JPH0380056B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a carbon monoxide (hereinafter referred to as CO) absorbent, and in particular to a carbon monoxide (hereinafter referred to as CO) absorbent, which selectively absorbs CO from a mixed gas containing CO, and which easily absorbs CO by changing pressure.
This article relates to a method for modifying a solid absorbent that has the property of absorbing and desorbing CO. CO is a basic raw material in synthetic chemistry, and research is progressing in various fields on the effective use of CO contained in coke oven exhaust gas. Regarding absorbents for separating and concentrating CO, copper aluminum tetrachloride (CuAlCl ₄ ) toluene solution (COSORB solution)
is well known. When this solution is used, there are drawbacks such as significant deterioration due to water despite its high absorption capacity and toluene as a solvent being mixed in during CO recovery. Moreover, in this solution method, it is necessary to rely on varying the temperature for absorption and desorption of CO, making it even more difficult to avoid contamination with toluene. The present invention was developed as a result of intensive research by the inventors to overcome these drawbacks. First, we will utilize the advantages of COSORB solution as they are, eliminate the above disadvantages, and use it as a solid CO absorption and separation agent that has high selectivity absorption and separation performance for CO and is extremely resistant to deterioration due to water and other poisonous gases. A water-resistant carbon monoxide absorbent containing cuprous chloride, aluminum chloride, an aromatic compound, and an acidic oxide was proposed (Japanese Patent Application No. 40292/1986). The absorbent has extremely high water resistance compared to COSORB solution, and the three components consisting of cuprous chloride, aluminum chloride, and aromatic compounds form a complex on acidic oxide to stabilize it, and the aromatic The group compounds exhibit some kind of interaction with acidic oxides that act as carriers, and are characterized by extremely high CO absorption capacity.
It is known that monovalent copper ions (Cu()) of cuprous chloride, which is the first component in the absorbent, absorb CO well. However, if the above-mentioned absorbent lacks even one of the four constituent components, an absorbent having water resistance cannot be provided. That is, the first component copper chloride, the second component aluminum chloride, the third component aromatic compound, and the fourth component acidic oxide are all essential components. Moreover, although this absorbent is water resistant, its bond with CO is extremely stable, so it was necessary to cause a larger change in the amount of absorption and desorption due to changes in temperature rather than pressure. However, porous materials that are effective in efficiently dispersing and supporting many acidic oxides, particularly the above-mentioned metal species active in CO absorption, exhibit only an extremely slow response to thermal fluctuations. Therefore, when these absorbents are used to separate and recover high-purity CO through absorption and desorption, the cycle requires an extremely long time. As a result of further investigation to overcome these shortcomings, we discovered that we could modify the CO absorbent to be highly pressure dependent. For example, by contacting the above-mentioned CO absorbent with a polar gas, it is possible to modify the CO absorbent into one in which absorption and desorption of CO largely depends on pressure fluctuations. To date, it is not clear what kind of changes are brought about in its structure, but its absorption selectivity is maintained, its absorption binding force is weakened, and CO, which is highly dependent on CO pressure fluctuations, is It seems that absorbent properties were developed. A possible reason is that the coordination state around the copper forming the complex is controlled and the copper
It is thought that the binding force with CO has changed within a range that does not reduce CO absorption selectivity. "Modification" as used in the present invention means that the CO absorption/desorption performance is modified, including a change in structure, or without a change in structure. The absorbent modified by the method of the present invention has an extremely large amount of CO2 due to pressure fluctuations compared to the absorbent before treatment.
It is characterized by showing the amount recovered. Therefore, by using the absorbent of the present invention, a recovery process that utilizes absorption and desorption of CO due to pressure fluctuations can be established, which reduces cycle time compared to CO recovery that utilizes temperature fluctuations. It became possible to make it extremely short. The absorbent targeted by the method of the present invention includes cuprous chloride, aluminum chloride, an aromatic compound, and a porous material, and aluminum chloride forms a complex with cuprous chloride and the aromatic compound to unify copper ions. It is an essential component that acts to maintain stable levels. Further, the aromatic compound as the third component is necessary to form a complex with cuprous chloride as the first component and aluminum chloride as the second component, and at the same time to provide water resistance, which is a characteristic of the absorbent of the present invention. be. Furthermore, the temperature range that can be used for its preparation and the method of the invention will depend on the type of aromatic compound forming the chain. For example, when toluene is used, it is stable up to about 120°C, but in general, when heated to a temperature 20 to 30°C higher than the boiling point of the aromatic compound used, the aromatic compound desorbs from the complex and is removed. is possible. Therefore, absorbent preparation, modification and CO
It is necessary to appropriately select the aromatic compound to be used depending on the operating conditions for absorption and desorption of. Generally, general-purpose materials such as benzene, toluene, xylene, and polystyrene are used. However, solvents that do not have the ability to dissolve copper chloride or aluminum chloride, low boiling point solvents, or highly volatile solvents are not preferred. The fourth component, the porous body, acts as a carrier to uniformly disperse and immobilize the complex consisting of cuprous chloride, aluminum chloride, and an aromatic compound. An example of a preferred porous material is an acidic oxide. Acidic oxides have either Brønsted acid sites, which are stable at low temperatures, or Lewis acid sites, which are easily generated at high temperatures, on their surfaces, and at the same time the complex is sufficiently dispersed, the aromatic compounds in the complex are Something that can maintain interaction is desirable. For example, alumina
These include silica, silica-alumina, silica-magnesia, and the like. On the other hand, if the surface area is too large, the pores become too small and the dispersibility of the complex compound decreases, which is not preferable. Usually in BET surface area
40-400 m ² /g, preferably 50-300 m ² /g is preferred. The amount of complex compound supported on the porous body is 100
1 as the sum of the first and second components per part by weight
-50 parts by weight, preferably 10-40 parts by weight. In this case, if aluminum chloride is present in excess,
It can also react with water to generate HCl, which can degrade the absorbent. Therefore, it is preferable to carry cuprous chloride in a slight excess. Furthermore, the aromatic compound is generally 0.1 to
It is supported so that it becomes 0.5 mol. In particular, the supported amount
It is preferably 0.25 mol or more. The modification of the present invention may be any treatment that can weaken the excessively strong CO absorption binding force to a preferable range. For example, this can be carried out by contacting a polar gas such as water vapor or hydrogen sulfide at room temperature or, if necessary, at an elevated temperature. One of the simple methods for such treatment is contact with water vapor. Specifically, the amount of water vapor is several times to several tens of times the number of moles of copper, generally 2 to 3 times the amount of water vapor, and divided into several to several dozen times, generally 4 to 10 times, at a temperature ranging from room temperature to 90°C. This can be done by making contact at the bottom. The CO separation absorbent that relies on the pressure fluctuation method in the present invention refers to an absorbent modified according to the present invention that is efficient in absorbing and separating CO by pressure fluctuation of CO, and is used in the present invention. The pressure range is e.g.
Selected between 20 atm and 10 torr. Naturally, any method for increasing product purity in the pressure fluctuation method of the present invention, such as interparticle purge method, pore purge method, purge method effective for porous absorbents, etc., is not precluded from being applied. That is, absorption is carried out using the absorbent of the present invention in a normally pressurized state, and then purged with product gas,
High purity CO can be efficiently recovered as a product by discharging unabsorbed gas and recovering the product gas under reduced pressure or reduced pressure. Examples of CO-containing gases to which the absorbent modified by the method of the present invention can be applied include blast furnace, converter, and coke oven gases in steel plants, and processed products thereof. The present invention will be explained in more detail below using Examples. Example: 54 g of cuprous chloride, 72 g of aluminum chloride, and 600 ml of toluene in a 3000 ml eggplant flask under dry nitrogen.
The mixture was dissolved and heated and kept at 60°C for 2 hours. The solution exhibited a transparent black color characteristic of a CuCl-AlCl ₃ -toluene complex solution. Here, cuprous chloride, aluminum chloride, and toluene were all commercially available special grade reagents (each manufactured by Wako Pure Chemical Industries, Ltd.) and used as they were. It was fired as a porous body at 550℃ for 3 hours.
200 g of activated alumina beads (manufactured by Sumitomo Alumina Co., Ltd., average pore diameter 116 Å, 8ET surface area 250 m ² /g) were placed in an eggplant flask, and the inside of the eggplant flask was sufficiently degassed using a vacuum pump, and then the pressure was increased with nitrogen. The above complex solution was returned and the porous body was immersed in the complex solution.
After immersing for 30 minutes, the pressure inside the eggplant flask was reduced (6 mmHg) using a vacuum pump, and the flask was evacuated at room temperature all day and night to sufficiently exhaust the toluene. Afterwards, the pressure was returned to nitrogen. Add nitrogen gas containing saturated water vapor to this material.
Contact for 10 minutes at a flow rate of 3.5/min, then 90℃
The sample was brought into contact with dry nitrogen in a heated state, and then cooled to room temperature. This operation was repeated eight times to obtain an absorbent. 40 g of this absorbent was filled into a stainless steel SUS-304 reactor with an inner diameter of 25 mm and a length of 100 mm.
A standard gas having the following composition was used as a raw material gas under reduced pressure. CO 66Vol% N ₂ 17Vol% CO ₂ 17Vol% The flow rate of this raw material gas at 25℃ and a total pressure of 1.1Kg/cm ² A
Aerated at 300Ncc/min for 5 minutes. After the absorption was completed, the pressure inside the reactor was reduced to 100 torr using a vacuum pump.
The time required to reduce the pressure was about 1 minute. The amounts and compositions of the raw material gas and recovered gas were as follows.

[Table] Comparative Example The method of the example was repeated except that 40 g of the absorbent which had not been subjected to the modification treatment (in this case, repeated contact with nitrogen gas containing a saturated amount of water vapor) of the example was used. The results were as follows.

【table】

Claims (1)

[Claims] 1. Absorbing and separating carbon monoxide through pressure fluctuations characterized by bringing a carbon monoxide absorbent made of a porous material, cuprous chloride, aluminum chloride, and an aromatic compound into contact with a polar gas. Method for modifying solid carbon monoxide absorbent. 2 Claim 1 in which the polar gas is water vapor
Modification method of terms. 3. The reforming method according to claim 1 or 2, wherein contact with the polar gas is carried out multiple times. 4. The reforming method according to any one of claims 1 to 3, wherein the contact with the polar gas is carried out under heating.