JPH10310422A - Heat-resistant low-silica zeolite and its production and use - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel LSX (low-silica zeolite), its industrial production method and use. SOLUTION: In the low-silica zeolite with the SiO2 /Al2 O3 molar ratio controlled to 1.9-2.1 and having sodium and/or potassium as metal cations, the content of low-silica faujasite-structure zeolite in the zeolite is controlled to >=88%, and the thermal decomposition temp. in an air atmosphere is 870-900 deg.C. An aluminate-contg. soln. and a silicate-contg. soln. are mixed at 0-60 deg.C, gelled and aged to prepare a slurry contg. an amorphous aluminosilicate, having 10-1,000 cP viscosity and >=10 m<2> /g specific surface and with the SiO2 /Al2 O3 molar ratio controlled to 1.9-2.1, and the slurry is crystallized to produce the low-silica zeolite for gas separation. Further, the low-silica zeolite for gas separation can be obt. by applying lithium ion exchange or alkaline earth metal ion exchange to the low-silica zeolite.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an SiO ₂ / Al ₂ O ₃ molar ratio having an unprecedented high heat resistance of 1.9 to 2.
The present invention relates to a novel low silica zeolite and an industrial production method and use thereof.

A new low-silica zeolite having a high heat resistance of SiO ₂ / Al ₂ O _{3 having a} molar ratio of 1.9 to 2.1 has high heat resistance even after various ion exchanges. It has excellent performance as a zeolite adsorbent for separating and concentrating oxygen from gas by an adsorption method or as a CO ₂ gas adsorbent.

[0003]

_2. Description of the Related Art The SiO ₂ / Al ₂ O ₃ molar ratio is from 1.9 to
2.1 low silica zeolite (hereinafter referred to as LSX)
Is an adsorbent matrix for producing oxygen, or CO ₂
It is known to have excellent performance as a gas adsorbent.

However, there has been no technology for industrially producing LSX, and the adsorbent obtained by ion exchange of LSX prepared by a conventionally proposed laboratory experiment method has poor heat resistance. , And did not lead to industrial practical use.

US Pat. No. 3,140,933, Japanese Patent Publication No. 5-2
No. 5,527, US Pat. No. 5,268,023 and the like have evaluated the performance of conventional LSX ion-exchanged with lithium.
No. 3,264, US Pat. No. 5,545,857 and the like show the performance of conventional LSX ion exchanged with calcium.

However, conventionally known LSX is based on a laboratory-scale synthesis technique in which a small amount of sample is prepared over many days, and cannot be mass-produced industrially. The LSX thus obtained had insufficient heat resistance.

The prior art discloses the following method with respect to a laboratory preparation method of LSX having a SiO ₂ / Al ₂ O ₃ molar ratio of 1.9 to 2.1.

For example, in GB 1,580,928 (corresponding Japanese patent: JP-A-53-8400), a mixture containing sodium, potassium, aluminate and silicate is crystallized at a temperature of 50 ° C. or less. Or 5
There is disclosed a method of aging at a temperature of 0 ° C. or lower and then crystallization in a temperature range of 60 ° C. to 100 ° C. However, in this method, it takes substantially 5 hours to prepare high-purity LSX.
It only discloses a non-industrial method that requires 0 hour or more, and the heat resistance of LSX obtained by the method is also insufficient. In addition, this patent is an East German patent 4
Although the range disclosed in Japanese Patent No. 3221 was reexamined in detail, LSX obtained by the method of East German Patent No. 43221 also had a low water adsorption amount and could not be obtained with high purity. By the way, these patents show an extremely wide range of conditions for preparing LSX, but include a range in which LSX cannot be obtained. The inventors of this patent later published scientific literature (Zeolite 198).
7. Vol. 7, p451-457), which provides a detailed report on the synthesis of LSX. In this document, a high purity LSX of 97% or more is obtained using a sealed plastic container.
However, LSX with improved heat resistance was not obtained by this method. Also, the method of implementation of the document is clearly described as a technique of a small-scale experimental method, and since it is a method in which the reaction is carried out by standing in an oven from ripening to crystallization, it cannot be adapted to an industrial large scale.

In US Pat. No. 4,859,217 (corresponding Japanese Patent Publication No. 5-25527), a mixture containing sodium, potassium and aluminate and a mixture containing silicate are mixed and gelled at a low temperature of 4 to 12 ° C. A method is disclosed in which the gel is aged at 36 ° C. and then heated to 70 ° C. for crystallization. However, the filing date of the patent (198
(June 30, 2007), it has been shown that gelation takes 2-3 days, and it was specified that it was important to avoid excessive mechanical energy.

[0010] From the above, the synthesis of LSX still requires a long time in the art and the application of mechanical energy, that is, the stirring cannot be performed, and further, the heat resistance is imparted to itself. The problem of being unable to do so was left unresolved.

On the other hand, as another method, US Pat.
No. 3,040 (corresponding Japanese patent: JP-A-61-22291)
No. 9) discloses that LSX can be obtained even by using kaolin clay as a raw material alumina source and silica source and stirring.

However, in this method, even if the reaction time is 100 hours or more, the LSX content in the entire zeolite is only about 60%, and the A
It was merely reaffirmed that the type zeolite was produced as a by-product and that the mechanical energy of stirring could not be applied to produce high-purity LSX. Furthermore, the resulting "macroscopically condensed object" has a particle size of more than 50 μm and is used to adsorb nitrogen gas in air by pressure swing adsorption method (hereinafter referred to as PSA method) to obtain high-purity oxygen gas. When used as a mother zeolite of a low-silica zeolite ion exchanger, nitrogen gas adsorption becomes insufficient, and is not suitable for use as a base material of a low-silica zeolite for PSA gas separation. Further, for the same reason, it is not suitable as a CO ₂ gas adsorbent.

[0013] As described above, it is common knowledge in the art that low-silica X-type zeolite (LSX) can be obtained in high-purity state only after being allowed to react in a stationary state for a long time. Manufacturing method, LS using it
There was no report on X and further improvement in heat resistance related thereto.

For this reason, it has only been confirmed and proposed in a laboratory that an adsorbent using LSX as a mother zeolite has high performance, and it has not been industrially feasible.

[0015] Oxygen gas production by the industrial PSA method is mainly used in steelmaking furnaces, glass melting furnaces, bleaching, fermentation, and the like. Since the adsorbent is used in units of several to several tens of tons at a time, Industrial in the industry refers to the implementation of an industrial production scale of more than a few tons, not a few kilometers at a time.

As the adsorbent using the LSX base material, those which have been exchanged with lithium ions and those which have been ion-exchanged with alkaline earth metal cations such as calcium and strontium, and those which have been exchanged with lithium cations and alkaline earth metals such as A cation exchanged with a complex cation has been reported. Both reports use LSX without heat resistance prepared on a laboratory scale as described above (eg, US
P5, 152, 813).

US Pat. No. 3,140,140 discloses that faujasite ion-exchanged with lithium ions is excellent in nitrogen adsorption.
No. 923, which shows that the higher the lithium ion exchange rate is, the higher the performance is, and that the SiO ₂ / Al ₂ O ₃ molar ratio is used up to 2.0 as faujasite. . However, the report does not mention the heat resistance of faujasite.

US Pat. No. 4,859,217 (corresponding Japanese Patent No. 5-25527) and US Pat.
8,023 and others, and the performance is reported in detail. However, even in this report, the conventional method was used for the preparation of LSX, which was inferior in heat resistance.

The inventor of US Pat. No. 4,859,217 (C
hien C.I. Chao) issued another patent, USP 5,
No. 174,979 points out that the faujasite ion-exchanged with lithium has a drawback that it is weak to heat, and as a countermeasure, heat resistance by faujasite by mixed ion exchange of lithium ion and alkaline earth ion is described. Reports improvement. However, in the case of faujasite by mixed ion exchange of lithium ions and alkaline earth ions, although the heat resistance is improved, the adsorption characteristics are remarkably reduced particularly in a low temperature range, and thus there is no value in improving the heat resistance.

An adsorbent using LSX as a mother zeolite and using an alkaline earth metal cation such as calcium or strontium as an exchange cation is disclosed in JP-A-61-2542.
No. 47, USP 5,173,462, USP 5,45
No. 4,857 and the like. However, all reports show that LSX based on a conventional laboratory experiment formulation as disclosed in GB 1,580,928 patent (corresponding Japanese patent: JP-A-53-8400) was used. The heat resistance was insufficient as in the case of lithium ion exchange.

[0021]

Although LSX may exhibit excellent performance, it cannot be manufactured industrially, and the conventional method has insufficient heat resistance of LSX. Therefore, it has been difficult to industrially perform gas separation or the like by the PSA method.

Therefore, a new LSX having high heat resistance and a method which can be industrially produced therefrom have been strongly desired.

[0023]

Means for Solving the Problems As a result of intensive studies on the industrial production technology of LSX, the present inventors have controlled the viscosity and BET specific surface area of the raw material gel according to the mixing conditions of the reaction raw materials and aged. And found that high-purity LSX can be obtained by stirring at the time of raising the temperature, and that the LSX obtained by such a method is a novel substance exhibiting unprecedented high heat resistance. Industrialization of the production of LSX, especially the production of a new LSX having heat resistance.
The present inventors have found that high heat resistance is maintained even in various cation exchange adsorbents using X as a mother zeolite, particularly lithium exchangers or alkaline earth exchangers, and that the novel substances have excellent air separation properties. The invention has been completed.

First, a method for producing the mother zeolite LSX of the present invention will be described.

The present inventors have conducted intensive studies on a method for synthesizing LSX having a SiO ₂ / Al ₂ O ₃ molar ratio of 1.9 to 2.1 under industrially advantageous and easy scale-up conditions. The solution containing the aluminate and the solution containing the silicate are mixed and gelled at a temperature of 0 ° C. or more and 60 ° C. or less, and the slurry is stirred so that the viscosity of the slurry becomes 10 cp to 10000 cp. Mixing so that the specific surface area of the contained amorphous aluminosilicate is 10 m ² / g or more and the molar ratio of SiO ₂ / Al ₂ O ₃ is from 1.9 to 2.1, which has been considered to be stationary. It has been found that LSX can be produced without aging.

Further, an aqueous solution of an alkali silicate having a SiO ₂ / (Na ₂ O + K ₂ O) molar ratio of less than 1.0 and Al ₂ O ₃ /
It has been found that by mixing with an aqueous solution of an alkali aluminate having a (Na ₂ O + K ₂ O) molar ratio of less than 1.0, a slurry under the above-mentioned conditions can be easily synthesized, and in particular, Na ₂ O / (Na ₂ O + K ₂ O) molar ratio is 0.
It has been found that a low silica zeolite having excellent heat resistance of 5 to less than 0.75, particularly 0.5 to less than 0.65 can be produced, and the present invention has been accomplished.

In the present invention, the LSX SiO ₂ /
Although the Al ₂ O ₃ molar ratio is theoretically 2.0, the LSX having a composition of 1.9 to 2.1 falls within the range of the present invention in consideration of a measurement error or the like in chemical composition analysis. Is clear.

The solution containing aluminate in the present invention may be obtained by dissolving commercially available sodium aluminate in water,
Examples thereof include those obtained by dissolving aluminum hydroxide with sodium hydroxide, and those obtained by mixing water, sodium hydroxide, and potassium hydroxide. here,
The concentration of the aluminum (Al) component in the solution containing aluminate is not particularly limited, but is 30% by weight or less, preferably 25% by weight or less as Al ₂ O ₃ . Within this range, the solution containing the aluminate has a low viscosity and can be easily mixed with the solution containing the silicate.

As the solution containing silicate used in the method of the present invention, commercially available sodium silicate or silica sand dissolved in sodium hydroxide, and water, sodium hydroxide and potassium hydroxide are further added thereto. Mixtures can be exemplified.

Silicon (Si) in a solution containing silicate
The concentration of the component is not particularly limited, but is 40% as SiO _2.
% By weight, preferably 30% by weight or less. Within this range, the solution containing the silicate has a low viscosity and is easy to mix.

The solution containing the aluminate and the solution containing the silicate are mixed and gelled. The mixing temperature at this time is in the range of 0 ° C. to 60 ° C. or less, particularly 20 ° C. to
The temperature is preferably in the range of 60 ° C or lower. The mixing temperature in the present invention indicates the temperature at the time when the mixing of the solution containing aluminate and the solution containing silicate is completed, and either the solution containing aluminate or the solution containing silicate deviates from this temperature. However, the temperature of the mixed solution at the end of mixing may be in the range of 0 ° C to 60 ° C, and does not specify the temperature of the raw material solution.

The reason for setting the temperature of the mixed solution in the range of 0 ° C. to 60 ° C. is that when the mixing temperature exceeds 60 ° C., by-products of A-type or P-type zeolite cannot be avoided and a single-phase LSX is synthesized. It is difficult to do so. On the other hand, 0 ° C or more
Although it is possible to synthesize LSX even at a mixing temperature of less than 0 ° C., it is necessary not only to use expensive cooling equipment such as a refrigerator, but also to apply a large amount of heat for aging and crystallization. More practically, the temperature is 20 ° C. or more.

A known method can be used for the mixing method and mixing order, and is not particularly limited. For example, a solution containing aluminate is charged into a reaction vessel, and a solution containing silicate is added thereto. Alternatively, a solution containing silicate may be poured into the reaction vessel, and a solution containing aluminate may be added to the reaction vessel.Additionally, water or the like may be poured into the reaction vessel, and the solution containing aluminate and the solution containing silicate may be simultaneously added. Any mixing method, mixing order, and the like may be used as long as the object of the present invention is achieved.

When the mixing is completed, the molar composition ratio is SiO ₂ / Al ₂ O ₃ 1.3 to 2.2 (Na ₂ O + K ₂ O) / SiO ₂ 2.0 to 4.5 Na ₂ O / (Na ₂ O + K ₂ O) 0.5 to 0.75 H ₂ O / (Na ₂ O + K ₂ O) 10 to 35, and especially Na ₂ O / (Na ₂ O + K ₂ O) 0.5 to 0.65 It is preferably within the range. If the respective molar ratios deviate from the range, impurities such as A-type zeolite, sodalite and P-type zeolite are generated in large amounts, and pure SiO ₂ /
Al ₂ O ₃ can not be obtained low-silica zeolite 1.9 to 2.1.

In the Na ₂ O / (Na ₂ O + K ₂ O) molar ratio of the present invention, in a particularly preferable composition range, it has conventionally been considered that a high purity LSX is not generated. For example, Z
eolite 1987 Vol. Page 7453, FIG.
According to the method, the LSX generation rate is less than 80%, and high purity LSX cannot be obtained by the conventional stationary reaction technology. (See Comparative Example 2) When the raw materials are mixed in this manner, usually, when the raw materials are mixed,
Alternatively, an amorphous aluminosilicate gel is formed after the mixing is completed.

Here, according to the conventional knowledge, a raw solution is mixed at a low temperature, a transparent solution in which each component is uniformly mixed is once prepared, and the temperature is raised to a point at which the stirring is stopped when gelation starts. Perform aging in a stationary state without applying mechanical energy (stop stirring before or simultaneously with gelation, and allow the aging, aging, and heating while maintaining the uniformity of the entire gel. performs location crystallization, the SiO ₂ / Al ₂ O ₃ molar ratio to synthesize LSX of 1.9-2.1) was considered to be essential.

However, the inventors of the present invention have conducted intensive studies focusing on the uniformity of the gel, and as a result, it has been found that it is important to keep the above-mentioned conventionally considered stationary state after final mixing and avoid excessive mechanical energy. A completely different method, that is, a novel method with high purity and high heat resistance by uniformly slurrying the entire gel so that the viscosity of the gel is in a certain range by, for example, vigorous stirring or the like. L
It has been found that SX can be manufactured.

In the present invention, it is essential to set the mixing conditions and stirring conditions of the raw materials so that the viscosity of the slurry to be formed is 10 cp to 10000 cp.

When the viscosity of the slurry is more than 10,000 cp, a portion where the slurry is agitated and a portion where the slurry stagnates are formed inside the reaction vessel, and it is considered that the uniformity of the whole gel is changed. It is difficult to obtain, which is not preferable. If the viscosity of the slurry is lower than 10 cp, the gel precipitates and separates in the crystallization step, so that it is difficult to obtain a single-phase LSX, which is not preferable. Therefore, in order to keep the viscosity of the slurry in the above range, it is preferable to carry out, for example, strong stirring to disintegrate and fluidize the gel formed during or after the mixing of the raw materials. The stirring method in that case is not particularly limited, and may be carried out using a known method.

Subsequently, the formed slurry is aged. The aging temperature and time are not particularly limited, but the temperature is preferably in the range of 20 ° C to 60 ° C. Within this range, aging does not require a long time, and generation of impurities that may be generated under high-temperature conditions can be suppressed. Specific examples of aging temperature and time include aging at 36 ° C. to 50 ° C. for 4 hours to 24 hours.

A slurry prepared so as to have a viscosity of 10 cp to 10000 cp and having excellent overall uniformity may be aged under stirring. After the slurry has reached the target ripening temperature, the whole is already uniform. Therefore, the slurry may be stirred or may be left standing without stirring.

As a result of further studies, the present inventors have found that, in addition to the above-mentioned slurry viscosity, the particles of the amorphous aluminosilicate gel formed are fine, and the specific surface area after aging is maintained at 10 m ² / g or more. It has been found that mixing the raw materials so that the SiO ₂ / Al ₂ O ₃ molar ratio is 1.9 to 2.1 is an essential condition for synthesizing a low silica faujasite type zeolite. If the amorphous aluminosilicate particles produced when the raw materials are mixed are fine and active, it is advantageous for the production of LSX. If the specific surface area can be maintained at 10 m ² / g or more even after aging, high purity LS can be obtained.
X can be generated. Here, if the specific surface area of the aged gel is less than 10 m ² / g, a large amount of by-product such as A-type zeolite cannot be avoided, and it is difficult to synthesize high-purity LSX. On the other hand, the upper limit of the specific surface area after aging is about 6
It is about 0 m ² / g.

By setting the mixing conditions of the raw materials so that the composition of the aged amorphous aluminosilicate particles is close to LSX, the LSX generation rate can be improved. That is, the amorphous aluminosilicate particles SiO ₂ / Al ₂ O ₃
The molar ratio needs to be 1.9 to 2.1. If the composition is out of this range, it is not preferable because by-products of A-type or P-type zeolite cannot be avoided.

The mixing conditions of the raw materials for obtaining the amorphous aluminosilicate particles having the above-mentioned physical properties include SiO ₂ /
An aqueous solution of an alkali silicate having a (Na ₂ O + K ₂ O) molar ratio of less than 1.0 and an Al ₂ O ₃ / (Na ₂ O + K ₂ O) molar ratio of 1.
By mixing with an aqueous solution of an alkali aluminate of less than 0, the mixture is less susceptible to fluctuations in the mixing conditions, has a specific surface area of not less than 10 m ² / g by aging and a SiO ₂ / Al
It has been found that a gel having a ₂ O ₃ molar ratio of 1.9 to 2.1 is produced. By this method, even when the mixing conditions slightly change, LSX can be stably manufactured without a change in the specific surface area or composition of the amorphous aluminosilicate particles by the BET method. The molar ratio of SiO ₂ / (Na ₂ O + K ₂ O) in the aqueous alkali silicate solution is less than 1.0, and the Al ₂ O ₃ /
By making the (Na ₂ O + K ₂ O) molar ratio less than 1.0,
It is composed of very fine particles regardless of the mixing temperature and mixing time, has a specific surface area of 10 m ² / g or more after aging even after aging, and has a composition of 1.9 in terms of SiO ₂ / Al ₂ O ₃ molar ratio. 2.1 amorphous aluminosilicate is obtained.

In the present invention, SiO ₂ / (Na ₂ O + K ₂ O)
When the molar ratio of Al ₂ O ₃ / (Na ₂ O + K ₂ O) is 1.0 or more, the mixing method, the mixing temperature, the time from the start to the end of the mixing, the change in the stirring rotation speed during the mixing, etc. The resulting amorphous aluminosilicate has a large variation in the surface area, composition, etc., and is fine and has a SiO ₂ / Al ₂ O ₃ molar ratio of 1.9.
It is difficult to stably obtain an amorphous aluminosilicate having a ratio of 2.1 to 2.1.

Next, the gel aged for a predetermined time is heated to be crystallized.

On a large industrial scale, it takes time to transfer heat to the inside of the gel, so that the temperature can be increased while stirring the gel. In this case, it is preferable to raise the temperature to the target crystallization temperature in as short a time as possible in order to suppress the generation of impurities, specifically, the temperature is raised within 3 hours, more preferably within 1 hour.

The method for raising the temperature of the gel is not particularly limited as long as the temperature is raised to the crystallization temperature in a short time. For example, a container for gelling and aging and a container for crystallization are used. And a method of raising the temperature while transferring the gel in a container for gelation and aging through a heat exchanger using a pump or the like to a crystallization container.

The crystallization is to suppress generation of impurities.
It is preferable to perform the reaction in a stationary state without stirring. The crystallization temperature is preferably about 60 to 90 ° C. in order to shorten the crystallization time and suppress generation of impurities on the high temperature side.

The crystallization time varies depending on the crystallization temperature, but in the present invention, usually about 4 to 12 hours is sufficient, and more time may be used. If the crystallization time is insufficient, it may not be completely crystallized, and amorphous amorphous aluminosilicate may remain.

The SiO ₂ / A synthesized as described above
l ₂ O ₃ molar ratio of filtering the LSX of 1.9 to 2.1, washed and dried. A known method can be used as a method of filtering, washing and drying.

According to the present invention, LSX having a SiO ₂ / Al ₂ O ₃ molar ratio of 1.9 to 2.1 can be produced by aging under stirring without cooling the mixture. Therefore, a new LSX that can be industrially manufactured and has excellent heat resistance can be manufactured.

Next, the ion exchanger using the LSX of the present invention, its thermal properties and applications will be described.

Surprisingly, the novel LSX of the present invention maintains heat resistance even after various ion exchanges,
X always has high heat resistance.

For example, LSX obtained by using the LSX of the present invention as a mother zeolite and ion-exchanged with lithium and / or alkaline earth metal is extremely high in the use of adsorbing and separating relatively polar gas components from a mixed gas. Can demonstrate performance.

The lithium exchange ratio of LSX in the present invention can be used from 75% to 100%, or from 75% to less than 88%. The higher the lithium exchange rate, the higher the performance, but the higher the cost of lithium, the higher the manufacturing cost.

On the other hand, the alkaline earth metal cation exchange rate is preferably 40% or more and 75%.

The lithium-exchanged LSX and alkaline-earth metal cation-exchanged LSX of the present invention are novel substances having excellent heat resistance, and are disclosed in US Pat. No. 3,140,933 and US Pat.
9,217, USP 5,268,023, USP
No. 3,140,932, USP 5,173,462,
USP 5,454,857, JP-A-61-25424
No. 7 low silica zeolite material or LS
It is a new substance different from X.

The thermal properties of the LSX of the present invention are the same as those of the conventional LSX.
Although completely different from the above, the ion exchange method does not require a special prescription, and a conventional method can be applied to the ion exchange operation of lithium ions or alkaline earth metal ions.

Conventionally, differential thermal analysis (DTA) is generally used for evaluating the thermal characteristics of zeolite.
US Pat. No. 5,174,979, JP-A-7-256094
And others.

The thermal decomposition temperature in the present invention is defined as the thermal decomposition temperature using the peak top temperature (first thermal decomposition center temperature) of the lowest exothermic reaction detected by DTA.

According to such a general evaluation method, the novel LSX of the present invention and an ion exchanger using the same always have higher heat resistance than the conventional LSX under the same exchange ion conditions.

The thermal decomposition temperature of the LSX of the present invention is 870 ° C. or more and 900 ° C. or less by the above-mentioned thermal decomposition temperature measurement, and is 5 ° C. or more, often 10 ° C. or more higher than the LSX according to the conventional method.

The ion-exchanged LSX also has a decomposition temperature rise close to 10 ° C. as compared with the case where the conventional LSX is used.

The LSX of the present invention has a purity of 95% or more,
Particularly, the purity is preferably 100% (single phase). LS
The purity of X is evaluated mainly by X-ray crystal structure analysis, and is determined by the ratio of the impurity peak to the LSX diffraction peak. Further, the amount of impurities can be cross-checked by reducing the amount of water adsorbed on LSX obtained in a single phase.

The adsorbent using the novel LSX of the present invention as a mother zeolite is used for a method of adsorbing a relatively polar gas from a mixed gas and purifying and separating the gas, for example, adsorbing nitrogen from air. To obtain high-purity oxygen, or a method of separating and removing harmful carbon monoxide gas from the gas after combustion.In particular, the pressure at which nitrogen is adsorbed from air to obtain high-purity oxygen In the swing adsorption separation method (PSA method), it exhibits excellent performance as a CO ₂ gas separation / recovery / removal agent.

[0067]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples.

The measuring methods in Examples and Comparative Examples are as follows.

(1) Method of Measuring Chemical Composition After dissolving a sample using nitric-hydrofluoric acid, an ICP emission spectrometer (Perkin Elmer, model: optima)
3000).

(2) Method for measuring crystal structure X-ray diffractometer (model: MXP-, manufactured by Mac Science)
It measured using 3). (3) Measurement method of water equilibrium adsorption amount The powder dried at 100 ° C was left in a desiccator at a relative humidity of 80% for 16 hours or more, and heated at 900 ° C for 1 hour, and the weight loss was measured.

(4) Method of measuring viscosity The viscosity was measured using a B-type viscometer manufactured by Tokimec in accordance with JIS-K-7117 (1987 edition).

(5) Method of Measuring Specific Surface Area by BET Method The measurement was performed using Flowsorb II2300 manufactured by Micromeritics Co., Ltd. (6) Method of Measuring Thermal Characteristics Using Differential Thermal Balance (DTA-TG) As a method for evaluating the heat resistance of zeolite, a general differential thermal analysis was performed using a differential thermal balance manufactured by Rigaku Denki (Thermoflex Model 81).
00) in the atmosphere up to 1000 ° C.

The heating rate was 10 ° C./min and the air flow rate was 50
Milliliter / min.

(7) Evaluation of Air Separation Characteristics Static saturation adsorption amounts (isotherms) of nitrogen and oxygen of the ion exchange LSX prepared in the present invention were measured by a gravimetric method.
From the measurement results, a typical air separation characteristic at 0.4 kg / cm ² as a set adsorption pressure in a recent industrial pressure swing adsorption method was obtained as a separation coefficient. The separation coefficient was calculated according to the following equation 1.

[0075]

(Equation 1)

The adsorption pressure conditions of the PSA method generally used at present are described in JP-A-8-71350 and 8-2.
It was set from an average value such as 39204.

Example 1 An aqueous solution of sodium aluminate (Na ₂ O = 20.0% by weight, Al ₂ O) was placed in a 3 liter stainless steel reaction vessel.
₃ = 22.5% by weight, Al ₂ O ₃ / Na ₂ O molar ratio = 0.6
8) 453 g, water 1060 g, sodium hydroxide (purity 99%) 181 g, reagent primary potassium hydroxide (purity 85
%) And kept at 36 ° C. using a water bath while stirring at 250 rpm. To this solution, 833 g of an aqueous sodium silicate solution (Na ₂ O = 3.8% by weight, SiO ₂ = 12.6% by weight, SiO ₂ / Na ₂ O molar ratio = 3.4) kept at 36 ° C. was added for 5 minutes and 50 minutes. It took over seconds. Approximately 3 minutes after the start of charging, the solution became cloudy and gelation started. During the charging, the viscosity of the whole gel increased, but no partial stagnation of the gel inside the reaction vessel occurred. At the end of the charging, the temperature of the slurry was 38 ° C., and the viscosity was 320 cp. The stirring was continued as it was, and aging was performed at 36 ° C. for 16 hours. A part of the aged slurry was sampled, filtered, washed and analyzed. At this time, the specific surface area of the gel was 20 m ² / g, and SiO ₂ /
The Al ₂ O ₃ molar ratio was 1.98. After aging, the gel slurry was transferred to a 3 liter stainless steel crystallization vessel through a SUS spiral heat exchange tube (8 mmφ) immersed in an 80 ° C. oil bath using a roller pump.
The temperature was raised. The gel temperature at the inlet of the crystallization vessel was 70 ° C., and the time required for liquid transfer and temperature rise was 20 minutes. After the gel transfer and temperature rise are completed, cover the crystallization vessel,
Crystallization was carried out for 8 hours in a hot-air dryer at ℃. The obtained crystals were sufficiently washed with pure water and then dried at 100 ° C. overnight. The structure of the obtained crystal powder was a single phase of faujasite-type zeolite as a result of X-ray diffraction, and the chemical composition thereof was found to be 0.67Na ₂ O · 0.3
3K is a _{2 O · Al 2 O 3 ·} 2.0SiO 2, the equilibrium water adsorption was 33.4%. The experimental conditions and results are shown in Table 1.

Example 2 The same experiment as in Example 1 was performed except that the aging temperature was set to 50 ° C. Due to the high aging temperature, the aging time was 8 hours, the viscosity during aging was 240 cps, and the gel BET value was 24 m ² / g. Thereafter, it was dried at 100 ° C. overnight.

The structure of the obtained crystal powder was a single phase of faujasite-type zeolite as a result of X-ray diffraction, and the chemical composition thereof was found to be 0.67Na ₂ O ·
A _{0.33K 2 O · Al 2 O 3} · 2.0SiO 2, the equilibrium water adsorption was 33.2%. The experimental conditions and results are shown in Table 1.

Example 3 The same sodium silicate solution (833 g), water (1060 g)
37.4 g of sodium hydroxide (purity: 99%) and 540 g of reagent-grade potassium hydroxide (purity: 85%) are charged and 250 r
While stirring at pm, the temperature was maintained at 10 ° C. using a water bath. To this solution, 453 g of the same aqueous solution of sodium aluminate as in Example 1 kept at 10 ° C. was introduced over 5 minutes and 30 seconds. Immediately after the start of charging, the liquid became cloudy and gelation started. During the charging, the viscosity of the whole gel increased, but no partial stagnation of the gel inside the reaction vessel occurred. After the completion of the introduction, the temperature of the slurry was 16 ° C., and the viscosity was 180 cp. The stirring was continued as it was, and aging was performed at 36 ° C. for 16 hours. A part of the aged slurry was sampled, filtered, washed and analyzed. At this time, the specific surface area of the gel was 22 m ² / g, and the molar ratio of SiO ₂ / Al ₂ O ₃ was 2.04. After aging, liquid transfer / heating, crystallization, washing, and drying were performed in the same manner as in Example 1.

The structure of the obtained crystal powder was a single phase of faujasite-type zeolite as a result of X-ray diffraction, and the chemical composition thereof was found to be 0.61 Na ₂ O.
A _{0.39K 2 O · Al 2 O 3} · 2.0SiO 2, the equilibrium water adsorption was 33.4%. The experimental conditions and results are shown in Table 1.

Example 4 A scale-up test was conducted using the same composition raw material as in Example 1 and using a 30 m ³ reactor. (10,000-fold scale-up) The raw materials were charged into the reaction vessel with stirring, and the temperature of the slurry at the end of the charging was 45 ° C and the viscosity was 300 cp. The stirring was continued as it was, and aging was performed at 45 ° C. for 12 hours. A part of the aged slurry was sampled, filtered, washed and analyzed. The specific surface area of the gel at this time was 25 m ² /
g and the SiO ₂ / Al ₂ O ₃ molar ratio was 2.02. After aging, the gel slurry was transferred to another 30 m ³ reaction tank (crystallization tank) by piping. During the liquid transfer, high-temperature steam was introduced into the piping, and the temperature was raised simultaneously. The gel temperature of the crystallization tank is 70 ° C, and the time required for liquid transfer and temperature rise is 30.
Minutes. After the transfer of the gel and the temperature rise, crystallization was allowed to stand for 8 hours without stirring.

After washing the obtained crystals with pure water,
Dried at ° C. As a result of X-ray diffraction, the structure of the obtained crystalline powder was 99% of faujasite-type zeolite, and as a result of composition analysis, the chemical composition thereof was 0.68Na
₂ O · 0.32 K ₂ O · Al ₂ O ₃ · 2.0 SiO ₂ , the water equilibrium adsorption amount was 33.1%, and 2.4 tons of LSX was obtained in about one day in one batch. . The experimental conditions and results are shown in Table 1. According to the method of the present invention, it was confirmed that LSX with extremely high purity can be produced in large quantities at a time from an industrial point of view.

Example 5 An aqueous solution of sodium aluminate (Na ₂ O = 20.0% by weight, Al ₂ O) was placed in a 3 liter stainless steel reaction vessel.
₃ = 22.5% by weight, Al ₂ O ₃ / Na ₂ O molar ratio = 0.6
8) 453 g, water 923 g, sodium hydroxide (purity 9
9%) 235 g, reagent primary potassium hydroxide (purity 85
%) And cooled in a water bath with ice while stirring at 90 rpm (about ２2 ° C.).

833 g of an aqueous solution of sodium silicate (Na ₂ O = 3.8% by weight, SiO ₂ = 12.6% by weight, SiO ₂ / Na ₂ O molar ratio = 3.4) cooled with ice and water were added to this solution. 137 g were charged over 5 minutes. The solution after the addition was translucent. After stirring was continued for 20 minutes after the completion of the charging, the temperature of the water bath was raised to 36 ° C. When the liquid temperature reached 25 ° C., the solution became cloudy and gelation started. The stirring was increased to 250 rpm as soon as the solution became cloudy. At this time,
Although the viscosity of the whole gel increased, no partial stagnation of the gel inside the reaction vessel occurred. The gel viscosity at this time is 12
It was 0 cp. The stirring was continued as it was at 36 ° C. for 48 hours.
Time aging was performed. After aging, the gel slurry was transferred to a 3 liter stainless steel crystallization vessel through a SUS spiral heat exchange tube (8 mmφ) immersed in an oil bath at 80 ° C. using a roller pump, and the temperature was raised. The gel temperature at the inlet of the crystallization vessel was 70 ° C., and the time required for liquid transfer and temperature rise was 20 minutes.

After the transfer of the gel and the heating, the crystallization vessel was capped and placed in a hot air circulating drier at 70 ° C. for crystallization for 16 hours. After thoroughly washing the obtained crystals with pure water,
Dried at 100 ° C. overnight. The structure of the obtained crystal powder is
As a result of X-ray diffraction, it was a faujasite type zeolite single phase, and as a result of composition analysis, the chemical composition was found to be 0.7
6Na ₂ O · 0.24K ₂ O · Al ₂ O ₃ · 2.0SiO ₂
Met. The water equilibrium adsorption amount of the obtained powder is 33.1%.
Further, the water equilibrium adsorption amount after exchanging all potassium in the crystals for sodium was 35.4%. The experimental conditions and results are shown in Table 1.

As shown in this example, in the present invention, even if the aging time and the crystallization time are lengthened, LSX can be stably obtained without generation of an impurity phase.

Example 6 An aqueous solution of sodium aluminate (Na ₂ O = 20.0% by weight, Al ₂ O) was placed in a stainless steel reaction vessel having an internal volume of 3 liters.
₃ = 22.5% by weight, Al ₂ O ₃ / Na ₂ O molar ratio = 0.6
8) 453 g, water 1060 g, sodium hydroxide (purity 99%) 235 g, reagent-grade potassium hydroxide (purity 85
%) And kept at 36 ° C. using a water bath while stirring at 250 rpm. To this solution, 833 g of an aqueous sodium silicate solution (Na ₂ O = 3.8% by weight, SiO ₂ = 12.6% by weight, SiO ₂ / Na ₂ O molar ratio = 3.4) kept at 36 ° C. was added for 5 minutes and 50 minutes. It took over seconds. Approximately 3 minutes after the start of charging, the solution became cloudy and gelation started. During the charging, the viscosity of the whole gel increased, but no partial stagnation of the gel inside the reaction vessel occurred. At the end of the charging, the temperature of the slurry was 38 ° C., and the viscosity was 320 cp. The stirring was continued as it was, and aging was performed at 38 ° C. for 24 hours. A part of the aged slurry was sampled, filtered, washed and analyzed. At this time, the specific surface area of the gel was 20 m ² / g, and SiO ₂ /
The Al ₂ O ₃ molar ratio was 1.98. After aging, the gel slurry was transferred to a 3 liter stainless steel crystallization vessel through a SUS spiral heat exchange tube (8 mmφ) immersed in an 80 ° C. oil bath using a roller pump.
The temperature was raised. The gel temperature at the inlet of the crystallization vessel was 70 ° C., and the time required for liquid transfer and temperature rise was 20 minutes. After the gel transfer and temperature rise are completed, cover the crystallization vessel,
Crystallization was carried out for 8 hours in a hot-air dryer at ℃. The obtained crystals were sufficiently washed with pure water and then dried at 100 ° C. overnight. The structure of the obtained crystalline powder was a faujasite-type zeolite single phase as a result of X-ray diffraction, and the chemical composition thereof was found to be 0.76 Na ₂ O · 0.2
A _{4K 2 O · Al 2 O 3} · 2.0SiO 2, the equilibrium water adsorption was 33.4%. The experimental conditions and results are shown in Table 1.

Comparative Example 1 US Pat. No. 4,859,217 (JP-B 5-25527)
Sodium silicate solution (N) cooled to 3 ° C. in a 0.5 liter stainless steel reaction vessel according to the method of
a ₂ O = 3.8% by weight, SiO ₂ = 12.6% by weight) 8
3.3 g, water 106 g, sodium hydroxide (purity 99
%) 23.5 g, reagent primary potassium hydroxide (purity 85
%) And kept at 5 ° C. in an ice bath with stirring at 250 rpm. The SiO ₂ /
The (Na ₂ O + K ₂ O) molar ratio was 0.33. To this solution was added an aqueous solution of sodium aluminate (Na ₂₎ maintained at 5 ° C.
O = 20.0% by weight, Al ₂ O ₃ = 22.5% by weight, Al
45.3 g of ₂ O ₃ / Na ₂ O molar ratio = 0.68) for 2 minutes 5
It was thrown in over 0 seconds. The liquid after mixing was a translucent solution, which gradually became semi-solid when kept at 5 ° C. and was completely solidified after 5 minutes.

The semi-solid mass is sealed and placed in a thermostatic drier.
Aging was performed at 6 ° C. for 48 hours, followed by crystallization at 70 ° C. for 16 hours.

A part of the aged slurry is sampled,
Filtered, washed and analyzed. The specific surface area of the gel at this time was 6
0 m ² / g and the SiO ₂ / Al ₂ O ₃ molar ratio was 2.02. After aging, the liquid was transferred and heated in the same manner as in Example 1,
Crystallized, washed and dried.

The structure of the obtained crystal powder was 99% faujasite-type zeolite as a result of X-ray diffraction, and the chemical composition was found to be 0.72Na _{2 as} a result of composition analysis.
O · 0.28K is a _{2 O · Al 2 O 3 ·} 2.0SiO 2,
The water equilibrium adsorption amount was 33.1%.

The experimental conditions and results are shown in Table 1.

Comparative Example 2 Using the conditions of Comparative Example 1, scale-up was attempted in a 500 liter jacketed reactor. Gel preparation temperature 5
Attempted to raise the jacket temperature from ℃ to the aging temperature of 36 ℃, but the temperature near the vessel wall was 36 ℃, but after 12 hours the inside had a temperature distribution of 25 ℃ or less, and after 48 hours the central temperature remained It was 30 ° C. or lower.

After 48 hours, the jacket temperature was raised to 80.degree. After 8 hours, the surface of the reaction vessel was at 70 ° C, but the temperature at the center was 40 ° C or less.

The reaction product obtained by the reaction having the temperature distribution as described above was evaluated by X-ray diffraction. As a result, the center was an amorphous gel having a low conversion, and the low silica type faujasite type was obtained even in the vicinity of the vessel wall. Almost no zeolite was found, which was a mixture of the impurity type A zeolite and others.

As described above, it has been found that uniformity in the reaction system is indispensable for the synthesis of high-purity LSX, and that application of mechanical energy by stirring is indispensable for industrial scale-up.

Comparative Example 3 Known Document (Zeolite 1987 vol. 7)
p. According to the method of 451), the composition of Example 3 was subjected to standing aging at 50 ° C. for 24 hours, and crystallization was allowed to stand at 100 ° C. for 3 hours.

A part of the aged slurry is sampled,
Filtered, washed and analyzed. The specific surface area of the gel at this time was 7
0 m ² / g and the SiO ₂ / Al ₂ O ₃ molar ratio was 2.02. After aging, the liquid was transferred and heated in the same manner as in Example 1,
Crystallized, washed and dried.

The structure of the obtained crystal powder was such that the powder obtained as a result of X-ray diffraction was a mixed phase containing a small amount of LSX phase and most impurities, and had a water equilibrium adsorption of 19.0%. . The experimental conditions and results are shown in Table 1.

[0101]

[Table 1]

In this method, the above literature (Zeolite
1987 vol. 7 p. No LSX was obtained as described in 451).

Examples 7 and 8 and Comparative Examples 4 and 5 The LSX powders of Example 4 and Comparative Example 1 and those powders were prepared by using 99% lithium exchange rate and 60% calcium exchange rate.
Were prepared, and each powder was hydrated in an atmosphere at a relative humidity of 80%. The powder is heated from room temperature to 1000 ° C in air.
Differential thermal analysis was performed in the range up to. The heating rate is 10 ° C /
Min and the air flow rate was 50 ml / min.

The results are shown in Table 1, and typical pyrolysis charts are shown in FIGS.

The thermal decomposition temperature of the LSX powder of the present invention was higher than that of the conventional LSX, and the effect was maintained even after ion exchange with lithium or alkaline earth metal.

Example 9 Using the LSX base material obtained in Example 1 and exchanging 99% of lithium as an exchange cation, USP 5,17
Based on the method disclosed in US Pat. No. 4,979,
The air separation characteristics (separation coefficient) of a heat resistant composition (87% lithium, 13% calcium, 13%) were evaluated. The results are shown in FIG.

Under the conditions proposed in the past, the performance was low, and the performance was particularly remarkable at low temperatures.

[Brief description of the drawings]

FIG. 1 shows Examples 1, 3, and 4 and Comparative Example 1.
FIG. 3 is a view showing a thermal decomposition chart of the low silica zeolite obtained in FIG.

FIG. 2 is a view showing a pyrolysis chart of the low silica zeolite obtained in Examples 7 and 8 and Comparative Examples 3 and 4.

FIG. 3 shows the low silica zeolite obtained in Example 8 and U
It is a figure which shows the comparison of the air separation characteristic (separation coefficient) of the conventional LSX obtained based on the method disclosed by SP5,174,979.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takashi Mohri 2-9-27 Nijigahama, Hikari-shi, Yamaguchi (72) Inventor Atsushi Harada 4-5-2-5-203, Shinnanyo City Government Office, Yamaguchi Prefecture

Claims (10)

[Claims] (1) The molar ratio of SiO ₂ / Al ₂ O ₃ is 1.9 to 2.
1, in a low silica zeolite having sodium and / or potassium as a metal cation, the content of the low silica faujasite type zeolite in the zeolite is 88% or more, and the thermal decomposition temperature in an air atmosphere is 870 ° C. A heat-resistant low-silica zeolite having a temperature of at least 900 ° C. 2. The heat-resistant low-silica zeolite according to claim 1, wherein the content of the low-silica faujasite-type zeolite is 95% or more. 3. A solution containing aluminate and a solution containing silicate are mixed, gelled and aged at a temperature of 0 ° C. or more and 60 ° C. or less, and have a viscosity of 10 cp to 10000 cp and a specific surface area of 10 m ² / g or more. _3. A heat-resistant slurry according to claim 1, wherein a slurry containing an amorphous aluminosilicate having a SiO ₂ / Al ₂ O ₃ molar ratio of 1.9 to 2.1 is prepared and crystallized. For producing a functional low silica zeolite. 4. The method for producing a heat-resistant low-silica zeolite according to claim 3, wherein the solution containing silicate is SiO ₂
/ (Na ₂ O + K ₂ O) is an aqueous alkali silicate solution having a molar ratio of less than 1.0, and the solution containing aluminate is Al
_A method for producing a heat-resistant low-silica zeolite, comprising mixing an aqueous alkali aluminate solution having a ₂ O ₃ / (Na ₂ O + K ₂ O) molar ratio of less than 1.0. 5. The method for producing a heat-resistant low-silica zeolite according to claim 3, wherein Na ₂ O / (Na ₂ O +) after mixing the solution containing aluminate and the solution containing silicate.
Method for producing a heat-resistant low-silica zeolite characterized in that K ₂ O) molar ratio is less than 0.50 to 0.75. 6. The method for producing a heat-resistant low-silica zeolite according to claim 5, wherein Na ₂ O / (Na ₂ O + K ₂ O)
A method for producing a heat-resistant low-silica zeolite, wherein the molar ratio is 0.50 or more and less than 0.65. 7. The heat-resistant low-silica zeolite according to claim 1 is exchanged with lithium ions, and the lithium exchange rate is 75% or more.
Lithium ion-exchanged low silica zeolite for gas separation of not more than 00%. 8. The lithium ion-exchanged low silica zeolite for gas separation according to claim 7, wherein the lithium exchange rate is 75% or more and less than 88%. 9. An alkaline earth metal ion exchange gas for gas separation wherein the heat-resistant low silica zeolite according to claim 1 is exchanged for alkaline earth metal ions to have an alkaline earth metal ion exchange rate of 40% to 75%. Silica zeolite. 10. A low-silica zeolite according to claim 7, wherein nitrogen gas in air is adsorbed by a pressure swing adsorption separation method (PSA method) to obtain high-purity oxygen gas. How to use silica zeolite.