CATALYST FOR THE GENERATION OF HYDROGEN AND/OR SYNTHESIS GAS, METHOD FOR OBTAINING SAME AND USE IN A STEAM REFORMING PROCESS

Abstract

The present invention addresses to a catalyst, and the method for obtaining the same, for generating hydrogen and/or syngas. More specifically, the present invention describes a catalyst based on nickel, molybdenum and tungsten, for steam reforming processes of natural gas or other hydrocarbon streams (refinery gas, propane, butane, naphtha or any mixture thereof) that presents high resistance to deactivation by coke deposition. According to the present invention, the catalyst has NiMoW as its active phase, in bulk form and/or supported on an alumina oxide and other high surface area oxide supports, and may also contain other promoters. Furthermore, the present invention teaches the production of a catalyst whose active phase of NiMoW has high activity for hydrocarbon steam reforming reaction.

Claims

1- A CATALYST FOR GENERATION OF HYDROGEN AND/OR SYNGAS THROUGH THE STEAM REFORMING PROCESS OF HYDROCARBONS, characterized in that: a) the active phase is formed by nickel, molybdenum and tungsten (NiMoW), where the atomic ratio of Ni/(Mo+W) is between 6:1 and 5:1 and the atomic ratio of Mo/W between 2:1 and 1:1; b) the surface area is in the range between 20 and 150 m.sup.2/g; c) it presents itself in bulk form or uses refractory oxide supports, with a surface area greater than 15 m.sup.2/g, in the proportion of 95% to 65% by weight in relation to the total composition; d) optionally, it contains an alkali metal in a concentration ranging from 0.2% to 15% by weight; e) optionally, it contains a promoter noble metal, selected from a group comprising Pt, Pd, Ru and Rh, and by combinations thereof in any proportions, in a concentration in the range of 0.01% to 1% by weight, calculated as a metallic element.

2- THE CATALYST according to claim 1, characterized in that the refractory oxide support is selected from a group comprising alumina, calcium and magnesium aluminates, zirconium oxides, titania, lanthanum and cerium oxides, hexa-aluminates, and mixtures thereof in any proportions.

3- THE CATALYST according to claim 1, characterized in that the active phase has an atomic ratio of Ni/(Mo+W) between 4:1 and 3:1.2 and atomic ratio of Mo/W between 1.2:1 and 0.8:1.

4- THE CATALYST according to claim 1, characterized in that the active phase has an atomic ratio of Ni/(Mo+W) between 3:1 and 0.5:1 and atomic ratio of Mo/W between 0.8:1 and 0.05:1.

5- THE CATALYST according to claim 1, characterized in that the final catalyst composition optionally contains from 95% to 65% by weight of refractory oxide supports, with an area between 20 m.sup.2/g and 100 m.sup.2/g;

6- THE CATALYST according to claim 1, characterized in that the alkali metal is preferably potassium, in a concentration ranging from 1% to 7% by weight, calculated as K.sub.2O.

7- THE CATALYST according to claim 1, characterized in that the promoter noble metal is preferably platinum.

8- THE CATALYST according to claim 1, characterized in that the promoter noble metal is present in concentrations ranging from 0.01% to 0.2% by weight, calculated as a metallic element.

9- A METHOD FOR OBTAINING THE CATALYST described in claim 1, characterized in that it comprises the following steps: a) preparing a solution, preferably an aqueous one, of a soluble salt of tungsten, chosen in the form of paratungstate and/or metatungstate in an ammoniacal medium; b) preparing a solution, preferably an aqueous one, containing nickel and molybdenum salts, chosen from the group of nitrates, acetates, carbonates, ammoniacal salts and ammoniacal complexes; c) mixing the solutions from step a) and b) and resolubilizing the precipitate formed with NH.sub.4OH solution; d) reflowing the solution for a period between 2 to 10 hours, until reaching a pH in the range between 5 and 8 and keeping the solution under stirring, for 1 to 24 hours, at room temperature; e) drying the NiMoW—NH.sub.4 precipitate, at a temperature in the range between 80 and 120° C., for 1 to 24 hours and calcining it at a temperature in the range between 200 and 650° C., for 1 to 24 hours; f) optionally, impregnating the trimetallic oxide on an inorganic oxide support, selected from alumina, calcium or magnesium aluminates, rare earth hexa-aluminates, titania or a mixture thereof, from step c); g) alternatively, repeating step f) until the desired content of the oxide on the inorganic support is reached; h) alternatively, co-solvents and other chemical compounds can be used in the aqueous solutions generated in steps a), b), and c) for better pH control, increased solubility and/or reduced solubility.

10- THE METHOD FOR OBTAINING THE CATALYST according to claim 9, characterized in that the calcination (step e)) is carried out, preferably, at temperatures in the range between 200 and 350° C.

11- THE METHOD FOR OBTAINING THE CATALYST according to claim 9, characterized in that the content of trimetallic oxide in the inorganic support varies between 5% and 35% (w/w), preferably between 12% and 20% (w/w).

12- THE METHOD FOR OBTAINING THE CATALYST according to claim 9, characterized in that the co-solvent of step h) can be nitric acid, sulfuric acid, phosphoric acid, ammonium hydroxide, ammonium carbonate, methanol, ethanol, acetone, hydrogen peroxide (H.sub.2O.sub.2), sugars or combinations of these compounds.

13- THE METHOD FOR OBTAINING THE CATALYST according to claim 9, characterized in that the calcination can be replaced by a direct reduction in flow of a reducing agent.

14- THE METHOD FOR OBTAINING THE CATALYST according to claim 9, characterized in that the reducing agent is selected from hydrogen, formaldehyde, methanol or natural gas.

15- A PROCESS FOR PRODUCTION OF HYDROGEN OR SYNGAS BY STEAM REFORMING, characterized in that there is: a) charging the reformer with the catalyst as defined in claims 1 to 8; b) “in situ” activating the catalysts in the presence of water vapor and a reducing agent selected from hydrogen, natural gas, ammonia and methanol; c) introducing the hydrocarbon charge, at the end of the activation, to start the production of hydrogen and/or syngas.

16- THE PROCESS FOR PRODUCTION OF HYDROGEN OR SYNGAS BY STEAM REFORMING according to claim 15, characterized in that the upper third of the reformer tubes is preferably charged with the catalyst.

17- THE PROCESS FOR PRODUCTION OF HYDROGEN OR SYNGAS BY STEAM REFORMING according to claim 15, characterized in that the hydrocarbon charge can be selected from a group comprising natural gas, refinery gas, liquefied petroleum gas, propane, butane, naphtha, and mixtures thereof in any proportion.

18- THE PROCESS FOR PRODUCTION OF HYDROGEN OR SYNGAS BY STEAM REFORMING according to claim 15, characterized in that it operates with steam/carbon ratios (mol/mol) at the inlet of the reformer tubes in the range between 0.5 and 6.0.

19- THE PROCESS FOR PRODUCTION OF HYDROGEN OR SYNGAS BY STEAM REFORMING according to claim 15, characterized in that is uses steam/carbon ratios lower than 1.5 and hydrocarbon charges containing C02 concentrations of up to 70%.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0047] The present invention will be described in more detail below, with reference to the attached figures which, in a non-limiting way of the inventive scope, represent examples of embodiment thereof.

[0048] FIG. 1 represents a graph of conversion as a function of time for the steam reforming reaction of methane at a temperature of 850° C. and 20 bar (2 MPa). The activity of the catalysts was initially measured using a vapor/carbon ratio of 3 and a GHSV of 36000 h.sup.−1 (baseline). During the deactivation step, the vapor/carbon ratio was reduced to 1.0 and the other reaction conditions were maintained;

[0049] FIG. 2 illustrates the XRD result of Examples 1 and 2;

[0050] FIG. 3 illustrates Scanning Electron Microscopy (SEM) micrographs—of the NiMoW catalyst (calcined at 300° C.)—magnifications of 2000, 10000 and 20000 times, respectively.

DETAILED DESCRIPTION OF THE INVENTION

[0051] So that they can be better understood and evaluated, both the NiMoW trimetallic catalyst, with high resistance to deactivation by coke, for use in hydrogen production processes and/or syngas generation, and its production process and the process using said catalyst to produce hydrogen and/or syngas by steam reforming of hydrocarbons, will now be described in detail.

[0052] The present invention concerns a catalyst used in the process of reforming hydrocarbons, in the presence of water vapor and absence of oxygen, for the production of hydrogen and/or syngas, characterized in that the hydrocarbon stream is natural gas, refinery gas, propane, butane or naphtha, or mixtures thereof, particularly suitable for working with low vapor/carbon ratios and having a low tendency to deactivate by carbon deposition.

[0053] The present invention addresses to the preparation of a trimetallic NiMoW catalyst with a surface area between 20 and 150 m.sup.2/g. The ammonia precursor formed can also be supported on a refractory support belonging, for example, to the group of aluminas, especially that of “alpha” and “theta-aluminas”, to calcium aluminates, or magnesium aluminates, to zirconium oxides, lanthanum or cerium, to hexa-aluminates, titania or even a mixture of these, in any proportions, which may additionally contain alkali metals, preferably potassium, in contents between 0.2% and 15%, preferably between 0.5% and 6% w/w (expressed as K.sub.2O). The surface area of the refractory support must be greater than 15 m.sup.2/g, more preferably between 20 m.sup.2/g and 100 m.sup.2/g. The particles of the refractory support and/or the oxide catalyst in its bulk form can be in the most varied forms, which are considered suitable for industrial use in the steam reforming process, which are selected among the spherical, cylindrical with a hole central (Rashing rings) and cylindrical with several holes, of these, preferably those with 4, 6, 7 or 10 holes, and the cylinder surface can also be wavy. The support and/or bulk catalyst particles are preferably in the range of 13 mm to 20 mm in diameter and 10 mm to 20 mm in height, with the smallest wall thickness between 2 mm and 8 mm, preferably between 3 mm and 6 mm.

[0054] The supported bulk trimetallic NiMoW catalyst is prepared via coprecipitation in ammoniacal medium (NH.sub.4OH) of a mixture of paratungstate and/or ammonium metatungstate, ammonium molybdate and nickel nitrate, reflow for 3 hours, aging, drying and calcination.

[0055] More specifically, the process of preparing the catalyst based on a trimetallic oxide of NiMoW, in bulk or supported form, follows the following steps: [0056] 1) preparing a solution, preferably an aqueous one, of a soluble salt of tungsten, preferably in the form of paratungstate and/or metatungstate in an ammoniacal medium; [0057] 2) preparing a solution, preferably an aqueous one, containing nickel and molybdenum salts, preferably within the group of nitrates, acetates, carbonates and ammoniacal compounds and/or complexes; [0058] 3) mixing both solutions and resolubilize the formed precipitate with NH.sub.4OH solution; 4) reflowing the solution for a period between 2 to 10 hours until the pH reaches values between 5 and 8, and wait for the slow formation and growth of the NiMoW—NH.sub.4 precipitate in suspension, under stirring, for 5 to 24 hours at room temperature. [0059] 5) drying the NiMoW—NH.sub.4 precipitate at temperatures between 80 and 120° C., for 1 to 24 hours, and calcinate it at temperatures between 200 and 650° C. for 1 to 8 hours, preferably between 200 and 350° C. [0060] 6) the impregnation of the trimetallic precursor, formed in step 3, on the inorganic oxide support, preferably alumina or calcium or magnesium aluminates or a mixture of these, can be carried out by using the pore volume techniques (wet spot), by the method of excess solution, precipitation, among others. [0061] 7) alternatively, the steps for impregnating the trimetallic precursor onto the inorganic support and subsequent drying and calcination can be repeated until the desired content of the oxide on the inorganic support is obtained. The percentages of the trimetallic precursor on the inorganic support can vary between 5% and 35% (w/w), preferably between 12% and 20% (w/w). [0062] 8) alternatively, the calcination of the catalyst (step 5) can be replaced by the direct reduction in flow of a reducing agent, selected from hydrogen, formaldehyde or methanol, under temperature conditions between 300 and 800° C., for 1 to 24 hours, followed by cooling by air flow, at temperatures between 20 and 60° C., for 1 to 5 hours, in order to prevent the catalyst from having a pyrophoric character when handled.

[0063] Additionally, compounds for pH control, solubility increase or to control the precipitation of solution components can be included as additives in the generated aqueous solutions. Non-limiting examples of these compounds are nitric acid, sulfuric acid, phosphoric acid, ammonium hydroxide, ammonia carbonate, hydrogen peroxide (H.sub.2O.sub.2), methanol, ethanol, sugars, etc. or combinations of these compounds.

[0064] The catalyst thus prepared needs to be activated, before industrial use, by reducing the nickel oxide phases to metallic nickel. Activation is preferably carried out “in-situ” in the industrial unit during the start-up procedure of the reformer, through the passage of a reducing agent, selected from natural gas, hydrogen, ammonia or methanol, in the presence of steam, at temperatures that vary between 400° C. and 550° C., at the top of the reactors, and from 750° C. to 850° C., at the exit of the same. The pressure during the activation step can be chosen, between 1 kgf/cm.sup.2 (98.1 kPa) up to the maximum design pressure of the unit. The duration of the reduction step is from 1 to 15 hours, preferably from 2 to 6 hours, its end being indicated by the wall temperature of the tubes, or by the methane content in the reactor effluent, in the case of using the mixture of natural gas and steam in the activation step, in accordance with conventionally established industrial practice. The “in situ” activation step of the catalyst is carried out as follows: [0065] a) heat the reformer containing the catalyst, with or without nitrogen flow, to temperatures around 50° C. above the dew point of the steam at the pressure chosen to carry out the activation process and from this moment on, introduce water steam into the reactor; [0066] b) start the activation procedure by passing a reducing agent, which can be natural gas, hydrogen, ammonia or methanol, together with water vapor, through the tubes of the reformers, while heating the primary reformer, so that the process gas temperatures at the inlet of the tubes are between 400° C. and 550° C. and the outlet temperatures between 750° C. and 850° C., at pressures ranging from 1 kgf/cm.sup.2 (98.1 kPa) to the maximum design pressure of the unit, typically of maximum 40 kgf/cm.sup.2 (3.923 MPa); [0067] c) maintain the operation for a period of 1 to 15 hours, preferably from 2 to 6 hours, or until the methane content in the reactor effluent gases stabilizes at a minimum level, indicative of the end of the activation process; [0068] d) introduce the hydrocarbon feed and adjust the operating conditions (steam/charge ratio; recycle/charge hydrogen ratio; reformer inlet and outlet temperature and pressure) in order to initiate the hydrogen production process.

[0069] The catalysts thus prepared can be used in the production of hydrogen and/or syngas by hydrocarbon steam reforming processes, at pressures ranging from 1 kgf/cm.sup.2 (98.1 kPa) to 50 kgf/cm.sup.2 (4.903 MPa), at temperatures from 400° C. to 850° C., which processes are characterized by the presence of a hydrocarbon and steam reaction step for the production of syngas (CO; CO.sub.2, H.sub.2 and methane).

[0070] The hydrocarbons suitable for this purpose are natural gas, refinery gas; liquefied petroleum gas (LPG), propane, butane or naphtha, or a mixture thereof. Typically, the stationary operating conditions of the hydrogen and/or syngas production period comprise: [0071] 1. Inlet temperature of the tubular reactors measured in the process gas of the primary reformer between 400° C. and 600° C. [0072] 2. outlet temperature of the tubular reactors measured in the process gas of the primary reformer between 700° C. and 900° C., preferably between 750° C. and 850° C. [0073] 3. outlet pressure of the tubular reactors of the primary reformer between 1 kgf/cm.sup.2 (98.1 kPa) and 50 kgf/cm.sup.2 (4.903 MPa), preferably between 10 kgf/cm.sup.2 (0.981 MPa) and 30 kgf/cm.sup.2 (2.942 MPa). [0074] 4. vapor/carbon ratio (mol/mol) between 1.5 and 5.0, preferably between 2.5 and 3.5, when using a charge consisting of natural gas, propane, butane and LPG. [0075] 5. vapor/carbon ratio (mol/mol) between 2.5 and 6.0, preferably between 2.6 and 4.0, when using the hydrocarbon charge containing naphtha.

[0076] FIG. 1 shows a graph of methane conversion as a function of time, for the methane steam reforming reaction, at a temperature of 850° C. and 20 bar (2 MPa), in order to compare the stability of the trimetallic NiMoW catalyst in relation to catalyst formulations traditionally found in the literature and in relation to a commercial catalyst (Benchmark). The activity of the various catalysts tested was initially measured using a vapor/carbon ratio of 3 and a GHSV of 36000 h.sup.−1 (baseline). In the deactivation step, the vapor/carbon ratio was reduced to 1.0 and the other reaction conditions were maintained. During the deactivation step, an increase in the pressure drop of the reactors containing NiMo oxide promoted with 0.1% of Rh, Pt and Pd was observed. The commercial reference catalyst (1G SR CENPES—Benchmark) also showed pressure drop. The high pressure drops observed in the reactor beds containing the above catalysts resulted in the interruption of these runs. The trimetallic NiMoW catalyst (tested in duplicate in bulk form) showed greater resistance to the coke deactivation process and showed a rapid recovery of activity when the steam/carbon ratio was returned to baseline. The bimetallic NiMo catalyst also showed a good recovery of activity with increasing vapor/carbon ratio.

EXAMPLES

[0077] The following examples illustrate the high resistance to coke deactivation of the catalyst of the present invention, without, however, being considered as limiting its content.

Example 1

[0078] This example illustrates the preparation of a bulk based NiMoW trimetallic catalyst. The tungsten-containing solution (solution A) was initially prepared in a 500 mL beaker. 9.6753 g of ammonium paratungstate, 150 ml of NH.sub.4OH (30 to 32% w/w) and 150 ml of H.sub.2O were added. The suspension initially formed (pH=13) was kept under stirring at 80° C. for one hour, resulting in a clear solution (pH=9.8), resulting from the transformation of paratungstate into metatungstate. The solution containing nickel and molybdate (solution B) was prepared in a 100 mL beaker. 21.5122 g of nickel nitrate and 30 ml of H.sub.2O were added. Kept under stirring for 5 minutes at room temperature (25° C.). Then 6.5432 g of ammonium molybdate was added. Keeping it under stirring for 5 min at room temperature (25° C.), resulting in a clear greenish solution with a pH close to 3.5. Solutions (A) and (B) were mixed in a single beaker. During mixing, the formation of a cyan-colored precipitate was observed. Soon after, 120 mL of NH.sub.4OH were added, resolubilizing the precipitate initially formed, resulting in a clear methylene blue solution (pH=10.7). The mixture was then transferred to a two-neck flask (1 L). This was kept under stirring and heating, in a silicone bath, under reflow for approximately 3 hours, and its pH and temperatures were measured every 30 min. The pH values were measured at a temperature close to room temperature, periodically withdrawing 5 mL aliquots. After 3 hours, the reflow system was withdrawn. After approximately 1.5 hours of reaction, turbidity and color change (blue to cyan) were observed, resulting from the precipitation process. When the reaction mixture reached a pH close to 7 (pH=7.3), the heating was stopped. The mixture was kept under stirring for approximately 15 hours to promote the slow formation and growth of the suspended NiMoW—NH.sub.4 precipitate. Filtration was carried out under vacuum and at room temperature, in a bunker funnel, using a quantitative filter paper. The filtrate (without washing) was dried in an oven at 120° C. for a period of approximately 24 hours, obtaining at the end of the process a mass of 14.4 g of NiMoW—NH.sub.4 precursor. FIG. 2 shows the result of the characterization of the crystalline phases present in the precursor (Example 01) by X-ray diffractometry (XRD). The chemical composition was obtained by X-ray fluorescence (XRF), with a molar ratio Ni/(Mo+W) of 2.6 and a molar ratio Mo/W of 0.6 being observed. This precursor, when dried at 120° C. and then calcined at 300° C., presented a BET area of 65 m.sup.2/g and an average pore diameter of 25 A. The analysis of the precursor calcined at 300° C. by X-ray diffractometry showed that NiMoW has low crystallinity (microcrystalline or nearly amorphous material).

[0079] The presence of segregated phases of metal oxides (NiO, MoO.sub.3 and WO.sub.3) was also not observed. The Scanning Electron Microscopy (SEM) results of the sample calcined at 300° C., shown in FIG. 3, show that the bulk catalyst is formed by plates (lamellae), which are presented in regular (rectangular) and irregular (rounded) geometric shapes. having different particle sizes.

Example 2

[0080] This example in accordance with the present invention illustrates the preparation of a bulk based NiMoW trimetallic catalyst. The tungsten-containing solution (solution A) was initially prepared in a 500 mL beaker. 4.80 g of ammonium paratungstate, 75 ml of NH.sub.4OH (30 to 32% m/m) and 75 ml of H.sub.2O were added. The initially formed suspension (pH=13) was kept under stirring, at a temperature between 80 and 90° C., for two hours, resulting in a clear solution (pH=9.8), resulting from the transformation of paratungstate into metatungstate. The solution containing nickel and molybdate (solution B) was prepared in a 100 mL beaker. 10.80 g of nickel nitrate and 15 ml of H.sub.2O were added. Kept under stirring for 5 min at room temperature (25° C.). Then 3.3 g of ammonium molybdate were added. Keeping it under stirring for 5 minutes at room temperature (25° C.), resulting in a clear greenish solution with a pH close to 3.5. Solutions (A) and (B) were mixed in a single beaker. During mixing, the formation of a cyan-colored precipitate was observed. Soon after, 50 mL of NH.sub.4OH was added, resolubilizing the initially formed precipitate, resulting in a clear methylene blue solution (pH=10.0). The mixture was then transferred to a two-neck flask (1 L). This was kept under stirring and heating, in a silicone bath, under reflow for approximately 3 hours, and its pH and temperatures were measured every 30 min. The pH values were measured at a temperature close to room temperature, periodically withdrawing 5 mL aliquots. After 3 hours, the reflow system was withdrawn. After approximately 1.5 hours of reaction, turbidity and color change (blue to cyan) were observed, resulting from the precipitation process. When the reaction mixture reached pH=7, the heating was stopped. The mixture was stirred for approximately 15 hours to promote the slow formation and growth of the suspended NiMoW—NH.sub.4 precipitate. Filtration was carried out at room temperature and under vacuum, in a bunker funnel, using a quantitative filter paper. The filtrate (without washing) was dried in an oven at 120° C. for a period of approximately 24 hours, obtaining at the end of the process a mass of 9 g of NiMoW—NH.sub.4 precursor. FIG. 2 shows the result of the characterization of the crystalline phases present in the precursor (Example 01) by X-ray diffractometry (XRD). The chemical composition was obtained by X-ray fluorescence (FRX), with a Ni/(Mo+W) molar ratio of 2.0 and a Mo/W molar ratio of 1.1. In the precursors of Examples 1 and 2, NiMoW—NH.sub.4, dried at 120° C., there is the presence of thermally unstable phases (oxy-ammoniacal hydroxides of Mo and W) that decompose during calcination at 300° C., in flow of N.sub.2.

Example 3

[0081] This example in accordance with the present invention illustrates the preparation of a trimetallic NiMoW catalyst in a similar manner to Example 2 up to the point where solutions (A) and (B) were mixed in a single beaker, resolubilized with 50 mL of NH.sub.4OH and transferred to a 1-liter double-necked flask. At this point, 20 mL of ethanol were added as a co-solvent and the mixture was kept under stirring and heating, in a silicone bath, under reflow for approximately 3 hours, with its pH and temperatures measured every 30 minutes. The pH values were measured at a temperature close to room temperature, periodically withdrawing 5 mL aliquots. After 3 hours, the reflow system was withdrawn. After approximately 1.5 hours of reaction, turbidity and color change (blue to cyan) were observed, resulting from the precipitation process. When the reaction mixture reached pH=7, the heating was stopped. The mixture was stirred for approximately 15 hours to promote the slow formation and growth of the suspended NiMoW—NH.sub.4 precipitate. At room temperature, filtration was carried out under vacuum, in a bunker funnel, using a quantitative filter paper. The filtrate (without washing) was dried in an oven at 120° C. for a period of approximately 24 hours, obtaining at the end of the process a mass of 9 g of NiMoW—NH.sub.4 precursor.

Example 4

[0082] This example in accordance with the present invention illustrates the preparation of a catalyst based on NiMoW trimetallic oxide in a similar manner to Example 2 up to the point where solutions (A) and (B) were mixed in a single beaker, 50 mL of NH.sub.4OH were resolubilized and transferred to a 1-liter double-necked flask. At this point, 100 grams of theta-alumina (SPH 508F from Axens, with a pore volume of 0.7 cm.sup.3/g in the shape of 3 to 4 mm diameter spheres) were added to the flask. The entire mixture was kept under stirring and heating, in a silicone bath, under reflow for approximately 3 hours, and its pH and temperatures were measured every 30 minutes. The pH values were measured at a temperature close to room temperature, periodically withdrawing 5 mL aliquots. After 3 hours, the reflow system was withdrawn. After approximately 1.5 hours of reaction, turbidity and color change (blue to cyan) were observed, resulting from the precipitation process. When the reaction mixture reached pH=7, the heating was stopped. The mixture was stirred for approximately 15 hours to promote the slow formation and growth of the suspended NiMoW—NH.sub.4 precipitate. At room temperature, filtration was carried out under vacuum, in a bunker funnel, using a quantitative filter paper. The filtrate (without washing) was dried in an oven at 120° C. for a period of approximately 24 hours, obtaining at the end of the process the NiMoW—NH.sub.4 precursor impregnated on theta-alumina.

Example 5

[0083] This example illustrates that the catalyst of the present invention is particularly suitable for industrial use and can be activated under operating conditions or even at low temperatures. The tests were conducted in a multipurpose combinatorial catalysis unit, capable of evaluating up to 16 catalysts at the same time, under the same process conditions and/or varying the conditions of each microreactor independently. The tests were carried out with 700 mg of the catalyst from Example 2 in the form of a powder with a granulometry less than or equal to 140 mesh. In the catalytic test, Ni.sub.0.2MoO.sub.x bimetallic oxide and promoted Ni.sub.0.2MoO.sub.x bimetallic oxide, respectively, with 0.1% of Rh, Pt and Pd were also evaluated. All samples were prepared in the laboratory in the same granulometry. By way of comparison of the advantage of this invention, 700 mg of a commercial nickel-based catalyst with high resistance to coke deactivation (Benchmark) was also evaluated. The activation reaction of bimetallic and trimetallic oxides was carried out with hydrogen at 400° C., with a heating rate of 1.5° C./min, remaining in this condition for 4 h. At the end of this stage, the temperature was increased to 500° C. at a rate of 1.5° C./min. The commercial catalyst was activated with hydrogen by using a heating rate of 1.5° C./min to a temperature of 205° C. At this temperature, steam was introduced until reaching a steam:hydrogen ratio in the range of 6 to 10 mol/mol and the temperature was raised to 750° C. at a rate of 1.5° C./min, maintaining the steam and hydrogen flow rate. The reactor remained in this condition for six hours to complete the reduction. The conditions established for the catalytic tests were: pressure of 20 bar (2 MPa) g, temperature of 850° C., steam/CH.sub.4 ratio of 3 mol/mol, H.sub.2/CH.sub.4 ratio of 0.05 mol/mol and GHSV of 36000 h.sup.−1. Effluent gases from the reactors were analyzed by gas chromatography using a thermal conductivity detector (TCD). Activity was measured by the degree of methane conversion. The deactivation step by coking was carried out by reducing the steam/carbon ratio from 3 mol/mol to 1 mol/mol and by keeping the other reaction conditions constant. After the deactivation step, the initial test condition was re-established by increasing the steam/carbon ratio. FIG. 1 shows the graph of methane conversion as a function of time for the methane steam reforming reaction, at a temperature of 850° C. and pressure of 20 bar (2 MPa), for the various catalysts. During the deactivation step, a great increase in the pressure drop of the reactors containing NiMo oxide promoted with 0.1% of Rh, Pt, and Pd was observed, generating flow reduction and clogging of the system. The commercial reference catalyst also showed a high pressure drop, making it impossible to continue this run. The trimetallic NiMoW catalyst (tested in duplicate in bulk form) showed greater resistance to deactivation by coke and showed a rapid recovery of activity when the initial test condition was restored (steam/carbon ratio 3). The non-promoted NiMo oxide bimetallic catalyst also showed a good recovery of activity with increasing vapor/carbon ratio.

[0084] Example 5 illustrates that the catalyst of the present invention has a resistance to deactivation by coke superior to those based on the prior art, returning to a high level of conversion, even after being subjected to severe coking conditions for long periods.

[0085] The results clearly demonstrate that the present invention advantageously achieves the desired objectives listed above. It should be clear, however, that such examples are merely illustrative, without constituting a limitation to the inventive concept described herein. Those usually versed in the art will be able to envision and practice variations, modifications, alterations, adaptations and equivalents that are appropriate and compatible with the matter in question, without, however, departing from the scope of the spirit and scope of the present invention.

[0086] In short, according to the present invention, the technological solution to reduce the deactivation of the catalyst by deposition of coke, with the consequent reduction of the pressure drop and increase of the campaign time of the units of generation of H.sub.2 and syngas, takes place through the catalyst based on nickel, molybdenum and tungsten. The catalyst described is especially suitable for use in industrial units with large capacity for the production of hydrogen or syngas by the steam reforming process, and can be used in the entire catalytic bed or in the upper half of the reactors, or preferably in the region of upper 30% of the reactors, due to its high resistance to deactivation by coke. Thus, the catalyst of the present invention advantageously presents economic gains, for not using noble metals in its composition and for reducing the energy consumption of the process, through the operation of the units with lower vapor/carbon molar ratios, which is possible due to its higher resistance to coke formation when compared to nickel-based catalysts of the state of the art. These economic advantages imply the reduction of production costs of syngas and/or hydrogen.