As a kind of polymer material with versatile product forms, polyurethane is widely used in many applications. Developing technologies that can use green and renewable raw materials as feedstock has become a research hotspot, as well as great significance to the polyurethane research in the future. Based on the relevant literatures of the last decade, this paper focuses on the basic methods and research progress for the synthesis of bio-based polyols and isocyanates from common renewable alternatives, such as vegetable oil(castor oil, soybean oil, tung oil, palm oil, etc.), lignocellulose, rosin, natural phenols(cardanol and tannin), sugars and other biomass resources. In addition, the research status of non-isocyanates was mentioned, and the unique advantages of these materials for the preparation of bio-polyurethane were listed. This article also comprehensively examines the future hurdles that hinder the utilization of these materials, and then the development prospects of bio-based polyurethane materials in different fields are outlooked.
The polymers based on dynamic borate bonds had certain self-healing ability and multiple responses to stimuli, and they could respond to biological signal changes by inducing topological recombination of physical/chemical structures in the materials. A variety of natural/non-natural polymer materials based on three different transesterification mechanisms of borate esters were reviewed in this paper, namely hydrolysis/re-esterification, transesterification between diol and borate and transesterification between borate and borate. It was a strategy to design a more stable tetrahedral borate structure through the synergistic effect of traditional covalent bond and borate dynamic covalent bond to solve the borate ester polymer short plate. Application potential of borate-based polymers in many fields was summarized, such as biomedicine, sensors and recyclable materials. The synergistic of borate ester bond and other dynamic bonds to prepare ideal polymer materials was mainly emphasized, such as hydrogels, organic gels, liquid crystal materials, recyclable nanomaterials, etc.
Biomass had negative carbon properties and met the requirements of green development as a typical renewable energy. Under relatively mild conditions, hydrothermal carbonization was the process of converting biomass into various functional carbon materials. This paper discussed recent advances of biomass-based porous carbon materials by the hydrothermal transformation from biomass, such as monosaccharides(glucose, fructose, and xylose), lignocellulosic fibers(cellulose, hemicellulose, and lignin) and chitosan. The effects of temperature, reaction time and raw material concentration on its structure and properties were mainly discussed, as well as its applications in gas adsorption, dye adsorption and heavy metal ion adsorption. The authors proposed future research directions for the hydrothermal synthesis of high performance and environmentally friendly porous carbon materials from biomass.
As a important biomass platform compound, γ-valerolactone(GVL) could be used as green solvent, polymer precursor, fuel, and fuel additive, etc. Therefore, catalytic conversion of biomass to GVL was one of the important ways to utilize resource-based bio material and alleviate the resource and energy crisis. Furfural underwent Meerwein-Ponndorf-Verley(MPV) transfer hydrogenation reaction to prepare GVL in one pot had the advantages of simple operation, economy, environmental protection, safety and reliability. It was a route with great industrialization potential in the field of GVL synthesis research, therefore, it had received extensive attention from academia and industry. This paper described the catalytic activity centers of Brønsted acid(B acid) and Lewis acid(L acid) required for each step of the conversion of furfural to GVL. The efficient solid catalysts for the preparation of GVL by the one-pot method from furfural were summarized in terms of catalyst construction methods and the structure of the carrier. Molecular sieves with hydrothermal stability and good mass transfer effect(e.g. beta molecular sieve, ZSM-5 molecular sieve, etc.) were found to be the commonly used carriers in this reaction. In addition, modification by molecular sieves with de-Al, or introducing active centers such as Zr and Hf compounds with L acid sites, and phosphotungstic acid with B acid sites are common means to construct efficient bifunctional catalysts for the this reaction. The causes of catalyst deactivation and regeneration methods were also summarized in this paper, and the effects of catalytic reaction conditions such as solvent and temperature on the reaction activity were analyzed. At the same time, some suggestions were provided for the design of new and efficient catalysts for this reaction.
Rosin was an important natural renewable forestry resource in our country, mainly composed of resin acids, which contained a tricyclic phenanthrene skeleton with conjugated double bond and carboxyl group, thus they could undergo various chemical reactions such as hydrogenation, disproportionation, addition, esterification, rearrangement and oxidation. Dehydroabietic acid whose skeleton contained an aromatic ring was obtained from rosin by catalytic disproportionation and purification. Based on the aromatic ring and carboxylic acid group, a variety of fluorescent derivatives could be developed, which opened up a new way for the high value utilization of rosin. In this paper, several types of fluorescent derivatives based on dehydroabietic acid aromatic ring, including acylated compounds, aromatic amines, heterocyclic compounds, Schiff base compounds and other compounds, and fluorescent derivatives based on carboxylic acid modification, such as dehydroabietylamine, heterocyclic compounds, and dehydroabietic acid carboxyl derivatives, were emphatically summarized. Their fluorescence properties and applications as luminescent materials in the fields of organic light-emitting devices, fluorescent probes and cell imaging, were reviewed. The current existing insufficient problems on the research of rosin-based fluorescent derivatives were discussed, such as the deficiency of blue and red light materials with high luminescence efficiency, lower luminescence efficiency in organic electroluminescent devices relying on solid film luminescence, and the insufficient research on the luminescence mechanism. In addition, development trends in the future were prospected.
Hydrothermal liquefaction was one of the thermochemical conversions of lignocellulosic biomass. It was considered as an environmentally friendly technology for using water as a solvent. In this review, research progress in hydrothermal liquefaction of lignocellulosic biomass in recent years was summarized and discussed. Analysis strategies of hydrothermal liquefaction products of lignocellulosic biomass were introduced. The hydrothermal liquefaction mechanism of lignocellulosic biomass, such as cellulose, hemicellulose and lignin, and composition and distribution of hydrothermal liquefaction products were analyzed. The effects of reaction temperature, reaction time, catalyst and co-solvent on hydrothermal liquefaction of lignocellulosic biomass were discussed. The characterization methods of liquefaction products such as biological oil, incoagulable gas and solid residue were introduced emphatically. Finally, suggestions were performed on the future development direction of wood fiber hydrothermal liquefaction.
5-Hydroxymethyl furfural(HMF) was a kind of important platform chemical compound, which was a precursor for producing liquid biofuel and many other important fine chemicals. The synthesis of HMF from biomass was one of the hot topics in the comprehensive utilization of biomass resources. Bamboo has the advantages of fast growth, short mature period, high yield and continuous use for years after once planting, and it contains a mass of cellulose. Glucose could be obtained from hydrolysis of the nature abundant cellulose, and HMF could be prepared by dehydration of glucose. Therefore, the catalytic conversion of bamboo to produce HMF had the advantages of abundant raw materials resources and green feasible technical route. In order to realize the efficient conversion of bamboo to HMF, the design and selection of catalytic system were the key factors. In this paper, the research on the preparation of HMF by catalytic conversion of bamboo in recent years was reviewed. Starting from the composition and characteristics of bamboo raw materials, the chemical composition and microstructure of bamboo were analyzed firstly, and then, the catalytic conversion mechanism was further elaborated. In particular, the influence mechanism on the preparation of HMF from bamboo by homogeneous catalyst, heterogeneous catalyst and other catalysts was analyzed in detail. The choice of solvent system was also discussed. Finally, combined with the development trend, the future development direction of its technology was proposed, which provided constructive suggestions for the development and industrial application of bamboo-based HMF technology.
Gleditsia sinensis thorn(GST) is widely distributed in China, which is commonly used in traditional Chinese medicine compatibility. However, few studies on its chemical composition and pharmacological activity hindered its further development and utilization. Based on the review of secondary metabolites containing saponins, flavonoids, triterpenoids, sterols, polyphenols, alkaloids, coumarins, indoles in GST, the research further introduced research progress of pharmacological activities of GST, such as anti-tumor, anti-bacterial, anti-oxidation, anti Human Immunodificiency Virus, anti-inflammatory, treatment of depression, treatment of prostate hyperplasia, treatment of endocrine disorders and immune regulation, providing a theoretical and application basis for the rational development and utilization of GST.
The problem of air pollution caused by flowing dust was becoming more and more prominent to the ecological environment and human health. Dust suppressants had attracted wide attention in the industry owing to their efficient dust suppression performance and convenient usage. At the same time, driven by the "Double Carbon" policy, dust suppressants had been developed towards green and environmental protection. Among them, bio-based dust suppressants prepared from biomass were highly favored owing to the advantages of renewable raw materials and degradability. This paper introduced the classification of dust suppressants(wetting type dust suppressant, bonded dust suppressant, agglomeration-based dust suppressant and composite dust suppressant) and dust suppression mechanism. The status of research and application progress of bio-based dust suppressants prepared from natural biomass raw materials such as starch, cellulose, guar gum, lignin and protein were described in detail, and the main research results of bio-based dust suppressants were listed. Through the introduction and analysis of biomass raw materials, it was shown that biomass raw materials in the preparation of dust suppressants had significant advantages such as degradable, renewable resources and a wide range of sources. It is proposed that the use of natural biomass as a raw material for dust suppressants would be the main research and development direction of dust suppressants under the new environmental protection model.
In the light of high energy consumption in sludge drying, a new process for sludge drying coupled with pyrolysis was proposed. The factors affecting the heat transfer of combustible gas(such as pyrolysis temperature and addition rate of poplar sawdust) and the influence of heating rate on pyrolysis products and system energy consumption were analyzed through the simulation with Aspen Plus software. The results indicated that when the co-pyrolysis of poplar sawdust and sludge was carried out, the addition rate of poplar sawdust must reach 43.5% to maintain a normal and stable operation of the system. When the pyrolysis temperature was 550 ℃, the yield of pyrolysis oil as the main component of combustible gas reached the maximum of 51.7%, and the system had the maximum heating capacity of 12.619 MJ/h. Additionally, it was found that when the heating rate increased, the yield of solid residue decreased, while the overall yield of pyrolysis oil and combustible gas increased. And when the heating rate decreased, the yield of pyrolytic oil and gas also decreased. Finally, the pilot plant scale-up test results showed that at a sludge feeding rate of 3 kg/h, the desired drying goal could be achieved at a minimum of residence time of 45 min and air flowrate of 40 L/min.
Using sodium lignosulfonate(LS) as a raw material and polyvinyl alcohol as an adhesive, a sodium lignosulfonate fluorescence membrane was prepared. The morphology and optical properties of LS were analyzed by fluorescence spectrometer and nano-size analyzer, and the quenching effect and mechanism of LS fluorescence by nitro compounds and non-nitro compounds were studied. Additionally, sodium lignosulfonate fluorescence membrane was applied for nitro-explosive detection. The results showed that LS had the property of aggregation induced emissions. The fluorescence quenching degree of LS by nitrobenzene and p-nitrophenol was as high as 90%, and the fluorescence of LS by m-dinitrobenzene was 56%, while benzene, toluene, phenol, terephthalic acid, terephthalaldehyde, o-phthalaldehyde and other nitro-free compounds almost had no fluorescence quenching effect on LS. This indicated that LS had high sensitivity and specific detection performances for nitrobenzene, m-dinitrobenzene, p-nitrophenol and other nitro-compound, which was mainly owing to the photoinduced electron transfer mechanism. The degrees of fluorescence extinction of the sodium lignosulfonate membrane immersed in the nitrobenzene solution, the m-dinitrobenzene solution and the p-nitrophenol solution were 89%, 78% and 100%, respectively. When the nitro compound solution was used to write on the fluorescent film, the handwriting could not be observed under sunlight, while the obvious fluorescence quenching phenomenon could be observed in the handwriting part under ultraviolet light.
Lignin contained abundant carbon atoms in its chemical structure, which could be used as filler in polymer materials to provide carbon source and promote flame retardant in the combustion process of polymer materials. The molecular structure of lignin contained active groups such as aromatic group, phenolic hydroxyl group and alcohol hydroxyl group. A series of lignin-based flame retardants could be obtained by introducing flame retardant elements or groups into the chemical structure of lignin through chemical modification. Starting from the structure of lignin, this paper summarized the domestic and foreign research progress of unmodified lignin, nitrogen and phosphorus modified lignin, and nitrogen and phosphorus modified lignin doped with copper or non-metallic elements like silicon as flame retardants in different polymeric materials, including physical synergistic flame retardant formulations, chemical modification preparation process and the comparison of flame retardancy effect before and after treatment. The flame retardant mechanism of the corresponding flame retardants was analyzed, including the oxygen isolation effect by the released non-combustible gas, the formation of dense non-combustible carbon layer, and the hindering effect on heat transfer. Additionally, the application prospect of lignin-based flame retardants was prospected.
This study focused on the treatment of refined soybean oil wastewater by Trichosporon fermentans. Firstly, the yeast was immobilized with sodium alginate and the prepared magnetic carrier, respectively. Then, the yeast, magnetic carrier, sodium alginate-immobilized yeast, and magnetic carrier-immobilized yeast were used to treat refined soybean oil wastewater, respectively. The comparative analysis of the treatment results showed that the magnetic carrier immobilized yeast treatment of refined soybean oil wastewater at 36 h was the best among the four substances. The pH value of 6.0 was more suitable for the growth of immobilized yeast on magnetic carrier. The OD600 value of yeast in wastewater treated after 36 h was 19.78. By studying the treatment of refined soybean oil wastewater by magnetic carrier specified yeast under different pH values and inoculation conditions, the optimal conditions for wastewater treatment were pH value 6.0, inoculation amount 10% and culture time 36 h. Under these conditions, chemical oxygen demand value was 2 430 mg/L.
Biomass energy was an ideal clean energy, with the advantages of renewable, diversity and could achieve zero carbon dioxide emissions. Biomass catalytic reforming to produce hydrogen was an effective, environmentally friendly and economical way of biomass thermochemical conversion and utilization. In this paper, the research progress of biomass catalytic reforming for hydrogen production was reviewed from the aspects of key reaction parameters in the process of biomass catalytic reforming: reaction temperature, ratio of water to carbon, reaction space velocity and catalyst. The effects of reaction parameters, catalyst selection and application on pyrolysis products were reviewed. The influence mechanism of natural ore catalyst, alkali metal catalyst, transition metal catalyst and spinel catalyst on the water vapor conversion characteristics of biomass was combed. The effective utilization way of improving the efficiency and stability of reforming reaction by developing stable catalyst with high activity through directional control was summarized. It was pointed out that the clear catalytic mechanism should be further explored from the perspective of the interaction mechanism between biomass and catalyst and the reaction mechanism of pyrolysis and gasification.
In order to explore the high-value utilization of agricultural and forestry waste, six common types of agricultural and forestry waste, including corn stalks, rice straw, soybean stalks, pine branches, bamboo branches, and biogas residue, were used as raw materials to prepare biochar by limiting oxygen and temperature controlling carbonization in vacuum tube furnace. The physicochemical properties and structural characteristics of biochar were analyzed by surface area analyzer, scanning electron microscope and Fourier transform infrared spectroscopy, and the adsorption capacity of biomass carbon on ammonia nitrogen and total phosphorus in swine wastewater was investigated. The results showed that six kinds of biomass carbons were alkaline, and the alkalinity of biogas residue biochar was stronger than that of plant biochar. The yield order of six kinds of biochar was as following: biogas residue biochar(64.83%) > soybean stalk biochar(57.22%) > rice straw biochar(48.80%) > corn stalk biochar(46.87%) > bamboo biochar(41.42%) > pine branch biochar(40.01%). Among them, the soybean stalk biochar had a larger specific surface area(5.84 m2/g) and developed pores. All six kinds of biochar contained abundant oxygen-containing functional groups on their surfaces, and both chemically stable C—H and benzene rings had strong stability. The six kinds of biochar had certain adsorption effects on ammonia nitrogen and total phosphorus in aquaculture wastewater, with corresponding adsorption capacities ranging from 20.00 to 31.00 mg/g and 4.00 to 6.69 mg/g, respectively. Soybean stalk biochar had the best adsorption effect on ammonia nitrogen and total phosphorus, with a saturated adsorption capacity of 31.00 mg/g and 6.69 mg/g, respectively.
Alkali lignin(AL) was separated and purified from papermaking black liquor by acidic precipitation. Then, quaternary ammonium lignin(QAL) was obtained by modifying AL with 3-chloro-2-hydroxypropyl trimethyl ammonium chloride. Using cellulose hydrogel(CEH) as matrix, antibacterial silver nanoparticles-quaternary ammonium lignin-cellulose hydrogel(Ag NPs-QAL-CEH) was prepared by impregnating with QAL and silver nitrate solutions. The structures of AL and QAL were characterized by Fourier transform infrared spectroscopy and the results showed that QAL was successfully prepared. The results of elemental analysis showed that the content of nitrogen increased from 0.6% to 5.9%. Ag NPs-QAL-CEH was characterized by X-ray diffraction and scanning electron microscopy. The results indicated that Ag NPs were obtained by reducing Ag+ with QAL, and Ag NPs-QAL was uniformly dispersed in the three-dimensional network structure of CEH. The antibacterial performance of the hydrogel showed that Ag NPs-QAL-CEH formed obvious inhibition zone against S. aureus and E. coli. Furthermore, with the increase of AgNO3 dosage, the diameters of antibacterial circle increased from 14.2 mm to 20.1 mm and 16.1 mm to 18.1 mm, respectively. When the mass concentration of AgNO3 was 7.87 g/L in 50 mL QAL solution(including 2.5 g QAL), the obtained Ag NPS-6-QAL-CEH had the best bacteriostatic effect, and the inhibitory rates against S. aureus and E. coli could reach more than 99.5%.
This paper expounded the origin and development of wood scrimber, and our country proposed new type of fibrous veneer high-performance wood scrimber manufacturing technology specific links research progress was summarized. In the rolling and loosening stage of the raw wood, the physical and mechanical properties of the wood scrimber were enhanced with the increase of dispersion degree. In the fibrous veneer modification stage, the modified treatment improved the fire prevention and mildew resistance of the wood scrimber, giving the wood scrimber versatility. In the gumming stage, the differences in mechanical strength and function of wood scrimber of different tree species under different soaking method and impregnation amount were summarized. The influence of the paving method and equipment on the strength and dimensional stability of wood scrimber was analyzed. The advantages and disadvantages of hot pressing method and cold pressing as well as hot curing in the pressing stage are summarized. Finally, based on the defects of wood scrimber and the high value-added utilization cases of existing wood materials, some new ideas were raised improving the strength of wood scrimber and expanding their application.
The coupling system of hydrogen peroxide and attapulgite was used to decolorize Camellia oleifera saponin. The effects of the amount of hydrogen peroxide, temperature, time, and attapulgite amount on the decolorization rate were investigated, and the optimal conditions for decolorization of saponins were explored. The advantages and disadvantages of different color evaluation methods, such as spectrophotometer, spectroradiometer, Lovibon colorimeter, color scale colorimeter, and visual photography, on the color determination of saponins were compared. The results showed that the optimum decolorization conditions were 6% H2O2, 80 ℃, 3 h, 3% attapulgite, and the milky white Camellia oleifera saponin. The results of five color evaluation methods are basically similar. The color of Camellia oleifera saponin could be accurately and quantitatively analyzed by spectrophotometer. The spectroradiometer method was suitable for color evaluation with small color difference. The Lovibond colorimeter method had advantages in the scene where a wide range of color analysis of Camellia oleifera saponin solution was required. Color scale colorimetry has simple operation and high feasibility. Visual photography could support the above methods.
In order to study the combustion characteristics of pellet fuel prepared by blending wheat residue and waste liquid in pulping process, the combustion thermodynamics and kinetics characteristics were analyzed by thermogravimetric test. The results showed that pulping waste liquid resulted in the secondary combustion stage of fixed carbon in the pellet fuel. The addition of pulping waste liquid was helpful to decrease the volatile content of pellet fuel, the ignition temperature, and maximum combustion rate temperature in the fixed carbon combustion stages, which had a positive synergistic effect on the combustion of pellet fuel. The thermogravimetric data were fitted with a first-order dynamics equation, and the correlation indexes of the prepared pellet fuel were all above 0.95. The addition of the pulping waste liquid reduced the activation energy and frequency factors of the pellet fuel in the volatile combustion and fixed carbon combustion stages, respectively. The activation energies of the corresponding stage when a solid mass fraction of 53% of the waste liquid were 72.85 and 83.52 kJ/mol, and the frequency factors were 2.82×106 and 3.73×105 min-1, respectively. The addition of the pulping waste liquid made the pellet fuel easier to burn, and the combustion process became stable and uneasy to deflagrate.
In this study, fiber cells and parenchyma cells of poplar were prepared from poplar by glacial acetic acid-hydrogen peroxide treatment. On this basis, the differences of enzymatic hydrolysis between fiber cells and parenchyma cells were investigated, and the influencing factors, water distribution and mechanical properties of the enzymatic hydrolysis process were analyzed. The results showed that parenchyma cells had higher accessibility of enzymatic reaction and the fermentable sugar content of parenchyma cells reached 208.6 g/L after 72 h of enzymatic hydrolysis, which was 8.5% higher than that of fibrous cells. With the same enzymatic hydrolysis efficiency of xylose(59%), the enzyme loading of parenchyma cells decreased by 50% compared to fibrous cells. The enzymatic hydrolysis rate of parenchyma cells increased by 15.4%-33.3% with the high solid system(the solid loading was more than 15 g/mL). The state of water distribution showed that parenchyma cells had weaker water binding effect during enzymatic hydrolysis process and had better liquefaction performance. The mechanical properties showed that the key stage determining the difference of enzymatic hydrolysis performance between fiber cells and parenchyma cells was the first 24 h. In addition, parenchyma cells had weak mechanical properties during enzymatic hydrolysis, which helped to save energy and shorten cycle time.