The batch process experimental setup consists of a two-necked conical flask, fitted with a reflux condenser and a vacuum pump. This was design for the purpose of the background study. The schematic diagram of the batch reactor experimental setup is shown in figure 4.1.
Figure 4.1: Experimental set-up for batch process esterification.
4.1.2 Batch Process Reactor and Round bottom flask
The batch process esterification setup consists of the thermometer, hot plate magnetic stirrer and round bottom flask batch reactor. The reactor was a three-necked round bottom conical flask of 500 mL capacity fitted with a condenser. One neck of the reactor was fitted with a glass reflux condenser with a spiral design which allows the flow of water through and out of the system. A three-necked round bottom flask of 500 mL capacity was used for the analysis. This reactor was purchased from Sigma- Aldrich, UK. Figure 4.2 shows the pictorial view of the round bottom flask that was used for the esterification process. Due to the even heat distribution that can be produced through the use of a heating mantle, the round bottom flask is the preferred option when the solvent is required to be heated at different temperatures.
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Figure 4.2: Pictorial view of a two neck-round bottom flask.
4.1.3 Volumetric Flask and Beaker
The different sizes of volumetric flask including 25mL, 50mL and 100mL volumetric flask used for the esterification reaction experiments were all purchased from Sigma-Aldrich, UK. The different size of beaker including 10mL, 25mL, 50mL, 75mL and 100mL beaker used for the experiments were all supplied by Fisher Scientific, UK.
4.1.4 Deionised water
The deionised water used for the experiments was collected from the water dispenser instrument (ELGA, England, UK) at the CPIMT (centre for process integration and membrane technology) Lab, School of Engineering, Robert Gordon University (RGU), Aberdeen, UK. The resistivity of the instrument was program at 18.9 mΩ cm.
4.1.5 Vacuum Pump and Reflux Condenser
The vacuum pump used for the batch process esterification was purchase from Fisher Scientific UK. The pump was used for the removal of water during the esterification process. Figure 4.3a shows the pictorial view of the vacuum pump that was used for the experiment. The reflux condenser used for the analysis was purchase from Fisher Scientific UK. The glass reflux condenser prevents the solvent mixture from evaporating out of the reaction system. The reflux condenser was a glass tube with two opening by the side of which the two vacuum pumps were connected for the water inlet and outlet through the system. Figure 4.3b shows the pictorial view of the reflux condenser that was used for the experiment.
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Figure 4.3: Pictorial view of vacuum pump (a) and reflux condenser (b).
4.1.6 Heating Mantle and Temperature Probe
The Barnstead Electrothermal model heating mantle was used to regulate the temperature of the esterification reactant in the rage of 0 to 1000 oC. The heating mantle was supplied by BioSurplus Inc, California, USA. Figure 4.4a shows the pictorial view of the heating mantle. Certified analytical digital EExia IICT4 Digitron thermometer supplied by Sifam Instrument Ltd, woodland, Torquay, UK connected to a metallic probe was used for test the temperature of the esterification reaction during the batch process esterification analysis. This instrument operates within the temperature range of -50 + 950 oC. Figure 4.4b shows the pictorial view of the temperature probe.
Figure 4.4: Pictorial diagram of the heating system (a) and Pictorial diagram of the temperature probe (b).
4.1.7 Magnetic stirrer
The magnetic stirrer was inserted into the beaker during each batch esterification reaction to ensure that the reactant solvent are well mix and was placed unto the electric stirrer to properly mixed the solvent
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with the different cation-exchange resin catalysts to achieve uniform esterification product before it was transferred into the batch reactor for the selective removal of water from the system at each temperature.
4.1.8 Cation-exchange resin selection
The catalysts were selected based on reviewing the literature to see what is obtainable in the literature. On reviewing the literature, it was found that different catalysts have been used for esterification of lactic acid with other alcohols in the presence of different amberlysts and the dowex catalysts but much work has not been carried out on esterification of lactic acid with ethanol to produce ethyl lactate [4,13,15]. Cation-exchange resin were also chosen because these catalysts possess higher mechanical stability, low cost, environmentally friendly are and chemically compatible with several liquids [50]. This catalyst offer several advantages over homogenous catalysts. They can be removed easily from the reaction medium and can be recycled. Additionally, the effect of the resin in the reaction system allow high selectivity and eliminate or reduce undesirable side reaction [116]. Also, they are commercially available in different shape and sizes and exist in solid form. The different cation-exchange resins used in the experiment were: amberlyst 36, amberlyst 15, amberlyst 16 and dowex 50W8x. These catalysts are commercial available solid cation-exchange resins supplied by Sigma-Aldrich, UK. Figure 4.5 shows the pictorial diagram of the different cation-exchange resins. Figure 4.5 shows the sample bottles of the different cation-exchange resins that were used for the esterification analysis.
Amberlyst 36 Dowex 50W8x
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Figure 4.5: Pictorial diagram of dowex 50W8x (a), amberlyst 36 (b), amberlyst 16 (c) and amberlyst 15 (d) sample bottles containing the fresh commercial available cation-exchange resins.
4.1.9 Lactic acid, Ethanol and Commercial Ethyl lactate solvent
Aqueous lactic acid (99.99wt%) solutions was used for the analysis and was purchased from Sigma- Aldrich, UK. This solution was used as received without and further purification or dilution. Analytical grade ethanol (99.98 wt%) solution was used for the analysis and was purchased from Sigma-Aldrich, UK. This solution was used as received without and further purification or dilution. Analytical grade ethyl lactate (99.99 wt%) solvent used for the analysis was purchased from Sigma-Aldrich, UK. This solution was used as received without any further purification or dilution. The commercial available ethyl lactate solvent was tested in other to compare the GC-MS results with that of the produced esterification reaction product. Figure 4.6 pictorial view lactic acid solvent bottle (a), ethanol (b) and ethyl lactate (c) solvent bottles.
Figure 4.6a-c: Pictorial view of lactic acid (a), ethanol (b) and ethyl lactate (c) solvent bottles.
Amberlyst 16 Amberlyst 15
c d
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The Hamilton HM80300 microliter TM pipette was used to measure the esterification product into the sample vial before the sample analysis with GC-MS. The dilution solvent was collected using the Hamilton pipette (1000mL of the dilution solvent) while the microliter pipette (10µL) was used to collect the esterification product for the analysis. Figure 4.7 shows the Hamilton HM80300 microliter TM pipette (a) and microliter pipette (10µL) (b). The Hamilton pipette was used to measure the required amount of diluting solvent.
Figure 4.7: Manual pipette with pipette tip (a) and Hamilton HM80300 microliter TM pipette (b).
4.1.11 Fume cupboard and Oven (Carbolite)
As the experiments involved using high concentrations of lactic acid, ethanol and cation-exchange resins. All the chemical preparations and cation-exchange resins cleaning process before each esterification process were carried out in the fume cupboard. The carbolite oven was used for drying of the cation-exchange resin catalysts after each catalyst cleaning process before it was used for the esterification reactions.