基于离子液体的N,N-二甲基乙酰胺回收工艺

doi:10.16085/j.issn.1000-6613.2019-0108

摘要/Abstract

摘要：

针对N,N-二甲基乙酰胺（DMAC）水溶液回收，研究和开发了以离子液体（IL）为萃取剂的萃取-精馏技术。通过COSMO-RS对384种IL组合在无限稀释条件下对DMAC的溶解能力C进行量化预测，优化获得了潜在的1-丁基-3-甲基咪唑三(五氟乙基)三氟磷酸[BMIm]FEP萃取剂。计算了[BMIm]FEP-DMAC-H₂O三元体系的液液相平衡数据，并通过NRTL方程拟合获得了二元交互参数，设计了萃取流程。研究结果表明：在DMAC初始含量为10%、[BMIm]FEP/DMAC水溶液质量比为2∶1、萃取塔理论板为20块时，可以回收水溶液中99.5%的DMAC。为进一步评价[BMIm]FEP作为萃取剂的可行性，对工艺进行了能耗计算，同时对比了纯精馏工艺和以氯仿为萃取剂的萃取-精馏工艺，结果表明，以[BMIm]FEP为萃取剂的萃取-精馏工艺更为节能，分别较前两者工艺节能90%和50%以上，在处理低浓度DMAC水溶液时，具有明显的优势。

关键词: N,N-二甲基乙酰胺, 离子液体, 萃取, 精馏, COSMO-RS

Abstract:

Focused on the recovery of dimethylacetamide (DMAC) from water, extraction-distillation method using ionic liquids as extractant was investigated and developed. First, solvent capacitys of DMAC with 384 types of ionic liquids at infinite dilution were calculated by COSMO-RS. After optimizing the structure of cations, [BMIm]FEP was finally determined as potential extractant. Then, the liquid-liquid phase equilibrium data of [BMIm]FEP-DMAC-H₂O were obtained, and binary interaction parameters were subsequently correlated by NRTL. Based on the binary interaction parameters, extraction process was designed by Aspen Plus. The designed result illustrated that when the initial concentration of DMAC was 10%, the mass ratio of [BMIm]FEP/water solution with DMAC was 2, and the number of theoretical plates reached 20, the recovery ratio of DMAC from water will be more than 99.5%. Finally, in order to evaluate the feasibility for using [BMIm]FEP as extractant, the energy consumption of three types of method were calculated. The result showed that compared with distillation method and the extraction-distillation method with chloroform, the energy cost of extraction-distillation method with [BMIm]FEP as extractant reduced 90% and 50%, respectively. It meant that the method was the most energy saving and the ionic liquid [BMIm]FEP showed its advantage for using as extractant to recover DMAC with low concentration from water.

Key words: dimethylacetamide, ionic liquid, extraction, distillation, COSMO-RS

中图分类号:

TQ028.4

秦磊,胡汉君,魏朋正,陈亮,漆志文. 基于离子液体的N,N-二甲基乙酰胺回收工艺[J]. 化工进展, 2019, 38(9): 3962-3968.

Lei QIN,Hanjun HU,Pengzheng WEI,Liang CHEN,Zhiwen QI. Dimethylacetamide recovery process based on ionic liquids[J]. Chemical Industry and Engineering Progress, 2019, 38(9): 3962-3968.

图/表 10

表1 IL[BMIm]FEP的临界性质

M	T _b /K	T _c /K	P _c/Pa	V _c /cm³·mol^-1	ω	Z _c
584.224	663.72	810.34	9.42×10⁵	1270.82	0.901	0.1752

图1 [BMIm]FEP萃取-精馏回收DMAC工艺流程

图2 精馏回收DMAC工艺流程

图3 氯仿萃取-精馏回收DMAC工艺流程

图4 无限稀释条件下各IL组合对DMAC的溶解能力预测

表2 不同链长IL对DMAC萃取能力和在水中溶解度的对数值

项目	[EMIm]FEP	[BMIm]FEP	[HMIm]FEP	[OMIm]FEP	[DMIm]FEP
C_i	19.85	19.66	19.56	19.26	18.01
$S i j ∞$	21.77	21.57	21.46	21.13	19.76
lgS	-3.76	-4.24	-4.69	-5.17	-5.67

表2 不同链长IL对DMAC萃取能力和在水中溶解度的对数值

项目	[EMIm]FEP	[BMIm]FEP	[HMIm]FEP	[OMIm]FEP	[DMIm]FEP
C_i	19.85	19.66	19.56	19.26	18.01
$S i j ∞$	21.77	21.57	21.46	21.13	19.76
lgS	-3.76	-4.24	-4.69	-5.17	-5.67

图5 [BMIm]FEP-DMAC-H2O三元液液相平衡COSMO-RS计算值及NRTL拟合值

表3 NRTL关联的[BMIm]FEP-DMAC-H2O三元体系二元交互参数

i组分	j组分	a_ij	a_ji	b_ij /K	B_ji /K	C_ij
DMAC	H₂O	26.5776	-6.4367	2459.6	-828.8	0.6972
DMAC	[BMIm]FEP	33.4097	0.5916	-4835.3	-3660.3	0.85
H₂O	[BMIm]FEP	21.1721	10.2584	1392.2	-2058.1	0.1726

图6 不同质量比下萃取塔理论板数与DMAC回收率之间的关系

表4 DMAC回收工艺的能耗对比

回收方法	精馏	萃取-精馏
萃取塔
萃取剂	—	氯仿	[BMIm]FEP
萃取剂用量/kg·h^-1	0	1400	2000
理论板塔板数	0	20	20
闪蒸罐
压力×10^-5/Pa	—	—	0.1
温度/K	—	—	363.7
闪蒸加热器热负荷/kW	—	—	78.65
塔顶换热器热负荷/kW	—	—	-15.70
塔釜换热器热负荷/kW	—	—	-56.58
精馏塔
回收比	0.5	0.5	0.8
理论板塔板数	20	8	20
塔顶冷凝器热负荷/kW	-847.37	-144.22	-6.09
塔釜再沸器热负荷/kW	946.34	187.81	8.79
塔顶换热器热负荷/kW	-79.61	-14.22	-0.48
塔釜换热器热负荷/kW	-8.14	-4.17	-1.98
总能耗
总热能/kW	946.34	187.81	87.44
总冷能/kW	-935.12	-162.61	-80.83
节能
总热能/%	0	80.2	90.8
总冷能/%	0	82.6	91.4

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