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Bio-oil derived from fast pyrolysis of oil palm empty fruit bunch (EFB) was catalytically reformed inside a stainless steel multichannel tubular reactor using steam and air as reforming agents. The catalyst used, denoted as Fe/AC, was an iron catalyst loaded on the coconut shell-derived activated carbon (AC) prepared by a new approach of impregnating iron from an aqueous solution onto the AC in a stepwise manner. Results indicate that a stepwise impregnation was able to minimise the agglomeration of iron particles on AC surface, allowing high loading of iron onto the AC without severely affecting Fe dispersion and catalyst pore properties. The highly reducible, highly efficient catalyst produced in this study was able to lower the concentration of tar in producer gas to lower than 100 mg/Nm3. The best composition of the burnable product gas was obtained with iron loading of 15 wt%, reaction temperature of 800 °C, steam-to-carbon molar ratio (S/C) of 1.0 and air equivalence ratio (ER) of 0.1, with gas composition of 33.5% H2, 21.0% CO, 14.0% CH4, 18.8% CO2 and 1% C2 hydrocarbons and a cold gas efficiency of 78.5%. [ABSTRACT FROM AUTHOR]

Stable free radicals are the long-lived macromolecule radicals formed in pyrolysis, and their reactions play an essential role in biochar formation. The alkali and alkaline earth metals (AAEMs) in biomass might be involved in the radical reactions during pyrolysis. Figuring out the effect of AAEMs on the reactions of stable free radicals can further understand the radical reaction mechanism and the formation of biochar in pyrolysis. In this paper, the in-situ electron paramagnetic resonance (EPR) spectroscopy was used to detect the stable free radicals in cocoanut pyrolysis, and the effect of AAEMs was analysed by the comparative experiments. The results indicate that the stable free radicals in nascent chars, which are generated from the thermal decomposition of biomass, could react and couple with each other. The AAEMs in biomass improve the activity of stable free radicals and promote the radical-radical coupling during high-temperature pyrolysis above 400 °C, which inhibits the condensation of aromatic structure and generates more weak bonds in hot nascent char. After stopping the heating, the weak bonds will be broken by cooling stress, thus inducing radical reactions and further changing the char structure. • In-situ EPR detection was used to study stable radicals during biomass pyrolysis. • Effect of alkali and alkali earth metals on stable radical reactions was analysed. • Nascent char formed in pyrolysis has secondary reaction after volatiles releasing. • Alkali and alkali earth metals promote coupling of stable radicals during pyrolysis. • Unstable structures formed by stable radicals coupling can be broken during cooling. [ABSTRACT FROM AUTHOR]

Highlights • Interactions among bio-oil fractions influence the coking mechanisms obviously. • Structure of cokes generated from bio-oil was strongly affected by the interactions. • Cokes from bio-oil are not simple mixture of cokes from bio-oil fractions. • Interactions increase the C O, O H and C O functional groups in cokes. • Interactions promote the O-containing species to be transformed into the cokes. Abstract Coke formation is one major problem during thermal conversion of bio-oil and its main components. Fundamental knowledge about the evolution of the structure of cokes is a prerequisite towards a deep understanding of coking of bio-oil. This study investigates the structure (morphology, elemental composition, O-containing functional groups and aromatic structures) of cokes generated from the pyrolysis of aromatic-rich fraction (ARF) and the aromatic-poor fraction (APF) of bio-oil. The effects of interactions of ARF and APF on properties of the coke formed during the pyrolysis of bio-oil are also studied. The results show that the cokes from the pyrolysis of APF (APF-cokes) are sponge-like while the cokes from the pyrolysis of ARF (ARF-cokes) have a dense structure. The matrix of cokes from the pyrolysis of the whole bio-oil (oil-cokes) is similar to the matrix of ARF-cokes, while its surface is similar to that of APF-cokes, which should be due to the interactions between different bio-oil fractions. The APF-cokes contain more C O, O H and C O functional groups than the ARF-cokes due to the higher O content of APF. Moreover, the interactions between ARF and APF can promote more O-containing species to be transformed as C O, O H and C O functional groups in the oil-cokes. The aromatic rings of ARF-cokes and APF-cokes can be cracked to form smaller ring systems at 300–500 °C, while it is opposite for the oil-cokes because the aromatic structures formed via the interactions between ARF and APF are more stable. At higher temperatures (>500 °C), the interactions (e.g. self-gasification) lead to the highly condensed cokes, while the secondary cokes, which are spherical particles, are preferentially consumed by the steam. [ABSTRACT FROM AUTHOR]

This study focuses on the effects of interactions among bio-oil components on the formation of aromatic structures of bio-oil during its thermal treatment processes at various temperatures and heating rates. A bio-oil sample and its extracted fractions were pyrolyzed in a fixed-bed reactor at 300–800 °C at different temperatures and heating rates. The results show that the pyrolytic products (including the yields and aromatic structures) from raw bio-oil and its extracted fractions are significantly different, which proves the existence of the interactions between the aromatic components and light components of the bio-oil. Additionally, those interactions are determined by the pyrolysis temperature and heating rate to different extents, which further leads to the evolution of aromatic structures during the pyrolysis of bio-oil. For example, owing to the presence of the aromatic-poor fraction, the aromatic compounds (especially ≥ 2 rings) from the pyrolysis of bio-oil are less than that of the aromatic-rich fraction at relatively low temperatures (≤ 500 °C), especially at slow heating rates. This is because the polymerization, as the main interactions, promotes the transformation of more aromatic compounds (over wide range of ring sizes) into coke at these conditions. At fast heating rates, among the complex interactions, the self-gasification of bio-oil is intensified at high temperatures (≥ 700 °C), resulting in lower secondary coke yields and tar yields as well as the concentration of aromatic compounds (especially ≥ 2 rings). [ABSTRACT FROM AUTHOR]

Highlights • Cokes generated at slow heating rates are imporous with smooth surface. • The radical concentration of cokes reaches highest at 600 °C then decreases rapidly. • Interactions among bio-oil components bring the O-functional groups into the coke. • The cokes are more condensed with bigger aromatic rings at high temperatures. Abstract Coke can be formed once the bio-oil was heated, even at very low temperatures, causing almost always serious problems in the upgrading and direct utilization of bio-oil. To minimize the negative impacts from coke formation, the key point is to fully understand the formation and evolution of coke during the thermal treatment of bio-oil. Thus, in this study, the cokes formed from the pyrolysis of bio-oil at different temperatures (300–800 °C) and heating rates were characterized by using a range of advanced analytical instruments. The evolution of cokes (e.g. morphology, elemental composition, chemical structure and concentration of radicals) with increasing temperature and heating rate was traced. The results show that the cokes generated at slow heating rates are imporous with smooth surface but porous at high temperatures and fast heating rates. The radical concentration of the cokes reaches the highest level at 600 °C, then decreases rapidly with further increasing temperature to form more free radicals, which promote the condensation reaction of aromatic systems to form larger ring structures of the coke at high temperatures, with lower H/C and O/C ratios. The O-containing functional groups could be brought into the coke via the interactions between light and heavy components of bio-oil. [ABSTRACT FROM AUTHOR]

The effects of the newly improvised catalyst preparation technique, namely ultrasonic spray precipitation (USP), on the physicochemical properties as well as the catalytic performance of Cu-Zn-Al-Zr catalyst in CO 2 hydrogenation reaction were studied. Spraying technique is advantageous in generating micro-droplets of catalyst precursors by providing high surface area contact during precipitation, while the incorporation of an ultrasonic irradiation can physically alter the surface morphology of the catalyst. In this study, Cu-Zn-Al-Zr catalysts were prepared using both USP and conventional precipitation (CP) techniques for comparison purposes. Structural analysis showed that USP technique dictated the formation of finer Cu crystallites with better particle uniformity. Meanwhile, TPR results revealed a good interaction between different elements in the catalyst with the formation of single form of oxide species. In terms of reactivity, USP-prepared catalyst outperformed CP catalyst for CO 2 conversion by 20.9% and also improved methanol selectivity and yield by 2.7 and 27%, respectively, while reducing noticeably the unwanted CO. It is believed that the improved surface basicity of USP catalyst, which has a great influence on reaction pathways of intermediate species, contributed significantly to the enhanced catalytic performance, and hence justifying the superiority of this new preparation technique over the conventional ones. [ABSTRACT FROM AUTHOR]

Sewage sludge, the inevitable by-product of municipal wastewater treatment plant operation, is a key issue in many countries due to its increasing volume and the impacts associated with its disposal. Thermochemical processing offers a new way of managing sewage sludge, not only by providing effective volume reduction, but also enabling transformation of carbon-rich organic fraction into valuable energy and fuel. Owing to some unique properties, sewage sludge differs from other solid fuels such as lignocellulosic biomass and coal, making its thermochemical conversion application somewhat complicated and challenging. This paper reviews the options of converting sewage sludge to energy and fuel via three main thermochemical conversion processes namely pyrolysis, gasification and combustion. The fundamental aspects of sewage sludge and its behaviour in each of thermochemical process are summarised. The challenges in adopting thermochemical conversion technology in sewage sludge management are addressed, and various alternative approaches deserving further consideration, such as the incorporation of pre-processing and co-utilisation, are discussed. [ABSTRACT FROM AUTHOR]

Lignocellulosic biomass can be converted to biochar, bio-oil and gas through reactions of non-volatile stabilised free radicals (SFRs) and volatile radicals during thermal conversion. In the process, the interactions between radicals from different biomass components play an essential role. Figuring out the interactions of radicals during pyrolysis holds the key to revealing the interaction mechanism of biomass components. In this study, the evolution of SFRs during the co-pyrolysis of cellulose and lignin was explored using in-situ electron paramagnetic resonance (EPR) detection. The interactions of cellulose- and lignin-derived radicals were analysed based on the variation of SFRs, thermogravimetric behavior and Raman spectrum measurement. The results indicate that the interactions of radicals influence char yield, char structure and the SFRs evolution during pyrolysis. The interaction of volatile radicals and SFRs increases the char yield and promotes the condensation of aromatic structure in biochar. At temperatures above 400 °C, the interaction between cellulose- and lignin-derived SFRs leads to the coupling of radicals, which forms an unstable structure in the hot nascent biochar. In the subsequent cooling process, the weak bonds from interactions may break due to the structure shrinkage, which promotes radical reactions and further changes the char structure. • Interactions during co-pyrolysis improve char yield and stabilised radicals content. • The relationship between stabilised radicals and char carbon skeleton was studied. • The interaction of stabilised radicals in nascent char causes the radicals coupling. • The weak bonds from interaction break to promote radical reactions during cooling. [ABSTRACT FROM AUTHOR]

This study experimentally investigates the gasification of nickel-preloaded oil palm biomass as an alternative catalytic approach to produce clean syngas. To eliminate the use of catalyst support, nickel was added directly to the oil palm mesocarp fiber via ion-exchange using an aqueous solution of nickel nitrate. Nickel species was found to disperse very well on the biomass at a nano-scale dispersion. The presence of the finely dispersed nickels on biomass enhanced syngas production and reduced tar content in the producer gas during the air gasification of biomass. It is believed that nickel particles attached on the biomass and its char promote the catalytic cracking of tar on their surface and supply free radicals to the gas phase to enhance the radical-driven gas-phase reactions for the reforming of high molecular weight hydrocarbons. The unconsumed nickel-containing char shows great potential to be re-utilised as a catalyst to further enhance the destruction of tar components in the secondary tar reduction process. [ABSTRACT FROM AUTHOR]

• Char structure was investigated via characterization of its extraction and residue. • Effects of pellet sizes on char structure were weakened by temperatures. • Polymerisation of extract is account for the structural difference of pellet chars. • Aromatisation degree of pellet char is related to its surface-area-to-volume ratio. Char structure can reflect the pyrolysis characteristics and affect the efficiency of gasification and combustion processes, while biomass pellet size and shape are critical for the heat and mass transfer, which in turn influence greatly char structure. The aim of this study is to experimentally study and compare the effect of aspect ratio (diameter/length) on char structure during the pyrolysis of sawdust pellet. Cylindrical sawdust pellets with similar masses and volumes but different diameters (6, 8, 12, 16 mm) were pyrolysed at various temperatures. The chars were separated into two phases (liquid extraction, solid residue) via microwave-assisted extraction. Experimental results show that the pellet with a low aspect ratio had a large char yield because of intra-particle volatile-char interaction especially at low temperature, while there was an optimum aspect ratio due to the change of residence time. The pellet with a high aspect ratio had an intense polymerisation, resulting in the formation of fused aromatic rings in char and residue. By increasing aspect ratio, there was a lowest surface area. This means that less heat entered from surface, and low thermal conductivity caused a slow decomposition. Due to large heat and mass transfer residence, more aromatic molecules with small weight formed in extracts of char, especially at high temperature. Besides, an increase in temperature weakened the differences in structural features of the pellet char caused by different aspect ratios. [ABSTRACT FROM AUTHOR]

In pyrolysis of biomass pellet, heterogeneity in char is almost inevitable, due to the intra-particle mass/heat transfer limitation. In this study, the effects of temperature (350–600 °C) and aspect ratio of a cylindrical sawdust pellet (Diameter = 6, 8, 12, or 16 mm) on the heterogeneity of char structure at radial and axial directions were investigated with a micro-Raman spectroscopy. Based on the spatial distribution of Raman band area ratios, heterogeneity index was proposed to quantify the degree of heterogeneity in char structures. Results show that the heterogeneity exists in both radial and axial directions and could be weakened by the increase of temperature or enlarging the variance between radius and height of the pellet through enhancing the average heat and mass transfer inside the pellet. The heterogeneity index of different biochar decreased with increasing surface-area-to-volume ratio. The char structures was the most heterogeneous (HI(A D /A G) = 5.399 × 10−5, HI(A D /A (Gr+Vr+Vl)) = 2.359 × 10−5) for the pellet with a diameter of 8 mm. • Effects of temperature and aspect ratio on heterogeneity in char were investigated. • The heterogeneity of char structure at radial and axial directions was quantified. • A heterogeneity index was proposed to reflect heterogeneous structure in char. • The heterogeneity of pellet char could be weakened by the increase of temperature. [ABSTRACT FROM AUTHOR]

[Display omitted] • Coke formation during bio-oil pyrolysis was inhibited via Ni/Al 2 O 3 mixing. • Influence of Ni/Al 2 O 3 mixing on aromatic structures of products was investigated. • Interaction among AF, LDO and Ni/Al 2 O 3 during bio-oil pyrolysis was revealed. • Mechanism for bio-oil pyrolysis with Ni/Al 2 O 3 mixing was proposed. Bio-oil can be converted to chemicals, carbon material, or syngas by various thermochemical processes which are always preceded with the pyrolysis step. In bio-oil pyrolysis, coke formation is almost inevitable, causing difficulties for further processing. In this study, bio-oil was mixed with Ni/Al 2 O 3 before it was fed for pyrolysis. Interesting results were observed whereby the effect of Ni/Al 2 O 3 mixing on coke formation shifted from promoting to inhibiting with increasing pyrolysis temperature. When the temperature was higher than 700 °C, contrary to the cases without mixing, the apparent decreases in coke yield were observed (e.g., the coke yield decreased by 10% at 800 °C). Comparative studies on bio-oil and its lignin-derived oligomer fraction indicated that the catalytic cracking of small molecules could enhance the formation of hydrogen radicals, which promoted thermal decomposition of lignin-derived oligomers, thus inhibiting coke formation via polymerization. [ABSTRACT FROM AUTHOR]

[Display omitted] • Polymerization electro-initiates on cathode surface, and propagates in bio-oil bulk phase. • Large molecules (MW > 800 Da) originally existed in bio-oil contributes to polymerization. • Aromatics, furans and levoglucosan are important polymerization reactants. • Increasing reaction time and current density can enhance polymerization of bio-oil. • Polymer layer forms on anode surface by polymerization. The electrochemical method provides a green route to upgrade bio-oil, but it is still challenged by the issue of bio-oil polymerization which restrains its application. This study investigates the polymerization behaviors of the bio-oil during its electrochemical upgrading under various current densities and different reaction time using macrophotography and multiple characterizations. The results show that the polymerization is not only electro-initiated on the cathode surface, but also electro-propagated in the bulk solution. The large molecules (MW > 800 Da) originally existed in the bio-oil are consumed in the polymerization. The small molecules (MW < 800 Da) can be produced from the polymerization of aromatics with 1–3 rings, furans and levoglucosan through cycloaddition, dehydration and demethoxylation. These small molecules can directly form solid products (coke) rather than leading to the increase of the large molecules. The polymerization can be enhanced by the increasing current density and reaction time. The rate of bio-oil polymerization can surpass the rate of coke formation as the reaction proceeds. The polymer layer also forms on the anode surface by polymerization during the electrochemical upgrading of bio-oil. [ABSTRACT FROM AUTHOR]

Abstract: Unsupported catalysts show great promise for the production of nanocarbon material. This study aims to investigate the formation of carbon nanofibres from the pyrolysis of acetylene using a non-porous mesh as a catalyst. Our results showed that temperature and total gas flow rate have significant effects on the formation of carbon nanofibres on the non-porous Ni mesh catalyst. Opposite effects of gas flow rate on the yield of carbon on Ni mesh surface were observed for the pyrolysis of acetylene at low (620°C) and high (750°C) temperature. Analysis of carbon nanofibres using scanning electron microscopy, FT-Raman spectroscopy and thermogravimetric analysis showed that the structural ordering in the produced carbon changed with the yield of carbon. [Copyright &y& Elsevier]

A kinetic investigation on the reduction of nanometer-sized nickel oxide particles (supported and unsupported) with hydrogen was carried out. The reduction behavior was found to be related to the average size of NiO crystallites. When the NiO crystallite size was less than about 20 nm, the dissociation of H2 was the key rate-limiting factor and remained unchanged almost throughout the reduction process. However, when the NiO crystallite size was >20 nm, its reduction kinetics changed with conversion, showing two kinetic compensation effects at lower and higher NiO conversion levels. It is believed that the movement and rearrangement of H atoms inside such bulk Ni/NiO solid could be an important aspect of the reduction kinetics, especially at higher (50%-90%) NiO conversion levels. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 667-676, 2011 [ABSTRACT FROM AUTHOR]

Abstract: In a typical industrial catalyst, a small amount of catalytically active species is finely dispersed inside a large amount of porous support material. The reactor volume is mainly occupied by the catalyst support, not by the catalytic species itself. The use of fluidised nanoparticles as catalyst without the need of a support may result in drastic reduction in catalytic reactor volume for major savings in capital and operating costs. Here we report for the first time the use of fluidised NiO nanoparticles to catalyse ethane–oxygen reaction at temperatures of 240–420°C. Our data indicate that the fluidised NiO nanoparticles exhibit very different characteristics from the traditional porous catalyst. The lack of a rigid porous structure in the fluidised NiO nanoparticle catalyst allows ethyl radicals to desorb from the catalyst surface into the gas phase to initiate further gas-phase radical chain reactions. Therefore, the ethane–oxygen reaction catalysed by the fluidised NiO nanoparticles shows some typical behaviour of gas-phase reactions. In contrast, the rigid porous structure in the NiO/SiO2 catalyst does not allow the radicals to desorb from catalyst surface into the bulk gas phase. [Copyright &y& Elsevier]

Abstract: The reduction of solid metal oxide by hydrogen or hydrocarbon gases represents a class of reactions that are important to various technological applications. This study investigates the reduction of unsupported NiO nanoparticles and silica-supported NiO with different reducing gases (hydrogen, methane and ethane) in the temperature range of 500–600°C. It was found that, in addition to the reaction and mass transfer of molecular species, the fates and activities of surface-formed radical species have to be considered in explaining the kinetics of nickel oxide reduction. It is believed that the desorption of hydrocarbon radicals from the particle surface has significantly slowed down the reduction of unsupported NiO nanoparticles. The ease with which a radical migrates from its generation site on a metallic island to the Ni–NiO surface boundary, on the other hand, is an important rate-determining factor in the reduction of silica-supported NiO. [Copyright &y& Elsevier]

Abstract: The catalytic reactions between O2 and hydrocarbons are an important class of reactions in energy and chemical industries. This study aims to investigate the complicated reactions involving reactive radicals on the catalyst surface and in the gas phase during the partial oxidation/combustion of light alkanes. In order to avoid intra-particle transport constraints associated with the traditional porous catalysts, a non-porous nickel mesh catalyst has been used in this study for the partial oxidation of ethane with O2 at 625°C at atmospheric pressure. The catalytic effects of the nickel mesh strongly depended on the flow rate of gas reactants passing through the mesh. At a low gas flow rate, the nickel mesh catalyst showed negative effects for the oxidation of ethane. At a high gas flow rate, the same catalyst showed positive catalytic effects. Our results can be explained by considering the selective/preferential adsorption and desorption of different radicals onto and from the catalyst surface. It is believed that the desorption of some surface generated radicals (e.g. OH radicals) may be greatly affected by the thickness of the mass transfer gas film around the mesh wires, which in turn is affected by the gas flow rate passing through the mesh. [Copyright &y& Elsevier]

Biomass pellet is a popular fuel, and pyrolytic char can be a promised carbon material, further understanding char structural evolution can promote its utilization. To deeply investigate the evolution of char chemical structure and its heterogeneity during biomass pellet pyrolysis process, a new method was developed to fragment the char in space, and the chemical structures of the fragmented sections were analyzed by a micro-Raman spectroscopy (equipped with a 532 nm laser). The first-order Raman spectra (800–1800 cm−1) of varied positions of sawdust pellet pyrolytic char were curve-fitted with 10 Gaussian bands to reveal the temporal and spatial evolutions. The results indicate that pyrolysis of sawdust pellet can be divided into two stages: i) the decomposition of raw biomass (temperature heterogeneity in pellet remains); ii) the condensation reactions of aromatic ring systems (temperature in pellet becomes uniform). The axial and radial heterogeneity of char chemical structure is mainly caused by heat transfer when the whole pellet temperature is uniform during heating. While mass transfer, in accordance with volatile diffusion, can eliminate the heterogeneity of char chemical structure by volatile-char interaction. The combined effects of heat and mass transfer lead to a heterogeneity in pellet char chemical structure. • An expanded Raman method by combining micro positioning and analysis was developed. • Chemical structure heterogeneity of sawdust pellet pyrolytic char was quantified. • Temporal and spatial evolutions of pyrolytic char chemical structure were revealed. • Combined effects of heat and mass transfer on char chemical structure were found. [ABSTRACT FROM AUTHOR]

Highlights • Effect of pre-reforming by Fe/bio-char catalyst on bio-oil reforming was studied. • Fe/bio-char pre-reforming increases the H 2 and CO yields from bio-oil reforming. • Fe/bio-char catalyst promotes the transformation of aromatics into light compounds. • Less coke was formed on Ni-based catalyst due to Fe/bio-char catalyst at 550–600 °C. • Pre-reforming promotes the formation of NiO and NiAl 2 O 4 on Ni-based catalyst. Abstract Ni-based catalyst is prone to the deactivation by coke deposition during the catalytic steam reforming of bio-oil. In order to optimize catalytic activity of the Ni-based catalyst, a two-stage catalytic reforming scheme was proposed whereby a low-temperature (350–600 °C) pre-reforming process with a less expensive catalyst was introduced prior to the Ni-based catalyst. To study this scheme, the reforming experiments with different combinations of Fe/bio-char (in the first stage) and Ni-Ca/γ-Al 2 O 3 (in the second stage) were conducted. In addition to the quantification of product yields, the tar and gas were characterized with an ultraviolet (UV) fluorescence spectroscopy, a gas chromatography/mass spectrometer (GC/MS) and a gas chromatography (GC). The results indicate that significant proportions of naphthalenes and polycyclic aromatics in the intermediate volatiles turned into furans, phenols and non-aromatics, which are easier to be reformed on Ni-based catalysts, via the Fe/bio-char pre-reforming, resulting in the increase of the final H 2 and CO yields of the overall process. At high pre-reforming temperatures (550–600 °C), the coke formation on Ni-based catalyst was significantly inhibited due to the Fe/bio-char pre-reforming. In addition, the results indicate that the spent Ni-based catalyst had more free NiO and NiAl 2 O 4 spinel than the fresh one, suggesting that the increase in the catalytic activity of Ni-based catalyst during the reforming process was promoted by Fe/bio-char pre-reforming. [ABSTRACT FROM AUTHOR]

Heavy components affect conversion behaviors of sludge-derived pyrolytic liquids during their utilization and contribute significantly to the formation of the notorious tar and soot during sludge gasification and combustion. Understanding the evolution of heavy components during pyrolysis is vital for developing a reliable sewage sludge utilization technology. This study investigates the compositions of oils from the pyrolysis of sewage sludge using an electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT ICR-MS). Hundreds of compounds with molecular mass higher than 400 Da were detected from the pyrolytic oil obtained at 450 and 650 °C. Higher pyrolysis temperatures promoted decomposition and polycondensation of large molecules and increased the amount of nitrogen-containing compounds in the liquid. Aromatic structured molecules consisting of carbon, hydrogen and nitrogen were the predominant compounds at 850 °C. From the results of this study, the evolution routes of heavy components in the pyrolytic liquid are proposed. [ABSTRACT FROM AUTHOR]

Bio-oil from the fast pyrolysis of biomass can be converted to solid carbon materials, chemicals and syngas by various thermochemical conversion methods. As a first step in all of these processes, bio-oil undergoes drastic components changes due to its exposure to the elevated temperature. Understanding the effects of heating rate on bio-oil transformation during its pyrolysis is therefore crucial for effective utilization of bio-oil. In this study, a bio-oil sample produced from the fast pyrolysis of rice husk at 500 °C was pyrolyzed in a fixed-bed reactor at temperatures between 300 and 800 °C at three different heating rates: fast (≈200 °C/s), medium (≈20 °C/s), and slow (≈0.33 °C/s). In addition to the quantification of coke and tar yields, the tar was characterized with an ultraviolet (UV) fluorescence spectroscopy, a gas chromatography/mass spectrometer (GC/MS) and a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS). Our results indicate that slow heating rates promote polymerization of bio-oil components, particularly at low temperatures (<500 °C), resulting in higher primary coke yields than that of the fast heating rates. Decomposition reaction was found to be pronounced at fast heating rates, causing decreases in the tar yields and abundance of light compounds. The increases in the yields of the secondary coke, the formations of more condensed aromatic structures and macromolecules ( m / z  > 500) were also promoted at fast heating rates via the more intense secondary reactions. [ABSTRACT FROM AUTHOR]

Hydrothermal carbonization (HTC) is an attractive, green technology for the management of sewage sludge. In this study, low-value secondary sewage sludge was subjected to an HTC treatment in a 1 L batch hydrothermal reactor and transformed into a high-energy-density hydrochar under varying HTC conditions (temperature of 150–300 °C, carbonization time of 30–150 min and a solid loading of 10–30%). The resulting hydrochar fuel characteristics were analyzed for ultimate and proximate analyses, functional group composition and energetic parameters. It was found that the hydrochar yield decreased with the increasing HTC temperature and reaction time, primarily due to the loss of organic volatile matter and functional groups. Under the optimum conditions of 150 °C, 30 min of carbonization time and 30% solid loading, 80.56% of the hydrochar was recovered, providing a maximum energy yield of 90.32% and a high heating value of 18.49 MJ/kg. Compared to the raw sewage sludge (H/C ratio of 2.67 and O/C ratio of 0.51), the hydrochar also had lower H/C and O/C atomic ratios of 1.42 and 0.18, respectively. The results suggest that significant dehydration and decarboxylation during the HTC treatment of sewage sludge have resulted in the formation of carbonaceous hydrochar with energetic properties close to the sub-bituminous coals. [ABSTRACT FROM AUTHOR]

Sewage sludge is an important class of bioresources whose energy content could be exploited using pyrolysis technology. However, some harmful trace elements in sewage sludge can escape easily to the gas phase during pyrolysis, increasing the potential of carcinogenic material emissions to the atmosphere. This study investigates emission characteristics of arsenic, cadmium and lead under different pyrolysis conditions for three different sewage sludge samples. The increased temperature (within 723–1123 K) significantly promoted the cadmium and lead emissions, but its influence on arsenic emission was not pronounced. The releasing rate order of the three trace elements is volatile arsenic compounds > cadmium > lead in the beginning of pyrolysis. Fast heating rates promoted the emission of trace elements for the sludge containing the highest amount of ash, but exhibited an opposite effect for other studied samples. Overall, the high ash sludge released the least trace elements almost under all reaction conditions. [ABSTRACT FROM AUTHOR]

The electrochemical method is becoming a promising approach to deliver the bio-oil upgrading objective at room temperature. However, it still faces the coke formation issue because of the easy polymerization nature of bio-oil. Interactions among components impact the polymerization during the electrochemical upgrading of bio-oil. This study investigates the effects of interactions between the aromatic-rich and aromatic-poor fractions (ARFs and APFs) of the bio-oil on polymerization under various reaction time and current densities. Coke yield differences provide direct evidence of the existence of interactions between ARFs and APFs during the electrochemical upgrading process. Our results indicate that the coke yields and its condensation level are decreased by the interactions. The surface area, pore volume and the functionalities content of the coke are increased by the interactions. In addition to polymerization, more types of reactions including hydrogenation and esterification are induced by the interactions, resulting in more types of products and less coke. The interactions can inhibit polymerization by consuming the coke precursors before their condensation. The interactions can also inhibit the anodic adsorption and oxidation, thus depressing polymerization and coke formation. Investigating the impacts of interactions between aromatic-rich and aromatic-poor fractions on polymerization of bio-oil in chronoamperometric electrochemical upgrading. [Display omitted] • Interactions of aromatic-rich and -poor fractions in bio-oil is proven existed in electrolysis. • Aromatic-poor fractions end-cap the reactive chains of polymerization precursors. • Interactions weaken the anodic adsorption and polymerization of bio-oil. • Interactions decrease the yields, surface areas and pore volumes of the coke. [ABSTRACT FROM AUTHOR]

• Fe/activated char shows high performance on bio-oil upgrading. • The fresh catalysts favor the production of aromatic hydrocarbons. • The regenerated catalysts by active agents facilitate the production of phenols. • The catalyst regeneration promotes the formation of γ-Fe 2 O 3 on the char surface. Char-supported metals as catalysts has attracted much attention due to the renewability and structural controllability of char. However, such catalysts can not be regenerated by the conventional calcination method, which is widely used in industy. In this study, the catalytic performance of char-supported Fe on bio-oil upgrading during pyrolysis of pine wood was first investigated. It was found that the typical components (acids, ketones, furans, etc) in bio-oil were completely converted to aromatic hydrocarbons over char-supported Fe, in which char acted not only as a support but also as a catalyst for the converison of bio-oil to phenols. Then, the spent char-supported Fe catalyst was regenerated by CO 2 or steam gasification. The results showed that only phenols could be produced over both CO 2 and steam regenerated catalysts, which was caused by the changes in carbon structure and surface functional groups of char as well as the species of Fe. The CO 2 regenerated catalyst was rich in C O groups and α-Fe 2 O 3 , while the H 2 O regenerated one mainly contained O C O groups and Fe/FeO. [ABSTRACT FROM AUTHOR]

• Eggshell-modified biochar shows prominent phosphorous adsorption performance. • Chemical adsorption process is the controlled step for eggshell-modified biochar. • Ca-P precipitation, hydrogen bonding, electrostatic attraction are adsorption step. • Adsorbed phosphates are mainly distributed inside pore size range of 15–50 nm. Biochar modified with calcium source is acted as an effective adsorbent for phosphorous recovery. In this research, eggshell is used as a low-cost and environmentally friendly calcium source to replace chemical reagents such as CaCO 3 , Ca(OH) 2 and CaCl 2 used in the modified biochar production. Biochar derived from rape straw and modified with eggshell shows prominent phosphorous adsorption performance (e.g., equilibrium adsorption amount, 109.7 mg/g). The kinetic and isotherm analysis demonstrate that chemical adsorption process is performed as the main controlled step for the modified biochar adsorption, and the phosphate adsorption process is composed of both monolayer adsorption and multi-layer adsorption. Moreover, it is found from the physicochemical structures comparison before and after phosphate adsorption that Ca-P precipitation, hydrogen bonding and electrostatic attraction are identified as main adsorption mechanisms. In addition, the adsorbed phosphates are mainly distributed inside the space with pore sizes of 15–50 nm. [ABSTRACT FROM AUTHOR]

• A novel one-step method for simultaneously producing a CNTs electrode material and H 2 was proposed. • Ni-Fe/Ni foam catalyst remarkably improved the H 2 production and pyrrole conversion compared with that of fresh Ni foam. • Nitrogen doped carbon nanotubes@Ni foam electrode has a large capacitance and an outstanding cyclability. Carbon nanotubes (CNTs) can be formed during catalytic reforming of hydrocarbons with H 2 co-production over Ni-based catalysts. Normally, the formed CNTs need to be separated from original catalysts in order to be coated on the substrates to make high performance electrodes. To simplify the traditional preparation process, a novel one-step method for simultaneously producing a CNTs electrode material and H 2 was proposed. A Ni-Fe modified Ni foam (Ni-Fe/NF) was chosen as both catalyst and electrode substrate to in situ grow nitrogen-doped carbon nanotubes (N-CNTs) during catalytic reforming of pyrrole. Pyrrole was selected as an N-containing model compound of biomass tar. The results showed that Ni-Fe nanoparticles on Ni-Fe/NF catalyst remarkably improved the H 2 production and pyrrole conversion, which increased by more than 20 times than those of fresh Ni foam. Besides, a significant amount of multi-walled CNTs with more than 40 graphite layers grew on the surface of spent catalyst and their diameters were mainly from 10 nm to 20 nm. N element was detected on the formed CNTs and the Graphitic-N was the main type of N-doping. The spent catalyst (N-CNTs@Ni foam) can be directly used as a composite electrode material with high performance and stability. Its electrochemical capacitance reached 855 mF/cm2 at a current density of 5 mA/cm2 and remained over 95% after 10,000 cycles. [ABSTRACT FROM AUTHOR]

In this work, two types of lanthanum-based MIEC perovskite oxides, namely La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF) and La 0.6 Sr 0.4 Co 0.2 Ni 0.8 O 3-δ (LSCNi), were deposited onto porous alumina hollow fibre (AHF) substrates and used for oxygen enrichment. Such structure was developed to shorten oxygen ion diffusion distances in dense membranes and simultaneously leading to higher oxygen flux. The perovskite oxides were prepared using Pechini sol-gel method and deposited via a vacuum-assisted technique. The deposition of lanthanum-based membranes onto the outer and inner sides of the porous AHF has been facilitated through numerous microchannels in the AHF substrates. The effects of operating temperature and argon sweep gas flowrate on oxygen permeation flux of lanthanum-based AHF membrane were investigated. The results revealed that the oxygen permeation flux of LSCF-AHF and LSCNi-AHF increased with operating temperatures due to the improvement of bulk diffusion and surface exchange properties after the lanthanum-based perovskite deposition. Higher oxygen flux was observed for LSCNi-AHF as LSCNi possessed balanced oxygen ionic and electronic conductivities as compared to LSCF membranes. Benefitting from improved oxygen activation and vacancy generation properties after Ni substitution into the B-site ion of LSC perovskite, a dramatic increased oxygen fluxes up to 4.5 mL/min·cm2 was observed at 950 °C. The present work demonstrated a feasible method for fabricating oxygen transport membrane (OTM) using porous AHF substrates [ABSTRACT FROM AUTHOR]

This study investigated the interaction of nickel species with alumina versus calcination temperature and nickel loading. A total of 22 Ni/Al 2 O 3 catalysts, calcined at the temperature from 500 to 1000 °C at a 50 °C increment, were employed for the study. High calcination temperature led to the formation of nickel–alumina spinel via the solid phase reaction, which shifted the reduction temperature to higher ranges. The catalyst, however, still achieved good activity after full reduction of the nickel–alumina spinel. Nevertheless, the high calcination temperature led to the collapse of the small pores and the formation of the big one, resulting in the significant decrease of specific surface area. At higher nickel loadings, more nickel species weakly interacted with alumina formed as the reactive center of alumina was saturated. With the increase of nickel loading, the catalytic activities were not varied much but the catalytic stability and the resistivity towards coking enhanced. The coke produced over the catalyst at low nickel loading tended to be amorphous, while the coke produced at the high nickel loading was more fibrous. Furthermore, the coke produced at the low loading contained more small aromatic rings and more oxygen-containing functional groups. The higher nickel loading possibly promoted the catalytic cracking reactions to form more catalytic coke while the low nickel loading probably favored the polymerization reactions to form the polymeric coke. In addition, the calcination at the higher temperature could enhance the stability of the catalysts, which might be related to the enlarged pore sizes. [ABSTRACT FROM AUTHOR]

Antibiotics are extensively used in treating infectious diseases for both humans and animals. However, they are generally not fully digested in the body and are released as active compounds into aquatic systems through domestic sewage treatment plants, where they can cause chronic toxicity and some potentially major health and environmental risks. Many researchers reported that conventional wastewater treatment processes cannot completely eradicate antibiotic residue and that these residues may be discharged to the receiving rivers and streams. Adsorption was claimed to be able to remove these contaminants even at low concentrations and under a variety of pH conditions. Biomass-based adsorbent materials have recently been used to remove antibiotics due to their wide availability, eco-friendly nature, good surface characteristics, and low cost. This study conducted a systematic review of biomass-based carbon adsorbents used for antibiotic removal. The surface chemistry and maximum antibiotic adsorption capacities were reviewed and discussed based on the type of biomass and chemical modification. The effect of influential variables such as pH, initial concentration of antibiotics and adsorbent dosage was also discussed in detail. After the screening process, four articles were found to be suitable for the detail analysis on reusable efficiency. Results of the detail analysis shows coconut shell and sawdust based-carbon adsorbent could remove antibiotics with 89% reusable efficiency after the fourth cycle of reuse. Overall, this systematic review ascribes the research work for synthesizing an excellent performance of biomass-based carbon adsorbent. • A systematic review on chemically modified biomass-based carbon adsorbent for the removal of antibiotics in water. • The performance of carbon adsorbent depends on the chemical and physical properties of the adsorbent surface. • Chemical modification is effective to enhance adsorption capacity for antibiotics removal. • Reusable efficiency of 89% is possible after four cycles of antibiotics removal. [ABSTRACT FROM AUTHOR]

Microwave-assisted extractions (MAEs) were carried out on Shenfu (SF) low-rank coal using four types of solvent, namely tetrahydrofuran, methanol, dichloromethane and ethyl acetate. Comparison with the traditional thermal extractions (TEs) indicated that MAEs were much more efficient in extracting organic components of SF coal. A large amount of aromatic compounds with 2–3 rings and rich branched alkanes could be extracted from coal by MAE. The results also showed that solvent polarity and the interaction between solvent and functional groups abundant in the extracts were the two main factors leading to differences of their MAE. Among the studied solvents, tetrahydrofuran could extract much more amount of polar compounds and its solution was rich in highly-condensed polycyclic aromatic compounds (PACs) with ≥ 4 rings. And this feature had relationship with its strongest interaction with the C O bond. Ethyl acetate, in contrast, showed strong interaction with the C O bonds and had good potential for the extraction of low-polarity compounds especially PACs with two aromatic rings and aliphatic compounds with long alkane chains. And for methanol and dichloromethane, their solvent polarity played dominant roles during the MAE procedures. The results provided more detailed mechanistic influences of different solvents on MAE of coal, and would help for the identification of a suitable solvent for efficient detection of components in organic substances, especially the extraordinary complex compounds in coal. [ABSTRACT FROM AUTHOR]

Ni-based catalysts are prone to be deactivated by carbon deposition. This study aims to investigate the influence mechanism of different types of carbon deposition on the activity of Ni/α-Al 2 O 3 catalyst at various steam-to-carbon (S/C) ratios during steam reforming of toluene for hydrogen production. At a low S/C ratio of 1, the catalytic activity of Ni/α-Al 2 O 3 was inhibited due to the covering and blocking of Ni active sites by the formation of amorphous carbon on the Ni surface. While at a high S/C ratio of 3, more than 80 wt% of carbon deposition was found to be self-growth carbon nanotubes (CNTs) with an average diameter of around 15 nm. The activity of Ni/α-Al 2 O 3 in steam reforming of toluene was unusually promoted, which can be attributed to the tip-growth mechanism of CNTs, whereby the Ni particles migrated to the tip or the surface of CNTs, resulting in the improved active site dispersion. [ABSTRACT FROM AUTHOR]

A study was carried out in both inert and CO 2 atmosphere to investigate the interaction mechanism of K 2 CO 3 with graphite and coal char during the catalytic gasification of coal char. The formation of K 2 CO 3 catalytic precursors was identified by using series of different techniques. The results obtained in an inert atmosphere show that the interaction between K 2 CO 3 and carbon readily took place at low temperature. For the K 2 CO 3 loaded graphite, the intermediate of C n K clusters formed by the interactions of K 2 CO 3 with carbon prevented the evaporation of K at low temperature. At temperatures above 800 °C, however, the C n K clusters were unstable, and decomposed to release K through vaporization. On the contrary, for the K 2 CO 3 loaded demineralized coal char, due to the presence of oxygen groups, K was tightly bonded to carbon during heating, forming a complex precursor containing O and K with high thermal stability. The reaction pathway of carbon-K 2 CO 3 interactions in an inert atmosphere are proposed for both char and graphite. The results of DRIFTs experiment suggest that CO 2 is chemisorbed by the K- catalytic precursors during CO 2 gasification to form potassium phenolate species and a covalently bound carbonate group (dimethyl carbonate). It is believed that these species act as active intermediates in the gasification process. [ABSTRACT FROM AUTHOR]

The existence form and structure properties of mobile phase (MP) in low-rank coals (LRCs) can significantly influence the initial stage of thermal conversion. In the present work, three Chinese LRCs, namely, Shenfu, Zhundong and Hongshaquan, were extracted with tetrahydrofuran using the microwave-assisted heating. The tetrahydrofuran-microwave-extracted (TME) portion as the representative of MP was further separated to four fractions defined as oil, resin, asphaltene and preasphaltene, respectively. Diffuse reflectance Fourier transform-infrared spectroscopy (DRIFT), gas chromatography/mass spectrometer (GC/MS), matrix-assisted laser desorption ionization time-of-flight mass spectrometer (MALDI-TOF-MS) and X-ray photoelectron spectroscopy (XPS) were used to comprehensively investigate the molecular characteristics of the derived materials. The results indicated that the studied TME portions were mainly consisted of asphaltenes and rich in highly branched aliphatic hydrocarbons due to the relatively low CH 2 /CH 3 and H ar /H al ratios. Para -alkyl substituted aromatic structures with 1–2 rings were the main aromatic structures in the TME portions. C O bonds were the main oxygen-containing structures in the TME portions and could be more likely seen in aliphatic compounds. Combining the MALDI-TOF-MS and DRIFT analyses, the ratio of aliphatic side chains and aromatic hydrogens (3000–2800 cm −1 /900–700 cm −1 , I 2 ) derived from IR spectra seemed to be a suitable parameter for assessing the average molecular weight (AMW) of the specific fraction in TME portion of LRCs when the ratio of C O/C O was at very low level. The results made a further explanation for the detailed chemical structure of mobile phase in coal and could be helpful for studying the formation mechanism of volatiles during pyrolysis process. [ABSTRACT FROM AUTHOR]

Abstract: Bark constitutes an important part of any woody biomass to be used for the production of second generation biofuels and chemicals. Pyrolysis followed by biorefinery is a promising technology for the efficient utilisation of all components from a woody crop. While significant efforts have been devoted to the investigation of the pyrolysis characteristics of wood, relatively less is known about the pyrolysis behaviour of bark. This study aims to clarify the effects of temperature on the yields and composition of bio-oil from the pyrolysis of eucalypts bark. The bark of mallee, a type of eucalypt grown for soil amendment in Western Australia, was pyrolysed between 300 and 580°C at fast heating rates in a fluidised-bed pyrolysis unit. The bio-oil liquid products separate into two phases. The bio-oil liquid products were analysed by GC–MS, Karl-Fischer titration, UV-fluorescence spectroscopy, ICP-OES and thermogravimetric analysis (TGA). These results are compared, when appropriate, to those obtained from the wood fraction. [Copyright &y& Elsevier]

• Char activity in volatile-char interactions varies with biomass components. • Xylan char rich in C O group is the most active for (benzyloxy)benzene conversion. • Char C(sp2) O group promotes the breaking of C(sp3) O in (benzyloxy)benzene. • Char C(sp3) O group promotes the breaking of C(sp2) O in (benzyloxy)benzene. • Lignin char is highly selective to monomers due to the abundant C O group. Char activity is a critical factor for the interactions between char and volatile, which are recognized to determine the final product distribution from biomass pyrolysis. To clarify the effect of biomass composition on char activity, the interactions between (benzyloxy)benzene as a volatile model compound and char samples obtained from cellulose, xylan, and lignin were studied. The (benzyloxy)benzene conversion increased from 0.64 % for no char to 6.31 %, 6.98 % and 53.5 % for lignin char, cellulose char, and xylan char, respectively, which were mainly derived from the contribution of surface C O groups and surface defects in the carbon structure. Especially, surface C(sp2) O groups and C(sp3) O groups on char respectively favored the breakage of C(sp3) O and C(sp2) O bonds in (benzyloxy)benzene. Despite the low activity, lignin char showed high selectivity to monomeric products due to the high content of surface C O groups, which were considered to induce the production of hydrogen radicals to stabilize the resulting intermediates. The findings of this study prove that the volatile-char interaction could be adjusted facilely by changing the hemicellulose content during feedstock pretreatments. [ABSTRACT FROM AUTHOR]

• Volatile–char interactions are important for the evolution of pyrolysis volatile. • Surface functional group on char contributes to volatile–char interactions. • CNT favors the cleavage of C–O bond in the β–5 dimer to produce dimeric products. • CNT–NH 2 promotes the breakage of C−C bonds in the β–5 dimer to yield monomers. This study investigated the interactions between volatile and char during biomass pyrolysis at 400 °C, employing a β–5 lignin dimer and amino-modified graphitized carbon nanotube (CNT–NH 2) as their models, respectively. The results demonstrated that both –NH 2 and its carrier (CNT) facilitated the conversion of the β–5 dimer, which significantly increased from 9.7% (blank run), to 61.6% (with CNT), and to 96.6% (with CNT–NH 2). CNT mainly favored the breakage of C–O bond in the feedstock to produce dimers with a yield of 55.5%, while CNT–NH 2 promoted the cleavage of both C–O and C–C bonds to yield monomers with a yield up to 63.4%. Such significant changes in the pyrolysis behaviors of the β–5 lignin dimer after the introduction of CNT–NH 2 were considered to be mainly caused by hydrogen-bond formations between –NH 2 and the dimeric feedstock/products, in addition to the π–π stacking between CNT and aromatic rings. [ABSTRACT FROM AUTHOR]