Increase In Carbon Yield Research Articles

Flame-retardant vegetable oil-based rigid polyurethane foam constructed with Mxene@HNT and hydrogel via layer-by-layer coating

Rigid polyurethane foam (RPUF) meets the demand for green environmental protection by utilizing vegetable oil as polyol. However, enhancing its flame retardancy is essential to address safety concerns for its widespread application across various commercial sectors. In this work, we successfully prepared Mxene@HNT, and then employed a layer-by-layer coating to immobilize Mxene@HNT onto RPUF surfaces using dual hydrogel (DH), thus creating the RPUF/M@H/DH flame retardant system. Comparative analysis against standard RPUF demonstrates significant enhancements in flame retardancy, achieving a ``V-0'' rating in the UL-94 vertical combustion test, with a limiting oxygen index (LOI) of 30.5 %. Notably, in cone calorimetry test (CCT), peak heat release rates (pHRR) and peak smoke production rates (pSPR) were reduced by 29.34 % and 14.95 % respectively for RPUF/M@H-3/DH, while experiencing a 151.5 % increase in carbonization yield (CY) compared to standard RPUF. Importantly, the mechanical properties of RPUF maintained well upon surface modification to obtain flame retardant RPUF/M@H/DH. Thus, this study offers a novel perspective on addressing both environmental concerns and flame retardancy requirements for RPUF.

Carbon Sequestration Potential of Manure-Derived Hydrochar Aided by Secondary Stabilization.

Hydrothermal carbonization (HTC) is a process that produces a carbon-rich solid from wet organic materials through the application of heat and pressure. Carbonized solids, previously correlated to long-term soil stability, may be considered for carbon sequestration through incorporation into soil. Chars produced by pyrolysis are known for exceptional stability in soil, but pyrolysis is expensive when applied to wet biomass, such as manure. Chars produced from manure by HTC show considerably improved potential for carbon sequestration relative to untreated manure, although not as great as that of chars produced by pyrolysis. This study focuses on producing and evaluating chars by HTC paired with pyrolysis and different methods of chemical oxidation for long-term carbon sequestration in soil. It is shown that a two-step process of pyrolysis following HTC produces a char that outperforms those produced by either individual process (HTC or pyrolysis) in carbon yield, carbon content, and, more importantly, soil carbon sequestration potential. It was found that acid-catalyzed HTC followed by pyrolysis resulted in a char with a 13% increase in carbon yield, a 51% increase in carbon content, and an atomic O/C ratio 64% smaller than the char produced by conventional pyrolysis.

Polyethylene-derived high-yield carbon material for upcycling plastic wastes as a high-performance composite filler

In this study, to address environmental challenges stemming from plastic wastes, we produced carbon material derived from polyethylene (PE-C) using thermal oxidation and carbonization processes. Prior to thermal oxidation, e-beam irradiation was employed to enhance oxidation reactions which facilitated transformation of linear chains to cyclic ladder structures, resulting in a threefold increase in carbonization yield compared to conventional methods. Our analysis using XRD, Raman spectroscopy, XPS, and SEM revealed that PE-C exhibited a crystal structure similar to commercial CB (C-CB). However, it featured three times more oxygen functional groups on its surface and consisted of individual particles without forming aggregates or agglomerates. We incorporated PE-C into a PA6 polymer matrix to create composite materials with various compositions, systematically comparing their electrical, thermal, and mechanical properties to C-CB/PA6. PE-C outperformed C-CB in terms of mechanical properties (65 MPa vs. 41 MPa) due to its surface oxygen functional groups, uniform dispersion even at high loadings, and a rough surface. Moreover, PE-C exhibited a lower surface area, which reduced interfacial thermal resistance and consequently enhanced thermal conductivity, resulting in a 16 % improvement compared to C-CB at 30 wt%.

3D-Printed Carbons with Improved Properties and Oxidation Resistance

In this paper, we show the preparation and characteristics of new 3D-printed porous carbons obtained by stereolithography (SLA) of a precursor resin followed by heat treatment. Their physical and textural properties can be tuned by using chemically modified biobased aromatic precursors as monomers. Thus, vanillin and polyflavonoids such as mimosa tannins can be used together as building blocks for SLA materials when functionalized with methacrylate groups by a solvent-free technique and mixed with a photosensitive resin. Adjusting the photosensitive formulations led to high thermal stability and an increase in carbon yield of up to 27%. The corresponding dense porous carbon materials showed outstanding mechanical properties, far exceeding those of other SLA-printed carbons and carbon foams, and a very low surface area, which improves their oxidation resistance compared to acrylate–tannin-derived carbon or activated carbons. This new approach to architecturally engineered carbons with tailored properties can therefore be used for the promising design of catalyst supports or sodium-ion batteries.

Balancing glucose and oxygen uptake rates to enable high amorpha-4,11-diene production in Escherichia coli via the methylerythritol phosphate pathway.

Amorpha-4,11-diene (AMD4,11) is a precursor to artemisinin, a potent antimalarial drug that is traditionally extracted from the shrubs of Artemisia annua. Despite significant prior efforts to produce artemisinin and its precursors through biotechnology, there remains a dire need for more efficient biosynthetic routes for its production. Here, we describe the optimization of key process conditions for an Escherichia coli strain producingAMD4,11 via the native methylerythritol phosphate (MEP) pathway. By studying the interplay between glucose uptake rates and oxygen demand, we were able to identify optimal conditions for increasing carbon flux through the MEP pathway by manipulating the availability of NADPH required for terpenoid production. Installation of an optimal qO2 /qglucose led to a 6.7-fold increase in product titers and a 6.5-fold increase in carbon yield.

Mild hydrotreating of bio-oils with varying oxygen content produced via catalytic fast pyrolysis

Several biomass catalytic fast pyrolysis oils produced over HZSM-5 at varying levels of catalyst of deactivation, and therefore exhibiting oxygen contents ranging from 6 wt% to 33 wt% (enabled due to catalyst deactivation) were subjected to mild hydrotreating over Ru/C at 140 °C. The purpose of this study was to evaluate the performance of these catalytic pyrolysis oils in this process, which is often used as a stabilization step prior to exposure of the bio-oil to more severe hydrodeoxygenation conditions in pyrolysis based biorefinery concepts. This will help better define the desired deoxygenation rate during CFP, and inform decisions about yield/quality and cost tradeoffs during CFP. High liquid product recoveries were achieved for the mild hydrotreating in all samples with varying O-contents, meaning the yield of hydrogenated liquids from biomass was nearly exclusively dependent on the catalytic pyrolysis step. However, a trend was observed that the bio-oils were more responsive to the hydrogenation with increasing oxygen content. For example, no aromatic ring hydrogenation was observed for the bio-oils with <20 wt% oxygen content but ring saturation was observed for bio-oils with oxygen contents of 25–30 wt%. The bio-oils with about 25–30% oxygen content had the largest increase in H/C ratio upon hydrogenation. This trend may be attributed in part to a solvent effect, where the more polar bio-oils acting as their own solvents, helped promote hydrogenation. With regard to product stability an increase in the average molecular weight of the bio-oils with >25 wt% oxygen content was observed for exposure to the hydrogenation conditions, suggesting some oligomerization occurred prior to hydrogenation in these cases. Taken together, bio-oils with about 25 wt% oxygen content responded well to the mild hydrotreatment and were stable to the conditions, and offered a 2–3 fold increase in carbon yield from biomass over the bio-oils that were more severely deoxygenated during catalytic pyrolysis. This suggests that severe reduction of oxygen in the CFP step may be not needed to economically produce fungible, stabilized biofuel intermediates in high carbon yield.

Improvements in the carbonisation of viscose fibres

The maximum theoretical carbon yield for the carbonisation of viscose fibres, which consist of the renewable resource cellulose, is 44%. In reality the carbon yield is just in the range of 20%. By chemical activation of viscose fibres, carbon yields of more than 30% were achieved along with a reduction of undesired tar formation by 75%. A further increase in carbon yield was realised by supplemental incorporation of carbon black into the cellulose matrix of the viscose fibres. The chemical activation did not change the state of chemical bonding of the carbon atoms and the supramolecular structure within the carbonised fibres. Also the fibre morphology remained unchanged in terms of shape of cross section and surface structure. However, activated viscose fibres delivered carbon fibres with a much higher specific surface area. Carbon fibres from activated viscose fibres provide a similar or even improved application potential as carbon fibres from standard viscose fibres.

Pyrolysis Behaviour and Kinetic of Coal Tar Pitch Modified with Paraformaldehyde

Coal tar pitch (CTP) was modified with paraformaldehyde (POM) within the presence of p-toluene sulfonic acid (PTS). CTP and the modified CTP (MCTP) were characterized by elemental analysis, X-ray diffractometer, scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FTIR). The pyrolysis behaviors of CTP and MCTP were studied by thermogravimetric analysis (TGA), and the pyrolysis kinetics were analyzed via Coats-Redfern method which based on the TGA data. Experimental results demonstrated that MCTP had a higher polymerization degree, leading to an increase in carbonization yield by 14 wt%. The anisotropic degree of CTP was increased after modification by POM. New phases were formed during modification, and their decomposition was to be suppressed when pyrolyzed, while they underwent more polymerisation reactions at higher temperatures. CTP had a single pyrolysis stage, which can be described by the second order reaction model (F2). And the activation energy of CTP pyrolysis was 38.32 kJ mol−1. The pyrolysis of MCTP contained three stages, which the third order reaction model (F3), the fourth order reaction model (F4) and the one-dimensional diffusion (D1) model were the most probable mechanisms for the three stages, respectively. The activation energies of the three stages were 56.20, 86.89 and 9.10 kJ mol−1, respectively.

Combining rational metabolic engineering and flux optimization strategies for efficient production of fumaric acid.

Fumaric acid is an important C4-dicarboxylic acid widely used in chemical, food, and pharmaceutical industries. Rational metabolic engineering together with flux optimization were performed for the development of an Escherichia coli strain capable of efficiently producing fumaric acid. The initial engineered strain, CWF4N overexpressing phosphoenolpyruvate carboxylase (PPC), produced 5.30 g/L of fumaric acid. Optimization of PPC flux by examining 24 types of synthetic PPC expression vectors further increased the titer up to 5.72 g/L with a yield of 0.432 g/g·glucose. Overexpression of the succinate dehydrogenase complex (sdhCDAB) led to an increase in carbon yield up to 0.493 g/g·glucose. Based on this mutant strain, citrate synthase (CS) was combinatorially overexpressed and balanced with PPC using 48 types of synthetic expression vectors. As a result, 6.24 g/L of fumaric acid was produced with a yield of 0.500 g/g·glucose. Fed-batch culture of this final strain allowed production of 25.5 g/L of fumaric acid with a yield of 0.366 g/g·glucose. Deletion of the aspA gene encoding aspartase and supplementation of aspartic acid further increased the fumaric acid titer to 35.1 g/L with a yield of 0.490 g/g·glucose.

Light-driven increase in carbon yield is linked to maintenance in the proteorhodopsin-containing Photobacterium angustum S14.

A type of photoheterotrophic bacteria contain a transmembrane light-driven proton pump called proteorhodopsins (PRs). Due to the prevalence of these organisms in the upper water column of the World’s Ocean, and their potential for light-driven ATP generation, they have been suggested to significantly influence energy and matter flows in the biosphere. To date, evidence for the significance of the light-driven metabolism of PR-containing prokaryotes has been obtained by comparing growth in batch culture, under light versus dark conditions, and it appears that responses to light are linked to unfavorable conditions, which so far have not been well parameterized. We studied light responses to carbon yields of the PR-containing Photobacterium angustum S14 using continuous culture conditions and light–dark cycles. We observed significant effects of light–dark cycles compared to dark controls, as well as significant differences between samples after 12 h illumination versus 12 h darkness. However, these effects were only observed under higher cell counts and lower pH associated with higher substrate concentrations. Under these substrate levels Pirt’s maintenance coefficient was higher when compared to lower substrate dark controls, and decreased under light–dark cycles. It appears that light responses by P. angustum S14 are induced by the energetic status of the cells rather than by low substrate concentrations.

Enhancing the carbon yield of cellulose based carbon fibres with ionic liquid impregnates

We report the use of ionic liquids as novel impregnates to enhance the carbon yield of cellulose based carbon fibres. It was found that ILs which contain a phosphate anion improved the carbon yield the most, with a 50% increase in carbon yield reported. Additionally the use of the ionic liquid impregnate lowered the depolymerization temperature by 70 °C, which reflects significant potential saving in the energy costs of carbonization.

Comparative Study of the Modification of Coal Tar Pitch for Higher Carbonization Yield and Better Properties

Parent coal tar pitch (CTP) was modified with boric acid (BA), cinnamaldehyde (CMA) and the mixture of BA and CMA, respectively. The parent CTP and three modified CTPs were characterized by elemental analysis, thermogravimetric analysis, Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy. The four samples were carbonized at different temperatures and resultant carbonized products were characterized by FT-IR spectroscopy, X-ray diffraction and polarized-light microscopy. The results show that the morphologies and carbonization behaviors of the parent CTP and modified CTPs are quite different. The carbonization yield of the CTP modified with the mixture of BA and CMA is higher than that of CTP modified with BA or CMA only. In addition, the modification of CTP with 7 g of BA and 10 ml of CMA results in an increase in carbonization yield by 5.64%. During the pyrolysis of modified CTPs, the dehydration of BA or the distillation of CMA occurs at the temperature lower than 300 °C, and methyl and methylene groups of the modified CTPs disappear gradually as temperature rises. Furthermore, the modification of CTP by the mixture of BA and CMA results in more intensive mesophase spheres than other modified CTPs, and the modified CTP is easier to be carbonized to form graphitic carbon.

Carbon growth evidences as a result of benzene pyrolysis

Large-scale production of microstructured carbon by benzene pyrolysis at 900°C has been investigated using a quartz plug flow reactor. It was found that a significant increase in carbon yield was achieved by filling the quartz reactor with porcelain tiles. Contrary to what is normally reported in the literature, both lamellar and spherical carbon, characterized by different morphologies and interlayer spacings, was obtained. Considerations about the carbon growth mechanism indicated that the formation of different carbon structures mainly depends on the environment in which the carbon spheres are nucleated.

Preparation and carbonization behavior of cinnamaldehyde modified coal tar pitch

In this paper, coal tar pitch (CTP) was modified with cinnamaldehyde (CMA) in the presence of p-toluene sulfonic acid. The parent CTP and CMA modified CTP were characterized by 1H nuclear magnetic resonance spectroscopy, elemental analysis and scanning electron microscopy. Carbonization behaviors of CMA modified CTPs were studied by thermogravimetric analysis, Fourier transform infrared spectroscopy and X-ray diffraction techniques. The results show that the carbonization behaviors of parent CTP and CMA modified CTPs are much different. The modification of CTP with CMA results in an increase in carbonization yield by 3.46–5.08% when 100g CTP was modified with 5–15ml of CMA. During the carbonization process, methyl and methylene groups of the CMA modified CTP gradually disappear while increasing temperature and its chemical structures change greatly when the temperature is higher than 400°C. In addition, the modification with CMA is beneficial for increasing graphitizability of CTP.

Thermal behavior of coal-tar pitch modified with BMI resin

Coal-tar pitch was modified with a bismaleimide (BMI) resin. Rheological properties and carbonization behavior of the pitch–BMI resin composites and optical texture of resultant semi-cokes were studied in this paper. The carbonization behavior was studied by thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy techniques. In addition, the optical texture of resultant semi-cokes was characterized by polarized-light microscopy. Results show that the BMI resin content has great effect on the viscosity of the pitch–BMI resin composites. When the BMI resin content is 40 wt.%, the rheological behavior of the pitch–BMI resin composite is similar to that of a thermosetting resin with a U-type curve. Moreover, the pitch–BMI resin composites have better thermal stability than coal-tar pitch. The addition of BMI resin results in an increase in carbonization yield by 6.5% when the BMI resin content is 40 wt.% of the pitch–BMI resin composite. Also, the BMI resin has great effect on formation of the optical textures. When the BMI resin content is 10 wt.% of the pitch–BMI resin composite, the addition of BMI resin clearly improves the development of anisotropy on carbonization and the optical texture is flow domain anisotropy. Furthermore, there are higher aromaticity and more condensed polynuclear structures in resultant semi-cokes with increasing heat treatment temperature.

Carbonization behavior of coal-tar pitch modified with divinylbenzene and optical texture of resultant semi-cokes

In this paper, coal-tar pitch is modified with divinylbenzene (DVB) in the presence of p-toluene sulfonic (PTS) acid. Carbonization behavior of the modified coal-tar pitch and optical texture of resultant semi-cokes are studied. The carbonization behavior is studied by thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy techniques, respectively. The optical texture of resultant semi-cokes is characterized by reflected polarized light microscopy. The results show that there are marked differences in carbonization behavior of coal-tar pitch and the modified pitches. The modification of coal-tar pitch results in an increase in carbonization yield by 10–18%. The modified pitches have many methyl and methylene functional groups, which gradually disappear and aromatization degree increases with increasing heat treatment temperature. Specially, the modification contributes to a notable improvement in the optical texture of resultant semi-cokes which varies from coarse-grained mosaics to domains.

Promotion of the yield and graphitic nature of filamentous carbon grown from Ni/SiO 2 doped with lithium bromide

The catalyzed growth of ordered filamentous carbon from a hydrogen/ethylene feedstock has been studied using Ni/SiO 2 doped with LiBr. The introduction of the alkali halide resulted in a significant increase in carbon yield while the catalytically generated carbon exhibited a higher degree of structural order. The latter has been determined from high-resolution transmission electron microscopy (HRTEM) and temperature programmed oxidation (TPO) analyses. Carbon yield and structural enhancement is linked to a restructuring of the active sites that facilitates a destructive chemisorption of ethylene and the dissolution and precipitation of carbon in an ordered fashion.

The effects of inherent solid particulates on the structure and mechanical properties of coal-tar pitch based C–C composites

Five unidirectional C–C composites were prepared using PAN-based carbon fibres and five pitches differing only in their inherent solid particles (QI) content. The results show that QI content affects the microstructure of the composite matrices The amount of smaller size crystalline structures (mosaic-like) increases with the increase of pitch QI content. On the other hand, QI particles also produce a significant increase in carbon yield, and consequently, composites show a higher percentage of carbon matrix. Mechanical properties, especially compressive strength, are also affected by the presence of QI particles. With the increase in QI content the mechanical properties of the composites are improved. However, this improvement always brings about a more brittle behaviour in the material, which is mainly due to the increase in the strength of fibre–matrix bonding. A good correlation between compressive and apparent interlaminar shear strength was found.

Oxidative stabilization of C/C tow pregs studied by light microscopy

Tow pregs obtained from polyacrylonitrile-based carbon fibres and a commercial binder coal-tar pitch were stabilized by oxidation at 548, 588 and 623 K for periods ranging between 1 and 15 h. The microstructural changes involved in the stabilization of tow pregs on the carbonized laminates were studied by light microscopy. Under the conditions studied, the oxidative stabilization of tow pregs produced a significant increase in carbon yield. At the same time, the development of porosity on carbonization was avoided and the size of the optical texture was reduced. However, the extreme oxidation of pitch components at the edges of the carbonized laminate adversely affected pitch binding capability and the sinterizability of the laminates.

Preparation of activated carbon cloths from viscous rayon. Part I. Carbonization procedures

Viscose rayon cloth was carbonized under a wide range of experimental conditions, including heating rate, isothermal stage near the temperature of decomposition, and preoxidation in air. Slower carbonization rates produce increases in yield, strength and micropore volume of the char, lower reactivity against gasification, and micropores with narrower entrances. The inclusion of an isothermal stage at temperatures near the beginning of the pyrolytic decomposition leads to a lower presence of constrictions in the char. Preoxidation with air produces an increase in carbonization yield and in breaking load; the presence of oxygen surface groups in the char are responsible for its higher reactivity to gasification.