KR100988579B1 - Oxide/Alumina Catalysts with Zirconium Oxide and Tin Oxide for the Preferential Oxidation of Carbon Monoxide and Method for Preparing the Same - Google Patents

Abstract

The present invention is a step up from previous researches using copper oxide and alumina that are stable to heat and moisture, showing an activity in the oxidation reaction of carbon monoxide, and zirconium oxide and tin which actively induces the movement of oxygen to improve the activity of the oxidation reaction. The present invention relates to a selective oxidation catalyst of carbon monoxide having a higher activity by adding an oxide to a copper oxide / alumina catalyst and a method for preparing the same.

The catalyst for the selective oxidation of carbon monoxide of the present invention is prepared by adding zirconium oxide and tin oxide to the copper oxide / alumina catalyst. In particular, the step of dissolving a zirconium precursor and a tin precursor in a solvent and adding alumina to prepare an alumina carrier using an initial impregnation method; And impregnating the alumina carrier into a reaction solution in which a copper precursor is dissolved.

Carbon monoxide, oxidation catalyst, copper oxide alumina catalyst, zirconium precursor, tin precursor, copper precursor

Description

Oxide / Alumina Catalysts with Zirconium Oxide and Tin Oxide for the Preferential Oxidation of Carbon Monoxide and Method for Preparing the Same}

The present invention relates to a copper oxide / alumina catalyst to which zirconium oxide and tin oxide are added for the selective oxidation of carbon monoxide. More specifically, compared to the conventional platinum-supported alumina catalyst, the addition of zirconium oxide and tin oxide facilitates the movement of oxygen, thereby increasing the efficiency of selective oxidation reaction of carbon monoxide, and using low-cost potential metal instead of expensive platinum. And it relates to a highly selective catalytic oxidation of carbon monoxide and a method for producing the same.

Recently, fuel cells have attracted much attention as a way to solve environmental and energy problems. Among them, the polymer electrolyte fuel cell supplies hydrogen gas to the anode, which is the anode, and oxygen gas, to convert the chemical energy of the two reactions into electrical energy. Such a polymer electrolyte fuel cell is a low-temperature fuel cell having a low driving temperature of 100 ° C. or less, and thus has high mobility, and thus, many studies have been conducted.

Meanwhile, hydrogen gas supplied to a fuel cell is difficult to utilize due to safety and storage problems, and thus, hydrogen is introduced through a reforming process rather than directly used. Gasoline or other hydrocarbons that are not electrochemically reactive cannot be used directly as fuels in fuel cells, so they are converted to hydrogen through the reforming process, which is used in fuel cells.

Scheme 1

CH ₄ + H ₂ O → CO + H ₂

By-product carbon monoxide is present in the hydrogen gas obtained through the reforming process, and more than a certain amount of carbon monoxide causes catalyst poisoning in the fuel cell. The water gas conversion process reduces the concentration of carbon monoxide to 1-3 mol% and produces hydrogen.

Scheme 2

CO + H ₂ O → CO ₂ + H ₂

It is very important to reduce the concentration to less than 10 ppm because the platinum-based catalyst of the polymer electrolyte fuel cell is poisoned by carbon monoxide. Therefore, additional selective carbon monoxide oxidation reactions such as the following procedure are essential.

Scheme 3

CO + 1 / 2O ₂ → CO ₂

Currently, as a selective oxidation catalyst of carbon monoxide, a platinum catalyst supported on alumina is mainly used, but in the case of platinum catalyst, an expensive precious metal catalyst having a limited reserve is required, and thus, a catalyst to replace the catalyst is required. Copper oxide among various potential metal oxides has been attracting attention as one of the metal catalysts to replace expensive platinum by showing low price and activity in carbon monoxide oxidation, but has a disadvantage that the activity is significantly lower than platinum catalysts. Various studies are currently underway to use such a potential metal catalyst in carbon monoxide oxidation.

An object of the present invention is a step up from the previous research using copper oxide showing the activity of the oxidation of carbon monoxide and alumina stable to heat and moisture, zirconium oxide to improve the activity of the oxidation reaction by actively inducing oxygen migration And adding a tin oxide to a copper oxide / alumina catalyst to provide a selective oxidation catalyst of carbon monoxide having a higher activity and a method for producing the same.

Another technical problem of the present invention is to provide a method for selectively oxidizing carbon monoxide using the prepared catalyst.

The catalyst for the selective oxidation of carbon monoxide of the present invention is characterized by the addition of zirconium oxide and tin oxide to the copper oxide / alumina catalyst.

Preferably, the supported amount of zirconium oxide and tin oxide is characterized in that 1-10% by weight based on the total weight.

Preferably, the supported amount of copper oxide is characterized in that 1-20% by weight based on the total weight.

In addition, the method for producing a catalyst for the selective oxidation of carbon monoxide of the present invention comprises the steps of dissolving a zirconium precursor and a tin precursor in a solvent and adding alumina to prepare an alumina carrier using an initial impregnation method; And impregnating the alumina carrier into a reaction solution in which a copper precursor is dissolved.

As described above, the carbon monoxide oxidation catalyst of the present invention is not economically expensive noble metals such as platinum and gold, but is more economical by using relatively inexpensive potential metals, and the addition of oxygen due to the addition of zirconium oxide and tin oxide There is an advantage of having a high activity compared to the conventional catalyst in converting carbon monoxide to carbon dioxide by actively inducing migration.

In addition, in the selective oxidation of carbon monoxide using the catalyst, it has a very good performance under the reaction conditions described in the present invention.

Hereinafter, the carbon monoxide oxidation reaction catalyst according to the present invention will be described in more detail with reference to Examples.

The catalyst of the present invention is prepared using a composite carrier utilizing zirconium oxide and tin oxide based on the active material described below and an alumina carrier which is a basic carrier.

Zirconium oxide and tin oxide added to the zirconium oxide and tin oxide prepared using the above materials can be charged to the reactor to perform the selective oxidation of carbon monoxide at various temperatures of 100 to 250 ℃. If the reaction temperature is less than 100 ℃ is not preferable because of the low activity, if it exceeds 250 ℃ in terms of energy efficiency and deactivation and stability of the catalyst is not preferable. In the case of the catalyst of the present invention, carrying out the reaction at 190 ° C is most preferred in terms of catalyst activity and stability.

The concentration of carbon monoxide and oxygen gas to be treated is suitably 5 v / v% or less of the gas to be treated, and the concentration can be properly adjusted by mixing with nitrogen, helium or argon gas as a carrier gas. When the selective oxidation of carbon monoxide is carried out using the catalyst according to the present invention, carbon monoxide and oxygen react selectively on the surface of the catalyst to produce carbon dioxide, which does not require additional removal process.

<Active substance>

Precious metals such as platinum, rhodium, ruthenium and gold are very efficient at converting carbon monoxide to carbon dioxide. However, given the limited supply of these precious metals and economic problems, it is difficult to commercialize them. Therefore, it is necessary to develop a catalyst that can replace them. Potential metals are cheaper than precious metals and are very economically superior. Among them, copper oxide is known to be active in the oxidation of carbon monoxide, but the activity of carbon monoxide oxidation is not as good as that of the noble metal catalyst. In order to increase the catalytic activity of copper oxide, a catalyst was prepared using the following zirconium oxide and tin oxide.

In the present invention, a catalyst was prepared by selecting copper oxide as the active material. The supported amount of copper oxide, which is the active substance, can be variously accessed in an amount of 1 to 40% by weight based on the total weight of the catalyst, but when it is less than 1% by weight, the active point is too small to provide sufficient catalytic activity, and 20% by weight is excessive. In the case of calcination process, copper oxide is caused to aggregate, so it is not sufficient to satisfy the activity. Therefore, it is preferable to prepare a catalyst carrying copper oxide in the range of 1 to 20% by weight.

<Base carrier>

The carrier is mainly used to disperse the active material to increase the contact between the metal surface active point and the reactant, and metal oxides such as alumina, silica, and titania are mainly used. Since alumina and titania, which have a strong mutual bonding force between the carrier and the active material, induce high dispersion of the active material, they are highly useful as carriers, and silica can produce a carrier having a high surface area.

In the present invention, a strong bond between the carrier and the active material reduces the amount of sintering of the active material and uses heat stable alumina. Alumina has various phases such as α series, β series, γ series, δ series, χ series, η series, θ series and κ series depending on the structure and manufacturing method. In the present invention, it is intended to use γ-alumina having a large surface area and excellent thermal stability.

<Composite carrier>

The present invention provides a composite catalyst in which a zirconium oxide and tin oxide are supported on alumina to facilitate oxygen migration and easily induce diffusion. Zirconium oxide and tin oxide are prepared at 1-10% by weight based on the total weight of the catalyst.

The present invention provides a method for producing a catalyst in which copper oxide is supported on an alumina composite carrier of zirconium oxide and tin oxide as in the following procedure.

Copper, zirconium and tin are very stable at room temperature in the solid state, making it difficult to mix with other materials. Therefore, in the present invention, these precursors were reacted to produce a desired form. Alumina was made from Degussa. The copper precursor used Cu (NO ₃ ). 2.5H ₂ O from Sigma Aldrich at 1-20% by weight. Zr precursor was used for Zr ℃ l ₂ · 8H ₂ O in the Sigma-Aldrich product with 1-10% by weight. The tin precursor used SnCl ₂ .2H ₂ O from Sigma Aldrich at 1-10% by weight.

Each metal precursor presented was dissolved in solvent water, impregnated with alumina, dried, and then calcined to remove impurities.

After the hydration reaction of the above step, the resultant is heat-treated at 80-120 ° C. to evaporate the solvent, and then oxidizes the metal precursor at 300-700 ° C. under air conditions. If the oxidation temperature is less than 300 ℃, the problem that the impurities of the metal precursor is not removed and there is a problem that the sufficient oxidation does not occur, the sintering modernization of the metal particles occurs above 700 ℃ to reduce the active area for the selective oxidation reaction of carbon monoxide It is not suitable.

Hereinafter, the catalyst production and analysis of the present invention through the examples, the reaction results will be described in more detail. These examples are only for illustrating the present invention, and the protection scope of the present invention is not limited by these examples.

Example 1 Preparation of Complex Catalyst

The catalyst of the present invention was prepared by dissolving a zirconium precursor and a tin precursor in water as a solvent, and then using 1 g of commercial alumina, using an initial impregnation method. Water present in the reactant was removed through a drying process of 100 ℃ and then calcining at 550 ℃ to remove the precursor impurities and to prepare an oxide catalyst. The sample obtained through this process was impregnated into a reaction solution in which a copper precursor was dissolved. Copper oxide / alumina catalyst to which zirconium oxide and tin oxide were added through a drying process and a calcination process at 550 ° C. was prepared.

In the case of alumina, alumina having various structures can be produced according to the manufacturing method. In the present invention, it is possible to maintain a γ-alumina structure having a large specific surface area and good thermal stability, and a firing process is performed at 550 ° C. in order to suppress sintering of the active metal material.

Comparative Example

A catalyst in which only copper oxide was supported on alumina without a zirconium oxide and tin oxide was prepared in order to show smooth oxygen migration and diffusion when the zirconium oxide and tin oxide were added. Prepared in the same manner as in Example 1, but proceeded from the step of dissolving the copper precursor to prepare a catalyst through a single firing process.

Experimental Example 1 Analysis of Reduction Amount According to Temperature of Prepared Catalyst

In order to confirm the surface chemical properties of the catalyst specified in the present invention, a reduction amount analysis was performed with temperature. As shown in FIG. 1, it is possible to grasp the tendency of the catalyst by increasing the temperature by 5 ° C. per minute from the room temperature and the reduction start temperature and the reduction amount. Hydrogen gas as a reaction gas and nitrogen gas as a carrier gas were injected at a constant ratio of 1% by volume to 9% by volume.

The peak appearing before 200 ° C. shown in FIG. 1 represents the reduction of copper oxide distributed on the surface, and the peak appearing at 230 ° C. is the reduction of copper oxide present therein. The zirconium oxide and tin oxide supported catalysts move to lower temperatures in both surface and internal reduction compared to the catalysts supported only with copper oxide, indicating that the zirconium oxide and tin oxide supported catalysts are easier to release oxygen than those made with copper oxide alone. it means.

Experimental Example 2 Analysis of Oxidation Amount According to Temperature of Prepared Catalyst

2 is a result of analyzing the amount of oxidation according to the temperature of the copper oxide / alumina catalyst to which zirconium oxide and tin oxide is added according to the present invention. It is possible to characterize the catalyst through the temperature and the amount of oxidation start oxidation by increasing the temperature by 5 ℃ per minute from room temperature. Oxygen gas, which is a reaction gas, and helium gas, which is a carrier gas, were mixed and flowed at a ratio of 1% by volume to 9% by volume. Since the oxidation of the filament may occur at high temperature when oxygen gas is flowed, most of the analyzes are carried out by reducing amount analysis method according to temperature rather than oxidation amount analysis method according to temperature, but in order to obtain more accurate results in the present invention. Oxidation amount analysis was performed according to temperature.

As shown in Fig. 2, the catalyst supporting zirconium oxide and tin oxide is oxidized at a higher temperature than the catalyst supporting only copper oxide. These results indicate that the oxygen adsorption of the zirconium oxide and tin oxide supported catalysts is lower than that of the copper oxide only catalysts.

Experimental Example 3 Conditions for Selective Oxidation of Carbon Monoxide

In the present invention, selective oxidation was performed using the catalysts prepared in Example 1 and Comparative Example 1. First, the reactor was filled with a catalyst and a reactor filled with a catalyst was installed in a heating furnace capable of controlling the temperature to 1000 ° C. And a thermocouple for measuring the temperature of the reactor and a power supply for temperature control was connected to the reactor. As described above, the experimental system for the selective oxidation of carbon monoxide was configured, and the selective oxidation of carbon monoxide was performed.

On the other hand, carbon monoxide, oxygen and hydrogen are mixed with a carrier gas such as nitrogen, helium or argon 1% by volume each. The concentration was adjusted to 1% by volume and 50% by volume, and selective oxidation of carbon monoxide was performed while gradually increasing the temperature of the reactor.

The catalyst according to the present invention performs oxidation of carbon monoxide in a temperature range of 50 ° C to 300 ° C, but substantial generation of carbon dioxide proceeds in a range of 100 ° C to 200 ° C.

The catalyst of the present invention was analyzed using gas chromatography to measure the concentration of gas exiting after the selective oxidation of carbon monoxide. The reaction rate of carbon monoxide to carbon dioxide was measured by detecting the reactant oxygen, carbon monoxide, hydrogen gas and carbon dioxide as a product while injecting helium as a carrier gas at a constant flow rate.

3 is a graph of oxidation reaction of carbon monoxide according to the temperature of the catalyst according to the present invention. The carbon monoxide oxidation activity is excellent in the order of a catalyst supporting only copper oxide on alumina, a catalyst additionally supporting tin oxide, and a catalyst additionally supporting zirconium oxide. As shown in FIG. 1 and FIG. 2, the results show that the catalyst is easily reduced at a lower temperature in view of Experimental Examples 1 and 2, which are easily reduced at lower temperatures and oxidized at higher temperatures. Oxidation at higher temperatures means easier release of oxygen and increased reactivity.

Thus, the copper oxide / alumina catalyst with the addition of zirconium oxide and tin oxide selectively oxidizes more carbon monoxide than the catalyst supporting only copper oxide.

As described in the experimental example of the present invention, the catalyst added with the zirconium oxide and tin oxide prepared by the present invention showed a high activity in converting carbon monoxide to carbon dioxide by actively inducing the movement of oxygen. Reduction of copper oxide was observed at lower temperatures and copper was oxidized at higher temperatures when compared to a catalyst prepared by supporting only copper oxide on alumina. When it is prepared by the addition of zirconium oxide and tin oxide, the binding of the active material and oxygen is weakened, and the oxygen is more easily discharged to increase the production of carbon dioxide. Therefore, the carbon monoxide selective oxidation reaction using the catalyst demonstrates excellent performance.

1 is a graph of reduction analysis on temperature change of a copper oxide composite catalyst carrying zirconia oxide and tin oxide in alumina according to the present invention.

2 is a graph of the oxidation analysis of the temperature change of the copper oxide composite catalyst carrying zirconia oxide and tin oxide in alumina according to the present invention.

Figure 3 is a graph of the oxidation of carbon monoxide according to the temperature of the catalyst according to the present invention.

Claims (7)

A copper oxide / alumina complex catalyst for selective oxidation of carbon monoxide, wherein zirconium oxide and tin oxide are added to a copper oxide / alumina catalyst. The copper oxide / alumina composite catalyst for selective oxidation of carbon monoxide according to claim 1, wherein the supported amount of zirconium oxide is 1-10% by weight based on the total weight. The copper oxide / alumina complex catalyst for selective oxidation of carbon monoxide according to claim 1, wherein the supporting amount of tin oxide is 1-10% by weight based on the total weight. The copper oxide / alumina complex catalyst for selective oxidation of carbon monoxide according to claim 1, wherein the supported amount of copper oxide is 1-20% by weight based on the total weight. The copper oxide / alumina complex catalyst for selective oxidation of carbon monoxide according to claim 1, wherein the alumina is γ-alumina. Dissolving a zirconium precursor and a tin precursor in a solvent, and adding alumina to prepare an alumina carrier using an initial impregnation method; Method for producing a copper oxide / alumina composite catalyst comprising the step of impregnating the alumina carrier into a reaction solution in which a copper precursor is dissolved. A method of selectively oxidizing carbon monoxide by supplying carbon monoxide, oxygen, hydrogen to a reactor filled with the copper oxide / alumina complex catalyst of any one of claims 1 to 5 and reacting at a temperature of 190 ° C.

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