Study on design of polymeric ionic liquids and the performance for selective oxidation of cyclohexane

doi:10.11949/0438-1157.20231301

Abstract

Abstract:

Different molecular weights of poly(vinylimidazole) were synthesized by using vinyl imidazole as a monomer and different amounts of initiators. Thermogravimetric (TG) analysis showed that the polymer had good thermal stability. A series of polymeric ionic liquids (PIL) were synthesized by quaternization of the optimal polymer with three different alkyl chain lengths: 1-chlorooctadecane, 1-chlorododecane, and 1-chlorohexane. The chemical structure and morphology of the polymeric ionic liquids were analyzed by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and contact angle testing. The catalytic performance of PIL-C₁₈, PIL-C₁₂, and PIL-C₆ for selective cyclohexane oxidation was investigated. Furthermore, PIL-C₁₂ was selected to conduct in-depth research on the influence of ion rates (PIL-C₁₂-X, X=10, 25, 50, 75, 100) on catalytic performance. The results showed that the length of alkyl chain segment and the ionic ratio could effectively influence the hydrophobicity and active site of the catalysts to improve the performance with the conversion of 21.8% and selectivity of 41.5% for cyclohexane oxidation to adipic acid.

Key words: polymeric ionic liquids, ionic rate, cyclohexane, catalytic, oxidation

摘要：

以乙烯基咪唑为单体，添加不同量的引发剂，采用常规热聚合中自由基聚合的方式，合成了不同分子量的聚乙烯基咪唑，热重（TG）分析表明该聚合物具有良好的热稳定性。采用季铵化反应，对最优聚合物进行1-氯代十八烷、1-氯代十二烷以及1-氯代正己烷三种不同烷基链长度的取代，合成系列聚合离子液体（PIL）。通过傅里叶红外光谱（FT-IR）、扫描电子显微镜（SEM）、X射线光电子能谱（XPS）、接触角等表征手段分析了聚合离子液体的化学结构及形貌特征，并考察了PIL-C₁₈、PIL-C₁₂、PIL-C₆催化环己烷选择性氧化为己二酸的性能，进而选取PIL-C₁₂深入研究了离子率对催化性能的影响规律。结果表明，烷基链段长度以及离子率可以有效调控亲疏水性和反应活性位点，进而提高反应性能，使得反应生成己二酸的转化率达到21.8%，选择性为41.5%。

关键词: 聚合离子液体, 离子率, 环己烷, 催化, 氧化

CLC Number:

O 26

Ruirui WANG, Ying JIN, Yumei LIU, Mengyue LI, Shengwen ZHU, Ruiyi YAN, Ruixia LIU. Study on design of polymeric ionic liquids and the performance for selective oxidation of cyclohexane[J]. CIESC Journal, 2024, 75(4): 1552-1564.

王瑞瑞, 金颖, 刘玉梅, 李梦悦, 朱胜文, 闫瑞一, 刘瑞霞. 聚合离子液体设计及催化环己烷选择性氧化性能研究[J]. 化工学报, 2024, 75(4): 1552-1564.

Figures/Tables 13

References 46

1	刘长军, 唐盛伟, 谭平华, 等. 环己烷液相非催化/催化氧化反应动力学特性比较[J]. 化工学报, 2008, 59(8): 1992-1999.
	Liu C J, Tang S W, Tan P H, et al. Comparison of kinetic behavior of non-catalytic/catalytic liquid-phase oxidation of cyclohexane[J]. Journal of Chemical Industry and Engineering (China), 2008, 59(8): 1992-1999.
2	Schuchardt U, Cardoso D, Sercheli R, et al. Cyclohexane oxidation continues to be a challenge[J]. Applied Catalysis A: General, 2001, 211(1): 1-17.
3	蹇建, 张嘉明, 佘祥, 等. V⁴⁺和V⁵⁺比例对钒磷氧催化NO₂氧化环己烷性能的影响[J]. 化工学报, 2023, 74(4): 1570-1577.
	Jian J, Zhang J M, She X, et al. Correlation with the redox V⁴⁺/V⁵⁺ ratio in VPO catalysts for oxidation of cyclohexane by NO₂ [J]. CIESC Journal, 2023, 74(4): 1570-1577.
4	Wang C H, Chen L F, Qi Z W. One-pot synthesis of gold nanoparticles embedded in silica for cyclohexane oxidation[J]. Catalysis Science & Technology, 2013, 3(4): 1123-1128.
5	梁学博, 胡伯羽, 袁永军, 等. 金属卟啉催化空气氧化环己烷反应的工艺优化[J]. 化工学报, 2007, 58(3): 794-800.
	Liang X B, Hu B Y, Yuan Y J, et al. Optimization of aerobic oxidation of cyclohexane catalyzed by metalloporphyrins[J]. Journal of Chemical Industry and Engineering (China), 2007, 58(3): 794-800.
6	Lawal N S, Ibrahim H, Bala M D. Facile peroxidation of cyclohexane catalysed by in situ generated triazole-functionalised schiff base copper complexes[J]. Catalysis Letters, 2022, 152(5): 1264-1275.
7	Chavan S A, Srinivas D, Ratnasamy P. Oxidation of cyclohexane, cyclohexanone, and cyclohexanol to adipic acid by a non-HNO₃ route over Co/Mn cluster complexes[J]. Journal of Catalysis, 2002, 212(1): 39-45.
8	Meireles A M, Guimarães A S, Querino G R, et al. Exploring manganese pyridylporphyrin isomers for cyclohexane oxidation: first-generation catalysts are better than third-generation ones[J]. Applied Organometallic Chemistry, 2021, 35(11): e6400.
9	Liu D C, Zhang B Q, Liu X F, et al. Cyclohexane oxidation over AFI molecular sieves: effects of Cr, Co incorporation and crystal size[J]. Catalysis Science & Technology, 2015, 5(6): 3394-3402.
10	Xie C J, Wang W, Yang Y P, et al. Enhanced stability and activity for solvent-free selective oxidation of cyclohexane over Cu₂O/CuO fabricated by facile alkali etching method[J]. Molecular Catalysis, 2020, 495: 111134.
11	Shen H M, Wang X L, Ning L, et al. Efficient oxidation of cycloalkanes with simultaneously increased conversion and selectivity using O₂ catalyzed by metalloporphyrins and boosted by Zn(AcO)₂: a practical strategy to inhibit the formation of aliphatic diacids[J]. Applied Catalysis A: General, 2021, 609: 117904.
12	Wan Y L, Guo Q, Wang K, et al. Efficient and selective photocatalytic oxidation of cyclohexane using O₂ as oxidant in VOCl₂ solution and mechanism insight[J]. Chemical Engineering Science, 2019, 203: 163-172.
13	Hereijgers B P C, Weckhuysen B M. Aerobic oxidation of cyclohexane by gold-based catalysts: new mechanistic insight by thorough product analysis[J]. Journal of Catalysis, 2010, 270(1): 16-25.
14	Guo C C, Chu M F, Liu Q, et al. Effective catalysis of simple metalloporphyrins for cyclohexane oxidation with air in the absence of additives and solvents[J]. Applied Catalysis A: General, 2003, 246(2): 303-309.
15	Wu M Z, Zhan W C, Guo Y L, et al. An effective Mn-Co mixed oxide catalyst for the solvent-free selective oxidation of cyclohexane with molecular oxygen[J]. Applied Catalysis A: General, 2016, 523: 97-106
16	Alkordi M H, Liu Y L, Larsen R W, et al. Zeolite-like metal-organic frameworks as platforms for applications: on metalloporphyrin-based catalysts[J]. Journal of the American Chemical Society, 2008, 130(38): 12639-12641.
17	Prabu M, Sharma S, Raja A, et al. Nitric acid free cyclohexane to adipic acid production using nickel and vanadium incorporated AlPO-5 molecular sieve[J]. Molecular Catalysis, 2023, 540: 113051.
18	Zhang S Y, Zhuang Q, Zhang M, et al. Poly(ionic liquid) composites[J]. Chemical Society Reviews, 2020, 49(6): 1726-1755.
19	Yan X C, Zhang F F, Zhang H N, et al. Improving oxygen reduction performance by using protic poly(ionic liquid) as proton conductors[J]. ACS Applied Materials & Interfaces, 2019, 11(6): 6111-6117.
20	陈艺飞, 王佳铭, 阮雪华, 等. 聚离子液体二氧化碳分离膜材料的研究进展[J]. 化工学报, 2021, 72(12): 6062-6072.
	Chen Y F, Wang J M, Ruan X H, et al. Research progress in poly(ionic liquids) materials for CO₂ membrane separation[J]. CIESC Journal, 2021, 72(12): 6062-6072.
21	Chen S X, An R, Li Y W, et al. Strategy of regulating the electrophilic/nucleophilic ability by ionic ratio in poly(ionic liquid)s to control the coupling reaction of epoxide[J]. Catalysis Science & Technology, 2021, 11(19): 6498-6506.
22	吴岳峰, 曲永芳, 李大欢, 等. 聚离子液体载MoO₂/Ag催化分子氧氧化苯乙烯的研究[J]. 化工学报, 2020, 71(11): 4990-4998.
	Wu Y F, Qu Y F, Li D H, et al. Study on oxidation of styrene with molecular oxygen catalyzed by MoO₂/Ag on polyionic liquid[J]. CIESC Journal, 2020, 71(11): 4990-4998.
23	Gou H B, Ma X F, Su Q, et al. Hydrogen bond donor functionalized poly(ionic liquid)s for efficient synergistic conversion of CO₂ to cyclic carbonates[J]. Physical Chemistry Chemical Physics, 2021, 23(3): 2005-2014.
24	Chen S H, Li Y W, Wang Z W, et al. Poly(ionic liquid)s hollow spheres nanoreactor for enhanced cyclohexane catalytic oxidation[J]. Journal of Catalysis, 2022, 411, 135-148.
25	Santanakrishnan S, Hutchinson R A. Free-radical polymerization of N-vinylimidazole and quaternized vinylimidazole in aqueous solution[J]. Macromolecular Chemistry and Physics, 2013, 214(10): 1140-1146.
26	Bunaciu A A, Udriştioiu E G, Aboul-Enein H Y. X-Ray diffraction: instrumentation and applications[J]. Critical Reviews in Analytical Chemistry, 2015, 45(4): 289-299.
27	李慧慧, 姚开胜, 赵亚南, 等. 离子液体调控合成Pt-Pd双金属纳米材料及其催化氨硼烷水解释氢[J]. 应用化学, 2023, 40: 597-609.
	Li H H, Yao K S, Zhao Y N, et al. Ionic liquid controlled synthesis of Pt-Pd bimetallic nanomaterials and their catalytic hydrogen interpretation by ammonia borane water[J]. Applied Chemistry, 2023, 40: 597-609
28	An R, Chen S X, Zhang R R, et al. Synthesis of propylene glycol methyl ether catalyzed by imidazole polymer catalyst: performance evaluation, kinetics study, and process simulation[J]. Chemical Engineering Journal, 2021, 405, 126636.
29	Allen M H, Hemp S T, Smith A E, et al. Controlled radical polymerization of 4-vinylimidazole[J]. Macromolecules, 2012, 45(9): 3669-3676.
30	Tang C W, Wang C B, Chien S H. Characterization of cobalt oxides studied by FT-IR, Raman, TPR and TG-MS[J]. Thermochimica Acta, 2008, 473(1/2): 68-73.
31	Silva A R, Mourão T, Rocha J. Oxidation of cyclohexane by transition-metal complexes with biomimetic ligands[J]. Catalysis Today, 2013, 203: 81-86.
32	Uno K, Tsutsumi O. Crystal structure and phase transition behavior of dioctadecyldimethylammonium chloride monohydrate[J]. Molecular Crystals and Liquid Crystals, 2012, 563(1): 58-66.
33	Gorjian H, Fahim H, Ghaffari Khaligh N. Poly(N-vinylimidazole): a biocompatible and biodegradable functional polymer, metal-free, and highly recyclable heterogeneous catalyst for the mechanochemical synthesis of oximes[J]. Turkish Journal of Chemistry, 2021, 45(6): 2007-2012.
34	Alshammari A, Kalevaru V, Martin A. Bimetallic catalysts containing gold and palladium for environmentally important reactions[J]. Catalysts, 2016, 6(7): 97.
35	Dugal M, Sankar G, Raja R, et al. Designing a heterogeneous catalyst for the production of adipic acid by aerial oxidation of cyclohexane[J]. Angewandte Chemie International Edition, 2000, 39(13): 2310-2313.
36	Raja R, Ratnasamy P. Oxidation of cyclohexane over copper phthalocyanines encapsulated in zeolites[J]. Catalysis Letters, 1997, 48(1/2): 1-10.
37	Lv H Y, Ren W Z, Liu P F, et al. One-step aerobic oxidation of cyclohexane to adipic acid using an Anderson-type catalyst [(C₁₈H₃₇)₂N(CH₃)₂]₆Mo₇O₂₄ [J]. Applied Catalysis A: General, 2012, 441/442: 136-141.
38	Dandapat S, Rao J L, Likhar P R, et al. One-step production of adipic acid from cyclohexane over stable oxides (CeO₂ & ZrO₂) using O₂: enhanced oxidation activity in acidic medium[J]. Catalysis Communications, 2022, 172: 106555.
39	Zou G Q, Zhong W Z, Xu Q, et al. Oxidation of cyclohexane to adipic acid catalyzed by Mn-doped titanosilicate with hollow structure[J]. Catalysis Communications, 2015, 58: 46-52.
40	Shahzeydi A, Ghiaci M, Farrokhpour H, et al. Facile and green synthesis of copper nanoparticles loaded on the amorphous carbon nitride for the oxidation of cyclohexane[J]. Chemical Engineering Journal, 2019, 370: 1310-1321.
41	Yuan E X, Zhou M X, Jian P M, et al. Atomically dispersed Co/C₃N₄ for boosting aerobic cyclohexane oxidation[J].Applied Surface Science, 2023, 613: 155886.
42	Cremer T, Kolbeck C, Lovelock K R J, et al. Towards a molecular understanding of cation-anion interactions: probing the electronic structure of imidazolium ionic liquids by NMR spectroscopy, X-ray photoelectron spectroscopy and theoretical calculations[J]. Chemistry, 2010, 16(30): 9018-9033.
43	Yu H, Peng F, Tan J, et al. Selective catalysis of the aerobic oxidation of cyclohexane in the liquid phase by carbon nanotubes[J]. Angewandte Chemie International Edition, 2011, 50(17): 3978-3982.
44	Wang Z H, Wu Y C, Wu C C, et al. Electrophilic oxygen on defect-rich carbon nanotubes for selective oxidation of cyclohexane[J]. Catalysis Science & Technology, 2020, 10(2): 332-336.
45	Su K Y, Zhang C F, Wang Y H, et al. Unveiling the highly disordered NbO₆ units as electron-transfer sites in Nb₂O₅ photocatalysis with N-hydroxyphthalimide under visible light irradiation[J]. Chinese Journal of Catalysis, 2022, 43(7): 1894-1905.
46	Fu Y, Zhan W C, Guo Y L, et al. Highly efficient cobalt-doped carbon nitride polymers for solvent-free selective oxidation of cyclohexane[J]. Green Energy and Environment, 2017, 2: 142-150.

VIM/g	DMF/ml	AIBN/mg
2	8	0.9
2	8	1.9
2	8	4.8
2	8	7.6

VIM/g	DMF/ml	AIBN/mg
2	8	0.9
2	8	1.9
2	8	4.8
2	8	7.6

聚合物	M_n	PDI	Y/%
PVIM-M₁	12320	1.8	94.3
PVIM-M₂	15320	2.2	93.4
PVIM-M₃	16040	2.7	83.2
PVIM-M₄	19830	2.9	80.9

聚合物	M_n	PDI	Y/%
PVIM-M₁	12320	1.8	94.3
PVIM-M₂	15320	2.2	93.4
PVIM-M₃	16040	2.7	83.2
PVIM-M₄	19830	2.9	80.9

Entry	Catalysts	Con/%	Sel/%
Entry	Catalysts	Con/%	K	A	KA	AA	Others
1	blank	0	0	0	0	0	0
2^①	VIM	2.8	51.9	35.4	87.4	10.1	2.6
3^①	PVIM-M₁	7.6	27.7	18.7	46.4	37.7	15.9
4^①	PVIM- M₂	8.1	28.1	21.6	49.7	31.2	19.1
5^①	PVIM- M₃	9.1	36.8	28.9	65.7	27.2	7.2
6^①	PVIM- M₄	10.9	35.0	19.7	54.7	34.3	11.1
7 ^②	VIM	4.4	24.3	16.4	40.7	40.0	19.3
8^②	PVIM-M₁	11.3	23.1	16.6	39.7	47.7	15.9
9^②	PVIM- M₂	11.9	34.0	20.7	54.7	37.2	7.2
10^②	PVIM- M₃	13.5	22.7	13.7	36.4	34.3	11.1
11^②	PVIM- M₄	12.3	24.4	16.3	40.7	41.2	19.2