Use of nanoporous ceramic membranes for carbon dioxide separation

Natural gas processes accounts for about 5.3 billion tonnes per year of carbon dioxide (CO2) emission to the atmosphere. At this rate of emission, the expectation will drastically rise if not curtailed. In order to achieve this, a cost-effective and environmental friendly technology is required. In recent times, membrane technology has been widely applied for CO2 removal from raw natural gas components. This article examines CO2 separation from natural gas, mainly methane (CH4), through a mesoporous composite membrane. A laboratory scale 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) was used to analyze the morphology of the membrane. Single gas permeation of helium (He), CH4, nitrogen (N2), argon (Ar) and CO2 were determined at permeation temperature range between 25 and 100°C and feed gauge pressure of 0.05 to 5.0 barg. Before silica modification, He recorded the highest flow rate (0.3745 l/min) while CO2 recorded the least flow rate (0.1351 l/min) at 0.4 barg and 25°C. After silica modification, CO2 flow enhances significantly (3.1180 l/min at 1.0 barg) compared to CH4 (2.1200 l/min at the same gauge pressure) due to the influence of surface flow mechanism. Temperature variation described the applicability of Knudsen diffusion for He. A combination of viscous, surface and Knudsen diffusion transport mechanisms were obtained throughout the experiment. Membrane thickness was also calculated to be 2.5 × 10−4 m

Initial study of heterogeneous catalysts behaviour and carrier gas permeation with catalytic inorganic ceramic membrane for lactic acid esterification applications.

Inorganic membranes continue to attract a lot of attention in various fields including industry and academia, due to the great potential they have shown in various applications. Recently, some studies have focused on the water -permeable metallic membrane reactor involving liquid-phase reversible reactions including esterification reactions. Among the membranes considered, inorganic membrane have been found to be the perfect membrane for the esterification reaction process because they can allow heterogeneous catalysts to be deposited easily on the surface of the membrane; this results in increase in the yield of products. The use of inorganic ceramic to selectively eliminate water from the reaction product during esterification of lactic acid is yet another important application that has attracted a lot of attention. In this work, the initial study of heterogeneous catalyst behaviour and carrier gas permeation with inorganic ceramic membrane for lactic acid esterification applications was carried out. Dowex 50W8x, Amberlyst 36, Amberlyst 15 and Amberlyst 16 cation-exchange resins were used as heterogeneous catalysts. The SEM/EDXA of the resin catalyst was investigated in order to determine the surface morphology of the resin. The EDXA of the catalysts showed the presence of sulphur which confirms the sulfonic acid group in the structure of the polymeric compound. The permeation properties of inorganic ceramic membrane with the carrier gases were also analysed between the gauge pressures of 0.01-1.00 bar at the temperature of 60oC (333 K). The membrane was coated twice using silica solution before the permeation experiments. The carrier gas permeance of the silica membrane showed a linear dependence on the inverse square root of the gas molecular weight indicating Knudsen mechanism of transport. Gases with highest viscosity value exhibited the least permeance indicating viscous flow contribution. It was concluded that Knudsen and viscous mechanisms plays a major role in the carrier gas permeation with inorganic ceramic membrane

Advanced membrane design for improved carbon dioxide capture.

A nano-structure tubular hybrid inorganic membrane capable of stripping carbon dioxide from flue gas stream was designed and tested at laboratory scale to improve compliance to various environmental regulations to cushion the effect of global warming. Single gas separation experiments using silica modified ceramic membrane was carried out to investigate individual gas permeation behaviors at different pressures and membrane eficiency after a dip coating method. Four gases; Nitrogen (N2), Carbon dioxide (CO2), Oxygen (O2) and Methane (CH4) were used. Plots of flowrate versus pressure were generated. Results show that the gas flow rate increases with pressure drop. However at above a pressure of 4bar, the flow rate of CO2 was much higher than the other gases, indicating dominance of a more selective adsorptive type transport mechanism

Advanced membrane design for improved carbon dioxide capture.

A nano-structure tubular hybrid inorganic membrane capable of stripping carbon dioxide from flue gas stream was designed and tested at laboratory scale to improve compliance to various environmental regulations to cushion the effect of global warming. Single gas separation experiments using silica modified ceramic membrane was carried out to investigate individual gas permeation behaviors at different pressures and membrane eficiency after a dip coating method. Four gases; Nitrogen (N2), Carbon dioxide (CO2), Oxygen (O2) and Methane (CH4) were used. Plots of flowrate versus pressure were generated. Results show that the gas flow rate increases with pressure drop. However at above a pressure of 4bar, the flow rate of CO2 was much higher than the other gases, indicating dominance of a more selective adsorptive type transport mechanism

The use of nano-composite ceramic membranes for gas separations.

The preparation of composite ceramic inorganic membranes using different types of support with the aim to achieving high selectivity for lower hydrocarbons was studied. The pore size of the unmodified support was determined. Upon modification of the support, the morphology was examined using scanning electron microscopy (SEM), which showed a reduction in the pore radius and pore size inorganic ceramic membrane consisting of a ceramic support and a zeolite layer. The permeance of nitrogen, carbon dioxide, helium, methane, propane and argon through the membrane at varying pressures was determined. The effect of the mean pressure of up to 0.1 MPa on the molar flux of the gases at 294K was determined

Preparation and characterization of palladium ceramic alumina membrane for hydrogen permeation.

In this study, a tubular palladium membrane has been prepared by an electroless plating method using palladium II chloride as a precursor with the intent of not having a completely dense film since its application does not require high hydrogen selectivity. The support used was a 15 nm pore sized tubular ceramic alumina material that comprised of 77% alumina and 33% titania. It has dimensions of 7 mm inner and 10 mm outer diameters respectively. The catalyst was deposited on the outside tube surface using the electroless deposition process. The membrane was morphologically characterized using scanning electron microscopy/energy dispersive x-ray analysis (SEM/EDXA) and liquid nitrogen adsorption/desorption analysis (BET) to study the shape and nature of the palladium plating on the membrane. The catalytic membrane was then inserted into a tubular stainless-steel holder which was wrapped in heating tapes so as to enable the heating of the membrane in the reactor. The gases used for permeation tests comprised H2, N2, O2 and He. Permeation tests were out at 573 K and at pressure range between 0.05 and 1 barg. The results showed that hydrogen displayed a higher permeation when compared to other gases that permeated through the membrane and its diffusion is also thought to include solution diffusion through the dense portions of the palladium in addition to Knudsen, convective and molecular sieving mechanisms occurring through cracks and voids along the grain boundaries. While high hydrogen selectivity is critically important in connection with hydrogen purification for fuel cells and in catalytic membrane reactors used to increase the yield of thermodynamically limited reactions such as methane steam reforming and water–gas shift reactions whereby the effective and selective removal of the H2 produced from the reaction zone shifts the equilibrium, it is not so important in situations in which the membrane has catalytic activity such that it is possible to carryout the reaction in situations where the premixed reactants are forced-through the membrane on which the catalysts is attached. This type of catalytically active membranes is novel and has not been tested in gas-solid-liquid reactions and liquid-solid reactions before. With such a reactor configuration, it is possible to achieve good feed stream distribution and an optimal usage of the catalytic material. The preparation and characterization of such membrane catalysts has gained increased interest in the process industries because it can be adapted to carryout the chemical reactions if one of the reactants is present in low concentration and an optimal reactant distribution results in a better utilization of the active catalytic material. However, there are concerns in terms of the high cost of palladium membranes and research on how to fabricate membranes with a very low content of the palladium catalyst is still ongoing. Work is currently underway to deploy the Pd/Al2O3 membrane catalysts for the deoxygenating of water for downhole injection for pressure maintenance and in process applications

Gas transport and characterization of inorganic ceramic membrane for lactic acid esterification.

Ethyl lactate is an important organic ester, which is biodegradable in nature and widely used as food additive, perfumery, flavor chemicals and solvent. Inorganic porous ceramic membrane has shown a lot of advantages in the equilibrium process of ethyl lactate separation. In this work, the transport characteristic of carrier gas including Nitrogen (N2), Helium (He), Argon (Ar) and Carbondioxide (CO2), with α-Al2O3 inorganic ceramic membrane used for ethyl lactate separation was investigated, at the pressure drop of 0.01-0.09bar and 298K. The carrier gas flow rate was molecular weight dependent in the order: He > Ar > N2 > CO2 with respect to pressure drop. The membrane pore size distribution was analysed using Scanning electron microscope coupled with energy dispersive x-ray analyser (SEM-EDXA). THIS PAPER WON CERTIFICATE OF MERIT(STUDENT) FOR INTERNATIONAL CONFERENCE ON CHEMICAL ENGINEERING 2014: MISS EDIDIONG OKO

Characterisation of inorganic composite ceramic membrane for lactic acid esterification processes.

The use of inorganic composite membranes in chemical industries has received a lot of attention more recently due to a number of exceptional advantages, including thermal stability and robustness. Inorganic membranes can selectively remove water from the reaction mixture during esterification reactions in order to enhance product formation. The characterisation of inorganic composite membranes used in this work including the determination of the pore diameter and specific surface area was performed using liquid nitrogen adsorption at 77 K. The membrane was modified once. The permeation test for the single gases including carbon dioxide (CO2), helium (He), nitrogen (N2) and argon (Ar) through the inorganic composite ceramic membrane was carried out at the gauge pressure range of 0.10-1.00 bar and at the temperature of 393 K. The order of the gas molecular weight was He < N2 < CO2 < Ar. The BET surface area of the dip-coated silica membrane showed a type IV isotherm characteristic of mesoporous structure with hysteresis. The BJH curve of the silica-membrane was in accordance with mesoporous classification