JPH05146671A - Photofixation method of carbon dioxide - Google Patents

Abstract

PURPOSE:To fixate carbon dioxide photochemically by a method wherein the light transmitting porous inorg. powder having an oxide semiconductor supported on a light transmitting porous base material is brought into contact with the composite photocatalytic material thermally fused to a light transmitting fluororesin, carbon dioxide and water and at the same time is irradiated with light. CONSTITUTION:The light transmitting porous inorg. powder 1 having an oxide semiconductor (e.g. TiO2) supported on a light transmitting porous base material (e.g. porous quartz glass) is brought into contact with the composite photocatalytic material thermally fused to a light transmitting fluororesin 2, carbon dioxide and water and at the same time is irradiated with light. As a result, an oxygen containing hydrocarbon compound is formed to fixate carbon dioxide photochemically. Also, since the light transmitting fluororesin is used, there is little decaying of the irradiated ultraviolet light. Moreover, the particle size of a catalyst is not subjected to changes during reaction and thus the photofixation reaction can be repeated with a satisfactory repeatability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for photochemically fixing carbon dioxide (CO ₂ ) using a composite material of an oxide semiconductor photocatalyst.

[0002]

_2. Description of the Related Art Conventionally, an immobilization method has been known in which CO ₂ is converted into methanol using titanium oxide (TiO ₂ ) powder.

[0003]

In the conventional method, TiO _{2 is used.}
This is an immobilization method in which CO ₂ gas is brought into contact with an aqueous solution in which the powder is dispersed, and at the same time, ultraviolet light is radiated to mainly convert it into methanol.

However, the conventional method has the following drawbacks. (1) Since powdered titanium oxide is used as the photocatalyst, much time is required for recovery and regeneration of the catalyst after the reaction. (2) In order to vigorously stir the catalyst dispersion solution during the reaction,
The catalyst particle size becomes finer.

[0005]

The present invention provides a photocatalyst composite material in which a light-transmitting porous inorganic powder having an oxide semiconductor supported on a light-transmitting porous base material is heat-welded to a light-transmitting fluorine resin. A method for photo-immobilizing carbon dioxide, which comprises producing an oxygen-containing hydrocarbon compound by bringing carbon dioxide and water into contact with each other and irradiating light at the same time.

That is, the present invention uses a photocatalyst composite material in which a light-transmitting porous inorganic powder is heat-welded to a light-transmitting fluororesin to suppress a change in catalyst particle size due to stirring during the reaction, Further, since the photocatalyst after the reaction can be rapidly recovered and regenerated, it is a method that makes it possible to repeat the carbon dioxide immobilization reaction with high accuracy.

The light-transmitting porous inorganic powder used in the present invention transmits ultraviolet rays to visible rays,
Moreover, those having pores of several Å to several tens of Å are used, and a specific example thereof is porous quartz glass. Also,
As the oxide semiconductor, an oxide semiconductor having physical properties suitable for CO ₂ light fixation is used, and its specific example is TiO 2.
₂ , WO ₃ , ZnO and the like. Further, as the transparent fluororesin, perfluoroethylene propylene resin (FEP), perfluoroacoxy resin (PFA),
Ethylene-tetrafluoroethylene resin (ETEE) or the like is used. As the type of light, light that can photoexcite the photocatalyst to be used is used. For example, when the photocatalyst is TiO ₂ , ultraviolet light is used.

[0008]

In order to eliminate the drawbacks of the reaction form in which the conventional photocatalyst powder is dispersed, the present invention uses the powder as a surface of a light-transmitting fluorine resin while maintaining the function of the porous photocatalyst having light-transmitting property. Since the photocatalyst composite material that has been heat-welded to is used, the utilization rate of ultraviolet light to be irradiated and the catalytic activity are almost the same as before, and at the same time, the change of the catalyst particle size is suppressed,
Moreover, since the catalyst is simply placed in the solution and is not dispersed, the filtration process of the photocatalyst after the reaction can be omitted.

[0009]

EXAMPLE The photocatalytic composite material used in the present invention was manufactured by the following method. Hydroxyl groups on the surface of the porous quartz glass substrate are reacted with titanium tetrachloride, which is a reaction gas, by a chemical vapor deposition (CVD) method to form a thin film containing titanium. afterwards,
A titanium dioxide thin film type catalyst was obtained through hydrolysis and calcination. This catalyst was further crushed to obtain an average particle size of 10
10 μm of porous photocatalyst powder was heated to 350 to 400 ° C. and heated to a temperature 50 to 100 ° C. lower than the melting point.
Fluorine resin film of 0 μm (FEP film, PFA
After spraying on both sides of the film, ETEE film,
It is compressed with a roll and heat-sealed to form a photocatalyst composite material.
₂ Adapted to photo-immobilization reaction.

The structure of this photocatalytic composite material is shown in FIG.
In FIG. 1, 1 is a TiO ₂ -supporting quartz glass powder, and 2 is a fluororesin.

FIG. 2 shows the configuration of the experimental apparatus. 1 is CO ₂
A supply nozzle, 2 is a reactor (diameter: 95 mm, height:
175 mm) and 3 is a reaction solution (pure water). 4 is a photocatalyst composite material created, 5 is a quartz jacket, 6
Is a 100 W high-pressure mercury lamp, and the reaction system was irradiated with ultraviolet rays. 7 is an outlet for excess CO ₂ (containing a product), and 8 is a magnetic stirrer for stirring the solution.

The experiment was conducted by using the photocatalyst composite material in which the prepared TiO ₂ thin film type catalyst was coated on a light-transmitting fluororesin at room temperature and atmospheric pressure by the following method. (1) The photocatalyst composite material is set in the reactor 2 as shown in FIG. 2, and 300 ml of pure water is injected. (2) Nitrogen gas is bubbled through the nozzle 1 while stirring with a stirrer 8 to discharge dissolved oxygen. (3) The bubbling gas is changed from N ₂ to CO ₂ and introduced at a rate of 100 ml / min. (4) The high pressure mercury lamp 6 is caused to emit light, and the reaction vessel is irradiated with ultraviolet light to carry out a CO ₂ photo-fixation reaction. (5) The products of the reaction were identified and quantified by analyzing the gas released from the outlets of the reaction solutions 3 and 7 during and after the reaction.

The production amount and the immobilization rate of the oxygen-containing hydrocarbon compound obtained in this experiment were almost the same as those in the case where the TiO ₂ thin film type photocatalyst powder was used.

[0014]

【The invention's effect】

(1) Since a fluororesin having light transmittance is used,
There is almost no attenuation of the ultraviolet light applied. (2) It is possible to repeat the photoimmobilization reaction with good reproducibility without changing the catalyst particle size during the reaction. (3) Since the composite material is highly flexible and strong in impact force, it can be applied to the cylindrical reactor as used in this example.

[Brief description of drawings]

FIG. 1 is a sectional view of a photocatalytic composite material used in the present invention.

FIG. 2 is an explanatory diagram of a CO ₂ light immobilization device according to an embodiment of the present invention.

Claims (1)

[Claims] 1. A photocatalyst composite material obtained by heat-welding a light-transmitting porous inorganic powder in which an oxide semiconductor is supported on a light-transmitting porous base material to a light-transmitting fluorine resin, and contacting carbon dioxide and water. A method for photo-immobilizing carbon dioxide, which comprises irradiating light at the same time to generate an oxygen-containing hydrocarbon compound.