KR100891903B1 - Nickel catalysts supported on alumina-zirconia oxide complex for steam reforming of liquefied natural gas and preparation methods therof - Google Patents

Abstract

Nickel catalysts dipped in alumina-zirconia oxide complex carrier in which zirconia is highly dispersed is provided to manufacture hydrogen gas by performing a reforming reaction of steam of liquefied natural gas. A method for manufacturing nickel catalysts dipped in alumina-zirconia oxide complex carrier in which zirconia is highly dispersed comprises the following steps of: activating a hydroxyl(OH) group on a alumina surface by adding a base catalyst in a alumina-dispersed organic solvent; obtaining a chelated zirconium precursor by using a chelating agent; grafting and reacting a solution by adding the chelated zirconium precursor; obtaining slurry; inducing a hydration and a condensation reaction of the zirconium precursor; drying the solution; obtaining the alumina - zirconia complex oxide carrier building after heating a material; dipping the nickel; drying an outcome; and gaining a nickel catalyst.

Description

Nickel catalysts for steam reforming of liquefied natural gas supported on alumina-zirconia composite oxide carrier and preparation method therefor {Nickel catalysts supported on alumina-zirconia oxide complex for steam reforming of liquefied natural gas and preparation methods therof}

The present invention relates to a nickel catalyst for steam reforming of liquefied natural gas, and more particularly, a nickel catalyst for steam reforming reaction for producing hydrogen gas from liquefied natural gas supported on a highly dispersed alumina-zirconia composite oxide carrier in which zirconia is dispersed, A method for producing the same and a method for producing hydrogen gas using the catalyst.

Hydrogen energy is in the spotlight as a future energy to replace the existing fossil fuel, and the market size is rapidly increasing. This stems from concerns about the depletion of existing fossil fuels and changes in global awareness of extreme environmental pollution resulting from excessive use of fossil fuels. In recent years, research on PEMFC, which uses hydrogen energy as a raw material, has been actively conducted with the goal of applying it to various fields such as large-scale factories, transportation vehicles, and residential power generators. The importance of energy is increasing. However, stable and efficient hydrogen gas production is essential for their commercial use.

Hydrogen gas production is widely known to be possible through catalytic reforming of organic materials including hydrocarbons such as methane, ethane, LNG, LPG, gasoline, diesel, naphtha, and alcohols such as methanol and ethanol. Catalytic reforming reaction is the main reaction is the steam reforming reaction that uses steam according to the type of the other reactants except the organic (Steam Reforming), partial oxidation using oxygen (Partial Oxidation), carbon dioxide reforming reaction using carbon dioxide (CO ₂ Reforming) and Autothermal Reforming, which uses oxygen and steam together, among which steam reforming has reached a very high technical level and has the highest ratio of hydrogen / carbon monoxide in the product. It is known to be the most suitable for the purpose of hydrogen gas production. In particular, steam reforming reaction using methane, which has huge reserves on the earth but has little utility other than heating, is known to be most suitable for the purpose of hydrogen gas production. In addition, methane-based liquefied natural gas (LNG) is also a raw material that is very well suited for the purpose of producing hydrogen gas through steam reforming reactions, since it can be effectively transported through a well-developed gas pipeline network in large cities. And it has a very suitable advantage as a reaction raw material of the domestic fuel cell reformer. Above all, however, it is important to select and develop a catalyst system that is suitable for each reactant, reaction type and reaction conditions and has excellent performance in order to achieve the purpose of efficient hydrogen gas production. It's going on.

Reforming catalysts for hydrogen gas production can be broadly classified into noble metal catalysts such as Ru, Pd, Pt, Ir, and nickel catalysts. The noble metal catalyst has the advantage of superior catalytic activity and no deactivation of the catalyst even in a long time operation compared to the nickel-based catalyst, but it is difficult to be widely used commercially because the price competitiveness is very low. On the other hand, nickel-based catalysts have high price competitiveness, and thus are highly applicable to commercial processes. In fact, in the steam reforming reaction of methane, which is widely known industrially, nickel-based catalysts produce hydrogen gas, but nickel-based catalysts are used. The problem of catalyst deactivation due to carbon deposition and catalyst sintering in the reforming reaction of various organic materials is very serious [Q. Ming, T. Healey, L. Allen, P. Irving, Catal. Today, Vol. 77, 51 (2002)]. In order to solve the problem of catalyst deactivation, harsh reaction conditions for supplying high temperature, high pressure, and excess water vapor are essential, which is not only economically inefficient, but also not particularly suitable for the purpose of producing a small amount of hydrogen gas. Therefore, developing a catalyst having high activity and stability in the steam reforming reaction, that is, a catalyst having a physical and chemical structure with high resistance to catalyst deactivation may be the most effective problem solving method. To this end, studies have been conducted to enhance catalyst activity and stability by adding a small amount of K, Na, Mg, Mo, and Ca to an existing nickel-based catalyst, which is much more competitive than precious metals [T. Borowiecki, G. Wojciech, D. Andrzej, Appl. Catal. A, Vol. 270, 27 (2004); JS Lisboa, DCRM Santos, FB Passos, FB Noronha, Catal. Today, Vol. 101, p. 15 (2005)]. Also nickel-base introduces a new carrier such as SiO _2, CeO ₂ and ZrO ₂ instead of conventional Al ₂ O ₃ as the carrier of the catalyst _{or, Al 2 O 3 -CeO 2,} Al 2 O 3 -ZrO 2 , and Al ₂ O _{It has also been} reported that complex oxide carriers such as ₃ -CeO ₂ -ZrO ₂ were prepared by co-precipitation, sol-gel and grafting to improve catalyst activity by using them as carriers for nickel-based catalysts. There is a bar. In particular, the introduction of ZrO ₂ and CeO ₂ enhances the water vapor adsorption capacity of the Ni / Al ₂ O ₃ catalyst and thus has a net function of suppressing carbon deposition in the steam reforming reaction. The present inventors have prepared alumina-zirconia composite oxide carrier having a surface modified by grafting zirconia on the surface of commercial alumina and utilizing the catalyst as a catalyst for nickel-based catalysts to exhibit high catalytic activity in steam reforming of liquefied natural gas. Has already reported [Korean Patent Application 10-2006-011847]. However, a case of preparing a carrier of a nickel-based catalyst for steam reforming of liquefied natural gas by a grafting method which can lower the expensive zirconium content in the alumina-zirconia composite oxide carrier, that is, improve the economic efficiency, has not yet been manufactured. Has not been reported. In addition, a carrier of a nickel-based catalyst for steam reforming of liquefied natural gas was prepared by preparing an alumina-zirconia carrier in which zirconia was highly dispersed through an effective grafting method that can enhance the dispersion of zirconia in an alumina-zirconia composite oxide. There are no examples of the application.

Accordingly, the present inventors have diligently researched to overcome the problems of the prior arts. As a result, when the zirconia is supported by a highly dispersed alumina-zirconia composite carrier to support a nickel catalyst for steam reforming reaction, the catalyst has excellent catalytic activity and stability. Confirmed that it can be prepared, the present invention was completed.

Accordingly, a main object of the present invention is to produce a nickel catalyst supported on alumina-zirconia composite oxide carrier in which zirconia is highly dispersed for producing hydrogen gas by steam reforming of liquefied natural gas.

Another object of the present invention is to provide a method for producing hydrogen gas from liquefied natural gas using the catalyst.

According to an aspect of the present invention, the present invention provides a nickel catalyst supported on alumina-zirconia (Al ₂ O ₃ -ZrO ₂ ) composite oxide carrier in which zirconia is highly dispersed.

In the present invention, the catalyst supported on the carrier means that the active ingredient is physically or chemically attached on the carrier, and in the case of the catalyst supported on the composite carrier prepared in the present invention, alumina having a high dispersion of zirconia is a main skeleton. To form nickel and evenly mixed nickel. The nickel catalyst supported on the alumina-zirconia composite oxide support of the present invention is highly dispersed by grafting a small amount of zirconia to increase the water vapor adsorption capacity to facilitate the vaporization of hydrocarbon species adsorbed on the catalyst surface. It is an excellent catalyst that does not show catalyst deactivation even in long term operation.

In the present invention, the steam reforming reaction refers to a process of producing hydrogen by reacting hydrocarbons such as liquefied natural gas with water vapor, and is generally known as the cheapest process for producing hydrogen from natural gas.

In the present invention, the zirconia-highly dispersed alumina-zirconia composite oxide is a small amount of zirconia is highly dispersed in a very small size so that the peak is not detected during X-ray diffraction analysis and the crystal structure of the commercial alumina as a carrier is maintained as it is. It means to be. In the present invention, zirconia can be highly dispersed by grafting chelated zirconium precursors.

In the nickel catalyst of the present invention, the composite oxide carrier preferably contains 1 to 10% by weight of zirconium, more preferably 3 to 7% by weight based on the total carrier, the zirconium content is 1 If it is less than the weight percent of zirconium by the effect of modifying the surface of the alumina is insignificant, it is not preferable, if it exceeds 10% by weight because the dispersion of zirconium is lowered and the economical efficiency is also reduced. In a specific embodiment of the present invention, as a specific example, the nickel catalyst Ni / AZ2 and Ni / AZ4 catalysts supported on the composite carrier having the zirconium content of 4.1 wt% and 6.7 wt% are stable even for a reaction time of about 1000 minutes. It was confirmed that the high catalytic activity, the nickel catalyst supported on a commercial alumina carrier (zirconium content 0% by weight) was confirmed that a sudden drop in activity (see Figure 4).

In the nickel catalyst of the present invention, the catalyst is preferably supported by 1 to 50% by weight of nickel on the composite oxide carrier with respect to the total catalyst in terms of the active side of the catalyst or in terms of economics of the catalyst production, more preferably nickel 15 It is appropriate that it is supported at -40% by weight, but if the supported amount of nickel is less than 1% by weight, the active point is too diluted to be preferable, and when it exceeds 50% by weight, the dispersion of the active point is uneven, which is not preferable.

According to another aspect of the present invention, the present invention provides a method for preparing a zirconia highly dispersed alumina-zirconia composite oxide carrier comprising the following steps:

a) dispersing alumina in an organic solvent, and then adding a base catalyst to activate hydroxyl (OH) groups on the surface of the alumina;

b) chelating the zirconium alkoxide using a chelating Ligand to obtain a zirconium precursor;

c) grafting by adding the chelated zirconium precursor of step b) to the solution obtained in step a);

d) washing the grafted solution in step c) with an organic solvent and centrifuging to obtain a slurry;

e) adding distilled water to the slurry obtained in step d) to induce hydration and condensation reaction of the zirconium precursor grafted at room temperature;

f) filtering the solution obtained in step e) and drying at 75-125 ° C. for 12-36 hours; And

g) heat treating the dried product obtained in step f) at 500-900 ° C. for 3-7 hours to obtain an alumina-zirconia composite oxide carrier.

According to another aspect of the present invention, the present invention provides a method for preparing a nickel catalyst supported on a zirconia highly dispersed alumina-zirconia composite oxide carrier comprising the following steps:

a) dispersing alumina in an organic solvent, and then adding a base catalyst to activate hydroxyl (OH) groups on the surface of the alumina;

b) chelating the zirconium alkoxide using a chelating Ligand to obtain a zirconium precursor;

c) grafting by adding the chelated zirconium precursor of step b) to the solution obtained in step a);

d) washing the grafted solution in step c) with an organic solvent and centrifuging to obtain a slurry;

e) adding distilled water to the slurry obtained in step d) to induce hydration and condensation reaction of the zirconium precursor grafted at room temperature;

f) filtering the solution obtained in step e) and drying at 75-125 ° C. for 12-36 hours;

g) heat treating the dried product obtained in step f) at 500-900 ° C. for 3-7 hours to obtain an alumina-zirconia composite oxide carrier;

h) impregnating nickel using a nickel precursor to the composite oxide carrier obtained in step g);

i) drying the resultant obtained in step h) at 75-125 ° C. for 12-36 hours; And

j) heat treating the dried product obtained in step i) at 500-900 ° C. for 3-7 hours to obtain a nickel catalyst supported on an alumina-zirconia composite carrier.

In the present invention, the zirconium precursor (zirconium precursor) in the step c) refers to a raw material that can be a zirconia (Zirconia) after the final reaction, zirconium is a very stable material to grind or evenly mix them into nano-sized particles It is very hard and does not dissolve in organic solvents such as alcohol. Therefore, in the embodiment of the present invention, the zirconia is not directly reacted or processed, but the precursor, which is a raw material of zirconia, is mixed, made into a form, and subjected to a reaction (chelation reaction, hydration reaction, condensation reaction, and high temperature heat treatment). It will make a carrier for the catalyst having. In addition, the zirconium precursor of the present invention may be used any precursor such as hydrate, oxide, etc. as long as the zirconium can be dissolved in an organic solvent.

In the present invention, the organic solvent in step a) may be used regardless of type, such as toluene, 2-butanol, benzene, ethylbenzene, trimethylbenzene, xylene, methyl ethyl ketone, methyl isobutyl ketone, acetone, ethyl One or more organic solvents selected from the group consisting of acetate, butyl acetate, n-hexane, isopropyl alcohol, trichloroethylene, 1,1,1-trichloroethane and pentane may be used, but toluene is preferred, and the base catalyst is ethyl Amine, diethylamine, triethylamine, trimethylamine, N-methylpyrrolidine, pyridine, 4- (N, N-dimethylamino) pyridine, 4- (N, N-diethylamino) pyridine, N, N One or more base catalysts selected from the group consisting of -dimethylformamide and 1-methyl-2-pyrrolidone may be used but triethylamine is preferred.

In the present invention, the grafting in the step c) is one of methods for supporting nanoparticles on the metal oxide carrier, the surface of the carrier by chemically bonding the same or different metal components to the functional group present on the surface of the metal oxide carrier Means to modify the physical and chemical properties of Therefore, it is a very effective method to control the physical and chemical properties of the surface while maintaining the mechanical and thermal stability of the matrix compared with the general supporting methods such as impregnation, coprecipitation, mechanical mixing.

In the catalyst production method of the present invention, the zirconium alkoxide in the step b) is zirconium butoxide (Zirconium Butoxide), zirconium Propoxide, zirconium tert-Butoxide (Zirconium tert-Butoxide), zirconium isopropoxide It is preferably selected from the group consisting of zirconium isopropoxide and mixtures thereof.

In the catalyst production method of the present invention, the chelating agent in step b) 2,4-pentanedione (2,4-Pentanedione), ethylenediaminetetraacetic acid (Ethylenediaminetetraacetic acid), trans-1,2-diamino It is preferably one selected from the group consisting of cyclo-1,2-Diaminocyclohexanetetraacetic acid and diethylenetriaminepentaacetic acid.

According to another aspect of the present invention, the present invention provides a catalyst composition for steam reforming reaction for producing hydrogen gas from liquefied natural gas containing the catalyst according to the present invention as an active ingredient.

According to another aspect of the invention, the present invention is the first step to charge the catalyst according to the present invention to the steam reforming reactor and the reaction temperature of 500 to 900 ℃ liquefied natural gas and water vapor at a space velocity of 1,000-500,000 ml / g Provided is a method for producing hydrogen gas from liquefied natural gas by a steam reforming reaction comprising a second step of passing a catalyst layer in a reactor with a catalyst.

The steam reforming reaction is performed while flowing the liquefied natural gas and steam together with a carrier gas (nitrogen) while maintaining the temperature of the reactor at 500 to 900 ° C. At this time, if the reaction temperature is less than 500 ° C, sufficient catalytic activity is achieved. Unexpectedly, when it is 900 degreeC or more, stability by the sintering of a catalyst falls, etc., and is unpreferable.

In the hydrogen gas production method of the present invention, the liquefied natural gas and water vapor in the second step is preferably passed through the catalyst layer in a volume ratio of 1:10 to 1: 1, the volume ratio of the liquefied natural gas and water vapor as a reactant is If it is less than 1:10, sufficient activity cannot be expected, and if it exceeds volumetric volume 1: 1, it is unpreferable in terms of energy efficiency.

In the hydrogen gas production method of the present invention, after the first step is characterized in that it further comprises a pretreatment process for reducing the catalyst charged in the reactor to a mixed gas of nitrogen and hydrogen. In general, in the steam reforming reaction of liquefied natural gas, since the active phase is a reduced nickel species, not nickel oxide species, it is preferable that all nickel catalysts undergo a pretreatment process of reducing with hydrogen before performing the reaction.

In the present invention, the mixed gas used in the pretreatment process is preferably a volume ratio of hydrogen and nitrogen is 1:15 to 1: 5, when the volume ratio is less than 1:15, sufficient reduction is not made, 1: 5 or more This is not economical because it exceeds the amount of hydrogen required for reduction.

Hereinafter, the present invention will be described in more detail with reference to Examples. Since these examples are only for illustrating the present invention, the scope of the present invention is not to be construed as being limited by these examples.

Preparation Example 1 Preparation of Alumina-Zirconia Composite Oxide Carrier According to the Present Invention

Toluene was used as the organic solvent, and commercially available alumina (Degussa) was used as the alumina. First, 3 g of alumina powder was added to 100 ml of toluene and dispersed with stirring. In addition, 0.6 ml of triethylamine (Triethylamine, Aldrich) as a base catalyst was added to the solution while stirring to sufficiently activate hydroxyl (OH) groups on the surface of commercial alumina. Zirconium alkoxide was chelated using a chelating ligand to prepare a chelated zirconium precursor, which was zirconium butoxide Aldrich), and 2,4-pentanedione (2,4-Pentanedione, Aldrich) was used as a chelating agent (Chelating Ligand). 2.4 ml of zirconium butoxide was reacted with 1.5 ml of 2,4-pentanedione to obtain a chelated zirconium precursor. Here, the chelated zirconium precursor which is reacted with alumina, that is, prepared as described above, is 15.2 wt% based on the alumina carrier. Considering that zirconia is mostly present in the form of ZrO ₂ , for example, AZ1 is 3.1 wt% of zirconium, 4.2 wt% of zirconia, 4.1 wt% of zirconium and 5.7 wt% of zirconia (see Table 1). .

The resultant obtained in the above step was used as a zirconium precursor and grafted by adding it to a solution containing activated alumina. The resultant obtained in the above step was used as a zirconium precursor and added to a solution containing alumina whose surface was activated, and was sufficiently grafted at room temperature for 5 hours. The grafted solution was washed and centrifuged three times with toluene and butanol sufficiently to remove unreacted zirconium precursors and reaction by-products. 100 ml of distilled water was added to the slurry obtained in the above step and maintained at room temperature for 5 hours to proceed with the hydration and condensation reaction of the grafted zirconium precursor. The solution obtained in the above step was filtered and dried in an oven at 100 ° C. for 5 hours. The dried powder was heat-treated at 700 ° C. for 5 hours to finally obtain an alumina-zirconia composite oxide carrier, which was named AZ1. Figure 1 is a schematic diagram of alumina-zirconia composite oxide carrier prepared according to the present invention, where acac means 2,4-pentanedione (2,4-Pentanedione) used as a chelating agent (Chelating Ligand).

Preparation Example 2 Preparation of Alumina-Zirconia Composite Oxide Carrier According to the Present Invention

Following the method of Preparation Example 1, but in order to increase the zirconium content of the finally obtained alumina-zirconia composite oxide carrier by repeating the method of Preparation Example 1 using the AZ1 carrier prepared in Preparation Example 1 instead of commercial alumina Finally, an alumina-zirconia composite oxide carrier was obtained, which was named AZ2. In order to further increase the content of zirconium, the procedure of Preparation Example 1 was repeated once using AZ2 instead of alumina to finally obtain an alumina-zirconia composite oxide carrier, which was named AZ3. In addition, in order to further increase the content of zirconium, using AZ3 instead of alumina, the process of Preparation Example 1 was repeated once to finally obtain an alumina-zirconia composite oxide carrier, which was named AZ4.

Preparation Example 3 Preparation of Nickel Catalyst Supported on an Alumina-Zirconia Carrier According to the Present Invention

Alumina-zirconia composite oxide carriers AZ1, AZ2, AZ3 and AZ4 carriers prepared in Preparation Example 1 and Preparation Example 2 were impregnated with 20 wt% nickel based on the entire supported catalyst, respectively, by a general impregnation method. To this end, 0.996 g of nickel nitrate hexahydrate (manufactured by Aldrich) is sufficiently dissolved in 1 ml of distilled water, and then 1 g of AZ1, AZ2, AZ3, and AZ4 carriers are added to each other so that sufficient impregnation may occur. Have gone through. After the above process and drying in an oven at 100 ℃ for 24 hours, the obtained powder was heat-treated at 700 ℃ for 5 hours to finally obtain a nickel catalyst supported on each alumina-zirconia composite oxide carrier, Ni / It was named AZ1, Ni / AZ2, Ni / AZ3, and Ni / AZ4.

Preparation Example 4 Preparation of Nickel Catalyst Supported on Commercial Alumina

After sufficiently dissolving 0.996 g of nickel nitrate hexahydrate (manufactured by Aldrich) in 1 ml of distilled water, 1 g of commercial alumina (manufactured by Degussa) was added and uniformly impregnated with a general impregnation method. After the above process and drying in an oven at 100 ℃ for 24 hours, the obtained powder was heat-treated at 700 ℃ for 5 hours to finally obtain a supported catalyst Ni / Al ₂ O ₃ , commercially available alumina for convenient labeling AZ0 The supported catalyst prepared was named Ni / AZ0.

Experimental Example 1. Constituents and Crystal Structure of the Alumina-Zirconia Composite Oxide Carrier According to the Present Invention

Table 1 shows the results of elemental analysis (ICP-AES) of alumina-zirconia composite oxide carriers (AZ1, AZ2, AZ3 and AZ4) and commercial alumina (AZ0) prepared by Preparation Examples 1 and 2 of the present invention. From this, it can be seen that as the number of grafting processes increases, the content of zirconium increases. However, it can be seen that the content of the grafted zirconium is less than 10% by weight, which means that the chelated zirconium precursor has three chelated ligands and one butoxide ligand. Because it has. Chelated Ligand mitigates the agglomeration of zirconium particles in the grafting reaction and prevents the three-dimensional growth of zirconia particles in the hydration and condensation of the grafted zirconium precursor. Because it plays a role. Figure 2 shows a graph of the results of X-ray diffraction analysis of the alumina-zirconia composite oxide carrier prepared by the present invention and commercial alumina. As can be seen in Figure 2, the characteristic peak of γ-alumina of the commercial alumina in all the carriers develop. From the grafting method according to the present invention it can be seen that even if zirconia is introduced, the crystal structure of the commercial alumina as a carrier is maintained as it is. It is also noteworthy that the AZ1, AZ2 and AZ3 carriers prepared by Preparation Examples 1 and 2 of the present invention do not develop characteristic peaks of zirconia (tetragonal phase of zirconia), which are prepared by Preparation Example 2 Even AZ4 carriers are only marginally developing. This is because the zirconia is highly dispersed on the alumina-zirconia composite oxide carriers AZ1, AZ2, AZ3 and AZ4 prepared by the methods of Preparation Examples 1 and 2 of the present invention, so that it is higher than the detection limit of X-ray diffraction analysis. This is because it is grafted small. In other words, it can be seen that in the case of the alumina-zirconia composite oxide carrier according to the present invention, zirconia could be highly dispersed by grafting a chelatated zirconium precursor.

TABLE 1 Elemental Analysis (ICP-AES) Results of Alumina-Zirconia Composite Oxide Supports (AZ1, AZ2, AZ3 and AZ4) and Commercial Alumina (AZ0) According to the Present Invention

Experimental Example 2 Crystal Structure of Nickel Catalyst Supported on an Alumina-Zirconia Composite Oxide Support According to the Present Invention

3 is a graph showing the results of X-ray diffraction analysis of the nickel catalyst for preparing hydrogen gas supported on the alumina-zirconia composite oxide carrier prepared according to the present invention, the nickel catalyst (Ni / AZ0) and commercial alumina (AZ0) supported on commercial alumina. It is shown. As can be seen in FIG. 3, it can be seen that characteristic peaks (dashed lines) of nickel oxide species appear on all catalysts, indicating that nickel was successfully supported on the alumina-zirconia composite oxide carrier. In the case of Ni / AZ0 catalyst without grafting, it can be seen that the alumina (440) diffraction peak is shifted at a low angle because nickel ions enter the lattice of alumina and expand the lattice of alumina. Is referred to as the nickel aluminate phase. Notably, the shift of the alumina 440 diffraction peaks seen in the nickel catalyst (Ni / AZ0) supported on commercial alumina is insignificant or does not appear on the nickel catalyst supported on the alumina-zirconia composite oxide carrier prepared by the present invention. In the case of the nickel catalyst supported on the zirconia highly dispersed alumina-zirconia composite oxide carrier according to the present invention, the grafted zirconia interacts with alumina to inhibit the interaction between nickel and alumina and consequently This is because the formation of the nickel aluminate phase was suppressed.

Example 1 Steam Reforming of Liquefied Natural Gas Using Nickel Catalyst Supported on an Alumina-Zirconia Composite Oxide Support

Hydrogen gas production reaction was carried out by steam reforming of liquefied natural gas consisting of a mixed gas of methane and ethane using five nickel supported catalysts prepared by the methods of Preparation Example 3 and Preparation Example 4. The liquefied natural gas, consisting of a mixture of methane and ethane used as reactants, consisted of 92% methane and 8% ethane. The catalyst was charged to the reactor for steam reforming, and the catalyst was reduced with a mixed gas of nitrogen (30 ml) and hydrogen (3 ml) at 700 ° C. for 3 hours before the reaction, and then the reaction was continuously passed through the catalyst layer in the reactor. This was allowed to proceed. The space velocity of the reactants was maintained at 27,000 ml / h · g-catalyst, and the volume ratio of the reactant water vapor / liquefied natural gas was maintained at 1.9. Steam reforming of liquefied natural gas was carried out at 600 ° C. The conversion rate of the liquefied natural gas and the composition of the hydrogen gas in the dry gas were respectively calculated by the following equations (1) and (2).

Figure 4 is a representative result showing the change in the liquefied natural gas conversion rate of the nickel-supported catalyst supported on some alumina-zirconia composite oxide carrier with the reaction time. Ni / AZ2 and Ni / AZ4 catalysts prepared according to the method of Preparation Example 3 of the present invention showed stable and high catalytic activity even for a reaction time of about 1000 minutes, but were commercially available alumina carrier prepared by the method of Preparation Example 4. In the case of the supported nickel catalyst (Ni / AZ0), a sudden decrease in activity was shown due to the carbon deposition reaction proceeding on the catalyst surface and the catalyst deactivation due to the sintering of the nickel particles. As described above, in the case of the nickel catalyst supported on the alumina-zirconia composite oxide carrier according to the present invention, a small amount of zirconia is highly dispersed and grafted to increase the water vapor adsorption capacity of the catalyst to vaporize the hydrocarbon species adsorbed on the catalyst surface. It was possible to maintain high activity without any catalyst deactivation even during long-term operation. Also, as mentioned above, high-dispersed zirconia interacted with alumina and inhibited formation of inactive phase nickel aluminate phase, resulting in high catalytic activity. It can be seen that.

5 and 6 show the conversion of liquefied natural gas and dry gas of the nickel catalyst supported on the alumina-zirconia composite oxide carrier and the nickel catalyst (Ni / AZ0) supported on the commercial alumina according to the zirconium content. It is a composition graph of hydrogen gas. 5 and 6, the conversion rate of liquefied natural gas and the composition of hydrogen gas in dry gas decreased in the order of Ni / AZ2> Ni / AZ3> Ni / AZ1> Ni / AZ4> Ni / AZ0. Among these catalysts, the activity of the Ni / AZ2 catalyst was found to be the best. This means that the nickel-supported catalyst supported on the alumina-zirconia composite oxide carrier according to the present invention has a surface structure and interaction between nickel and the carrier suitable for steam reforming of liquefied natural gas according to the amount of zirconia included. For the purpose of producing hydrogen gas by steam reforming of liquefied natural gas according to the present invention, it can be seen that the Ni / AZ2 catalyst has the most suitable physical and chemical structure. In addition, it can be seen that all catalysts prepared by the present invention exhibit superior catalytic activity compared to nickel catalysts (Ni / AZ0) supported on commercial alumina. From this, a small amount of zirconia is grafted as intended in the present invention. It can be seen that the alumina-zirconia composite oxide carrier prepared by grafting) is very effective as a carrier of the nickel supported catalyst for steam reforming reaction.

As described above, according to the present invention, the nickel-supported catalyst supported on the zirconia-highly dispersed alumina-zirconia composite oxide carrier is superior to the nickel catalyst supported on the commercial alumina carrier for a long time in the steam reforming reaction of liquefied natural gas. It showed excellent and stable catalytic activity. In addition, by grafting a small amount of zirconia, a carrier of a nickel supported catalyst suitable for producing hydrogen gas by steam reforming of liquefied natural gas can be produced very economically.

1 is a schematic view of preparing an alumina-zirconia composite oxide carrier according to the present invention.

Figure 2 is a graph of the X-ray diffraction analysis of the alumina-zirconia composite oxide carrier prepared according to the present invention and commercial alumina.

3 is a graph showing the results of X-ray diffraction analysis of a nickel catalyst supported on an alumina-zirconia composite oxide carrier prepared according to the present invention, a nickel catalyst supported on commercial alumina and commercial alumina.

FIG. 4 is a graph showing a change in liquefied natural gas conversion rate of the nickel catalyst for hydrogen gas production supported on the alumina-zirconia composite oxide support prepared by the present invention and the nickel catalyst supported on commercial alumina according to the reaction time.

5 is a graph illustrating the liquefied natural gas conversion of the nickel catalyst supported on the alumina-zirconia composite oxide carrier and the nickel catalyst supported on the commercial alumina according to the zirconium content after 400 minutes from the start of the reaction.

FIG. 6 is a graph showing the composition of hydrogen gas in the dry gas of a nickel catalyst supported on an alumina-zirconia composite oxide carrier and a nickel catalyst supported on commercial alumina after 400 minutes from the start of the reaction.

Claims (12)

Alumina-zirconia composite oxide carrier in which zirconia is highly dispersed by grafting zirconium precursors chelated to alumina; And nickel supported on the alumina-zirconia composite oxide carrier. The nickel catalyst of claim 1, wherein the alumina-zirconia composite oxide carrier comprises 1 to 10% by weight of zirconium based on the total carrier. delete Method for preparing a zirconia highly dispersed alumina-zirconia composite oxide carrier comprising the following steps: a) dispersing alumina in an organic solvent, and then adding a base catalyst to activate hydroxyl (OH) groups on the surface of the alumina; b) chelating the zirconium alkoxide using a chelating Ligand to obtain a zirconium precursor; c) grafting by adding the chelated zirconium precursor of step b) to the solution obtained in step a); d) washing the grafted solution in step c) with an organic solvent and centrifuging to obtain a slurry; e) adding distilled water to the slurry obtained in step d) to induce hydration and condensation reaction of the zirconium precursor grafted at room temperature; f) filtering the solution obtained in step e) and drying at 75-125 ° C. for 12-36 hours; And g) heat treating the dried product obtained in step f) at 500-900 ° C. for 3-7 hours to obtain an alumina-zirconia composite oxide carrier; A method for preparing a nickel catalyst supported on a zirconia highly dispersed alumina-zirconia composite oxide carrier comprising the following steps: a) dispersing alumina in an organic solvent, and then adding a base catalyst to activate hydroxyl (OH) groups on the surface of the alumina; b) chelating the zirconium alkoxide using a chelating Ligand to obtain a zirconium precursor; c) grafting by adding the chelated zirconium precursor of step b) to the solution obtained in step a); d) washing the grafted solution in step c) with an organic solvent and centrifuging to obtain a slurry; e) adding distilled water to the slurry obtained in step d) to induce hydration and condensation reaction of the zirconium precursor grafted at room temperature; f) filtering the solution obtained in step e) and drying at 75-125 ° C. for 12-36 hours; g) heat treating the dried product obtained in step f) at 500-900 ° C. for 3-7 hours to obtain an alumina-zirconia composite oxide carrier; h) impregnating nickel using a nickel precursor to the composite oxide carrier obtained in step g); i) drying the resultant obtained in step h) at 75-125 ° C. for 12-36 hours; And j) heat treating the dried product obtained in step i) at 500-900 ° C. for 3-7 hours to obtain a nickel catalyst supported on an alumina-zirconia composite carrier. According to claim 5, wherein the zirconium alkoxide in step b) is zirconium butoxide (Zirconium Butoxide), zirconium propoxide (Zirconium Propoxide), zirconium tert-Butoxide (Zirconium tert-Butoxide), zirconium isopropoxide ( Zirconium Isopropoxide) and a method for producing a nickel catalyst, characterized in that selected from the group consisting of them. According to claim 5, wherein the chelating agent in step b) 2,4-pentanedione (2,4-Pentanedione), ethylenediaminetetraacetic acid (Ethylenediaminetetraacetic acid), trans-1,2-diaminocyclohexane Tetraacetic acid (trans-1,2-Diaminocyclohexanetetraacetic acid) and diethylenetriaminepentaacetic acid (Diethylenetriaminepentaacetic acid) A method for producing a nickel catalyst, characterized in that one selected from the group consisting of. delete delete delete delete delete

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