Patent Application
20120302431
Pursuant to 35 U.S.C. §119 and the Paris Convention Treaty, this application claims the benefit of Chinese Patent Application No. 201110139082.4 filed May 26, 2011, the contents of which are incorporated herein by reference.
1. Field of the Invention
The invention relates to the categories of pollution control technology and environmental catalytic materials, and more particularly to a composite catalyst for oxidation removal of organic pollutants in waste gas and waste fluid as well as a preparation method thereof.
2. Description of the Related Art
Conventional catalysts used for degradation of organic pollutants in waste gas belong to the V2O5/TiO2 system, mainly using vanadium pentoxide as an active ingredient. However, such catalysts have a restricted application because on the one hand the activation temperature of such catalysts is 200-500° C. and the catalysts almost show no activity under low temperature (i.e. within 100° C.), and on the other hand it is extremely difficult to prepare the evenly distributed V2O5 particles. Moreover, V2O5, as an active ingredient, is highly poisonous and harmful to the environment. Furthermore, the V2O5/TiO2 system using vanadium pentoxide as the active ingredient cannot be used for waste fluid treatment. For waste fluid treatment, a system using TiO2 as the active ingredient is generally used to degrade organic pollutants therein. However, the system is complicated in preparation processes and high in production costs. Thus, it is urgent to develop a new type of catalyst with a low activation temperature, simple preparation processes, and high performance-to-price ratio.
In view of the above-described problems, it is one objective of the invention to provide a composite catalyst with a low activation temperature and high performance-to-price ratio. The composite catalyst can be used for oxidation of organic pollutants in waste gas under low temperatures and also has excellent catalytic effects on organic pollutants in waste fluid.
Another objective of the invention is to provide a preparation method for the composite catalyst.
To achieve the above objective, in accordance with one embodiment of the invention, there is provided a composite catalyst for oxidation of organic pollutants in waste gas and waste fluid under low temperatures, the composite catalyst comprising dispersed and cationic surface modifier-modified attapulgite as a catalyst carrier and nano-Au as an active ingredient, wherein the nano-Au accounts for 0.5-1.5 wt. % of the attapulgite, an average diameter of the attapulgite is 18-22 nm, a length of the attapulgite is 100-1000 nm, and a particle diameter of the nano-Au is 1-7 nm.
Attapulgite is a type of clay mineral, with a chemical formula of Mg5Si8O20(OH)2(OH2)4.4H2O, and having an intermediate structure between a chain structure and a layered structure, a rich porous structure, and a large specific surface area. The attapulgite is cheap and has extremely high adsorbability and the nano-Au has high catalytic performance. Therefore, in this invention, the attapulgite and nano-Au are synthesized into a material with extremely high catalytic performance under low temperatures.
Furthermore, an advantage of the invention is that the T50 temperature (T50 refers to a catalytic reaction temperature when the degradation rate of organic pollutants reaches 50%) of the composite catalyst to the organic pollutants in waste gas is 100° C. lower than that of the conventional catalysts. In other words, the composite catalyst provided by the invention still has catalytic activities within 100° C.
The removal rate of organic pollutants in waste gas may reach 99% under room temperature after the composite catalyst is stored under cold temperature for a period of time.
In another aspect, the invention provides a method for preparing a composite catalyst, the method comprising:
In a class of this embodiment, the attapulgite is dispersed in an aqueous solution of sodium hexametaphosphate, sodium pyrophosphate, or sodium dodecyl sulfonate, particularly an aqueous solution of sodium hexametaphosphate.
In a class of this embodiment, the cationic surface modifier is selected from the group consisting of cetyltrimethylammonium bromide (CTAB), octadecyl trimethyl ammonium chloride, and dodecyltrimethylammonium chloride, particularly CTAB.
Preferably, the method for preparing the composite catalyst comprises:
In a class of this embodiment, a concentration of the precursor solution of aurum is 0.5-1.5 mmol/L.
In a class of this embodiment, the precursor solution of aurum is auric chloride acid (HAuCl4.4H2O).
Advantages of the invention are summarized below:
1. A nano-Au supported composite catalyst using attapulgite as the carrier is obtained in the invention for the first time. The attapulgite has a rich porous structure and a large specific surface area, which is favorable for high dispersion of aurum. Moreover, the nano-Au particle is within 1-7 nm, the number of active sites is increased and catalytic efficiency of aurum is improved, therefore, it is helpful for the catalytic reaction and its efficiency is improved accordingly.
2. The composite catalyst prepared in accordance with the invention can be used for catalytic oxidation of organic pollutants under low temperatures and the T50 temperature for catalytic reaction of organic pollutants is greatly reduced, therefore the catalytic reaction can be conducted under the temperature of 100° C. After the composite catalyst is stored under cold temperature for a period of time, its removal rate to organic pollutants under room temperature can still reach 99%.
3. The composite catalyst prepared in accordance with the invention can be used for catalytic oxidation of organic pollutants in waste water. It has catalytic effects on organic pollutants both in waste gas and waste fluid and it has wider applications compared with conventional catalysts.
4. The attapulgite, as one of the raw materials used in the invention, is a type of natural nano-mineral and it is cheap and easily accessible.
5. The preparation method provided by the invention is simple. The attapulgite, after dispersion and surface modification, is helpful for the achievement of high dispersion and controllable dimensions of aurum, so that the organic pollutants and the aurum in active sites can be fully contacted to improve the catalytic efficiency.
For further illustrating the invention, experiments detailing a composite catalyst and preparation method thereof are described below. It should be noted that the following examples are intended to describe and not to limit the invention.
Dissolve 0.041 g of auric chloride acid in 200 mL of deionized water, maintain the obtained solution at a constant temperature of 20° C. and add 4.0 M of ammonia solution to adjust the pH value to 9, slowly add 1.307 g of attapulgite to the mixed solution after the attapulgite has been dispersed using sodium hexametaphosphate (mass ratio between the sodium hexametaphosphate and the attapulgite is 1%) and modified using CTAB (0.5 g/100 mL), heat the solution to the temperature of 60° C. and stir magnetically, and add 4.0 M of ammonia solution to adjust the pH value to 9 and maintain the constant temperature for 60 mins. Afterwards, take out the obtained product and wash it twice with the deionized water, dry in an oven under the temperature of 80° C. for 12 hrs, bake under the temperature of 300° C. for 2 hrs, and finally grind the obtained product to obtain the composite catalyst.
Catalytic conditions: total gas flow is 240 mL/min, volume content of the o-dichlorobenzene is 3%, and space velocity is 30,000 h−1.
Catalytic effects: the removal rate of o-dichlorobenzene under the room temperature is 90%. Compared with the activation temperature during the catalytic degradation of the o-dichlorobenzene with conventional catalysts as described in some documents, the activation temperature is greatly reduced by using the composite catalyst provided by the invention.
Dissolve 0.082 g of auric chloride acid in 200 mL of deionized water, maintain the obtained solution at a constant temperature of 20° C. and add 4.0 M of ammonia solution to adjust the pH value to 10, slowly add 3.921 g of attapulgite to the mixed solution after the attapulgite has been dispersed using sodium pyrophosphate and modified using octadecyl trimethyl ammonium chloride, heat the solution to the temperature of 60° C. and stir magnetically, and add 4.0 M of ammonia solution to adjust the pH value to 10 and maintain the constant temperature for 60 mins. Afterwards, take out the obtained product and wash it until no chloride ion detected, dry in an oven under the temperature of 80° C. for 18 hrs, bake under the temperature of 300° C. for 2 hrs, and finally grind the obtained product to obtain the composite catalyst.
Catalytic conditions: the same as Example 1.
Catalytic effects: the removal rate of o-dichlorobenzene under the room temperature is 99%.
Dissolve 0.123 g of auric chloride acid in 200 mL of deionized water, maintain the obtained solution at a constant temperature of 20° C. and add 4.0 M of ammonia solution to adjust the pH value to 11, slowly add 11.763 g of attapulgite to the mixed solution after the attapulgite has been dispersed using sodium dodecyl sulfonate and modified using dodecyltrimethylammonium chloride, heat the solution to the temperature of 60° C. and stir magnetically, and add 4.0 M of ammonia solution to adjust the pH value to 11 and maintain the constant temperature for 60 mins. Afterwards, take out the obtained product and wash it until no chloride ion detected, dry in an oven under the temperature of 80° C. for 24 hrs, bake under the temperature of 300° C. for 2 hrs, and finally grind the obtained product to obtain the composite catalyst.
Catalytic conditions: the same as Example 1.
Catalytic effects: the removal rate of o-dichlorobenzene under the room temperature is 94%.
Dissolve 0.041 g of auric chloride acid in 200 mL of deionized water, maintain the obtained solution at a constant temperature of 20° C. and add 4.0 M of ammonia solution to adjust the pH value to 10, slowly add 3.921 g of attapulgite to the mixed solution after the attapulgite has been dispersed using sodium hexametaphosphate and modified using CTAB, heat the solution to the temperature of 60° C. and stir magnetically, and add 4.0 M of ammonia solution to adjust the pH value to 10 and maintain the constant temperature for 60 mins. Afterwards, take out the obtained product and wash until no chloride ion detected, dry in an oven under the temperature of 80° C. for 18 hrs, bake under the temperature of 300° C. for 2 hrs, and finally grind the obtained product to obtain the composite catalyst.
Catalytic conditions: methyl orange 25 mg/L, the usage amount of the composite catalyst is 50 mg/L, the usage amount of 30% H2O2 is 2 mL/L, and UV irradiation at 25 W.
Catalytic effects: the removal rate of methyl orange under the room temperature is 80% within 100 mins.
While particular embodiments of the invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201110139082.4 | May 2011 | CN | national |
