Nonaqueous Interfacial Polymerization-Derived Polyphosphazene Films for Sieving or Blocking Hydrogen Gas

A series of cyclomatrix polyphosphazene films have been prepared by nonaqueous interfacial polymerization (IP) of small aromatic hydroxyl compounds in a potassium hydroxide dimethylsulfoxide solution and hexachlorocyclotriphosphazene in cyclohexane on top of ceramic supports. Via the amount of dissolved potassium hydroxide, the extent of deprotonation of the aromatic hydroxyl compounds can be changed, in turn affecting the molecular structure and permselective properties of the thin polymer networks ranging from hydrogen/oxygen barriers to membranes with persisting hydrogen permselectivities at high temperatures. Barrier films are obtained with a high potassium hydroxide concentration, revealing permeabilities as low as 9.4 × 10-17 cm3 cm cm-2 s-1 Pa-1 for hydrogen and 1.1 × 10-16 cm3 cm cm-2 s-1 Pa-1 for oxygen. For films obtained with a lower concentration of potassium hydroxide, single gas permeation experiments reveal a molecular sieving behavior, with a hydrogen permeance of around 10-8 mol m-2 s-1 Pa-1 and permselectivities of H2/N2 (52.8), H2/CH4 (100), and H2/CO2 (10.1) at 200 °C.</p

Comparing amine- and ammonium functionalized silsesquioxanes for large scale synthesis of hybrid polyimide high-temperature gas separation membranes

PolyPOSS-imide membranes are promising for separating H2 from larger molecules (CO2, N2, CH4) at temperatures up to 300 °C. Their fabrication involves two steps: interfacial polymerization of POSS and 6FDA, followed by thermal imidization. This work provides a systematic study of the effects of cations on membrane properties and performance. For this, two distinct POSS molecules were used: functionalized with -NH3+Cl− or, so far unexplored, -NH2. The ammonium groups are partially deprotonated by using three different bases, LiOH, NaOH, and KOH. We demonstrate that the introduced cations affect the film thickness but not the molecular composition of the polyamic acid. All polyamic acids can be imidized, but the cations reduce the imidization kinetics as well as the loss of organic crosslinkers. For flat disc membranes, at 200 °C, the absence of cations results in comparable permeability combined with higher selectivity for H2/N2. This, and the possibility to discard adding a base, motivated a scale-up study of the new POSS. For tubular membranes, much higher ideal and mixed gas selectivities are found than for membranes where NaOH was added. Results indicate that the new route allows more reproducible production of defect free membranes and has potential for larger-scale polyPOSSimide fabrication.publishedVersio

Stability investigation of polyPOSS-imide membranes for H2 purification and their application in the steel industry

In the present work, the high-temperature and long-term hydrothermal stability of novel polyPOSS-imide membranes for high-temperature hydrogen separation is investigated. The polyPOSS-imide membranes are found to exhibit an appropriate stability up to 300 C. Above this temperature the membrane selectivity rapidly decreases, which is seemingly related to changes in the molecular structure coupled to silanol condensation forming siloxane groups. Surprisingly, the exposure of the membrane to temperatures of up to 300 C even increases the H2 permeance together with the selective feature of the polyPOSS-imide layer. Subsequently, the long-term hydrothermal stability of the polyPOSS-imide membranes was investigated over a period of close to 1000 h at 250 C exposing the membrane to 10 mol% steam in the feed. An increase in H2/CH4 selectivity was observed upon water addition, and even though a minor drop was noticed over time during the hydrothermal operation, the selectivity exceeds the initial selectivity obtained in the dry feed atmosphere. After the removal of steam from the feed, the performance returns to its original state prior to the exposure to any steam showing appropriate steam stability of the polyPOSS-imide membranes. A conceptual process design and assessment was performed for application of these membranes involving a combination of carbon reuse and electrification of the steel making process with co-production of hydrogen. The results indicate a CO2 avoidance of 14%. The CO2 reduction achieved using renewable electricity in the proposed scheme is a factor 2.76 higher compared to a situation where the same renewable electricity would be fed in the electricity grid.publishedVersio

Cyclomatrix polyphosphazene organic solvent nanofiltration membranes

In this work, we report the synthesis and characteristics of cyclomatrix polyphosphazene membranes based on interfacial polymerization between 1,1-tris(4-hydroxyphenyl)ethane and hexachlorocyclotriphosphazene on top of alumina or polyacrylonitrile supports. The potential of alumina-supported thin film composite membranes as organic solvent nanofiltration membranes has been confirmed with a polystyrene-based molecular weight cutoff of 347 ± 120 Da and 503 ± 220 Da in acetone and toluene, respectively. Also, the resulting alumina-supported TFC membrane showed a methylene blue rejection (Mw = 319 g mol−1) of 98.2 ± 2.3%, 92 ± 1.7%, and 93 ± 0.5% in water, ethanol, and acetone, respectively. Furthermore, a thin film composite membrane has been prepared with a polyacrylonitrile support via interfacial polymerization to validate the preparation technique for polymeric supports and facilitate industrial implementation. The resulting membrane showed higher permeance and lower rejection than the alumina-supported membrane due to the presence of pinholes in the selective layer on top of the polyacrylonitrile supports. Our results clearly show the great potential of cyclomatrix polyphosphazene membranes as organic solvent nanofiltration membranes. However, for polyacrylonitrile-supported membranes, the preparation method needs further investigation

Polyoctahedral silsesquioxane hexachlorocyclotriphosphazene membranes for hot gas separation

There is a need for gas separation membranes that can perform at high temperatures, for example, for CO2 capture in industrial processes. Polyphosphazenes classify as interesting materials for use under these conditions because of their high thermal stability, hybrid nature, and postfunctionalization options. In this work, thin-film composite cyclomatrix polyphosphazene membranes are prepared via the interfacial polymerization reaction between polyhedral oligomeric silsesquioxane and hexachlorocyclotriphosphazene on top of a ceramic support. The prepared polyphosphazene networks are highly crosslinked and show excellent thermal stability until 340 °C. Single gas permeation experiments at temperatures ranging from 50 to 250 °C reveal a molecular sieving behavior with permselectivities as high as 130 for H2/CH4 at the low temperatures. The permselectivities of the membranes persist at the higher temperatures; at 250 °C H2/N2 (40), H2/CH4 (31) H2/CO2 (7), and CO2/CH4 (4), respectively, while maintaining permeances in the order of 10−7 to 10−8 mol m−2 s−1 Pa−1. Compared to other types of polymer-based membranes, especially the H2/N2 and H2/CH4 selectivities are high, with similar permeances. Consequently, the hybrid polyphosphazene membranes have great potential for use in high-temperature gas separation applications

سیدحسین حکیم الگوی اخلاق در طبابت

Iranians or Persians have contributed to ethics, particularly medical ethics from ancient times and this is a historical fact which can be noticed by studying history of medicine in Persian and Islamic world. Persians physicians have specific place in the history of medicine, and one of them is Seyed Hossein Hakim, who was a great physician in 13th&nbsp;century. Ayatollah Seyed Hossein Hakim; the son of Haj Seyed Ali Shooshtari, who was born and lived in Shooshtar, Khuzistan Province, Iran in 13 century. He went to advance studies in medicine and Shia in Islamic seminaries; he became an Ayatollah and returned to Shooshtar where lived for the rest of his life as a physician and a religious leader. He was in charge of local mosque, served the locals in many different ways. He managed his patients according to Avicenna’s textbook “Canon in Medicine”. He was inquisitive and perspicacious. He was very talented and hardworking, and gradually he became a famous expert in medicine. After a while he earned a strong recommendation from Seyed Ali Tabib, one of the authorities in medicine in that region because of his personality and reliability, but also due to his impressive work ethics, and the citizens of Shooshtar asked from him to become the formal physician of their city. He had special characters including mild manner and due was very humble. So his memories are still alive after so many years. The purpose of this study is to introduce seyed Hossein Hakim as a physician who showed excellence and professionalism in medicine and medical ethics.با بررسی و مطالعه برگ‌های تاریخ پزشکی کهن در تمدن ایران و اسلام می‌توان دریافت که ایرانیان از همان زمان‌های پیشین به رعایت موازین اخلاقی به ویژه در طب توجه ویژه‌ای داشته‌اند و دانشمندان و حکیمان بزرگی در این سپهر از کهن تاکنون درخشیده‌اند. یکی از حکیمان بزرگ و عالی قدری که در این مسیر خوش درخشیده است سیدحسین حکیم (ره) می‌باشد. آيت‌ا... حاج سيدحسين حكيم فرزند عالم و عارف نامدار، حاج سيدعلي شوشتري در قرن سيزدهم هجري قمری می‌زیسته است. وی در روزگاران جواني در نجف به تحصيل علوم و تكميل دروس فقهی اشتغال یافت و پس از رسيدن به پایه اجتهاد در شوشتر ساكن شد و در همانجا به عنوان امام جماعت یکی از مساجد منسوب شد و به اداي نماز جماعت و خدمت‌رساني به مردم در امور مختلف مشغول بود. به دنبال درمان برخی بیماران بر اساس دستورات پزشکی ابن سینا در کتاب قانون و نیز مهارت و استعداد ذاتی و خدادادی و ذکاوت سیدحسین حکیم در زمینه طب بالینی و تجربی و بنا به درخواست برخی اطبای معروف دزفول از جمله سیدعلی طبیب و همچنین استقبال چشمگیر و رضایت مردم از ایشان در این امر، این حکیم فرزانه به امر طبابت اشتغال یافت. از ویژگی‌های شاخص این حکیم توانا، منش اخلاقی و رفتاری والای ایشان در تعامل با مردم و در امر طبابت و درمان بود به طوری که نیکی‌های اخلاقی و رفتاری وی سال‌ها پس از درگذشت ایشان همچنان بر سر زبان‌ها جاری بود. هدف از این مطالعه، معرفی سیدحسین حکیم به عنوان طبیبی توانمند و الگویی ارزشمند در عرصه اخلاق پزشکی و به عنوان خادمی دلسوز برای مردم در حوزه طبابت و درمان است.&nbsp

Molecular characterization of CO2/CH4 and CO2/N2 gas separation under very high temperatures and pressures in hybrid organic-inorganic network membranes

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High-temperature molecular screening of hybrid polyOAPS-imide networks based on octa(aminophenyl)silsesquioxane for increased thermomechanical resistance

International audienceA new family of hybrid hyper-cross-linked thin films based on inorganic polyhedral oligomeric silsesquioxane (POSS) cages covalently bound with short organic imides has recently been developed using interfacial polycondensation followed..