FT-IR of Neat Triethylene Tetrammonium Lactate after Absorbing Carbon Dioxide 

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... chemicals used in the experiments were of analytical grade. Triethylene tetramine (TETA, CDH), Lactic acid (LOBA CHEMIE), concentrated hydrochloric acid (Sigma Aldrich), methyl orange indicator (Sigma Aldrich) were used without purification. Carbon dioxide (CO 2 , 99.99%) and nitrogen (N 2 , 99.99%) gases were purchased from Sigma Aldrich. Purity of gases was checked by ULTIMA-2100 series gas chromatograph of Nettle make. All solutions were prepared using de-ionised water in volumetric glassware. Equi-molar quantities of triethylenetetramine and lactic acid were taken in a three – necked round bottom flask equipped with a reflux condenser, a pressure funnel, and a mechanical stirrer. Initially, triethylenetetramine was taken in the round bottom flask and then lactic acid added drop by drop using a pressure funnel with constant stirring at 120 rpm using the mechanical stirrer. As the neutralization reaction produces a lot of heat, which is equal to -9 kcal/ mol, the round bottom flask was kept in an ice-water mixture. To avoid any contamination with air, the reaction mixture was placed under N 2 atmosphere. It was then stirred for several hours at room temperature. The completion of reaction was monitored by TLC. The product was a pale yellow viscous liquid. Product was then washed with dichloromethane 2-3 times to remove 0 impurities. Residual water is removed by vacuum heating at 80 C for 12 hours. The ionic liquid was finally stored-in an air tight flask. The water content of the ionic liquid was analysed using the TGA analysis and found to be 0.01% (w/w). Figure 1 shows the mechanism of reaction between triethylenetetramine (TETA) and lactic acid. The structure of synthesized protic ionic liquid was elucidated using FT- 1 13 IR, H NMR, C NMR, and Mass spectroscopy. FT-IR Data IR spectra of triethylenetetrammonium lactate before (Figure 2) and after the carbon dioxide absorption (Figure 3) were compared for identification of changes due to carbon-dioxide absorption is given in Table 1. Qualitative H and C NMR experiments for molecular- structural determination were run at room temperature using a Bruker 300 MHz spectrometer. An NMR sample of TETAL was prepared in deuterated DMSO- d 6 . To avoid any disturbance between the deuterated solvent and the analyzed mixture, a capillary tube was use to load DMSO-d 6 with the sample in NMR 1 tube. The residual proton in DMSO-d 6 was used as the H NMR external reference at 2.50 ppm. The proton present in Triethylenetetrammonium Lactate in different environment is shown in Figure 4. C NMR spectra were obtained for the neat TETAL and after absorbing carbon dioxide in order to investigate the nature of the carbon dioxide bound species being formed. There was no signal for the carbamate carbon around 159 – 165 ppm in neat TETAL. In carbon di-oxide absorbed TETAL sample a signal is observed at 163.54 ppm that is attributed to the carbamate carbon (Figure 5(a) & Figure 5(b)). 13 C NMR: δC (300 MHz; DMSO -d 6 ) 39.5 ppm: For Lactate ion: 179.38(- COOH), 67.68(-CHOH), 22.1(CH 3 ); TETA ion: 40, 45, 50 (CH 2 N, NH 2 , NH) 1 HNMR: δH (300 MHz; DMSO -d 6 ): 1.119 (s, 3H, CH 3 ), 2.347, 2.724, 2.593(CH N), 4.4, (br s, NH, NH ); The molecular mass of Triethylenetetrammonium Lactate is 244.44 g -1 mole depicted from the mass spectrum of TETAL in Figure 6. Thermogravimetric analysis (TGA) was performed using a Thermo Gravimetric Analyzer of Netzsch Instruments under a nitrogen atmosphere. The samples were weighed , and then heated from room temperature to 300 °C at a ramping rate of 10 °C·min −1 . TGA analysis for the pure TETAL shows that o the sample is stable and does not loss weight until 150 C, Figure 7 indicating that TETAL is more stable than the corresponding polyamine TETA as a result of the salt formation. The dynamic viscosity was measured for the system TETAL as a function of temperature from 273 to 388 K using Anton Paar MCR302 SN81193479. Watanabe et al. (Tsuzuki et al., 2009) reported that the three main factors for viscosity of ionic liquids are size, shape, and interaction between the anion and the cation. The interaction forces between anion and cation are columbic forces, van der Waals forces, and hydrogen-bonding. Out of these forces in neat ionic liquid the columbic forces are responsible and in carbon dioxide absorbed ionic liquid hydrogen-bonding mainly cause viscosity. The viscosity of ionic liquid directly influences the diffusivity of ions in the solution. The experimental viscosity of TETAL as a function of temperature is given by Figure ...