离子液体萃取剂萃取精馏分离丙酸甲酯+甲醇共沸物

doi:10.11949/0438-1157.20230517

摘要/Abstract

摘要：

以离子液体（ILs）[BMIM][NTF₂]和[HMIM][NTF₂]为萃取剂，萃取精馏分离丙酸甲酯+甲醇共沸物，通过分子模拟分析了ILs促进目标共沸物的分离机理；基于汽液平衡实验数据，获得新的NRTL热力学模型参数；选用常规的二组分双塔分离流程，实现了目标共沸体系的分离。作为对比，同时构建了以苯酚为萃取剂的萃取精馏和变压精馏流程。基于Aspen Plus软件平台，分析了上述各流程分离单元主要操作参数对分离过程性能的影响，考察并对比了各流程能耗、年总成本（TAC）和碳排放。结果表明：离子液体工艺可实现丙酸甲酯+甲醇共沸物的有效分离，产品纯度达到99.9%（质量分数），[HMIM][NTF₂]工艺与[BMIM][NTF₂]、苯酚及变压精馏工艺相比，TAC降低11.68%~43.68%、CO₂排放减少32.11%~68.46%。结果可为共沸物丙酸甲酯+甲醇分离新工艺设计及优化提供理论支撑和实际指导。

关键词: 离子液体, 萃取精馏, 共沸物, 变压精馏, TAC计算

Abstract:

Using ionic liquids [BMIM][NTF₂] and [HMIM][NTF₂] as entrainer, the separation of the azeotropic mixture for methyl propionate + methanol through extractive distillation was investigated. The mechanism for extractive distillation separation was analyzed by molecular structure optimization. Based on the experimental data from literature and the authors’ previous work, the new thermodynamic model parameters of NRTL were obtained. The conventional two-column process for the separation of binary mixture was employed for the investigated system in this work. As a comparison, the process of extractive distillation and pressure swing distillation using phenol as entrainer was constructed at the same time. Based on the Aspen Plus simulation software, the influence of the main operation parameters of the above-mentioned separation process on the separation performance was analyzed, and the energy consumption, annual total cost (TAC) and CO₂ emission of each process were calculated and compared. The results show that the ionic liquid process can separate the investigated azeotrope, and the purity of the product can reach to 99.9%(mass). The process with [HMIM][NTF₂] entrainer can decrease, 11.68%—43.68% TAC and 32.11%—68.46% CO₂ emission. The results of this work would provide theoretical basis and practical guide for the design and optimization of the separation process for azotropic methyl propionate + methanol mixture.

Key words: ionic liquids, extractive distillation, azeotrope, pressure swing distillation, TAC calculation

中图分类号:

TQ 28.8

王俐智, 杭钱程, 郑叶玲, 丁延, 陈家继, 叶青, 李进龙. 离子液体萃取剂萃取精馏分离丙酸甲酯+甲醇共沸物[J]. 化工学报, 2023, 74(9): 3731-3741.

Lizhi WANG, Qiancheng HANG, Yeling ZHENG, Yan DING, Jiaji CHEN, Qing YE, Jinlong LI. Separation of methyl propionate + methanol azeotrope using ionic liquid entrainers[J]. CIESC Journal, 2023, 74(9): 3731-3741.

图/表 15

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物质	分子结构优化	相互作用能/(kJ/mol)
[BMIM]⁺ +丙酸甲酯		-83.53
[BMIM]⁺ +甲醇		-11.72
[HMIM]⁺ +丙酸甲酯		-104.59
[HMIM]⁺ +甲醇		-48.95
[NTF₂]^-+丙酸甲酯		-58.42
[NTF₂]^-+甲醇		-17.97
苯酚+丙酸甲酯		-12.80
苯酚+甲醇		-4.47
甲醇+丙酸甲酯		-4.36

物质	分子结构优化	相互作用能/(kJ/mol)
[BMIM]⁺ +丙酸甲酯		-83.53
[BMIM]⁺ +甲醇		-11.72
[HMIM]⁺ +丙酸甲酯		-104.59
[HMIM]⁺ +甲醇		-48.95
[NTF₂]^-+丙酸甲酯		-58.42
[NTF₂]^-+甲醇		-17.97
苯酚+丙酸甲酯		-12.80
苯酚+甲醇		-4.47
甲醇+丙酸甲酯		-4.36

组分 i	组分 j	Δg_ij	Δg_ji	ΔT/K	Δy₁
MEOH	MP	291.225	102.277	0.08	0.0017
MEOH	[BMIM][NTF₂]	-88.141	2744.110	0.3035	0.0062
MP	[BMIM][NTF₂]	792.627	-319.243	0.3035	0.0062
MEOH	[HMIM][NTF_2]	353.792	-433.952	0.4517	0.0071
MP	[HMIM][NTF₂]	-636.198	347.593	0.4517	0.0071
MEOH	BF^①	-159.758	-68.302	2.12	0.052
MP	BF^①	-123.557	-317.395	2.12	0.052

组分 i	组分 j	Δg_ij	Δg_ji	ΔT/K	Δy₁
MEOH	MP	291.225	102.277	0.08	0.0017
MEOH	[BMIM][NTF₂]	-88.141	2744.110	0.3035	0.0062
MP	[BMIM][NTF₂]	792.627	-319.243	0.3035	0.0062
MEOH	[HMIM][NTF_2]	353.792	-433.952	0.4517	0.0071
MP	[HMIM][NTF₂]	-636.198	347.593	0.4517	0.0071
MEOH	BF^①	-159.758	-68.302	2.12	0.052
MP	BF^①	-123.557	-317.395	2.12	0.052

参数	萃取精馏			变压精馏
参数	[BMIM][NTF₂]	[HMIM][NTF₂]	苯酚	常规流程	热集成流程
萃取塔(高压塔)
理论级	34	34	34	34	34
摩尔溶剂比	1.60	0.80	2.10	—	—
进料塔板数	26	20	26	25	25
质量回流比	0.25	0.22	1.20	1.65	1.67
压力/bar	1	1	1	9
萃取剂进料位置	5	2	4	—	—
萃取剂流量/(kg/h)	67099.60	35793.90	19763.40	—	—
冷凝负荷/kW	-882.38	-885.06	-1547.80	-3267.86	-2018.78
加热负荷/kW	3455.03	2484.78	3524.34	4083.18	4067.28
闪蒸罐(溶剂回收塔/低压塔)
温度/℃	150	150	—	—
压力	30 Pa	30 Pa	0.4 bar	1 bar
加热负荷/kW	514.95	210.38	1145.39	4463.04	3534.31
冷凝负荷/kW	—	—	-1501.61	-4875.94	-5415.36
理论级	—	—	20	34	34
进料位置	—	—	5	15	13
质量回流比	—	—	4.48	5.36	6.06
换热器
热负荷/kW	-2612.68	-1334.53	-1503.00	-101.80	-101.84
甲醇产品流股
温度/℃	64.20	64.20	64.20	64.20	64.20
甲醇纯度	0.999	0.999	0.999	0.999	0.999
产品流量/(kg/h)	2300.65	2298.75	2300.84	2298.41	2298.41
丙酸甲酯产品流股
温度/℃	150.00	150.00	53.57	166.02	25
丙酸甲酯纯度	0.999	0.999	0.999	0.999	0.999
产品流量/(kg/h)	2488.11	2490.01	2490.19	2490.36	2490.35
溶剂回收流股
温度/℃	150.00	150.00	151.05	—
甲醇质量分数	0	0	0	—
丙酸甲酯含量/ppm	0.3	43	25	—
溶剂质量分数	0.999997	0.999957	0.999975	—
工艺总加热负荷/kW	3970.0	2695.2	4669.7	8546.2		7601.6
工艺总冷凝负荷/kW	-3495.1	-2219.6	-4552.4	-8245.6		-7536.0