Increasing Carbonization Temperature Research Articles

Developing self-activated lignosulfonate-based porous carbon material for ethylene adsorption

This study applied lignosulfonate as raw material to develop porous carbon for ethylene adsorption, followed by testing for this material's ethylene adsorption efficiency and capacity. The results indicated that the gas released (CH4, H2, CO, and CO2) during pyrolysis could generate a pore structure on lignosulfonate-based carbon surface, regarded as the self-activated mechanism. Pore structure formation increased pore volume and resulted in generation of various pore shapes. When carbonization temperature was less than 800 °C, specific surface area of the samples increased with temperature, and it decreased otherwise. Moreover, with increasing carbonization temperature, the samples’ carbon content increased but hydrogen content decreased. Ethylene adsorption uptake increased as carbonization temperature increased. Adsorption capacity was maximum when carbonization temperature was 800 °C. It was influenced by the pore structure, and specifically, it increased as micropore volume increased. In addition, physical adsorption was the main mechanism of ethylene adsorption for the lignosulfonate-based porous carbon, leading to efficient adsorption-desorption cycles. Finally, its application as an ethylene scavenger can potentially transcend currently available products.

Nickel nanoparticle/carbon catalysts derived from a novel aqueous-synthesized metal-organic framework for nitroarene reduction

Carbon-supported, non-noble metal-based catalysts derived from metal-organic frameworks (MOFs) are attractive alternatives to noble metal-based systems, but typical syntheses of the starting MOFs are not desirable from an environmental and practical perspective (e.g., they rely on non-innocuous organic solvents and long reaction times). Here, we report the preparation of a Ni-based MOF in aqueous medium, at moderate temperature (95 °C) and in a short reaction time (<30 min), which was used as a sacrificial template to access a family of Ni nanoparticle/carbon hybrids that were then tested as catalysts in the reduction of 4-nitrophenol (4-NP). The MOF-derived hybrids exhibited a mesoporous texture, with specific surface areas between ∼250 and 450 m2 g−1 depending on the carbonization temperature applied to the MOF, as well as high Ni contents (between ∼36 and 57 wt%). Notwithstanding the latter, the metal was homogeneously distributed throughout the carbon matrix in the hybrid and was quite resistant to extensive agglomeration and sintering, even at temperatures as high as 1000 °C. With increasing carbonization temperature, the Ni component was seen to go through different crystal phases, i.e., Ni3C phase → Ni hexagonal close-packed phase → Ni face-centered cubic phase. The results of the catalytic tests suggested the former and latter phases to be the most active towards the reduction of 4-NP, with catalytic activity values as high as 0.039 mol4-NP molNi−1 min−1.

The evolution of the structure, mechanical, and gas separation properties of P84 hollow fiber membranes from the polymer to the carbon stage

To provide insight into the formation process of carbon molecular sieve (CMS) hollow fiber membranes (HFMs), P84 co-polyimide HFMs were thermally treated at 200, 250, 300, 350, 400, 550, 650, and 800 °C. TG-MS was used to study the weight loss and released gases at all temperatures. In situ SEM, HIM (helium ion microscope) and in situ XRD were used to investigate the structural evolution of P84 HFMs. The structural evolution and changes in the mechanical properties and gas separation performance of P84 HFMs from the polymer to the carbon stages were divided into three stages (sub-Tg, intermediate, and carbon stages) by their Tg (322 °C) and Td (460 °C). The substructure of P84 HFMs began to collapse during the intermediate stage, which impeded the gas permeance of P84 CMS HFMs. At the carbon stage, the permeance of CO2, O2, N2, and CH4 decreased with the increased carbonization temperature; however, the H2 permeance reached a maximum at 650 °C due to the partial pyrolysis and structural reorganization of P84 CMS HFMs.

2D DUT-8(Ni)-derived Ni@C nanosheets for efficient hydrogen evolution

The development of high-performance, low-cost, and high-stability catalysts for electrocatalytic hydrogen evolution reaction is a key step in the green and sustainable production of hydrogen energy. Herein, we prepared 2D Ni@C nanosheets by high-temperature carbonization of 2D MOFs DUT-8(Ni). It was used as a highly efficient hydrogen evolution catalyst in alkaline solution. We compared the properties of the composites obtained at different carbonization temperatures. It was found that the DUT-8(Ni) was not completely decomposed at low temperatures, and the Ni NPs had lower crystallinity, so the composites show poor electrocatalytic performance. With the increase of carbonization temperature, DUT-8(Ni) was completely decomposed, and the crystallinity of Ni NPs gradually increased, and the electrocatalytic performance gradually improves. However, when the temperature was 800 °C, the electrochemical surface area of the composite reduced, the electrocatalytic performance decreased slightly. The Ni NPs were uniformly embedded on the 2D carbon nanosheets. The carbon nanosheets matrix provides good electrical conductivity. At the same time, the Ni NPs coated the thin graphite carbon layer can effectively prevent particle agglomeration. This method provides an idea for the preparation of 2D high-performance electrocatalysts.

Strategies for Scalable Gas-Phase Preparation of Free-Standing Graphene

The preparation of graphene with high quality serves as a prerequisite for its usage. Traditional methods of graphene production, represented by liquid-phase exfoliation and chemical vapor depositi...

Alterations of the Chemical Compositions, Surface Functionalities, and Nitrogen Structures of Cage Layer Chicken Manure by Carbonization to Improve Nitrogen Bioavailability in Soil

Carbonization of cage layer chicken manure (CLCM) can improve its bio-recalcitrance which might improve nitrogen (N) bioavailability in soil. However, temperature(s) to exhibit appropriate variations in the chemical makeup of the manure during carbonization in order to achieve this objective is unknown. In this study, we investigated the alterations in chemical compositions, surface functionalities, and N speciation initiated by different carbonization temperatures (350, 500, and 650 °C) and the effects of these alterations on N bioavailability in soil. The objective was to identify suitable temperature condition(s) for the conversion of CLCM into a carbonized product of appropriate bio-recalcitrance that is capable of improving N bioavailability in soil more than the un-carbonized CLCM. The results showed an increased bio-recalcitrance of the manure with increasing carbonization temperatures due to drastic changes in the chemical makeup and accumulation of heterocyclic aromatic N structures. Subsequently, these alterations in the chemical makeup and state of the organic N species in the manure affected N bioavailability in soil. Notably, N bioavailability of CLCM and benefits on plants were improved when soil was supplied with CLCM that was altered at 350 °C. With these observations, we concluded that alterations in chemical and surface structural compositions and N speciation at 350 °C are optimum for instituting the required bio-recalcitrance to CLCM in order to improve N bioavailability in soil for plants.

Multistage Self-Assembly Strategy: Designed Synthesis of N-doped Mesoporous Carbon with High and Controllable Pyridine N Content for Ultrahigh Surface-Area-Normalized Capacitance

Nitrogen doping could improve the performance of carbon materials in electrocatalysis, CO2 adsorption, and energy storage. [1]However, the control of the doping type and the amount of nitrogen (N)-...

Immobilization of Hg(II) on high-salinity Spirulina residue-induced biochar from aqueous solutions: Sorption and transformation mechanisms by the dual-mode isotherms

Removal of Hg(II) by biochar (BC) is a promising remediation technology. The high-salinity Spirulina residue (HSR) is a hazardous waste generated during extracting the pigment phycocyanin under high salinity conditions. Although HSR-derived BC (HSRBC) exhibited the excellent sorption capacity of Hg(II), the involved mechanisms have been rarely studied. In this study, we investigated the specific properties and Hg(II) sorption mechanisms of HSRBCs. Chloride and calcium minerals were formed in HSRBCs. Increments in carbonization temperature (from 350 to 700 °C) or time (from 90 to 540 min) led to the enhancement of aromaticity, porosity, and positive charge, but cracked oxygen-containing groups and C–N bonds. Further increase in carbonization temperature or time decreased the sorption of Hg(II). At environmentally relevant concentration of Hg(II) (2–4 mg/L), the sorption capacity (6.1–12.7 mg/g) obtained in HSRBC350 was comparable to activated carbon. Based on dual-mode isotherm, surface sorption accounted for 75–88% uptake, while precipitation accounted for 12–25% uptake. In addition, the C–O, CO, and CC groups were responsible for the monodentate/bidentate complexation and reduction, while Cl− triggered Hg2Cl2 precipitation. Overall, this study provided a new insight in creating an excellent Hg(II) sorbent from hazardous waste, and revealed the sorption mechanisms for Hg(II) uptake.

Carbon Nanofibers Production via the Electrospinning Process

Electrospun fibers with different concentrations of polyacrylonitrile (PAN) were synthesized and the results are reported in this study. The aim was to obtain carbon nanofibers for manufacturing gas diffusion layers for proton exchange membrane (PEM) fuel cells. The electrospun fibers obtained were carbonized at 1200 °C, 1300 °C, and 1400 °C, in order to have nanofibers with more than 96% of carbon atoms. The scanning electron microscopy (SEM) results revealed an increase in the diameter from 400–700 nm at 1200 °C to 1000–1400 nm at 1300 °C and 1400 °C. The Raman measurements disclose a higher degree of crystallinity for the sample carbonized at elevated temperatures. The surface area was estimated from the Brunauer–Emmett–Teller (BET) method and the results revealed an increase from 40.69 m2g−1 to 66.89 m2g−1 and 89.92 m2g−1 as the carbonization temperature increased. Simultaneously, the pore volume increased with increasing carbonization temperature. The Fourier-transform infrared spectroscopy (FTIR) spectra reveal that during carbonization treatment, C≡N triple bonds are destroyed with the appearance of C=N double bonds. Decreasing the ID/IG intensities’ ratio from ~1.07 to ~1.00 denotes the defects reduction in carbonaceous materials due to the graphitization process. Therefore, the carbon fibers developed in optimum conditions are appropriate to be further used to produce gas diffusion layers for Proton-exchange membrane fuel cells (PEMFC).

Development and Characterization of Activated Carbons Derived from Lignocellulosic Material

Activated carbon is a multipurpose material due to its unique properties such as high surface area and pore volume. The reduced carbon source from coal has led to the development of activated carbon from lignocellulosic material. However, there is limited literature reported the use of swat bamboo (Gigantocholoa verticillata) as an activated carbon precursor. In this research, swat bamboo has been converted to activated carbons under different carbonization temperatures of 550, 650, and 750OC and activation durations of 1.5 and 2 h. The results show that at activation time of 1.5 h, increasing carbonization temperature affecting the higher pore volume and surface area gained. The optimal characteristics of activated carbon were obtained at a carbonization temperature of 750OC and activation time of 1.5 h. This due to the activated carbon produced in this condition has the highest pore volume, surface area, and adsorption capacity of 0.138 cm3/g, 135.30 m2/g, and 95.776 cm3/g, respectively. Its average pore diameter was 2.053 nm with fix carbon of 75.26% and C of 76.79%. It has a monomodal pore size distribution with the highest adsorption of 0.056 cm3/g/nm occurred at a pore size of 1.516 nm.

Functionalized Cellulose for the Controlled Synthesis of Novel Carbon-Ti Nanocomposites: Physicochemical and Photocatalytic Properties.

Carbon–Ti nanocomposites were prepared by a controlled two-step method using microcrystalline cellulose as a raw material. The synthesis procedure involves the solubilization of cellulose by an acid treatment (H3PO4 or HNO3) and the impregnation with the Ti precursor followed of a carbonization step at 500 or 800 °C. The type of acid treatment leads to a different functionalization of cellulose with phosphorus- or oxygen-containing surface groups, which are able to control the load, dispersion and crystalline phase of Ti during the composite preparation. Thus, phosphorus functionalities lead to amorphous carbon–Ti composites at 500 °C, while TiP2O7 crystals are formed when prepared at 800 °C. On the contrary, oxygenated groups induce the formation of TiO2 rutile at an unusually low temperature (500 °C), while an increase of carbonization temperature promotes a progressive crystal growth. The removal of Orange G (OG) azo dye in aqueous solution, as target pollutant, was used to determine the adsorptive and photocatalytic efficiencies, with all composites being more active than the benchmark TiO2 material (Degussa P25). Carbon–Ti nanocomposites with a developed micro-mesoporosity, reduced band gap and TiO2 rutile phase were the most active in the photodegradation of OG under ultraviolet irradiation.

Low-cost lignite-derived hard carbon for high-performance sodium-ion storage

Sodium-ion batteries are regarded as the most promising alternative candidates for lithium-ion batteries. Hard carbon, as a kind of anode materials, has been demonstrated to deliver high specific capacity and stable cycling performance. However, it is still difficult to strike the balance between the relatively high cost and the superior electrochemical performance. We successfully fabricated low-cost lignite-derived hard carbons (a-LCs) with easy scale-up method. The microstructure, morphology and surface information of the obtained a-LCs are evaluated by X-ray diffraction, Raman spectrum and Fourier transform infrared spectrometer. By changing carbonization temperature, a-LCs’ microstructure and defect composition can be tuned and quite different sodium-ion storage behaviors can be seen. When carbonization temperature increases, the carbon microcrystallites grow and defects decay, resulting in a decrease in defect absorption capacity and an increase in graphitic-like nanodomain intercalation capacity. Particularly, a-LC carbonized at 1200 °C (a-LC-1200) can deliver a high capacity of 256 mAh g−1 with the initial Coulombic efficiency of 82%. Besides, it also exhibits a superior rate performance of 210, 197, 180, 168 and 146 mAh g−1 at current rates of 1, 2, 5, 10 and 20C (defined that 1C = 200 mA g−1), respectively. It solves the above problems very well and displays great commercial value.

Preparation of a novel nitrogen-containing graphitic mesoporous carbon for the removal of acid red 88

A novel nitrogen-containing graphitic mesoporous carbon was prepared through MnO-templated method using polyacrylonitrile (PAN) as both carbon and nitrogen sources, and MnCO3 as both template and catalyst precursors. The effects of preparation conditions on the physicochemical properties of obtained samples were systematically investigated. The results showed that as the decrease of the weight ratios of PAN and MnO (2:1–1:4), the increase of carbonization temperature (700–900 °C) and pre-oxidation temperature (180–200 °C), the samples had higher specific surface area, mesopores volume and ratios, up to 507 m2/g, 0.824 cm3/g and 96.83%, respectively. Moreover, the prepared samples presented relatively high graphitic degree and nitrogen contents (~2.21%). The adsorption capacity for acid red 88 (AR88) was as high as 309 mg/g, which were dramatically affected by the mesoporous properties and C- and N-containing groups on the surface of prepared carbon. The rich graphic carbon and pyridine-N in mesoporous carbon generated π-π dispersion and electrostatic interaction with AR88, respectively, which jointly were responsible for the adsorption process. The results of the isotherm and kinetic studies indicated that the AR88 adsorption on mesoporous carbon could be well depicted using Langmuir model and pseudo-2nd-order model.

Mechanistic insights into acetaminophen removal on cashew nut shell biomass-derived activated carbons.

Activated carbons prepared from cashew nut shells by chemical activation with phosphoric acid were tested for the removal of acetaminophen. It was found that an increase in carbonization temperature resulted in increased pore volume and decreased amount of surface functional groups. Potentiometric titration analysis indicated that the majority of surface groups on carbons are acidic. Detailed surface characterization by FT-IR, XPS, and thermal analyses indicated the involvement of surface functional groups in the removal of acetaminophen either via hydrogen bonding or by acid hydrolysis. The carbon obtained at 600°C, which contains high amount of carboxylic groups and high pore volume, exhibited the highest adsorption capacity. For this carbon, the removal of acetaminophen took place mostly via acid hydrolysis with the formation of p-aminophenol and acetic acid adsorbed on the surface. Carbon obtained at 400°C was found to have the highest density of acidic functional groups, which resulted in dimerization reactions and pore blockage. No direct correlation was observed between the adsorption capacities of carbons and their textural or surface characteristics. This suggests the complexity of acetaminophen removal by the cashew nut shell-derived activated carbons, governed by their surface chemistry and supported by high surface area accessible via micro/mesopores.

Vermiculite modification increases carbon retention and stability of rice straw biochar at different carbonization temperatures

Biochar is considered a promising material for sequestering CO2 from the atmosphere, thus helping to alleviate climate change when returned to the soil. Biochar stability is the most decisive factor determining its C sequestration potential. Mineral modification may improve biochar characteristics, but systematic research on the effect of mineral modification on the C retention and stability of biochar and the associated mechanisms is limited. Therefore, in this study, rice straw was used to produce biochar at various temperatures (300, 400, 500, 600, and 700 °C), with vermiculite as a modified mineral material. Several methods including thermogravimetric analysis, Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and nuclear magnetic resonance (NMR) spectroscopy were used to evaluate the effect of vermiculite modification and carbonization temperature on biochar stability. Biochar yield and C retention ratio decreased with increasing temperatures but increased by 13.5–38.8% and 5.2–22.1%, respectively, after vermiculite modification. The ratios of C thermal weight loss, atomic H/C, and C oxidation loss in the biochar were reduced with increasing carbonization temperature, indicating improved thermal, aromatization, and chemical oxidation stability. A trade-off that did not compromise C sequestration potential was optimized at 700 and 600 °C for the unmodified and modified biochar, respectively. Furthermore, the total mineral content of the biochar, particularly Fe, Al, Mg, and Si, were increased by vermiculite modification. FTIR results showed that chemical bonds, such as Si–O–C and Fe–O, were formed or enhanced on the biochar surface after vermiculite modification. This was further certified by the XPS survey spectra. NMR results indicated that biochar stability was enhanced by increasing the aromatization rate during carbonization, that is, by the conversion of C from alkyl and carbonyl C to aromatic C. This study provides a basis for research into and the development of functional biochar and its application in C sequestration.

Synthesis and characterization of coconut pith char adsorbents for carbon dioxide capture

The emission of carbon dioxide (CO 2 ) from anthropogenic sources has become a public concern. Several effective and affordable post combustion CO 2 capture technology has been reported and one of the approaches is through adsorption process. This study focused the adsorption onto low-cost adsorbent that can be produced from waste biomass through carbonization method. Coconut pith (CP) was used as precursor and carbonized at temperature of 300 and 700oC under ambient condition. The chemical and physical properties showed that the surface area, pore volume, ash, moisture and carbon content of chars increased, while the yield content decreased with increasing carbonization temperatures. The char adsorbent carbonized at higher temperature (CP700) showed the better performance with CO 2 adsorption capacity of 10.00 mmol/g at 25oC. It was revealed that carbonization temperature greatly affects the properties of CP, hence influence the ability of the adsorbent to capture the CO 2 . Hence, these unique properties and adsorption performance showed that char adsorbent enable to be used as an effective adsorbent for CO 2 capture and thus improving environmental quality and sustainability.

Natural nanofiber-based stacked porous nitrogen-doped carbon/NiFe2O4 nanohybrid nanosheets

The traditional hydrolysis/hydrothermal two-step preparation method of carbon/inorganic nanohybrid material usually exhibit the disadvantage of aggregation and precipitation. Therefore, the above method has certain difficulty in the synergistically regulation of the aggregation morphology and microscopic morphology of carbon/inorganic nanohybrid materials. In this paper, cellulose nanofiber and chitin nanofiber are used as the carrier material of inorganic nanomaterials, which can maintain the uniform and stable dispersed state during the hydrolysis of metal ions and hydrothermal treatment. The uniform inorganic nanoparticles uniformly distributed in the randomly stacked nanosheets even if the total content of metal ions increases to 6 mmol. The natural nanofibers/NiFe2O4 nanoparticles composite nanosheets with adjustable stacked pore structure can be prepared from natural nanofibers/NiFe2O4 nanoparticles composite hydrogel via unidirectional freeze-shaping. The carbonization temperature and carbonization time are more effective in synergistically regulation of the stacked porous nitrogen-doped carbon/NiFe2O4 nanohybrid nanosheets. Extending carbonization time or increasing carbonization temperature not only allows the growth of inorganic nanomaterials, but also causes damage to the nanosheets (such as broken pore and the small, wrinkled morphology of the nanohybrid nanosheets). NC/NiFe2O4-1.5/700/3 exhibits the highest gravimetric capacitance (up to 458 F g−1 at a constant current density of 0.5 A g−1).

Unveiling Carbon Ring Structure Formation Mechanisms in Polyacrylonitrile-Derived Carbon Fibers.

As the demand for electric vehicles (EVs) and autonomous vehicles (AVs) rapidly grows, lower-cost, lighter, and stronger carbon fibers (CFs) are urgently needed to respond to consumers' call for greater EV traveling range and stronger safety structures for AVs. Converting polymeric precursors to CFs requires a complex set of thermochemical processes; a systematic understanding of each parameter in fiber conversion is still, to a large extent, lacking. Here, we demonstrate the effect of carbonization temperature on carbon ring structure formation by combining atomistic/microscale simulations and experimental validation. Experimental testing, as predicted by simulations, exhibited that the strength and ductility of PAN CFs decreased, whereas the Young's modulus increased with increasing carbonization temperature. Our simulations unveiled that high carbonization temperature accelerated the kinetics of graphitic phase nucleation and growth, leading to the decrease in strength and ductility but increase in modulus. The methodology presented herein using combined atomistic/microscale simulations and experimental validation lays a firm foundation for further innovation in CF manufacturing and low-cost alternative precursor development.

Preparation of activated carbon from black wattle bark waste and its application for phenol adsorption

Black wattle bark waste is generated in large amounts by tannin extraction industries, which leads to an environmental problem. In literature there are few reports about reusing this waste, mainly in adsorption processes. An activated carbon from black wattle bark waste was produced, characterized and applied for phenol adsorption. Activated carbon was produced under different carbonization and activation conditions, being characterized and applied as an adsorbent for phenol removal from aqueous solution. The results showed that phenol adsorption capacity increased with the increase of carbonization temperature and of activating agent ratio and, decreased with the increase of carbonization time. Activated carbon presented a micro/mesoporous structure and the surface area was 414.97 m2 g−1. FTIR analysis showed that lactone and quinone groups compose the surface chemistry of the activated carbon. The adsorption kinetics followed the pseudo-second order model. The Weber-Morris model showed that the adsorption occurred by film and intra-particle diffusion, and the increase in stirring rate led to an increase in film diffusion. Temperature increase led to an increase in phenol adsorption capacity, and the highest value was around 98.57 mg g−1, obtained at 55 °C. The Freundlich isotherm model was the more suitable to represent the equilibrium data. Thermodynamic study indicated that phenol adsorption onto the developed activated carbon was a spontaneous, favorable, endothermic and entropy-controlled process. The activated carbon can be used in two cycles with a slight decrease in the equilibrium adsorption capacity and presented a good efficiency to remove phenolic compounds in a simulated industrial effluent.

N-doped porous carbons with increased yield and hierarchical pore structures for supercapacitors derived from an N-containing phenyl-riched copolymer

N-doped porous carbon-based materials (NPCMs) with hierarchical pore structures have been considered to be a suitable alternative to meet the ever-increasing demands for supercapacitors; however, the universally low yield of the NPCMs has restricted their practical applications. Herein, a series of NPCMs with hierarchical pore structures are synthesized with significantly increased yields through the carbonization of the copolymer made from 2,4,6-tris(chloromethyl)mesitylene and p-phenylenediamine. The development of the hierarchical pore structures and the N content of the NPCMs show opposite dependences on the increasing carbonization temperature. The NPCM exhibits the best capacitive ability only if the sufficiently developed hierarchical structures and moderate N content are achieved simultaneously. Therefore, NPCM-600 that is carbonized at 600°C with an excellent yield of 53.6% (wt.), large specific surface area of 1778m2g−1, and N content of 4.13% (wt.) yields an ideal specific capacitance of 298Fg−1 at the current density of 1Ag−1 and a perfect cycling stability of the capacitance after 10,000 cycles at 10Ag−1. The yield of the NPCM-600 is considerably higher than those for many other recently reported NPCMs. NPCM-600 also shows better capacitance than those of the other reported NPCMs, such as NOPC-bis-CN-3 (167Fg−1) and CHCPB-K-600 (260Fg−1).