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摘要: 在加压固定床反应器上研究了Fe催化剂在不同比表面积煤焦中分散性对催化加氢气化性能的影响，利用XRD、BET、H2-TPR、FT-IR、TEM、拉曼光谱对煤焦及催化剂进行了分析表征。结果表明，煤焦活性位点和石墨化程度并非影响催化气化反应的唯一因素，而催化剂的分散性对反应影响更大。煤焦的比表面积越大，Fe催化剂在煤焦表面的分散更均匀，催化剂活性组分平均晶粒粒径越小，并可以促进煤催化加氢气化中间相产物Fe3C的生成，甲烷收率越高。对于比表面积较高的900-char，在氢气压力为2 MPa，温度为750 ℃，Fe负载量为5%（质量分数）时，催化加氢气化甲烷收率可达53%。在900-char上考察了Fe催化剂负载量对催化加氢气化的影响，甲烷收率呈先增加后降低的趋势，Fe负载量存在饱和点。Abstract: The effect of dispersibility of Fe on coal chars with different specific surface areas on the catalytic hydrogasification performance was studied in a pressurized fixed bed reactor. The chars and catalysts were characterized by XRD, BET, H2-TPR, FT-IR, TEM and Raman spectroscopy. The results show that the active site and graphitization degree of coal char are not the only factors affecting the catalytic gasification reaction, but the dispersion of catalyst has a greater impact on the reaction. The larger the specific surface area of coal char is, the more uniform the Fe catalyst disperses on the surface of coal char and the smaller the average grain size of the active component of catalyst is, which can promote the formation of the catalytically hydrogenated mesophase product Fe3C and methane yield. For 900-char with higher specific surface area, the methane yield can reach 53% when the hydrogen pressure is 2 MPa, the temperature is 750℃ and the Fe loading is 5%. The effect of Fe catalyst loading on the catalytic hydrogasification was investigated with 900-char. It is found that the methane yield increases first and then decreases, and the Fe loading has a saturation point.
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Key words:
- iron /
- hydrogasification /
- catalytic /
- dispersion /
- saturation point
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图 1 催化加氢气化加压固定床反应装置示意图
Figure 1 Schematic diagram of pressurized fixed bed reactor for catalytic hydrogasification
1: mass flowmeter; 2: cutoff valve; 3: pressure gauge; 4: electric furnace; 5: ball valve; 6: reactor; 7: K thermocouple; 8: sample; 9: quartz sand; 10: reducing pressure valve; 11: back pressure valve; 12: circulating cooling system; 13: temperature control system; 14: GC; 15: wet air flowmeter
图 2 不同温度预处理煤焦的拉曼分峰拟合谱图
Figure 2 Raman peak fitting of coal char pretreated at different temperatures
(a): De-char; (b): 750-char; (c): 800-char; (d): 850-char; (e): 900-char; (f): 950-char
图 3 不同温度预处理煤焦红外光谱谱图
Figure 3 Infrared spectra of coal char pretreated at different temperatures
图 5 不同比表面积煤焦负载Fe-Ca的XRD谱图
Figure 5 XRD patterns of Fe-Ca loaded on different surface coal chars
1: Ca(OH)2; 2: FeO; 3: Fe2O3; 4: Fe3O4; 5: Fe3C; 6: Fe
图 6 比表面积对催化加氢气化甲烷收率的影响
Figure 6 Effect of specific surface area on the methane yield of catalytic hydrogasification
(a): wCH4of 5Fe-t-char; (b): VCH4 of 5Fe-t-char; (c): wCH4 of 10Fe-t-char; (d): VCH4 of 10Fe-t-char
图 7 煤焦比表面积对甲烷收率的影响
Figure 7 Effect of specific surface area of coal char on methane yield
图 8 催化剂添加量对加氢气化甲烷收率的影响
Figure 8 Effect of catalyst addition on the yield of methane in hydrogasification
(a): wCH4 of xFe-900-char (x=3, 5, 10, 15)(wCH4/%); (b): VCH4 of xFe-900-char (x=3, 5, 10, 15)
图 9 负载5%Fe的900-char中添加Ca(a、b)和未添加Ca(c、d)加氢气化反应前(a、c)和后(b、d)的TEM照片
Figure 9 TEM diagrams of 900-char loaded with 5% Fe or Ca (a, b) and without Ca (c, d) before (a, c) and after (b, d) hydrogasification
表 1 不同温度预处理煤焦的元素分析
Table 1 Ultimate analysis of char samples at different pretreatment temperatures
Sample Ultimate analysis wdaf/% C H N S O* De-char 93.200 0.450 1.210 0.150 4.990 750-char 94.220 1.334 1.660 0.214 2.572 800-char 93.420 1.282 1.320 0.214 3.764 850-char 91.920 1.684 1.890 0.270 4.506 900-char 91.630 1.326 1.550 0.220 5.027 950-char 92.550 1.334 1.270 0.249 4.597 *: by difference 
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表 2 不同温度预处理煤焦的孔结构
Table 2 Pore structure parameters of char samples pretreated at different temperatures
Sample BET surface area A/(m2·g-1) Pore volume v/(cm3·g-1) Average pore size d/nm De-char 4.8 0.003 7.75 750-char 58.3 0.042 2.88 800-char 155.7 0.061 1.56 850-char 381.8 0.156 1.63 900-char 701.8 0.302 1.72 950-char 612.1 0.263 1.72
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表 3 不同温度预处理煤焦的拉曼分峰拟合面积比
Table 3 Parameters of Raman peak fitting area ratio of coal char pretreated at different temperatures
Sample ID1/IG ID3+D4/IG IG/IAll De-char 1.95 4.23 0.139 750-char 2.96 3.68 0.131 800-char 2.08 5.98 0.120 850-char 1.65 4.93 0.132 900-char 2.23 4.57 0.128 950-char 1.98 4.96 0.126
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表 4 不同比表面积煤焦负载5%Fe-1%Ca的XRD表征相关参数
Table 4 XRD characterization parameters of coal chars with different specific surfaces loaded with 5%Fe-1%Ca
Sample Chem form Average crystallite size d/nm dFe dFe3C 5Fe-750-char FeO，Fe2O3, Fe3O4 - - 5Fe-800-char FeO - - 5Fe-850-char Fe, Fe3C 52.94 35.18 5Fe-900-char Fe, Fe3C 43.62 21.05 5Fe-950-char Fe, Fe3C 49.43 26.38
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