JPH02194838A - Reducing reaction method of substance dissolved in water by hydrogen - Google Patents

Abstract

PURPOSE:To efficiently perform reduction of substance dissolved in water by hydrogen by treating silica with silane compd. contg. amino group and impregnating this silica with a palladium salt aq. soln. and drying the silica and thereafter reducing it at 300-500 deg.C in a vapor phase to obtain a palladium catalyst and bringing the substance dissolved in water into contact with hydrogen while utilizing the palladium catalyst. CONSTITUTION:A catalyst reducing reaction with hydrogen is obtained by treating silica with silane compd. contg. amino group (e.g. 3- aminopropyltrialkoxysilane) and impregnating this silica with a palladium salt aq. soln. and drying the silica and thereafter reducing it at 300-550 deg.C in a vapor phase. For example, ferric ion contained in plating waste liquid can be reduced by adding this catalyst to this waste liquid. As silica utilized for a carrier, silica having mean small pore diameter not smaller than about 400Angstrom is preferably utilized. Further weight of silica per 1g modified silica necessary to carry about 0.1-10wt.% palladium is properly regulated to about 0.1-20 millimol.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for reducing substances dissolved in water, such as the reduction of ferric ions (Fe) in the waste water of methane, the reduction and removal of dissolved oxygen, etc. This relates to a hydrogen reduction reaction method for substances dissolved in .

[Prior Art] When inorganic ions and dissolved oxygen in an aqueous solution are reduced with hydrogen, a catalyst in which Pd or pt is supported on activated carbon, alumina, silica, or an ion exchange resin is used.

Since these carriers are hydrophilic, when used in water, the active sites are covered with water, making it difficult for hydrogen gas to reach the active sites, resulting in insufficient activity and a long reaction time. Ta.

In order to improve this point, catalysts have been proposed that use a carrier with a hydrophobic surface or a hydrophobic polymer as a carrier.

For example, an example using a fluororesin as a carrier [Detection et al.
Catalyst J vol, 23. No, 4. p293(19
81)] has been shown to be effective in reducing Cu'' and No3-, but fluororesin is expensive and ethanol or There are problems in that it is necessary to use an organic solvent such as acetone.

A method has also been proposed in which silica is modified with a hydrophobic silanizing agent and then an active metal is supported, but in this case as well, it is necessary to use an organic solvent such as ethanol or acetone to support the catalytic active component. Since a solvent recovery step is required during catalyst production, the cost of the catalyst increases, which is undesirable.

[Problems to be Solved by the Invention] The present invention uses a palladium-supported catalyst that is easy to manufacture because the catalytic active component can be supported as an aqueous solution, and that also exhibits excellent activity even in water because it becomes hydrophobic when used. The purpose of the present invention is to provide a reaction method for reducing a substance dissolved in water with hydrogen.

[Means for Solving the Problems] The hydrogen reduction reaction method for a substance dissolved in water according to the present invention involves impregnating silica treated with a silane compound having an amino group with an aqueous solution of a palladium salt and drying it for 300 minutes. ~
It is characterized in that it is brought into contact with hydrogen in the presence of a palladium catalyst that has been reduced in a gas phase at 550°C.

The larger the pore diameter of the silica used as the carrier, the higher the activity, so it is preferable, and it is particularly desirable to use silica with an average pore diameter of 400 Å or more.

Examples of the silane compound having an amino group include 3-aminopropyltrialkoxysilane, N-(2-aminoethyl)-3-aminopropyltrialkoxysilane, and the like.

When a silica carrier and a silane compound having an amino group are brought into contact with each other in water or any other solvent, or when a silica carrier is impregnated with a silane compound having an amino group, the silane compound having a silanol group and an amine group of the silica is The silica support is modified by the reaction.

The amount of organic amino groups in this modified silica is controlled by the amount of the silane compound having amino groups.

The amount of organic amine groups in the modified silica may be determined depending on the target amount of palladium supported, but it is 0.1 to 10% by weight.
The amount of amino groups per gram of modified silica required to support palladium is about 0.1 to 2.0 mmol.

Then, when the aqueous solution of the palladium salt is brought into contact with the modified silica, the palladium ions undergo ion exchange, form a complex with the organic amino group, and are fixed on the silica carrier. Therefore, the dispersibility of palladium is good, and since most of the palladium ions in the solution are immobilized, loss of palladium can be reduced.

Palladium-supported silica at this point is hydrophilic;
After drying, the silica is reduced in a gas phase at 300 to 550'C to decompose the amino groups and make the silica hydrophobic.

Gas phase reduction can be carried out by a conventional method using H2, GO, etc. in a gas stream. However, it is necessary to carry out the reaction in a temperature range of 300°C to 550°C, and sufficient reduction will not occur at temperatures below 300°C. Further, at temperatures exceeding 550°C, dispersion of palladium becomes significantly poor.

The present invention will be specifically explained below using Examples.

[Example 1] 200 g of silica for carriers having an average pore diameter of 40,000 (manufactured by Catalysts Kasei Kogyo ■) was mixed with 3-aminopropyltriethoxysilane in an amount such that the amount of organic amino groups was 0.3 mmol/g silica. It was added to the solution dissolved in pure water and stirred at room temperature for 4 hours to effect silanization.

The product was then filtered, washed with water, and dried at 110°C for 5 hours to obtain silane-modified silica.

A palladium chloride aqueous solution was added in an amount such that the palladium content was 0.5% by weight to 50 g of this silane-modified silica to form a complex of palladium chloride and organic amino groups on the silica carrier, and the solution was filtered. It was dried at 110°C.

This was reduced in a gas phase at 400°C, 1500°C, or 550°C in a hydrogen stream to obtain a hydrogen reduction reaction catalyst.

4.5g of F e ”fi in a 200rnJ2 flask
/β ferric sulfate aqueous solution was added, 3.5 mg of the above catalyst pulverized to 100 mesh or less was added as Pd, hydrogen initial pressure was 900 Torr, temperature was 25±1
The reaction was carried out at ℃, and the results of determining the initial activity of the catalyst are shown in FIG. 1 by circles. In Figure 1, the horizontal axis is the reduction temperature of the catalyst (°C
), the vertical axis is the initial activity of the catalyst [(H2moj2/g-Pd
-min)XIO2].

[Example 2] 200 g of silica for carriers with an average pore diameter of 400 (manufactured by Fuji Davison ■, trade name CARIACT) was purified with 3-aminopropyltriethoxysilane in an amount such that the amount of organic amino groups was 03 mmol/g silica. It was added to the solution dissolved in water and stirred at room temperature for 4 hours to effect silanization. Then, filter and wash with water.
It was dried at 110° C. for 5 hours to obtain silane-modified silica.

To 50 g of this silane-modified silica, an aqueous solution of Baladium chloride in an amount such that the palladium content was 0.5% by weight was added to form a complex of palladium chloride and organic amino groups on a silica carrier, and the solution was filtered. The mulberry was then dried at 110°C. 300℃, 400℃, 500℃ or 550℃
The catalyst was reduced in a gas phase in a hydrogen stream to obtain a catalyst for hydrogen reduction reaction.

Put 70 mQ of ferric sulfate aqueous solution with F e "a degree of 4.5 g/C into a 200 mm flask, add 3.5 mg of the above catalyst pulverized to 100 mesh or less as Pd,
The reaction was carried out at an initial hydrogen pressure of 900 Torr and a temperature of 25±1° C., and the results of determining the initial activity of the catalyst are shown in FIG. 1 by the symbol Δ.

[Comparative Example 1] The silica for carrier having an average pore diameter of 400 used in Example 2 was impregnated with an aqueous solution of palladium chloride in an amount such that the palladium content was 0.5% by weight, and dried at 110°C. C1400°C or 500°C in a gas phase reduction in a hydrogen stream to obtain a hydrogen reduction reaction catalyst.

A ferric sulfate aqueous solution of 70 m°C with a F e concentration of 4.5 g/°C was placed in a 200 m12 flask, and 3°5 mg of the above catalyst pulverized to 100 mesh or less was added as Pd.
The reaction was carried out at an initial hydrogen pressure of 900 Torr and a temperature of 25±1° C., and the results of determining the initial activity of the catalyst are shown in FIG. 1 with a mark ◇.

As shown in Figure 1, in the case of Examples 1 and 2, in which the palladium catalyst was supported on silica modified with a silane compound having an amino group, the palladium catalyst was supported on silica that had not been modified. It can be seen that higher initial activity can be obtained than in Comparative Example 1, which uses a palladium catalyst.

In addition, the reduction treatment temperature of the catalyst itself in the example is 300 to 550.
It can be seen that a temperature range of 400 to 500°C is preferable. On the other hand, the catalyst of Comparative Example 1 shows a tendency for the initial activity to decrease when the reduction treatment temperature of the catalyst itself becomes 400 degrees or higher.

[Example 3 and Comparative Example 2.3] Example 2, in which a 70m°C aqueous ferric sulfate solution with an Fe31 concentration of 4.5g/°C was placed in a 200mm flask, subjected to reduction treatment at 0400°C, and ground to 100 meshes or less. The same catalyst used in Comparative Example 1 was added with 3.5 mg of Pd, and the same catalyst used in Comparative Example 1 was reduced at 0400°C and pulverized to 100 mesh or less.
．． After adding 5 mg of palladium chloride and ■activated carbon (manufactured by Niphas Kagaku ■) with an aqueous solution of palladium chloride in an amount that makes the palladium content 0.5% by weight, and drying at 110°C,
3.5 mg of Pd was added to each of the catalysts that had been reduced in the gas phase in a hydrogen stream at 00°C and pulverized to 100 meshes or less, and reacted at an initial hydrogen pressure of 900 Torr and a temperature of 25 ± 1°C, and after 10 minutes. Table 1 shows the results of measuring the amount of hydrogen consumed (integrated value: 2 mmol) after 20 minutes, 30 minutes, and 40 minutes.

It can be seen that in the case of the Examples in Table 1, the amount of hydrogen consumed increases rapidly and reaches the saturation value, that is, the reaction is rapid.

[Example 4] Fe reduction in an aqueous solution was carried out by the method described in Example 1 using silica with different average pore diameters and using a catalyst prepared by the method described in Example 1 and subjected to reduction treatment at 400°C. The results of measuring the amount of hydrogen consumed (integrated value = mmol) during the
Shown in the table.

(Left below) Pure water with a pH of 7.2, including Table 2, was flowed at SV = '120 h- with a large excess of hydrogen at 5 mA/min, and the dissolved oxygen concentration of the outlet liquid was measured and the activities were compared. .

Since the outlet concentration became stable several minutes after the start of the reaction, the measured values after 10 minutes are shown in Table 3.

From Table 3 and Table 2, the larger the pore diameter of the carrier silica, the higher the activity (
It can be seen that it is preferable to use a palladium catalyst using silica having an average pore diameter of 400 Å or more as a carrier.

[Example 5 and Comparative Examples 4 and 5] ■ 0.5 g of the same catalyst as that used in Example 3, except that the particles were sized to 32 to 48 mesh, ■ Comparative Example 2, except that the particles were sized to 32 to 48 mesh. The same catalyst used in 0.
A glass tube with an inner diameter of 5 mm was filled with 0.5 g of the same catalyst used in Comparative Example 3, except that the catalyst was sized to a size of 32 to 48 mesh, and 5 p of dissolved oxygen was added to the tube at room temperature.
It is shown that the outlet oxygen concentration is the lowest when pm is the example.

[Example 6 and Comparative Examples 6 and 7] 50 mβ of a cupric sulfate aqueous solution with a concentration of 0.1 mol/°C was placed in a 200 rr + j2 flask, and 2.5 mg of the same catalyst used in Example 3 was added as Pd. What was added,
■2. Using the same catalyst as that used in Comparative Example 2 with Pd.
5 mg of the same catalyst as used in Comparative Example 3 and 2.5 mg of Pd of the same catalyst used in Comparative Example 3 were added at an initial hydrogen pressure of 900 Torr and a temperature of 25
Table 4 shows the results of measuring the amount of hydrogen consumed (integrated value = mmol) after 10 minutes, 20 minutes, 30 minutes and 40 minutes after the reaction was carried out at ±1°C.

This is a diagram showing the initial activity when hydrogen reduction of Fe'' ions is performed using different catalysts, where the 0 mark is for Example 1, the Δ mark is for Example 2, and the ◇ mark is for Comparative Example 1. The horizontal axis is the reduction temperature of the catalyst (℃), and the vertical axis is the initial activity of the catalyst [(H2
mo°C/g-Pd-mfn) x 102.

Claims (1)

[Claims] 300-550 after impregnating and drying an aqueous solution of palladium salt on silica treated with a silane compound having an amino group.
A hydrogen reduction reaction method for a substance dissolved in water, characterized by contacting it with hydrogen in the presence of a palladium catalyst reduced in a gas phase at °C.