JPH06226037A - Method for making either of organic solvent vapor or moisture in gas selectively adsorbed and removing the same - Google Patents

Abstract

PURPOSE:To make either of a solvent or moisture selectively absorbed and remove it by changing the rotating speed of a honeycomb-shaped adsorption rotor at the time of adsorption of the solvent or the moisture by using zeolite having mesopores as an adsorbent. CONSTITUTION:The honeycomb-shaped rotor 4 using the zeolite having the mesopores as the adsorbent is rotated and the air contg. the org. solvent vapor and the moisture is passed through an adsorption zone 7 and heating air 12 for regeneration through a regeneration zone 8, respectively, by which either of desorption and adsorption regeneration is continuously executed. The rotating speed of the honeycomb-shaped adsorption rotor 4 is changed at this time. The org. solvent vapor is then preferentially adsorbed away when the rotating speed of the rotor 4 is low and the moisture is preferentially adsorbed away when the rotating speed is high.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for selectively adsorbing and removing organic solvent vapor and moisture contained in air and other inert gases by using a honeycomb adsorption rotor.

[0002]

2. Description of the Related Art Zeolite has an aluminosilicate as a main component and selectively adsorbs moisture and other gas molecules such as organic solvent vapor according to its molecular diameter due to the difference in the diameter of the pores generated by the elimination of the water of crystallization. For this reason, it is used as an adsorbent as a molecular sieve.

As an element for a dehumidifier, for example, Japanese Patent Laid-Open No. 54-54
No. -19548, a rotary regeneration type dehumidifier made of a cylindrical honeycomb structure obtained by attaching a molecular sieve (4A, 13X, etc.) to a sheet of asbestos paper, glass fiber paper, etc., corrugated and laminated. In addition, JP-A-63-24
No. 0921 proposes a dehumidifying material having a honeycomb structure obtained by adding a binder to powders of A-type, X-type, Y-type, etc. synthetic zeolite or mordenite and other natural zeolite powder, and by extrusion molding or press molding. On the other hand, organic solvent vapor,
As a rotary adsorption element for adsorbing and separating a malodorous gas or the like from the air, for example, JP-A-53-50068 proposes an element formed into a honeycomb structure from paper containing fibrous activated carbon.

[0004]

The above-mentioned zeolite is an inorganic substance composed of aluminosilicate, has no danger of ignition, and is capable of selectively adsorbing gas molecules according to its molecular diameter, as is called molecular sieve. However, when trying to adsorb and separate organic solvent vapor, malodorous gas or the like from the air, since moisture always coexists in the air, moisture is always adsorbed together with the organic solvent vapor, malodorous gas and the like. The diameter of water molecules is 2.8Å, whereas the molecular diameter of organic solvent or malodorous gas is, for example, benzene or 6.7Å, cyclohexane is 6.1Å, etc., which are all larger than the diameter of water molecules, for example, zeolite with a pore size of about 4Å. Although it is possible to adsorb and separate only the moisture by using, it is possible to adsorb and separate only the organic solvent vapor or the malodorous gas in the coexistence of a large amount of the moisture by using, for example, a zeolite having a pore size of about 10Å. Rather, it preferentially adsorbs moisture, and the adsorption of organic solvent vapors or malodorous gas is hindered by the preferentially adsorbed water molecules, and therefore the absolute humidity of the treated air is high (eg 8g). / Kg or more), it is not possible to efficiently adsorb and separate organic solvent vapors or malodorous substances.

Activated carbon is called a hydrophobic adsorbent and preferentially adsorbs non-polar molecules such as hydrocarbons, but since it is combustible, there is a risk of ignition if hot air at a temperature of 130 ° C. or higher is used for desorption and regeneration. Further, depending on the type of the adsorbed solvent, a large amount of heat is generated by adsorption, and a honeycomb rotor using activated carbon often causes an ignition accident due to the heat of adsorption, and is extremely difficult to use. Furthermore, when this rotor is used for a certain period of time and activated when it becomes less active due to attachment of oil with a high boiling point, etc., in order to activate it, high temperature treatment at around 350 ° C must be performed, but hot air is used for this high temperature treatment. However, there was a defect that it was necessary to activate using superheated steam.

As described above, the present invention treats air containing both organic solvent vapor and moisture using a honeycomb-shaped adsorption rotor using zeolite as an adsorbent, which has excellent heat resistance and does not pose a risk of ignition. Therefore, either the organic solvent vapor or the moisture content in the air is selectively adsorbed and removed.

[0007]

[Means for Solving the Problems] Zeolite has pores (micropores) having a constant inner diameter of about 3Å to 10Å depending on the type thereof, and as described above, the moisture content is mainly due to the difference in the pore diameter. Other gas molecules such as organic solvent vapor can be selectively adsorbed according to the molecular diameter, and some zeolites have mesopores in addition to the above-mentioned micropores. (What is Mesopore? “IUPAC Manual of of
Symbols and Terminology ”
Appendix 2, Pt. 1, Colloid
and Surface Chemistry, Pur
e and Appl. Chem. , 31 , 578 (1
972) recommends to refer to pores having an inner diameter of 20 to 500Å. )

FIG. 2 shows adsorption equilibrium isotherms of n-hexane in air at 27 ° C. for two types of zeolite.
In the figure, the horizontal axis represents the logarithm logP / Ps of the ratio between the vapor pressure P of n-hexane and the saturated vapor pressure Ps of n-hexane, and the vertical axis represents the adsorption amount [mmol] of n-hexane per 1 g of zeolite. In the figure, A is US-having mesopores as zeolite
Ex and B show the case where "silicalite" having no mesopore is used. In the case where zeolite having no mesopores is used for n-hexane vapor adsorption, for example, when vapor pressure is gradually increased as shown by the curve B in FIG. 2, the adsorption equilibrium isotherm does not rise sharply from high vapor pressure to low vapor pressure. The adsorption equilibrium isotherm on transition to vapor pressure does not cause the hysteresis phenomenon, ie the adsorbed vapor does not cause capillary condensation.

On the other hand, the zeolite having mesopores has a remarkably high adsorption capacity in a high vapor pressure atmosphere as shown by the curve A in FIG. 2, and when the vapor pressure of the atmosphere gradually increases, it rapidly rises and the vapor pressure decreases. A curve showing the equilibrium adsorption amount when the vapor pressure is gradually increased (adsorption curve, shown as "adsorption" in the figure) and a curve showing the equilibrium adsorption amount when the vapor pressure is gradually decreased from the high vapor pressure (desorption curve, figure (Indicated as “desorption” in the middle) does not coincide with the phenomenon of so-called hysteresis (history), which indicates that multi-layer adsorption and capillary condensation occur.

Natural zeolite, the crystal particles of synthetic zeolite obtained by the direct synthesis method do not have mesopores, but synthetic zeolite, for example, zeolite of Na-Y zeolite in which the skeleton structure of micropores is changed, is used for the production process. In this way, fine grooves are created in the crystal grains of the raw material.
It has a pore size of 5 to 100Å and is almost equivalent to mesopores.

Zeolite mentioned earlier that "rather preferentially adsorbs moisture, and adsorption of organic solvent vapor or malodorous gas is inhibited by preferentially adsorbed water molecules."
Depending on the skeleton structure that forms the micropores, there are some that preferentially adsorb organic solvent vapor or the like over water vapor. For example, in UOP's zeolite 628 or 173, micropores preferentially adsorb organic solvent vapors, and mesopores preferentially adsorb large amounts of water vapor by capillary condensation. (UK issued ZEOLITES magazine, 1986 (Vo
1.6) Please refer to page 74 of the March issue)

Here, a honeycomb-shaped adsorption rotor carrying a powder of zeolite having mesopores is rotated, and an inert gas containing organic solvent vapor and moisture such as air is passed through the adsorption zone of the honeycomb-shaped adsorption rotor to regenerate it. In the operation of passing a high temperature gas for desorption and repeating it alternately to adsorb and desorb organic solvent vapor and moisture continuously, the rotation of the adsorption rotor should be 5 times as shown in FIG.
-10r. p. h. When the speed is low, the adsorption and desorption of the organic solvent vapor on the micropores and the adsorption and desorption of the water vapor on the mesopores are completely performed, but the rotation speed of the adsorption rotor is 15 to 20 r. p. When the speed is increased to about h, the desorption of the organic solvent adsorbed on the micropores is insufficient because the heating time in the regeneration zone is insufficient, and the effective surface area for adsorption is reduced. The desorption of minutes is well carried out, where the effective surface area of adsorption is not reduced. Further, the rotation of the adsorption rotor is set to 28 r. p. h. When the speed is made moderate, the effective surface area for adsorption in the micropores is further reduced, and desorption of the moisture adsorbed in the mesopores is gradually insufficient, and the effective surface area for adsorption is again reduced.

That is, generally, when the rotational speed of the adsorption rotor is gradually increased, the adsorption rate gradually increases, reaches a maximum value, and then gradually decreases. However, when zeolite having mesopores is used as an adsorbent, adsorption of organic solvent vapor The number of rotations of the adsorption rotor when the adsorption rate of water vapor is maximum is higher than the number of rotations of the adsorption rotor when the rate is maximum.

The present inventors have arrived at the present invention by discovering the above facts, that is, the present invention uses a honeycomb-shaped adsorption rotor carrying a zeolite having mesopores as an adsorbent, and uses an organic solvent vapor and a wet solvent. An inert gas containing, for example, air is fed into the honeycomb holes of the adsorption rotor to slow down the rotation speed of the adsorption rotor to preferentially remove the organic solvent vapor by adsorption, or increase the rotation speed of the adsorption rotor. Then, the moisture is preferentially adsorbed and removed.

[0015]

[Example 1] A small amount of pulp and a small amount of binder were added to silica / alumina-based elastic fibers to have a low density of an apparent specific gravity of 0.3 to 0.55 (basis weight: 60 to 150 g /
m about ^2), papermaking inorganic fiber paper width 400mm thickness of about 0.10 to 0.30 mm, the wave wavelength of P 3.4 m
m and a wave height h of 1.8 mm (see FIG. 4) are corrugated using an adhesive to obtain a single wave molded body 1 as shown in FIG. 4, and the single wave is formed on the core material 2 as shown in FIG. Diameter 50 having a large number of small through holes 3 formed by winding the molded body 1 and penetrating both end surfaces
A honeycomb cylindrical body having a length of 0 mm and a length L of 400 mm is formed, and is fired at a high temperature to remove organic substances.

Zeolite 628 or 173 or xNa ₂ O.Al manufactured by UOP, Illinois, USA as zeolite
_{2 O 3 · ySiO 2 · zH} 2 O ( where y ≒ 5 to 33, pore diameter approximately 8 Å) powder was dispersed in an aqueous sol of silica or alumina, the honeycomb-shaped cylinder was immersed in the resulting sol, The above zeolite was adhered to the fiber gaps and surfaces of the inorganic fiber papers 1 and 2 with silica or alumina fine particles as a binder and dried at high temperature to obtain a honeycomb adsorption rotor.

As shown in FIG. 1, for example, a honeycomb-shaped adsorption rotor obtained in a cylindrical shape as shown in FIG. 5 has the adsorption rotor 4 rotatably held in a casing 5 and a separator 6 to form a processing zone 7 and a regeneration zone 8. Separated, and the suction rotor 4 is rotated by the geared motor 9 and the drive belt 10,
The treated air 11 containing moisture and organic solvent vapor is fed into the treatment zone 7, and the high-temperature regenerated air 12 is fed into the regeneration zone 8 to adsorb moisture or organic solvent vapor in the treated air 11 to dry air or The clean air 13 is obtained. In the figure, 14 is a pulley, 15 is a tension pulley, 16
Is a rubber seal, and 17 is a regenerated air heater.

The rotation speed of the rotor 4 is 4 to 24 r. p.
h. , Regenerated air amount to treated air amount is 1:10, treated inlet air temperature is 20 ° C., humidity is 17 g / kg ′, toluene vapor content is 200 ppm, regeneration inlet air temperature is 140.
C., humidity 17 g / kg ', and process air and regeneration air flow rates of 2 m / sec. FIG. 6 shows the removal amount of water vapor and toluene vapor, that is, the adsorption amount, and the removal rate when the adsorption operation was performed under the conditions. Here, the steam removal rate means a value obtained by subtracting the ratio of the steam content rate of the process outlet air and the steam content rate of the process inlet air from one. Even if the concentration of toluene vapor in the treatment inlet air varies within the range of 10 to 1000 ppm, the removal rate of toluene vapor hardly changes.

[0019]

[Comparative Example] Zeolite having almost no mesopores obtained by direct synthesis as zeolite ("Sumerlite" manufactured by UOP, USA, silica / alumina molar ratio of 3 or more)
In the same manner as in Example 1, the fine particles of No. 3 were used to fix the zeolite fine particles to the honeycomb cylindrical body using an inorganic binder to obtain a honeycomb adsorption rotor.

The honeycomb adsorption rotor 4 thus obtained is assembled and used as shown in FIG. The rotation speed of the rotor 4 is 4 to 24 r. p. h. , Regenerated air amount to treated air amount 1:10, treated inlet air temperature 20 ° C., humidity 17 g / kg ′, methyl ethyl ketone vapor content 20
0 ppm, regeneration inlet air temperature 140 ° C, humidity 17
g / kg ', the flow velocity of treated air and regenerated air is 2 m / s
FIG. 8 shows the removal rates of water vapor and methyl ethyl ketone vapor when the adsorption operation was performed under the condition of ec.

[0021]

As is apparent from the adsorption data of Example 1, that is, FIG. 6 and FIG. 7, when the zeolite having mesopores is used as the adsorbent, the moisture content is higher than the optimum number of revolutions for the purpose of solvent adsorption. The optimum rotation speed for adsorption is higher, and the optimum rotation speed for solvent adsorption is 9r. p. h. In the case of the solvent adsorption rate of 98%, the moisture adsorption rate is about 37%, and the organic solvent vapor is preferentially adsorbed. On the other hand, the optimum rotational speed of 21r. p.
At h, the moisture adsorption rate increases to 64%, the organic solvent vapor adsorption rate decreases to about 80%, and the moisture is preferentially adsorbed. That is, by increasing the rotation speed of the honeycomb adsorption rotor, the moisture contained in the air or other inert gas is preferentially adsorbed, and by lowering the rotation speed, the organic solvent vapor can be preferentially adsorbed and removed. I have. In the practice of the present invention, other adsorbents can of course be used together.

On the other hand, when zeolite having almost no mesopores is used as the adsorbent, the moisture adsorption from the optimum rotational speed when solvent vapor adsorption is aimed is clear, as is clear from the adsorption data of the control example. Optimum number of revolutions for the purpose is large, but optimal number of revolutions for adsorbing moisture is 15
r. p. h. In, the solvent vapor adsorption rate is much higher than the moisture adsorption rate. That is, even if the rotation speed is changed, the removal rate of moisture is extremely low and it cannot be used for adsorption removal of moisture.

[Brief description of drawings]

1 is a partially cutaway perspective view of an apparatus used to carry out the method of the present invention.

FIG. 2 is a graph showing an adsorption equilibrium isotherm of zeolite.

FIG. 3 is a graph illustrating adsorption on micropores and mesopores.

FIG. 4 is a perspective view showing a one-sided molded body.

FIG. 5 is a perspective view showing a honeycomb cylindrical body.

FIG. 6 is a graph showing adsorption amounts of organic solvent vapor and moisture according to an embodiment of the present invention.

FIG. 7 is a graph showing adsorption rates of organic solvent vapor and moisture according to an embodiment of the present invention.

FIG. 8 is a graph showing adsorption rates of organic solvent vapor and moisture according to a control example.

[Explanation of symbols]

 3 Small through hole 4 Honeycomb adsorption rotor 7 Processing zone 8 Regeneration zone 11 Processing air 12 Regeneration air

Claims (4)

[Claims] 1. A honeycomb-shaped adsorption rotor formed by molding into a honeycomb-shaped cylindrical body having a large number of small through-holes penetrating at both end faces, and the powder of zeolite having mesopores appearing on the wall surface of the small through-holes. When rotating, the gas containing the organic solvent vapor and moisture is passed through the adsorption zone of the honeycomb adsorption rotor and the desorption high-temperature gas is passed through the regeneration zone, by changing the rotational speed of the honeycomb adsorption rotor. A method for selectively adsorbing and removing organic solvent vapor and moisture therein. 2. A honeycomb-shaped cylindrical body having a large number of small through holes is formed by laminating low-density papers containing inorganic fibers as a main component,
The organic solvent vapor in a gas and wetness according to claim 1, wherein a honeycomb adsorption rotor formed by impregnating and fixing zeolite powder having mesopores on the fiber gaps and surfaces of the paper of the honeycomb cylindrical body with an inorganic binder is used. A method for selectively adsorbing and removing the components. 3. The organic solvent vapor and the moisture in the gas according to claim 2, wherein the paper is fired before and / or after laminating the low-density paper containing inorganic fibers as a main component. Method. 4. A flat sheet made of inorganic fiber paper having a thickness of about 0.10 to 0.3 mm and a wavelength of about 2.5 to 6.5 mm,
4. A gas according to claim 2 or 3, wherein a honeycomb-shaped cylindrical body is used which is formed by alternately laminating corrugated sheets having a wave height of about 1.0 to 4.0 mm and forming small through holes having a length of about 100 to 600 mm. A method for selectively adsorbing and removing organic solvent vapor and moisture.