Oxygen Permselective Membrane Research Articles

A comparative study of membrane reactor and cylindrical reactor using multi-objective optimization for methane reforming process

Multi-objective optimization (MOO) of methane reforming process has been performed for hydrogen and oxygen perm-selective membrane reactor (MR) considering three objectives, namely H2 yield maximization, CO2 minimization and reactor length minimization. The performance of the MR has been compared with that of the cylindrical reactor (CR) using the same objective functions. Four MOO problems have been formulated and solved in this work. Among these, three problems consist of 2-objectives, while one has 3-objectives. Comparative results and discussions of the two reactors are presented based on the multi-objective pareto curve analysis and the trends of decision variables. The results in this work indicate that MR performs better than CR in all the four multi-objective scenarios. We further optimize the reactor with the above mentioned all the three objectives to produce syngas with different (H2/CO) ratios in the product stream. This is especially useful for producing the syngas targeting a specific end application.

Oxygen Permeability of Fully Conjugated Polymers Consisting of (Di)ethynylene and Phenylene Groups Synthesized by Glaser or Sonogashira Coupling Polycondensation

Fully conjugated polymers are candidates as rigid polymers for good oxygen permselective membrane materials. In this study, we synthesized a series of such polymers with a rigid backbone consisting of (di)ethynylene and phenylene groups and alkyl side groups by Glaser or Sonogashira coupling polycondensation. Some of these polymers gave self-supporting membranes and their oxygen permselectivities were influenced by the alkyl groups. Oxygen permselectivities of polymers containing diynes in the main chain were determined for the first time.

Ultrahigh oxygen permeability of chemically-modified membranes of novel (co)polyacetylenes having a photodegradative backbone and crosslinkable side chains

Four new partly modified membranes of novel (co)polyacetylenes having a photodegradative backbone and crosslinkable side chains showed excellent performances as oxygen permselective membranes, that is, ultrahigh oxygen permeability (PO2) with relatively high oxygen permselectivity (α = PO2/PN2). In α vs. PO2 plots, two of them showed a performance close to Robeson's upper bound 2008 and the other two exceeded Robeson's upper bound 1991. The combination of the rigid main chain of the (co)polymers, the regular structure of the supramolecular polymer, and the flexible crosslinking structure may have produced these excellent performances.

Synthesis and oxygen permeation of novel well-defined homopoly(phenylacetylene)s with different sizes and shapes of oligosiloxanyl side groups

Six new silicon-containing phenylacetylenes having short oligosiloxane substituents with different sizes and shapes have been synthesized. Homopolymerization of the monomers yielded the corresponding homopoly(substituted phenylacetylene)s with high molecular weights and good solubility. These comb-shaped homopolymers gave self-standing membranes whose PO2 and PO2/PN2 could be measured. We discuss the effect of the chemical structures on their membrane performances together with the other seven related polymers we synthesized before and commercially available cross-linked polydimethylsiloxane (PDMS). While the homopolymers with linear oligodimethylsiloxanes (ODMS) show very high PO2 values which are higher than PDMS, the homopolymers with branched ODMS show high PO2/PN2 values which are close to that of poly(phenylacetylene) (poly(PA)) and, in addition, had ten times higher PO2 than poly(PA). Introduction of the branched spherical ODMS substituents increases PO2 without any drop of PO2/PN2 and introduction of the linear ODMS substituents increases PO2 largely which is higher than that of PDMS. It was found that the chemical structures, i.e., the shapes of the ODMS substituents were more important than that of composition for determining their performance as oxygen permselective membrane materials. In conclusion, oxygen permeation could be tuned by changing sizes and shapes of the ODMS side groups.

Subnanoporous Highly Oxygen Permselective Membranes from Poly(conjugated hyperbranched macromonomer)s Synthesized by One-Pot Simultaneous Two-Mode Homopolymerization of 1,3-Bis(silyl)phenylacetylene Using a Single Rh Catalytic System: Control of Their Structures and Permselectivities

Novel well-defined complex polymers, polymers of acetylene-type macromonomers having silylene–vinylene–phenylene–ethynylene hyperbranches, investigated as a new class of subnanoporous oxygen permselective membrane materials, were synthesized very easily by one-pot simultaneous two-mode homopolymerization of a single monomer with a single catalyst. For this “simultaneous polymerization” we synthesized AB2-type monomers (1,3-bis(dimethylsilyl)phenylacetylenes) containing one terminal triple bond and two Si–H groups. The resulting poly(hyperbranched macromonomer)s had high molecular weights, low densities, high solubility, and good self-membrane forming ability. They had higher oxygen permselectivities (α = PO2/PN2) than any other reported polymers having similar oxygen permeabilities (PO2). These excellent polymer membranes could be obtained only by the simultaneous polymerization. In the one-pot simultaneous polymerization, the two different modes of polymerizations, i.e., addition polymerization of the tr...

A microbial electrode based on the co-electrodeposition of carboxyl graphene and Au nanoparticles for BOD rapid detection

Biochemical oxygen demand (BOD) is an international regulatory index for evaluating organic water pollution, which requires to be rapidly detected. In this paper, a microbial electrode for rapid BOD sensing has been developed. Carboxyl graphene (GN-COOH) and Au nanoparticles (AuNPs) have been co-electrodeposited on the electrode and microorganisms (Bacillus subtilis) have been immobilized onto the modified electrode through covalent bonding. The modification process has been investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning electron microscope (SEM), fluorescence microscope and Fourier transform infrared spectroscopy (FT-IR). The AuNPs with an average particle size of 30nm are dispersed in the GN-COOH film. The co-electrodeposited film not only facilitates the electron transfer between electrode and reagents, but also creates a biocompatible microenvironment and a rough surface with more sites for cell immobilization. Compared with the traditional BOD electrode including immobilized microbial film and oxygen permselective membrane, the B. subtilis/rGN-COOH-AuNPs/Au electrode simplifies the structure for more effective mass transfer. After modification parameters’ optimization, the response time for detection has been shortened to 3min. The proposed BOD electrode shows a linear range from 2 to 15mg/L, indicating its potential in BOD rapid detection.

Oxygen Permselectivities of Novel Multi-bridged Copolymers Synthesized by Imine Metathesis between N-Imines and C-Imines in the Pendant Groups of Two Poly(substituted acetylene)s

New types of multi-bridged copolymers were designed and examined as oxygen permselective membrane materials. The multi-bridged copolymers were synthesized by imine metathesis reactions between N-imine (synthetic equivalent of amine)-containing poly(substituted acetylene)s and C-imine (synthetic equivalent of aldehyde)-containing poly(substituted acetylene)s in the membrane state. The resulting copolymers maintained good self-membrane forming ability. The introduction of multibridge structures enhanced both oxygen permselectivities and oxygen permeabilities simultaneously.

A single-layer structured microbial sensor for fast detection of biochemical oxygen demand

In this paper, a novel biochemical oxygen demand (BOD) sensor based on a single layer of immobilized microorganisms on electrode for fast detection is investigated. Instead of the previous two-layer structure of oxygen permselective membrane and microorganism membrane, a single layer structure using electrodes as the support for microorganism immobilization has been studied. Amino functional groups on the surface of microorganisms have been bonded with carboxyl modified electrodes. Without extra supports for immobilization, mass transfer resistances are reduced, which facilitates fast current response. Bacillus subtilis cells with high biodegradation ability are obtained after 12h cultivation. The immobilization process has been investigated by CV and EIS. B. subtilis cultivation time, response time and linear range have been optimized. The proposed sensor can reach equilibrium in 5min which has the advantage for real-time BOD determination in the future. The linear range is 5–30mg/l with correlation coefficient of 0.978 and limit of detection of 1.65mg/l.

Preparation and characterization of an oxygen permselective polydimethylsiloxane hollow fibre membrane

Simple preparation of a polydimethylsiloxane (PDMS) hollow fibre air separation membrane by a condensation reaction between the hydroxyl-end groups and hydride groups of polysiloxane reactants over a porous hollow fibre support.

Synthesis of a Fluorine-Containing Cis-Cisoidal One-Handed Helical Polyphenylacetylene and Application of Highly Selective Photocyclic Aromatization Product on Oxygen Permselective Membrane.

A novel phenylacetylene monomer having a perfluorinated alkyl group (M-F) was synthesized and polymerized in a chiral catalytic system to yield a one-handed helical polymer. The ability and efficiency of the chiral induction of the fluorine-containing monomer in the helix-sense-selective polymerization (HSSP) was much higher than those of a monomer having the corresponding alkyl group (M-H) we reported before. The resulting polymer showed cis-cisoidal one-handed helical conformation, and was suitable for highly selective photocyclic aromatization (SCAT) to give a 2D surface modifier (). Oxygen permselectivity through a base polymer membrane was highly enhanced from 1.83 to 2.36 by adding a small amount (1-5 wt%) of the 2D surface modifier . The improvement was thought to be caused by improvement of solution selectivity on the membrane surface which the 2D surface modifier effectively covered.

Synthesis gas production in a novel hydrogen and oxygen perm-selective membranes tri-reformer for methanol production

Tri-reforming is a synergetic combination of carbon dioxide reforming, steam reforming and partial oxidation of methane in a single unit for effective production of synthesis gas. In this study, a novel multi-tubular fixed bed tri-reformer assisted with hydrogen and oxygen perm-selective membranes is proposed for synthesis gas production for methanol synthesis reactor. This reactor can be used instead of conventional steam methane reformer (SMR) and conventional auto-thermal reformer (ATR). A distributed mathematical model is developed for tri-reformer membrane reactor which consists of three sides for synthesis gas production. Air is fed co-currently into the oxygen perm-selective membrane in the inner tube and oxygen permeates into the reaction side for oxidative reforming of methane. Selective permeation of hydrogen via the Pd-based membrane is achieved by co-current flow of sweeping gas through the permeation side. The results of tri-reformer are compared with the corresponding predicted results by HYSIS simulation software under the same feed condition. The superiorities of this novel configuration to optimized tri-reformer without any membrane (Arab Aboosadi, Z., Jahanmiri, A.H., Rahimpour, M.R., 2011. Optimization of tri-reformer reactor to produce synthesis gas for methanol production using differential evolution (DE) method. Appl. Energy. 88, 2691–2701) are in-situ oxygen production (44.7% saving in supplying oxygen from external), high methane conversion and hydrogen yield at lower reactant input temperature and reduction of hot spot temperature in the catalytic bed.

Oxygen Permselective Membranes from DNA-Lipid Complexes

Oxygen Permselective Membranes from DNA-Lipid Complexes

Steady-state modeling and bifurcation behavior of circulating fluidized bed membrane reformer–regenerator for the production of hydrogen for fuel cells from heptane

The production of hydrogen for fuel cells by steam reforming of heptane is investigated in a Circulating Fluidized Bed Membrane Reformer-Regenerator ( CFBMRR) system (A.I.Ch.E. Journal 49(5) (2003) 1250). Palladium based hydrogen permselective membranes are used for hydrogen removal and dense perovskite oxygen permselective membranes are used for oxygen introduction. A series of pseudo-steady-state simulations show that when the catalyst is not regenerated, the circulating nickel reforming catalyst deactivates quickly and the “half catalyst activity life” for efficient production of hydrogen is quite short, especially at high temperatures. Efficient continuous catalyst regeneration can keep the catalyst activity high ( ∼ 1.0 ) . With continuous catalyst regeneration, autothermal operation for the entire adiabatic reformer–regenerator system is achievable when the exothermic heat generated from the catalyst regenerator is sufficient to compensate for the endothermic heat consumed in the riser reformer. This type of autothermal operation becomes less likely at high steam to carbon feed ratios. This is due to the fact that carbon deposition rate decreases leading to the decrease of autothermal circulating feed temperature and energy-based hydrogen yield (adiabatic hydrogen yield in autothermal reformer–regenerator system). Multiplicity of the steady states for the reformer is possible for this configuration. With the steam to carbon feed ratio as the bifurcation parameter, multiplicity occurs between the two bifurcation points 1.444 and 2.251 mol/mol. In this multiplicity region, the energy-based hydrogen yield at the upper steady state with high regenerator output temperature is surprisingly the lowest one. While it is the highest one at the lower steady state with low regenerator output temperature. The maximum energy-based hydrogen yield is about 15.58 moles of hydrogen per mole of heptane fed at the lower steady-state when steam to carbon feed ratio is very close to the bifurcation value of 1.444 mol/mol. After removing the sweep gas steam by downstream cooling and de-humidification, the product hydrogen from steam reforming of hydrocarbons can be used for fuel cells with high purity ( ∼ 100 % ) .

Development of a Novel Reactor Concept for the Partial Oxidation of Methane to Syngas

The gas-to-liquid process, consisting of the partial oxidation of methane (POM) followed by the Fischer–Tropsch reaction, is a promising alternative to conventional oil processing for the production of liquid fuels. The cost of a conventional POM process is mainly determined by cryogenic air separation and could be greatly reduced by using oxygen permselective perovskite membranes instead. These membranes operate at temperatures similar to POM processes and can thus be integrated into a catalytic membrane reactor. To investigate the implications of this integration an adiabatic thermodynamic analysis has been carried out for both oxygen- and air-based POM processes, focusing on the influence of the feed temperature and composition on the syngas yield and quality. This analysis revealed that much higher feed temperatures are required for air-based POM processes to reach similarly high syngas yields. Because the Fischer–Tropsch reaction is carried out at much lower temperatures, recuperative heat exchange becomes essential for air-based POM processes. This is preferably carried out inside the reactor using the reverse flow concept, since external heat transfer at elevated temperatures is expensive. To combine the POM reaction, air separation and recuperative heat exchange into a single apparatus a reverse-flow catalytic membrane reactor (RFCMR) is proposed.

Modelling of a Reverse Flow Catalytic Membrane Reactor for the Partial Oxidation of Methane

Gas-To-Liquid (GTL) processes have great potential as alternative to conventional oil and coal processing for the production of liquid fuels. In GTL-processes the partial oxidation of methane (POM) is combined with the Fischer-Tropsch reaction. An important part of the investment costs of a conventional GTL-plant is related to cryogenic air separation. These costs could be substantially reduced by separating air with recently developed oxygen perm-selective perovskite membranes, which operate at similar temperatures as a POM reactor. Integration of these membranes in the POM reactor seems very attractive because oxygen reacts at the membrane surface resulting in a high driving force over the membrane increasing the oxygen permeation.Because the POM-reaction is only slightly exothermic, the natural gas and air feed have to be preheated to high operating temperatures to obtain high syngas yields and because the Fischer-Tropsch reactor operates at much lower temperatures, recuperative heat exchange is essential for an air-based POM process. External heat transfer at elevated temperatures is expensive and therefore recuperative heat exchange is preferably carried out inside the reactor, which can be achieved with the reverse flow concept. To combine the POM reaction, air separation and recuperative heat exchange in a single apparatus a novel, multi-functional reactor is proposed, called the Reverse Flow Catalytic Membrane Reactor (RFCMR). In this reactor a relatively uniform temperature profile should be established at the membrane section and the temperature fronts should be located in the inert in- and outlet sections.To study the RFCMR concept, reactor models have been developed assuming a shell-and-tube geometry, based on models that are commonly used to describe conventional reverse flow reactors. Simulations of the novel reactor concept revealed that a small amount of methane has to combusted on the air side to create the reverse flow behaviour. Also a small amount of steam has to be injected distributively along the perovskite membrane section to maintain the centre of the reactor at nearly isothermal conditions. With these modifications it was found that the desired temperature profile could indeed be created in the RFCMR and that high overall syngas yields can be achieved.

Highly Oxygen Permselective Membrane of Cobalt-Complexed Polyazomethine Containing Tridentate Ligand and Oligosiloxane in the Repeating Pairs of the Main Chain

Highly Oxygen Permselective Membrane of Cobalt-Complexed Polyazomethine Containing Tridentate Ligand and Oligosiloxane in the Repeating Pairs of the Main Chain

Highly oxygen permselective membrane prepared from cobalt‐complexed polyazomethine containing a ligand and a tri‐ or tetrasiloxane in the main chain

AbstractTwo types of polyazomethines containing repetitive pairs of a tridentated ligand and an oligodimethylsiloxane in the backbone were synthesized and complexed with cobalt ion. The resulting polymer complex membranes showed very good oxygen permselectivity at 1 atm pressure difference, which is very close to the upper boundary line in an α vs. Po2 plot of data reported in the literature. The complexes are thought to function as oxygen carrier.

Poly(p-substituted phenylacetylene) with perfluoroalkyloxydimethylsilyl side groups for oxygen and ethanol permselective membrane

p-(1H,1H,2H,2H-perfluorodecyloxydimethylsilyl)phenylacetylene(ACf8) and p-(1H,1H,2H,2H-Perfluorohexyloxydimethylsilyl)phenylacetylene(ACf4) were synthesized and copolymerized with p-trimethylsilylphenylacetylene(ASi). The resulting copolymers, copoly(ACf8/ASi) and copoly(ACf4/ASi), were fabricated to tough membranes showing high oxygen permeabilities(Po2) of 10-8 cc(STP)·cm/cm2·s·cmHg and high oxygen permselectivities(α=Po2/Pn2) of more than 2.7. In particular, a copoly(ACf4/ASi) containing 15.1 mol% of ACf4 unit showed the best result: Po2=3.51x10-8 cc(STP)·cm/cm2·s·cmHg and α=3.04. The values were in a top level and very close to those of ‘upper bound’ line in an α-Po2 plot of data in the literature. In addition, copoly(ACfn/ASi) membranes were ethanol permselective owing to water repellency of the perfluoroalkyl groups. Copoly(ACf4/ASi) membranes showed better oxygen and ethanol permselectivity than copoly(ACf8/ASi) membranes.

末端にアルコキシシリルスチレンを持つパーフルオロアルカンの合成，重合と得られたポリマーの酸素及びエタノール選択透過膜への利用

末端にアルコキシシリルスチレンを持つ2種のパーフルオロアルカンを合成, 重合し, 酸素及びエタノール選択透過膜への利用を検討した. p- (1H, 1H, 2H, 2H-パーフルオロアルキルオキシジメチルシリル) スチレンをバルク共重合することにより丈夫な膜を得ることができ, この膜は優れた酸素選択透過性を有していた (α=3.36, PO2=6.99×10-9cc (STP) ・cm/cm2・s・cmHg). このポリマーを少量架橋ポリジメチルシロキサン (PDMS) に添加した膜は高いエタノール選択透過性を示した (αEtOH=22.3, P=2.06×10-2g・m/m2・h). いずれもパーフルオロアルキル基の性質が透過に効果的に生かされた結果であると考えられた. またp- (1H, 1H, 2H, 2H-パーフルオロアルキルジアルコキシシリル) スチレンのパーフルオロアルキル基の性質とアルコキシキ基の反応を生かしてPDMS膜の酸素選択透過性を改善することができた.

Novel organosilicon‐containing polymers for an oxygen permselective membrane

AbstractSynthesis and gas permeation measurements of several types of polymers from methylstyrene derivatives containing mono‐and bis(trialkylsilyl) group(s) were carried out. Upon radical homo‐and co‐polymerization of silicon‐containing monomers high‐molecular‐weight polymers were obtained. Results from gas permeation measurements showed that these types of silicon‐containing polymers exhibit fairly high oxygen permselectivity (ratio of oxygen and nitrogen permeation coefficients P/P = 3,1 − 4,6), keeping the oxygen permeation coefficients (P) in the range of between 1,4 · 10−9 and 4,5·10−9 cm3 (STP) · cm · cm−2 · s−1 · cmHg−1. From time lag measurements, it was found that permeation coefficients are dependent on the solubility of gases in the membranes rather than on diffusivity. Actually, the oxygen solubility coefficients increase with increasing silicon content in the polymers. Permselectivity of oxygen against nitrogen is governed by polymer constitution rather than by silicon content.