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Wang Y.,Huazhong University of Science and Technology | Gruender M.,PBI Performance Products Inc. | Xu S.,Huazhong University of Science and Technology
Industrial and Engineering Chemistry Research | Year: 2014

Phenol is an important commodity in chemical industries and dewatering is a critical process in its application. In this work, polybenzimidazole (PBI) membranes with various morphologies are employed for phenol dehydration via pervaporation, including flat-sheet dense membranes, single-layer and dual-layer hollow fiber membranes. Effects of cross-linking modification and post-thermal treatment on the performance of PBI flat-sheet dense membranes were investigated; effects of the operation temperature and feed composition are also studied, not only in terms of flux and separation factor, but also of the intrinsic permeance and selectivity of the membrane. In order to achieve a higher permeation flux, PBI single-layer hollow fiber membranes of thinner selective layers were developed and studied with the effect of different spinning parameters. The preliminary study of dual-layer PBI/PBI and PBI/poly(vinylidene fluoride) (PVDF) dual-layer hollow fiber membranes are also carried out to explore the potential of high-performance composite membranes for phenol dehydration. The promising separation performance of PBI membranes exhibited via benchmarking shows its great potential for phenol dehydration, and it may open new perspectives for the development of high-performance membranes for the pervaporation dehydration of phenol or other corrosive organics. © 2014 American Chemical Society. Source


Wang Y.,National University of Singapore | Chung T.S.,National University of Singapore | Neo B.W.,National University of Singapore | Gruender M.,PBI Performance Products Inc.
Journal of Membrane Science | Year: 2011

Operating conditions play a significant role in determining the separation performance of a pervaporation process, because they not only manipulate the driving forces to transport permeants but also affect the physicochemical properties of the pervaporation membrane itself. In this study, fundamental governing equations have been derived to correlate separation performance with system operation conditions and intrinsic separation characteristics of the pervaporation membrane. Polybenzimidazole/polyetherimide (PBI/PEI) dual-layer hollow fiber membranes were chosen to study the pervaporation dehydration of ethylene glycol (EG) under different testing protocols. The effects of operational parameters such as operation temperature, permeate pressure, feed composition and operation duration on performance indicators (flux and separation factor, permeance and selectivity) have been investigated. Experimental results show that an increase in operation temperature results in an increase in flux and selectivity, but a decrease in permeance and separation factor. In addition to other factors, decreasing sorption, less EG-water clusters and lower membrane-EG affinity with increasing temperature, play essential roles for the opposite trends. Both flux and permeance decrease with an increase in permeate pressure, while both separation factor and selectivity have an up-and-down trend. An increase in EG composition in the feed from 50 to 90. wt.% results in a lower water flux and permeance, but EG flux and permeance first increase and then decrease. This is due to the combined effect of water-induced membrane swelling and the formation of an EG boundary layer upon the membrane surface. The long-term test up to 33 days proves the membrane durability for EG dehydration. This work may provide useful insights to pervaporation fundamentals, system design and scale up for the EG dehydration. © 2011 Elsevier B.V. Source


Wang Y.,National University of Singapore | Gruender M.,PBI Performance Products Inc. | Chung T.S.,National University of Singapore
Journal of Membrane Science | Year: 2010

Ethylene glycol is an important commodity in chemical industries and dewatering is a critical process in the production and recycle of ethylene glycol. In this work, we have developed dual-layer polybenzimidazole/polyetherimide (PBI/PEI) hollow fiber membranes for ethylene glycol dehydration via pervaporation. Three types of membranes have been prepared; namely, (1) PBI flat dense membranes; (2) PBI single-layer hollow fiber membranes; and (3) PBI/PEI dual-layer hollow fiber membranes. PBI flat dense membranes have the lowest separation performance due to severe swelling. PBI single-layer hollow fiber membranes show better separation performance in terms of permeation flux and separation factor but have very low tensile strains. The dual-layer PBI/PEI hollow fiber membranes have the best separation performance due to (1) unique combination of the superior physicochemical properties of the PBI selective layer and the less swelling characteristics of the PEI supporting layer, and (2) synergistic effects of molecularly designed membrane morphology via dual-layer co-extrusion. The effects of spinning parameters of PBI single-layer and PBI/PEI dual-layer hollow fiber membranes on pervaporation performance have been investigated. A thermal treatment of PBI/PEI dual-layer hollow fiber membranes at 75°C can significantly enhance the separation performance. Compared with other polymeric membranes, the newly developed PBI/PEI dual-layer hollow fiber membranes have much better separation factors and slightly lower fluxes for the ethylene glycol dehydration. It is believed that the science and engineering of designing PBI/PEI dual-layer hollow fiber membranes with an ultra-thin functional separation layer and a synergic supporting layer may open new perspective for the development of next-generation high-performance multilayer membranes for liquid separations. © 2010 Elsevier B.V. Source


Wang Y.,National University of Singapore | Shung Chung T.,National University of Singapore | Gruender M.,PBI Performance Products Inc.
Journal of Membrane Science | Year: 2012

In this study, a novel sulfonated polybenzimidazole (SPBI) membrane has been developed and investigated for pervaporation dehydration of acetic acid, via a two-step sulfonation modification technique-sulfonation with sulfuric acid followed by a thermal treatment at 450°C. Both steps are found indispensible in order to produce a stable SPBI membrane with enhanced acid resistance and superior separation performance. Effects of the sulfuric acid concentration and thermal treatment duration have been investigated and found to have significant impact on the pervaporation performance of the resultant SPBI membranes. Various characterizations (FTIR, XPS, TGA and XRD) are employed to elucidate the physicochemical changes of membranes as a function of chemical and thermal modifications. In addition, effects of pervaporation temperature and feed composition are studied not only in terms of flux and separation factor, but also of membrane intrinsic permeance and selectivity. The best pervaporation performance of the SPBI membrane has a flux of 207g/m 2/h and a separation factor of 5461 for dehydration of a 50/50wt% acetic acid/water feed solution at 60°C, which not only outperforms the conventional distillation process, but also surpasses most other polymeric pervaporation membranes reported in literature. It is therefore believed that the novel developed SPBI membrane may have great potential for pervaporation dehydration of acidic organics, as well as other applications that demand acid-proof materials. © 2012 Elsevier B.V. Source


Patent
PBI Performance Products Inc. | Date: 2014-06-27

A process for producing a solution blend of a polybenzimidazole (PBI) and a polyetherketoneketone (PEKK). The PBI is mixed with sulfuric acid at a temperature between 40 C. and 80 C. for 30 minutes to 2 hours to produce a PBI solution then cooled to room temperature to form a cooled PBI solution. Then PEKK is added to the cooled PBI solution to form a mixture and that mixture is stirred from 30 minutes to 2 hours at room temperature to form a stirred mixture. The stirred mixture is poured into an excess of water being stirred swiftly to form an aqueous mixture. The aqueous mixture is filtered to produce a blend. The blend is washed with water and dried. The resulting blend can yield a blend in all proportion from 1/99 PBI/PEKK to 99/1 PBI/PEKK.

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