Development of CO2 Selective Poly（Ethylene Oxide）-Based Membranes： From Laboratory to Pilot Plant Scale

Membrane gas separation is one of the most promising technologies for the separation of carbon dioxide （CO2） from various gas streams. One application of this technology is the treatment of flue gases from combustion processes for the purpose of carbon capture and storage. For this application, poly（ethylene oxide）-containing block copolymers such as Pebax or PolyActiveTM polymer are well suited. The thin-film composite membrane that is considered in this overview employs PolyActiveTM polymer as a selective layer material. The membrane shows excellent CO2 permeances of up to 4 m^3（STP）.（m^2·h·bar）^-1 （1 bar = 105 Pa） at a carbon dioxide/nitrogen （CO2/N2） selectivity exceeding 55 at ambient temperature. The membrane can be manufactured reproducibly on a pilot scale and mounted into fiat-sheet membrane modules of different designs. The operating performance of these modules can be accurately predicted by specifically developed simulation tools, which employ single-gas permeation data as the only experimental input. The performance of membranes and modules was investigated in different pilot plant studies, in which flue gas and biogas were used as the feed gas streams. The investigated processes showed a stable separation performance, indicating the applicability of PolyActiveTM polymer as a membrane material for industrialscale gas processing.

A hybrid zeolitic imidazolate framework Co-IM-mIM membrane for gas separation

A zeolitic imidazolate hybrid membrane(Co-IM-mIM) containing two imidazolate ligands deposited on a macroporous α-alumina support was prepared by pre-depositing and secondary growth technique. XRD, TGA and SEM characterizations demonstrate that a stable and thin, but dense and pure-phase Co-IM-mIM membrane can be obtained on the macroporous-alumina discs in Teflon-lined autoclave at 120 °C after pre-depositing by dip-coating at room temperature. No visible cracks, pinholes or other defects were observed on the membrane layer. The gas separation studies of Co-IM-mIM membrane were carried out at 25 °C and 1×10~5 Pa, showing ideal selectivity of 6.95, 5.25, 3.40 for H_2/CO_2, H_2/N_2 and H_2/CH_4, respectively, and a permeance of 17.37× 10^(-6) mol/(m^2·s·Pa) for H_2. The influence of temperature and trans-membrane pressure on hydrogen separation and permeation was also carried out. The gas permeation and selectivity demonstrate that this membrane may have potential applications for efficient H_2 separation.

Nicotinamide Adenine Dinucleotide and Adenosine Triphosphate Oscillations Caused by Gradual Entry of Substrates within Mitochondria

Nicotinamide adenine dinucleotide (NAD) oscillation was observed when the isolated mitochondria were immersed in a pyruvate solution. In addition, when an adenosine diphosphate (ADP) was added to the mitochondrial suspension containing pyruvate, adenosine triphosphate (ATP) oscillation was observed as well as NADH oscillation. At this time, the pH within mitochondria also oscillated. It was found that the oscillatory reaction of NADH caused by the membrane permeation of pyruvate continues, causing the oscillation of NADH and H+ in the subsequent reactions. The pH oscillation led to the ATP oscillation. It is considered that the oscillatory reaction caused by the gradual entry of pyruvate into mitochondria was thought to be carried over to both the citric acid cycle and the respiratory chain, ultimately leading to the ATP oscillation in oxidative phosphorylation. Similarly, it was found that membrane permeation of malate causes the gradual occurrence of NADH, at which point NADH oscillates, followed by an oscillatory reaction of the respiratory chain, and finally ATP oscillation. It was found that the oscillations of NADH and ATP occur without going through the citric acid cycle. Oscillations of NADH and other intermediates in both the citric acid cycle and respiratory chain were also confirmed by experiments using semipermeable membranes. These results support our hypothesis that the gradual entry of the substrate by membrane permeation triggers an oscillatory reaction of the enzyme, which is also carried over to subsequent reactions.

Enhanced Oxidative Coupling of Methane with Oxygen Permeation Membrane

Oxidative coupling of methane to ethylene is of high importance to the future of light olefin industry.However,the carbon atom efficiency is normally below 50%in gas phase reaction which is limited to the overoxidation of methane to carbon dioxide with oxidants.Here we present an alternative approach of electrochemical oxidation of methane in an oxygen permeation membrane reactor and show the highest conversion of methane and C2 selectivity of 28%and 40.2%at 1150℃,respectively.We prepare the 100-μm-thick perovskite(La0.8 Sr0.2)1-x Cr0.5 Fe0.5 O3-δ(LSCrF)dense membrane(La0.8 Sr0.2)1-xCr0.5 Fe0.5O3-δ(LSCrF–Fe)(x=0,0.02,0.05 and 0.10)scaffolds while the excess of Fe would be exsolved on porous skeleton to create metal-oxide interfaces toward methane oxidation.The metal-oxide interfaces not only facilitate the activation of C–H bond in methane but also enhance the coking resistance.

Cobalt-free gadolinium-doped perovskite Gd_xBa_(1-x)FeO_(3-δ) as high-performance materials for oxygen separation

Cobalt-free oxides GdxBal-xFeO3-σas（0.01 _〈 x _〈 0.1 ） were achieved by a solid state reaction method. It is found that GdxBal-xFeO3-σas（0.025 _〈 x _〈 0.1） exhibits the cubic perovskite structure. Among GdxBal-xFeO3-σas （0.025 -〈 x -〈 0.1 ）, the GdxBal-xFeO3-σas （GBF2.5） membrane shows the outstanding phase structure stability and the highest oxygen permeation, which can reach 1.44 ml. cm- 2. rain- 1 at 950 ℃ under air/He oxygen partial pressure gradient. The GBF2.5 membrane was successfully operated for more than 100 h at 800 ℃ and the oxygen permeation flux through the membrane is 0.62 ml. cm- 2. rain- 1. After 100 h oxygen permeation experiment at 800℃, X-ray diffraction （XRD） and energy dispersive X-ray spectrometer （EDXS） demonstrate that the GBF2.5 exhibits phase structure stability even at intermediate temoerature.

A CO and CO2 tolerating (La0.9Ca0.1)2(Ni0.75Cu0.25)O4+δ Ruddlesden-Popper membrane for oxygen separation

A series of novel dense mixed conducting ceramic membranes based on K2NiF4-type(La1-xCax)2(Ni0.75Cu0.25)O4+δwas successfully prepared through a sol-gel route.Their chemical compatibility,oxygen permeability,CO and CO2 tolerance,and long-term CO2 resistance regarding phase composition and crystal structure at different atmospheres were studied.The results show that higher Ca contents in the material lead to the formation of CaCO3.A constant oxygen permeation flux of about 0.63 mL·min−1·cm−2 at 1173 K through a 0.65 mm thick membrane was measured for(La0.9Ca0.1)2(Ni0.75Cu0.25)O4+δ,using either helium or pure CO2 as sweep gas.Steady oxygen fluxes with no sign of deterioration of this membrane were observed with increasing CO2 concentration.The membrane showed excellent chemical stability towards CO2 for more than 1360 h and phase stability in presence of CO for 4 h at high temperature.In addition,this membrane did not deteriorate in a high-energy CO2 plasma.The present work demonstrates that this(La0.9Ca0.1)2(Ni0.75Cu0.25)O4+δmembrane is a promising chemically robust candidate for oxygen separation applications.