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The role of coal in iron and steel metallurgy is analyzed through the routes for steel manufacturing, current levels of steel production, and forecasts for the future. Coal as an essential raw material in different metallurgical processes is discussed, emphasizing the functions of metallurgical coke in ironmaking via the blast furnace. The potential of biomass as an additive in cokemaking and as an injectant in a blast furnace to mitigate fossil CO2 emissions is also addressed.

Concerns about energy security, energy prices and climate change led scientific research towards sustainable solutions to fossil fuel as renewable energy sources coupled to hydrogen as energy vector and carbon capture and conversion technologies. Among the technologies investigated in the last decades, biomass gasification acquired great interest owing to the possibility to obtain low cost and CO2 negative emission hydrogen production from a large variety of everywhere available organic wastes. Upstream and downstream treatment were then studied in order to maximize hydrogen yield, reduce the content of organic and inorganic contaminants under the admissible levels for the technologies which are coupled with, capture, and convert carbon dioxide. However, studies which analyse a whole process made of all those technologies is still missing. In order to fill this lack, the present paper investigated the coexistence of Hydrothermal Carbonization (HTC), Sorption Enhance Gasification (SEG), Hot Gas Cleaning (HGC), and CO2 conversion by Dielectric Barrier Discharge (DBD) plasma reactor for H2 production from biomass waste by means of Aspen Plus software. The proposed model aimed to identify and optimise the performance of the plant by varying operating parameters (such as temperature, CaO/biomass ratio, separation efficiency, etc.). The carbon footprint of the global plant is 2.3 kg CO2/kg H2, lower than the latest limit value imposed by the European Commission to consider hydrogen as “clean”, that was set to 3 kg CO2/kg H2. The hydrogen yield referred to the whole plant is 250 gH2/kgBIOMASS.

This study investigates the suitability of different lignocellulosic sources, namely eucalyptus, apple bagasse, and out-of-use wood, for injection into blast furnaces (BFs). While wastes possess carbon potential, their high moisture renders them unsuitable for direct energy utilization. Additionally, the P and K impurities, particularly in apple bagasse, can pose operational and product quality challenges in BF. Thus, different thermochemical processes were performed to convert raw biomass into a more suitable carbon fuel. Low-temperature carbonization was selected for eucalyptus, yielding a biochar with properties closer to the low-rank coal. Hydrothermal carbonization was chosen for apple bagasse and out-of-use wood, resulting in hydrochars with enhanced fuel characteristics and fewer adverse inorganic species but still limiting the amount in binary PCI blends. Thermogravimetry evaluated the cause–effect relationships between coal and coal- and bio-based chars during co-pyrolysis, co-combustion and CO2-gasification. No synergistic effects for char formation were observed, while biochars benefited ignition and reactivity during combustion at the programmed temperature. From heat-flow data in combustion, the high calorific values of the chars were well predicted. The CO2-gasification profiles of in situ chars revealed that lignin-rich hydrochars exhibited higher reactivity and conversion than those with a higher carbohydrate content, making them more suitable for gasification applications.

Waste-derived hydrochars are presented for the first time as promising materials to reduce the consumption of natural resources and the carbon footprint of the cement industry, while eliminating waste and sequestering a high amount of carbon in civil infrastructures. Rice husk (RH) and stabilized organic waste from a mixed municipal waste mechanical-biological treatment plant (SOW) were subjected to hydrothermal carbonization at 200 °C for 2 h and the resulting hydrochars were thoroughly evaluated as cement substitutes in fresh and hardened mortars. Compared to the control, mortars with 1.25–5 wt% of cement replaced by hydrochar from stabilized organic fraction caused a decrease in compressive strength of about 50–60% at 28 days of curing, while flexural strength was diminished by about 38–47%. The use of rice husk-derived hydrochar led to a reduction of 32–47% in compressive strength and of 22–34% in flexural strength. With compressive and flexural strengths of 27–41 and 3.31–4.92 MPa, respectively, blended mortars (28 days) display good prospects for use in plastering, rendering, masonry, partition panels and low-load paving. On the other hand, substituting 5 wt% of cement by hydrochar decreases the thermal conductivity and increases electrical resistivity of the mortar by 25–30%, which enhances thermal insulation properties and potential durability. This approach opens a new avenue for large-scale application of biowaste hydrochars as secondary raw materials for sustainable construction.

Nowadays aquaculture provides animal protein of quality for human consumption, necessary to maintain the high world population, thus supporting fisheries production constrained by overexplotitation of fishing (FAO, 20222). However, it is important to produce it in a cost-effective and sustainable way. Since 2012, biochar is starting to be included in animal feed (Gerlach & Schmidt, 2012). Biochar is obtained by pyrolisis from organic waste in a low-to-no oxigen thermal process, reusing by-products from other industries (European Biochar Foundation - EBC 2012). This product has been shown to improve nutrien intake efficiensy, absorb toxin and generally improve animal health besides improving the quality of the effluent water (O'Toole et al., 2016, Toth and DU, 2016, Schmidht et el, 2019), making it a good candidate for its inclusion y aquafeeds. This study aims to test the putative improvement produced by the dietary inclusion of biochar in Senegalese sole, a species of great interest in Spain.

The rapid spread of invasive Pampas grass (PG) is having not only ecosystems impact, but also significant economic and social effects. The tonnes of bulky waste from the plant disposal require proper treatment to avoid seed dispersal, greenhouse gas emissions and landscape damage. In the pursuit of zero-waste management, hydrothermal treatment (HT) appears as a challenging alternative. The possibility of mobile HT systems offers an alternative to accomplish on-site both the PG waste management and the application of the resulting by-products within a circular framework. As a first step, this research shows that, without a prior drying step, the hydrothermal treatment at 100-230 °C under autogenous water vapor pressure for only 30 min allows safe seeds inertization, while a stable carbon-enriched solid and an aqueous stream are generated. Prolonging the process for 2 h has no profitable effects. As the reaction temperature increases, the PG residue is converted into a material with 49–58 wt% of carbon, 41–32 wt% of oxygen and 3–4 wt% of ash. The pH (~6.3), low electrical conductivity (1.21–0.86 dS/m), high carbon content, open porosity (5–8 m2/g) and improved performance in seed germination and in the early growth test suggest the potential of HT-solids derived at 100–120 °C as amendment to sequester carbon in the soil and improve its physico-biological properties. The phytotoxicity detected in the peat/lignite-like solids obtained at 200–230 °C limits its application in soil, but calorific values of 22–24 MJ/kg indicate their suitability as CO2-neutral fuel. The agrochemical analysis of the liquid by-products indicates poor value on their own, but their use supplemented with compost may be an option.

Hydrothermal carbonization makes feasible the integral and profitable recovery of industrial apple waste within a zero-residue bio-economy. 82–96% of the energy and 80–93% of the C in the apple bagasse are retained in the solids generated by hydrothermal treatment at 180 and 230 °C for 2 and 4 h. Such processes stabilize the apple waste and lead to CO2 neutral solid fuels with calorific value close to 30 MJ/kg. The agrochemical properties of the solid by-products suggest their potential to improve soil quality. Aqueous streams containing valuable phenolic compounds and saturated fatty acids are generated simultaneously, which provide additional cost-effectiveness. The by-products characteristics can be suited to the final application by selecting the reaction temperature, whereas the process duration has less impact. Optical microscopy and reflectance measurements are presented, for the first time, as powerful tools for assessing the biomass transformation when subjected to hydrothermal treatment under different conditions.

The implementation of sustainable strategies based on the integral valorization of residues is the most efficient way to achieve a profitable circular economy. This comprehensive study highlights the potential of apple waste from juice and cider production as a precursor of porous carbons and provides guidelines to achieve a wide spectrum of physicochemical properties. Hydrothermal carbonization (HTC) of apple bagasse is proposed as a feasible integrated process with zero waste that allows stabilizing this highly pollutant residue in the form of a carbon-enriched solid while extracting valuable compounds in the aqueous phase. The liquid fraction resulting from HTC at 200 °C contains a high total phenolic content and antioxidant activity, the major products being catechol (1,2-dihydroxybenzene) and 5-hydroxymethyl-2-furfural (HMF). The successful upgrading of the solid byproduct into porous carbons provides additional advantage for a more cost-effective waste management. It is reported that a simple one-step activation leads to apple-derived carbons with specific surface areas up to 2000 m2 g–1 and electrochemical capacitances as high as 260–290 F g–1. Their excellent performance as supercapacitor electrodes make them very promising for the storage of electrical energy from renewable sources.

With the awareness of the need for low-cost carbons for supercapacitors, the recycling of biomass wastes as precursors of activated carbons is focusing great interest. The comparison of a diversity of carbons derived from residues of industrial processing of grapes, apples and cherries reveals the utility of physical activation to achieve better volumetric performance in aqueous supercapacitors. Whereas the high porosity development of the materials obtained by KOH activation (mostly around 1500–2000 m2 g-1) provides a superior gravimetric capacitance up to nearly 300 F g-1 in 2 M H2SO4, the low density of the electrodes reduces the volumetric capacitance to 60–130 Fcm−3. Porous carbons produced by steam or CO2 reaches higher efficiency for compact devices. The physically activated materials display an ultramicroporous structure with standard surface areas of around 900 m2 g−1 and, therefore, their gravimetric capacitance is limited to 100–150 F g-1. However, harnessing the balance of porosity, density and good packaging, the corresponding electrodes reach 80–170 F cm−3, without sacrificing power delivery by the supercapacitor. Higher carbon yield and lower environmental impact represent additional advantages of the physical activation to produce biomass wastes derived-carbons.

Graphene shows substantial promise in improving the technical performance of a range of applications. For its development and before its potential mass adoption, it is critical to understand the associated cradle-to-grave life cycle environmental impacts. Previous studies on graphene environmental performance do not include end of life and the potential environmental credits generated by graphene reuse. This study undertakes a cradle-to-grave approach to evaluating graphene applications, considering a case study of supercapacitors manufactured with graphene and activated carbon active materials. The analysis includes active materials commercial-size production, supercapacitors production, supercapacitors use phase in an automotive application, and their end of life in which both devices are recycled. With current material performance and energy mixes, the graphene-based supercapacitor would increase impacts in all environmental categories analysed, ranging from 27% higher human toxicity to 213% greater ozone depletion and showing a 48% increase in GHG emissions. This unfavourable result arises due to the tested graphene material exhibiting inferior specific capacitance to the activated carbon comparator, as well as a more energy-intensive production process. Prospective analysis considers hypothetical performance where both active materials reach their theoretical specific capacitance, and the decarbonisation of electricity generation. The environmental impacts of both the activated carbon and graphene supercapacitors are reduced in these prospective scenarios, with the graphene based supercapacitor becoming the least impacting solution due to its lower active material requirements. The graphene-based device shows 36% lower GHG emission and overall shows lower impacts ranging from 14% less mineral, fossil and renewable resource depletion to 43% less photochemical ozone formation. These results support graphene as a valid candidate material for substituting activated

This study presents a challenging approach that addresses the efficient management of the organic fraction of municipal solid waste (OFMSW) by hydrothermal carbonization (HTC) for the development of novel sustainable low-CO2 building materials. Mild HTC treatment at 180 °C for 2 h transformed low-grade OFMSW into a renewable carbonaceous solid (hydrochar), which displays promising properties for application in particleboards. Taking advantage of the presence of extractives acting as natural binders, the hydrochar particles with sizes of <0.3 mm, 0.3–1 mm, and 1–2 mm agglomerate successfully by simple pressing at 3 MPa for 7 min at room temperature (∼ 25 °C). The resulting binderless monolithic probes display a density of 838 and 883 kg/m3 for the finest and coarsest grain sizes, respectively, and approximately 30% porosity. The mechanical resistance is enhanced by the use of larger particle sizes, and values of modulus of rupture and tensile strength of 21.64 MPa and 18.99 MPa are reached, respectively. The thermal conductivity of the probes in the range of 0.091–0.132 W/(m∙K) suggests the potential of OFMSW-derived hydrochar for thermal insulation panels.

We present a simple and effective alternative which optimizes electrodes based on low-cost carbons for high-performance supercapacitors. The combination with reduced graphene oxide (rGO) greatly improves the operation of microporous carbons easily produced by one-pot activation of grape seeds. The use of composite electrodes with rGO lowers the supercapacitor resistance and enables a much higher rate capability. The mixture of rGO flakes and particles of a highly porous carbon obtained by KOH activation allows retaining the high capacitance of 260 F g−1 of the standard electrodes at 1 mA cm−2 in aqueous H2SO4 whereas the value at 200 mA cm−2 is increased by around 2.4 times. Consequently, at high current density, the capacitor assembled with these composites stores eight times more energy and the power density is multiplied by four. The synergy between rGO and an ultramicroporous carbon produced by CO2-activation results extremely profitable, the cell assembled with composite electrodes reaching three times more energy and power at 200 mA cm−2 than the best performance of the standard counterpart. More importantly, the higher density of the composite electrodes leads to a capacitance of around 200 F cm−3 which translates into a remarkable improvement in the supercapacitor operation normalized to volume.

This work shows relevant inconsistencies found in a paper recently published in Electrochim. Acta and how the conclusions are challenged by a more detailed textural characterization of a microporous carbon monolith.

A comprehensive comparison of symmetrical supercapacitors assembling carbon electrodes with exclusively microporous, mesoporous or combined micro-mesoporous networks provides a critical outlook on the influence of pores size on the performance with ionic liquid-based electrolyte 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIm-TFSI) dissolved in acetonitrile. Contrary to widespread claims, the results for an electrodes set involving carbons of different origin indicate that the presence of large pores does not ensure a better supercapacitor performance. At low current density, the capacitance is basically determined by the surface in pores above 0.8 nm, regardless of the pore size distribution. In addition, the beneficial effect of large pores on the response rate of the supercapacitor cannot be concluded in a straightforward manner. On the contrary, wide porosity in electrodes has detrimental effects that should not be underestimated as far as the competitiveness of the final device is concerned. The greater amount of electrolyte required by larger pores will increase both the weight and the cost of the cell. More importantly, the widening of carbon pores (even in the range of micropores) notably reduces the density of the corresponding electrodes and, consequently, the supercapacitor performance in volumetric terms may not be suitable for practical applications.

An efficient alternative for the management and valorization of the huge amount of seasonal wastes generated by winery industries is shown. Sustainable porous carbons were successfully prepared by one-pot activation of grape bagasse, stalks and oil free-seeds. Benefiting from the high moisture of these residues, a prior hydrothermal carbonization increases the activation yield and generates carbons with less oxygen content and inorganic impurities. The mild physical or chemical activation of winery wastes resulted in highly microporous carbons with specific surface SBET up to 2053 m2/g and great potential for environmental protection and electrical energy storage. They are excellent sorbents for CO2 capture under post- and pre-combustion conditions (16 and 69 wt%, respectively) and achieve superior electrochemical capacitance of nearly 300 F/g in aqueous electrolyte and 180 F/g in ionic liquid based-medium.

The successful tailoring of the ultramicroporosity remarkably increases the CO2 uptake capacity of low cost-carbons derived by a simple one-pot physical activation of olive stones, coffee grounds, almond shells and grape seeds. A porous network dominated by ∼40–46% of ultramicropores below 0.5 nm and no significant presence of pores above 0.7 nm boosts the CO2 uptake at 1 bar and 298 K around 40% compared to materials with similar micropore volume. A slight ultramicropore widening causes the drop to a standard pattern that depends mainly on the micropore volume. The detailed analysis of the CO2 isotherms within the Dubinin´s theory provides simple clues for the optimization of carbons for CO2 capture at ambient temperature and atmospheric pressure. Thus, a general pattern of around 7.2 mmol of CO2 captured per cm3 of ultramicropores is found for a variety of activated carbons and carbide derived-carbons with characteristic energy Eo of 29–22 kJ/mol. This feature is typical of materials with average micropore sizes from 0.65 to 1 nm. An enhancement of up to 10 mmol CO2/cm3 is achieved by carbons with Eo ranging between 30 and 32 kJ/mol which correlates with an extremely homogeneous porosity with average dimensions around 0.5 nm. The excellent fit of the present carbons into general patterns exclusively based on the textural features reveals no significant influence of their surface functionalities on the CO2 adsorption performance.

This research is focused in the missing link between the specific surface area of carbons surface and their electrochemical capacitance. Current protocols used for the characterization of carbons applied in supercapacitors electrodes induce inconsistencies in the values of the interfacial capacitance (in F m−2), which is hindering the optimization of supercapacitors. The constraints of both the physisorption of N2 at 77 K and the standard methods used for the isotherm analysis frequently lead to a misleading picture of the porosity. Moreover, the specific surface area of carbons loses their meaning when the supercapacitor operates with organic electrolytes and ionic liquids and the actual surface involved in charge storage has to be assessed by molecular probes suiting the critical dimensions of the ions. In the case of certain carbons such as graphene type-materials, the voltage-driven mechanism may facilitate the access of electrolyte ions to spaces between carbon layers, providing a larger area than that estimated by gas adsorption. Finally, the morphological and porous features of carbons can be extremely modified when they are processed in electrodes. Due to their impact, all these issues should not be neglected and the characterization protocols must be adapted for this specific application of carbons.

In this work, the incorporation of dicyanamide building blocks in organic–inorganic hybrid compounds is found to be a promising strategy for the synthesis of multiwalled carbon nanotubes embedded with magnetic nanoparticles (M@CNTs). Following a novel one-step, scalable and fast synthetic route, M@CNTs are obtained by simple calcination of the organic–inorganic hybrid perovskite [TPrA][M(dca)3] (TPrA = tetrapropylammonium, M = Ni2+ and Co2+, dca = dicyanamide). The resulting M@CNTs (M = Ni and Co) display a regular morphology and an essentially mesoporous network of ∼250 m2 g−1, whereas the Co@CNT composite displays a broad pore size distribution (PSD) up to 6 nm, Ni@CNTs show a strictly controlled unimodal PSD, centered at around 5 nm. Monitoring of their thermal decomposition by X-ray diffraction, electron microscopy, thermogravimetric and spectroscopic analyses allows proposing a calcination mechanism and establishing the conditions to obtain optimal materials. Moreover, magnetization studies reveal a ferromagnetic behaviour of the obtained M@CNTs, with small coercive fields due to the size of the magnetic nanoparticles. In addition, preliminary assays of oil adsorption–desorption capacity reveal a promising potential for spilled oil recovery using this easily-synthesized materials. All these physicochemical properties make these composites good candidates for other nitrogen-rich CNT common applications.

Carbon based-supercapacitors are widely used in numerous applications but the knowledge of the specific role of carbon features in their performance is still insufficient. The main aim of this work is to warn readers that the current interpretation of the device operation, mostly based on powdered carbon properties, may be misleading in certain cases and should be complemented with the physicochemical characterization of the corresponding electrodes. Ordered mesoporous carbons highly enriched in surface functionalities were prepared by carbonization of 3-aminobenzoic acid into SBA-15 template. These carbons achieved a specific capacitance as high as 220 F/g in 2 M H2SO4 aqueous electrolyte. The pseudocapacitance contribution ranged between 35 and 70% of the overall capacitance. It was shown that the structural and textural changes underwent by these advanced carbons during their processing in form of electrodes prevented the full exploitation of their outstanding properties for high-power applications. This makes a difference regarding conventional, disordered activated carbons, which virtually preserve their structure during electrode preparation.

Helical-ribbon carbon nanofibers produced on an industrial scale were successfully converted in highly functionalized graphene nanoplatelets by using a slight modification of the Hummers oxidation method. The duration of the oxidative process severely affected the interlayer spacing in the resulting nanoplatelets and, consequently, they showed very different exfoliation behavior. Therefore, it was possible to obtain a variety of graphene-related products through their ultrasonication or thermal treatments such as exfoliation-reduction by flash-pyrolysis in air at temperatures between 400 and 1000 °C or standard activation with CO2 at 800 °C. Detailed comparison of the functionalized carbon nanoplatelets, graphene oxides, reduced graphene oxides and activated carbon nanoplatelets reveals the wide spectrum of their properties with specific surface areas in the range of 4–500 m2 g−1, oxygen content from 38 to 5 wt% and different structural ordering. This study also underlines the impact of the structural, textural and chemical changes experienced by the carbon nanofibers along the various processes on the performance as supercapacitor electrodes. This preliminary study, based on cyclic voltammetry in 2 M H2SO4 aqueous electrolyte, is a summary of the strengths and weaknesses of the different graphene-related materials for this application. The helical-ribbon carbon nanofibers displayed only 10 F g−1, the capacitance of the functionalized graphene nanoplatelets greatly rose to 104 F g−1 with clear contributions from pseudocapacitance. Values around 100–120 F g−1 were found for the graphene oxides and activated graphene nanoplatelets although a marked resistive character is detected. Flash-pyrolysis at 1000 °C leads to lower capacitance (79 F g−1) but much quicker charge propagation. Among all these materials, the lower-cost functionalized graphene nanoplatelets displayed the better behavior for aqueous supercapacitors.

The results obtained for binder-free electrodes made of carbon monoliths with narrow micropore size distributions confirm that the specific capacitance in the electrolyte (C2H5)4NBF4/acetonitrile does not depend significantly on the micropore size and support the foregoing constant result of 0.094 ± 0.011 F m−2.

All rights reserved. Biocarbon monoliths were obtained from Eucalyptus grandis and the influence of wood anisotropy on the electrical and electrochemical performance as supercapacitor electrodes was studied. They were produced from wood pieces cut along the transversal and longitudinal direction of the tree trunk, followed by pyrolysis and, for some of them, also by activation with CO2. Monoliths with drilled channels were also obtained. All the monoliths were characterized by SEM, nitrogen adsorption/desorption isotherms, electrical conductivity measurements and electrochemical measurements, the latter in 2M aqueous H2SO4 electrolyte. Electrical conductivity and specific capacitance are higher for the transversal carbon monoliths than for the longitudinal ones. The electrical conductivity reaches values up to 27 S cm-1 for the transversal monolith. The specific capacitance reaches values up to 260 F g-1for the transversal monolith that was activated and drilled. However, the highest volumetric capacitance, of 90 F cm-3, is found for the longitudinal monolith that was activated and non-drilled. The energy density and power density, both referred to gravimetric and volumetric magnitudes, reach values as high as 36 Wh kg-1 and 12 Wh L-1, and 2181 W kg-1 and 783 W L-1, respectively. Comparison with a commercial powder activated carbon is provided.

A graphite oxide, obtained on a large scale at low cost as an intermediate in the graphene production, achieves specific capacitances (159 Fg−1 in H2SO4 and 82 Fg−1 in (C2H5)4NBF4 in acetonitrile) that compete with those of activated carbons and largely surpass the values obtained with graphene nanoplatelets. More promising, the high electrode density leads to volumetric capacitances of 177 and 59 F cm−3 in the aqueous and the organic electrolytes, respectively, which are above most data reported for carbons. In the aqueous electrolyte, the graphite oxide stands out on energy density when compared to graphene nanoplatelets and on power capability if compared to an activated carbon commercialized for supercapacitors, whereas in the organic electrolyte, the limited interlayer spacing restricts the mobility of the larger ions into the expanded graphitic structure. This study also illustrates that the specific surface of carbons measured by standard gas adsorption may not be a relevant parameter as it does not always match the electrochemically active area involved in the energy storage.

Specific capacitance of carbons in aqueous KOH electrolyte seems to have two contributions, a double-layer capacitance and a pseudocapacitance. Moreover, the specific capacitance increases as the specific surface area does. Here, we report that the pseudocapacitance is associated with the K+ ion and the double-layer capacitance with both K+ and OH- ions. The former ion dominates the capacitance of a real two-electrode supercapacitor. Two microporous carbon monoliths with surface areas similar for micropores below 0.63 nm but different for larger micropores are chosen. There is a correlation between the double-layer capacitance due to those ions and the surface areas due to micropores with sizes above a certain value. It provides information on the size of those ions as they are electroadsorbed at the double layer. The dielectric permittivity associated with the K+ and OH - ion is discussed in relation to the confinement of these electroadsorbed ions in the micropores. © 2014 American Chemical Society.

This paper examines the recovery of carbon fibres from a composite used in the aeronautical industry, via a combined process of thermolysis and gasification in an air atmosphere. The waste was thermolysed at 500 C, 600 C or 700 C in a pilot plant to determine the optimum thermolysis temperature. The solid residues produced - char covered carbon fibres - were characterized by SEM and XPS. The optimum time for the gasification of the char covering the fibres was determined in a combined thermolysis/gasification assay. After thermolysis at the optimum temperature (500 C), 12 l/h of pure air were injected into the reactor and char gasification performed at 500 C for 30-180 min. The optimum gasification time was 30 min. Longer gasification times led to the production of fibres of smaller diameter with oxidized surfaces and reduced tensile strength. The optimally recovered fibres showed about 70% of the tensile strength of virgin fibres and some 90-96% of their elasticity. © 2013 Elsevier B.V. All rights reserved.

Chars were obtained by the pyrolysis of waste wood samples of different origin - silver fir (Abies alba), holm oak (Quercus ilex), stone pine (Pinus pinea) and Pyrenean oak (Quercus pyrenaica) - at 600 ÌŠC in a pilot scale installation. The thermo-chemical characteristics of the resulting materials were fully investigated using a combination of standard techniques. The char yield ranged from 23 wt% to 29 wt%, depending on the precursor wood. The recovery of C achieved was 42-51 wt%, increasing with the hemicellulose content of the wood. In addition, the chars had low volatile matter (8-12 wt%) and ash (2.0-8.5 wt%) contents. The higher heating values of the chars were relatively high (31-35 MJ kg-1) and comparable to that of a semi-anthracite (silver fir and stone pine chars) or medium-volatile bituminous coal (holm and Pyrenean oak chars). Their combustion intervals, and ignition, volatilization and burnout temperatures, were similar to those of commercial coals. The chars had a microporous structure (pore size < 2 nm) with BET surface areas in the range 314-405 m2 g-1. Their treatment by CO2 at 800 ÌŠC resulted in activated carbons with pore sizes below 0.89 nm and BET surface areas of 543-815 m2 g -1. © 2013 Elsevier B.V. All rights reserved.

The char produced in the thermolysis of granulated scrap tyres has few market outlets, reducing the economic viability of the thermolytic process. This paper reports the potential of this char as a low-cost precursor of porous carbons. The tyre-derived char was demineralized in either alkaline or acidic media to reduce its ash, zinc, sulfur, and silica contents. The lowest impurity content was achieved with an HNO3/H2O treatment. The resulting demineralized char was then subjected to activation by KOH or CO2. The Brunauer-Emmett-Teller (BET)-specific surface area of the activated carbon produced by the KOH treatment was 242 m2/g, whereas that of the CO2-activated carbon was 720 m2/g. The textural properties of the latter product were similar to those of some commercial activated carbons. The use of tyre-derived char as a precursor of porous carbons could render the thermolytic treatment of scrap tyres more economically attractive.

The optimization of carbon-based supercapacitors is of great technological importance for electrical energy storage. This challenge stresses the relevance of current attempts to increase the surface-related capacitance C/S (F m−2) of carbons. We show that for microporous carbons this property is practically constant for pore widths between 0.7 and 1.8 nm. The study is based on two independent approaches: (i) the effective surface area accessible to the ions, which may differ considerably from the BET-surface and (ii) the volumetric capacitance in the micropores. One obtains 0.094 F m−2 in (C2H5)4NBF4/acetonitrile and approximately 0.100 F m−2 in aqueous H2SO4 after correcting for pseudo-capacitance effects. This pattern is supported by recent modelling which takes into account the solvent. It is also suggested that constant values of the surface based-capacitance may reflect a gradual decrease of the dielectric constant of the electrolytes in smaller micropores due to desolvation.

[EN] Pyrolysis is a technology with a promising future in the recycling of scrap tyres. This paper determines the thermal decomposition behaviour and kinetics of granulated scrap tyres (GST) by examining the thermogravimetric/derivative thermogravimetric (TGA/DTG) data obtained during their pyrolysis in an inert atmosphere at different heating rates. The model-free methods of Friedman, Flynn-Wall-Ozawa and Coats-Redfern were used to determine the reaction kinetics from the DTG data. The apparent activation energy and pre-exponential factor for the degradation of GST were calculated. A comparison with the results obtained by other authors was made.

[EN] The influence of thermolysis temperature (range 500–700 °C) on the products produced from granulated scrap tyres (GST) (2–6 mm Ø) in a semi-batch pilot plant that uses several fixed bed reactors in parallel (GRAUTHERMIC-Tyres® process) was examined. This pilot unit consisted of six vertical fixed bed reactors in parallel, each with a capacity of 12 kg GST. Thermolysis proceeded in a normal air atmosphere. The solid (char), liquid (tyre-derived oil [TDO]) and gaseous products generated at each temperature were characterised. The incondensable gas fraction was used to produce electricity via a gas turbine. The yields of the gas, TDO and char fractions were 15–22 wt.%, 34–46 wt.% and 39–44 wt.% respectively, values that represent major recoveries from the GST feedstock. The TDOs were mainly a mixture of aliphatic and aromatic hydrocarbons and had very high GCVs (41–43 MJ/kg), higher than those of conventional liquid fuels. A large increase was seen in the polycyclic aromatic hydrocarbon content above 550 °C. The non-condensable gases obtained had a high GCV value (64–83 MJ/Nm3), and produced 4.1–6.5 kWh electricity/g of GST in a gas turbine. The chars had a GCV of 27–28 MJ/kg, high ash (17–21 wt.%) and zinc contents, and an essentially macroporous texture with a low BET surface area (46–78 m2/g). The thermolysis of GSTs with co-generation of gases by the GRAUTHERMIC-Tyres® method would appear to be a viable means of valorising GST.

[EN] This study analyses and compares the behaviour of 5 commercial porous carbons in the ionic liquid N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR14TFSI) and its mixture with propylene carbonate (PC) as electrolytes. The results of this investigation show that the existence of a distribution of pore sizes and/or constrictions at the entrance of the pores leads to significant changes in the specific capacitance of the investigated materials. The use of PYR14TFSI as an electrolyte has a positive effect on the EDLC energy storage, but its high viscosity limits the power density. The mixture 50 : 50 wt% propylene carbonate–PYR14TFSI provides high operative voltage as well as low viscosity and thus notably enhances EDLC operation.

Highly porous carbons were obtained from solid wastes generated in the chemical and the mechanical processing of birch wood (substandard kraft cellulose, hydrolysis lignin, chips and bark). NaOH-chemical activation of these residues at 575–800 °C resulted in an efficient process to produce carbons with specific surface areas well above 1000 m2 g−1 and average pore widths of 1–1.7 nm. Comparative evaluations have shown the potentiality of wood wastes-based carbons in applications related to environmental protection. Activated carbons derived from chips- and bark-birch wood displayed specific capacitances as high as 308 F g−1 in the H2SO4 aqueous electrolyte and 200 F g−1 in the (C2H5)4NBF4/acetonitrile organic medium. Moreover, their capacitive performance at high current density competed well with that found for commercial carbons used in supercapacitors. Wood-derived carbons also proved to be highly promising for CO2 capture in power stations, achieving uptakes under post- and pre-combustion conditions of 11–16 wt.% and 49–91 wt.%, respectively.

The study of 26 microporous carbons with average pore widths Lo between 0.7 and 1.8 nm shows that the volume-related capacitance Cmi (F cm− 3) in the organic electrolyte (C2H5)4NBF4/acetonitrile is an inverse function of the average micropore width Lo. This means that for a given micropore volume Wo, the gravimetric capacitance C (F g− 1) is larger for carbons with smaller pores due to the higher surface to volume ratio. Furthermore, the increase of Cmi (F cm− 3) in smaller pores suggests that the surface-related capacitance C (F m− 2) should be relatively constant in slit-shaped micropores. This has important technological consequences for the design of carbon-based supercapacitors.

[EN] This work reports the effect of pressure on the steam/oxygen gasification at 1000 °C of the char derived from low temperature–pressure distillation of granulated scrap tyres (GST). The study was based on the analysis of gas production, carbon conversion, cold gas efficiency and the high heating value (HHV) of the product. For comparison, similar analyses were carried out for the gasification of coals with different rank. In spite of the relatively high ash (≈12 wt.%) and sulphur (≈3 wt.%) contents, the char produced in GST distillation can be regarded as a reasonable solid fuel with a calorific value of 34 MJ kg−1. The combustion properties of the char (EA ≈ 50 kJ mol−1), its temperature of self-heating (≈264 °C), ignition temperature (≈459 °C) and burn-out temperature (≈676 °C) were found to be similar to those of a semi-anthracite. It is observed that the yield, H2 and CO contents and HHV of the syngas produced from char gasification increase with pressure. At 0.1 MPa, 4.6 Nm3 kgchar−1 of syngas was produced, containing 28% v/v of H2 and CO and with a HHV around 3.7 MJ Nm−3. At 1.5 MPa, the syngas yield achieved 4.9 Nm3 kgchar−1 with 30% v/v of H2–CO and HHV of 4.1 MJ Nm−3. Carbon conversion significantly increased from 87% at 0.1 MPa to 98% at 1.5 MPa. It is shown that the char derived from distillation of granulated scrap tyres can be further gasified to render a gas of considerable heating value, especially when gasification proceeds at high pressure.

Procedimiento e instalación para el tratamiento de neumáticos granulados fuera de uso a través de un proceso de destilación de los materiales poliméricos que componen los neumáticos fuera de uso, tales como caucho natural y sintético; y de la gasificación del residuo sólido o negro de carbono.

[EN] The invention relates to a method and unit for processing granulated end-of-life tyres using a process comprising: distillation ofthe constituent polymer materials ofthe end-of-life tyres, such as natural and synthetic rubber; and gasification ofthe carbon black or solid residue., [ES] Procedimiento e instalación para el tratamiento de neumáticos granulados fuera de uso a través de un proceso de destilación de los materiales poliméricos que componen los neumáticos fuera de uso, tales como caucho natural y sintético; y de la gasificación del residuo sólido o negro de carbono.

This paper examines the surface-related capacitance C/S of carbons with average micropore widths between 0.73 and 1.80 nm, using 1–2 M H2SO4, 6 M KOH and 1 M (C2H5)4NBF4 in acetonitrile as electrolytes. Following corrections for pseudocapacitance effects for the aqueous electrolytes and the use of an average surface area suggested by independent techniques, different from the BET area, it appears that C/S is practically independent of the micropore width. The analysis of the data with the help of recent models suggests that the dielectric constants ɛr of the different electrolytes may decrease with the pore size. It is surprising that the coexistence of two sets of values for the surface area of microporous carbons and its consequence on C/S have not received more attention in the past.

The study of 28 porous carbons shows that the specific capacitance in the electrolyte (C2H5)4NBF4/acetonitrile is relatively constant between 0.7 and 15 nm (0.094 ± 0.011 F m−2). The increase in pores below 1 nm and the lower values between 1 and 2 nm reported earlier are not observed in the present work.

[EN] This paper reports the pyrolytic treatment of granulated scrap tires (GST) in a pilot distillation unit at moderate temperature (550 °C) and atmospheric pressure, to produce oil, char and gas products. Tire-derived oil is a complex mixture of organic C5–C24 compounds, including a very large proportion of aromatic compounds. This oil has a high gross calorific value (∼43 MJ kg−1) and N and S contents of 0.4% and 0.6%, respectively, falling within the specifications of certain heating fuels. The distillation gas is composed of hydrocarbons; methane and n-butane are the most abundant, investing the distillation gas with a very high gross calorific value (∼68 MJ N m−3). This gas is transformed into electric power by a co-generation turbine. The distillation char is mostly made of carbon but with significant inorganic impurities (∼12 wt%). The quality of the solid residue of the process is comparable to that of some commercial chars. The quantity of residual solids, and the qualities of the gas, liquid and solid fractions, are similar to those obtained by conventional pyrolytic treatments of waste tires. However, the simplicity of the proposed technology and its low investment costs make it a very attractive alternative.

[EN] This work deals with the preparation and characterization of carbon materials that display a variety of structural characteristics by means of the templating technique and catalytic graphitization. Their behaviour as electrodes in electrochemical capacitors or as electrocatalytic supports is also studied. In the first part of the work mesoporous carbon materials were prepared by means of the templating technique. For this purpose, HMS mesostructured silica was used as template. The structural characteristics of the silica materials and, consequently, of the carbon materials were controlled by modifying the synthesis temperature of the silica and by carrying out hydrothermal post-treatment. Carbon materials prepared in this way are characterized by a high textural porosity (~ 50 % of total pore volume corresponds to the textural porosity) and a tunable pore size (~ 2 – 11 nm). Their behaviour as electrodes in electrochemical capacitors was studied. The results showed the influence of both the total surface area and oxygen content on their performance in an electrochemical capacitor. In the second part of the work graphitic mesoporous carbon materials were prepared by combining the templating and the catalytic graphitization techniques. A mesoporous silica xerogel was used as template and different non-graphitizing polymeric precursors were employed as carbon source (polyfurfuryl alcohol, phenolic resin and sucrose). In this case, the structural characteristics of the carbon materials were controlled by modifying the carbon precursor, the catalyst, the amount of catalyst used, the precarbonization temperature and the final carbonization temperature. The carbon materials obtained are characterized by an accessible porosity, a high surface area (up to ~ 1000 m2•g-1), a high pore volume (0.3 – 1.40 cm3•g-1), and a high proportion of graphitic structures. The final part of the work was focused on the preparation of graphitic carbon nanostructures (capsules, ribbons, [ES] En la presente memoria se plantea la preparacion y caracterizacion de materiales de carbono con diferentes caracteristicas estructurales mediante el empleo de las tecnicas de nanomoldeo y grafitizacion catalitica. Asi mismo, se estudia el comportamiento de los materiales preparados como electrodos de condensadores electroquimicos o como soportes de electrocatalizadores. En la primera parte del trabajo se estudio la preparacion de materiales de carbono mesoporoso mediante la tecnica de nanomoldeo. Para ello, se empleo como nanomolde una silice mesoestructurada de tipo HMS. Las caracteristicas estructurales de los materiales de silice y, por consiguiente, de los materiales de carbono, han sido controladas mediante la modificacion de la temperatura de sintesis de la silice y mediante la realizacion de un tratamiento hidrotermal adicional. Los materiales de carbono asi preparados se caracterizan por poseer una elevada porosidad textural (~ 50 % del volumen total de poros corresponde a la porosidad textural) y un tamano de poro controlable (~ 2 – 11 nm). A continuacion, se estudio el comportamiento de estos materiales como electrodos en condensadores electroquimicos, mostrando la influencia que tienen, tanto su superficie total como su contenido en grupos oxigenados, sobre dicho comportamiento. En una segunda parte del trabajo se sintetizaron materiales grafiticos de carbono mesoporoso mediante la combinacion de las tecnicas de nanomoldeo y grafitizacion catalitica. Como nanomolde se empleo un xerogel de silice mesoporosa y como fuente de carbono diferentes precursores polimericos no grafitizables (alcohol polifurfurilico, resina fenolica y sacarosa). En este caso, el control de las caracteristicas estructurales de los materiales de carbono se realizo mediante la modificacion del precursor de carbono, el catalizador y la cantidad de catalizador empleada, la temperatura de precarbonizacion y la temperatura final de carbonizacion. Estos materiales de carbono se caract

This study shows that standard techniques used for carbons characterization, such as physical adsorption of CO2 at 273 K and N2 at 77 K, can be used to assess, with a good accuracy, the maximum capacity of carbons to capture CO2 under post- and pre-combustion conditions. The analysis of the corresponding adsorption isotherms, within the general theoretical framework of Dubinin's theory, leads to the values of the micropore volume, Wo, and the characteristic energy, Eo, of the carbons, which provide direct information on the equilibrium CO2 uptake of the carbons at different pressures and temperatures. Although in special cases slightly higher values can be obtained, an overall assessment of the textural parameters for a large variety of activated carbons, indicates that a CO2 uptake upper-bound around 10–11 wt% seems to be realistic for standard activated carbons under post-combustion conditions. In the case of pre-combustion conditions, this limit would not exceed 60–70 wt%.