SYNTHESIS OF Pt/PTA-MIL-101(Cr) AND ITS CATALYTIC PERFORMANCE FOR n-HEPTANE ISOMERIZATION

Abstract

Abstract: The 0.4%Pt/PTA-MIL-101(Cr) metal-acid bifunctional catalysts with different doping amounts of PTA were prepared by modifying organometallic skeleton material MIL-101(CR) with phosphotungstic acid (PTA) and were first applied to n-heptane isomerization. The synthesized samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), N2 adsorption-desorption, thermal gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), X-ray fluorescence (XRF) and acid-base titration. The results show that the synthesized samples are mesoporous-microporous composite materials with typical octahedral structure, regular pore structure and high specific surface area; the framework and thermal stability of MIL-101(Cr) are not damaged; the Keggin structure of PTA can be maintained in the catalyst, which can provide a good acidic environment for the catalytic reaction and the higher dispersity of Pt in MIL-101(Cr). Through the evaluation of n-heptane isomerization performance of the catalyst, it was found that the best match between the acid sites and metal sites of the catalyst was the most suitable for catalyzing n-heptane isomerization, when the reaction temperature was 260 ℃ and the doping content of PTA was 30%, and the conversion of n-heptane and the selectivity of iso-heptane could reach 69.1% and 93.7%,respectively.

Key words: MIL-101(Cr), phosphotungstic acid, platinum, n-heptane, isomerization

References

[1] Ferey G, Mellot-Draznieks C, Serre C, et al. A Chromium Terephthalate-Based Solid with Unusually Large Pore Volumes and Surface Area[J]. Science, 2005, 309(5743): 2040-2042.
[2] 何奕工，李奋，王蓬，等. 杂多酸催化剂的吸附，酸性和物化性质[J]. 石油炼制与化工，1996，27(8): 12-16.
[3] 刘平，冯晓奇，王军，等. 正庚烷异构化催化剂的研究进展[J]. 常州大学学报(自然科学版)，2017，29(3): 25-33.
[4] 王海彦, 周定. 负载磷钨酸催化剂制备与催化性能[J]. 化工学报，2001，52(9): 842-845.
[5] 严家其，谈瑛，李勇飞，等. 金属有机框架MIL-100(Cr)和MIL-101(Cr)负载磷钨酸催化合成双酚F[J]. 化工学报，2015，66(2): 576-583.
[6] 丁建伟，王睿，于美青，等. MIL-101固载磷钨酸催化氧气氧化脱硫性能[J]. 化工学报，2016，67(S1): 283-288.
[7] Deng Q, Nie G K, Pan L, et al. Highly selective self-condensation of cyclic ketones using MOF-encapsulating phosphotungstic acid for renewable high-density fuel[J]. Green Chemistry, 2015, 17(8): 4473-4481.
[8] 杨新丽，刘洋，戴维林，等. 新型HPWs/MIL-101催化剂的制备及其对环戊烯选择氧化反应的催化性能. 石油化工，2014，43(7): 759-766.
[9] 刘晓萍，王清遐，孙新德，等. 负载杂多酸催化剂上的正丁烷异构化. 天然气化工，2002，17(3): 17-20.
[10] 高善彬，迟克彬，杨晓东，等. 正构烷烃在Pt/SAPO-11催化剂上加氢异构反应性能[J]. 化工学报，2016，67(12): 5024-5030.
[11] Peyrovi M H, Parsafard N, Anajafi H R. Catalytic performance of micro-mesoporous materials as the supports for Pt catalysts in n-heptane isomerization[J]. Chemical Physics Letters, 2018, 713: 32-38.
[12] Triwahyono S, Jalil A A, Izan S M, et al. Isomerization of linear C5-C7 over Pt loaded on protonated fibrous silica@Y zeolite (Pt/HSi@Y)[J]. Journal of Energy Chemistry, 2019, 28(10): 163–171.
[13] Sabyrov K, Jiang J, Yaghi O M, et al. Hydroisomerization of n-Hexane using Acidified Metal-Organic Framework and Platinum Nanoparticles[J]. Journal of the American Chemical Society, 2017, 139(36): 12382-12385.
[14] Zalomaeva O, Kovalenko K A, Chesalov Y A, et al. Iron tetrasulfophthalocyanine immobilized on metal organic framework MIL-101: synthesis, characterization and catalytic properties[J]. Dalton Trans, 2011, 40(7): 1441-1444.
[15] 章涵，王俊二，董浩，等. 磷钨酸负载MOFs功能化磁性复合材料催化氧化脱硫. 无机化学学报，2020，36(8): 1475-1484.
[16] Zhuo N, Lan Y Q, Yang W B, et al. Adsorption of three selected pharmaceuticals and personal care products (PPCPs) onto MIL-101(Cr)/natural polymer composite beads[J]. Separation and Purification Technology, 2016, 177: 272-280.
[17] Banach E M, Stil H A, Geerlings H. Aluminium hydride nanoparticles nested in the porous zeolitic imidazolate framework-8[J]. Journal of Materials Chemistry, 2011, 22(2): 324-327.
[18] El-Shall M S, Abdelsayed V, Khder A E R S, et al. Metallic and Bimetallic Nanocatalysts Incorporated into Highly Porous Coordination Polymer MIL-101. Journal of Materials Chemistry, 2009, 19(41): 7625-7631.
[19] Hu X F, Lu Y K, Dai F N, et al. Host-guest synthesis and encapsulation of phosphotungstic acid in MIL-101 via "bottle around ship": an effective catalyst for oxidation desulfurization[J]. Microporous and mesoporous materials, 2013, 170: 36-44.
[20] Zhao M, Yuan K, Wang Y, et al. Metal-organic frameworks as selectivity regulators for hydrogenation reactions[J]. Nature, 2016, 539(7627): 76-80.
[21] Blomsma E, Martens J A, Jacobs P A. Mechanisms of Heptane Isomerization on Bifunctional Pd/H-Beta Zeolites[J]. Journal of Catalysis, 1996, 159(2): 323-331.
[22] Rutenbeck D, Papp H, Freude D, et al. Investigations on the reaction mechanism of the skeletal isomerization of n-butenes to isobutene: Part I. Reaction mechanism on H-ZSM-5 zeolites[J]. Applied Catalysis A General, 2001, 206(1): 57-66.
[23] Samad J E, Blanchard J, Sayag C, et al. The controlled synthesis of metal-acid bifunctional catalysts: The effect of metal:acid ratio and metal-acid proximity in Pt silica-alumina catalysts for n-heptane isomerization[J]. Journal of Catalysis, 2016, 342(Complete): 213-225.
[24] Guisnet, Michel. "Ideal" bifunctional catalysis over Pt-acid zeolites[J]. Catalysis Today, 2013, 218-219(Complete): 123-134.
[25] 于宁，龙军，周涵，等. 正庚烷脱氢生成烯烃反应机理的模拟研究[J]. 石油化工，2013，29(2): 181-185.