WO2018141648A1

WO2018141648A1 - Iron-doped nickel methanation catalysts

Info

Publication number: WO2018141648A1
Application number: PCT/EP2018/051995
Authority: WO
Inventors: Klaus Koehler; Oliver THOMYS; Kai-Olaf Hinrichsen; Franz KOSCHANY; Thomas Burger
Original assignee: Clariant Produkte (Deutschland) Gmbh; Wacker Chemie Ag; Technische Universität Muenchen
Priority date: 2017-01-31
Filing date: 2018-01-26
Publication date: 2018-08-09

Abstract

The invention relates to a catalyst for the methanation of carbon monoxide and/or carbon dioxide, comprising aluminum oxide, an Ni active mass and Fe, characterized in that the molar Ni/Fe ratio in the catalyst is 4.0 to 25.0, preferably 5.0 to 10.0, and particularly preferably 6.5 to 7.5. The invention also relates to a method for producing a catalyst according to the invention, comprising the following steps: a) co-precipitation from a solution containing Al, Ni and Fe in a dissolved form in order to obtain a precipitate, b) isolating the precipitate of step a), c) drying the isolated precipitate of step b), and d) calcining the dried precipitate of step c).

Description

Iron-doped nickel methanation catalysts

The energy supply through the so-called renewable energy photovoltaic and wind energy suffers from the problem of weather and daytime dependent fluctuations in electricity production. To ensure security of supply, a way has to be found to intercept weather and time-dependent fluctuations in electricity production. One potential method of chemically storing energy is the power-to-gas process, which uses excess electricity to split water into hydrogen and oxygen by electrolysis. Hydrogen in which the energy is stored after the electrolysis of water can itself be stored only with great effort or transported to the consumer. After the power-to-gas process, the hydrogen is therefore converted in a further step with carbon dioxide, which acts in the atmosphere as a greenhouse gas harmful to the climate, in the methanation reaction to methane and water. Methane can be easily stored in existing infrastructures, which have capacities for storage in the range of several months, can be transported almost lossless over longer distances and can be reconverted in times of energy demand. The methanation reaction, which is associated with high energy release and usually catalyzes, forms the heart of the process. The high exothermicity of the reaction (-165 kJ / mol) gives rise to two direct problems. On the one hand, the thermodynamic equilibrium limits the maximum achievable methane yield at high temperatures. For the feeding of methane into the natural gas network, a purity of 95% is necessary in Germany. This results in the demand for a high catalyst activity, so that at industrially applied reaction pressures at low temperatures higher yields of methane can be achieved.

The high exothermicity of the methanation reaction may cause hot spot formation in the reactor under adiabatic reactor operation. This leads to the development of high temperatures locally, which can damage the catalyst. There is therefore a strong interest in developing catalyst systems that are as stable as possible in order to minimize costs for catalyst replacement / downtime and material costs. Furthermore, there is a need for highly active and selective catalysts for the methanation reaction of C0 ₂ . For the methanation reaction mainly nickel-based catalysts are used, but there are also approaches with other active metals, such as Ru thenium or rhodium. In addition to aluminum oxide, the oxides of silicon, titanium and zirconium are also used as carriers. Such systems are described, for example, in the publications CN 104043454 A, CN 103480375 A, CN 102091629 A, CN 104888783 A and WO 20081 10331 A1.

Additionally one finds catalysts, which contain not only an active metal, but are promotiert. It is known from the literature that a promotion with iron or manganese can have a positive influence on the catalyst performance. A doping of nickel-based methanation catalysts with iron is described, for example, in CN 104399482 A, CN 104399466 A, CN 104209127 A, CN 102872874 A, CN 101703933 A, CN 101537357 A, WO 2007025691 A1, CN 103706366 A, CN 104028270 A and CN 101745401 A. by Pandey et al., Journal of Industrial and Engineering Chemistry (2016), 33, 99-107, and Gao, et al., RSC Advances (2015), 5 (29), 22759-22776.

CN 104399482 A and CN 104399466 A disclose a natural ore loaded iron containing nickel catalyst for methanization and the production thereof. Nickel oxide makes up 2 to 15% by weight of the catalyst. Based on the redox capacity of the carrier and the resulting interaction between iron and the nickel loading and the measures for adjusting the nickel loading capacity, the calcination temperature of the carrier, the calcination temperature of the catalyst, the reduction temperature of the catalyst and the like made a bimetallic iron-nickel methanation catalyst. The catalyst thus prepared is characterized by a low nickel loading capacity, high activity, good stability, high strength and the like. The catalyst is useful in a process for C0 ₂ / CO methanation of coke oven gas, coal or biomass based synthesis gas and the like under various H / C ratios. CN 104209127 A relates to a bimetallic nickel / iron methanation catalyst and the preparation and use thereof. In a ratio of 0.7 to 1 ml of soluble salt solution to 1 g of alumina carrier, the alumina carrier is immersed in the prepared soluble salt solution. In a ratio of 0.7 to 1 ml of a soluble nickel salt solution to 1 g of the additive-containing carrier, the carrier is immersed in the nickel salt solution to obtain a nickel-containing carrier. In a ratio of 0.7 to 1 ml of an iron salt solution to 1 g of the nickel-containing carrier the nickel-containing carrier is dipped in the iron salt solution to be subsequently dried and calcined to obtain a catalyst containing 2.5 to 10% by weight of nickel oxide, 2.5 to 10% by weight of iron oxide, 0.01 to 5 wt .-% of an additive, wherein the additive is at least one element selected from lanthanum, cerium, barium, and magnesium. The catalyst thus prepared exhibits a greatly increased activity in cryogenic methanation, has reduced costs and improves methane selectivity and stability.

CN 102872874 A relates to a nickel-based loaded catalyst used for the methylation in a suspension, a production process and the use thereof. The nickel-based loaded catalyst consists of 10 to 40% by weight of NiO, 56 to 90% by weight of a carrier and 0 to 4% by weight of an adjuvant. The nickel-based loaded catalyst is prepared by the steps of preparing a soluble salt solution with 0.5 to 1.3 g / ml nickel nitrate and the excipient; adding a catalyst carrier and a soluble organic fuel to the salt solution in tandem; impregnation for 6 to 24 hours with stirring; heating the solution, for concentration, in a water bath at a temperature of 60 to 90 ° C, after impregnation or heating to directly ignite the solution at a temperature of 300 to 700 ° C; isolating the post-combustion powder, grinding and granulating the powder, and reducing for 2 to 6 hours with a reducing gas in a fixed bed reactor at a temperature of 500 to 700 ° C.

CN 101537357 A relates to a methanation catalyst produced from synthetic gas. The methanation catalyst comprises the following components: 1 to 20% iron oxide, 1 to 30% cobalt oxide, 1 to 30% nickel oxide, 0 to 10% of a rare earth oxide, 0 to 10% molybdenum oxide, and 50 to 97% silicon carbide support. The preparation of the methanation catalyst comprises the silicon carbide material, which is chemically stable and has good thermal conductivity, as a catalyst support for producing a methanation catalyst by synthetic gas.

WO 2007025691 A1 relates to a process for the hydrogenation of carbon oxides comprising contacting a gas mixture containing carbon oxides and hydrogen with a catalyst comprising a bimetallic iron-nickel or iron-cobalt alloy as an active catalyst material, applied to an oxidic support. The support preferably has a surface area> 20 m ² / g. CN 103706366 A describes a catalyst comprising 15 to 55% of an active component, 1 to 6% of a 1. catalytic promoter, 3 to 15% of a second catalytic promoter and, moreover, a catalytic support, wherein the active component is nickel oxide, the catalytic support is Al ₂ O ₃ , the 1. catalytic promoter is one selected from lanthanum oxide, cerium oxide or samarium oxide, the second catalytic promoter is at least one of magnesium oxide, manganese oxide, iron oxide and zirconium oxide. The production method comprises the steps of dissolving a reducing agent in water to obtain a reducing solution, mixing in nickel nitrate, aluminum nitrate, the 1. Metal salt and the 2nd metal salt in water to obtain a raw material solution and adding the reducing mixture to the raw material solution with uniform stirring to obtain a 1. To obtain solution, adding an alkali solution to the 1st Solution with vigorous stirring to obtain a 2nd solution, transfer to a sealed reactor and conduct a reaction at 100 to 200 ° C for 10 to 15 hours, cool to room temperature, filter and wash to pH 6 to 7, drying at 80 to 120 ° C for 4 to 30 hours and calcining at 300 to 550 ° C for 2 to 12 hours to obtain a catalyst in which the reducing agent is one selected from formaldehyde, hydrazine hydrate, sodium hypophosphite and Ascorbic acid, wherein the 1. A metal salt of at least one selected from magnesium nitrate, manganese nitrate, iron nitrate and zirconium nitrate, the alkali metal solution is an aqueous solution of sodium carbonate, sodium hydroxide, potassium carbonate, ammonium carbonate, urea or NH ₃ ^* H ₂ 0 is. The catalyst may be mixed with a binder (calcium aluminate), a lubricant (graphite) and water and then pressed in particulate form. The catalyst is suitable for the methanation of coal gas at high temperature and high pressure to produce synthetic natural gas.

CN 104028270 A discloses a methanation catalyst comprising 5 to 60 wt .-% of a catalytically active NiO component, based on the total weight of the catalyst and otherwise Al ₂ 0 ₃ , which also 1 to 25 wt .-%, based on the total weight of Catalyst, may participate in participating component M, wherein the co-acting component M is selected from one or more oxides of the metals Ce, Ca, Co, La, Sm, Zr, Ba, Mn, Fe, Mo, Ti and Cu. The document also provides a method of making the methanation catalyst which comprises mixing the precursor of the catalytically active component, the precursor of the co-acting component M and a catalyst support according to the proportion in the methanation catalyst composition, adding an organic fuel and the thoroughly mixing and drying to form a gel-like product, carrying out a combustion reaction, cleaning and drying to obtain the final product.

CN 101745401 discloses a supported sulfur-resistant methanation catalyst which is characterized in that it comprises a main metal M as active component, a second metal M1 as auxiliary and S as support material, the weight ratio between M1, M and S being between 0 Where M is one or more of Mo, W and / or V, the second metal M1 is one or more of Fe, Co, Ni, Cr, Mn, La , Y and / or Ce and the support S Zr0 ₂ , Al ₂ 0 ₃ , MgO or Ti0 ₂ . The supported sulfur-resistant methanation catalyst is prepared by a sol-gel method.

It is the object of the invention to provide a methanation catalyst for the methanation of carbon monoxide and / or carbon dioxide which, with high activity and selectivity, has an improved stability compared to catalysts of the prior art.

This object is achieved by a catalyst for the methanation of carbon monoxide and / or carbon dioxide comprising aluminum oxide and a Ni active composition which contains Fe, characterized in that the molar Ni / Fe ratio in the catalyst is 4.0 to 25.0, preferably 5.0 to 10.0, and more preferably 5.0 to 6.0.

The stability of the catalyst in the sense of the application means the property of the catalyst to deactivate as little as possible under reaction conditions and to maintain the high selectivity / activity as far as possible.

The alumina need not be stoichiometric Al 2 O 3, but may be a non-stoichiometric alumina.

Also, the molar Ni / Fe ratio may be in the range of 4.5 to 8.0, preferably in the range of 5.0 to 7.0, most preferably in the range of 5.3 to 5.5.

The promoter Fe may be contained completely or partially in the Ni active material. The catalyst may contain other promoters in addition to Fe, but it may also contain exclusively the promoter Fe. The oxidation states of Al, Ni and the promoters can vary depending on the treatment of the catalyst. Al, Ni and the promoters are typically present as metal cations (eg, Al ^3+, Ni ^2+, Fe ^2+, Fe ^3+). After calcination, eg in air, high oxidation states or the maximum oxidation states can be achieved. Becomes the catalyst is reduced at temperatures above room temperature, for example under reaction conditions with hydrogen, AI, Ni and the promoters can assume lower oxidation states or occur partially or completely in the oxidation state 0. The charge balance to the metal cations is carried out by negatively charged oxygen atoms (0 ^{2 ~} ).

The catalyst according to the invention may contain other components besides aluminum oxide (AlO x with x <1.5) Ni and Fe (as well as the oxygen anions necessary for charge equalization), but it may also consist exclusively of aluminum oxide, Ni and Fe. Also, the Ni active material in addition to Fe may contain further promoters, but it may also contain only the promoter Fe. The latter has the advantage that then the active material or the catalyst consists of comparatively inexpensive and less toxic elements. Preferably, the catalyst does not contain any of the elements selected from Ta, In, Cu, Ce, Cr, Bi, Mn, P, B, Sb, Sn, Si, Ti, Zr, Co, Rh, Ru, Ag, Ir, Pd and Pt , Preferably, the catalyst does not contain a noble metal. Preferably, the catalyst does not contain Mn.

The atomic Al / Ni ratio may be between 0.5 and 1.5, preferably between 0.8 and 1.2, more preferably the Al / Ni ratio is approximately 1.

The catalysts according to the invention can advantageously have crystallites in the Ni active composition with a diameter of less than 20 nm, preferably less than 10 nm. The Ni active material may also consist entirely or substantially of crystallites with a diameter of less than 20 nm, preferably less than 10 nm. The Ni active material is preferably in a metallic state. The C0 ₂ absorption capacity of the catalysts at 35 ° C may be greater than 150 μηιοΙ / g and is preferably in the range between 150 to 250 μηιοΙ / g, more preferably, between 180 to 210 μηιοΙ / g.

The BET surface area (SBET) of the catalyst according to the invention may be greater than 100 m ² / g, preferably greater than 200 m ² / g, or in the range between 200 and

400 m ² / g, preferably in the range between 200 and 300 m ² / g and in particular in the range between 200 and 250 m ² / g.

The specific metal surface area (Swiet) of the catalyst according to the invention is preferably greater than 5 m ² / g, preferably greater than 10 m ² / g, or in the range between 5 and 25 m ² / g, preferably in the range between 10 and 20 m ² / g, or in the range between 9 and 12 m ² / g. Furthermore, the invention relates to a process for the preparation of a methanation catalyst, comprising the steps:

a) co-precipitation from a solution containing Al, Ni and Fe in dissolved form to obtain a precipitate,

b) isolating the precipitate from step a),

c) drying the isolated precipitate from step b) and

d) calcining the dried precipitate from step c). It is preferred here that the solution from step a) is an aqueous solution and Al, Ni and Fe are present dissolved in the aqueous solution as ionic compounds.

Al is preferably dissolved as aluminum nitrate, aluminum trichloride or aluminum sulfate. Ni is preferably dissolved as nickel nitrate, nickel dichloride, nickel sulfate, nickel acetate or nickel carbonate. Fe is preferably in the oxidation state II or III and is dissolved as iron nitrate, iron or trichloride, iron acetate, iron sulfate or iron hydroxide.

Preferably, Al, Ni and Fe are in dissolved form as ionic compounds in the aqueous solution and have the same anion, which may be, for example, nitrate.

The coprecipitation is carried out by adding the solution containing Al, Ni and Fe to a basic solution or by adding a basic solution to the proposed solution containing Al, Ni and Fe. Alternatively, the solution containing Al, Ni and Fe and the basic solution are simultaneously added to a vessel which may already contain a solvent such as water and is mixed therein. The basic solution has a pH greater than 7, preferably in the range of 8 to 10, and preferably contains an alkali hydroxide and / or an alkali carbonate. For example, the basic solution is an aqueous solution of sodium hydroxide and sodium carbonate. The coprecipitation is preferably carried out under temperature control, so that the temperature of the solution is approximately room temperature or, for example, 30 ° C.

After precipitation by coprecipitation, the precipitate in the solution is preferably more preferably for at least 30 minutes, preferably longer than 1 hour aged for more than 12 hours. The aging is preferably carried out by stirring the precipitate at approximately room temperature in the solution (mother liquor). The precipitate obtained by the coprecipitation is isolated, for example by filtering. The filtering can be done in a suitable manner, for example by a filter press.

The isolated precipitate is preferably washed, for example with distilled water, until a neutral pH is reached.

In the following, the isolated precipitate can be dried, for example at elevated temperature in air. Preferably, the drying takes place at a temperature between 70 ° C and 90 ° C for a period longer than 4 hours, preferably longer than 12 hours.

The isolated precipitate is calcined, this can be done in air at a temperature between 300 ° C to 600 ° C, preferably 400 ° C to 500 ° C and in a period of 3 to 10 hours, preferably 5 to 7 hours.

The catalyst according to the invention is intended to be used in particular in the methanation of carbon monoxide and / or carbon dioxide. The methanation of carbon dioxide can be represented by the following reaction equation: 4H ₂ + C0 ₂ -> CH ₄ + 2H ₂ 0

The methanation of carbon monoxide can be represented by the following reaction equation:

3H ₂ + CO -> CH ₄ + H ₂ O

In the method for carrying out the methanation, the reaction gas containing carbon dioxide and / or carbon monoxide or a mixture of both is contacted with the catalyst at a temperature higher than 200 ° C. The figures show the catalytic behavior of the iron-doped catalysts Fe2, Fe4, Fe7 and Fe10 before and after aging. Figure 1: Catalytic test results for Fe2 (example).

Figure 2: Catalytic test results for Fe4 (example).

FIG. 3: Catalytic test results for Fe7 (example).

FIG. 4: Catalytic test results for Fe10 (comparative example). FIG. 5: Normalized WTY (CH4) as a function of the aging time for Fe711 in comparison to Nill at an aging temperature of 450 ° C.

FIG. 6: Normalized WTY (CH4) as a function of the aging time for Fe711 in comparison to Nill at an aging temperature of 350 ° C.

methods

Elemental analysis

The determination of the composition of the calcined catalysts was carried out by means of inductively coupled plasma optical emission spectroscopy (ICP-OES). 50 mg of catalyst were dissolved in 50 ml of 1 molar phosphoric acid (VWR, pA) at 60 ° C. To dissolve any brownstone formed, 50 mg Na ₂ S0 ₃ (Sigma Aldrich, pA) was added to the solution. After cooling, the solutions were diluted 1/10 and filtered by 0.1 μηι filters (Pall). The calibration solutions were prepared at 1, 10 and 50 mg I ^-1 (Merck). Determination of metal concentrations was performed using an Agilent 700 ICP-OES.

Specific Surface Determination The specific surface area of the catalysts (SBET) was determined by N ₂ -BET analysis on a NOVA 4000e (Quantachrome). For this purpose, 100 mg of catalyst were degassed for 3 hours at 120 ° C and then absorbed adsorption and Desorptionsiso- therme in the p / p ₀ range of 0.007 to 1. To determine the BET surface area, the data points in the p / p ₀ range of 0.007 to 0.28 were used. chemisorption

Chemisorption experiments were performed on an Autosorb 1C (Quantachrome). Before the measurement, 100 mg of catalyst were activated at 500 ° C in 10% H ₂ in N ₂ for 6 hours. The heating ramp was 2 Kmin ^-1 . The determination of the metal surface (SMET) was carried out according to DIN 66136-2 (Ver., 2007-01) and was carried out by means of H ₂ chemisorption at 35 ° C. For this purpose, 20 adsorption points were recorded equidistant from 40 mmHg to 800 mmHg. The equilibration time for the adsorption was 2 min, the thermal equilibrium 10 min. To determine the metal surface, a metal atom / H stoichiometry of 1 was used. For the CC chemisorption measurements to determine the CO ₂ uptake capacities (U (C0 ₂ )), the equilibration time for the adsorption was set to 10 min with otherwise unchanged parameters. Before the absorption of the chemisorption data, any kinetic inhibition of CO 2 chemisorption under these conditions was experimentally excluded. Metal surfaces and CC uptake capacities were extrapolated to a pressure of 0 mmHg according to the extrapolation method.

In situ X-ray powder

X-ray powder diffraction (in-situ XRD) measurements of reduced and deactivated catalyst samples were performed with a STOE Stadi P diffractometer using Cu-Ka radiation, a Ge (1 1 1) monochromator, and a Dectris MYTHEN 1 K detector performed. For this, about 3 mg of catalyst sample were transferred into glass capillaries with a diameter of 0.5 mm under Ar atmosphere. The capillary was then melted off. The XRD data were recorded for 2Θ = 5-90 ⁵ with 0.5 ⁵ per step and 1, 7 steps min ¹ . The determination of the average crystallite sizes of the metal particles was carried out according to the Scherrer equation using the Ni (Fe) reflection at 2Θ = 51 .3-51 .7.

synthesis

The catalysts were prepared by coprecipitation and the atomic ratio of nickel and aluminum was adjusted to 1. To study the effect of iron on catalyst behavior, iron (III) nitrate was added to the salt solution of nickel and aluminum nitrate during catalyst synthesis. To study the effect of manganese on catalyst behavior, manganese (II) nitrate was added to the salt solution of nickel and aluminum nitrate during catalyst synthesis. The purity of all chemicals used was pa Water was purified by a Millipore filter system and the degree of purity verified by conductivity measurements. The synthesis was carried out in a double-walled, 3 l stirred tank. The water-filled double jacket allowed the temperature of the synthesis approach to 30 ° C via a thermostat, two baffles provided for an improved mixing. For stirring, a KPG stirrer with 150 revolutions min.

¹ for use. For the synthesis, 1H ₂ 0 was placed in the stirred tank and adjusted to pH = 9 ± 0.1. The dosage of the mixture of dissolved nitrates was 2.5 ml min ^-1 . At the same time, the controlled addition of the precipitating reagent was used to maintain the pH. As starting materials molar solutions of the respective nitrates were used (Ni (N0 ₃₎ 2 * 6H ₂ 0, AI (N0 ₃₎ ₃ ^* 9H ₂ 0, Fe (N0 ₃₎ ₃ ^* 9H ₂ 0 and Mn (N0 ₃₎ ₂ ^* 4H ₂ 0). These became, as in table

2, to a total volume of 120 ml min ^-1 before dropping into the reactor. The precipitation reagent was a mixture of 0.5M NaOH and 0.5 M Na ₂ C0 ₃ solutions of equal volume, for the metering of which a titrator was used. With constant stirring, the suspension was aged overnight in the mother liquor, the precipitate was then filtered off and washed with H ₂ 0 until the filtrate had a neutral pH. After drying at 80 ° C in a drying oven overnight, the dried precipitate (precursor) was heated at a heating rate of 5 K min ^-1 to 450 ° C and calcined for 6 hours under synthetic air. Activity and stability measurement

In order to be able to compare different catalysts in terms of their activity in terms of C0 ₂ methanation, a test program was developed which provides information on their activity and stability. The results of this test program are shown in FIGS. 1 to 4. For this purpose, 25 mg of catalyst in the sieve fraction 150-200 μηι were diluted with nine times the amount of SiC and incorporated into the reactor. The measurement steps carried out successively in the order of reduction, shrinkage, S-curve 1, aging and S-curve 2 are listed in detail in Table 1.

Table 1: Parameters of the measurement steps for determining the activity and stability profile

To determine the temperature-C0 ₂ -Umsatz curves, the temperature in the specified range was gradually increased by 25 ° C and each determines the activity. A comparison of the two S-curves before and after 32 hours of aging at 500 ° C gives an insight into the stability of the systems in terms of high temperatures. As a measure of the activity, the temperature T ₇ 5, i was determined, which is necessary in order to achieve a C0 ₂ conversion of 75% during the measuring step S-curve 1. For this purpose, the temperature in the specified range was gradually increased by 25 ° C. Therefore, the lower T ₇ 5, i, the higher the activity of the catalyst.

As a measure of the activity after aging, the temperature T ₇ 5.2, which is necessary in order to achieve a C0 ₂ conversion of 75% during the measuring step S-curve 2, was determined representatively. For this purpose, the temperature in the specified range was gradually increased by 25 ° C. The lower T _{7 is} 5.2, therefore, the higher the activity of the catalyst after aging.

Calculating the difference of T ₇₅ , i and T ₇₅ , 2 from the two conversion temperature characteristics, one obtains a measure of the stability of the catalyst. Again, the lower the difference, the more stable the catalyst. For better comparability, all specific activities and stabilities were normalized to those of the un-promoted nickel-alumina (Ni) catalyst. Such Ni / AIO _x catalyst systems are known in the art, so this catalyst is suitable as the starting system. The normalization results from: normalized activity = * »/ ^ ⁾

T _{7S 1} (dot cat.)

T _{75 2} (Ni / AlO _x )

Normalized stability = ^{T? S} (dot cat.)

T _{7 S 1} (dot cat)

The results in FIGS. 1 to 4 show that the promotion of a Ni / AlO _x catalyst with iron, with a Ni / Fe ratio in the catalyst of 4.0 to 25.0, leads to a significant increase in the catalyst stability. In Figures 5 and 6, respectively, the normalized WTY (CH4) was recorded as a function of the aging time for Nill compared to Fe711. The measurement took place under differential conditions at 230 ° C., 4 bar, 600 NIJ (g _ka th), H ₂ / CO ₂ / Ar = 4/1/75, the aging took place at 450 ° C. (FIG. 5) and 350 ° C (Figure 6) at 8 bar, 18 NIJ (g _cat h), H ₂ / C0 ₂ / Ar = 4/1/5. Under normalized WTY (CH4) (WTY = "weight time yield" also "mass-time yield"), the mass flow of methane formed per catalyst mass and time, normalized to the initial WTY (CH ₄ ) at t = Oh understood. This size can be used as a measure of the catalyst activity.

50 mg of the calcined catalyst was mixed with 450 mg Fe-free SiC (ESK) and placed in a quartz glass-coated tube reactor (4 mm ID). The catalyst bed was fixed with quartz wool plugs and positioned in the isothermal zone of a furnace. The catalyst temperature would be measured via a thermocouple in the catalyst bed. The catalyst was contacted with a heating rate of 2 K min-1 in 5% H2 in Ar with 50 min- NL ¹ to 485 ⁵ C. and reduced there for 5 h.

After cooling to 230 ° C., the initial catalyst activity was measured under differential reaction conditions at 4 bar and 600 NL g _ka ¹ Ir ¹ (H ₂ / CO ₂ / Ar = 4/1/75, GHSV = 800,000 hr ¹ ). For aging, the catalyst was heated at a heating rate of 5 K min ¹ and maintained at the aging temperature (350 ° C and 450 ° C) at 8 bar and 18 NL g _ka ¹ h ¹ (H ₂ / C0 ₂ / Ar = 4 / 1/5, GHSV = 24,000 hr ¹ ). The aging time was 2 h in the initial deactivation treatment and 4 h in all further treatments. After each aging step, the catalyst bed was cooled to 230 ° C before the catalyst activity was re-determined under the above conditions to follow the catalyst deactivation in the kinetic regime under conditions free of product or equilibrium limitations. These cycles were repeated to obtain catalysts aged for 0, 6, 40 and 72 hours. The aged catalysts were transferred under Ar atmosphere to a glovebox, from which further characterization studies were prepared.

Examples

Table 2: Molar metal salt solutions used in co-precipitation

Table 3: Composition of the calcined catalysts

Table 4: Characterization data of the catalysts

a normalized to mass of the calcined catalyst ^b normalized to mass of the calcined catalyst

Table 5: Results of the catalytic test reaction

Table 6: Characterization data at different aging times

a normalized to the mass of the calcined catalyst

b normalized to mass of the reduced catalyst

c determined by XRD, Ni (Fe) reflection at 2Θ = 51 .3-51 .7 ⁰

Claims

Claims:

1 . A catalyst for the methanation of carbon monoxide and / or carbon dioxide, comprising aluminum oxide, a Ni active composition, and Fe, characterized in that the molar Ni / Fe ratio in the catalyst is 4.0 to 25.0, preferably 5.0 to 10.0 and more preferably 5.0 to 6.0.

2. A catalyst according to claim 1, characterized in that the Ni active material crystallites having a diameter of less than 20 nm, preferably less than 10 nm.

3. Catalyst according to one of the preceding claims, characterized by a C0 ₂ -aufnahmekapazität at 35 ° C of greater than 200 μηιοΙ, preferably 200 to 300 μηιοΙ per gram of catalyst.

4. Use of a catalyst according to one of the preceding claims, for the methanation of carbon monoxide and / or carbon dioxide with gaseous hydrogen.

5. A process for the preparation of a catalyst according to claim 1, comprising the steps:

b) isolating the precipitate from step a),

c) drying the isolated precipitate from step b) and

d) calcining the dried precipitate from step c).

6. The method according to claim 5, characterized in that the solution from step a) is an aqueous solution.

7. The method according to claim 5 or 6, characterized in that the precipitate is aged in the solution for at least 30 minutes.

8. The method according to claim 5 to 7, characterized in that the isolated precipitate from step b) is washed.

9. The method according to claim 5 to 8, characterized in that the Al, Ni and Fe are present in dissolved form, as ionic compounds in the solution and these ionic compounds have the same anion.

10. The method according to claim 9, characterized in that the anion is nitrate, sulfate, a halide, chloride, or acetate.

1 1. Method according to one of claims 5 to 10, characterized in that Fe is present in the solution of step a) in the oxidation state II or III.

12. The method according to claim 5, characterized in that the calcination of the dried precipitate takes place at a temperature of 300 to 600 ° C in air.

13. A process for the methanation of carbon dioxide and / or carbon monoxide in which a gas containing carbon dioxide and / or carbon monoxide is brought into contact with a catalyst according to claim 1.

14. The method of claim 13, wherein the gas is contacted with the catalyst at a temperature above 200 ° C in contact.