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Title: Separation of switchgrass bio-oil by water/organic solvent addition and pH adjustment

Abstract

Applications of bio-oil are limited by its challenging properties including high moisture content, low pH, high viscosity, high oxygen content, and low heating value. Separation of switchgrass bio-oil components by adding water, organic solvents (hexadecane and octane), and sodium hydroxide may help to overcome these issues. Acetic acid and phenolic compounds were extracted in aqueous and organic phases, respectively. Polar chemicals, such as acetic acid, did not partition in the organic solvent phase. Acetic acid in the aqueous phase after extraction is beneficial for a microbial-electrolysis-cell application to produce hydrogen as an energy source for further hydrodeoxygenation of bio-oil. Organic solvents extracted more chemicals from bio-oil in combined than in sequential extraction; however, organic solvents partitioned into the aqueous phase in combined extraction. When sodium hydroxide was added to adjust the pH of aqueous bio-oil, organic-phase precipitation occurred. As the pH was increased, a biphasic aqueous/organic dispersion was formed, and phase separation was optimized at approximately pH 6. The neutralized organic bio-oil had approximately 37% less oxygen and 100% increased heating value than the initial centrifuged bio-oil. In conclusion, the less oxygen content and increased heating value indicated a significant improvement of the bio-oil quality through neutralization.

Authors:
 [1];  [2];  [1];  [2];  [3];  [4]
  1. Georgia Inst. of Technology, Atlanta, GA (United States)
  2. Univ. of Tennessee, Knoxville, TN (United States). Institute of Agriculture
  3. Univ. of Tennessee, Knoxville, TN (United States). Bredesen Center for Interdisciplinary Research and Education; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  4. Georgia Inst. of Technology, Atlanta, GA (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Bioenergy Technologies Office (EE-3B)
OSTI Identifier:
1240548
Grant/Contract Number:
AC05-00OR22725
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Energy and Fuels
Additional Journal Information:
Journal Volume: 30; Journal Issue: 3; Journal ID: ISSN 0887-0624
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
09 BIOMASS FUELS

Citation Formats

Park, Lydia Kyoung-Eun, Ren, Shoujie, Yiacoumi, Sotira, Ye, X. Philip, Borole, Abhijeet P., and Tsouris, Costas. Separation of switchgrass bio-oil by water/organic solvent addition and pH adjustment. United States: N. p., 2016. Web. doi:10.1021/acs.energyfuels.5b02537.
Park, Lydia Kyoung-Eun, Ren, Shoujie, Yiacoumi, Sotira, Ye, X. Philip, Borole, Abhijeet P., & Tsouris, Costas. Separation of switchgrass bio-oil by water/organic solvent addition and pH adjustment. United States. doi:10.1021/acs.energyfuels.5b02537.
Park, Lydia Kyoung-Eun, Ren, Shoujie, Yiacoumi, Sotira, Ye, X. Philip, Borole, Abhijeet P., and Tsouris, Costas. Fri . "Separation of switchgrass bio-oil by water/organic solvent addition and pH adjustment". United States. doi:10.1021/acs.energyfuels.5b02537. https://www.osti.gov/servlets/purl/1240548.
@article{osti_1240548,
title = {Separation of switchgrass bio-oil by water/organic solvent addition and pH adjustment},
author = {Park, Lydia Kyoung-Eun and Ren, Shoujie and Yiacoumi, Sotira and Ye, X. Philip and Borole, Abhijeet P. and Tsouris, Costas},
abstractNote = {Applications of bio-oil are limited by its challenging properties including high moisture content, low pH, high viscosity, high oxygen content, and low heating value. Separation of switchgrass bio-oil components by adding water, organic solvents (hexadecane and octane), and sodium hydroxide may help to overcome these issues. Acetic acid and phenolic compounds were extracted in aqueous and organic phases, respectively. Polar chemicals, such as acetic acid, did not partition in the organic solvent phase. Acetic acid in the aqueous phase after extraction is beneficial for a microbial-electrolysis-cell application to produce hydrogen as an energy source for further hydrodeoxygenation of bio-oil. Organic solvents extracted more chemicals from bio-oil in combined than in sequential extraction; however, organic solvents partitioned into the aqueous phase in combined extraction. When sodium hydroxide was added to adjust the pH of aqueous bio-oil, organic-phase precipitation occurred. As the pH was increased, a biphasic aqueous/organic dispersion was formed, and phase separation was optimized at approximately pH 6. The neutralized organic bio-oil had approximately 37% less oxygen and 100% increased heating value than the initial centrifuged bio-oil. In conclusion, the less oxygen content and increased heating value indicated a significant improvement of the bio-oil quality through neutralization.},
doi = {10.1021/acs.energyfuels.5b02537},
journal = {Energy and Fuels},
number = 3,
volume = 30,
place = {United States},
year = {Fri Jan 29 00:00:00 EST 2016},
month = {Fri Jan 29 00:00:00 EST 2016}
}

Journal Article:
Free Publicly Available Full Text
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Cited by: 6works
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  • Cited by 3
  • Bio-oil aqueous phase contains a considerable amount of furans, alcohols, ketones, aldehydes and phenolics besides the major components of organic acids and anhydrosugars. The complexity of bio-oil aqueous phase limits its efficient utilization. To improve the efficiency of bio-oil biorefinery, this study focused on the separation of chemical groups from bio-oil aqueous phase via sequential organic solvent extractions. Due to their high recoverability and low solubility in water, four solvents (hexane, petroleum ether, chloroform, and ethyl acetate) with different polarities were evaluated, and the optimum process conditions for chemical extraction were determined. Chloroform had high extraction efficiency for furans, phenolics,more » and ketones. In addition to these chemical groups, ethyl acetate had high extraction efficiency for organic acids. The sequential extraction by using chloroform followed by ethyl acetate rendered that 62.2 wt.% of original furans, ketones, alcohols, and phenolics were extracted to chloroform, over 62 wt.% acetic acid was extracted to ethyl acetate, resulting in a high concentration of levoglucosan (~53.0 wt.%) in the final aqueous phase. Chemicals separated via the sequential extraction could be used as feedstocks in biorefinery using processes such as catalytic upgrading of furans and phenolics to hydrocarbons, fermentation of levoglucosan to produce alcohols and diols, and hydrogen production from organic acids via microbial electrolysis.« less
  • Despite the potential carbon-neutrality of switchgrass bio-oil, its high acidity and diverse chemical composition limit its utilization. The objectives of this research are to investigate pH neutralization of bio-oil by adding various alkali solutions in a batch system and then perform neutralization using process intensification devices, including a static mixer and a centrifugal contactor. The results indicate that sodium hydroxide and potassium hydroxide are more appropriate bases for pH neutralization of bio-oil than calcium hydroxide due to the limited solubility of calcium hydroxide in aqueous bio-oil. Mass and total acid number (TAN) balances were performed for both batch and continuous-flowmore » systems. Upon pH neutralization of bio-oil, the TAN values of the system increased after accounting the addition of alkali solution. A bio-oil heating experiment showed that the heat generated during pH neutralization did not cause a significant increase in the acidity of bio-oil. The formation of phenolic compounds during neutralization was initially suspected of increasing the system’s overall TAN value because some of these compounds (e.g., vanillic acid) act as polyprotic acids and have a stronger influence on the TAN value than monoprotic acids (e.g., acetic acid). The amount of phenolics in separated bio-oil phases, however, did not change significantly after pH neutralization. In conclusion, process intensification devices provided sufficient mixing and separation of the organic and aqueous phases, suggesting a scale-up route for the bio-oil pH neutralization process.« less
  • To efficiently utilize water-soluble compounds in bio-oil and evaluate the potential effects of these compounds on processes such as microbial electrolysis, our study investigated the physico-chemical properties of bio-oil and the associated aqueous phase generated from switchgrass using a semi-pilot scale auger pyrolyzer. Combining separation and detection strategies with organic solvent extraction, an array of analytical instruments and methods were used to identify and quantify the chemical constituents. Separation of an aqueous phase from crude bio-oil was achieved by adding water (water: crude bio-oil at 4:1 in weight), which resulted in a partition of 61 wt.% of the organic compoundsmore » into a bio-oil aqueous phase (BOAP). GC/MS analysis for BOAP identified over 40 compounds of which 16 were quantified. Acetic acid, propionic acid, and levoglucosan are the major components in BOAP. In addition, a significant portion of chemicals that have the potential to be upgraded to hydrocarbon fuels were extracted to BOAP (77 wt.% of the alcohols, 61 wt.% of the furans, and 52 wt.% of the phenolic compounds in crude bio-oil). Valorization of the BOAP may require conversion methods capable of accommodating a very broad substrate specificity. Ultimately, a better separation strategy is needed to selectively remove the acidic and polar components from crude bio-oil to improve economic feasibility of biorefinery operations.« less
  • Cited by 9