Synthesis of n-hexyl acetate via reactive distillation catalyzed by mixed ionic liquids

doi:10.11949/0438-1157.20201652

Abstract

Abstract:

Ionic liquid catalytic reactive distillation is a green and effective method to improve the conversion rate of the transesterification equilibrium reaction. The mixture of 1-propylsulfonate-3-methylimidazolium trifluoromethane sulfonate ([PSO₃HMIm][OTf]) and 1-octyl-2,3-dimethylimidazolium bis((trifluoromethyl)sulf-onyl)imide ([OMMIm][Tf₂N])) were utilized as the catalyst for transesterification of methyl acetate with n-hexanol, and the reaction kinetics of the transesterification were measured. The effects of mixing ratio, reaction temperature, initial molar ratio of reactants and concentration of catalyst on reaction rate and the conversion of methyl acetate, and recovery performance of the catalyst were investigated. The reaction kinetic equation of the transesterification catalyzed by mixed ionic liquids was obtained by the correlation of experimental data. Based on the reaction kinetics, the reactive distillation process for transesterification of methyl acetate and n-hexanol was simulated, and the effects of theoretical stage number, reflux ratio, feed position, theoretical stages in reaction section, catalyst amount and liquid holdup on the reactive distillation column were analyzed. Under the optimized operating conditions, hexyl acetate product with purity of 0.9993 was obtained by the reactive distillation process.

Key words: ionic liquids, catalysis, reaction kinetics, reactive distillation, process simulation

摘要：

离子液体催化反应精馏是提高酯交换平衡反应转化率的一种绿色有效方法。以离子液体1-丙基磺酸-3-甲基咪唑三氟甲烷磺酸盐（［PSO₃HMIm］［OTf］）和离子液体1-辛基-2，3-二甲基咪唑双（三氟甲烷磺酰）亚胺盐（［OMMIm］［Tf₂N］）的混合物作为乙酸甲酯和正己醇进行酯交换反应合成乙酸正己酯的催化剂，测定了酯交换反应动力学。探讨了混合比、反应温度、反应物初始摩尔比、催化剂浓度对反应速率和乙酸甲酯转化率的影响，考察了催化剂的回收性能。利用实验数据回归得出混合离子液体催化酯交换反应动力学方程。在反应动力学的基础上进行了乙酸甲酯和正己醇的酯交换反应精馏流程模拟，分析了理论板数、回流比、进料位置及反应段塔板数、催化剂用量、持液量等参数对反应精馏塔的影响。在优化的操作条件下，获得纯度为0.9993的乙酸正己酯产品。

关键词: 离子液体, 催化, 反应动力学, 反应精馏, 过程模拟

CLC Number:

TQ 032.4

Zhenxing SONG, Xianbao CUI, Ying ZHANG, Xuemei ZHANG, Jie HE, Tianyang FENG, Jixiao WANG. Synthesis of n-hexyl acetate via reactive distillation catalyzed by mixed ionic liquids[J]. CIESC Journal, 2021, 72(8): 4155-4165.

宋振兴, 崔现宝, 张缨, 张雪梅, 何杰, 冯天扬, 王纪孝. 混合离子液体催化反应精馏合成乙酸正己酯[J]. 化工学报, 2021, 72(8): 4155-4165.

Figures/Tables 19

Table 1 The reagents used in experiment

试剂名称	纯度/%	供应商
乙酸甲酯(MeOAC)	99.0	上海阿拉丁生化科技股份有限公司
甲醇(MeOH)	99.8	凯玛特化工科技有限公司
正己醇(HeOH)	99.8	凯玛特化工科技有限公司
乙酸正己酯(HeAC)	99.0	上海麦克林生化科技有限公司
1-丙基磺酸-3-甲基咪唑三氟甲烷磺酸盐([PSO₃HMIm][OTf])	99.0	兰州奥力科化工有限公司
1-丁基磺酸-3-甲基咪唑硫酸氢盐([BSO₃HMIm][HSO₄])	99.0	兰州奥力科化工有限公司
N-丁基磺酸吡啶三氟甲烷磺酸盐([BSO₃HPy][OTf])	99.0	兰州奥力科化工有限公司
1-丁基磺酸-3-甲基咪唑三氟甲烷磺酸盐([BSO₃HMIm][OTf])	99.0	兰州奥力科化工有限公司
1-丁基磺酸-3-甲基咪唑盐酸盐([BSO₃HMIm][Cl])	99.0	兰州奥力科化工有限公司
1-辛基-2,3-二甲基咪唑双(三氟甲烷磺酰)亚胺盐([OMMIm][Tf₂N])	99.0	兰州奥力科化工有限公司

Fig.1 Effects of different ionic liquid catalysts on transesterification

Fig.2 Effect of different molar ratio of [OMMIm][Tf2N]∶[PSO3HMIm][OTf] on transesterification

Fig.3 Effects of catalyst concentration on transesterification

Fig.4 Initial reaction rate versus IL catalyst concentration

Fig.5 Effects of reaction temperature on transesterification

Fig.6 Effect of initial molar ratio of n-hexanol to methyl acetate on the transesterification

Fig.7 Performance of recovered mixed ionic liquid catalyst

Table 2 NRTL model parameters

i	j	B_ij/K	B_ji/K	α_ij
乙酸甲酯	甲醇	214.419	139.516	0.3
乙酸甲酯	正己醇	522.257	-222.8145	0.3
乙酸甲酯	乙酸正己酯	499	-336.127	0.3
甲醇	正己醇	516.202	-301.081	0.3364
甲醇	乙酸正己酯	101.869	180.573	0.3
正己醇	乙酸正己酯	-144.421	354.82	0.3
乙酸甲酯	[PSO₃HMIm] [OTf]	5360.95	-3043.333	0.2
乙酸甲酯	[OMMIm][Tf₂N]	9079.14	-536.9	0.3
甲醇	[PSO₃HMIm] [OTf]	1676.0488	-2365.70732	0.3
甲醇	[OMMIm][Tf₂N]	-301.5	6230.09	0.3
正己醇	[PSO₃HMIm] [OTf]	-855.274	-1808.009	0.2
正己醇	[OMMIm][Tf₂N]	-4.3407	-1432.65	0.3
乙酸正己酯	[PSO₃HMIm] [OTf]	1723.06632	-1685.6435	0.2
乙酸正己酯	[OMMIm][Tf₂N]	610.14752	-1299.8232	0.3
[PSO₃HMIm] [OTf]	[OMMIm][Tf₂N]	2256.214	1710.3584	0.3

Fig.8 Effect of reaction temperature on chemical equilibrium constant

Table 3 Calculation results of standard reaction enthalpy

组分	Δ_fH⁰/(kJ/mol)	Δ_r $H_{c a l}^{0}$ /(kJ/mol)	Δ_r $H_{e x p}^{0}$ /(kJ/mol)
乙酸甲酯	-411.9	5.2	7.67
正己醇	-320.5
甲醇	-200.9
乙酸正己酯	-526.3

Table 3 Calculation results of standard reaction enthalpy

组分	Δ_fH⁰/(kJ/mol)	Δ_r $H_{c a l}^{0}$ /(kJ/mol)	Δ_r $H_{e x p}^{0}$ /(kJ/mol)
乙酸甲酯	-411.9	5.2	7.67
正己醇	-320.5
甲醇	-200.9
乙酸正己酯	-526.3

Fig.9 Flow chart of catalytic reactive distillation

Fig.10 The effect of catalyst flow rate

Fig.11 The y-x phase diagram of methyl acetate methanol system with different concentrations of mixed ionic liquid catalyst

Fig.12 The effect of theoretical plates

Table 4 The effect of feeding position and number of spacer plates

离子液体进料位置	正己醇进料位置	乙酸甲酯混合物进料位置	反应段进料间隔板数	收率	乙酸正己酯纯度
5	30	50	20	0.9180	0.9242
5	24	50	26	0.9454	0.9497
5	20	50	30	0.9617	0.9648
5	15	50	35	0.9672	0.9711
15	15	50	35	0.9669	0.9702
5	10	50	40	0.9783	0.9809
10	10	50	40	0.9788	0.9811
5	6	46	40	0.9636	0.9688
5	8	48	40	0.9710	0.9746
5	10	50	40	0.9783	0.9809
5	12	52	40	0.9619	0.9650

Fig.13 The effect of reflux ratio

Fig.14 The effect of liquid holdup of tray

Fig.15 Liquid concentration profiles in the reactive distillation column

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