Bio-oil Components Research Articles

Supercritical Carbon Dioxide Extraction of Lignocellulosic Bio-Oils: The Potential of Fuel Upgrading and Chemical Recovery

Bio-oils derived from the thermochemical processing of lignocellulosic biomass are recognized as a promising platform for sustainable biofuels and chemicals. While significant advances have been achieved with regard to the production of bio-oils by hydrothermal liquefaction and pyrolysis, the need for improving their physicochemical properties (fuel upgrading) or for recovering valuable chemicals is currently shifting the research focus towards downstream separation and chemical upgrading. The separation of lignocellulosic bio-oils using supercritical carbon dioxide (sCO2) as a solvent is a promising environmentally benign process that can play a key role in the design of innovative processes for their valorization. In the last decade, fundamental research has provided knowledge on supercritical extraction of bio-oils. This review provides an update on the progress of the research in sCO2 separation of lignocellulosic bio-oils, together with a critical interpretation of the observed effects of the extraction conditions on the process yields and the quality of the obtained products. The review also covers high-pressure phase equilibria data reported in the literature for systems comprising sCO2 and key bio-oil components, which are fundamental for process design. The perspective of the supercritical process for the fractionation of lignocellulosic bio-oils is discussed and the knowledge gaps for future research are highlighted.

Experimental study on composition evolution of biomass pyrolysis vapors with condensing temperature in a vertical tubular condenser

The experiments on bio-oil recovery in a vertical tubular condenser with two flumes were conducted for speculating the componential distribution of walnut shell pyrolysis vapors during condensation. Bio-oil elements and functional groups from different locations of condenser were compared with each other. Aromatic H and H in phenolic OH were concentrated in the top and middle bio-oil and their percentage were improved with increasing water bath temperature. Ten representative compounds in bio-oil were chosen for quantitative analysis. As water bath temperature increased from 273 K to 353 K, the recovered water decreased by 85% whereas the guaiacol and its derivatives (guaiacols) merely decreased by 40%. Vapor distributions of water, acetic acid, furfural and guaiacols were simulated by the back analysis of bio-oil components. According to the simulated results, tubular condenser can be properly lengthened for promoting the recovery of specific components at high water bath temperatures.

Roles of furfural during the thermal treatment of bio-oil at low temperatures

The reactive O-containing species in bio-oil could induce the polymerization of bio-oil during its thermal treatment, which affects the relevant utilization of bio-oil significantly. Furans, as the highly reactive O-containing species in bio-oil, play important roles during the thermal treatment of bio-oil. In this study, furfural was chosen as the representative of the furans in bio-oil to investigate its roles during the thermal treatment of bio-oil. The raw bio-oil with and without the addition of extra furfural (10 wt% of bio-oil) and pure furfural were pyrolyzed in a fixed-bed reactor at 200–500°C. The results show that the interactions among furfural and bio-oil components can take place prior to the evaporation of furfural (< 140°C) to form the intermediates, then these intermediates could be further polymerized to form large molecular compounds, and coke can be formed via the interactions at temperatures ≥ 300°C. At temperatures ≤ 300°C, furfural mainly interacts with anhydrosugars. As the temperature further increases, the aromatics are involved in the interactions to form coke. The increased percentage of the coke formed via the interactions is in a linear relation with the conversion of furfural during the pyrolysis at 300–500°C (no coke formed at 200°C). Meanwhile, more non-aromatic light components (≤ C6) and less aromatics in the tars could be formed due to the interactions.

Preparation of hydrogen storage carbon materials using bio-oil heavy components as carbon-containing precursor

A new method for preparing carbon materials using bio-oil heavy components has been proposed and their hydrogen capacity at low temperature was explored. The effects of different templates and mass ratio of template to bio-oil on specific surface area, pore size distribution and yield of carbon materials were studied. The thermal decomposition pathway of calcium citrate was proposed. Carbon materials prepared by calcium citrate have larger specific surface area (1688 m2 g−1), more uniform pore size distribution and higher yield (17.76%). The specific surface area and the microporosity first increased and then decreased with increasing mass ratio of template to bio-oil, and reached the maximum value when the mass ratio was 1:1. The yield of carbon materials increased with increasing mass ratio. Hydrogen adsorption capacity (0.73–1.80 wt%) of carbon materials increased along with the increase of specific surface area and microporosity. Furthermore, the interaction between carbon and hydrogen molecules is strong, as shown by the isosteric heat of adsorption of between 6.13 and 10.56 kJ/mol. This paper provides an economical and environmental-friendly method for the preparation of hydrocarbon storage materials, and also a new idea for the utilization of bio-oil heavy components.

Investigation of Hydrogen Production from Bio-Oil Substances Using Aspen Plus

In this study, a base-case process diagram was established and simulated in Aspen Plus to explore effect of temperature on hydrogen production. The evaluated compounds were acetic acid, ethylene glycol, acetone, ethyl acetate and m-xylene, which are representative of the main bio-oil derived components. UNIQUAC was used as property model to simulate the process in Aspen Plus. Bio-oil components conversions, mass and molar fractions, and the molar flow rates of hydrogen were studied over a range of temperature starting from 30 °C to 1100 °C. The results obtained from the simulation suggest that all of the five components reach approximately 100% conversion with acetic acid to be the first to reach 100% conversion. The reactor temperature for 100% conversion of the components increases in the following orders: acetic acid &amp;gt; ethylene glycol &amp;gt; ethyl acetate &amp;gt; acetone &amp;gt; m-xylene. It was found that at high temperatures m-xylene was able to produce highest mass fraction of hydrogen and the order was the following: m-xylene&amp;gt; ethyl acetate &amp;gt; acetone &amp;gt; ethylene glycol &amp;gt; acetic acid. Such simulation approaches can be exploited for robust design and optimization of hydrogen production reducing operating cost and taking this process one step closer to industrialization.

Cross-polymerisation between the model furans and carbohydrates in bio-oil with acid or alkaline catalysts

Understanding the potential cross-polymerisation between the main components in bio-oil is essential to develop the method to minimize the coking in hydrotreatment of bio-oil or to maximize the production of carbon material from bio-oil. In this study, the potential cross-polymerisation between furfural and the sugars (xylose and glucose) and the impacts of acid/base catalysts on the polymerisation reactions were investigated. The results indicated that the cross-polymerisation of furfural/xylose and furfural/glucose existed in absence of catalyst, and the extent was more significant for that between furfural and glucose. The strong acid promoted the cross-polymerisation while the weak organic acid like acetic acid and the strong base like NaOH did not. The cross-polymerisation of furfural/sugars produced the more hydrophilic carbonaceous spheres that tended to merge to form bigger particles. The polymerisation of furfural involved opening of the furan ring via hydrolysis, forming oxygen-containing intermediates, while glucose/xylose were more reactive towards polymerisation reaction via dehydration route. The polymers from the sugars were more aliphatic than that from furfural, especially for that from glucose, leading to their lower thermal stabilities. The cross-polymerisation also affected the size/abundance of the π-conjugated structures in the soluble polymers and the relative ratio of the CO/CC in the resulting insoluble polymer.

Selective adsorption of bio-oils’ molecules onto rubber surface and its effects on stability of rubberized asphalt

Abstract This study examines the merits of surface activation of rubber using various bio-oils to improve rubber-asphalt interaction. To do so a hybrid method combining microwave irradiation and bio-chemical treatment was used to graft biomolecules onto the exterior surface of the rubber. Five surface activated rubbers were prepared using waste vegetable oil, wood pellet, miscanthus, corn stover, and castor oil. The effectiveness of each oil was examined by measuring the chemisorption of the bio-oil and elastic recovery of bitumen containing rubber particles treated with each bio-oil. Our quantum-based density functional theory calculations showed presence of both physical and chemical interactions between polar aromatic components of bio-oils and rubber. Among studied bio-oils, wood-based bio-oil found to have the highest content of polar aromatics such as phenolic resins leading to its enhanced interaction with rubber. This was evidenced in percent recovery, which was nearly doubled (from 13% to 24%) when wood-based bio-oil molecules were grafted onto the surface of rubber. Overall, wood-based bio-oil was shown to adsorb well to the rubber surface and reduce its tendency to separate from bitumen by 82%. The study results showed how composition of bio-oil affects its efficacy to activate rubber surface. It also proved the technical merits of using surface activated rubber to reduce segregation between rubber and bitumen which commonly occurs in rubberized asphalt. Therefore, the outcome of this study promotes recycling of waste tire to promote sustainability in pavement construction.

Approaches to investigate the role of chelation in the corrosivity of biomass-derived oils

The need to provide the U.S. market with a renewable liquid fuel energy source from a non-food feedstock stream has gained considerable traction due to benefits such as improved energy efficiency, reduced environmental impacts, and enhanced national security. Practical achievement of these goals via biomass and bio-waste utilization involves production of liquid intermediates containing corrosive, reactive species like carboxylic acids, ketones, aldehydes, and hydroxyaldehydes. Such mixtures challenge materials of containment, processing, and transport. It is widely recognized that the smaller organic acids, such as acetic and formic, are corrosive and can remove protective surface oxides on alloys used in bio-oil processing infrastructure, and ketones can swell sealing polymers. However, literature shows, and findings herein confirm, larger carboxylic acids and bidentate alcohols are present. This highlights the potential for synergistic, detrimental effects of constituents in bio-oil corrosion, including direct reactivity of small acids compounded with the possibility of mobilization of protective metal oxide layers via chelation by larger acids and oxygenates. The question of whether species beyond small acids can significantly contribute to corrosion requires analytical approaches previously not applied to bio-oil corrosion studies and certainly not previously applied corroboratively. This work introduces a combination of optical, mass spectral, and electrochemical impedance spectroscopies with an incubation approach to study metal mobilization, to facilitate elucidating chelation's role in bio-oil corrosive pathways. To enable systematic study of these oxygenates' material compatibility individually and in combination, a model matrix of bio-oil constituents was also developed based on identification of key components of real bio-oils.

Reactive and non-reactive solvents as bio-oil blends: a computer-aided molecular design approach

This paper presents a systematic framework of computer-aided molecular design (CAMD), to design solvents that can improve the critical properties of bio-oil. CAMD tools have been used in this work to improve the key properties of bio-oil such as heating value, water content, viscosity, acidity and stability in storage. The design of both non-reactive and reactive solvents has been covered in this work. In both cases, the main objective was to design solvents that form the bio-oil solvent blend with minimum solvent content. In order to model the bio-oil, five major components in the bio-oil are used and the solvent design problem focussed on designing this surrogate solvent. Mixing rules have been employed to estimate the properties of various bio-oil solvent blends. The main objective is to compute the minimum amount of solvent needed by identifying the optimal combination of functional groups for the solvent molecules. The improvement in properties had been tracked using group contribution models. This work also presents a framework to design solvents that improve bio-oil properties by undergoing chemical reactions with the bio-oil components. In order to ensure the homogeneity after solvent addition, miscibility test between solvent and bio-oil is conducted using appropriate thermodynamic models. Based on the results, the use of mixtures of alkene and alcohol is more recommended as the optimal blend solvents since the mass fraction and viscosity could be balanced to meet the final heating value target and viscosity constraints of the blends.

Assessing the chemical composition of heavy components in bio-oils from the pyrolysis of cellulose, hemicellulose and lignin at slow and fast heating rates

The certain challenge for the utilization of bio-oil is to investigate the nature and formation of reactive large molecular (heavy) components (>200 Da) in bio-oil. In order to investigate the chemical composition of the heavy components in the bio-oils from the pyrolysis of cellulose, hemicellulose and lignin, the molecular formulas of the heavy compounds and the large aromatic structures were obtained based on the results from the Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS) and the ultraviolet fluorescence (UV-F) spectrometer. The results indicated that both the oxygen content and yield of the heavy components showed the highest in the cellulose-oil and the lowest in the lignin-oil. The large molecular compounds were formed mainly via the recombination of the O-containing species, which could be changed at different temperatures and heating rates. Large amount of heavy saccharide and phenolic species existed in cellulose-oil and hemicellulose-oil, while almost no saccharide species and little phenolic species were detected in the lignin-oil. The main heavy components in the lignin-oil were lipids rather than the phenolic species. The heavy components in the bio-oil from the biomass should be mainly derived from the pyrolysis of the cellulose individually or the interactions among the three components.

Hydrotreating of Guaiacol and Acetic Acid Blends over Ni2P/ZSM-5 Catalysts: Elucidating Molecular Interactions during Bio-Oil Upgrading.

Catalytic hydrodeoxygenation (HDO) is an effective technology for upgrading pyrolysis bio-oils. Although, in the past years, this process has been extensively studied, the relevance of the cross-reactivity between the numerous chemical components of bio-oil has been scarcely explored. However, molecular coupling can be beneficial for improving the bio-oil characteristics. With the aim of gaining a better understanding of these interactions, this work investigates the catalytic hydrodeoxygenation of mixtures of two typical components of pyrolysis bio-oils: guaiacol and acetic acid. The catalytic tests were carried out employing a bifunctional catalyst based on nickel phosphide (Ni2P) deposited over a commercial nanocrystalline ZSM-5 zeolite. The influence of both hydrogen availability and temperature on the activity and product distribution, was evaluated by carrying out reactions under different H2 pressures (40–10 bar) and temperatures (between 260 and 300 °C). Using blends of both substrates, a partial inhibition of guaiacol HDO occurred because of the competence of acetic acid for the catalytic active sites. Nevertheless, positive interactions were also observed, mainly esterification and acylation reactions, which could enhance the bio-oil stability by reducing acidity, lowering the oxygen content, and increasing the chain length of the components. In this respect, formation of acetophenones, which can be further hydrogenated to yield ethyl phenols, is of particular interest for biorefinery applications. Increasing the temperature results in an increment of conversion but a decrease in the yield of fully deoxygenated molecules due to the production of higher proportion of catechol and related products. Additional experiments performed in the absence of hydrogen revealed that esterification reactions are homogeneously self-catalyzed by acetic acid, while acylation processes are mainly catalyzed by the acidic sites of the zeolitic support.

Analysis of property variation and stability on the aging of bio-oil from fractional condensation

A series of experiments on bio-oil storage and property measurement were conducted to compare the stability of multi-stage bio-oil from fractional condensation at normal pressure and temperature. The samples from bio-oil stored for 0, 5, 15, 35, 75 days were analyzed for chemical components, moisture, pH and thermophysical properties. During storage, moisture, thermal conductivity, specific heat capacity and viscosity exhibited upward tendencies whereas pH and higher heating value decreased gradually. The properties varied more frequently in the early period of storage due to active components in fresh bio-oil. The relative contents of aliphatic compounds with small molecular weights were significantly reduced after storage but those of phenols were improved slightly. The bio-oil from high condensing temperature showed fewer changes of properties and components during long-term storage. Bio-oil aging was mainly consequent on the reaction of polymerization and oxidation, and results indicated that the bio-oil obtained from 90 °C condensing temperature was more appropriate for combustion and processing because of ample high value-added components and stable properties.

Study on kinetics and bio-oil production from rice husk, rice straw, bamboo, sugarcane bagasse and neem bark in a fixed-bed pyrolysis process

In this study, rice husk, rice straw, bamboo, sugarcane bagasse, and neem bark were pyrolyzed in a fixed-bed pyrolyzer to examine the influence of operating conditions, such as the temperature of the pyrolysis process, residence time of volatiles, and reactor length, on the yield of bio-oil and individual gas components. The temperature of pyrolysis was varied from 350 to 650 °C at increments of 50 °C, and the length of the reactor was varied from 45 to 60 cm at intervals of 5 cm. The maximum bio-oil production of 46.93 wt% and the pyrolysis char of 26.2 wt% was obtained for bamboo at 450 °C. The highest amount of clean syngas (carbon monoxide and hydrogen) was produced for neem bark (52.61 vol%). The gaussian distributed activation energy model data exhibited a superior fit with the experimental data compared with the single-reaction model for bio-oil and all other individual component gases. The presence of C–H, CC, alcohols and phenolic compounds indicated that the bio-oil obtained from all the biomass species could potentially be used as fuel. The steady-state mass and energy balances for the entire pyrolysis plant were obtained using the Aspen Plus simulation.

The CBS values of ΔfHo298.15 and So298.15 of the phenoxy radicals, formed by abstraction of H atom from the components of surrogate bio-oil

In the present work, the standard thermochemical properties of the most thermochemically stable radicals, produced by abstraction of the hydrogen atom from 2,4-dimethylphenol (2,4-xylenol), 2-methoxy-4-methylphenol, 3-methoxy-4-formylphenol (vanillin), are determined using the results of RO/CBS-4M and RO/CBS-QB3 calculations. It is found that the formation of phenoxy radicals is the most thermochemically favorable pathway for the H atom abstraction from the considered compounds.The consistent values of the standard enthalpies of formation of the most thermochemically stable structures are determined using the RO/CBS-4M and RO/CBS-QB3 thermochemistry of the homodesmotic reactions, as well as using the correction dependencies.The values of the standard entropies of these compounds, calculated in the present work, are also reported.

Are the typical organic components in biomass pyrolyzed bio-oil available for leaching of alkali and alkaline earth metallic species (AAEMs) from biomass?

In this study, six dominant organic compounds in biomass pyrolyzed bio-oil, composed of acidic compound (acetic acid) and non-acidic compound (furfural, hydroxyacetone, ethylene glycol, phenol, and guaiacol) were used to remove AAEMs from different lignocellulosic biomass (rice husk, cotton stalk, and fir sawdust) by leaching pretreatment. Other four conventional solutions (deionized water, hydrochloric acid solution, aqueous phase bio-oil, and simulated bio-oil) were selected as control eluents. Results showed that the removal rate of AAEMs was highly affected by the types of immersion solutions, pH values, and the species of biomass. Majority of K in biomass could be removed by leaching of acetic acid. Ca was more difficult to be removed by leaching of water and acetic acid, but could be removed by leaching of HCl. In general, the removal rate of K was highest among the four species of AAMEs by using five non-acidic components, followed by Na, Mg, and Ca. The use of five non-acidic solutions was significantly benefit for the remove of K, Mg, and Na, but, was less useful in removal of Ca in rice husk and fir sawdust. However, the removal rates of Ca in cotton stalk by leaching of phenol, guaiacol, and hydroxyacetone were increased to nearly three times than water leaching. A synergistic effect for removing AAEMs occurred between acetic acid and non-acidic components in bio-oil, indicating that the non-acidic compounds also play an important role in leaching of AAEMs.

Investigation on fuel properties and engine performance of the extraction phase liquid of bio-oil/biodiesel blends

In this paper, biodiesel was used to upgrade bio-oil by extracting the high-quality fuel fractions in bio-oil through solvent extraction. After the extraction, the upper layer blends of biodiesel and the high-quality bio-oil components, also called the “extraction phase liquid”, was obtained and denoted as EPBB. Firstly, Thermogravimetric (TG) and Fourier transform infrared (FTIR) analyses indicated that the light components originally in bio-oil, such as alcohols, ethers, ketones and carboxylic acids were extracted from bio-oil to biodiesel and formed the EPBB. Then the fuel properties of EPBB were measured at different temperatures. The results showed that the density of EPBB was higher, while its viscosity, surface tension and lower heating value (LHV) were lower than those of biodiesel. Accordingly, EPBB revealed better atomization and evaporation characteristics as compared to biodiesel. Finally, the engine performance of EPBB was tested on an unmodified direct-injection diesel engine. When compared with biodiesel, the ignition delay of EPBB was longer, the premixed combustion duration was longer, while the total combustion duration was shorter. The fuel economy of EPBB was comparable to that of biodiesel, and the NOx, soot, CO and UHC emissions of EPBB were all lower than those of biodiesel.

Adsorption of Major Nitrogen-Containing Components in Microalgal Bio-Oil by Activated Carbon: Equilibrium, Kinetics, and Ideal Adsorbed Solution Theory (IAST) Model

This study provides a fundamental understanding of the adsorption process for nitrogenous compound removal from microalgal bio-oil over activated carbon (AC) and offers a useful model based on the ...

Investigations on pyrolysis of microalgae Diplosphaera sp. MM1 by TG-FTIR and Py-GC/MS: Products and kinetics

In this work, pyrolysis characteristics and kinetics of microalgae Diplosphaera sp. MM1 cultivated in different mediums were investigated by TG-FTIR and Py-GC/MS. Harvested MM1s biomass varied with the changing in proximate and ultimate analyses presented different weight loss behaviors. The weight loss of MM1s cultivated in dairy and winery wastewater in main pyrolysis region was ~48.4 wt% and ~52.9 wt%, respectively, and both showed secondary weight loss after 570 °C. However, MM1 harvested from BG-11 medium exhibited maximum weight loss of ~63.5 wt% and no secondary weight loss. Further, the activation energies of MM1s harvested from dairy and winery wastewater (176.3 kJ/mol and 130.4 kJ/mol, respectively) were lower than that of BG-11medium (189.4 kJ/mol). The best mechanism function for MM1s pyrolysis was third-order f(α) = (1-α)3. Py-GC/MS results of MM1 cultivated in winery wastewater showed highest contents of C4–C10 and C11–C21 that characterized the carbon level of gasoline and diesel, respectively, which are the major components of bio-oils.

Local Wood’s Bio-Oil Upgrading Using Non-sulfided (Co, Mo)/USY Catalyst

In this present study, the non-sulfided (Co, Mo)/USY has used as a catalyst on the hydrotreating and hydrocracking (HC) reactions for upgrading the quality of bio-oil. The bio-oils were obtained from sengon, coconut, meranti, and bangkirai woody biomass by pyrolysis method at a temperature of 300 °C and atmospheric pressure. Meanwhile, the hydrotreating and HC reactions were done with a flow reactor at 300 °C, under H2 gas flow (20 mL/min). The composition of bio-oil and upgrading bio-oil were analyzed by Gas Chromatography-Mass Spectrometry (GC-MS). The resulted show that the main component of bio-oil is levoglucosan, while the main product of upgrading bio-oil is methyl format. Bio-oil with the highest yield obtained from meranti on the HC reaction that used Co-Mo/USY catalyst.

Application of Lecithin-templated Mesoporous Silica Microparticles for the Specific and Selective Removal of Phospholipids

Phospholipids are among the many components of algae bio oil, and they harbor the trans-esterification process by poisoning the catalyst, hence the need for they removal prior to this process is crucial. Mesoporous silica materials are feasible and viable candidates for the selective removal of phospholipids by tailoring their surface morphology using different surfactants (templates) for specific and selective adsorption. In this study, the adsorption of phospholipids using lecithin template mesoporous silica microparticles (Leci-MSM) was investigated. Comparative studies using cetyltriammoniumbromide mesoporous microparticles (CTAB-MSM) were also carried out. Both Leci-MSM and CTAB-MSM were synthesized via sol-gel process, packed into mini columns and used for column breakthrough adsorption studies. Scanning electron micrographs revealed a particle size of 5.0 µm for Leci-MSM and 2.95 µm for CTAB-MSM. Textural analysis by BET and BJH exhibited a surface area of 425 and 1210 m2/g for Leci-MSM and CTAB-MSM, respectively. A pore volume of 1.59 and 2.77 cc/g for Leci-MSM and CTAB-MSM, respectively, were also obtained. In addition, Leci-MSM revealed a column breakthrough volume of 28 mL at 41 min, while for the CTAB-MSM was 46 mL at 53 min. The actual adsorption capacity recorded by Leci-MSM was 11.34 mg/g and 8.71 mg/g for CTAB-MSM.