JPS6260471B2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Industrial Application Field The present invention relates to energy utilization technology, and more specifically, hydrogen, which is a high-energy, clean fuel, is produced from an aqueous solution of ethyl alcohol using light energy. The present invention relates to a method for manufacturing.

(b) Conventional technology Since the opening of oil shocks in 1971, the development of energy alternatives to petroleum has been progressing, with emphasis on the production of alcohol through fermentation of biomass and the production of hydrogen, a clean, high-energy fuel. For example, in Brazil, the potato variety majiyoka is cultivated and fermented to produce alcohol, and gasohol, which is a mixture of gasoline and alcohol, has already been put to practical use to run cars. However, when producing alcohol by fermenting biomass, distillation must be performed because pure alcohol cannot be obtained, and distillation requires a large amount of energy.
On the other hand, since the only combustion product of hydrogen is water, it does not pollute the air like fossil fuels and is as clean as electricity. Also, hydrogen is 200~
It can be used at any temperature from as low as 300°C to as high as 2000°C, and is also used as a raw material for ammonia synthesis and as fuel for fuel cells and rockets. Recently, research has been progressing on direct steel manufacturing using hydrogen as a reducing agent, hydrogen automobiles, and heat pumps using hydrogen storage alloys. Therefore, if hydrogen could be easily generated from an aqueous alcohol solution, there would be no need for distillation, and high-energy, non-polluting hydrogen could be directly obtained as a fuel. Recently, it was discovered that hydrogen is generated when semiconductor powder is dispersed in an aqueous alcohol solution and irradiated with light, and research on this catalyst is currently underway. However, in previous research, in order to generate hydrogen, it was necessary to support titanium dioxide with expensive noble metals such as platinum or palladium, or to use catalysts such as silicon whose surface was modified with platinum or polypyrrole. (For example, T.Sakata, T.Kawai, Chem.
Phys. Letters. 80 , 341 (1981), Y. Taniguchi, H.
Yoneyama, H. Tamura, Chemistry Letters,
1983 , 269). In addition, media using cadmium sulfide were highly toxic and caused deterioration such as photolysis, making them useless (for example, T.
Sakata, Energy and Resources, 4320 (1983)). Furthermore, when titanium dioxide is used, its large bandgap causes a reaction to occur only when light has short wavelengths, and it is said that energy use efficiency is poor when using light with a lot of long wavelengths and low energy, such as sunlight. There were flaws.

(c) Purpose of the invention In view of the above points, the present invention is free from toxicity concerns.
The purpose of this method is to stably and economically generate hydrogen from an aqueous solution of ethyl alcohol even when using low-energy light such as sunlight.

(d) Structure of the Invention In order to achieve the above object, the present inventors conducted intensive research and found that titanium dioxide powder and silicon powder were mixed, dispersed in an aqueous solution of ethyl alcohol, and irradiated with light. It was discovered that hydrogen is generated when Commercially available reagents for titanium dioxide and silicon used in the present invention may be used as they are, but performance is better if they are partially reduced by heating in a vacuum or in a hydrogen stream. Further, titanium dioxide having a rutile structure is more preferable than anatase structure. Titanium dioxide and silicon powders can be added separately to an aqueous solution of ethyl alcohol, but performance is better if they are thoroughly rubbed together in a mortar to make them stick together before adding. In addition, silicon can be partially coated on the surface of titanium dioxide powder by chemical vapor deposition, physical vapor deposition, sputtering, etc., or vice versa.
The surface of silicon powder may be partially coated with titanium dioxide. The smaller the particle size of the powder, the better for better dispersion in the solution and for easier reaction with light and solution. The container for carrying out this reaction may be made of any material, such as glass, quartz, or plastic, as long as it does not react with ethyl alcohol or water and is transparent and allows light to pass through. The powders of titanium dioxide and silicon may be stirred with a stirring bar or stirrer, dispersed in a solution, and then irradiated with light, or they may be spread on the bottom of a container and irradiated with light from below. Alternatively, it may be applied by brushing onto the inside of the light-irradiated surface of the container. The weight ratio of titanium dioxide and silicon used in the present invention is preferably 0.1 to 10. Further, examples of the light source used in the present invention include a mercury lamp, a xenon lamp, a halogen lamp, an incandescent lamp, the sun, etc. Even sunlight, which has a large amount of long wavelength light and low energy, can sufficiently generate hydrogen. When irradiating with light, it is preferable to aerate the solution with nitrogen or an inert gas to remove dissolved air. The solution used in the present invention is an aqueous solution containing ethyl alcohol, as long as it contains ethyl alcohol and water, and may be a fermentation liquid before squeezing out the alcohol.
Ethyl alcohol or water alone produces almost no hydrogen even when exposed to low-energy light such as sunlight. In conventional methods, hydrogen was obtained as a mixture with methane, carbon dioxide, and carbon monoxide, but the method according to the present invention has the advantage of obtaining highly pure hydrogen. Note that formic acid is produced in the solution.

(e) Examples of the invention Hereinafter, typical examples of the present invention will be shown.

Example 1 200 ml of ethyl alcohol and 200 ml of water were placed in a 400 ml quartz container and sufficiently aerated with argon gas. After mixing titanium dioxide (rutile) powder and p-type silicon powder and reducing them by heating in a vacuum, 1 g
was added to the quartz container. And while stirring
Light with an intensity of approximately 1 mW/cm ² from a 100 W high-pressure mercury lamp was irradiated, and the gas generated was analyzed using a gas chromatograph. As a result, 4μ per hour
Generation of mol of hydrogen was observed.

Example 2 50 ml of ethyl alcohol and 50 ml of water were placed in a 100 ml Pyrex flask and thoroughly aerated with nitrogen gas. After reducing titanium dioxide (rutile) powder by heating it in a vacuum, put 0.5g into a mortar,
0.05g of p-type silicon powder and 0.05g of n-type silicon powder
g was added, ground well, mixed, and added to the flask. Then, while stirring, light of about 0.1 mW/cm ² from a 100 W high-pressure mercury lamp was irradiated, and the generated gas was analyzed using a gas chromatograph. As a result, it was observed that 5 μmol of hydrogen was generated per hour.

Example 3 After reducing titanium dioxide (rutile) powder by heating in a vacuum, 0.2 g was placed in a mortar, 0.4 g of silicon powder was added, ground well, mixed, and placed in a flask in the same manner as in Example 2. In addition, light was irradiated. As a result, generation of 4 μmol of hydrogen per hour was observed.

Example 4 After reducing titanium dioxide (rutile) by heating the powder in a vacuum, put 0.3 g in a mortar, add 0.3 g of silicon powder, grind well, mix, and place in a flask in the same manner as in Example 2. In addition, light was irradiated. As a result, generation of 7 μmol of hydrogen per hour was observed. The purity of the generated hydrogen was over 95%, the rate of generation did not change even after more than 200 hours had passed after the start of light irradiation, and no deterioration of the catalyst was observed. In addition, formation of formic acid was observed on the solution side.

Comparative Example 1 After heating titanium dioxide (rutile) powder in a vacuum to reduce it, 0.6 g was placed in a mortar and ground well, and then irradiated with light in the same manner as in Examples 1 and 2. However, no hydrogen generation was observed.

Comparative Example 2 After 0.6 g of silicon powder was placed in a mortar and ground well, light irradiation was performed in the same manner as in Examples 1 and 2, and almost no hydrogen generation was observed.

(f) Effects of the Invention As explained above, the present invention makes it possible to easily produce hydrogen, which is a clean, high-energy fuel, by dispersing titanium dioxide and silicon powder in an aqueous solution of ethyl alcohol and irradiating it with light. It is made available to you. The method of the present invention is economical because it does not use expensive precious metals, the titanium dioxide and silicon used in the present invention are non-toxic and safe, and hydrogen is obtained with high purity and can pass through Pyrex glass. Since hydrogen can be generated even with low-energy light, it has great economic effects in terms of effective use of solar energy.

Claims (1)

[Claims] 1. A hydrogen production method characterized by mixing titanium dioxide powder and silicon powder, dispersing the mixture in an aqueous solution containing ethyl alcohol, and irradiating the mixture with light.