Pure and mixed gas CH4 and n-C4H10 permeability and diffusivity in poly(1-trimethylsilyl-1-propyne)

Pure and mixed gas n-C₄H₁₀ and CH₄ permeability coefficients in poly(1-trimethylsilyl-1-propyne) (PTMSP) are reported at temperatures from −20 to 35 °C. CH₄ partial pressures range from 1.1 to 14.6 atm, and n-C₄H₁₀ partial pressures range from 0.02 to 1.8 atm. CH₄ permeability decreases with increasing n-C₄H₁₀ upstream activity (f/f_sat) in the feed. For example, at −20 °C, CH₄ permeability decreases by more than an order of magnitude, from 52,000 to 1700 Barrer, as n-C₄H₁₀ activity increases from 0 to 0.73. In contrast, n-C₄H₁₀ mixed gas permeability is essentially unaffected by the presence of CH₄. The depression of CH₄ permeability in mixtures is a result of competitive sorption and blocking effects, which reduce both CH₄ mixture solubility and diffusivity, respectively. Diffusion coefficients of n-C₄H₁₀ and CH₄ in mixtures were calculated from mixture permeability and mixture solubility data. The CH₄ concentration-averaged diffusion coefficient generally decreases as n-C₄H₁₀ activity increases. On the other hand, the n-C₄H₁₀ diffusion coefficient is essentially unaffected by the presence of CH₄. Pure and mixed gas activation energies of permeation and diffusion of CH₄ and n-C₄H₁₀ are reported. The mixed gas n-C₄H₁₀/CH₄ permeability selectivity increases with increasing n-C₄H₁₀ activity and decreasing temperature, and it is higher than pure gas estimates would suggest. Mixture diffusivity selectivity also increases with increasing n-C₄H₁₀ activity. The difference between pure and mixed gas permeability selectivity arises from both solubility and diffusivity effects. The dual mode mixed gas permeability model describes the mixture permeability data reasonably well for n-C₄H₁₀. However, the model must be modified to accurately describe the methane data by accounting for the decrease in methane diffusivity due to the presence of n-C₄H₁₀ (i.e., blocking). Even though the penetrant concentrations are rather significant at some of the conditions considered, no evidence is observed for phenomena such as multicomponent coupling that would require a model more complex than the binary form of Fick's law. That is, Fick's law in its simplest form adequately describes the experimental data.     

PTMSP及其共聚物膜对有机液/水体系的PV分离

制备了聚三甲基硅丙炔均聚物 (PTMSP) .研究了PTMSP均质膜 ,三甲基硅丙炔(TMSP)与五甲基二硅丙炔 (PMDSP)共聚物膜对含少量有机溶剂水溶液的渗透汽化 (PV )特性 .所选用的有机溶剂包括乙醇、异丙醇、四氢呋喃、二氯甲烷、乙酸乙酯等 .从膜的溶胀特性、溶解度系数及扩散系数的测定结果 ,分析了膜材质的结构与PV特性之间的关系 .     

Effects of synthesis conditions on the pervaporation properties of poly[1‐(trimethylsilyl)‐1‐propyne] useful for membrane bioreactors

An integrated fermentation and membrane‐based recovery (pervaporation) process has certain economical advantages in continuous conversion of biomass into alcohols. This article presents new pervaporation data obtained for poly[1‐(trimethylsilyl)‐1‐propyne] (PTMSP) samples synthesized in various conditions. Three different catalytic systems, TaCl₅/n‐BuLi, TaCl₅/Al(i‐Bu)₃, and NbCl₅ were used for synthesis of the polymers. It was found that the catalytic system has a significant influence over the properties of membranes made from PTMSP. Although a combination of a high permeation rate and a high ethanol–water separation factor (not less than 15) was provided by all PTMSP samples, the PTMSP samples synthesized with TaCl₅/n‐BuLi showed significant deterioration of membrane properties when acetic acid was present in the feed. In contrast, the PTMSP samples synthesized with TaCl₅/Al(i‐Bu)₃ or NbCl₅ showed stable performance in the presence of acetic acid. When using a multicomponent mixture of organics and water, the copermeation of different organic components results in lower separation factor for both ethanol and butanol. These data are consistent with nanoporous morphology of PTMSP. It was demonstrated that pervaporative removal of ethanol improved the overall performance of the fermentation process. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2271–2277, 2004     

Molecular dynamics simulation of diffusion of gases in pure and silica-filled poly(1-trimethylsilyl-1-propyne) [PTMSP]

Nanocomposites have been extensively applied, and molecular dynamics simulation techniques have been applied to study the diffusion of gases (H₂, O₂, N₂, CO₂, CH₄, n-C₄H₁₀) through pure and filled with silica particle poly(1-trimethylsilyl-1-propyne) [PTMSP]. The aim for this research is to explore and investigate the effect of silica particle on the diffusion of gases in polymer. The diffusion coefficients of gases were determined via NVT molecular dynamics simulation using the COMPASS force field up to 500 or 1000 ps simulation time. We have focused on the effect of the concentration and the size of the silica particles on diffusion coefficients of gases and the changes of free volume and translational dynamics and intermolecular energies. It has been found that the addition of silica particle to PTMSP increased the diffusion coefficients of gases by enhancing the free volume of polymer.     

Fibers spinning from poly(trimethylsilylpropyne) solutions

This study for the first time directs in assessment of the necessary conditions for spinning fibers from poly[1-(trimethylsilyl)1-propyne], one of the best for gas separation. It includes a search of appropriate solvents, investigation of rheological properties of solutions, a preparation of dopes with reasonable polymer content and a choice of effective coagulants based on their solubility parameters in frames of wet fiber spinning. The fibers were obtained with diameter of 7 ± 1 μm and strength of up to 200 MPa. The morphology of the surface and core of the PTMSP fibers was distinctively different: dense skin and friable core. From the viewpoint of membrane properties, it looks like asymmetrical membrane. In addition, the hollow fibers we prepared by dry spinning method. Overall, the stable fiber spinning process from PTMSP solutions was developed for the first time, and monolith and hollow PTMSP fibers of good quality were obtained. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48511.     

Crosslinking poly(1-trimethylsilyl-1-propyne) and its effect on solvent resistance and transport properties

Poly(1-trimethylsilyl-1-propyne) (PTMSP) has been crosslinked using 3,3′-diazidodiphenylsulfone to improve its solvent resistance. This study reports the influence of crosslinker content on the solubility properties of PTMSP, its density, and its gas sorption and transport properties. Crosslinking PTMSP renders it insoluble even in excellent solvents for the uncrosslinked polymer. Gas permeability and fractional free volume (FFV) decreased as crosslinker content increased, while gas sorption was unaffected by crosslinking. Therefore, the reduction in permeability upon crosslinking PTMSP was due to decreases in diffusion coefficients. Permeability reductions due to crosslinking could be offset by adding nanoparticles to the films. The addition of 30 wt.% fumed silica nanoparticles increased the permeability of crosslinked PTMSP by approximately 80%. In mixed gas permeation experiments, when the composition of the feed gas was 98 mol% CH₄ and 2 mol% n-C₄H₁₀, uncrosslinked PTMSP had an n-C₄H₁₀/CH₄ selectivity of 31 and an n-C₄H₁₀ permeability of 114,000 barrers at 35 °C and 14 atm feed fugacity. At the same conditions, crosslinked PTMSP containing 5 wt.% crosslinker had an n-C₄H₁₀/CH₄ selectivity of 28 and an n-C₄H₁₀ permeability of 73,000 barrers, and crosslinked PTMSP containing 5 wt.% crosslinker and 30 wt.% fumed silica nanoparticles had an n-C₄H₁₀/CH₄ selectivity of 21 and an n-C₄H₁₀ permeability of 110,000 barrers.     

Pure and mixed gas CH4 and n-C4H10 sorption and dilation in poly(1-trimethylsilyl-1-propyne)

Pure and mixed gas n-C₄H₁₀ and CH₄ sorption and dilation in poly(1-trimethylsilyl-1-propyne) (PTMSP) are reported at temperatures ranging from −20 to 35 °C. The presence of n-C₄H₁₀ in the mixture considerably reduces CH₄ solubility. For example, CH₄ solubility (in the limit of zero CH₄ fugacity) at 25°C decreases from 4.0 (pure gas) to 0.78 cm³(STP)/(cm³ polymer atm) in the presence of n-C₄H₁₀ at an activity of 0.60. At −20 °C, CH₄ solubility decreases by almost an order of magnitude, from 10.2 (pure gas) to 1.22 cm³(STP)/(cm³ polymer atm) in the presence of n-C₄H₁₀ at an activity of 0.61. In contrast, n-C₄H₁₀ mixture sorption properties are not measurably affected by the presence of CH₄. The dual mode sorption model parameters for CH₄ and n-C₄H₁₀ in PTMSP were determined from pure and mixed gas sorption measurements, and this model can adequately describe the sorption data. The n-C₄H₁₀/CH₄ mixed gas solubility selectivity in PTMSP decreases as temperature increases and as n-C₄H₁₀ activity increases. For example, at 25 °C, the n-C₄H₁₀/CH₄ solubility selectivity decreases from 250 to 120 as n-C₄H₁₀ activity increases from 0.02 to 0.25. At −20 °C and an n-C₄H₁₀ activity of 0.24, the n-C₄H₁₀/CH₄ solubility selectivity is 590. Penetrant-induced volume dilation of PTMSP can be adequately modeled by assuming that all swelling is caused by penetrant molecules sorbed in the polymer's dense equilibrium region (i.e., the Henry's law region) during sorption. However, the best fit partial molar volumes in the Henry's law region for the dilation data are considerably lower than the penetrant partial molar volumes in liquids, suggesting that further theoretical efforts are needed to develop predictive models of volume dilation in high free volume glassy polymers.     

聚1-三甲基硅基-1-丙炔膜的热处理改性

探索了聚１三甲基硅基１丙炔（ＰＴＭＳＰ）膜的热处理与其渗透汽化稳定性的关系．热处理方法可明显改善ＰＴＭＳＰ膜的稳定性．