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At least 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Oil‐Soluble Polymer Brush Grafted Nanoparticles as Effective Lubricant Additives for Friction and Wear Reduction

Abstract The development of high performance lubricants has been driven by increasingly growing industrial demands and environmental concerns. Herein, we demonstrate oil‐soluble polymer brush‐grafted inorganic nanoparticles (hairy NPs) as highly effective lubricant additives for friction and wear reduction. A series of oil‐miscible poly(lauryl methacrylate) brush‐grafted silica and titania NPs were synthesized by surface‐initiated atom transfer radical polymerization. These hairy NPs showed exceptional stability in poly(alphaolefin) (PAO) base oil; no change in transparency was observed after being kept at −20, 22, and 100 °C for ≥55 days. High‐contact stress ball‐on‐flat reciprocating sliding tribological tests at 100 °C showed that addition of 1 wt % of hairy NPs into PAO led to significant reductions in coefficient of friction (up to ≈40 %) and wear volume (up to ≈90 %). The excellent lubricating properties of hairy NPs were further elucidated by the characterization of the tribofilm formed on the flat. These hairy NPs represent a new type of lubricating oil additives with high efficiency in friction and wear reduction.

Wright, Roger A. E.↗
DOE OSTI2019

Revealing the Distribution of Metal Carboxylates in Oil Paint from the Micro‐ to Nanoscale

Abstract Oil paints comprise pigments, drying oils, and additives that together confer desirable properties, but can react to form metal carboxylates (soaps) that may damage artworks over time. To obtain information on soap formation and aggregation, we introduce a new tapping‐mode measurement paradigm for the photothermal induced resonance (PTIR) technique that enables nanoscale IR spectroscopy and imaging on highly heterogenous and rough paint thin sections. PTIR is used in combination with μ‐computed tomography and IR microscopy to determine the distribution of metal carboxylates in a 23‐year old oil paint of known formulation. Results show that heterogeneous agglomerates of Al‐stearate and a Zn‐carboxylate complex with Zn‐stearate nano‐aggregates in proximity are distributed randomly in the paint. The gradients of zinc carboxylates are unrelated to the Al‐stearate distribution. These measurements open a new chemically sensitive nanoscale observation window on the distribution of metal soaps that can bring insights for understanding soap formation in oil paint.

Ma, Xiao↗
DOE OSTI2016

Oil-Soluble Polymer Brush Grafted Nanoparticles as Effective Lubricant Additives for Friction and Wear Reduction

Developments of high performance lubricants are driven by increasingly growing industrial demands and environmental concerns. We demonstrate oil-soluble polymer brush-grafted inorganic nanoparticles (hairy NPs) as highly effective lubricant additives for friction and wear reduction. A series of oil-miscible poly(lauryl methacrylate) brush-grafted silica and titania NPs were synthesized by surface-initiated atom transfer radical polymerization. Moreover, these hairy NPs showed exceptional stability in poly(alphaolefin) (PAO) base oil; no change in transparency was observed after being kept at -20, 22, and 100°C for ≥55 days. High-contact stress ball-on-flat reciprocating sliding tribological tests at 100°C showed that addition of 1 wt% of hairy NPs into PAO led to significant reductions in coefficient of friction (up to ≈40%) and wear volume (up to ≈90%). The excellent lubricating properties of hairy NPs were further elucidated by the characterization of the tribofilm formed on the flat. These hairy NPs represent a new type of lubricating oil additives with high efficiency in friction and wear reduction.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Revealing the Distribution of Metal Carboxylates in Oil Paint from the Micro- to Nanoscale

Oil paints comprise pigments, drying oils, and additives that together confer desirable properties, but can react to form metal carboxylates (soaps) that may damage artworks over time. To obtain information on soap formation and aggregation, we introduce in this study a new tapping-mode measurement paradigm for the photothermal induced resonance (PTIR) technique that enables nanoscale IR spectroscopy and imaging on highly heterogenous and rough paint thin sections. PTIR is used in combination with μ-computed tomography and IR microscopy to determine the distribution of metal carboxylates in a 23-year old oil paint of known formulation. Results show that heterogeneous agglomerates of Al-stearate and a Zn-carboxylate complex with Zn-stearate nano-aggregates in proximity are distributed randomly in the paint. The gradients of zinc carboxylates are unrelated to the Al-stearate distribution. These measurements open a new chemically sensitive nanoscale observation window on the distribution of metal soaps that can bring insights for understanding soap formation in oil paint.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Matrix Extension Validation of AOCS Ce 2c‐11 for Omega‐3 Polyunsaturated Fatty Acids in Conventional Foods and Dietary Supplements Containing Added Marine Oil

Abstract Marine oils are commonly added to conventional foods and dietary supplements to enhance their contents of omega‐3 polyunsaturated fatty acids (PUFA), including eicosapentaenoic acid (EPA; 20:5n‐3) and docosahexaenoic acid (DHA; 22:6n‐3), which have been associated with numerous potential health benefits. This study compared American Oil Chemists’ Society (AOCS) Official Methods Ce 2b‐11 and Ce 2c‐11 for determining EPA and DHA in foods and dietary supplements and found that AOCS Ce 2c‐11 produces significantly higher analyzed values, which could be attributed to a more comprehensive breakdown of the sample matrix and derivatization of fatty acids. Our subsequent food matrix extension validation of AOCS Ce 2c‐11 demonstrated that the method produces true, accurate, sensitive, and precise determinations of EPA, DHA, and total omega‐3 PUFA in foods and dietary supplements containing added marine oil, including those formulated with emulsified and microencapsulated oils. The method detection limits for EPA and DHA were 0.012 ± 0.002 and 0.011 ± 0.003 mg g −1 , respectively (means ± SD). The analyzed contents of EPA (1.26–386 mg serving −1 ), DHA (1.37–563 mg serving −1 ), and total omega‐3 PUFA (2.69–1270 mg serving −1 ) were reported for 27 conventional food and dietary supplement products. Eighteen products declared contents of DHA, EPA + DHA, or total omega‐3 PUFA on product labels, and the analyzed contents of those fatty acids varied from 95 to 162% of label declarations for all but two of the products.

Li, Ziyi↗
DOE OSTI2021

Response surface methodology guided adsorption and recovery of free fatty acids from oil using resin

The presence of free fatty acids interferes with the conversion of plant oils to biodiesel. In this work, four strong and weak base resins were evaluated for the removal of free fatty acids (FFA) from oil. Amberlite FPA 51 showed the highest adsorption capacity of FFA. A resin concentration above 3% could enable a higher percentage FFA adsorption. The adsorption process fitted a pseudo-first-order kinetic model and achieved equilibrium in approximately 8 h. A full factorial design was used to optimize the resin and FFA concentrations at a fixed temperature (40°C). A ratio of resin to fatty acid concentrations above 1.875 was sufficient for 70% adsorption and the amount adsorbed continued to increase with further added resin. A two-step washing of resin using hexane and ethanol recovered approximately 67.55%±4.05% of the initially added fatty acid. The resin that was used was regenerated with 5% NaOH and re-used for a minimum of three consecutive cycles. However, the adsorption capacity diminished to 75% of the initial cycle in cycles 2 and 3. Thus, the work presents a resin-based process for deacidification of oil to reduce fatty acid content of oil for biodiesel production.

09 BIOMASS FUELS↗
DOE OSTI2020

Microwave‐assisted hydrodistillation of the essential oil from Algerian Pimpinella anisum seeds

Abstract Essential oils (EOs) from anise seeds ( Pimpinella anisum ) collected in the Algerian region were extracted by microwave‐assisted hydrodistillation (MAHD) and hydrodistillation (HD). The oil yield (%), chemical composition, energetic consumption and the antimicrobial properties were evaluated of the obtained EO. The yields obtained by both processes were 2.81 ± 0.01% for 90 minutes and 3.30 ± 0.05% for 330 minutes for MAHD and HD, respectively. The determination of the chemical composition of EOs by GC‐MS revealed the presence of a majority compound, trans ‐anethole 81.52% and 91.31% for MAHD and HD, respectively. The other main compounds present in the oils for MAHD and HD were, respectively: methyl chavicol (estragole) (0.63%‐1.39%), cis ‐anethole (0.23%‐0.34%), anisaldehyde (1.1%‐1.57%), anisyl methyl ketone (0.28%‐0.13%), trans ‐methyl isoellgenol (0.31%‐0.17%), γ ‐himachalene (0.5%‐0.36%), trans ‐pseudoisoeugenyl 2‐methylbutyrate (6.53%‐2.53%) and epoxy‐pseudoisoeugenyl 2‐methylbutyrate (2.01%‐0.56%). The EO obtained by MAHD detected other compounds, fenchone 0.41%, limonene 0.68%, cis ‐jasmolacatone extra C 0.41%, trans ‐isolongifolanone 0.2% and α ‐himachalene 0.16%. The energetic consumption by MAHD was significantly less than HD. Theoretical data from mathematical modelling were compared with practical data, and the coefficient of determination was between 0.93 and 0.97. The sensibility of bacterial strains to the essential oil obtained by MAHD is marked relatively to that obtained by HD, and for the sensibility of fungal strains, it was conserved. The MAHD process revealed a good yield of anise seeds EOs while reducing extraction time and energetic consumption. The EO extracted by this process revealed the presence of other compounds while improving antibacterial activity.

Boumahdi, Yamina↗
DOE OSTI2017

New Approaches to Study of Thermodynamic Parameters of Oil Disperse Systems

Crude oil and heavy petroleum products are oil disperse systems whose properties depend largely on their thermodynamic state. To determine the thermodynamic parameters and aggregative stability of oil disperse systems, it is proposed to use the inverse gas chromatographic method, which allows calculation of the free surface energy, entropy, and enthalpy of the oil disperse systems from the retention volume.

02 PETROLEUM↗
DOE OSTI2018

Catalytic Aquathermolysis of High-Viscosity Oil Using Iron, Cobalt, and Copper Tallates

The results of a study of the composition of active forms of the catalyst formed upon degradation of the precursor, based on the results of physical modeling of a sample of high-viscosity oil having high asphaltene and resin contents, are presented. Oil-soluble iron, cobalt, and copper tallates were used as the objects of the study. The composition of the separated powder of the active form of the catalyst was determined by X-ray diffraction analysis, and the catalyst particle size was determined by scanning electron microscopy. The SARA (saturate, aromatic, resin and asphaltene) analysis data revealed a marked decrease in high-molecular-weight oil components due to thermocatalytic cracking. The basic transformation mechanism is breakdown of the high-molecular-weight compounds along the sulfur-bearing bonds, as indicated by elemental CHNS (carbon, hydrogen, nitrogen and sulfur) analysis data. It is shown that the cobalt- and copper-based oil-soluble complexes turn are converted to sulfide forms and the iron-based complex is converted to the oxide form. According to the results of scanning electron microscopic analysis of the catalyst, the particle size is about 60 nm.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Pyrolysis Oil-Based Lipid Production as Biodiesel Feedstock by Rhodococcus opacus

Light oil from pyrolysis, which accounts for ~10 % carbon yield of the starting biomass, is a complex aqueous product that is difficult to utilize and usually discarded. This work presents the feasibility of light oil as a sole carbon source to support the growth of Rhodococcus opacus (R. opacus) that in turn accumulate triacylglycerols as biodiesel feedstock. Two types of bacteria (R. opacus PD630 and DSM 1069) were selected in this study. Research results showed that after short adaption periods both strains can grow well on this complex carbon source, as proved by the consumption of oligomers and monomers in light oil. Lipid content by R. opacus PD630 and DSM 1069 was observed up to 25.8 % and 22.0 % of cell dry weight, respectively. Palmitic and stearic acids were found to be the predominant fatty acids in these bacterial cells. In addition, the light oil-based lipid production can be enhanced by reducing the pH value from 7 to 4, especially in case of DSM 1069.

09 BIOMASS FUELS↗
DOE OSTI2022

Co-processing catalytic fast pyrolysis oil in an FCC reactor

Here, studies of co-processing catalytic fast pyrolysis (CFP) oil with vacuum gas oil (VGO) are conducted in a Davison Circulating Riser (DCR). The CFP oil (CFPO) for this study was produced by upgrading fast-pyrolysis vapors from pine in an ex-situ fixed-bed reactor. CFPOs were co-processed at up to a volume fraction of 0.05 with VGO at 521 degrees C and 257 kPa. The yields of oil, aqueous phase, tail gas, and coke were measured. The amount of coke was determined from the carbon containing components in the regenerator flue gas. A compositional analysis was conducted with gas chromatography and elemental analyzers. The organic liquids were distilled into gasoline, jet-fuel, diesel, and resid fractions. A biocarbon analysis was conducted on the organic phase and its individual boiling-point fractions. The results show a small decrease in liquid yield and a generally increased gas yield when co-processing CFPO with VGO. The experiments showed that 75%-100% of biocarbon is incorporated into liquid fuels relative to fossil carbon, depending on catalyst and CFPO. The measurements indicate that cracked CFPO components are predominantly included in the jet-fuel and diesel fractions. A techno-economic analysis (TEA) estimated the minimum fuel selling price (MSFP) for fuel-range products derived from FCC co-processing of CFPO at 24 to 29 $\$$/GJ ($\$$2.90 to $\$$3.50 per gasoline-gallon equivalent; GGE) at a yield of 4.87-7.14 GJ/t(biomass) or 40-58 GGE/t.

09 BIOMASS FUELS↗
DOE OSTI2022

Feedstock and Catalyst Impact on Bio-Oil Production and FCC Co-Processing to Fuels

NREL's thermochemical biomass conversion research is focused on ex-situ upgrading of biomass fast-pyrolysis (FP) vapors as an efficient route to completely biogenic pyrolysis-based fuel precursors, fuels, and value-added chemicals depending on catalyst and process conditions. A near term pathway being developed uses these liquids for co-processing with petroleum feedstocks to assess biogenic carbon incorporation in hydrocarbon fuel feedstocks for potential refinery use. In this work, the impact of feedstock and catalyst on catalytic fast pyrolysis oil (CFPO) composition was determined with the oils then assessed for biogenic fuel production via FCC (fluidized catalytic cracking) co-processing. Biomass vapors were generated via fast pyrolysis with destabilizing vapor components (char, inorganics, tar aerosols) removed by hot gas filtration to produce clean vapors more responsive to catalytic upgrading. A Davison Circulating Riser (DCR), a petroleum industry standard for fluidized catalytic cracking (FCC) catalyst evaluation, was coupled to a custom pyrolyzer system designed to produce consistent-composition pyrolysis vapors as feed to the DCR. Pyrolysis vapors, derived from pure hardwood and softwood, were upgraded using commercially available modified zeolite-based catalysts to produce CFPOs. These upgraded oils were analyzed via 31P and 13C NMR spectroscopy, GCxGC-TOF/MS, carbonyl and ultimate analysis (CHNO), and simulated distillation (SIMDIS) to assess both oil chemistry and distillation behavior as they relate to catalyst and feedstock type for producing fungible hydrocarbon product liquids. These exploratory vapor-phase-upgrading results demonstrated the feasibility of producing refinery-compatible hydrocarbon fuel intermediates entirely from biomass-derived fast-pyrolysis vapors using an industry-accepted DCR system for catalytic upgrading. The FCC co-processing results demonstrated the feasibility of using CFPOs with VGO feeds in FCC refinery operations to produce biogenic carbon containing fuels.

biogenic carbon↗
DOE OSTI2027

Hydrotreating pine-derived catalytic fast pyrolysis oil to jet fuel: Process durability and impact of operating conditions

Hydrotreating woody biomass-derived catalytic fast pyrolysis (CFP) oil to jet fuel has the potential to enhance energy security due to the large abundance of forest and woody resources. CFP oil produced from pine over ZSM-5 was hydrotreated over sulfided NiMo/Al 2 O 3 for 410 h to study the impact of hydrotreating conditions (pressure, temperature, and weight hourly space velocity (WHSV)). The degree of deoxygenation remained high across the tested hydrotreating conditions, and the products contained < 0.01 wt% oxygen. Increasing hydrotreating pressure from 84 to 125 bar enhanced hydrogenation of aromatic rings and the formation of cycloalkanes and increasing the temperature from 385 to 400 degrees C enhanced cracking and the formation of jet-range molecules. Decreasing the weight hourly space velocity from 0.2 to 0.1 g/(g cat h) further enhanced cracking and led to higher gasoline- and lower jet fuel-range fractions. The highest jet fuel fraction (49 wt%) was obtained at 400 degrees C, 125 bar, 0.2 g/(g cat h) WHSV. CFP oils produced from pine over phosphorous-modified ZSM-5 were hydrotreated at this condition for 588 h to investigate the process durability. The hydrogenation performance of the catalyst gradually stabilized in approximately 300 h after which the product composition remained constant. Of the final hydrotreated CFP oil, 53 wt% fell in the jet fuel range with most of the tested fuel properties meeting ASTM D4054 and/or ASTM D7566 specifications. The freeze points were < -50 degrees C vs. guideline of < -40 degrees C and the viscosities at -20 degrees C were 3.8-4.1 mm 2 /s vs guideline of 8 mm 2 /s. Increasing the fraction of cycloalkanes could increase the cetane number and heating value, which did not meet the guidelines.

09 BIOMASS FUELS↗
DOE OSTI2025

Palm oil deoxygenation with glycerol as a hydrogen donor for renewable fuel production using nickel-molybdenum catalysts: The effect of support

Palm oil, one of the most widely used vegetable oils, offers significant potential as a sustainable feedstock for biofuel production. This study explores the deoxygenation of palm oil using glycerol as a hydrogen donor, with nickel-molybdenum (NiMo) catalysts supported on commercial alumina (Al 2 O 3 ), and zeolite (HZSM-5) comparing with self-prepared zirconia (ZrO 2 ). The catalysts were synthesized via incipient wetness impregnation and evaluated for their performance in biofuel production. NiMo/Al 2 O 3 exhibited the lowest oxygen removal efficiency (68.5 %), while NiMo/HZSM-5 achieved a higher oxygen removal (74.3 %) but also demonstrated the highest coke formation. The type of support material influenced the resulting biofuel range, with NiMo/HZSM-5 and NiMo/ZrO 2 favoring jet fuel production, whereas NiMo/Al 2 O 3 was more suitable for diesel production. Notably, NiMo/ZrO 2 exhibited the highest performance in palm oil deoxygenation while minimizing coke formation. These findings highlight NiMo/ZrO 2 as a promising catalyst for efficient and stable biofuel production, with the support material significantly influencing product yield and fuel quality.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Preference of multi-walled carbon nanotube (MWCNT) to single-walled carbon nanotube (SWCNT) and activated carbon for preparing silica nanohybrid pickering emulsion for chemical enhanced oil recovery (C-EOR)

The aim of this research was to determine the best nano hybrid that can be used as a Pickering emulsion Chemical Enhanced Oil Recovery (C-EOR). Therefore, we have prepared different carbon structures nano hybrids with SiO{sub 2} nano particles with different weight percent using sol-gel method. The as-prepared nano materials were characterized with X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM) and Thermal Gravimetric Analysis (TGA). Pickering emulsions of these nanohybrids were prepared at pH=7 in ambient temperature and with distilled water. Stability of the mentioned Pickering emulsions was controlled for one month. Emulsion phase morphology was investigated using optical microscopic imaging. Evaluation results demonstrated that the best sample is the 70% MWCNT/SiO{sub 2} nanohybrid. Stability of the selected nanohybrid (70% MWCNT/SiO{sub 2} nanohybrid) was investigated by alteration of salinity, pH and temperature. Results showed that the mentioned Pickering emulsion has very good stability at 0.1%, 1% salinity, moderate and high temperature (25 °C and 90 °C) and neutral and alkaline pH (7, 10) that is suitable for the oil reservoirs conditions. The effect of the related nano fluid on the wettability of carbonate rock was investigated by measuring the contact angle and interfacial tension. Results show that the nanofluid could significantly change the wettability of the carbonate rock from oil wet to water wet and can decrease the interfacial tension. Therefore, the 70% MWCNT/SiO{sub 2} nanohybrid Pickering emulsion can be used for Chemical Enhanced Oil Recovery (C-EOR).

36 MATERIALS SCIENCE↗
DOE OSTI2015

Evaluation of Biomass-Derived Distillate Fuel as Renewable Heating Oil

The utilization of advanced biofuels in stationary applications, such as home heating, is considered as an early entry point for biomass-derived fuels into the distillate fuel market sector. Two renewable fuels produced by a biomass fluidized catalytic cracking (BFCC) process, followed by hydroprocessing and fractionation, were tested. The evaluation was performed on a pure (100%) distillate fraction, 50% blend of the distillate fraction with petroleum-based heating oil, and 20% blend of a heavier gas oil fraction. Combustion experiments were carried out in a transparent quartz chamber and a typical oil-fired residential boiler. The flame stability, size, and shape produced by the fuels were examined. The flue gas was analyzed for O 2 , CO, NO x , and smoke. The elastomer compatibility test was performed with nitrile slabs at 43 °C for 1 month. Fuel stability was examined at 80 °C for 1 week. The results from the combustion studies suggest that the distillate fuel blends could be used as alternative fuels to No. 2 heating oil, even up to 100% without any operational issues. The distillate fuels were found to be stable. and the nitrile slab volume swell (~10%) suggests that the fuel could be compatible to legacy elastomers.

09 BIOMASS FUELS↗
DOE OSTI2016

Energy Intensity and Greenhouse Gas Emissions from Tight Oil Production in the Bakken Formation

The Bakken formation has contributed to the recent rapid increase in U.S. oil production, reaching a peak production of >1.2 × 106 barrels per day in early 2015. In this study, we estimate the energy intensity and greenhouse gas (GHG) emissions from 7271 Bakken wells drilled from 2006 to 2013. We model energy use and emissions using the Oil Production Greenhouse Gas Emissions Estimator (OPGEE) model, supplemented with an open-source drilling and fracturing model, GHGfrack. Overall well-to-refinery-gate (WTR) consumption of natural gas, diesel, and electricity represent 1.3%, 0.2%, and 0.005% of produced crude energy content, respectively. Fugitive emissions are modeled for a “typical” Bakken well using previously published results of atmospheric measurements. Flaring is a key driver of emissions: wells that flared in 2013 had a mean flaring rate that was ≈500 standard cubic feet per barrel or ≈14% of the energy content of the produced crude oil. Resulting production-weighted mean GHG emissions in 2013 were 10.2 g of CO2 equivalent GHGs per megajoule (henceforth, gCO2eq/MJ) of crude. Between-well variability gives a 5–95% range of 2–28 gCO2eq/MJ. If flaring is completely controlled, Bakken crude compares favorably to conventional U.S. crude oil, with 2013 emissions of 3.5 gCO2eq/MJ for nonflaring wells, compared to the U.S. mean of ≈8 gCO2eq/MJ.

Brandt, Adam R.↗
DOE OSTI2017

Characterization of the Water-Soluble Fraction of Woody Biomass Pyrolysis Oils

This paper reports a study of the chemical composition of the water soluble (WS) fraction obtained by cold water precipitation of two commercial wood pyrolysis oils (BTG and Amaron). The fraction studied accounts for between 50.3 and 51.3 wt. % of the oils. With the most common analytical techniques used today for the characterization of this fraction (KF titration, GC/MS, hydrolysable sugars and total carbohydrates), it is possible to quantify only between 45 and 50 wt. % of it. Our results confirm that most of the total carbohydrates (hydrolysable sugars and non-hydrolysable) are soluble in water. The ion chromatography hydrolysis method showed that between 11.6 and 17.3 wt. % of these oils were hydrolysable sugars. A small quantity of phenols detectable by GC/MS (between 2.5 and 3.9 wt. %) were identified. It is postulated that the unknown high molecular weight fraction (30-55 wt. %) is formed by highly dehydrated sugars rich in carbonyl groups and WS phenols. The overall content of carbonyl, carboxyl, hydroxyl and phenolic compounds in the WS fraction were quantified by titration, Folin-Ciocalteu, 31P-NMR and 1H-NMR. The WS fraction contains between 5.5 and 6.2 mmol/g of carbonyl groups, between 0.4 and 1.0 mmol/g of carboxylic acid groups, between 1.2 and 1.8 mmol/g phenolic -OH, and between 6.0 and 7.9 mmol/g of aliphatic alcohol groups. Translation into weight fractions of the WS was done by supposing surrogate structures for the water soluble phenols, carbonyl and carboxyl groups and we estimated the content of WS phenols (21-27 wt. %), carbonyl (5-14 wt.%), and carboxyl (0-4 wt.%). Together with the total carbohydrates (23-27 wt.%), this approach leads to > 90 wt. % of the WS material in the bio-oils being quantified. We speculate the larger portion of the difference between the total carbohydrates and hydrolysable sugars is the missing furanic fraction. Further refinement of the suggested methods and development of separation schemes to obtain and quantify sub-fractions with homogeneous composition (e.g. carbohydrates, high molecular weight WS phenols, furans, and dehydrated sugars) warrant further investigation.

Stankovikj, Filip↗