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    30 July 2022, Volume 56 Issue 4 Previous Issue   
    Research Report
    Effects of Torrefaction Pretreatment on the Preparation and Properties of Activated Carbon from Corn Straw by Phosphoric Acid Activation
    Ruting XU, Xincheng LU, Kang SUN, Chang TAN, Yanping ZHANG
    2022, 56 (4):  1-8.  doi: 10.3969/j.issn.1673-5854.2022.04.001
    Abstract ( 161 )   HTML ( 1752629425 )   PDF (700KB) ( 266 )   Save

    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.

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    Pyrolysis Characteristics and Kinetic Analysis of Corn Straw
    Huanhuan ZHAO, Wenting XING, Xianglin SONG, Yake LI, Liya ZHANG, Liucheng WANG
    2022, 56 (4):  9-14.  doi: 10.3969/j.issn.1673-5854.2022.04.002
    Abstract ( 179 )   HTML ( 1900544142 )   PDF (553KB) ( 271 )   Save

    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.

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    Removal Performance and Mechanism of Lead and Cadmium in Water by Corn Straw Biochar
    Jianbing ZHAO, Junbo ZHU, Changfu ZHUANG, Zhifeng ZHENG, Shuangqing LI, Xuemei LI
    2022, 56 (4):  15-24.  doi: 10.3969/j.issn.1673-5854.2022.04.003
    Abstract ( 159 )   HTML ( 253329571 )   PDF (2311KB) ( 208 )   Save

    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.

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    Effect of Hydrogen Peroxide-acetic Acid Pretreatment on Enzymatic Hydrolysis and Fermentation of Sugarcane Bagasse
    Fanyang MENG, Ning LI, Zhengjun SHI, Haiyan YANG, Ping ZHAO, Jing YANG
    2022, 56 (4):  25-31.  doi: 10.3969/j.issn.1673-5854.2022.04.004
    Abstract ( 147 )   HTML ( 2022719613 )   PDF (2348KB) ( 222 )   Save

    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.

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    Preparation and Characterization of Whole Component Aerogel of Corn Straw
    Yaru LI, Xiaomin SONG, Wenbiao XU, Xixin DUAN, Junyou SHI, Xiangyu LI
    2022, 56 (4):  32-38.  doi: 10.3969/j.issn.1673-5854.2022.04.005
    Abstract ( 126 )   HTML ( 1544552508 )   PDF (2223KB) ( 215 )   Save

    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.

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    Review Comment
    Research Progress on Furfural Hydrogenation Using Metal Catalysis in Aqueous Medium
    Haihong XIA, Minghao ZHOU, Changzhou CHEN, Peng LIU, Jing LI, Jianchun JIANG
    2022, 56 (4):  39-48.  doi: 10.3969/j.issn.1673-5854.2022.04.006
    Abstract ( 142 )   HTML ( 1133642388 )   PDF (721KB) ( 221 )   Save

    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.

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    Research Progress on Preparation of Levulinic Acid and Esters from Lignocellulose by Sulfate Catalyst
    Linshan WEI, Jun YE, Kui WANG, Jianchun JIANG
    2022, 56 (4):  49-57.  doi: 10.3969/j.issn.1673-5854.2022.04.007
    Abstract ( 100 )   HTML ( 1267793968 )   PDF (644KB) ( 240 )   Save

    In this paper, the heterogeneous catalytic conversions of lignocellulose to high value-added platform compounds of levulinic acid and esters were studied. The research progress and trend of the direct conversion of lignocellulose to levulinic acid and esters using sulfate as catalytic system at home and abroad were reviewed. Firstly, the basic information of levulinic acid/esters and their application in industrial production were summarized. The preparation process of levulinic acid/esters using different sulfate catalysts was compared, and the law of the conversion of lignocellulose to levulinic acid/esters under the synergy effects of different solvent systems was deeply analyzed. And, the mechanism of direct conversion of lignocellulose catalyzed by sulfate catalysts was also summarized. Finally, the problems of existing process were discussed, and the development direction of this research field was prospected.

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    Research Progress of Biomass-based Porous Materials on Thermal Insulation Materials
    Lei WANG, Xinyuan BI, Fei YE, Yibei LIU, Min WU, Peng LU
    2022, 56 (4):  58-66.  doi: 10.3969/j.issn.1673-5854.2022.04.008
    Abstract ( 142 )   HTML ( 1313161311 )   PDF (5477KB) ( 270 )   Save

    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.

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    Research Progress on Lignin Depolymerization and Liquid Phase Catalytic Degradation
    Haohan JIANG, Shuangming LI, Sansan YU
    2022, 56 (4):  67-76.  doi: 10.3969/j.issn.1673-5854.2022.04.009
    Abstract ( 161 )   HTML ( 1602226222 )   PDF (864KB) ( 256 )   Save

    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.

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