Tobacco in Sichuan, Guizhou, and Fujian was selected as raw materials, and the essential oil of tobacco was extracted by distillation in water. Gas chromatography-mass spectrometry(GC-MS) was used to analyze the composition and content of tobacco essential oil from different production areas, and the influences of different production areas on the yield and composition of the product were compared. The results showed that the average yields of tobacco from Fujian, Sichuan, and Guizhou were 0.139 1%, 0.085 1%, and 0.107 5%, respectively, and the corresponding contents of neophytadiene were 39.86%, 36.12%, and 44.88%, respectively. According to the comparison analysis, the tobacco produced in Fujian had the highest oil yield and moderate characteristic aroma; the tobacco essential oil produced in Guizhou had moderate oil yield, prominent tobacco aroma, and obvious licorice aroma; the tobacco essential oil produced in Sichuan had the highest oil yield, and weaker aroma.
Hydrogen-rich syngas production from biomass gasification is considered as one of the most promising hydrogen production methods because of its clean and renewable raw materials and the diversity of product application. Catalysts play an important role in controlling the composition of biomass gasification products and the pyrolysis of tar. In this paper, the methods of hydrogen production from fossil energy, water decomposition, and biomass were reviewed, and the advantages, limitations, and existing problems of hydrogen production from biomass gasification were also analyzed. And, the influence factors of biomass gasification(gasification agent, reaction temperature, and catalyst) and the kinds of catalyst and its characteristics which used for biomass gasification(nickel-based, dolomite and alkali, and alkaline earth metal catalysts) were emphatically introduced. The research status of biomass gasification for making hydrogen rich syngas and catalysts in China and abroad were analyzed, and the prospects of the development of catalytic gasification for making hydrogen-rich syngas were discussed. The problems to be solved and the research direction were proposed.
As a kind of renewable forest product resource with abundant yield and low price, rosin is widely used in food, agriculture, rubber, ink, coating, and other fields. The tricyclic diterpene structure of rosin possesses extreme hydrophobicity, and hydrophilic groups can be introduced into rosin by means of catalytic isomerism, Diels-Alder addition, and other means to prepare high value-added and biodegradable green surfactants. Rosin-based surfactant literatures and patents published in China and abroad were retrieved from four categories: anionic, cationic, nonionic and amphoteric surfactants. The surfactants with the anion of carboxylate, sulfonates, sulfates, and phosphates, and the cation of quaternary, polyols and polyoxyethylene nonionic surfactants, and betaine and amine oxide amphoteric ionic surfactants were analyzed especially. The industrialization development of new technologies and new products of rosin-based surfactants were discussed, and the potential application fields of rosin-based surfactants instead of traditional surfactant were proposed. Meanwhile, the research and industrialization development of rosin-based surfactants were also evaluated and prospected.
Using corn straw as raw material, the characteristics and kinetics of its pyrolysis were studied by TG. The physicochemical properties of corn straw before and after pyrolysis were analzed according to the TG and DTG curves. Activation energy of corn straw pyrolysis were calculated using the isoconversional models of Flynn-Wall-Ozawa(FWO) and Kissinger-Akahira-Sunose(KAS), and the thermal degradation mechanism was investigated by the master-plot and Coats-Redfern(C-R) methods. The results showed that the pyrolysis process of corn straw could be divided into 4 stages: drying dehydration stage, transition stage, main pyrolysis stage, and carbonization stage. The pyrolysis curve shifted to the high temperature side with the increasing heating rate. The apparent activation energies calculated by FWO and KAS were 181.7 and 181.5 kJ/mol, respectively. The pyrolysis mechanism equation of corn straw was calculated using the master-plot method and C-R method, which follows Avrami-Erofeev equation. When α=0.1-0.5, n=3, f(α)=1/3(1-α)[-ln(1-α)]-2, and when α=0.5-0.7, n=2, f(α)=1/2(1-α)[-ln(1-α)]-1.
In order to solve the low crosslinking activity resulted from protein denaturation of high-temperature soybean meal(HTSM), the thermal-alkali activation of HTSM was proposed, and the effects of sodium hydroxide(NaOH) dosage on the structure and properties of HTSM and HTSM-based adhesive were evaluated based on the FT-IR, XRD, XPS, TGA analysis and other traditional methods. The results revealed that thermal-alkali activation could not only unfold HTSM's globular structure to release the buried active group but also hydrolyze partial peptide into amino and carboxyl groups. Then, the crosslinking reactions between reactivated HTSM and crosslinking agent was increased, and the obtained soybean protein adhesive had equivalent thermal and water resistances with the adhesive prepared by low-temperature soybean meal due to the formation of sufficient crosslinked networks. The results of thermal-alkali activation showed that the most preferable NaOH dosage was 2%(mass fraction), and the acetaldehyde value of HTSM was 4.28 mg/g(reactivated HTSM). Correspondingly, the adhesive viscosity was 59.8 Pa·s, the soaked wet bonding strength was 1.48 MPa(63 ℃ for 3 h), the boiling-dry cycled wet bonding strength was 0.96 MPa, the boiling-water-insoluble content was 79.73%, the mass-residue ratio was 40.87%, and the temperature for maximal degradation rate was 306.1 ℃.
The effects of torrefaction pretreatment on the preparation and properties of activated carbon by phosphoric acid using corn straw as the raw materials were studied. The results showed that the contents of carbon and fixed carbon were increased and the volatile content was reduced using torrefaction pretreatment which increased the quality of pyrolytic carbon. The effect of torrefaction temperature was stronger than that of torrefaction time. By torrefaction pretreatment, the specific surface area of activated carbon increased firstly and then decreased, the total pore volume and the mesoporosity decreased, while the microporosity increased significantly. The adsorption performance of activated carbon could be improved by torrefaction pretreatment. As 100 g corn straw with the particle size of 154-450 μm were pretreated under the torrefaction temperature of 240 ℃ and torrefaction time of 60 min, the pretreated corn straw contained carbon, fixed carbon, and ash with the mass fractions of 51.32%, 27.64% and 4.72%, respectively. The activated carbon was prepared from the pretreated corn straw under the impregnation ratio of 1∶4(i.e., the mass ratio of the pretreated corn straw and 55% phosphate acid), dipping temperature of 140 ℃, dipping time of 90 min, activated temperature of 400 ℃, activated time of 60 min, the specific surface area of the obtained activated carbon reached 1 317.05 m2/g, and the values of iodine adsorption, methylene blue adsorption, and caramel decolorization were 876 mg/g, 210 mg/g and 100%, respectively.
As the most abundant renewable resource on the earth, lignocellulosic biomass not only has huge reserves but also has a significant advantage on carbon balance in the utilization process. It has gradually become one of the most promising renewable energy sources. Among the lignocellulose lignin is the largest and only renewable aromatic compound raw material in the nature. It plays a very important role in the conversion of biomass fuels, especially the depolymerization production of benzene chemical products. Based on the brief chemical structure description of lignin, this paper summarized the depolymerization methods of lignin in recent years, such as high-temperature thermal depolymerization, biological enzyme depolymerization, catalytic thermal depolymerization, photocatalytic depolymerization, and solvent pyrolysis. The mechanism, advantages and disadvantages of acid and alkali catalytic system as well as hydrogenation and oxidation catalytic system in the process of liquid-phase catalysis were deeply analyzed. Additionally, the problems existed in the depolymerization methods of lignin at this stage were also summarized, and the developing direction in the future was proposed.
Biochar was prepared by high-temperature pyrolysis with bulk agricultural waste corn straws as raw material, and the performance of biochar on heavy metal removal was investigated through the adsorption experiments of lead and cadmium in water.The results showed that the corn straw biochar obtained at 800 ℃ was mainly in the form of block and rod, the pore structure was micropores, and the alkali metals and alkaline earth metals in the ash were dominated. The maximum adsorption capacities of Pb2+ and Cd2+ were 94.79 and 24.47 mg/g, respectively, when the adsorption temperature was 25 ℃, pH value was 4, adsorption time was 960 min, and the mass concentrations of Pb2+ and Cd2+ were 429.24 and 280.34 mg/L. The removal process of lead and cadmium in water by biochar followed the pseudo-second-order kinetic equation and the Freundlich isotherm model. When the initial mass concentrations of lead and cadmium were all 150 mg/L, the obtained equilibrium adsorption capacities were 69.0 and 24.4 mg/g, respectively. Thermodynamic analysis showed that the process belongs to endothermic and entropy increasing. Additionally, Pb2+ could significantly antagonize the removal of Cd2+ in binary metal ion solution.The adsorption mechanism of corn straw biochar indicated that the removal of both metal ions was the combination of physical adsorption and chemical precipitation.
Sugarcane bagasse(SCB) was pretreated by hydrogen peroxide-acetic acid(HPAC). The pretreated SCB was used as raw material for enzymatic hydrolysis, and then the hydrolysate was fermented for ethanol. The effects of pretreatment on enzymatic hydrolysis and fermentation of SCB were discussed. The results showed that HPAC pretreatment removed 88.85% lignin and retained 90.10% cellulose in the substrate when 20 g SCB was added with 150 mL aqueous hydrogen peroxide(i.e., 75 mL hydrogen peroxide(30%) and 75 mL water) and 150 mL acetic acid(99%), the amount of sulfuric acid was 0.5% of the HPAC solution volume, and the reaction was preformed at 70 ℃ for 2 h. The enzyme accessibility of substrate was 80.30 mg/g, which increased by 38.26% and 31.08% compared with those of hydrogen peroxide pretreatment (HP/70-SCB) and acetic acid pretreatment(AC/70-SCB) under the same conditions, respectively, and the surface coverage of lignin decreased from 0.66 to 0.22. After hydrolysis with enzyme dosage of 5 FPIU/g(substrate), the yield of glucose was 87.63%, which was 6.89 and 20.62 times than those of HP/70-SCB and AC/70-SCB, respectively. The mass concentration of ethanol produced by fermentation was 7.57 g/L, which was 7.65 and 22.94 times than those of HP/70-SCB and AC/70-SCB, respectively.
Lignin amine(AL) was prepared by modifying corn cob via Mannich reaction, and then AL was mixed with water-based polyamide(PAE) and polyethylene glycol diglycidyl ether(PEGDE). Soybean meal was used as raw material to prepare soybean gum with high solid content by AL/PAE/PEGDE modification. The properties of soybean gum were characterized and tested, and the FT-IR results showed that the absorption peak of amide Ⅰ of the soybean meal adhesive modified with AL, PAE, and PEGDE after curing shifted from 1632 cm-1 to 1640 cm-1, and amide Ⅱ shifted from 1533 cm-1 to 1538 cm-1. And the shift suggested that the cured adhesive possessed a dense and cross-linking structure. The TGA results also showed that the network structure between PAE, PEGDE, AL, and protein molecules was more compact, and the rheological behavior analysis showed that the cured soybean meal adhesive had the characteristics of pseudoplastic fluid. The solid content in the modified adhesive was as high as 42.5%, while the apparent viscosity was simply 3 746 mPa·s, which was suitable for application in plywood industry. The wet bonding strength of the prepared plywood reached 0.86 MPa and the pass rate was 100%, which meet the national standard for type II plywood(bonding strength≥0.70 MPa, and the pass rate≥90%).
Conversion of biomass into high value-added chemicals was an effective way to solve the current problems of fossil energy depletion and global warming. 5-Hydroxymethylfurfural(HMF) was considered as one of the most important platform compounds, which could be used to prepare many high value organic compounds through oxidation, hydrogenation, and ring-opening reactions. Among its derivatives, 2, 5-furandicarboxylic acid(FDCA) could be regarded as the most promising chemical, which could replace the widely used petroleum-based polyester terephthalic acid(PTA) to synthesize biodegradable polyester polyethylene furanoate(PEF). This article systematically reviewed the new processes for preparing FDCA from HMF through electrocatalytic oxidation, photocatalytic oxidation, and biocatalysis. These catalytic methods were different from traditional pyrolysis catalytic methods, which did not requiring high temperature and pressure as well as harmful solvents and expensive catalysts, and had the characteristics of high efficiency, greenness, and sustainability. However, there were still some problems, such as electrocatalysis needed special and stable electrolytes and high requirements for instruments and equipment; photocatalysis had the problems of high cost and low energy conversion rate; biocatalysis had long preparation cycles and the inhibited intermediates. By analyzing the results obtained by these methods and the existing problems, it provided feasible ideas for the efficient catalytic conversion of FDCA in the future.
Furfural is the bridge connecting raw biomass to the biorefinery industry. The reductive transformations of furfural in aqueous medium is an important way to prepare a wide variety of fine chemicals. Plenty of downstream products can be obtained by heterogeneous catalyst, such as(tetrahydro) furfuryl alcohol, 2-methyl(tetrahydro) furan, lactone, levulinate, cyclopentanone, cyclopentanol, and so on. The activity of catalyst mainly depends on the properties of metal and support, as well as reaction conditions, such as temperature, time, solvent, and pressure and so on. The research progress of furfural hydrogenation for preparing cyclopentanone and cyclopentanol using different non-noble metal(Cu, Ni, and Co) and precious metals(Pd, Ru, Pt, and Au) based catalyst were summarized. It was found that Ru, Pd, Au, and Cu-based catalysts have higher selectivity than other catalysts, and Cu-Ni bimetallic catalysts have excellent catalytic activity and selectivity, while their stability needs to be improved. The mechanism of the hydrogenation reaction on the metal surface was discussed, and the results showed that the aqueous medium and weaker Lewis acid sites play an important role in the reaction of ring rearrangement. Meanwhile, the future research direction of the hydrogenation reaction of furfural in aqueous medium is proposed.
Environment protection, energy saving, and high efficiency are the main research directions for thermal insulation materials in the future, and the development of thermal insulation materials based on biomass is the future trend. Biomass-based porous materials refer to the porous materials prepared from renewable biomass as the precursor, which have the wide raw materials and diverse preparation methods. They have excellent characteristics, such as high porosity, low density, light weight, and so on, which has great application potential in the field of thermal insulation. In this paper, the heat preservation mechanism of the porous materials was overviewed, and the research progress on the cellulose, starch, chitosan, plant protein porous material in recent years was reviewed. The surfactant foaming method, freeze-drying method, pore-forming agent method, mould hot pressing method, solvent exchange phase separation in the application of biomass-based porous material preparation were also highlighted. Finally, the existing problems of biomass-based porous insulation materials are analyzed, and the future research directions of porous insulation materials are also prospected.
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.
Our country has the most abundant genera and species of Pinaceae plant in the world, including ten genera: Pinus, Picea, Cathaya, Pseudotsuga, Larix, Pseudolarix, Cedrus, Tsuga, Keteleeria and Abies. The liposoluble substance in pine needles from Pinaceae plant contain some compound with novel structure and significant bioactivity. In this paper, the domestic and foreign research progress on extraction method, chemical constituents, biological activity, and its application in biomedical and agricultural field of liposoluble substance from pine needles are reviewed. It mainly includes acidic materials and neutral materials. The main extraction solvents were petroleum ether, dichloromethane, and n-hexane. The application of liposoluble substance from pine needles in the development of drugs, green ecological and safe feed additives, plant protection agents, veterinary drugs, and plant growth promoters were also introduced. Suggestions for future study on protection and utilization of pine needles resources from Pinaceae plant, as well as research and development of liposoluble substance from pine needles are proposed.
Lignin-based carbon quantum dots(CQDs) were prepared with calcium lignosulfonate as precursor by molecular self-assembly and ultrasound-assisted method at room temperature. The effects of calcium lignosulfonate and NaBH4 on the fluorescence property of CQDs were studied, and the synthesis condition of CQDs was also optimized. The optimal preparation conditions were as follows: the mass concentration of calcium lignosulfonate was 60 g/L, the mass concentration of reducing agent NaBH4 was 50 g/L. The structural morphology and optical properties of CQDs were confirmed by transmission electron microscopy(TEM), infrared spectroscopy(FT-IR), X-ray photoelectron spectroscopy(XPS), UV-visible spectroscopy(UV-vis), and fluorescence spectroscopy(FL). The experimental results showed that CQDs had small particle size((9.5±0.5)nm), uniform distribution, no agglomeration phenomenon, excellent optical properties, and fluorescence quantum yield of 12.4%. In addition, CQDs were used to investigate the effect of different silver ion concentrations on the fluorescence intensity. The results showed that CQDs had good fluorescence recognition and sensitivity to Ag+, with a linear detection range(R2=0.998) of 0-250 μmol/L and a detection limit of 525 nmol/L. Meanwhile, CQDs fluorescence showed excellent selectivity and low cytotoxicity, which was expected to show potential application value in biosensing and environmental detection fields.
Corn straw was used as raw material to prepare the whole component aerogels of corn straw by dissolving in lithium bromide solution and tert-butanol solution replacement. The experimental conditions were optimized by single factor test, and the properties of aerogels were characterized by scanning electron microscope(SEM), Fourier transform infrared spectroscopy(FT-IR), N2 adsorption-desorption test, and optical contact angle test. The results showed that the gelation time of the whole components of corn stalk dissolved in lithium bromide was less than 10 min under different conditions. The density of whole components aerogel of corn stalk was as low as 0.027 4 g/cm3, and the specific surface area was 98.434 8 m2/g under the optimal conditions, i.e., the mass fraction of lithium bromide was 66%, the reaction temperature was 130 ℃, the solid-liquid ratio was 1∶45(g∶g), and the reaction time was 50 min. Furthermore, the aerogel had super hydrophilic and super lipophilic properties, and the maximum adsorption rates of deionized water and soybean oil were 15.04 and 18.78 g/g, respectively. The SEM result showed that the prepared aerogel had two dimensional sheet and three dimensional network structure, and the FT-IR result indicated that the aerogels contained cellulose, hemicellulose and lignin, and the hydrogen bond network in cellulose was destroyed.
Biomass is important renewable resources, mainly containing cellulose, hemicellulose, and lignin. Hemicellulose is the second most abundant component in plant cell walls, and it can be hydrolyzed to prepare important chemicals and modified to prepare multifunctional materials. This article reviews the research progress of molecular simulation of biomass hemicellulose, including the molecular simulation study of the morphology of hemicellulose macromolecules and its binding mode to cellulose, and the molecular simulation research on the preparation of chemicals and materials from hemicellulose. It can be concluded that the interaction of hemicellulose with cellulose and lignin in the cell wall and its macromolecular morphology have significant influence on the extraction and utilization of cellulose, hemicellulose, and lignin. Molecular simulation is helpful to understand the process mechanism and has important theoretical guiding significance for the improvement of reaction efficiency. Finally, the development and application of molecular simulation in hemicellulose research are prospected. The blank areas of hemicellulose molecular simulation are pointed out, mainly including the production of bio-oil by hemicellulose liquefaction, xylose isomerization to produce xylulose, the binding interaction between hemicellulose and lignin, and other hemicellulose-based materials, which requires further exploration and research.
Sodium hydroxide-polyethylene glycol-urea mixed solution was used to activate wood fiber under freezing, and then the binder-free fiberboard was prepared. By comparing the mechanical properties of binder-free bonding fiberboard, the better freezing activation process of eucalyptus fiber was determined. The freezing activation effect of wood fiber was characterized by FT-IR, XRD, DSC, TG and XPS. The results showed that the better freezing conditions were as follows: the mass ratio of sodium hydroxide, polyethylene glycol, and urea was 7∶4.2∶12, the mass ratio of activator(i.e, the total mass of sodium hydroxide and urea) and wood fiber was 1∶12, the freezing temperature was -15 ℃ and the freezing time was 45 min. The water absorption thickness expansion rate, internal bonding strength, static bending strength, and elastic modulus of the prepared fiberboard increased by 45%, 238%, 177%, and 129% of the performance requirements in GB/T 11718—2009 Medium Density Fiberboard, respectively. The freezing activation treatment could destroy the hydrogen bond between the cellulose in the wood fiber, improve the reaction activity of hydroxyl and increase the number of active hydroxyl, produce new crystals while expanding the cellulose lattice, and reduce the thermal stability of the wood fiber.
The method of water bath oscillation assisted with ethanol extraction was used to optimize the extraction process of polyphenols from Malus asiatica Nakai, and the composition of polyphenols was analyzed. The optimal extraction conditions of unripe M. asiatica were the volume fraction of ethanol 50%, solid-liquid ratio of 1∶25(g∶mL), water bath oscillation time with 50 min, and water bath oscillation temperature of 30 ℃ via the orthogonal experiment. Under these conditions, the polyphenol yield could reach(7.875±0.008) mg/g. Similarly, the optimal extraction conditions of ripe M. asiatica were the volume fraction of ethanol 60%, solid-liquid ratio of 1∶25(g∶mL), water bath oscillation time with 30 min, and water bath oscillation temperature at 40 ℃, correspondingly, the polyphenol yield could reach(10.259±0.020) mg/g. The results of liquid chromatography showed that there were four kinds of polyphenols in the unripe M. asiatica, including chlorogenic acid(22.03%), proanthocyanidin B2(8.875%), epicatechin(5.95%), and phloperidin(1.259%). These four kinds of polyphenols accounted for 38.117% of the total polyphenols. Meanwhile, the above four kinds of polyphenols in the ripe M.asiatica were 41.075%, 5.641 3%, 8.325 2%, and 0.499 8%, respectively. In addition, (+)-catechtin was also found with the fraction of 7.244 4%, and the above five kinds of polyphenols accounted for 62.786 5% of the toal polyphenols in the ripe M. asiatica. However most unknow polyphenols were not detected in the ripe M. asiatica. The ripe fruit had more polyphenol and nutrition than that in the unripe one.