Patent Application
20180140993
The present invention is related to the field of absorption of carbon dioxide (CO2) in gas phase using liquid absorbent systems. Due to the nature of the components of the combined system of liquids used in the present invention, the process corresponds to chemisorption, which was evaluated at 30° C. and 3 atmospheres of the aforementioned gas. Of course, these conditions are not limiting.
The separation of CO2 from gas mixtures emitted from stationary sources has become crucial. For gas mixtures such as natural gas, shale gas and syngas, the elimination of CO2 considerably improves the fuel properties of these blends; in addition, the combination of CO2 with water is very corrosive for pipes and equipment for transportation and storage of these gases.
CO2 emissions from the combustion of fossil fuels became a worldwide concern since their increase in the atmosphere is related to the world's growing demand for energy and at the same time, CO2 is one of the gases that contribute to the greenhouse effect, which is responsible for global warming and climate change. Although the development of new energy sources with low emissions should be the long-term goal of our society, in the near future, the development of CO2 capture with efficient storage and recycling technologies is probably the only available strategy to control the CO2 level emitted into the atmosphere.
The use of technologies for the capture, storage and processing of CO2 may provide a medium-term solution to mitigate environmental impacts and enable mankind to continue using natural resources that generate energy from fossil fuels, at least until renewable energy technologies are completely ready for large-scale use.
For the removal of CO2 in gaseous-post-combustion streams, different technologies have been developed such as chemical absorption with amines and sodium hydroxide and physical absorption with solvents such as methanol, N-methylpyrrolidone, dimethyl ether and polyethylene glycol, however, all these processes have many operational problems such as corrosion, loss of solvents in vapor form and high toxicity, which require systems that operate at low temperatures and very high pressures.
In recent years, the use of novel ionic liquids (ILs) as solvents has been described. These ILs have low toxicity, do not cause corrosion problems and have vapor pressures close to zero, so no losses are generated by evaporation. For example, in the international patent application WO2014/178991, a mixture of ILs (ethyl tris (Propyl/butyl phosphonium) with other solvents such as N-methylpyrrolidone and propylene glycol dimethyl ether was used for the physical absorption of CO2. These mixtures have improved the absorption of CO2 in comparison with the physical absorption of other solvents.
In the international patent application WO2012/017183, a process for separating CO2 from a gas mixture based on the chemical absorption with 1-ethyl-3-methylimidazolium [EMIM] or 1-propyl-3-methylimidazolium containing acetate as anion in admixture with guanidinium acetate or 1-butyl-3-methylimidazolium acetate was proposed.
On the other hand, the US patent US2011/0223084 describes a CO2 capture process using ILs functionalized with sulfur. The international patent application WO2014/166781 A1 proposes a CO2 capture process using ILs, which exhibits a phase change upon CO2 absorption, and from which the gas can be released by heating and the absorbent can be regenerated in the same process.
As for the Chinese patent application CN104415642A, it describes a process with high performance of CO2 capture using ILs with amino groups derived from amino acids such as lysine, serine, valine, glycine and arginine in admixtures with diethanolamine and water.
Similarly, patent applications EP2174700, CN102895844A, WO2014/166781, CN102527192A, CN104524297A, CN104418322A and CN10248911A disclose the use of other ILs for CO2 capture meanwhile the Chinese patent application CN102531991A shows the invention of novel ILs with multiamine functionalized imidazole derivatives such as pyrrole, indole, carbazole, pyrazol, 1,2,4-1-H-triazole, 1-H-triazole, purine, piperidine, imidazoline and piperazine and their preparation method.
Amino acids have also been employed for this purpose, for example, in the international patent application WO2014/166781, a process of CO2 capture is described using common solvents such as water and ethanol amino acids. Meanwhile application EP0671200 describes a CO2 capture process from flue gas using a mixture of amino acid salts with piperazine and a copper compound dissolved in water.
As explained before and as far as known by the applicant, the present invention overcomes by far the references cited above by providing a combined CO2 absorption system using amino acids dissolved in tetra methylammonium (TMA) ILs whose anions are derived from amino acids such as alanine (Ala), lysine (Lys) or glycine (Gly), for example.
Likewise, another objective of the present invention is to provide aqueous mixtures of ILs and amino acids with higher absorption capacity than their individual components.
In order to clearly understand the combined system of CO2 absorption using ILs and amino acids, which is the object of the present invention, the description of the figures featured in it is offered without limiting its scope:
The present invention is a novel application for CO2 absorption from gaseous mixtures using a system of aqueous solutions of amino acids and ILs. In the best of our knowledge, these mixtures of components have not been reported for this application.
The preparation of the amino acid solutions using alanine, lysine and glycine is performed at 3 wt. % in distilled water meanwhile ILs based on tetramethylammonium are purified and until the time of use, they have no traces of residual solvents, which ensures that the CO2 absorption is due solely to the amino acid and the corresponding IL aqueous solution.
The composition of the liquid system consists of 5 grams of pure tetramethylammonium glycinate or tetramethylammonium lysinate and 5 grams of aqueous IL, 3 wt. % of the corresponding amino acid. The evaluation conditions are 30° C. and 3 atmospheres of CO2.
To measure the absorption capacity of a liquid system with respect to a gas (or gas mixture) under saturation conditions, a cell was designed and built to operate at constant volume and variable pressure, and to be immersed in a temperature-controlled bath. The cell is equipped with a magnetic stirrer. The previously described arrangement is called gas absorption system using liquid mixtures. Calculations are performed by using the ideal gas law.
Through the data collected from the pressure drop versus time experiment, keeping constant the temperature and amount of absorbent material, it is possible to know the amount of absorbed gas and thereby calculate the gas absorption capacity (CO2 in the case of this invention) of the system conformed by the aqueous solution of amino acid and the corresponding IL under saturation conditions.
Table 1 shows a comparison between the results of the present invention and those reported in the literature. It is observed that monoethanolamine (MEA) has an intermediate absorption capacity evidenced by the results achieved with ILs and their mixtures. However, it is noteworthy to emphasize that the conditions are not the same, e.g., the concentration reported for MEA is 30 wt. %, and in the case of the present invention is 3 wt. %, which makes evident that the system proposed here employs a lower solute concentration.
Examples related to the combined liquid system for CO2 absorption based on ILs and amino acids, which is the object of the present invention and described above, are presented without limiting its technical scope.
Here, the general experimentation procedures to evaluate each combined system comprising a mixture of IL and aqueous amino acid are disclosed. The total amount of liquid in the present examples is fixed at 10 grams of sample when used as pure IL, namely tetramethylammonium lysinate (LysTMA) and glycinate tetramethylammonium (GlyTMA), and in the case of mixtures, the system was conformed with 5 grams of pure IL and 5 grams of aqueous amino acid solution (3 wt. %).
The isotherms for CO2 absorption were obtained at 303 K using an initial pressure of 3 atm
Following the general experimentation procedure, the absorption of a tetramethyl ammonium lysinate+3% aqueous alanine mixture was measured. The evaluation conditions were 3 atmospheres of CO2 and 30° C. In
Following the general experimentation procedure, the absorption of a tetramethyl ammonium lysinate+3% aqueous lysine mixture was measured. The evaluation conditions were 3 atmospheres of CO2 and 30° C. The CO2 absorption was 704.7 mmol of CO2/mol of absorbent.
Following the general experimentation procedure, the absorption of a tetramethyl ammonium lysinate+3% aqueous glycine mixture was measured. The evaluation conditions were 3 atmospheres of CO2 and 30° C. The CO2 absorption was 650.34 mmol of CO2/mol of absorbent.
Following the general experimentation procedure, the absorption of a tetramethyl ammonium glycinate+3% aqueous lysine mixture was measured. The evaluation conditions were 3 atmospheres of CO2 and 30° C. The CO2 absorption was 350.36 mmol of CO2/mol of absorbent.
Following the general experimentation procedure, the absorption of a tetramethyl ammonium glycinate+3% alanine aqueous mixture was measured. The evaluation conditions were 3 atmospheres of CO2 and 30° C. The CO2 absorption was 349.96 mmol of CO2/mol of absorbent.
Following the general experimentation procedure, the absorption of a tetramethyl ammonium glycinate+3% aqueous lysine mixture was measured. The evaluation conditions were 3 atmospheres of CO2 and 30° C. The CO2 absorption was 365.83 mmol of CO2/mol of absorbent.
| Number | Date | Country | Kind |
|---|---|---|---|
| MX/A/2016/015269 | Nov 2016 | MX | national |
