Bio-oil Components Research Articles

Olive pomace waste conversion to bio-fuel by application of integrated configuration of pyrolysis/hydrodeoxygenation process

Bio-oil obtained from non-catalytic pyrolysis of biomass, consists of a large number of oxygenated compounds. Hence, it is essential for the bio-oil to go through upgrading processes such as hydrodeoxygenation (HDO) to reform these compounds to aliphatic and aromatic hydrocarbons. This study works towards this purpose by initially deriving raw bio-oil from olive pomace waste biomass in a non-catalytic pyrolysis process at temperature of 400–700 ºC. Then for reducing the oxygen content of derived bio-oil, HDO of the raw bio-oil over NiMo/Al2O3 catalyst was performed in a batch reactor, in varying operational parameters: temperature of 200–250 °C, reaction time of 1–3 h, hydrogen pressure of 2–6 bar and catalyst: bio-oil ratio of 1:20, 1:10, 1:5. The results revealed that the catalytic HDO is an appropriate procedure, as fatty acids as the main oxygenated components in bio-oil were reduced from 81.8 % to 56.7 %, aldehydes and ketones were entirely removed, and there was a noticeable rise in aliphatic hydrocarbons from 2.8 % to 33.9 % at temperature of 250 ºC, hydrogen pressure of 6 bar and reaction duration of 3 h. In addition, by raising the catalyst to bio-oil ratio to 1:5, the content of fatty acids reached 47.6 %. Furthermore, a comparison was made between the O/C and H/C ratios of the obtained biofuels and the raw bio-oil, which results exhibited that this method worked successfully in substituting oxygen atoms of the raw bio-oil with hydrogen atoms.

Hydrothermal Liquefaction of Microalgae to Bio-oil Using Zeolite Catalysts

Mesoporous zeolite silica-alumina catalysts were investigated for their impact on the hydrothermal liquefaction (HTL) to convert Nannochloropsis oculata into bio-oil. The commercial catalysts were characterized using characterization instruments which are XRD, SAP, and TPD-NH3 analysis, revealing distinctive structural and physicochemical properties. The catalytic screening was conducted at varied reaction temperatures (160–240 °C), durations (60–120 min), and catalyst loadings (1–5 wt.%). The result revealed that ZSM-5 demonstrates effectiveness as a catalyst for the HTL of Nannochloropsis oculata, yielding high bio-oil production under optimized conditions. Strong acid sites and high surface area density are highlighted as the key factors contributing to the catalyst's enhanced performance in promoting valuable bio-oil components.

Effects of Interactions among Cellulose, Hemicellulose, and Lignin on the Formation of Heavy Components in Bio-oil during Oxidative Pyrolysis

Effects of Interactions among Cellulose, Hemicellulose, and Lignin on the Formation of Heavy Components in Bio-oil during Oxidative Pyrolysis

Catalytic conversion of biomass pyrolysis volatiles over composite catalysts of activated carbon and HY zeolite

Bio-oil has complex compositions and high oxygen content, which restricts its high-value utilization. Commercial activated carbon (AC) and HY zeolite were used as composite catalysts to study their effect on pyrolysis volatiles from rice straw and poplar sawdust by changing the mixing modes of two catalysts. The results showed that the loading modes of AC and HY zeolite obviously affected the products distribution and bio-oil components. The lowest yield of bio-oil was obtained when HY zeolite and AC were mechanically mixed at a mass ratio of 1:1 (YACM). But the loading mode of YACM was beneficial to the deoxidation and aromatic hydrocarbon generation. Under the mode of YACM, the aromatics content in rice straw and poplar sawdust bio-oil can be increased from 13.8% and 8.0% without catalyst to 56.4% and 53.1%, respectively. However, the layered loading with upper HY zeolite and lower AC (YTACL) was favorable for formation of phenolic compounds. The selectivity to monocyclic and bicyclic aromatic hydrocarbons followed the order of YTACL > ACTYL > YACM, and YACM > ACTYL > YTACL, respectively. Compared with HY zeolite, AC catalyst possessed smaller pore size and fewer acidity, and the active sites of AC were conducive to rearrangement of furan compounds to generate cyclopentanone, 2-cyclopentenone and methyl-cyclopentenone, and further rearrangement to form phenol. Therefore, the loading mode of YTACL exhibited a promotion effect on the formation of phenol, cresol, toluene, ethylbenzene and p-xylene. The strong acidic sites of HY zeolite were favorable for the aromatization, so the loading mode of ACTYL had good selectivity to the formation of naphthalene, methylnaphthalene, anthracene and pyrene. This work will provide a guide for products regulation from biomass pyrolysis and enrich aromatics and phenols in bio-oil.

Intrinsic promotion mechanism of calcium oxide on ketone production during catalytic fast pyrolysis of biomass via experiment and density functional theory simulation

CaO modified with acetic acid solution or sodium hydroxide (H-CaO/OH-CaO) was used to explore the relationship between the physical and chemical properties of CaO and the components of bio-oil during the pyrolysis of rice straw (RS) and model compounds via experiment and density functional theory(DFT) simulation. The results showed that the modification changed the properties of CaO, and thus the catalytic performance on production of bio-oil components. H-CaO with the larger number of strong basic sites (1.10 ∼ 2 times than commercial CaO) and the longer Ca-O bond length showed the better selectivity and performance on formation of ketones (the maximum relative content in bio-oil reached 43 %). The conversion pathway of cellulose/hemicellulose was changed by H-CaO, which promoted the formation of ketones. The easier combining of H-CaO with the pyrolysis primary products due to the longer Ca-O bond was the key to its better performance.

Two-stage hydrothermal liquefaction of Spirulina: Experimental observations, energy analysis and techno-economic assessment

The intensification of environmental pollution and significant consumption of fossil fuels has led to widespread attention on developing renewable resources. As a carbon-containing renewable energy source, Spirulina is characterized by its fast growth cycle and wide distribution. Currently, one of the research hotspots is the conversion of Spirulina into bio-oil through hydrothermal liquefaction. However, studies on the two-stage hydrothermal liquefaction of Spirulina predominantly concentrate on the product yield or composition. There is relatively little research on thermodynamic (energy) analysis and techno-economic assessment during the reaction process. The main bio-oil components from two-stage hydrothermal liquefaction of Spirulina are ketones and acids with 44.9 % and 34.1 %, respectively. Compared to no-catalysis, two-stage hydrothermal liquefaction of Spirulina over HZSM-5, alkili-modified HZSM-5, and Ni@alkali-modified HZSM-5 increase the relative content of hydrocarbons to 6.6 %, 32.9 % and 48.1 %, respectively. Energy analysis and techno-economic assessment are conducted with Aspen Plus simulation, revealing a exergy efficiency of 56.4 % for the catalytic two-stage hydrothermal liquefaction of Spirulina compared with 43.6 % over no-catalyst. The primary losses occur in the first stage of the reaction process (248.6 kW) and the cooling process (10.7 kW) for catalytic two-stage hydrothermal liquefaction of Spirulina. The hourly price of producing 1 kg bio-oil with a catalyst is $3.67, while without a catalyst, it is $4.54 kg−1; obtaining a unit of chemical exergy costs $0.14×10−3 kJ−1 through catalysis. Moreover, the fluctuations in the prices of sulfuric acid and catalysts are most sensitive to the cost price of bio-oil with or without catalysts in the two-stage hydrothermal liquefaction process, with the values being 10.06 % and 8.10 %. This study has important significance for efficient transformation and energy utilization of Spirulina.

Interaction mechanisms among Cellulose, Hemicellulose, and lignin in Nitrogen-Rich pyrolysis under K and Ca Presence: Intermediate evolution and product formation

To optimize the targeted production efficiency of high-value nitrogen-containing compounds (NCCs: pyrrole, pyridine, nitriles, amides), this study extensively analyzed the interactions among cellulose, hemicellulose, and lignin under K and Ca presence during nitrogen-rich pyrolysis. By establishing a theoretical model, it confirmed how the three components interact during the pyrolysis process. The highest yield of biochar was observed with Ca. The proportion of NCCs in bio-oil increased by 4.45% with the addition of Ca and decreased by 1.81% with K. GC–MS characterization compared the evolution of intermediate chemical structures during the reaction with the formation of final products, specifically tracing NCCs generation pathways in bio-oil. First-time definition of bio-oil component conversion rates during nitrogen-rich pyrolysis. Aldehydes, ketones (with minimum conversion rates of 92.62% and 71.37%, respectively), and furans were identified as the most easily converted components into NCCs. Correlation analysis of bio-oil components supported this finding. Possible reaction pathways for NCCs generation during nitrogen-rich pyrolysis of ternary mixtures under mixed Ca or K addition conditions were identified. Additionally, the introduced machine learning model exhibited a high R2 value of 0.95 in predicting the product yields of ternary mixtures nitrogen-rich pyrolysis. This validates its effectiveness in handling interacting component systems. These results reveal interaction mechanisms among biomass three components in nitrogen-rich pyrolysis under K and Ca presence, offering new insights for optimizing NCCs production.

Mechanism, thermochemistry, and kinetics of formation of PhC(O)H and HOPhC(O)H during unimolecular decomposition of P-PhC(O2•)HPhOH.

Bisphenols are one of the main components of bio-oil, produced during the pyrolysis of lignin-containing biomass. Synthetic bisphenols are used in polycarbonate plastics, epoxy resins, and thermal papers. Their mechanism of oxidation is important for the determination of the fire safety of these materials and the possibility of using them as additives in fuels for the decrease and description of ignition delays, as well as for the determination of their health risk assessment in medicine. One representative of bisphenols is p-benzylphenol (p-PhCH2PhOH), which is formed during the fast pyrolysis of lignine-containing biomass. Its thermochemistry of oxidation has been partially studied previously. It is shown that the reaction of chain oxidation of p-PhCH2PhOH is thermochemically favorable at low temperatures. However, these studies consider only two pathways of this reaction: (1) the chain oxidation of RH by RO2• and (2) the tautomerization of R'HO2• to R'O2H with following production of R'O• and OH radicals. At the same time, the reactions of intramolecular rearrangement of RO2•, produced PhC(O)H and •PhOH or HOPhC(O)H and •Ph, are not reported but can be an important part of its oxidation mechanism. The five DFT (M06-2X (i = 1), B3LYP (i = 2), wB97XD (i = 3), M08HX (i = 4), MN15 (i = 5)) approaches with 6-311 + + G(d,p) basis set are used for the determination of standard enthalpies of atomization (ΔraH°(Xi)) of considered compounds (molecules, radicals, and transition states). These values of ΔraH°(Xi) are corrected using the empirical linear calibration dependencies, reported previously. The different calibration dependencies are used for the hydrocarbons (including the aromatics and simple oxygenated derivatives) and for the peroxides. The corrected values of ΔraH°(Xi, CORR) are used according to Hess's law for the determination of ΔfH°(Xi, CORR). The most consistent values of ΔfH°(X, MEAN) are derived from the coordination of the values of ΔfH°(Xi,CORR) using the intersection of their values of standard deviations (3SDi). These values of ΔfH°(X, MEAN), as well as the B3LYP values of S°(X), which are accounting the frequencies correction and internal rotations, as well as their temperature dependencies, are used for the determination of thermochemistry of considered reactions and of the calculation, within transition state theory (TST), of the values of high pressure limits of the rate constant. The values of H°(Xi), S°(Xi), and G°(Xi) are calculated using the Gaussian 16w program. The considered mechanism is prepared using ISIS/Draw package. The temperature dependencies of thermochemical properties and the values of rate constants are determined using the ChemRate program (v.1.5). The optimized structures are visualized using the Chemcraft package.

Evolution of heavy components in bio-oil during oxidative pyrolysis of cellulose, hemicellulose, and lignin

Biomass oxidative pyrolysis introduces restricted oxygen into the reaction zone, realizing autothermal pyrolysis to address the heat supply challenges inherent in large-scale applications. However, heavy components (＞200 Da) in bio-oil are critical precursors that lead to coke formation upon heating, which hinders the utilization of bio-oil. In this study, the conventional and oxidative pyrolysis experiments of cellulose, hemicellulose, and lignin in a fix-bed reactor were conducted at temperatures ranging from 300 °C to 800 °C, aiming to investigate the evolution of heavy components in bio-oil during biomass oxidative pyrolysis. The results showed that the addition of oxygen promoted the generation of bio-oil. Compared to conventional pyrolysis, the addition of oxygen mostly increased the yields of cellulose-oil, hemicellulose-oil, and lignin-oil by 28.21 %, 10.94 %, and 16.84 %, respectively. Further comprehensive analysis revealed that oxygen promoted the depolymerization of three components at a lower temperature range (＜ 500 °C). With increasing temperatures, oxygen enhanced the polymerization of volatiles from cellulose and lignin, where oxygen, acting as a binder, promoted the generation of phenolic compounds of heavy components in lignin-oil. Conversely, as the temperature increased, oxygen enhanced the oxidative decomposition of volatiles from hemicellulose, inhibiting the generation of heavy components in hemicellulose-oil. To sum up, this study presented a global evolution route of heavy components in bio-oil during oxidative pyrolysis of three components.

Electrocatalyst hydrogenation of lignol-derived compounds: Conversion regularity and product selectivity

Phenolic derivatives, crucial components of bio-oil, require thorough understanding of their electrocatalytic hydrogenation (ECH) properties for efficient bio-oil utilization. This study investigated guaiacol, a representative phenolic derivative in bio-oil, focusing on its ECH mechanism, conversion, and product selectivity under varied conditions (temperature: 40–80 °C, perchloric acid concentration: 0.2–1.0 mol/L, current intensity: ((–10)–(–150) mA). Additionally, this study also explored the influence of intermediate products (2-methoxycyclohexanone and cyclohexanone) on both the conversion rate and the selectivity of the products. The experiment had revealed that guaiacol's ECH conversion rate improved with higher temperature and current intensity, whereas an increase in perchloric acid concentration negatively affected the conversion. Significantly, the presence of intermediate products, especially 2-methoxycyclohexanone, markedly enhanced the ECH conversion of guaiacol. Investigating further into the ECH mechanism of other phenolic derivatives, including phenol, pyrocatechol, guaiacol eugenol, and vanillin, as well as their combination, revealed a trend where conversion rates inversely correlated with the complexity of the functional groups on the benzene ring. Specifically, phenol, with its simpler structure, showed the highest conversion rate at 89.34%, in stark contrast to vanillin which, owing to its more complex structure, exhibited the lowest at 46.79%. In our multi-component mixture studies, it was observed that synergistic and competitive interactions significantly alter ECH conversion rates, with some mixtures showing enhanced conversion rate indicative of synergistic effects.

Ionic liquid lubricity enhancement with bio-oil derived from microwave pyrolysis of bamboo

In response to the growing demand for environmentally friendly lubrication, this study explores the potential of bio-oil-infused lubricants. The investigation focuses on the interaction between bio-oil, derived from raw bamboo (Phyllostachys edulis) through microwave pyrolysis at power levels between 500 and 800 W at 700 ∘C, and the protic ionic liquid, [Oley][Oleic]. The bio-oil, predominantly composed of diethyl phthalate (DEP) and fatty acid methyl ester (FAME), is blended with [Oley][Oleic] at concentrations of 1.0, 2.0, and 5.0 wt%. Friction measurements using a ball-on-disk setup reveal a substantial 58.9% reduction in friction and a 30.6% reduction in wear when [Oley][Oleic] is combined with bio-oil pyrolysed with a microwave power of 800 W. To maintain a low coefficient of friction (CoF) and wear for [Oley][Oleic], it is imperative to aim for an optimal DEP:FAME ratio in the bio-oil of approximately 2.0, within concentrations ranging from 0.2 to 1.0 wt%. The study highlights the complex tribological balance among viscosity, load-bearing capacity, and the chemical nature of bio-oil components, contributing to enhanced lubricity. As industries increasingly seek eco-friendly lubrication, this study offers a valuable knowledge base for developing sustainable and high-performance lubricants derived from renewable biomass sources.

Maximized energy recovery by catalytic co-pyrolysis of dewatered sewage sludge and polystyrene to contribute in bio-circular economy: Synergistic compositional analysis of bio-oil and syngas through artificial neural networking

Sewage sludge and polystyrene are considered very challenging for the waste management authorities in urban centers across the globe. In the current study, catalytic co-pyrolysis of the dewatered sludge (DS) and waste polystyrene (PS) was conducted. The co-pyrolysis of DS and PS; 60% polystyrene+40% dewatered sludge was concluded as optimum ratio with 11.21% higher energy production as compared with other compositions. The produced bio-oil were investigated having higher slags/wax and lower aromatics. Therefore, ZSM-5 (3% weight basis) catalyst was employed, and it had enriched the bio-oil quality, provided higher aromatic hydrocarbon yields with reduced wax and slag formation. To understand the thermodynamic behavior of all dewatered sewage sludge and polystyrene, detailed TGA analysis was carried out. The relative abundance of the aromatic hydrocarbons was identified by GC-MS and FTIR analysis. The synergist compositional analysis of the bio-oil and syngas was carried out by using artificial neural networking techniques. The aromatic components in bio-oil were found to have positive correlations when catalyst were employed. The proposed energy recovery model had capacity of generating 20,863 KWh/d of electrical energy, dealing 10 tons/d of biowaste: and leads the societies towards cleaner environment and positive contribution to bio-circular economy.

Experimental analysis and numerical simulation of biomass pyrolysis

AbstractFinding alternatives to fossil fuels is extremely important for economic and environmental considerations. Biomass pyrolysis stands out as an efficient method for generating fuels and chemical intermediates. This study explored the influence of wood particle size (ranging from 1 to 3 cm) and pyrolysis temperature (ranging from about 300 to 480 °C) on the process. Characterization of wood residues utilized energy-dispersive X-ray (EDX) and field emission scanning electron microscopy (FE-SEM) to comprehend surface morphology and resultant biochar structure. Results revealed a significant temperature-dependent impact on pyrolysis product concentrations. Biomass composition analysis indicates lignin, hemicellulose, extractive contents, and cellulose percentages at 11.23%, 39%, 2.15%, and 47.62% mass/mass, respectively. Reduction in particle size to less than 2 mm enhances heat transfer, elevating overall bio-oil production. Major bio-oil components comprise phenolics, acids, alcohols, aldehydes, and ketones. Optimal conditions are identified at a wood particle size of 1 cm and a heating temperature of 480 °C. For every 1.0 kg of wood biomass residues, bio-oil, syngas, and biochar yields are 0.38 kg, 0.22 kg, and 0.4 kg, respectively. Notably, the agreement between Aspen Plus simulation and experimental findings underscored the robustness of the study.

Study on the effect of transition zone-condensation field for the evolution and selective condensation of biomass pyrolysis vapors

The effect of regulating the transition zone temperature and the intensity of the condensation field on the characteristic parameters and important components of bio-oil was studied during the pyrolysis of cotton straw. A new approach was provided to improve the possibility for refined condensation of biomass pyrolysis vapors, increase the bio-oil yield and recovery of important components. The Logistic model effectively tracked the evolution of the characteristic components of the bio-oil and comprehensively demonstrated the selective condensation effect of the biomass pyrolysis vapors. It was found that higher transition zone temperatures improved pyrolysis vapors condensation. The temperature gradient affected the content of important components in bio-oil. Adjusting the transition zone temperature promoted the initial separation of unfavorable components such as water in the bio-oil, and the enrichment of critical organic components was achieved in combination with the condensation field. The high transition zone temperature and weak condensation field contributed to an increase in the recovery of total phenolic compounds from 0.69 wt% to 8.20 wt%.

Production of bio-oil from Tung seed residues in a fluidized-bed reactor

The current paper presents research on bio-oil production from Tung seed residues fed at 500 g/h via fast pyrolysis in a fluidized-bed. The objective was to investigate the influence of temperature on bio-oil production in a pyrolysis process. Three portions Tung residues were studied, Tung seed outer shells (TO), Tung seed inner shells (TI), and pressed residues of oil seeds (RS), all having particle sizes of 0.150–0.500 mm. The process temperatures were 350–500 °C. The physical and chemical properties of pressed residue particles were characterized by ASTM standard methods. Bio-oil component identification was done using GC-MS. Experimentally derived data showed an optimal pyrolysis temperatures for all three types of Tung residues (TO, TI and RS) of 400 °C, yielding respective maximum bio-oil yields of 53.46, 52.81, and 62.85 wt% on a dry basis (db). Apart from having highest bio-oil yield, RS produced bio-oil with the highest carbon content, leading to its greatest lower heating value (LHV), 28.05 MJ/kg (db). The main bio-oil components were acids, nitrogen compounds, and hydrocarbons. Char yield was reduced with increased temperature. Tung seed outer shells produced the highest char level (39.26 wt%) while RS gave highest char quality in term of density and heating value.

Mechanism of formation of p-benzylenephenol peroxide radical (p-PhC(O2•)HPhOH).

The reactions of radicals with O2 play the important role in the biological, medicinal, and industrial processes. The mechanism of this reaction is studied previously for the alkane, alkene, alkyne, phenols, and close-related radicals. According to these studies, the formation of intermediates in these reactions is predicted only for the aromatic radicals. Thus, the Van der Waals complexes of O2 with phenyl or benzyl radicals are predicted, as well as the π-π cluster for benzene. However, the possibility of the formation of such intermediate π-π clusters in the case of bisphenol radicals and the thermochemistry of its formation is not studied. Bisphenols are one of the main components of bio-oil, produced during pyrolysis of lignin-contained biomass. Synthetic bisphenols are used in polycarbonate plastics, epoxy resins, and thermal papers. Their mechanism of oxidation is important for the determination of fire safety of these materials, the possibility of using them as additives for fuels for the decreasing and the description of the ignition delays, as well as for the determination of its health risk assessment in medicine. The five DFT (M06-2X (i = 1), B3LYP (i = 2), wB97XD (i = 3), M08HX (i = 4), MN15 (i = 5)) approaches with 6-311 + + G(d,p) basis set are used for the determination of standard enthalpies of atomization (ΔraHo(Yi)) of considered compounds (molecules, radicals, and transition states). These values of ΔraHo(Yi) are corrected using the empirical linear calibration dependencies, reported previously. The different calibration dependencies are used for the hydrocarbons (including the aromatics and simple oxygenated derivatives) and for the peroxides. The corrected values of ΔraHo(Yi, CORR) are used according to Hess's law for the determination of ΔfHo(Yi, CORR). The most consistent values of ΔfHo(Y, MEAN) are derived from the coordination of the values of ΔfHo(Yi, CORR) using the intersection of their values of standard deviations (3SDi). These values of ΔfHo(Y, MEAN), as well as the B3LYP values of So(Y), which are accounting the frequency correction and internal rotations, as well as their temperature dependencies, are used for the determination of thermochemistry of considered reactions and of the calculation, within transition state theory (TST), of the values of high-pressure limits of the rate constant. The values of Ho(Yi), So(Yi), and Go(Yi) are calculated using the Gaussian 16w program. The temperature dependencies of thermochemical properties and the values of rate constants are determined using the ChemRate program (v.1.5). The optimized structures are visualized using the Chemcraft.

Influence of low-density polyethylene addition on nitrogen transformation during sludge protein pyrolysis

Co-pyrolysis of sludge and waste plastics is a long-term strategic approach for producing valuable fuels. However, sludge is characterized by a high protein content, which serves as a significant source of nitrogenous components in bio-oil. To improve the quality of pyrolysis products, the present study investigated the effect of low-density polyethylene (LDPE) on nitrogen transformation during the pyrolysis of sludge protein (SP). The study findings indicated that LDPE addition reduced the amount of solid residue owing to the interaction between SP and H radicals generated by LDPE pyrolysis. The thermal weight loss difference consistently remained below 0 when the SP-to-LDPE mixing ratio was 7:3, indicating that LDPE promotes the pyrolysis of SP. For the analysis of nitrogen-containing products during pyrolysis, LDPE addition significantly reduced the levels of nitrogen-containing compounds in the bio-oils of glutamate (Glu), histidine (His), and tyrosine (Tyr). Specifically, at 600°C, Glu, His, and Tyr in the bio-oils decreased by 31.4%, 33.3%, and 34.38%, respectively. No significant changes were observed in the nitrogen content within the pyrolysis char of Glu and His. However, all three amino acids exhibited a significant increase in the formation of NOx precursors due to the attack on the nitrogen positions of the heterocyclic nitrogen species by the H radicals generated by LDPE. This study contributes to research on the impact of LDPE on nitrogen migration and conversion during the pyrolysis of SP, laying the foundation for subsequent studies on pollutant removal reactions.

Enhanced mono-aromatics production by the CH4-assisted pyrolysis of microalgae using Zn-based HZSM-5 catalysts

This study presents the catalytic pyrolysis of microalgae, Chlorella vulgaris (C. vulgaris), using pure CH4 and H2-rich gas evolved from CH4 decomposition on three different HZSM-5 catalysts loaded with Zn, Ga, and Pt, aimed specifically at producing high-value mono-aromatics such as benzene, toluene, ethylbenzene, and xylene (BTEX). In comparison with that for the typical inert N2 environment, a pure CH4 environment increased the bio-oil yield from 32.4 wt% to 37.4 wt% probably due to hydrogen and methyl radical insertion in the bio-oil components. Furthermore, the addition of bimetals further increased bio-oil yield. For example, ZnPtHZ led to a bio-oil yield of 47.7 wt% in pure CH4. ZnGaHZ resulted in the maximum BTEX yield (6.68 wt%), which could be explained by CH4 activation, co-aromatization, and hydrodeoxygenation. The BTEX yield could be further increased to 7.62 wt% when pyrolysis was conducted in H2-rich gas evolved from CH4 decomposition over ZnGaHZ, as rates of aromatization and hydrodeoxygenation were relatively high under this condition. This study experimentally validated that the combination of ZnGaHZ and CH4 decomposition synergistically increases BTEX production using C. vulgaris.

Comparison of lignocellulosic-based biomass pyrolysis processes by multi-scale molecular characterization

Nowadays, biomass is considered one of the key solutions for the energy transition as a renewable energy source. It can be converted by pyrolysis into bio-oil, which can be used for producing biofuels or valuable chemicals. However, bio-oils produced from pyrolysis present high oxygen content and it is necessary to use advanced pyrolysis processes to improve the quality of the bio-oils. In this study, three bio-oils produced by different pyrolysis processes: fast pyrolysis (FP), catalytic fast pyrolysis (CFP), and reactive catalytic fast pyrolysis (RCFP) were analyzed using different analytical techniques. A first bulk analysis was performed using proximate and ultimate analysis and gel permeation chromatography with refractive index and UV detection (GPC-RI and GPC-UV), which provided crucial information on the elemental composition and mass distribution of the bio-oil components. A deeper investigation at the molecular level was performed using Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FTICR MS) and High-Performance Thin Layer Chromatography (HPTLC) to determine detailed molecular classification of the bio-oil components. Finally, a fractionation method using flash chromatography (FC) was used to provide a more accurate chemical description. The obtained fractions were analyzed by two-dimensional "comprehensive" gas chromatography (GC×GC) coupled with mass spectrometry (MS) and flame ionization detector (FID), HPTLC, and FTICR MS. The results show that the bio-oils produced from FP and CFP are very similar chemically spoken. The bio-oil from RCFP has less oxygenated products and more unsaturated hydrocarbon species. Therefore, RCFP process was found to be the best process for producing oils with a low O/C ratio.

Importance of interaction of varied components in formation of carbon nanospheres via bio-oil pyrolysis

Bio-oil has a high tendency towards coking upon heating, which can be the feedstock for production of carbonaceous materials with particular morpholpgy. Herein, production of carbon nanospheres via bio-oil pyrolysis at 800–1100 °C was conducted. The results revealed that the increasing temperature promoted the formation of carbon-rich structures of the nanospheres. The primary precursors for carbon spheres were identified as small gas-phase molecules. The competitive production of carbon spheres and flake carbon was observed, while carbon spheres gradually became the main product at higher pyrolysis temperature (>1000 °C). Furthermore, the abundance of aromatic organics was a critical factor for carbon nanosphere formation. Among the typical model components, the yields of carbon nanosphere at 1100 °C followed the order: guaiacol (38.2 wt%) > furfural (36.6 wt%) > heavy components (28.5 wt%). While acetic acid, acetone, and methanol as model compounds showed a yield of 0 wt%. The degree of interactions among bio-oil components also influenced the yield and properties of the produced carbon nanospheres. The addition of guaiacol to bio-oil facilitated the production of carbon spheres and graphitization, achieving a substantial yield of 12.7 wt% at 900 °C. However, the addition of methanol leads to a decrease in yield of carbon nanospheres.