Experimental Study of Carbon Dioxide Absorption in Diethyl Ethanolamine (DEEA) in the Presence of Titanium Dioxide (TiO2)

Fossil fuels are the main source of CO2 emissions into the atmosphere, which are sources of air pollutants. Environmental research has confirmed that atmospheric CO2 concentration has risen from 280 ppm in 1800 to 358 ppm in 1994 (an increase of 27.86%). Russia, the United States, China, the rest of the Asian countries, Latin American countries, and African countries accounted for 27, 22, 11, 13, 4, and 3% of the total global CO2 production, respectively. Various processes based on hydrogen sulfide and other acidic gases such as carbon dioxide, carbon disulfide, mercaptans, and carbonyl sulfide have been introduced for natural gas sweetening. One of these processes involves the use of solvents. In the present research, a device that measures solubility of gases in liquids was employed to measure solubility of CO2 in solvent DEEA in the presence of TiO2 at different solvent concentrations (10, 15, 20% w/w), various pressures (5, 10, and 15bar) and different TiO2 concentrations (0.05 and 0.1% w/w) at ambient temperature. Results showed that solubility increased from 25.8 to 42.4% v/v at constant pressure and without the presence of a nanoparticle in the absence of TiO2 at solvent concentrations ranging from 10 to 15% w/w. At a constant concentration of the solvent (15% w/w), solubility increased from 31.8 to 36.7% when the pressure was raised from 10 to 15 bar. Moreover, solubility increased from 32.7 to 36.7% v/v at constant solvent concentration (15% w/w) and pressure (15bar) when TiO2 concentration was raised. © 2020 by SPC (Sami Publishing Company), Reproduction is permitted for noncommercial purposes. K E Y W O R D S


Introduction
In 1999, Iran with 263 million tons ranked first in CO2 production in the Middle East (showing a 45.6% increase compared to 1990). Chemical industries in Iran produced 58.4 million tons of the total 263 million tons of this gas [1][2][3][4].
Different countries have come up with numerous ways to reduce CO2 levels as this gas causes accumulation greenhouse gases, increases global temperatures, contributes to sea level rise, and causes droughts and acid rain [5][6][7][8][9].
Many studies have been carried out on increasing CO2 absorption by using chemical solvents. Specifically, CO2 absorption by amines is the most common technology employed for this purpose. Since amines of different types have their specific disadvantages when used for CO2 absorption (e.g. corrosion, low absorptive capacity, high energy requirement for reduction, etc.) [10][11][12][13][14][15][16], various studies have been carried out in recent years to upgrade and improve CO2 absorption by amines. One of these studies is the combination of third type amines with a first or second type amine, the combination of amines with ionic fluids, and the addition of nanoparticles to amines. in DEEA in a laboratory system to measure the volume of CO2 absorption in solvents. The research variables include solvent concentration, initial pressure, and concentration of TiO2 NPs. Thermodynamic studies will then be carried out on the data, response surface methodology will be employed in designing the experiments, and results will be analyzed using the Design-Expert software.
In this present study various processes based on hydrogen sulfide and other acidic gases such as carbon dioxide, carbon disulfide, mercaptans, and carbonyl sulfide have been introduced for natural gas sweetening.
One of these processes involves the use of solvents. Also a device that measures solubility of gases in liquids will be employed to measure solubility of CO2 in solvent DEEA in the presence of TiO2 at different solvent concentrations (10, 15, 20% w/w), various pressures (5, 10, and 15bar) and different TiO2 concentrations (0.05 and 0.1% w/w) at ambient temperature.

Theory
As is well known, CO2 absorption into an amine solution combines both physical and chemical absorptions. In order to obtain theCO2equilibrium solubility, the concentration of CO2in the aqueous solution needs to be calculated.  [23].

P=
(1) The EOS must be rewritten in terms of the compressibility coefficient Z to perform the calculations. Equation 2 is obtained in terms of Z by using the Peng-Robinson EOS.
In Equation 14, the volume of the carbon dioxide gas is calculated under standard conditions (pressure of 1 atm and temperature of 25˚C).

Results
In this work, the solubility of carbon dioxide in DEEA solution was measured with/without of titanium dioxide nanoparticle with various concentrations and pressures, so the experimental results are presented in this section.

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To study the actual solubility behavior of CO2 in DEEA, its solubility was calculated and investigated by using the Peng-Robinson EOS. Results obtained from these calculations are presented in Table 1.  10 13 As shown in Table 1

The effect of different parameters on solubility
In Figures 1-6, effects of each parameter (pressure, NP, and solvent) are presented individually or in combination according to what was stated in Table 1.       concentrations higher than 15% w/w and pressure in the 5-15 bar range. Fig. 7 shows that, at the pressure of 10 bar, the simultaneous use of the NP concentration range 0-0.1% w/w and the solvent concentration higher than 15% w/w results in the highest solubility percentage.   3 Standard volume ω Acentric factor

Conflict of interests
The authors declare that there is no conflict of interests regarding the publication of this paper.