Hierarchical porous carbons (HPC) were fabricated from lignin by hard template method using Beta and Y zeolites as templates. Textural properties were dictated by the hard template, obtaining a ...bi-modal pore size distribution with similar micropore sizes but different mesopore sizes. These HPCs provide a well-connected and developed porosity that show capacitance values near to 140 F g−1 in 1 M H2SO4 at 1 A g−1 and a capacitance retention of ca. 50% and 40% when the specific current is increased from 1 to 64 A g−1 for the Y and the Beta-based carbons, respectively. A symmetric capacitor working at 1.2 V with energy densities of 4.2 Wh kg−1 at 1.3 kW kg−1 has been obtained using the Beta-based HPC. Asymmetric in mass design allowed to operate the capacitor safely at 1.4 V, yielding an energy density of 6.3 Wh kg−1 at 1.3 kW kg−1, an increase of 50% with respect to the symmetric configuration, while keeping a maximum power near to 50 kW kg−1. This capacitor has an energy density comparable to that of a symmetric supercapacitor built using a commercial activated carbon of much higher porosity development, outperforming it in terms of energy, coulombic efficiencies and maximum power.
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•Green supercapacitors constructed with lignin-based HPC in aqueous electrolyte.•Asymmetric design allowed to safely expand the voltage to 1.4 V.•Performance comparable to commercial activated carbon in spite of its lower porosity.•Higher power densities can be achieved with the HPC compared to commercial AC.
In this study, the production of activated carbon (AC) through the chemical activation of waste tire (WT) using H3PO4 and KOH for H2 production by SCWG of oily sludge (OS) donated by Persian Gulf ...Star Oil Company was investigated. H3PO4 was the best activating agent based on some pretests results, and then the synthesis of AC was optimized using Response Surface Methodology. Based on BET surface area of synthesized ACs, thirty combinations of the four variables namely; activation temperature (350–550 °C); activation time (1–4 h); H3PO4 to WT ratio (1–3 w.w−1); and H3PO4 concentration (20–40 wt%) were optimized. CHNS, TGA, FE-SEM, and EDS-mapping analyses were used to characterize the AC and catalyst synthesized in optimum condition (activation temperature: 450 °C; activation time: 2.5 h; H3PO4 to WT ratio: 2 w.w−1; and H3PO4 concentration: 40 wt%), which presented a surface area of 170 m2 g−1. Finally, Ni was impregnated on the optimized AC with different loadings (5–15 wt%) to evaluate its performance in H2 production by SCWG of OS. Although H2 yield in catalytic experiments was higher than that observed in non-catalytic experiment, results showed that the maximum H2 selectivity was 66% in SCWG of OS using AC impregnated with 10 wt% Ni.
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•The effect of activation condition on AC performance in SCWG was investigated.•Total produced gas increased with both WT-derived AC activated by KOH and H3PO4.•H3PO4 was found to be the best activator based on SCWG of OS experiments.•Ni10%/OAC increased both total produced gas and H2.•The highest amount of H2 was found to be 1.80 mmol.gfeed−1.
Biomass valorization to produce fuels and platform chemicals is one of the most relevant strategies to change the energetic scenario and the currently unsustainable petrochemical industry. Pyrolysis ...offers the possibility of integrating biomass-derived oils (bio-oil) into this well-established industry, and the adaptation of already in-use technology, as hydrotreatment units, eases this transition. This new concept of biorefinery could also be improved from an environmental point of view by using carbon-based catalysts produced from biomass waste. In this work, we have reviewed hydrodeoxygenation (HDO) of bio-oil as a key process for the development of these biorefineries. The most relevant results on HDO mechanisms and catalysts are highlighted, with the main focus on activated carbon-supported catalysts. Special attention has been paid to those variables and requirements for a potential industrial implementation, such as the use of raw bio-oil, continuous reactors, and available kinetic models in the literature for reactor design. In addition, a final critical revision has been made with the perspectives, main gaps, and challenges for the integration of bio-oil HDO in a biorefinery.
Influence of phosphorus on functionalization of activated carbons with nitric acid has been reviewed in this study. Results indicate that during treatment with nitric acid, phosphorus-containing ...carbons seem to graft more surface nitrogen, particularly as nitro groups, than those without phosphorus, where the nitrogen is found in lower oxidation state. A reaction pathway has been proposed to clarify the oxidation/nitration mechanism of phosphorus-containing carbons. The model consists of three independent mechanisms occurring simultaneously, with each one involving different phosphorus species present in the activated carbons.
Activated carbons prepared using polyaniline (PAni), a N-containing precursor, doped with different anions were successfully employed in this work as electrode materials for capacitive deionization. ...The aim of this research was to investigate the effect of chloride (Cl−), p-toluenesulfonate (PTS−), dodecylbenze-sulfonate (DBS−) and polystirenesulfonate (PSS−) as PAni dopants on the textural and electrochemical properties of PAni activate carbon (PAC) and evaluate their performance for desalination. It was demonstrated that textural PAC properties such as microporosity could be properly tuned, resulting in a suitable proportion of micro- and mesoporosity by using different doping anions. Furthermore, it was observed that the higher the oxygen content the higher the electrode hidrophilicity due to introduction of surface polar groups, as identified by XPS. These groups were found to be the most important variable influencing on the PAC electrosorption capacity and energy efficiency. The highest specific adsorption capacity (14.9 mg g−1), along with the lowest specific energy consumption, was obtained using the PTS-doped PAC electrode. Considering its high capacity, low-cost and ease of synthesis, PAC/PTS seems to be a promising electrode for CDI.
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•Lignin based activated carbons remove high amounts of SO2 in presence of O2 and H2O.•SO2 adsorption takes place on micropores higher than 7Å except when H2O is presented.•Catalytic ...oxidation of SO2 can be explained by an Eley-Rideal mechanism.•Formation of H2SO4 occurs between SO3 adsorbed and water vapor.•Breakthrough curves are successfully described by the model proposed.
Adsorption of SO2 on an activated carbon obtained by chemical activation of kraft lignin with zinc chloride was studied in a laboratory column. The presence of oxygen and water vapor in the inlet stream increases the SO2 adsorption capacity of the carbon, due to the surface oxidation of the SO2 to SO3 and the subsequent hydration to H2SO4. Desorption of the SO2 chemisorbed at temperatures in the range of 150–300°C produces carbon gasification, forming oxygen surface groups that decompose mainly as CO at higher temperatures (>−500°C). The presence of CO2 in the inlet gas decreases the SO2 adsorption capacity of the carbon. However, the presence of NO does not produce any significant change in the adsorption of SO2, at the studied conditions. The breakthrough curves of the SO2 adsorption are predicted adequately by a rigorous mathematical model that takes into account the catalytic oxidation of SO2 by an Eley-Rideal mechanism and the reaction between adsorbed SO3 and water vapor to produce H2SO4, followed by the elution of the adsorbed H2SO4 that releases the active sites.
Chlorinated organic compounds (COCs) are persistent organic pollutants often found in groundwater near industrial sites or in industrial wastewaters. Adsorption into activated carbon is a common ...strategy to remediate these waters, but spent activated carbon results in a toxic residue to manage. To avoid the transport of the chlorinated compounds out of the site, the in-situ regeneration of the spent activated carbon can be considered for reuse to implement a circular economy. In this work, the regeneration of a commercial granular activated carbon (GAC) has been carried out using thermally activated sodium persulfate (TAP). GAC was previously saturated in 1,2,4-trichlorobenzene (124-TCB) as the model compound. The initial adsorption value was 350 mg124‑TCB·gGAC –1. First, the nonproductive consumption of sodium persulfate was studied at different temperatures using nonsaturated GAC. Then, the regeneration of the saturated GAC (5 g) was studied by an aqueous solution (166 mM) of TAP (1 L) at a temperature range from 20 to 80 °C. The possible recovery of the adsorption capacity was studied after 3 h of treatment in three successive adsorption–regeneration cycles at the selected temperature (60 °C). The physicochemical changes of the GAC were also investigated before and after the regeneration treatments. The results evidence the significant deposition of sulfate on the GAC after each treatment of regeneration, which avoids the recovery of the initial adsorption capacity. Therefore, each regeneration cycle was necessarily followed by a washing step at 60 °C to remove this sulfate. After that, the regeneration treatment achieved a stable and high recovery of the initial adsorption capacity of about 48.2%.
Dehydration of methanol to produce dimethyl ether (DME) was studied at relatively high temperatures (400–600 °C) on biomass-derived phosphorus-containing carbon impregnated with a zirconium salt. ...Highly thermally stable zirconium phosphate surface groups could be obtained on the final catalyst, which were responsible for the high stability and selectivity to DME of the catalyst at temperatures lower than 400 °C. However, harder operation conditions, closer to those of the industrial process, were evaluated to analyze the changes of the catalyst surface properties with the reaction temperature and the possible causes of deactivation. Thus, high methanol conversion and selectivity to DME were also observed in the temperature range of 400–600 °C, although deactivation was detected. Coke deposition was responsible for a decrease in microporosity and surface concentration of zirconium and phosphorus of the catalyst. Temperature-programmed desorption, 31P magic angle spinning nuclear magnetic resonance, and X-ray photoelectron spectroscopy results suggest that the Zr–O–P groups from zirconium phosphate species were responsible for the long-term stability of the catalyst and that the C–O–P-type active sites were deactivated very fast. However, coke deposition on Zr–O–P-type active sites caused a slow and irreversible deactivation, while deposited coke on the C–O–P-type active sites was easily eliminated by the oxidative treatment in air. A reaction scheme that accounted for the gas product distribution and the production of coke was proposed. A kinetic model for coke formation as a function of time on stream that successfully represents the experimental results was also propounded, which yielded a value for the activation energy for the production of coke of 124 kJ/mol.
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