KR102436299B1 - Composite comprising nickel supported on porous alumina carrier and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a composite containing nickel supported on a porous alumina carrier and a method for preparing the same, and by reducing the size of nickel particles acting as a surface active site and improving dispersibility, excellent activity and selectivity when used as a catalyst A composite and a method for preparing the same may be provided.

Description

Composite comprising nickel supported on porous alumina carrier and manufacturing method thereof

The present invention relates to a composite including nickel supported on a porous alumina carrier and a method for preparing the same.

The demand for environmentally friendly and sustainable renewable energy is increasing due to climate change and future depletion of fossil fuels. Biomass is one of the renewable raw materials for producing biogas and liquefied biofuel.

Recently, in order to convert biomass into energy or fuel, various means such as gasification, liquefaction, and pyrolysis of biomass have been sought, and among them, gasification of biomass is receiving the most attention because of its excellent energy recovery rate. However, tar produced by biomass gasification may cause serious problems in devices such as engines and control valves by condensation and crystallization of tar in subsequent processes. Therefore, tar must be removed from the product produced through biomass gasification, and a technology for converting tar into other materials is very important.

Currently, steam reforming is being used to remove tars produced by biomass gasification. In steam reforming, tar is used to produce synthesis gas and hydrogen fuel. However, tar produced by biomass gasification contains various contaminants including particles, nitrogen and sulfur-containing compounds as well as condensates of hydrocarbons.

Therefore, in the steam reforming process, the relationship between the active site and molecular structure of the catalyst and the conversion of tar is very complicated, and aromatic ring compounds such as benzene, toluene, naphthalene and phenol or aromatic hydrocarbons containing oxygen are used. Therefore, the mechanism of tar removal through steam reforming is being investigated.

So far, metal catalysts such as ruthenium (Rh), nickel (Ni), and cobalt (Co) have been developed as catalysts for steam reforming, and among them, nickel catalysts are mainly used as commercial catalysts in terms of cost and performance. In particular, a Ni/Al ₂ O ₃ catalyst in which nickel is supported on an alumina carrier is widely used due to its high conversion rate and hydrogen yield.

When a Ni/Al ₂ O ₃ catalyst is used, the nickel dispersion or nickel particle size on the alumina carrier directly affects the catalyst performance in the steam reforming reaction. When the dispersion degree of nickel is high, the resistance to coke generation is strong, and the mobility of the nickel particles is weakened by increasing the distance between the nickel particles, so that aggregation (cluster) of the nickel particles can be minimized even at a high temperature. In addition, when the size of the nickel particles is small, the active point increases, thereby increasing the reaction rate and activity.

In order to increase the catalytic activity, a method of increasing the active point by using a metal that can replace nickel or another metal together with nickel has been mainly studied so far. In particular, Catal, who studied the catalytic activity and selectivity in steam reforming reaction by modifying the surface by adding potassium (K) to the Ni/Al ₂ O ₃ catalyst. Sci. Technol. 7 (2017) 3613-3625. et al., which disclose that electrons can be donated from potassium to nickel to increase the electron density of the nickel clusters and thus have higher nickel activity in steam methane reforming.

However, in the steam reforming reaction of the Ni/Al ₂ O ₃ catalyst, the effect of adding potassium has not yet been revealed. There are many opposing views, such as promoting the sintering rate of nickel, and these negative views continue to be cited.

On the other hand, the size and dispersion of the catalyst particles can be improved by changing the shape and structure of alumina in addition to the method of binding the promoter (other metal) to the Ni/Al ₂ O ₃ catalyst, but the form of the porous alumina carrier in the steam reforming reaction And there is no report on the catalytic activity of an alumina carrier having a hierarchical pore structure including meso and macro pores at the same time.

Republic of Korea Patent Publication No. 10-2003-0077629

An object of the present invention is to provide a composite having excellent activity and selectivity when used as a catalyst by reducing the size of nickel particles and improving dispersibility in a composite containing nickel as a surface active site, and a method for preparing the same.

The present invention provides a composite comprising a porous alumina carrier and nickel supported on the porous alumina carrier, and the nickel particle size is 0.5 to 4 nm.

As an embodiment of the present invention, the porous alumina carrier has a hierarchical pore structure including mesopores and macropores at the same time, mesopores are formed inside the macropore wall, and mesopores and macropores are interconnected can be

As an embodiment of the present invention, it is possible to provide a composite in which X/Y > 1 is satisfied, X represents the average size (nm) of mesopores of the composite, and Y represents the size (nm) of nickel particles.

As an embodiment of the present invention, it is possible to provide a composite further comprising 0.3 to 3% by mass of potassium based on the total mass of the porous alumina carrier and nickel.

In addition, the present invention includes a porous carrier and a transition metal supported on the porous carrier, wherein the porous carrier simultaneously contains mesopores and macropores, and mesopores are formed inside the macropore wall, and the mesopores and macropores It has a hierarchical pore structure in which pores are interconnected, and provides a complex satisfying the following general formula (1).

[General Formula 1] X/Y > 1;

In Formula 1, X represents the average size (nm) of the mesopores of the composite, and Y represents the size (nm) of the transition metal particles.

In addition, the present invention comprises the steps of mixing a polymer colloid with an alumina precursor dissolved in a solvent, filtering and washing the mixture to obtain a porous alumina carrier, and impregnating the porous alumina carrier with a nickel precursor solution, wherein the Washing provides a method for preparing a complex that is performed using a mixture of alcohol and water.

In an embodiment of the present invention, the ratio of the alcohol to water may be 1:5 to 4:5.

In an embodiment of the present invention, the solvent may be 2-butanol.

As an embodiment of the present invention, the alumina precursor may be aluminum tri-sec-butoxide.

As an embodiment of the present invention, the polymer colloid may be prepared by emulsifier-free emulsion polymerization of a composition containing a styrene monomer.

In one embodiment of the present invention, the size of the polymer particles dispersed in the polymer colloid may be 200 to 900 nm.

As an embodiment of the present invention, the method for preparing the composite may further include impregnating the potassium precursor solution into the porous alumina carrier.

As an embodiment of the present invention, the potassium precursor solution may be impregnated so that the potassium content is 0.3 to 3% by mass based on the total mass of the porous alumina carrier and nickel.

In addition, the present invention may provide a catalyst for steam reforming reaction including the composite according to the present invention.

The composite including nickel supported on a porous alumina carrier according to the present invention and a method for preparing the same have a small size of nickel particles and high dispersion, so that the catalytic activity is excellent and the selectivity is high.

1 is (a) Preparation Example 5, (b) Comparative Example 1, (c) Comparative Example 2, (d) Comparative Example 3, (e) Preparation Example 1, (f) Example according to an embodiment of the present invention SEM images of Example 1, (g) Example 2 and (h) Example 3.
2 is a TEM image of (a) Preparation Example 5, (b) Preparation Example 1, (c) Comparative Example 3, and (d) Example 3 according to an embodiment of the present invention.
3 is a nitrogen adsorption-desorption isotherm and pore size distribution according to an embodiment of the present invention.
Figure 4 illustrates the surface of the composite according to an embodiment of the present invention.
5 is (a) Preparation Example 5, (b) Comparative Example 1, (c) Comparative Example 2, (d) Comparative Example 3, (e) Preparation Example 1, (f) Example according to an embodiment of the present invention Example 1, (g) Example 2 and (h) Example 3 are graphs showing XRD patterns measured after calcining in air and reducing in hydrogen at 600°C.
6 is a graph showing the change in the reaction rate with time of the composite prepared according to an embodiment of the present invention.
7 is (a) Preparation Example 5, (b) Comparative Example 1, (c) Comparative Example 2, (d) Comparative Example 3, (e) Preparation Example 1, (f) Example according to an embodiment of the present invention Example 1, (g) Example 2 and (h) Example 3 is a graph showing XRD patterns measured after 2 hours of use in the steam reforming reaction.

Since the present invention can have various changes and can have various embodiments, specific embodiments are illustrated in the drawings and will be described in detail in the detailed description.

However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention.

In the present invention, terms such as "comprises" or "have" are intended to designate that the features, numbers, steps, operations, components, parts, or combinations thereof described in the specification exist, but one or more other features It is to be understood that this does not preclude the possibility of the presence or addition of numbers, steps, operations, components, parts, or combinations thereof.

Accordingly, the configuration shown in the embodiment described in this specification is only one of the most preferred embodiments of the present invention and does not represent all the technical spirit of the present invention, so various equivalents that can be substituted for them at the time of the present application and variations.

The present invention provides a composite comprising a porous alumina carrier and nickel supported on the porous alumina carrier, and the nickel particle size is 0.5 to 4 nm.

The alumina is an oxide of aluminum, represented by the general formula of Al ₂ O ₃ , and is the most important material in ceramics, which is a non-metallic inorganic material obtained through a heat treatment process. By using alumina as the material of the porous carrier, a large surface area can be obtained, and excellent catalytic activity can be exhibited by interaction with nickel.

The porous carrier refers to a material containing a large number of pores therein, and refers to an object containing a material exhibiting activity in order to achieve the purpose of the task. In addition, the pores may be classified into macropores having a size of 50 nm or more, mesopores having a size of 2 to 50 nm, and micropores having a size of 2 nm or less according to their size.

The nickel composite supported on the porous alumina support may be prepared by impregnating a nickel precursor into the porous alumina support by incipient wetness impregnation.

At this time, nickel acts as a surface active site of the composite, and the size of the nickel particles is 4 nm or less, for example, 0.5 to 4 nm, 0.5 to 3.5 nm, 0.5 to 3.0 nm, 1 to 2.5 nm, 1.5 to 2.3 nm, or It may be 1.8 to 2.1 nm.

The size of the nickel particles may be measured from an X-ray diffraction (XRD) pattern using Debye-Scherrer's equation of Equation 1 below.

[Equation 1]

는 X-선 방사선 파장이며,

는 브랙각(Bragg angle),

는 특정 회절 피크에서의 FWHM(full sidth at half maximum)이다.In Equation 1, k = 0.9 as a shape factor,

is the X-ray radiation wavelength,

is the Bragg angle,

is the full sidth at half maximum (FWHM) at a specific diffraction peak.

The composite of the present invention has the effect of increasing the number of active sites on the nickel surface because the size of the nickel particles is very small as described above. Therefore, there is an effect of increasing the methane conversion rate and carbon selectivity when used as a catalyst in the steam reforming reaction.

The size of the nickel particles as described above is affected by the shape and structure of the porous alumina carrier, and may vary depending on the components and ratios of the washing mixture when manufacturing the composite.

The porous alumina carrier may have a hierarchical pore structure in which mesopores and macropores are simultaneously included, mesopores are formed inside the macropore walls, and mesopores and macropores are interconnected.

That is, the porous alumina carrier of the present invention is a macro-mesoporous having mesopores and macropores at the same time, and the macropores are three-dimensionally connected through the walls of the pores. It contains mesopores.

The hierarchical pore structure as described above can be formed by mixing a polymer colloid with an alumina precursor dissolved in a solvent, followed by filtering and washing. In this case, the washing liquid used for washing preferably has a ratio of alcohol and water of 1:5 to 4:5. activity is excellent.

By having a hierarchical pore structure of macro-mesopores as described above, it may have a larger surface area than a carrier having only macropores. In particular, the stability of the macropore structure is enhanced, and the regeneration of the catalyst can be increased. In addition, the mass transfer resistance can be reduced through the fine pores of the mesopores, the dispersibility of nickel can be improved, and the size of the nickel particles can be formed small. Therefore, the alumina carrier having the hierarchical pore structure has an effect of increasing the activity of the catalyst in the steam reforming reaction.

In addition, as an embodiment, the present invention may provide a composite satisfying the following general formula (1).

[General formula 1]

X/Y > 1;

In Formula 1, X represents the average size (nm) of the mesopores of the composite, and Y represents the size (nm) of the nickel particles.

In this case, the average size of the mesopores may be 5 to 15 nm, for example, 6 to 14 nm, 7 to 13 nm, 8 to 12 nm, or 10 to 11 nm.

In the composite satisfying Formula 1, since the average size of the mesopores is larger than the size of the nickel particles, the nickel particles may be distributed inside the mesopores. For this reason, the phenomenon (cluster) of aggregation of nickel particles can be prevented, and the dispersion degree of nickel can be improved. Therefore, there is an effect that the active sites of nickel are relatively increased, and the activity is excellent when used as a catalyst.

The composite of the present invention may further include 0.3 to 3% by mass of potassium based on the total mass of the porous alumina carrier and nickel. Specifically, potassium may be 0.3 to 2.5 mass%, 0.3 to 2 mass%, 0.3 to 1.5 mass%, 0.3 to 1 mass%, or 0.3 to 0.7 mass%, based on the total mass of the alumina carrier and nickel.

By having the content of potassium as described above, there is an effect of increasing the degree of dispersion of nickel in the composite by the interaction of nickel-potassium-alumina. In addition, it is possible to control the ratio of potassium to the active surface of nickel to be below a certain value through an appropriate interaction between potassium and alumina.

In particular, in the case of a complex to which potassium is added, potassium occupies a certain portion of the active site area of nickel due to the interaction between nickel and potassium, thereby reducing the activity of the complex. The ratio of the active site area of nickel reduced by potassium can be adjusted to 0.3 or less. The active site area of nickel reduced by potassium with respect to the active site area of nickel can be measured by various methods capable of measuring the area covered by the area of potassium with respect to the area of nickel exposed on the complex, for example, , it can be measured by comparing the amount of hydrogen adsorbed to nickel before adding potassium and the amount of hydrogen adsorbed to nickel after adding potassium.

In addition, the present invention includes a porous carrier and a transition metal supported on the porous carrier, wherein the porous carrier simultaneously contains mesopores and macropores, and mesopores are formed inside the macropore wall, and the mesopores and macropores It is a hierarchical pore structure in which pores are interconnected, and a complex satisfying the following general formula 1 may be provided.

[General Formula 1] X/Y > 1;

In Formula 1, X represents the average size (nm) of the mesopores of the composite, and Y represents the size (nm) of the transition metal particles.

The porous carrier has a uniform hierarchical pore structure in which mesopores and macropores are interconnected, thereby providing a composite in which the size of the transition metal particles supported on the porous carrier is smaller than the pore size of the porous carrier.

As described above, when the size of the transition metal particles satisfies the general formula 1, which is smaller than the pore size of the porous carrier, the transition metal particles can be widely dispersed in the porous carrier and can inhibit the aggregation of particles, so when used as a catalyst There is an excellent effect of activity.

At least one selected from the group consisting of alumina, silicon dioxide, titania and zirconia may be used as the porous carrier, but is not limited as long as it is a ceramic-based material capable of simultaneously forming macropores and mesopores.

The transition metal is not particularly limited as long as it has catalytic activity, but at least one selected from the group consisting of nickel (Ni), ruthenium (Ru), rhodium (Rh), platinum (Pt), iridium (Ir) and palladium (Pd) Can be used.

In addition, the composite of the present invention comprises the steps of mixing a polymer colloid with an alumina precursor dissolved in a solvent, filtering and washing the mixture to obtain a porous alumina carrier, and impregnating the nickel precursor solution into the porous alumina carrier. can be manufactured.

In this case, a mixture of alcohol and water may be used during the washing, and a ratio of alcohol and water may be 1:5 to 4:5. For example, the ratio of the alcohol to water may be 2:5 to 4:5, 1:4 to 3:4, or 1:3 to 2:3. In the case of having the above ratio, the porous alumina carrier can form a hierarchical pore structure having macropores and mesopores at the same time, and can have excellent activity when used as a catalyst because of its wide surface area.

The alcohol is not limited as long as it is an alcohol having a low molecular weight, but is preferably at least one selected from the group consisting of methanol, ethanol and isopropyl alcohol.

The alumina precursor may be aluminum tri-sec-butoxide. Aluminum tri-sec-butoxide may contribute to the formation of uniform mesopores by penetrating between polymer particles used as templates for macropore formation. In particular, the symmetrical structure of aluminum tri-sec-butoxide and the chain length of tri-sec-butoxide make it possible to obtain a uniform mesopore size when tri-sec-butoxide is removed by calcination.

The solvent may be 2-butanol, and 2-butanol is suitable because it can lower the viscosity of aluminum tri-sec-butoxide.

The polymer colloid may be prepared by emulsifier-free emulsion polymerization of a composition comprising sodium styrene sulfonate, styrene monomer, and potassium persulfate. have.

The polymer colloid prepared by the above method may have a polymer particle size of 200 to 900 nm, for example, 200 to 800 nm, 200 to 700 nm, 200 to 600 nm, 250 to 500 nm, 250 to 400 nm, or 300 to 350 nm. can be The size of the polymer particles plays a role in determining the size of macropores in the hierarchical macro-mesopore structure of the composite.

In addition, the method for preparing the composite according to the present invention may further include the step of impregnating a potassium precursor solution into a porous alumina carrier, wherein the potassium precursor solution contains 0.3 to 3 mass of potassium based on the total mass of the porous alumina carrier and nickel % may be impregnated.

Specifically, the content of potassium with respect to the total mass of the porous alumina carrier and nickel may be 0.3 to 2.5 mass % or 0.4 to 2.3 mass %, and when it exceeds the above range, negative in the interaction of nickel-alumina-potassium By increasing the effect, the activity may decrease when used as a catalyst.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples of the present invention. These Examples and Comparative Examples are merely presented by way of example in order to explain the present invention in more detail, and the scope of the present invention is not limited thereto.

<Example>

Preparation of polymer colloids

450 g of deionized water was put into the reactor, maintained at 70° C., and stirred at 350 rpm. 0.3 g of sodium styrene sulfate and 0.02 g of sodium methacrylate were added to the reactor, and after 10 minutes, 60 g of styrene monomer was added to the reactor. After one hour, 0.25 g of potassium persulfate was added as an initiator, and then polymerization was carried out for 18 hours in a nitrogen atmosphere. The size of the polystyrene particles in the polymer colloid was measured by a field-emission scanning electron microscope (FE-SEM) and a particle size analyzer.

Preparation of porous alumina carrier

[Production Example 1]

As an alumina precursor, 10 g of aluminum tri-sec-butoxide (ASB, Sigma aldrich) was added to 10 g of 2-butanol (butanol, Sigma aldrich) as a solvent, followed by stirring to completely dissolve. A polymer colloid containing polystyrene particles having a size of about 320 nm was added and stirred for 4 hours. After filtration, the mixture was completely washed with a mixture of ethanol and water in a ratio of 1:3, and dried at 70° C. for 24 hours. The polystyrene particles were removed by calcination by maintaining at 600° C. for 6 hours at 1° C./min in a muffle furnace to obtain a porous alumina carrier.

[Production Example 2]

A porous alumina carrier was prepared in the same manner as in Preparation Example 1, except that in Preparation Example 1, the ratio of ethanol to water was 2:3.

[Production Example 3]

A porous alumina carrier was prepared in the same manner as in Preparation Example 1, except that in Preparation Example 1, washing was performed only with ethanol, not with a mixture of ethanol and water.

[Production Example 4]

A porous alumina carrier was prepared in the same manner as in Preparation Example 1, except that in Preparation Example 1, washing was performed only with water, not with a mixture of ethanol and water.

[Production Example 5]

A porous alumina carrier was synthesized using the sol-gel method. 6.0 g of cetyltrimethylammonium bromide (CTAB, Sigma aldrich) was added to a mixture containing 525 ml of deionized water and 225 ml of ethanol, and vigorously stirred at 60° C. for 20 minutes. After 10 ml of ammonium hydroxide was added to the solution, 30 g of aluminum tri-sec-butoxide was added dropwise while stirring. After stirring at 60° C. for 3 hours, the solid product was filtered and dried at 100° C. for 24 hours. Thereafter, it was calcined at 600° C. for 6 hours to obtain a porous alumina carrier.

Preparation of the complex

[Example 1]

The porous alumina carrier prepared in Preparation Example 1 was impregnated with an aqueous solution of Ni(NO ₃ ) ₂ ㆍ6H ₂ O (Sigma aldrich Korea) precursor salt in an amount of 8% by mass by Incipient wetness impregnation to obtain nickel. A supported porous alumina composite was prepared. The composite was dried at room temperature for 24 hours and in an oven at 100° C. for 5 hours, and then calcined in a kiln at 600° C. for 4 hours.

[Example 2]

The aqueous solution of KNO ₃ (Sigma aldrich Korea) precursor salt impregnated with nickel prepared in Preparation Example 1 was impregnated with an initial wet impregnation method so as to be 0.5 mass % of potassium based on the total mass of the porous alumina carrier and nickel. A porous alumina composite was prepared. The composite was dried at room temperature for 24 hours and in an oven at 100° C. for 5 hours, and then calcined in a kiln at 600° C. for 4 hours.

[Example 3]

It was prepared in the same manner as in Example 2, except that in Example 2, potassium was impregnated so as to be 2% by mass.

[Comparative Example 1]

A composite was prepared in the same manner as in Example 1, except that the porous alumina carrier prepared in Preparation Example 5 was used.

[Comparative Example 2]

A composite was prepared in the same manner as in Example 2, except that the porous alumina carrier prepared in Preparation Example 5 was used.

[Comparative Example 3]

A composite was prepared in the same manner as in Example 3, except that the porous alumina carrier prepared in Preparation Example 5 was used.

Experimental example

Preparation Examples 1 to 5, Examples 1 to 3 and Comparative Examples 1 to 3 were measured for physical properties by the following method, and the results are shown in FIGS. 1 to 8, [Table 1] and [Table 2].

BET surface area and pore size distribution were measured by nitrogen adsorption-desorption isotherms (Micromeritics ASAP 2020, Norcross, USA). The composite was measured after pretreatment at 300° C. for 6 hours.

XRD (X-ray diffraction) was measured using a Rigaku RAD-3C diffractometer (Rigaku Corporation, Japan), and the size of nickel particles from the XRD pattern was determined by Debye-Scherrer's equation of Equation 1 below. was used.

[Equation 1]

는 X-선 방사선 파장이며,

는 브랙각(Bragg angle),

는 특정 회절 피크에서의 FWHM(full sidth at half maximum)이다.In Equation 1, k = 0.9 as a shape factor,

is the X-ray radiation wavelength,

is the Bragg angle,

is the full sidth at half maximum (FWHM) at a specific diffraction peak.

The surface morphology of the composite was confirmed using SEM (JEOL JSM-600F, JEOL, Japan) and TEM (JEM-2100F, JEOL, Japan) images.

division Ethanol (V): Water (V) surface area
(m ² /g) pore size
(nm) pore volume
(cm ³ /g) Macro pore size (nm) Preparation Example 1 MaAl 1: 3 266.2 11.5 One 250 Preparation 2 MaAl 2:3 260.4 10.9 0.8 260 Preparation 3 MaAl 1: 0 310.9 7.4 1.18 not formed Preparation 4 MaAl 0 : 1 192.7 7.8 0.64 290 Preparation 5 MeAl - 314.2 9.5 1.24 -

The porous alumina carrier prepared by the method of Preparation Examples 1, 2 and 4 had a hierarchically uniform pore structure including macropores and mesopores at the same time, but the porous alumina carrier prepared by the method of Preparation Example 3 had macropores. It did not form and only had mesopores. In the porous alumina carrier of Preparation Example 5, a carrier having only mesopores was formed by the sol-gel method.

However, in the case of Preparation Example 4, the surface area was low, and it was found that a certain amount of ethanol was required to form a high surface area. This suggests that the shape and structure of the porous carrier may change depending on the washing solution used in the washing process.

division surface area
(m ² /g) pore
size
(nm) pore
volume
(cm ³ /g) nickel
size
(nm) acid
part
(mmol/g) nickel
part
(mmol/g) K area/
N area Preparation Example 1 MaAl 266.2 11.5 One - 1.008 - - Example 1 Ni-MaAl 221.5 10.8 0.81 1.8 0.768 0.017 - Example 2 0.5K/Ni-MaAl 202.1 10.2 0.69 2.1 0.545 0.017 0 Example 3 2K/Ni-MaAl 199.5 10.4 0.68 2.1 0.465 0.014 0.18 Preparation 5 MeAl 314.2 9.5 1.24 - 1.929 - - Comparative Example 1 Ni-MeAl 177.7 4 0.25 4.7 0.714 0.012 - Comparative Example 2 0.5K/Ni-MeAl 172 5.1 0.29 8.2 0.419 0.008 0.33 Comparative Example 3 2K/Ni-MeAl 168.8 5.1 0.29 7.9 0.47 0.006 0.5

Referring to Table 2, the composites of Examples 1 to 3 have a larger surface area and larger pore size (mesopores) and pore volume than the composites of Comparative Examples 1 to 3, but the size of the nickel particles is much larger small things can be seen.

That is, in the composites of Examples 1 to 3, it can be seen that the size of the nickel particles is smaller than the size of the pores, so that it is possible to access the inside of the pores. In addition, the small size of the nickel particles means that the aggregation phenomenon of the nickel particles is small compared to Comparative Examples 1 to 3. This may be due to the hierarchical pore structure of the porous alumina carrier.

In addition, in the composites of Examples 1 to 3, the active site of nickel is higher than that of Comparative Examples 1 to 3, and in particular, when comparing Examples 2 and 3 and Comparative Examples 2 and 3 in which potassium is further added, potassium is a nickel active site It can be seen that the area covered by Therefore, when the composite according to the present invention is used as a catalyst, it is expected that the catalytic activity of the nickel is greater than that of Comparative Examples 1 to 3 because the active site area of nickel is wide.

To analyze the reason for this difference, SEM, TEM, and nitrogen adsorption-desorption isotherms were analyzed. The SEM and TEM results of the composite surface are shown in FIGS. 1 and 2, and the nitrogen adsorption-desorption isotherm is shown in FIG. 3 .

It can be seen from the SEM and TEM images that the composites of Preparation Examples 1 and 1 to 3 have a hierarchical pore structure having mesopores and macropores at the same time.

In Examples 1 to 3 using the porous alumina carrier of Preparation Example 1, uniform macropores were maintained even with the addition of nickel and/or potassium. In Comparative Examples 2 and 3 using the porous alumina carrier having only mesopores of Preparation Example 5, potassium oxide (K ₂ O) increased as the content of potassium increased. K ₂ O is produced as a result of removing nitrate by calcining potassium nitrate at 600 °C. However, in Examples 2 and 3 using Preparation Example 1, almost no K ₂ O was observed, which in the case of Examples 2 and 3 K ₂ O particles were too small, in the pores of the carrier prepared in Preparation Example 1 This seems to be because it is well distributed.

Referring to FIG. 2 , the size of the nickel particles in Example 1 was much smaller than that of Comparative Example 1. This means that the nickel and potassium oxide particles have much better dispersibility in the porous alumina carrier having a hierarchical pore structure.

The nitrogen adsorption-desorption isotherms and pore size distributions are shown in FIG. 3 . In the case of Preparation Example 1, it can be seen that the size of the mesopores is larger than that of Preparation Example 5. However, in Examples 1 to 3 using the carrier of Preparation Example 1, there was little change in pore size and volume even after the addition of nitrogen and/or potassium, but in Comparative Examples 1 to 3 using the carrier of Preparation Example 5, large There was a decrease. This means that in Comparative Examples 1 to 3, the nickel particles blocked the mesopores or a new phase was formed by the interaction between nickel and the alumina carrier. That is, in the case of Examples 2 and 3 using the carrier of Preparation Example 1, the size of the nickel particles is small, and the dispersion degree is small without change in the pore size and volume due to the interaction between Ni-K-Al ₂ O ₃ even when potassium is added. has a high effect, but in Comparative Examples 2 and 3 using the carrier of Preparation Example 5, potassium rather weakens the Ni-Al ₂ O ₃ interaction, thereby reducing the size and volume of pores.

For better understanding, the surface of the composite is shown in FIG. 4 . After the porous alumina carrier was impregnated with nickel, the surface of the carrier using Preparation Example 5 was highly coated with NiAl ₂ O ₄ (green) and nickel oxide (dark green). Although this phenomenon also appeared on the surface of the carrier using Preparation Example 1, the BET surface area was larger because the coverage was lower than that of the carrier using Preparation Example 5.

In the second step of impregnating the porous alumina carrier with potassium, the impregnated potassium exists in three forms: potassium oxide (purple triangle), potassium aluminate (KAlO ₂ , orange rectangle) and potassium atom (interacting with nickel).

When the carrier of Preparation Example 5 is used, the K-NiAl ₂ O ₃ interaction is reduced by the surface coating of NiAl ₂ O ₄ , and the number of potassium oxide and potassium atoms increases. On the other hand, when the carrier of Preparation Example 1 is used, K—NiAl ₂ O ₃ interaction occurs strongly to generate more potassium aluminate on the surface, and to reduce potassium atoms interacting with the nickel active site.

5 shows XRD patterns measured after calcining Examples and Comparative Examples in air and reducing in hydrogen at 600°C. The presence of a characteristic XRD peak for nickel oxide at 2θ = 43.4 ° indicates that the calcined catalyst was not completely reduced in hydrogen at 600 °C for 2 h. In addition, one sharp XRD peak for metallic nickel was observed in the comparative example. was clearly observed in the complex. In addition, in the Example, the peak for metallic nickel appeared widely. The particle size of nickel in the Example was much smaller than that of the comparative example, which means that the pores were blocked in the comparative example due to the size of the large nickel particles, and the pore size and volume were greatly reduced.

In addition, shifts of peaks occurred in alumina XRD after nickel impregnation from 2θ = 45.8°, 60.5° and 66.8° to 2θ = 45.4°, 59.9° and 66.3°. This indicates that a new nickel aluminate-like spinel phase was formed as a result of the interaction of nickel and alumina at the interface.

<Catalyst Activity Test>

0.25 g of the composite powder was put into a tube reactor with an inner diameter of 9.1 mm, and 0.1 ml/min of 1-methyl naphthalene (1-MN) and 0.4 ml/min of water were added at 600° C. for 2 hours in the steam reforming reaction. was measured, and the results are shown in Tables 3 and 4.

The steam reforming reaction may be represented by Chemical Formulas 1 to 3 below.

(Formula 1) Steam reforming

C ₁₁ H ₁₀ + 11H ₂ O → 11CO + 16H ₂

(Formula 2) Water gas shift reaction (Water gas shift)

11CO + 11H ₂ O → 11CO ₂ + 11H ₂

(Formula 3) overall reaction

C ₁₁ H ₁₀ + 22H ₂ O → 11CO ₂ + 27H ₂

In product analysis, H ₂ , CO, CO ₂ , CH ₄ and C ₂ -C ₄ gases were analyzed through gas chromatography-TCD (Acme 6100 GC, YL Instrument, Korea). The liquid product was analyzed by gas chromatography (Agilent 6890 N Network GC, Agilent Technologies, USA). The amount of coke was measured by thermogravimetric analysis (TG Q50, TA instrument, USA).

In addition, each measured value was expressed as a result by the following formula.

(Equation 1) Carbon selectivity of gaseous product (mol, %) =

(Equation 2) Carbon selectivity of liquid product (mol, %) =

(Equation 3) Conversion (mol, %) =

(Formula 4) Gas phase composition (mol%) =

(Equation 5) Reaction rate (mol%) =

(Equation 6) TOF(turnover frequency, H ₂ ) =

division conversion rate
(%) Carbon selectivity (%) Liquid product distribution (%) coke gas Liquid A B C blank test 6.2 3.3 26.1 70.6 5 84 11 Preparation Example 1 MaAl 13.9 0.3 47 52.7 23 67 10 Example 1 Ni-MaAl 20.1 0.5 56.9 42.5 6 86 8 Example 2 0.5K/Ni-MaAl 23.1 0.5 65.4 34.1 10 79 11 Example 3 2K/Ni-MaAl 20.4 0.4 55.1 44.4 13 76 10 Preparation 5 MeAl 11.5 0.4 22.9 76.8 27 65 8 Comparative Example 1 Ni-MeAl 16.1 0.3 49.8 49.9 22 77 One Comparative Example 2 0.5K/Ni-MeAl 11.3 0.6 48.9 50.5 31 61 7 Comparative Example 3 2K/Ni-MeAl 6.9 0.7 55.2 44.1 26 52 21

In Table 3, A represents a ring-opened hydrocarbon, B represents a cyclic hydrocarbon, and C represents a condensed hydrocarbon.

Referring to Table 3, it can be seen that the conversion rates and carbon selectivity of the composites of Examples 1 to 3 are much higher than those of Comparative Examples 1 to 3. In particular, Examples 1 to 3 have a high ratio of B (aromatic hydrocarbon) such as naphthalene or a benzene ring compound, whereas Comparative Examples 1 to 3 have a decreased fraction of B, and a relatively light A (ring-opened hydrocarbon) ratio increased. did.

In addition, in Examples 1 to 3, the conversion increased and then decreased again as the content of potassium increased, whereas in Comparative Examples 1 to 3, the conversion decreased according to the addition of potassium, and as the content increased, the conversion further decreased. This means that the activity of the composite in the steam reforming reaction according to the addition of potassium is affected by the shape and structure of the porous alumina carrier.

division H ₂ CO CO ₂ CH ₄ C ₂ + TOF(H ₂ ) H ₂ /
(CO+CO ₂ ) (mol/mol.h) blank test 0 0 0 66 34 Preparation Example 1 MaAl 0 0 5 62 33 0 Example 1 Ni-MaAl 28 26 9 20 17 577 0.8 Example 2 0.5K/Ni-MaAl 43 26 7 14 10 952 1.26 Example 3 2K/Ni-MaAl 41 26 9 16 7 950 1.16 Preparation 5 MeAl 0 0 6 66 28 0 Comparative Example 1 Ni-MeAl 28 29 38 3 2 736 0.42 Comparative Example 2 0.5K/Ni-MeAl 18 8 12 48 15 430 0.9 Comparative Example 3 2K/Ni-MeAl 0 0 22 38 40 0

In steam reforming, 1-MN is oxidized to CO and H ₂ by reactive oxygen species, whereas in steam cracking, hydrocarbons are ring-opened and CO ₂ is released. Referring to Table 4, Comparative Examples 1 to 3 show a high CO ₂ and low CO ratio, it can be seen that steam cracking is relatively dominant.

In Examples 2 and 3, the ratio of CH ₄ and C ₂ + is low, and the ratio of CO and H ₂ has a high gas composition, which indicates that an additional active nickel site was generated by the interaction of K-Al ₂ O ₃ it means.

Comparing Examples 2 and 3, the conversion rate and TOF value increase and then decrease again as the content of potassium increases, which has a positive effect on the dispersion degree of nickel up to a certain content of potassium according to the K-Ni interaction. , appears to be due to reducing the area of nickel active sites when the content of potassium becomes too high. However, in Comparative Examples 2 and 3, nickel was not uniformly dispersed compared to Examples 2 and 3, so that the nickel active site was immediately reduced by potassium due to an increase in the potassium content. showed

6 shows the reaction rate with respect to time of the stream. The composite according to Preparation Example 5 and Comparative Examples 1 to 3 showed a very large decrease in the reaction rate compared to the composites of Preparation Examples 1 to 1 to 3. This means that the nickel active site can be changed to nickel oxide to show inertness.

The XRD pattern of the catalyst used in FIG. 7 is shown, and it can be clearly seen that nickel oxide was formed after 2 hours of reaction. Table 5 shows the quantified ratios of the nickel phase of the used and fresh catalysts.

division complex used new complex NiO Ni NiAl ₂ O ₄ NiO Ni NiAl ₂ O ₄ Example 1 Ni-MaAl 24 11 65 23 11 66 Example 2 0.5K/Ni-MaAl 27 23 50 24 27 48 Example 3 2K/Ni-MaAl 23 31 46 21 33 45 Comparative Example 1 Ni-MeAl 11 27 61 4 33 62 Comparative Example 2 0.5K/Ni-MeAl 28 18 54 11 33 56 Comparative Example 3 2K/Ni-MeAl 66 0 34 42 21 37

Referring to Table 5, it can be seen that in the composites used in Comparative Examples 1 to 3, the ratio of nickel oxide (NiO) was sharply increased compared to that of the new composite. On the other hand, in Examples 1 to 3, the amount of change in nickel oxide of the composite used in comparison with the new composite was insignificant.

It seems that the adsorption of potassium, surface oxidizing species, and nickel forms a Ni-O-K bond, which promotes the change of nickel to nickel oxide. In Comparative Examples 2 and 3, the coverage area of potassium with respect to the nickel area was high, It appears that the nickel active sites are rapidly reduced.

Claims (14)

porous alumina carrier; and
Containing nickel supported on a porous alumina carrier,
The size of the nickel particles is 1.5 to 2.3 nm,
The porous alumina carrier has a hierarchical pore structure including mesopores and macropores at the same time, mesopores are formed inside the macropore wall, and the mesopores and macropores are interconnected,
and a composite having an average size of mesopores of 8 to 12 nm of the porous alumina carrier,
The composite is a catalyst for steam reforming reaction having a conversion rate of 20.1% to 23.1% represented by Equation 3 during the steam reforming reaction:
[Equation 3]

In Formula 3, 1-MN is 1-methyl naphthalene.
delete delete The method of claim 1,
The composite is a catalyst for steam reforming reaction further comprising 0.3 to 3% by mass of potassium based on the total mass of the porous alumina carrier and nickel.
delete A method for preparing the catalyst for the steam reforming reaction according to claim 1, comprising:
mixing a polymer colloid with an alumina precursor dissolved in a solvent;
filtering and washing the mixture to obtain a porous alumina carrier; and
impregnating the nickel precursor solution into the porous alumina carrier;
The washing is a method for producing a catalyst for steam reforming reaction is performed using a mixture of alcohol and water.
7. The method of claim 6,
The ratio of the alcohol and water is 1:5 to 4:5. Method for producing a catalyst for steam reforming reaction.
7. The method of claim 6,
The solvent is 2-butanol (2-butanol) method for producing a catalyst for steam reforming reaction.
7. The method of claim 6,
The alumina precursor is aluminum tri-sec-butoxide (aluminum tri-sec-butoxide) is a method for producing a catalyst for steam reforming reaction.
7. The method of claim 6,
The method for producing a catalyst for steam reforming reaction wherein the polymer colloid is prepared by emulsifier-free emulsion polymerization of a composition containing a styrene monomer.
7. The method of claim 6,
The method for producing a catalyst for steam reforming reaction wherein the size of the polymer particles dispersed in the polymer colloid is 200 to 900 nm.
7. The method of claim 6,
A method for preparing a catalyst for steam reforming reaction further comprising the step of impregnating a potassium precursor solution into a porous alumina carrier.
13. The method of claim 12,
The method for producing a catalyst for steam reforming reaction wherein the potassium precursor solution is impregnated so that the potassium content is 0.3 to 3 mass % based on the total mass of the porous alumina carrier and nickel.


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