Exploring the pyrolysis of tar-rich coals under the catalysis of cerium-modified magnetic core-shell HZSM-5
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摘要:
【目的】富油煤是集煤、油气属性为一体的宝贵煤炭资源，催化热解是实现其绿色低碳开发的重要途径。然而，高效可回收催化剂的研发仍面临着极大的挑战。【方法】以HZSM-5@SiO2@MgFe2O4 (HSMF)为原料，采用水热法与碱改性制备具有多级孔结构的HZSM-5@SiO2@MgFe2O4 (mHSMF)，再通过沉淀法制备铈改性mHSMF (5-CeO2/mHSMF)；并利用固定床反应器考察了5-CeO2/mHSMF对神府富油煤热解产物的调控作用及其抗积炭性能。【结果和结论】结果表明，CeO2改性有助于在HSMF表面形成微−介孔多级孔道结构；在5-CeO2/mHSMF催化剂上，650 ℃、N2气氛、反应1 h的条件下，神府富油煤焦油产率达到13.38%，是格金试验焦油产率的176%；相较于原煤热解，催化热解得到的焦油中脂肪烃类及苯类化合物含量分别增加了3.04%和3.07%，煤气中H2和CH4含量提高了10.49%；经CeO2改性后，催化剂的抗积炭性能增幅达86.1%，积炭量仅为11.60 mg/g，且积炭趋于稳定的石墨化结构。5-CeO2/mHSMF对神府富油煤催化热解产物的分布及组成具有明显调控作用，并表现出良好的抗积炭效果和磁性可回收性能。
Abstract:ObjectiveTar-rich coals are valuable resources integrating coal, tar, and gas properties. Catalytic pyrolysis serves as a significant approach for achieving green and low-carbon development of tar-rich coals. However, the research and development of efficient and recyclable catalysts for the pyrolysis of tar-rich coals remains highly challenging.
MethodsWith HZSM-5@SiO2@MgFe2O4 (HSMF) as the raw material, this study prepared HZSM-5@SiO2@MgFe2O4 (mHSMF) with a hierarchical porous structure using the hydrothermal method and alkali modification, followed by the preparation of cerium-modified mHSMF (5-CeO2/mHSMF) using the precipitation method. Employing a fixed-bed reactor, this study investigated the regulatory effects of 5-CeO2/mHSMF on the pyrolysis products of tar-rich coals from the Shenfu block, along with the anti-carbon deposition performance of 5-CeO2/mHSMF.
Results and ConclusionsThe results indicate that the CeO2-based modification of HSMF was conducive to the formation of a hierarchical porous structure comprising micropores and mesopores on the surface of HSMF. Through pyrolysis at 650°C in the N2 atmosphere for 1 hr using 5-CeO2/mHSMF as a catalyst, the coals exhibited a tar yield of 13.38%, equivalent to a tar yield of 176% in the Gray-King assay. Compared to the pyrolysis of raw coals, the catalytic pyrolysis exhibited increases in the aliphatic-hydrocarbon and benzene-compound contents in tar of 3.04% and 3.07%, respectively and an increase in the H2 and CH4 content in coal gas of 10.49%. Through CeO2-based modification, the catalyst enhanced the anti-carbon deposition performance by 86.1%, with carbon deposits of merely 11.60 mg/g and tending to form a stable graphitized structure. Overall, 5-CeO2/mHSMF manifests significant regulation of the distribution and composition of the products from the catalytic pyrolysis of coals in the Shenfu block, along with encouraging anti-carbon deposition performance and magnetic recyclability.
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图 2 CeO2浸渍改性MgFe2O4系列催化剂XRD图谱
Fig. 2 XRD patterns of CeO2-modified MgFe2O4 catalysts prepared using the impregnation method
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图 3 催化剂SEM电镜图
(a) HZSM-5；(b) HZSM-5(mH)；(c) 5-CeO2/mH；(d) 5-CeO2/mH/SMF；(e)、(f) 5-CeO2/mHSMF
Fig. 3 Scanning electron microscope images of catalysts
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图 7 催化剂CO2-TPD曲线及 mH、5-CeO2mH的CO2-TPD拟合曲线
Fig. 7 Temperature-programmed CO2 desorption (CO2-TPD) curves of the various catalysts and fitted CO2-TPD curves of mH and 5-CeO2/mH
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图 8 不同催化剂下焦油组分
1. None；2. 5-CeO2/mH；3. MgFeCeOx；4. 5-CeO2/SMF；5. 5-CeO2/mHSMF；6. 5-CeO2/mH/SMF
Fig. 8 Proportions of tar components from pyrolysis under different catalysts
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图 10 改性催化剂反应前后的FT-IR谱图
Fig. 10 FT-IR spectra of modified catalysts before and after reactions
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图 11 改性催化剂反应后Raman谱图
Fig. 11 Raman spectra of modified catalysts before and after reactions
表 1 神府煤的工业分析与元素分析
Table 1 Proximate and ultimate analyses of tar-rich coals from the Shenfu block
工业分析w/% 元素分析w/% Mad Ad Vd FCd* Cd Hd Nd Od* St 4.17 6.62 36.06 57.32 66.73 4.81 1.34 20.06 0.44 注：*表示差减法计算结果；St为全硫。 
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表 2 水热法铈改性系列催化剂比表面积与孔结构参数
Table 2 Specific surface areas and pore structure parameters of cerium-modified catalysts prepared using the hydrothermal method
催化剂 SBET/(m2·g−1) Smicro/(m2·g−1) Sext/(m2·g−1) DBJH/nm Vtotal/(10−2 cm3·g−1) mH 297.80 229.30 68.51 4.87 12.02 5-CeO2/mHSMF 245.91 148.64 97.27 7.87 7.46 5-CeO2/mH/SMF 134.27 — 135.77 9.10 22.02 MgFeCeOx 8.99 3.14 5.85 23.71 0.16 5-CeO2/mH 259.52 203.60 55.92 10.71 4.94 注：SBET为催化剂的比表面积；Smicro为催化剂微孔的比表面积；Sext为催化剂的外比表面积；DBJH为催化剂的孔径；Vtotal为催化剂的孔体积。
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表 3 5-CeO2/mHSMF中主要金属元素相对含量
Table 3 Relative contents of major metal elements in 5-CeO2/mHSMF
元素 结合能/eV 半峰宽/eV 原子百分比/% 相对误差/% 质量分数/% O 1s 531.20 4.07 53.90 1.69 37.80 Fe 2p3/2 712.20 3.32 3.00 0.41 7.20 Mg 1s 1307.20 4.08 7.40 0.79 7.80 Ce 3d5/2 884.20 8.18 5.10 0.42 31.00
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表 4 浸渍法CeO2改性催化剂的热解产物质量分数
Table 4 Mass fractions of products from pyrolysis under CeO2-modified catalysts prepared using the impregnation method
% 催化剂 焦油产率 热解水产率 气体产率 半焦产率 无 8.37 6.95 13.76 70.92 5-CeO2/MgFe2O4 11.61 6.08 13.40 68.91 5-CeO2/SMF 10.58 6.41 13.92 69.09 5-CeO2/HSMF 13.08 6.42 12.81 67.69
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表 5 水热法CeO2改性催化剂的热解产物质量分数
Table 5 Mass fractions of products from pyrolysis under CeO2-modified catalysts prepared using the hydrothermal method
% 催化剂 焦油产率 热解水产率 气体产率 半焦产率 无 8.37 6.95 13.76 70.92 5-CeO2/mH 8.61 6.59 16.13 68.67 MgFeCeOx 10.85 5.22 14.34 69.59 5-CeO2/mHSMF 13.38 5.17 14.09 67.36 5-CeO2/mH/SMF 11.47 6.01 14.26 68.26
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表 6 不同催化剂下热解煤气组成占比
Table 6 Pyrolysis gas composition under different catalysts
% 催化剂 H2 CH4 CO2 CO C2H4 C2H6 C3H6 C3H8 无 24.52 32.07 18.92 16.53 1.83 2.97 1.91 1.25 5-CeO2/mH 25.72 38.51 14.32 10.89 1.56 3.52 3.01 2.47 MgFeCeOx 21.42 41.67 13.52 12.26 2.38 4.61 2.26 1.88 5-CeO2/mHSMF 31.22 36.86 11.93 11.68 1.05 4.62 1.29 1.35 5-CeO2/mH/SMF 22.96 39.42 16.31 10.39 0.83 4.93 3.52 1.64
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表 7 热解煤焦油GC/MS组成占比
Table 7 Proportions of the GC/MS components of coal tar from pyrolysis
% 催化剂 苯类 酚类 脂肪烃 稠环芳烃 其他 无 1.86 17.73 15.69 34.82 29.90 HZSM-5 2.57 17.23 16.43 31.04 32.73 5-CeO2/mH 2.88 18.13 17.95 30.23 30.81 MgFeCeOx 4.73 17.33 18.25 31.02 28.67 5-CeO2/mHSMF 4.93 16.96 18.73 29.51 29.87 5-CeO2/mH/SMF 4.06 18.25 17.12 30.91 29.66
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