جستجوی مقالات مرتبط با کلیدواژه "pervaporation" در نشریات گروه "شیمی"

In this report, mixed matrix membranes which are supported by polyethersulfone and sulfonated polyethersulfone prepared for dehydration of isopropanol. The prepared membranes are composed of a porous sublayer from polyethersulfone/sulfonated polyethersulfone and a composite top layer of poly(vinyl alcohol) and titanate nanotubes. In fact, hydrothermally-synthesized titanate nanotubes are dispersed in poly(vinyl alcohol). Moreover, the sulfonated polyethersulfone are used to investigate the effects of the porous sublayer on mass transport and the separation performance of the membranes. Next, the ability of the prepared membranes were studied for pervaporation separation of 90 wt% aqueous isopropanol mixture at 50 . The obtained results indicate that the thickness and chemical properties of the support have had a significant influence on pervaporation results. Totally, decreasing the difference between hydrophilicity of top layer and support has resulted in formation of an ideal interface between the layers. Furthermore, the presence of sulfone groups in interface, formation of hydrogen bounds among hydroxyl groups of poly(vinyl alcohol) and sulfone groups of the sublayer are responsible for enhanced compatibility between the layers. As a result, selective separation of water through the membranes was obtained. In addition, the results indicated that the support led to existence of an additional mass transport in isopropanol dehydration as well as requiring the physical support for the resultant membranes. The obtained results showed that when 4 wt% titanate nanotubes were dispersed in poly(vinyl alcohol) which was supported by sulfonated polyethersulfone the flux and separation factor were about  0.29 kg/m2 h and 4828, respectively.

Dehydration of organic compounds to achieve highly pure and valuable products constitutes one of the most important chapters in the chemical industry. In the present study, mixed matrix membranes (MMMs) including poly(vinyl alcohol) and modified ZIF-8 mineral phase by cationic surfactant of CTAB, were evaluated in terms of their performance in dehydration of isopropanol in the pervaporation process. The prepared nanocrystals and membranes were characterized by Fourier-transform infrared spectroscopy, gas adsorption-desorption, Thermal gravimetric analysis, X-ray crystallography, and Field emission scanning electron microscopy. Microscopic images showed that the presence of CTAB changed the morphology of ZIF-8 nanoparticles from rhombic dodecahedral to truncated rhombic dodecahedral. The effect of unmodified ZIF-8 loading from 1 to 10 wt.% in membranes on the separation performance of isopropanol feed containing 10 wt.% water at 30 °C was investigated. Then, based on the optimal loading, the separation performance of MMM containing 5 wt.% of surfactant-modified nanoparticles was evaluated which proved success in achieving better performance in comparison with pure polymer membranes and MMM containing unmodified nanoparticles by presenting the permeation flux of 0.942 kg/m2h and separation factor of 174.

Alcohol dehydration is accomplished by various processes, especially pervaporation with increased attention and applications. Many hydrophilic polymeric membranes have been prepared and used for alcohol dehydration. Polyvinyl alcohol (PVA) is one of the most important polymeric membranes in this regard. In this study, modification of the prepared polyvinyl alcohol membranes by blending method them with Agarose (Aga) in order to achieve higher separation performance is studied. PVA/Aga blended membranes are prepared and used for separation of ethanol/water solution using pervaporation process. The structure of the membranes was investigated using SEM and contact angle tests. In the carried out experiments, pervaporation operating temperature and pressure are kept fixed at 30 °C and - 830 mbar abs, respectively, and effects of the feed composition and the blending ratio on the membrane separation parameters are studied. The results showed that membranes have enhanced separation performance for water/ethanol mixtures. The highest selectivity as infinity and flux of 0.243 kg/m2h was obtained for the 50 wt. % Aga membrane and the feed mixture of 30 wt. %. The 60 wt. % Aga membrane selectivity and flux for dehydration of the feed mixture containing 70 wt. % ethanol are obtained as infinity and 0.838kg/m2h, respectively.

Sulfur present in gasoline results in air pollution by SOx emissions. With the mixtures of thiophene/n-hexane making up the model gasoline, PDMS/PA composite membrane was used for sulfur removal from gasoline by pervaporation. Effects of sulfur content (0.3-0.6 wt.%), feed temperature (30-50 ºC), permeate pressure (23-100 mmHg) and feed flow rate (30-90 L/h) were investigated on pervaporation separation of n-hexane/thiophene binary mixtures. Douglas design was used to research the effects of operating parameters on total fluxes. Experimental results indicated that sulfur content and feed flow rate have negligible effects on total flux in comparison with feed temperature and permeate pressure. Increasing feed temperature, sulfur content, feed flow rate and decreasing permeate pressure, increase total flux. According to significance of feed temperature and permeate pressure, effects of these investigated on thiophene enrichment factors. Thiophene enrichment factor increased with decreasing feed temperature and permeate pressure. The highest enrichment factor of thiophene was obtained to be 1.5 at a feed temperature of 30 ºC and a permeate pressure of 23 mmHg.