KR100963778B1 - Manufacture method of catalyst for the carbon dioxide reforming of methane, and its reforming reaction - Google Patents

Abstract

The present invention relates to a method for preparing a carbon dioxide reforming reaction catalyst of methane and a reforming method using the same. The present invention comprises a first step of preparing a catalyst by supporting a silica mesoporous molecular sieve carrier in an aqueous solution in which nickel nitrate is dissolved, followed by drying and firing after impregnation treatment; And a second step of further supporting the catalyst prepared in the first step in an aqueous solution of a cocatalyst, drying and calcining. According to the present invention, since the deterioration of activity due to coke is prevented, there is an advantage in that the conversion of methane and carbon dioxide and the yield of mixed gas can be stably maintained.

Reforming reaction, catalyst, coke

Description

Manufacture method of catalyst for the carbon dioxide reforming of methane, and its reforming reaction

The present invention relates to a method for preparing a carbon dioxide reforming reaction catalyst of methane and a reforming method using the same, and more particularly, to a carbon dioxide reforming reaction catalyst of methane which can be usefully used in synthetic reactions requiring a low H 2 / CO ratio. It relates to a manufacturing method and a reforming method using the same.

Gases that affect global warming include carbon dioxide, chlorofluorocarbons (CFCs), nitrous oxide (N ₂ O), and methane (CH ₄ ), with carbon dioxide accounting for about 55% or more.

As a result, efforts to regulate carbon dioxide emission have been expanded internationally, and development of related process technology or alternative energy that improves energy efficiency, and recycling of carbon dioxide is important.

Recycling carbon dioxide is a method of reacting carbon dioxide with methane to produce a mixture of hydrogen and carbon monoxide. Methane, which has abundant reserves and occupies 80% of natural gas, is the subject of active research in that it can react with carbon dioxide to obtain high value-added syngas as a chemical.

The reforming reaction of methane by carbon dioxide is shown in Scheme (1) below.

CH ₄ + CO ₂ → 2H ₂ + 2CO scheme (1)

CH ₄ + H ₂ O → 3H ₂ + CO scheme (2)

CO ₂ + H ₂ → CO + H ₂ O scheme (3)

2CO → C + CO₂ Scheme (4)

CO + H ₂ → C + H ₂ O Scheme (5)

CH₄ → C + 2H₂ Scheme (6)

CO₂ → C + O₂ Scheme (7)

Here, scheme (2) is a steam reforming scheme. As shown in the above reaction scheme, the carbon dioxide reforming reaction of the reaction formula (1) has a characteristic that the molar ratio of H 2 / CO of the synthesis gas obtained is lower than that of the steam reforming reaction and is an endothermic reaction.

In addition, the hydrogen generated in the reaction formula (1) reacts with carbon dioxide, which is a reactant, and the reverse water gasification of the reaction formula (3) proceeds. When the reverse water gasification proceeds, water is generated. Accordingly, the steam reforming reaction of Scheme (2) also participates in the reforming reaction of carbon dioxide.

Reaction enthalpy in the case of Scheme 1 is a △ H ° ₂₉₈ = 247.44kJ / mol to the enthalpy of the reaction formula _{(2) △ H ° 298 =} 206.28kJ / slightly larger than endothermic mol. Standard free energy change of carbon dioxide reforming reaction by methane is ΔG ^o above 640 ° C. <0 is known, the side reaction of water gasification reaction (Water Gas Shift Reaction, the reverse reaction of the reaction formula (3)) is 815 ℃, Boudouard reaction of Scheme 4 is △ G ^o below 710 ℃ <0. Therefore, in order to suppress side reactions in the reforming reaction of carbon dioxide and to convert to syngas, a high temperature of 700 ° C. or more is required.

And, depending on the reaction conditions, the carbon precipitation reaction corresponding to the reaction formulas (4) to (7) proceeds to produce coke, so that the catalyst may be deactivated.

The carbon dioxide reforming reaction has been focused on researches on the selection of catalysts and carriers and on the evaluation of the influence of reaction conditions across the country and abroad.

Carbon dioxide reforming catalysts can be broadly divided into two types: nickel-supported catalysts and noble metal catalysts such as platinum, palladium, and rhodium.The supported catalysts show good activity and stability but are economically unlikely to be industrialized. It is preferable to use the nickel-supported catalyst system which is widely used as a catalyst.

However, in the case of nickel catalyst, as described above, there is a problem such as resistance to coke formation, deactivation due to phase change when reacting at high temperature, sintering of metal components, etc. This is expected to accelerate.

The biggest problem with carbon dioxide reforming is the deactivation of the catalyst due to the deposition of carbon over time.

Nickel-based catalysts tend to deposit carbon more easily than precious metal catalysts. The use of precious metal catalysts shows little or no deactivation. However, since there is a practical problem due to the high catalyst price, studies related to the improvement of the nickel catalyst are required to prevent deactivation by carbon deposition.

The present invention is to solve the conventional problems as described above, the object of the present invention is to produce a catalyst using nickel, which is relatively cheaper than the noble metal catalyst while ensuring safety, can prevent the deactivation by carbon deposition It is to provide a method for preparing a carbon dioxide reforming reaction catalyst of methane and a reforming method using the same.

The present invention is to solve the conventional problems as described above, the present invention comprises a first step of supporting the silica mesopore molecular sieve carrier in an aqueous solution of nickel nitrate dissolved, dried after the impregnation treatment and firing; And a second step of further supporting the catalyst prepared in the first step in an aqueous solution of a cocatalyst, drying and calcining.

In the first step, the nickel is supported on the silica mesopore molecular sieve carrier in the range of 5-15 wt%.

In the second step, the promoters are calcium and potassium as basic metal oxides.

The calcium and potassium are simultaneously supported in the range of 1 ~ 7wt% on the catalyst prepared in the first step.

The nickel is supported on the silica mesoporous molecular sieve carrier in the range of 5-15 wt%, and the promoters are potassium and calcium.

A filling step of filling the reactor prepared by the above method into a reactor; A dilution step of diluting the reaction gas methane and carbon dioxide with helium after the filling step and a reaction step of supplying the methane and carbon dioxide to the reactor after the dilution step for reforming reaction.

In the dilution step, the methane, carbon dioxide and helium are mixed in a molar ratio of 1: 1: 3.

In the reaction step, the temperature of the reactor is adjusted to 500 ~ 700 ℃ range.

According to the present invention has the following effects.

First, since the present invention uses a wide surface area silica mesoporous molecular sieve as a carrier, it is possible to evenly distribute the nickel to prevent carbon accumulation by methane.

Second, in the present invention, the coke of calcium and potassium is additionally applied, so that the accumulated coke can be converted into carbon monoxide.

Therefore, using the carbon dioxide reforming reaction catalyst of methane according to the present invention can prevent catalyst deactivation by coke deposition. As a result, the carbon resistance is improved, thereby improving the stability of the methane and carbon dioxide conversion and the yield of the mixed gas.

Hereinafter, a method for preparing a carbon dioxide reforming reaction catalyst of methane according to the present invention and a preferred embodiment of the reforming method using the same will be described in detail.

The catalyst of the present invention is prepared by supporting nickel on a silica mesoporous molecular sieve (ZSM-5, MCM-41, KIT-1) carrier and adding basic metal oxides of calcium and potassium.

Silica mesoporous molecular sieves (ZSM-5, MCM-41, KIT-1) carriers serve to disperse nickel evenly with a large surface area and well developed pore structure. In addition, the silica-based molecular sieve carrier has a high adsorption capacity for carbon dioxide. This prevents the accumulation of carbon by methane, which favors the reforming reaction of carbon dioxide.

Nickel is preferably supported on the mesopore molecular sieve in the range of 5-15 wt%, and more preferably 5-10 wt%. This is to increase the conversion rate of methane and carbon dioxide. When it is loaded below 5wt%, the yield of carbon monoxide is low, and when it exceeds 15wt%, the conversion rate of methane and carbon dioxide increases over time, but the yield of carbon monoxide is drastically reduced by coke. Because.

The yield of carbon monoxide is highest when the nickel loading is 10 wt% and then decreases. However, the reduced carbon monoxide yield is partly compensated by the addition of basic metal oxides of calcium and potassium. However, considering the high price of nickel, the range of loading is limited to 15wt%.

Potassium and calcium are added as cocatalysts to reduce coke and increase the binding of nickel. Calcium and potassium increase in temperature as 2CO → C + CO ₂ Reaction and CO + H ₂ → increases the reverse reaction rate of C + H ₂ O to convert the accumulated coke to carbon monoxide

Acidic carbon dioxide is strongly adsorbed by the basic promoter to cover most of the surface, thereby inhibiting excessive dehydrogenation of methane on nickel and preventing coke formation. This is because the coke formed by the carbon dioxide reforming reaction of methane is not a type of encapsulation that surrounds the nickel and blocks the active site, but a single crystal that grows in one direction with little direct influence on the active site of the catalyst.

The basic metal oxide of calcium and potassium is preferably added in the range of 1 ~ 7wt%. This is because the addition of 1 to 7wt% shows stable conversion of methane or carbon dioxide and increased yield of carbon monoxide. And, if it exceeds 7wt%, the yield of carbon monoxide decreases below the reference point. The basic metal oxides of calcium and potassium show stable conversion of methane or carbon dioxide and the highest yield of carbon monoxide when 3wt% is added.

Next, the manufacturing method of the carbon dioxide reforming reaction catalyst of methane which consists of the above-mentioned component is demonstrated.

In the present invention, nickel is mixed at various weight ratios, dried and calcined at appropriate temperature conditions, and potassium and calcium are added thereto as cocatalysts to prepare a carbon dioxide reforming reaction catalyst of methane.

A method for preparing a carbon dioxide reforming reaction catalyst of methane includes the first step of preparing a catalyst by supporting a silica mesoporous molecular sieve carrier in an aqueous solution of nickel nitrate, drying, and sintering after impregnation; And a second step of baking the catalyst prepared in the first step by further supporting the calcium oxide and the potassium oxide, drying and calcining.

In the first step, the silica mesoporous molecular sieve carrier is prepared by impregnating nickel at 60 ° C. using ethanol instead of distilled water in consideration of hydrothermal stability. The amount of nickel supported is prepared in the range of 5-15 wt%, and calcium and potassium oxide are added in the range of 1-7 wt.

Next, the reforming method using the carbon dioxide reforming reaction catalyst of methane which consists of the above-mentioned component is demonstrated.

The reforming method using the catalyst of the present invention includes a filling step of filling the catalyst into the reactor; A dilution step of diluting the reaction gas methane and carbon dioxide with helium after the filling step; and a reaction step of supplying the methane and carbon dioxide diluted in the dilution step to the reactor and reforming the reaction at a predetermined temperature.

The temperature is preferably in the range of 500 to 700 ° C. This is because the conversion of methane and carbon monoxide is low when the temperature of the reactor is less than 500 ° C., and the conversion of methane and carbon monoxide is excellent when it exceeds 700 ° C., but it is not preferable in terms of energy efficiency.

In the reforming method according to the present invention, carbon dioxide and methane are diluted with helium to prevent reactor blockage due to decomposition of methane and dissociation of carbon monoxide. At this time, methane: carbon dioxide: helium is mixed at 1: 1: 3. This is because the yield of carbon monoxide shows the maximum value when the molar ratio of carbon dioxide and methane is 1: 1.

Hereinafter, the operation of the above-described carbon dioxide reforming reaction catalyst of methane and its preparation method will be described in detail with reference to the following examples.

(Example)

1. Preparation of Carbon Dioxide Reforming Catalyst of Methane

The various carriers of alumina (Al ₂ O ₃ ), lanthanum (LaO ₃ ), ZSM-5 and silica mesopore molecular sieves were immersed in an aqueous solution of nickel nitrate and a rotary evaporator was used. Stirred slowly at &lt; RTI ID = 0.0 &gt; Thereafter, moisture was evaporated in a weak vacuum to prepare a nickel-supported catalyst by impregnation. At this time, the carrier of the pure silica mesopore molecular sieve was prepared by impregnating the catalyst at 60 ° C. using ethanol instead of distilled water in consideration of hydrothermal stability.

All catalysts prepared by the above method were dried at 120 ° C. in a vacuum oven for 12 hours, heated to 550 ° C. at a rate of 4.5 ° C./min while blowing nitrogen (N ₂ ), and then fired in an air atmosphere for 4 hours. .

Nickel loading was prepared in the range of 5 wt% to 15 wt%, and calcium and potassium oxide were added in the range of 1 wt% to 7 wt% as a promoter.

In order to support the cocatalyst, nickel was firstly supported according to each content, followed by drying and calcining, followed by further supporting calcium oxide and potassium oxide, followed by drying for 12 hours, and then firing for 4 hours.

2.Reforming Reaction Using Methane Carbon Dioxide Reforming Catalyst

All the catalysts described above are reduced for 3 hours in a hydrogen atmosphere of 700 ° C. before the reaction, and then the reaction is performed under atmospheric pressure.

Catalytic reaction uses a quartz fixed bed reactor 10. The molar ratio of the reaction gas methane and carbon dioxide is adjusted to 1: 1, diluted with helium, and reacted at 500 to 700 ° C.

The reaction temperature is controlled using a temperature controller 11 connected to a thermocouple installed in the catalyst bed inside the reactor. The flow rate of methane, carbon dioxide, and helium, which is a carrier gas, was controlled by a flow regulator (MFC) 13.

The reforming reaction of methane is caused by pressure in the reactor due to coke deposited due to decomposition of methane at the active site of reduced nickel metal, dissociation of carbon monoxide, etc., or severe blockage of the reactor can cause methane and carbon dioxide to helium. Diluted reaction gas was introduced and reacted.

The ratio of methane, carbon dioxide, and helium was maintained at 1: 1: 3, and experiments were made with varying molar ratios. To see the effect of the molar ratio of the reactants, the molar ratio of methane to carbon dioxide was adjusted in the range of 0.3 to 3, and the space velocity of the reaction gas was adjusted to 20,000 to 80,000 l / kg · h.

Reaction products were analyzed using a gas analyzer (GC) (15) and helium and nitrogen were used as carrier gas for silica and Porapak Q columns, respectively. The specific surface area of the catalyst was obtained from the nitrogen adsorption isotherm obtained after pretreatment in vacuo for about 3 hours at a temperature of 340 ° C. X-ray diffraction analysis was performed to determine the state of the carrier before and after the preparation of the catalyst. Scanning electron microscope was used to determine the coke shape after the catalytic reaction, and the differential weight gravimetric (TG-DTA) analysis was used to heat the catalyst used for the reaction to 700 ° C. at a rate of 10 ° C./min, accompanied by weight loss and exothermic peaks. The degree of formation of the coke was compared.

And, the reforming reaction of the catalyst prepared and analyzed by the above-described process will be described as each experimental example.

Experimental Example 1 In order to confirm the influence of the carrier in the reforming reaction of the catalyst prepared by the example, the following experiment was performed using the reactor shown in FIG.

Experimental conditions and results are shown in Table 1 below.

Table 1 shows the results of carbon dioxide reforming reaction experiments of a catalyst prepared by supporting 5 wt% nickel on various carriers and ICI 46-1, which is a commercial nickel supported catalyst.

catalyst

S _BET (m ² / g)
Conversion rate (%) Yield (%) CH ₄ CO ₂ CO 0.5h 4h 0.5h 4h 0.5h 4h Ni / AL ₂ O ₃ 270.12 53 45 62 47 45 42 Ni / La ₂ O ₃ 16.44 61 56 70 67 47 42 ICI46-1 28.58 75 55 76 71 53 48 Ni / ZSM-5 310.69 75 73 76 73 57 57 Ni / MCM-41 798.01 74 75 76 76 59 59 Ni / KIT-1 815.87 75 76 76 76 61 61

Experimental conditions [T = 650 ℃, CH ₄ : CO ₂ : He = 1: 1: 3, Space velocity (F / W) = 40,000 1 / kg · h, Ni loading: 5wt%]

As a result, the conversion rate of methane and carbon dioxide of the nickel catalyst supported on the silica mesopore molecular sieve such as Ni / ZSM-5, Ni / MCM-41, Ni / KIT-1 was Ni / Al ₂ O ₃ , Ni / La ₂ O ₃ , better than ICI 46-1, it was found that the carbon monoxide yield is high. In addition, it can be seen that the catalyst supported on the silica mesopore molecular sieve shows stable conversion even if the reaction time is longer.

Experimental Example 2 In order to confirm the effect of the nickel loading in the reforming reaction of the catalyst prepared according to the example, the following experiment was performed using the reactor shown in FIG.

Experimental conditions and results are shown in Table 2 below.

Table 2 shows the results of the reaction experiment at 650 ℃ and 700 ℃ while changing the amount of nickel supported.

Temperature (℃)
Ni loading amount (wt%)
% Conversion yield(%) CH ₄ CO ₂ CO
700



3 71 70 60 5 78 76 63 7 83 84 64 10 87 88 67 12 88 89 64 15 90 91 63 17 92 93 61
650

3 70 68 58 5 75 76 60 10 77 77 61 15 78 82 58 17 80 83 56

Same conditions at the time of experiment [CH ₄ : CO ₂ : He = 1: 1: 3, space velocity (F / W) = 40,000 1 / kg · h]

As a result, as the loading of nickel increased up to 15%, the total amount of nickel, the active site, increased, and the conversion rate of methane and carbon dioxide increased constantly. The yield of carbon monoxide was highest when the nickel loading was 10wt%, and it was found that when the nickel was more than 10wt%, it gradually decreased due to the coke formed rapidly over time.

Experimental Example 3 In order to confirm the effect of the addition of the basic promoter in the reforming reaction of the catalyst prepared in Example, the following experiment was conducted using the reactor shown in FIG.

Experimental conditions and results are shown in Table 3 below.

Table 3 shows the results of the modification reaction experiments varying the amount of basic promoter added.

catalyst % Conversion yield(%) CH ₄ CO ₂ CO Ni / KIT-1 87 90 67 Ni / Ca, K 1wt% / KIT-1 88 92 71 Ni / Ca, K 3wt% / KIT-1 87 92 74 Ni / Ca, K 5wt% / KIT-1 86 92 70 Ni / Ca, K 7wt% / KIT-1 85 93 70 Ni / Ca, K 9wt% / KIT-1 85 92 68

Experimental conditions [T = 700 ℃, CH ₄ : CO ₂ : He = 1: 1: 3, Space velocity (F / W) = 40,000 1 / kg · h, Ni loading: 10wt%]

To determine the exact effect of the promoter, temperature and nickel loadings were tested under conditions of stable conversion of methane or carbon dioxide and highest yield of carbon monoxide.

As a result of comparing the activity of nickel and nickel-supported catalysts with calcium (Ca) and potassium (K) oxides, the amount of calcium (Ca) and potassium (K) oxides up to 1 ~ 7wt% was increased. When a stable conversion of methane or carbon dioxide and the yield of carbon monoxide increased. In particular, the loading of calcium and potassium showed the highest yield of carbon monoxide at 3wt%.

.

In Experimental Example 1, from the results of Experimental Example 3, a catalyst in which 10 wt% nickel was supported on a silica mesoporous molecular sieve support and 3 wt% of calcium and potassium was further supported in the carbon dioxide reforming reaction. Based on this, the effect of the change in the reaction temperature, the molar ratio of the reactants and the space velocity on the catalytic activity was tested through Experimental Example 4.

Experimental Example 4: In order to confirm the reforming reaction characteristics of the catalyst according to the reaction conditions when reacted for a long time based on the conditions derived from the results of Experimental Example 3 in Experimental Example 1, the reaction temperature, Experiments were carried out with varying conditions of molar ratio and space velocity of the reactants.

Carbon dioxide reforming reaction of methane was tested under the conditions of Table 4, and the results are shown in the graph of FIG.

Ni loading amount (wt%) Support amount of calcium and potassium (wt%) F / W 1 / kg CH ₄ : CO ₂ : He 10 3 40,000 1: 1: 3

As a result, the carbon dioxide reforming reaction of methane is a severe endothermic reaction, the conversion rate increases as the reaction temperature increases. And CH ₄ → C + 2H ₂ The reaction is favored by forward reaction, with 2CO → C + CO ₂ and CO + H ₂ ¡Æ since the reaction of C + H ₂ O is favorable, the degree of coke formation is affected by the difference in the rates of the three reactions.

Also through the experimental results of Figure 2 it can be seen that as the reaction temperature increases the conversion of methane and carbon dioxide increases. In addition, the values are approximated to the thermodynamic equilibrium conversion at temperatures above 650 ° C.

In case of excess carbon dioxide than methane, the conversion rate was almost 100% compared with the relatively low amount of the substance, and the excess amount decreased. Accordingly, as the ratio of methane to carbon dioxide increases, the conversion rate of methane decreases and the conversion rate of carbon dioxide increases. The yield of hydrogen and carbon monoxide was maximum when the molar ratio of reactants was 1: 1.

     Table 5 shows the results of the carbon dioxide reforming reaction of methane with the change of space velocity. Here, the space velocity per hour is calculated as the inflow rate of the total reactant relative to the weight of the unit catalyst. The space velocity changed the total flow rate while maintaining the reaction temperature at 700 ° C. and the catalyst at 0.3 g. Space velocity
(1 / kg · h) % Conversion yield(%) CH ₄ CO ₂ CO 20,000 93 94 80 40,000 87 92 74 60,000 83 86 65 80,000 81 83 62

Experimental conditions [T = 700 ℃, CH ₄ : CO ₂ : He = 1: 1: 3, W = 0.3g, Ni loading: 10wt%, calcium and potassium loading: 3wt%]

As a result, as the space velocity increases, as the reaction time of the reaction gas shortens with the catalyst, the conversion rate of methane and carbon dioxide decreases and the yield of carbon monoxide decreases.

Carbon dioxide reforming reaction of methane was tested under the conditions of Table 6, and the results are shown in the graph of FIG. Table 6 shows that the reaction was continuously performed for about 20 hours to determine the change in activity according to the reaction time of the Ni / Ca / K / KIT-1 catalyst.

Reaction temperature (℃) CH ₄ : CO ₂ : He Space speed (1 / kg · h) Ni loading amount (wt%) Support amount of calcium and potassium (wt%) 700 1: 1: 3 40,000 10 3

As a result, it was confirmed that the conversion rate and the carbon monoxide yield of a certain reactant were continuously maintained.

Within the scope of the basic technical idea of the present invention, many other modifications are possible to those skilled in the art, and the scope of the present invention should be interpreted based on the appended claims. will be.

1 is a schematic configuration diagram of an apparatus for realizing a reforming reaction using a carbon dioxide reforming reaction catalyst of methane according to the present invention.

Figure 2 is a graph showing the conversion of methane and carbon dioxide and the yield of carbon monoxide according to the reaction temperature of the results of Table 4 experiment.

3 is a graph showing the conversion of methane and carbon dioxide and the yield of carbon monoxide over time as a result of the experiment of Table 6.

Explanation of symbols on the main parts of the drawings

10: quartz fixed bed reactor 11: temperature controller

13: Flow controller (MFC) 15: Gas analyzer (GC)

Claims (8)

A first step of preparing a catalyst by supporting a silica mesoporous molecular sieve carrier in an aqueous solution in which nickel nitrate is dissolved, drying, and calcining after impregnation; And a second step of additionally supporting the catalyst prepared in the first step in the cocatalyst aqueous solution, and drying and firing the same. The nickel is supported on the silica mesopore molecular sieve carrier in the range of 5-15 wt%, The promoters are calcium and potassium as basic metal oxides, The calcium and potassium is a method for producing a carbon dioxide reforming reaction catalyst of methane, characterized in that supported on the catalyst prepared in the first step in the range of 1 ~ 7wt%. delete delete delete delete A filling step of filling the reactor prepared by the method of claim 1 into a reactor; A dilution step of diluting the reaction gases methane and carbon dioxide with helium after the filling step; A reaction step of reforming and supplying methane and carbon dioxide diluted in the dilution step to the reactor; In the dilution step, Methane, carbon dioxide, and helium are mixed at a molar ratio of 1: 1: 3, In the reaction step, Reforming method using a carbon dioxide reforming reaction catalyst of methane, characterized in that the temperature of the reactor is maintained in the range of 500 ~ 700 ℃. delete delete

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