KR20120037821A - Ni-based hydrotalcite-like catalyst for diesel steam reforming, preparing method thereof, and producing method of hydrogen using the same - Google Patents

Abstract

PURPOSE: Nickel-based hydrotalcite catalyst for modifying the vapor of diesel, a method for manufacturing the same, and a method for manufacturing hydrogen based on the modification of diesel using the same are provided to improve the yield of hydrogen. CONSTITUTION: Nickel-based hydrotalcite catalyst for modifying the vapor of diesel is represented by chemical formula 1. In chemical formula 1, A is one or more alkali earth metal oxides; B is one or more Group 8B precious metal atoms; a is the content of the alkali earth metal in catalyst and is between 0 and 10 weight%; b is the content of the Group 8B precious metal atoms and is between 0 and 10 weight%; either of the alkali earth metal or the Group 8B precious metal atoms is more than or equal to 0 weight%; and x and y are the molar ratio of Ni and Mg; x is between 0.2 and 0.9; and y is between 0.5 and 5.5.

Description

TECHNICAL FIELD The present invention relates to a nickel-based hydrotalcite catalyst for steam reforming of diesel, a process for producing the same, and a process for preparing hydrogen by a reforming reaction of diesel using the same, hydrogen using the same}

The present invention relates to a nickel-based quasi-hydrotalcite catalyst for steam reforming of diesel and a process for its preparation. The present invention also relates to a method for producing hydrogen by using the catalyst in the reforming reaction of diesel.

Generally, hydrogen is produced by more than 90% of natural gas reforming. In addition, it is produced from gasification of coal, electrolysis of water, thermochemical cycle and biomass. However, for several decades, It has been reported that producing hydrogen through hydrogen is economical.

Methods for producing hydrogen by reforming fossil fuels include steam reforming, partial oxidation reforming using oxygen, autothermal reforming in which steam reforming and partial oxidation reforming are combined in an appropriate manner, and currently commercialized steam reforming processes It is known as a suitable process for mass production of hydrogen. Therefore, the development of a new catalyst for the production of hydrogen at a high yield by the steam reforming reaction and the improvement of the steam reforming process have been actively carried out.

In the reforming process, prevention of catalyst deactivation by carbon deposition of the reforming catalyst is pointed out as the most important problem. Since the carbon deposition can be thermodynamically calculated by the molar ratio of hydrogen atoms to carbon atoms in the reactants and the molar ratio of oxygen atoms to carbon atoms, in the existing steam reforming process of methane and propane, water vapor is used to prevent catalyst deactivation due to carbon deposition When the molar ratio of hydrogen atoms to carbon atoms and the molar ratio of oxygen atoms to carbon atoms are increased, the water gasification reaction is relatively accelerated during the reaction, and the product is obtained in a molar ratio of hydrogen: carbon monoxide of 3: 1 or more. Which is suitable for the process. At present, the steam reforming process of methane used industrially is operated at a temperature of 730 ~ 860 ° C and a pressure of 20 ~ 40 atm, where the molar ratio of methane: water vapor is 1: 4 ~ 6.

On the other hand, the reforming reaction of diesel is more advantageous than the reforming reaction of liquefied natural gas (LNG) and liquefied petroleum gas (LPG) at the same reaction temperature. However, The catalyst has a problem that the durability of the catalyst is considerably lower than that of LNG and LPG due to the poisoning problem. Therefore, a catalyst study is needed to overcome this problem.

In the commercial steam reforming reaction, nickel-based catalysts are mainly used. Therefore, in order to develop a reforming catalyst superior to the existing steam reforming catalyst, it is required not only to have resistance to carbon deposition but also to have thermal stability and mechanical stability. In order to satisfy this, it is necessary to have a high specific surface area such as alumina carrier, Selection of carrier is very important.

As a conventional methane steam reforming catalyst, Ni / Al ₂ O ₃ [Numaguchi, T., Ind. Eng. Chem. Res., 30, 447-453, 1991). As a naphtha reforming catalyst, TiO ₂ / MgO and Pt-Re / Al ₂ O ₃ [Teresita, FG and Carlos, RA, Ind. Eng. Chem. Res., 31, 1283 ~ 1288, 1992), the reported catalysts point out to be a problem of rapid deactivation of the catalyst by carbon deposition. A zirconia supported nickel catalyst in which cobalt is added to nickel as a steam reforming catalyst of a hydrocarbon compound has been disclosed [US Pat. No. 4,026,823]. In another method, a suitable ratio of a metal such as lanthanum, cerium, A catalyst supported on alumina, silica, magnesia, zirconia or the like, which is a common carrier, has been disclosed [US Pat. No. 4,060,498]. And a steam reforming catalyst of a hydrocarbon compound carrying iridium on a mixed carrier of zirconia and alumina, respectively (US Pat. Nos. 4,297,205 and 4,240,934). However, in the case of the above methods, there is a problem that when the present invention is applied to a steam reforming reaction at a high space velocity, the activity becomes low or the catalyst becomes inactive. Therefore, in order to use the steam reforming reaction, the reaction activity, thermal stability at a high temperature, It is necessary to improve the carrier or to disperse the active metal in a small size and high dispersion. Further, after a carrier is prepared by adding a small amount of manganese oxide and cerium oxide to an alumina carrier, a multicomponent hydrocarbon having a proper molar ratio of noble metals such as Pt, Pd, Rh and Ir and an alkaline earth metal such as Ni, A catalyst for reforming a compound and a process for modifying a hydrocarbon compound using the catalyst have been disclosed [WO 2002/38268, WO 2002/78840]. However, since the catalyst is composed of a multi-component catalyst, it is difficult to produce a catalyst and it takes a lot of time. Since the noble metal is used as an active metal, the production cost is high. Under the condition of a high temperature region and a high space velocity In order to produce hydrogen at a high concentration by applying it to steam reforming, it is necessary to manufacture a multicomponent catalyst by a simpler process, lower the production cost of the catalyst by inhibiting the use of a noble metal, It is necessary to improve the catalyst so that there is no change in activity even at a space velocity.

A catalyst using hydrotalcite precursors has been prepared and a literature has been known in which an oxidation reaction of methane and a reforming reaction of methanol (U.S. Patent No. 5,354,932, U.S. Patent No. 6,071,433) are used. The metal oxide catalyst using hydrotalcite as a precursor, which is known in the U.S. patent, is applied to a reaction proceeding at 300 ° C or less in consideration of the collapse of the characteristic layered structure of hydrotalcite in a temperature range of 300 to 400 ° C or more. Therefore, in order to use this catalyst for the reaction such as the modification of the hydrocarbon compound proceeding at a temperature of 300 ° C or more, a metal that can maintain its activity by forming a new structure even after the layered structure collapse of the hydrotalcite It is important to do. In JP-A-11-276893, a metal oxide catalyst having hydrotalcite as a precursor using noble metals (Rh, Pd, Ru) and Ni as an active metal was prepared and carbon dioxide reforming reaction of methane was carried out. However, in spite of the use of expensive precious metals, the conversion of methane was more than 90% at 800 ℃, and the conversion rate decreased sharply in the temperature range below 600 ℃. Methane conversion rate of about 50%), the methane conversion rate was reported not to exceed 30%.

On the other hand, it is known that when calcium is added to a nickel catalyst for reforming a hydrocarbon compound, it has durability against carbon deposition during the reaction. Z.I. Zhang et al. [Z. I. Zhang and X. E. Verykios, Catal. Today, 21, 589-595, 1994, a carbon dioxide reforming experiment of methane was carried out using a catalyst in which 10 wt% of Ca was added to a-alumina impregnated with nickel. As a result, The activity and stability of the catalyst are improved when the catalyst is operated for a longer time than the catalyst. Juliana da S. Lisboa et al. [Juliana da S. Lisboa, Danielle CRM Santos, Fabio B. Passos, Fabio B. Noronha, Catal. As a result of conducting steam reforming experiments on methane using a catalyst containing 5 to 10% by weight of alkaline earth metals such as magnesium and calcium in the same catalyst, as in the carbon dioxide reforming experiment, The activity and the durability of the catalyst are improved. When the carbon immersed in the methane steam reforming reaction is converted into carbon dioxide by combustion, the amount of carbon deposited on the catalyst decreases, thereby increasing the activity and durability of the catalyst. And calcium affect the combustion of the deposited carbon.

Also, a catalyst prepared by adding calcium to a catalyst prepared by impregnating? -Alumina with nickel instead of? -Alumina [Angeliki A. Lemonidou, Iacovos A. Vasalos, Appl. Catal. A :, 228, 227 ~ 235, 2002], the conversion of methane to methane was about 80% at a temperature of 750 ° C for about 50 hours, And the catalyst activity and durability are lowered.

As described above, it is difficult to predict the applicability of the catalyst showing durability against carbon deposition, which is likely to occur in large amounts in the diesel reforming of the present invention.

On the other hand, the present inventors have found that a catalyst for reforming a nickel-based liquefied petroleum gas vapor using a pseudo hydrotalcite exhibiting superior performance over existing methane steam reforming catalysts under the reaction conditions of low vapor / -2007-0043201), and a nickel-based liquefied petroleum gas steam reforming catalyst (Korean Patent Laid-Open No. 10-2010-0090492) using Rh-added similar hydrotalcite. However, these catalysts are judged to have excellent performance as a catalyst for diesel reforming, but the continuous study of the inventors has confirmed the need for the development of improved catalysts that exhibit complete durability against carbon deposition under severe conditions. According to the literature published so far, a catalyst which is used in the steam reforming reaction of a liquefied petroleum gas mixed with a hydrocarbon compound has a catalyst which has durability against carbon deposition under severe conditions and which is resistant to sulfur poisoning by catalysts There is no way.

The present inventors not only improved the manufacturing cost of the catalyst by using the catalyst with a minimized amount of the noble metal, but also improved the deactivation of the catalyst by the carbon deposition in the diesel reforming reaction as compared with the conventional catalyst, Based catalysts. As a result, a precursor of a hydrotalcite structure composed of aluminum and magnesium cations was prepared. Then, a portion of the magnesium was substituted with nickel to uniformly disperse nickel on the surface and inside of the catalyst, and then an alkaline earth metal and a part of the Group 8B noble metal were partially added The nickel-based catalysts of the composition A _a -B _b -Ni _x / Mg _y Al were prepared so that the ratio of the respective metal components was optimized to maintain a specific range. This catalyst is a catalyst for diesel reforming reaction, which has a comparatively high specific surface area as compared with a conventional catalyst, and is a catalyst in which nickel component is highly dispersed while reducing the amount of expensive noble metal, and is applied to a diesel reforming reaction to produce hydrogen at a high yield And it is confirmed that the carbon deposition of the catalyst at a low carbon-to-carbon water vapor and a low temperature condition, which are harsh reaction conditions compared to the prior art, is minimized and that the catalytic activity is superior to that of the conventional commercial catalyst and the invented catalyst, It was completed.

The present invention is characterized by a nickel-based pseudohydrotalcite catalyst for steam reforming reaction of diesel represented by the following formula (1).

[Chemical Formula 1]

A _a -B _b -Ni _x / Mg _y Al

Wherein A is at least one kind of alkaline earth metal oxide, B is at least one kind of 8B group noble metal atom, a is 0 to 10 wt% in terms of the content of alkaline earth metal in the catalyst, 0 to 10% by weight, with the proviso that the content of the alkaline earth metal and the Group 8B noble metal can not be 0% by weight at the same time, and x and y are the molar ratios of Ni and Mg to Al in the range of 0.2? ? Y? 5.5.

Also,

Preparing a hydrotalcite precursor solution by dissolving an aluminum precursor, a magnesium precursor, and a sodium carbonate in water such that the molar ratio of aluminum, magnesium, and carbonic acid is 1: 0.5 to 5.5: 1;

Adding a nickel precursor to the hydrotalcite precursor solution so that a molar ratio of aluminum to nickel is 1: 0.2 to 0.9, and then adding sodium hydroxide to prepare a precipitate solution;

Preparing an alkaline earth metal precursor and an 8B group noble metal precursor by adding the alkaline earth metal precursor and the 8B group noble metal precursor to the precipitation solution so that the content of the alkaline earth metal in the catalyst is 0 to 10 wt% and the content of the 8B group noble metal is 0 to 10 wt% And

Filtering the mixed solution to recover the precipitate, followed by drying and calcining;

The present invention is directed to a method for preparing a nickel-based hydrotalcite catalyst for steam reforming of diesel represented by the above formula (1).

The present invention also provides a method for producing hydrogen by the steam reforming reaction of diesel under the nickel-based pseudohydrodithium catalyst represented by the above formula (1).

The nickel-based hydrotalcite catalyst for the steam reforming reaction of diesel according to the present invention can obtain a high concentration of hydrogen at a high yield while suppressing carbon deposition when applied to the steam reforming reaction of diesel, The present invention can be applied to a high temperature and high gas space velocity which is difficult to apply as a steam reforming catalyst. In addition, the stability of the catalyst is excellent due to suppression of carbon deposition depending on the reaction time.

FIG. 1 shows a graph showing the relationship between the CaO-Ni _{0 .5} / Mg _{2 .5} Al (Ca 3 wt%) catalyst of Catalyst 2 of the present invention in the steam reforming reaction of decahydronaphthalene (C ₁₁ H ₁₀ ) and n-hexadecane In which hydrogen is used as a catalyst.
Figure 2 is a catalyst versed one of _{CaO-Ni 0.5 / Mg 2.5 Al} (Ca 1 % by weight) catalyst and Comparative Catalyst versed one of Ni _0.5 / Mg _2.5 Al catalyst and the comparison catalyst versed _{2 Ni / γ-Al 2 O} 3 catalyst of Is a graph comparing the durability of the catalyst represented by the selection of hydrogen with respect to the reaction time in applying the steam reforming reaction of decahydronaphthalene.

Hereinafter, the present invention will be described in detail.

The present invention relates to a nickel-based pseudohydrotalcite catalyst for steam reforming reaction of diesel represented by the following formula (1).

[Chemical Formula 1]

A _a -B _b -Ni _x / Mg _y Al

Wherein A is at least one kind of alkaline earth metal oxide, B is at least one kind of 8B group noble metal atom, a is 0 to 10 wt% in terms of the content of alkaline earth metal in the catalyst, 0 to 10% by weight, with the proviso that the content of the alkaline earth metal and the Group 8B noble metal can not be 0% by weight at the same time, and x and y are the molar ratios of Ni and Mg to Al in the range of 0.2? ? Y? 5.5.

The nickel-based pseudohydrotalcite catalyst of the present invention is a 100? Forming a specific surface area in the range of 300 m ² / g. This is a precursor _{^{[(M 2 +) 1-}} x (M 3 +) x (OH -) 2] x + [(A n -) x / n] o 2 in the hydrotalcite structure having a general formula of mH ₂ O Nickel is partially filled in the voids in the structure formed when the metal (M ²⁺ ) and the trivalent metal (M ³⁺ ) form a brucite-type layer, The specific surface area is increased. Marking a nickel-containing catalyst of similar hydrotalcite structure in the earlier alkaline earth naejineun noble metal is added in the present invention as hydrotalcite formula _{^{[(Ni 2+) x (Mg}} 2+) y (Al 3+) (OH -) 2 ] ^{1-x / y} [(CO ₃ ^2- ) _{(x / y) / n} ] mH ₂ O. Here, x and y are molar ratios of Ni and Mg to Al, 0.2? X? 0.9, 0.5? Y? 5.5, and m represents the number of water in hydration.

If the molar ratio x of nickel to aluminum in the above formula (1) is less than 0.2, the reaction site may decrease and the catalyst may be inferior in activity. If the mole ratio of x is larger than 0.9, the catalyst may be large enough to form whisker carbon. And deactivation of the catalyst due to carbon deposition during the reforming reaction may occur. If the molar ratio y of magnesium to aluminum is less than 0.5, the catalytic activity may be lowered, and if it exceeds 5.5, the specific surface area of the hydrotalcite precursor may be decreased, which may also cause a decrease in catalytic activity.

In the above formula (1), magnesium, calcium, strontium (Sr) or barium (Ba) may be used as the alkaline earth metal, and calcium is preferably used. The effect of improving the catalytic activity on decahydronaphthalene (C ₁₁ H ₁₀ ), which is a main component of the diesel, can be obtained by containing an alkaline earth metal. The content of the alkaline earth metal in the catalyst is preferably 0 to 10% by weight, and more preferably 1 to 10% by weight. If the content of the alkaline earth metal is too small, the effect on the effect due to the addition is insignificant. On the other hand, if the content exceeds 10 wt%, the alkaline earth metal particles may cover the nickel particles serving as active sites and the catalytic activity may be reduced, which is not preferable . In addition, the catalyst of the present invention may contain a Group 8B noble metal for improving the catalytic activity to n-hexadecane, another major component of diesel. Ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir) or platinum can be used as the Group 8B precious metal. The content is preferably from 0 to 10% by weight, more preferably from 0.1 to 5% by weight. However, even if the content of the noble metal exceeds 10% by weight, it is preferable to select the above range because the benefit of the catalytic activity due to the increase is insignificant.

The present invention also relates to a process for preparing a nickel-based hydrotalcite catalyst for steam reforming of diesel represented by the above formula (1).

In the step of dissolving an aluminum precursor, a magnesium precursor and a sodium carbonate in water to prepare a hydrotalcite precursor solution such that the molar ratio of aluminum, magnesium and carbonic acid is 1: 0.5 to 5.5: 1, the aluminum precursor and the magnesium precursor are nitrates , An acetone salt, an acetate salt, a halogenated flame and an acetoacetonate salt may be used, and it is preferable to use nitrates. The sodium carbonate can be prepared by stabilizing a brucite-type layer formed of a magnesium ion (Mg ²⁺ ) as a divalent metal and an aluminum ion (Al ³⁺ ) as a trivalent metal together with a hydroxyl group (OH ^- ) anion And acts as an anion to enable the formation of the hydrotalcite structure.

The nickel precursor is added to the hydrotalcite precursor solution so that the molar ratio of aluminum to nickel is 1: 0.2 to 0.9, and then sodium hydroxide is added to prepare a precipitate solution. The nickel precursor is nickel nitrate , An acetone salt, an acetate salt, a halogenated flame and an acetylacetonate salt. The solution containing the nickel precursor was agitated vigorously at room temperature for 30 to 60 minutes and then sodium hydroxide was added to adjust the pH to 8 to 10 to obtain a precipitate in which the precipitate was formed, The precipitate solution is aged at 60-80 ° C for 4-8 hours to obtain a pseudo hydrotalcite structure substituted with nickel.

The alkaline earth metal precursor and the 8B group noble metal precursor are added to the precipitation solution such that the content of the alkaline earth metal in the catalyst is 0 to 10 wt% and the content of the 8B group noble metal is 0 to 10 wt% The precursor of the earth metal and the precursor of the Group 8B metal may be at least one selected from nitrate, acetone, acetate, halogenate and acetylacetonate of each metal and may be aged at 60 to 80 ° C for 12 to 18 hours The alkaline earth metal and Group 8B noble metal are contained in the similar hydrotalcite structure.

Thereafter, the mixed solution is filtered to recover the precipitate, and the nickel-based pseudohydrodithium catalyst for steam reforming reaction of the diesel represented by Formula 1 is recovered through drying and calcination steps. Filtration is carried out by using distilled water until no hydroxide ions or sodium ions are observed. If the calcination temperature is lower than 800 ° C, the solidification of the nickel-metal solidification during the calcination process is not good, so that the particle size of the nickel is not sufficiently small and the catalyst activity may not be exhibited. If the temperature is higher than 900 ° C., sintering of the catalyst may occur and the catalytic activity may decrease. Therefore, it is preferable to maintain the above temperature range.

The present invention also relates to a method for producing hydrogen through a steam reforming reaction of diesel under the nickel-based pseudohydrodithium catalyst represented by the formula (1).

The steam reforming reaction of the diesel is preferably performed using a tubular fixed bed catalytic reactor. As a pretreatment before the reaction, the catalyst of A _a -B _b -Ni _x / Mg _y Al was treated with a sieve of 80-100 mesh to fill only the catalyst having a particle size of 150-250 mu m into the reactor, It is preferable to use it after reduction with hydrogen. The reactants diesel and water vapor are adjusted so that the molar ratio of carbon and water vapor is 1: 1 ~ 3 and injected into the reactor. If the molar ratio of water vapor is too small, carbon deposition may occur rapidly in a short period of time, resulting in deterioration of catalytic activity. On the other hand, if the molar ratio of water vapor is more than 3, hydrogen production is reduced and energy cost due to excessive water vapor supply is further increased It is preferable to select the above range. In the case of diesel, it actually consists of a mixture of various liquid hydrocarbon compounds. In the examples of the present invention, n-hexadecane and decahydronaphthalene (C ₁₁ H ₁₀ ), which are major components of diesel, were used as simulated fuel for diesel. The steam reforming reaction of the diesel is preferably carried out at a reaction pressure of 1 to 30 atm and a reaction temperature of 700 to 900 ° C. If the reaction pressure is too low, there is a possibility that the catalyst deactivation due to carbon deposition is likely to occur. The decomposition and methanation reaction of the diesel fuel may proceed and the generation of hydrogen may be reduced. If the reaction temperature is lower than 700 ° C, there may be a problem that the carbon deposition due to the puddle reaction proceeds thermodynamically further, resulting in deactivation of the catalyst. If the temperature exceeds 900 ° C, sintering of the catalyst proceeds to decrease the catalytic activity . In addition, the space velocity of the reaction is good to maintain such that 10,000 ~ 90,000 h ^-1, if the space velocity is less than 10,000 h ^-1 and the pressure drop due to the increase of the retention time of the reactants in the reactor occurs methanation reaction than the modified and There may be a problem that the decomposition of the hydrocarbon further proceeds to increase the methane production and thus the hydrogen production, and when the amount exceeds 90,000 h ^-1 , the reactant does not sufficiently contact with the catalyst, .

The nickel-based hydrotalcite catalyst for the steam reforming reaction of diesel according to the present invention is excellent in the stability of the catalyst due to the suppression of carbon deposition when applied to the steam reforming reaction of diesel, The present invention can be applied to a high temperature and high gas space velocity environment which is difficult to apply as a steam reforming catalyst for methane and propane. Further, by improving the resistance to carbon, it is possible to apply even under a condition that the molar ratio of water vapor to diesel is relatively low.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited by the following Examples.

[Example]

Catalyst Preparation 1: CaO-Ni _0.5 / Mg _2.5 Preparation of Al (Ca 1 wt%) catalyst

_{Al (NO 3) 3? 9H} 2 O 5g, Mg (NO 3) 2? 6H 2 O 9.49g, Na 2 CO ₃ was dissolved in 0.63g with distilled water, each 20 mL, Al (NO in aqueous solution of Na ₂ CO _{3 3} ) ₂ and Mg (NO ₃ ) ₂ aqueous solution were respectively added dropwise to prepare a hydrotalcite precursor solution and stirred for 30 minutes. An aqueous solution prepared by dissolving 0.89 g of Ni (NO ₃ ) ₂ ? 6H ₂ O in 10 mL of distilled water was added dropwise to the hydrotalcite precursor solution and stirred for 30 minutes. Then, a 5M aqueous NaOH solution was added dropwise until the pH reached 10, To produce a precipitate solution, which was stirred for 30 minutes. It was then aged at 60 ° C for 4 hours in a water bath atmosphere so that the precipitate could be made into a similar hydrotalcite structure. Thereafter, an aqueous solution prepared by dissolving 0.12 g of Ca (NO ₃ ) _{2 in} 10 mL of distilled water was added dropwise to the precipitation solution to prepare a mixed solution, which was stirred for 2 hours and then aged in an oven maintained at 60 ° C. for 12 hours. Then, the mixed solution was washed with distilled water at about 40 ° C. until the hydroxide ion and sodium ion were not observed, and the precipitate was collected by filtration, and the recovered precipitate was dried at 80 ° C. for 1 to 2 hours. The dried precipitate was fired at 850 ° C for 5 hours in an air atmosphere to prepare a catalyst for steam reforming of diesel having highly dispersed nickel added with calcium as a cocatalyst. The prepared catalyst had a composition of CaO-Ni _0.5 / Mg _2.5 Al (Ca 1 wt%) and a surface area of 145.8 m ² / g.

Catalyst Preparation 2: CaO-Ni _0.5 / Mg _2.5 Preparation of Al (Ca 3 wt%) catalyst

The same procedure as in Catalyst Preparation 1 was carried out except that the amount of Ca (NO ₃ ) ₂ added was 0.38 g. The prepared catalyst had a composition of CaO-Ni _0.5 / Mg _2.5 Al (Ca 3% by weight) and a surface area of 134.2 m ² / g.

Catalyst Preparation 3: MgO-Ni _0.5 / Mg _2.5 Preparation of Al (Mg 1 wt%) catalyst

But the same manner as in the catalyst versed 1, Ca (NO _{3) 2} instead of the Mg (NO _{3) 2} was added 0.12 g. The prepared catalyst had a composition of MgO-Ni _0.5 / Mg _2.5 Al (Mg 1 wt%) and a surface area of 104.4 m ² / g.

Catalyst Preparation 4: CaO-Rh-Ni _0.5 / Mg _2.5 Preparation of Al (Ca 1 wt%, Rh 0.3 wt%) catalyst

In the same manner as in Catalyst Preparation 1, 0.23 g of RhCl ₃ was added together with Ca (NO ₃ ) ₂ . The prepared catalyst had a composition of CaO-Rh-Ni _0.5 / Mg _2.5 Al (Ca 1 wt%, Rh 0.3 wt%) and had a surface area of 109.6 m ² / g.

Catalyst Preparation 5: Rh-Ni _0.5 / Mg _2.5 Preparation of Al (Rh 0.3 wt%) catalyst

The procedure of Example ₁ was repeated except that 0.16 g of RhCl ₃ was added instead of Ca (NO ₃ ) ₂ . The prepared catalyst had a composition of Rh-Ni _0.5 / Mg _2.5 Al (Rh 0.3 wt%) and had a surface area of 114.6 m ² / g.

Comparative Catalyst Preparation 1: Ni _0.5 / Mg _2.5 Preparation of Al catalyst

2.5 g of Al (NO ₃ ) ₃ ? 9H ₂ O, 4.75 g of Mg (NO ₃ ) ₂ ? 6H ₂ O, 0.31 g of Na ₂ CO ₃ and Ni ₃ ) ₂ ? 6H ₂ O was used to prepare a catalyst. The prepared catalyst had a composition of Ni _{0 .5} / Mg _{2 .5} Al and a surface area of 174.4 m ² / g.

Comparative Catalyst Preparation 2: Ni / γ-Al ₂ O ₃ Preparation of Catalyst

In order to compare the performance with the catalyst prepared in the present invention, the Ni / γ-Al ₂ O ₃ catalyst most commonly used in the steam reforming process of commercial natural gas was prepared by impregnation. A catalyst having 20 wt% of nickel supported on? -alumina was prepared, and drying and firing conditions were the same. The surface area of the prepared Ni / γ-Al ₂ O ₃ catalyst was 91.3 m ² / g.

division catalyst Nickel loading
(weight %) BET surface area
(m ² / g) Active metal surface area
(m ² / g) catalyst
Manufacturing example One CaO-Ni _0.5 / Mg _2.5 Al
(Ca 1% by weight) 20.0 145.8 6.3 2 CaO-Ni _0.5 / Mg _2.5 Al
(Ca 3% by weight) 20.0 126.3 6.7 3 MgO-Ni _0.5 / Mg _2.5 Al
(Mg 1% by weight) 20.0 104.4 4.5 4 CaO-Rh-Ni _0.5 / Mg _2.5 Al
(Ca 1% by weight, Rh 0.3% by weight) 20.1 109.6 7.0 5 Rh-Ni _0.5 / Mg _2.5 Al
(Rh 0.3% by weight) 20.3 114.6 3.1 Comparative Catalyst
Manufacturing example One Ni _0.5 / Mg _2.5 Al 10.0 174.4 2.8 2 Ni / γ-Al ₂ O ₃ 20.0 91.3 1.7 Nickel loading: analyzed by ICP / MS
BET surface area: analyzed by Quantachrome's Autosorb-1
Active metal surface area: Analyzed by Autochem-II from Micromeritrics

The properties of the prepared catalysts are summarized in Table 1. Prepared by the hydrotalcite structure in which calcium is added as shown in Table 1 as the precursor _{A a -B b -Ni x / Mg} y Al The surface area of the active metal is higher than that of the Ni / γ-Al ₂ O ₃ catalyst prepared by the impregnation method.

Example 1: Preparation of CaO-Ni _0.5 / Mg _2.5 Steam reforming of decahydronaphthalene using Al (Ca 1 wt%) catalyst

The CaO-Ni _0.5 / Mg _2.5 Al (Ca 1% by weight) catalyst prepared in Preparation 1 of the catalyst 1 was treated with a sieve of 80-100 mesh to prepare only the catalyst having a particle size of 150-250 μm into the tubular fixed- And then reduced with hydrogen at 750 DEG C for 10 hours before the initiation of the reaction. Decahydronaphthalene (C ₁₁ H ₁₀ ) was used as a fuel for diesel. At a reaction temperature of 800 ° C, the mass ratio of carbon to water vapor was 1: 3, and the space velocity of the reactant was 10,000 h ^-1. Mass flow Controller was used to inject the gas into the reactor and the steam reforming reaction of the diesel was performed for 64 hours. The durability of the catalyst for long term stability and carbon deposition was evaluated. The composition of the gas before and after the reaction was analyzed by a gas chromatograph directly connected to the reaction apparatus, and a Carbosphere column was used for gas separation.

The conversion of diesel was 100% and the hydrogen selectivity was maintained at about 69.2% for about 63 hours after the start of the reaction. At this time, almost no hydrocarbon compounds of C ₂ or more were detected, and the selectivities of carbon monoxide and carbon dioxide varied from 18 to 22% and 9 to 12%, respectively. As the reaction time increased, the selectivity of carbon monoxide gradually decreased, The selectivity of carbon dioxide increased gradually.

Also, no sign of carbon deposition such as pressure rise in the reactor during the 63 - hour reaction process was observed, and the carbon deposition after the reaction was found to be almost free of carbon deposition.

Example 2: CaO-Ni _0.5 / Mg _2.5 Steam Reforming of Decahydronaphthalene Using Al (Ca 3 wt%) Catalyst

The CaO-Ni _0.5 / Mg _2.5 Al (Ca 3 wt%) catalyst prepared in Example 2 of the catalyst was used as the catalyst in Example 1.

The conversion of diesel was 100%, and as shown in FIG. 1, the selectivity of hydrogen was maintained at about 71.4% for about 78 hours after the start of the reaction. At this time, almost no hydrocarbon compounds of C ₂ or more are detected, and the selectivities of carbon monoxide and carbon dioxide are changed in the range of 15 to 25% and 8 to 13%, respectively. As the reaction time is increased, the selectivity of carbon monoxide is gradually decreased, The selectivity of carbon dioxide increased gradually.

In addition, no signs of carbon deposition such as a pressure rise in the reactor during the 78 - hour reaction process were observed, and carbon deposition was observed in the collected catalysts.

Example 3: CaO-Rh-Ni _0.5 / Mg _2.5 Steam reforming reaction of decahydronaphthalene using Al (Ca 1 wt%, Rh 0.3 wt%) catalyst

Except that CaO-Rh-Ni _0.5 / Mg _2.5 Al (Ca 1 wt%, Rh 0.3 wt%) catalyst prepared in Preparation Example 4 of the catalyst was used as the catalyst.

The conversion of diesel was 100% and the hydrogen selectivity was maintained at 69.6% for about 78 hours after the start of the reaction. No signs of carbon deposition such as pressure rise in the reactor during the 78 hour reaction process were observed, and carbon deposition was observed to be almost nonexistent even after the reaction.

Example 4: Rh-Ni _0.5 / Mg _2.5 Steam reforming of decahydronaphthalene using Al (Rh 0.3 wt%) catalyst

The catalyst was prepared in the same manner as in Example 1 except that Rh-Ni _0.5 / Mg _2.5 Al (Rh 0.3 wt%) catalyst prepared in Preparation 5 of the catalyst was used as a catalyst.

The conversion of diesel was 100% and the selectivity of hydrogen was maintained at 68.3% for about 50 hours after the start of the reaction. No signs of carbon deposition, such as pressure build up in the reactor, were observed for 50 hours under the experimental conditions.

Example 5: CaO - Ni _0.5 / Mg _2.5 Steam reforming of n-hexadecane using Al (Ca 3 wt%) catalyst

The procedure of Example 2 was repeated except that n-hexadecane was used instead of decahydronaphthalene as a diesel fuel.

The conversion of diesel was 100%, and hydrogen selectivity was maintained at about 74.2% for about 78 hours after the start of the reaction as shown in Fig. At this time, almost no hydrocarbon compounds and methane of C ₂ or more were detected, and the selectivities of carbon monoxide and carbon dioxide were maintained in the range of 12 to 21% and 8 to 18%, respectively.

In addition, no signs of carbon deposition such as a pressure rise in the reactor during the 78 - hour reaction process were observed, and carbon deposition did not occur in the collected catalysts.

Example 6: MgO-Ni _0.5 / Mg _2.5 Steam reforming reaction of n-hexadecane using Al (Mg 1 wt%) catalyst

The steam reforming reaction of n-hexadecane was carried out in the same manner as in Example 1 except that MgO-Ni _0.5 / Mg _2.5 Al (Mg 1 wt%) catalyst prepared in Catalyst Preparation Example 3 was used.

The conversion of diesel was 100%, and hydrogen, carbon monoxide, carbon dioxide and methane were produced, and almost no hydrocarbon compounds of C ₂ or more were detected. The selectivity of hydrogen was maintained at 61.6% for 53 hours after the initiation of the reaction. No signs of carbon deposition such as pressure rise inside the reactor were observed.

Example 7: Rh-Ni _0.5 / Mg _2.5 Steam reforming reaction of n-hexadecane using Al (Rh 0.3 wt%) catalyst

The procedure of Example 4 was repeated except that n-hexadecane was used instead of decahydronaphthalene as a diesel fuel.

The conversion of diesel was 100%, and hydrogen selectivity was maintained at about 64.1% for about 53 hours after the start of the reaction. At this time, almost no hydrocarbon compounds of C ₂ or more were detected, and there was no sign of carbon deposition such as a pressure rise inside the reactor during the reaction time of 53 hours.

Example 8: Preparation of CaO-Ni _0.5 / Mg _2.5 Steam reforming of mixed diesel using Al (Ca 1 wt%) catalyst

The procedure of Example 1 was repeated except that decahydronaphthalene and n-hexadecane were mixed at a weight ratio of 1: 1 and used as a diesel fuel for simulation.

The conversion of diesel was 100%, and the selectivity of hydrogen was maintained at about 64.1% for about 78 hours after the start of the reaction. At this time, almost no C ₂ or more hydrocarbon compounds and methane were detected, and the selectivities of carbon monoxide and carbon dioxide were maintained in the range of 9 to 15% and 13 to 19%, respectively.

In addition, no signs of carbon deposition such as a pressure rise in the reactor during the 78 - hour reaction process were observed, and carbon deposition did not occur in the collected catalysts.

Example  9: CaO - Ni _{0 .5} / Mg _{2 .5} Al ( Ca  1 wt%) Water vapor of quasi-diesel using a catalyst Reforming reaction

Decahydronaphthalene, n-hexadecane and aromatic compound 1-methylnaphthalene were mixed at a weight ratio of 3: 5: 2, which is similar to the actual diesel fuel, and a small amount of sulfur component Thioprene) was added as a diesel fuel.

The conversion of diesel was 100%, and hydrogen selectivity was maintained at 62.7% for about 78 hours after the start of the reaction. At this time, almost no C ₂ or more hydrocarbon compounds and methane were detected, and the selectivities of carbon monoxide and carbon dioxide were maintained in the range of 10 to 14% and 11 to 17%, respectively. No signs of carbon deposition such as pressure rise in the reactor during the course of the reaction were observed and a small amount of carbon deposition occurred in the catalysts collected after the reaction.

Comparative Example 1: Ni _0.5 / Mg _2.5 Steam reforming of decahydronaphthalene using Al catalyst

The same procedure as in Example 1 was carried out except that the Ni _0.5 / Mg _2.5 Al catalyst prepared in Comparative Example 1 of Comparative Catalyst was used as a catalyst.

The hydrogen selectivity was maintained at about 66.4% for about 45 hours after the start of the reaction, but the selectivity of hydrogen began to decrease after 45 hours, and the reactor was blocked by the carbon deposited after 53 hours I could not. The selectivity of methane and C ₂ or more hydrocarbon compounds increased. This is probably due to the deactivation of the diesel fuel, not the reforming reaction, due to the deactivation of the catalyst due to carbon deposition during the reaction.

Comparative Example 2: Ni /? - Al ₂ O ₃ Steam Reforming of Decahydronaphthalene Using Catalysts

The procedure of Example 1 was repeated except that Ni / γ-Al ₂ O ₃ prepared in Comparative Example 2 of Comparative Catalyst 2 Catalyst.

From 3 hours after the steam reforming reaction of the diesel, the deactivation of the catalyst in which the selectivity of hydrogen decreased due to the carbon deposition began to appear. After 10 hours of reaction, the reactor pressure was increased by the deposited carbon and the reaction was stopped.

Comparative Example 3: Ni _0.5 / Mg _2.5 Steam reforming of n-hexadecane using Al catalyst

The same procedure as in Comparative Example 1 was carried out except that n-hexadecane was used instead of decahydronaphthalene as a simulated fuel for diesel.

The conversion of diesel was 100%, but the selectivity of hydrogen tended to decrease gradually after the start of the reaction. It was confirmed that carbon deposition occurred in the catalyst collected after the reaction.

Comparative Example 4: Ni /? - Al ₂ O ₃ Steam reforming of n-hexadecane using catalyst

The same procedure as in Comparative Example 2 was carried out except that n-hexadecane was used as a simulated fuel for diesel instead of decahydronaphthalene.

From 3 hours after the steam reforming reaction of the diesel, the deactivation of the catalyst in which the selectivity of hydrogen decreased due to the carbon deposition began to appear. After 10 hours of reaction, the reactor pressure was increased by the deposited carbon and the reaction was stopped.

FIG. 2 is a graph showing the results of a comparison of a CaO-Ni _{0 .5} / Mg _{2 .5} Al (Ca 1 wt%) catalyst of Catalyst Preparation 1, a Ni _{0 .5} / Mg _{2 .5} Al catalyst of Comparative Catalyst 1 and a Ni / γ-Al ₂ O ₃ catalyst for the steam reforming reaction of decahydronaphthalene is a graph comparing the durability of the catalyst represented by the selection of hydrogen with respect to the reaction time. As shown in FIG. 2, the nickel-based hydrotalcite catalyst for the steam reforming reaction of the diesel of the present invention represented by A _a -B _b -Ni _x / Mg _y Al has a selectivity for application to steam reforming of diesel, It was confirmed that the durability against deposition and the long-term stability are superior to those of conventional catalysts, so that it is possible to stably produce hydrogen at a high concentration at a high yield.

Claims (10)

A nickel-based pseudohydrotalcite catalyst for steam reforming of diesel represented by the following formula (1)
[Chemical Formula 1]
A _a -B _b -Ni _x / Mg _y Al
Wherein A is at least one kind of alkaline earth metal oxide, B is at least one kind of 8B group noble metal atom, a is 0 to 10 wt% in terms of the content of alkaline earth metal in the catalyst, 0 to 10% by weight, with the proviso that the content of the alkaline earth metal and the Group 8B noble metal can not be 0% by weight at the same time, and x and y are the molar ratios of Ni and Mg to Al in the range of 0.2? ? Y? 5.5.
The nickel-based hydrotalcite catalyst for steam reforming of diesel fuel according to claim 1, wherein a in Formula 1 is 1 to 10 wt%.
The nickel-based pseudo hydrotalcite catalyst for steam reforming of diesel according to claim 1,
(2)
B _b -Ni _x / Mg _y Al
B is at least one kind of 8B group noble metal atom, b is 0.1 to 5 wt% in terms of the content of the Group 8B noble metal in the catalyst, x and y are molar ratios of Ni and Mg to Al, 0.9, and 0.5? Y? 5.5.
Preparing a hydrotalcite precursor solution by dissolving an aluminum precursor, a magnesium precursor, and a sodium carbonate in water such that the molar ratio of aluminum, magnesium, and carbonic acid is 1: 0.5 to 5.5: 1;
Adding a nickel precursor to the hydrotalcite precursor solution so that a molar ratio of aluminum to nickel is 1: 0.2 to 0.9, and then adding sodium hydroxide to prepare a precipitate solution;
Preparing an alkaline earth metal precursor and an 8B group noble metal precursor by adding the alkaline earth metal precursor and the 8B group noble metal precursor to the precipitation solution so that the content of the alkaline earth metal in the catalyst is 0 to 10 wt% and the content of the 8B group noble metal is 0 to 10 wt% And
Filtering the mixed solution to recover the precipitate, followed by drying and calcining;
A method for preparing a nickel-based pseudo hydrotalcite catalyst for steam reforming of diesel represented by the following formula (1)
[Chemical Formula 1]
A _a -B _b -Ni _x / Mg _y Al
Wherein A is at least one kind of alkaline earth metal oxide, B is at least one kind of 8B group noble metal atom, a is 0 to 10 wt% in terms of the content of alkaline earth metal in the catalyst, 0 to 10% by weight, with the proviso that the content of the alkaline earth metal and the Group 8B noble metal can not be 0% by weight at the same time, and x and y are the molar ratios of Ni and Mg to Al in the range of 0.2? ? Y? 5.5.
5. The method of claim 4, wherein the aluminum precursor, the magnesium precursor, the nickel precursor, the alkaline earth metal precursor, and the Group 8B precursor are at least one selected from nitrate, acetone, acetate, Wherein the hydrothermal reaction is carried out in the presence of a catalyst.
5. The method of claim 4, wherein the calcination is performed at 800 to 900 < 0 > C.
A process for producing hydrogen by steam reforming reaction of diesel under a nickel-based pseudohalide catalyst represented by the following formula (1)
[Chemical Formula 1]
A _a -B _b -Ni _x / Mg _y Al
Wherein A is at least one kind of alkaline earth metal oxide, B is at least one kind of 8B group noble metal atom, a is 0 to 10 wt% in terms of the content of alkaline earth metal in the catalyst, 0 to 10% by weight, with the proviso that the content of the alkaline earth metal and the Group 8B noble metal can not be 0% by weight at the same time, and x and y are the molar ratios of Ni and Mg to Al in the range of 0.2? ? Y? 5.5.
8. The method of claim 7, wherein the diesel comprises n-hexadecane, decahydronaphthalene, or a mixture thereof.
The method for producing hydrogen according to claim 7, wherein the reforming reaction has a molar ratio of carbon to steam of 1: 1 to 3.
The method of claim 7, wherein the reforming reaction is a reaction pressure of 1 ~ 30 atm, reaction temperature 700 ~ 900 ℃ and a space velocity of 10,000 ~ 90,000 h of reaction ^- of the hydrogen by the steam reforming of diesel, characterized in that for performing at ^first Gt;

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