KR101269621B1 - Mesoporous nickel-M-alumina aerogel catalyst and preparation method thereof - Google Patents

Abstract

The present invention relates to a medium-porous nickel-M-alumina aerogel catalyst, a method for preparing the same, and a method for producing hydrogen gas by steam reforming of liquefied natural gas (LNG) using the catalyst. Nickel-M-alumina aerogel catalyst which is used for the production of hydrogen gas by steam reforming of natural gas, in which the atomic ratio of enhancer (M) / aluminum is in the range of 0.001 to 0.1 and the atomic ratio of nickel / aluminum is in the range of 0.01 to 1, The present invention relates to a method for producing hydrogen gas by the steam reforming reaction of liquefied natural gas using the catalyst, and according to the present invention, in addition to the reaction activity as compared to conventional nickel-based catalysts, Since the resistance can be maximized, hydrogen gas of high purity can be produced efficiently for a long time.

Description

Mesoporous nickel-M-alumina aerogel catalyst and preparation method

The present invention relates to a medium-porous nickel-M-alumina aerogel catalyst, a method for preparing the same, and a method for producing hydrogen gas by steam reforming of a liquefied natural gas (LNG) using the catalyst.

Hydrogen energy, which has been spotlighted as the future energy, has much advantages as a next-generation energy source to replace fossil fuels because it has superior advantages over existing fossil fuels and nuclear power, which have limited reserves. Its importance is growing due to performance and market expansion. In particular, hydrogen energy has an advantage that it is easy to use as a fuel for direct combustion or fuel cell, because it has an advantage that almost no pollutant is discharged except that a very small amount of nitrogen is generated during combustion.

Recently, research on commercialization of PEMFC / Polymer Electrolyte Membrane Fuel Cell, which can produce electric energy using hydrogen energy as a raw material, has been conducted in factories, transportation vehicles, and residential power generators. It is actively progressed with the aim of applying to various aspects of the company. However, in order to commercialize the polymer electrolyte fuel cell, it is a priority to develop a catalytic process capable of stably and efficiently producing and supplying high purity hydrogen gas.

Catalytic reforming to produce hydrogen from hydrocarbons and alcohols involves steam reforming, auto-thermal reforming and partial oxidation depending on the type of reactants used with the hydrocarbons and alcohols. And Carbon Dioxide Reforming.

However, among the known reforming reactions, it is known that steam reforming reactions having excellent hydrogen yields are suitable for producing hydrogen for fuel cells. In particular, the catalytic process for producing hydrogen from natural gas through steam reforming reaction is widely known as a suitable process for commercial hydrogen gas production. Although natural gas has a huge reserve in the world, it mainly consists of lower gas such as methane and ethane. Because it has no utility value except for heating purpose, it does not add much value by itself. Liquefied natural gas, produced by liquefying natural gas at cryogenic temperatures, has very low sulfur content and easy transport and storage compared to other fossil raw materials, so it has been used as a cogeneration, gas heating, cold heat utilization industry and transportation raw material. Although used, it has recently attracted attention as an effective raw material for producing and supplying hydrogen to reformers mounted in various vehicles and household generators.

However, in order to stably produce and supply high quality and high purity hydrogen gas for a long time, it is important to select and develop a steam reforming catalyst system that is suitable for steam reforming of liquefied natural gas and at the same time very active.

Rh>Ni>Ir>Pd

Pt>Co

Fe의 순으로 감소하는 것으로 알려져 있다[G. Jones, J.G. Jakobsen, S.S. Shim, J. Kleis, M.P. Andersson, F. Abild-Pedersen, T. Bligaard, S. Helveg, B. Hinnemann, J.R. Rostrup-Nielsen, I. Chorkendorff, J. Sehested, J.K. Norskov, J. Catal. 259권 147쪽 (2008년)]. 귀금속계 촉매인 Ru 및 Rh 촉매가 가장 우수한 반응활성을 나타내지만 이들 귀금속계 촉매는 가격경쟁력이 매우 낮은 단점이 있기 때문에 비귀금속계 촉매 중에서 비교적 높은 활성을 갖는 니켈계 촉매가 상업적인 공정에 가장 많이 이용되고 있다.
It is known that Group 8-10 transition metals can be used as a reforming catalyst for steam reforming reactions of hydrocarbons and alcohols. Among them, commercially available catalysts include noble metal catalysts such as Ru, Rh, Ir, Pd and Pt, and Ni. And non-noble metal catalysts such as Co and Fe. Reaction activity in the steam reforming reaction of the noble metal and the non-noble metal catalyst is Ru

Rh>Ni>Ir> Pd

Pt> Co

It is known to decrease in order of Fe [G. Jones, JG Jakobsen, SS Shim, J. Kleis, MP Andersson, F. Abild-Pedersen, T. Bligaard, S. Helveg, B. Hinnemann, JR Rostrup-Nielsen, I. Chorkendorff, J. Sehested, JK Norskov, J Catal. 259 vol. 147 (2008)]. Although noble metal catalysts Ru and Rh catalysts show the best reaction activity, nickel catalysts having relatively high activity among non-noble metal catalysts are most used in commercial processes because these noble metal catalysts have the disadvantage of very low price competitiveness. It is becoming.

However, nickel-based catalysts are vulnerable to catalyst deactivation due to carbon deposition in steam reforming of methane, and deactivation problems due to poisoning by sulfur and sintering of active particles are serious and do not exhibit stable activity for a long time. In order to solve this problem, commercial processes require harsh reaction conditions such as supplying high temperature (more than 800 ° C.), high pressure (20 to 40 bar), and excess water vapor to suppress deactivation of nickel-based catalysts. Economics are not only very poor but also unstable. In particular, in the process for the production of hydrogen gas in small scale and household, it is difficult to apply such harsh reaction conditions because stability is very important such as operating at a relatively low temperature. Therefore, it has a physical and chemical structure that is highly resistant to nickel deposition, carbon deposition and sintering, etc., which have high activity and stability in small steam reforming reactions, and thus design catalysts that solve the deactivation problem and improve the catalyst performance itself. It is essential to develop.

In fact, studies have been made to increase the stability of nickel catalysts by adding a small amount of an additive such as alkali or alkaline earth metals to nickel catalysts, thereby increasing resistance to deactivation of nickel particles. There are disadvantages that can only reduce the original reaction activity [JS Lisboa, DCRM Santos, FB Passos, FB Noronha, Catal. Today, Vol. 101, p. 15 (2005)]. In addition, through the introduction of a carrier having superior oxygen storage capacity such as ceria and zirconia, it is possible to increase the resistance of the nickel catalyst to carbon deposition by promoting the oxidation reaction of the surface carbon species of the nickel catalyst. Although reported, these ceria and zirconia carriers are not only physically unstable compared to commercially available alumina carriers, but also have a significantly lower price competitiveness (Korean Patent No. 336,968 / Korean Patent No. 858,924). In addition, the present inventors have developed a mesoporous nickel-based catalyst through the sol-gel method and the casting method to perform the polymerization of carbon species adsorbed and dissolved on the catalyst surface in the steam reforming reaction. At the same time, it has been reported to promote the vaporization reaction relatively, resulting in stable and high reaction activity in the steam reforming reaction of liquefied natural gas [JG Seo, MH Youn, IK Song, Catal. Surv. Asia, Vol. 14, p. 1 (2010) / JG Seo, MH Youn, JC Jung, IK Song, Int. J. Hydrogen Energy, Vol. 35, pp. 6738 (2010) / Korean Patent No. 883,790].

However, the reaction activity of the nickel-based catalyst is known to be affected by the physical and chemical properties of the carrier as well as the properties of the nickel metal itself. Therefore, research has been conducted to control the physical and chemical properties of alumina, which is mainly used as a carrier, for the production of efficient nickel-based catalysts. In particular, many studies on medium-porous alumina have been conducted [JG Seo, MH Youn, KM Cho, S. Park, IK Song, J. Power Sources, Vol. 173, 943 (2007)]. Since the nickel metal particles are very evenly dispersed on the surface of the alumina having a medium pore structure, the distance between the reaction active sites is relatively far from that of the nickel-based catalyst having no pore structure, so that the polymer of the surface carbon species occurs at the nickel-alumina interface. This is because it suppresses the gasification reaction and promotes the gasification reaction, and as a result, it is possible to suppress the catalyst deactivation by carbon deposition and sintering of nickel particles.

However, the simple chemical composition of nickel and alumina is not only limited to maximizing the dispersibility of nickel active particles on the surface of nickel-based catalysts, but is also very vulnerable to the reduction of activity due to sintering of nickel particles under long-term steam reforming operation conditions. have.

As a result of the intensive efforts, the present inventors have found a medium-porous nickel-M-alumina aerogel catalyst which has excellent dispersibility of nickel-containing metal particles and very high resistance to carbon deposition and particle sintering, which enables stable operation for a long time. The present invention has been completed by successfully preparing and producing hydrogen gas through steam reforming of liquefied natural gas.

An object of the present invention is not only excellent dispersibility of metal particles containing nickel in the hydrogen gas production by the steam reforming reaction of liquefied natural gas but also highly resistant to carbon deposition and particle sintering, which enables stable operation for a long time. To provide a medium-porous nickel-M-alumina aerogel catalyst and a method of manufacturing the same.

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

According to one aspect of the present invention, there is provided a mesoporous nickel-M-alumina aerogel catalyst mixed with an enhancer (M) / aluminum ratio of 0.001 to 0.01 and a nickel / aluminum ratio of 0.01 to 1.

According to one embodiment of the invention, the enhancer (M) is Ni, Ce, La, Y, Cs, Fe, Co, Mg, Cu, Pt, Au, Pd, Rh, Yb, Ag, Ru, Ir, Os It may be at least one selected from the group consisting of Au, V, Sn and Ca.

According to one embodiment of the invention, the catalyst may have an average pore size of 2 to 50 nm and an average particle size of 2 to 100 nm.

According to another aspect of the invention, i) dissolving an aluminum precursor in a heated alcohol solvent; Ii) forming a transparent alumina sol (Sol) by partially hydrating by mixing water, acid and alcohol in the solution; Iii) adding a nickel precursor and a promoter (M) precursor to the alumina sol (Sol) to form a nickel-M-alumina hybrid sol (Sol); Iii) cooling the nickel-M-alumina hybrid sol (Sol) to room temperature and then forming a nickel-M-alumina hybrid gel (Gel) through a hydration and condensation reaction with a mixed solution of water and alcohol; Iii) aging the nickel-M-alumina hybrid gel (Gel); Iii) drying the aged nickel-M-alumina hybrid gel (Gel) using supercritical carbon dioxide; And iii) heat-treating the dried nickel-M-alumina hybrid gel (Gel) to provide a method for preparing a medium-porous nickel-M-alumina aerogel catalyst.

According to one embodiment of the invention, the aluminum precursor is aluminum nitrate nonahydrate (Aluminum Nitrate Nonahydrate), aluminum fluoride trihydrate (Aluminum Fluoride Trihydrate), aluminum phosphate hydrate (Aluminum Phosphate Hydrate), aluminum chloride hexahydrate (Aluminum It may be at least one selected from the group consisting of Chloride Hexahydrate, Aluminum Hydroxide, Aluminum Sulfate Hexadecahydrate, and Aluminum Ammonium Dodecahydrate.

According to an embodiment of the present invention, the nickel precursor is nickel nitrate hexahydrate (Nickel Nitrate Hexahydrate), nickel chloride hexahydrate (Nickel Chloride Hexahydrate), nickel acetate tetrahydrate (Nickel Acetate Tetrahydrate) and nickel bromide hydrate (Nickel Bromide) Hydrate) may be one or more selected from the group consisting of.

According to an embodiment of the present invention, the enhancer (M) precursor is a metal acetate hydrate (Metal Acetate Hydrate), metal nitrate hydrate (Metal Nitrate Hydrate), metal chloride hydrate (Metal Chloride Hydrate) and metal bromide hydrate (Metal Bromide hydrate) Hydrate) may be one or more selected from the group consisting of.

According to one embodiment of the invention, the step iii) may be carried out at a temperature of 30 to 80 ℃ and a pressure of 100 to 300 atm.

According to one embodiment of the invention, the step iii) may be carried out at a temperature of 500 to 900 ℃.

According to another aspect of the invention, the step of filling the catalyst in a steam reforming reactor; And ii) passing a mixed gas consisting of liquefied natural gas and water vapor through a catalyst layer in a reactor at a space velocity of 1,000 to 500,000 ml / g-catalyst.h, to produce hydrogen gas from liquefied natural gas by steam reforming reaction. This is provided.

According to one embodiment of the present invention, before the step ii) may further comprise the step of reducing the catalyst charged in the reactor to a mixed gas of nitrogen and hydrogen.

According to one embodiment of the invention, the volume ratio of the nitrogen and hydrogen may be 1/10 to 1/2.

According to one embodiment of the present invention, the liquefied natural gas and water vapor volume ratio may be 1/10 to 1/1.

According to one embodiment of the invention, the steam reforming reaction may be carried out at a reaction temperature of 500 to 900 ℃.

The medium-porous nickel-M-alumina aerogel catalyst according to the present invention shows a high conversion rate and hydrogen yield of liquefied natural gas without deactivation for a long time in the steam reforming of liquefied natural gas, and does not include the nickel-alumina enhancer (M). Compared with nickel catalysts supported on aerogels and commercially available alumina carriers, the dispersion of metal particles is excellent and high resistance to carbon deposition and particle sintering.

1 is an X-ray diffraction analysis of Ni-M-Al ₂ O ₃ (M = Ni, Ce, La, Y, Cs, Fe, Co and Mg) airgel catalysts prepared by Examples 1 to 8 of the present invention. The result graph.
FIG. 2 is X-rays after reduction of Ni-M-Al ₂ O ₃ (M = Ni, Ce, La, Y, Cs, Fe, Co and Mg) airgel catalysts prepared by Examples 1 to 8 of the present invention. It is a graph of diffraction analysis results.
3 is a comparison of Ni-M-Al ₂ O ₃ (M = Ni, Ce, La, Y, Cs, Fe, Co and Mg) airgel catalyst prepared by Examples 1 to 8 according to the reaction time Graph of change in liquefied natural gas conversion rate (left) and graph of hydrogen yield change (right) (★ / Ni-La-) of nickel catalyst (Ni / Al ₂ O ₃ -commercial) supported on commercial alumina prepared in Example 1 Al ₂ O ₃ , ○ / Ni-Ce-Al ₂ O ₃ , ● / Ni-Y-Al ₂ O ₃ , ■ / Ni-Cs-Al ₂ O ₃ , □ / Ni-Ni-Al ₂ O ₃ , ▲ / Ni-Fe-Al ₂ O ₃ , Δ / Ni-Co-Al ₂ O ₃ , ◆ / Ni-Mg-Al ₂ O ₃ , ◇ / Ni / Al ₂ O ₃ -commercial).
Figure 4 is Ni-M-Al ₂ O ₃ (M = Ni, Ce, La, Y, Cs, Fe) prepared by Examples 1 to 8 of the present invention according to the type of enhancer (M) after the reaction time 400 minutes , Co and Mg) is a graph comparing the reaction activity of the airgel catalyst.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is capable of various modifications and various embodiments, and specific embodiments are illustrated in the drawings and described in detail in the detailed description. It is to be understood, however, that the invention is not to be limited to the specific embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. In the following description of the present invention, if it is determined that the detailed description of the related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted.

The present invention provides a mesoporous nickel-M-alumina aerogel catalyst mixed with a promoter (M) / aluminum ratio of 0.001 to 0.1 and a nickel / aluminum ratio of 0.01 to 1.

Aerogels generally refer to porous gels in which a solvent is removed and air enters between the meshes of the gels. In the present invention, a nickel-M-alumina hybrid gel is used for aging, drying, And it refers to the morphological features of the medium-porous nickel-M-alumina catalyst prepared by heat treatment at high temperature. The medium porosity nickel-M-alumina aerogel catalyst of the present invention facilitates the vaporization of hydrocarbon species adsorbed on the catalyst surface due to the well-developed medium pores and highly dispersed nickel particles, thereby suppressing carbon deposition and sintering of nickel particles. Catalyst deactivation by is an excellent catalyst which hardly appears even during long time operation.

The atomic ratio of the enhancer (M) / aluminum in the mesoporous nickel-M-alumina aerosol catalyst may be 0.001 to 0.1, preferably 0.01 to 0.05, in terms of catalyst activity and economics of catalyst preparation. If the atomic ratio of enhancer (M) / aluminum is less than 0.001, not only is the distribution probability of the enhancer (M) too low, but also the enhancer binds too strongly to the structure of the alumina in the finally obtained catalyst to form an inert M-aluminate phase. It may form and may not function as an enhancer (M). When the atomic ratio of the enhancer (M) / aluminum exceeds 0.1, the effect of improving the dispersion of the particles containing nickel is insignificant, and the excess enhancer (M) may inhibit the catalytic activity by interfering with the surface exposure of nickel serving as the active site. In addition, the atomic ratio of nickel / aluminum in the mesoporous nickel-M-alumina aerosol catalyst may be 0.01 to 1, preferably 0.1 to 1 in terms of catalyst activity and economics of catalyst production. If the atomic ratio of nickel / aluminum is less than 0.01, not only is the nickel active point too diluted, but also undesirable, and in the finally obtained catalyst, the nickel binds too strongly to the structure of the alumina to form an inert nickel-aluminate phase. When the atomic ratio of nickel / aluminum exceeds 1, the dispersion of active sites is not uniform, and the interaction between nickel and alumina is so weak that the sintering phenomenon and carbon deposition of nickel particles are too weak. The resistance to this can be very low.

The enhancer (M) is Ni, Ce, La, Y, Cs, Fe, Co, Mg, Cu, Pt, Au, Pd, Rh, Yb, Ag, Ru, Ir, Os, Au, V, Sn and Ca It may be one or more selected from the group consisting of.

The mesoporous nickel-M-alumina aerogel catalyst of the present invention may have an average pore of 2 to 50 nm and an average particle size of 2 to 100 nm.

The present invention also provides a method for preparing a mesoporous nickel-M-alumina aerogel catalyst. The method for preparing the medium-porous nickel-M-alumina aerogel catalyst is specifically made of the following steps.

First, the aluminum precursor is dissolved in the heated alcohol solvent. The alcohol solvents include all representative alcohols such as ethanol, methanol, propanol, isopropanol, 1-butanol and 2-butanol. Among them, it is most preferable to use ethanol, and it is preferable to dissolve by adding and stirring the alumina precursor under an alcohol solvent heated to 50 to 100 ° C. In addition, all aluminum alkoxides may be used as the aluminum precursor, preferably, aluminum sec-butoxide, aluminum ethoxide, aluminum tert-butoxide. 1 type selected from the group consisting of aluminum isopropoxide, aluminum tri-sec-Butoxide, and aluminum tri-tert-Butoxide. It may be abnormal.

Then, a transparent alumina sol (Sol) is formed by partially hydrating by mixing water, acid and alcohol in a solution in which the aluminum precursor is dissolved.

Thereafter, a nickel precursor and a promoter (M) precursor are added to the alumina sol (Sol) to form a nickel-M-alumina hybrid sol (Sol). At this time, since the alumina sol is in a heated state, it is preferable to use it after cooling to about 20 to 80 ° C. In addition, the nickel precursor is not particularly limited and generally all nickel precursors that can be used in preparing a catalyst may be used. Preferably, nickel acetate tetrahydrate, nickel nitrate hexahydrate, and nickel are used. It may be at least one selected from the group consisting of chromide hexahydrate (Nickel Chloride Hexahydrate) and nickel bromide hydrate (Nickel Bromide Hydrate), more preferably may be nickel acetate tetrahydrate (Nickel Acetate Tetrahydrate). The enhancer (M) precursor is not particularly limited and generally all metal precursors that can be used in preparing a catalyst may be used. Preferably, metal acetate hydrate and metal nitrate hydride are used. It may be one or more selected from the group consisting of metal chloride hydride (Metal Chloride Hydrate) and metal bromide hydride (Metal Bromide Hydrate), more preferably may be metal acetate hydrate (Metal Acetate Hydrate).

Then, the nickel-M-alumina hybrid sol (Sol) is cooled to room temperature, and then a nickel-M-alumina hybrid gel (Gel) is formed through a hydration and condensation reaction with a mixed solution of water and alcohol, and then the nickel The -M-alumina hybrid gel (Gel) is aged. At this time, the aging is preferably aged at room temperature for 1 to 15 days.

Thereafter, the aged nickel-M-alumina hybrid gel (Gel) is dried using supercritical carbon dioxide. The drying process may be carried out under conditions of a general supercritical section of carbon dioxide, but is preferably performed at a temperature of 30 to 80 ℃ and a pressure of 100 to 300 atm.

Thereafter, when the dried nickel-M-alumina hybrid gel (Gel) is heat treated, a nickel-M-alumina aerogel catalyst is prepared. The heat treatment may be performed in a temperature range of 500 to 900 ℃. If the temperature is less than 500 ℃ may not exhibit sufficient activity in the steam reforming reaction of liquefied natural gas, if the temperature exceeds 900 ℃ sintering of the catalyst due to the sintering of the nickel particles collapses to obtain the desired catalytic activity Can't.

In addition, the present invention comprises the steps of filling the medium reformed nickel-M-alumina aerogel catalyst in a steam reforming reactor; And passing the mixed gas consisting of liquefied natural gas and water vapor through a catalyst layer in the reactor at a space velocity of 1,000 to 500,000 ml / g-catalyst.h, providing a method for producing hydrogen gas from liquefied natural gas by steam reforming reaction. do.

It is preferable to further include a pretreatment process of filling the catalyst in the reformer reactor and then reducing the catalyst charged in the reactor into 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 a nickel oxide species, it is preferable to undergo a pretreatment process in which all nickel catalysts are reduced with hydrogen before performing the reaction. In the mixed gas used in the pretreatment, the volume ratio of hydrogen and nitrogen is preferably 1/10 to 1/2. If the volume ratio of hydrogen and nitrogen of the mixed gas is less than 1/10 may not be sufficient reduction, if more than 1/2 exceeds the amount of hydrogen required for reduction is not economical.

In the production of hydrogen gas according to the present invention, the mixed gas and the nitrogen gas have a volume ratio of liquefied natural gas and water vapor in the mixed gas at a space velocity of 1,000 to 500,000 ml / g-catalyst and h at a ratio of 1/10 to 1/1. It is preferable to pass the layer. If the volume ratio of liquefied natural gas and water vapor is less than 1/10, sufficient activity cannot be expected. If the volume ratio exceeds 1/1, it is not preferable in terms of energy efficiency.

In addition, the reaction temperature when producing hydrogen gas according to the present invention may be 500 to 900 ℃. If the reaction temperature is less than 500 ℃ can not describe sufficient catalytic activity, if the reaction temperature exceeds 900 ℃ stability may be lowered due to sintering of the catalyst.

Hereinafter, the present invention will be described in more detail with reference to Examples. It should be understood, however, that these examples are for illustrative purposes only and are not to be construed as limiting the scope of the present invention.

Example  One: Medium porosity  nickel- Ni Preparation of Alumina Aerogel Catalysts

After dissolving 7 g of aluminum secondary-butoxide (Aluminum sec-Butoxide, manufactured by Sigma-Aldrich) as an aluminum precursor in an ethanol solvent heated to 80 ° C., ethanol / nitric acid / water (40 ml) was added to the solution while maintaining the temperature at 80 ° C. /0.1 ml / 0.3 ml) A partial hydration reaction was carried out while slowly adding the mixed solution to obtain a uniform and transparent alumina sol (Sol) in water. The alumina sol (Sol) was cooled to 60 ° C., followed by 2.3 g of nickel acetate tetrahydrate (manufactured by Sigma-Aldrich) dispersed in 10 ml of ethanol as a nickel precursor and nickel acetate hydrate (manufactured by Sigma-Aldrich) as a precursor (M) 0.5 g was added to obtain a nickel-Ni-alumina hybrid sol (Sol). The obtained nickel-M-alumina hybrid sol (Sol) is cooled to room temperature (25 ° C), and then ethanol / water (5 ml / 0.6 ml) mixed solution is slowly injected to hydrate and condense the nickel-Ni-alumina hybrid gel. (Gel) was obtained and aged for 7 days at room temperature (25 ℃). The aged gel was then dried in a supercritical carbon dioxide atmosphere at 50 ° C. and 170 atm for 24 hours to obtain a medium porosity nickel-Ni-alumina aerogel. Finally, the obtained nickel-Ni-alumina airgel was heat-treated in an air atmosphere at 700 ° C. for 5 hours using an electric furnace to prepare a medium-porous nickel-Ni-alumina airgel catalyst, which was named Ni-Ni-Al ₂ O ₃ . .

Example  2: Medium porosity  nickel- Ce Preparation of Alumina Aerogel Catalysts

Medium porosity in the same manner as in Example 1 using 0.2 g of cerium (III) acetate hydrate (Sigma-Aldrich) instead of nickel acetate hydrate (Sigma-Aldrich) as the enhancer (M) precursor of Example 1 Nickel-Ce-alumina aerogel catalysts were prepared and named Ni-Ce-Al ₂ O ₃ .

Example  3: Medium porosity  nickel- La Preparation of Alumina Aerogel Catalysts

Medium pores in the same manner as Example 1 using 0.2 g of lanthanum (III) acetate hydrate (Sigma-Aldrich) instead of nickel acetate hydrate (Sigma-Aldrich) as the enhancer (M) precursor of Example 1 A star nickel-La-alumina aerogel catalyst was prepared and named Ni-La-Al ₂ O ₃ .

Example  4: Medium porosity  Preparation of Nickel-Y-Alumina Aerogel Catalysts

Medium porosity in the same manner as in Example 1 using 0.2 g of yttrium (III) acetate hydrate (Sigma-Aldrich) instead of nickel acetate hydrate (Sigma-Aldrich) as the enhancer (M) precursor of Example 1 Nickel-Y-alumina aerogel catalysts were prepared and named Ni-Y-Al ₂ O ₃ .

Example  5: Medium porosity  nickel- Cs Preparation of Alumina Aerogel Catalysts

Medium porosity in the same manner as in Example 1 using 0.1 g of cesium (III) acetate hydrate (Sigma-Aldrich) instead of nickel acetate hydrate (Sigma-Aldrich) as the enhancer (M) precursor of Example 1 Nickel-Cs-alumina aerogel catalysts were prepared and named Ni-Cs-Al ₂ O ₃ .

Example  6: Medium porosity  nickel- Fe Preparation of Alumina Aerogel Catalysts

Medium porosity nickel-Fe in the same manner as in Example 1 using 0.2 g of iron acetate hydrate (Sigma-Aldrich) instead of nickel acetate hydrate (Sigma-Aldrich) as the enhancer (M) precursor of Example 1 An alumina airgel catalyst was prepared and named Ni-Fe-Al ₂ O ₃ .

Example  7: Medium porosity  nickel- Co Preparation of Alumina Aerogel Catalysts

Medium porosity nickel-Co in the same manner as in Example 1 using 0.3 g of cobalt acetate hydrate (Sigma-Aldrich) instead of nickel acetate hydrate (Sigma-Aldrich) as the enhancer (M) precursor of Example 1 An alumina airgel catalyst was prepared and named Ni-Co-Al ₂ O ₃ .

Example  8: Medium porosity  nickel- Mg Preparation of Alumina Aerogel Catalysts

Medium-porous nickel-Mg in the same manner as in Example 1, using 0.5 g of magnesium acetate hydrate (Sigma-Aldrich) instead of nickel acetate hydrate (Sigma-Aldrich) as the enhancer (M) precursor of Example 1 An alumina aerogel catalyst was prepared and named Ni-Mg-Al ₂ O ₃ .

Comparative example  1: commercial alumina On the carrier Supported  Preparation of Nickel Catalyst

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

Test Example  1: chemical composition of nickel-M-alumina aerogel catalyst, Specific surface area , Pore volume and average pore size

Chemical composition and specific surface area, pore volume and average pore size of Ni-M-Al ₂ O ₃ (M = Ni, Ce, La, Y, Cs, Fe, Co and Mg) catalysts prepared in Examples 1 to 8 Is shown in Table 1.

division Ni Of Al Atomic ratio M / Al Atomic ratio Total M content
(weight%) Specific surface area  (m ² g ^-One ) Pore volume ( cm ³ g ^-One ) Average pore size ( nm ) Example  One( Ni - Ni - Al ₂ O ₃ ) 0.29 0.06 27.7 310 2.13 22.9 Example  2( Ni - Ce - Al ₂ O ₃ ) 0.31 0.05 29.5 274 1.63 18.0 Example  3 ( Ni - La - Al ₂ O ₃ ) 0.30 0.05 28.7 301 1.85 18.3 Example  4( Ni -Y- Al ₂ O ₃ ) 0.31 0.05 28.5 271 1.52 16.1 Example  5 ( Ni - Cs - Al ₂ O ₃ ) 0.30 0.05 27.9 280 1.71 16.7 Example  6 ( Ni - Fe - Al ₂ O ₃ ) 0.29 0.06 27.3 258 1.80 19.4 Example  7 ( Ni - Co - Al ₂ O ₃ ) 0.29 0.07 28.0 253 1.30 14.0 Example  8( Ni - Mg - Al ₂ O ₃ ) 0.29 0.07 26.8 264 1.53 16.8

As shown in Table 1, first, the Ni / Al atomic ratio of 0.29 to 0.31 and the enhancer (M) / Al atomic ratio of 0.05 to 0.07 are mesoporous nickel-M-alumina aerogel containing the enhancer (M) of the present invention. It can be seen that both the nickel and the promoter were successfully introduced into the catalyst by the catalyst preparation method. In addition, it can be seen that all aerogel catalysts exhibit the properties of typical mesoporous materials such as relatively good specific surface area, pore volume and average pore size.

In particular, Ni-Ni-Al ₂ O ₃ using Ni as an enhancer, that is, a catalyst composed of only nickel and alumina, showed the best physical properties. It is noteworthy that despite the fact that the total metal content of each catalyst is not significantly different, all other catalysts have a lower specific surface area, smaller pore volume, and smaller average pore size than Ni-Ni-Al ₂ O ₃ . Physical properties are inferior. From this, it can be seen that the properties of the metal as the enhancer (M) affect the structural and chemical properties of the final catalyst in the preparation of the medium-porous nickel-M-alumina aerogel catalyst including the enhancer (M).

Test Example  2: X-ray of nickel-M-alumina aerogel catalyst diffraction  analysis

1 shows X-ray diffraction of a Ni-M-Al ₂ O ₃ (M = Ni, Ce, La, Y, Cs, Fe, Co and Mg) airgel catalyst prepared by Examples 1 to 8 of the present invention. The graph of the analysis result is shown. It is noteworthy in FIG. 1 that all the catalysts produced do not develop characteristic peaks corresponding to metals as nickel (solid line) in the oxidation state and enhancers (M) in the respective oxidation state. This is because it is evenly distributed in the size of 2 nm or less, which is the detection limit of XRD analysis. It is also found that the diffraction peaks (dotted lines) of gamma-alumina are shifted at low angles in all catalysts, from which nickel particles, which are distributed and interact relatively uniformly on the surface of alumina, are incorporated into the lattice of alumina (Incorporation). ) And a stable nickel-aluminate phase is shown.

Test Example  3: X-ray after reduction of nickel-M-alumina aerogel catalyst diffraction  analysis

2 shows X- after reduction of the Ni-M-Al ₂ O ₃ (M = Ni, Ce, La, Y, Cs, Fe, Co and Mg) airgel catalysts prepared by Examples 1 to 8 of the present invention. The graph shows the result of the line diffraction analysis. As shown in FIG. 2, it can be seen that the characteristic peak (solid line) corresponding to the metal nickel in the zero-valent state is well developed in all the reduced catalysts. In addition, it can be seen that the diffraction peaks (dotted lines) of gamma-alumina are returned to their original angles. From this, the oxidation of nickel is completely transferred to metal nickel, which is an active phase of the steam reforming reaction, through the reduction process of the present invention. can do. However, in the case of Ni-Co-Al ₂ O ₃ , the characteristic peaks corresponding to the nickel in the oxidized state developed at θ = 37, 43, and 63 degrees, respectively, indicating that the nickel and the metal nickel in the oxidized state exist simultaneously. .

Test Example  4: Medium porosity  Hydrogen Sorption of Nickel-M-Alumina Catalysts

Hydrogen adsorption analysis of the Ni-M-Al ₂ O ₃ (M = Ni, Ce, La, Y, Cs, Fe, Co and Mg) airgel catalyst prepared in Examples 1 to 8 are shown in Table 2. All the catalysts prepared to obtain the data in Table 2 were reduced in a hydrogen atmosphere at 700 ° C. for 3 hours, and the amount of hydrogen gas adsorbed at 50 ° C. was measured. Based on the amount of hydrogen adsorbed, the metal dispersion and average particle size were calculated and arranged under the assumption that H / Nis = 1, that is, one hydrogen atom chemically adsorbed to one active particle.

division Hydrogen adsorption amount (μm o lg-catalyst ^-One ) M dispersion
(%) Average particle size
( nm ) Example  One( Ni - Ni - Al ₂ O ₃ ) 157.4 5.1 19.4 Example  2( Ni - Ce - Al ₂ O ₃ ) 175.9 5.7 18.7 Example  3 ( Ni - La - Al ₂ O ₃ ) 179.0 5.8 17.2 Example  4( Ni -Y- Al ₂ O ₃ ) 173.8 5.6 19.1 Example  5 ( Ni - Cs - Al ₂ O ₃ ) 168.7 5.5 19.3 Example  6 ( Ni - Fe - Al ₂ O ₃ ) 151.2 4.9 20.0 Example  7 ( Ni - Co - Al ₂ O ₃ ) 148.1 4.8 22.4 Example  8( Ni - Mg - Al ₂ O ₃ ) 132.7 4.3 25.1

As shown in Table 2, the hydrogen adsorption amount and the metal dispersity are Ni-La-Al ₂ O ₃ > Ni-Ce-Al ₂ O ₃ > Ni-Y-Al ₂ O ₃ > Ni-Cs-Al ₂ O ₃ > Ni-Ni-Al ₂ O ₃ > Ni-Fe-Al ₂ O ₃ > Ni-Co-Al ₂ O ₃ > Ni-Mg-Al ₂ O _{3 It} was reduced in the order. In addition, it can be seen that the average particle size shows the opposite trend. From this, depending on the type of promoter, the chemical properties of the medium-porous nickel-M-alumina aerogel catalyst including the promoter (M), in particular, the dispersion and average particle size of metals known to be closely related to the reaction activity are sensitively affected. I can see it. In particular, it can be confirmed that Ni-La-Al ₂ O ₃ including a lanthanum as the enhancer (M) has the highest metal dispersion and the smallest average particle size.

Test Example  5: Medium porosity  Using Nickel-M-Alumina Aerogel Catalysts Liquefied natural  gas( LNG Water vapor Reforming reaction  Characterization

Hydrogen gas production was carried out by steam reforming of liquefied natural gas consisting of a mixed gas of methane and ethane using the catalysts prepared in Examples 1 to 8 and Comparative Example 1.

The liquefied natural gas consisting of a mixture of methane and ethane used as a reactant was composed of 92% by volume of methane and 8% by volume of ethane. After the catalyst was charged into the reactor for steam reforming, 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 the reactants were continuously passed through the catalyst layer in the reactor. The reaction was allowed to proceed. The space velocity of the reactants was maintained at 27,000 ml / g-catalyst and h, and the volume ratio of liquefied natural gas and water vapor was maintained at 5/10. The steam reforming reaction of liquefied natural gas was performed at 600 ° C. It became. The conversion rate and the hydrogen yield of the liquefied natural gas were respectively calculated by the following equations (1) and (2).

3 is a graph showing the liquefied natural gas conversion change graph (left) and the hydrogen yield change graph (right) according to the reaction time of the catalysts prepared in Examples 1 to 8 and Comparative Example 1 of the present invention. As shown in FIG. 3, in the case of the nickel catalyst supported on the commercial alumina prepared in Comparative Example 1, the deactivation tendency due to carbon deposition and particle sintering is noticeable as the reaction time elapses. In contrast, all of the medium-porous nickel-M-alumina aerogel catalysts (M = Ni, Ce, La, Y, Cs, Fe, Co and Mg) prepared in Examples 1 to 8 of the present invention were reacted for about 1000 minutes. It shows relatively stable reaction activity. These results indicate that Ni-M-Al ₂ O ₃ (M = Ni, Ce, La, Y, Cs, Fe, Co and Mg) aerogel catalysts are formed by carbon deposition and nickel particle sintering in steam reforming of liquefied natural gas. This means that the resistance to deactivation is very good.

This can be interpreted as the well-developed medium pore structure and relatively evenly dispersed nickel particles effectively suppress the polymerization and deposition reaction of surface carbon species and promote the vaporization reaction. From this, it can be seen that the medium-porous nickel-M-alumina aerogel catalyst including the enhancer (M) according to the present invention is a very efficient catalyst capable of stably producing high purity hydrogen gas through steam reforming of liquefied natural gas. .

FIG. 4 shows an enhancer of Ni-M-Al ₂ O ₃ (M = Ni, Ce, La, Y, Cs, Fe, Co and Mg) airgel catalysts prepared in Examples 1 to 8 after the reaction time of 400 minutes. A graph showing the reaction activity according to the type of (M) is shown. As shown in FIG. 4, the reaction activity including liquefied natural gas conversion and hydrogen yield is Ni-La-Al ₂ O ₃ > Ni-Ce-Al ₂ O ₃ > Ni-Y-Al ₂ O ₃ > Ni-Cs -Al ₂ O ₃ > Ni-Ni-Al ₂ O ₃ > Ni-Fe-Al ₂ O ₃ > Ni-Co-Al ₂ O ₃ > Ni-Mg-Al ₂ O _{3 It} can be seen that in order of decreasing, among the catalysts prepared in Examples 1 to 8 of the present invention Ni-La-Al having the highest metal dispersion and the smallest average particle size ₂ O ₃ showed the highest reaction activity. It is noteworthy here that these results are closely related to the metal dispersion and average particle size of the mesoporous nickel-M-alumina aerogel catalyst mentioned in the data in Table 2. This is because the adsorption reaction of the liquefied natural gas, which is a rate-determining step, in the reactor operation of the steam reforming reaction of the liquefied natural gas proceeds more smoothly with a catalyst having a higher metal dispersion and a small average particle size. It is interpreted as obtained.

While the present invention has been particularly shown and described with reference to specific embodiments thereof, those skilled in the art will appreciate that such specific embodiments are merely preferred embodiments and that the scope of the present invention is not limited thereby. something to do. It is therefore intended that the scope of the invention be defined by the claims appended hereto and their equivalents.

Claims (14)

Mixed with a promoter (M) / aluminum atomic ratio of 0.001 to 0.1 and a nickel / aluminum atomic ratio of 0.01 to 1,
The enhancer (M) is at least one selected from the group consisting of Ni, Ce, La, Y, Cs, Fe, Co, Mg, Rh, Yb, Ru, Ir, Os, and Ca, liquefied natural by steam reforming reaction. Medium porosity nickel-M-alumina aerogel catalyst for producing hydrogen gas from gas.
delete The method of claim 1,
The catalyst is a medium-porous nickel-M-alumina aerogel catalyst, characterized in that it has an average pore size of 2 to 50 nm and an average particle size of 2 to 100 nm.
Iii) dissolving the aluminum precursor in a heated alcohol solvent;
Ii) forming a transparent alumina sol (Sol) by partially hydrating by mixing water, acid and alcohol in the solution;
Iii) Nickel precursor and metal acetate hydrate (Metal Acetate Hydrate), Metal Nitrate Hydrate, Metal Chloride Hydrate and Metal Bromide Hydrate (Metal Bromide Hydrate) in the alumina sol (Sol) Adding at least one enhancer (M) precursor selected from the group consisting of to form a nickel-M-alumina hybrid sol (Sol);
Iii) cooling the nickel-M-alumina hybrid sol (Sol) to room temperature and then forming a nickel-M-alumina hybrid gel (Gel) through a hydration and condensation reaction with a mixed solution of water and alcohol;
Iii) aging the nickel-M-alumina hybrid gel (Gel);
Iii) drying the aged nickel-M-alumina hybrid gel (Gel) using supercritical carbon dioxide; And
Iii) heat-treating the dried nickel-M-alumina hybrid gel (Gel);
Method for producing a medium-porous nickel-M-alumina aerogel catalyst for producing hydrogen gas from liquefied natural gas by steam reforming reaction comprising a.
5. The method of claim 4,
The aluminum precursor may be aluminum nitrate nonahydrate, aluminum fluoride trihydrate, aluminum phosphate hydrate, aluminum chloride hexahydrate, aluminum hydroxide Aluminum Hydroxide, Aluminum Sulfate Hexadecahydrate and Aluminum Ammonium Dodecahydrate (Aluminum Ammonium Dodecahydrate) The preparation of a medium-porous nickel-M-alumina aerogel catalyst characterized in that at least one selected from the group consisting of Way.
5. The method of claim 4,
The nickel precursor is one selected from the group consisting of Nickel Nitrate Hexahydrate, Nickel Chloride Hexahydrate, Nickel Acetate Tetrahydrate, and Nickel Bromide Hydrate. Method for producing a medium-porous nickel-M-alumina aerogel catalyst, characterized in that above.
delete 5. The method of claim 4,
The step iii) is a method for producing a medium-porous nickel-M-alumina aerogel catalyst, characterized in that carried out at a temperature of 30 to 80 ℃ and a pressure of 100 to 300 atm.
5. The method of claim 4,
The step iii) is a method for producing a medium-porous nickel-M-alumina aerogel catalyst, characterized in that carried out at a temperature of 500 to 900 ℃.
Iii) charging the catalyst according to claim 1 to a steam reforming reactor; And
Ii) A method for producing hydrogen gas from liquefied natural gas by steam reforming comprising passing a mixed gas consisting of liquefied natural gas and water vapor through a catalyst bed in a reactor at a space velocity of 1,000 to 500,000 ml / g-catalyst.h.
The method of claim 10,
Reducing the catalyst charged in the reactor to the mixed gas of nitrogen and hydrogen before the step ii), the method of producing hydrogen gas from liquefied natural gas.
12. The method of claim 11,
The volume ratio of nitrogen and hydrogen of the mixed gas is a hydrogen gas from liquefied natural gas, characterized in that 1/10 to 1/2.
The method of claim 10,
Hydrogen gas from liquefied natural gas, characterized in that the volume ratio of the liquefied natural gas and water vapor of the mixed gas is 1/10 to 1/1.
The method of claim 10,
The steam reforming reaction is a hydrogen gas production method, characterized in that carried out at a reaction temperature of 500 to 900 ℃.

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