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In order to slow down the greenhouse warming caused by excessive CO₂ emissions and effectively exploit the byproducts produced during the biofuel production process, N-doped porous biochars derived from the byproducts of microalgae (chlorella and spirulina) pyrolysis by combining urea and KOH modification were synthesized in this article to remove CO₂ in simulated flue gas. The physicochemical properties of the microalgae porous biochars were investigated via characterization tools, involving pH, Brunauer–Emmett–Teller (BET), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared spectroscopy (FTIR). CO₂ adsorption kinetics, thermodynamics, and CO₂ adsorption performance were also studied. Results reveal that the functional groups and specific surface areas of microalgae biochars are substantially increased via urea and KOH modification, and nitrogen-containing functional groups (mainly involving N–H, C–N, etc.) are major adsorption sites for CO₂ adsorption. The key control step for CO₂ adsorption is external mass transfer, and the CO₂ adsorption process over the microalgae porous biochars is mainly physical adsorption. Moreover, the chlorella-based porous biochars CNK-2 and spirulina-based porous biochars SNK-2 have optimal CO₂ removal performances, and their maximum adsorption capacities, respectively, reach 3.44 and 3.09 mmol/g at 25 °C. The results of regeneration studies demonstrate that, after 10 regeneration experiments, CNK-2 and SNK-2 still possess high CO₂ sorption performances (reaching 3.09 and 2.78 mmol/g, respectively), exhibiting good regeneration potential.

Anthropogenic emissions of greenhouse gases into the atmosphere is inducing global warming, ocean acidification, polar ice melting, rise in sea level, droughts and hurricanes, thus threatening human health and the global economy. Therefore, there is a need to develop cost-effective technologies for CO2 capture. For instance, solution absorption is promising due to a large processing capacity, high flexibility and reliability, and rich experience in engineering applications. Nonetheless, actual commercial solutions, solvents and processes for CO2 capture suffer from slow reaction kinetics, low absorption capacity, high-energy consumption, susceptibility to corrosion, toxicity, low stability and high costs. Therefore, current research focuses on developing more economical, effective, green and sustainable technologies. Here we review 2015–2020 findings on CO2 capture using liquid absorption methods. Methods are based on various solutions, solvents and processes such as carbonate solution, ammonia solution, amine-based solution, ionic liquid, amino acid salt, phase changing absorbent, microcapsulated and membrane absorption, nanofluids and phenoxide salt solution. We discuss absorption performance, absorption mechanism, enhancement pathways and challenges. Amine- and NH3-based absorbents are widely used, yet they are limited by high regeneration energy, corrosiveness and degradation, reagent loss and secondary pollution caused by NH3 escape. Phase changing absorbents are getting more attention due to their lower cost and lower energy penalty. The incorporation of membrane and microencapsulation technologies to absorbing solvents could enhance CO2 absorption performance by reducing corrosion and increasing selectivity. Adding nanoparticles to solvents could improve CO2 absorption performance and reduce energy requirement. Besides, solvent blends and promoter-improved solvents performed better than single and non-promoted solvents because they combine the benefits of individual solvents and promoters.

Potassium hydroxide-impregnated char sorbents (KOH/char) prepared via an ultrasonic-assisted method were used for SO2 removal from flue gas. The desulfurization experiment was analyzed using a fixed-bed reactor under 40–150 °C temperature range, using simulated flue gas. X-ray diffraction (XRD), Fourier-transform infrared spectroscopy, and scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS) were used to analyze both the chemical and physical characteristics of the sorbents. The analyzed results exposed that the complete elimination of SO2 from flue gas was achieved when using the char/KOH sorbent with a mass ratio of char to KOH of 11:1. It was noted that temperature had a substantial influence on the desulfurization performance with sulfur capacity maximized at 100 °C. Experimental results also revealed that a small amount of O2 present in the solvent could improve the SO2 removal efficiency of the sorbent. The analyzed XRD patterns showed that K2SO4 was the main desulfurization product, which was consistent with the SEM/EDS analysis. The experimental results were well-described with the Lagergren first-order adsorption kinetics model with the activation energy (Ea) of the SO2 adsorption by KOH/char sorbent of 20.25 kJ/mol.

The development of advanced electrode materials for next-generation rechargeable lithium batteries with high specific capacity and energy density and long life is promising to meet the demand for e...

This study reports the role of pressure (0.1-4.0 MPa) and temperature (600 oC-900 °C) in flash pyrolysis of palm kernel shell (PKS). The main objective was to study the extent to which pressure affects the mechanism of pyrolysis reactions to enhance the selective production of target products. Higher pressures and temperatures selectively promoted the generation of polycyclic aromatic hydrocarbon (PAHs) and H2 gas. Bio-oil samples generated at lower temperatures and pressures were mainly composed of phenolics. Increasing pressure and temperature favored the selective formation of phenanthrene, fluoranthene, pyrene, fluoranthene, and fluorene, which reached 96.17 area%. Elevated temperatures and pressures enhanced hydrogen transfer into light gaseous phase. The yield of H2 peaked at 40.82 gH2/kg.PKS at 900 ⁰C and 2.0 MPa. The results obtained in this study implied that the pyrolysis of biomass at elevated pressures is an effective method for poly-generation of hydrogen gas and chemical feedstock, in partic...

A few-layer graphene (FLG) composite material was synthesized using a rich reservoir and low-cost coal under the microwave-assisted catalytic graphitization process. X-ray diffraction, Raman spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy were used to evaluate the properties of the FLG sample. A well-developed microstructure and higher graphitization degree were achieved under microwave heating at 1300 °C using the S5% dual (Fe-Ni) catalyst for 20 min. In addition, the synthesized FLG sample encompassed the Raman spectrum 2D band at 2700 cm−1, which showed the existence of a few-layer graphene structure. The high-resolution TEM (transmission electron microscopy) image investigation of the S5% Fe-Ni sample confirmed that the fabricated FLG material consisted of two to seven graphitic layers, promoting the fast lithium-ion diffusion into the inner surface. The S5% Fe-Ni composite material delivered a high reversible capacity of 287.91 mAhg−1 at 0.1 C with a higher Coulombic efficiency of 99.9%. In contrast, the single catalyst of S10% Fe contained a reversible capacity of 260.13 mAhg−1 at 0.1 C with 97.96% Coulombic efficiency. Furthermore, the dual catalyst-loaded FLG sample demonstrated a high capacity—up to 95% of the initial reversible capacity retention—after 100 cycles. This study revealed the potential feasibility of producing FLG materials from bituminous coal used in a broad range as anode materials for lithium-ion batteries (LIBs).

Metal-supported few-layer graphene (FLG) was synthesized via microwave-assisted catalytic graphitization owing to the increasing demand for it and its wide applications. In this study, we quickly converted earth-abundant and low-cost bituminous coal to FLG over Fe catalysts at a temperature of 1300 °C. X-ray diffraction, Raman spectroscopy, transmission electron microscopy, and N2 adsorption–desorption experiments were performed to analyze the fabricated metal-supported FLG. The results indicated that the microwave-irradiation temperature at a set holding-time played a critical role in the synthesis of metal-supported FLG. The highest degree of graphitization and a well-developed pore structure were fabricated at 1300 °C using a S10% Fe catalyst for 20 min. High-resolution transmission electron microscopy analysis confirmed that the metal-supported FLG fabricated via microwave-assisted catalytic graphitization consisted of 3–6 layers of graphene nanosheets. In addition, the 2D band at 2700 cm−1 in the Raman spectrum of the fabricated metal-supported FLG samples were observed, which indicated the presence of few-layer graphene structure. Furthermore, a mechanism was proposed for the microwave-assisted catalytic graphitization of bituminous coal. Here, we developed a cost-effective and environmental friendly metal-supported FLG method using a coal-based carbonaceous material.

A reflux classifier system was employed to concentrate large sized inertinite-rich particles (1.6–2.0 mm) from two different ranked coking coals A and B. The impact of these concentrates on swelling, permeability and volatile evolution rates of another two coking coals C and D was investigated using the Computer Aided Thermal Analysis (CATA) and Dynamic Elemental Thermal Analysis (DETA) techniques. The results indicated that the concentrated inertinite-rich particles contained inertinite up to 75% for both coals A and B. When 25% inertinite particles were blended with 75% coal C or D by mass, the low rank inertinite concentrates A caused higher extents of effect on swelling and permeability than the high rank inertinite concentrates B, leading to higher softening temperatures with smaller plastic ranges. During swelling, inertinite concentrates B can compress volatile evolution rates of both coals C and D, however, inertinite concentrates A promoted volatile evolution rate of coal C. Concentrates from both coals A and B can compress the utilization of volatiles for driving swelling, the blend containing concentrate A used nearly half of volatiles that coals C and D themselves used for driving swelling. This study suggested that the additive internite concentrates not only provided a pathway for gas diffusion, but also interacted with the blended coals, which affected thermoplasticity of the whole blends.

Low-rank coals may undergo low-temperature oxidation and self-heating during mining, freightage, and handling. The oxidation of coal changes its structure which will be relected in the behaviour of coal water. A differential scanning calorimetry study was conducted to investigate the impact of low-temperature oxidation on the nature of water in a Chinese lignite and its drying behavior. The lignite sample was oxidized in the air at temperatures of 30–180 °C. The results showed that the lignite samples that underwent low-temperature oxidation did not contain any freezable bound water. It was found that the amount of non-freezable water in the oxidized samples reached the highest value of 67.38 mass% after oxidation at 80 °C. The Fourier transform infrared spectroscopy and the static sessile drop analysis results suggested that the concentration of oxygen functionalities and hydrophilicity of lignite samples peaked after oxidation at 80 °C, which in turn increased the tendency for the absorption of water as non-freezable water. It was also found that the types of water in the oxidized samples had a profound impact on its drying behavior, where free water showed higher drying rates compared with freezable bound water and non-freezable water. The coal sample pre-oxidized at 80 °C required higher energy for pre-drying compared with the raw coal, which was attributed to the higher proportion of non-freezable water after oxidation.

This paper investigates the impact of biomass components (i.e. cellulose and lignin) on direct production of carbon nanotubes (CNTs) from renewable biomass by means of microwave pyrolysis at low temperature. Palm Kernel Shell (PKS) was treated using two methods to isolate its bio-components, i.e. cellulose and lignin. The treated PKS samples were then pyrolyzed under microwave at 600 °C. Scanning electron microscopy (SEM) analysis revealed the formation of a large number of CNTs on the surface of cellulose bio-chars, while no CNTs were formed from lignin under the same pyrolysis conditions. It was inferred that cellulose was the component responsible for the formation of CNTs during microwave pyrolysis of biomass. High-resolution transmission electron microscope (HRTEM) analysis revealed that CNTs formed under such conditions had a multiwall structure. Raman spectroscopy analysis showed that the carbon order of CNTs increased when cellulose was used instead of the raw biomass for the synthesis of CNTs. Further analysis of the volatiles showed that unlike lignin, the volatile matter derived from cellulose were rich in monosaccharides such as D-Glucopyranose and glucopyranose which were postulated to have acted as an effective carbon source for the formation of CNTs. Self-extrusion of volatiles rich in monosaccharides and hydrocarbons during pyrolysis of cellulose, followed by the condensation and re-solidification of volatiles on the softened cellulose particles at elevated temperatures was proposed as the mechanism of formation of CNTs. The findings of this study may pave the way for the development of an effective, sustainable, and low-cost method for large scale production of CNTs from renewable biomass.

A green and cost-effective strategy was developed to synthesize porous graphitic carbons from coal tar pitch using commercially available CaCO3 nanoparticles as template without any further activation. The prepared porous graphitic carbons have well-developed hierarchical porous structure with moderate specific surface area (∼236.3 m2 g−1) and large pore volume (∼2.871 cm3 g−1), cross-linked carbon skeleton with relatively high levels of graphitic feature and enriched in oxygen/nitrogen-containing functional groups. Such unique microstructure characteristics of porous graphitic carbons not only can endow sufficient available space or active sites for Li-ions storage, but also can provide favorable and efficient channels for the Li-ions/electrons transportation. The prepared porous graphitic carbon PGC-3 applied as anode for lithium-ion batteries (LIBs) shows a large reversible capacity of 707 mAh g−1 at 0.05 A g−1, and presents a superior rate capability with high reversible capacities of 299 mAh g−1 and 248 mAh g−1 even at the extremely high current densities of 3 A g−1 and 5 A g−1, respectively. Moreover, such porous graphitic carbon also exhibits an outstanding long-term electrochemical stability and excellent cycling performance with over 93.5% capacity retention after 1000 cycles. This study paves a promising and universal way for large-scale production of porous graphitic carbons porous from coal tar pitch for high performance anode materials used in LIBs.

An in-situ study on the formation mechanism of plsatic layer was carried out by using a 4 kg laboratory-scale coke oven under controlled heating conditions. The coke oven rig enabled in-situ measurements of internal gas pressure (IGP) and temperature profiles in five locations in the coal charge and allowed sampling of semi-coke which consisted of the coke/semi-cokes, the plastic layers and loose coal. Six Australian coking coals with varying properties were used in the coking experiments. The semi-coke samples were scanned by micro-CT at the Imaging and Medical Beamline at Australian Synchrotron to study the physical structure transitions inside the thermoplastic regions and investigate the fissure patterns at the coke/semi-coke sides. The thicknesses of the plastic layers in different locations inside the coal charge were estimated from the measured temperature profiles and the initial softening temperatures and the solidification temperatures measured from the Gieseler fluidity tests. The results showed that the thicknesses of the plastic layers increased from the heating wall to the center of the coal charge. The IGP curves measured in different locations were used to obtain the maximum IGP values and the IGP termination temperatures across the coal charge. The difference in the extents of fissuring appeared to influence the maximum IGPs measured at the center of the oven. The higher extent of fissurin appeared to facilitate the release of volatile matterfrom the thermoplsatic region through the semi-coke sides, thus leading to lower maximum IGPs at the center. It was found that the extents of the fissuring and the maximum IGPs at the center were sensitive to the coal properties such as the petrographic properties, Gieseler maximum fluidity and volatile matter content.

CO2 mineralisation by industrial wastes is a promising option for mitigating carbon emissions safely and permanently with low material cost. But there is still absence of a detailed understanding on how fly ash properties affect the carbonation reactions. To fill this knowledge gap, five coal combustion fly ashes, Beijing (BJ), Wuhai (WH), Hazelwood (HW), Yallourn (YA) and Loy Yang (LY) ashes, from China and Australia were selected for carbonation studies. Experiments were performed in a batch reactor at 40 and 140 °C with 20 bar initial CO2 pressure, 200 g/L solid to liquid ratio, 450 rpm stirring rate to compare the carbonation performance of the five fly ashes and the effect of fly ash properties on carbonation reactions. Then BJ, YA and HW ashes were then selected for further study in a wide temperature range (40–220 °C) because of their higher CO2 sequestration capacity than the other two ashes. Quantitative X-ray diffractometry (XRD) with Rietveld refinement was used to characterize the crystalline and amorphous phases in fresh and carbonated fly ashes. Scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS) were used to characterize morphological and elemental properties of fresh and carbonated fly ash samples. Compared to LY and WH ashes, BJ, YA and HW ashes displayed much higher CO2 sequestration capacity due to the higher fraction of reactive Ca/Mg-bearing crystalline phases, including lime (CaO) and portlandite (Ca(OH)2) in BJ ash, periclase (MgO) and srebrodolskite (Ca2Fe2O5) in YA ash, and periclase and brucite (Mg(OH)2) in HW ash. Compared to YA and WH ashes, BJ ash displayed faster kinetics of carbonation reactions because the reactant phases of BJ ash were mainly Ca-bearing phases which have higher reactivity with CO2 than Mg-bearing phases. Also, particle size and morphological analyses indicated that the reacted particles displayed a lower porosity and pore area than the fresh sample due to the new precipitates not only depositing on the active surface, but also filling the pores of the fly ash particles, which was responsible for the reduced kinetics with time.

TiO2 nanostructures that feature a two-dimensional (2D) morphology have attracted extensive attention in environment processing and energy conversion fields owing to their peculiarly large surface area and superior transfer efficiency of photogenerated carriers. In this work, we proposed a hybrid approach including a plasma electrolyte oxidation (PEO) and ion exchange strategy to in situ synthesize TiO2 nanosheets on a flexible Ti mesh substrate, in which the layered Na2Ti2O5 nanosheets were fabricated as a template. The TiO2 nanosheets are crystalline anatase phase and exhibit excellent photocatalytic activity and stability in removing phenol. With the modification of the Pt cocatalyst, the phenol degradation performance has been significantly enhanced. More importantly, the in situ grown TiO2 nanosheets on the flexible Ti mesh provide strong substrate adhesion that enables superior photocatalytic stability for cyclic degradation of phenol. It can be expected that the synthetic strategy proposed in this work can pave a solid way toward the in situ growth of various TiO2-based composite nanophotocatalysts with sufficient active sites and excellent photocatalytic properties, and thus, it will open up more opportunities for environment processing and energy conversion.

Fuel blending is one of the most effective ways to use biomass to reduce the use of coal. In this study, co-combustion characteristics including NOx emissions, unburned carbon (UBC), and the char reactivity of coal, biomass, and pretreated biomass blends were investigated by using a lap scale drop tube furnace (DTF) and thermogravimetric analyzer (TGA) to evaluate the availability of pretreated biomass from torrefaction or ashless technology to a pulverized coal boiler. In addition, scanning electron microscopy (SEM) was used to analyze the morphology of biomass and pretreated biomass to observe the physical differences between raw samples and their chars. In the results, NOx showed a linear correlation with the content of inherent fuel-N of biomass except in blending cases with ashless biomass. This indicated that the yields of NOx in these cases were higher than both that of single coal and ashless biomass. In addition, UBC declined with increasing the biomass blending ratio for all blending cases, and this can be explained by examining the fuel ratio and SEM images of the fuel samples. Finally, blends with coal and torrefied biomass showed higher char reactivity and lower activation energy than that with ashless biomass as the blending ratio increased. Overall, this paper indicates that it is better to increase the blending ratio of pretreated biomass than raw biomass up to 30% for enhanced reactivity and reduced emissions.

The aim of this study was to characterize the pyrolysis behavior of the plastic layer formed during the coking process in a 4 kg laboratory-scale coke oven facility. The 4 kg coke oven rig was used to produce semi-coke samples that included the plastic layer. The semi-coke samples were analyzed by using the Synchrotron Micro-CT to characterize their physical structures and identify the plastic layer features. Sectioned plastic layer samples corresponding to softening, maximum fluidity, and resolidification of coal were obtained for five coking coals of varying thermoplastic properties. Pyrolysis behavior and structural changes of the plastic layer samples were analyzed by a thermogravimetric analyzer coupled with a Fourier transform infrared spectroscopy (TG-FTIR) and an attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). The TG-FTIR analysis allowed the characterization of the changes in pyrolysis behavior including volatile matter yields, the changes in aliphatic and aromatic C–H structures in the sectioned plastic layer samples. These structure changes agreed well with the ATR-FTIR analysis which also showed chemical structure changes across the plastic layer. The results suggest that the aliphatic C–H bonds of the five coals underwent the greatest reduction with the progression of the coking process in the coal charge. It was observed that the aliphatic C–H across the thermoplastic layer region varied with the thermoplastic properties of the parent coal. This implies that the aliphatic structures in coal may have played a significant role in the development of thermoplastic properties during the formation of the plastic layer.

Porous graphene has attracted considerable attention for its promising potential application in energy storage devices due to its unique porous structure combined with inherent electronic characteristics of graphene. Herein, a cost effective and environmentally friendly strategy is developed to prepare porous graphene via graphitization coupled with liquid oxidation-rapid thermal reduction using anthracite as a precursor. The prepared porous graphene has microstructure features such as highly continuous corrugated nanosheets with micro-meso-macro hierarchical porous structure, high specific surface area (640 m2 g−1) and large pore volume (3.792 cm3 g−1) with large amount of structural defects and nanopores, which provides sufficient active sites for lithium ions storage and offers favorable pathways for the fast transportation of lithium ions and electrons. When used as anode materials for lithium-ion batteries, such porous graphene exhibits a high reversible capacity of 770 mAh·g−1 at current density of 0.1 C, and possesses an outstanding rate capability with desirable capacities of 274 mAh·g−1 and 224 mAh·g−1 even at high current densities of 10 C and 20 C. Moreover, such porous graphene also demonstrates superior cycling performance up to 98.0% of the initial reversible capacity retention after 110 cycles. This study paves a promising approach to the large-scale production of porous graphene from coal for high performance anode materials used in lithium-ion batteries.

Microwave-assisted chemical vapor deposition (CVD) was employed for the synthesis of carbon nanotubes (CNTs) on pine nut shell (PNS) chars. The impact of reaction temperature, catalyst, carbon source, and the renewable carbon substrate on the synthesis of the CNTs were investigated. Microwave irradiation, the type of carbon source, and the presence of nickel catalyst were found to be the governing factors during the formation and growth of CNTs at low temperatures. 600 °C was found to be the optimum temperature for the formation of the CNTs. The high-resolution transmission electron microscope (HRTEM) results showed that the CNTs synthesized at 600 °C had a multiwall structure and a d-spacing of 0.34 nm. The diameter and length of CNTs were ~50 nm and 2600–3200 nm, respectively. Raman spectroscopy analysis revealed that a high degree of carbon order was achieved at 600 °C due to the formation of CNTs on the surface of bio-char. The formation and growth mechanisms of CNTs under microwave irradiation were proposed and discussed.

The impact of pressure on the carbon structure of a Chinese bituminous coal was investigated using a pressurized entrained-flow reactor in the temperature and pressure ranges of 700-900 °C and 0.1-4.0MPa, respectively. Pyrolysis pressure had a significant influence on the physiochemical and carbon structure of chars. The specific surface area and the swelling ratio of chars reached their highest values at 1.0MPa. Fourier transform infrared spectroscopy (FTIR) analysis showed that higher pressures enhanced the decomposition of functional groups in chars. Raman spectroscopy analysis results revealed that at elevated pressures, the organic matrix and functional groups were removed from the char structure, leading to higher ordering of the carbon structure. During X-ray diffraction (XRD) analysis, parameters such as the stacking height (Lc), interlayer spacing (d002) and lateral size of the graphite structures (La) were used to evaluate the graphitic structures in chars. The results showed an increase in Lc, La, and the average number of graphene sheets with pyrolysis pressure, indicating a more ordered carbon structure at elevated pressures. The d-spacing of char was in the range of 3.34-3.37 A, similar to typical graphitic structures.

A series of Mn0.15Fe0.05/fly-ash catalysts have been synthesized by the co-precipitation method using coal fly ash (FA) as the catalyst carrier. The catalyst showed high catalytic activity for low-temperature selective catalytic reduction (LTSCR) of NO with NH3. The catalytic reaction experiments were carried out using a lab-scale fixed-bed reactor. De-NOx experimental results showed the use of optimum weight ratio of Mn/FA and Fe/FA, resulted in high NH3-SCR (selective catalytic reduction) activity with a broad operating temperature range (130&ndash, 300 &deg, C) under 50000 h&minus, 1. Various characterization methods were used to understand the role of the physicochemical structure of the synthesized catalysts on their De-NOx capability. The scanning electron microscopy, physical adsorption-desorption, and X-ray photoelectron spectroscopy showed the interaction among the MnOx, FeOx, and the substrate increased the surface area, the amount of high valence metal state (Mn4+, Mn3+, and Fe3+), and the surface adsorbed oxygen. Hence, redox cycles (Fe3+ + Mn2+ &harr, Mn3+ + Fe2+, Fe2+ + Mn4+ &harr, Mn3+ + Fe3+) were co-promoted over the catalyst. The balance between the adsorption ability of the reactants and the redox ability can promote the excellent NOx conversion ability of the catalyst at low temperatures. Furthermore, NH3/NO temperature-programmed desorption, NH3/NO- thermo gravimetric-mass spectrometry (NH3/NO-TG-MS), and in-situ DRIFTs (Diffuse Reflectance Infrared Fourier Transform Spectroscopy) results showed the Mn0.15Fe0.05/FA has relatively high adsorption capacity and activation capability of reactants (NO, O2, and NH3) at low temperatures. These results also showed that the Langmuir&ndash, Hinshelwood (L&ndash, H) reaction mechanism is the main reaction mechanism through which NH3-SCR reactions took place. This work is important for synthesizing an efficient and environmentally-friendly catalyst and demonstrates a promising waste-utilization strategy.

This study addresses the in-situ microwave catalytic reforming of volatile matter from palm kernel shell (PKS) over iron-loaded activated carbon (Fe/AC) catalysts. The impacts of catalyst composition on the secondary gas-phase reactions and distribution of products were studied at 500 °C. It was found that the Fe/AC catalyst promoted the yield of light gases. Using the 1%-Fe/AC catalyst, the yield of gaseous fraction peaked at 37.09 wt%. The selectivity of the deoxygenated products was promoted in the presence of Fe. Catalytic reforming of PKS pyrolysis vapors over Fe/AC drastically enhanced the generation of phenol and H2, the concentrations of which reached 75.09 area% and 75.12 vol%, respectively. Catalytic pyrolysis of syringol and guaiacol as model compounds showed that Fe/AC catalyst promoted the demethoxylation and deoxygenation reactions to selectively generate phenol which was explained by oxophilic reactivity of the active Fe sites.

Alternative fuels are still needed to compensate for the energy shortages caused by fossil fuel depletion. The paper aims to brief the types of alternative fuels used for the past 30 years. Moreover, it includes the recent types of biofuels (especially biodiesel) and their blends with studies on the performances and the exhaust emissions for different engines. In this study, previous studies were analysed, the challenges faced by the researchers were examined, and incentives for using biodiesel fuel in engines were discussed. The engine performance and emissions when using biodiesels and their blends in different engine models were also surveyed. All biodiesels and their blends have demonstrated the ability to reduce emissions such as carbon oxide (CO), carbon dioxide (CO2), nitrogen oxide (NOx), particulate matter (PM) and hydrocarbon (HC) under various operating conditions, as well as the ability to improve the performance of the gas turbine. It is necessary to understand the combustion properties of fuels for their use in an engine. The contribution of this review is to help the engine manufacturers and researchers develop further research relating to readjusting and optimising the biodiesel engine and its relevant system.

The transformation of nitrogen in microalgae during entrained-flow pyrolysis of Chlorella vulgaris was systematically investigated at the temperatures of 600–900 °C and pressures of 0.1–4.0 MPa. It was found that pressure had a profound impact on the transformation of nitrogen during pyrolysis. The nitrogen retention in bio-char and its content in bio-oil reached a maximum value at 1.0 MPa. The highest conversion of nitrogen (50.25 wt%) into bio-oil was achieved at 1.0 MPa and 800 °C, which was about 7 wt% higher than that at atmospheric pressure. Higher pressures promoted the formation of pyrrolic-N (N-5) and quaternary-N (N-Q) compounds in bio-oil at the expense of nitrile-N and pyridinic-N (N-6) compounds. The X-Ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) results on bio-chars clearly evidenced the transformation of N-5 structures into N-6 and N-Q structures at elevated pressures. The nitrogen transformation pathways during pyrolysis of microalgae were proposed and discussed.

The present dataset describes the entrained-flow pyrolysis of Microalgae Chlorella vulgaris and the results obtained during bio-char characterization. The dataset includes a brief explanation of the experimental procedure, experimental conditions and the influence of pyrolysis conditions on bio-chars morphology and carbon structure. The data show an increase in sphericity and surface smoothness of bio-chars at higher pressures and temperatures. Data confirmed that the swelling ratio of bio-chars increased with pressure up to 2.0 MPa. Consequently, changes in carbon structure of bio-chars were investigated using Raman spectroscopy. The data showed the increase in carbon order of chars at elevated pressures. Changes in the chemical structure of bio-char as a function of pyrolysis conditions were investigated using FTIR analysis. Keywords: Microalgae, Bio-char, Particle swelling, Pressurized pyrolysis

Pressurized entrained-flow pyrolysis of Chlorella vulgaris microalgae was investigated. The impact of pressure on the yield and composition of pyrolysis products were studied. The results showed that the concentration of H2 in bio-gas increased sharply with increasing pyrolysis pressure, while those of CO, CO2, CH4, and C2H6 were dramatically decreased. The concentration of H2 reached 88.01 vol% in bio-gas at 900 °C and 4 MPa. Higher pressures promoted the hydrogen transfer to bio-gas. The bio-oils derived from pressurized pyrolysis were rich in nitrogen-containing compounds and PAHs. The highest concentration of nitrogen-containing compounds in bio-oil was achieved at 800 °C and 1 MPa. Increasing pyrolysis pressure promoted the formation of nitrogen-containing compounds such as indole, quinoline, isoquinoline and phenanthridine. Higher pyrolysis pressures led to increased sphericity, enhanced swelling, and higher carbon order of bio-chars. Pressurized pyrolysis of biomass has a great potential for poly-generation of H2, nitrogen containing compounds and bio-char.

An earth-abundant and low cost bituminous coal was used as precursor to prepare synthetic graphite materials through preliminary carbonization coupled with further high temperature graphitization treatment at 2000–2800 °C. The microstructure characteristics of the obtained synthetic graphite materials were characterized by means of X-ray diffraction, scanning electron microscope, transmission electron microscope, Raman spectroscopy and nitrogen adsorption–desorption. The results show that the microstructures of synthetic graphite materials are strongly dependent on the graphitization temperature. The synthetic graphite graphitized at 2800 °C has perfect ordered layered structure with high graphitization degree and relatively large surface area with well-developed mesopores, which offers a favorable pathway for the electrochemical intercalation-deintercalation of lithium ions in carbon matrix. Such synthetic graphite applied as anode materials for lithium-ion batteries presents a maximum reversible capacity of 310.3 mAh·g − 1 at current rate of 0.1C and still remains as high as 143.9 mAh·g − 1 at current rate of 5C. Moreover, the synthetic graphite also exhibits superior rate capability and outstanding cycling performance with over 95.3% initial capacity retention after 100 cycles. This study demonstrates a promising feasibility for large-scale production of synthetic graphite materials from bituminous coal for high performance lithium-ion batteries.

Hollow carbon nanofibers (HCNFs) were formed on the bio-char surface during microwave pyrolysis of pine nut shell in the temperatures range of 400–700 °C without the use of any additional catalyst, except activated carbon added as a microwave absorber. Scanning electron microscopy (SEM) analysis showed that HCNFs were only formed on microwave pyrolysis chars and not fixed-bed chars, suggesting that microwave irradiation had a major influence on their formation. High resolution transmission electron microscope (HRTEM) results showed that the synthesized HCNFs at 500 °C and 600 °C had a diameter of about 400 nm and length of 1400–5000 nm. HCNFs had multi-walled structure with a d-spacing of about 0.35 nm. Unlike fixed-bed bio-chars, the X-ray diffraction (XRD) analysis of the microwave bio-chars showed typical graphite peak at around 2θ = 26.3° with the strongest peak observed in 600 °C bio-char. Raman spectroscopy analysis revealed that the highest degree of carbon order of HCNFs was achieved at 600 °C, which agreed well with XRD analysis results. Detailed analysis of the volatiles evolved during microwave pyrolysis suggested that hydrocarbons in bio-oil such as benzene and alkenes and CO, CO2, methane, and ethane in bio-gas acted as the carbon source during formation of HCNFs.

Bio-char has been applied to soil as an amendment to improve soil water holding capacity due to its porous nature. In this study the behavior of water in bio-char was investigated for better understanding mechanisms of water retention by bio-char. Bio-chars with different structures were prepared by partial gasification of peanut shell (PT) and palm kernel shell (PKS). It was observed that the BET surface area and total pore volume of bio-char increased with gasification conversion. Water holding capacity and water adsorption rate showed a direct correlation with micropore volume of bio-char, suggesting that physical structure of bio-char played a key role during interaction with water. These results indicated that partial gasification is a promising method for production of bio-char suitable for soil remediation. Two types of freezable water i.e. freezable free water (FFW) and freezable bound water (FBW) were directly detected in bio-char samples during Differential Scanning Calorimetry (DSC) analysis. The phase transition temperature of freezable bound water correlated well with pore size distribution of bio-chars. The presence of non-freezable (NFW) water in bio-char was also confirmed from the difference between total water content of samples and the sum of FFW and FBW. The amount of FFW showed an indirect correlation with micropore volume of bio-chars, suggesting that FFW is present in macropores. However, an opposite trend was observed for FBW and NFW in bio-chars, indicating that these two types of water were present in micropores. The low-temperature XRD results were used to define the boundary between the freezable and non-freezable water in bio-char samples.

Catalytic graphitization of biomass-based carbon has been used to synthesize graphene nanostructures with extraordinary electrochemical properties. To further improve the structural properties of these graphene nanostructures, it is critical to gain a deeper understanding of the formation mechanism and influence of process variables on the structural features of the resulting material. Here, we report the impact of various parameters such as catalyst loading, temperature, holding time, and catalyst salt precursor on the low-temperature catalytic graphitization of activated carbon (AC). Quantitative X-ray diffraction (XRD) analysis results show that at 20 wt% catalyst loading, reaction temperature of 1400 °C, and holding time of 30 min, a complete graphitization of amorphous carbon was achieved. In situ XRD and transmission electron microscopy (TEM) results indicated that the dissolution-precipitation and metal-induced graphitization are the primary mechanisms under which graphitized carbon was formed. Furthermore, it was found that the rate of graphitization under microwave irradiation is significantly higher than conventional heating, mainly owing to the enhanced precipitation of graphitic carbon caused by both carbon saturation and temperature fluctuation of the catalyst particles.

This work introduces nanostructured carbon-based composite with enriched CNTs and microstructural defects from pomelo peel biomass precursors through successive chemical pretreatment, heteroatom N, S dual-doping and transition metal oxide loading (Ta2Oy) and its application for electrochemical oxygen reduction reaction (ORR) at room temperature. During the microwave pyrolysis process, volatile N, S-containing species from trithiocyanuric acid reactant were trapped and doped into carbonaceous biomass precursor to achieving the rich-defect porous nanotubes and abundant cavity structure. The effect of biomass pretreatment on the textural and structural properties of biochar and formed CNTs were systematically investigated. The impacts of single doping (N) using melamine and dual-doping (N, S) with trithiocyanuric acid on the structural and electrochemical characteristics of biochar were evaluated. An optimized PP-NS-600-Ta-900 electrocatalyst displayed remarkable ORR activity with a half-wave potential of 0.82 V (vs. RHE), a limiting current density of −5.75 mA cm−2 and an electron transfer number of 3.85. The results offer a useful archetypical template to design and construct reliable CNTs enriched biomass-derived biochar for possible electrochemical energy and storage application, illustrating its viability for utilization as ORR electrocatalyst in potential applications, like fuel cells and metal-air batteries.

A series of novel iron-based deep eutectic solvents (DESs) as denitrification sorbents were evaluated to capture NO from simulated flue gases. The application of Fe(II) EG-ChCl DESs demonstrated the efficiency of absorption performance with the complete removal of NO and zero secondary pollution. In this study, mixtures of Ferric chloride (FeCl2), Ethylene glycol (EG), and Choline chloride (ChCl) were prepared using Fe(II) EG-ChCl DESs. Experimental results showed that the best performance for denitrification was achieved when DES solutions were treated at 60 °C, the gas flow rate of 50 mL/min, 5% partial pressure of steam, and the concentration of Fe(II) was 0.1 mol/L. Furthermore, excellent stability for denitrification was observed for the Fe(II) EG-ChCl DESs during five absorption–desorption cycles. The absorption reaction of Fe(II) EG-ChCl DESs maintained a first-order reaction kinetics with a reaction rate constant of 1.1 × 106 (L/mol·s) for the denitrification reaction. The FT-IR result indicated that there was a chemical interaction between Fe2+ and NO, and Fe2+ was the absorptive active species.

The presence of kaolinite as mineral in coal may significantly influence coking properties of coal, therefore affects quality of coke that is produced from such coals. In this paper, the effect of kaolinite addition on pyrolysis behaviour of coal was examined by blending kaolinite with a medium rank, high vitrinite, low ash coal. Thermoplasticity of coal was characterised by using a Gieseler Plastometer. Char and tar samples were collected through pyrolysis at 450 °C in a Gray-King apparatus. The functional groups of the char samples were measured using FT-IR spectroscopy, while tar compositions were characterised using GC/MS. The results indicated that under the test conditions, addition of up to 5 wt% of kaolinite could increase the coal fluidity, attributed to the decrease in CH 3 /CH 2 ratio in the residual char. The proportion of C O/C C bonds affected the plastic range. Furthermore, the results showed that kaolinite addition suppresses the evolution of low molecular compounds in tar phase. This study provides useful information for optimising coal blending in cokemaking industry.

This study reports the synergy effect during co-pyrolysis of Hailar lignite (HL) and palm kernel shell (PKS) biomass under microwave irradiation in the temperature range of 400–600 °C. The results showed that the synergy effect promoted the yields of tar and gas during co-pyrolysis experiments. Gas chromatography-mass spectrometry (GC–MS) analysis of tar showed that the formation of aliphatic hydrocarbons was promoted during co-pyrolysis of lignite and PKS biomass in expense of single-ring aromatic compounds, aliphatic carboxylic acids, alcohols, aldehydes, and ketones. The synergy effect also promoted the formation of H2 and CO during co-pyrolysis. A two-stage pyrolysis reactor was used in order to investigate the mechanism of synergy during co-pyrolysis by isolating the secondary pyrolysis reactions. The two-stage pyrolysis results showed that secondary pyrolysis reactions were mainly responsible for synergy effect, resulting in higher gas and lower tar yields as a result of secondary tar cracking. HL and PKS chars promoted the formation of aliphatic hydrocarbons, CO, and CH4 as a result of decarbonylation, decarboxylation, and demethylation reactions. Reforming of methane over HL and PKS chars led to an increase in concentrations of H2 and CO during secondary pyrolysis reactions.

Four hydrogen bond acceptors (HBAs) with different carbon chain length substituents, including methyl-triphenyl phosphonium bromide (MTPB), ethyl-triphenyl phosphonium bromide (ETPB), propyl-triphenyl phosphonium bromide (PTPB), and butyl-triphenyl phosphonium bromide (BTPB), combined with ethylene glycol (EG) were developed to synthesize four low-viscosity deep eutectic solvents (DESs). In this study, the effect of different substituents in DESs on low-concentration SO2 absorption was systematically studied at 30–70 °C. Experimental results show that the EG-MTPB DES has a higher SO2 absorption capacity and a lower viscosity than other DESs. The reason for the higher SO2 absorption capacity of EG-MTPB DES was described by viscosity experiments and quantum chemical calculations. It was shown that the strong polarization ability of the CH3 group promotes the absorption of SO2 by DESs. 1H NMR and FTIR results indicated that chemical interactions primarily exist between the S of SO2 and Br, and the O of SO2 and the H atom of EG form hydrogen bonds. The density functional theory (DFT) results also confirm that the charge of the Br atom migrated to the S atom. Also, thermostability and regeneration experiments showed that the EG-MTPB DES exhibits good stability and can thus be used for industrial flue gas desulfurization.

Attempts were made to construct the molecular structures of vitrinite samples from four bituminous with different ranks and to investigate the correlation of molecular structures to thermoplastic properties of vitrinite by using a number of advanced analytical techniques combined with theoretical methods. The Gieseler plastometry and caking index showed that the Ewirgol vitrinite had a high fluidity (MF = 17675 ppm), wide plastic range (ΔT = 105.1 °C) and good caking properties (G = 99.32). Various analytical technique, e.g. Solid-state 13C nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction analysis and Raman spectroscopy, provided comprehensive structural information for establishing molecular models of vitrinite samples with Density Functional Theory. These molecular models showed that the Ewirgol vitrinite had more cyclic aliphatic structures that contribute significantly to the fluidity development and caking properties. These cyclic aliphatic structures could be precursors of the aromatic rings in liquid molecules during coking and provide transferable hydrogens that saturate the free radicals in the thermoplastic range. The cyclic aliphatic structures may facilitate the formation of such molecular structures with an appropriate molecule size that maintains the mobile phase in the thermoplastic range to develop fluidity.

To better understand the role of microwave and the mechanisms of thermal cracking and catalytic reforming of lignocellulosic bio-oils, this study compares the difference in the reaction characteristics between microwave-assisted and conventional heating of representative bio-oil model compounds. Syringol and guaiacol were selected as bio-oil model compounds. The effects of the heating method on the conversion of the model compound and the yield and composition of products were systematically investigated in the temperature range of 600–700 °C. The results showed that high reaction temperature and microwave-assisted heating favoured the conversion of model compounds, and the conversions of syringol were generally higher than those of guaiacol under the same conditions (temperature, heating method). The heating method was found to greatly influence the yield and composition of products. The bio-oil obtained from conventional thermal cracking of model compounds contained phenolics, aromatic hydrocarbons, aryl alkyl ethers, and oxygen-containing heterocyclic compounds. In contrast, microwave-induced polarisation of poorly stable methoxy groups promotes the formation of phenolics, the concentration of the phenolic in the guaiacol and syringol bio-oil reached 62.5–66.17 area% and 85.18–87.65 area%, respectively, in the temperature range of 600–700 °C. Catalytic reforming of model compounds showed that activated carbon catalyst drastically promoted the phenol formation, particularly under microwave-assisted heating, the phenol concentration reached 93.9–97.97 area% in bio-oil during catalytic reforming of guaiacol. The formation of electron-hole pairs on the active metal sites induced by microwave radiation possibly enhanced the demethoxylation to selectively generate phenol due to the strong electron-donating ability of the methoxyl group. Microwave-assisted catalytic reforming of the model compounds was also beneficial for H2 formation because of the direct dehydrogenation of methyl radicals and the gas-phase reactions. The H2 concentrations of 81.07–82.41 vol.% and 75.2–79.16 vol.% were obtained during microwave-assisted catalytic reforming of guaiacol and syringol, respectively.

Arsenic is extremely toxic and its release has caused great environmental concerns. Coal combustion is considered to be one of the major anthropogenic emission sources. Arsenic removal technology from coal combustion can be divided into three categories: pre-combustion removal, removal during combustion and post-combustion removal. The post-combustion removal is also called removal from flue gas, which includes several technological developments, namely, the removal using existing air pollutant control devices (APCDs), adsorption, traditional oxidation and advanced oxidation based on removal principle. This review summarizes the latest advances of these arsenic removal technologies. The performance, mechanism and characteristics of arsenic removal technologies were overviewed and analyzed. The merits and drawbacks, and the challenges and prospects of each arsenic removal technologies were discussed. It was found that pre-combustion removal, removal during combustion and removal using APCDs can achieve arsenic removal to a degree, but their removal efficiencies are usually low. Injection of adsorbent into the flue gases can achieve higher arsenic removal efficiency. Calcium-based adsorbents were found to be one of the most efficient ones for arsenic removal. Their shortcoming is the high-temperature sintering and deactivation caused by competitive adsorption of acidic gases. Other adsorbents suffer from low activity, small specific surface area, high cost, or/and little recovery. Further development of advanced adsorbents that are anti-sintering, anti-deactivation, large specific surface area, low-cost, separable, and recyclable should be the main focus in future research. Collaborative control of multiple systems such as removal during combustion, removal using APCDs or/and tail adsorption/oxidation is a promising strategy. Advanced oxidation technologies (AOTs) can achieve high arsenic removal efficiency (90–100%), recovery of arsenic resources and potential simultaneous removal of multi-pollutants, possessing good prospect.

A simple, cost-effective, and environmentally friendly route was developed to synthesize graphene nanosheets from humic acid via preliminary carbonization coupled with oxidation-exfoliation-thermal reduction. Such graphene nanosheets have a high specific surface area (495 m 2 ·g − 1 ) with large pore volume (2.987 cm 3 ·g − 1 ), unique interconnected mesoporous structure and uniform oxygen-containing functional groups in layered graphene framework, which offer a favorable and efficient pathway for the electrolyte propagation and transportation. The electrodes of supercapacitors made from these graphene nanosheets exhibit a maximum specific capacitance of 272 F·g − 1 at the current density of 50 mA·g − 1 in aqueous electrolyte, and possess excellent rate capability, low resistance, superior cycling performance with over 96.5% initial capacitance retention after 8000 cycles. The corresponding supercapacitors deliver a desirable energy density of 6.47 Wh·kg − 1 at a powder density of 2250 W·kg − 1 . This study demonstrates a promising synthesis route for large-scale production of graphene nanosheets from renewable and green humic acid for high performance supercapacitors.

Hollow carbon nanofibers (HCNFs) were found to have formed during microwave pyrolysis of palm kernel shell (PKS) at 500 and 600 °C. The formation of HCNFs was only observed during microwave pyrolysis and not the fixed-bed pyrolysis, indicating that microwave played a key role in formation of HCNFs. X-ray diffraction (XRD) analysis of microwave bio-chars showed typical carbon diffractions at 2θ = 26.3° and 43.2°, indicating good graphitic structure of HCNFs, especially for bio-chars prepared at 600 °C. High resolution transmission electron microscope (HRTEM) results revealed multiwall nature of the HCNFs with carbon layer spacing of 0.34 nm. Two major tubular and bamboo-shape structures were observed for HCNFs. With increasing microwave pyrolysis temperature from 500 to 600 °C, the yield of HCNFs increased from 5.85 wt.% to 9.88 wt.%. Raman spectroscopy analysis showed that with increasing pyrolysis temperature to 600 °C, the I D / I G ratio decreased from 0.95 to 0.86, indicating higher order of the carbon layers of the HCNFs. Energy dispersive X-ray spectroscopy (EDS) showed the presence of Fe, K, and Ca in HCNFs structure which may have played a catalytic role during their formation and growth. Mechanism of formation and growth of HCNFs under microwave irradiation were proposed and discussed. The HCNFs-coated bio-char has great potential for removal of heavy metals from waste water.

Behavior and nature of water in biomass significantly influence the thermochemical conversion processes. This study investigates the characteristics and behavior of water in lignocellulosic and microalgal biomass using differential scanning calorimetry (DSC) and low-temperature X-ray diffraction (XRD) methods. Pine sawdust (PS), peanut shell (PT), and microalgae (MA) samples with different water contents were used and analyzed systematically. Freezable free water was detected in all biomass samples through DSC analysis. Different from PS and PT, a shift in the position of freezable free water peaks was observed during freezing process of MA on DSC, which was attributed to the strong hydrophilicity of this biomass. No freezable bound water was observed in the biomass samples. However, significant amount of non-freezable bound water was detected in all biomass samples. The freezing enthalpies of freezable free water in PS, PT, and MA ranged between 319.04 and 297.7 kJ/kg which were in good agreement with that of bulk water. The boundary between freezable and non-freezable water in the biomass samples was clearly defined combining DSC and XRD analyses. The amount of non-freezable bound water in biomass samples directly correlated with the relative concentration of oxygen functional groups in biomass samples.

The oligomers having the blue photoluminescence and conductivities of 5 × 10–7–7.4 × 10–4 S m–1 after doping by iodine are extracted successfully from coal tar pitches which were dealt with by the air oxidization method at 350°C. Meanwhile, it is observed that extracted materials have the blue photoluminescence with the fluorescence quantum yield of 7–10.2%. In these cases, we used the solutions of toluene and pyridine to extract these functional materials from coal tar pitches. Consequently, we consider these extracted materials showing the advantages in the application of fabricating the electronic devices, because it can decrease the production cost remarkably than use of the materials obtained by general organic synthesis methods. Finally, this research also can provide the one of beneficial references for solving the serious problem of overproduction of coal tar pitches in China. The oligomers having the blue photoluminescence and conductivities of 5 × 10–7–7.4 × 10–4 S m–1 after doping by iodine are extracted successfully from coal tar pitches which were dealt with by the air oxidization method at 350°C. Meanwhile, it is observed that extracted materials have the blue photoluminescence with the fluorescence quantum yield of 7–10.2%. In these cases, we used the solutions of toluene and pyridine to extract these functional materials from coal tar pitches. Consequently, we consider these extracted materials showing the advantages in the application of fabricating the electronic devices, because it can decrease the production cost remarkably than use of the materials obtained by general organic synthesis methods. Finally, this research also can provide the one of beneficial references for solving the serious problem of overproduction of coal tar pitches in China.

Catalytic microwave pyrolysis of peanut shell (PT) using Fe3O4, Na2CO3, NaOH, and KOH for production of phenolic-rich bio-oil was investigated. The effects of catalyst type, pyrolysis temperature, and biomass/catalyst ratio on product distribution and composition were studied. Among four catalysts tested, Na2CO3 significantly increased the selectivity of phenolic compounds in bio-oil during microwave pyrolysis. The highest phenolics concentration of 57.36% (area) was obtained at 500 °C and PT:Na2CO3 ratio of 8: 1. The catalytic effect to produce phenolic compounds among all the catalysts tested can be summarized in the order Na2CO3>Fe3O4>KOH>NaOH. Using KOH and NaOH as catalyst resulted in formation of bio-oil with enhanced higher heating value (HHV) and lower oxygen content, indicating that these catalysts enhanced the deoxygenation of bio-oil. The scanning-electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) analysis of char particles showed the melting of magnetite and vaporizationcondensation of mineral salt catalysts on char particle, which was attributed to extremely high local temperatures during microwave heating.

Fly ash is a potential source of highly reactive feedstock for CO 2 mineral carbonation. It does not require pre-treatment, but it has a low carbonation rate and efficiency. To address these issues, we studied the carbonation performance and mechanism of a fly ash from Shenfu coal of China. The effects of temperature, solid to liquid ratio and gas flow rate on the carbonation efficiency of the fly ash were systematically investigated in a direct mineralisation process. Our results indicated that calcium in lime and portlandite had a higher reactivity towards CO 2 than that in other calcium bearing phases either crystalline or amorphous. Solely increasing the temperature did not improve carbonation efficiency. However, experiments in a batch reactor under elevated temperature (140, 180, and 220 °C) and pressure conditions (10 and 20 bar) using recyclable additives showed that a combination of high temperature and pressure significantly improved carbonation efficiency in the presence of 0.5 mol/L Na 2 CO 3 . Our multiple-cycle experiments showed that Na 2 CO 3 facilitated the precipitation of calcium carbonate and was well regenerated in the process.