Catalysts for the production of hydrogen and / or synthesis gas, methods for obtaining the same, and their use in steam reforming processes.

Abstract

The present invention relates to catalysts for producing hydrogen and / or synthesis gas and methods for obtaining the same. More specifically, the present invention describes nickel, molybdenum, and tungsten-based catalysts for the steam reforming process of natural gas or other hydrocarbon streams (refinery gas, propane, butane, naphtha, or any mixture thereof), which exhibit 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 alumina oxide and other high surface area oxide supports, and may contain other promoters. Furthermore, the present invention teaches the preparation of catalysts in which the NiMoW active phase has high activity for the steam reforming reaction of hydrocarbons.

Description

[Technical Field]

[0001] The present invention relates to a catalyst for producing hydrogen and / or synthesis gas from hydrocarbon steam reforming and a method for obtaining the same.

[0002] More specifically, the present invention relates to a nickel, molybdenum, and tungsten-based catalyst for steam reforming processes of natural gas or other hydrocarbon streams (purified gas, propane, butane, naphtha, or any mixture thereof), which has high resistance to deactivation due to coke deposition. The active phase, composed of nickel, molybdenum, and tungsten, also provides high catalytic activity for the reforming reaction, extends the campaign time of the hydrogen production unit, and reduces the cost of producing hydrogen and synthesis gas. [Background technology]

[0003] Steam catalytic reforming is a major industrial process for converting natural gas and other hydrocarbons into synthesis gas and hydrogen. This process has been widely studied to obtain hydrogen for refining processes and synthesis gas for the production of synthetic fuels (GTLs), methanol, ammonia, urea, and petrochemicals (Tao, Y., "Recent Advances in Hydrogen Production Via Autothermal Reforming Process (ATR)": A Review of Patents and Research Articles Recent Patents on Chemical Engineering, v.6, pp.8-42, 2013; Li, D., Tomishige, K., "Methane reforming to syngas over Ni catalysts modified with noble metals", Applied Catalysis A:General, v.408, pp.1-24, November 2011).

[0004] Currently, gases rich in hydrogen and carbon monoxide are known as synthesis gas and are produced industrially, mainly by steam reforming processes of methane or naphtha. The main reactions occurring in the steam reforming process are shown below (reactions 1, 2, and 3): CnHm + nH2O = nCO + (n + 1 / 2m)H2 (endothermic reaction) Reaction 1 CH4 + H2O = CO + 3H2 (endothermic, 206.4 kJ / mol) Reaction 2 CO + H2O = CO2 + H2 (exothermic, -41.2 kJ / mol) Reaction 3

[0005] The steam reforming process can have different configurations depending on the type of charge (filling, injector) and the desired application of the hydrogen-rich gas produced. Steam reforming is typically carried out by introducing pre-purified hydrocarbons (charge) and steam into a reforming reactor. Such a reactor consists of metal tubes with an outer diameter of 7-15 cm and a height of 10-13 m, and is placed inside a heating furnace that supplies the heat necessary for the reaction. This assembly of metal tubes and heating furnace is called a primary reformer.

[0006] Typical charge inlet temperatures in a primary reformer are in the range of 400°C to 550°C, output temperatures in the range of 750°C to 950°C, and pressures of 10 kgf / cm². 2 (0.981 MPa) ~ 35 kgf / cm² 2 (3.432 MPa) is common. These harsh conditions require the use of special metal alloys to fabricate the pipes. Due to their high cost, reformers account for a significant portion of the fixed costs of the process.

[0007] Catalysts used in steam reforming must possess characteristics such as high activity, a reasonably long lifespan, good heat transfer, low pressure loss, high thermal stability, and excellent mechanical strength. The activity of a steam reforming catalyst can be defined by industry-known parameters such as approach temperature, methane content in the primary reformer effluent, and reforming tube wall temperature (Rostrup-Nielsen, JR, "Catalytic Steam Reforming", Spring-Verlag, 1984).

[0008] Among the main problems that lead to a decrease in the activity of nickel-based catalysts on refractory supports, carbon (coke) deposition stands out (Rostrup-Nielsen, JR, "Coking on nickel catalysts for steam reforming of hydrocarbons," Journal of Catalysis, v.33, pp.184-201, 1974, and Borowiecki, T., "Nickel catalytics for steam reforming of hydrocarbons: direct and indirect factors informing the Coking rate," Applied Catalysis, v.31, pp.207-220, 1987), poisoning by sulfur compounds (Rostrup-Nielsen, JR, "Catalytic Steam Reforming," Spring-Verlag, 1984), and chloride contamination and deactivation due to exposure to high temperatures (sintering) (Sehested, J., Carlsson, A., Janssens, TVW, Hansen, PL, Datye, AK, "Sintering of Nickel Steam-Reforming"). "Sintering of nickel steam-reforming catalysts: effects of temperature and steam and hydrogen pressures”, Journal of Catalysis, v. 223, pp. 432-443, April 2004).

[0009] The adverse effects on catalyst activity caused by the low reduction degree of nickel oxide species present in the catalyst are not well known in the literature. Typically, catalysts used industrially in steam reforming processes are generally 10m 2 It consists of nickel oxide species deposited on a low-surface-area refractory support with a minimum of less than / g.

[0010] Such species need to be reduced to metallic nickel so that the catalyst exhibits activity in converting hydrocarbons to hydrogen. Typically, this reduction process is carried out in the reactor itself, in the presence of a considerable amount of water vapor, using a reducing agent selected from hydrogen, ammonia, methanol, and natural gas. If the degree of reduction of the nickel oxide species to metallic nickel is low, the catalytic activity is impaired. This situation is more serious at the top of the reactor where the temperature is low, and it is known that it is difficult to reduce nickel oxide species to metallic nickel at low temperatures (Kim, P., Kim, Y., Kim, H., Song, IK, i, J. "Synthesis and characterization of mesoporous alumina with incorporated the partial oxidation of methane of syngas", Applied Catalysis A: General, 272, pp. 157)-166, September 2004).

[0011] The literature indicates that specific characteristics of supported nickel catalysts affect their reduction rate, such as the nickel content present (Kim, P., Kim, Y., Kim, H., Song, IK, Yi, J. "Synthesis and characterization of mesoporous alumina with incorporated for use in the partial oxidation of methane into syngas," Applied Catalysis A: General, v.272, pp.157-166, September 2004), the temperature used in the sintering process during its manufacture (Teixeira, ACSC, iudici, R. "Deactivation of steam reforming catalysts by sintering: experiments and simulation," Chemical Engineering Science, v.54, pp.3609-3618, July 1999), and the type of refractory support. A common trend in the literature is that steam reforming catalysts using magnesium aluminate or calcium aluminate supports are capable of promoting the reduction of nickel oxide species to metallic nickel at higher temperatures than those based on alpha-alumina.

[0012] Steam reforming catalysts that are not easily reduced but use basic supports such as magnesium aluminate or calcium aluminate are recommended for processing coke-forming charges such as naphtha or natural gas containing hydrocarbons with chains longer than C4. According to the literature, it is desirable to use supports with a high surface area in the preparation of steam reforming catalysts, which theoretically can increase the dispersion of the active phase (metallic nickel) and, as a result, enhance the steam reforming activity.

[0013] Patent application PI1000656-7 teaches the preparation of a nickel-type steam reforming catalyst supported on magnesium aluminate accelerated by an alkali metal, particularly potassium, which exhibits high resistance to coke deactivation and higher activity than materials of the prior art.

[0014] Patent documents WO91113831 and US4,880,757 teach the preparation of high-surface-area magnesium aluminate by adding promoters such as zirconium oxide to the formulation. However, in practice, the activity of nickel-based steam reforming catalysts on high-surface-area supports is observed to be lower than expected, and even lower than the activity of similar catalysts on low-surface-area supports.

[0015] According to the literature, cerium is widely used as a catalyst support and / or catalyst in the steam reforming reaction of methane because it possesses sufficient heat resistance and mechanical strength, as well as a high oxygen storage capacity (Purnomo, A., Gallardo, S., Abella, L., Salim, C., Hinode, H. "Effect of ceria loading on the carbon formation during low temperature methane steam reforming over a Ni / CeO2 / ZrO2 catalyst", React Kinet Catal Lett, v.95, pp.213-220, 2008, and Andreeva, D., Idakiev, V., Tabakova, T., Ilieva, L., Falaras, P., Bourlinhos, A., Travolos, A. "Low-temperature water-gas shift reaction over Au / CeO2 catalysts", Catalysis). (Today, v.72, pp.51-57, February 2002). This last feature greatly contributes to the removal of carbonaceous precursors formed on the surface of the support by oxidation.

[0016] When the catalyst is in a reduced state, oxygen vacancies exist on the cerium surface. Even if oxygen is not present in the gas phase, the generated water and / or CO2 can function as an oxidizing medium. H2O and / or CO2 molecules dissociate on the surface of the material, and the generated atomic oxygen re-oxidizes the cerium. The numerous vacancies promote the mobility of atomic oxygen, which can also act as an oxidant for carbonaceous deposits (Sekini, Y., Haraguchi, M., Matsukata, M., Kikuchi, E. "Low temperature steam reforming of methane over metal catalyst supported on Ce x Zr 1-x O2 in a electric field", Catalysis Today, v.171, pp.116 - 125, August 2011, Koo, K.Y., Seo, D.J., Yonn, W.L., Bin, S. "Coke study on MgO - promoted Ni / Al2O3 catalyst in combined H2O and CO2 reforming of methane for gas to liquid (GTL) process", Applied Catalysis A General, v.340, pp.183 - 190, June 2008, and Vagia, E.C., Lemonidou, A.A. "Investigations on the properties of ceria - zirconia - supported Ni and Rh catalysts and the performance in acetic acid steam reforming", Journal of Catalysis, v.269(2010), pp.388 - 396, February 2010).

[0017] Studies involving the modification of Al2O3 supports with CeO2 and La2O3 have shown that the addition of CeO2 and La2O3 to catalysts containing 7% (m / m) Ni / Al2O3 alters the morphological properties of the catalyst, leading to an increase in the specific surface area and dispersion of nickel, and consequently improving catalytic properties. The addition of 6% (m / m) cerium to the 7% (m / m) Ni / Al2O3 catalyst resulted in an approximately 10% improvement in methane conversion rate at 550°C (methane conversion rate without cerium = 70%, methane conversion rate with cerium = 82%). A 7%(m / m)Ni / Al2O3 catalyst promoted with 6%(m / m)La2O3 achieved a conversion rate at 550°C that was almost the same as that obtained with materials without promoter addition (methane conversion rate using lanthanum-promoted catalyst = 74%) (Dan, M. et al., "Comparison of supported nickel catalysts, metal additives and support reforming for low-temperature methane vapor reforming," Reaction Kinetics Mechanisms and Catalysis, v.105, pp.173-193, February 2012).

[0018] According to the literature (Liu, CJ, Ye, J., Jiang, J., Pan., Y., "Progresses in the Preparation of Coke Resistant Ni-based Catalyst for Steam and CO2 Reforming of Methane," ChemCatChem, v.3, pp.529-541, February 2011), a key aspect of developing coke-resistant Ni catalysts is crystallite size control. It is worth emphasizing that the use of CeO2 and ZrO2 as both promoters and supports has advantages in increasing activity and, more importantly, in suppressing the tendency to produce coke.

[0019] Document PI0903348-3 teaches that the low activity of nickel catalysts on high-surface-area supports results from the fact that it is more difficult to reduce nickel oxide species to metallic nickel. This phenomenon is observed particularly under industrial conditions where a large amount of steam is in excess during the reduction step and can be explained by the increased interaction of nickel oxide species with the high-surface-area support (Bittencourt, R.C.P, Cavalcante, R.M., Silva, M.R.G., Fonseca, D.L., Correa, A.A.L. “Avaliacao (c with cedilla, a with tilde) comparativa entre gama-alumina e alfa-alumina como suporte de catalisadores de reforma a vapor pela tecnica (e with acute) de TPR na presenca (c with cedilla) de vapor ” - 14 th Brazilian Congress of Catalysis, 2007 and Bittencourt,.C.P., Correa, A.A.L., Fonseca, D.L., ello, G.C., Silva, M.R.G., Nascimento, T.L.P.M., “Caracterizacao (c with cedilla, a with tilde) por reducao (c with cedilla, a with tilde) a temperatura programada (TPR) de catalisadores de reforma a vapor - aplicacao (c with cedilla, a with tilde) em condicoes (c with cedilla, second o with tilde) industriais ” - 15 th Brazilian Congress of Catalysis, 2009).

[0020] Clearly, from the perspective of industrial application, there is a desire for methods to increase the degree of reduction of nickel oxide species in high-surface-area supports, particularly θ-alumina type high-surface-area supports, calcium aluminate, magnesium aluminate, and mixtures. A technically feasible method to minimize the problems associated with the difficulty of reducing catalysts under industrial conditions in primary reformers is to pre-reduce them, i.e., subject the catalyst to a reduction treatment during its manufacturing stage and then passivate it so that it can be safely transported without the risk of flammability. By adopting a pre-reduction procedure, it is possible to increase the nickel content in primary reformers, especially under industrial conditions where it is carried out in the upper sections of tubes at low temperatures, as it can be easily reduced. However, although technically possible, if commercially available pre-reduction steam reforming catalysts exist, adopting this type of procedure means an increase in fixed investment for having the appropriate equipment, leading to an increase in the cost of the final product.

[0021] From the standpoint of preparing steam reforming catalysts, it is highly desirable to have a practical method for controlling the degree of nickel reduction that can be applied to different supports, particularly supports having a high surface area. The literature teaches the use of a second metal in formulations of supported nickel-type catalysts for the production of hydrogen and / or synthesis gas in partial oxidation processes.

[0022] For example, Patent Document US7,223,354 reports an invention of a catalyst for the production of synthesis gas by partial oxidation of light hydrocarbons, using a nickel-based catalyst in a solid solution having magnesium oxide promoted by at least one promoter selected from the group consisting of Cr, Mn, Mo, W, Sn, Re, Rh, Ru, Ir, La, Ce, Sm, Yb, Lu, Bi, Sb, In, and P.

[0023] The literature indicates the use of Pt group metals as active metals or active promoters in steam reforming catalyst formulations (Wei, J., Iglesia, E. "Reaction Pathways and Site Requirements for the Activation and Chemical Conversion of Methane on Ru-Based Catalysts", Journal of Physical Chemistry B, v.108, pp.7253-7262, April 2004; Rostrupnielsen, JR, Hansen, JHB "CO2-Reforming of Methane over Transition Metals", Journal of Catalyst, v.144, pp.38-49, November 1993; Wei, J., Iglesia, E. "Structural requirements and reaction pathways in methane activation and chemical catalyzed by rodium", Journal of Catalysis, v. 225, pp. 116-127, July 2004, and Wei, J., Iglesia, E. "Isotopic and kinetic assessment of the mechanism of methane reforming and decomposition reactions on supported iridium catalysts", Physical Chemistry Chemical Physics, v. 6, pp. 3754-3759, 2004, Nitz, M., et al. “Structural Origin of the High Affinity of a Chemically Evolved Lanthanide-Binding Peptide”, Chemie International Edition, v.43, pp.3682-3685, July 2004, and Wei, J. Iglesia, E.("Mechanism and Site Requirements for Activation and Chemical Conversion of Methane on Supported Pt Clusters and Turnover Rate Comparisons of Noble Metals," Journal of Physical Chemistry B, v.108, pp.4094-4103, March 2004). However, catalysts produced using Pt group metals are far more expensive than those produced using nickel, but they have a lower tendency to form carbon.

[0024] Patent documents EP1,338,335 describe a steam reforming catalyst consisting of a support made of aluminum oxide and cerium oxide, with cobalt or nickel in a content of 0.1% (0.1%) w / w to 20% w / w, and components selected from the group consisting of Pt, Pd, Ru, Rh, and Ir in a content of 0.1% (0.1%) to 8% w / w.

[0025] U.S. Patent Document 4,998,661 describes a steam reforming catalyst containing at least one metal oxide selected from nickel oxide, cobalt oxide, or platinum oxide on a support composed of alumina and an oxide selected from the group of Ca, Ba, or Mr.

[0026] Patent document US7,309,480 describes a steam reforming catalyst comprising at least one active metal selected from the group Pt, Pd, or Ir on a support. However, it does not mention the use of a metal promoter to increase the reduction rate of the catalytic nickel oxide species.

[0027] The document in question teaches that using a metal-based promoter in a nickel-type steam reforming catalyst on a refractory support has the effect of reducing the coke content.

[0028] Patent document US4,060,498 describes using silver at a level of at least 2 mg per 100 grams of nickel-based catalyst as a promoter to suppress coke formation.

[0029] US Patent Documents 5,599,517 describe using a metal selected from the group consisting of Ge, Sn, and Pb as a promoter to reduce coke formation in a nickel-based catalyst at concentrations of 1% to 5%, 0.5% to 3.5%, and 0.5% to 1% (w / w), respectively. In all of these patent documents, the metal is added as a promoter to reduce the rate of coke formation, which has the undesirable effect of reducing the activity of the catalyst.

[0030] Patent document WO2007 / 015620 describes a nickel-based steam reforming catalyst impregnated with Ru or Pt in a range of 0.001% to 1.0% w / w, which can exhibit steam reforming activity in a temperature range of 380 to 400°C without performing a preliminary reduction step. According to this invention, a catalyst for use in a fuel cell in a small hydrogen production station subjected to frequent stop-and-start cycles has the advantage of eliminating the need for auxiliary equipment for supplying reducing agents such as hydrogen or ammonia.

[0031] Given the high prices of precious metals such as Ru and Pt, for their use in steam reforming catalysts to be commercially successful, especially in large units that use large quantities of catalyst, their use must be strictly limited to what is necessary. In large steam reforming units, promoters (co-catalysts, accelerators) are only needed in the reactor inlet region, which is the lowest temperature range, to increase the reduction rate of the nickel oxide phase. Furthermore, the reduction procedures for steam reforming catalysts using natural gas (or propane or butane) as a feedstock and those using naphtha as a feedstock must be distinguished. According to industrial practice and recommendations of commercial catalyst manufacturers, it is essential to perform a reduction step involving the addition of a reducing agent (which may be natural gas, hydrogen, ammonia, or methanol) before introducing the naphtha feedstock into the reactor. This reduction step is carried out in the presence of a large excess of steam, and its purpose is to prevent the degradation of catalyst function due to the rapid and excessive formation of coke that would result from the direct supply of steam and naphtha on the non-reducing catalyst. Thus, industrial steam reforming plants using naphtha as a raw material possess the necessary equipment and conditions for the pre- and essential processes of catalytic reduction. The literature also indicates that the addition of noble metals to supported nickel oxide catalysts is advantageous for the reduction of nickel oxide species to metallic nickel using dry H2 as a reducing agent (Nowak, E.J., Koros, R.M. "Activation of supported nickel oxide by platinum and palladium," Journal of Catalysis, v.7, pp.50-56, January 1967, and Li, X., Chang, J.S., Park, SE "CO2 reforming of methane over zirconia-supported nickel catalysts, I. Catalytic specificity," Reaction Kinetics Catalysis Letters, v.67, pp.375-381, July 1999).

[0032] The literature also indicates that the presence of water vapor hinders the reduction of supported nickel oxide (Richardson, JT, Lei, M., Turk, B., Forster, K., Twigg, V. "Reduction of model steam reforming catalysts: NiO / α-Al2O3", Applied Catalysis A: General, v.10, pp.217-237, March 1994, and Zielinski, J. "Effect of water on the reduction of nickel / alumina catalysts: Catalyst characterization by temperature-programmed reduction", Journal of Chemical Society, Farady Transactions, v.93, pp.3577-3580, 1997).

[0033] Reference PI0903348-3 teaches that a low precious metal content can eliminate the adverse effects of water vapor on the reduction rate of nickel oxide species, especially when using high surface area supports.

[0034] Therefore, while there are several citations and descriptions in the specialized literature of processes involving the use of a second metal in the preparation of nickel-based steam reforming catalysts on refractory supports, these processes do not characterize the use of a second metal to accelerate the reduction rate of nickel oxide species in the presence of steam and with catalysts prepared using high-surface-area supports. Furthermore, the document PI0903348-3 teaches the use of an accelerating catalyst only in the low-temperature region of a steam reforming process reactor, more specifically in the upper section of the reactor, preferably to a depth of up to 30% from the top of the primary reformer, which can be broadly applied to the raw materials supplied to the process and the types of supports used to prepare the catalyst.

[0035] The literature also shows that gold can be used as a promoter in Ni / MgAl2O4 and Ni / Al2O3 catalysts to enhance resistance to coke deactivation (Dan, M. et al., "Supported neckel catalysts for low temperature methane steam reforming," "Reaction Kinetics Mechanisms and Catalysis, v.105, pp.173-193, February 2012," and Chin, YH et al., "Structure and reactivity investigations on supported bimetallic Au-Ni catalysts used for hydrocarbon stem reforming," Journal of Catalysis, v.244, pp.153-162, December 2006). According to the literature, binary Ni-Au systems do not form massive alloys, but only surface alloys. In this alloy, gold blocks sites involved in carbon formation (Chin, YH et al., "Structure and reactivity investigations on supported bimetallic Au-Ni catalysts used for hydrocarbon steam reforming," Journal of Catalysis, v.244, pp.153-162, December 2006). The Ni-Au / Al2O3 catalyst showed a 10% increase in CH4 conversion rate (X=85%) compared to the Ni / Al2O3 catalyst (X=75%) in a steam reforming reaction at 550°C.The reaction rate per active site (turnover frequency - TOF) of the Au-promoted catalyst was slightly higher than that obtained with the Ni / Al2O3 catalyst (Dan, M. et al., "Supported nickel catalysts for low temperature methane steam reforming: Comparison between metal additives and support modification," Reaction Kinetics Mechanisms and Catalysis, v.105, pp.173-193, February 2012). The literature also teaches the use of La, Rh, and B as promoters to improve dispersion and increase resistance to coke formation in the Ni / MgAl2O4 catalyst (Ligthart, DAJM, Pieterse, JAZ, Hensen, EJM, "The role of promoters for Ni catalysts in low temperature (membrane) steam methane reforming," Applied Catalysis A General, v.405, pp.108-119, October 2011). Lanthanum was selected as a promoter because it improves metal dispersion and prevents coke formation. Boron, on the other hand, inhibits carbon diffusion in the bulk. Rhodium was selected due to its resistance to coke formation and its high activity in steam reforming of methane.

[0036] Regarding coke formation, the literature teaches the use of additives such as Sn, Sb, Bi, Ag, Zn, and Pb in nickel-based catalysts at concentrations ranging from 1–2% (m / m). The addition of these metals contributes to reducing coke deposition, and the proposed suppression mechanism was based on the hypothesis that the interaction between the p or d electron levels of these metals and 3d electrons can prevent the formation of carbon (2p)-nickel (3d) bonds involved in the formation of nickel carbide (coke precursor). The best ratio of steam reforming rate to coke formation rate was obtained when 1.75% (m / m) of Sn was added. The Sn-enhanced catalyst showed much higher activity and a lower coke formation rate compared to the unenhanced Ni catalyst under similar reaction conditions (Trimm, DL, "Catalysts for the control of coking during steam reforming," Catalysis Today, v.49, pp.3-10, February 1999).

[0037] Furthermore, the use of nickel / α-alumina catalysts promoted by oxides of Mo (0.5%), W (2.0%), Ba (2.0%), K (1.0%), and Ce (0.2%, 0.5%, 1.0%, 2.0%) in the n-butane steam reforming reaction has also been taught in the literature. Catalysts with added cerium were observed to exhibit increased metal area and activity compared to catalysts without a promoter. Catalysts promoted with other metals showed a decrease in both metal area and activity. Regarding the tendency for coke formation, catalysts promoted with K, Ba, Mo, and W showed a slower deactivation process than catalysts promoted with Ce and catalysts promoted without a promoter.Regarding resistance to coke deactivation, the best results were obtained by adding 0.5% WO3 or MoO3 (Armor, JN, "The Multiple Roles for Catalysis in the Production of H2", Applied Catalysis A: General, v.21, pp.159-176, 1999; Barelli, L., Bidini, G., Corradetti, A., Desideri, U. "Production of hydrogen through the carbonation-calcination reaction applied to CH4 / CO2 mixtures", Energy, v.32, pp.834-843, May 2007; Borowiecki, T, Golebiowski (e with cedilla), A., Ryczkowski, J., Stasinska, B. "The influence of promoters on the coking rate of nickel catalysts in the steam reforming of hydrocarbons", Studies in Surface Science and Catalysis, v. 119, pp. 711, 1998 and Borowiecki, T., Golcebiowski, A. "Influence of molybdenum and tungsten additives on the properties of nickel steam reforming catalysts", Catalysis Letters, v. 25, pp. 309-313, September 1994).

[0038] The use of Ni / Al2O3 catalysts promoted with up to 2% molybdenum for the steam methane reforming reaction has also been taught in the literature (Maluf, S., Assaf, E.M. "Ni catalysts with Mo promoter for methane steam reforming", Fuel, v.88, pp. 1547 - 1553, September 2009). Reactions carried out at a steam / carbon ratio equal to 4 showed that all the prepared catalysts (0.00%, 0.05%, 0.5%, 1.0% and 2.0% molybdenum) exhibited high activity and stability. However, when the steam / carbon ratio was decreased to 2.0, the catalysts containing 0.00%, 0.5%, 1.0%, and 2.0% molybdenum showed deactivation after about 400 minutes of reaction, and only the catalyst promoted with 0.05% molybdenum showed stability against coke formation over a long period (reaction over 30 hours). In the case of the catalyst containing 0.05% Mo, the reason for such behavior is thought to be that an electronic interaction between molybdenum species and nickel species may occur. In this case, MoO x species transfer electrons to metallic Ni. This effect results in an increase in the electron density of the Ni sites, reducing the number of available sites but making them more active. Thus, the methane dehydrogenation reaction occurs at a lower rate, resulting in a lower amount of carbon formation. In this case, the small amount of carbon formed in the form of filaments will be more easily gasified. With a large amount of molybdenum, the active Ni sites by MoO x species are blocked, which may lead to the formation of "clusters" on the catalyst surface and reduce the electron transfer efficiency.

[0039] As seen above, the potential of using nickel in combination with other metals, particularly noble metals, has been widely studied to increase activity, resistance to carbon formation, and enable the use of the same catalyst for different charges in the steam reforming process. However, the use of noble metals such as Ru and Pt in steam reforming catalyst formulations, even if only in the function of promoters (used in very small amounts), directly impacts the cost of hydrogen and / or synthesis gas production. Therefore, the search for catalysts with lower production costs, high hydrothermal stability, and high resistance to coke formation remains a challenge to overcome. Nevertheless, for non-noble metal catalysts, deactivation and carbon deposition are the main obstacles to the development of new materials.

[0040] In this regard, the present invention teaches a novel steam reforming catalyst, based on a NiMoW-type active system, available in bulk form or supported on alumina oxide and other oxide supports, which has high resistance to deactivation by coke. This catalyst also has the advantage of lower steam consumption, as it allows operation at a lower steam / carbon ratio, which is desirable when it is required to obtain synthesis gas with a low H2 / CO ratio for use in petrochemical processes (GTL, methanol, etc.). Furthermore, its manufacturing cost is lower compared to catalysts containing precious metals.

[0041] When this catalyst is operated under low vapor / carbon ratio conditions, its high resistance to deactivation by coke formation may be related to the formation of molybdenum and tungsten carbides, which still maintain a certain ability to promote the reforming reaction via a carbonization / oxidation mechanism. This mechanism has been documented in the literature when these carbides are used in dry reforming reactions (Zhang, A. et al., "In-situ synthesis of nickel modified molybdenum carbide catalyst for dry reforming of methane," Catalysis Communications, v.12, pp.803-807, April 2011; Shi, C. et al., "Ni-modified Mo2C Catalysis for methane dry reforming," combined Catalysis A: General, v.431-432, pp.164-170, July 2012; York, APE, Claridge, JB, Brungs, AJ, Tsang, SC and Green, MLH (1997), "Molybdenum and Tungsten Carbides as Catalysts for the Conversion of Methane to Syngas using Stoichiometric Feedstocks," Chemical Communications, pp.39-40, 1997). β-Mo2C was active in dry reforming, steam reforming, and partial oxidation of methane to synthesis gas under conditions of 8 bar (0.8 MPa) pressure and temperatures in the range of 847–947°C without showing carbon deposition on the surface. In the periodic oxidation / recarbonization mechanism of carbides, Mo2C is involved in the oxidation of CO2 (CO2 → CO + 1 / 2O2) (MoO2). x ) is involved in the activation of nickel (Ni 0 ) is involved in the decomposition of CH4 (CH4 → C(s) + 2H2), and then molybdenum oxide becomes Ni 0The catalyst is recarbonized autothermally by carbon deposited on the site (Zhang, A. et al., "In-situ synthesis of nickel modified molybdenum carbide catalyst for dry reforming," Catalysis Communications, v.12, pp.803-807, April 2011, and Shi, C. et al., "Ni-modified Mo2C catals for methane dry reforming," Applied Catalysis A:General, v.431-432, pp.164-170, July 2012). However, in this case, equal consumption rates of CO2 and CH4 are necessary for the catalyst to maintain its activity and stability during a long campaign period.

[0042] In this scenario, the present invention teaches the production of a catalyst in which the activated NiMoW phase has high activity for hydrocarbon steam reforming reactions, nickel is the primary cause of the decomposition of methane into H2 and C(or more), and other metals have a synergistic effect on catalyst activity and resistance to coke formation. In this case, when the NiMoW catalyst operates under low steam / carbon ratio conditions, it is assumed that molybdenum and tungsten carbides are formed, still maintaining a certain ability to promote the reforming reaction via a carburizing / oxidation mechanism, and thus mitigating the resulting deactivation due to carbon deposition of the nickel active site. When the steam-carbon ratio returns to its original level, it is assumed that decarburization of the catalyst is promoted, increasing its activity for the steam reforming process. The literature WO2018 / 117339, WO00 / 42119, US2019 / 0126254, and BR1120180156159 teaches a method for preparing NiMoW catalysts used in sulfide form for hydrogenation refining reactions / processes (desulfurization, hydrodenitrification, hydrocracking, etc.) streams of petroleum and derivatives. Hydrogenation reactions and processes are entirely different from steam reforming reactions, both in terms of the reactants and products involved, kinetics, thermodynamics and reaction mechanisms, and process conditions (in particular, temperature, pressure and space velocity). There is no literature in the art disclosing a NiMoW catalyst with high resistance to coke deactivation for producing hydrogen and / or synthesis gas from steam reforming of hydrocarbons as in the present invention.

[0043] In the present invention, the trimetallic form of NiMoWo (not a sulfide) is used directly in the steam reforming process of a hydrocarbon stream in an unprecedented manner. In the present invention, the trimetallic NiMoW catalyst is prepared by coprecipitation in an ammoniacal medium of a mixture of ammonium paratungstate and / or metatungstate, ammonium molybdate and nickel nitrate, reflow for 3 hours, aging, drying and calcination.

[0044] Commercial hydrocarbon steam reforming catalysts have poor resistance to hot water and coke deactivation, which leads to shorter campaign times for hydrogen and synthesis gas production units, resulting in increased CAPEX and more frequent production shutdowns.

[0045] To increase the campaign time of hydrogen production units and thus reduce the cost of producing hydrogen and synthesis gas, the present invention proposes a nickel, molybdenum, and tungsten-based catalyst for steam reforming hydrocarbon streams (natural gas, purified gas, propane, butane, or naphtha, or mixtures thereof) for the production of hydrogen and / or synthesis gas, and proposes a catalyst with high resistance to deactivation by carbon deposition (coke). According to the present invention, the catalyst for the reforming process has NiMoW as its active phase in bulk form and / or supported on alumina oxide and other high-surface-area oxide supports, and may contain other promoters. The present invention teaches the production of a catalyst in which the NiMoW active phase has high activity for the steam reforming reaction of hydrocarbons, showing that nickel is mainly responsible for the decomposition of H2 and C(or more) of methane, and the other metals have a synergistic effect considering catalyst activity and resistance to coke formation.

[0046] According to the present invention, the catalyst is particularly suitable for use in large-capacity industrial units for the production of hydrogen or synthesis gas by steam reforming processes, and can be used to increase campaign time and minimize the production cost of synthesis gas and / or hydrogen by exhibiting high resistance to deactivation by coke in the entire catalyst bed or the upper half of the reactor, preferably in the area 30% above the reactor.

[0047] The present invention also offers further economic benefits by not substituting nickel with a precious metal (resulting in lower costs for catalyst production), enabling operation at low vapor / carbon ratios, and providing greater resistance to deactivation processes due to coke formation, thus contributing to an extended campaign time for hydrogen and synthesis gas production units.

[0048] Furthermore, the greater resistance of the catalyst to deactivation in this invention can reduce the frequency of stock replacement operations, which involve greater operational risks. As a result, less solid waste (heavy metals) is generated, and the costs associated with the disposal of spent catalysts are reduced.

[0049] Another further advantage of the catalyst of the present invention is that, due to the formation of an active phase such as Mo2C and WC carbide, natural gas with high concentrations of CO2 (up to 70%), such as natural gas from pre-salt and other hydrocarbon streams containing high levels of CO2, can be used as a steam reforming charge with less steam than conventionally used. Higher resistance to deactivation due to sulfur poisoning is also expected. [Overview of the Initiative]

[0050] The present invention aims to achieve high resistance to deactivation due to carbon deposition (coke) in hydrocarbon steam reforming catalysts (natural gas, purified gas, propane, butane or naphtha, or mixtures thereof) for the production of hydrogen and / or synthesis gas. This catalyst also does not deactivate at lower steam / carbon ratios than conventional catalysts and can be used with fluids containing high levels of CO2 (up to 70%). The catalyst for the steam reforming process is NiMoW-based and is supported in bulk form and / or on alumina oxide and other high-surface-area oxide supports. Therefore, the present invention has the advantage of not substituting nickel with a noble metal, enabling operation at lower steam / carbon ratios, and exhibiting greater resistance to deactivation by coke formation than nickel-only based catalysts according to the state of the art, thus minimizing the cost of synthesis gas and / or hydrogen production.

[0051] The present invention will be described in more detail below with reference to the accompanying drawings, which illustrate embodiments of the invention in a non-limiting manner. [Brief explanation of the drawing]

[0052] [Figure 1] This graph shows the time dependence of the conversion rate in the steam reforming reaction of methane at a temperature of 850°C and a pressure of 20 bar (2 MPa). The catalyst activity was first measured using a steam / carbon ratio of 3 and GHSV36000h-1 (baseline). During the deactivation process, the steam / carbon ratio was reduced to 1.0 while maintaining other reaction conditions. [Figure 2] This figure shows the XRD results for Examples 1 and 2. [Figure 3] These are scanning electron microscope (SEM) images of a NiMoW catalyst (calcined at 300°C), shown at magnifications of 2000x, 10000x, and 20000x, respectively. [Modes for carrying out the invention]

[0053] To better understand and appreciate them, both a NiMoW trimetal catalyst with high resistance to deactivation by coke, and its production process, for use in hydrogen production processes and / or synthesis gas production, and a process using the catalyst to produce hydrogen and / or synthesis gas by steam reforming of hydrocarbons are described in detail here.

[0054] The present invention relates to a catalyst used in a process of reforming hydrocarbons in the presence of water vapor and in the absence of oxygen for the production of hydrogen and / or synthesis gas. Hydrocarbon streams are natural gas, refined gas, propane, butane or naphtha, or mixtures thereof, and are particularly well-suited for operation at low vapor / carbon ratios and are characterized by a low tendency to be deactivated by carbon deposition.

[0055] This invention relates to 20-150m 2This invention relates to the preparation of a trimetallic NiMoW catalyst having a surface area of ​​15 m² / g. The formed ammonia precursor can be supported in any proportion on a refractory support belonging to, for example, alumina, particularly the group of "alpha" and "θ-alumina" alumina, calcium aluminate or magnesium aluminate, zirconium oxide, lanthanum or cerium, hexa-aluminate, titania, or mixtures thereof, and may further contain alkali metals, preferably potassium, in a content of 0.2% to 15%, preferably 0.5% to 6% w / w (expressed as K2O). The surface area of ​​the refractory support is 15 m² / g. 2 It must be greater than / g, more preferably 20m 2 / g~100m 2 It must be / g. The particles of the refractory support and / or bulk form of the oxide catalyst may be in the most diverse forms considered suitable for industrial use in steam reforming processes, and these can be selected from spherical, cylindrical with a central hole (lashing ring), and cylindrical with several holes, preferably with 4, 6, 7, or 10 holes, and the cylindrical surface may be corrugated. 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 a minimum wall thickness of 2 mm to 8 mm, preferably 3 mm to 6 mm.

[0056] The supported bulk trimetallic NiMoW catalyst is prepared by coprecipitation in an ammoniacal medium (NH4OH) of a mixture of paratungstate and / or ammonium metatungstate, ammonium molybdate, and nickel nitrate, followed by 3 hours of reflow, aging, drying, and calcination.

[0057] More specifically, the process for preparing catalysts based on NiMoW trimetal oxide in bulk or supported form follows these steps: 1) Prepare a solution of a soluble salt of tungsten, preferably in the form of a paratungstate and / or metatungstate, in an ammoniacal medium, preferably an aqueous solution. 2) Prepare a solution containing nickel salts and molybdenum salts, preferably nitrates, acetates, carbonates, and ammonia compounds and / or complexes, preferably an aqueous solution. 3) Mix both solutions and redissolve the resulting precipitate with NH4OH solution. 4) Reflow the solution for 2-10 hours until the pH reaches a value of 5-8, and allow the NiMoW-NH4 precipitate in the suspension to slowly form and grow at room temperature for 5-24 hours under stirring. 5) The NiMoW-NH4 precipitate is dried at a temperature of 80-120°C for 1-24 hours, and then calcined at a temperature of 200-650°C for 1-8 hours, preferably at 200-350°C. 6) Impregnation of the inorganic oxide support, preferably alumina, calcium aluminate, magnesium aluminate, or a mixture thereof, with the trimetal precursor formed in step 3 can be carried out using pore volume technique (wet spot), particularly by the excess solution method, precipitation method, etc. 7) Alternatively, the process of impregnating an inorganic support with a trimetal precursor, then drying and calcining, can be repeated until a desired content of oxide on the inorganic support is obtained. The proportion of trimetal precursor on the inorganic support can vary from 5% to 35% (w / w), preferably from 12% to 20% (w / w). 8) Alternatively, the calcination of the catalyst (step 5) can be replaced by directly reducing a stream of a reducing agent selected from hydrogen, formaldehyde, or methanol at a temperature of 300-800°C for 1-24 hours, followed by cooling with an airflow at a temperature of 20-60°C for 1-5 hours, in order to prevent the catalyst from igniting during handling.

[0058] Furthermore, compounds for controlling pH, increasing solubility, or controlling the precipitation of solution components may be included as additives in the resulting aqueous solution. Non-limiting examples of these compounds include nitric acid, sulfuric acid, phosphoric acid, ammonium hydroxide, ammonium carbonate, hydrogen peroxide (H2O2), methanol, ethanol, sugars, or combinations thereof.

[0059] The catalyst thus prepared needs to be activated before industrial use by reducing the nickel oxide phase to metallic nickel. Activation is preferably performed "in situ" in the industrial unit during the reformer startup procedure, passing a reducing agent selected from natural gas, hydrogen, ammonia, or methanol in the presence of vapor at temperatures varying between 400°C and 550°C at the top of the reactor and between 750°C and 850°C at the outlet. The pressure during the activation process is 1 kgf / cm². 2 The pressure can be selected from 98.1 kPa up to the unit's maximum design pressure. The duration of the reduction process is 1 to 15 hours, preferably 2 to 6 hours, and its completion is indicated by the tube wall temperature or the methane content in the reactor effluent, according to conventional industrial practice, when a mixture of natural gas and steam is used in the activation process. The "in situ" activation process of the catalyst is carried out as follows: a) With or without a nitrogen stream, the reformer containing the catalyst is heated to a temperature approximately 50°C higher than the dew point of water vapor at a pressure selected to carry out the activation process, and water vapor is introduced into the reactor at this point. b) While heating the primary reformer, the activation procedure is initiated by passing a reducing agent such as natural gas, hydrogen, ammonia, or methanol through the reformer tubes along with water vapor. The process gas temperature at the pipe inlet is 400°C to 550°C, the outlet temperature is 750°C to 850°C, and the pressure range is 1 kgf / cm². 2 (98.1kPa) up to the unit's maximum design pressure (typically up to 40kgf / cm²) 2 The pressure should be within the range of (3.923 MPa). c) Maintain operation for 1 to 15 hours, preferably 2 to 6 hours, or until the methane content in the reactor effluent stabilizes at a minimum level indicating the end of the activation process. d) In order to start the hydrogen production process, introduce the hydrocarbon feed and adjust the operating conditions (steam / charge ratio, recirculation / charge hydrogen ratio, reformer inlet and outlet temperatures and pressures).

[0060] The catalyst thus prepared can be used to produce hydrogen and / or synthesis gas by a hydrocarbon steam reforming process at a pressure of 1 kgf / cm². 2 (98.1kPa)~50kgf / cm 2 The pressure range is (4.903 MPa), the temperature is 400°C to 850°C, and these processes are characterized by the presence of hydrocarbon and steam reaction steps for the production of synthesis gas (CO, CO2, H2, and methane).

[0061] Suitable hydrocarbons for this purpose include natural gas, refined gas, liquefied petroleum gas (LPG), propane, butane or naphtha, or mixtures thereof. Typically, steady-state operating conditions during the hydrogen and / or synthesis gas production period include the following: 1. The inlet temperature of the tubular reactor, measured using the processed gas from the primary reformer, is between 400°C and 600°C. 2. The outlet temperature of the tubular reactor, measured in the process gas of the primary reformer, is 700°C to 900°C, preferably 750°C to 850°C. 3. The outlet pressure of the tubular reactor in the primary reformer is 1 kgf / cm². 2 (98.1kPa)~50kgf / cm 2 (4.903 MPa), preferably 10 kgf / cm² 2 (0.981 MPa) ~ 30 kgf / cm² 2 (2.942 MPa) 4. When using charges consisting of natural gas, propane, butane, and LPG, the vapor / carbon ratio (mol / mol) is 1.5 to 5.0, preferably 2.5 to 3.5. 5. When using a hydrocarbon charge containing naphtha, the vapor / carbon ratio (mol / mol) is 2.5 to 6.0, preferably 2.6 to 4.0.

[0062] Figure 1 shows a time function graph of the methane conversion rate at a temperature of 850°C and 20 bar (2 MPa) to compare the stability of the trimetallic NiMoW catalyst in the methane steam reforming reaction with conventionally found catalyst formulations in the literature and commercially available catalysts (Benchmark). The activity of the various catalysts tested was first measured at a steam / carbon ratio of 3 and GHSV 36,000 h-1 Measurements were taken using (baseline). In the deactivation process, the steam / carbon ratio was reduced to 1.0, while other reaction conditions were maintained. During the deactivation process, an increase in pressure drop was observed in the reactor containing NiMo oxides promoted with 0.1% Rh, Pt, and Pd. A commercially available reference catalyst (1G SR CENPES-Benchmark) also showed a pressure drop. The large pressure drops observed in the reactor beds containing the above catalysts led to the interruption of these operations. The trimetallic NiMoW catalyst (tested twice in bulk form) showed greater resistance to the coke deactivation process and exhibited rapid recovery of activity when the steam / carbon ratio was returned to baseline. The bimetallic NiMo catalyst also showed good recovery of activity with increasing steam / carbon ratio.

[0063] Examples The following examples illustrate the high resistance of the catalyst of the present invention to coke deactivation, but are not intended to limit its scope.

[0064] Example 1 This example demonstrates the preparation of a bulk-based NiMoW trimetal catalyst. A tungsten-containing solution (Solution A) was first prepared in a 500 mL beaker. 9.6753 g of ammonium paratungstate, 150 ml of NH4OH (30-32% w / w), and 150 ml of H2O were added. The initially formed suspension (pH=13) was kept stirred at 80°C for 1 hour, and the paratungstate was converted to metatungstate, resulting in a clear solution (pH=9.8). A nickel and molybdate-containing solution (Solution B) was prepared in a 100 mL beaker. 21.5122 g of nickel nitrate and 30 ml of H2O were added. The mixture was stirred at room temperature (25°C) for 5 minutes. Next, 6.5432 g of ammonium molybdate was added. This was stirred at room temperature (25°C) for 5 minutes, yielding a clear green 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. Immediately thereafter, 120 mL of NH4OH was added to redissolve the initially formed precipitate and obtain a clear methylene blue solution (pH=10.7). The mixture was then transferred to a two-necked flask (1 L). This was heated and stirred in a silicon bath with reflow for approximately 3 hours, and the pH and temperature were measured every 30 minutes. The pH value was measured at a temperature close to room temperature by periodically taking 5 mL aliquots. After 3 hours, the reflow system was removed. After approximately 1.5 hours of reaction, turbidity and a change in color (from blue to cyan) due to the precipitation process were observed. Heating was stopped when the reaction mixture reached a pH close to 7 (pH=7.3). The mixture was kept stirred for approximately 15 hours to promote the slow formation and growth of the suspended NiMoW-NH4 precipitate. Filtration was performed at room temperature, under vacuum, using quantitative filter paper in a bunker funnel. The filtrate (unwashed) was dried in an oven at 120°C for approximately 24 hours, yielding a mass of 14.4 g of NiMoW-NH4 precursor at the end of the process. Figure 2 shows the characterization of the crystalline phase present in the precursor (Example 01) by X-ray diffraction (XRD). The chemical composition was obtained by X-ray fluorescence (XRF), and it was observed that the molar ratio Ni / (Mo+W) was 2.6 and the molar ratio Mo / W was 0.6. When this precursor was dried at 120°C and then calcined at 300°C, it yielded 65 m2 The BET area and average pore size of 25 Å(A) per g are shown. Analysis of the precursor calcined at 300°C by X-ray diffraction revealed that NiMoW has low crystallinity (microcrystalline or nearly amorphous).

[0065] No segregated phases of metal oxides (NiO, MoO3, and WO3) were observed. As shown in Figure 3, scanning electron microscopy (SEM) results of the sample calcined at 300°C reveal that the bulk catalyst is lamellar, exhibiting regular (rectangular) and irregular (round) geometric shapes, and having different particle sizes.

[0066] Example 2 This example according to the present invention demonstrates the preparation of a bulk-based NiMoW trimetal catalyst. A tungsten-containing solution (Solution A) was first prepared in a 500 mL beaker. 4.80 g of ammonium paratungstate, 75 ml of NH4OH (30-32% m / m), and 75 ml of H2O were added. The initially formed suspension (pH=13) was held at 80-90°C with stirring for 2 hours, and the paratungstate was converted to metatungstate, resulting in a clear solution (pH=9.8). A nickel and molybdate-containing solution (Solution B) was prepared in a 100 mL beaker. 10.80 g of nickel nitrate and 15 ml of H2O were added. The mixture was stirred for 5 minutes at room temperature (25°C). Next, 3.3 g of ammonium molybdate was added. This was stirred for 5 minutes at room temperature (25°C) to obtain a clear green 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. Immediately thereafter, 50 mL of NH4OH was added to redissolve the initially formed precipitate and obtain a clear methylene blue solution (pH=10.0). The mixture was then transferred to a two-necked flask (1 L). This was heated and stirred in a silicon bath with reflow for approximately 3 hours, and the pH and temperature were measured every 30 minutes. pH values ​​were measured at near room temperature by periodically taking 5 mL aliquots. After 3 hours, the reflow system was removed. After approximately 1.5 hours of reaction, turbidity and a change in color (from blue to cyan) due to the precipitation process were observed. Heating was stopped when the reaction mixture reached pH=7. The mixture was stirred for approximately 15 hours to promote the slow formation and growth of the suspended NiMoW-NH4 precipitate. Filtration was performed at room temperature, under vacuum, using quantitative filter paper and a bunker funnel. The filtrate (unwashed) was dried in an oven at 120°C for approximately 24 hours, yielding a NiMoW-NH4 precursor with a mass of 9 g at the end of the process. Figure 2 shows the characterization results of the crystalline phase present in the precursor (Example 01) by X-ray diffraction (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-NH4 dried at 120°C contains a thermally unstable phase (oxyammonia hydroxide of Mo and W) that decomposes during calcination at 300°C in an N2 flow.

[0067] Example 3: This embodiment of the present invention describes the preparation of the trimetallic NiMoW catalyst in the same manner as in Example 2, up to the point where solutions (A) and (B) are mixed in a single beaker, redissolved in 50 mL of NH4OH, and transferred to a 1 liter double-neck flask. At this point, 20 mL of ethanol is added as a cosolvent, and the mixture is kept in a silicon bath under reflow heating with stirring for approximately 3 hours, while the pH and temperature are measured every 30 minutes. The pH value was measured at a temperature close to room temperature, by periodically taking out 5 mL aliquots. After 3 hours, the reflow system was removed. After approximately 1.5 hours of reaction, turbidity and a change in color (from blue to cyan) due to the precipitation process were observed. Heating was stopped when the reaction mixture reached pH=7. The mixture was stirred for approximately 15 hours to promote the slow formation and growth of the suspended NiMoW-NH4 precipitate. Filtration was performed at room temperature under vacuum using quantitative filter paper in a bunker funnel. The filtrate (without washing) was dried in an oven at 120°C for approximately 24 hours, yielding 9 g of NiMoW-NH4 precursor at the end of the process.

[0068] Example 4: The present invention describes the preparation of a NiMoW trimetal oxide-based catalyst in the same manner as in Example 2, up to the point where solutions (A) and (B) are mixed in a single beaker, 50 mL of NH4OH is redissolved, and the mixture is transferred to a 1 liter double-neck flask. At this point, 100 grams of θ-alumina (SPH 508F from Axens, Inc., which is spherical with a diameter of 3-4 mm and 0.7 cm²) are added. 3A porosity (having a pore volume of / g) was added to a flask. The entire mixture was heated and stirred, and held in a silicone bath under reflow for approximately 3 hours, with the pH and temperature measured every 30 minutes. The pH value was measured at near room temperature by periodically taking 5 mL aliquots. After 3 hours, the reflow system was removed. After approximately 1.5 hours of reaction, turbidity and a change in color (blue to cyan) due to the precipitation process were observed. Heating was stopped when the reaction mixture reached pH=7. The mixture was stirred for approximately 15 hours to promote the slow formation and growth of the suspended NiMoW-NH4 precipitate. The mixture was filtered at room temperature under vacuum using quantitative filter paper through a bunker funnel. The filtrate (unwashed) was dried in an oven at 120°C for approximately 24 hours, and at the end of the process, a θ-alumina-impregnated NiMoW-NH4 precursor was obtained.

[0069] Example 5: This example demonstrates 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 multi-purpose combinatorial catalyst unit capable of evaluating up to 16 catalysts simultaneously, under the same process conditions and / or by independently varying the conditions of each microreactor. The tests were conducted using 700 mg of the catalyst from Example 2 in powder form with a particle size distribution of 140 mesh or less. The catalyst tests included Ni containing 0.1% Rh, Pt, and Pd, respectively. 0.2 MoO x Bimetallic oxides and accelerated nickel 0.2 MoO xBimetallic oxides were also evaluated. All samples were prepared to the same particle size in the laboratory. To compare the advantages of the present invention, 700 mg (Benchmark), a commercially available nickel-based catalyst with high resistance to coke deactivation, was also evaluated. The activation reactions of bimetallic and trimetallic oxides were carried out with hydrogen at 400°C at a heating rate of 1.5°C / min and maintained at this state for 4 hours. At the end of this stage, the temperature was increased to 500°C at a rate of 1.5°C / min. The commercially available catalyst was activated with hydrogen by raising the temperature to 205°C using a heating rate of 1.5°C / min. At this temperature, steam was introduced until a steam-to-hydrogen ratio in the range of 6-10 mol / mol was reached, and the temperature was increased to 750°C at a rate of 1.5°C / min while maintaining the steam and hydrogen flow rates. The reactor was maintained at this state for 6 hours to complete the reduction. The conditions established for the catalyst test were a pressure of 20 bar (2 MPa), a temperature of 850°C, a vapor / CH4 ratio of 3 mol / mol, an H2 / CH4 ratio of 0.05 mol / mol, and GHSV 36,000 h -1 The effluent gas from the reactor was analyzed by gas chromatography using a thermal conductivity detector (TCD). Activity was measured by the degree of methane conversion. Deactivation by coking was performed by reducing the steam / carbon ratio from 3 mol / mol to 1 mol / mol while keeping other reaction conditions constant. After the deactivation step, the initial test conditions were re-established by increasing the steam / carbon ratio. Figure 1 shows the time function graph of the methane conversion rate for the methane steam reforming reaction at a temperature of 850°C and a pressure of 20 bar (2 MPa) for various catalysts. During the deactivation step, a significant increase in pressure drop was observed in the reactor containing NiMo oxides promoted with 0.1% Rh, Pt, and Pd, resulting in reduced flow and system clogging. Commercial reference catalysts also showed high pressure drops, making it impossible to continue this operation. The trimetallic NiMoW catalyst (replicated and tested in bulk form) showed greater resistance to deactivation by coke and exhibited rapid recovery of activity when the initial test conditions were restored (water vapor / carbon ratio of 3). The unenhanced NiMo oxide bimetal catalyst also showed good recovery of activity with increasing water vapor / carbon ratio.

[0070] Example 5 demonstrates that the catalyst of the present invention returns to a high level of conversion rate even after being exposed to harsh coking conditions for a long period of time, and has better resistance to deactivation by coke than those based on the prior art.

[0071] The results clearly demonstrate that the present invention advantageously achieves the desired objectives listed above. However, it is clear that such examples are merely illustrative and do not constitute a limitation on the inventive concept described herein. Those skilled in the art will be able to envision and implement modifications, alterations, changes, adaptations, and equivalents that are appropriate and suitable to the spirit and scope of the present invention.

[0072] In short, according to the present invention, a technical solution to reduce catalyst deactivation due to coke deposition is provided by a nickel, molybdenum, and tungsten-based catalyst, resulting in a reduction in pressure drop and an increase in the campaign time of the H2 and synthesis gas production unit. The catalyst described is particularly suitable for use in industrial units with large volumes for the production of hydrogen or synthesis gas by steam reforming processes, and due to its high resistance to deactivation by coke, it can be used in the entire catalyst bed, or in the upper half of the reactor, or preferably in the upper 30% area of ​​the reactor. Thus, the catalyst of the present invention has the advantage of providing economic benefits such as not using noble metals in its composition and reducing process energy consumption through the operation of the unit at a lower steam / carbon molar ratio, which is made possible by its higher resistance to coke formation compared to state-of-the-art nickel-based catalysts. These economic benefits mean a reduction in the cost of producing synthesis gas and / or hydrogen.

Claims

1. A catalyst for the production of hydrogen and / or synthesis gas by a hydrocarbon steam reforming process, a) The active phase is formed of nickel, molybdenum, and tungsten (NiMoW), with an atomic ratio of Ni / (Mo+W) between 6:1 and 0.5:1, and an atomic ratio of Mo / W between 2:1 and 0.05:

1. b) Surface area: 20–150 m² ２ It is within the range of / g, c) Existing in bulk form, or 15 m ２ A catalyst using a refractory oxide support having a surface area exceeding / g.

2. The catalyst according to claim 1, wherein the refractory oxide support is selected from the group comprising alumina, calcium aluminate, magnesium aluminate, zirconium oxide, titania, lanthanum, cerium oxide, hexaaluminate, and mixtures thereof.

3. The final catalyst composition contains the refractory oxide support, and the surface area of ​​the refractory oxide support is 20 m². ２ / g to 100m ２ The catalyst according to claim 1, wherein the value is between / g.

4. The catalyst according to claim 1, comprising an alkali metal in a concentration ranging from 0.2% by weight to 15% by weight.

5. A method for obtaining a catalyst, a) A step of preparing a solution of a soluble salt of tungsten selected in the form of a paratungstate and / or metatungstate in an ammoniacal medium, b) A step of preparing a solution containing nickel and molybdenum salts selected from the group consisting of nitrates, acetates, carbonates, ammoniacal salts and ammoniacal complexes, c) Mix the solutions from steps a) and b) and the resulting precipitate with NH ４ The process involves redissolving the solution with an OH solution, d) Reflowing the solution for 2 to 10 hours until the pH reaches a range of 5 to 8, and maintaining the solution at room temperature under stirring for 1 to 24 hours, e) NiMoW-NH ４ The process involves drying the aforementioned precipitate at a temperature in the range of 80 to 120°C for 1 to 24 hours, and then calcining it at a temperature in the range of 200 to 650°C for 1 to 24 hours. f) A step of impregnating an inorganic oxide support selected from alumina, calcium aluminate, magnesium aluminate, rare earth hexaaluminate, titania, or a mixture thereof, from step c) above with trimetal oxide, g) Repeating step f) until the oxide on the inorganic support reaches a desired content, h) A method for obtaining the catalyst according to claim 1, comprising the step of using a cosolvent and other chemical compounds in the aqueous solution produced in steps a), b) and c) for better pH control, increased solubility and / or decreased solubility.

6. The method for obtaining the catalyst according to claim 5, wherein the calcination (step e) is carried out at a temperature in the range of 200 to 350°C.

7. A method for obtaining the catalyst according to claim 5, wherein the content of the trimetal oxide in the inorganic oxide support varies between 5% and 35% (w / w).

8. The cosolvent in step h) above is nitric acid, sulfuric acid, phosphoric acid, ammonium hydroxide, ammonium carbonate, methanol, ethanol, acetone, hydrogen peroxide (H ２ O ２ A method for obtaining the catalyst according to claim 5, which may be sugars or a combination thereof.

9. A method for obtaining the catalyst according to claim 5, wherein the calcination can be replaced by direct reduction in a flow of reducing agent.

10. A method for obtaining the catalyst according to claim 9, wherein the reducing agent is selected from hydrogen, formaldehyde, methanol, or natural gas.

11. A process for producing hydrogen or synthesis gas by steam reforming, a) A step of charging a reformer with the catalyst described in claims 1 to 4, b) A step of activating the catalyst "in situ" in the presence of water vapor and a reducing agent selected from hydrogen, natural gas, ammonia, and methanol, c) A process for producing hydrogen or synthesis gas by steam reforming, comprising the step of introducing a hydrocarbon charge at the end of the activation to start the production of hydrogen and / or synthesis gas.

12. A process for producing hydrogen or synthesis gas by steam reforming according to claim 11, wherein the upper third of the reformer is charged with the catalyst.

13. The process for producing hydrogen or synthesis gas by steam reforming according to claim 11, wherein the hydrocarbon charge can be selected from the group including natural gas, purified gas, liquefied petroleum gas, propane, butane, naphtha, and mixtures thereof.

14. A process for producing hydrogen or synthesis gas by steam reforming according to claim 11, wherein the steam / carbon ratio (mol / mol) at the inlet of the reformer is operated in the range of 0.5 to 6.

0.

15. A steam / carbon ratio of less than 1.5 and CO at a concentration of up to 70% ２ A process for a method of producing hydrogen or synthesis gas by steam reforming according to claim 11, using the hydrocarbon charge containing the same.

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