Ngozi Claribelle Nwogu

Preparation, Characterization and Molecular Transport of a Supported Silica Membrane for Gas Separation

This paper presents the synthesis and hydrodynamic characteristics of a surface-modified ceramic membrane. The porous support consists of gamma-alumina and a titanium wash-coat. Single gas permeation through the membranes was measured at 298 and 373 K using H2, N2, Ar, CO2 and CH4. The membranes showed separation factors that are consistent with Knudsen diffusion mechanism. Structural characteristic and pore size distribution of the modified silica membrane were analyzed with liquid nitrogen adsorption at 77 K to obtain gas adsorption/desorption isotherm of membrane materials. The adsorption/desorption curve for the surface-modified silica ceramic membrane showed a type IV/V isotherm which indicates a mesoporous structural make-up. Scanning electron microscopy (SEM) images show that membrane surface has a dense silica film and were defect-free. Energy dispersive x-ray analysis (EDXA) confirms the formation of silica films and indicating the presence of C, O, Al, Si, Cl and Ti elements on the modified support. H2 permselectivity to N2 (H2/N2 = 4.37) is higher than the ideal Knudsen value of 3.74. Results from the experiments have helped explain the effect of dissimilarity in the mass-transfer on the gas permeation through the hybrid ceramic membranes.

Characterization of an Alumina Membrane Using Single Gas Permeation

This paper discusses the results of initial experiments carried out using a commercially available alumina membrane. The paper also reveals the important features of ceramic membranes as well as the different transport mechanisms that could take place through these membranes. The experimental results were based on single gas permeation method involving He, O2, CO2 and N2. The effect of trans-membrane pressure drop, gas molecular mass, kinetic diameter, permselectivity, temperature and permeance were studied and discussed. Helium showed a faster flowrate through the membrane and the order of flow was He > O2 > N2 > CO2.

Catalytic Membrane Reactor for VOC Destruction 1

Platinum-alumina (Pt/γ-Al2O3) membrane was prepared using evaporative-crystallization deposition method for volatile organic compounds (VOCs) destruction. SEM-EDXA observation, BET measurement, permeability assessment and the catalytic oxidation of propane, n-butane and propylene representing VOC was obtained. Remarkable propane conversion of VOC with Pt catalyst was achieved at moderate temperature. The temperature at which the catalytic combustion takes place for the VOC is lower than the one obtained from the literature for the same VOC on Pt/γ-Al2O3 catalysts. The conversion was achieved by varying the reaction temperature using flow-through catalytic membrane reactor operating in the Knudsen flow regime.

Characterization of Gamma-Alumina Ceramic Membrane

This paper presents the experimental results of different methods of characterization carried out on a gamma alumina ceramic membrane. A commercial gamma alumina mesoporous membrane has been used. The pore size, specific surface area and pore size distribution values were calculated with the use of a nitrogen adsorption-desorption instrument. The images from the scanning electron microscopy (SEM) showed the membranes’ morphological structure. Gas permeation tests were carried out on the membrane using a variety of single and mixed gases at a temperature range between 25–200 °C and gauge pressure range of 0.05–1 bar. Graphs of flow rate versus temperature were obtained. The results were therefore used to explain the effect of temperature on the flow rate of the various gases. At a pressure drop of 0.5 bar for example, the flow rate for N2 was relatively constant up to 150 °C before decreasing with further increase in temperature, while for O2, it continuously decreased with an increase in temperature.

Investigation of Flue Gas and Natural Gas Separation Using Silica Composite Membranes Formed on Porous Alumina Support

The overall goal of this paper is to foster the development of new membrane technologies to improve manufacturing efficiency and reduce CO2 emissions. Hence, a silica composite ceramic membrane with extremely low defect concentrations has been prepared through three successive dip-coating steps in a silica solution. An asymmetric structure was obtained by the deposition of silica layer on top of a combination of titanium and α-Al2O3 support. The morphology of the three step homogenous silica layer was analysed by scanning electron microscope and Energy dispersive x-ray analyzer. The transport property of the membranes was carried out at room temperature and at pressure differences ranging from 1 to 2 bar. The fabricated membrane has reproducible high permeance for CO2. Interestingly, an almost equal flow rate was observed for CH4 and N2 at a pressure of 2 bar. Separation factors obtained from CO2/CH4 and CO2/N2 are comparatively higher than Knudsen separation values.

Hydrogen Permeation Using Nanostructured Silica Membranes

This study examines hydrogen (H2) transport and separation factors for various gases on mesoporous membrane for unmodified and dip-coated silica membrane. Single gas permeation of H2, N2, CH4, Ar and CO2 were determined at permeation temperature of 298–373 K and feed gauge pressure of 0.1 to 0.9 barg. H2 permaetion rose from 3.3 to about 6.4 l/min at 0.9 bar. H2 selectivity over N2, CH4, Ar and CO2 for the dip-coated silica membrane at 298 K and 0.9 bar was 2.93, 2.18, 3.51 and 3.61 respectively. Observation of the permeation of these membranes revealed that the transport of gases is governed by a combination of activated transport and knudsen flow.

Experimental study of carbon dioxide separation with nanoporous ceramic membranes

This paper examines carbon dioxide (CO2) separation from natural gas, mainly methane, through a 15 nm alumina tubular ceramic membrane before and after silica modification. A laboratory scale of tubular silica membrane with a permeable length of 348 mm, I.D and O.D of 7 and 10 mm respectively was used in this experiment. Scanning electron microscopy (SEM) i.e. inner surface, outer surface and cross sectional area of the membrane were analyzed in this experiment. Single gas permeation of helium, methane, nitrogen, argon and carbon dioxide were determined at permeation temperature range between 25°C and 100°C and feed gauge pressure of 0.05 to 1.0 barg. Helium recorded the highest flow rate (0.3745 l/min) while carbon dioxide recorded the least flow rate (0.1351 l/min) at 0.4 barg and 25°C before silica modification. After silica modification, the flow rate of CO2 rose to 3.1180 l/min at 1.0 barg whereas CH4 recorded 2.1200 l/min at the same gauge pressure. Temperature variation described the applicability of Knudsen diffusion. A combination of viscous, surface and Knudsen diffusion mechanisms were obtained throughout the silica modification experiment.