渗透汽化和真空膜蒸馏在氨基甲酸酯脱水中的比较

doi:10.16085/j.issn.1000-6613.2024-1829

摘要/Abstract

摘要：

非光气工艺合成异氰酸酯时生成中间产物1,6-六亚甲基二氨基酸酯（HDC），含水5%~15%（质量分数），需将其含水量降至300mg/kg以下。本文分别采用NaA分子筛和聚四氟乙烯（PTFE）膜，探讨了通过蒸汽渗透（VP）和真空膜蒸馏（VMD）实现HDC深度脱水的可行性。首先测试HDC的熔点范围，确定了物料脱水的操作温度在118~120℃。并依据膜通量和运行稳定性等指标，筛选出最佳的NaA分子筛管式膜和PTEE多孔中空纤维膜，进一步考察了料液温度、渗透侧压力对膜脱水性能的影响，优化运行条件以减缓膜污染。实验结果表明，在118℃、10kPa条件下，NaA分子筛膜与PTFE膜在HDC脱水过程中均能稳定运行，达到300mg/kg的脱水目标。在长时间干燥实验中，NaA分子筛膜的干燥速率为1185g/(m²·h)，36h后出现膜污染且无法恢复；而PTFE膜具有更高的干燥速率，达到1712g/(m²·h)，连续运行80h，干燥速率基本不变，运行稳定性和抗污染性更好。最后建立了VMD和VP的干燥模型，分析了两种膜干燥过程中的传质阻力控制因素，膜尤其是NaA涂层的阻力更大。

关键词: 1,6-六亚甲基二氨基酸酯, 蒸汽渗透, 真空膜蒸馏, 膜筛选, 干燥模型

Abstract:

The synthesis of isocyanate by non-photogas process generates an intermediate product, 1,6-hexamethylene dicarbamate (HDC), which contains 5%—15% of water and needs to be reduced to less than 300mg/kg. In this work, the feasibility of deep dehydration of HDC by vapor permeation (VP) and vacuum membrane distillation (VMD) was investigated using NaA molecular sieves and PTFE membranes. The melting point range of HDC was firstly tested, and the operating temperature for HDC dehydration was determined to be in the range of 118—120℃. And the optimal NaA tubular membrane and PTEE porous hollow fiber membrane were screened based on the membrane flux and running stability. The effects of feed temperature and permeate pressure on membranes' dehydration performance were further investigated. The experimental results showed that both NaA and PTFE membranes could reach the dehydration target of 300mg/kg at 118℃ and 10kPa. In the long- time drying experiment, the drying rate of NaA membrane was 1185g/(m²·h), and membrane fouling appeared at 36h and membrane performance could not be recovered. While PTFE membrane had a higher drying rate of 1712g/(m²·h), and the drying rate kept stable in an 80h test, showed better stability and anti-fouling resistance. Finally, the drying models of VP and VMD were established, and the factors of mass transfer resistance in the VP and VMD process were analyzed during HDC dehydration. Membranes, especially NaA-coated ones, exhibited particularly high resistance.

Key words: 1,6-hexamethylene dicarbamate dehydration, vapor permeation, vacuum membrane distillation, membrane screening, drying models

中图分类号:

TQ028

余子昱, 陈晓飞, 侯春光, 岳殿鹤, 彭跃莲, 安全福. 渗透汽化和真空膜蒸馏在氨基甲酸酯脱水中的比较[J]. 化工进展, 2025, 44(6): 3247-3257.

YU Ziyu, CHEN Xiaofei, HOU Chunguang, YUE Dianhe, PENG Yuelian, AN Quanfu. Comparative study of vapor pervaporation and vacuum membrane distillation in dicarbamate dehydration[J]. Chemical Industry and Engineering Progress, 2025, 44(6): 3247-3257.

图/表 13

图1 浸没式真空膜蒸馏和蒸汽渗透装置

图2 HDC粉末的FTIR图

图3 HDC粉末的1H-NMR谱图

表1 不同含水量HDC的熔点

状态	不同含水量HDC的熔点/℃
状态	35%	20%	16%	11%	9%	6%	4%	2%	0.6%	0.4%	0.3%
初熔	82.5	82.3	85.7	86.9	92.7	113.6	113.5	113.7	113.2	113.7	113.6
终熔	84.9	84.7	92.5	87.3	94.7	114.6	114.9	114.4	114.2	115.0	114.7

图4 低含水量HDC粉末的DSC图和饱和蒸气压曲线

表2 NaA分子筛膜的性能

膜编号	膜通量^①/g·m²·h^-1	渗透侧含水量^①/%	活化能^②/kJ·mol^-1	HDC平均干燥速率^③/g·m²·h^-1
A	931~990	99.4~99.9	37.2	542
B	1097~1176	99.6~99.8	37.3	556
C	944~970	99.3~99.6	30.4	486
D	133~147	99.3~99.8	27.3	547
E	266~274	99.5~99.9	40.9	828

图5 5种NaA分子筛膜两次连续HDC脱水时的干燥速率曲线（料液120℃、冷侧压力为0）

图6 料液温度和渗透侧压力对NaA分子筛膜脱水性能的影响（膜面积0.001m2）

图7 料液温度和渗透侧压力对PTFE膜脱水性能的影响（膜面积0.001m2）

图8 干燥过程中水蒸气分压在NaA分子筛膜和PTFE膜中的分布

表3 用于模型计算的膜参数

参数	NaA分子筛膜	PTFE膜
多孔层厚度/m	2×10^{-3 [27]}	3.5×10^-4
多孔层孔径/m	5.6×10^{-7 [27]}	4×10^-7
孔隙率/%	0.65^[27]	0.42
弯曲因子	2^[27]	5.94
p_i	0.1×10^{-4 [26]}	—
q_i	0.16×10^{-4 [26]}	—
r_i	0.14×10^{-4 [26]}	—

表4 HDC两种含水量时NaA分子筛膜和PTFE膜脱水的传质系数、推动力和干燥速率（120℃、0kPa）

参数	HDC含水量为15000mg/kg时		HDC含水量为300mg/kg时
参数	NaA分子筛膜	PTFE膜	NaA分子筛膜	PTFE膜
K_L/g·m^-2·s^-1·Pa^-1	10.8×10^-5		9.2×10^-5
K_M/g·m^-2·s^-1·Pa^-1	2.6×10^-5	—	2.6×10^-5	—
K_S/K $S'$ /g·m^-2·s^-1·Pa^-1	5.59×10^-5	4.0×10^-5	5.59×10^-5	4.0×10^-5
总传质系数K/g·m^-2·s^-1·Pa^-1	1.52×10^-5	2.92×10^-5	1.49×10^-5	2.79×10^-5
推动力P_f-P_p/kPa	35.04		0.50
计算值N/g·m^-2·h^-1	1917	3683	27	50
实验值J/g·m^-2·h^-1	1556	2400	206	350
误差	-23%	-53%	87%	86%

表4 HDC两种含水量时NaA分子筛膜和PTFE膜脱水的传质系数、推动力和干燥速率（120℃、0kPa）

参数	HDC含水量为15000mg/kg时		HDC含水量为300mg/kg时
参数	NaA分子筛膜	PTFE膜	NaA分子筛膜	PTFE膜
K_L/g·m^-2·s^-1·Pa^-1	10.8×10^-5		9.2×10^-5
K_M/g·m^-2·s^-1·Pa^-1	2.6×10^-5	—	2.6×10^-5	—
K_S/K $S'$ /g·m^-2·s^-1·Pa^-1	5.59×10^-5	4.0×10^-5	5.59×10^-5	4.0×10^-5
总传质系数K/g·m^-2·s^-1·Pa^-1	1.52×10^-5	2.92×10^-5	1.49×10^-5	2.79×10^-5
推动力P_f-P_p/kPa	35.04		0.50
计算值N/g·m^-2·h^-1	1917	3683	27	50
实验值J/g·m^-2·h^-1	1556	2400	206	350
误差	-23%	-53%	87%	86%

图9 两种膜长时间脱水时的稳定性

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