JPH05184912A - Carbonaceous resource circulating device - Google Patents

Abstract

PURPOSE:To regenerate carbonaceous resources by applying decomposition treatment to carbon dioxide. CONSTITUTION:Iron oxide is used as a catalyst raw material and the activation treatment of iron oxide, the decomposition treatment of carbon dioxide and the generation treatment of carbonaceous resource gas are performed. Iron oxide whose activity is lost by the decomposition treatment of carbon dioxide generating carbonaceous resource gas such as methane or methanol useful as resource energy gas is returned to the original iron oxide by the generation treatment of carbonaceous resource gas and this iron oxide is again subjected to activation treatment to be used in the decomposition treatment of carbon dioxide. As the heat required in the reaction, the waste heat of exhaust gas can be reutilized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbonaceous resource circulation system for decomposing carbon dioxide to regenerate it into carbonaceous resources such as methane and methanol useful as resource energy gas.

[0002]

2. Description of the Related Art Global warming countermeasures using CO ₂ will be promoted for the time being, centering on energy conservation, but when the fossil fuel consumption increases significantly due to industrialization in developing countries and rapid economic growth in Eastern European countries. Has the problem of not being able to deal with it. There are problems in the use of nuclear energy in terms of safety and location conditions, and there is no other alternative energy that can be used immediately as a primary energy source. For the next several decades, it will be effective in addition to using fossil fuels. There seems to be no countermeasure. In order to continue to use fossil fuels without causing global warming, it is essential to develop CO ₂ fixation and removal technology.

As a technique for separating and recovering CO ₂ , conventionally,
Chemical absorption method, physical absorption method, membrane separation method, etc. have been studied, and as decomposition and removal technology, semiconductor photocatalyst method, metal colloid catalyst, metal complex, photochemical reduction method using oxygen, etc., electrochemical reduction method, chemical Methods using fixed conversion reactions (reactions with bases, rearrangement reactions, dehydration reactions, addition reactions), methods using biotechnology, etc. are being studied. However, all of them have problems in practical use, such as reaction efficiency, cost, energy, and incidence of secondary pollution.

[0004]

SUMMARY OF THE INVENTION An object of the inventors have recently the CO ₂ just oxygen defects magnetite using the catalyst 250
We have found a completely new reaction that decomposes to carbon at ~ 350 ° C with an efficiency close to 100%, and we have proceeded with research on this reaction. Prospect of practical use of decomposition and removal of CO ₂ in the exhaust gas utilizing this reaction has been standing.

An object of the present invention is to further develop the decomposition treatment of CO ₂ using oxygen-deficient magnetite and to provide a carbonaceous resource circulation system including reuse of a catalyst.

[0006]

To achieve the above object, in the carbonaceous resource circulation system according to the present invention,
A carbonaceous resource circulation system including iron oxide as a catalyst raw material, activation treatment of iron oxide, decomposition treatment of carbon dioxide gas, and generation treatment of carbonaceous resource gas. Is a process in which hydrogen is reacted with iron oxide to produce oxygen-deficient iron oxide, and water is produced as a reaction product. Carbon dioxide is decomposed by using activated iron oxide as a catalyst to convert carbon dioxide into carbon. The carbon produced by the decomposition is deposited on the surface of the iron oxide, and the oxygen is taken into the oxygen-deficient iron oxide. It is a process to generate carbonaceous resource gas by reacting carbon deposited on the surface of the substance with other components, and is a process for removing the deposited carbon on the surface of iron oxide to regenerate it into an iron oxide that can be activated. ..

Further, the method further comprises a step of reacting carbon-attached iron oxide with water to generate hydrogen as a reaction product prior to the carbonaceous resource gas generation treatment.

Further, the other component used for the generation treatment of the carbonaceous resource gas utilizes hydrogen or water generated as a reaction product in another treatment step and produces ethylene or ethanol.

Further, the carbon dioxide decomposition treatment includes a reaction of forming carbon monoxide by combining carbon generated by the reduction of carbon dioxide with oxygen as a reaction product.

[0010]

[Function] By passing hydrogen gas through magnetite at 290 ° C., oxygen-deficient activated magnetite (oxygen-defective magnetite) is synthesized and reacted with CO ₂ to give 290
Decomposes completely (100%) in 4 hours at ℃. Oxygen of CO ₂ becomes O ^2- and is taken into oxygen defects, and C becomes carbon and deposits on the surface of magnetite. Also 350 ° C
Then, the CO ₂ decomposition reaction was completed in about 4 minutes. When magnetite with carbon deposited on the surface is reacted with water at 400 ° C. and then with hydrogen at 650 ° C., H ₂ gas is selectively generated. The amount of hydrogen generated is about four times the amount required to form oxygen-deficient magnetite. Waste heat of exhaust gas (40
(0 ° C.) makes it possible to effectively extract hydrogen energy or hydrogen resources from waste heat using this hydrogen generation reaction. Moreover, when hydrogen is generated by reacting with water and then further reacting with water under certain conditions, CH ₃ O
H is selectively generated. Therefore, by combining the above reactions, it became possible to construct a carbon resource circulation system of CO ₂ —CH ₄ or CO ₂ —CH ₃ OH. Moreover, all the reaction products can be reused in the system, and the magnetite, which is the catalyst raw material, returns to magnetite after activation, reaction, and carbon deposition, so that a completely closed system can be realized. Is.

FIG. 1 (a) shows a flow chart of the CO ₂ --CH ₄ carbon resource recycling system. This system
It consists of first to fourth steps.

The first step is a magnetite activation treatment. The activation treatment is a deoxidation treatment of magnetite. By this treatment, magnetite becomes oxygen-defective magnetite (activated magnetite), and when hydrogen is used for activation, H ₂ O is produced as a by-product.

Magnetite crystallographically has a spinel type structure and is cubically closest packed with oxygen, and +2 valent Fe and +3 valent Fe are 1: in the gap (Asite, Bsite). It is blocked at a ratio of 2. It is represented stoichiometrically as Fe ₃ O ₄ . Cation-rich magnetite with the same spinel structure (oxygen-deficient magnetite Fe ₃ O (
_It was unclear whether such a substance was present) because it has never been synthesized. Assuming that there is a reaction of Fe ₃ O ₄ + δH ₂ = Fe ₃ O _4-δ + δH ₂ O, Fe ₃ O ₄ and H ₂ were reacted at various temperatures. In the conventional phase equilibrium diagram, F at 400 ° C or lower
There is no width on the Fe ₃ O ₄ side between e ₃ O ₄ and αFe). After all, among Fe ₃ O ₄ and alpha iron, and the whether the width of the solid solution is present when the O ^2- ions are withdrawn from the Fe ₃ O _4, or Fe ₃ O _4-δ can form How is it?

The relationship between the weight change and the X-ray diffraction data was carefully examined between 260 and 350 ° C. 280 ° C
Then, after 1, 2 and 4 hours, 0.16, 0.43 respectively
The weight decreased to 0.84%, and it was found from the result of X-ray diffraction measurement that the spinel structure was retained. Table 1 shows the chemical composition of magnetite having a spinel structure estimated from these weight changes, assuming that the spinel structure is retained. Both compositions are represented as oxygen-deficient magnetite. When the X-ray diffraction precision measurement was performed on the sample after 4 hours, the lattice constant was 0.8418 nm (FIG. 2). This value is the value of stoichiometric magnetite (0.
83967 nm), indicating that the crystals are slightly wider than the stoichiometric one. It is considered that this is because, due to the partial defect of oxygen, a large amount of cations were confined in the crystal and the lattice spacing was widened. While ventilating H ₂ gas,
By confirming H ₂ O by gas chromatography on the outlet side, oxygen in the lattice reacts with hydrogen gas and H ₂ O
It is presumed to be removed as ₂ O.

[0015]

[Table 1] Chemical composition of oxygen deficient magnetite obtained by passing H ₂ at 290 ° C. ─────────────────── Time for passing H ₂ Fe ₃ O _4-x ─────────────────── 1 0.0307 2 0.0816 3 0.1563 ───────────────────

After the magnetite was sufficiently dried at 200 ° C. for 2 days, its weight change was measured by a thermobalance. Two
The composition of magnetite after drying at 00 ° C. is Fe ₃ O ₄ . ₅₁₇
Met. Oxygen is in excess compared to stoichiometric composition. This is because the surface of magnetite particles having a particle size of 1 μm or less is oxidized. The temperature was raised to 290 ° C at about 8.3 ° C / min while passing hydrogen, and 290 ±
It was kept at 0.5 ° C (PI suppression). Fe after about 40 minutes
₃ O ₄ . _The weight was reduced to the composition of ₀₀ (stoichiometric composition), but further weight reduction was observed after that, and Fe was 100 minutes later.
₃ O ₃ . The composition changed to ₈₃₈ . This sample is rapidly cooled and X
Figure 2 shows the lattice constant measured by line diffraction analysis.
Is. The chemical analysis value is Fe ₃ O ₃ . _{It was 84} , which was in agreement with the result of the thermobalance. As described above, it was confirmed that oxygen ions in the spinel structure escaped by passing hydrogen gas at 300 ° C., and oxygen-deficient magnetite represented by Fe ₃ O ₄ −δ exists. From this experimental result, it was revealed that the previously assumed reaction of Fe ₃ O ₄ + δH ₂ = Fe ₃ O ₄ −δ + δH ₂ O is actually occurring.

The existence of such oxygen-deficient magnetite has not been reported until now, but this time the reaction of forcibly removing oxygen by reaction with hydrogen was carried out at a relatively low temperature as a solid chemical reaction of 290 ° C. Therefore, it is considered that stable acquisition was possible for the first time.

The second step is a CO ₂ decomposition process. When the activated magnetite was exposed to CO ₂ at a temperature of 280 ° C. to 350 ° C., the CO ₂ was completely decomposed (˜100%) after 2 hours as shown by the curve A in FIG.
Further, as shown by the curve B, the pressure in the reaction system decreased almost in agreement with the decomposition of CO ₂ . This indicates that the decomposition of CO ₂ is not accompanied by the generation of any gas as a reaction product. In fact, by gas chromatography, CO ₂
It was confirmed that no other gas was generated. Also,
Table 2 shows the analysis results of carbon by the elemental analyzer. It was deposited on carbon or magnetite in an amount about twice the amount of CO _{2 in the} reaction cell. The large reaction amount is due to the H in the cell at the start of the reaction.
₂ gas when substituted with CO ₂ gas, CO ₂ gas is reacted precipitated conceivable carbon because magnetite hydrochloric acid solution (1: 1) is treated, dissolved magnetite part, become carbon content and soot It was observed that a black turbidity remained. The carbon content was collected by filtration with a glass filter (1 μ) and weighed by a gravimetric method. This result is almost in agreement with the elemental analysis, and it was confirmed that carbon was certainly deposited on the magnetite surface by the reaction.

[0019]

[Table 2] Carbon content in magnetite after the decomposition reaction of CO ₂ ───────────────────────── mmol ─────── ─────────────────── CO ₂ Initial total amount 1.28 Carbon in magnetite after reaction 2.51 Carbon in magnetite before reaction 0.15> ── ───────────────────────

Since generation of gases such as CO and O ₂ was not confirmed, it is considered that oxygen in CO ₂ was taken into oxygen-defective magnetite. This can be expressed by the formula: CO ₂ → C + 2 (O ²⁻ ), where (O ²⁻ ) means that oxygen ions are incorporated into oxygen defect sites in the oxygen defect magnetite. From the result of X-ray diffraction measurement, it was confirmed that no carbide was formed after the reaction, and it is presumed that C in the formula exists as carbon powder on the magnetite surface. Also X
The lattice constant by line diffraction measurement and the composition by chemical analysis were in agreement with those of stoichiometric magnetite (Fig. 2). Considering these things, CO due to oxygen-defective magnetite
The decomposition reaction of ₂ can be written as

Fe ₃ O _4-δ + 1 / 2δCO ₂ = Fe ₃ O ₄ + 1 / 2δC [Fe ₃ O ₄ Cτ (τ = 1 / 2δ)] Carbon on the right side is deposited on the surface of the magnetite, Considering this carbon as a component in the product,
_It is expressed as ₃ O ₄ Cτ (τ = 1 / 2δ), and this is referred to as carbon-deposited magnetite.

FIG. 4 shows the results of examining the decomposition reaction of CO ₂ at 350 ° C. The curve in the figure shows the change in internal pressure read by the pressure gauge. After the induction for about 2 minutes, 1 atm of CO ₂ was almost completely decomposed in about 4 minutes to be in a vacuum state. It is noteworthy that the reaction rate is overwhelmingly high, although the temperature is only 50 ° C. higher than the result at 300 ° C. in FIG. This is probably because the mobility of oxygen ions migrating through oxygen deficiency sites changes critically with temperature. The reason why the mobility changes critically with temperature is unknown, but it is interesting as a characteristic property of oxygen-defective magnetite crystals.

The strong reducing power for decomposing CO ₂ into carbon is considered as follows. Oxygen-deficient magnetite has a metastable crystal structure formed in a non-equilibrium state, and is an unstable compound in that sense. At room temperature, it gradually reacts with oxygen and takes on oxygen ions, and changes into more stable spinel structure Fe ₃ O ₄ . The unstable crystal structure of oxygen-defective magnetite is inferred from the broadening of the peak width in the X-ray diffraction pattern. Thus, it has a strained spinel structure as compared to stoichiometric magnetite. It is considered that the strong reducing power for reducing CO ₂ to carbon arises from such an unstable spinel structure trying to change to a more stable spinel structure. When oxygen ions are incorporated into the crystal in an attempt to adopt a stable spinel structure, the crystal tries to emit electrons from the surface as a negative charge in order to maintain electric neutrality. In oxygen-deficient magnetite, +2 valent Fe exists as an atom capable of emitting an electron, but it is considered that an abnormal reduction potential is generated due to the instability of the crystal of oxygen-defective magnetite.

For metallic iron, this time, 300 ° C
It is impossible to decompose CO ₂ in the vicinity and in a highly efficient and fast reaction. This is considered to be largely due to the change in crystal structure of metallic iron when the metal becomes a metal oxide with the decomposition of CO ₂ . There is a considerable difference in reaction efficiency from the state in which oxygen ions permeate while retaining the spinel structure as in this case. As another cause, it is conceivable that metal reacts with the formation of carbide to reduce the reactivity with CO ₂ .

The third step is a hydrogen gas generation process using carbon-deposited magnetite. As described above, when oxygen-deficient magnetite and CO ₂ are reacted, magnetite having carbon deposited on the surface [carbon-deposited magnetite: Fe ₃
O ₄ C τ (τ = 1 / 2δ)] is formed. Here C
The reaction with H ₂ O was investigated on the carbon-deposited magnetite that is the product of the reaction with O ₂ . The results are shown in Table 3. The reaction time was 40 minutes in each case, but at 400 ° C. or higher, the reaction was almost completed in 5 minutes. At 400 ° C., hydrogen was selectively generated, and at 600 ° C., the amount of hydrogen generated was reduced to about half, and CO and CO ₂ were generated at almost the same amount. As described above, it was found that hydrogen gas can be selectively generated from water at 400 ° C. by using the carbon-deposited magnetite.
The generated amount of 49.3 ml / g at 400 ° C. corresponds to almost four times the required amount of forming oxygen deficient magnetite from magnetite as described later. Therefore, if hydrogen gas generated by this reaction is used in the first step, it is possible to regenerate magnetite and repeat the carbon dioxide decomposition process. The remaining excess hydrogen gas after subtracting the amount of hydrogen used for regeneration can be used as hydrogen fuel or a chemical raw material.

[0026]

[Table 3] Products produced by reacting carbon-attached magnetite with water ────────────────────────── Temperature (℃) H ₂ CO CO ₂ (ml / g) ────────────────────────── 400 14.8 0.48 1.02 600 9.0 9.0 11.2 12. 3 ──────────────────────────

Table 4 shows the relationship between the amount of carbon and the amount of hydrogen generated in the carbon-deposited magnetite. Hydrogen is not observed in a simple mixture of ordinary activated carbon and magnetite. In addition, no hydrogen is generated even with magnetite alone before being activated by hydrogen. On the other hand, hydrogen is generated in magnetite activated with hydrogen (oxygen deficient magnetite) and carbon-deposited magnetite. What is interesting is that the amount of carbon in the carbon-deposited magnetite is 0.25.
%, The amount of hydrogen generated does not depend on the amount of carbon, which will be described later. Moreover, whereas in the activated magnetite has been a stoichiometric magnetite after the reaction, the carbon precipitated magnetite was supposed to compositions that are partially oxidized _{(Fe 3 O 4. 12)} . Furthermore, in the carbon-deposited magnetite, there was almost no difference in the amount of carbon before and after the reaction at 200 to 400 ° C.

[0028]

[Table 4] H ₂ generation amount when water is reacted with carbon-deposited magnetite ───────────────────────────── H ₂ generation Amount (ml / g) ──────────────────────────── Magnetite 0 Activated carbon mixed magnetite 0 Carbon precipitated magnetite 0.15wt% 7.33 0.25 wt% 40.2 0.50 wt% 40.6 0.80 wt% 44.7 ─────────────────────────────

The fourth step is a methane generation process using carbon-deposited magnetite. Hydrocarbons are produced by the reaction between carbon-deposited magnetite and hydrogen gas.
At this time, if CO ₂ coexists, the reaction is accelerated. Table 5 shows the relationship between hydrocarbon composition and temperature. The reaction time was 30 minutes, and no change in the composition due to the reaction time was observed. At 300 ° C., no hydrocarbon gas is generated, and the deposited carbon does not react with hydrogen. But 650
At ℃, ethane was slightly generated, but most of the carbon reacted with hydrogen and changed to methane (650 in the table).
The amount of methane generated at ℃ is almost in agreement with the theoretical amount calculated from the amount of carbon in carbon-deposited magnetite). After the reaction, it was found by the X-ray diffraction measurement that all the samples maintained the spinel structure.

[0030]

[Table 5] Hydrocarbon yield when carbon precipitating magnetite is reacted with water ───────────────────────── Temperature CH ₄ C ₂ H ₆ (℃) (ml / g) (ml / g) ───────────────────────── 300 0 0 450 1.19 0 650 3.87 0.011 ─────────────────────────

When the magnetite obtained after generating methane (carbon content is 0.05% or less) is used in the first step, that is, when hydrogen gas is passed at 300 ° C. and CO ₂ is reacted with it, CO ₂ Was completely disassembled. The magnetite recovered after the methane generation reaction is
It was confirmed that it can be reused for the CO ₂ decomposition reaction in the second step. In addition, the sample reacted with hydrogen at 300 ℃,
It was oxygen-deficient magnetite. Like this, 30
By treatment with hydrogen at 0 ° C., it was found that the carbon-deposited magnetite can be regenerated into oxygen-defective magnetite even with carbon deposited.

FIG. 1B is a diagram showing a flow chart of the CO ₂ --CH ₃ OH carbon circulation system. Also in this system, the first to third steps are the same as those of the CO ₂ -C.
H ₄ is the same as the carbon cycle system. In this system,
As a fourth step, H ₂ O is reacted with carbon-deposited magnetite. The reaction temperature is about 400 ° C., and when the water vapor is condensed by cooling, methanol (CH ₃
OH) is produced. In addition, in the third step, when carbon-deposited magnetite is reacted with air at 300 ° C., C
It has been found that O occurs. Methanol can also be synthesized by reacting this CO with the H ₂ gas. Methanol itself is in demand and also occupies an important position as a chemical raw material, and various organic chemicals are manufactured using methanol as a starting material. As described above, the CO ₂ removal and decomposition technology using magnetite of this time can be expected as a technology for recycling carbon dioxide.

The above, in FIG. 1 (a), as will be apparent to the flow chart of system (b), CO ₂ is removed by the system as CH ₄ or CH ₃ OH, caused by combustion of CH ₄ or CH ₃ OH The CO ₂ can be reintroduced into the system and used for the production of CH ₄ or CH ₃ OH. Further, as the resulting H ₂ O byproducts, generation and H _2, CH ₃
A major feature is that the gas generated in the system can be used for the operation of the system or can be used as a resource energy gas by using it for the production of OH and further for the use of H ₂ for the active treatment of magnetite. Moreover, since the magnetite used for the catalyst returns to the original magnetite after being activated and deposited with carbon, no waste is generated.

In the present invention, heat energy is required when methane gas is generated, but other than that, the heat quantity of the exhaust gas can be effectively utilized in all the reactions. CO _{2 in} exhaust gas
Are removed to obtain carbon-deposited magnetite, which is reacted with water to generate hydrogen gas. The hydrogen gas obtained here is supplied to both the reactivation of magnetite and the generation of methane gas, and the methane gas is used as a fuel, and the CO ₂ generated at this time is converted to C by the reactivated magnetite.
Collect as.

[0035]

As described above, according to the system of the present invention, since the waste heat can be used in terms of energy, it is possible to reuse the carbonaceous energy gas generated with considerably high efficiency as a fuel. As a matter of course, since this system does not generate CO ₂ gas, it has an effect of solving the problem of global warming caused by CO ₂ .

[0036]

EXAMPLES Examples of the present invention will be shown below.

Example 1 Step 1: In FIG. 5, magnetite (Fe ₃ O ₄ )
10 g of No. 1 was sandwiched with quartz wool 4 and packed in a quartz column 2, and hydrogen gas (100
0 ml) to obtain oxygen-deficient iron oxide.

Step 2: Next, carbon dioxide was introduced into the column and reacted at 300 ° C. to deposit carbon on the magnetite surface. This iron oxide contained 0.3% carbon. When the hydrogen consumed at this time was calculated from the carbon deposition amount, it was found that it was 112 ml out of the total amount of 1000 ml.

Step 3: A quartz cell is filled with 10 g of the carbon-adhered iron oxide prepared in Step 2 and 400 steam is added.
Contacted at ° C. After reacting for 30 minutes, 450 ml of hydrogen gas was produced in the reaction cell. 0.2 in iron oxide after reaction
It contained 7% carbon. The ratio of divalent iron to total iron was 0.26. It can be seen that this is in an oxidized state compared to the stoichiometric magnetite ratio (0.33). In other words, it is considered that oxygen was taken from water into the magnetite lattice, but the actual amount of hydrogen generated was more than three times higher than this. Although the details of the reaction mechanism are unknown, it is considered that magnetite with carbon deposited catalytically decomposes water into hydrogen and oxygen at present. It is highly possible that the generated oxygen is adsorbed on the magnetite surface.

Further, 10 g of the carbon adhering iron oxide after the reaction prepared in step 2 was filled in a quartz cell, and the inside of the reaction cell was depressurized (5 × 10 ⁻⁴ Torr) with a vacuum pump at 500 ° C. for 2 hours. I left it. The ratio of divalent iron to total iron in magnetite was 0.26, but this operation resulted in 0.33, that is, stoichiometric magnetite. It is also presumed that the oxygen adsorbed on the surface can be removed. The carbon deposited on the magnetite did not change.

Step 4: Hydrogen 2 produced in Step 3
When 25 ml was reacted at 500 ° C., it was confirmed that methane was generated. Carbon in the magnetite after this reaction was 0.011%.

Incidentally, 10 g of magnetite (Fe ₃ O ₄ ) obtained in the step 4 after the methanation reaction was filled in a quartz column, and hydrogen gas (1000 m) was supplied at 300 ° C. for 5 hours.
It was reacted with 1) to obtain oxygen-deficient iron oxide. The hydrogen used was a portion (225 ml) generated in Step 3.

Next, as the treatment of step 2, carbon dioxide was introduced into the column and reacted at 300 ° C. to deposit carbon on the surface of magnetite. 0.3 in this iron oxide
It contained% carbon. By this operation, it was found that magnetite and hydrogen can be repeatedly used for carbon dioxide decomposition reaction. As described above, it is understood that a cycle in which carbon resources are finally converted to methane can be constructed by combining the reactions from step 1 to step 4.

(Example 2) Step 3: 10 g of the carbon-adhered iron oxide prepared in Step 2 of Example 1 was filled in a quartz cell and steam was heated at 400 ° C.
Contacted with. After the reaction for 180 minutes, 290 ml of hydrogen gas was generated in the reaction cell.

Step 4: When cooled to 25 ° C. to condense steam, 0.02 g of methanol was detected in the water tank. The magnetite after the reaction can be reused for carbon dioxide decomposition in the same manner as in Example 1. The procedure is shown below.

Step 1: Carbon-adhered iron oxide 1 after reaction
0 g was filled in a quartz cell, and the pressure in the reaction cell was reduced by a vacuum pump (5 × 10 ⁻⁴ Torr) at 500 ° C. for 2 hours.
Left for hours. Thereafter, the magnetite was activated by reacting with 1000 ml of hydrogen containing hydrogen generated and recovered in Example 3 described later at 300 ° C. for 5 hours.

Step 2: Next, carbon dioxide was introduced into the column and reacted at 300 ° C. to deposit carbon on the surface of the magnetite. This iron oxide contained 0.3% carbon. By this operation, it was found that magnetite and hydrogen can be repeatedly used for carbon dioxide decomposition reaction.

Example 3 A quartz cell was filled with 10 g of the carbon adhering iron oxide after the reaction used in step 2 of Example 1, and the reaction was performed with air gas (100 ml) at 550 ° C. for 2 hours. As a result of gas chromatographic analysis, CO is 15 ml
It turned out that it happened.

[Brief description of drawings]

FIG. 1 is a diagram showing a flow chart of the system of the present invention, in which (a) is a CO ₂ —CH ₄ circulation system, and (b) is a system.
Shows a chart of the CO ₂ -CH ₃ OH.

FIG. 2 is a diagram showing changes in the lattice constant of oxygen-defective magnetite.

FIG. 3 is a diagram showing decomposition characteristics of CO ₂ by oxygen-defective magnetite.

FIG. 4 is a diagram showing changes in internal pressure of a decomposition reaction of CO ₂ by oxygen-defective magnetite at 350 ° C.

FIG. 5 is a diagram showing an experimental device used in an example of the present invention.

[Explanation of symbols]

 1 magnetite 2 quartz column 3 electric furnace

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location C10J 3/72 6958-4H

Claims (4)

[Claims] 1. A carbonaceous resource circulation system comprising iron oxide as a catalyst raw material, which comprises an activation treatment of iron oxide, a decomposition treatment of carbon dioxide gas, and a generation treatment of carbonaceous resource gas. The activation process of a substance is a process of reacting hydrogen with an iron oxide to generate oxygen-deficient iron oxide, which produces water as a reaction product. The decomposition process of carbon dioxide gas is a catalyst of activated iron oxide. As carbon dioxide is reduced to carbon, carbon generated by decomposition is deposited on the surface of iron oxide, and oxygen is taken into oxygen-deficient iron oxide, generating carbonaceous resource gas. The treatment is a treatment in which carbon deposited on the surface of the iron oxide is reacted with other components to generate a carbonaceous resource gas, and the deposited carbon on the iron oxide surface is removed to form an iron oxide that can be activated. Carbon characterized by being regenerated Resource recycling system. 2. The method according to claim 1, further comprising a step of reacting carbon-attached iron oxide with water to generate hydrogen as a reaction product prior to the carbonaceous resource gas generation treatment. Carbon resource recycling system. 3. The other component used for the treatment of carbonaceous resource gas generation utilizes hydrogen or water generated as a reaction product in another treatment step, and produces ethylene or ethanol. Claim 1 or 2 characterized by
The carbonaceous resource recycling system described in. 4. The carbon dioxide decomposing treatment includes a reaction of forming carbon monoxide by combining carbon generated by the reduction of carbon dioxide with oxygen as a reaction product. Carbon resource recycling system.