An anti-freezing hydrogel electrolyte(SPI-PVA-PAAm/LiCl) was synthesized, in which soybean protein isolates (SPI), ployvinyl alcohol(PVA) and acrylamide(AAm) were used as raw materials, ammonium persulfate(APS) was used as the initiator, N, N'-methylenebisacrylamide(MBAA) was used as the covalent crosslinker, LiCl was used as the electrolyte salt, and N, N, N', N'-tetramethylethylenediamine(TEMED) was used as the accelerator. Under low temperature conditions, the mechanical properties of the hydrogel electrolyte were analyzed, and the electrochemical properties of the solid-state supercapacitor based on this hydrogel electrolyte were investigated. The results showed that the hydrogel electrolyte had excellent anti-freezing propertity, because a certain molar concentration of LiCl reduced the freezing point of pure water in the hydrogel electrolyte and inhibited the crystallization behavior of water molecules. When the environmental temperature was reduced from 25℃ to -20℃, the hydrogel electrolyte still showed good mechanical properties and ionic conductivity. With the increase of the amount of LiCl, the compression performance of the hydrogel electrolyte firstly increased and then decreased, and the ionic conductivity increased. After 10 cycles of 80% compression strain, the stress retention rate, plastic deformation rate and energy loss coefficient of the hydrogel electrolyte with LiCl concentration of 5 mol/L(S-Li-5) were more than 100%, less than 25% and 0.33, respectively. The hydrogel electrolyte with LiCl concentration of 15 mol/L(S-Li-15) and CNTs were used to assemble the solid supercapacitor whose electrochemical performance was evaluated. When the ambient temperature was reduced from 25℃ to -20℃, the specific capacitance of assembled supercapacitor calculated by GCD curve could be maintained above 80%, and 0-70% compression strain could be withstood without damage, and the supercapacitor could still work normally; In addition, when the current density was 8.12 A/g, the capacitance retention rate of the device was higher than 91% after 1 000 cycles at -20℃.
As a natural material with good biocompatibility and biodegradability, nano-cellulose has unique structure and excellent mechanical properties. It has been widely used in the construction of electrochemical energy storage system of lithium-ion batteries(LIBs), and has made significant progress. This thesis provided an overview of the preparation and modification methods of cellulose nanofibrils(CNF), cellulose nanocrystals(CNC) and bacterial cellulose(BC) in the context of the application of advanced energy storage devices LIBs and green materials nanocellulose, and reviewed the research progress on the application of nanocellulose in the field of LIBs. It was mainly divided into three aspects: first, nanocellulose-based flexible LIBs electrodes; second, carbon materials derived from nano cellulose as electrodes; third, nano cellulose derived battery separator. Finally, some problems in this field were analyzed, summarized and prospected.
Desirable pine resources are the basis for the sustainable, high value-added and fine chemical utilization of pine oleoresin. According to the chemical composition and structural characteristics of pine oleoresin, combined with the analysis of the current situation of pine oleoresin resources as well as their deep processing and utilization industries, the demand for individuation pine resources is discussed from the perspective of fine utilization. By the perspectives of production, processing, utilization and benefits, intensive high-quality pine oleoresin resources are needed, which have strong oleoresin exudation, long-lasting resinosis, good quality, and easy processability. And by the perspective of deep processing and utilization, individuation oleoresin resources are needed further, which have higher quality, more useful, more balanced or more outstanding specific components. To research and breed individuation pine resources such as pimaric-type rosin, isopimaric-type rosin, mercusic-type rosin, α-pinene-type turpentine, β-pinene-type turpentine, 3-carene-type turpentine, β-phellandrene-type turpentine and longifolene-type heavy turpentine, are scientifically important and applicably valuable for the fine chemical utilization, high value-added deep processing of rosin and turpentine. It is recommended to focus on the main oleoresin-tapping pine species such as P. massoniana, P. kesiya var. langbianensis, P. elliottii, P. elliottii×P. caribaea, P. latteri Mason, etc., and carry out more integrative and interdisciplinary researches on oleoresin chemistry, fine chemicals, genomics, metabolomics, genetic breeding, resource cultivation, and chemical engineering of forest products.
Supercapacitors are a new type of green energy storage device with the advantages of fast charging and discharging and long service life. The electrode material is the core component of supercapacitors. The carbon from biomass is considered as a good choice for the preparation of activated carbon because of its wide variety, low price, environmental friendly, porous structure and rich in hetero-atoms, and it is the most popular electrode material for commercial applications. This paper reviewd the effects of pore structure and specific surface area on the performance of electrochemical energy storage of activated carbon, summarized the common pore structures of biomass activated carbon such as tubular, lamellar, honeycomb and network and their electrochemical properties, and analyzed the effects of different biomass components on the performance of activated carbon from three categories: plant-based, animal-based and microbial-based. Finally, the traditional methods of preparing activated carbon and the new preparation methods in recent years were briefly introduced. The problems and challenges of biomass activated carbon were pointed out. Some suggestions were provided to guide the selection of precursors for biomass activated carbon.
Global warming caused by greenhouse gas emissions is a pressing environmental problem. Given that CO2 is the most significant greenhouse gas, research into materials that can efficiently adsorb CO2 has attracted considerable attention. Compared with other adsorption materials, porous materials offer a large specific surface area with high chemical and thermal stabilities and also feature good adsorption capacity, selectivity, cyclicity, and fast adsorption kinetics; therefore, they are widely used as solid adsorbents for CO2 capture. This review systematically introduces five types of porous carbon materials coal/petroleum-coke-activated carbons, biomass porous carbons, carbon aerogels, metal-organic-framework-derived carbons, and carbon nanomaterials that have been developed in recent years. Furthermore, the four primary methods used to prepare these materials for CO2 adsorption (i.e., high temperature carbonization and activation, hydrothermal carbonization, sol-gel processing and the template method) are presented. Emphasis is placed on their structure-performance relationship with CO2 adsorption. Simultaneously, the mechanism whereby CO2 is adsorbed by porous carbons with a pore texture is reviewed, in addition to the surface chemistry. Lastly, current challenges pertaining to CO2 adsorption are summarized, and future development trends are also prospected.
Miscanthus-based lignocellulosic nanofibrils(LCNF) was produced by using citric acid pretreatment followed by the high-pressure homogenization with using miscanthus straw fiber as raw material. LCNF was cross-linked with 4, 4'-diphenyl-methane-diisocyanant(MDI) by using triethylamine as catalyst to obtain aerogel with high oil absorption capacity. The properties of aerogels were characterized by cold field emission scanning electron microscope, Fourier transform infrared spectrometer(FT-IR), thermogravimetric analyzer, and optical contact angle analyzer, and the oil absorption performance of aerogel was determined by gravimetric method. The results showed that the modified LCNF aerogel exhibited obvious multi-level rough micro/nanostructure with good thermal stability, hydrophobicity, and oil absorption capacity; the maximum weight loss temperature and water contact angle were 353.6℃ and 152.2°, respectively. FT-IR showed that cross-linking reaction was occurred between the hydroxylgroup on LCNF and the isocyanate group of MDI. When the mass ratio of LCNF to MDI was 1:4, the water contact angle of themodified aerogel was 138.1°, and the oil absorption performance was the bestwith chloroform absorption capacity of 41.6 g/g.
Cellulose and chitosan are the two most abundant natural biomass polymers on the earth. The novel, green and functional composite nanofibers derived from cellulose and chitosan were expected to be obtained by electrospinning, which can further expand their applications. The selection and development of the optimum solvent system is a crucial prerequisite and guarantee for the preparation of high-quality nanofibers by electrospinning. The characteristics, dissolution effects, mechanisms and spinning performance of the main solvent systems(including organic solvents, aqueous solvents and ionic liquid solvents) for electrospun cellulose, chitosan single and composite nanofibers were reviewed, which could provide a theoretical reference for the high value-added nano-utilization of cellulose and chitosan as well as the development of functional biocomposite nanofibers.
Pollution by heavy metals is a serious environmental problem. Lignocellulose offers the advantages of high-capacity storage, renewability, and biodegradability, while offering excellent adsorption performance and being easy to recycle. As such, it is being increasingly used as a magnetic adsorbent for the removal of metal ions from polluted water. Starting with a brief description of magnetic nanomaterials, this review focuses on the preparation of cellulose-, lignin-, and hemicellulose-based magnetic adsorption materials, both domestically and overseas, summarizing and comparing their abilities to adsorb different heavymetal ions. In addition, the adsorption abilities and factors influencing the removal of different heavy metal ions are discussed in detail. Finally, future development directionsfor lignocellulose-based magnetic adsorbents are discussed.
Effects of liquid hot water pretreatment(LHWP) on the chemical composition, enzymatic digestibility, and xylooligosaccharides(XOS)concentration were investigated in Bambusa emeiensis. In addition, the physical and chemical structural variationsof thesamples before and after the pretreatment were studied using a X-ray diffraction(XRD)spectrometer and Fourier transform infrared spectroscopy(FT-IR). Results indicated that the xylan content was significantly decreased after LHWP, while the contents of glucan and lignin increasing accordingly. LHWP improved the enzymatic digestibility of the bamboo chips feedstock, and the enzymatic hydrolysis yield reached the maximum of 79.0%(glucan) and 92.0%(xylan) at a pretreatment intensity coefficiency of 4.50. However, the XOS concentration reached the maximum value(8.7 g/L)at an intensity coefficiency of 3.96(relative mass percentage of 55.3%), and decreased thereafter as the pretreatment strength was further increased. Finally only 0.5 g/L(relative mass percentage of 3.1%)XOS was obtained in the pretreatment prehydrolysate at an intensity coefficiency of 4.50.
In this study, we developed an integrated scheme of biomass grading utilization, based on an agricultural park, by collecting straw biomass pyrolysis data, establishing a pyrolysis product database, and establishing an SVM biomass pyrolysis product model of the database. The product model was used to optimize individualized planting based on the scheme. When the treatment capacity was 400 kg/h, the scheme enabled disposal of 25%-50% of the returning straw, compared with that in the traditional straw-returning scheme. In the straw treatment project and fertilizer purchase, the park could save on nearly 30% of the related expenditure, and the optimization scheme could reduce expenditure by nearly 4%.
In this article, the research progress of electrochemical technology of lignin depolymerization recently, including micro electrochemical expression of lignin depolymerization, types of catalysts, electrode materials and electrode mechanism of electrochemical reactor and other strategies, were reviewed. The frontier research of lignin depolymerization by electrochemical technology combined with ionic liquid catalysis system, biological enzyme catalysis system and photocatalysis technology were analyzed. The influences of electrode material and current density on electrocatalytic efficiency were summarized, and the challenges as well as the opportunities of the application of electrochemical technology were presented.
The deprotonation process of a typical tannic acid, 1, 2, 3, 4, 6-penta-O-galloyl-β-D-glucopyranose(PGG), and its parent compound methyl gallate(MeG) was studied by pH potentiometric titration and spectrophotography. The dissociation constants of PGG and MeG were calculated by chemometric methods using the Reactlab Equilibrium software. Concentration profiles of the fully protonated PGG and its two deprotonated forms at different pH values were also predicted by the chemometric method. The results showed that the deprotonation of phenolic hydroxyl of PGG was found with the increasing of pH value, and fully deprotonated forms of PGG existed at pH>11. These formed negative ions of oxygen can further coordinate with metal ions. Spectroscopic studies showed that there were two deprotonated forms of PGG, and the corresponding pKa values were 10.84±0.03 and 10.62±0.02. There was only one deprotonated form of MeG during titration, and the corresponding pKa value was 9.68±0.02.
Two kinds of lignin were extracted from moso bamboo(Phyllostachys heterocycla) hydrolysis residue by hydrogen peroxide method and methanol method. The process of catalytic reductive hydrogenolysis was investigated. The results of two kinds of lignin conversion and product distribution were compared at the same reaction temperature and reaction time. Meanwhile, the optimal conditions of hydrogen peroxide lignin conversion were optimized. When the reaction temperature was 220 ℃, the reaction time was 60 min, lignin extracted by hydrogen peroxide could be converted entirely into soluble substance, and the monomer yield was 14.85%. The soluble substance yield of lignin extracted by methanol method was 96.8%, the monomer yield was 7.13%. The results showed that the conversion efficiency of hydrogen peroxide lignin to aromatic chemicals was higher than that of methanol lignin at reductive hydrogenolysis. The reductive hydrogenolysis process restored the benzoquinone of hydrogen peroxide lignin to the aromatic structure. The side chains in the product were mainly carbonyl, carboxyl, aldehyde, and alkane groups.
A choline chloride-urea(molar ratio of 1:2) based deep eutectic solvent(DES) system was used as a non-hydrolytic pretreatment media to prepare the cellulose nanofibrils(CNF) from bleached kraft poplar pulp by using microfluidizer. The properties of CNF were characterized by elemental analysis, scanning electron microscope(SEM), Fourier transform infrared spectroscopy(FT-IR), thermogravimetric analysis and X-ray diffraction analysis. Furthermore, the polymerization degree(DP) of CNF and the energy consumption were calculated. The results showed that DES pretreatment could promote the swelling of pulp fibers, which was beneficial to fibrillation during the microfluidization process. The microfluidization treatment, was performed 15 times. It was found that compared with the energy consumption(4.35×107 kW·h/t) of raw materials without DES pretreatment, the energy consumption(2.44×107 kW·h/t) of raw materials with DES pretreatment decreased by 43.91%. whereas the crystallinity indexes(ICr) of CNF prepared before and after pretreatment were 54% and 44%, respectively. However, DES pretreatment had no obvious effect on the polymerization degree of fiber raw materials. DES pretreatment also reduced the thermal stability of CNF. The increase of homogenization times could promote the fibrillation of fibers, and reduce the crystallinity and polymerization degree of cellulose at the same time. FT-IR analysis showed that choline cations interacted with anionic groups of cellulose fibers through static electricity during DES pretreatment. Elemental analysis showed that nitrogen-containing residues remained in CNFs.
Based on the freeze-drying process and chemical vapor deposition technology, polyvinyl alcohol(PVA) was compounded with cellulose to enhance the mechanical compressibility and dimensional stability of cellulose(CE) aerogels, followed by the fabrication of highly elastic, hydrophobic, and porous CE/PVA composite aerogels. The effects of PVA content on the mechanical properties of CE/PVA composite aerogels were studied. As the mass fraction of PVA increased, the compressive strength of cellulose aerogels increased. When the amount of PVA was 15% of the mass of cellulose, the compressive strain increased to 66 kPa, which was increased by 6.5 times. Simultaneously, the influences of silane modification on the microstructure, thermal stability, hydrophobicity, specific surface area and physical properties of composite aerogels were explored, and the results showed that S-CE/PVA composite aerogel modified by methyltriethoxysilane(MTES) had a denser lamellar structure, the initial decomposition temperature rose to 314.6℃, the water contact angle was as high as 115°, the specific surface area was 109.42 cm3/g, the density was 0.045 g/cm3, and the porosity was greater than 95%.
Hydrodeoxygenation(HDO) process of phenolic compound is an important process for upgrading and refining bio-oil to high value-added chemicals and high-quality liquid fuel, in which the catalyst plays a vital role. Research on the catalytic process of hydrodeoxygenation of bio-oil model compound phenols has important reference significance for bio-oil upgrading and refining. Phenolic compound hydrodeoxygenation catalysts mainly include precious metal catalysts, non-precious metal catalysts and bimetallic catalysts. This paper summarized the advantages and disadvantages of various catalysts, and briefly described the mechanism of various catalysts in the process of phenol hydrodeoxygenation. And the catalyst was evaluated for substrate conversion, product selectivity, and catalyst stability.
Maleopimaric anhydride(MPA) was prepared from rosin by Diels-Alder addition, and then maleopimaric epoxy resin(MPA-ER) was prepared by esterification and closed-loop reaction. The structures of MPA and MPA-ER were characterized by FT-IR and 1H NMR.A series of MPA-ER/MWCNTs composites were prepared by blending multi-wall carbon nanotubes(MWCNTs) with MPA-ER, the mechanical and thermal properties of the composites were characterized, and the effects of MWCNTs addition on the mechanical and thermal properties of maleopimaric epoxy nanocomposites were investigated. The results of FT-IR and 1H NMR showed that MPA and MPA-ER were successfully prepared. MWCNTs were well dispersed in MPA-ER, and the cross-section had river-shaped texture features. The mechanical properties of MPA-ER/MWCNTs were significantly improved by adding MWCNTs. When the addition of MWCNTs was 1.2%(calculated by the mass of MPA-ER, similarly hereinafter), the mechanical properties of the composite MPA-ER/MWCNTs(1.2) were optimized. Its impact toughness, tensile strength, bending strength and elongation at break were 15.11 kJ/m2, 40.42 MPa, 105.45 MPa and 14.80%, which increased by 159%, 160%, 102% and 135% compared with those of MPA-ER, respectively.At the same time, in cone calorimeter test, the peak heat release rate and carbon residue rate of MPA-ER/MWCNTs(1.2) composite were 324 kW/m2 and 9.18%, respectively.Compared with MPA-ER, the peak heat release rate decreased by 14%, and the carbon residue rate increased by 68%, which indicated that the addition of MWCNTs also improved the thermal stability and flame retardancy of MPA-ER/MWCNTs.The improvement of flame retardancy of MPA-ER/MWCNTs(1.2) composites was mainly attributed to the effective increase of crosslinking density of epoxy resin by adding MWCNTs, and forming a relatively dense carbon layer in the interior of epoxy resin, and then the flame retardant effect was achieved by partially isolating the external heat and air.
With the depletion of petroleum resources and the increasingly serious white pollution, the preparation of bio-based poly(ethylene 2, 5-furandicarboxylate)(PEF) from lignocellulosic resources has become one of the research hotspots in the fields of biorefinery and green chemical industry. Compared with petroleum-based plastics, such as poly(ethylene terephthalate)(PET) and polycarbonate(PC), PEF not only has excellent thermal properties and mechanical strength, but also has more obvious advantages in gas barrier properties, which is considered as a perfect substitute for PET. However, PEF also has some drawbacks, including low elongation at break, dark color, difficult degradation and slow deep crystallization speed. Therefore, it is necessary to modify PEF before practical application. In this paper, the research progresses of PEF modification, including copolymerization, blending and other modification methods were reviewed. The effects of different diols or diacid modified monomers, catalyst types, reaction modes, additives on the properties of PEF were summarized, and the developing trend and application prospects of modified PEF were discussed.
As an important part of renewable energy, biomass resources have a wide range of sources. However, large-scale application is limited due to the properties of biomass, such as dispersion, low bulk density, low calorific value, and high hygroscopicity. Solid briquette fuel is one of the important ways to promote the large-scale application of biomass, which can replace coal and other fossil fuels. As one of the pretreatment methods to improve the physical and chemical properties of briquette fuel, torrefaction can improve the hydrophobicity of biomass briquette fuel and optimize its physical and chemical properties, which is a research hot topic at home and abroad. In this paper, the factors of torrefaction pretreatment and characteristics of torrefaction products were summarized, the factors and the lignin bonding mechanism of the pelletization process were analyzed, the influence of torrefaction pretreatment on the preparation of clean solid fuel was described, and the application of torrefaction and upgrading solid fuel process was prospected. This paper provides reference for promoting the development and application of biomass briquette fuel in China.
Nitrogen-doped activated carbon was fabricated by one-step pyrolysis with Chinese fir sawdust as raw material, melamine solid waste(oxhydryl and amino triazine, OAT) as nitrogen-rich source, alkali/urea system as solvent. The effects of activation temperatures and melamine solid waste dosage on adsorption performance and electrochemistry performance of activated carbon were investigated. X-ray photoelectron spectroscopy(XPS) and specific surface area analyzer were used to study the surface structure and pore structure of the material. Cyclicvoltammetry(CV) curves, galvanostatical charge/discharge(GCD) and electrochemical impedance spectroscopy(EIS) were used to test the electrochemical performance of samples. The results showed that with the increase of melamine solid waste content, the yield and adsorption performance of activated carbon samples increased first and then decreased; the addition of melamine solid waste was beneficial to increase the yield, nitrogen content, adsorption performance and electrochemical performance of nitrogen-doped activated carbon. The specific surface area and pore structure of carbon materials affected the electrochemical performance of activated carbon samples. When the activation temperature was 900 ℃ and the melamine solid waste content was 15%, the yield of nitrogen-doped activated carbon was 34.2%, the iodine adsorption value was 1 116 mg/g, and the methylene blue adsorption value was 165 mg/g, specific surface area was 1 324 m2/g, nitrogen content was 3.5%. In the 6 mol/L KOH electrolyte, the specific capacitance could reach 193 F/g when the current density was 1 A/g.
Nanocellulose is a kind of nano-sized cellulose extracted from natural cellulose. It not only has the basic characteristics of cellulose, but also has large specific surface area, unique strength and optical properties originated from nano-size. However, the presence of free hydroxyl groups in cellulose is hydrophilic, which reduces the stiffness of nanocellulose materials in humid environments and limits its application fields. Therefore, hydrophobic modification of nanocellulose can expand its scope of application. This article reviewed the methods of hydrophobic modification of nanocellulose in recent years, including physical adsorption modification, esterification/acetylation modification, graft copolymerization, silane coupling agent modification, etc., and summarized the research results of the above methods, as well as the advantages and disadvantages. And the future development direction was prospected in order to provide reference for hydrophobic modification research.
Dehydroabietic acid(DA) reacted with 3-glycidyloxypropyltriethoxysilane(GTS) to synthesize dehydroabietic acid-based cross-linking agent(DAG), and then DAG was combined with TiO2, catalyst dibutyltin dilaurate, and hydroxyl polysiloxane(PDMS) to fabricate the TiO2 modified dehydroabietic acid cross-linked the room temperature vulcanized silicone rubber(TiO2-DAG/RTVSR). The microscopic morphology, mechanical properties, thermal stability, and hydrophobicity of the samples were investigated. The results showed that DAG and TiO2 were uniformly dispersed in the dehydroabietic acid cross-linked silicone rubber. Compared with DAG/RTVSR-3 obtained by only adding DAG, when the addition of TiO2 was 7%, the tensile strength of the obtained TiO2-DAG/RTVSR-4 increased from 0.65 MPa to 0.98 MPa which increased by 50.8%, and the elongation at break increased from 250% to 317%.The 5% mass loss temperature of silicone rubber increased from 324.5℃ to 338.8℃ as the addition of TiO2 increased from 0% to 7%; and the swelling degree decreased, which indirectly reflected the increase in the degree of cross-linking.The contact angle gradually decreased with the increasing of TiO2 amount. These results indicated that the synergistic effect of dehydroabietic acid with rigid structure and TiO2 into the molecular chain of silicone rubber could effectively enhance the mechanical properties and thermal stability of room temperature vulcanized silicone rubber.In summary, silicone rubber with 7% TiO2 had the best performance.
Due to the excellent physical and chemical properties such as high specific surface area, large porous volume and adjustable structure morphology, porous carbon materials have been proven to show outstanding adsorption performance for water pollutants. Lignin is a kind of natural and abundant biomass resource. It has the characteristics of high carbon content, low cost, and easy to modification. Thus, it has been regarded as an ideal precursor for replacing traditional fossil resources to prepare porous carbon materials. This review focuses on the preparation methods of lignin-based porous carbon materials and the application research progress in the adsorption and degradation of heavy metal ions, dyes, aromatic compounds, and antibiotics from water. Based on the problems existing in the application of water purification treatment, the development trend of lignin-based porous carbon materials is also prospected.
As a medical plant with a long history, the Usnea species of lichen are widely distributed in China. However, the research about its chemical composition and activity is rare, delayed, and the basic data accumulation is weak, which restricts its further development and utilization.The primary metabolites polysaccharide(lichenan, isolichenan, galactomannan, and heteropo-lysaccharide) and fatty acids, and secondary metabolites(single benzene ring derivatives, depsides, depsidones, and benzofuran) of the Usnea species of lichen are reviewed in this article.The research progress of the bioactivity of lichen polysaccharide and lichen acid are introduced. Lichen polysaccharides have functions of antioxidation and antitumor; and lichen acids have functions of insecticidal, antibacterial, anticancer, antitumor, antioxidation, antivirus, antiinflammatory, liver-protecting, detoxication, and enzyme inhibition.
Larch-based N-doped carbon foam was prepared with larch sawdust as carbon source and urea as nitrogen source via phenol liquefaction-physical foaming-activation method. Morphology, surface chemical properties and pore structure of the prepared carbon foams were analyzed by SEM, XRD, XPS, TG and N2 adsorption-desorption isotherm. CO2 adsorption capacity and CO2/N2 adsorption selectivity of the materials were tested as well. Effects of nitrogen doping and activation temperature on CO2 adsorption performance were investigated. The results showed that carbon foam had the crystal structure of disordered stacking of graphene layers, and its disorder increased with the rise of activation temperature. Nitrogen doping reduces the size of cell and thermal stability. Nitrogen-doped carbon foam exhibited typical microporous structure with the maximum micropore content of 95.83%. The microporous pore size of nitrogen-doped carbon foams(NCF-4-900, NCF-6-900 and NCF-8-900) which were prepared under the conditions of activation temperature of 900 ℃ and urea doping amounts of 4, 6 and 8 g were mainly concentrated at 0.50, 0.81 and 1.26 nm, and the mesoporous pore size was concentrated in about 3.85 nm.The materials contained 3 types of nitrogen and they were mainly pyridine nitrogen(N-6) and pyrrole nitrogen(N-5) when the activation temperatures were 700 and 800 ℃. With the activation temperature reaching 900 ℃, some N-5 and N-6 were transformed into quaternary nitrogen(N-Q) with better thermal stability, and pyrrolic N was dominant. CO2 adsorption capacity increased with the rise of activation temperature. NCF-8-900 had the highest adsorption capacity(up to 3.19 mmol/g at 25 ℃ and 100 kPa) and excellent CO2/N2 adsorption selectivity of 118.63.
Lignin is an amorphous, highly cross-linked polyphenol aromatic polymer with a wide range of sources and rich carbon content, and is suitable for the preparation of porous carbon materials. Using lignin to prepare porous carbon is an important way to solve the problem that lignin is difficult to be used efficiently. It can solve environmental pollution and realize resource utilization. This article mainly introduced the research status of the preparation of microporous activated carbon with lignin as carbon precursor by physical and chemical activation method and the preparation of mesoporous carbon materials by template method in recent years. The pore structure and morphology of porous carbon materials prepared by different methods were compared and analyzed, as well as their application progress in adsorption, catalysis and electrochemistry.
This article reviews the recent research progress of preparation of 2, 5-furandiformaldehyde(DFF) by the oxidation of 5-hydroxymethylfurfural(HMF) with transition metal-based catalysts. The application of manganese-based, copper-based, vanadium-based, iron/cobalt-based and other catalytic systems in the preparation of DFF by HMF oxidation is mainly introduced. The effects of different reaction conditions on the catalytic performance of the catalyst are analyzed in detail, the reaction mechanism of different catalysts is explained, and the advantages and disadvantages of different catalysts are summarized. In addition, based on the analysis of the existed problems in the current catalyst catalysis process, the development prospects of the transition metal-based catalysts catalyzed by HMF oxidation to prepare DFF are also prospected.
Lignin-based intumescent flame retardant(Lig-T) with carbon source, acid source and gas source was synthesized successfully by grafting nitrogen and phosphorus elements. The structure of the flame retardant Lig-T was proved by Fourier transform infrared spectrometer(FT-IR), elements analysis and X-ray photoelectron spectroscopy(XPS). The Lig-T was added to the epoxy resin with different mass fractions to obtain Lig-T/EP composite material. Thermogravimetric analysis, underwriters laboratories 94(UL-94) vertical buring test, oxygen index(LOI) test and cone calorimetry(Cone) test were used to investigate the thermal stability and flame retardancy of composite materials. The results showed that when the mass fraction of the Lig-T was 20%, the composite material 20% Lig-T/EP could reach the UL-94 V-0 level, the oxygen index value was as high as 28.5%, and the mass fraction of the residue increased from 14.8% to 20.2%.With the increase of the mass fraction of Lig-T, the total amount of heat release and the total amount of smoke released during the combustion process of the composite material decreased.