JPS62273029A - Medium for separating hydrogen - Google Patents

Abstract

PURPOSE:To obtain a hydrogen separating medium supporting a Pd membrane without a possibility in damaging the same, by forming a membrane based on Pd covering the pore parts of the surface of a heat resistant porous body having a large number of small pores. CONSTITUTION:A porous body having heat resistance withstanding temp. of 300 deg.C or more, no reactivity with gas to be treated and uniform pores with a pore size of 20-30,000Angstrom is used. This porous body is used in a cylindrical or plate like shape having a thickness of 1-0.2mm. After said porous body is washed and activated, a Pd membrane is formed by chemical plating. Chemical plating is performed by a method wherein a liquid such as alcohol or water is preliminarily infiltrated in the porous body and Pd is precipitated using a plating bath based on [Pd(NH3)4]Cl2.H2O. The thickness of the membrane is about 0.001mm when a pore size is 3,000Angstrom and a required plating time is about 17hr.

Description

[Detailed description of the invention] 3. Detailed description of the invention [Purpose of the invention] (Industrial application field) The present invention relates to a hydrogen separation medium.

(Conventional technology) Gas separation methods using membranes have been attracting attention in recent years as an energy-saving thinning technology.

A membrane mainly composed of Pd (P
(referred to as Pd1lfi method)
It has been known. Conventionally, Pd1PI was produced by drawing Pd or an alloy mainly composed of Pd to form a thin film, and this film was used by supporting it with a support frame.

There is a lower limit to the thickness of the membrane that can be obtained by the stretching method, and since this membrane is used while being supported by a support frame, it is necessary to provide it with mechanical strength sufficient to withstand such support methods. However, if a too thin membrane is used, the membrane is likely to be damaged during use.

For this reason, it is necessary to use a relatively thick Pd film of about 60 to 100 JL, which increases the amount of expensive Pd used, and has the disadvantage that the hydrogen permeation rate is relatively low.

(Problems to be Solved by the Invention) The present invention aims to solve the above-mentioned problems that the prior art had.

[Structure of the Invention (Means for Solving the Problems)] The present invention has been made to solve the above-mentioned problems. The present invention provides a groove separation medium characterized in that a film mainly composed of Pd is formed to cover the openings on the surface side of the groove.

Next, the present invention will be explained in more detail.

In the present invention, the porous body has a temperature of 300°C or higher;
It preferably has heat resistance that can withstand temperatures of 400°C or higher, does not have reactivity with the gas to be treated, and has a temperature of 20 to 30°C.
It is suitable to use a porous body having uniform pores of 0 QOA, preferably 40 to 5,000 A.

Examples of such a porous body include a sintered body of fine ceramic particles such as AJLzOi, and porous glass, but it is preferable to use porous glass.

As the porous glass, Hicor glass or 5i0245
~70wt%, 820.8~30wt%, CaO3~2
5wt%, Alt035~L5wt%, Na2O3~
8%, K2O1~5%, NazO+, o4~
Glass having a composition of 13wt,%, Mg00S8wt% (hereinafter referred to as glass A) or 5i0245~70w
t%, Bz03a ~30 wt%, CaO3 ~25
Glass having a composition of wt%, A1.035-15% (
(hereinafter referred to as glass B) is heat treated to produce B20:l, CaO
Porous glass (hereinafter referred to as porous glass A or B) obtained by phase separation and dissolving and removing this phase is suitable. A particularly suitable hydrogen separation medium can be obtained by forming a Pd film by the method.

It is appropriate to use a cylindrical or plate-shaped porous body having a thickness of 1 to 0.2 @a+ as the above-mentioned porous body, and such a porous body is attached to raw glass molded into a predetermined shape. It can be obtained by performing phase separation treatment and dissolution treatment.

In order to obtain porous glass A or B in the present invention, glass A or B having the above-mentioned composition is used. Among these components, SiO
nzox has the effect of reducing the brittleness of the porous glass obtained as an auxiliary component. On the one hand, B2O3 functions as an auxiliary component that forms the framework of the porous glass, but on the other hand, in cooperation with GaQ, it has the effect of producing minute phase separation through heat treatment. And CaO generated in this way
Porous glass is formed by dissolving and removing the separated phase containing 1B203 as a main component.

As can be seen from the above explanation, B2O3 is an important factor that determines the size of the pores, and the amount of B2O3 transferred into the mucus phase and removed, or conversely, the amount of B2O3 remaining in the porous glass
It was found that the amount of □03 has a close relationship with the uniformity of the diameter of the small pores.

A suitable porous body can be obtained by keeping the above components within the above ranges.

Glasses A and B are molded into a predetermined shape and then heat treated (:aO
, B20z (hereinafter referred to as Cab, B20° phase). The higher the heat treatment temperature and the longer the heat treatment time, the thicker the CaO and B20□ phases become.
Therefore, the diameter of the small pores in the resulting porous glass tends to increase, and by selecting the heat treatment conditions, the diameter of the small pores can be increased by 50%.
It can be any desired value in the range of 0 to 50,000 OOA. The porous glass thus obtained has small pores of uniform diameter and is extremely suitable for achieving the object of the present invention.

Heat treated glass is HCI H2SO, HNO.

The CaO1B and OY phases are dissolved and removed by immersing the sample in an acid such as Note that prior to acid treatment, it is desirable to etching the surface for a short time with an HF solution.

As mentioned above, the diameter of the small pores in the resulting porous glass can be controlled by the heat treatment conditions, but the diameter of the small pores depends on the B20. This B, 0. It has been found that the amount of is influenced by the conditions of heat treatment and acid treatment. It has been found that particularly favorable results can be obtained by setting these conditions so that B2O3 desirably remains in an amount of 0.5 wt% or more.

Desirable processing conditions are as follows.

Heating temperature 600 to 850℃ Heating time 2-48hr, preferably 12-24hr Type of acid 80 sentences,! (2S04.114G.

Acid concentration o, oi~2. ON, preferably 0.1-1
, ON Treatment time 2-20hrs, preferably 4-16hrs
A chemical plating method can be suitably used as a method for forming a Pd film on the above-mentioned porous body at a temperature of 50 to 95°C, preferably 80 to 90°C.

It is desirable to perform cleaning to remove stains adhering to the surface of the porous body before applying chemical plating, and an example of a suitable stain removal method is an ultrasonic cleaning method using trichlorethylene. After washing with trichlorethylene, wash with lower alcohol such as ethanol.
It is also possible to replace trichlorethylene remaining in the porous body with alcohol and then dry it.

Thereafter, prior to chemical plating, it is appropriate to activate the porous body and deposit activated Pd onto the porous body.

For example, suitable activation results can be obtained by alternately performing immersion treatment with a 5nC12 solution and a PdCl2 solution. 5 as a preferable treatment liquid composition
nC1z ・2Hz01 gin + 37%HC sentence
1m sentence, PdC sentence 20.1 g/view+37% IC sentence 0.1 an/fL can be exemplified. In addition,
When processing with these solutions is performed alternately, it is appropriate to perform sufficient washing with pure water after the processing path of one of the solutions.

Next, by immersing the porous body in a plating solution as shown below, Pd is deposited on the Pd formed by the above-mentioned treatment.
can be precipitated to form a Pd film covering the openings on the surface side of the porous body. At this time, it is appropriate to form the Pd film only on the necessary portions of the porous body by masking or the like.

For example, when forming a Pd film on the outer surface of a cylindrical porous body, by closing both end faces of the cylinder, Pd film is formed only on the outer surface.
d film can be formed. Or [Pd(NH,
) 41 When using a plating solution mainly composed of C2.H2O, by soaking a liquid such as alcohol or water into the small pores of the porous body, Pd15j is added to the inside of the small pores.
A Pd film can be formed only on the surface of the porous body without forming a Pd film.

Among the above means, the use of lower alcohols is particularly effective in achieving the objects of the present invention.

[This is thought to be because Pd(NHz)nl C1z has no solubility in lower alcohols@ A solution having the following composition is exemplified as a plating solution suitably used to form Pd1ii by chemical plating.

[Pd(NH3)41 (:immun2・H,85,4%2
Na-EDTA 67.2g/l
NH4OH350gr/ 1 H2NNH,・Hzo 0.46■l
/text The smaller the thickness of the Pd film, the higher the hydrogen permeation rate, and the amount of expensive Pd used can be reduced, but if the thickness is made too small, pinholes will form in the Pdl and gases other than hydrogen will leak. Moreover, Pd becomes easily damaged during use. This tendency increases as the diameter of the small hole opening increases.

It is not possible to determine the thickness of the Pd film for each small hole; the minimum thickness of the Pd film is determined by the maximum diameter of the small hole. If there is variation in the diameter of the small pores, and even a small number of small pores with large diameters exist, the thickness of the Pd film must be increased according to the diameter of the large pores in order to completely prevent the leakage of gases other than H2. Most of the other small holes need to be filled with unnecessarily thick Pd.
It will be covered with a membrane.

Porous glass A and B have uniform small pore diameters with little variation.
Therefore, there is no need to use unnecessarily thick Pdl, and moreover, by using this porous glass and using chemical plating method, Pd1
It has been found that a hydrogen separation medium with very suitable properties can be obtained by forming 11.

A suitable thickness of the Pd film is about 0.001@m when the diameter of the small hole is 3,000 A.

The time required for plating needs to be increased as the thickness of the PD film increases; however, in the case of a thickness of 0.001 mm, the time required for plating is approximately 17 hours. - When a mixed gas containing hydrogen is supplied to one side of the above-mentioned separation medium for hydrogen, the medium allows only hydrogen to permeate, and pure hydrogen flows out from the other side of the medium.

The permeation rate of hydrogen is proportional to the difference in hydrogen pressure (partial pressure of hydrogen in the case of a mixed gas) on both sides of the medium, and when the pressure difference is zero,
Hydrogen does not escape.

Further, the higher the temperature, the higher the permeation rate, and increases almost linearly as the temperature rises.

For example, using a cylindrical medium, pure hydrogen is continuously supplied from the inside of the medium by continuously supplying a mixed gas from below to the outside of the medium 1 and discharging bleed gas from above the outside as shown in Figure 1. It can be taken out.

The permeation rate of hydrogen is extremely high, at 500℃ and pressure difference of 2
kg/cm'', it is about 26 cg/cnf-min, and this value reaches 5 to 7 times that of the conventional Pd patterning method.

The bleed gas is removed with hydrogen partial pressure equal to the internal hydrogen pressure. Therefore, by controlling the internal hydrogen pressure to be extracted, it is possible to control the composition of the bleed gas and the fractionation rate of hydrogen.

Note that the hydrogen separation medium of the present invention can be produced by forming Pd1ii on glass that has been subjected to phase separation treatment by chemical plating, and then performing acid treatment to dissolve and remove the phase separation to form a porous body. It is also possible to form a Pd film by sputtering or vapor phase method instead of chemical plating.By using a Pd-based film such as an alloy of Pd and Ag, water-based Brittleness can also be improved.

(Function) By forming a Pd film covering the surface openings of the porous body and using the porous body as a support for Pd15I,
Supports thin Pd without fear of damage.

[Example 1] 5i(1249wt%-B10:I 18wt%, C
a013wt%, AfL20i 9wt%,
Ha, 05wt%, 02wt%, MgO
0.5 am thick made of glass having a composition of 4 wt%,
A cylindrical body with an inner diameter of foam and a length of 500IIIm is rotated at 710°.
The phase mainly composed of (:aO, B, and 03) was separated by heating at C for 20 hr, and then etched for 30 ml with a 2% HF solution. A porous body with a small pore size of 1 and 100 A was obtained by dissolving and removing the main phase. Next, ultrasonic cleaning was performed using trichlorethylene and ethanol. Cleaning with ethanol has a degreasing effect, but the cleaning with ethanol was also carried out for 30 minutes with the purpose of replacing it with trichlorethylene, which is almost insoluble in water. After the process, vacuum drying was carried out for about 4 to 5 hours.At this time, the next surface activation treatment was carried out after the process of 0 or more, which is enough time for the porous glass to have almost no smell of ethanol. I did it.

Activation of the substrate surface was performed using a two-component method. That is, (S
n(:iz ・2H201g/l + 37%tt
ci1mu/i) and Pd(:JLa activation treatment (P
dC120,1g/i+ 37zHC sentence 0. I l
In order to make the palladium nuclei on the 0 surface as dense as possible, each dipping time was 1 minute, and the dipping was repeated 10 times alternately. (After each sample was removed from the solution, it was thoroughly washed with pure water.) Since the purpose of these treatments was to plate only the outer surface, the top and bottom were covered with plating tape (manufactured by Scotch). The porous glass, which has undergone zero surface activation to prevent liquid from entering the tube, is immersed in ethanol after replacing the upper and lower blinding tape and washing with pure water. [Pd(883) 4] CJL, HzO 5.
4 gr, 67.2 g of 2 NaEDTA, 811
40) 350 gr of 1 and 0.4 tan of HJ NH* 20 were added to a plating solution at 50°C for 17 hours.
Soaked.

Note that this plating solution was replaced once every hour in order to keep the plating speed as constant as possible. The porous glass that had been plated for a predetermined period of time was cut at the upper and lower blind portions, and the cut edges were trimmed to have a length of 25.4 cm. Thereafter, it was ultrasonically cleaned with pure water and ethanol, and then vacuum dried to obtain a hydrogen separation medium.

This hydrogen separation medium 1 was fixed to an outer tube 3 made of stainless steel using an O-ring 2 to form a test apparatus as shown in FIG. For heating, the outside of the test device was insulated with mica, a nichrome wire was wound on top of the insulator, and the test equipment was kept warm with Kaoru. The experimental temperature was measured at the center of the inner tube (12 cm from the upper and lower O-rings).

A mixed gas of H2/Nt'' 1 (mol) is continuously supplied from the supply hole 4, a bleed gas is discharged from the discharge hole 5, and a pure lk of 99.99% or more is supplied from the lower extraction hole 6.
It was possible to obtain hydrogen with a pressure of g/c.

Note that 7 is a supply hole for pure hydrogen for purging, and 8 is a thermocouple.

Figure 2 shows the pressure of the mixed gas (kg/c) (hydrogen partial pressure is at this point) on the horizontal axis, and the hydrogen permeation rate (+a1/kg/cm).
) is a graph showing the relationship between hydrogen permeation rate and pressure on the vertical axis. Figure 3 shows the relationship between gas composition and pressure with gas composition (hydrogen mole fraction) on the vertical axis and mixed gas pressure on the horizontal axis. In this graph, the straight line a shows the composition of the obtained hydrogen gas, and the curved line shows the composition of the bleed gas.

It has been found that as the pressure of the mixed gas increases, the molar fraction of hydrogen in the bleed gas decreases, that is, the fractionation rate of hydrogen increases, and the permeation rate of hydrogen increases. The hydrogen content obtained was always 99.99% or more.

The thickness of the Pd film was approximately 0.001 mm.

(Example 2) Si0250 wt%, B, 0.20 wt%, (
:ao 1 jwt%, AlzOx 10wt%,
Na2O4wt%, K, 01wt%, Mg01wt
An experiment similar to that in Example 1 was conducted using glass having a composition of 99.99% or higher, and hydrogen gas with a purity of 99.99% or higher was obtained. Example 2 is the same as Example 1 except that the heating temperature for phase separation was 720° C., the heating time was 20 hours, and the plating time was 25 hours.

Figure 4 shows the amount of hydrogen gas supplied (+Jl/win) contained in the mixed gas at a hydrogen pressure difference of 5 kg/c and a temperature of 400°C.
) is the vertical axis, and the amount of hydrogen gas obtained (zentate/ll1n
) is the vertical axis, and the two are in a proportional relationship,
It turns out that the hydrogen permeation rate depends on the H2 partial pressure in the gas mixture.

Furthermore, Pd@(1) thickness is &IC! It was about O.GOLmm.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing how to use the hydrogen separation medium of the present invention,
Figure 2 is a graph showing the relationship between mixed gas pressure and hydrogen permeation rate, Figure 3 is a graph showing the relationship between mixed gas pressure and gas composition, and Figure 4 is the gas supply amount and hydrogen gas acquisition. It is a graph showing the relationship between quantities. In the figure, 1 is a hydrogen separation medium, 4 is a supply hole, 5 is a discharge hole, and 6 is an extraction hole. Figure 2 Figure 3

Claims (3)

[Claims] (1) A hydrogen separation medium characterized in that a film mainly composed of Pd is formed on the surface of a heat-resistant porous body having a large number of small pores to cover the openings on the surface side of the small pores. (2) The hydrogen separation medium according to claim 1, wherein the porous body is porous glass. (3) The medium for hydrogen separation according to claim 1 or 2, wherein the small pores have a size of 20 to 30,000 Å.