Heavy Bio-oil Research Articles

Nanoarchitectonics of hierarchical porous biochars from heavy bio-oil by coupling calcium salts assisted template carbonization and K2CO3 activation for high-performance supercapacitors

Biochar derived from biomass has shown potential as electrode materials for supercapacitors, but controlling its pore structure is a challenge. Additionally, coking issues have limited the industrial application of heavy bio-oil, which could be used to prepare carbonous biochar as a substitute for biomass. Herein, to widen the utilization of bio-oil and to control the pore structure, this study introduces a novel approach to utilize heavy bio-oil and regulate pore structure by combining the hard template method and activation method, in which calcium citrate tetrahydrate (CCT), calcium acetate and calcium carbonate act as templates and K2CO3 acts as activator. Through CCT-assisted template carbonization at 700 °C and K2CO3 activation with a mass ratio of 1:2, a hierarchical porous biochar (CCT-700–1:2) with a specific surface area of 2213.09 m2 g−1 was successfully synthesized. The CCT-700–1:2 electrode shows outstanding capacitive performance with a specific capacitance of 213.86 F g−1 at 0.5 A. The assembled solid-state symmetric supercapacitor displays impressive rate capability, maintaining the capacity retention ratio being 69.7 % at 20 A g−1. Furthermore, it demonstrates exceptional cycle stability and the capacitance retention is around 98 % even after 60,000 cycles. The symmetric supercapacitors also show the high energy density being 16.36 W h kg−1 at 250 W kg−1. This study presents a hopeful method for producing sustainable carbon materials by bio-oil used as energy storage devices, enhancing the potential utilizations of biomass derived products in the area of supercapacitors.

Preparation of heavy bio-oil-based porous carbon by pyrolysis gas activation and its performance in the aldol condensation for aviation fuel as catalyst carrier

Due to the high molecular weight, high viscosity and strong instability of heavy bio-oil from rape straw, it is necessary to explore new high-value utilization methods. Heavy bio-oil based carbon material (HBC) was prepared via carbonization and activation assisted by pyrolysis gas, and the basic Mg-Zr-O catalysts using HBC as the carrier (Mg-Zr-O/HBC) was synthesized for the aldol condensation of cyclopentanone to produce aviation fuel precursor. The effect of activation condition on the physicochemical properties of HBC and Mg-Zr-O/HBC were evaluated, the evolution of gas component before and after activation was explored, and the catalytic performance of Mg-Zr-O/HBC in the aldol condensation of cyclopentanone for the synthesis of aviation fuel was tested. Instead of traditional KOH activation, pyrolysis gas activation was beneficial for the reduced pollution and increased calorific value of the gas, making it an environmentally friendly method. The results showed that the activation of biochar (BOC) was improved with lower pyrolysis gas flow, higher activation temperature and longer activation time. The pore structure of carbon material was significantly improved, and the specific surface area was boosted from 15.25 m2/g3 to 627.61 m2/g3. Mg-Zr-O was evenly distributed on HBC, and a large number of weak and medium basic sites were found in Mg-Zr-O/HBC, which was quite favorable for the aldol condensation. In the aldol condensation of cyclopentanone, Mg-Zr-O/HBC presented the excellent production of the targeted C10+C15 condensates of 84.95 %, which was comparable to that prepared with KOH as activator. After 8 repeated runs, the yield of the targeted condensates remained at 73.33 %. In general, it provided an environmentally friendly strategy for the preparation of HBC and the high-value utilization of pyrolysis gas assisted by pyrolysis gas for the activation of BOC.

In situ hydrodeoxygenation of heavy bio-oil using a Ce/Fe-based oxygen carrier in methanol-zero valent aluminum media

Resource recovery from solid organic wastes, such as degradable plastics, and upgrading raw bio-oil are important ways for reducing carbon and pollution emissions. Hydrodeoxygenation (HDO) is a common thermochemical treatment to upgrade crude bio-oil. In this study, in order to realize in situ HDO during the hydropyrolysis of heavy bio-oil and degradable plastics, a reduced Fe/Ce oxygen carrier (OC) was used to catalytically remove oxygen from organics under the methanol-zero valent aluminum (ZV Al) media, where the hydrogen was produced during pyrolysis instead of a direct hydrogen supply. The results showed that the reduced OC captured the oxygen from the pyrolysis products of heavy bio-oil and degradable plastic, representing the multi-selectivity of reduced OC to phenols, ketones, etc. The ZV Al system promoted the production and utilization of hydrogen, as evidenced by the increased hydrogen content in gas phase and hydrocarbon content in liquid phase. The hydrocarbon component distribution in the liquid phase increased clearly when hydropyrolysis with degradable plastics addtion, but the excess degradable plastics addition caused increasing of the liquid product viscosity, and decreasing of the liquid products yield for the higher ash content in degradable plastic, and a higher ZV Al amount was required to maintain the hydropyrolysis. Molecular dynamics simulations verified the synergistic effect of degradable plastics and bio-oil by the pyrolysis behavior in different systems and temperatures, and the pyrolysis pathways were proposed. This non-autocatalytic system realized the resource recovery and heavy bio-oil upgrading using an Fe/Ce OC.

Fe-catalyzed low-temperature hydrothermal liquefaction of coffee shells: Influence of operating parameters on bio-oil yield, distribution of bio-oil products

Coffee shells were hydrothermally liquefied under FeCl3 catalysis to produce crude bio-oils at temperatures ranging from 190 to 300 °C. This study investigated the impact of operational parameters (hydrothermal temperature, residence time, Fe3+ catalyst concentration, extraction solvents) on the bio-oil yield. Optimized hydrothermal conditions resulted in a conversion rate of 68.47 % for coffee shells, leading to an 11.51 % yield of light bio-oil extracted from the aqueous phase and a 35.99 % yield of heavy bio-oil from the solid phase. The chemical composition and distillate distribution of the bio-oil were determined through organic element analysis, GC-MS analysis, and TG/DTG analysis. The light bio-oil primarily consisted of furfural derivatives and phenolic derivatives; however, it only accounted for approximately 14.50 % of the total energy recovered from the feedstock. The components present in heavy bio-oils varied depending on the extraction solvents used but mainly comprised fatty acids and their derivatives. Acetone extraction yielded the highest amount of bio-oil; however, its high O/C ratio reduced its higher heating value (HHV). Ethanol extraction also resulted in higher yields but TG/DTG analysis indicated that these fractions contained more refractory volatiles and solid residues compared to other solvents used for extraction. In comparison, n-hexane extraction had a lower yield than both previous methods but offered a lower O/C ratio and higher HHV instead. Our study demonstrated that Fe-catalyzed hydrothermal liquefaction is an efficient method for obtaining value-added compounds and hydrocarbon fuels from coffee shells.

LIQUEFACTION OF COFFEE BIOMASS WITH RESIDUAL GLYCERIN: A STUDY OF RENEWABLE FUEL PRODUCTION

The present study analyzes the hydrothermal liquefaction of residual coffee biomass using glycerin from the production of biodiesel through the homogeneous route. The reactions occurred by varying the glycerol/water ratio (1:0, 1:1, and 1:2) and the solvent/biomass ratio (70 and 90%) with heating at 180°C for 30 minutes (mixing phase) and at 250°C for 15 minutes. The products obtained were identified as light bio-oil (BOL), heavy bio-oil (BOP), gaseous fraction (FG), and solids (SOL). These products were submitted to characterization through density, thermogravimetry, and viscosity analyses. The condition that generated the highest oil yields was the one where 70% solvent and a glycerin/water ratio of 1:2 were used, producing approximately 83% of bio-oils. In this perspective, coffee biomass and residual glycerin were suitable for use in the hydrothermal liquefaction process.

Platform chemicals recovery from spent coffee grounds aqueous-phase pyrolysis oil

Spent coffee grounds (SCG) are a valuable biogenic waste diffused on a global scale, containing a significant amount of extractives. The aim of this study is to characterize the pyrolysis oil fractions, under various process conditions, targeting their potential applications as biofuels and source of valuable chemicals. Pyrolysis tests were carried out in the range of 400–550 °C with a laboratory-scale screw reactor and a two-step solvent extraction process, was conducted for the aqueous bio-oil phase. The results showed that heavy organic bio-oil resulted in a carbon rich biofuel, with a carbon content of up to 63 % (w/w) and HHV up to 34.8 MJ/kg. Chloroform was selective in extracting xantines (68–74 % of the peak area), furans, phenols, and fatty acids from the aqueous phase, while the ethyl acetate extract was abundant in p-benzoquinone (70–83 % of the peak area), a key-player chemical for the petrochemical industry. The residual unextracted water phase is very rich in organic acids i.e. acetic, propionic, and formic-whose concentration is in the range 47 g/L and 87.9 g/L. The results of this study outline how solvent extraction is a promising technique for extracting valuable chemicals to improve the economic potential of spent coffee grounds pyrolysis-based biorefinery.

Algae pyrolysis in alkaline molten salt: Products transformation

Algae pyrolysis in alkaline molten salt is a promising technology for hydrogen production, but the pyrolysis products transformation has not clearly been described up-to-date. Moreover, the complex bio-oil especially heavy bio-oil fraction directly influences the products transformation pathways, while limiting the hydrogen production yield and application. Both the light and heavy bio-oil fractions are investigated in detail and the effect of alkaline molten salt on products transformation is obtained. Molten salt promotes the cyclization and aromatization of linear alkenes, thereby increasing aromatic compound content and hydrogen production. The decarbonation of Na2CO3 and the deoxygenation of NaOH lead to the methane release, in turn reducing hydrogen production. The heavy compounds tend to polymerize at higher temperatures into compounds with higher molecular weights and unsaturation, while generating hydrogen. As the temperature rises, char reacts with molten salt to form hydrogen and disappears at 650 °C, while aromatics in light compounds condense into heavy compounds, which then grow to form soot-like at 600 °C, accompanying hydrogen release. Based on the relationship between products transformation, hydrogen release and alkaline molten salt effect, strategies to improve the hydrogen yield and purity of AMSP process are proposed.

Hydrodeoxygenation of heavy lignin bio-oil to oxygenated fuel catalyzed by CuxNiy/MgO

Novel techniques for upgrading heavy lignin bio-oil, the phenolic oligomer from lignin depolymerization, are of great significance for achieving better utilization efficiency of carbon element in lignin. In this study, we proposed an efficient approach for producing high-quality oxygen-containing fuel from the renewable lignin bio-oil via the C-O bond cleavage and the subsequent hydrogenation over the Cu and Ni supported on alkaline MgO. Noticeably, the optimized Cu6Ni20/MgO resulted in inspiring yields of ethylbenzene (88.6%) and cyclohexanol (98.3%) from lignin dimers, and a colorless fuel with a high-heating value of 31.4 MJ kg−1 from the realistic lignin bio-oil. The results of catalyst characterization also unveiled that introducing Cu species reduced the formation of NiMgOx solid solution, which increased the content of Ni0 and consequently promoted the performance of upgrading lignin bio-oil. Furthermore, the recondensation of phenolic oligomers could be effectively restrained by the alkaline MgO. In addition, a plausible mechanism was proposed. Therefore, this work opens a promising avenue to designing efficient strategies for utilizing the heavy components from lignin depolymerization.

Evaluation of stirring rate and pH on phenolic compounds recovery from palm kernel shell heavy phase bio-oil

This study aims to develop an efficient separation method for phenolic compounds derived from the heavy phase of bio-oil produced by the pyrolysis of palm kernel shell. Two variables were investigated during phenolic compound extraction using dichloromethane, i.e., stirring rate and pH of the solution. In both variables, the composition, yield, and distribution coefficient of the extracted phase were investigated. The results showed that the phenolic compounds' extraction favors high stirring rate and it obtained more results at more acidic conditions (lower pH). The best conditions for phenolic compounds were at 300 rpm of stirring rate and pH 4, which resulted in 77.88 % of yield and a 1.13 distribution of coefficient for the total phenols. The findings of this research will contribute to the better separation of phenolic compounds in bio-oil for improving its fuel characteristics as well as producing value-added chemicals.

Understanding the synergistic effect during co-liquefaction of cellulose and hemicellulose (xylan) in subcritical water

Hydrothermal liquefaction (HTL) is a promising technology for conversion lignocellulosic biomass into bio-oil, however, the interactions between biomass components are not well understood. Microcrystalline cellulose (MCC) and xylan were used as model components for cellulose and hemicellulose in the HTL process considering the influence of temperature, reaction time and solvent to solid ratio. Synergistic interactions occurring between MCC and xylan could enhance both the bio-oil and heavy bio-oil (HBO) yields, and MCC contributed more to the oil yield. In terms of HBO yield, it was in the order of MCC (20.8%) > MCC-xylan (19.4%) > xylan (17.5%). Regarding to the bio-oil chemical compositions, interactions promoted the formation of 5-hydroxymethylfurfural and inhibited some carbonyl groups. Higher temperatures led to lower H/C and O/C of the HBO from MCC-xylan, which also increased the HHV of HBO. The synergies identified in this work provide new insight into potential interactions between biomass components.

Effect of molten salt on re-pyrolysis behaviors of heavy bio-oil

The effects of KCl-ZnCl2 molten salt on the pyrolysis characteristics and pyrolysis products of heavy bio-oil at 400, 500 and 600 °C were studied. The results showed that molten salt increased the solid yield of heavy bio-oil pyrolysis and decreased the gas yield. Some compounds such as phenol, cresol, ethylphenol and 4-propylphenol had good enrichment effect, especially the relative concentration of cresol increased from 8.82% to 20.85% at 400 °C, while the relative concentration of phenol increased from 2.18% to 8.62% at 600 °C. During formation of char, molten salt reduced the content of carbon and increased the content of oxygen, increased the BET surface area and total pore volume of pores. Molten salt promoted formation of pore structure of the solid product and increased its average pore diameter.

Adsorption effects and regeneration characteristics of heavy bio-oil template porous carbon on Congo red

Adsorption effects and regeneration characteristics of heavy bio-oil template porous carbon on Congo red

Effect of condensation-assisted solid media on the production of bio-oil by fast pyrolysis of cassava residues in a free-fall reactor

This research elucidates the effect of condensation-assisted media on the production of bio-oil from a mixture of cassava stalk and rhizome in a free-fall fast pyrolysis reactor. The media were non-porous solid substances including steel balls and glass beads, and porous solid substances including silica gel and 3A molecular sieve. For experiments with solid media, the biomass feed rate was fixed at 100 g/h and the total run duration was varied to 60, 90 and 120 min to vary the total amounts of biomass feed to 100, 175 and 250 g, respectively. The use of solid media did not significantly influence the total bio-oil yields and hardly affected the yields of heavy bio-oil. The highest increase of the heavy bio-oil was achieved when applying 3A molecular sieve and 250 g of biomass in which the yield was increased from 40.2 to 53.8 wt%. It was found that the bio-oils from low-temperature condensers were separated into two phases, namely light bio-oil and aqueous liquid. The yield of the light bio-oil increased from ∼1 to 8.8 wt% when the 3A molecular sieve was applied. According to the bio-oil analysis, all solid media could ameliorate the bio-oil water and oxygen contents as well as their heating values. It is for the first time discovered that the use of 3A molecular sieve as a condensation-assisted medium while producing bio-oil could effectively and significantly improve the bio-oil quality. Comparing the non-condensation-assisted media with the 3A molecular sieve, the water content of heavy bio-oil was reduced from 29 wt% to 10 wt% and the HHV was increased from ∼22 MJ/kg to 26 MJ/kg. Importantly, the heating value of the light bio-oil produced with the aid of 3A molecular sieve was as high as 31 MJ/kg.

Co-pyrolysis of heavy bio-oil and disposable masks pyrolysate with Ce/Fe-based oxygen carrier catalyst

Hydrodeoxygenation (HDO) of heavy components of bio-oils is an effective way to improve the quality of bio-oil into fuel oil. Up to now, in-situ hydrogenation technology is a popular upgrading approach because of its economy, simplicity and efficiency, and the developing suitable hydrogenation catalyst and hydrogen donor is one of the key issues. In light of that, the effects of different reaction temperatures and times in the high pressure reactor on the in-situ hydrogenation of heavy bio-oil were investigated and the upgrading experiments of heavy bio-oil were carried out with the addition of the reduced Ce/Fe-based oxygen carrier (OC) and mask pyrolysate. The results showed that the reduced Ce/Fe-based OC played a dual function of carrying oxygen and catalysis, and the disposable mask pyrolysate was an excellent hydrogen donor to transport active hydrogen. Compared with the untreated bio-oil oxygenated compounds, the physicochemical properties and yield of the liquid products obtained by HDO of heavy bio-oil were higher. Under the action of active hydrogen, the oxygenated compounds could be converted into hydrocarbons (6.34 % to 41.24 %-68.54 %) by HDO. The effective hydrogen-to-carbon ratio ((H/C) eff) of the liquid products (1.08 to 1.74–1.94) and the higher heating value (HHV) (27.75 MJ/kg to 31.64–37.05 MJ/kg) were increased. Particularly, the liquid products collected at 300℃ and 30 min had better performance (HHV 37.05 MJ/Kg and liquid yield 68.45 %). In addition, the liquid products had excellent fluidity. Therefore, the liquid products basically had the characteristics of fuel oil. This work might provide a reference for recycling disposable masks.

Biomass pyrolysis polygeneration with bio-oil recycling: Co-pyrolysis of heavy bio-oil and pine wood leached with light bio-oil for product upgradation

The liquid products obtained from pyrolysis of biomass include light bio-oil and heavy bio-oil. The former contains large amounts of water and organic acids, while the latter contains more of pyrolysis lignin and phenolic compounds. Herein, a new method of pine wood co-pyrolysis polygeneration along with bio-oil recycling was proposed for upgradation of pyrolysis products. Light bio-oil was used for leaching of pine sawdust, instead of the traditional acid leaching pretreatment, followed by its co-pyrolysis with heavy bio-oil. The synergistic effect during co-pyrolysis polygeneration was studied. Results showed that leaching pretreatment could effectively remove the alkali metals (95.6 % of K) from pine wood, which improved the quality and energy yield of bio-oil during the subsequent pyrolysis. The maximum increase in mass yield and energy yield of bio-oil were 6.7 % and 7.1 %, respectively. The co-pyrolysis of pine wood and heavy bio-oil had obvious synergistic effect, which increased the mass yield of biochar (maximum increase: 3.3 %) and pyrolysis gas, while reducing the water and relative acids contents of bio-oil and improving the contents of CO and C2+ gases in the gaseous products. The maximum differences between the experimental and theoretical HHVs of biochar and bio-oil were 1.01 MJ/kg and 1.94 MJ/kg, respectively. Thus, this method provides a potential way to classify and utilize light and heavy components of bio-oil and also provides a basis for biomass pyrolysis polygeneration technology.

Integrated catalytic pyrolysis and catalytic upgrading of Leucaena leucocephala over natural catalysts

Catalysts are used to improve the properties of the bio-oil produced through biomass pyrolysis. In this study, natural minerals, such as natural zeolite and dolomite, were used for the catalytic upgrading of the pyrolysis of Leucaena leucocephala. Pyrolysis was performed using an in-house designed fluidized bed system wherein the catalyst beds can be placed in two locations. Dolomite and zeolite catalyst beds were placed in the primary fluidized bed and/or secondary hot filter reactors. Four catalyst configurations were utilized in this study. The effects of the type and location of the catalyst on the catalytic activity and product selectivity were investigated. The highest light bio-oil fraction was obtained using the dolomite catalyst situated at the primary and secondary reactors. On the other hand, the configuration in which the natural zeolite catalyst was placed in the two reactors produced heavy bio-oil that was mainly composed of hydrocarbons. The viscosity, flash point, and fly point of the bio-oil produced in this work fall within the standard values for fuel oils. In particular, the viscosity of the bio-oil produced using the catalysts was lower by 60% of that of the product obtained through noncatalytic biomass pyrolysis. The pyrolysis system employed in this study is a promising technology for catalytic biomass pyrolysis processes.

Investigation on co-hydropyrolysis of heavy bio-oil with degradable plastics

Reducing the acidity and viscosity of heavy bio-oil is one of the main tasks of bio-oil treatment. The sharp increase in the consumption of degradable plastics requires an effective route for their recycling. In this study, heavy bio-oil was used as the organic solvent of degradable plastics in a co-hydropyrolysis process with lower temperature in reaction kettle. Employing an orthogonal experimental design, and with the maximum total energy yield of co-hydropyrolysis process as the target, the optimal reaction parameters were determined by the degradable plastics all pyrolyzed. The liquidity of the liquid phase increased significantly and the viscosity is decreased. The hydrocarbon content in the liquid-phase products increased, and the amount of organic acids decreased significantly from 183.9 mg/g to 72.1 mg/g according to KOH solution titration. A total energy yield of 86.27% was achieved with a calorific value of the bio-oil product of 25.6 MJ/kg and coke product of 26.93 MJ/kg. The active component of the iron-based oxygen carrier is completely transformed from FeO to Fe3O4, which prompted the pyrolysis of oxygen-containing organic matter and the uptake of the products by the fuel oil. This work developed a way to resource the heavy bio-oil and degradable plastics.

Fast oxidative pyrolysis of eucalyptus wood residues to replace fossil oil in pulp industry

This study evaluates the potential of the oxidative fast pyrolysis (OFP) of eucalyptus wood residues (EWR) for producing bio-oil to replace fossil fuels in the lime kilns of the pulp industry. OFP is an alternative to inert-atmosphere fast pyrolysis where separate heat addition stage is not required. OFP was studied by characterizing the fuel using proximate and elemental chemical analyses, thermogravimetric analysis and heating value. Then, OFP experiments in a pilot-scale autothermal fluidized reactor were done with EWR. Pyrolysis products were gases, bio-char and bio-oil (heavy and light). The gases were burnt, and the energy used for heating the fluidization air. Heavy bio-oil energy yield of 30% and 21.4 MJ kg−1 lower heating value indicate good potential for fuel applications. The results were used to model and evaluate industrial-scale cases. Integration with the pulp mill recovery boiler and steam cycle allows easy recovery of the considerable waste heat from the process itself, as well as the combustion of solid and gaseous residues. Economic analysis indicates profitability for OFP of fine EWRs from the mill. A higher net present value, but longer payback period, was obtained for a larger OFP plant using purchased feedstock. Stand-alone production was found unprofitable.

Ice template-assisting activation strategy to prepare biomass-derived porous carbon cages for high-performance Zn-ion hybrid supercapacitors

Biomass-derived porous carbons are desirable electrode material for supercapacitors, but the blocked carbon morphology leading to the poor accessibility and long diffusion distance hinders the practical application. Exposing the inner carbon space for smooth ion transport is crucial for the enhanced capacitive performance. Herein, porous carbon cages were prepared from heavy bio-oil using an ice template-assisting activation method. Ice crystals played crucial roles in the fabrication of cage-like morphology. By tuning the volume, ice crystals grew as templates to create cavities, prevent the shrinkage of carbon framework and transport activators into carbon bulks for high accessible surface area. The resultant porous carbons possess open structure with hollow cavities and layered shells, allowing the both excellent energy and power performance for symmetric supercapacitors and Zn-based hybrid supercapacitors. The assembled Zn-based hybrid supercapacitors achieve a favorable energy density of 119.02 Wh kg−1.

Exploring the compatibility between hydrothermal depolymerization of alkaline lignin from sugarcane bagasse and metabolization of the aromatics by bacteria

Although hydrothermal treatments for biomass fractionation have been vastly studied, their effect on the depolymerization of isolated lignins in terms of yield, composition, and compatibility of the produced lignin bio-oils with bioconversion is still poorly investigated. In this study, we evaluated the hydrothermal depolymerization of an β–O–4′-rich lignin extracted from sugarcane bagasse by alkaline fractionation, investigating the influence of temperature (200–350 °C), time (30–90 min), and solid-liquid ratio (1:10–1:50 m.v−1) on yield of bio-oils (up to 31 wt%) rich in monomers (light bio-oils). Principal Components Analysis showed that the defunctionalization of the aromatic monomers was more pronounced in the most severe reaction conditions and that the abundance of more hydrophobic monomers increased in more diluted reactions. While the high-molecular-weight (heavy) bio-oil generated at 350 °C, 90 min, and 1:50 m.v−1 failed to support bacterial growth, the corresponding light bio-oil rich in aromatic monomers promoted the growth of bacteria from 9 distinct species. The isolates Pseudomonas sp. LIM05 and Burkholderia sp. LIM09 showed the best growth performance and tolerance to lignin-derived aromatics, being the most promising for the future development of biological upgrading strategies tailored for this lignin stream.