JP7251251B2 - Carbon dioxide separation composition - Google Patents

Description

The present invention relates to a carbon dioxide separation liquid.

In recent years, separation and recovery of carbon dioxide have attracted attention due to the problem of global warming, and many carbon dioxide absorbents have been developed.

Aqueous solutions of amines, especially monoethanolamine solutions, are most commonly used as carbon dioxide absorption solutions. Monoethanolamine is inexpensive and readily available industrially, but has the characteristic that it does not release carbon dioxide absorbed at low temperatures unless it is heated to a temperature of 120° C. or higher. If the carbon dioxide release temperature is higher than the boiling point of water, a large amount of energy is required to recover carbon dioxide due to the high latent heat and specific heat of water.

Therefore, amines with lower carbon dioxide dissipation temperature and lower carbon dioxide recovery energy than monoethanolamine have been developed. For example, aminomethylpropanol (see, for example, Patent Document 1), ethylaminoethanol (see, for example, Patent Document 2), and isopropylaminoethanol (see, for example, Patent Document 3) have been proposed. By protecting the amino group with a bulky substituent, all of these can inhibit the formation of a strong bond between carbon dioxide and the amine, and can reduce the dissipation energy of carbon dioxide. Since it is a molecular amine, it has a low boiling point and large losses due to evaporation. Moreover, the price is high for industrial use. N-methyldiethanolamine (see, for example, Patent Document 4) is also known as an amine with a high boiling point, but its absorption and emission of carbon dioxide are low.

JP-A-06-343858 JP-A-08-089756 Japanese Patent Application Laid-Open No. 2007-217344 WO 99/051326 pamphlet

The present invention has been made in view of the above problems, and an object thereof is to provide a carbon dioxide separation composition using an amine that releases carbon dioxide at low temperatures.

As a result of intensive studies on amines that absorb and dissipate carbon dioxide, the present inventors have found that an aqueous solution of an amine obtained by adding propylene oxide to diethylenetriamine dissipates absorbed carbon dioxide more efficiently than when diethylenetriamine is used as it is. The inventors have found a novel fact that it is possible to achieve the present invention.

That is, the present invention is a carbon dioxide separation composition as shown below.

[1] A carbon dioxide separation composition comprising an amine obtained by adding propylene oxide to diethylenetriamine and water.

[2] The carbon dioxide according to [1] above, wherein the amine obtained by adding propylene oxide to diethylenetriamine is N-(2-hydroxypropyl)diethylenetriamine and/or N,N''-bis(2-hydroxypropyl)diethylenetriamine. isolated composition.

[3] The carbon dioxide separation composition according to [1] or [2] above, wherein the concentration of water is 30 to 95% by weight.

[4] The carbon dioxide separation composition according to any one of [1] to [3] above, further comprising phosphoric acid and/or a phosphate.

[5] The carbon dioxide separation composition according to any one of [1] to [4] above, further comprising a zinc (II) compound and/or a copper (II) compound.

[6] The carbon dioxide separation composition according to any one of [1] to [5] above, further comprising polyethylene polyamine having 5 or more amino groups.

The present invention will be described in detail below.

The essential components of the carbon dioxide separation composition of the present invention are an amine obtained by adding propylene oxide to diethylenetriamine and water.

The diethylenetriamine used in the carbon dioxide separation composition of the present invention is a polyethylenepolyamine having 3 amino groups, and is industrially easily available as a single compound. Diethylenetriamine also absorbs carbon dioxide and can be desorbed by heating, but its desorption efficiency is low and high energy is required to separate carbon dioxide. Therefore, the inventors have found that the carbon dioxide diffusion efficiency is increased by adding propylene oxide to improve the separation performance of diethylenetriamine.

In the carbon dioxide separation composition of the present invention, the propylene oxide to be added to diethylenetriamine is not particularly limited, and those widely distributed industrially can be used.

In the carbon dioxide separation composition of the present invention, the addition method of propylene oxide to diethylenetriamine is also not particularly limited. Generally known addition methods such as a method of mixing and heating and a method of using an acid catalyst can be used. In the method of heating, secondary alcohols such as N-(2-hydroxypropyl)diethylenetriamine and/or N,N''-bis(2-hydroxypropyl)diethylenetriamine are produced, and in the method of using an acid catalyst, primary and a secondary alcohol are produced. When an acid catalyst is used, residual acid is preferably removed because it inhibits the absorption of carbon dioxide.

The carbon dioxide separation composition of the present invention is used as an aqueous solution. Water is required as a solvent for the amine, which is the addition of propylene oxide to diethylenetriamine, and for converting carbon dioxide to carbonate. If water is not used or water is insufficient, when the amine obtained by adding propylene oxide to diethylenetriamine reacts with carbon dioxide, the liquid becomes viscous or solidifies, causing problems such as clogging of equipment. more likely to occur. In addition, the amine and carbon dioxide form a carbamate, which increases the dissipation energy of carbon dioxide.

The concentration of water in the carbon dioxide separation composition of the present invention is preferably 30-95% by weight, more preferably 50-90% by weight. If the concentration is less than 30% by weight, the liquid becomes viscous, and equipment troubles tend to occur.

Phosphoric acid and/or phosphate salts can be added to the carbon dioxide separation compositions of the present invention. Phosphoric acid includes orthophosphoric acid, pyrophosphoric acid (diphosphoric acid), metaphosphoric acid (polyphosphoric acid) and the like, and any form may be used. Phosphates include amines, ammonium salts with ammonia, alkali metal salts with lithium, sodium, potassium, etc., alkaline earth metal salts with calcium, magnesium, barium, etc., aluminum salts, titanium salts, iron salts, nickel salts. etc., but it does not matter which one is used. Emission of carbon dioxide is facilitated by using phosphoric acid and/or phosphates. In addition, when treating exhaust gas containing metal components in exhaust gas such as coal-fired power generation, capture of various metal components contained in the exhaust gas is promoted.

A zinc (II) compound and a copper (II) compound can be added to the carbon dioxide separation composition of the present invention. Zinc(II) compounds are zinc(II) salts, zinc(II) oxide, zinc(II) hydroxide, zinc(II) fluoride, zinc(II) chloride, zinc(II) bromide, Zinc (II) halides such as zinc (II) iodide, zinc (II) nitrate, zinc (II) sulfate, zinc (II) sulfide, zinc (II) carbonate, zinc (II) oxide, zinc (II) hydroxide ), zinc (II) formate, and zinc (II) acetate. Copper (II) compounds are copper (II) salts, copper (II) oxides, copper (II) hydroxides, copper (II) fluoride, copper (II) chloride, copper (II) bromide, Copper (II) halides such as copper (II) iodide, copper (II) nitrate, copper (II) sulfate, copper (II) sulfide, copper (II) carbonate, copper (II) oxide, copper (II) hydroxide ), copper (II) formate, and copper (II) acetate. These zinc (II) compounds and copper (II) compounds can be used together with amines. Amines to be used are preferably ethyleneamines and ethanolamines.

A polyethylene polyamine having 5 or more amino groups can be added to the carbon dioxide separation composition of the present invention. Polyethylene polyamine is a general term for amines having a plurality of ethylene chains and amino groups at both ends of the ethylene chains. In the carbon dioxide separation composition of the present invention, the greater the number of amino groups in polyethylene polyamine, the more efficiently absorbed carbon dioxide can be dissipated. Polyethylene polyamine having 5 or more amino groups is particularly effective. Polyethylene polyamines having 5 or more amino groups have a low proportion of primary amino groups that are difficult to diffuse carbon dioxide. Examples of polyethylene polyamines having 5 or more amino groups include tetraethylenepentamine, pentaethylenehexamine, and hexaethyleneheptamine. These polyethylene polyamines are difficult to obtain industrially as single compounds, and are generally distributed as mixtures of isomers that are difficult to separate by distillation. Tetraethylenepentamine includes linear tetraethylenepentamine, branched N,N-bis(2-aminoethyl)diethylenetriamine, N-(3,6-diazahexyl)-N'-(3- Azapropyl)piperazine and N-(3,6,9-triazanonyl)piperazine are distributed as a mixture of four amines having 5 amino groups. Polyethylene polyamine having a boiling point higher than that of pentaethylenehexamine is a mixture of more amines, but in the carbon dioxide separation composition of the present invention, there is no problem even if it is used as a mixture. Also, other fractions of polyethylene polyamine, such as tetraethylenepentamine and pentaethylenehexamine, may be used in combination.

Other well-known amines such as monoethanolamine, diethanolamine, N-methyldiethanolamine, aminomethylpropanol, isopropylaminoethanol, and the like may be added to the carbon dioxide separation compositions of the present invention. Alcohols, polyols such as ethylene glycol and glycerin, and polyethylene glycol may also be added.

The carbon dioxide separation composition of the present invention can be applied to carbon dioxide separation methods widely known as chemical absorption methods. In the chemical absorption method, a carbon dioxide separation composition is brought into contact with a gas containing carbon dioxide to selectively absorb carbon dioxide, and then the carbon dioxide is released by applying a high temperature or reduced pressure. Generally, the temperature at which carbon dioxide is diffused is 100°C or higher, but when the carbon dioxide separation composition of the present invention is used, carbon dioxide can be diffused even at a temperature of 100°C or lower.

INDUSTRIAL APPLICABILITY The carbon dioxide separation composition of the present invention can dissipate absorbed carbon dioxide with high efficiency, so that it can separate carbon dioxide with low energy and is industrially very useful.

The present invention will be described in more detail by the following examples, but the invention is not limited to these. The following abbreviations were used to simplify the notation.

MEA: Monoethanolamine DETA: Diethylenetriamine (manufactured by Tosoh Corporation)
PO: propylene oxide DETA-PO: N-(2-hydroxypropyl)diethylenetriamine DETA-2PO: N,N''-bis(2-hydroxypropyl)diethylenetriamine P8: amine having more amino groups than pentaethylenehexamine having 6 amino groups is a polyethylene polyamine mixture (manufactured by Tosoh Corporation)
ZnCu: Catalyst in which zinc (II) chloride, copper (II) chloride, and DETA are mixed at a molar ratio of 1:1:8 Example 1 (synthesis of DETA-PO)
100 g of DETA was placed in a three-necked flask equipped with a condenser and a thermometer, heated to 60° C., and 56.3 g of PO was added dropwise over 2 hours while stirring. After that, the temperature was raised to 95° C. and heated for 1 hour to synthesize DETA-PO.

Example 2 (Synthesis of DETA-2PO)
A 3-neck flask equipped with a condenser and a thermometer was charged with 52.1 g of DETA-PO, heated to 60° C., and 18.8 g of PO was added dropwise over 2 hours while stirring. Then, the temperature was raised to 95° C. and heated for 1 hour to synthesize DETA-2PO.

Example 3
100 g of carbon dioxide-absorbing liquid was prepared by adding 70 g of pure water to 30 g of DETA-PO. This was supplied by a pump from the top of an absorption tower set at 40° C., and a 40% carbon dioxide-nitrogen mixed gas was supplied from the bottom at 500 mL/min to absorb carbon dioxide. The absorbent was recycled to the upper part of the absorption tower until it no longer absorbed carbon dioxide. The amount of carbon dioxide absorbed was 52.5 L per 1 kg of the absorbent. When this was supplied to a stripping tower heated to 90° C., 17.0 L of carbon dioxide was stripped per 1 kg of the absorbent. The results are shown in Table 1.

Examples 4-7, Comparative Examples 1-2
A carbon dioxide absorbing solution was prepared from the amines and additives shown in Table 1, and the same method as in Example 3 was used to evaluate the carbon dioxide absorbing performance and releasing performance. The results are shown in Table 1.

Claims (3)

N-(2-hydroxypropyl)diethylenetriamine and/or N,N''-bis(2-hydroxypropyl)diethylenetriamine, water , and phosphoric acid and/or phosphate , the water concentration being 30 to 95 wt. % carbon dioxide separation composition. consisting of N-(2-hydroxypropyl)diethylenetriamine and/or N,N''-bis(2-hydroxypropyl)diethylenetriamine, water, and a zinc (II) compound and/or a copper (II) compound , the concentration of water being A carbon dioxide separation composition that is between 30 and 95% by weight . N-(2-Hydroxypropyl)diethylenetriamine and/or N,N''-bis(2-hydroxypropyl)diethylenetriamine, water, and a polyethylenepolyamine mixture containing 6 amino groups and an amine having more amino groups than pentaethylenehexamine as the main component. and wherein the concentration of water is 30-95% by weight .