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.
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.
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.
The epoxy monomer 1, 3, 3'-tri-oxirane-2'-methoxy-benzophenone(DEBP) was synthesized with vanillic acid, m-diphenol, epichlorohydrin and so on as raw materials by simple two-step method. And DEBP was structurally characterized and determined via FT-IR, and was then mixed with 4, 4'-diaminodiphenylsulfone(DDS), followed by heating and curing to obtain DEBP/DDS epoxy resin. For comparative purpose, commercially used diglycidyl ether of bisphenol A(DGEBA) was cured with the identical curing agent was used as a control. The results showed that DEBP monomer had higher curing activity than that of DGEBA monomer. The glass transition temperature of DEBP/DDS epoxy resin was 183℃, which was higher than that of DGEBA/DDS. The DEBP/DDS epoxy resin outperformed DGEBA/DDS epoxy resin in terms of flexural and tensile properties. The flexural modulus and strength of DEBP/DDS epoxy resin were measured as 2 437.8 and 98.6 MPa and the tensile modulus and strength of DEBP/DDS were 2 523.4 and 71.1 MPa. The cured DEBP/DDS also demonstrated excellent flame retardant property. The char residue at 800℃ reached 35%, the limiting oxygen index(LOI) was 34%, the UL 94 level was V-0 and the total heat release was measured as 17.8 kJ/g. This research suggested that without indroducing any flame retardant element, an intrinsic flame-retarding epoxy resin was synthesized with bio materials.
Rosin is an important biomass resource in China, and its main component resin acid contains tricyclophenylene skeleton strong hydrophobic rigid group and carboxyl weak hydrophilic group. Rosin can be used to disperse inorganic nano materials and reduce the aggregation of inorganic nano materials. The surfactant with excellent hydrophilic and lipophilic properties can be obtained by chemical modification of acid double bond and carboxyl group of rosin resin, which has better "fusion" with inorganic materials. Rosin based surfactant can be used as template and dispersing agent to prepare a variety of inorganic functional materials. The rosin based small molecule/inorganic hybrid materials and rosin modified polymer/inorganic hybrid materials can be obtained by designing functional rosin derivatives to bond with inorganic materials. Based on the structural characteristics and chemical properties of rosin and its derivatives, the application of rosin and its derivatives in inorganic functional materials was reviewed, and the application prospect of rosin derivatives in the development of inorganic functional materials was prospected.
Corn straw enzymatic hydrolyzed lignin carbon LC1, LC2and LC3 were prepared using purified corn straw enzymatic hydrolyzed lignin as carbon source and carbonized at high temperature under N2 conditions for 1, 2 and 3 h. SEM, TEM and nitrogen adsorption/desorption curve were used to analyze the prepared carbon materials. The results showed that LC1, LC2 and LC3 had microporous, mesoporous and macroporous structures with specific surface areas of 894.75, 1 376.74 and 776.47 m2/g, respectively. The pore volumes of the samples were 0.41, 0.70 and 0.40 cm3/g, respectively. XRD and Raman spectrum showed that the order of the enzymatic hydrolyzed lignin carbon increased with the prolongation of carbonization time. XPS analysis showed that the enzymatic hydrolyzed lignin carbon mainly contained C, O and N(small amount) elements. The electrochemical properties of LC1, LC2 and LC3 were tested using a three-electrode system. The results showed that LC2 had the highest specific capacitance of 222.2 F/g at 0.2 A/g current density, and the specific capacitance of LC2 reached 149 F/g at higher current density of 20 A/g. Further study on its practical application in supercapacitors, the results showed that LC2 assembled symmetric supercapacitor had the largest specific capacitance per electrode and the highest capacitance retention(70.2%). At 1 A/g current density, the LC2 supercapacitor showed good rate performance and electrochemical stability after 5 000 charge-discharge cycles. Moreover, a series battery composed of symmetric LC2 supercapacitor could directly light the LED lamp.
The effects of pretreatment with γ-valerolactone/p-toluenesulfonic aci aqueous solution coupling systemGVL/TsOH aq) an Cyrene/p-toluenesulfonic aci aqueous solution coupling systemCyrene/TsOH aq) on the chemical composition an enzymatic hyrolysis of maso bamboo were stuie. The results showe that the hemicellulose separation rates (SH) an lignin separation rate (SL) in GVL/TsOH aq system with 75 g/L TsOH an the solvent volume ratio of 4:1 were 98.5% an 98.4%, respectively, after pretreatment at 130℃ for 60 min, an the cellulose retention rate (RC) was 91.5%. In contrast, the Cyrene/TsOH aq system with 30 g/L TsOH an the solvent volume ratio of 0.8:1 was pretreate maso bamboo at 120℃ for 60 min, the RC was 87.3%, while the SH an SL were 85.5% an 79.4%, respectively. Characterization results of soli samples after pretreatment showe that after pretreatment with GVL/TsOH aq, the ense structure of lignocellulose of the samples was effectively estroye, an most of the amorphous hemicellulose an lignin were separate, with a crystallinity of 68.27%. Besies, the structure was closer to microcrystalline cellulose, an more free hyroxyl groups were expose, which was conucive to the subsequent enzymatic hyrolysis an saccharification process. The enzymatic hyrolysis results emonstrate that the glucose yiel of the soli sample obtaine by GVL/TsOH aq pretreatment (773 mg/g) was significantly higher than that of the sample obtaine by Cyrene/TsOH aq (306 mg/g), which was 19.3 times of that of bamboo. The two solvent systems coul be effectively recycle, an the separation rate of lignin an the retention rate of cellulose in GVL/TsOH aq system coul reach 90.3% an 91.5% respectively, an 94.8% of solvent coul be recovere after three cycles.
Mesoporous activated carbon was prepared from poplar lignin by phosphoric acid activation. The effects of activation temperature(400-900 ℃) and mass ratio of phosphoric acid and lignin(impregnation ratio, 1∶1-4∶1) on the structure of activated carbon LAC-x-y(x represented the impregnation ratio, y represented the activation temperature) were investigated by pore structure, XRD and Raman spectroscopy analysis. The relationship between the electrochemical performance of activated carbon and its structure was investigated by means of electrochemical characterization. Pore structure analysis results showed that increasing the temperature and impregnation ratio was beneficial to the formation of mesopore, but too high temperature would lead to the collapse of pore structure, and too high impregnation ratio would lead to the increase of ash content, which would lead to the degradation of the performance of activated carbon. XRD and Raman spectroscopy results showed that increasing the temperature could improve the degree of graphitization of activated carbon, while increasing the impregnation ratio could decrease the degree of graphitization. Under the activation temperature of 800 ℃ and impregnation ratio of 2∶1, the activated carbon LAC-2-800 had the best performance, with specific surface area of 1 031 m2/g, mesopore ratio of 61% and average pore size of 3.31 nm. As the electrode material of supercapacitor, the specific capacitance reached 165 F/g at 1 A/g current density, and 136 F/g at 10 A/g current density. After 5 000 cycles at 1 A/g current density, the specific capacitance value could keep at 78.1% of the initial value.
Stimulus-responsive hydrogels, as a new class of functional polymer materials, can actively sense the difference of the external environment and reflect the change to the outside world by specific ways such as swelling or contraction, and show a great application potential in many fields of life and production. As a renewable natural resources, biomass has been widely applied in the preparation of stimulus-responsive hydrogels in recent years. Particularlly for rapid development of engineering technology and applications, including controllable/active polymerization and click chemistry, dynamic covalent bond, supramolecular self-assembly and super molecular aggregation state regulatory molecules, etc, is able to overcome the instrisic structure defects of biomass macromolecule to a certain extent, and fabricate the stimulus-responsive hydrogels containing unique molecular structure of biomass raw materials, which promoted the development of new green synthesis strategies, multi-functional technology, simple modular synthesis technology, modern biotechnology and other technologies. Based on the stimulus-responsive methods and types of stimulus-responsive hydrogels, this paper assembles six types of hydrogels, including temperature response, acid-base response, light response, electric response, magnetic response and multiple response and highlights the effect of the unique molecular structure of biomass raw materials on the performance of the stimulus-responsive hydrogels. Also, the applications of biomass-based hydrogels with different environmental responses in the fields of drug controlled release, biological tissue engineering, biosensors, adsorption materials, cell culture and antibacterial materials were summarized, and the future development direction of biomass-based hydrogels was prospected.
Using dehydroabietic acid (DA) and 6-aminocaproic acid as the raw materials, a rosin-based amino acid surfactant (R-6) was synthesized via reactions of chlorination, amidation and saponification reactions.The 1H NMR and 13C NMR signals of dehydroabietic acid were analyzed by using 2D NMR techniques, and the structure of the final product was also confirmed by 1H NMR and FT-IR.The solubility, surface tension and foam properties of R-6 were investigated.The results showed that at room temperature, R-6 showed excellent solubility of above 800 mmol/L in water.The critical micelle concentration (Ccmc) of the surfactant was 5.89 mmol/L, and the surface tension (γcmc) corresponding to Ccmc was 40.46 mN/m.With the increase of surfactant concentration, R-6 exhibited strong ability in stabilizing foams.When the concentration of R-6solution was 10 mmol/L, the foam half-life was as high as 1 966 min.
The 2.5 mm bamboo charcoal ultra-thick electrode material was prepared by direct carbonization of bamboo which preserved its straight pore structure. The bamboo charcoal materials Z-700, Z-800, and Z-900 were prepared at 700, 800 and 900 ℃, which were characterized by SEM, XPS, Raman spectra analysis. The results showed that the original bamboo structure was maintained after carbonization. Among them, the carbonized sample Z-900 owned a higher BET specific surface area(SBET) of 483 m2/g, total pore volume(Vtotal) of 0.23 cm3/g, mesoporous pore volume(Vmes) of 0.05 cm3/g, and micropore volume(Vmic) of 0.18 cm3/g. Electrochemical performance tests showed that the specific capacitance of the prepared ultra-thick bamboo charcoal electrode Z-900 was as high as 22.0 F/cm2 in the 6 mol/L KOH electrolyte with the current density of 10 A/m2. When the current density was 200 A/m2, the specific capacitance still reached 14.5 F/cm2 and the capacitance retention rate was 65.9%. The symmetric supercapacitor Z-900//Z-900 assembled with ultra-thick bamboo charcoal electrode Z-900 owned a specific capacitance of 14 F/cm2 at the current density of 10 A/m2, which had a discharge time of 3 500 s, an energy density of 4.9 W·h/m2, and a power density of 5 W/m2. At the current density of 100 A/m2, the coulomb efficiency could reach 99.8% after 10 000 cycles, and the capacitance retention was 88%, which demonstrated that Z-900 had an excellent electrochemical stability.
The effects of pretreatment temperature and time on the content of the hydrolysate of poplar during thermal hydrolysis were investigated. The reaction kinetic models of xylose and glucose in the hydrolysis solution were established by using the modified Saeman biphasic kinetic model. The reaction rate constants of monosaccharides generation and degradation under different conditions were determined by nonlinear fitting curve. The activation energy of lignocellulosic hydrolysis reaction was obtained by linear fitting of Arrhenius formula. The results showed that xylan was divided into an easy-to-hydrolyse fraction and a difficult-to-hydrolyse fraction during the pretreatment of poplar. The activation energies of easy-to-hydrolyse(Ef) and difficult-to-hydrolyse(Es) xylan were 78.35 kJ/mol and 88.97 kJ/mol, respectively. The activation energy of xylose degradation(E2) was 80.17 kJ/mol. Furthermore, the activation energy of glucan degradation(E3=48.06 kJ/mol) was significantly lower than that of glucose degradation(E4=90.18 kJ/mol). These results indicated that glucose was more stable than xylose, and the mild treatment conditions of hydrothermal pretreatment could realize the dissolution of hemicellulose accompanied by reducing the degradation of cellulose and monosaccharide.
The allyl ether modified lacquer(AGE-L) was successfully prepared by the reaction of lacquer with allyl glycidyl ether(AGE), and subsequently reacted with methacrylic anhydride(MAA) to form a novel lacquer-based monomer with ether bond and ester bond(MAA-AGE-L). Their structures were then characterized by FT-IR, 1H NMR and 13C NMR, and their physical and chemical properties were tested. Additionally, the UV and oxygen(air) curing processes of raw lacquer, AGE-L and MAA-AGE-L were investigated, and the mechanical properties as well as the resistances to chemical media of the cured films were also studied. The results confirmed the successful synthesis of AGE-L and MAA-AGE-L, which were all brownish red liquids. The hydroxyl value of AGE-L was 193 mg/g, the iodine value was 1.89 g/g and the viscosity was 400 mPa·s. The hydroxyl value of MAA-AGE-L was 20 mg/g, the iodine value was 1.39 g/g and the viscosity was 2 000 mPa·s. Compared with lacquer, the surface drying time of MAA-AGE-L was shortened from 2 h to 50 min in presence of the oxygen(air) environment at 30 ℃ with the relative humidity of 80%, and the UV curing surface drying time was shortened from 50 s to 10 s. The pencil hardness of the cured film was H when AGE-L was irradiated by ultraviolet light for 120 s, whereas the pencil hardness of the paint film cured under oxygen(air) for one week was 2H. Moreover, they exhibited good adhesion, flexibility and impact strength. Allyl-modified lacquer films obtained by two curing methods had good water resistance, ethanol resistance, salt water resistance and acid resistance.
In order to explore the mechanism of the alkaline ionic liquids tetrabutylammonium hydroxide (TBAH) in the pretreatment of eucalyptus, the response surface analysis method was used to design the model, and the optimal conditions[JP]for the pretreatment of eucalyptus with ionic liquid TBAH were pretreatment time 57.19 min, pretreatment[JP]temperature 71.98℃, and TBAH mass fraction 11.78%.The model was proved to be scientific accurate and practical.By comparing the composition[JP]of feedstock, NaOH, tetrabutylammonium fluoride (TBAF) and TBAH pretreated eucalyptus samples, Fourier infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) were carried out for comparing the composition of feedstock with that of NaOH, tetrabutylammonium fluaride (TBAF) and TBAH pretreating eucalyptus samples, which aimed to analyze pretreatment reaction mechanism.The results showed that in the pretreatment, [TBA]+ could effectively degrade lignin and reduce the crystallinity; OH- could degrade hemicellulose.Under the combined action of[TBA]+ and OH-, the hemicellulose of eucalyptus samples was degraded from 26.8% to 18.0%, and the lignin was degraded from 26.3% to 15.0%;the crystallization index increased[JP]from 42.39% to 54.11%;and TBAH pretreatment would destroy the complete, dense and uniform structure of the surface of eucalyptus samples; TBAH pretreated eucalyptus wood sample was enzymatically hydrolyzed for 72 h, the yield of reducing sugar was 365.62 mg/g, and the conversion rate of cellulose was 69.24%.
N and P co-doped carbon aerogels(NPCA) were prepared from cattail inflorescence with NH4H2PO4 as dopant by pretreatment with acidic sodium chlorite, ultrasonic cell fragmentation, freeze-drying and carbonization at high temperature. The surface morphology, pore structure, crystalline structure and surface chemical composition of NPCA were characterized by SEM, N2 adsorption/desorption, XRD and XPS. The effects of doping amounts and carbonization temperatures on the electrochemical properties of NPCA were systematically studied. The results of research showed that NPCA was a three-dimensional network structure that composed of amorphous carbon. The nitrogen element on the surface of NPCA existed in the form of pyridine nitrogen(N-6), pyrrole nitrogen(N-5), graphitization nitrogen(N-Q) and oxidation state of nitrogen(N-X), and the phosphorus element existed in the form of P—O and P—C. The pore structure and surface chemical structure of NPCA were greatly affected by doping amount of NH4H2PO4 and carbonization temperature. The optimum preparation conditions of NPAC were that the mass ratio of cattail-based cellulose to ammonium dihydrogen phosphate was 1∶2 and the carbonization temperature was 800 ℃. The NPAC-2-800 prepared under this condition has rich pore structure and surface functional groups. Furthermore, the specific surface area was 599.88 m2/g, the total pore volume was 0.27 cm3/g, the micropore volume was 0.20 cm3/g, and the average pore size was 3.69 nm, the N and P contents of NPCA were 5.69% and 5.12%, respectively. The electrochemical properties of the NPCA were measured by three electrode system in 6 mol/L KOH solution. The specific capacitance of NPCA-2-800 was 249 F/g at a current density of 1 A/g, which was 133.4% higher than that of the undoped sample(106.7 F/g), and had good rate performance.
Pretreatment was a key step in sugar platform -based biomass refinery using lignocellulosic biomass as raw material. In this paper, the advantages and disadvantages of the commonly used methods such as dilute acid/alkali, steam explosion, liquid hot water, microwave, subcritical CO2, ionic liquids, deep-eutectic solvents, organosolv, milling/grinding, and biological, and the research progress of subsequent enzymatic hydrolysis and fermentation were reviewed. Furthermore, the application of the co-production of ethanol and platform chemicals in the pretreatment of biomass feedstock at home and abroad based on Aspen Plus and techno-economic analysis were introduced. Finally, the drawbacks of Aspen Plus in biomass pretreatment for ethanol production were summarized and the further research directions were proposed.
The modified coconut shell activated carbons were prepared by loading CuCl2, carbonization and CO2 activation. The Cu-loaded activated carbons were labeled as AC3, AC4, AC5, and AC7 to represent the mass fractions of cupric salt solutions 0.3%, 0.4%, 0.5% and 0.7%, respectively. The Cu-loaded activated carbons were characterized by means of N2 adsorption isotherm, SEM, XRD and XPS. Their dynamic adsorption-desorption performance was measured by the gravimetric method. After modification, the acidic oxygenated groups on the surface of activated carbon decreased. The results showed that cupric salt existed in two forms, i.e., CuO and Cu2O. It was found that the presence of Cu loading led to the decreasing of surface area and pore volume of modified sample, and the increasing of the surface area and proportion of micropore. AC5 showed the largest values of the surface area(733.20 m2/g) and proportion(72.99%) of micropore. Furthermore, AC5 had the optimal equilibrium adsorption capacity(356.40 mg/g) which increased by 33.38% compared to the raw sample, and the optimal equilibrium adsorption time(118.80 min) which increased by 33.38%. Moreover, the adsorption performance of AC5 was better than the activated carbons in the organic gas filter cartridge(3M-3301 CN and 3M-6001 CN). After five cycles of adsorbents regeneration test, 80% of adsorption capability was still able to be reserved. The Cu-loaded activated carbons improved the adsorption performance by transforming the style from physical adsorption to physical-chemical adsorption through complexation of π-bonds in benzene with hollow d-orbitals in Cu2+.
Hollow mesoporous silica microspheres SiO2-1 and SiO2-2 were prepared by sol-gel and hydrothermal synthesis using dichloride-N, N'-bis (3-hydrorosin loxy-2-hydroxypropyl) tetramethylenediamine (DHRT) as template agent and ethyl orthosilicate as silicon source.SEM, TEM, FT-IR, XRD and nitrogen adsorption-desorption were used to characterize SiO2-1 and SiO2-2.The results showed that silicon dioxide microspheres with amorphous structure were successfully prepared by both methods; the agglomeration phenomenon between silica particles gradually disappeared with the increase of the amount of template agent (0.1-1 g); SiO2-1 was mainly loose microsphere with patterns, and SiO2-2 was hollow microsphere with the wall thickness of 80-85 nm.The average particle size distributions of SiO2-1 and SiO2-2 prepared with different template dosages (0.3-1 g) were 0.22-0.33 μm and 0.34-0.41 μm, respectively.The morphology and particle size of SiO2-1-0.7 and SiO2-2-0.7 prepared by two methods exhibited good morphology and low particle size, with specific surface area of 561.52 and 463.41 m2/g, cumulative pore volume of 0.35 and 0.42 m3/g, and average pore size of 2.56 and 3.66 nm, respectively.Zeta potential analysis showed that the formation of SiO2 hollow mesoporous structure was mainly caused by the cooperative self-assembly process between the oligomer obtained by hydrolyzing polycondensation of ethyl orthosilicate and the template agent.
Matrix solid-phase dispersion was proposed to extract polyphenols in Toxicodendron vernicifluum (Stokes) F. A. Barkl. (Shaanxi lacquer tree). The MSPD conditions to extract polyphenols established by the single factor test were ZSM-22 as the adsorbent, adsorbent/sample ratio of 2:1 (g: g), grinding for 2 min, and use of 8 mL of 70% methanol as the elution solvent. Under these conditions, the polyphenols content of MSPD extraction was (466 ±2. 05)mg/g(calculated by gallic acid). An efficient and accurate method for identification of polyphenols in Shaanxi lacquer tree was established by HPLC-IT-TOF/MS. According to mass spectrometry, fragmentation pathway combined with published reports, total of 10 components were identified, including 3 gallic acid derivatives and 7 flavonoids as follows: gallic acid, methyl gallate, ethyl gallate, fustin, taxifolin, garbanzol, isorhamnetin, quercitrin, fisetin, sulfuretin. It was beneficial to the discovery and identification of compounds in Shaanxi lacquer tree by matrix solid-phase dispersion coupled with HPLC-IT-TOF/MS, and it could be significance for the analysis and quantification of extracts from Shaanxi lacquer tree samples.
Using the synthesized molybdenum-vanadium homopolyacid Na6[α-Mo6V2O26]·16H2O as catalyst and p-toluene sulfonic acid as acid catalyst, the catalytic performance of the molybdenum-vanadium homopolyacid for the selective conversion of cellulose to formic acid(FA) was investigated under aqueous medium and O2 atmosphere. The experimental results showed that the synthesized molybdenum-vanadium homopolyacid exhibited strong oxidizing property. Under the conditions of 0.2 g of cellulose, 0.1 g of Na6[α-Mo6V2O26]·16H2O, 0.15 g of p-toluene sulfonic acid, 10 mL of deionized water, O2 pressure of 1 MPa, and temperature of 140 ℃ were reacted for 3 h, the conversion rate of cellulose reached 98%, and the yield of formic acid was 47%. In addition, catalytic performance of the catalyst for the conversion of monosaccharides(xylose and glucose) into formic acid was studied, and the conversion of xylose to formic acid had the highest yield of 63%.
In order to improve the hydrophilicity of PVC membrane, lignin/PVC membrane was prepared by polymer blending method.The cross-sectional morphology of the film was characterized by scanning electron microscope (SEM).The effects of lignin dosage, pore-forming agent type and dosage on the hydrophilicity of the membrane were studied by measuring the water absorption, porosity, membrane flux and membrane surface contact angle.The results showed that the lignin/PVC membrane had multilevel pores.After adding lignin, the water absorption, porosity, hydrophilicity and the membrane flux of the membrane were significantly improved.When the dosage of lignin was 0.06 g, the dosage of PVC was 3.0 g, and the action time of porogen was 10.5 h, the comprehensive performance of lignin/PVC membrane was the best.Compared with PEG400, the PPG200 and PEG200 with lignin had better hydrophilicity.When the dosages of PEG200 and PPG200 were 0.6 g, the surface contact angles of the membranes were 75.7° and 77.9°, the porosities were 12.6% and 7.1%, the water absorption rates were 114.7% and 94.8%, and the membrane fluxes were 135.5 and 372.6 L/(m2·h), respectively.
Epoxy itaconate resin(IE) was synthesized by esterification of itaconic acid(IA) with epoxy resin E51. The IE was then reacted with different half-terminated isocyanates to prepare epoxy itaconate resin modified with isocyanate(DIHIE) in order to improve the UV curing activity. In next, the chemical structure and particle size distribution of IE and DIHIE were characterized by FT-IR, 1H NMR and laser particle sizer. The results showed when the molar ratio of carboxyl group to epoxy group was 2∶[KG-*9]1, the reaction temperature and time was 90 ℃ for 4 h, and the amount of catalyst N, N-dimethylbenzylamine was 3% of the total amount of reactants, while the conversion rate of the IA was about 95%. The half-terminated isocyanate intermediate was synthesized from isophorone diisocyanate(IPDI) and hydroxyethyl methacrylate(HEMA), and then it reacted with IE to obtain IPDIHIE. IPDIHIE was synthesized with acetone as solvent, which was carried out at acetone reflux temperature(56 ℃) for 8 h. The storage stability of the DIHIE dispersion was better when triethanolamine(TEOA) was used as neutralizing agent. The UV curing activity of the resins were improved obviously after being modified by half-terminated isocyanate. The curing time was shortened from 100 s to less than 60 s after modification. The pencil hardness of paint film could reach 4H and the adhesion performance was excellent. Moreover, all of them were about 1 grade.
In recent years, levulinic acid has been considered as a key biobased platform compound and attracted wide attention, which can be utilized in the synthesis of many high value-added chemicals. Among them, levulinates, as a class of important chemical products, can be used in alternative fuels, edible spices, plasticizers and other fields, especially as alternative fuels, which provides a feasible reference scheme for sustainable development. In this paper, the recent research progress on the catalytic synthesis of levulinates in the field of biomass conversion was reviewed. The reaction performances and related mechanisms were introduced involving in several approaches, such as the esterification of levulinic acid, the alcoholysis of furfuryl alcohol, the conversion of monosaccharides and cellulosic materials, respectively. The synthesis of levulinates was summarized and prospected.
In order to enhance the flame retardancy of polysiloxane, a novel flame retardant rosin grafted polysiloxane(RGSO) was synthesized by the amidation reaction of rosin and amino-polysiloxane. The synthesized flame retardant was employed as a part of the soft segment to produce flame-retarding rigid polyurethane foam(RPUF) by "one-pot" process. The flame retardant rigid polyurethane foams(RPUF-1-RPUF-4) were obtained with the rosin amounts of 5, 10, 15 and 20 g. The structure of the flame retardants was characterized by FT-IR and Py-GC/MS. The microstructure, thermal stability, flame retardant property and compressive strength of the RPUFS were analyzed. The results showed that the hydrogenated phenanthrene ring structure of rosin inhibited the gas release of cyclosioxane and promoted the compactness of the silica-rich carbon layer, and invested the materials with excellent flame retardant since it become shielding layer coated on the substrate surface and effectively insulated thermal and oxygen flame retardant. Compared with unmodified RPUF(P-RPUF), the limited oxygen index(LOI) value of the modified sample(RPUF-3) increased by 37.1%, and the peak heat release rate(PHRR) of the modified sample decreased by 44.8%. The fire growth rate(FIGRA) of the modified materials decreased from 10.99 kW/(m2·s) to 4.33 kW/(m2·s), which indicated that the introduction of RGSO could significantly enhance the flame retardant performance of RPUF. Meanwhile, the rigid hydrogenated phenanthrene ring structure of rosin improved the compressive strength of the modified RPUF. The compressive strength of RPUF-4 was 366.7 kPa, which was higher than that of S-RPUF(112.5 kPa).
The hydrolysis of 5-chloromethyl furfural(CMF) in pure water or water/acetone system to 5-hydroxymethyl furfural(HMF) was studied. The effects of hydrolysis reaction conditions(such as solvent system, alkali neutralizer, temperature and CMF addition amount) on the hydrolysis of CMF were investigated, and the kinetics of the hydrolysis reaction was analyzed. The results showed that the water/acetone system is helpful to reduce the side reaction of HMF, and the addition of sodium disulfite(Na2S2O4) could further prevent the generation of humus. The optimal hydrolysis conditions are as follows: 1 g CMF was added with 0.35 g CaCO3 in a mixture of 10 mL water/acetone with volume ratio of 1∶4, and incubated at 353.15 K for 28 min. Under these conditions, the CMF conversion rate was 97%, the yield of HMF was 85%, and the yield of by-product levulinic acid(LA) was 6%. The separation rate of HMF increased from 50% to 86% with the addition of Na2S2O4. The kinetic study results showed that the activation energy of CMF hydrolysis was 12.3 kJ/mol and the hydrolysis rate constant k1=5.56exp(-1.23×104/RT) in water/acetone system.
Tannic acid(TA) is a kind of multi hydroxyl aromatic biomass. The thermal properties of TA were analyzed by thermogravimetric experiment, the carbonization process of TA was observed by muffle furnace heating experiment, the apparent activation energy was observed by KAS and Ozawa method, and the most probable function was determined by Satava method. Thermogravimetric analysis showed that TA entered the state of rapid weight loss at about 182 ℃; when the temperature reached 800 ℃, the carbon residue of TA in nitrogen atmosphere was 15.29%. In air atmosphere, the carbon residue was 1.97% due to the second rapid weight loss in the temperature range of 436-538 ℃. It was found in the macro carbonization experiment that TA would form an expanded carbon layer when heated. Among them, a hollow carbon layer appeared at 100-200 ℃, and a solid carbon layer was formed at 300-400 ℃, which had obvious expansion, integrity, compactness and good gloss. It had the potential to become a new carbon source in intumescent flame retardants. The results of thermal decomposition kinetics showed that the apparent activation energy of thermal decomposition of TA in nitrogen atmosphere was 494 kJ/mol, lgA was 111.32, and the most probable mechanism function of rapid weight loss stage was G(α)=[-ln(1-α)]1/n, n=0.105 3, and its thermal decomposition mechanism belonged to random nucleation and subsequent nucleation growth reaction.
Chlorogenic acid was extracted from Eucommia ulmoides leaves by natural deep eutectic solvent (NADES) with ultrasonic assistance.Its antioxidant activity was investigated.Firstly, the better natural deep eutectic solvent system was screened, and then based on the single factor test, the extraction process was optimized through the response surface and the antioxidant activity of chlorogenic acid from E.ulmoides leaves was investigated.The results showed that the better solvent system was composed of betaine, L-lactic acid and water, and the ratio of each component was 1:1:4, and water consumption in eutectic solvent was 5 mol.The optimum conditions for E.ulmoides chlorogenic acid extract were liquid-to-material ratio of 30:1(mL: g), extraction temperature 40℃, extraction time 42 min, ultrasonic power 340 W.Under these conditions, the yield of chlorogenic acid was 31.46 mg/g, which increased by 18.23% and 14.82% respectively compared with the extraction solvent of water (26.61 mg/g) or 60% ethanol (27.40 mg/g).The antioxidant activity of chlorogenic acid extract from E.ulmoides leaves was studied in vitro.The results showed that the NADES extract had strong scavenging ability to DPPH·, ABTS·, and·OH, with IC50 of 75.16, 19.98 and 314.20 mg/L, respectively.Its antioxidant capacity was stronger than those of water extract and alcohol extract, but slightly lower than that of Vc.
Cellulose, hemicellulose and lignin contents in P.eduli.residues were determined by van's method.Cellulose in Pueraria edulis Pampan.residue was sequentially treated with sodium chlorite and sodium hydroxide as treatment reagents.Various factors including mass fraction of sodium chlorite and sodium hydroxide, reaction temperature and reaction time were optimized.In addition, the morphology, crystal structure, chemical structure, and thermal stability of P.edulis residue, P.edulis residue after chlorite treatment, and P.edulis cellulose (P.edulis residue after further treatment with sodium hydroxide) were characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), Fourier transform infrared spectrum (FT-IR) and differential thermal gravimetric analysis, respectively.The results demonstrated that the content of cellulose in original P.edulis residue was 59%, which was increased to about 84% after treatment by 4% sodium chlorite at 100℃ for 120 min, and could further reach 94% after treated by 15% sodium hydroxide at 80℃ for 120 min.Ultimately, the crystal texture of P.edulis cellulose was ascribed to cellulose Ⅰ with the crystallinity of 71.5%.The maximum pyrolysis temperature of P.edulis cellulose was determined as 356℃, strongly demonstrating its good thermal stability.
In order to explore the antioxidant activity of cinnamon polysaccharides, the protein was removed from the water extract of cinnamon(CE)to obtain crude polysaccharides. By using cellulose ion column DE-52 and propylene dextran gel S-300, the cinnamon neutral polysaccharides(CNP) was obtained. The relative molecular mass(Mr) of CNP was determined by gel permeation chromatography(GPC), and the monosaccharide component of CNP were determined by pre-column derivatization high performance liquid chromatography. The connection modes of its monosaccharides were determined by methylation method and nuclear magnetic resonance method. The in vitro chemical model was used to study the scavenging effects of CNP on DPPH· and ABTS+·. The results indicated that the weight average relative molecular mass(Mw) of CNP was 3 630 and the main monosaccharide was glucose. Three kinds of connection modes of monosaccharides were 1, 4, 5-Ac3-2, 3, 6-Me3-Glu, 1, 5-Ac2-2, 3, 4, 6-Me4-Glu, and 1, 5, 6-Ac3-2, 3, 4-Me3-Glu. The determination results of free radicals scavenging by CNP showed that when the mass concentration of CNP was 2 g/L, the DPPH· scavenging rate reached the maximum of 84%, the ABTS+· scavenging rate reached 60%. Although the free radical scavenging rate of CNP was lower than that of Vc, the DPPH· scavenging effect was comparable to that of Vc when the concentration of CNP reached 0.5 g/L. Therefore, the antioxidant activity of cinnamon neutral polysaccharide was good and had good development value.
Based on mechanical force effect, graphite nanosheets/bamboo charcoal(GN/BC) composites with excellent electrochemical performance were prepared by high-energy ball milling and pulverization, and high-temperature carbonization using bamboo charcoal and flake graphite as raw materials. Meanwhile, the high-temperature porous bamboo charcoal(PBC) prepared without flake graphite was used as the control sample under the same conditions. The surface morphology and structure of the material were characterized by X-ray diffraction(XRD), Raman spectroscopy(Raman), scanning electron microscope(SEM) and specific surface area and pore distribution analyzer. The electrochemical performance of the product was tested by a three-electrode system. The results showed that the addition of flake graphite with higher crystallinity could improve the crystallinity of the composites. High-energy ball milling could break the graphite flakes into nanostructures and embed them in the bamboo charcoal. The specific surface area of the prepared GN/BC was 863.47 m2/g, the total pore volume was 0.56 cm3/g, the micropore volume was 0.26 cm3/g, and the average pore diameter was 2.58 nm. At a current density of 1A/g, the composite material had a high specific capacitance of 280.97 F/g and good rate performance.