Preparation, characterization and carrier gas transport characteristics of inorganic and organic membranes for application in lactic acid esterification with ethanol.

Ethyl lactate (EL) plays a major role as green solvent and also a replacement for most petrochemical solvents. The esterification process of lactic acid and ethanol to produce EL is an equilibrium-limiting reaction and the selective removal of one of the reaction products can be improved using a membrane reactor and when coupled with a heterogeneous catalyst offers an opportunity for process intensification. This thesis investigates the batch process esterification reaction involving lactic acid (LA) and ethanol (EL) in the presence of a water selective membrane using different cation-exchange resin catalysts. The product was analysed using gas chromatograph coupled with mass spectrometry detector (GC-MS). The analytical methods used for the characterisation of the cation-exchange resins and membrane include Fourier transform infrared coupled with attenuated total reflectance (FTIR-ATR), scanning electron microscopy attached to energy dispersive analyser (SEM/EDAX), Liquid nitrogen physisorption and nuclear magnetic resonance (NMR) respectively. A novel method was developed for carrying out esterification reaction in a gaseous phase system using a flat sheet polymeric membrane. Prior to the esterification reaction, different carrier gases were tested with ceramic membrane to determine the suitable carrier gases for the analysis of esterification product. The four carrier gases used for the permeation test were argon (Ar), helium (He), carbon dioxide (CO2) and nitrogen (N2). A 15nm pore size commercially available tubular ceramic support, consisting of 77%Al2O3 and 23%TiO2 with the porosity of 45% was used for the carrier gas investigation. The support was modified with silica based on the sol-gel dip-coating techniques. The dip-coated membrane exhibited a higher molar flux with He (0.046mol m-2s-1) and Ar (0.037mol m-2s-1) with a much lower flux for N2 (0.037mol m-2s-1) and CO2 (0.035 mol m-2s-1) at 0.30 bar. Helium gas with the highest permeation rate were identified as the suitable carrier gas for the analysis of esterification product with GC-MS. The esterification reaction in the presence of four cation-exchange resins to produce ethyl lactate was carried out between 60-160 oC in a batch and membrane processes to determine the effectiveness resin catalysts for LA esterification. The effect of external mass transfer diffusion limitation between the liquid components and the resin catalysts was avoided by increasing the agitation time of the esterification reaction. The percentage conversion rate of the lactic acid feed from the batch process esterification was found to be in the range of 98.6 to 99.8%. The reaction kinetics of the esterification reaction was described based on two simplified mechanisms of Langmuir Hinshelwood model to describe the adsorption components on the surface of the catalysts. The lactic acid feed gave a conversion rate of up to 100 % confirming the effectiveness of the acetate membrane impregnated resin catalysts in the selective removal of water for the separation of ethyl lactate. The significance of producing ethyl lactate through batch process intensified by a water-selective membrane processes can be recommended for industrial LA production

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

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

Batch process esterification of lactic acid catalysed by cation-exchange resins for the production of environmental-friendly solvent.

In this work, batch wise esterification of lactic acid and ethanol was carried out using different cation-exchange resins including amberlyst 15, amberlyst 16, dowex 50W8x and amberlyst 36 as heterogeneous catalysts. The Zeiss EVO LS10 Scanning electron microscopy/energy dispersive x-ray analyser (SEM/EDXA) was used to examine the surface morphology of the resin catalysts before and after the esterification reaction process. The EDXA of the catalysts showed the presence of sulphur with the highest peak on the spectra. The SEM of the commercial resin catalysts showed a clear surface with no crack before the esterification reaction. Amberlyst 36 showed a greater thermal stability after the esterification reaction process. The order of the surface integrity from the SEM morphology of the resin catalysts after the esterification process was Amberlyst 36 > dowex 50W8x. Gas chromatography equipped with mass spectrometry (GC- MS) detector was used to analyse the reaction products. Ion 45 on the mass spectra confirmed that the esterification product was in accordance with the library mass spectra of the commercial ethyl lactate solvent. The agitation time was found to increase with increase in concentration indicating a non-mass transfer limitation at 60 oC. The reaction product catalysed with amberlyst 36 was found to elute at faster at 1.441 min in contrast to the commercial ethyl lactate solvent at 2.124 min indicating a higher reaction rate of the resin catalysts

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

Novel zeolite-polyurethane membrane for environmental applications and gas separations.

This research work investigates the effect of polyurethane polymer on the separation of CO2, CH4 and C3H8 through a zeolite/polyurethane mixed matrix membrane. A methodology based on the modification of porous ceramic inorganic support with the aim to achieve high selectivity for the hydrocarbons has been developed. Polyurethane-zeolite nanoparticles were prepared by combined blending and casting method. The physical properties of the zeolite/polyurethane mixed matrix membrane were investigated by Scanning Electron Microscope (SEM), Fourier Transform Infra-Red spectroscopy (FTIR) and Nitrogen physisorption (BET). These confirmed the homogenous and nanoscale distribution of zeolite particles in the polyurethane-zeolite membrane. The Nitrogen physisorption measurements showed the hysteresis isotherm of the membrane corresponding to type IV and V that is indicative of a mesoporous membrane. The surface area and the pore size determined using the Barrett, Joyner, Halenda (BJH) desorption method showed a pore diameter of 3.320 nm, a pore volume of 0.31ccg-1 and surface area of 43.583 m2 g-1. Single gas permeation tests were carried out at a pressure range of 0.01 to 0.1 MPa. The membrane showed the permeance of CH4 to be in the range of 5.189 × 10-7 to 1.78 × 10-5 mol s-1 m-2 Pa-1 and a CH4/C3H8 selectivity of 3.5 at 293 K. On the basis of the results obtained it can be concluded that for the recovery of volatile organic compounds the addition of polyurethane polymer to the zeolite membrane did not increase the performance of the membrane

Design and Evaluation of Gas Transport through a Zeolite Membrane on an Alumina Support

This chapter details the synthesis and applications of zeolite membranes (gas separation and zeolite membrane reactors). Gas separation is still not carried out at industrial level for zeolite membranes. Related areas, such as the possibility of incorporating a zeolite membrane in a reactor for possible catalytic action of the zeolite particles and scale-up issues are also discussed. The basic concept of mass transport through the zeolite layer has been presented. Zeolites can enhance the selectivity of methane more which can lead to the reduction of greenhouse gases in the atmosphere

Impacts of Traffic Volumes on Air Quality in Uyo Urban, Akwa Ibom State, Nigeria.

Anecdotal evidence suggests that motor vehicle emissions constitute a major source of atmospheric pollution in Uyo Urban. In the current study, major air pollutants (Carbon Monoxide, Nitrogen Oxides, Sulphur Oxides and SPM) were sampled in Twenty one location points. Samples were taken at three different time intervals of the day corresponding to morning peak, evening peak and afternoon off-peak periods. Using regression analysis and GIS, spatio-temporal and linear relationships between the pollutants and volume of vehicular movement were analysed. The result is a spatial surface pollution map reflecting pollution concentration in each point in the study area. The  four major pollutants were detected at all times and locations while the concentration of CO and NO2 showed a mean concentration level greater than the Federal Environmental Protection Agency limits and the recommended municipal (local) standard. This was predominantly during morning and evening peak. Though this study did not cover all the traffic junctions in the whole city of Uyo Urban, findings from the twenty one sampling points suggest that the city is under the threat of traffic related pollution and is possibly more susceptible further pollution given increasing population influx and vehicular traffic. Improved road network and construction of modern roundabouts could help reduce peak period traffic in the nearest future. Keywords: Traffic volumes, air quality, air pollution, vehicular emissio

Integration of gas transport through a composite catalytic inorganic ceramic membrane for environmental gas separation processes.

This work presents the transport behaviour of carrier gases with inorganic ceramic membrane used for environmental gas separations at 289K and 0.01-1 bar. The gases tested include: Helium (He), Nitrogen (N2), Carbon dioxide (CO2) and Argon (AR). The Knudsen ideal selectivity ration of 0.95, 0.3 and 0.79 for Ar/CO2, He/CO2 and N2/CO2 gas respectively was slightly higher that the theoretical selectivity of the gases. The gas permeance was found to decrease with increase in gauge pressure indicating mass transfer limitation. However, at a relatively low pressure of 0.1 bar, Knudsen diffusion mechanism was dominant for He and N2 gases flow across the modified ceramic membrane in relation to the inverse proportionality of the square root of their molecular weights. Scanning electron microscopy (SEM) was used to determine the pore size distribution of the {esc}ga{esc}s-Al2O3 ceramic support