JPH04235738A - Catalyst for reducing carbon dioxide - Google Patents

Abstract

PURPOSE:To keep catalytic activity over a long period of time by reducing the wt. of a ruthenium catalyst and increasing the specific surface area thereof by preparing a carbon dioxide reducing catalyst by supporting ruthenium on a heat-resistant fiber. CONSTITUTION:A carbon dioxide reducing catalyst is obtained by supporting a predetermined amount of ruthenium on a heat-resistant fiber sich as an alumina fiber, a silica fiber or an activated carbon fiber. This carbon dioxide reducing catalyst can be reduced in its wt. and extended in its life in order to reduce catalyst replacing frequency, and is effective for the oxygen recovery system in a space vehicle. In an embodiment of the reduction of carbon dioxide, a reactor is filled with a predetermined amount of the ruthenium catalyst 2 wherein ruthenium is supported on the activated carbon fiber and carbon dioxide 4 and hydrogen gas 5 are allowed to flow in a mixer 6 when the layer of the catalyst 2 reaches predetermined temp. by a temp. controller 3 and the gaseous mixture is introduced into the reactor 1 to reduce carbon dioxide by the hydrogen gas.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalyst for reducing carbon dioxide gas, and more particularly to a catalyst used in a carbon dioxide reduction reaction in a carbon dioxide reduction oxygen recovery system.

0002

2. Description of the Related Art One aspect of a conventional carbon dioxide reduction method will be explained with reference to FIG. In Figure 1, reactor 1 has a diameter of 3 mm.
, 3 mm long pelleted ruthenium catalyst 2 (support:
Alumina) is filled with a certain amount. The two layers of ruthenium catalyst are heated to about 400° C. by the temperature regulator 3. After the two layers of ruthenium catalyst reach approximately 400°C, carbon dioxide gas 4 and hydrogen gas 5 are flowed into gas mixer 6, and the mixed gas is sent to reactor 1, whereby carbon dioxide gas is reduced by hydrogen gas, and methane gas 7 and water 8 are produced. The amount and volume of the ruthenium catalyst 2 packed into the reactor 1 were 340 g and 340 cm3, respectively.

0003

[Problems to be Solved by the Invention] Conventional carbon dioxide reduction methods have the following drawbacks. (1) Ruthenium used as a carbon dioxide reduction catalyst is heavy because alumina pellets are used as a support. (2) Therefore, it is disadvantageous when launching a carbon dioxide reduction oxygen recovery system for spacecraft using a spacecraft. (3) Since the pellet-shaped catalyst has a small specific surface area, the reaction rate will decrease if a part of it is poisoned.

[0004] In order to solve the above-mentioned problems, the present invention aims to provide a catalyst for reducing carbon dioxide gas, which can be made lighter and have a larger specific surface area, thereby extending its life.

[0005]

[Means for Solving the Problems] The present invention is a catalyst for reducing carbon dioxide gas, which is characterized by having ruthenium supported on heat-resistant fibers.

[0006] Examples of the heat-resistant fibers used in the present invention include alumina fibers, silica fibers, and activated carbon fibers.

[0007]

[Function] When compared with the conventional ruthenium catalyst in which ruthenium metal is impregnated with alumina pellets, the catalyst for carbon dioxide reduction of the present invention has the following characteristics: (1) In order to have the same performance as a catalyst, the catalyst of the present invention has to It only requires about 1/7 of the weight of the catalyst, making it possible to significantly reduce the weight. (2) In the present invention, the specific surface area of the catalyst is much larger,
It is possible to extend the life of the catalyst. (3) As a catalyst for spacecraft, the catalyst of the present invention is extremely advantageous for the reasons shown in items (1) and (2) above.

[0008]

EXAMPLE Hereinafter, the effect of an example of the catalyst of the present invention will be demonstrated according to the flow shown in FIG. 1. In FIG. 1, reactor 1
The operation was carried out in the same manner as in the prior art described above, except that the ruthenium catalyst 2 having activated carbon fiber as a carrier was filled in the ruthenium catalyst.

[0009] The carbon dioxide reduction reaction depends on the gas molar ratio (H2/
By increasing the CO2) to 4.1 or higher, the reaction rate is approximately 10
It was 0%. In this test, the weight of the ruthenium catalyst 2 packed into the reactor 1 was 50 g, and the conventional catalyst (carrier: alumina pellets, catalyst component: ruthenium) had a reaction rate of about 1.
Approximately 350g was required to achieve 00%.

The test conditions for this test are as follows. - Carbon dioxide gas inflow rate...0.35 l/min - Hydrogen gas inflow rate...1.44 l/min - Catalyst packing volume...340cm3 (40φ x 270mm) - Reactor internal pressure...・1kg/cm2 G ・Carbon dioxide reduction rate... Analyze the reactor outlet gas with a gas chromatograph

The catalyst of the present invention used in the above test was produced in the following manner. Activated carbon fibers (wire diameter 1 to 10 μm: commercially available) are heated in a 10% nitric acid solution for 2 to 3 hours, filtered, washed with water, and dried. After dissolving ruthenium in aqua regia, heat and concentrate to make it hydrochloric-acidic, and add warm water to make about 80 ml. Add the dried activated carbon fibers to this solution. Next, formalin (3
After adding about 8 ml of NaOH solution (30w
t%) until the solution becomes slightly alkaline. After that, the activated carbon fibers were taken out from the solution, washed with water, and then
Dry at 50°C. The catalyst produced by the above steps was used as an example catalyst.

0012

[Effect of the invention] When a spacecraft launches a system that recovers oxygen by reducing carbon dioxide generated by human breathing inside a spacecraft, the weight of the carbon dioxide reduction catalyst is reduced and the frequency of catalyst replacement is required. It is essential to extend the life of the catalyst in order to reduce the amount of carbon dioxide, and the catalyst of the present invention has the following effects. (1) The catalyst of the present invention is 1/7 the weight of a conventional product and has catalytic performance comparable to that of a conventional product. (2) The product of the present invention has a larger specific surface of the catalyst than the conventional product,
This makes it possible to extend the life of the catalyst, reducing the frequency of catalyst replacement and reducing the workload of the crew.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a carbon dioxide gas reduction reaction step.

Claims (1)

[Claims] 1. A catalyst for reducing carbon dioxide gas, characterized by comprising ruthenium supported on heat-resistant fibers.