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首页> 外文学位 >Novel pervaporation for separating acetic acid and water mixtures using hollow fiber membranes.
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Novel pervaporation for separating acetic acid and water mixtures using hollow fiber membranes.

机译：使用中空纤维膜分离乙酸和水混合物的新型全蒸发。

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Commercial pure terephthalic acid (PTA) manufacturing generates process streams mainly containing acetic acid (HAc) and water. A large financial incentive exists to replace the costly and energy intensive distillation column used to recycle HAc-water mixtures. This work focuses on the development of pervaporation technology to separate HAc-water mixtures using a hollow fiber-based membrane unit.; Currently a 250 mum outer diameter MatrimidRTM hollow fiber is used in industry for gas separation. Due to the difference between gas and liquid separations, the fiber performance associated with high flux in pervaporation is limited by a pressure change inside the bore along the axial direction of the fiber. A mathematical model was developed to describe the bore pressure change in pervaporation in this work, which demonstrated that spinning a large bore size fiber was a good solution to minimize the bore pressure change.; Spinning technology has been adapted to obtain a large bore size defect-free MatrimidRTM hollow fiber. In addition to a large bore size, the asymmetric fiber exhibits an intrinsically defect-free selective layer supported on an open porous substrate. This eliminates the post-treatment with a "caulking layer" and has a special advantage for aggressive liquid separation.; A proof of concept was provided by testing both small and large bore size defect-free fibers with a model 20% wt HAc feed in a pervaporation system at 101.5°C. The membrane selectivity (∼25) and water flux (∼4.5 kg/m2hr) were increased by about 150% with a diameter (O.D. ∼ 500 mum) twice as large as the regular fiber. Further, a decrease in the HAc flux was observed with the increased bore size due to the reduction in HAc-induced plasticization.; Sub-Tg thermal annealing was used to stabilize the fiber by suppressing HAc-induced plasticization. This improves the polymer discrimination of shape and size for penetrants although no chemical reaction occurs with thermal annealing. The resulting membrane selectivity was increased from 10 to about 95 using a large bore size defect-free annealed fiber with acceptable water flux (∼1.5 k g/m 2hr) for 20% wt HAc concentration feed streams.; These improvements make MatrimidRTM hollow fiber membranes very attractive for future scale-up and commercial development.
机译：商业纯对苯二甲酸（PTA）生产产生的工艺流主要包含乙酸（HAc）和水。存在巨大的经济诱因，以取代用于再循环HAc-水混合物的昂贵且耗能的蒸馏塔。这项工作着重于渗透蒸发技术的发展，该技术使用中空纤维基膜单元分离HAc-水混合物。目前，工业上使用250微米外径的MatrimidRTM中空纤维进行气体分离。由于气体和液体分离之间的差异，与全蒸发中的高通量有关的纤维性能受到孔内沿纤维轴向的压力变化的限制。建立了一个数学模型来描述这项工作中渗透过程中孔压力的变化，这表明纺制大孔径的纤维是使孔压力变化最小的好方法。纺丝技术已适应获得大口径的无缺陷MatrimidRTM中空纤维。除了较大的孔径外，不对称纤维还具有支撑在开放式多孔基材上的本质上无缺陷的选择性层。这样就消除了用“填缝层”进行的后处理，并具有主动液体分离的特殊优势。通过在101.5°C的全蒸发系统中使用20％wt HAc模型进料测试小口径和大口径尺寸的无缺陷纤维，提供了概念验证。膜的选择性（〜25）和水通量（〜4.5 kg / m2·hr）增加了约150％，直径（外径〜500 mum）是普通纤维的两倍。此外，由于HAc诱导的塑化的减少，随着孔径的增加，观察到了HAc通量的减少。 Sub-Tg热退火用于通过抑制HAc诱导的塑化来稳定纤维。尽管通过热退火不会发生化学反应，但是这改善了聚合物对渗透剂的形状和尺寸的辨别力。使用大孔径，无缺陷的退火纤维将可接受的水通量（〜1.5 k g / m 2小时）用于20％wt HAc浓度的进料流，所得的膜选择性从10提高至约95。这些改进使MatrimidRTM中空纤维膜对未来的规模扩大和商业开发非常有吸引力。

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