Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Inorganic carbon containing
Reexamination Certificate
2000-10-12
2002-10-15
Bell, Mark L. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Inorganic carbon containing
C502S183000, C502S185000, C252S06251C, C252S062560, C252S062610, C252S062620, C252S062630, C428S402000, C428S407000, C428S690000
Reexamination Certificate
active
06465390
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to porous composite particles and a process for producing the porous composite particles, and more particularly, to porous functional composite particles having not only a high catalytic by incorporating therein a large amount of a functional filling material having various catalytic property, but also a high adsorption ability to malodorous substances and harmful substances by uniformly distributing fine pores having an average pore diameter of especially not more than 5 nm in the surface and inside portions thereof, thereby exhibiting an excellent catalytic activity, and a process for producing such porous functional composite particles.
Hitherto, various studies have been made to solve problems of environmental pollution by chemical substances. In particular, in recent years, dioxins contained in an exhaust gas discharged upon incineration of combustible wastes cause significant social problems.
Also, with the recent tendency toward comfortableness, safety, hygiene and ecology, so-called amenity catalysts for living equipment or household appliances such as deodorization catalysts, water-treatment catalysts and combustion catalysts have been favorably used in ordinary amenity spaces. For this reason, it has been strongly required to provide catalysts for these purposes capable of exhibiting an excellent catalytic activity.
In order to remove malodorous substances or harmful substances in air, there have been used (1) a method of absorbing these substances into acid or alkali solutions; (2) a method of oxidizing these substances by using an oxidizing agent such as potassium permanganate and ozone, or by combusting at a high temperature; (3) a method of absorbing or adsorbing these substances into an adsorbent such as activated carbon and zeolite; or the like.
However, the method (1) cannot exhibit a sufficient removal effect, and rather tends to cause additional problems such as treatment or disposal of the resultant waste liquid containing the harmful substances or the like. In the method (2), the waste gas produced after the oxidation treatment must be post-treated to remove chlorine or ozone contained therein. Further, in the case where the high-temperature combustion is conducted, increased costs are required therefor. In the method (3), the absorbent used therein exhibits only a limited absorption capacity, thereby requiring complicated regeneration or replacement operations.
In order to solve these problems, there have been conventionally proposed various methods for improving the catalytic activity of catalysts used. For example, there are known a method of using a fluidized bed catalyst comprising a porous catalyst carrier having a surface area of 1 to 350 m
2
/g and a pore volume of 0.4 to 3.0 cc/g such as silica, alumina or zirconia, and a catalyst component such as iron, cobalt or nickel which is carried on a pore surface of the carrier in an amount equivalent to one atom layer (Japanese Patent Application Laid-Open (KOKAI) No. 58-109138(1983)); a method of using a carbon monoxide conversion catalyst formed by carrying a catalyst component containing chromium as a main component on porous heat-resistant zeolite (Japanese Patent Application Laid-Open (KOKAI) No. 61-8138(1986)); a method of using a mixture of activated carbon as an absorbent and calcium oxide, iron oxide, manganese oxide, aluminum oxide or the like as a promoter for decomposition of pollutants (Japanese Patent Application Laid-Open (KOKAI) No. 4-110035(1992)); or the like.
Also, there are known spherical composite particles composed of magnetic particles and carbon (Japanese Patent Application Laid-Open (KOKAI) No. 6-231931(1994)).
At present, it has been strongly required to provide catalysts capable of exhibiting an excellent catalytic activity. However, such catalysts fulfilling the above requirements have not been provided yet.
Specifically, in the method described in Japanese Patent Application Laid-Open (KOKAI) No. 58-109138(1983), the catalyst is carried on the pore surface of the carrier only in such a small amount corresponding to five atom layers at most, i.e., the amount of the catalyst itself carried thereon is insufficient, thereby failing to exhibit a sufficient removal effect.
In the method described in Japanese Patent Application Laid-Open (KOKAI) No. 61-8138(1986), the amount of the catalyst carried is also as small as 2 to 20 parts by weight based 100 parts by weight of the carrier, thereby failing to obtain a sufficient removal effect. Further, the porous carrier used therein is in the form of a honeycomb-like or hollow-cylindrical molded product and, therefore, can be used only in limited applications.
In addition, in the method described in Japanese Patent Application Laid-Open (KOKAI) No. 4-110035(1992), since the individual particles cannot exhibit both of adsorption property and catalytic, it is difficult to effectively adsorb and decompose pollutants and harmful substances.
In the method described in Japanese Patent Application Laid-Open (KOKAI) No. 6-231931(1994), the spherical composite particles used therein are so designed as to achieve a dense structure composed of magnetic particles and carbon in order to keep the strength of the composite particles and, therefore, do not have a porous structure having pores therein.
As a result of the present inventors' earnest studies for solving the above problems, it has been found that by polymerizing phenols with aldehydes in an aqueous medium in the presence of a filling material to produce granulated composite particles containing a phenol resin as a binder; subjecting the reaction mixture to solid-liquid separation to separate the obtained granulated composite particles therefrom; and heat-treating the composite particles at a temperature of 400 to 800° C. in an inert atmosphere to carbonize the phenol resin, the obtained porous composite particles have not only a high catalytic (ability as catalyst) but also a high adsorption ability, thereby exhibiting an excellent catalytic activity. The present invention has been attained based on the finding.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide porous composite particles having not only a high catalytic but also a high adsorption property, thereby exhibiting an excellent catalytic activity.
It is another object of the present invention to provide a process for producing porous composite particles having not only a high catalytic but also a high adsorption property.
To accomplish the aims, in a first aspect of the present invention, there are provided porous composite particles comprising 80 to 98% by weight of a filling material and 2 to 20% by weight of carbon, and having an average pore diameter of not more than 5 nm when measured with respect to pores existing in both the surface and inside portions of the particles, an average particle size of 1 to 1,000 &mgr;m and a specific surface area of 45 to 200 m
2
/g.
In a second aspect of the present invention, there is provided a process for producing porous composite particles which comprises the steps of polymerizing phenols with aldehydes in an aqueous medium in the presence of a filling material using a basic catalyst as an initiator to produce granulated composite particles containing a phenol resin as a binder; subjecting the reaction mixture to solid-liquid separation to separate said granulated composite particles therefrom; drying the obtained granulated composite particles to obtain dried composite particles containing a water-soluble phenol resin-forming component in an amount of 0.6 to 5 mg/liter when measured according to the test method for utensils and toys 3,1,5,3 defined in the Japanese Food Sanitation Law; and heat-treating the dried composite particles at a temperature of 400 to 800° C. in an inert atmosphere to carbonize the phenol resin.
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described in detail below.
First, the porous composite particles according to the present invention is described.
T
Hakata Toshiyuki
Okita Tomoko
Bell Mark L.
Hailey Patricia L.
Toda Kogyo Corporation
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