Patent Application
20070297974
A silicon-containing inorganic compound utilized in a method of the present invention is described utilizing industrial waste, such as that from an insulator, optical fiber, silicon dioxide fine powder (white soot) produced by manufacturing of the optical fiber, and tip material (waste silica glass) produced in the pulling process of the optical fiber.
The inorganic compound is crushed into a grain having a diameter of 0.1 μm-0.1 mm to obtain high formation reaction of a solid acid catalyst.
The optical fiber as a raw material is thin and easy to handle such that the optical fiber is cut out to be received into a pressure chamber. The optical fiber is occasionally coated with a protective resin. The protective resin, however, is very thin such that it is not necessary to remove the protective resin from the optical fiber.
When the insulator is used as the raw material and has a high aluminum content, the insulator is utilized for an aluminum-containing inorganic compound besides the silicon-containing inorganic compound. In this case, the insulator is utilized with other silicon-containing inorganic compounds such as the optical fiber, silicon dioxide fine powder, and tip material, which contain low aluminum content. The raw material is adjusted to have a weight ratio of SiO2/Al2O3 of at least 1,000 with reduced weight of silicon and aluminum, respectively.
It is preferable to utilize the insulator of the industrial waste as the aluminum-containing inorganic compound. Coal ash, pulverized clay stone, pulverized china, pulverized porcelain, aluminum dross, and metal aluminum may also utilized for the raw material besides the insulator. These materials are also crushed into a grain having a diameter of 0.1 μ-0.1 mm to obtain high formation reaction of the solid acid catalyst.
It is necessary that the raw material utilized in the method of the present invention has a weight ratio of SiO2/Al2O3 of at least 1,000 in order to achieve fast manufacturing and produce a large size of grain of the solid acid catalyst compared to the conventional method. More preferably, the weight ratio SiO2/Al2O3 is at least 10,000.
A template agent of the raw material is essential to control the shape and size of pores of the solid acid catalyst. A structure of (≡Si—O—), which forms a main structure of the solid acid catalyst, covers the template agent as the shape and size of the template agent are important.
The template agent of the raw material of the present invention utilizes a combination of a quarternary ammonium salt and a compound having the same structure of the quarternary ammonium salt. The possible template agents area compound having a formula of
formula (1), a combination A of a compound having a formula of
formula (2), and a compound having a formula of R8X, a combination B of a compound having a formula of R9NHR10 and a compound having a formula of R11X, and a combination C of a compound having a formula of NH2R12 and a compound having a formula of R13X, where R1-R13 are alkyl groups and X is a halogen atom or OH.
Preferably, the combination of the quarternary ammonium salt and the compound having the same structure of the quarternary ammonium salt has a tetrahedron structure to avoid damage to the main structure of (≡Si—O—) of the solid acid catalyst. When the combination A is utilized for the template agent, R5-R8 have preferably the same alkyl group. The carbon number thereof is preferably 2-5 to enhance catalytic function of the solid acid catalyst.
When the combination B is utilized for the template agent, R9-R11 have preferably the same alkyl group. The carbon number thereof is preferably 2-5. A compounding ratio of the compound of formula (2) to the compound of R8X is preferably 1:2 or near that ratio. When the combination C is utilized for the template agent, R12 and R13 have preferably the same alkyl group. The carbon number thereof is preferably 2-5. A compounding ratio of the compound of NH2R12 to the compound of R13X is preferably 1:3 or near that ratio.
Any one of the above templates (one combination) can be utilized or a combination containing at least two of the template agents can also be utilized. The weight ratio of the template agent is adjusted to 0.1-0.5 with respect to the weight of silicon in the raw material. When the weight ratio is less than 0.1, the reaction rate decreases and results in low productivity. When the weight ratio is more than 0.5, a reaction among the organic compounds, or side reaction, occurs and decreases the effect of the template agent or prevents the reaction of the solid acid catalyst. Preferably, the weight ratio of the template agent is 0.15-0.45.
The method of manufacturing the solid acid catalyst of the present invention includes blending of a compound having a formula of R14COR15, where R14 and R15 are alkyl group, or ketone. In one embodiment, R14 and R15 can be the same and have a carbon number of 2-10. One example of a suitable ketone is diethyl ketone. The raw material contains the ketone with a weight ratio of 0.01-5 with respect to the weight of silicon content. When the weight ratio of the ketone to the silicon content is less than 0.01, the reaction rate decreases and results in low productivity. When the weight ratio is more than 5, a reaction between the organic compounds, or side reaction, occurs and wastes the raw material or prevents the reaction of the solid acid catalyst.
The method of the present invention also includes blending water with the raw material. The water is present in a weight ratio of 2-50 with respect to the weight 1 of the silicon content in the raw material. When the weight ratio is less than 2, it becomes hard to turn the intermediate substance into a slurry and assist the reaction. When the ratio is more than 50, the concentration of the slurry becomes too low resulting in low reaction rate.
The raw material also contains sodium hydroxide. The sodium hydroxide extracts the silicon component from the silicon-containing inorganic compound of the raw material to form the main structure of (≡Si—O—). The sodium hydroxide is contained with a weight ratio of 0.01-1 with respect to the weight 1 of the silicon content in the raw material. When the ratio is less than 0.01, the reaction rate decreases and is not practical. When the ratio is more than 1, the desired product is not attained resulting in low productivity. Preferably, the ratio is 0.02-0.5.
The sodium chloride is present in a weight ratio of 0.005-2 with respect to the weight 1 of the silicon content in the raw material. When the ratio is less than 0.005, the reaction rate decreases and is not practical. When the ratio is more than 2, the desired product is not attained resulting in low productivity. Preferably, the ratio is 0.05-0.5.
The raw material is placed in a closed chamber (reaction chamber) and subjected to a heat treatment (a first heat treatment) for forming the main structure of (≡Si—O—) in the solid acid catalyst. A temperature of the first heat treatment is preferably 100-250° C. When the temperature is lower than 100° C., a period of time of the heat treatment becomes longer and not practical. When the temperature is higher than 250° C., manufacturing costs become high. Preferably, the temperature of the heat treatment is 140-180° C.
The reaction time is preliminarily determined. For example, at 140° C., the reaction time is usually 10-20 hours. The reaction time generally becomes longer and shorter as the temperature of the heat treatment becomes lower and higher, respectively.
After the first heat treatment, usually after cooling, the intermediate substance is removed from the reaction chamber, and water and alcohol are added to the intermediate substance for washing the intermediate substance. Then, the intermediate substance is dried and is subjected to a second heat treatment in an atmosphere containing oxygen.
The second heat treatment removes the template agent from the main body structure containing mainly the structure of (≡Si—O—) formed at the first heat treatment. The template agent is oxidized with oxygen in the atmosphere, for example oxygen gas in air, and removed with oxidization. The second heat treatment is carried out at a temperature of at least 500° C., though the main structure of (≡Si—O—) has heat resistance. The solid acid catalyst is manufactured through the oxidation process.
A fine powder of silicon dioxide (white soot) produced during manufacturing of an optical fiber is utilized as a raw material and has a weight ratio SiO2/Al2O3of 10,000. Tetra-propylammonium bromide is utilized for a template agent.
7 kg of the silicon dioxide powder, 3 kg of tetra-propylammonium bromide, 0.5 kg of sodium hydroxide, and 89.4 kg of water are dissolved together to form an alkaline solution. The alkaline solution is charged into a pressure (reaction) chamber and kept at a temperature of 110° C. for 80 hours (a first heat treatment). The internal pressure of the chamber is 0.04 Mpa higher than atmosphere.
After the first heat treatment, the alkaline solution is filtered and dried to obtain an intermediate substance. The template agent is still present inside the intermediate substance.
The intermediate substance is then heat treated at a temperature of 550° C. for 10 minutes in air (a second heat treatment) and 4.9 kg of a solid acid catalyst is obtained. A diameter of the grains measured is 1-3.5 μm with a mean diameter of 1.74 μm.
The solid acid catalyst is analyzed with X-ray diffraction analysis.
Comparing
The first heat treatment used in Example 1 is changed from 110° C. for 80 hours, to 150° C. for 8 hours. The internal pressure of the chamber is 0.37 MPa higher than atmosphere. 5.2 kg of the solid acid catalyst is obtained. A diameter of the grains measured is 4.5-11.0 μm with a mean diameter of 6.64 μm. The X-ray spectra confirm that the solid acid catalyst is a zeolite of ZSM-5 type.
The first heat treatment used in Example 1 is changed from 110° C. for 80 hours, to 180° C. for 1 hour. The internal pressure of the chamber is 0.90 MPa higher than atmosphere. 6.45 kg of the solid acid catalyst is obtained. A diameter of the grains measured is 7.5-12.0 μm with a mean diameter of 9.95 μm. The X-ray spectra confirm that the solid acid catalyst is a zeolite of ZSM-5 type.
From the above Examples, as the temperature of the first heat treatment increases in a range of 110-180° C., the reaction time decreases and the diameter of the grains of the solid acid catalyst becomes larger and a yield of the solid acid catalyst increases.
According to the method of the present invention, the industrial waste such as from the manufacture of insulators, optical fiber, fine powder of silicon dioxide (white soot) produced at the manufacturing of the optical fiber, and tip material (silica glass) produced at the pulling process of the optical fiber can be utilized as the raw material for manufacturing the solid acid catalyst with good productivity and low cost. The solid acid catalyst has large diameter grains and provides a high-performance catalyst. The solid acid catalyst of the present invention can be applied to not only the field of decomposition of NOx but also other fields requiring low price of solid acid catalyst.
