Edidiong Okon

Evaluation and Characterisation of Composite Mesoporous Membrane forLactic Acid and Ethanol Esterification

Recently, the use of inorganic composite mesoporous membranes in chemical industries has received a lot of attention due to a number of exceptional advantages including thermal stability and robustness. Inorganic mesoporous membranes can selectively remove water from the reaction product during lactic esterification reactions in order to enhance product yield. In this work, the characterization and evaluation of a catalytic mesoporous membrane with 15 nm pore size was tested with different carrier gases before employing the gases for lactic acid and ethanol esterification product analysis with Gas Chromatography coupled with mass spectrometry (GC-MS). The membrane was coated once with silica solution before the permeation test with carrier gases. Helium (He), nitrogen (N2), argon (Ar) and carbon dioxide (CO2) were used for the permeation tests conducted at the feed pressure of 0.10–1.00 bar and at the temperature of 413 K. The gas flow rate showed an increase with respect to feed pressure indicating Knudsen flow as the dominant transport mechanism. The order of the gas flow rate with respect to the feed pressure drop was Ar>CO2>He>N2. The morphological characteristic of the membrane was determined using scanning electron microscopy coupled with energy dispersive x-ray analyzer (SEM/EDXA). The SEM result of the membrane showed the distribution of the silica on the surface of the membrane. The surface area and pore size distribution of the silica membrane was analyze using liquid nitrogen adsorption/desorption method. The surface area results obtained from the Brunauer-Emmett-Teller (BET) isotherm for the 1st and 2nd dip-coated membranes were 1.497 and 0.253 m2/g whereas the Barrette-Joyner-Halenda (BJH) curves for the pore size of the 1st and 2nd dip-coated membranes were 4.184 and 4.180 nm respectively, corresponding to a mesoporous structure in the range of 2-50 nm. The BET isotherms of the silica membranes showed a type IV isotherm with hysteresis. The BJH curve for the 2nd dip-coated membrane showed a 4% reduction in pore size after the modification process.

Gas Transport Through Inorganic Ceramic Membrane and Cation-Exchange Resins Characterization for Ethyl Lactate Separation

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 Carbon dioxide (CO2), with α-Al2O3 inorganic ceramic membrane used for ethyl lactate separation was investigated, at the pressure drop of 0.01–0.09 bar and 298 K. 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). The SEM surface of the commercial cation-exchange resin catalysts before esterification showed a defect-free surface.

Study of the Selectivity of Methane over Carbon Dioxide Using CompositeInorganic Membranes for Natural Gas Processing

Natural gas is an important fuel gas that can be used as a power generation fuel and as a basic raw material in petrochemical industries. Its composition varies extensively from one gas field to another. Despite this variation in the composition from source to source, the major component of natural gas is methane with inert gases and carbon dioxide. Hence, all natural gas must undergo some treatment with about 20% of total reserves requiring extensive treatment before transportation via pipelines. The question is can mesoporous membrane be highly selective for methane and be used for the treatment of natural gas? A methodology based on the use of dip-coated silica and zeolite membrane was developed. A single gas permeation test using a membrane reactor was carried out at a temperature of 293 K and a pressure range of 1 × 10-5 to 1 × 10-4 Pa. The permeance of CH4 was in the range of 1.15 × 10-6 to 2.88 × 10-6 mols-1m-2Pa-1 and a CH4/CO2 selectivity of 1.27 at 293 K and 0.09 MPa was obtained. The pore size of the membrane was evaluated using nitrogen adsorption and was found to be 2.09 nm. The results obtained have shown that it is possible to use a mesoporous membrane to selectively remove carbon dioxide from methane to produce pipeline quality natural gas. There is a need for further study of the transport mechanism of methane through the membrane since this is essential for the separation of other hydrocarbons that could be present as impurities.

Membrane and Resins Permeation for Lactic Acid Feed Conversion Analysis

The process intensification of cellulose acetate membrane impregnation with resin catalysts and carrier gas transport with membrane was carried out. The different catalysts used were amberlyst 36, amberlyst 16, dowex 50w8x and amberlyst 15. The carrier gases used for the analysis of the esterification product were tested with a silica membrane before being employed for gas chromatography analysis. The different carrier gases tested were helium (He), nitrogen (N2), argon (Ar) and carbon dioxide (CO2). The experiments were carried out at the gauge pressure range of 0.10–1.00 bar at the temperature range of 25–100 °C. The carrier gas transport results with the membrane fitted well into the Minitab 2016 mathematical model confirming the suitability of Helium gas as a suitable carrier gas for the analysis of lactic acid feed with GC-MS. The esterification reaction of lactic acid and ethanol catalysed with the cellulose acetate membrane coupled with the different cation-exchange resins gave a conversion rate of up to 100%.

An Experimental Analysis of Lactic Acid Esterification Process Using Langmuir-Hinshelwood Model

In this study, esterification of lactic acid and ethanol to produce ethyl lactate using different cation-exchange resin catalysts was performed at 100 °C. The catalysts used for the esterification process were amberlyst 16 and dowex 50W8x cation-exchange resins. Two simplified mechanisms based on Langmuir-Hinshelwood model were employed to describe the components that adsorbed most on the surface of the catalysts. Fourier Transform Infrared (Nicolet iS10 FTIR) was employed to verify the rationality of the mechanisms. FTIR of the esterification product reflected C=O, H=O and C=C bonds on the spectra confirming water and ethanol as the most adsorbed components. The kinetic study of the retention time and the peak areas of the esterification produced with the different catalysts were compared using an autosampler gas chromatography/mass spectrometry (autosampler GC-MS). The chromatogram of the esterification product catalysed by amberlyst 16 showed a faster elution at 1.503 mins with the peak area of 1229816403 m2 in contrast to the dowex 50W8x. The BET surface area and BJH pore size distribution of the resin catalysts were determined using liquid nitrogen adsorption (Quantachrome, 2013) at 77 K. The BET surface area results of amberlyst 16 resin catalysts was found to be 1.659m2/g compared to 0.1m2/g for the dowex 50W8x. The BJH results of the catalysts exhibited a type IV isotherm with hysteresis confirming that the materials were mesoporous with pore size in the region of 2 – 50 nm.

Single Gas Permeation on ó-Alumina Ceramic Support

This study examines the characterization (SEM-EDXA observation, BET measurement) and gas transport through a commercial tubular alumina mesoporous (20 and 500 Co) support. Single gas permeation of helium (He), hydrogen (H2), nitrogen (N2) and carbon dioxide (CO2) was measured at a temperature of 450°C and feed pressures between 0.85 up to 1.0 bar. Observation of the permeance of the alumina support revealed that the transport of the gases under these conditions is governed by Knudsen diffusion. Selectivity of 2.7 was obtained for He/N2 at 1 bar. The selectivity obtained is comparable to the theoretical Knudsen value (2.65) for He/N2.