JPH04193342A - Production of zeolite adsorption separating agent - Google Patents

Abstract

PURPOSE:To obtain a zeolite adsorption separating agent having high adsorption capacity without losing the adsorption capacity of the zeolite powder as possible by calcining a zeolite molded body in a gas flow having -30 deg.C or lower dew point. CONSTITUTION:The zeolite molded body to be calcined may be a molded body comprising a material not calcined or already calcined. As for a uncalcined molded body, a dry molded body is used, which is prepared by usual molding method and dried. The flowing gas is introduced to a tower packed with a drier such as zeolite to remove water in the gas and to make the dew point of the gas to -30 deg.C or lower. If the molded body is calcined in a gas having the dew point higher than -30 deg.C, the adsorption capacity of the calcined body decreases by about >=10% compared to the estimated value from the adsorption amt. in a powder state. Decrease in the adsorption amt. can not be suppressed even by increasing the flow amt. or speed of the gas, or calcining time. On the other hand, by calcining in a gas flow of -30 deg.C or lower dew point, decrease in the adsorption amt. is at most 5%. Further, by controlling the gas flow amt., decrease in the adsorption amt. can be reduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a zeolite molded body used as an adsorption/separation agent, for example, for separating and concentrating oxygen from a mixed gas containing nitrogen and oxygen as main components by an adsorption method. The present invention relates to a method for producing a zeolite adsorption/separation agent suitable for use in the following purposes.

[Prior Art] Zeolite is a crystalline aluminosilicate having a pore size on the molecular order of several angstroms, and many types of zeolite have been artificially synthesized, including those with structures that do not exist in nature. Many of these zeolites can be used as adsorption/separation agents by replacing exchangeable cations in zeolite crystals with other cations through ion exchange.

It is widely used industrially as a catalyst. Currently, the zeolites most commonly used industrially are A-type zeolite and faujasite-type zeolite.

Hereinafter, a description will be given using type A zeolite as an example. A type-t'
Olide usually contains sodium ions in its crystals in its synthesized state, and its pore size is 4 angstroms, but for example, A-type zeolite, which has been adjusted to a pore size of 5 angstroms by exchanging calcium ions, contains hydrocarbons. It is widely used for selective adsorption separation of paraffin from a mixture, separation of n-butylene, a raw material for producing butadiene, from a butane-butylene fraction, separation and concentration of oxygen from air, etc.

Type A zeolite with a pore size of 5 angstroms is usually produced as follows. First, synthetic sodium A-type zeolite powder is ion-exchanged in a calcium chloride aqueous solution, and sodium ions with an equivalent fraction of 0.67 or more are exchanged with calcium ions to adjust the pore size to 5 angstroms. After separation from the mother liquor, wash with water. When used as a molded article, a binder is further added and molded. Clay-based binders are often used as binders. After adding a molding aid such as carboxymethyl cellulose,
Water is mixed and kneaded thoroughly, and the mixture is molded using a conventional molding method such as extrusion molding. After drying, it is fired at a temperature of 450 to 700°C to form a pore size of 5 that has physical strength that can withstand industrial use.
A type A zeolite adsorption/separation agent of angstroms is obtained.

[Problems to be solved by the invention] The adsorption capacity of zeolite adsorption/separation agents produced using conventional techniques is not necessarily high, and if an agent with a higher adsorption capacity can be produced, the amount of adsorbent can be reduced and the adsorption device can be made smaller. ,
It is possible to reduce power costs.

As methods for increasing adsorption capacity, reduction of the amount of binder added during molding, development of binderless technology, and cationic species are being considered. In particular, regarding the calcination step, which is essential for the production of adsorption/separation agents, it has been known that the adsorption capacity decreases during calcination. , or firing methods under extremely low pressure have been proposed, but none of these methods can be said to be industrially effective.

The present invention provides a method for producing a zeolite adsorption/separation agent that has a high adsorption capacity and suppresses as much as possible a decrease in adsorption amount during firing of a zeolite molded body.

[Means and effects for solving the problem] The present inventors
The present invention was achieved by intensively studying the relationship between the properties of the flowing gas and the adsorption capacity during firing of the zeolite molded body.

The present invention will be explained below.

The zeolite molded body used for firing in the present invention may be either an unfired molded body or a fired molded body.

Examples of the unfired molded body include a dry molded body formed by a normal molding method and dried.

Further, examples of the fired molded body include molded bodies that have already been fired and have been subjected to ion exchange treatment or the like.

The ionic species contained may be monovalent cations or divalent cations, but the effect is greater when divalent cations are used. The ion exchange method may be performed in the form of a powder or, of course, in the form of a molded body. As for the firing method, an external heating method or an internal heating method can be considered, but either method may be used. The firing temperature is preferably 350 to 600°C; if it is too high, the zeolite crystal itself will collapse. The circulating gas is passed through a tower filled with a desiccant such as zeolite to remove moisture from the gas and lower its dew point to -3.
The temperature shall be below 0℃. When firing with a gas whose dew point is higher than 130° C., the adsorption capacity of the fired compact decreases by about 10% or more compared to the value estimated from the amount of adsorption in the powder state. Even if the gas flow rate and speed are increased or the firing time is lengthened, the decrease in the amount of adsorption cannot be suppressed. On the other hand, when firing under gas flow with a dew point of -30° C. or lower, the decrease can be suppressed to at most 5%, and can be further reduced by controlling the gas flow rate.

The essential reason why calcination under gas flow with a low dew point is effective is not clear, but it is thought to be due to the fact that water adsorbed to the zeolite crystal is quickly released from the crystal. .

[Effects of the Invention] As is clear from the above explanation, according to the method of the present invention, the adsorption capacity of the zeolite powder is increased by firing the zeolite compact under gas flow with a dew point of -30°C or lower. Zeolite adsorption/separation with high adsorption capacity can be obtained without damaging as much as possible, and can be used as a high-performance adsorbent.

[Example code] Hereinafter, the present invention will be specifically explained with reference to Examples.

The adsorption characteristics of the conventional type 5A zeolite adsorption/separation agent (hereinafter referred to as A) and the adsorption/separation agent according to the present invention (hereinafter referred to as B) in the following Examples and Comparative Examples are summarized as follows.

The results of measuring the nitrogen adsorption capacity of A and B according to the static adsorption capacity measurement method show that the nitrogen adsorption capacity of the adsorption/separation agent B of the present invention is lower than that of the adsorption/separation agent A of the conventional method under the conditions of -10°C and 700 mmHg. It is about 10% larger than that.

Furthermore, the dynamic characteristics were measured using a dynamic evaluation method, and the results showed that the amount of product oxygen gas extracted at a concentration of 93 vol.
It is. On the other hand, in the adsorption/separation agent B of the present invention, 64 to 65N
l/Kg -h, and an increase of 6 to 8% is observed. An increase in the amount of product oxygen extracted means a decrease in the oxygen generation power consumption rate, and compared to the conventional adsorption separation agent A, the adsorption separation agent B of the present invention reduces the oxygen generation power consumption rate by approximately 8%. It can be achieved. Further, by improving the PSA system to take advantage of the adsorption characteristics of the adsorption/separation agent B of the present invention, for example by optimizing operating conditions such as adsorption pressure and adsorption time, further reduction in the unit power consumption for oxygen generation can be expected.

As described above, it can be seen that the adsorption/separation agent according to the present invention has a remarkable effect in reducing the unit power consumption for adsorption/desorption processing compared to conventional adsorption/separation agents.

Each measurement method in Examples and Comparative Examples is as follows.

Static adsorption capacity measurement method Static adsorption capacity was measured by the capacitance method. As pretreatment conditions, activation was performed at 350° C. for 2 hours under a pressure of 0.001 mmHg or less. After introducing nitrogen gas, maintain the adsorption temperature and adsorption pressure at -10°C and 700mmHH, respectively, and after reaching sufficient equilibrium, increase the adsorption capacity fi (Nc c/g).
was measured.

Dynamic Evaluation Method Using the dynamic evaluation apparatus shown in FIG. 1, the amount of product oxygen gas taken out and its oxygen concentration were determined according to the following operating procedure. Note that the operation temperature was 25°C.

Approximately 1300 g of zeolite adsorption/separation agent is packed into the adsorption tower (7). During the adsorption process, the blower (1) absorbs 0.2 kg.
The solenoid valves (2, 4, 5) are opened to allow air compressed to /cm2G to flow through the adsorption tower.

The flow rate at that time was adjusted using a flow meter (9). During the regeneration process, the solenoid valves (2, 4, 5) were closed, the solenoid valve (3) was opened, and the pressure was reduced by the vacuum pump (12).

The ultimate pressure at this time was kept constant at 180 mmHg.

During the pressure recovery step, the solenoid valve (3) is closed, and the solenoid valve (4) is opened to restore pressure in the adsorption tower with the product oxygen gas in the pressure accumulation tower (8). The time for each step was 1 minute, and the operation of the solenoid valve was controlled by a sequencer. The oxygen concentration of the product oxygen gas is
After the value became steady, it was read with an oxygen concentration meter (10), and the accurate amount of product oxygen gas taken out was calculated from the value of the integrated flow meter (11).

The pressure was read with a pressure gauge (8).

Example 1 Powder (approximately 100 mesh or less) of commercially available sodium A-type zeolite (Zeolum A4, manufactured by Tosoh Corporation) 100
parts by weight, 25 parts by weight of a kaolin clay-based binder, and 3 parts by weight of an organic molding aid (carboxymethyl cellulose sodium salt), further added water and kneaded, and using an ordinary extrusion molding machine, the inner diameter was 1. The molded product was extruded through a .5 mm die to obtain a molded product with a length of approximately 5 to 15 mm. This molded product was dried in a ventilation drying oven at a temperature of 110° C. until the moisture content of the molded product became 25% by weight or less. Next, it was fired in a furnace at 600°C for 2 hours while flowing air with a dew point of -59°C. The binder is crystallized into A-type zeolite from the fired compact by the method described in Japanese Patent Application No. 2-97517,
A binderless type A zeolite molded body was made. Approximately 300 g of this compact was packed into a column with an inner diameter of 60 mm and a length of 200 mm, and an aqueous solution of IN calcium chloride was heated to 80° C. and passed from the bottom of the column to the top at a flow rate of 4.2 CC/min. The circulation time was 12 hours.

After the flow of the calcium chloride aqueous solution was completed, the calcium chloride aqueous solution in the column was drained and washed with distilled water. after that,
The molded body was dried until the moisture content became 25% by weight or less. As a result of measuring the calcium ion exchange rate of the dried molded body by atomic absorption spectrophotometry, the ratio with aluminum atoms contained in the zeolite crystal (2XCa/AI
) was 0.928. The sample prepared in this manner is hereinafter referred to as "Sample-1".

Activation of "Sample-1" to commercialize it as an adsorption/separation agent was performed according to the following procedure. "Sample-1" approx. 85
0 cc was filled into a tubular furnace with an inner diameter of 40 mm and a length of 670 mm, and baked at a temperature of 400 °C for 1 hour while flowing air with a dew point of -59 °C (humidity = 0.00125 VO 1%) at a flow rate of 8 liters/min to activate the product. It became. The nitrogen adsorption capacity of the adsorption/separation agent prepared in this manner was measured based on a static adsorption capacity measuring method, and was found to be 30.5 Ncc/g. In addition, as a result of measuring dynamic performance based on a dynamic evaluation method,
It was 63.7N 1/Kg-h.

Example 2 The same operations as in Example 1 were carried out, except that the activation firing of "Sample-1" was carried out while flowing air at a flow rate of 16 liters/minute. The nitrogen adsorption capacity of the adsorption separation agent prepared in this way was measured based on the static adsorption capacity measurement method, and the result was 30.9Ncc/g.
Met. Further, the dynamic performance was measured based on a dynamic evaluation method, and the result was 64.5N1/Kg-h.

Example 3 In Example 2, the same operation as in Example 2 was performed except that "Sample-1" was fired at a temperature of 360°C. The nitrogen adsorption capacity of the adsorption separation agent prepared in this way was measured based on the static adsorption capacity measurement method, and the result was 31.4Ncc.
/g. Furthermore, the dynamic performance was measured based on a dynamic evaluation method, and the result was 64.3N1/Kg-h.

Example 4 The same operation as in Example 1 was performed except that the activation firing of "Sample-1" was performed while circulating air at a flow rate of 24 liters/min. The nitrogen adsorption capacity of the adsorption separation agent prepared in this way was measured based on the static adsorption capacity measurement method, and the result was 30.6Ncc/g.
Met. In addition, as a result of measuring dynamic performance based on the dynamic evaluation method, it was 64.4N! /Kg-h.

Comparative Example 1 The same operation as in Example 1 was performed except that the activation firing of "Sample-1" was performed in air with a dew point of -19°C (humidity: 0.1 lvo 1%). The nitrogen adsorption capacity of the adsorption/separation agent prepared in this manner was measured based on a static adsorption capacity measurement method, and was found to be 28.5 Ncc/g. Further, the dynamic performance was measured based on a dynamic evaluation method, and the result was 60, ONI/Kg-h.

Comparative Example 2 In Comparative Example 1, activation firing of "Sample-1" was performed while air was flowing at a flow rate of 16 liters/min.
performed the same operation. The nitrogen adsorption capacity of the adsorption/separation agent prepared in this manner was measured based on a static adsorption capacity measuring method, and was found to be 28.1N cc/g. In addition, as a result of measuring dynamic performance based on the dynamic evaluation method, 5
It was 9.6N1/Kg-h.

Comparative Example 3 In Comparative Example 1, activation firing of "Sample-1" was performed while air was flowing at a flow rate of 24 liters/min.
performed the same operation. The nitrogen adsorption capacity of the adsorption/separation agent prepared in this manner was measured based on a static adsorption capacity measuring method, and was found to be 28.0 Ncc/g. Furthermore, the dynamic performance was measured based on a dynamic evaluation method, and the result was 59.9N1/Kg·h.

Comparative Example 4 In Comparative Example 1, the same operations as in Comparative Example 1 were performed except that the activation firing of "Sample-1" was performed at a temperature of 360°C. As a result of measuring the nitrogen adsorption capacity of the adsorption separation agent prepared in this way based on the static adsorption capacity measurement method, it was found that 28
．． It was 9Ncc/g. Further, the dynamic performance was determined based on a dynamic evaluation method, and the result was 52.4N1/Kg-h.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a dynamic evaluation device for adsorption/separation agents. 1: Floor 2-5: Solenoid valve 6: Pressure gauge 7: Adsorption tower 8: Pressure accumulator 9: Flowmeter 10: Oxygen concentration meter 11: Integral flow meter 12: Vacuum pump Patent applicant: Tosoh Corporation

Claims (2)

[Claims] (1) When producing a zeolite adsorption/separation agent, the dew point -
A method for producing a zeolite adsorption/separation agent, which comprises firing under gas flow at a temperature of 30°C or lower. (2) The method for producing a zeolite adsorption/separation agent according to claim 1, wherein the zeolite adsorption/separation agent is made of A-type zeolite, X-type zeolite, or a mixture thereof.