Separation of methanol-acetonitrile azeotrope by ionic liquid extractive distillation

doi:10.16085/j.issn.1000-6613.2024-0197

Abstract

Abstract:

In order to effectively separate the methanol-acetonitrile azeotrope system, N-octylpyridinium hexafluorophosphate imide salt ([Opy][PF₆]) was selected as entraining agent, and the isobaric vapor-liquid equilibrium of methanol-acetonitrile-[Opy][PF₆] ternary system was determined. The isobaric vapor-liquid equilibrium (VLE) data of ternary system were obtained, and the influence of ionic liquid on the vapor-liquid equilibrium of methanol-acetonitrile was investigated. The experimental data were correlated with the non-random two-liquid (NRTL) models and the binary interaction parameters were obtained. The separation mechanism was explained by intermolecular interaction energy and excess enthalpy analysis. And the results showed that the addition of [Opy][PF₆] could increase the relative volatility of methanol relative to acetonitrile and make the salting-out effect more pronounced. The NRTL model was in good agreement with the experimental results, and these data were correlated by NRTL model in Aspen Plus software. It was found that when the molar fraction of [Opy][PF₆] was 0.0345, the system was no longer azeotropic. Aspen Plus software was used to simulate the extractive distillation process and optimize the process parameters, and the best operating conditions of the extractive distillation process were obtained. The simulation results could be used as guidance for further extractive distillation experiment and process design.

Key words: methanol, acetonitrile, extractive distillation, ionic liquids, Aspen Plus

摘要：

为实现甲醇-乙腈共沸体系的高效分离，本文选取N-辛基吡啶六氟磷酸盐（[Opy][PF₆]）为萃取剂，在101.325kPa下对甲醇-乙腈-[Opy][PF₆]三元物系进行等压气液相平衡的测定，获得了三元体系等压气液相平衡（VLE）数据，探究离子液体对甲醇-乙腈气液相平衡的影响，将实验数据与非随机双液（NRTL）模型相关联，得到二元相互作用参数。通过过量焓、高斯分析解释分离机理，结果表明[Opy][PF₆]的加入可提高甲醇相对于乙腈的相对挥发度，[Opy][PF₆]的含量增加使盐析效果更明显，NRTL模型与实验结果具有良好的一致性，通过Aspen Plus软件中的NRTL模型关联这些数据，发现当[Opy][PF₆]的物质的量分数为0.0345时，体系不再共沸，使用Aspen Plus软件模拟萃取精馏流程并优化工艺参数，得到萃取精馏过程的最佳操作条件。模拟结果可作为下一步萃取精馏实验和流程设计的指导。

关键词: 甲醇, 乙腈, 萃取精馏, 离子液体, Aspen Plus

CLC Number:

TQ028.3

HAN Yingna, LI Li, ZHANG Linzi, AN Jinze, LI Wenxiu, ZHANG Tao. Separation of methanol-acetonitrile azeotrope by ionic liquid extractive distillation[J]. Chemical Industry and Engineering Progress, 2025, 44(2): 660-668.

韩英娜, 李丽, 张林子, 安金泽, 李文秀, 张弢. 离子液体萃取精馏分离甲醇-乙腈共沸物[J]. 化工进展, 2025, 44(2): 660-668.

Figures/Tables 16

References 18

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T/K	x₁	y₁	γ₁	γ₂
338.00	0.972	0.964	0.980	2.229
337.90	0.946	0.934	0.979	2.136
337.60	0.910	0.898	0.991	1.994
337.30	0.860	0.855	1.010	1.846
337.20	0.761	0.784	1.050	1.620
337.50	0.695	0.744	1.079	1.483
338.00	0.588	0.687	1.154	1.322
339.70	0.413	0.592	1.325	1.140
341.10	0.312	0.524	1.471	1.082
342.90	0.230	0.456	1.621	1.039
345.40	0.146	0.355	1.807	1.022
348.10	0.088	0.257	1.954	1.009
351.00	0.045	0.156	2.067	0.998

T/K	x₁	y₁	γ₁	γ₂
338.00	0.972	0.964	0.980	2.229
337.90	0.946	0.934	0.979	2.136
337.60	0.910	0.898	0.991	1.994
337.30	0.860	0.855	1.010	1.846
337.20	0.761	0.784	1.050	1.620
337.50	0.695	0.744	1.079	1.483
338.00	0.588	0.687	1.154	1.322
339.70	0.413	0.592	1.325	1.140
341.10	0.312	0.524	1.471	1.082
342.90	0.230	0.456	1.621	1.039
345.40	0.146	0.355	1.807	1.022
348.10	0.088	0.257	1.954	1.009
351.00	0.045	0.156	2.067	0.998

T/K	x₃	x₁	x₁ʹ	y₁	α₁₂	γ₁	γ₂
338.35	0.200	0.759	0.948	0.981	2.392	1.264	0.805
338.35	0.200	0.737	0.921	0.970	2.426	1.293	0.809
338.15	0.200	0.710	0.887	0.958	2.468	1.330	0.809
338.05	0.200	0.668	0.835	0.937	2.533	1.382	0.830
338.15	0.200	0.626	0.783	0.916	2.599	1.441	0.841
338.45	0.200	0.555	0.693	0.876	2.713	1.544	0.875
338.75	0.200	0.477	0.596	0.826	2.836	1.666	0.919
339.75	0.200	0.393	0.492	0.763	3.011	1.804	0.961
340.95	0.200	0.311	0.388	0.685	3.156	1.951	1.014
342.85	0.200	0.213	0.266	0.562	3.366	2.146	1.092
345.85	0.200	0.135	0.168	0.423	3.536	2.291	1.152
349.65	0.200	0.078	0.098	0.287	3.661	2.343	1.167
352.75	0.200	0.036	0.045	0.152	3.761	2.377	1.187
353.65	0.200	0.020	0.024	0.085	3.809	2.420	1.223
338.35	0.050	0.873	0.919	0.936	1.283	1.044	1.436
338.35	0.050	0.842	0.886	0.912	1.326	1.055	1.404
338.35	0.049	0.801	0.842	0.882	1.399	1.073	1.353
338.35	0.048	0.748	0.786	0.845	1.489	1.101	1.305
338.45	0.050	0.681	0.717	0.808	1.653	1.150	1.228
338.85	0.050	0.599	0.631	0.759	1.847	1.211	1.160
339.45	0.051	0.511	0.538	0.706	2.059	1.290	1.111
340.55	0.050	0.420	0.442	0.646	2.301	1.375	1.065
342.15	0.051	0.318	0.335	0.571	2.645	1.511	1.026
344.45	0.049	0.230	0.242	0.488	2.986	1.635	0.993
347.55	0.050	0.147	0.155	0.378	3.322	1.766	0.977
350.85	0.050	0.084	0.089	0.257	3.556	1.856	0.972
353.95	0.049	0.041	0.043	0.147	3.809	1.944	0.963
355.55	0.050	0.023	0.024	0.089	3.940	1.992	0.960
337.55	0.021	0.911	0.931	0.930	0.996	1.026	1.812
337.35	0.021	0.882	0.901	0.905	1.056	1.040	1.731
337.25	0.020	0.844	0.862	0.875	1.129	1.055	1.642
337.25	0.023	0.796	0.815	0.843	1.223	1.077	1.547
337.35	0.020	0.740	0.755	0.806	1.345	1.104	1.442
337.65	0.023	0.674	0.690	0.766	1.475	1.139	1.358
338.15	0.022	0.579	0.593	0.714	1.713	1.210	1.245
339.05	0.020	0.476	0.485	0.649	1.963	1.294	1.167
340.15	0.022	0.378	0.386	0.588	2.269	1.414	1.109
342.15	0.021	0.245	0.251	0.481	2.769	1.649	1.069
344.65	0.022	0.174	0.178	0.403	3.132	1.777	1.030
348.35	0.021	0.100	0.102	0.279	3.423	1.869	1.007
351.45	0.022	0.055	0.057	0.183	3.741	1.971	0.984
353.15	0.021	0.030	0.031	0.108	3.842	2.022	0.990

T/K	x₃	x₁	x₁ʹ	y₁	α₁₂	γ₁	γ₂
338.35	0.200	0.759	0.948	0.981	2.392	1.264	0.805
338.35	0.200	0.737	0.921	0.970	2.426	1.293	0.809
338.15	0.200	0.710	0.887	0.958	2.468	1.330	0.809
338.05	0.200	0.668	0.835	0.937	2.533	1.382	0.830
338.15	0.200	0.626	0.783	0.916	2.599	1.441	0.841
338.45	0.200	0.555	0.693	0.876	2.713	1.544	0.875
338.75	0.200	0.477	0.596	0.826	2.836	1.666	0.919
339.75	0.200	0.393	0.492	0.763	3.011	1.804	0.961
340.95	0.200	0.311	0.388	0.685	3.156	1.951	1.014
342.85	0.200	0.213	0.266	0.562	3.366	2.146	1.092
345.85	0.200	0.135	0.168	0.423	3.536	2.291	1.152
349.65	0.200	0.078	0.098	0.287	3.661	2.343	1.167
352.75	0.200	0.036	0.045	0.152	3.761	2.377	1.187
353.65	0.200	0.020	0.024	0.085	3.809	2.420	1.223
338.35	0.050	0.873	0.919	0.936	1.283	1.044	1.436
338.35	0.050	0.842	0.886	0.912	1.326	1.055	1.404
338.35	0.049	0.801	0.842	0.882	1.399	1.073	1.353
338.35	0.048	0.748	0.786	0.845	1.489	1.101	1.305
338.45	0.050	0.681	0.717	0.808	1.653	1.150	1.228
338.85	0.050	0.599	0.631	0.759	1.847	1.211	1.160
339.45	0.051	0.511	0.538	0.706	2.059	1.290	1.111
340.55	0.050	0.420	0.442	0.646	2.301	1.375	1.065
342.15	0.051	0.318	0.335	0.571	2.645	1.511	1.026
344.45	0.049	0.230	0.242	0.488	2.986	1.635	0.993
347.55	0.050	0.147	0.155	0.378	3.322	1.766	0.977
350.85	0.050	0.084	0.089	0.257	3.556	1.856	0.972
353.95	0.049	0.041	0.043	0.147	3.809	1.944	0.963
355.55	0.050	0.023	0.024	0.089	3.940	1.992	0.960
337.55	0.021	0.911	0.931	0.930	0.996	1.026	1.812
337.35	0.021	0.882	0.901	0.905	1.056	1.040	1.731
337.25	0.020	0.844	0.862	0.875	1.129	1.055	1.642
337.25	0.023	0.796	0.815	0.843	1.223	1.077	1.547
337.35	0.020	0.740	0.755	0.806	1.345	1.104	1.442
337.65	0.023	0.674	0.690	0.766	1.475	1.139	1.358
338.15	0.022	0.579	0.593	0.714	1.713	1.210	1.245
339.05	0.020	0.476	0.485	0.649	1.963	1.294	1.167
340.15	0.022	0.378	0.386	0.588	2.269	1.414	1.109
342.15	0.021	0.245	0.251	0.481	2.769	1.649	1.069
344.65	0.022	0.174	0.178	0.403	3.132	1.777	1.030
348.35	0.021	0.100	0.102	0.279	3.423	1.869	1.007
351.45	0.022	0.055	0.057	0.183	3.741	1.971	0.984
353.15	0.021	0.030	0.031	0.108	3.842	2.022	0.990

组分i	组分j	α_ij	(Δg_ij /R) /J·mol^-1	(Δg_ji /R) /J·mol^-1	ARD/％
甲醇	乙腈	0.4950	171.70	166.84	0.98
甲醇	[Opy][PF₆]	0.1000	-240.33	-21.77
乙腈	[Opy][PF₆]	0.1926	856.77	-1233.94