CATALYSTS, PROCESSES FOR OBTAINING AND PROCESSES FOR STEAM REFORMING

Abstract

The present invention refers to processes for obtaining steam reforming catalysts containing nickel, cerium, lanthanum and copper oxides, free from potassium or alkali metals, preferably with the oxide layer being located externally with a thickness of less than 0.5 mm on the support particle, preferably the support being based on alumina, magnesium aluminate, hexaaluminates or mixtures thereof. The catalysts according to present invention show high activity, resistance to thermal deactivation and resistance to coke accumulation in the steam reforming reaction of hydrocarbons.

Claims

1. A steam reforming catalyst comprising: a) an inorganic oxide support selected from theta-alumina, magnesium aluminate, hexaaluminates, or a mixture thereof, having a surface area above 15 m.sup.2/g; and b) a mixture of nickel, copper, lanthanum, and cerium oxides, with the total nickel content, expressed as nickel oxide (NiO) between 5 and 25% w/w; the copper content expressed as copper oxide (CuO) between 0.5 to 5% w/w, a Ni/(La+Ce) atomic ratio between 3 to 5 and a Ce/Al atomic ratio between 1 to 4.

2. The steam reforming catalyst according to claim 1, wherein the inorganic oxide support has a surface area above 60 m.sup.2/g.

3. A process for obtaining the steam reforming catalyst of claim 1, comprising the following steps: a) preparing a solution in a polar solvent, of a nickel salt, in the form of nickel nitrate, acetate or carbonate together with copper, lanthanum, and cerium salts in the form of nitrates; b) impregnating the solution containing the nickel, copper, cerium, and lanthanum salts in an inorganic oxide support selected from theta-alumina, magnesium aluminate, hexaaluminates, or a mixture thereof, by means of the wet spot technique or by placing the support of inorganic oxide in an excess of solution to form an impregnated material; and c) drying the impregnated material in air, at a temperature ranging between 50° C. and 150° C., and for a time interval in a range of values between 1 and 24 hours, and then calcining the impregnated material in air at a temperature ranging between 250° C. and 650° C., and for a time interval in a range of values between 1 and 4 hours.

4. The process for obtaining the steam reforming catalyst according to claim 3, wherein the polar solvent is water.

5. A process for obtaining the steam reforming catalyst of claim 1, comprising the following steps: a) preparing a solution in a polar solvent, of a nickel inorganic salt, in the form of nickel nitrate, acetate, or carbonate together with lanthanum and cerium salts in the form of nitrates; b) impregnating the solution containing the nickel, cerium, and lanthanum salts in an inorganic oxide support selected from theta-alumina, magnesium aluminate, or hexaaluminates, by means of the wet spot technique or by placing the support of inorganic oxide in an excess of solution to form an impregnated material; c) drying the impregnated material in air, at a temperature ranging between 50° C. and 150° C., and for a time interval in a range of values between 1 and 24 hours, and then calcining the impregnated material in air at a temperature ranging between 250° C. and 650° C., and for a time interval in a range of values between 1 and 4 hours; d) preparing a solution in a polar solvent, of an inorganic copper salt, in the form of nitrate; e) impregnating the material consisting of the inorganic oxide support and nickel, cerium, and lanthanum oxides with the solution containing the copper salt by means of the wet spot technique or by placing the inorganic oxide support in an excess of solution; and f) drying the impregnated material in air, at a temperature ranging between 50° C. and 150° C., and for a time interval in a range of values between 1 and 24 hours, and then calcining the impregnated material in air at a temperature ranging between 250° C. and 650° C., and for a time interval in a range of values between 1 and 4 hours.

6. The process for obtaining the steam reforming catalyst according to claim 5, wherein the polar solvent is water.

7. A steam reforming catalyst comprising: a) an inorganic oxide support selected from theta-alumina, magnesium aluminate, hexaaluminates, or a mixture thereof, having a surface area above 15 m.sup.2/g; and b) a mixture of nickel, copper, lanthanum, and cerium oxides, with the total nickel content, expressed as nickel oxide (NiO) deposited on the outside of the support particles at a depth equal to or less than 1 mm, with the content nickel oxide in this layer ranging between 5 and 25% w/w; the copper content expressed as copper oxide (CuO) between 0.5 to 5% w/w, a Ni/(La+Ce) atomic ratio ranging between 3 to 5 and a Ce/Al atomic ratio ranging between 1 to 4.

8. The steam reforming catalyst according to claim 7, wherein the inorganic oxide support has a surface area above 60 m.sup.2/g.

9. The steam reforming catalyst according to claim 7, wherein the mixture of nickel, copper, lanthanum, and cerium oxides is deposited on the outside of the support particles at a depth equal to or less than 0.5 mm.

10. A process for obtaining the steam reforming catalyst of claim 7, comprising the following steps: a) impregnating the inorganic oxide support, selected from theta-alumina, magnesium aluminate, or hexaaluminates with a glycerine and water solution; b) drying the inorganic support at a temperature ranging between 50° C. and 150° C. to remove the water; c) impregnating the support with the pores partially occupied by glycerin with an aqueous solution of soluble salts of nickel, copper, lanthanum, and cerium using the wet spot technique; and d) drying the inorganic oxide support at 50° C. to 150° C. for 1 to 4 hours and then calcining in air at 350° C. to 650° C. for 1 to 4 hours to obtain a layer of nickel, copper, lanthanum, and cerium oxides, located on the outer surface of the support particles.

11. The process for obtaining the steam reforming catalyst according to claim 3, wherein the final calcination step is replaced with a direct reduction comprising the following steps: a) contacting the steam reforming catalyst with a flow of a reducing agent, selected from hydrogen, formaldehyde, methanol, or natural gas in the presence of water vapor at a temperature ranging from 300° C. to 800° C. and for a time interval in a range of values between 1 to 5 hours; and b) cooling in a flow of N.sub.2 and subjecting the reduced catalyst to an air flow at a temperature in a range of values between 20° C. to 100° C., and for a time interval in a range of values between 1 to 5 hours.

12. A process of steam reforming of hydrocarbon streams comprising conducting the hydrocarbon stream with the steam reforming catalyst of claim 1, carried out in the presence of water vapor and hydrogen, temperatures ranging between 450° C. to 950° C., pressures between 10 kgf/cm.sup.2 to 50 kgf/cm.sup.2 and water vapor/carbon ratio between 1 to 5 mol/mol.

13. The process of steam reforming of hydrocarbon streams according to claim 12, wherein the temperature ranges between 550° C. to 930° C. pressures between 20 kgf/cm.sup.2 to 40 kgf/cm.sup.2 and water vapor/carbon ratio between 2.5 to 3.5 mol/mol.

14. The process of steam reforming of hydrocarbon streams according to claim 12, wherein the hydrocarbon stream comprises natural gas, liquefied petroleum gas, naphtha, or gases containing olefins.

15. The process for obtaining the steam reforming catalyst according to claim 5, wherein the final calcination step is replaced with a direct reduction comprising the following steps: a) contacting the steam reforming catalyst with a flow of a reducing agent, selected from hydrogen, formaldehyde, methanol, or natural gas in the presence of water vapor at a temperature ranging from 300° C. to 800° C. and for a time interval in a range of values between 1 to 5 hours; and b) cooling in a flow of N.sub.2 and subjecting the reduced catalyst to an air flow at a temperature in a range of values between 20° C. to 100° C., and for a time interval in a range of values between 1 to 5 hours.

16. The process for obtaining the steam reforming catalyst according to claim 10, wherein the final calcination step is replaced with a direct reduction comprising the following steps: a) contacting the steam reforming catalyst with a flow of a reducing agent, selected from hydrogen, formaldehyde, methanol, or natural gas in the presence of water vapor at a temperature ranging from 300° C. to 800° C. and for a time interval in a range of values between 1 to 5 hours; and b) cooling in a flow of N.sub.2 and subjecting the reduced catalyst to an air flow at a temperature in a range of values between 20° C. to 100° C., and for a time interval in a range of values between 1 to 5 hours.

17. A process of steam reforming of hydrocarbon streams comprising conducting the hydrocarbon stream with the steam reforming catalyst of claim 7, carried out in the presence of water vapor and hydrogen, temperatures ranging between 450° C. to 950° C., pressures between 10 kgf/cm.sup.2 to 50 kgf/cm.sup.2 and water vapor/carbon ratio between 1 to 5 mol/mol.

18. The process of steam reforming of hydrocarbon streams according to claim 17, wherein the temperature ranges between 550° C. to 930° C., pressures between 20 kgf/cm.sup.2 to 40 kgf/cm.sup.2 and water vapor/carbon ratio between 2.5 to 3.5 mol/mol.

19. The process of steam reforming of hydrocarbon streams according to claim 17, wherein the hydrocarbon stream comprises natural gas, liquefied petroleum gas, naphtha, or gases containing olefins.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0057] The present invention will be described in more detail below, with reference to the attached figures which, in a schematic and non-limiting way, represent examples of the configuration thereof. In the drawings, there are:

[0058] FIG. 1 illustrating a comparison of resistance to coke deposition between a commercial catalyst for steam reforming of natural gas, propane and butane (CGN) and the same catalyst promoted with 1% w/w CuO (EXAMPLE 1). This figure shows how the mere addition of CuO to a commercial catalyst does not bring the benefits of increased build-up resistance and coke;

[0059] FIG. 2 illustrates a comparison of resistance to coke deposition between a catalyst prepared according to the state of the art of NiO/alpha-alumina type (EXAMPLE 2) and the same catalyst promoted with 1% w/w CuO (EXAMPLE 3). This figure shows that the addition of CuO by catalyst preparation methods in accordance with the state of the art does not bring the benefits of greater resistance to coke build-up;

[0060] FIG. 3 illustrating a comparison of resistance to coke deposition between commercial heavy natural gas (CGNP) and naphtha (CNF) steam reforming catalysts and catalysts in accordance with the present invention containing 1% w/w CuO (EXAMPLE 5) and 5% w/w CuO (EXAMPLE 6). This figure illustrates that catalysts prepared in accordance with the present invention have greater resistance to coke accumulation than materials in accordance with the state of the art.

[0061] FIG. 4 illustrating a comparison of resistance to coke deposition between catalysts prepared in accordance with the present invention, containing 1% w/w CuO, prepared by the impregnation process in steps (EXAMPLE 4) and by the preferred embodiment of simultaneous impregnation (EXAMPLE 6). The figure illustrates why the simultaneous impregnation embodiment is preferred, as it simplifies the catalyst preparation process and allows for better performance;

[0062] FIG. 5 illustrating an external and internal aspect of catalyst particles prepared in accordance with the present invention containing copper, nickel, lanthanum and cerium oxides prepared by the eggshell process on a magnesium aluminate type support (EXAMPLE 8). The darkest region in the particles indicates the presence of nickel and/or copper oxide;

[0063] FIG. 6 illustrating a comparison between the coke build-up resistance of commercial heavy natural gas (CGNP) and naphtha (CNF) steam reforming catalysts with a catalyst prepared in accordance with the present invention containing oxides of copper, nickel, Lanthanum and cerium prepared by the eggshell process on a magnesium aluminate type support (EXAMPLE 8C).

DETAILED DESCRIPTION OF THE INVENTION

[0064] The present invention discloses catalysts for the production of hydrogen or hydrogen-rich gases by the steam reforming of hydrocarbons, provided with high resistance to coke accumulation, high activity and resistance to deactivation by sintering of the active phase, characterized by comprising a mixture of copper, nickel, lanthanum and cerium oxides on an inorganic oxide support selected from theta-alumina, magnesium aluminate, hexaaluminates or a mixture thereof having a surface area above 15 m.sup.2/g, preferably above 60 m.sup.2/g.

[0065] The mixture of oxides used comprises copper, nickel, lanthanum and cerium oxides, and the nickel content expressed as nickel oxide (NiO) is between 5 and 25% w/w; the copper content expressed as copper oxide (CuO) between 0.5 to 5% w/w. The meaning of “expressed as” in the present invention is used for the purpose of determining the composition, and in practice the nickel or copper species can assume other chemical structures on the catalyst. The Ni/(La+Ce) atomic ratio is between 3 to 5 and the Ce/Al ratio between 1 to 4.

[0066] The process for obtaining the catalyst according to the present invention for the production of a mixture of gases rich in hydrogen and carbon monoxide, in the preferred embodiment, comprises the following steps: [0067] a) preparing a solution in a polar solvent, preferably water, of a nickel salt, preferably nickel nitrate, acetate or carbonate together with copper, lanthanum and cerium salts, preferably in the form of nitrates; [0068] b) impregnate the solution containing the nickel, copper, cerium and lanthanum salts in an inorganic oxide support selected from theta-alumina, magnesium aluminate or hexaaluminates, by means of the wet spot technique or by placing the said support of inorganic oxide in an excess of solution; [0069] c) drying the impregnated material in air, at a temperature comprised between 50° C. and 150° C., and for a time interval comprised in a range of values between 1 and 24 hours, and then calcining the impregnated material in air at a temperature comprised between 250° C. and 650° C., and for a time interval comprised in a range of values between 1 and 4 hours;

[0070] Optionally, steps a), b) and c) of the above process can be repeated more than once until the desired NiO content in the inorganic oxide support is reached.

[0071] In a second embodiment, the catalyst according to the present invention can be prepared by adding copper as a promoter in a step subsequent to the addition of nickel, cerium and lanthanum in the formulation. The process for obtaining the catalyst according to the present invention in this embodiment comprises the following steps: [0072] a) preparing a solution in a polar solvent, preferably water, of a nickel salt, preferably nickel nitrate, acetate or carbonate together with lanthanum and cerium salts, preferably in the form of nitrates; [0073] b) impregnate the solution containing the nickel, cerium and lanthanum salts in an inorganic oxide support selected from theta-alumina, magnesium aluminate or hexaaluminates, by means of the wet spot technique or by placing the said support of inorganic oxide in an excess of solution; [0074] c) drying the impregnated material in air, at a temperature comprised between 50° C. and 150° C., and for a time interval comprised in a range of values between 1 and 24 hours, and then calcining the impregnated material in air at a temperature comprised between 250° C. and 650° C., and for a time interval comprised in a range of values between 1 and 4 hours; [0075] d) preparing a solution in a polar solvent, preferably water, of an inorganic copper salt, preferably in the form of nitrate; [0076] e) impregnate the material consisting of the inorganic oxide support and nickel, cerium and lanthanum oxides with the solution containing the copper salt by means of the wet spot technique or by placing said inorganic oxide support in an excess of solution; [0077] f) drying the impregnated material in air, at a temperature comprised between 50° C. and 150° C., and for a time interval comprised in a range of values between 1 and 24 hours, and then calcining the impregnated material in air at a temperature comprised between 250° C. and 650° C., and for a time interval comprised in a range of values between 1 and 4 hours;

[0078] In a third embodiment, the catalyst according to the present invention can be prepared depositing nickel, copper, lanthanum and cerium oxides on the outside of the support particles in a layer with a maximum thickness of 1 mm, preferably less than 0.5 mm on the support particles, featuring an eggshell type of catalyst. The process for obtaining the catalyst according to the present invention in this embodiment comprises the following steps: [0079] a) impregnating the inorganic oxide support, selected from theta-alumina, magnesium aluminate or hexaaluminates with a glycerine and water solution; [0080] b) drying the inorganic support at temperatures between 50° C. and 150° C. to remove the water; [0081] c) impregnating the support with the pores partially occupied by glycerin with an aqueous solution of soluble salts of nickel, copper, lanthanum and cerium, preferably using the wet spot technique; [0082] d) drying the inorganic oxide support at 50° C. to 150° C. for 1 to 4 hours and then calcining in air at 350° C. to 650° C. for 1 to 4 hours to obtain a layer of nickel, copper, lanthanum and cerium oxides, located on the external surface of the support particles and with a penetration depth in these particles of less than 1 mm, preferably less than 0.5 mm;

[0083] Optionally, the above steps can be repeated until the desired nickel oxide content is obtained.

[0084] The catalysts thus prepared are in the oxidized state and must be activated by reduction to obtain the active phase of metallic nickel promoted by metallic copper and lanthanum and cerium oxides. The reduction is typically carried out at the industrial unit by passing a reducing gas, selected from hydrogen or gases rich in hydrogen, ammonia, methanol or natural gas, free from sulfur, in the presence of steam, with a molar ratio steam/H.sub.2 or steam/carbon between 6 to 8 at temperatures in the order of 550° C. at the inlet of the reformer tubes to 850° C. at the outlet of these tubes, for periods comprised between 4 to 10 hours.

[0085] Alternatively, the catalyst can be produced in the pre-reduced state, replacing the calcination steps in the catalyst production process with a step of direct reduction in flow of a reducing agent, which can be selected from hydrogen, formaldehyde or methanol. Said direct reduction can occur at a temperature comprised in a range of values between 300° C. and 800° C., and for a period of time comprised in a range of values between 1 and 5 hours. Then, the material can be cooled and subjected to an air flow at a temperature comprised within a range of values between 20° C. and 60° C., and for a period of time comprised within a range of values between 1 and 5 hours, in order to prevent the material from having a pyrophoric feature when handled.

[0086] The inorganic oxide support is selected from the group consisting of theta-alumina, magnesium aluminate and hexaluminates or mixtures thereof. The support can be cylindrical or sphere-shaped particles containing one or multiple holes, its outer surface being smooth or preferably containing undulations to increase the outer area. The dimensions, diameter and length of the support particles are comprised between 10 and 25 cm. Preferably, the support has a surface area, measured by the nitrogen adsorption technique, above 15 m.sup.2/g, preferably above 60 m.sup.2/g.

[0087] The present invention further discloses a process for producing hydrogen or hydrogen-rich gases by the steam reforming reaction, using a catalyst consisting of nickel, copper, cerium and lanthanum oxides with a nickel oxide content between 5 and 25% w/w; the copper oxide content between 0.5 to 5% m/m, the Ni/(La+Ce) atomic ratio between 3 to 5 and the Ce/Al atomic ratio between 1 to 4, on an inorganic oxide support selected among theta-alumina, magnesium aluminate, hexaaluminates or mixtures thereof.

[0088] The process for the production of hydrogen or hydrogen-rich gases according to the present invention consists of contacting a stream of hydrocarbons, selected from natural gas, liquefied petroleum gas, naphtha and refinery gas or other gases containing olefins, such as those resulting from Fischer-Tropsch processes, known in the state of the art as residual gas together with water vapor and preferably hydrogen with the catalyst consisting of nickel, copper, cerium and lanthanum oxides on an inorganic oxide support. The process can be carried out at temperatures between 450° C. and 950° C., preferably between 550° C. and 930° C., pressures between 10 kgf/cm.sup.2 to 50 kgf/cm.sup.2, preferably between 20 kgf/cm.sup.2 to 40 kgf/cm.sup.2 and water vapor/carbon ratio between 1 to 5 mol/mol, preferably between 2.5 to 3.5 mol/mol. The catalyst is placed within a multiplicity of fixed bed catalytic reactors within an oven, the assembly being known in the primary reformer.

EXAMPLES

[0089] Next, for the invention to be able to be better understood, experiments are presented that illustrate the invention, without, however, being considered limiting. In these experiments, catalysts are prepared according to the state of the art process and according to the present invention, with the objective of making a comparative analysis of the coke deposition and catalytic activity indices, when the catalysts are used in a process of steam reform.

Example 1

[0090] This example illustrates the use of copper to promote a commercial NiO/support type steam reforming catalyst used for the steam reforming of natural gas, propane, and butanes.

[0091] A commercial steam reforming catalyst for light natural gas (identified as CGN) was promoted with 1% w/w of copper oxide, where 30 grams of CGN catalyst, previously ground in the particle size range below 170 mesh, were impregnated by the method of wet point with 6 ml of aqueous solution containing 0.92 grams of Cu(NO.sub.3)2.3H.sub.2O. Then, the material was calcined at 450° C. for 4 hours to obtain a catalyst containing around 1% w/w CuO nominal. The catalyst showed a specific area of 10 m.sup.2/g.

[0092] The commercial catalyst and the catalyst in accordance with EXAMPLE 1 had their steam reforming activity measured on commercial AutoChem II equipment (Micromerits). The experiments were carried out using 50 mg of catalyst ground in the range lower than 170 mesh.

[0093] Initially, a step of reduction of the nickel and copper oxide phases was carried out at a temperature of 750° C., at atmospheric pressure, for two hours, by passing 40 mL/min of a mixture containing 10% Hz/argon saturated with water vapor at 50° C. on the catalyst. Hydrogen consumption in this step was monitored by thermal conductivity. After the reduction period, the methane steam reforming reaction was carried out, passing a stream of methane (99.99%) saturated in water vapor at 90° C., which corresponds to a steam/carbon ratio of 2.3 mol/mol, at reaction temperatures of 500° C.; 550° C. and 600° C., atmospheric pressure and a space velocity (GHSV) of 96,000 h.sup.−1 on a dry basis.

[0094] The effluent gases from the reactor were analyzed by gas chromatography and the activity measured by the degree of conversion of methane. Table 1 presents the results of the catalytic activity, measured by the degree of methane conversion at different temperatures, and shows that the addition of copper reduces the methane conversion activity in the steam reforming reaction.

TABLE-US-00001 TABLE 1 Comparative activity of steam reforming of methane of a commercial NiO/support type steam reforming catalyst and the same catalyst promoted by 1% w/w of CuO SAMPLE Type 500° C. 550° C. 600° C. CGN Commercial for natural gas, 22.6 36.5 49.9 propane and butane EXAMPLE 1 CuO/NiO/support 19.5 36.4 50.0 (commercial) Note: Catalyst from EXAMPLE 1 containing 1% w/w copper expressed as CuO.

[0095] The commercial catalyst (CGN) and the catalyst according to EXAMPLE 1 had the resistance to coke accumulation measured in thermogravimetric analysis equipment (TGA Mettler Toledo) TGA/SDTA851E.

[0096] The tests were carried out using 25 mg of ground catalyst in a range of lower than 170 mesh. Initially, a sample reduction step was performed by passing 40 mL/min of a mixture containing 10% (v/v) of hydrogen in argon saturated with water vapor at 15° C. together with 40 mL/min of nitrogen (shielding gas) with temperature programming ranging from 100° C. to 650° C. at the rate of 10° C./min, maintained for 1 hour. Afterwards, the temperature was reduced to 350° C. and the resistance to coke deposition was measured replacing the stream of Hz/Argon with a synthetic stream consisting of 21.9% hydrogen; 13.2% CO; 15.9% CO.sub.2, 43.62% CH.sub.4, 1.77% nitrogen and 0.20% ethylene saturated with water vapor at 15° C. with temperature programming from 350° C. to 700° C. at the rate of 5° C./min. The results are presented in the form of percentage change in mass with the coke deposition reaction temperature, the reduced catalyst mass having been normalized to 100% before the start of the coke formation step. In this type of representation, catalysts having a higher rate of coke deposition exhibit a greater increase in the percentage of mass and/or a lower temperature at which the beginning of the increase in mass is observed, indicating the beginning of coke deposition.

[0097] As can be seen in FIG. 1, the coke deposition rate on the commercial catalyst CGN and on this commercial catalyst promoted with 1% copper oxide (EXAMPLE 1) show that there was an unwanted reduction in the resistance to carbon deposition by the addition of copper to the commercial steam reforming catalyst, according to the state of the art.

[0098] This example illustrates that commercial steam reforming catalysts, according to the state of the art, do not benefit from the addition of copper oxide to their formulation, since copper reduces the activity, as shown in Table 1, but it also reduces resistance to coke buildup.

Example 2

[0099] This example illustrates the preparation of a nickel oxide-based catalyst on a low specific area support, according to the state of the art, where 304 grams of alpha-alumina (Alcoa A2G) having specific area of 1.8 m.sup.2/g were impregnated by the wet point method with 82 ml of an aqueous solution containing 61.30 grams of Ni(NO.sub.3).sub.2.6H.sub.2O. Then, the material was dried at 95° C. for one night and after that calcined at 450° C. for 4 hours to obtain a catalyst containing 5% NiO on alpha-alumina. The procedure was repeated two more times to obtain a catalyst containing 15% NiO supported alpha-alumina. The catalyst showed a specific area of 3.4 m.sup.2/g.

Example 3

[0100] This example illustrates the preparation of a low specific area supported nickel oxide based catalyst promoted with copper, according to the state of the art. The catalyst was prepared in accordance with EXAMPLE 2 and then promoted with copper, where 99 grams of the catalyst were impregnated by the wet point method with 26.5 ml of an aqueous solution containing 3.01 grams of Cu(NO.sub.3).sub.2.3H.sub.2O. Then, the material was calcined at 450° C. for 4 hours to obtain a catalyst with a nominal composition of 1% CuO, 15% NiO on alpha-alumina. The catalyst showed a specific area of 2.3 m.sup.2/g.

[0101] Catalysts prepared according to EXAMPLES 2 and 3 had the catalytic activity and resistance to coke deposition experimentally measured as described in EXAMPLE 1. Table 2 shows that the use of copper to promote the NiO/alpha-alumina type catalyst reduces its activity while FIG. 2 shows that there was a deterioration in the resistance to coke deposition by the addition of copper oxide as a promoter to the catalyst. This example illustrates that NiO/alpha-alumina type catalysts, according to the state of the art, are not benefited by the addition of copper oxide to their formulation.

TABLE-US-00002 TABLE 2 Comparative activity of steam reforming of methane of NiO/alpha- alumina catalysts and the same catalyst promoted with copper oxide. SAMPLE Type 500° C. 550° C. 600° C. EXAMPLE 2 NiO/alpha-alumina 35.7 47.5 57.4 EXAMPLE 3 CuO/NiO/alpha-alumina 26.2 41.1 54.1 Note: Catalyst from EXAMPLE 3 containing 1% copper expressed as CuO.

Example 4

[0102] This example illustrates the preparation of a catalyst based on nickel, lanthanum and cerium oxides on a theta-alumina type support, where 100 grams of theta-alumina (SPH 508F from Axens, with pore volume of 0.7 cm.sup.3/g in the shape of spheres of 3 mm to 4 mm in diameter, specific area of 85.5 m.sup.2/g determined by the N2 adsorption technique) were impregnated by the wet point method with 70 ml of aqueous solution containing 2.95 grams of La(NO.sub.3).sub.3.6H.sub.2O, 8.82 grams of Ce(NO.sub.3).sub.3.3H.sub.2O and 33.03 grams of Ni(NO.sub.3).sub.2.6H.sub.2O. Then, the material was dried at 60° C. for 2 hours, heated in static air from 60° C. to 120° C. at the rate of 1° C./min, and then up to 250° C. at the rate of 1.4° C./min. The following material was calcined at 450° C. for 4.5 hours to obtain a Ni—Ce—La-theta-alumina type catalyst containing 7.6% (w/w) of NiO, 1.0% (w/w) of La.sub.2O.sub.3 and 3,0% w/w of Ce.sub.2O.sub.3. The catalyst had a specific area of 83.7 n.sup.2/g determined by the technique of adsorption of N2 in commercial equipment (Micromerits).

Example 5

[0103] This example illustrates the preparation of a catalyst according to the present invention based on copper, nickel, lanthanum and cerium oxides on a supported theta-alumina type.

[0104] The addition of copper oxide as a promoter was carried out with 100 grams of the catalyst prepared in accordance with EXAMPLE 4, impregnated by the wet point method with 65 mol of an aqueous solution containing 2.98 grams of Cu(NO.sub.3).sub.2.3H.sub.2O. Then, the material was dried at 95° C. for one night and calcined at 450° C. for 4 hours to obtain a catalyst of the Cu—Ni—Ce—La-theta-alumina type with nominal content of 1.0% (w/w) of CuO 7.5% (w/w) of NiO, 1.0% (w/w) of La.sub.2O.sub.3 and 3.0% w/w of Ce.sub.2O.sub.3 which after activation had the copper and nickel oxide phases reduced to copper and nickel metals. The catalyst showed a specific area of 76 m.sup.2/g.

Example 6

[0105] This example illustrates the preparation of a catalyst according to the present invention based on copper, nickel, lanthanum and cerium oxides on a supported theta-alumina type. The catalyst was prepared according to EXAMPLE 4 and then promoted with copper.

[0106] The addition of copper as a promoter was carried out with 100 grams of the catalyst prepared according to EXAMPLE 4 impregnated by the wet point method with an aqueous solution containing 15.54 grams of Cu(NO.sub.3).sub.2.3H.sub.2O to obtain a Cu—Ni—Ce—La-theta-alumina type catalyst with nominal composition of 5.0% (w/w) of CuO 7.2% (w/w) of NiO, 0.9% (w/w) of La.sub.2O.sub.3 and 2.9% w/w of Ce.sub.2O.sub.3. The catalyst had a specific area determined by the N2 adsorption technique of 60 m.sup.2/g.

[0107] Catalysts prepared according to EXAMPLES 4, 5 and 6 had the catalytic activity and resistance to coke deposition experimentally measured as described in EXAMPLE 1. For comparison, two commercial nickel oxide steam reforming catalysts containing potassium, supported on refractory materials used for heavy natural gas (CGNP) and for naphtha (CNF), containing medium and high potassium content, respectively, were included. The results in Table 3 show that the catalysts prepared according to the present invention have high steam reforming activity, superior to commercial catalysts according to the state of the art.

[0108] FIG. 3 shows that surprisingly, the addition of copper oxide to the catalyst formulation increases resistance to coke build-up, unlike what was observed for state of the art catalysts as illustrated in FIGS. 1 and 2, where the addition of copper oxide to catalyst formulation reduces resistance to coke buildup. The catalysts according to the present invention have high steam reforming activity and resistance to coke deposition, therefore, they are suitable for industrial use, without presenting the disadvantages of using alkali metals, such as potassium, of the catalysts obtained according to the state of the art.

[0109] Copper added to the catalyst according to the present invention makes it possible to increase the resistance to the build-up of coke. It is believed that this unexpected effect, considering that the addition of copper reduces the resistance to the build-up of coke when added to a state-of-the-art catalyst formulation, is due to the combination of the catalyst composition, containing lanthanum and cerium oxides, with the use of a support having high surface area, selected among theta-alumina, magnesium aluminates and hexaaluminates.

TABLE-US-00003 TABLE 3 Comparative methane steam reforming activity of catalysts according to the present invention and commercial catalysts according to the state of the art. SAMPLE Type 500° C. 550° C. 600° C. CGNP Commercial for heavy 22.0 43.4 55.0 natural gas CNF Commercial for naphtha 27.6 37.4 47.4 EXAMPLE 4 NiO—Ce.sub.2O.sub.3—La.sub.2O.sub.3/theta- 41.8 47.3 56.2 alumina EXAMPLE 5 CuO/NiO—Ce.sub.2O.sub.3—La.sub.2O.sub.3/ 35.8 47.2 55.9 theta-alumina EXAMPLE 6 CuO/NiO—Ce.sub.2O.sub.3—La.sub.2O.sub.3/ 36.5 46.7 55.7 theta-alumina Note: Catalyst of EXAMPLES 5 and 6 containing 1% copper and 5% copper, respectively, expressed as CuO. Commercial catalysts of type K/NiO/support for heavy natural gas (CGNP) and for naphtha (CNF).

Example 7

[0110] This example illustrates the preparation of a catalyst according to the present invention based on copper, nickel, lanthanum and cerium oxides on a support of the alumina type, with copper being added simultaneously with the other elements, where 100 grams of theta-alumina (SPH 508F from Axens, with pore volume of 0.7 cm.sup.3/g in the shape of spheres from 3 mm to 4 mm in diameter, specific area of 85.5 m.sup.2/g determined by the N2 adsorption technique) were impregnated with 70 ml of aqueous solution containing 2.96 grams of La(NO.sub.3).sub.3.6H.sub.2O, 8.82 grams of Ce(NO.sub.3).sub.3.3H.sub.2O, 33.34 grams of Ni(NO.sub.3).sub.2.6H.sub.2O and 2.70 grams of Cu(NO.sub.3).sub.2.3H.sub.2O by the wet spot technique. Then, the material was dried at 60° C. for 2 hours, heated in static air from 60° C. to 120° C. at the rate of 1° C./min, and then up to 250° C. at the rate of 1.4° C./min. Then the material was calcined at 450° C. for 4.5 hours to obtain a Cu—Ni—Ce—La-theta-alumina catalyst containing nominal content of 7.6% (w/w) of NiO, 1.0% (w/w) of La.sub.2O.sub.3, 3.0% w/w of Ce.sub.2O.sub.3 and 1.0% of CuO. The catalyst showed a specific area of 61.6 m.sup.2/g determined by the technique of N2 adsorption in commercial equipment (Micromerits).

[0111] The catalysts prepared in accordance with the present invention in the embodiment of sequential (EXAMPLE 5) and simultaneous (EXAMPLE 7) impregnation had the catalytic activity and resistance to coke deposition experimentally measured as described in EXAMPLE 1. The results show that the catalysts according to the present invention, in the preferred embodiment of a preparation process by simultaneous impregnation with copper, nickel, lanthanum and cerium salts, which allows to simplify the catalyst production process with a consequent reduction of costs, allow to obtain higher activity values, as shown in the Table 4 associated and a greater resistance to coke build-up, as shown in FIG. 4.

TABLE-US-00004 TABLE 4 Comparative activity of steam reforming methane of catalysts in accordance with the present invention by the step process (EXAMPLE 5) and by the preferred embodiment of simultaneous impregnation (EXAMPLE 7). SAMPLE Type 500° C. 550° C. 600° C. EXAMPLE 5 CuO/NiO—Ce.sub.2O.sub.3—La.sub.2O.sub.3/ 35.8 47.2 55.9 theta-alumina (steps) EXAMPLE 7 CuO—NiO—/ 40.7 50.1 59.8 Ce.sub.2O.sub.3—La.sub.2O.sub.3 theta-alumina (simultaneous) Note: Catalysts containing 1% copper expressed as CuO.

Example 8

[0112] This example illustrates the preparation of a catalyst according to the present invention based on copper, nickel, lanthanum and cerium oxides on a support of the magnesium aluminate type, with copper being added simultaneously with the other elements and the copper oxide and oxide of the elements forming a surface layer on the support with a small penetration depth, featuring an eggshell type of catalyst.

[0113] The catalyst was prepared with 100 grams of a magnesium aluminate type support (DYTECH, Ceraguard 1616, with dimensions 16×16×7 mm, in the shape of a ring with 6 holes) which were broken into smaller pieces and then immersed in a solution of 80% w/w of glycerin in water at room temperature for 10 minutes. After being separated from the solution, they were kept at 70° C. for 2 hours to remove the aqueous phase, leaving 80% of the pore volume of the support occupied with glycerin. The pellets were then impregnated by the wet spot technique with an aliquot of 6.38 ml of an aqueous solution containing 5.16 grams of copper nitrate (Cu(NO.sub.3).sub.2.3H.sub.2O), 40 grams of nickel nitrate (Ni(NO.sub.3)..sub.2.6H.sub.2O), 3.56 grams of lanthanum nitrate (La(NO.sub.3).sub.3.6H.sub.2O) and 10.72 grams of cerium nitrate (Ce(NO.sub.3).sub.3.6H.sub.2O) in 80 ml of water. The material was then dried at 70° C. for 2 hours and calcined at 400° C. for 2 hours to obtain the catalyst containing oxides of the elements of copper, nickel, lanthanum and cerium on the surface of the pellets, as shown in FIG. 5. The procedure of impregnating with the aqueous solution of glycerin, drying and calcinating followed by the impregnation with the solution of copper, nickel, lanthanum and cerium elements, followed by drying and calcinating was repeated twice more to obtain the catalysts identified in the different steps as EXAMPLE 8A, 8B and 8C, respectively.

[0114] The catalysts had the methane steam reforming catalytic activity measured experimentally as described in EXAMPLE 1. For the coke build-up resistance test, the catalyst was initially activated by reduction in a flow of hydrogen at 700° C. for 1 hour and then exposed at a temperature of 600° C. for 15 minutes to a stream of methane saturated in water vapor maintained at 10° C. for coke deposition. The reactor temperature was then reduced to 350° C. in nitrogen flow. Upon reaching 350° C., the nitrogen flow was replaced with synthetic air and a temperature program from 350° C. to 650° C. was started at a rate of 10° C./min to remove the coke. The release of CO.sub.2, indicating coke removal, was monitored by mass spectrometry.

[0115] Table 5 shows that the catalyst activity was dependent on the number of impregnation steps, and therefore it can be easily adjusted to the maximum value, thus being suitable for use in industrial practice.

[0116] The catalysts still showed activity similar to that observed with commercial catalysts according to the state of the art (Table 3), but with the advantage of using a lower content of metals and promoters in their formulation. Under the conditions of the coking resistance experiments, the sample prepared in accordance with the present invention (EXAMPLE 8C) did not show a significant accumulation of coke, as commercial catalysts, according to the state of the art, used for the steam reforming of heavy natural gas (CGNP) and naphtha (CNF) had a high release of CO.sub.2, indicating a high coke content as illustrated in FIG. 6.

TABLE-US-00005 TABLE 5 Methane steam reforming activity of catalysts according to the present invention in eggshell embodiment. SAMPLE Type 500° C. 550° C. 600° C. EXAMPLE 8A CuO—NiO— 17.2 23.9 30.8 Ce.sub.2O.sub.3—La.sub.2O.sub.3/ magnesium aluminate (one impregnation step) EXAMPLE 8B CuO—NiO— 26.0 35.2 42.7 Ce.sub.2O.sub.3—La.sub.2O.sub.3/ magnesium aluminate (two impregnation steps) EXAMPLE 8C CuO—NiO— 22.9 32.1 41.4 Ce.sub.2O.sub.3—La.sub.2O.sub.3/ magnesium aluminate (three impregnation steps)

Example 9

[0117] This example illustrates the additional surprising advantage, in addition to allowing for greater activity and greater resistance to coke buildup, of the use of copper oxide in the catalyst formulation in accordance with the present invention in increasing resistance to thermal deactivation (sintering).

[0118] After measuring the steam reforming activity of the catalysts of EXAMPLES 4 and 5, as described in EXAMPLE 1, an accelerated deactivation step was carried out at high temperatures, simulating the aging of the catalyst in the industrial process, by exposing the catalyst in flow of Hz/water vapor at a temperature of 900° C. for 6 hours. After this period, the conditions described in EXAMPLE 1 were returned and the steam reforming activity was measured again. The results are shown in Table 6 and show that surprisingly the presence of copper also contributes to increase the resistance to thermal deactivation of the catalysts according to the present invention.

TABLE-US-00006 TABLE 6 Initial methane steam reforming activity and after deactivation period at 900° C. for 6 hours in H.sub.2/ steam flow. Methane conversion values determined at a temperature of 550° C. Initial Steam reforming steam activity after reforming thermal Sample Type activity deactivation EXAMPLE 4 NiO—Ce.sub.2O.sub.3—La.sub.2O.sub.3/theta- 47.3 19.1 alumina EXAMPLE 5 CuO/NiO—Ce.sub.2O.sub.3— 47.2 35.5 La.sub.2O.sub.3/theta-alumina

[0119] It should be noted that, although the present invention has been described with respect to the attached drawings, modifications and adaptations can be made by those skilled in the art, depending on the specific situation, but provided that it is within the inventive scope defined herein.