JP5238527B2 - Carbon dioxide absorption separation method and carbon dioxide absorption separation agent - Google Patents

Description

  The present invention relates to a carbon dioxide absorption separation method and a carbon dioxide absorption separation agent. More specifically, exhaust gas generated from energy plants and chemical plants using hydrocarbon-based raw materials and fuels such as coal-fired power plants, exhaust gases generated from automobiles, etc. The present invention relates to a carbon dioxide absorption separation method and a carbon dioxide absorption separation agent for recovering carbon dioxide.

  Reducing carbon dioxide emissions from coal-fired power plants has become an urgent task due to the recent interest in global warming and the background of stricter regulations. Therefore, as a method for reducing the amount of carbon dioxide emissions, the collection of carbon dioxide with chemical absorbents has attracted a great deal of attention as well as the reduction of emissions due to the high efficiency of power plants.

  As a specific absorbent, absorption by amine has been studied for a long time (for example, Patent Document 1). In this case, for example, the carbon dioxide gas is brought into contact with the alkanolamine aqueous solution in the absorption tower to absorb the carbon dioxide gas, and then the carbon dioxide absorption liquid is heated to desorb and recover the carbon dioxide gas in the desorption tower. .

  Here, monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), methyldiethanolamine (MDEA), diisopropanolamine (DIPA), diglycolamine (DGA), etc. are known as alkanolamines. However, monoethanolamine is usually used.

  However, for example, when an aqueous solution of alkanolamine such as MEA is used as the absorbing solution, although the carbon dioxide absorption capacity per unit volume is excellent, the corrosiveness of the material of the device is high, so expensive corrosion-resistant steel is used for the device. It was necessary to reduce the amine concentration in the absorbing solution. Further, since the absorbed carbon dioxide gas is difficult to desorb, it is necessary to desorb and recover by heating the desorption temperature to a high temperature of 120 ° C.

  On the other hand, desorption by heat treatment at such a high temperature requires a large amount of energy, so it is not suitable in an era where energy saving and resource saving are required, and is a major factor hindering practical use.

  In order to solve the above problems, a mixture of various amines in which piperazine is added to alkanolamine is used as a carbon dioxide absorbent (Patent Document 2), and a mixture in which lower alkyl piperazine is similarly added to alkanolamine is used. Attempts have been made to use it as a carbon dioxide gas absorbent (Patent Document 3). Attempts have also been made to use a crosslinked polymer of vinylamine and polyvinylamine as a carbon dioxide adsorbent (Patent Document 4).

  According to these methods, the heat treatment temperature when desorbing the carbon dioxide absorbed by the carbon dioxide absorbent can be reduced to about 70 ° C to 90 ° C. However, the heat treatment needs to be performed on the entire absorbent that has absorbed carbon dioxide gas. Therefore, although the heat treatment temperature can be reduced, the heat treatment still requires a large amount of energy. I was trying.

JP-A-3-151015 JP 2006-240966 A WO99 / 51326 JP-A-6-190235

  In view of the above-described problems, the present invention provides a carbon dioxide absorption separation method and a carbon dioxide absorption separation agent that can reduce energy required for releasing and recovering absorbed carbon dioxide, that is, carbon dioxide. With the goal.

One embodiment of the present invention includes a step of contacting a gas containing at least carbon dioxide with a basic aqueous solution to absorb carbon dioxide, and a protein that decomposes the protein by cleaving the peptide bond of the protein in the basic aqueous solution. A method for absorbing and separating carbon dioxide, comprising the step of contacting with a decomposing enzyme to separate and release carbon dioxide from the basic aqueous solution.

One embodiment of the present invention includes a basic aqueous solution, and a proteolytic enzyme that degrades the protein by cleaving the peptide bond of the protein arranged separately from the basic aqueous solution. The present invention relates to a carbon dioxide absorbing / separating agent.

  ADVANTAGE OF THE INVENTION According to this invention, the carbon dioxide absorption separation method and carbon dioxide absorption separation agent which can reduce the energy required when discharge | releasing and collect | recovering absorbed carbon dioxide, ie, a carbon dioxide, can be provided.

  The contents of the present invention are shown in detail below.

(Carbon dioxide absorption separation agent)
First, the carbon dioxide absorption / separation agent used in the carbon dioxide absorption / separation method of the present invention will be described. As described above, the separating agent includes a basic aqueous solution and an enzyme. Hereinafter, each component will be described.

<Basic aqueous solution>
The basic aqueous solution in this embodiment is not particularly limited as long as it can absorb carbon dioxide through a chemical reaction or the like, but generally a basic organic compound, specifically, an organic compound having an organic base is dissolved in water. By forming.

  Examples of such organic compounds include aliphatic primary amines, aliphatic secondary amines, aliphatic tertiary amines, hydrates thereof, quaternary ammonium hydroxides, or two or more selected from these. A mixture etc. can be illustrated. Moreover, monoethanolamine, dimethylethanolamine, methyldiethanolamine, piperazine, trimethylamine, trimethylamine hydrate, etc. can be illustrated.

  These organic compounds exhibit a relatively high pH value when dissolved in water and exhibit high absorption characteristics for carbon dioxide.

  The pH value of the basic aqueous solution is preferably 11 or more. In this case, although the reason is not clear, the absorption rate of carbon dioxide into the basic aqueous solution increases.

  Moreover, in order to implement | achieve the said pH value, although it can achieve by making content of the said organic compound in the said basic aqueous solution into 20 to 80 weight%, for example, a pH adjuster etc. are needed. Can be used.

  Furthermore, since the carbon dioxide is contained in, for example, exhaust gas from an energy plant, various harmful gases may be included in addition to the carbon dioxide. Therefore, in the basic aqueous solution, other compounds such as nitrogen-containing compounds and antioxidants are arbitrarily selected so that the basic carbon dioxide absorption capacity of the basic use liquid by the toxic gas is not impaired and the basicity can be sufficiently secured. You may contain in the ratio.

<Enzyme>
The enzyme in this embodiment is a proteolytic enzyme and needs to be an enzyme that degrades a protein by cleaving the peptide bond of the protein.

  As described above, the basic aqueous solution contributes to absorption of carbon dioxide, but the enzyme promotes separation of the carbon dioxide after absorbing carbon dioxide with the basic aqueous solution. It is.

  The present inventors have intensively studied to reduce the energy required for releasing and recovering carbon dioxide, and in a vast experiment, in a field completely different from the field related to the absorption of carbon dioxide. The scope of study was expanded to a certain field related to biochemistry. As a result, it has been found that an enzyme that cleaves a peptide bond of a protein contributes to separation of carbon dioxide absorbed by the basic aqueous solution as described above.

  The principle of promoting carbon dioxide separation by the enzyme has not yet been completely clarified. For example, in the case where the basic aqueous solution contains an amino group-containing organic compound, the reaction represented by the following formula (1): After the organic compound reacts with carbon dioxide to form an amide compound based on the formula, the amide bond of the amide compound is divided based on the reaction formula as shown in the following formula (2), It is possible to separate.

  Therefore, in view of such a reaction process, the enzyme can be considered as an amide bond hydrolase. However, the above explanation is based solely on the present inventors' consideration, and even if actual separation promotion of carbon dioxide occurs on a different principle, carbon dioxide absorbed in the basic aqueous solution as long as the enzyme described above is used. There is no substitute for promoting the separation of As a result, the feasibility of the present invention is not denied.

  Examples of the above-described enzyme include protease and peptidase.

  Commercially available proteases and peptidases include protease S “Amano” G (registered trademark), protease A “Amano” G (registered trademark), protease M “Amano” G (registered trademark), and protease P “Amano” 3G (registered trademark). ), Protease N “Amano” G (registered trademark), Neurase F3G (registered trademark), Proreza-FG-F (registered trademark), Papain W-40 (registered trademark), Peptidase R (registered trademark), Umamizyme G ( Registered trademark) and Bromelain F (registered trademark) (all available from Amano Enzyme Inc.).

  Other commercially available proteases include Protin SD-AY10 (registered trademark), Protin SD-AC10F (registered trademark), Protin SD-PC10F (registered trademark), Protin SD-NY10 (registered trademark), Samoaase PC10F (registered trademark) Trademark) (all available from Daiwa Kasei Co., Ltd.).

  Further, other commercially available proteases include Esperase (registered trademark), Alcalase (registered trademark), Neutrase (registered trademark), Durazym (registered trademark), Savinase (registered trademark), Pyrase (registered trademark), spleen trypsin NOVO ( PTN), Bio-Feed® Pro and Clear-Lens® Pro (all available from Novo Nordisk A / S, Bagsvaerd, Denmark).

  Other commercially available proteases include Maxatase (R), Maxacal (R), Maxapem (R), Opticlean (R) and Purafect (R) (all available from Genencor International Inc. or Gist-Brocades ).

  In addition, it is preferable to contain the said enzyme in the said basic aqueous solution in the ratio of 0.5 weight part-5 weight part, for example. If the amount is less than 0.5 parts by weight, the effect of the enzyme cannot be sufficiently achieved, and if the amount exceeds 5 parts by weight, the effect of promoting the separation of carbon dioxide cannot be improved. There is a problem that the high cost associated with the separation of carbon dioxide increases due to an increase in the amount used.

  The enzyme can be directly put into the basic aqueous solution to be contained. Preferably, the enzyme is put in the basic aqueous solution in a state of being supported on a carrier, or is made independent as the carrier, for example, a filter. It can also exist as

  Thus, handling the enzyme is facilitated by supporting the enzyme on a carrier. In particular, if the carrier is made of a water-insoluble one, both the enzyme and the carrier can be reused, and the cost associated with carbon dioxide separation can be reduced.

  As the carrier, for example, a porous membrane and particles can be used. The pore diameter of the porous membrane and the size of the particles are appropriately determined depending on the type of enzyme used, the constituent material of the carrier, the supporting method described below, and the like. Further, by configuring the carrier from the porous membrane, as described above, the carrier itself can be used as a filter in a state where the enzyme is supported.

  As a loading method, a general-purpose method can be used. A carrier binding method in which the carrier is immobilized on a carrier by covalent bond, physical adsorption, ionic bond, or the like, or a crosslinking method in which a bifunctional or carrier-functional reagent crosslinks and insolubilizes. , Encapsulated in polymer gels, μ capsules, liposomes, micelles, etc. that are produced by polymerizing or associating low molecular weight compounds or transferring high molecular compounds from a soluble state to an insoluble state, hollow fibers or ultrafiltration membranes (See Introduction to Enzyme Engineering, Biotechnology Textbook Series 8, Tatsuo Tanaka, published by Corona).

  As the carrier used in the carrier binding method, the covalent bonding method includes cellulose, agarose, dextran, chitin, chitosan beads, amino acid polymer, polystyrene, ethylene-maleic acid copolymer, polyacrylamide, polyvinyl alcohol, nylon, ion exchange resin, glass. Beads, nickel silica alumina, zirconia, ceramics, physical adsorption method, sand, carbon, activated carbon, silica gel, alumina, celite, molecular sieve, titania, stainless steel, ion binding method, Amberlite, cellulose, crosslinking method, maleimide Derivatives, aryl halides, isocyanates, imide esters, glutaraldehyde, hexamethylene diisothiocyanate, bisdiazobenzidine, comprehensive methods, collagen, fibrin, albu , Casein, cellulose fiber, agar, alginic acid, carrageenan, agarose, polyacrylamide, poly-2-hydroxyethylmethacrylic acid, polyvinyl chloride, γ-methylpolyglutamic acid, polydimethylacrylamide, polyurethane, nylon, polystyrene, polyurea, ethylcellulose, silicone Derivatives.

(CO2 absorption separation method)
Next, a method for absorbing and separating carbon dioxide using the above-mentioned solution for absorbing and separating carbon dioxide will be described.

  First, the basic aqueous solution described above is prepared, a gas containing at least carbon dioxide is brought into contact with the basic aqueous solution, and the carbon dioxide is absorbed based on a reaction formula as shown in, for example, the formula (1). At this time, it is sufficient that the gas and the basic aqueous solution can be in contact with each other. For example, by a bubble stirring tank, a gas dispersion type absorption device using a bubble tower, a spray tower, a spray chamber, a scrubber, a wet wall tower, and a packed tower. Existing carbon dioxide absorption equipment such as a liquid dispersion type absorption device can be used. From the viewpoint of carbon dioxide absorption efficiency, absorption using a carbon dioxide absorption tower filled with a filler is preferred.

  Next, an enzyme is contained in the basic aqueous solution, for example, in a state of being supported on a carrier, and the basic aqueous solution is heated to release carbon dioxide absorbed in the basic aqueous solution. In addition, it is preferable that the temperature in this case is 25 degreeC-70 degreeC from a viewpoint of an absorption rate and absorption efficiency. That is, according to this aspect, carbon dioxide absorbed at such a low temperature can be released, and the temperature can be sufficiently lowered as compared with the conventional temperature of about 120 ° C. necessary for carbon dioxide release. can do. Therefore, the energy required for separating absorbed carbon dioxide can be sufficiently reduced.

  In addition, as described above, when the carrier containing the enzyme is used as a separate filter, the basic aqueous solution is similarly passed through the filter while being heated in a range of, for example, 25 ° C to 70 ° C. To separate and release the absorbed carbon dioxide.

  Examples are shown below.

Example 1
A monoethanolamine 5 mol / L aqueous solution was used as a basic aqueous solution. This basic aqueous solution was set to 30 ° C., and carbon dioxide was aerated at a flow rate of 1 L / min and absorbed for about 30 minutes. Thereafter, the basic aqueous solution was brought to 40 ° C. and passed through a membrane carrying 0.5% by weight of protease M “Amano” G with respect to polyvinyl alcohol to separate and release carbon dioxide. The amount of carbon dioxide released was measured using a carbon dioxide concentration meter. It was found that about 60% of the carbon dioxide absorbed after 30 minutes was separated and released.

(Example 2)
Carbon dioxide was absorbed and separated in the same manner as in Example 1 except that protease P “Amano” 3G was used instead of protease M “Amano” G. As a result, it was found that about 70% of the carbon dioxide absorbed after 30 minutes was separated and released.

(Example 3)
Carbon dioxide was absorbed and separated in the same manner as in Example 1 except that the amount of protease M “Amano” G supported on polyvinyl alcohol was increased from 0.5 wt% to 5 wt%. As a result, it was found that about 75% of the carbon dioxide absorbed after 30 minutes was separated and released.

Example 4
Carbon dioxide was absorbed and separated in the same manner as in Example 1 except that peptidase R was used instead of protease M “Amano” G. As a result, it was found that about 60% of the carbon dioxide absorbed after 30 minutes was separated and released.

(Example 5)
Carbon dioxide was absorbed and separated in the same manner as in Example 1 except that protease P “Amano” 3G was used instead of protease M “Amano” G. As a result, it was found that about 50% of the carbon dioxide absorbed after 30 minutes was separated and released.

(Example 6)
Carbon dioxide was absorbed and separated in the same manner as in Example 1 except that the amount of protease M “Amano” G supported on polyvinyl alcohol was increased from 0.5 wt% to 5 wt%. As a result, it was found that about 50% of the carbon dioxide absorbed after 30 minutes was separated and released.

(Example 7)
Carbon dioxide was absorbed and separated in the same manner as in Example 2 except that peptidase R was used instead of protease M “Amano” G. As a result, it was found that about 45% of the carbon dioxide absorbed after 30 minutes was separated and released.

(Comparative Example 1)
Carbon dioxide was absorbed and separated in the same manner as in Example 1 without using a membrane on which 0.5% by weight of protease M “Amano” G was supported on polyvinyl alcohol. As a result, it was found that about 20% of the carbon dioxide absorbed after 30 minutes was separated and released.

(Comparative Example 2)
Carbon dioxide was absorbed and separated in the same manner as in Example 5 without using a membrane on which 0.5% by weight of protease M “Amano” G was supported with respect to polyvinyl alcohol. As a result, it was found that about 40% of the carbon dioxide absorbed after 30 minutes was separated and released.

  As is apparent from the examples and comparative examples, according to the present invention, when an enzyme such as protease M “Amano” G that cleaves peptide bonds of proteins is allowed to act on a basic aqueous solution, about 40 ° C. It can be seen that 45% or more of the absorbed carbon dioxide can be released in such a low temperature and a short time of 30 minutes. On the other hand, when carbon dioxide is separated without using the enzyme as described above, it can be seen that only about 40% or less of carbon dioxide can be separated and released under the same conditions.

  As mentioned above, although this invention was demonstrated in detail based on the said specific example, this invention is not limited to the said aspect, All the changes and deformation | transformation are possible unless it deviates from the category of this invention.

  For example, in the above examples, monoethanolamine is used to prepare a basic aqueous solution, but the above-described aliphatic primary amine, aliphatic secondary amine, aliphatic tertiary amine, hydrates thereof, Similar results are obtained even when quaternary ammonium hydroxide, dimethylethanolamine, methyldiethanolamine, piperazine, trimethylamine, trimethylamine hydrate, or the like is used.

  That is, as is apparent from the above prior art and the detailed description of the present invention described above, the present invention is mainly characterized by bringing a basic aqueous solution into contact with an enzyme, and separating and releasing carbon dioxide from the basic aqueous solution. There is. Therefore, in the above-described embodiments, monoethanolamine is used for preparing the basic aqueous solution from the viewpoint of availability, etc., and it is essential that the basic aqueous solution contains monoethanolamine. It is not something to do.

Claims (11)

Contacting a gas containing at least carbon dioxide with a basic aqueous solution to absorb carbon dioxide;
Contacting the basic aqueous solution with a proteolytic enzyme that degrades the protein by cleaving the peptide bond of the protein , separating and releasing carbon dioxide from the basic aqueous solution;
A method for absorbing and separating carbon dioxide, comprising:   The method for absorbing and separating carbon dioxide according to claim 1, wherein the pH value of the basic aqueous solution is 11 or more. The method for absorbing and separating carbon dioxide according to claim 1 or 2 , wherein the enzyme is supported on a carrier. The method for absorbing and separating carbon dioxide according to claim 3 , wherein the carrier is at least one of a porous membrane and particles.   The method for absorbing and separating carbon dioxide according to claim 4, wherein the porous membrane and the particles are insoluble in water. The temperature at the time of carbon dioxide separation of the basic aqueous solution is in the range of 25 ° C to 70 ° C, and the method for absorbing and separating carbon dioxide according to any one of claims 1 to 5 . A carbon dioxide absorption / separation agent comprising: a basic aqueous solution; and a proteolytic enzyme that decomposes the protein by cleaving a peptide bond of the protein arranged separately from the basic aqueous solution . The carbon dioxide absorption / separation agent according to claim 7 , wherein a pH value of the basic aqueous solution is 11 or more. The carbon dioxide absorption / separation agent according to claim 7 or 8 , wherein the enzyme is supported on a carrier. The carbon dioxide absorption / separation agent according to claim 9 , wherein the carrier is at least one of a porous membrane and particles. The carbon dioxide absorption / separation agent according to claim 10 , wherein the porous membrane and the particles are insoluble in water.