Effect of Mg-modification on the catalytic performance of Pt/ZSM-22 with low Pt content in n-alkane hydroisomerization

doi:10.16085/j.issn.1000-6613.2024-0379

Abstract

Abstract:

Mg-modified PtMg/ZSM-22 catalyst with low-content Pt (Pt mass fraction 0.1%) was prepared by incipient wetness co-impregnation method using ZSM-22 as the support. N₂adsorption, temperature programmed desorption of NH₃, Py-FTIR, OH-FTIR, and 2,6-DTBPy-FTIR were applied to characterize the catalysts. The results revealed that Mg-modification reduced the specific surface area, the micropore volume, the amount of medium-strong Brønsted sites, and the total acid sites on Pt/ZSM-22 catalysts. The hydroisomerization performance of the catalysts was evaluated using n-dodecane as the model reactant in a fixed-bed reactor. The results of n-dodecane hydroisomerization showed that the selectivity of the i-dodecane increases significantly after the modification of the Mg promoter. An i-dodecane yield of 84.3% were obtained on the Pt0.5Mg/ZSM-22 catalyst. According to the results of the reaction and catalyst characterization, the effects of the Mg promoter on the texture properties, acidity, and catalytic performance of the bifunctional catalysts were discussed.

Key words: catalyst, molecular sieves, alkane, hydroisomerization, Mg-additive, texture properties, acidity

摘要：

以ZSM-22分子筛为载体，采用共浸渍法制备了Mg改性低Pt载量（Pt质量分数0.1%）的PtMg/ZSM-22催化剂，采用N₂物理吸附、NH₃程序升温脱附（NH₃-TPD）、吡啶吸附红外光谱（Py-FTIR）、羟基红外光谱（OH-FTIR）和2,6-二叔丁基吡啶吸附红外光谱（2,6-DTBPy-FTIR）等手段对催化剂进行表征，结果表明Mg的引入降低了Pt/ZSM-22催化剂的比表面积和微孔体积，以及中强B酸量和总酸量。以正十二烷为模型原料，在固定床反应器上考察了催化剂的加氢异构化性能。反应结果表明，与未改性的Pt/Z22催化剂相比，引入Mg助剂后的Pt0.5Mg/ZSM-22催化剂上异构体选择性显著提升，实现84.3%的异构体收率。结合表征结果和反应评价，探讨了Mg助剂对催化剂孔道性质、酸性质以及异构化性能的影响。

关键词: 催化剂, 分子筛, 烷烃, 加氢异构, Mg助剂, 孔道性质, 酸性

CLC Number:

TQ032

BI Wentao, WANG Xuelin, QU Wei, WANG Congxin, TIAN Zhijian. Effect of Mg-modification on the catalytic performance of Pt/ZSM-22 with low Pt content in n-alkane hydroisomerization[J]. Chemical Industry and Engineering Progress, 2025, 44(3): 1355-1367.

毕文涛, 王学林, 曲炜, 王从新, 田志坚. Mg改性对低铂载量Pt/ZSM-22烷烃加氢异构性能的影响[J]. 化工进展, 2025, 44(3): 1355-1367.

Figures/Tables 19

References 39

1	AN Kwangjin, ALAYOGLU Selim, MUSSELWHITE Nathan, et al. Designed catalysts from Pt nanoparticles supported on macroporous oxides for selective isomerization of n-hexane[J]. Journal of the American Chemical Society, 2014, 136(19): 6830-6833.
2	PASTVOVA Jana, KAUCKY Dalibor, MORAVKOVA Jaroslava, et al. Effect of enhanced accessibility of acid sites in micromesoporous mordenite zeolites on hydroisomerization of n-hexane[J]. ACS Catalysis, 2017, 7(9): 5781-5795.
3	郑仁垟. 金属-分子筛双功能催化剂的结构设计及其烷烃异构研究进展[J]. 化工进展, 2021, 40(7): 3785-3790.
	ZHENG Renyang. Advances in structure design and alkane isomerization performance of metal-zeolite bifunctional catalyst[J]. Chemical Industry and Engineering Progress, 2021, 40(7): 3785-3790.
4	Yuchao LYU, ZHAN Weilong, WANG Xiaoxing, et al. Regulation of synergy between metal and acid sites over the Ni-SAPO-11 catalyst for n-hexane hydroisomerization[J]. Fuel, 2020, 274: 117855.
5	Yuchao LYU, YU Zhumo, YANG Ye, et al. Metal-acid balance in the in-situ solid synthesized Ni/SAPO-11 catalyst for n-hexane hydroisomerization[J]. Fuel, 2019, 243: 398-405.
6	KIM Myoung Yeob, LEE Kyungho, CHOI Minkee. Cooperative effects of secondary mesoporosity and acid site location in Pt/SAPO-11 on n-dodecane hydroisomerization selectivity[J]. Journal of Catalysis, 2014, 319: 232-238.
7	陈治平, 王苗苗, 韦晓艺, 等. 复合分子筛在烃类异构化反应中的应用研究进展[J]. 化工进展, 2022, 41(5): 2404-2415.
	CHEN Zhiping, WANG Miaomiao, WEI Xiaoyi, et al. Application of composite molecular sieve in hydrocarbon isomerization[J]. Chemical Industry and Engineering Progress, 2022, 41(5): 2404-2415.
8	ALVAREZ F, RIBEIRO F R, PEROT G, et al. Hydroisomerization and hydrocracking of alkanes 7. influence of the balance between acid and hydrogenating functions on the transformation of n-decane on PtHY catalysts[J]. Journal of Catalysis, 1996, 162(2): 179-189.
9	Yoshio ONO. A survey of the mechanism in catalytic isomerization of alkanes[J]. Catalysis Today, 2003, 81(1): 3-16.
10	GUISNET Michel. “Ideal” bifunctional catalysis over Pt-acid zeolites[J]. Catalysis Today, 2013, 218: 123-134.
11	WANG Dongxu, LIU Jiancong, CHENG Xusheng, et al. Trace Pt clusters dispersed on SAPO-11 promoting the synergy of metal sites with acid sites for high-effective hydroisomerization of n-alkanes[J]. Small Methods, 2019, 3(5): 1800510.
12	CLAUDE Marion C, MARTENS Johan A. Monomethyl-branching of long n-alkanes in the range from decane to tetracosane on Pt/H-ZSM-22 bifunctional catalyst[J]. Journal of Catalysis, 2000, 190(1): 39-48.
13	PARMAR Snehalkumar, PANT Kamal K, JOHN Mathew, et al. Hydroisomerization of n-hexadecane over Pt/ZSM-22 framework: Effect of divalent cation exchange[J]. Journal of Molecular Catalysis A: Chemical, 2015, 404: 47-56.
14	CHEN Yujing, LI Chuang, CHEN Xiao, et al. Synthesis and characterization of iron-substituted ZSM-23 zeolite catalysts with highly selective hydroisomerization of n-hexadecane[J]. Industrial & Engineering Chemistry Research, 2018, 57(41): 13721-13730.
15	LEE Seung-Woo, Son-Ki IHM. Characteristics of magnesium-promoted Pt/ZSM-23 catalyst for the hydroisomerization of n-hexadecane[J]. Industrial & Engineering Chemistry Research, 2013, 52(44): 15359-15365.
16	PENG Yan, WANG Xuelin, WANG Congxin, et al. Boosting catalytic performance via electron transfer effect for hydroisomerization on a low-Pt-content PtCeO_x/zeolite catalyst[J]. Chem Catalysis, 2023, 3(2): 100505.
17	XIONG Shuxiang, SUN Jiazheng, LI Huiyan, et al. The synthesis of hierarchical ZSM-22 zeolite with only the PHMB template for hydroisomerization of n-hexadecane[J]. Microporous and Mesoporous Materials, 2024, 365: 112895.
18	ZHANG Lei, GAO Yifei, BAI Xuerui, et al. Ni catalyst on ZSM-22 nanofibers bundles with good catalytic performance in the hydroisomerization of n-dodecane[J]. Fuel, 2024, 357: 129885.
19	张海鹏, 王树振, 马梦茜, 等. ZSM-22分子筛合成及其正十二烷烃临氢异构化性能: 模板剂和动态晶化的影响[J]. 化工进展, 2024, 43(1): 414-421.
	ZHANG Haipeng, WANG Shuzhen, MA Mengxi, et al. Synthesis of ZSM-22 molecular sieve and its n-dodecane hydroisomerization performance: Effect of template agent and dynamic crystallization[J]. Chemical Industry and Engineering Progress, 2024, 43(1): 414-421.
20	HAYASAKA Kazuaki, LIANG Duoduo, HUYBRECHTS Ward, et al. Formation of ZSM-22 zeolite catalytic particles by fusion of elementary nanorods[J]. Chemistry, 2007, 13(36): 10070-10077.
21	Guang LYU, WANG Congxin, WANG Ping, et al. Pt/ZSM-22 with partially filled micropore channels as excellent shape-selective hydroisomerization catalyst[J]. ChemCatChem, 2019, 11(5): 1431-1436.
22	余姮, 董焕能, 刘茜桐, 等. MgO修饰的HZSM-5分子筛对甲苯甲醇烷基化反应性能的影响[J]. 厦门大学学报(自然科学版), 2023, 62(1): 78-84.
	YU Heng, DONG Huanneng, LIU Xitong, et al. Effects of MgO-modified HZSM-5 zeolites on the performance of alkylation reaction of toluene with methanol[J]. Journal of Xiamen University (Natural Science), 2023, 62(1): 78-84.
23	KOKOTAILO G T, SCHLENKER J L, DWYER F G, et al. The framework topology of ZSM-22: A high silica zeolite[J]. Zeolites, 1985, 5(6): 349-351.
24	WANG Congxin, TIAN Zhijian, WANG Lei, et al. One-step hydrotreatment of vegetable oil to produce high quality diesel-range alkanes[J]. ChemSusChem, 2012, 5(10): 1974-1983.
25	Kinga GÓRA-MAREK, TARACH Karolina, CHOI Minkee. 2, 6-di-tert-butylpyridine sorption approach to quantify the external acidity in hierarchical zeolites[J]. The Journal of Physical Chemistry C, 2014, 118(23): 12266-12274.
26	SONG Hyunjoon, RIOUX Robert M, HOEFELMEYER James D, et al. Hydrothermal growth of mesoporous SBA-15 silica in the presence of PVP-stabilized Pt nanoparticles: Synthesis, characterization, and catalytic properties[J]. Journal of the American Chemical Society, 2006, 128(9): 3027-3037.
27	ALLIAN Ayman D, TAKANABE Kazuhiro, FUJDALA Kyle L, et al. Chemisorption of CO and mechanism of CO oxidation on supported platinum nanoclusters[J]. Journal of the American Chemical Society, 2011, 133(12): 4498-4517.
28	辛勤, 罗孟飞. 现代催化研究方法[M]. 北京: 科学出版社, 2009: 290.
	XIN Qin, LUO Mengfei. Modern catalytic research methods[M]. Beijing: Science Press, 2009: 290.
29	MUKERJI R J, BOLINA A S, BROWN W A. A RAIRS and TPD investigation of the adsorption of CO on Pt{211}[J]. Surface Science, 2003, 527(1/2/3): 198-208.
30	BISCHOFF H, JAEGER N I, SCHULZ-EKLOFF G. FTIR study of the particle size dependent chemisorption of CO on Pt dispersed within a faujasite matrix[J]. Zeitschrift Für Physikalische Chemie, 1990, 2710(1): 1093-1102.
31	MAO Dongsen, YANG Weimin, XIA Jianchao, et al. Highly effective hybrid catalyst for the direct synthesis of dimethyl ether from syngas with magnesium oxide-modified HZSM-5 as a dehydration component[J]. Journal of Catalysis, 2005, 230(1): 140-149.
32	CORMA A, FORNÉS V, FORNI L, et al. 2, 6-di-tert-butyl-pyridine as a probe molecule to measure external acidity of zeolites[J]. Journal of Catalysis, 1998, 179(2): 451-458.
33	UNGUREANU A, HOANG T V, Trong ON D, et al. An investigation of the acid properties of UL-ZSM-5 by FTIR of adsorbed 2, 6-ditertbutylpyridine and aromatic transalkylation test reaction[J]. Applied Catalysis A: General, 2005, 294(1): 92-105.
34	Frédéric THIBAULT-STARZYK, STAN Irina, Sònia ABELLÓ, et al. Quantification of enhanced acid site accessibility in hierarchical zeolites—The accessibility index[J]. Journal of Catalysis, 2009, 264(1): 11-14.
35	DE LUCAS Antonio, RAMOS María Jesús, DORADO Fernando, et al. Influence of the Si/Al ratio in the hydroisomerization of n-octane over platinum and palladium beta zeolite-based catalysts with or without binder[J]. Applied Catalysis A: General, 2005, 289(2): 205-213.
36	CHOUDHURY Indranil R, HAYASAKA Kazuaki, THYBAUT Joris W, et al. Pt/H-ZSM-22 hydroisomerization catalysts optimization guided by Single-Event MicroKinetic modeling[J]. Journal of Catalysis, 2012, 290: 165-176.
37	BROSIUS Roald, KOOYMAN Patricia J, FLETCHER Jack C Q. Selective formation of linear alkanes from n-hexadecane primary hydrocracking in shape-selective MFI zeolites by competitive adsorption of water[J]. ACS Catalysis, 2016, 6(11): 7710-7715.
38	NIU Pengyu, LIU Ping, XI Hongjuan, et al. Design and synthesis of Pt/ZSM-22 catalysts for selective formation of iso-dodecane with branched chain at more central positions from n-dodecane hydroisomerization[J]. Applied Catalysis A: General, 2018, 562: 310-320.
39	MARTENS J A, JACOBS P A, WEITKAMP J. Attempts to rationalize the distribution of hydrocracked products. I qualitative description of the primary hydrocracking modes of long chain paraffins in open zeolites[J]. Applied Catalysis, 1986, 20(1/2): 239-281.

样品	比表面积^①/m²·g^-1	微孔比表面积/m²·g^-1	外比表面积/m²·g^-1	微孔体积^①/cm³·g^-1	Pt粒径^②/nm	Pt分散度^②/%	Pt粒径^③/nm
Z22	184.4	144.3	40.1	0.071	—	—	—
Pt/Z22	166.7	131.5	35.2	0.065	2.4	45.6	1.9
Pt0.5Mg/Z22	108.3	70.1	38.2	0.034	1.7	67.6	1.6
Pt1Mg/Z22	55.9	22.5	33.4	0.011	1.6	68.3	1.5

样品	比表面积^①/m²·g^-1	微孔比表面积/m²·g^-1	外比表面积/m²·g^-1	微孔体积^①/cm³·g^-1	Pt粒径^②/nm	Pt分散度^②/%	Pt粒径^③/nm
Z22	184.4	144.3	40.1	0.071	—	—	—
Pt/Z22	166.7	131.5	35.2	0.065	2.4	45.6	1.9
Pt0.5Mg/Z22	108.3	70.1	38.2	0.034	1.7	67.6	1.6
Pt1Mg/Z22	55.9	22.5	33.4	0.011	1.6	68.3	1.5

样品	酸度/mmol·g^-1
样品	弱酸量	中强酸量	总酸量
Pt/Z22	0.27	0.22	0.49
Pt0.5Mg/Z22	0.26	0.16	0.42
Pt1Mg/Z22	0.26	0.15	0.41

样品	酸度/mmol·g^-1
样品	弱酸量	中强酸量	总酸量
Pt/Z22	0.27	0.22	0.49
Pt0.5Mg/Z22	0.26	0.16	0.42
Pt1Mg/Z22	0.26	0.15	0.41

样品	酸类型/μmol·g^-1						酸类型(150℃，B)/μmol·g^-1	χ	C_M/C_A
	150℃			300℃
	B	L	B/L	B	L	B/L
Pt/Z22	112.7	22.5	5.0	95.6	15.7	6.1	8.7	0.08	0.024
Pt0.5Mg/Z22	41.7	31.5	1.3	36.9	30.4	1.2	8.5	0.21	0.094
Pt1Mg/Z22	11.6	36.1	0.3	7.7	23.8	0.3	6.8	0.59	0.453