Liquid-liquid equilibria for quaternary systems polyoxymethylene dimethyl ethers + water + cyclohexane + sodium chloride

doi:10.11949/0438-1157.20190758

Abstract

Abstract:

Polyoxymethylene dimethyl ethers (DMM_n) are low molecular acetal polymer, which were considered as new environmentally friendly diesel additive. The liquid-liquid equilibria (LLE) data of the systems (DMM_1—4 + water + cyclohexane + NaCl) at T = 293.15, 308.15 K and pressure p = 101.325 kPa were measured. According to the verification with the Eisen-Joffe equation, the experimental data has good consistency with R² being approximately unity. Under the salting effect of NaCl, the separation effect of oil-water is improved obviously and the distribution coefficients of DMM_1—4 are greater than 1. When the content of NaCl is 10%(mass), the water in the organic phase is negligible. All the experimental LLE data obtained were correlated with the NRTL and the CHEN-NRTL activity coefficient models. The results show that the CHEN-NRTL model is superior to NRTL model for these systems at studied temperature. The experimental data and model parameters obtained from the fitting will provide an effective reference for the process simulation of DMM_n product extraction and distillation.

Key words: polyoxymethylene dimethyl ethers, liquid-liquid equilibria, cyclohexane, CHEN-NRTL

摘要：

聚甲氧基二甲醚(DMM_n)是一种低分子缩醛类聚合物，被认为是新型环保柴油添加剂。研究了常压下，293.15 K和308.15 K时DMM_1~4+水+环己烷+氯化钠体系的液液相平衡。经Eisen-Joffe方程关联检验，各体系的液液平衡数据具有良好的一致性。在氯化钠盐析作用下，体系油水分离效果得到明显的改善，DMM_1~4的分配系数均大于1；当NaCl的含量为10%(质量)时，有机相中的水可忽略不计。对平衡数据采用NRTL和CHEN-NRTL热力学模型关联拟合，结果表明CHEN-NRTL模型更适用于描述此体系在研究温度下的液液平衡关系。实验数据以及拟合得到的模型参数将为DMM_n的产物萃取及精馏的过程模拟提供有效参考。

关键词: 聚甲氧基二甲醚, 液液平衡, 环己烷, CHEN-NRTL

CLC Number:

TQ 028.4

Chaoxing KOU, Yang LIU, Aiwu ZENG. Liquid-liquid equilibria for quaternary systems polyoxymethylene dimethyl ethers + water + cyclohexane + sodium chloride[J]. CIESC Journal, 2020, 71(2): 507-515.

寇超兴, 刘洋, 曾爱武. 聚甲氧基二甲醚+水+环己烷+氯化钠四元体系的液液平衡研究[J]. 化工学报, 2020, 71(2): 507-515.

Figures/Tables 12

Fig.1 Schematic diagram of liquid-liquid equilibrium flask

Table 1 Experimental LLE data and distribution coefficients (D1) for system (DMM1 + water + cyclohexane + NaCl)

T/K	DMM₁(1)+水(2)+环己烷(3)+氯化钠(4)								分配系数(D₁)
	有机相				水相
	$W 1 Ⅰ$	$W 2 Ⅰ$	$W 3 Ⅰ$	$W 4 Ⅰ$	$W 1 Ⅱ$	$W 2 Ⅱ$	$W 3 Ⅱ$	$W 4 Ⅱ$
293.15	0.7279	0.0052	0.2669	0.0000	0.2842	0.7158	0.0000	0.0000	2.56
	0.5776	0.0026	0.4198	0.0000	0.1623	0.7814	0.0000	0.0564	3.56
	0.5135	0.0017	0.4847	0.0000	0.1180	0.7802	0.0000	0.1018	4.35
	0.3659	0.0009	0.6332	0.0000	0.0768	0.7881	0.0000	0.1350	4.76
	0.2188	0.0002	0.7811	0.0000	0.0478	0.7943	0.0000	0.1579	4.58
	0.1160	0.0000	0.8839	0.0000	0.0239	0.7899	0.0000	0.1862	4.85
308.15	0.7082	0.0055	0.2862	0.0000	0.2651	0.7349	0.0000	0.0000	2.67
	0.5890	0.0031	0.4079	0.0000	0.1497	0.7930	0.0000	0.0573	3.93
	0.5220	0.0018	0.4762	0.0000	0.1093	0.7872	0.0000	0.1034	4.77
	0.3491	0.0007	0.6502	0.0000	0.0634	0.8023	0.0000	0.1342	5.50
	0.2143	0.0002	0.7856	0.0000	0.0402	0.7992	0.0000	0.1606	5.33
	0.1123	0.0001	0.8876	0.0000	0.0204	0.7932	0.0000	0.1864	5.51

Table 1 Experimental LLE data and distribution coefficients (D1) for system (DMM1 + water + cyclohexane + NaCl)

T/K	DMM₁(1)+水(2)+环己烷(3)+氯化钠(4)								分配系数(D₁)
	有机相				水相
	$W 1 Ⅰ$	$W 2 Ⅰ$	$W 3 Ⅰ$	$W 4 Ⅰ$	$W 1 Ⅱ$	$W 2 Ⅱ$	$W 3 Ⅱ$	$W 4 Ⅱ$
293.15	0.7279	0.0052	0.2669	0.0000	0.2842	0.7158	0.0000	0.0000	2.56
	0.5776	0.0026	0.4198	0.0000	0.1623	0.7814	0.0000	0.0564	3.56
	0.5135	0.0017	0.4847	0.0000	0.1180	0.7802	0.0000	0.1018	4.35
	0.3659	0.0009	0.6332	0.0000	0.0768	0.7881	0.0000	0.1350	4.76
	0.2188	0.0002	0.7811	0.0000	0.0478	0.7943	0.0000	0.1579	4.58
	0.1160	0.0000	0.8839	0.0000	0.0239	0.7899	0.0000	0.1862	4.85
308.15	0.7082	0.0055	0.2862	0.0000	0.2651	0.7349	0.0000	0.0000	2.67
	0.5890	0.0031	0.4079	0.0000	0.1497	0.7930	0.0000	0.0573	3.93
	0.5220	0.0018	0.4762	0.0000	0.1093	0.7872	0.0000	0.1034	4.77
	0.3491	0.0007	0.6502	0.0000	0.0634	0.8023	0.0000	0.1342	5.50
	0.2143	0.0002	0.7856	0.0000	0.0402	0.7992	0.0000	0.1606	5.33
	0.1123	0.0001	0.8876	0.0000	0.0204	0.7932	0.0000	0.1864	5.51

Table 2 Experimental LLE data and distribution coefficients (D2) for system (DMM2 + water + cyclohexane + NaCl)

T/K	DMM₂(1)+水(2)+环己烷(3)+氯化钠(4)								分配系数(D₂)
	有机相				水相
	$W 1 Ⅰ$	$W 2 Ⅰ$	$W 3 Ⅰ$	$W 4 Ⅰ$	$W 1 Ⅱ$	$W 2 Ⅱ$	$W 3 Ⅱ$	$W 4 Ⅱ$
293.15	0.7083	0.0063	0.2854	0.0000	0.2259	0.7741	0.0000	0.0000	3.13
	0.5441	0.0033	0.4526	0.0000	0.1229	0.8215	0.0000	0.0556	4.43
	0.4681	0.0020	0.5300	0.0000	0.0816	0.8187	0.0000	0.0998	5.74
	0.3239	0.0009	0.6753	0.0000	0.0518	0.8160	0.0000	0.1323	6.26
	0.1595	0.0003	0.8402	0.0000	0.0276	0.8193	0.0000	0.1531	5.78
	0.0867	0.0001	0.9133	0.0000	0.0153	0.8008	0.0000	0.1839	5.65
308.15	0.7121	0.0064	0.2814	0.0000	0.2190	0.7810	0.0000	0.0000	3.25
	0.5625	0.0032	0.4343	0.0000	0.1266	0.8169	0.0000	0.0565	4.44
	0.4662	0.0020	0.5317	0.0000	0.0738	0.8259	0.0000	0.1002	6.31
	0.3524	0.0012	0.6464	0.0000	0.0459	0.8194	0.0000	0.1347	7.69
	0.1569	0.0004	0.8427	0.0000	0.0206	0.8212	0.0000	0.1582	7.62
	0.0877	0.0002	0.9121	0.0000	0.0109	0.8034	0.0000	0.1856	8.02

Table 2 Experimental LLE data and distribution coefficients (D2) for system (DMM2 + water + cyclohexane + NaCl)

T/K	DMM₂(1)+水(2)+环己烷(3)+氯化钠(4)								分配系数(D₂)
	有机相				水相
	$W 1 Ⅰ$	$W 2 Ⅰ$	$W 3 Ⅰ$	$W 4 Ⅰ$	$W 1 Ⅱ$	$W 2 Ⅱ$	$W 3 Ⅱ$	$W 4 Ⅱ$
293.15	0.7083	0.0063	0.2854	0.0000	0.2259	0.7741	0.0000	0.0000	3.13
	0.5441	0.0033	0.4526	0.0000	0.1229	0.8215	0.0000	0.0556	4.43
	0.4681	0.0020	0.5300	0.0000	0.0816	0.8187	0.0000	0.0998	5.74
	0.3239	0.0009	0.6753	0.0000	0.0518	0.8160	0.0000	0.1323	6.26
	0.1595	0.0003	0.8402	0.0000	0.0276	0.8193	0.0000	0.1531	5.78
	0.0867	0.0001	0.9133	0.0000	0.0153	0.8008	0.0000	0.1839	5.65
308.15	0.7121	0.0064	0.2814	0.0000	0.2190	0.7810	0.0000	0.0000	3.25
	0.5625	0.0032	0.4343	0.0000	0.1266	0.8169	0.0000	0.0565	4.44
	0.4662	0.0020	0.5317	0.0000	0.0738	0.8259	0.0000	0.1002	6.31
	0.3524	0.0012	0.6464	0.0000	0.0459	0.8194	0.0000	0.1347	7.69
	0.1569	0.0004	0.8427	0.0000	0.0206	0.8212	0.0000	0.1582	7.62
	0.0877	0.0002	0.9121	0.0000	0.0109	0.8034	0.0000	0.1856	8.02

Table 3 Experimental LLE data and distribution coefficients (D3) for system (DMM3 + water + cyclohexane + NaCl)

T/K	DMM₃(1)+水(2)+环己烷(3)+氯化钠(4)								分配系数(D₃)
	有机相				水相
	$W 1 Ⅰ$	$W 2 Ⅰ$	$W 3 Ⅰ$	$W 4 Ⅰ$	$W 1 Ⅱ$	$W 2 Ⅱ$	$W 3 Ⅱ$	$W 4 Ⅱ$
293.15	0.5321	0.0047	0.4632	0.0000	0.1267	0.8733	0.0000	0.0000	4.20
	0.3865	0.0028	0.6106	0.0000	0.0671	0.8760	0.0000	0.0568	5.76
	0.3074	0.0016	0.6910	0.0000	0.0463	0.8512	0.0000	0.1025	6.64
	0.1961	0.0008	0.8031	0.0000	0.0336	0.8319	0.0000	0.1345	5.83
	0.1115	0.0002	0.8883	0.0000	0.0167	0.8279	0.0000	0.1554	6.67
	0.0544	0.0001	0.9455	0.0000	0.0088	0.8057	0.0000	0.1855	6.16
308.15	0.5312	0.0056	0.4632	0.0000	0.1393	0.8607	0.0000	0.0000	3.81
	0.4314	0.0031	0.5656	0.0000	0.0673	0.8755	0.0000	0.0572	6.41
	0.3383	0.0021	0.6596	0.0000	0.0412	0.8553	0.0000	0.1035	8.20
	0.2027	0.0006	0.7966	0.0000	0.0273	0.8360	0.0000	0.1367	7.41
	0.1121	0.0002	0.8878	0.0000	0.0123	0.8287	0.0000	0.1591	9.13
	0.0517	0.0001	0.9482	0.0000	0.0064	0.8034	0.0000	0.1901	8.03

Table 3 Experimental LLE data and distribution coefficients (D3) for system (DMM3 + water + cyclohexane + NaCl)

T/K	DMM₃(1)+水(2)+环己烷(3)+氯化钠(4)								分配系数(D₃)
	有机相				水相
	$W 1 Ⅰ$	$W 2 Ⅰ$	$W 3 Ⅰ$	$W 4 Ⅰ$	$W 1 Ⅱ$	$W 2 Ⅱ$	$W 3 Ⅱ$	$W 4 Ⅱ$
293.15	0.5321	0.0047	0.4632	0.0000	0.1267	0.8733	0.0000	0.0000	4.20
	0.3865	0.0028	0.6106	0.0000	0.0671	0.8760	0.0000	0.0568	5.76
	0.3074	0.0016	0.6910	0.0000	0.0463	0.8512	0.0000	0.1025	6.64
	0.1961	0.0008	0.8031	0.0000	0.0336	0.8319	0.0000	0.1345	5.83
	0.1115	0.0002	0.8883	0.0000	0.0167	0.8279	0.0000	0.1554	6.67
	0.0544	0.0001	0.9455	0.0000	0.0088	0.8057	0.0000	0.1855	6.16
308.15	0.5312	0.0056	0.4632	0.0000	0.1393	0.8607	0.0000	0.0000	3.81
	0.4314	0.0031	0.5656	0.0000	0.0673	0.8755	0.0000	0.0572	6.41
	0.3383	0.0021	0.6596	0.0000	0.0412	0.8553	0.0000	0.1035	8.20
	0.2027	0.0006	0.7966	0.0000	0.0273	0.8360	0.0000	0.1367	7.41
	0.1121	0.0002	0.8878	0.0000	0.0123	0.8287	0.0000	0.1591	9.13
	0.0517	0.0001	0.9482	0.0000	0.0064	0.8034	0.0000	0.1901	8.03

Table 4 Experimental LLE data and distribution coefficients (D4) for system (DMM4 + water + cyclohexane + NaCl)

T/K	DMM₄(1)+水(2)+环己烷(3)+氯化钠(4)								分配系数(D₄)
	有机相				水相
	$W 1 Ⅰ$	$W 2 Ⅰ$	$W 3 Ⅰ$	$W 4 Ⅰ$	$W 1 Ⅱ$	$W 2 Ⅱ$	$W 3 Ⅱ$	$W 4 Ⅱ$
293.15	0.5468	0.0051	0.4481	0.0000	0.1334	0.8666	0.0000	0.0000	4.10
	0.4441	0.0027	0.5533	0.0000	0.0681	0.8721	0.0000	0.0598	6.52
	0.3123	0.0015	0.6863	0.0000	0.0411	0.8549	0.0000	0.1040	7.60
	0.1923	0.0008	0.8069	0.0000	0.0270	0.8370	0.0000	0.1360	7.13
	0.1154	0.0002	0.8844	0.0000	0.0173	0.8245	0.0000	0.1582	6.66
	0.0542	0.0000	0.9458	0.0000	0.0096	0.8028	0.0000	0.1875	5.62
308.15	0.5736	0.0048	0.4216	0.0000	0.0923	0.9077	0.0000	0.0000	6.22
	0.4370	0.0028	0.5602	0.0000	0.0536	0.8851	0.0000	0.0613	8.15
	0.3599	0.0019	0.6382	0.0000	0.0321	0.8619	0.0000	0.1059	11.20
	0.2407	0.0009	0.7584	0.0000	0.0214	0.8384	0.0000	0.1402	11.26
	0.1203	0.0002	0.8795	0.0000	0.0105	0.8295	0.0000	0.1600	11.50
	0.0613	0.0000	0.9387	0.0000	0.0065	0.8022	0.0000	0.1913	9.50

Table 4 Experimental LLE data and distribution coefficients (D4) for system (DMM4 + water + cyclohexane + NaCl)

T/K	DMM₄(1)+水(2)+环己烷(3)+氯化钠(4)								分配系数(D₄)
	有机相				水相
	$W 1 Ⅰ$	$W 2 Ⅰ$	$W 3 Ⅰ$	$W 4 Ⅰ$	$W 1 Ⅱ$	$W 2 Ⅱ$	$W 3 Ⅱ$	$W 4 Ⅱ$
293.15	0.5468	0.0051	0.4481	0.0000	0.1334	0.8666	0.0000	0.0000	4.10
	0.4441	0.0027	0.5533	0.0000	0.0681	0.8721	0.0000	0.0598	6.52
	0.3123	0.0015	0.6863	0.0000	0.0411	0.8549	0.0000	0.1040	7.60
	0.1923	0.0008	0.8069	0.0000	0.0270	0.8370	0.0000	0.1360	7.13
	0.1154	0.0002	0.8844	0.0000	0.0173	0.8245	0.0000	0.1582	6.66
	0.0542	0.0000	0.9458	0.0000	0.0096	0.8028	0.0000	0.1875	5.62
308.15	0.5736	0.0048	0.4216	0.0000	0.0923	0.9077	0.0000	0.0000	6.22
	0.4370	0.0028	0.5602	0.0000	0.0536	0.8851	0.0000	0.0613	8.15
	0.3599	0.0019	0.6382	0.0000	0.0321	0.8619	0.0000	0.1059	11.20
	0.2407	0.0009	0.7584	0.0000	0.0214	0.8384	0.0000	0.1402	11.26
	0.1203	0.0002	0.8795	0.0000	0.0105	0.8295	0.0000	0.1600	11.50
	0.0613	0.0000	0.9387	0.0000	0.0065	0.8022	0.0000	0.1913	9.50

Table 5 Parameters of Eisen-Joffe equation and squared correlation coefficient (R2) for LLE experimental data at T = 293.15, 308.15 K

体系	T/K	α	β	γ	δ	R²
DMM₁+水+环己烷+氯化钠	293.15	0.75845	-0.86395	0.80493	2.27939	0.99261
DMM₁+水+环己烷+氯化钠	308.15	0.79312	1.58171	0.88853	2.00423	0.99450
DMM₂+水+环己烷+氯化钠	293.15	1.14847	6.87358	1.39844	2.76749	0.99496
DMM₂+水+环己烷+氯化钠	308.15	1.49646	13.19755	1.99038	0.66807	0.99637
DMM₃+水+环己烷+氯化钠	293.15	0.33747	0.51728	0.33090	2.84090	0.99324
DMM₃+水+环己烷+氯化钠	308.15	-0.02208	1.29493	-0.10597	4.32424	0.99243
DMM₄+水+环己烷+氯化钠	293.15	-0.42509	0.34158	-0.63149	5.84396	0.99828
DMM₄+水+环己烷+氯化钠	308.15	0.75792	2.95484	0.64482	2.87294	0.99203

Fig.2 Distribution coefficients(D1—4) at different sodium chloride mass fractions for DMM1—4 + H2O + CHX + NaCl system

Table 6 NRTL and CHEN-NRTL binary interaction parameters for DMMn (n) + water (5) + cyclohexane (6) + NaCl (7) system

组分		NRTL					CHEN—NRTL
RMSD		0.0192^①; 0.0219^②; 0.0147^③; 0.0135^④					0.0079^①; 0.0062^②; 0.0078^③; 0.0056^④
i	j	a_ij	a_ji	b_ij	b_ji	c_ij	A_ij	A_ji	B_ij	B_ji	C_ij
1	5	3.42	2.68	778.88	83.09	0.3	8.17	3.15	3495.94	139.66	0.3
1	6	4.21	0.96	1290.43	104.15	0.3	1.36	2.42	-151.5	-62.99	0.3
1	7	0.84	3.58	-270.61	837.8	0.3	4.74	-0.23	-169.14	3027.07	0.2
2	5	1.34	8.36	1596.1	-1519.51	0.3	8.13	3.47	2551.03	256.51	0.3
2	6	0.6	8.05	1047.89	-2439.65	0.3	0.89	1.49	5.5	93.17	0.3
2	7	80	80	10000	10000	0.3	1.58	-4.13	-1300.63	4095.23	0.2
3	5	0.8	4.19	930.32	-566.98	0.3	16.64	3.45	5006.78	208.13	0.3
3	6	1.22	-2.32	-478.42	973.29	0.3	0.3	2.73	-258.7	224.45	0.3
3	7	-9.36	25.14	1108.92	-5537.16	0.3	5.14	-3.83	-293.41	4163.99	0.2
4	5	3.52	19.75	22.51	-5211.83	0.3	8.42	3.38	2673.32	300.25	0.3
4	6	16.59	-25.09	-5330.52	8174.9	0.3	0.25	2.4	-174.42	289.15	0.3
4	7	6.15	28.69	768.87	-5428.21	0.3	4.86	-4.28	-366.7	3989	0.2
5	6	-0.46	5.21	-108.27	1565.56	0.3	-0.94	3.73	-96.68	512.76	0.3
5	7	-2.41	5.63	-1574.48	1670.29	0.3	4.02	2.06	-1465.35	-3453.34	0.2
6	7	-3.13	0.3	-54.14	515.91	0.3	0	0	0	0	0.2

Fig.3 Relationship between experimental values xexp and calculated values xcal by NRTL model and CHEN-NRTL model for (DMM1 + water + cyclohexane + NaCl) system

Fig.4 Relationship between experimental values xexp and calculated values xcal by NRTL model and CHEN-NRTL model for (DMM2 + water + cyclohexane + NaCl) system

Fig.5 Relationship between experimental values xexp and calculated values xcal by NRTL model and CHEN-NRTL model for (DMM3 + water + cyclohexane + NaCl) system

Fig.6 Relationship between experimental values xexp and calculated values xcal by NRTL model and CHEN-NRTL model for (DMM4+ water + cyclohexane + NaCl) system

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