Bio-oil Components Research Articles

Catalytic hydrothermal liquefaction of microalgae over reduced graphene oxide support Ni catalyst

In this study, a reduced graphene oxide (RGO) material loaded with nickel was prepared, and to the best of the authors' knowledge, it was the first time that RGO material used as a catalyst in the hydrothermal liquefaction (HTL) of microalgae. The effect of RGO support Ni catalyst on the yield and quality of bio-oil derived from HTL of Spirulina was studied in this research. The results showed that the catalyst could improve the yield of bio-oil, and the performance in improving the quality of bio-oil was significantly increased. GC–MS analysis showed that RGO catalyst could promote the formation of hydrocarbons. When the loading amount of Ni was 5%, the oxygen content of bio-oil was the lowest (14.79%), and when the loading amount of Ni was increased to 25%, the content of hydrocarbons was the highest (11.41%). In addition, RGO catalyst also increased the content of low boiling point components (<400°C) in bio-oil from 68% to 81%. This study can provide valuable information for the further application of graphene in microalgae HTL and the production of high-quality bio-oil in the future.

Performance and characterization of phenol-formaldehyde resin with crude bio-oil by model compound method.

In order to clarify the effects of crude bio-oil for phenol-formaldehyde resin, the phenol-formaldehyde resin with bio-oil model compounds (BMPF) were prepared by model compound method. The bonding strength and aging resistance of BMPF were determined, and their microstructure and chemical bonds were also analyzed by scanning electron microscope, Fourier transform infrared spectroscopy, and nuclear magnetic resonance analysis, respectively. The results showed that the components of crude bio-oil had various degrees of effects on the BMPF performance, and the most obvious one is the phenols. The phenols and the ketones of bio-oil had positive effects on the bonding strength. The ketones had the biggest effect on the surface smoothness of BMPF film. But all components of bio-oil could inordinately improve the aging resistance of BMPF. The structural analysis indicated that the effects of bio-oil components on the BMPF performance by changing the resin structure. The CH2 peak in FT-IR and the methylene bridges intensity in NMR of phenol-free BMPF and ketone-free BMPF were smaller, while the results of aldehyde-free BMPF and acid-free BMPF were opposite. And the influence degree of BMPF structure was basically consistent with that of BMPF performance. These results could provide a basis for the modification of phenol-formaldehyde resin by crude bio-oil.

The reusing of waste bio-oil as additive on enhanced urea-based selective non-catalytic reduction denitrification

Pyrolysis polygeneration has been proven to be effective in solid waste recycling, while cleaner production is hindered by nitrogen oxide emissions and waste oil utilization. In this study, waste bio-oil was proposed as additive for promoting urea-based selective non-catalytic reduction (SNCR) denitrification efficiency to establish bio-oil reusing process and the influence of waste bio-oil on promoting SNCR denitrification were investigated. Then the effects of temperature, bio-oil components and fly ash on SNCR denitrification characteristics were explored. The results illustrated that 5 wt% bio-oil additives would widen the optimum denitrification temperature window by 24.8 % (from 210.25 to 262.43 °C), reduce the reduction temperature by 62.11 °C (from 944.04 to 881.93 °C), and increase the denitrification efficiency by 21 %. Among the main components in waste bio-oil, acetic acid was more effective than phenol and furfural in promoting SNCR denitrification under 900 °C, a large amount of OH was produced to promote the reduction of NH3 and HNCO. In addition, the existence of fly ash could promote urea oxidation and reduce denitrification efficiency because of the catalytic effect of CaO and Fe2O3 on urea oxidation.

Co-pyrolysis of chitin with nitrogen carriers: Kinetics, product characterization and bio-oil analysis

Considering the depletion of fossil fuels and the cumbersome traditional synthesis process of chemical compounds containing nitrogen, there is increased interest in direct production of nitrogenous compounds (bio-oil) from nitrogen-rich pyrolysis of biomass. In this study, a new strategy for the preparation of both nitrogen-rich bio-oil and biochar by co-pyrolysis of chitin and nitrogen carriers was proposed. Four different nitrogen carriers (urea, ammonium acetate, glutamate, and polyurethane) were selected and the thermal behavior of the mixtures as well as the synergistic competitive effects between the pyrolytic volatiles were characterized. Simultaneously, the properties of the co-pyrolysis products and the distribution of the main components in bio-oil were analyzed. The results showed that co-pyrolysis of chitin and nitrogen carriers had a synergistic effect. Glutamate had the most significant inhibitory effect on volatile gases, while only polyurethane promoted the release of volatile gases. Compared to the pyrolysis of chitin alone, the addition of urea, ammonium acetate and polyurethane effectively reduced the activation energy of the reaction. The addition of nitrogen carriers promoted the production of amines. Co-pyrolysis of urea and glutamate (40%) increased the content of nitrogenous compounds by 14.84% and 3.41%, respectively. However, the addition of ammonium acetate and polyurethane hindered the conversion of oxygenated compounds to nitrogen-containing compounds. In addition, the formation pathways of chitin pyrolysis and co-pyrolysis products were summarized. This work expanded the boundaries of high-value utilization of chitin.

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.

Performance evaluation of aged asphalt rejuvenated with various bio-oils based on rheological property index

This study examines the performance of aged asphalt rejuvenated with various bio-oils based on rheological properties and rejuvenation mechanism. Castor oil, gutter oil, soybean oil, straw oil, and vegetable oil were chosen to explore the effects of bio-oils characteristics on the rejuvenated asphalt properties. The contents of each kind of bio-oil were set at 3%, 6%, 9%, and 12%. The high-speed shear apparatus was first used to prepare the aged asphalt rejuvenated with the bio-oils. The temperature sweep (TS) test was used to evaluate the high-temperature permanent deformation resistance of rejuvenated asphalt, and then its high-temperature elastic resilience was measured by using the multiple stress creep recovery (MSCR) test. The rutting and low-temperature crack resistances of aged asphalt rejuvenated with bio-oils were later evaluated by utilizing the frequency sweep (FS) and bending beam rheometer (BBR) tests, respectively. Finally, the functional groups of asphalt before and after regeneration were observed by conducting Fourier transform infrared reflection (FTIR) test, and the relationship between the chemical components of bio-oils and rheological property index of aged asphalt rejuvenated with bio-oils was analyzed by carrying out gas chromatography-mass spectrometry (GC-MS). The results showed that gutter oil and vegetable oil had an apparently adverse influence on G*/sinδ of aged asphalt. Castor oil, soybean oil, and straw oil better improved the recovery rate of aged asphalt, reduced its non-recoverable creep compliance, and effectively enhanced elastic resilience and resistance to its permanent deformation. Gutter oil and vegetable oil made aged asphalt have better low-frequency sensitivity, and most favorable influenced on the crack resistance; The recommended contents of castor oil, gutter oil, soybean oil, straw oil, and vegetable oil were 6.21%∼6.75%, 4.50%∼4.58%, 5.84%∼6.05%, 6.31%∼6.55%, and 5.17%∼5.68%, respectively. The rejuvenation of aged asphalt by adding bio-oils was a physical process; From the perspective of bio-oil composition, it is meaningful to compare and analyze other indexes to scientifically evaluate the extent of rejuvenation.

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.

Influence of graphite/alumina on co-pyrolysis of Chlorella vulgaris and polypropylene for producing bio-oil

The effects of Graphite/Alumina (GP/Al2O3) compound additives with different addition amounts (10%, 20%, 30% and 40%) and different mixing ratios (10:0, 7:3, 5:5, 3:7 and 0:10) on co-pyrolysis characteristics, product yield and bio-oil components of Chlorella vulgaris (CV) and polypropylene (PP) were studied by microwave thermogravimetry and GC-MS. The results indicated that compared with the C8P2 (CV:PP = 8:2) group, 30% G10A0 (GP:Al2O3 = 10:0) could greatly improve pyrolysis efficiency, but the contents of hydrocarbons and alcohols in bio-oil decreased and the content of acids increased. 40% G0A10 could increase the content of hydrocarbons and decrease the content of phenols in bio-oil, but the yield of bio-oil was 3.16% lower than that of C8P2 group. For 40% compound additive groups, GP/Al2O3 could increase the production of bio-oil without increasing energy consumption, and the contents of hydrocarbons and alcohols in bio-oils increased. The maximum contents of hydrocarbons and alcohols appeared in the 40% G7A3 group, 29.56% and 34.60% respectively. In addition, alkyl-cyclohexane accounted for 65.95% of hydrocarbons in 40% G7A3 group. Therefore, the content of alkyl-cyclohexane can be controlled purposefully to be used in chemical fields such as organic synthesis and preparation of antistatic coatings, so as to expand the application of bio-oil.

Hydrodeoxygenation of Bio-oil Components Containing a Guaiacol Fragment in the Presence of a Ruthenium-Suppoting Mesoporous Aluminosilicate Catalyst

Hydrodeoxygenation of Bio-oil Components Containing a Guaiacol Fragment in the Presence of a Ruthenium-Suppoting Mesoporous Aluminosilicate Catalyst

Insights on the acetic acid pretreatment of wheat straw: Changes induced in the biomass properties and benefits for the bio-oil production by pyrolysis

This work discloses how the pretreatment of wheat straw with acetic acid (AA) solutions modifies the biomass composition, strongly affecting the pyrolysis product distribution. AA in diluted solutions is a renewable and eco-friendly reagent, being also one of the main components of the pyrolysis bio-oil* (water-free basis). In comparison with water and diluted ammonia treatments, AA washing leads to a higher removal degree of alkali and alkaline-earth elements (AAEMs) from the biomass ash. In addition, the AA pretreatment reduces the content of char and gas precursors, as is the case of soluble lignin and extractives. Consequently, the bio-oil* yield is drastically increased up to ∼53 wt% during the pyrolysis of the AA washed wheat straw, being much higher than the value obtained for the raw biomass (∼35 wt%). Likewise, the bio-oil* composition is highly improved by the pretreatment with AA, dramatically increasing the concentration and yield of levoglucosan, which is a valuable precursor to produce both advanced biofuels and bio-based chemicals. In contrast, the opposite occurs during the pyrolysis of the extracted matter samples, recovered from the washing solutions, since its high content of AAEMs, lignin and extractives promotes the formation of char and gases in the detriment of the bio-oil fraction. Based on a preliminary techno-economic analysis, it is concluded that pretreatment with AA solutions may improve significantly the economic performance of the wheat straw pyrolysis process. This is due to the increased incomes coming from the higher yield of both bio-oil* and levoglucosan that largely compensate the additional capital and fresh AA costs.

Coupling effect of pyrolysis temperature and condensing temperature on the enrichment of high value-added phenolic compounds in bio-oil from pyrolysis of crop straw

Pyrolysis experiments were performed using cotton straw and corn straw as raw materials at 723 and 773 K. The variations in condensation efficiency, moisture, and content of important components in bio-oil condensed from pyrolysis vapors were investigated in a water-bath condensation temperature of 313–363 K. The condensing efficiency, moisture, and content of important components of bio-oil increased with increased pyrolysis temperature. The single pyrolysis temperature provided limited control over the quality of bio-oil. The variation in condensing temperature affected the condensing of pyrolysis vapors. As the condensing temperature increased, the moisture in bio-oil was reduced by 200%, and the maximum content of the important components was elevated. The phenol content of the target bio-oil increased by 340.40%. For guaiacol and its derivatives, the relationship between condensing temperature and their content was analyzed using a polynomial fitting function to explore the phase-transition patterns.

Components Interaction of Cotton Stalk under Low-Temperature Hydrothermal Conversion: A Bio-Oil Pyrolysis Behavior Perspective Analysis

The conversion of agricultural and forestry waste biomass materials into bio-oil by mild hydro-thermal technology has a positive effect on extending the agricultural industry chain and alleviating the world energy crisis. The interaction investigation of biomass components during bio-oil formation can be significant for the efficient conversion of lignocellulose when different raw materials are fed together. In this paper, a bio-oil pyrolysis behavior (thermogravimetric analysis, TG) perspective component interaction investigation of cotton stalks under low-temperature hydro-thermal conversion (220 °C) was studied. Cellulose, hemi-cellulose, lignin, and protein were used as lignocellulose model components, by their simple binary blending and multi-variate blending and combined with thermo-gravimetric analysis and gas chromatography-mass spectrometry (GC-MS) characterization and analysis. The interaction of different model components and real biomass raw material components in the hydro-thermal process was explored. Results showed that the components of hydro-thermal bio-oil from cotton stalks were highly correlated with the interactions between cellulose, hemi-cellulose, lignin, and protein. During the hydro-thermal process, cellulose and hemi-cellulose inhibit each other, which reduces the content of ketones, aldehydes, ethers, and alcohols in bio-oil. Interaction between cellulose and lignin was obvious, which promotes the formation of oligomers, such as ketones, aldehydes, esters, phenols, and aliphatic, while inhibiting the production of aromatic and multi-hybrid compounds. Otherwise, there was no obvious interaction effect between hemi-cellulose and lignin or between lignin and protein. This research will guide the industrialization of lignocellulose, especially the possible co-feed hydro-thermal conversion technology.

Bio-Oil Production from Multi-Waste Biomass Co-Pyrolysis Using Analytical Py–GC/MS

Background: Bioenergy attracts much attention due to the global demand for renewable and sustainable energy resources. Waste biomass feedstocks—date pits, coffee waste, and cow dung—require efficient and environmentally friendly waste-management technologies such as pyrolysis. Fast pyrolysis occurs at fast heating rates (10–100 °C/s), generates high bio-oil yields, and is the most widely used process for biofuel generation. The aim of the study is to compare the effect of pyrolysis between single, binary, and ternary feeds on thermal degradation behavior and bio-oil composition. Methods: Thermogravimetric analysis (TGA) was conducted at 30 °C/min from room temperature to 850 °C to understand the thermal degradation behavior of the biomasses. A Pyroprobe® reactor—a micro-scale pyrolyzer—was used to conduct the fast pyrolysis at 500 °C with a heating rate of 10 °C/s, and the volatile contents were quantified using a gas chromatograph–mass spectrometer (GC/MS). Results: The (TGA) showed three main stages of decomposition following dehydration, devolatilization, and char degradation for the different single and multiple feeds. According to the identified compounds, the bio-oil components are broadly identified as aldehydes, amines, aliphatic, aromatics, alcohols, furans, ketones, and acids. The three single-biomass pyrolysis products have four compounds in common, acetic acid and ketone groups (acetic acid, 2-propanone, 1-hydroxy-, benzyl methyl ketone, and 1,2-cyclopentanedione). Conclusion: The bio-oil generated from the feeds comprises great potential for volatiles, diesel, and gasoline production with carbon atoms ranging from C2–C33. Future studies should focus on understanding the effect of procedural parameters, including blending ratio, temperature, and heating rates, on bio-oil composition. Additional molecular techniques should be employed to understand biomass components’ reaction mechanisms to produce useful bio-oil products.

Catalytic cracking of model compounds of bio-oil: Characteristics and mechanism research on guaiacol and acetic acid

The unstable oxygenates of raw bio-oil limit its high-value utilization, which renders the refinement process necessary. Catalytic cracking is one of the promising refining methods and HZSM-5 was found to be an effective catalyst. To investigate the reaction mechanism of catalytic cracking of the oxygenated components in bio-oil, guaiacol and acetic acid, are employed for the catalytic conversion over HZSM-5 and metal modified zeolite Zn/HZSM-5 in a self-designed micro-reactor. Herein, the mechanism of pyrolysis and catalytic cracking was calculated by density functional theory (DFT). For guaiacol, the selectivity of salicylaldehyde decreased from 57.41% to 41.84% and 40.31% over HZSM-5 and Zn/HZSM-5, respectively. In the catalytic cracking over Zn/HZSM-5, the yield of aromatic hydrocarbon increased. More specifically, benzene appeared in the liquid product. For acetic acid, the removal of the oxy-functional group was further promoted by Zn/HZSM-5, the as-formed ketene intermediate continues to react with zeolite catalysts, generating acetyl cation, and finally formed CO and ethylene. Zn/HZSM-5 has a better effect on promoting the reaction of ketene and methoxide since the energy barrier of the rate-determining step in this reaction decreased from 163.27 kJ/mol to 151.19 kJ/mol. Demethoxylation and dehydration were considered to be favored by Lewis acid sites.

The characteristics and evolution of nitrogen in bio-oil from microalgae pyrolysis in molten salt

Microalgae pyrolysis in molten salt is a promising way to produce high-quality bio-oil. This study provides deep insights into the characteristics of nitrogen-containing compounds (NCCs) during protein-rich spirulina platensis pyrolysis in a ternary eutectic carbonate (Li2CO3-Na2CO3-K2CO3) at different temperatures (450–600 °C). The results indicate that the molten carbonate significantly reduces the NCCs contents in bio-oil and heavy bio-oil by 25.89 % and 62.38 % respectively, which is due to the intensified removal of nitrogenous functional groups (CN, CN of the primary amide, and CN) in NCCs. The molten carbonate also intensifies the direct cleavage of amino acids and the conversion of amides/amines to form nitrile compounds but inhibits the dehydration of hexadecanamide to form hexadecanenitrile in bio-oil light components. Concerning the heavy components in bio-oil, molten carbonate intensifies the depolymerization of NCCs and plays an important role in intensifying the cyclane ring opening, double bond breaking, and cleavage of a benzene ring of NCCs. Finally, the possible pathways for nitrogen evolution in bio-oil are proposed, which can provide guidance for the high-quality bio-oil production by molten salt pyrolysis of algae.

Contribution of atmospheric pressure chemical ionization mass spectrometry for the characterization of bio-oils from lignocellulosic biomass: Comparison with electrospray ionization and atmospheric pressure photoionization

Bio-oils obtained from lignocellulosic biomass pyrolysis present a very promising alternative to replace petroleum-based fuels. At the molecular level, these materials are highly complex organic mixtures comprising thousands of species covering a large range of mass and polarity. Compared to petroleum, they present a high amount of oxygen containing compounds, limiting their direct use in the classical refining system. To understand and improve both the conversion and upgrading processes, an advanced molecular description of the raw and upgraded bio-oils is required. The most powerful technique for the molecular characterization of such sample is Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS), thanks to its very high mass accuracy and resolving power. It allows assigning unambiguously a unique molecular formula to each m/z signal. Besides, the use of different ionization sources ensures an extensive molecular description and enables to assess the efficiency of different catalytic chemical treatments. In this study, we report the characterization of a pine pyrolysis bio-oil by the three main atmospheric pressure ionization sources: electrospray (ESI), atmospheric pressure photoionization (APPI) and atmospheric pressure chemical ionization (APCI) in positive mode coupled to FTICR analyzer. In addition, different solvents and dopants were used to ensure a comprehensive description of the molecular content. Regardless of the atmospheric pressure ionization sources used, C0–100H0–300O0–15 molecular formulas are mainly obtained with lignocellulosic biomass-based bio-oils. Nevertheless, depending on the ionization source, the ions relative intensity are significantly different in respect with their double bound equivalent (DBE), oxygen to carbon ratio (O/C) and hydrogen to carbon ratio (H/C). For example, the APPI source has shown the efficient ionization of aromatic (high DBE and low H/C) less polar (low O/C) molecules compared to the ESI source which efficiency ionized more polar species with high oxygen atom content (high O/C). APCI source has proven to be particularly useful for bio-oil characterization as it demonstrates the presence of an aliphatic distribution in addition to the other bio-oil components also ionized by APPI and ESI.

Hydrogenation of Lignin Bio-Oil Components over Catalysts Based on Porous Aromatic Frameworks

This study focuses on the hydrogenation of model lignin bio-oil components over ruthenium and platinum catalysts synthesized from a porous aromatic framework, namely PAF-30. This PAF represents a polymeric support with developed porosity and high chemical and thermal stability. The effects of the guaiacol concentration, process temperature, and reaction time on the product composition were identified in the catalytic hydrogenation of guaiacol as a common component of lignin bio-oil. Various guaiacol derivatives were hydrogenated, and the hydrogenate composition was investigated. It was demonstrated that, within one hour at 250°C and a hydrogen pressure of 3 MPa, guaiacol can be hydrogenated exhaustively into 2-methoxycyclohexanol (64%) and cyclohexanol (64%) over the ruthenium catalyst and into a mixture of various hydrogenation products over the platinum catalyst.

Study the effect of zeolite pore size and acidity on the catalytic pyrolysis of Kraft lignin

In this study, three zeolites with different pore sizes and acidity, H-Beta, HY and HZSM-5, were used for the preparation of bio-oil by catalytic pyrolysis of Kraft lignin at 600 °C. The three-dimensional sizes and kinetic diameters of the bio-oil components were calculated using quantum chemical calculations, and the bio-oil was analyzed by heteronuclear single quantum coherence nuclear magnetic resonance (HSQC-NMR). The effects of zeolite acidity and pore size on the bio-oil upgrading process were studied for the pyrolysis products of Kraft lignin. The results showed that optimum pore size of the zeolites ranged from 6.500 Å–8.400 Å during the catalyzed pyrolysis of lignin. Among the zeolites, the H-Beta zeolite is the most effective in the lignin pyrolysis. The results also showed that the pore size and acidity of the zeolites had a significant effect on the product yields, coking and deoxygenation. The pore size affects the coking and dehydration reactions, while the acidity can promote the rearrangement of ether bonds or the breaking of lignin side chains and deoxygenation reactions. This study would be beneficial to improve the zeolite catalytic activity and minimize the oxygen content in bio-oil produced from the pyrolysis of Kraft lignin.

Investigating properties and intermolecular interactions of sludge bio-oil modified asphalt

Bio-asphalt is a binder composed of bio-oil and petroleum asphalt under certain conditions. In this study, sludge bio-oil (wt 10%) was added into matrix asphalt to prepare sludge bio-asphalt for the first time. The effects of sludge bio-oil on asphalt performance and the essence of interaction between components were investigated using performance test, molecular dynamics (MD) simulation, and density functional theory (DFT). Chemical analysis showed that the ester compound containing ester functional group (COOH) was the main component of sludge bio-oil. Physical and rheological tests were performed to examine whether the properties of sludge bio-asphalt could be improved. The results found that sludge bio-oil can be used to soften the hard asphalt. Furthermore, the existence of bio-oil reduced complex modulus G* of master curves and stiffness, also increased Jnr and m-value, which means that sludge bio-oil had a positive effect on the low-temperature thermal cracking resistance performance while sacrificing the high-temperature rutting resistance performance to some extent. Fourier infrared spectroscopy (FTIR) and fluorescence spectrum (FM) analysis indicated that sludge bio-oil evenly dispersed in the asphalt, and the bio-asphalt structure resembled that of the conventional binder. The results of MD simulation further showed that O atom of COOH and H atom in the asphalt molecules formed hydrogen bond (OH⋯O, OH⋯C) interaction. This changed originally existed conformational packing of agglomeration and further prevented the agglomeration of component molecules. In addition, the analysis of cohesive energy density (CED) and solubility parameters (SP) revealed that sludge bio-oil significantly influenced the compatibility of asphaltene-asphaltene, resin-resin, and asphaltene-resin components. These, in turn, may explain some of the observed improvements in rheological properties.

Process optimization and technoeconomic environmental assessment of biofuel produced by solar powered microwave pyrolysis

Microwave pyrolysis of corn stover has been optimized by Response surface methodology under different microwave power (500, 700, and 900 W) and three ratios of activated carbon additive (10, 15, and 20%) for obtaining maximum bio-oil yield followed by biochar. The optimal result has been evaluated and the environmental and techno-economic impacts of using solar-powered microwave heating have been tested. The optimal pyrolysis condition found to be 700 W microwave power and 10% of activated carbon. The yields of both bio-oil and biochar were about 74 wt% under optimal condition. The higher heat values of 26 MJ/kg and 16 MJ/kg were respectively achieved for biochar and bio-oil. The major components of bio-oil were hydrocarbons (36%) and phenols (28%) with low oxygen-containing compounds (2%) and acids (2%). Using the solar-powered system, 20,549 tonnes of CO2 can be mitigated over the lifetime of the set-up, resulting in USD 51,373 in carbon credit earnings, compared to 16,875 tonnes of CO2 mitigation and USD 42,167 in carbon credit earnings from a grid electricity system. The payback periods for solar-powered and grid-connected electrical systems are estimated to be 1.6 and 0.5 years, respectively, based on biochar and bio-oil income of USD 39,700 and USD 45,400.