Tubular Support Research Articles

Preparation of CHA zeolite (chabazite) crystals and membranes without organic structural directing agents for CO2 separation

CHA zeolite (chabazite) crystals and membranes were prepared from organic structural directing agents-free (OSDA-free) gels. Chabazite membranes were grown on the tubular alumina supports. The effect of cesium and fluoride salts on the crystallization of chabazite crystals and membranes were investigated. Highly crystalline chabazite and uniform chabazite membranes were only obtained from the gel containing the cesium and fluoride salts. Single CO2, N2 and CH4 permeances and mixed gas separations in CO2/N2 and CO2/CH4 binary mixtures through chabazite membranes were measured. Temperature and pressure affected the permeances and separation selectivities in two mixtures. The best membrane showed CO2/N2 and CO2/CH4 separation selectivities as high as 16 and 46 together with CO2 permeances of ~ 1.0 × 10-7 mol/(m2 s Pa) at a high temperature of 473 K in equimolar dry CO2/N2 and CO2/CH4 binary mixtures, respectively. The CO2/N2 and CO2/CH4 selectivities lost only 11% and 15%, and CO2 permeances lost only 18% and 20% in equimolar wet CO2/N2 and CO2/CH4 mixtures (8% in mole of water vapor) at 473 K compared to these values in dry mixtures, respectively. The OSDA-free chabazite membranes were hydrothermally stable in the presence of vapor water for 4 d at 378 K.

RETRACTED: Enhanced gas separation performance using carbon membranes containing nanocrystalline cellulose and BTDA-TDI/MDI polyimide

This paper presents the derivation of carbon membranes from BTDA-TDI/MDI polyimide (PI) prepared via a dip-coating technique on an inorganic tubular support surface, followed by a heat treatment (stabilization and carbonization) under N2 gas flow. In order to enhance the gas separation performance of the resultant carbon membrane, a synthesized nanocrystalline cellulose (NCC) using tissue paper as an additive was added into the dope solution at various carbonization temperatures of 600, 700, 800, and 900 °C. The NCC was prepared by extracting the unprinted area of a newspaper and was processed as an additive in the polymer solution. The chemical structure, morphological structure, and gas permeation properties of the resultant membrane were analyzed. Special attention was given to the physicochemical characteristics of the resulting PI/NCC-based carbon membrane and its corresponding gas permeation properties. Pure gas permeation tests were performed using CO2, CH4, O2, and N2 at room temperature. The gas permeation data demonstrated that the carbon membrane exhibited an excellent performance compared to the polymeric membrane. Enhancement in both gas permeance and selectivity were observed in the NCC-containing carbon membranes prepared at carbonization temperature of 800 °C, with the CO2/CH4 selectivity of 68.2 ± 3.3, the CO2/N2 selectivity of 66.3 ± 2.2, and the O2/N2 selectivity of 9.3 ± 2.5, with respect to the neat carbon membrane. By manipulating various carbonization temperatures, carbon membranes with different structures and properties were obtained.

Resistance of tubular piles shear silk along surfaces

The results of piles tests in sea muddy soils underlain by loams and clays are presented at port berths in Odessa region. Piles length 28.0 and 34.0 m have been made of metal pipes with a diameter of 1400 mm with a wall thickness of 16 mm. From the sea water surface to the silt roof is 15.0 m. The lower end of the two tubular supports (piles) has been located above the silt sole that enables the test piles to be brought to "breakdown" and determine its resistance (silt) along the outer and inner surfaces. According to the test results, the piles are increased by 6 m that enables to use the underlying soils as a bearing layer. Tests of piles have been carried out according to the standard procedure, for the reference system, two additional tubular supports with a diameter of 1400 mm were placed in the vicinity of the test subjects.

Propylene-Selective Thin Zeolitic Imidazolate Framework Membranes on Ceramic Tubes by Microwave Seeding and Solvothermal Secondary Growth

Zeolitic imidazolate framework (ZIF-8) membranes have attracted tremendous interest for their high-resolution kinetic separation of propylene/propane mixtures. Current polycrystalline ZIF-8 membranes are supported mostly on planar ceramic substrates (e.g., alumina disks) because of their high thermal, chemical, and mechanical stabilities and facile manufacturing in the labs. Planar supports are, however, not scalable for practical separation applications owing to their low packing density (typically 30–500 m2/m3). On the other hand, ceramic tubes provide order-of-magnitude higher packing densities than planar supports (i.e., much higher membrane areas per module). Here, we report polycrystalline ZIF-8 membranes with thicknesses of ~1.2 μm grown on the bore side of commercially-available ceramic tubes using the microwave seeding and secondary growth technique. The tubular ZIF-8 membranes showed excellent propylene/propane separation factors of ~80, exceeding all currently-reported ZIF-8 membranes on ceramic tubes. It was found that the secondary growth time was critical to enhance the propylene/propane separation factor of the membranes. Membranes were also grown on the shell side of tubular supports, showing the versatility of our technique.

Regeneration of Trachea Graft with Cartilage Support, Vascularization, and Epithelization

The repair and functional reconstruction of long-segment tracheal defects is always a great challenge in the clinic. Finding an ideal substitute for tracheal transplantation is the only way to solve this problem. To address these problems, the current study proposed a series of novel strategies. For large-volume cartilage regeneration, a cartilage sheet technique (without any extra materials) was adopted to avoid the inflammatory reaction triggered by the materials and form homogeneous, mature cartilage in autologous goat model. For vascularization, the flat trapezius fascia flap with double blood supply was separated by microsurgical techniques to achieve stable pre-vascularization of the regenerated cartilage and grafted epithelium simultaneously. Finally, transplantation of the oral mucosal epithelium was used to realize epithelialization. By integrating the above strategies, a vascularized and epithelialized tracheal tissue with tubular cartilage support was successfully constructed in a goat model, which provides an ideal tracheal substitute for the repair and permanent functional reconstruction of long-segment tracheal defects. Funding: This research was supported by The National Key Research and Development Program of China (2017YFC1103900), The Key Research and Development Program of Shandong (2016GGB14002), National Natural Science Foundation of China (31400830, 31700837 and 81571823), Shanghai Science and Technology Committee (16QB1400600), and Program for Shanghai Outstanding Medical Academic Leader, Graduate Student Innovation Fund of Shanghai Jiao Tong University School of Medicine (BXJ201831, to Zongqi Yin.), and PUMC Youth Fund and the Fundamental Research Funds for the Central Universities (3332014047). Declaration of Interest: We declare that we have no conflicts of interest. Ethical Approval: Animal experiments were approved by the Shanghai Jiao Tong University Committee on Animal Care and were conducted by the Key Laboratory of Tissue Engineering at Shanghai Ninth People’s Hospital, affiliated with Shanghai Jiao Tong University in China. All experiments involving animals were performed in accordance with the approved guidelines.

Exploiting pyrolysis protocols on BTDA‐TDI/MDI (P84) polyimide/nanocrystalline cellulose carbon membrane for gas separations

ABSTRACTTubular carbon membranes were fabricated by the blending of BTDA‐TDI/MDI (P84) polyimide with nanocrystalline cellulose in a controlled pyrolysis process, specifically the pyrolysis environment (He, Ar, and N2) and the thermal soak time (30–120 min). The carbon membrane layer on a tubular support is converted to carbon matrix at 800 °C with a heating rate of 3 °C min−1. The effects of these controlled pyrolysis conditions on the gas permeation properties have been investigated. The results revealed that the pyrolysis under Ar gas environment at 120 min of thermal soak time have the best gas permeation performance with the highest CO2/CH4 selectivity of 68.2 ± 3.3 and CO2 permeance of 213.6 ± 2.2 GPU. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 46901.

Mechanism and application of concrete-filled steel tubular support in deep and high stress roadway

The concrete-filled steel tubular (CFST) support has been proposed as a new passive support form for controlling the stability of surrounding rock in deep roadway. To explore the mechanism of CFST support in deep roadway, the mechanical performances of U-steel support and CFST support were compared by theoretical calculation and numerical simulation with the engineering background of 11031 ventilation roadway in Pingmei coal mine. Then, the section shape of CFST was optimized and the special-shaped CFST support was put forward. The special-shaped CFST support was applied to 11031 ventilation roadway of U36-steel support failed to control. The results indicate that: The ultimate bearing capacity of CFST support is much greater than that of U-steel support. The CFST support can provide great supporting force to the roof-floor and two sides of roadway. It can be applied to the roadway with large horizontal stress. The section bending modulus and ultimate bearing capacity of the special-shaped CFST support are greater than those of the circular CFST support. The displacements of 11031 ventilation roadway supported by the special-shaped CFST support was not great. So, the special-shaped CFST support can effectively control the surrounding rock in 11303 ventilation roadway.

Influence of intermediate layers in tubular carbon membrane for gas separation performance

The main objective of this study is to determine the best intermediate layer for tubular carbon membranes for H2 and He separation. Intermediate layer was applied to strengthen interfacial adhesion between selective carbon layers and tubular support. Three different intermediate layers (alumina powder, carbon molecular sieve (CMS), and carbon pencil) had been evaluated to compare their influence towards the performance of gas separation of the carbon membrane. Tubular carbon membrane was fabricated from PI/NCC-based polymer blends which had been carbonized under Argon atmosphere at 800 °C with a heating rate of 3 °C/min. Based on the scanning electron microscopic (SEM) observations, carbon membrane with alumina powder as an intermediate layer had formed a smoother surface compared to other types of intermediate layers. A high performance of tubular carbon membrane was obtained by employing alumina powder as an intermediate layer, which exhibited the best selectivity of H2/N2 and He/N2 of 447.31 ± 1.45 and 471.72 ± 2.19, respectively.

Silica Membranes for Wetland Saline Water Desalination: Performance and Long Term Stability

In this study, silica thin film pH=6 (precursor TEOS:tetraethyl ortosilicate) developed from sol gel process and deposited (2 layers) directly onto alumina substrate(tubular support with 100 nm pore size) without depositing interlayer (interlayer-free).Then, the desalination process via pervaporation was applied to test the membranesperformanceusing artificial saline water and wetland saline water. Results show the decrease of water flux (1.9 to 1.43 kg m-2 h-1) and salt rejection(97 to 95%) when using artificial salty water (0-7.5 wt%) and the long-term stability of silica membrane was stable at 1.7 kg m-2 h-1 for over 100 hours when using wetland saline water as a feed.

Fabrication of high performance macroporous tubular silicon carbide gas filters by extrusion method

Hot gas filtration requires high performance tubular filters, but low permeability, low strength, and high sintering temperature of silicon carbide (SiC) filters limit their use. In this work, a high permeability tubular SiC support was fabricated with high strength at a sintering temperature of 1200 °C, when 100 µm SiC particles were used as aggregate, sodium dodecyl benzene sulfonate (SDBS) was used as sintering aid and organic additives were used as binders. Plasticity of the mixed particles was optimized by adjusting the ratios of methylcellulose, paraffin, and glycerol. The porosity, pore diameter, gas permeation coefficient, and bending strength of the SiC ceramic support reached 45.0%, 34.2 µm, 4.6 × 10–12 m2, and 22.8 MPa, respectively. Furthermore, compared to the cold isostatic pressure (CIP) technique, the extrusion method led to sharper peak of the pore diameter distribution, achieved higher bending strength, and had a more homogeneous microstructure.

Impact of stabilization environment and heating rates on P84 co-polyimide/nanocrystaline cellulose carbon membrane for hydrogen enrichment

These past few decades, the separation of various gas mixtures problems in order to obtain high purity gases can be overcome by the introduction of membrane-based technology. This current research was focusing on the development of tubular carbon membranes (TCMs) from polymeric precursors for the separation of hydrogen and nitrogen. The fabrication of TCMs involved the dip coating technique and was using P84 co-polyimide as the main precursor by blending of nanocrystaline cellulose (NCC) as an additive. It was believed a slight adjustment on time, temperature, or environment of the carbonization protocol for the commercially available PI/NCC membranes can alter the final properties of the carbons produced. The modifications on the carbonization parameters such as stabilization conditions and heating rates during fabrication of PI/NCC-based carbon membranes could also affect their gas separation performance. A large variety of TCMs for gas separation have been developed by simple carbonization of a PI/NCC deposited on a ceramic tubular support. Herein, in this study, the effect of different heating rates (1, 3, 5, and 7 °C/min) and stabilization environment (Argon, Nitrogen, and Helium) were investigated for all resultant TCMs. As a result, it was observed that stabilization under Argon environment with heating rate of 3 °C/min produced carbon membranes with the best H2/N2 separation and the highest selectivity of 434.68 ± 1.39, respectively.

Iono-molecular Separation with Composite Membranes V. Nitro-phenol separation on n-alkyl alcohols supported liquid membranes

In this work are ongoing recent related studies on the separation of nitrophenols by composite membranes using this time an HFCLM membrane based on n-lower alkyl alcohols (C6, C8 si C10) on a well-characterized tubular polypropylene support . The results of nitrophenol separation, at a concentration of 5 mg / L in the source phase of pH 4.8, indicate the following optimal parameters of hydrodynamic regime, solvent and pH: source phase flow of 4.0 L / min, receiver phase rate 0.3 L / min; n-octanol, membrane solvent; the pH of the receiving phase that ensures maximum separation efficiency between 10 and 11; pH that ensures selective separation of m- and p-nitrophenols from m-nitrophenol between 8 and 10.The efficiency of nitrophenol separation through polypropylene capillary polymeric n-alcohol composite membranes reaches more than 90% at established working conditions, but operation below pH 12 will be considered in order not to cause membrane instability on the support.

Corrosion behavior analyses of metallic membranes in hydrogen iodide environment for iodine-sulfur thermochemical cycle of hydrogen production

HI decomposition in Iodine-Sulfur (IS) thermochemical process for hydrogen production is one of the critical steps, which suffers from low equilibrium conversion as well as highly corrosive environment. Corrosion-resistant metal membrane reactor is proposed to be a process intensification tool, which can enable efficient HI decomposition by enhancing the equilibrium conversion value. Here we report corrosion resistance studies on tantalum, niobium and palladium membranes, along with their comparative evaluation. Thin layer each of tantalum, palladium and niobium was coated on tubular alumina support of length 250 mm and 10 mm OD using DC sputter deposition technique. Small pieces of the coated tubes were subject to immersion coupon tests in HI-water environment (57 wt% HI in water) at a temperature of 125–130 °C under reflux environment, and simulated HI decomposition environment at 450 °C. The unexposed and exposed cut pieces were analyzed using scanning electron microscope (SEM), energy dispersive X-ray (EDX) and secondary ion mass spectrometer (SIMS). The extent of leaching of metal into liquid HI was quantified using inductively coupled plasma-mass spectrometer (ICP-MS). Findings confirmed that tantalum is the most resistant membrane material in HI environment (liquid and gas) followed by niobium and palladium.

Influence of Anode Functional Layers on Electrochemical Performance and Mechanical Strength in Microtubular Solid Oxide Fuel Cells Fabricated by Gel-Casting

Anode-supported microtubular solid oxide fuel cells (mT-SOFCs) using samaria-doped ceria (SDC) as electrolyte were fabricated, varying the composition and number of anode functional layers (AFLs), by combining the aqueous gel-casting and spray-coating techniques. Suitable aqueous slurry formulation of NiO–SDC was prepared using agarose as a gelling agent for gel-casting of tubular supports. Afterward, 40:60 and 50:50 NiO:SDC (wt %) as AFLs and SDC electrolyte were deposited by spray-coating and subsequently co-sintered. Finally, mT-SOFCs with 2.5 mm outer diameter and thicknesses of 380 μm support; 0, 12, and 24 μm AFLs; 15 μm electrolyte; and 30 μm cathode were obtained. The influence of AFLs on the performance and mechanical integrity was investigated for the three cells. For this purpose, electrochemical and mechanical tests at both macroscopic and micro-/nanometric scales (at the AFLs region) were determined by flexural strength and nanoindentation techniques, respectively. The results evidence that t...

Decolorization of Dyeing Effl uent by Novel Ultrafi ltration Ceramic Membrane from Low Cost Natural Material

This paper is devoted to the application of new low cost ceramic ultrafi ltration membranes material coming from the Tunisian ores (mud) which is usually considered as disastrous for the environment. A ceramic tubular support previously elaborated from mud was coated in the lumen side by slip casting method. After sintering at 650°C, the coated membrane shows homogeneous layer without cracks, with a pore diameter of 11 nm. The coating has the thickness of ~9 µm and water permeability of the prepared membrane is 90 L/h.m2.bar. Then the prepared membrane has been applied for treating of dyeing wastewater under 5 bar pressure. The result was interesting with a permeate fl ux of 65 l/h.m2, pollutants retention rate of 90% for COD and almost a total retention of turbidity and color, respectively. The membrane can then be regenerated by using a chemical washing.

MgO as a non-pyrolyzable pore former in porous membrane supports

The gas permeability of Y0.03Zr0.97O2 (3Y-TZP) porous supports from thermoplastic feedstocks has been improved by adding MgO as a non-pyrolyzable pore former. Common pyrolyzable pore formers such as graphite often produce tortuous and narrow pore channels with low gas permeability, limiting the performance of oxygen transport membranes or other membranes relying on gas transport to the active membrane surface. Thermoplastic feedstocks for extrusion of tubular 3Y-TZP supports were prepared with four different amounts of pyrolyzable pore formers and/or MgO as non-pyrolyzable pore former. The MgO was removed after sintering by leaching in acetic acid. With this technique we obtained porosities above 70 vol% and gas permeabilities above 3∙10−14 m2. Compared to samples with only pyrolyzable pore formers, the non-pyrolyzable pore former increases the gas permeability and reduces the tortuosity.

Performance evaluation of graphene oxide (GO) nanocomposite membrane for hydrogen separation: Effect of dip coating sol concentration

In recent years, molecular-sieve graphene oxide (GO) membranes have shown a great potential to realize high-flux and high-selectivity mixture separation, at low energy cost. Hence, in this study, GO nanocomposite membranes were prepared for hydrogen separation. To this purpose, the modified tubular γ-alumina supports were prepared by coating boehmite sol on α-alumina support. Then, the GO top layer was coated on the modified γ-alumina support using GO colloidal sol prepared by modified hummer method. Consequently, effects of various concentrations of dip-coating sol were evaluated on GO graphene membrane performance, in terms of hydrogen separation at various pressure gradient and temperatures. Regarding to characterization analyses, uniform GO layer formation was confirmed on modified support. As a result of gas permeance test of GO nanocomposite membrane, pressure gradient effect was positive on membrane performance, while negative effect on H2/CO2 and H2/N2 selectivities was indicated versus lowest concentration of dip coating sol. On the other, for all cases, negative effect was observed for hydrogen selectivity versus temperature. In particular, for the best GO membrane sample, at room temperature and 3 bar pressure gradient, H2/CO2 and H2/N2 values were obtained 38.5 and 16.5 (H2 permeance equal 5.9 ∗ 10−7 mol/m2 s Pa), respectively, while these parameters values at 473 K and 1 bar pressure gradient were 15.7, 10.6 (H2 permeance equal 7.6 ∗ 10−7 mol/m2 s Pa). Moreover, regarding to effects of dip-coating sol concentration, the best choice was introduced sample 1 (with highest concentration of dip coating sol) from performance viewpoint.

ZnO Nanorod-Induced Heteroepitaxial Growth of SOD Type Co-Based Zeolitic Imidazolate Framework Membranes for H2 Separation.

Up to now, the fabrication of well-intergrown Co-based zeolitic imidazolate framework (ZIF) membranes on porous tubular supports is still a major challenge. We report here a heteroepitaxial growth for preparing well-intergrown Co-based ZIFs (ZIF-67 and ZIF-9) tubular membranes with high performance and excellent thermal stability by employing a thin layer of ZnO nanorods acting as both nucleation centers and anchor sites for the growth of metal-organic framework membranes. The results show that well-intergrown Co-ZIF-67 and Co-ZIF-9 membranes are successfully achieved on the ZnO nanorod-modified porous ceramic tubes. This highly active heteroepitaxial growth may be attributed to the fact that the (Zn,Co) hydroxy double salt intermediate produced in situ from ZnO nanorods acts as heteroseeds and enables the uniform growth of Co-based membranes. The H2/CO2 selectivity of the as-prepared Co-ZIF-9 tubular membrane could reach about 23.8 and the H2/CH4 selectivity of Co-ZIF-67 tubular membrane is as high as 45.4. Moreover, the membranes demonstrate excellent stability because of the ZnO nanorods as linkers between the membrane and substrate.

Pore plugging synthesis and characterization of silicalite‐1 membranes using tubular TiO2 supports: Effect of support pore size on membrane performance

AbstractIn this study, we present a detailed synthesis procedure and characterization of porous inorganic silicalite‐1 membranes. The membranes were synthesized in‐situ using a pore plugging method with the inclusion of a 12 h thermal break promoting secondary growth within the active layer pores of the tubular TiO2 supports. The effect of the support pore size on membrane performance was examined with pore sizes ranging from 0.3 μm to 1.4 μm. Characterization using SEM and EDS analysis confirm the penetration and formation of silicalite‐1 crystals within porous supports up to a depth of 10–12 µm for all membranes. With the exception of the membranes synthesized on the support with 1.4 μm pore size, all membranes were more permeable to probe gas N2 compared to He. The highest ideal N2/He selectivity of 2.3 ± 0.5 was observed for the membranes synthesized on supports with 0.8 μm pore size. Single gas permeance for the membranes was high, ranging between 3.7 × 10−7 and 1.3 × 10−5 mol/m2sPa, and was independent of gas kinematic diameter with the order of permeation being CH4 > CO2 > N2 > He. Binary equimolar CO2/N2 separation experiments show better membrane CO2/N2 permselectivity compared to the ideal selectivity calculated from the single gas experiments. Comparing the observed membrane gas diffusivity and the adsorbate gas uptake rate within the zeolite material alone shows that these favourable selective properties are the result of adsorption surface diffusion and that Knudsen diffusion is minimized.

Fabrication of silica ceramic membrane via sol-gel dip-coating method at different nitric acid amount

Fabrication of silica ceramics via the sol-gel method has offered more advantages over other methods in the fabrication of ceramic membrane, such as simple operation, high purity homogeneous, well defined-structure and complex shapes of end products. This work presents the fabrication of silica ceramic membrane via sol-gel dip-coating methods by varying nitric acid amount. The nitric acid plays an important role as catalyst in fabrication reaction which involved hydrolysis and condensation process. The tubular ceramic support, used as the substrate, was dipped into the sol of Tetrethylorthosilicate (TEOS), distilled water and ethanol with the addition of nitric acid. The fabricated silica membrane was then characterized by (Field Emission Scanning Electron Microscope) FESEM and (Fourier transform infrared spectroscopy) FTIR to determine structural and chemical properties at different amount of acids. From the XRD analysis, the fabricated silica ceramic membrane showed the existence of silicate hydrate in the final product. FESEM images indicated that the silica ceramic membrane has been deposited on the tubular ceramic support as a substrate and penetrate into the pore walls. The intensity peak of FTIR decreased with increasing of amount of acids. Hence, the 8 ml of acid has demonstrated the appropriate amount of catalyst in fabricating good physical and chemical characteristic of silica ceramic membrane.