KR101331391B1 - Palladium/titania catalyst for formaldehyde, carbon monoxide and hydrogen oxidation in the air at room temperature and manufacturing method using the same - Google Patents

Abstract

The present invention relates to a palladium / titania catalyst and a method for producing the same, which is a palladium / titania catalyst in which a palladium precursor is supported on a titania carrier, having palladium / titania catalyst having the ability to remove formaldehyde and carbon monoxide contained in air at room temperature and a method for producing the same. By oxidizing, volatile organic compounds and toxic gases such as formaldehyde and carbon monoxide in indoor air can be oxidized and removed at room temperature without a separate energy source, and are very economical catalysts compared to the conventional catalysts for removing harmful substances. To provide a market-competitive palladium / titania catalyst.

Description

Palladium / Titania catalyst having the ability to remove formaldehyde, carbon monoxide and hydrogen contained in the air at room temperature, and a method for preparing the same.

The present invention relates to a palladium / titania catalyst and a method for producing the same, and more particularly, to a palladium / titania catalyst capable of removing various harmful contaminants in air and a method for producing the same.

Recently, as awareness of indoor pollution is increasing day by day, formaldehyde (HCHO), which accounts for the largest amount of aldehydes, which occupies a large amount of indoor pollutants, is emerging as a very harmful factor for the human body.

Formaldehyde is known as a major causative agent such as building syndrome, sick house syndrome, and chemical hypersensitivity, and when exposed to the human body, it causes eye irritation, tearing, upper airway irritation, asthma attacks, convulsions, vomiting and diarrhea. It is well known to have a more sensitive effect on vulnerable groups such as children, children and the elderly.

Sources of formaldehyde are generated from insulation, textiles, cabinets, sinks, flooring, heating fuel combustion processes, smoking, household goods, medicines, adhesives, etc., which are mostly used indoors. Considering living indoors, the risks and impacts are serious.

Such formaldehyde, as well as volatile organic compounds (VOCs) including the same, are widely known for their danger indoors.

In recent years, accidents caused by gas poisoning frequently occur in saunas or jjimjilbangs in baths, and the gas in question is widely known as an accident due to carbon monoxide poisoning. Carbon monoxide causes problems such as vomiting and dizziness at low concentrations, but exposure to high concentrations for more than a certain time leads to death, which is a social problem.

 Various techniques are known for treating contaminants present in the room, and the catalytic oxidation method is known as the best method in that the contaminant can be directly transferred to a harmless substance to the human body. However, existing methods known as catalytic contaminant removal methods require additional heat energy or light energy, which places many restrictions on their use.

Meanwhile, due to the recent Fukushima nuclear accident, the importance and seriousness of technical problems related to hydrogen concentration control in nuclear reactors are highlighted. In a nuclear power plant, a large amount of hydrogen is generated by the oxidation reaction of nuclear fuel clad Zircaloy in a serious accident involving core melting. Hydrogen generated at this time has a risk of spontaneous ignition and explosion when it reaches a certain concentration. In the case of the Fukushima nuclear accident, the energy supply of equipment capable of handling the generated hydrogen was cut off, resulting in the release of radioactive materials to the outside due to an explosion caused by the increase in the concentration of hydrogen in the reactor. Therefore, there is an urgent need for a method that can treat hydrogen without a separate energy source.

Republic of Korea Patent Publication No. 2007-93183 discloses a gypsum board that can efficiently absorb formaldehyde, Republic of Korea Patent Publication No. 2001-91269 is able to adsorb formaldehyde using activated clay, stone powder, activated carbon Adsorbents are disclosed. However, these prior arts have a problem of requiring periodic exchange of adsorbent absorbers due to the use of simple adsorption or absorption rather than the fundamental solution of the causative agent.

In addition, Korean Patent Laid-Open No. 2006-92168 discloses a technique for removing formaldehyde and VOCs using a visible light sensitive photocatalyst. However, the method using a photocatalyst requires a separate light source in the formaldehyde removal reaction, and in order to obtain excellent efficiency, the contact time with the catalyst has to be increased, which causes a problem that the volume of the reactor and the capacity to process the reactor are small.

Most of the formaldehyde removal catalysts and removal technologies studied to date are mostly composed of batch reaction experiments, not experiments in a continuous flow reactor. In this method, oxidation and adsorption coexist, and therefore, oxidation reaction efficiency is strictly determined. Hard to mention

In addition, the Republic of Korea Patent Publication No. 2010-37499 discloses a technique for producing a catalyst for oxidizing formaldehyde at room temperature using a platinum / titania catalyst, platinum is one of the precious precious metals among the precious metals, the market competitiveness is low, carbon monoxide The technique for removing hydrogen is not disclosed.

Meanwhile, Tang X. et al. (4) (Tang X .; Chen J .; Huang X .; Xu Y .; Shen W., Appl. Catal. B-Environ., 2008, 81 115-121) and Zhang C. et al. Two (Zhang C .; He H .; Tanaka K., Appl. Catal. B-Environ., 2006, 65, 37-43) said that palladium can be treated with platinum as the main active metal. Reported little activity at room temperature.

Accordingly, the present invention has been made to solve the above problems, and the air containing the reactants is completely passed through the catalyst layer without any energy source in removing hydrogen as well as formaldehyde and carbon monoxide contained in the indoor air. The present invention provides a catalyst which can be oxidized and released into water (H ₂ O) and carbon dioxide (CO ₂ ), which are harmless to the human body, and can be economically produced.

According to an aspect of the present invention,

(1) A palladium / titania catalyst in which a palladium precursor is supported on a titania carrier, which provides a palladium / titania catalyst having the ability to remove formaldehyde and carbon monoxide contained in air at room temperature.

(2) The palladium / titania catalyst according to (1), wherein the palladium / titania catalyst further has a hydrogen removal ability contained in the air at room temperature.

(3) The palladium / titania according to (1) or (2), wherein the palladium precursor is palladium chloride (PdCl ₂ ) or palladium nitrate dihydrate (N ₂ O ₆ Pd.2H ₂ O). To provide a catalyst.

(4) The palladium precursor according to (3), wherein the content of palladium / titania catalyst is 0.25 to 5 parts by weight based on 100 parts by weight of the carrier.

The present invention for solving the another problem,

(5) preparing a palladium / titania catalyst by sequentially supporting, drying, and calcining by using a palladium precursor and a titania support, and further comprising a reducing step under a reducing gas atmosphere after the calcining step; It provides a method for producing a palladium / titania catalyst according to the.

(6) The method for producing a palladium / titania catalyst according to (5), wherein the reduction step is performed by maintaining the temperature at 500 to 700 ° C. for 0.5 to 5 hours in a furnace in a hydrogen atmosphere. .

(7) The method for producing a palladium / titania catalyst according to (5), wherein the palladium precursor is palladium chloride (PdCl 2) or palladium nitrate dihydrate (N ₂ O ₆ Pd · 2H ₂ O). To provide.

(8) The method for producing a palladium / titania catalyst according to the above (7), wherein the palladium precursor is 0.25 to 5 parts by weight based on 100 parts by weight of the carrier.

(9) The method for producing a palladium / titania catalyst according to the above (5), wherein the palladium / titania catalyst is extruded into a particle or a single body.

(10) The palladium / titania according to the above (5), wherein the palladium / titania catalyst is coated on any one structure selected from the group consisting of a metal plate, a metal fiber, a ceramic filter, a metal filter and a honeycomb. Provided are methods for preparing a catalyst.

According to the palladium / titania catalyst of the present invention and a method for preparing the same, volatile organic compounds such as formaldehyde and carbon monoxide and toxic gases in room air can be oxidized and removed at room temperature without a separate energy source. Compared to solvent catalysts, the catalyst is very economical and has an effect of providing a palladium / titania catalyst having excellent market competitiveness.

1 is a graph showing the formaldehyde removal rate according to the space velocity of the catalyst according to Examples 1 to 3,
Figure 2 is a graph showing the results of XPS analysis for the catalyst according to Examples 1 to 3.

Hereinafter, the present invention will be described in detail with reference to preferred embodiments. Prior to this, terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms, and the inventor should appropriately interpret the concepts of the terms appropriately The present invention should be construed in accordance with the meaning and concept consistent with the technical idea of the present invention. Accordingly, it is to be understood that the constituent features of the embodiments described herein are merely the most preferred embodiments of the present invention, and are not intended to represent all of the inventive concepts of the present invention, so that various equivalents, And the like.

The present invention provides a palladium / titania catalyst having a palladium precursor supported on a titania carrier, having a formaldehyde and carbon monoxide removal ability contained in air at room temperature, and further having a hydrogen removal ability. It will be described below in detail through the manufacturing process of the palladium / titania catalyst according to the present invention.

The palladium / titania catalyst according to the present invention uses a general wet-impregnation method, and is prepared by carrying out a series of drying, calcining and reducing processes after supporting a palladium precursor on a titania support.

That is, the present inventors found that the palladium is reduced through the reduction process to artificially change the physical properties of the palladium / titania catalyst to act as an active metal specific for the removal of formaldehyde, carbon monoxide and hydrogen in air at room temperature. The present invention has been reached.

First, in order to support palladium, which is an active metal, 0.25 to 5 parts by weight of the palladium precursor is dissolved in an aqueous solution based on 100 parts by weight of the titania support. When the content of the palladium precursor is less than 0.25 parts by weight, the catalytic activity may be lowered. As the content is increased, the catalytic activity efficiency is improved, but when it exceeds 5 parts by weight, it is not preferable in view of the effect of increasing the activity compared to the content.

In addition, the palladium precursor is not particularly limited to its kind, but it is preferable to use palladium chloride (PdCl ₂ ) or palladium nitrate dihydrate (N ₂ O ₆ Pd.2H ₂ O) which is economical and has excellent supporting efficiency.

Next, the titania support quantified into the aqueous solution in which the palladium precursor is dissolved as described above is mixed and sufficiently mixed to prepare a slurry. The titania support preferably has a specific surface area of at least 100 m 2 / g in order to ensure that palladium has a high degree of dispersion and specific surface area in the final catalyst.

Subsequently, the palladium precursor is supported on the titania support by removing water in the slurry through a predetermined process. At this time, in order to completely remove the water contained in the fine pores, it is preferable to dry sufficiently for more than 24 hours in a drying facility.

The dried sample is then calcined. At this time, the manufacturing process is somewhat different depending on the type of palladium precursor used. Specifically, when palladium chloride (PdCl ₂ ) is used, a reduction process is added before firing to exclude chlorine which is an inert element, and when the palladium precursor containing no chlorine is used, the reduction step is unnecessary.

The firing process is to control the dispersibility and specific surface area of the active metal through the heat treatment of the prepared catalyst, to remove impurities from the catalyst itself, and to increase the bonding strength between the active metal and the support. In the case of the palladium / titania catalyst according to the present invention, the active metal Palladium can also be used to produce catalysts that are effective in removing formaldehyde, carbon monoxide and hydrogen, even when fired at temperatures below 500 ° C, a relatively low temperature.

After the calcining process, the reducing process is carried out under a reducing gas atmosphere such as hydrogen or ammonia, and in the case of hydrogen atmosphere, it may be carried out by maintaining at a temperature of 500 to 700 ° C. for 0.5 to 5 hours. At this time, the reducing gas atmosphere may be formed by a gas of 5 to 40% by volume composition, the furnace is a tube-type furnace, a convection (convection) furnace, grate furnace, etc. may be used. .

The palladium / titania catalyst production method according to the present invention controls the growth of the crystal phase of the support and the degree of dispersion of palladium through such a reduction process, and also controls the formaldehyde, carbon monoxide and hydrogen removal activity by controlling the oxidation value of palladium. Got mad.

The palladium / titania catalyst prepared as described above shows excellent oxidation at room temperature through the following action.

First, in the case of formaldehyde removal, reduced palladium converts formaldehyde to formate species, is converted to carbon monoxide while losing hydrogen, and then oxidized to carbon dioxide by oxygen in the air and oxygen of the catalyst (see Formula 1 below). In addition, even in the case of carbon monoxide and hydrogen, it is oxidized to carbon dioxide and water by oxygen in the air and oxygen of the catalyst, respectively (see Formulas 2 and 3 below).

[Formula 1]

HCHO + O ₂ → CO ₂ + H ₂ O

(2)

2CO + O ₂ → 2CO ₂

(3)

2H ₂ + O ₂ → 2H ₂ O

When the palladium / titania catalyst prepared according to the present invention is actually applied, it can be used by coating on structures such as metal plates, metal fibers, ceramic filters, metal filters, honeycombs, and the like.

It is also possible to add a small amount of binder to the catalyst and to use it by extrusion processing into a granular or monolith type. At this time, the catalyst is preferably pulverized uniformly to a particle size of 1 ~ 20㎛ coating or extrusion. When the particle size is less than 1 μm, it may not be economical due to the fine grinding step, and when the particle size is larger than 20 μm, uniformity and adhesion of the coating or extrudates may be reduced.

On the other hand, the form of the catalyst in the present invention is not limited, and various forms such as honeycomb, slate, plate, pellets, etc. are possible.

Comparative Example

Palladium chloride (PdCl ₂ ) or palladium nitrate dihydrate (N ₂ O ₆ Pd? 2H ₂ O) was quantitated 0.5 parts by weight based on 100 parts by weight of the titania support, and dissolved in distilled water at room temperature. At this time, in the case of palladium chloride (PdCl ₂ ), the temperature of distilled water was dissolved after raising the temperature to 60 ℃. Subsequently, the titania support quantified in the dissolved aqueous solution was prepared to form a slurry, and the slurry was then stirred and heated at 70 ° C. using a vacuum evaporator, and dried at a temperature of 80 ° C. to 120 ° C. for at least 24 hours to provide fine pores. The moisture contained was completely removed.

In this case, when palladium chloride (PdCl ₂ ) is used as a palladium precursor, chlorine of the catalyst is excluded in a 30% hydrogen / nitrogen atmosphere at 300 ° C. for 3 hours, and calcined at 400 ° C. for 4 hours in an air atmosphere, and palladium is prepared. When palladium nitrate dihydrate (N ₂ O ₆ Pd.2H ₂ O) containing no chlorine is used as a precursor, it is prepared by applying only a calcination process under an air atmosphere at 400 ° C. for 4 hours.

Example  One

A catalyst was prepared in the same order as in Comparative Example, but after the calcining process, a catalyst was prepared by reducing for 1 hour under a 30% hydrogen / nitrogen atmosphere at a temperature of 500 ° C.

Example  2

A catalyst was prepared in the same manner as in Example 1, except that Example 1 was treated at a temperature of 600 ° C.

Example  3

A catalyst was prepared in the same manner as in Example 1, except that Example 1 was treated at a temperature of 700 ° C.

Example  4

A catalyst was prepared in the same manner as in Example 2, except that Example 2 contained 0.25 part by weight of the palladium precursor with respect to 100 parts by weight of the titania support.

Example  5

A catalyst was prepared in the same manner as in Example 2, except that Example 2 contained 1 part by weight of the palladium precursor with respect to 100 parts by weight of the titania support.

Example  6

A catalyst was prepared in the same manner as in Example 2, except that Example 2 contained 2.5 parts by weight of the palladium precursor based on 100 parts by weight of the titania support.

Example  7

A catalyst was prepared in the same manner as in Example 2, except that 5 parts by weight of the palladium precursor was contained in 100 parts by weight of the titania support.

The above comparative examples and examples are briefly summarized and shown in Table 1 below.

division Manufacturing method Reduction Treatment Temperature (℃) Palladium content (parts by weight) Comparative Example Support → Drying → (Reduction) → Firing - 0.5 Example 1

Support → Drying → (Reduction) → Firing → Reduction 500 0.5 Example 2 600 0.5 Example 3 700 0.5 Example 4 600 0.25 Example 5 600 One Example 6 600 2.5 Example 7 600 5

[ Experimental Example  One]

In order to compare the formaldehyde removal performance with the catalyst according to the embodiment, the formaldehyde removal rate was measured using the catalyst according to the comparative example and the results are shown in Table 2 below. At this time, a mixed gas comprising 20 ppm of formaldehyde, 8% by volume of water, and 21% by volume of oxygen is injected into the reaction column equipped with a catalyst, and the reaction temperature is maintained at 25 ° C to react and generate at a space velocity of 30,000 / hour. The amount of carbon dioxide produced was measured using a non-dispersive infrared gas analyzer (ZKJ-2, Fuji Electric Co.).

division Comparative Example Formaldehyde Removal Rate (%) 0

Referring to Table 2, it can be seen that the catalyst according to the comparative example finished in the calcination process cannot oxidize formaldehyde at all.

[ Experimental Example  2]

In order to compare the formaldehyde removal performance of the catalyst prepared by the reduction treatment after the calcination process with the comparative examples, the catalysts according to Examples 1 to 3 were tested under the same conditions as in Experimental Example 1. At this time, the experiment with varying the space speed to 30,000 ~ 120,000 / hour and the results are shown in Figure 1 and Table 3 below.

division Space speed Example 1 Example 2 Example 3
Formaldehyde Removal Rate (%) 30,000 / hour 100 100 100 60,000 / hour 76 98 81 90,000 / hour 56 88 74 120,000 / hour 41 77 69

Referring to Table 3, at the space velocity 30,000 / hour, all of the catalysts according to Examples 1 to 3 exhibited a formaldehyde removal rate of 100%, and a high space velocity of 60,000 / hour or more for the palladium / titania catalyst reduced at 600 ° C. It can be seen that the formaldehyde removal rate is superior to that of the catalyst treated at 500 ° C and 700 ° C at.

[ Experimental Example  3]

In order to determine the formaldehyde removal performance according to the palladium content in the catalyst prepared by reduction after the calcination process, the catalysts according to Examples 2, 4 and 5 were tested under the same conditions as in Experimental Example 1 and the results are shown in Table 4 below. Indicated. At this time, the space velocity was tested at 90,000 / hour conditions.

division Example 4 Example 2 Example 5 Palladium content (parts by weight) 0.25 0.5 One Formaldehyde Removal Rate (%) 76 88 100

Referring to Table 4, it can be seen that the formaldehyde removal rate increases as the palladium content increases.

[ Experimental Example  4]

In order to determine the effect on the formaldehyde removal rate according to the physicochemical change of the active metal palladium, carbon monoxide-chemical adsorption (CO-chemisorption) for the analysis of the dispersion and specific surface area of the active metal for the catalysts according to Examples 1 to 3 XPS (ESCALAB 201, VG Scientific Co.) analysis for the analysis and oxidation of the active metal was performed and the results are shown in Table 5 and FIG. 2.

division Example 1 Example 2 Example 3 Reduction Treatment Temperature (℃) 500 600 700 Palladium Dispersion (%) 13.32 20.75 14.58 Palladium Specific Surface Area (㎡ / g) 59.37 92.47 64.97

First, referring to Table 5, it can be seen that among the reduced catalysts, palladium in the reduced catalysts at the temperature of 600 ° C. has the highest dispersibility and specific surface area.

In addition, referring to Figure 2, it can be seen that the + divalent palladium is changed to the zero-valent palladium as the reduction temperature increases.

Thus, the catalyst according to the present invention shows that it is possible to change the dispersion degree and specific surface area and the oxidation value of palladium by hydrogen reduction, thereby enhancing the formaldehyde removal rate at room temperature.

[ Experimental Example  5]

In order to determine the carbon monoxide removal capacity of the palladium / titania catalyst according to the present invention, the carbon dioxide removal rate of the catalyst according to Examples 2, 4, 5 and 6 was measured and the results are shown in Table 6 below. At this time, a mixed gas containing 100 ppm carbon monoxide, 8% by volume of water and 21% by volume of oxygen is injected into a reaction column equipped with a catalyst, and the reaction temperature is maintained at 25 ° C. to react at a space velocity of 30,000 / hour and is generated. The amount of carbon dioxide was measured using a non-dispersive infrared gas analyzer (ZKJ-2, Fuji Electric Co.).

division Example 4 Example 2 Example 5 Example 6 Palladium content (parts by weight) 0.25 0.5 One 2.5 Carbon monoxide removal rate (%) 15 54 72 99

Referring to Table 6, it can be seen that the carbon monoxide removal rate increases as the content of palladium, the active metal, increases. It can be seen that the excellent efficacy.

[ Experimental Example  6]

In order to determine the hydrogen removal ability of the palladium / titania catalyst according to the present invention, the hydrogen removal rate of the catalysts according to Examples 6 and 7 was measured and the results are shown in Table 7 below. At this time, the catalyst is subjected to a mixed gas including 1.5 vol% hydrogen, 8 vol% moisture and 21 vol% oxygen, and a mixed gas including 0.1 vol% hydrogen, 8 vol% moisture and 21 vol% oxygen. It is injected into the reaction tower, and the reaction temperature is maintained at 25 ° C. to react at a space velocity of 120,000 / hour, and the composition of the discharged gas is measured by gas chromatography (TCP-HP 6890 PLUS GC, Aglient. Measured.

division Example 6 Example 7 Palladium content (parts by weight) 2.5 5 Hydrogen injection amount (vol%) 1.5 0.1 1.5 0.1 Hydrogen removal rate (%) 100 100 100 100

Referring to Table 7, since the hydrogen removal rate of 1.5% by volume and 0.1% by volume of hydrogen is shown, the palladium / titania catalyst according to the present invention is excellent in removing formaldehyde and carbon monoxide as well as hydrogen removal. You can see that.

On the other hand, only the temperature of the catalyst changed due to the difference in heat transfer rate due to the change in the calorific value and the amount of catalyst during the oxidation of hydrogen, at which time the temperature of the catalyst increased and stabilized While looking at, the maximum temperature and the temperature of the catalyst is shown in Table 8 by measuring the time until the stabilized in the vicinity of the maximum temperature is increased at 25 ℃.

division Example 6 Example 7 Palladium content (parts by weight) 2.5 5 Hydrogen injection amount (vol%) 1.5 0.1 1.5 0.1 Catalyst maximum temperature (℃) 87 32 90 33 Stabilization time (seconds) 180 232 318 498

Referring to Table 8, the maximum temperature of the catalyst varies depending on the concentration of hydrogen and the amount of active metal in the catalyst, but does not rise to a temperature capable of igniting hydrogen, and natural convection may occur due to the temperature rise. These results indicate that the palladium / titania catalyst according to the present invention can be applied to a passive autocatalytic hydrogen recombiner (PAR) system.

Claims (10)

delete delete delete delete Forming a palladium / titania catalyst by sequentially supporting, drying and firing processes using a palladium precursor and a titania support, and further including a reduction process under a reducing gas atmosphere after the firing process, including formaldehyde and carbon monoxide included in air at room temperature And a method for producing a palladium / titania catalyst having a hydrogen removal ability,
The reduction process is carried out by maintaining at a temperature of 500 ~ 700 ℃ 0.5 ~ 5 hours in a furnace of hydrogen atmosphere,
The palladium precursor is included in the content of 2.5 to 5 parts by weight with respect to 100 parts by weight of the support, the hydrogen removal ability is a method for producing a palladium / titania catalyst, characterized in that the hydrogen removal rate measured according to the following method .
[Measurement of hydrogen removal rate]
A mixed gas containing 1.5% by volume of hydrogen, 8% by volume of water, and 21% by volume of oxygen is injected into a reaction column equipped with a catalyst, and the reaction temperature is maintained at 25 ° C to react and discharge at a space velocity of 120,000 / hour. The composition of the gas was measured by gas chromatography (TCP-HP 6890 PLUS GC, Aglient. Co.) to measure the hydrogen removal rate. delete The method of claim 5,
The palladium precursor is palladium chloride (PdCl 2) or palladium nitrate dihydrate (N ₂ O ₆ Pd.2H ₂ O) A method for producing a palladium / titania catalyst, characterized in that. delete The method of claim 5,
The palladium / titania catalyst is a method for producing a palladium / titania catalyst, characterized in that the extrusion process in a granular or monolithic. The method of claim 5,
The palladium / titania catalyst is a method for producing a palladium / titania catalyst, characterized in that the coating on any one structure selected from the group consisting of metal plate, metal fiber, ceramic filter, metal filter and honeycomb.

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