole Wood Back Extraction Flow Diagram
Wood Chips
Pretreatments
Hydrolysis +
Fermentation
Celluloses
Hemicelluloses
Back Extraction
Aqueous Solution
Mixed Acids + Solvent
LL Extraction
Lowering pH
Solid Lignin
Mixed
Acids
HCL,
Phosphoric Acid
Dilute Aqueous NaOH
Solvent
Acids Salts
Acid Salts
Concentration
Lowering pH
CaCO3
Acids Salts
Water
Evaporator
TDO
Dry Acids Salts
Biofuels +
Chemicals
Acidify
HCL
Sodium Chloride
Mixed Acids
Concentration

28. Acid Moles VS Caustic Moles
Note: Total moles of hexanoic and heptanoic acids in pure CYANEX 923 is 0.04, NaOH is diluted in DI-water

29. Removal % VS Aqueous: Organic Volume Ratio
1: : : : : : : : : :10
Note: Extraction for clean system, initial total moles of mixed acids in pure CYANEX 923 is 0.3, NaOH is diluted in DI-water, 3 molar ratio of NaOH in aqueous to mixed acids in organic, at room temperature

30. Solvent Recyclability through Back Extraction
Note: Initial total acids concentration is 33 g/L in aqueous solution, the extraction conditions were pH 1, volume ratio of 1:1 and room temperature. The back extraction conditions were a 3 to 1 molar ratio of NaOH to acids and at room temperature

31. Conclusions
Liquid-liquid extraction recovered mixed acid from two systems:
Clean system ( mixed acid in D-water )
Mixed acids from fermentation broth
Best extraction conditions have been determined
The distillation not working
Not work for long chain acids
Due to an azeotrope formation
Back extraction by dilute sodium hydroxide
Acid salts or mixed acids concentration

32. Future Works Back Extraction Distillation
Well know on an azeotrope (break azeotrope)
Using different solvents
Back Extraction
Using different strong basic solution
Acids concentration
Scale up for a pilot plant

33. Acknowledgment University of Jeddah Dr. G. Peter van Walsum
Thesis Committee members (Dr. van Heiningen, Dr. Wheeler, Dr. Genco and Dr. Cole)
Diane Smith (Analytical Support)
Dr. Yang Yu (Mixed Acids Fermentation)
Nick Hill (Technical Support)