Effect of Si/Al ratio of HZSM-5 zeolites on catalytic upgrading of coal pyrolysis volatiles
-
摘要: 采用不同硅铝比的HZSM-5作为煤热解挥发物提质催化剂,研究了催化剂酸性特征对挥发物提质后的焦油品质、催化剂积炭的影响。结果表明,随着硅铝比的增加,HZSM-5的强酸和弱酸量均降低;硅铝比从23增大到310时,催化剂积炭量从120.1 mg/g-catalyst降到23.9 mg/g-catalyst。并且,HZSM-5中强酸与弱酸位点的比值越高,焦油中轻质组分的含量越高。随硅铝比的降低,HZSM-5酸性增强,所得焦油中芳烃组分含量逐渐提高,这表明,HZSM-5在催化煤热解过程中促进了挥发物的氢转移、环化、芳构化反应,从而生成了更多的芳烃组分。Abstract: The effects of SiO2/Al2O3 ratio of HZSM-5 on the tar quality and coke formation during catalytic upgrading of coal pyrolysis volatiles were investigated. The results showed that the carbon deposition amount decreased with the increase of the SiO2/Al2O3 ratio of HZSM-5 due to the decrease of strong and weak acid amount. When the SiO2/Al2O3 ratio increased from 23 to 310, the carbon deposition amount decreased from 120.1 mg/g-catalyst to 23.9 mg/g-catalyst. Moreover, the higher ratio of strong and weak acid amount led to lighter fraction in tar. With the decrease of SiO2/Al2O3 ratio, the acid strength was enhanced so that the aromatics content in the tars decreased, indicating that the stronger acidic sites promoted the dehydrogenation, cyclization and aromatization reactions of volatiles, thus leading to higher yield of aromatics during catalytic coal pyrolysis.
-
Key words:
- zeolite /
- acidity /
- coal pyrolysis /
- catalytic upgrading /
- coke deposition
-
表 1 淖毛湖煤的工业分析和元素分析
Table 1 Proximate and ultimate analyses of Naomaohu coal
Proximate analysis
(dry base) w/%Ultimate analysis
(dry and ash-free base) w/%A V FC C H S N Oa 7.16 47.78 45.06 74.77 5.67 0.27 0.93 18.36 a: by difference 表 2 不同硅铝比的HZSM-5的酸性位点数量特征对比
Table 2 Acidity of HZSM-5 with different SiO2/Al2O3 ratio
Catalyst Weak acid Strong acid Ratio of quantity of strong
and weak acidic sitestemperature at
maximum/℃quantity
/(μmol∙g−1)temperature at
maximum/℃quantity
/(μmol∙g−1)HZ23 139.7 2285 387.7 602.4 0.264 HZ50 124.3 1438 384.7 313.2 0.218 HZ80 118.5 891.3 378.8 268.3 0.301 HZ280 115.6 415.5 357.0 191.9 0.462 HZ310 141.4 396.4 356.5 171.8 0.433 表 3 不同硅铝比HZSM-5的结构特征
Table 3 Structural characters of HZSM-5 with different SiO2/Al2O3 ratio
Catalyst Specific surface area A/(m2∙g−1) Pore volume
v/(cm3∙g−1)SBETa Smicrob Smesoc HZ23 422.3 308.1 114.2 0.089 HZ50 414.6 243.2 171.4 0.136 HZ80 489.8 264.4 225.4 0.174 HZ280 407.9 224.6 183.3 0.153 HZ310 588.6 435.0 153.6 0.243 a: BET method; b: t-plot method; c: Smeso = SBET − Smirco 表 4 不同硅铝比HZSM-5上的积炭量
Table 4 Carbon deposition over HZSM-5 with different SiO2/Al2O3 ratio
Catalyst HZ23 HZ50 HZ80 HZ280 HZ310 Specific C
deposition/(mg·g−1) *120.1 99.0 73.8 26.5 23.9 *: specific C deposition refers to the deposited carbon in mg on per gram HZSM-5 表 5 不同硅铝比HZSM-5积炭的丙酮可溶物GC-MS表征
Table 5 The acetone-soluble matter of coke over HZSM-5 with different SiO2/Al2O3 ratio
Name Formula Content w/% HZ23 HZ50 HZ80 HZ280 HZ310 4-methyl-3-penten-2-one C6H10O 42.91 84.24 34.76 12.37 20.23 4-methyl-4-penten-2-one C6H10O 3.79 3.38 3.91 2.46 3.32 Tetramethyl-oxirane C6H12O 53.26 9.28 61.15 85.14 76.4 Toluene C7H8 0.03 0.15 0.02 0.02 0.03 2,3,4-trimethyl-pentane C8H18 0.01 0.07 0.01 0.02 Others 2.88 0.16 表 6 HZSM-5催化煤热解所得焦油的元素分析
Table 6 Ultimate analysis of tars obtained over HZSM-5 with different SiO2/Al2O3 ratio
Catalyst Uitimate analysis w/% H/C
(mol ratio)C H O a N S Without
catalyst78.31 8.991 11.39 0.881 0.428 1.378 HZ23 82.02 8.648 8.454 0.686 0.192 1.265 HZ50 80.37 8.263 10.40 0.728 0.239 1.234 HZ80 78.22 8.163 12.57 0.835 0.213 1.252 HZ280 80.53 8.612 9.84 0.814 0.214 1.283 HZ310 79.97 8.605 10.42 0.819 0.186 1.291 a: by difference 表 7 HZSM-5催化煤热解所得焦油中组分分布
Table 7 The component distribution of tars obtained over HZSM-5 with different SiO2/Al2O3 ratio
Catalyst Content w/% SAHs USHs AHs HCHs Without catalyst 38.1 10.6 13.1 38.2 HZ23 11.4 0.5 56.4 31.7 HZ50 10.6 0.4 58.4 30.6 HZ80 13.7 52.7 33.6 HZ280 21.9 46.6 31.5 HZ310 16.3 35.8 47.9 -
[1] 敦启孟, 陈兆辉, 皇甫林, 周杨, 余剑, 高士秋, 刘鸿雁. 温度和停留时间对煤热解挥发分二次反应的影响[J]. 过程工程学报,2018,18(1):140−147.DUN Qi-meng, CHEN Zhao-hui, HUANG Fu-Lin, ZHOU Yang, YU Jian, GAO Shi-qiu, LIU Hong-yan. Influences of temperature and residence time on secondary reactions of volatiles from coal pyrolysis[J]. Chin J Process Eng,2018,18(1):140−147. [2] 陈兆辉, 高士秋, 许光文. 煤热解过程分析与工艺调控方法[J]. 化工学报,2017,68(10):3693−3707.CHEN Zhao-hui, GAO Shi-qiu, XU Guang-wen. Analysis and control methods of coal pyrolysis process[J]. Chin J Chem Eng,2017,68(10):3693−3707. [3] WANG D, CHEN Z, ZHOU Z, WANG D, YU J, GAO S. Catalytic upgrading of volatiles from coal pyrolysis over sulfated carbon-based catalysts derived from waste red oil[J]. Fuel Process Technol,2019,189:98−109. doi: 10.1016/j.fuproc.2019.03.003 [4] WANG D, WANG D, YU J, CHEN Z, LI Y, GAO S. Role of alkali sodium on the catalytic performance of red mud during coal pyrolysis[J]. Fuel Process Technol,2019,186:81−87. doi: 10.1016/j.fuproc.2018.12.023 [5] 陈兆辉, 敦启孟, 石勇, 高士秋. 热解温度和反应气氛对输送床煤快速热解的影响[J]. 化工学报,2017,68(4):1566−1573.CHEN Zhao-hui, DUN Qi-meng, SHI Yong, GAO Shi-qiu. Effects of pyrolysis temperature and atmosphere on rapid coal pyrolysis in transport bed reactor[J]. Chin J Chem Eng,2017,68(4):1566−1573. [6] REN X Y, CAO J P, ZHAO X Y, YANG Z, LIU T L, FAN X, ZHAO Y P, WEI X-Y. Catalytic upgrading of pyrolysis vapors from lignite over mono/bimetal-loaded mesoporous HZSM-5[J]. Fuel,2018,218:33−40. doi: 10.1016/j.fuel.2018.01.017 [7] REN X Y, CAO J P, ZHAO X Y, SHEN W Z, WEI X Y. Increasing light aromatic products during upgrading of lignite pyrolysis vapor over Co-modified HZSM-5[J]. J Anal Appl Pyrolysis,2018,130:190−197. doi: 10.1016/j.jaap.2018.01.010 [8] LIU T L, CAO J P, ZHAO X Y, WANG J X, REN X Y, FAN X, ZHAO Y P, WEI X Y. In situ upgrading of Shengli lignite pyrolysis vapors over metal-loaded HZSM-5 catalyst[J]. Fuel Process Technol,2017,160:19−26. doi: 10.1016/j.fuproc.2017.02.012 [9] LI Q, FENG X, WANG X, WU T, ZHU Y, LI S. Pyrolysis of Yulin coal over ZSM-22 supported catalysts for upgrading coal tar in fixed bed reactor[J]. J Anal Appl Pyrolysis,2017,126:390−396. doi: 10.1016/j.jaap.2017.05.004 [10] AMIN M N, LI Y, RAZZAQ R, LU X, LI C, ZHANG S. Pyrolysis of low rank coal by nickel based zeolite catalysts in the two-staged bed reactor[J]. J Anal Appl Pyrolysis,2016,118:54−62. doi: 10.1016/j.jaap.2015.11.019 [11] YANG Z, CAO J P, REN X Y, ZHAO X Y, LIU S N, GUO Z X, SHEN W Z, BAI J WEI X Y. Preparation of hierarchical HZSM-5 based sulfated zirconium solid acid catalyst for catalytic upgrading of pyrolysis vapors from lignite pyrolysis[J]. Fuel,2019,237:1079−1085. doi: 10.1016/j.fuel.2018.10.049 [12] HE Y, YAN L, LIU Y, BAI Y, WANG J, LI F. Effect of SiO2/Al2O3 ratio of HZSM-5 zeolites on the formation of light aromatics during lignite pyrolysis[J]. Fuel Process Technol,2019,188:70−78. doi: 10.1016/j.fuproc.2019.02.004 [13] ILIOPOULOU E F, STEFANIDIS S D, KALOGIANNIS K G, DELIMITIS A, LAPPAS A A, TRIANTAFYLLIDIS K S. Catalytic upgrading of biomass pyrolysis vapors using transition metal-modified ZSM-5 zeolite[J]. Appl Catal B: Environ,2012,127:281−290. doi: 10.1016/j.apcatb.2012.08.030 [14] ZHAO J P, CAO J P, WEI F, FENF X B, YAO N Y, ZHAO Y P, ZHAO M, ZHAO X Y, ZHANG J L, WEI X Y. Catalytic reforming of lignite pyrolysis volatiles over sulfated HZSM-5: Significance of the introduced extra-framework Al species[J]. Fuel,2020,273:117789. [15] GALADIMA A, MURAZA O. In situ fast pyrolysis of biomass with zeolite catalysts for bioaromatics/gasoline production: A review[J]. Energ Convers Manage,2015,105:338−354. doi: 10.1016/j.enconman.2015.07.078 [16] LONG R Q, YANG R T. Temperature-programmed desorption/surface reaction (TPD/TPSR) study of Fe-exchanged ZSM-5 for selective catalytic reduction of nitric oxide by ammonia[J]. J Catal,2001,198(1):20−28. doi: 10.1006/jcat.2000.3118 [17] COSTA C, LOPES J M, LEMOS F, RIBEIRO F R. Activity-acidity relationship in zeolite Y[J]. J Mol Catal A: Chem,1999,144(1):221−231. doi: 10.1016/S1381-1169(98)00367-7 [18] LI Y, AMIN M N, LU X, LI C, REN F, ZHANG S. Pyrolysis and catalytic upgrading of low-rank coal using a NiO/MgO-Al2O3 catalyst[J]. Chem Eng Sci,2016,155:194−200. doi: 10.1016/j.ces.2016.08.003 [19] MIN Z, ASADULLAH M, YIMSIRI P, ZHANG S, WU H, LI C Z. Catalytic reforming of tar during gasification. Part I. Steam reforming of biomass tar using ilmenite as a catalyst[J]. Fuel,2011,90(5):1847−1854. doi: 10.1016/j.fuel.2010.12.039 [20] MIURA K. Mild conversion of coal for producing valuable chemicals[J]. Fuel Process Technol,2000,62(2/3):119−135. [21] REN X Y, CAO J P, ZHAO X Y, YANG Z, LIU S N, WEI X Y. Enhancement of aromatic products from catalytic fast pyrolysis of lignite over hierarchical HZSM-5 by piperidine-assisted desilication[J]. ACS Sustainable Chem Eng,2018,6(2):1792−1802. doi: 10.1021/acssuschemeng.7b03185 [22] REN X Y, CAO J P, ZHAO X Y, YANG Z, WANG Y J, CHEN Q, ZHAO M, WEI X Y. Catalytic conversion of lignite pyrolysis volatiles to light aromatics over ZSM-5: SiO2/Al2O3 ratio effects and mechanism insights[J]. J Anal Appl Pyrolysis,2019,139:22−30. doi: 10.1016/j.jaap.2019.01.003