Synthesis and hydroisomerization performance of n-C12 over ZSM-48 molecular sieve with low silicon-aluminum ratio
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摘要: 通过静态水热合成法，溴化六甲二铵作为结构导向剂合成出系列低硅铝比的ZSM-48沸石分子筛（Si/Al < 100），所合成样品中最低硅铝比为38.6（ICP-AES），这将拓宽ZSM-48高硅沸石分子筛的应用范围。制备Pt负载双功能催化剂，用于正构十二烷临氢异构催化反应。结果表明，硅铝比的改变可以影响催化剂的活性，投料硅铝比为70的双功能催化剂具有最优的催化性能，但硅铝比改变对异构产物的分布没有明显的影响，其异构产物以支链在中间位的异构体为主。Abstract: A series of ZSM-48 zeolites with low Si/Al ratios (Si/Al < 100) were synthesized by hydrothermal synthesis method using hexamethydiammonium bromide as the structure directing agent. ICP-AES results showed that the Si/Al ratio of the synthesized sample was as low as 38.6, indicating the zeolite could be widely used. Pt supported on ZSM-48 with different Si/Al ratios were used for n-paraffin hydroisomerization. The catalytic reaction results showed that Pt/HZSM-48 with Si/Al ratio of 70 exhibited the best catalytic performance. However, the distribution of isomers had not been affected by Si/Al ratio of the ZSM-48, and the central-branched isomers were the main hydroisomerization products.
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Key words:
- ZSM-48 zeolite /
- low Si/Al ratio /
- n-dodecane /
- hydroisomerization /
- bifunctional catalyst
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图 2 不同Si/Al比ZSM-48分子筛的NH3-TPD谱图
Figure 2 NH3-TPD profiles of the ZSM-48 molecular sieves with different Si/Al ratios
图 3 不同Si/Al比ZSM-48分子筛的SEM照片
Figure 3 SEM images of the ZSM-48 molecular sieve with different Si/Al ratios
(a): Si/Al=50; (b): Si/Al=70; (c): Si/Al=90
图 4 不同Si/Al比ZSM-48分子筛TEM照片及Pt粒径分布
Figure 4 TEM images and Pt particle size distribution of the ZSM-48 molecular sieve with different Si/Al ratios
(a), (a′): 50; (b), (b′): 70; (c), (c′): 90
图 5 氮气吸附-脱附等温线(a)和DFT孔径分布图(b)
Figure 5 N2 adsorption-desorption isotherms(a) and DFT pore size distribution curves(b)
图 6 催化剂的催化性能评价
Figure 6 Catalytic performance of the catalysts
(reaction conditions: H2/n-dodecane=1200, LHSV=2.0 h-1, p=2.0 MPa)
图 7 不同催化剂上单支链(a)和多支链(b)异构产物的选择性
Figure 7 Selectivity to mono-branched and di-branched isomers over the bifunctional catalysts
(reaction conditions: H2/n-dodecane=1200, LHSV=2.0 h-1, p=2.0 MPa)
图 9 催化剂Pt/HZSM-48-70的TEM照片
Figure 9 TEM images of the Pt/HZSM-48-70 catalysts
(a): fresh catalyst; (b): used catalyst
表 1 样品元素含量
Table 1 Elemental content of the samples
Sample Si/(mg·L-1) Al/(mg·L-1) Si/Al ZSM-48-50 19.62 0.49 38.6 ZSM-48-70 15.14 0.32 45.6 ZSM-48-90 18.86 0.31 58.7 
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表 2 样品的酸含量
Table 2 Acid content of the samples
Sample Peak
temperature
t /℃NH3
uptake/
(μmol·g-1)Total
NH3 uptake/
(μmol·g-1)HZSM-48-50 236 217 471 436 254 HZSM-48-70 235 222 422 435 200 HZSM-48-90 234 183 369 426 186
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表 3 样品的EDS分析数据
Table 3 EDS analysis data of the samples
Sample watom/% Si/Al Si Kα Al Kα ZSM-48-50 97.3 2.7 36.3 ZSM-48-70 97.8 2.2 44.2 ZSM-48-90 98.2 1.8 54.8
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表 4 样品的孔结构参数
Table 4 Pore structure parameter of the samples
Sample ABET/
(m2·g-1)Amic/
(m2·g-1)Ames/
(m2·g-1)vtotal/
(cm3·g-1)vmic/
(cm3·g-1)vmes/
(cm3·g-1)Relative
crystallinityHZSM-48-50 208 118 90 0.24 0.05 0.19 69.5 HZSM-48-70 269 163 106 0.33 0.07 0.26 73.3 HZSM-48-90 215 123 92 0.20 0.05 0.15 86.5
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表 5 不同催化剂的正十二烷异构产物分布
Table 5 Results of n-dodecane isomerization over the catalysts
Catalyst Pt/HZSM-48-50 Pt/HZSM-48-70 Pt/HZSM-48-90 Pt/HZSM-48-200 Temperature t/℃ 320 320 340 360 Conversion x/% 52.16 46.38 55.59 51.3 sT/% 78.56 92.65 77.97 82.61 sMB/% 53.40 70.82 54.89 57.96 sDB/% 25.16 21.83 23.06 24.65 sMB/sDB 2.12 3.24 2.38 2.35 s/% 2-methylundecane 10.71 15.05 11.26 11.68 3-methylundecane 12.13 15.87 12.27 13.06 4-methylundecane 10.53 13.80 10.76 11.47 5-methylundecane 18.55 24.65 19.40 20.59 6-methylundecane 1.48 1.45 1.20 1.16 2, 4-dimethyldecane 0.57 0.43 0.53 0.51 2, 5-dimethyldecane 1.63 1.37 1.65 1.77 2, 6-dimethyldecane 5.93 5.13 5.81 6.52 2, 7-dimethyldecane 3.31 2.72 3.08 3.45 2, 8-dimethyldecane 2.03 1.89 2.11 2.46 2, 9-dimethyldecane 2.84 2.55 2.66 2.94 3, 3-dimethyldecane 0.72 0.59 0.74 0.78 3, 7-dimethyldecane 0.00 0.60 0.00 0.35 3, 8-dimethyldecane 0.87 0.00 0.79 1.03 Methylethylnonane 4.36 4.96 3.57 3.12 Other isomer 2.89 1.59 2.14 1.74
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[1] MARTENS J A, VANBUTSELE G, JACOBS P A, DENAYER J, OCAKOGLU R, BARON G, MUÑOZ ARROYO J A, THYBAUT J, MARIN G.B. Evidences for pore mouth and key-lock catalysis in hydroisomerization of long n-alkanes over 10-ring tubular pore bifunctional zeolites[J]. Catal Today, 2001, 65(2/4): 111-116. [2] BAUER F, FICHT K, BERTMER M, EINICKE W D, KUCHLING T, GLÄSER R. Hydroisomerization of long-chain paraffins over nano-sized bimetallic Pt-Pd/H-beta catalysts[J]. Catal Sci Technol, 2014, 4(11): 4045-4054. doi: 10.1039/C4CY00561A [3] SCHLENKER J L, ROHRBAUGH W J, CHU P, VALYOCSIK E W, KOKOTAILO G T. The framework topology of ZSM-48: A high silica zeolite[J]. Zeolites, 1985, 5(6): 355-358. doi: 10.1016/0144-2449(85)90124-1 [4] 李瑞丰, 杜艳泽, 唐静思, 陈晓芳, 秦波, 郑家军, 孙晓勃, 潘梦, 李鹏, 高禾鑫, 张鸿雁.一种低硅铝比ZSM-48分子筛的合成方法: CN, 105967202A[P]. 2016-09-28.LI Rui-feng, DU Yan-ze, TANG Jing-si, CHEN Xiao-fang, QING Bo, ZHENG Jia-jun, SUN Xiao-bo, PAN Meng, LI Peng, GAO He-xin, ZHANG Hong-yan. Method for synthesizing low silicon to aluminum ratio ZSM-48 molecular sieve: CN, 105967202A[P]. 2016-09-28. [5] ZHANG Y J, MA Y H, CHE S A. Synthesis of lamellar mesostructured ZSM-48 nanosheets[J]. Chem Mater, 2018, 30(6): 1839-1843. doi: 10.1021/acs.chemmater.8b00146 [6] ROSALES HERNA'NDEZ M C, MENDIETA WEJEBE J E, VA'ZQUEZ ALCA'NTARA J I, MIRANDA RUVALCABA R, GARCI'A SERRANO L A, TRUJILLO FERRARA J. Immobilization of cytochrome P-450 on MCM-41 with different silicon/aluminum ratios[J]. Microporous Mesoporous Mater, 2005, 80(1/3): 25-31. http://www.sciencedirect.com/science/article/pii/S1387181104004779 [7] 赵国良, 滕加伟, 宋庆英, 谢在库, 陈庆龄. AlSi-ZSM-48沸石分子筛的合成及其催化性能[J].催化学报, 2003, 2: 119-122. doi: 10.3321/j.issn:0253-9837.2003.02.011ZHAO Guo-liang, TEN Jia-wei, SONG Qing-ying, XIE Zai-ku, CHEN Qing-ling. Synthesis and catalytic performance of AlSi-ZSM-48 zeolite molecular sieve[J]. Chin J Catal, 2003, 2: 119-122. doi: 10.3321/j.issn:0253-9837.2003.02.011 [8] 张淼. ZSM-48分子筛的合成、改性及十六烷加氢异构性能[D].大连: 大连理工大学, 2017. http://cdmd.cnki.com.cn/Article/CDMD-10141-1017035089.htmZHANG Miao. Synthesis and modification of ZSM-48 zeolite and their performance for hydroisomerization of hexadecane[D]. Dalian: Dalian University of Technology, 2017. http://cdmd.cnki.com.cn/Article/CDMD-10141-1017035089.htm [9] KUNIO S, HAYAKAWA T. The effects of seeding in the synthesis of zeolite ZSM-48 in the presence of tetramethylammoniumion[J]. Microporous Mesoporous Mater, 2005, 77(2/3): 131-137. http://www.sciencedirect.com/science/article/pii/S1387181104003403 [10] ZHAO G L, TENG J W, ZHANG Y H, XIE Z K, YUE Y H, CHEN Q L, TANG Y. Synthesis of ZSM-48 zeolites and their catalytic performance in C4-olefin cracking reactions[J]. Appl Catal A: Gen, 2006, 299: 167-174. doi: 10.1016/j.apcata.2005.10.022 [11] ZHANG M, CHEN Y J, WANG L, ZHANG Q M, TSANG C W, LIANG C H. Shape selectivity in hydroisomerization of hexadecane over Pt supported on 10-ring zeolites: ZSM-22, ZSM-23, ZSM-35, and ZSM-48[J]. Ind Eng Chem Res, 2016, 55(21): 6069-6078. doi: 10.1021/acs.iecr.6b01163 [12] LI H R, LIU C L, WANG Y, ZHENG J J, FAN B B, LI R F. Synthesis, characterization and n-hexane hydroisomerization performances of Pt supported on alkali treated ZSM-22 and ZSM-48[J]. RSC Adv, 2018, 8(51): 28909-28917. doi: 10.1039/C8RA04858D [13] ZHANG Q Q, MING W X, MA J H, ZHANG J L, WANG P, LI R F. De novo assembly of a mesoporous beta zeolite with intracrystalline channels and its catalytic performance for biodiesel production[J]. J Mater Chem A, 2014, 2(23): 8712-8718. doi: 10.1039/C4TA00030G [14] NIU P Y, XI H J, REN J, LIN M G, WANG Q, JIA L T, HOU B, LI D B. High selectivity for n-dodecane hydroisomerization over highly siliceous ZSM-22 with low Pt loading[J]. Catal Sci Technol, 2017, 7(21): 5055-5068. doi: 10.1039/C7CY01661A [15] MICHEL G. "Ideal" bifunctional catalysis over Pt-acid zeolites[J]. Catal Today, 2013, 218: 123-134. http://d.old.wanfangdata.com.cn/NSTLQK/NSTL_QKJJ0231732357/ [16] LIU S Y, REN J, ZHU S J, ZHANG H K, LV E J, XU J, LI Y W. Synthesis and characterization of the Fe-substituted ZSM-22 zeolite catalyst with high n-dodecane isomerization performance[J]. J Catal, 2015, 330: 485-496. doi: 10.1016/j.jcat.2015.07.027 [17] LIU S Y, REN J, ZHANG H K, LV E J, YANG Y, LI Y W. Synthesis, characterization and isomerization performance of micro/mesoporous materials based on H-ZSM-22 zeolite[J]. J Catal, 2016, 335: 11-23. doi: 10.1016/j.jcat.2015.12.009 [18] SOUVERIJNS W, HOUVENAGHEL A, FEIJEN E J P, MARTENS J A, JACOBS P A. Isomerization of 1-cyclohexyloctane on Pt/H-ZSM-22 bifunctional zeolite catalyst[J]. J Catal, 1998, 174(2): 201-209. doi: 10.1006/jcat.1998.1968 [19] MARTENSJ A, SOUVERIJNSW, VERRELST W, PARTON R, FROMENT G F, JACOBS P A. Selective isomerization of hydrocarbon chains on external surfaces of zeolite crystals[J]. Angew Chem Int Ed, 1995, 34(22): 2528-2530. doi: 10.1002/anie.199525281 -
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