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30 November 2022, Volume 56 Issue 6 Previous Issue   
Research Report
Preparation of Lignin-derived Formed Activated Carbon by Compounding Raw Materials
Wei XU, Junli LIU, Kang SUN, Xincheng LU, Ruting XU, Yanping ZHANG
2022, 56 (6):  1-7.  doi: 10.3969/j.issn.1673-5854.2022.06.001
Abstract ( 72 )   HTML ( 1539 )   PDF (1774KB) ( 106 )  

Lignin-derived formed activated carbon was prepared from alkali lignin and fir sawdust using phosphoric acid as the activator. The effects of alkali lignin mass fraction, impregnation ratio, activation temperature, and activation time on the properties of activated carbon were investigated. The results showed that the surface wettability of alkali lignin compounded with fir sawdust(alkali lignin mass fraction of 50%) was significantly improved, and the instantaneous water contact angle decreased from 133.2°(alkali lignin) to 86.6°(compound raw materials). The thermal expansion coefficient in the expansion temperature range decreased from 2 365 μm/(m·℃)(alkali lignin)to 45 μm/(m·℃)(compound raw materials). Under optimal technological conditions of alkali lignin mass fraction of 50%, impregnation ratio of 1.5:1(mass ratio of pure phosphoric acid to compound raw materials), activation temperature at 500℃, and activation time for 90 min, the prepared activated carbon had the iodine adsorption value of 1 070 mg/g as well as the methylene blue adsorption value of 255 mg/g. The yield and strength of activated carbon were 41.76% and 90%, respectively. The specific surface area and pore volume were 1 646 m2/g and 0.795 cm3/g respectively, where the pore volume with pore diameter less than 5 nm occupied for 97.2% in the total pore volume.

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Correlation Analysis Between Characteristics of Feedstock and Thermogravimetric/Pyrolytic Characteristics of Herb Residues
Yun ZHOU, Haiping YANG, Jun ZOU, Zihao LIU, Hanping CHEN
2022, 56 (6):  8-16.  doi: 10.3969/j.issn.1673-5854.2022.06.002
Abstract ( 47 )   HTML ( 1535 )   PDF (677KB) ( 85 )  

In order to understand the relationship between the pyrolysis characteristics of herb residues and their composition & structure, the composition structure and chemical composition of 10 typical Chinese planted herb residues were determined, and the pyrolysis weight loss characteristics were carried by the thermogravimetric analyzer. Through the correlation analysis between the characteristics of the feedstock and the pyrolysis process behavior, the physical factors affecting the pyrolysis process of herb residues and the associated coupling mechanism were discussed. Results showed that herb residues were detected with high content of nitrogen and sulfur. The root samples had high cellulose content and the leaf samples had high lignin content. The ability of thermal decomposition to remove volatile matter of leaves, stems, and seeds of herb residue samples were poor, and the activation energy of pyrolysis obtained by Coats-Redfern integration method was basically within 100 kJ/mol. Roots of herb residue samples were easier to devolatile, and the activation energy was higher than 110 kJ/mol. Among them, yam sample had the strongest pyrolysis ability to devolatilize, with the activation energy of 169.83 kJ/mol. The lowest activation energy was obtained in the artemisia annua sample, and the correspongding value was 64.32 kJ/mol. Cellulose and lignin were the two main physical properties affecting pyrolysis devolatilization and activation energy. The content of cellulose and lignin could be used to predict the pyrolysis devolatilization ability and activation energy of herb residues.

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Effect of Steam Explosion and Puffing Modification on the Structure of Corn Stalks and the Mechanical Properties of Composite Boards
Xinpeng ZHAO, Qingbo ZHOU, Yan ZHENG, Haibin YU
2022, 56 (6):  17-23.  doi: 10.3969/j.issn.1673-5854.2022.06.003
Abstract ( 38 )   HTML ( 1285 )   PDF (4294KB) ( 83 )  

The corn stalks were expanded by means of single-screw steam explosion to obtain different types of puffed corn straws, which were compounded with polypropylene resin(PP) to prepare a straw composite board. The changes of fiber before and after the explosion were investigated by scanning electron microscopy(SEM), reflected infrared(ART-FTIR), thermogravimetric analysis(TGA), differential scanning calorimetry(DSC), and Bauer fiber screening tests. The SEM results showed that corn stalks could effectively carry out the "three elements separation" through steam explosion, so that the surface structure of the stalks changed from smooth and regular to fibrous and powdery fragments. Meanwhile, the TGA, DSC and ATR-FTIR results showed that there was no obvious change in the fiber structure during the puffing process, while the hemicellulose and lignin were partially thermally decomposed. The mechanical properties of the straw composite board prepared by expanded corn stalks and PP were tested. Comparing with the board prepared by unexpaned corn stalks as the raw material, the impact resistance and tensile strength of steam expanded corn stalks increased by 15.69% and 17.24%, respectively.Similarly, the impact strength of boards prepared by expanded corn stalks modified by acrylates compolymer and ethylene-vinyl acetate copolymer increased by 156.74% and 100.98%, respectively, and the tensile strength increased by 83.42% and 12.03%, respectively.

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Thermogravimetric Characteristics and Dynamic Analysis of Pinus Sylvestriformis
Yuesan YANG, Wei XUE, Huachao ZHANG
2022, 56 (6):  24-30.  doi: 10.3969/j.issn.1673-5854.2022.06.004
Abstract ( 41 )   HTML ( 1023 )   PDF (609KB) ( 89 )  

In order to obtain the pyrolysis characteristics of Pinus Sylvestriformis and prevent forest fires, the pyrolysis process was carried out using the branches, cones, bark, and pine needles of P. Syluestriformis. The pyrolysis kinetics analysis was conducted by the Coats-Redfern method, and the influence of various factors on the pyrolysis of P. sylvestriformis was explored using the cones as the research object. Experimental results showed that the pyrolysis process of the four materials could be divided into four stages, where the mass loss rate of the main weightless stage occupied about 60%. The higher heating rate, the less sufficient pyrolysis. There was a thermal hysteresis phenomenon, where the minimum mass loss rate was 80.34% at 25℃/min. Particle size had little influence on TG and DTG curves. The smaller particle size, the more uniform internal and external heating, and the maximum mass loss rate of the materials with a particle size of 0.20 mm was 91.18%. There was a peak of weight loss in the main weight loss stage under nitrogen atmosphere, and two peaks of weight loss under air atmosphere. The pyrolysis time of P. sylvestriformis cones in high pure air was longer, the pyrolysis was more complete, and the promotion effect was stronger, with the weight loss rate of 98.14%. The results of pyrolysis kinetic analysis showed that the optimal mechanism function of the four materials was "three-dimensional diffusion". The branches had the highest activation energy(157.04 kJ/mol), and the lowest value was found in pine needles(98.19 kJ/mol). In addition, the activation energies for the cones and bark were 148.08 and 115.04 kJ/mol, respectively. Therefore, special attention should be paid to the fire prevention of pine needles and bark.

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Comparison on the Determination of Tara Tannin Content with UV Spectrophotometry and Hide Powder Method
Lihua TANG, Liangliang ZHANG, He ZHANG
2022, 56 (6):  31-35.  doi: 10.3969/j.issn.1673-5854.2022.06.005
Abstract ( 37 )   HTML ( 1023 )   PDF (470KB) ( 85 )  

Five kinds of tara tannin with different contents were determined and compared by UV spectrophotometry and hide powder method, and the significance test of tannin content determination results was carried out by SPSS software. The results showed that there was no significant difference in the determination of tannin content of high-puritytaratannin(93%) measured by UV spectrophotometry and hide powder method(P>0.05).However, the experimental results of the four kinds of tara tannins with the content of 60% have significant differences(P < 0.05), and the tannin contents measured by hide powder method were all higher than those measured by UV spectrophotometry, where the difference was about 1.5%-2.0%. And the correction constant i.e., p=1.03, in the formula for determining the taratannin content by UV method was calculated. The results of UV-Vis absorption spectrum and high performance liquid chromatography analysis showed that the maximum absorption peaks of tara tannin and gallic tannin were both at 276 nm. At the same mass concentration, the absorption peak intensity of tara tannin was higher than that of gallic tannin. The peaking time of tara tannin was mainly in 20-40 min, and the peaking time of gallic tannin was mainly in 30-45 min.

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Pyrolysis Characteristics and Kinetics Analysis of Algae Residue
Si LI, Shaojian JIANG, Changzhu LI, Xudong LIU, Aihua ZHANG, Zhihong XIAO
2022, 56 (6):  36-42.  doi: 10.3969/j.issn.1673-5854.2022.06.006
Abstract ( 40 )   HTML ( 1025 )   PDF (611KB) ( 93 )  

The effect of heating rate in N2 atmosphere on the pyrolysis characteristics of chlorella after Soxhlet fat extraction was studied by thermogravimetric experiment. The rapid pyrolysis experiment in tubular furnace under N2 atmosphere showed that at 400℃, the pyrolysis conversion rate was the highest, where the yield of biooil and the pyrolysis gas were 57.6% and 10% respectively. The pyrolysis kinetics of algal residue was analyzed and compared by equal conversion methods of FWO and KAS. The results showed that the pyrolysis curve of algal residue could be divided into three stages, where the main pyrolysis stage was 155-800℃. There were two weight loss peaks in the DTG curve of algal residue. With the increase of heating rate, TG and DTG curves shifted to the high temperature zone, and the maximum weight loss rate and residual solid mass increased. Under N2 atmosphere, the apparent activation energy and pre-exponential factor of the main pyrolysis stage of algal residue were 228.46 kJ/mol and 2.49×1021 min-1, respectively. At this stage, the pyrolysis data of algal residue was well simulated using FWO and KAS method, and the linear fitting correlation coefficient (R2) was above 0.96. The best pyrolysis function was dα/dT=2.49×1021/β exp(-228.46/(RT))(1-α)8.

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Modification of Peanut Shell Biochar and Its Adsorption Properties of Pb2+
Xianglin SONG, Yake LI, Dong LI, Liucheng WANG
2022, 56 (6):  43-50.  doi: 10.3969/j.issn.1673-5854.2022.06.007
Abstract ( 49 )   HTML ( 1023 )   PDF (1184KB) ( 111 )  

In this study, peanut shell was used as raw material to produce biochar by pyrolysis, and the product of biochar was modified by NaOH and KMnO4, respectively. Characterization results showed that the microstructure of the modified biochar was relatively dispersed, the pore size was decreased, and the stability was enhanced. The specific surface area of NaOH modified peanut shell biochar(AB) and KMnO4 modified peanut shell biochar(MnB) increased up to 3.178 times and 5.065 times than that of peanut shell biochar(B), respectively. When KMnO4 was used as modifying agent, manganese oxide was successfully fixed on the biochar. The zero point charge (pHPZC) of B, AB, and MnB were 2.193, 2.888, and 2.466, respectively. The adsorption performance of Pb2+ using biochar before and after modification was investigated. It was found that the optimum pH values for the adsorption of Pb2+ using B, AB, and MnB were 4.5-6.5, 5.5-6.5 and 5.0-6.5, respectively. When the removal rate of Pb2+ was the same, the biochar dosage was MnB < AB < B, and the equilibrium adsorption time of Pb2+ using AB and MnB was shortened by 180 and 480 min, respectively. The adsorption kinetics model and isotherm model showed that the Pb2+ adsorption process was controlled by chemisorption in three biochars, and the order of adsorption rates was MnB>AB>B. The maximum theoretical adsorption amounts of AB and MnB were 53.19 and 80.65 mg/g, which were 1.38 and 2.10 times than that of B, respectively.

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Review Comment
Research Progress of NOx Control Technology in Biomass-fired Boiler
Xinyue GAO, Shizhen YUAN, Junjie WENG, Pengbo ZHAO, Chang'an WANG, Defu CHE
2022, 56 (6):  51-60.  doi: 10.3969/j.issn.1673-5854.2022.06.008
Abstract ( 43 )   HTML ( 1311 )   PDF (671KB) ( 102 )  

China was rich in biomass resources with various types, which could be directly used for combustion. With the proportion of installed biomass power generation capacity increasing year by year, environmental protection requirements were enhancing, and the flue gas emissions control of biomass power plants was more strictly. The inital nitrogen oxide emissions of biomass boiler fluctuated greatly, the alkali metal content of fly ash in flue gas was high, and the humidity was high. The biomass boilers denitration technology was facing major challenges. Based on the comparative analysis of the characteristics of biomass fuel combustion and flue gas emissions, the development status, advantages, and disadvantages of the widely used traditional denitrification technology and the new developing denitrification technology were analyzed. Traditional denitrification technologies included low nitrogen combustion technology, selective catalytic reduction technology, and selective non-catalytic reduction technology. New denitrification technologies included plasma denitrification technology, ozone oxidation denitrification technology, biomass activated carbon desulfurization and denitrification technology, ZYY dry desulfurization and denitrification technology, low temperature oxidation absorption synergistic semi-dry denitrification technology, liquid biological calcium denitrification technology, and solid polymer denitrification technology. Moreover, the technical problems, cost problems, and operation period of biomass boilers technology were also discussed.

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Novel Catalytic Process for Preparing FDCA from HMF
Jiawei CAI, Kanghui LI, Yongquan JIANG, Shuping WU
2022, 56 (6):  61-70.  doi: 10.3969/j.issn.1673-5854.2022.06.009
Abstract ( 104 )   HTML ( 1215 )   PDF (1018KB) ( 126 )  

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.

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Research Progress of Heteroatom-doped Biomass-based Carbon Materials
Tianhe WANG, Lin LIN, Jing LIU, Qiang ZHANG, Wenbiao XU, Junyou SHI
2022, 56 (6):  71-80.  doi: 10.3969/j.issn.1673-5854.2022.06.010
Abstract ( 76 )   HTML ( 1535 )   PDF (2747KB) ( 109 )  

Biomass-based carbon materials had the advantages of low cost, wide source, good electrical conductivity, and good electrochemical stability. Through heteroatom doping, the performance of biomass-based carbon materials was further improved. This paper summarized the methods of introducing heteroatoms into biomass-based carbon materials(in-situ doping and diffusion doping) and their respective advantages and disadvantages. The types of heteroatom doping(nitrogen doping, oxygen doping, phosphorus doping, sulfur doping, halogen doping, and multi-element co-doping) and the effects of heteroatom doping on the structure and properties of biomass-based carbon materials were briefly described. The applications of heteroatom doped carbon materials in energy storage, adsorption separation, and catalytic oxidation were reviewed, and the development direction of heteroatom-doped biomass-based carbon materials was also prospected.

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