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.
Anthocyanin is a kind of flavonoid which mainly exists in plants. It has strong biological activities such as anti-cancer and anti-oxidation, and is widely used in the field of nutrition and health care. Most anthocyanins are extracted directly from plants by physical or chemical means, but the yield is low, and the extracted anthocyanins are mostly mixtures due to the restrictions of time, region and season. Biosynthesis of anthocyanins have attracted much attention by researchers worldwide in recent years. As the biosynthesis of anthocyanins can be controlled artificially and the purity of the obtained products is high, it has been widely studied. Anthocyanins cannot exist stably in the environment, and need to be modified by glycosylation, acylation and methylation to increase their stability. The modified anthocyanins can be synthesized by microorganisms and significant color changes can be seen in the medium. The biosynthesis and modification of anthocyanins were reviewed in this paper, and the preparation technology of anthocyanin synthesis from plants and microorganisms was briefly introduced, the factors affecting anthocyanin synthesis were analyzed, and finally the future research direction of anthocyanin was predicted.
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.
5-Hydroxymethylfurfural (HMF) is one of the most important biomass-based platform molecules and widely used in the preparation of multifunctional compounds such as fine chemicals, key pharmaceutical intermediates, functional polyesters, solvents and liquid fuels. At present, the preparation of HMF is a hot spot in the field of biomass research, and the raw materials and methods for preparing HMF have been continuously expanded. This paper reviews the main preparation methods and research progress of HMF. Catalysis systems for HMF preparation is systematically described, including the types of the catalysts (mineral acids, ionic liquids, metal chlorides, solid acids and others) used in the catalytic process and the solvent systems. Then, the preparation paths and applications of important derivatives from HMF are summarized. Finally, suggestions for future research on HMF are provided based on the understanding of problems existing in the current research.
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 the most abundant renewable aromatic polymer in nature, which complex structure and compact connection with cellulose and hemicellulose through covalent bond and hydrogen bond make it difficult to be separated efficiently. Deep eutectic solvents (DES) is a novel kind of green ionic liquid, which has been successfully applied to lignin isolation due to its unique physical and chemical properties. The research progress of dissolution and extraction of lignin by deep eutectic solvents (DES) is reviewed in detail. From the point of view of the mechanism of dissolving lignin by DES, the effects of different factors(composition, proportion, pH value, functional groups of DES, water content of system, raw material, reaction time, temperature, catalyst, co-solvent, and so on) on lignin removal were emphatically expounded. Based on the research progress of DES in lignin extraction, the research progress and futuer application of lignin extraction were summarized and 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.
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.
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.
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.