KR101419041B1 - A method for low-temperature reduction of nitrous oxide using a reductant over platinum group bi-metallic catalysts containing copper as a primary component - Google Patents

Abstract

The present invention relates to a process for producing a suboxide (including gold and silver) contained in a gas expander exhaust gas such as a nitric acid production plant and an adipic acid production plant by using hydrogen as a reducing agent on a platinum group (including gold and silver) There is an excellent effect of providing a method of effectively removing nitrogen at low temperature and high space velocity.

Description

[0001] The present invention relates to a method for removing nitrous oxide in an exhaust gas on a platinum-group binary metal catalyst having copper as a first component by a low-temperature catalytic reduction method primary component}

The present invention relates to a method for removing nitrous oxide (N ₂ O) in exhaust gas using hydrogen as a reducing agent on a catalyst composed of a platinum bivalent metal containing copper as a first component. More particularly, the present invention relates to a process for producing nitrous oxide contained in a gas expander exhaust gas such as a nitric acid production plant, an adipic acid production plant, and the like, , ≪ / RTI > including hydrogen) as a reducing agent on a binary metal catalyst at low temperature and high space velocity.

In Kyoto Protocol adopted by Kyoto, Japan in 1997, six greenhouse gases (CO ₂ ), methane, nitrous oxide (NO ₂ ), hydrogen fluoride, perfluorocarbons and sulfur hexafluoride were designated for practical reduction of greenhouse gases. Respectively. Since the global warming potential (GWP) of the remaining gases, referred to as 'non-CO ₂ greenhouse gases', is relatively high, the proportion of total greenhouse gas emissions is high, A high reduction effect can be achieved.

The main anthropogenic sources of nitrous oxide, which is representative of 'non-CO ₂ greenhouse gases' that cause global warming, are those that produce chemical products such as nitric acid, adipic acid, caprolactam, acrylonitrile, glyoxylic acid, It is representative of migrants such as circles and cars. Since the GWP of carbon dioxide is 1 and the GWP of nitrous oxide is 310, the effect of causing nitrous oxide from the above sources is 310 times that of carbon dioxide. Thus, removing 1 tonne of nitrous oxide from industrial processes has the same effect as reducing 310 tonnes of carbon dioxide. The concentration levels of nitrous oxide emitted from representative large-scale and small-scale fixed and mobile sources described above represent very different exhaust gas compositions depending on the characteristics of the sources.

There are direct catalytic decomposition, catalytic reduction, pyrolysis, etc. as technologies for reducing nitrous oxide emitted from industrial processes, and nitric acid production plant, adipic acid production plant, and caprolactam production plant are the major sources of nitrous oxide in Korea . Nitrous oxide discharged at high concentration in adipic acid production plant is reduced by pyrolysis technology or direct catalytic decomposition method. In nitric acid production plant, the amount of nitrous oxide emission is reduced by catalytic decomposition and catalytic reduction method.

The most widely applied method for the effective removal of nitrous oxide from the adipic acid production plant, which is a representative large-scale nitrous oxide emission source, is the catalytic cracking process. Since the temperature at the position where the catalytic reactor is installed is 400 to 650 ^{° C} , it is necessary to minimize the sintering of the metal or metal oxide used as the active ingredient at such a reaction temperature. Further, since 0.3 to 3% of H ₂ O coexists at high temperature, not only strong hydrothermal stability is required but also durability against O ₂ present in the range of 4 to 15% should be considered. Typical commercial catalysts include CuAl ₂ O ₄ / Al ₂ O ₃ , Ag-CuO / Al ₂ O ₃ and Ag / Al ₂ O _{3 of} BASF, CoO-NiO / ZrO ₂ of DuPont, CuO / Al ₂ O _{3 of} Asahi This is well known.

On the other hand, cobalt (Co) or iron (Fe) ion-exchanged zeolite catalysts capable of removing nitrous oxide at a relatively low reaction temperature (300 to 600 ° C.) have been developed. In order to achieve the nitrogen removal rate, a reaction temperature of about 500 ° C is required. A small amount of noble metals may be added to lower the required high reaction temperature, which is desirable for improving the catalytic activity at low temperatures, but this results in an increase in catalyst production cost.

The concentration of nitrous oxide emissions from nitric acid production plants, which correspond to another large source of nitrous oxide emissions, depends on the process pressure and temperature, the composition of the Gaussian type catalyst (platinum / rhodium ratio), use time, space velocity, ammonia (NH ₃ ) The residence time in the oxidation reactor, the design of the catalytic reactor, and the like (Press-Ramirez et al., Appl. Catal. B, 44, 117, 2003). Particularly, the nitrous oxide emission concentration greatly differs between before and after the absorption tower, from the area from the Gauss reactor to the heat exchanger (referred to as "process-gas") for the ammonia oxidation reaction, from the rear of the absorption tower to the gas expander (Hereinafter referred to as " tail-gas ") and regions after the gas expander (referred to as" end-of-pipe-gas " And the required catalytic properties have large differences.

The so-called process gas decomposition method, which removes nitrous oxide in the process gas region using a catalyst, should be capable of effectively removing the nitrous oxide concentration of 1.5 to 2.5%, and the nitrogen monoxide (NO) present in 95 to 97% That is, high selectivity is required, and catalyst properties having strong durability even at a high temperature of 800 ° C or more are required. In the tail gas decomposition method or the tail gas catalytic reduction method, the emission concentration of nitrous oxide is greatly reduced to 300 to 3,500 ppm, but the exhaust gas temperature of 400 ° C or more is still lower than the exhaust gas temperature And H ₂ O at a level of 0.3 to 3% coexist, so that a catalyst having a high reaction activity at a corresponding temperature and a strong hydrothermal stability is required.

In the so-called tail gas catalytic reduction method, although the tail gas has a composition similar to that of the tail gas, since the temperature of the exhaust gas is the lowest (100 to 300 ° C) since it is the rear end of the gas expander, Are required. The catalytic cracking method may be applied at the end gas condition, but since the temperature of the exhaust gas is low as described above, the exhaust gas must be reheated, which is not an effective method in the actual field.

In the prior art patents, a method of removing nitrous oxide at a relatively high temperature of 300 ° C or higher by using a zeolite catalyst mainly containing iron and a reducing agent (ammonia, hydrocarbon) is proposed.

Korean Patent No. 10-0801451 deals with a device for removing nitrous oxide produced by a nitric acid production plant by catalytic cracking. A catalyst layer composed of zeolite containing at least one iron between the heat exchanger directly below the ammonia oxidation reactor and the absorption tower is passed to remove the nitrous oxide produced from the ammonia oxidation reaction. At this time, the preferable temperature of the catalyst layer is from 350 to 600 DEG C, and a separate reducing agent corresponds to the direct decomposition method of the process gas.

In PCT / JP2009 / 051739, a method for reducing and removing nitrous oxide by contacting an exhaust gas containing nitrous oxide with a reducing agent in the presence of a catalyst, comprising the steps of: contacting the nitrous oxide decomposition catalyst with the nitrous oxide decomposition catalyst And the exhaust gas temperature or the amount of the reducing agent to be added is controlled. Wherein the catalyst is a noble metal catalyst supported on iron-containing zeolite, alumina or zeolite carrier, and the reducing agent is selected from the group consisting of methane, propane and ammonia. . However, this patent focuses on reheating the exhaust gas to maintain a high temperature around 400 DEG C and controlling the addition amount of the reducing agent.

Meanwhile, Korean Patent No. 10-0858010 discloses a method for removing nitrous oxide in a process gas or a tail gas generated from a nitric acid production process on a zeolite catalyst exchanged with iron or hydrogen ions. Here, Since the temperature is 200 to 600 캜, it corresponds to a high-temperature process.

In Nippon Shokubai, a catalyst for decomposing nitrous oxide and a method for removing nitrous oxide using the same (PCT / JP2007 / 060284) are disclosed. At least one of alkali metals, alkaline earth metals, magnesium and rare earths is selected and at least nickel, cobalt, A method for removing nitrous oxide by direct decomposition at a high temperature of 450 ° C or higher using a catalyst composed of iron, manganese, silver, ruthenium, platinum, rhodium, gold, palladium and iridium, Which is different from the present invention.

Korean Patent No. 10-0937594 discloses a catalyst for removing nitrous oxide or nitrous oxide and nitrogen oxides (NO _x ) at the same time, and a method for removing the catalyst. In this patent, a zeolite system in which iron (Fe) and phosphorus (P) are modified is proposed in the above patent, and the selective reduction decomposition method employing direct decomposition or using at least one selected from ammonia and hydrocarbons as a reducing agent is adopted. It is required to have a high temperature of 420 to 650 DEG C in order to achieve the nitrous oxide removal rate of the level.

In addition, an attempt to simultaneously remove nitrous oxide and nitrogen oxides (NOx) has been proposed in Korean Patent No. 10-0824225. This is because ammonia is injected as a reducing agent in the presence of iron-supported zeolite catalyst, Lt; RTI ID = 0.0 > 350 C < / RTI >

The above-mentioned methods for removing nitrous oxide and nitrogen oxide include a catalytic decomposition method in which nitrous oxide is directly decomposed on a catalyst without using any reducing agent in the high temperature (process gas), middle temperature (tail gas) and low temperature (end gas) And a catalytic reduction method for reducing nitrous oxide on a catalyst using a reducing agent such as ammonia, hydrocarbon and the like. Particularly, a catalytic reduction method in which nitrous oxide is reduced using a zeolite catalyst in which iron ions have been exchanged in the presence of a reducing agent such as ammonia or hydrocarbon, which is a typical commercial technique for removing nitrous oxide under tail gas and end gas conditions , A high temperature reaction temperature of 300 DEG C or more is required to achieve the level of nitrous oxide removal efficiency required in an industrial field.

Typical problems of existing catalysts for removal of nitrous oxide discharged from a large-scale fixing source such as nitric acid and adipic acid production process are as follows. Specifically,

(1) Of the catalytic cracking methods widely used in nitric acid production plants, the process gas cracking method requires a very high temperature of 800 to 1,000 ° C. and requires a reaction temperature of 440 ° C. or more even in the tail gas decomposition method;

(2) Even in the case of the catalysts for removing nitrous oxide, which is applied to the adipic acid production plant, the process gas decomposition method requires a reaction temperature of 850 to 1,000 ° C and the tail gas decomposition method requires a high temperature of 500 ° C or more;

(3) the application of the process gas decomposition method requires a very high level of thermal stability of the catalyst and causes the catalytic activity loss and the service life shortening due to the catalyst sintering at high temperature;

(4) In the case of the tail gas decomposition method, even at a relatively low temperature of 440 to 550 ° C, an auxiliary fuel, mainly natural gas, is required to reheat a large amount of exhaust gas to a target reaction temperature, The point where an additional

And the like.

In order to solve the above problems, the present inventors have proposed a method of removing nitrous oxide in exhaust gas by a low-temperature catalytic reduction method in Patent Application No. 10-2011-0022098, wherein 0.2 to 0.5 wt% In the presence of a platinum group metal catalyst, hydrogen peroxide as a reducing agent at a low reaction temperature of 100 to 200 DEG C at a high efficiency to a level required in the industrial field has been proposed. However, Based catalyst composed of only a metal of the series, and thus the present invention has been accomplished.

Therefore, the object of the present invention is to overcome the above-described problems of the prior art and to significantly improve the removal efficiency of nitrous oxide, while being cheaper in terms of the production cost than the platinum group single component catalyst, which was a disadvantage of the prior art of the present inventor To provide an active multicomponent catalyst.

Another object of the present invention is to provide a process for producing an exhaust gas purifying catalyst, which is capable of removing nitrogen oxides in an exhaust gas at a tail gas exhausting position of a nitric acid or adipic acid producing plant using the catalyst system, The goal is to achieve nitrous oxide removal rates as high as 90% or higher, which is industrially required at high speeds.

The object of the present invention is to provide a method of producing a multi-component copper-platinum catalyst by supporting nanoparticle size of platinum on a support surface and adding relatively inexpensive copper as a first component to the support surface, thereby reducing the amount of expensive platinum At the same time, the following reactions 1 to 4 are simultaneously carried out on the platinum surface Pt _s and the copper surface Cu _s , thereby reducing the nitrous oxide to hydrogen as a reducing agent at a lower space velocity.

<Reaction Scheme 1>

Pt _s + N ₂ O? N ₂ + Pt _s O

<Reaction Scheme 2>

Pt _s O + 3 / 2H _{2 -} > Pt _s H + H ₂ O

<Reaction Scheme 3>

Cu _s + ½N ₂ O → ½Cu _s -O-Cu _s + ½N ₂

<Reaction Scheme 4>

Pt _s H + ½Cu _s -O-Cu _s → Pt _s + Cu _s + ½H ₂ O

The other object of the present invention is achieved by removing nitrous oxide contained in the exhaust gas discharged from a nitric acid production plant, an adipic acid production plant, etc. at a low reaction temperature and a high space velocity and at a level applicable to actual field using hydrogen as a reducing agent do.

It is still another object of the present invention to provide a multicomponent catalyst for use in a method for removing nitrous oxide, which comprises a platinum group metal (including gold and silver) on a support such as silicon dioxide, titanium dioxide, aluminum trioxide, zeolite ) Precursor ions are firstly exchanged and then copper precursor ions are exchanged again, and then the precursor ions are reduced and then reduced.

According to the present invention, a multi-component catalyst made of copper and a noble metal is used to remove a large amount of nitrous oxide contained in the exhaust gas discharged from a nitric acid production plant, an adipic acid production plant, etc., The present invention has a remarkable effect that it is possible to remove nitrous oxide with high efficiency at a level applicable to actual field by using hydrogen as a reducing agent at a much lower reaction temperature and a very high reactor space velocity as compared with the conventional commercial catalytic process.

Further, according to the present invention, compared to our patent application No. 10-2011-0022098, it is possible to reduce the content of noble metal which is relatively expensive, and at the same or higher level of nitrous oxide removal efficiency at a much higher reactor space velocity There is an effect that can be achieved.

FIG. 1 shows that when the reaction temperature was changed from 135 ° C. to 150 ° C. under the reaction conditions of the reactor having a space velocity of 389,000 h ^-1 , a nitrous oxide concentration of 500 ppm and a hydrogen concentration of 500 ppm, Graph showing the nitrous oxide removal rate on a bimetallic catalyst supported with copper and 1.13 wt% platinum.

In the present invention, the multi-component catalyst is not limited to the order of supporting or supporting the noble metal and copper used as the catalyst component on the support.

As the multicomponent catalyst component in the present invention, the noble metal may be rhodium, palladium or ruthenium in addition to platinum, and gold or silver may be selected. As the multicomponent catalyst component, the number of components selected from the above-listed noble metals other than copper is not limited.

Further, the support is not limited to only the above supports, and more preferably, a hydrophobic support having as low a water absorption and adsorption performance as possible in the reaction of removing nitrous oxide by selecting the one having a broad specific surface area desirable.

On the other hand, the content of the noble metal including the gold and silver supported on the support is not particularly limited, but is preferably 0.05 to 5 wt%, more preferably 0.1 to 2 wt%, based on the total weight of the support and the noble metal, Lt; / RTI &gt; When the content of the noble metal is less than the above range, it is difficult to achieve the nitrous oxide removal rate required at the actual site at a low reaction temperature and a high space velocity. When the content exceeds the above range, the catalyst production cost is increased.

The content of copper supported on the support is not particularly limited, but is preferably 0.1 to 20% by weight, more preferably 0.3 to 10% by weight, based on the total weight of the support and copper. When the content of copper is lower than the above range, the role of copper as a multicomponent catalyst component is lowered and the effect of reducing the manufacturing cost of the catalyst is decreased. If the content is larger than the above range, the particle size of copper becomes too large It is possible to reduce the participation of the noble metal in the removal of nitrous oxide due to the covering of the noble metal component by copper.

In the present invention, the lower reaction temperature is a temperature selected from 30 to 300 캜, which is lower than 350 캜, which is generally employed in the conventional catalytic process (tail gas decomposition and reduction), more preferably 100 to 200 / RTI &gt; When the reaction temperature is lower than 100 ° C, water generated during the reaction is not smoothly desorbed from the catalyst surface, and the reaction activity with time decreases. When the reaction temperature is higher than 200 ° C, the exhaust gas (tail gas) The operation cost is increased.

In the present invention, the space velocity is defined as the exhaust gas flow rate per powder catalyst unit volume filled in the reactor. In the present invention, the high space velocity is calculated as the total flow rate of two kinds of reactants per unit volume of the multicomponent powder catalyst packed in the reactor, that is, carrier gas containing nitrous oxide and hydrogen, and the flow rate is 50,000 to 1,000,000 h ^-1 , And more preferably 50,000 to 800,000 h ^-1 . At a space velocity of less than 50,000 h ^{-1, the} removal rate of nitrous oxide is excellent, but the catalyst cost is excessive due to a large amount of catalyst, and in order to effectively treat a large amount of exhaust gas required in actual industrial sites such as nitric acid production plant and adipic acid production plant There is a difficulty. If the space velocity is greater than 800,000 h ^-1 , the amount of catalyst required can be reduced, so that the catalyst cost can be significantly reduced, but the nitrous oxide removal rate is lowered.

The method of supporting the noble metal (including gold and silver) and copper on the support is not particularly limited by the method used in the present invention. The method of preparing the catalyst includes a wet-type supporting method, an impregnation method, Precipitation method and the like can be used. In a more preferred method, the ion exchange method may be applied to produce particles of noble metal and copper supported on the surface of the support at a nanoparticle size of 0.5 to 50 nm.

In the present invention, the term "binary metal oxide catalyst for removing nitrous oxide" means a catalyst capable of reducing nitrous oxide at a low temperature of 100 to 200 DEG C while reducing the weight percentage of expensive noble metal, The catalyst exhibits excellent nitrous oxide removal efficiency even at higher space velocities than catalysts composed only of platinum group precious metals.

Hereinafter, the method of the present invention for removing nitrous oxide in exhaust gas by a low temperature catalytic reduction method on a platinum group bimetallic catalyst having copper as a first component will be described in more detail by way of example, but the scope of the present invention is not limited to these embodiments It is needless to say that the numerical value and the low-cost metal can be adopted and changed among those skilled in the art, and design changes having different values and physical properties are included in the scope of the present invention.

< Example >

< Comparative Example  1>

(1.13 wt% Pt / SiO ₂ ) supported on a silicon dioxide (SiO ₂ ) support with a flow rate of 200 cm 3 / min at 570 ° C. for 4 hours with air (99.999% ₂ ) was prepared by the following ion exchange method.

300 mL of tertiary distilled water was added to the beaker and a few drops of ammonium hydroxide (NH ₄ OH, 25-28%) solution was added with stirring to adjust the pH to 9.8. The fired silicon dioxide was slowly added thereto, and the mixture was thoroughly mixed for 30 minutes. Thereafter, 0.284 g of tetraamine platinum chloride (Pt (NH ₃ ) ₄ Cl ₂ .xH ₂ O, 99.995%), which is a precursor of platinum metal, Dissolved in 1 mL of distilled water was slowly added thereto. Ammonium hydroxide was added periodically every 2 hours to maintain the pH of the solution at 9.8 for 8 hours and then filtered through a filter. The sample in which the platinum precursor was ion-exchanged was collected, placed in a dryer at 120 ° C., dried thoroughly for 12 hours, and placed in a sample bottle and stored in a desiccator.

When titanium dioxide, aluminum sesquioxide (Al ₂ O ₃ ) and ZSM-5 were used as supports for tetraamine platinum ions (Pt (NH ₃ ) ₄ ²⁺ ), the pH of 300 mL of the third distilled water was adjusted to 10.1 and 11.0 Was prepared in the same manner as described above.

The catalyst in which the tetraamine platinum ion (Pt (NH ₃ ) ₄ ²⁺ ) was exchanged on the silicon dioxide surface obtained by the above-mentioned production method was reduced in the following manner before it was used in the reaction.

The desired amount of the sample was put into a ¼ "x 10" Pyrex reactor and heated to 400 캜 at a heating rate of 5 캜 / min while flowing nitrogen (99.999%) at 200 cm 3 / min, and then maintained for 1 hour. Thereafter, Pt (NH ₃ ) ₄ ²⁺ was reduced to platinum metal (Pt ⁰ ) while hydrogen (99.999%) was flowed at 400 ° C. at a flow rate of 200 cm 3 / min for 1 hour, Lt; RTI ID = 0.0 &gt; 375 C &lt; / RTI &gt; and purged for 30 minutes. The nitrogen stream was maintained at a desired reaction temperature (110 to 135 ° C), and then a nitrous oxide removal reaction was carried out using a continuous flow fixed bed catalytic reactor.

The same method as above was applied to the reduction of Pt (NH ₃ ) ₄ ²⁺ ion-exchanged to titanium dioxide, aluminum sesquioxide and ZSM-5 to platinum metal.

Silicon dioxide (SiO ₂ ) and titanium dioxide (TiO ₂ ) used as a support in a continuous flow type fixed-bed reactor are filled in an amount of 0.2 to 0.3 g, respectively, and a stream of nitrogen at a desired reaction temperature, typically 110 ° C., 500 ppm of nitrous oxide (99.999%) and 0 ppm or 500 ppm of hydrogen (99.999%) as a reducing agent were tested to test their activity as catalysts.

The concentration of nitrous oxide was analyzed by gas chromatography equipped with a thermal conductivity detector and a Porapak Q column, and the removal rate of nitrous oxide was calculated according to the following equation (1).

<Formula 1>

Since the catalytic activity tends to decrease with the reaction time during the nitrous oxide removal reaction, the reaction time was treated as another parameter to examine the nitrous oxide removal rate. The results of the experiment of Comparative Example 1 of the present invention are shown in the following < Table 1.

The results of Comparative Example 1 Comparative Example
number Pt weight of Pt / SiO ₂ (%) Nitrous oxide
Concentration (ppm) Hydrogen concentration
(ppm) Reaction temperature
(° C) Space velocity
(h ^-1 ) Nitrogen Dioxide Removal Rate (%) Reaction time (h) 0 0.1 0.25 0.5 One One 1.13 500 0 110 388,800 100 3 0 0 0

As can be seen from the results of the experiment of Comparative Example 1 in Table 1, when the reducing agent, hydrogen, was not present in 1.13 wt% Pt / SiO ₂ used as a comparative catalyst in the present invention, the nitrous oxide removal rate was 5% And no nitrous oxide removal performance was observed after 15 minutes.

< Comparative Example  2 and Comparative Example  3>

The 1.13 wt% Pt / SiO ₂ catalyst prepared above was reacted at a reaction temperature of 110 DEG C and 135 DEG C under a reaction condition of a space velocity of 388,800 h < ^-1 > (powder basis), 500 ppm of hydrogen reducing agent and 500 ppm of nitrous oxide, The removal rate was examined, and the results are shown in Table 2 below.

 The results of Comparative Example 2 and Comparative Example 3 Comparative Example
number Pt / SiO ₂ Pt
weight(%) Suboxide
Nitrogen concentration
(ppm) Hydrogen
density
(ppm) Reaction temperature
(° C) Space velocity
(h ^-1 ) Nitrogen Dioxide Removal Rate (%) Reaction time (h) 0 One 3 5 15 25 35 40 2 1.13 500 500 110 388,800 100 11 6 4 2 One 2 One 3 1.13 500 500 135 388,800 100 22 16 14 7 5 3 2

As can be seen from the results of Comparative Example 2 and Comparative Example 3 shown in Table 2, the removal rate was 100% with the initiation of reaction at the reaction temperature of 110 ° C., but the removal rate rapidly decreased with the elapse of the reaction time, Showed a nitrous oxide removal rate of 5% or less. Although the removal rate of nitrous oxide is higher than 110 ° C at 135 ° C, the activity level is generally low for use as a catalyst for removing nitrous oxide in the exhaust gas discharged from a nitric acid manufacturing plant or an adipic acid manufacturing plant.

< Example  1 to Example  3>

Bimetallic catalysts composed of copper and a noble metal used in the present invention were prepared as follows.

As described in <Comparative Example 1>, first, 0.1 to 1.5% by weight of platinum ion-exchanged catalysts were prepared on a silicon dioxide support, and then reduced with hydrogen in a manner similar to that described in <Comparative Example 1> of 0.1 to 1.5 wt.% Pt / SiO ₂ Catalyst. To further support 0.1 to 5% by weight of copper, a predetermined amount of copper nitrate (Cu (NO ₃ ) ₂ .xH ₂ O, 99.999%), which is a precursor of copper metal, was added to a solution containing 300 mL of tertiary distilled water And then the reduced 0.1 to 1.5 wt% Pt / SiO ₂ catalyst was slowly added to the copper nitrate solution while stirring in a beaker. This was stirred for 8 hours with vigorous stirring, filtered through a filter, recovered, and placed in a dryer at 120 ° C. for 12 hours to obtain a copper-platinum catalyst of the desired weight percentage supported on the silicon dioxide. Hereinafter, it is referred to as a Cu-Pt / SiO ₂ catalyst.

Titanium dioxide, aluminum sesquioxide and ZSM-5 as substrates other than silicon dioxide were also prepared in the same manner as described above.

The Cu-Pt catalysts prepared by the above process were reduced in the following manner before performing the nitrous oxide removal reaction.

A desired amount of the catalyst powder sample was placed in a ¼ "x 10" Pyrex reactor and heated to 300 캜 at a heating rate of 5 캜 / min while flowing nitrogen (99.999%) at 200 cm 3 / min, and then maintained for 1 hour. Thereafter, hydrogen (99.999%) was flowed at 300 ° C at a flow rate of 200 cm 3 / min for 4 hours, and the copper ions and platinum ions supported on the support were reduced to copper (Cu ⁰ ) and platinum (Pt ⁰ ) Lt; RTI ID = 0.0 &gt; cm3 / min. &Lt; / RTI &gt; While the nitrogen flow was maintained, the target reaction temperature was lowered to 90 to 150 DEG C, and the nitrous oxide removal rate was measured under the desired reaction conditions.

The nitrous oxide removal rates of different weight percent Cu-Pt / SiO ₂ catalysts prepared and reduced as described above were measured at a reaction temperature of 110 ° C, a space velocity of 388,800 h ^-1 , a nitrous oxide concentration of 500 ppm and a hydrogen concentration of 500 ppm The reaction conditions were investigated.

As can be seen from the results of Example 1 shown in Table 3 below, the 0.57 wt% Cu-1.13 wt% Pt / SiO ₂ catalyst showed 94% NO 2 removal efficiency . Compared to the results of the same 1.13 wt% Pt / SiO ₂ catalyst as in Comparative Example 2 in Table 2, the removal rate of nitrous oxide was 5% or less after 3 hours from the initiation of the reaction under the same reaction conditions, Of copper was added, so that the reaction of the nitrous oxide was very accelerated.

 Results of Examples 1 to 3 Example
number Cu with Cu-Pt / SiO ₂
Pt weight (%) Suboxide
Nitrogen concentration
(ppm) Hydrogen
density
(ppm) Reaction temperature
( ^{° C} ) Space velocity
(h ^-1 ) Nitrous oxide removal rate (%) Reaction time (h) Cu Pt 0 One 3 5 15 25 One 0.57 1.13 500 500 110 388,800 100 93 94 93 93 94 2 1.84 1.13 500 500 110 388,800 100 100 100 100 100 100 3 3.01 1.13 500 500 110 388,800 100 100 100 100 100 100

The results of Example 2 and Example 3 in Table 3 show the nitrogen dioxide removal rate with the elapse of the reaction time when the weight percentage of copper is increased. When the copper content is higher than 1.84% by weight, , And exhibited a catalytic activity of 100% even on a 3.01 wt% Cu-Pt catalyst, which was higher than this.

< Example  4 to Example  6>

The results of Example 5 and Example 6 in Table 4 below show the nitrous oxide removal rate of 0.57 wt% Cu-1.13 wt% Pt / SiO ₂ catalyst at different reaction temperatures. As can be seen from the results of Example 4, at a reaction temperature of 90 ° C, the nitrous oxide removal rate gradually decreased with the elapse of the reaction time, and showed a removal efficiency of 36% at 25 hours. And the reaction temperature of higher than 125 ℃ and 135 ℃ 110 ℃ pulled reliably receive all the nitrous oxide removal rate of 100% during the reaction of 25 hours, regardless of the reaction time, 1 is the space velocity of the reactor 389,000 h ^-1, When the reaction temperature was changed from 135 ° C to 150 ° C under the reaction conditions of 500 ppm of N 2 O and 500 ppm of hydrogen, the reaction was carried out on a binary metal catalyst supported with 0.57% by weight of copper and 1.13% A graph showing the nitrous oxide removal rate.

Results of Examples 4 to 6 Example
number Cu with Cu-Pt / SiO ₂
Pt weight (%) Suboxide
Nitrogen concentration
(ppm) Hydrogen
density
(ppm) Reaction temperature
(° C) Space velocity
(h ^-1 ) Nitrous oxide removal rate (%) Reaction time (h) Cu Pt 0 One 3 5 15 25 4 0.57 1.13 500 500 90 388,800 100 74 59 52 43 36 5 0.57 1.13 500 500 125 388,800 100 100 100 100 100 100 6 0.57 1.13 500 500 135 388,800 100 100 100 100 100 100

< Example  7 to Example  9>

The results of Examples 7 to 9 in the following Table 5 were obtained under the same reaction conditions as in Example 1 except for the space velocity, that is, at a reaction temperature of 110 DEG C, a nitrous oxide concentration of 500 ppm and a hydrogen concentration of 500 ppm, It shows the nitrous oxide removal rate when the speed is changed. In Example 1, a space velocity of 388,800 h ^-1 lower than 364,500 h ^-1 of the space velocity used in the showed the nitrous oxide removal rate of 100%, as expected, a high space velocity of 388,800 h ^-1 than 486,000 h ^-1 to 583,200 h ^{-1 in} the space velocity of 78% and 52%, respectively.

Results of Examples 7 to 9 Example
number Cu with Cu-Pt / SiO ₂
Pt weight (%) Suboxide
Nitrogen concentration
(ppm) Hydrogen
density
(ppm) Reaction temperature
(° C) Space velocity
(h ^-1 ) Nitrous oxide removal rate (%) Reaction time (h) Cu Pt 0 One 3 5 15 25 7 0.57 1.13 500 500 110 364,500 100 100 100 100 100 100 8 0.57 1.13 500 500 110 486,000 100 78 78 76 77 78 9 0.57 1.13 500 500 110 583,200 100 53 51 49 52 53

< Example  10th Example  11>

In the results of Example 10 and Example 11 shown in Table 6 below, the same reaction conditions as in Example 1 except for the catalyst, namely, the reaction temperature of 110 ° C, the concentration of nitrous oxide of 500 ppm, the hydrogen concentration of 500 ppm and the hydrogen concentration of 388,800 h ^The removal rate of nitrous oxide of 0.48 wt% Cu-1.21 wt% Pt / Al ₂ O ₃ catalyst and 0.52 wt% Cu-1.04 wt% Pt / ZSM-5 catalyst under a space velocity of ^-1 is shown as a function of reaction time. In Example 10, the nitrous oxide removal rate of about 83% was observed stably for 25 hours, and in Example 11, the nitrous oxide removal rate of about 77% was obtained.

Results of Example 10 and Example 11
Example
number
catalyst Suboxide
Nitrogen concentration
(ppm) Hydrogen
density
(ppm) reaction
Temperature (℃) space
speed
(h ^-1 ) Nitrous oxide removal rate (%) Reaction time (h) 0 One 3 5 15 25 10 0.48 wt% Cu-
1.21 wt% Pt / Al ₂ O ₃ 500 500 110 388,800 100 83 84 82 81 83 11 0.52 wt% Cu-
1.04 wt% Pt / ZSM-5 500 500 110 388,800 100 77 75 76 78 76

As described above, the present invention can effectively remove nitrous oxide contained in exhaust gas downstream of a gas expander at a low temperature and a high space velocity using hydrogen as a reducing agent on a platinum group binary metal catalyst composed of a copper as a low-cost metal as a first component It is a very useful invention in the green technology industry related to the reduction of greenhouse gas use because of its excellent effect.

Claims (7)

delete The noble metal of the noble metal size is supported on the support surface and is reduced and then copper is added as the first component and reduced again so that the nitrous oxide removal reaction occurs simultaneously on the copper and platinum group noble metal surfaces. And a reducing agent is injected into the catalytic reactor to reduce the amount of expensive platinum, and at the same time, the reaction temperature of 100 ° C to 200 ° C and the reaction temperature of 50,000 h ^-1 to 800,000 at a reactor space velocity of h ^-1 , nitrous oxide in the exhaust gas discharged from a nitric acid, adipic acid production plant or the like is removed. The low temperature catalyst reduction method according to claim 2, wherein the reducing agent is hydrogen. The low-temperature catalyst reduction method according to claim 2, wherein the multicomponent copper-platinum group metal catalyst comprises 0.05 to 5% by weight of platinum group noble metal based on the total weight of the support and noble metals. The method of claim 2, wherein the multicomponent copper-platinum group metal catalyst is a low-temperature catalyst reduction method for removing nitrous oxide, wherein the content of copper as a first component is 0.1 to 20% by weight based on the total weight of the support and copper . delete delete

Images