JPH07284667A - Catalytic alloy for decomposition of fluorocarbon - Google Patents

Abstract

PURPOSE:To obtain a catalytic alloy having high activity, proof against hot H2O, HCl and HF and undergoing no deterioration of the activity even by a catalytic reaction by using an alloy of a valve metal having catalytic activity and maintaining it with Co or Ni assisting the metal in exhibiting the catalytic activity and Mo and Cr promoting catalytic activity and remarkably improving durability. CONSTITUTION:This catalytic alloy is an alloy consisting of <=20at.% Mo, 25-80at.%, in total, of Ni and/or Co and the balance essentially one or more kinds of elements selected from among Ti, Zr and Nb or an alloy consisting of <=20at.%, in total, of Mo and Cr, 25-80at.%, in total, of Ni and/or Co and the balance essentially one or more kinds of elements selected from among Ti, Zr and Nb.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention decomposes used CFCs into carbon dioxide, hydrogen fluoride and hydrogen chloride to render them harmless.
As a highly active catalyst to be reused, the present invention relates to a metal material that continues to have a high activity even if hydrofluoric acid and hydrochloric acid that attack metals are produced by CFC decomposition.

[0002]

2. Description of the Related Art Freon destroys the ozone layer, and thus unnecessary freon must be decomposed and rendered harmless. For the decomposition of CFCs, a method of mixing with a large amount of methane and burning, a method of reacting with water at high temperature and high pressure, a plasma decomposition method, a supercritical hydrolysis method, a reduction method and the like have been tried.

On the other hand, the present inventors have paid attention to the fact that the amorphous alloy is a single-phase solid solution containing various kinds of elements having different properties, and create a material having new characteristics by forming a solid solution alloy. Through research, we have found a number of amorphous alloys with various excellent properties. In particular, the two inventors of the present invention have conducted research on a catalyst for reacting CFCs with water at low temperature to produce hydrogen fluoride, hydrogen chloride and carbon dioxide based on the results of conventional research on amorphous alloy electrode catalysts. As a result, they found that a high-performance catalyst can be obtained from an amorphous alloy, and filed as Japanese Patent Application No. 2-45661. Japanese Patent Application No. 2-4566
No. 1 consists of the following three inventions.

(1) One or two of Nb and Ta 20-
70 atomic%, 0.5 to 20 atomic% of one or more elements selected from the group of Ru, Pd, Rh, Pt, and Ir, and the balance to an amorphous alloy consisting essentially of one or two elements of Ni and Co. An amorphous alloy catalyst for CFC decomposition, which is characterized by being activated by immersion in hydrofluoric acid. (2) One or two kinds of Ti and Zr, 20 to 80 atomic%,
An amorphous alloy containing 0.5 to 20 atomic% of one or more elements selected from the group of Ru, Pd, Rh, Pt, and Ir, and the balance substantially one or two elements of Ni and Co of 10 atomic% or more is used. An amorphous alloy catalyst for CFC decomposition, which is characterized by being activated by immersion in hydrofluoric acid. (3) One or two of Nb and Ta and 70 atomic% or less and T
A total amount of 20 to 80 atoms including one or two of i and Zr (including the amount of one or two of Nb and Ta described above), R
0.5 to 20 atomic% of one or more elements selected from the group consisting of u, Pd, Rh, Pt and Ir, the balance being substantially Ni and C
An amorphous alloy catalyst for CFC decomposition, which comprises subjecting an amorphous alloy consisting of 10% by atom or more of one or two kinds of o to an activation treatment by immersion in hydrofluoric acid. As a result of further continuing these studies, the present inventors have found that a metal or an alloy exhibits excellent catalytic activity even without containing a platinum group element, and Japanese Patent Application No. 2-2411.
Filed as No. 87. Japanese Patent Application No. 2-241187 (Japanese Patent Application Laid-Open No. 4-122443) comprises the following two inventions.

(1) A catalyst material for decomposing fluorocarbons, which is a metal selected from the group consisting of Ti, Zr and Nb and an alloy composed of two or more elements. (2) A catalyst for decomposing CFCs, which is an alloy consisting of 80% by atom or less of one or two kinds of Ni and Co and the balance substantially one or more elements selected from the group of Ti, Zr and Nb. material.

The present inventors have conducted research to improve the durability of these CFC-decomposing catalyst materials. As a result, by adding an element resistant to oxidation and halogenation at high temperature, not only the durability but also the activity can be improved. The present invention has been achieved by finding improvements.

[0007]

The easiest, simplest and cheapest way to thoroughly decompose CFCs to inorganics without leaving harmful organic halides is to react with water vapor,
It decomposes into O ₂ , HCl and HF. For this purpose, a catalyst with excellent performance is required, but high temperature H
_No catalyst has been found that survives ₂ O, HCl and HF and remains active. Therefore, the advent of highly active and high temperature H ₂ O, HCl and HF resistant catalysts is awaited.

[0008]

According to the present invention, a CFC decomposition reaction based on the principle that waste CFC is reacted with water and converted into CO ₂ , HCl and HF can be carried out at a low temperature. Highly active and high-temperature H ₂ O and HC produced
We have developed a catalytic alloy that can withstand l and HF.
The technical constitution of the present invention is as follows: (1) The content of Mo is 20 atomic% or less and one or two kinds of Ni and Co in total of 25 to 80 atomic%, and the balance is substantially from the group of Ti, Zr and Nb. A catalyst alloy for decomposing CFCs, which is an alloy consisting of one or more elements selected, and (2) 20 atomic% or less in total of Mo and Cr and 1 or 2 kinds of Ni and Co in total. 25-
A CFC decomposition catalyst alloy characterized by being an alloy comprising 80 atomic% and the balance substantially consisting of one or more elements selected from the group consisting of Ti, Zr and Nb, and the CFC decomposition catalyst alloy of the present invention is It has a high activity and is composed of a valve metal that carries and sustains the catalytic activity, and an alloy of Co or Ni that aids the expression of the catalytic activity and Mo and Cr that promotes the catalytic activity and significantly improves the durability. It is intended to provide a catalyst alloy which withstands high temperature H ₂ O, HCl and HF and whose activity is not impaired by catalytic reaction.

Table 1 below shows the constituent elements and the content of the present invention. Many metal catalysts are easy to produce and are highly active in specific chemical reactions. However, the biggest difficulty in using a metal catalyst for the decomposition of CFCs by the reaction with steam is that even if the CFCs and steam are initially catalytically decomposed, the steam and the generated hydrogen fluoride and hydrogen chloride will quickly invade them. It dissolves in water or turns into an inactive halide and cannot maintain its activity. On the other hand, Ti, Zr, and Nb, which are the main components of the alloy of the present invention, can maintain the catalytic activity of the catalytic reaction between CFC and steam even if they are changed to halides. Furthermore, Mo and Cr have excellent resistance to an environment in which oxidation and halogenation act simultaneously. That is, as a catalyst alloy that decomposes fluorocarbons into hydrogen fluoride, hydrogen chloride, and carbon dioxide by causing water vapor to act thereon, a catalyst alloy having high performance and capable of sustaining high activity even when hydrogen halide is produced has the above composition. Realized by metals and alloys.

The reasons for limiting the composition of each component in the present invention will be described.

[0011] Ti, Zr and Nb are the metals on which the present invention is based, and even if they are converted to halides by the action of hydrogen fluoride and hydrogen chloride produced by the reaction of freon and steam, they are freon and steam. It is an element that does not lose its performance as a catalyst for the catalytic reaction with.

[0012] Ni and Co act as a catalyst for the catalytic reaction of CFCs and water vapor, but they are slowly attacked by the action of hydrogen fluoride and hydrogen chloride produced by themselves. However, Ni and Co are necessary elements for forming an amorphous alloy, promote the catalytic action of forming an amorphous alloy of a single-phase solid solution, and are not easily attacked.

Mo and Cr have excellent resistance to the environment in which oxidation and halogenation simultaneously act, and when these are added as alloying elements, the resistance of the alloy to the action of water vapor, hydrogen fluoride and hydrogen chloride remarkably increases. As a result, it is an element that also improves the catalytic activity. Therefore,
Simultaneous addition of Mo or Mo and Cr is extremely effective for improving the catalytic activity and durability. However, in these alloys, when the content exceeds 20 atomic%, the amorphous structure becomes a liquid quenching method. In some cases, it becomes difficult to obtain the above, and it becomes difficult to exhibit the catalytic activity due to the formation of the corrosion resistant surface film. Therefore, the total content of Mo or Mo and Cr needs to be 20 atomic% or less.

The addition of one or more of Ni and Co is indispensable for producing an amorphous alloy, but the sum of Mo or Mo and Cr and the sum of one or two of Ni and Co is less than 25 atomic%. If it exceeds 80 atomic%, Ti, Zr, and Nb, which are the essential metals of the present invention, become excessive or insufficient for forming an amorphous single-phase alloy, making it difficult to form an amorphous alloy. Therefore, the total amount of Mo or Mo and Cr is increased. And any one of Ni and Co
The seed or the sum of the two must be 25-80 atomic%.

[0015]

EXAMPLES The present invention will now be described with reference to examples. Example 1 For the purpose of investigating the catalytic performance of a sample metal, since the shape of the ribbon is convenient, a sample was prepared using a method of rapidly quenching and solidifying a liquid alloy that is widely used for preparing an amorphous alloy. The apparatus used is shown in FIG. The part surrounded by the dotted line is filled with an inert gas after being evacuated. In the figure, 2 is a quartz tube having a vertical nozzle 3 at its lower end, and a raw material 4 and an inert gas for preventing the raw material from being oxidized can be fed from an inlet 1 provided at the upper end of the quartz tube 2. it can. A heating furnace 5 is installed around the quartz tube 2 to heat the raw material 4. A high-speed rotation roll 7 is placed vertically below the nozzle 3 and rotated by a motor 6.
To prepare a ribbon-shaped alloy sample, a raw material 4 having a predetermined composition is placed in a quartz tube 2, the apparatus is first evacuated to about 10 ⁻⁵ Torr, and then an inert gas is filled. Next, the raw material 4 is heated and melted by the heating furnace 5, and the molten metal is sprayed by the motor 6 onto the outer peripheral surface of the roll 7 which is rotating at a high speed of 1000-10000 rpm, by using a pressurized inert gas. By this method, for example, a thickness of 0.1 mm and a width of 10
The alloy of the present invention can be obtained as a long thin plate having a length of mm and a length of several meters.

Raw material metals were mixed so that the composition of Mo was 1, 5, 10, 15 atomic% and Zr was 40 atomic% and the balance was Ni, and a raw material alloy was prepared by argon arc melting. By remelting these alloys in an argon atmosphere and melting and quenching and solidifying using the single roll method shown in FIG. 1,
A ribbon-shaped catalyst alloy having a thickness of about 0.02 mm, a width of about 1 mm and a length of about 6 m was obtained. Catalyst alloy 0.28 thus obtained
g was packed in a stainless steel tube having an inner diameter of 8 mm to form a reaction tube, and the reaction tube was placed in an electric furnace. CFC-12 freon is blown up from the bottom of warm water, CFC-12 freon containing water is flown into the reaction tube, and CFC-12 freon and CO ₂ amount at the outlet of the reaction tube are measured by gas chromatography and HF and HCl are measured by water chromatography. It was collected in and measured. The obtained results are shown in Table 2. However, if the catalyst activity did not decrease at all even after 240 hours, the life of the catalyst of 0.28 g was set to 240 hours or more, and the experiment was stopped.

[0017] As shown in Table 2, it was revealed that the alloy of the present invention has high activity and extremely high durability as compared with the high activity alloy of the comparative example.

Example 2 Raw material metals were mixed so as to have the composition shown in Table 3, and a raw material alloy was prepared by an argon arc melting furnace. These alloys were remelted in an argon atmosphere and melt-quenched and solidified using the single roll method shown in FIG.
A metal thin plate having a length of 01-0.05 mm, a width of 1-3 mm and a length of 3-20 m was obtained. As the Ni used for comparison, a thin plate having a thickness of 0.005 mm produced by rolling 20 steps was cut into a ribbon having a width of about 1 mm and used. 0.2-0.5 g of the catalyst alloy material thus obtained was packed in a stainless steel tube having an inner diameter of 8 mm to form a reaction tube, which was placed in an electric furnace. CFC-12 freon is blown up from the bottom of warm water to contain water.
-12 CFC is flown into the reaction tube, and CF at the reaction tube outlet
The amounts of C-12 freon and CO ₂ were measured by gas chromatography, and HF and HCl were recovered and measured in water. The results obtained are shown in Table 3. However, if the catalyst activity does not decrease even after 240 hours, 0.28
The life of the catalyst alloy of g was 240 hours or more, and the experiment was stopped.

[0019] As described above, it is clear that the catalyst alloy for decomposing CFCs of the present invention has a high activity that allows CFCs to react with water vapor at a low temperature and decompose into CO ₂ , HF, and HCl, which can be sustained. became.

On the other hand, when ribbon-shaped Ni was used, it was attacked by hydrogen fluoride and hydrogen chloride and dissolved in water. Therefore, when 2.05 g of chlorofluorocarbon was decomposed per 1 g of ribbon-shaped Ni, the ribbon-shaped Ni was lost.

[0021]

INDUSTRIAL APPLICABILITY As described above, the catalyst alloy of the present invention has a high catalytic activity capable of decomposing CFC at a relatively low temperature, and is a reaction product of H ₂ O with HF and HC.
It is a catalyst alloy for CFC decomposition that has excellent durability against oxidation and halogenation by l.

Further, the highly active and durable catalyst alloy of the present invention is easily made by sputtering on a suitable carrier and is excellent in practicality.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of an apparatus for producing an alloy of the present invention.

[Explanation of symbols]

 1 Inlet 2 Quartz Tube 3 Vertical Nozzle 4 Raw Material 5 Heating Furnace 6 Motor 7 High Speed Rotating Roll

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Asahi Kawashima 37-17 Hiyoridai, Taichiro-ku, Sendai-shi, Miyagi Prefecture (72) Inventor Katsuhiko Asami 2-5-3 Taichiro, Taihaku-ku, Sendai-shi, Miyagi Prefecture

Claims (2)

[Claims] 1. Mo and 20 atomic% or less and Ni and Co
The catalyst alloy for decomposing CFCs, characterized in that it is an alloy consisting of 25-80 atomic% in total with one or two of the above and the balance substantially consisting of one or more elements selected from the group of Ti, Zr and Nb. . 2. The total of Mo and Cr is 20 atomic% or less and the total of one or two of Ni and Co is 25-8.
A catalyst alloy for decomposing CFCs, which is an alloy containing 0 atomic% and the balance consisting essentially of one or more elements selected from the group consisting of Ti, Zr and Nb.