Process for producing a chromium-free supported catalyst for the water-gas shift reaction, catalyst obtained by said process, and related use

Abstract

The present invention proposes the development of a catalyst to be used under higher process efficiency operating conditions, with the potential to replace traditional catalysts, such as Fe-Cr, and which is less expensive than catalysts based on noble metals. The production process for this catalyst is described, as is use of said catalyst in the water-gas shift (WGS) reaction.

Description

[0001] PROCESS FOR PRODUCING A CHROMIUM-FREE SUPPORTED CATALYST FOR A GAS-WATER DISPLACEMENT REACTION, CATALYST OBTAINED BY SAID PROCESS AND RELATED USES

[0002] Field of invention

[0003]

[0001] The present invention proposes the development of a catalyst to be used in operating conditions with greater process efficiency, with the potential to replace traditional catalysts, such as Fe-Cr, and which presents a lower cost than catalysts based on noble metals. The production process of such a catalyst has been described, as well as the use of said catalyst in a gas-water shift reaction.

[0004]

[0002] Therefore, the present invention is mainly situated in the field of catalysis and industrial chemical processes, with emphasis on the production of hydrogen in a more efficient and economical way, through the development of a new catalyst.

[0005] Fundamentals of the invention

[0006]

[0003] Hydrogen generation is one of the great challenges of the future, and many chemical and petrochemical processes require large quantities of it. The use of natural gas as a hydrogen generation source is still seen as one of the most viable alternatives, whose efficiency can be improved through the development of a more active and / or selective catalyst.

[0007]

[0004] In order to maximize H2 production, the additional step of carbon monoxide oxidation is carried out through the water-gas shift reaction, “Water-Gas Shift Reaction” - WGS. Its main application in refineries is to increase hydrogen production for the hydroprocessing of streams that will originate, for example, fuels and / or lubricants.

[0008]

[0005] The execution of the gas-water displacement reaction can be carried out in two stages, aiming to overcome the thermodynamic and kinetic limitations inherent to this reaction. At higher temperatures, the favorable kinetics can be exploited, making it possible to minimize the volume of catalyst, while at lower temperatures, the catalyst can take advantage of thermodynamic equilibrium due to the reaction being exothermic.

[0009]

[0006] The first stage of the gas-water shift reaction corresponds to the High Temperature Shift (HTS) stage, with the reaction occurring in the range of 350-500°C, using Fe2O3-Cr2O3 as a catalyst. After the HTS stage, the gaseous feedstock is cooled and the reaction is carried out at low temperatures, between 200-250°C, this stage being designated as Low Temperature Shift (LTS), in which CuO-based catalysts are used, which normally also contain ZnO and Al2O3 in their composition.

[0010]

[0007] Iron and chromium oxide catalysts for HTS can also be doped with magnesium, aluminum, copper, and zinc oxides to enhance their thermal stability. Conventional Fe2O3-Cr2O3 catalysts are composed of 80-90% iron oxide and 8-10% chromium oxide, and the balance is achieved with promoters and stabilizers.

[0011]

[0008] Currently, chromium-free catalyst formulations for HTS are desired because chromium is carcinogenic and presents a high environmental risk. Alternatives to iron (Fe) are also being sought, since caution is needed in its activation process, as this step can lead to a greater reduction of iron oxide than necessary, resulting in the formation of metallic iron, which can catalyze undesirable reactions.

[0012]

[0009] The Fe2O3-Cr2O3 catalyst is still used for the WGS reaction for the high-temperature reaction step, HTS. However, there is interest in discontinuing the use of chromium in the catalytic formulation due to environmental concerns, as it is highly carcinogenic and banned in Europe.

[0013]

[0010] In this sense, noble metal catalysts have proven to be attractive alternatives for the WGS reaction, since they are more active than Fe-Cr catalysts and, in general, more tolerant to sulfur poisoning. However, platinum is a high-cost material, which can be a barrier to the use of the catalyst on an industrial scale.

[0014]

[0011] In the petroleum industry, there is a continuous search for cost reduction to maintain competitiveness, and increasing energy efficiency in processes is a way to optimize refining activities. However, there is a gap in the area of ​​catalysts or alternative processes that are more energy-efficient than the approaches that have existed so far. The use of Cobalt (Co) as an active phase for gas-water shift reactions at high temperatures presents itself as a promising avenue.

[0015]

[0012] Among the prior art documents that have already addressed the problem, the following references (patent and non-patent) are cited, for example:

[0016]

[0013] Patent CN109201071, published on 15 / 01 / 2019, describes a sulfur-tolerant WGS reaction catalyst containing cobalt oxide as the active phase and molybdenum oxide and niobium oxide as promoters. The method includes: (1) mixing a compound containing the element cobalt, a compound containing the element molybdenum, a compound containing the element niobium, a transport precursor and water; (2) extruding the product obtained and performing the first drying and roasting step; (3) the product obtained in step (2) is subjected to treatment in aqueous medium at 20-150°C for 0.5-10 h, and then subjected to the second drying and roasting. The catalyst was evaluated at 450°C. The product presented in this document differs from that of the present invention in distinct aspects.The first is the presence of molybdenum, and the use of this component in conjunction with cobalt for hydrotreating catalysts in sulfur-contaminated streams is common knowledge in the industrial field. The absence of molybdenum and the lack of need for a sulfidation pre-step for the catalyst to exhibit activity are characteristics that result in innovation and advantage of the present invention. The methodologies for preparing the catalysts are also different. From the description, the method used in the document in question resembles a physical mixing followed by thermal treatments that produces a catalyst that can be classified as bulk catalyst. Whereas the present invention describes a cobalt catalyst supported on a mixed oxide prepared by co-precipitation.The catalyst composition is also a distinguishing factor between the materials. Besides molybdenum being the component with the highest concentration, niobium oxide is present in low concentrations (0.5-10% by mass, preferably 1-5%), which characterizes its use as a promoter. In contrast, in the catalyst of the present invention, the use of niobium allowed the formation of a mixed oxide that enables its bifunctional action. Finally, it is mentioned in the description of document CN109201071 that the catalyst undergoes a sulfidation step with H2S, so the active forms in the reaction will be molybdenum sulfide and cobalt sulfide, which are different from the proposed invention.

[0017]

[0014] Patent CA2675767, filed on 12 / 18 / 2003, refers to a method and catalysts for generating a hydrogen-rich gas from a mixture of gases containing carbon monoxide, such as synthesis gas, and water at a maximum of 450°C. The invention includes methods using platinum-free catalysts containing (a) Ru, its oxides or mixtures; (b) Co, Mo, their oxides or mixtures; and (c) at least one of Li, Na, K, Rb, Cs, Ti, Zr, Cr, Fe, La, Ce, Eu, their oxides and mixtures. The catalyst can also be supported on different materials, such as aluminum, zirconium, titanium, cerium, magnesium, lanthanum, niobium, zeolite, perovskite, silica, yttria, or iron oxide. Unlike the catalyst of the present invention, the materials that originate from the possibilities claimed in the aforementioned document have the noble metal Ruthenium as a component, which, according to the description, acts as the active phase.It is also characterized by the association of cobalt with molybdenum.

[0015] Application CN1 16212867A, published in 2023, describes a catalyst for use in gas-water shift reactions, as well as a method for its preparation and application. This document discloses a catalyst for use in gas-water shift reactions composed of Pt / NaNbOa-CeC, the active component of the catalyst is Pt and the Pt content is from 0.5% to 10% of the total mass of the catalyst; and the carrier is the compound oxide NaNbOa-CeC. Furthermore, the Pt / NaNbOa-CeC catalyst support was prepared by a technique different from that described by the present invention. The deposition-precipitation synthesis used in the cited document consists of a hybrid method, in which an insoluble material is added to the precipitating solution.As can be observed from the aspects presented by this methodology, the resulting material probably consists of the deposition of one oxide on the surface of another, and not the insertion of Niobium (Nb) into the crystalline lattice of Ceria (CeC), as is the case with the support of the invention, which makes these materials structurally different.

[0018]

[0016] International patent application WO2007001164, published in 2007, describes a metal oxide catalyst for hydrogen generation and a method for producing it. This application discloses a metal oxide catalyst for hydrogen generation and a method for producing the same metal oxide catalyst, with the aim of increasing hydrogen production yield and reducing hydrogen production costs by using a cheaper metal oxide catalyst. The hydrogen generation catalyst contains at least one metal oxide, wherein the metal oxide contains at least one transition metal oxide; the metal oxide contains at least one transition metal oxide bonded to at least one transition metal oxide; the transition metal may be Nb or Ce; and the metal oxide may be Co oxide.However, the process for producing hydrogen is the hydrolysis of sodium borohydride, which consists of the reaction of NaBH4 (in solution) with water, therefore it is a liquid-phase reaction. Whereas, in the present invention, in the gas-water shift reaction, carbon monoxide (gas) reacts with water vapor on the surface of a solid catalyst, thus being a gas-solid system; that is, the hydrogen production processes are completely distinct. Furthermore, according to the description of the catalytic test experiment in this WO, a static system was employed in which the reagents are introduced into a reaction vessel (reactor). In the catalytic test performed to evaluate the product of the present invention, a continuous system was used, in which the reaction mixture flows through the reactor.

[0019]

[0017] Application KR102023267, published in 2018, describes a preparation of alkali metal or alkaline earth metal-promoted cobalt-based catalysts for the gas-water shift reaction. This document discloses a cobalt-based catalyst for a gas-water shift reaction, containing an alkali metal or alkaline earth metal added as a co-catalyst, and a method for producing it. Specifically, for this purpose, a cobalt / cerium oxide catalyst containing an alkali metal or alkaline earth metal as the co-catalyst is prepared, and the stability of the cobalt / cerium oxide catalyst containing the co-catalyst becomes superior to that of a cobalt / cerium oxide catalyst. The product of this document differs from the catalyst of the present invention, which does not contain an alkali or alkaline earth metal in its composition. This is because, in the KR document, the third element of the cobalt and cerium-based catalyst is a promoter.The range presented regarding the content of alkali metal or alkaline earth metal (1 to 2.5% by mass) corroborates that these elements act as promoters in the catalyst. Promoters can be classified as structural, selective, and electronic. As alkali and alkaline earth metals are referenced in KR as "co-catalysts," they can be considered as electronic promoters. Thus, the main synergy of these elements would be with the active phase Cobalt, which differs from the use of Niobium in the present invention, which was employed to form a mixed oxide support with Cerium.

[0020]

[0018] The article entitled "Effects of niobium addition on active metal and support in Co-CeO2 catalyst for the high temperature water-gas shift reaction," published in 2021, describes a catalyst composed of Cobalt, Cerium, and Niobium, prepared by co-precipitation, which exhibits stability in HT-WGS reactions. Furthermore, the article entitled "Restructuring Co-CoOx Interface with Titration Rate in Co / Nb-CeC Catalysts for Higher Water-Gas Shift Performance," published in 2023, discloses a catalyst of Cobalt (Co), Cerium (Ce), and Niobium (Nb) that exhibits stability under severe reaction conditions (450 e C) for the production of hydrogen through the WGS reaction, prepared by means of co-precipitation.

[0021]

[0019] The catalysts prepared in the last two references cited above differ from the present invention because they were prepared by co-precipitation of the three elements of interest (Co, Nb, and Ce), which does not guarantee the deposition of cobalt on the surface, and a bulk catalyst may have been formed. In the present invention, the cobalt catalyst is supported on the pre-formed mixed oxide of niobium and cerium. Furthermore, regarding the preparation methodology, different reagents were used, such as the precipitating agent, in the two references where KOH was used, and in the invention, NH4OH. The precipitating agent alters the pH and introduces new ions to the system and, therefore, the use of different reagents can alter the properties of the catalysts formed. There was also a difference in relation to the niobium precursor reagent, since, in both references, NbCls was used, which needed to be initially solubilized in ethanol.

[0022]

[0020] The differences in preparation methodologies and composition demonstrate that the catalysts in the two references cited and in the invention are different materials. This is because the textural and structural properties of a catalyst are strongly influenced by the materials and techniques used in its preparation. Thus, catalysts prepared using different reagents, synthetic routes, or even drying / calcination temperatures can become different catalysts, affecting their activity for the reactions of interest.

[0023]

[0021] The article entitled Development of Co-Nb-CeC Catalyst for Hydrogen Production from Waste-Derived Synthesis Gas Using Techno-Economic and Environmental Assessment, published in 2022, discloses a catalyst made of Cobalt (Co), Cerium (Ce), and Niobium (Nb), which exhibits stability under severe reaction conditions (500 eC) for hydrogen production through the WGS reaction, which presents economic and ecological viability. The catalysts presented in this article share similarities with the catalysts from the last two articles presented above regarding the precipitating agent KOH, the NbCls precursor solubilized in ethanol, and the low niobium content. This 2022 article evaluates a catalyst prepared by dry impregnation of cobalt; however, it presents a significant difference in composition due to the very low niobium content (0.5% by mass). According to the results of the temperature-programmed reduction analysis with hydrogen, it is possible to verify that the interactions between the components of the materials do not occur in the same way in the catalysts of the cited reference and the invention, indicating that factors such as synthesis methodology and composition make the catalysts different. The aforementioned article only mentions the existence of peaks due to the reduction of cobalt (CO3C). WhatO-> What 0) and surface cerium. No peaks related to niobium reduction were mentioned. However, for the catalyst of the invention, the high niobium content influenced the reduction profile of the material. The reduction profile of the pure Nb2Os-CeO2 mixed oxide showed three hydrogen consumption regions, with peaks at approximately 515°C, 690°C, and 950°C. The reduction profile of pure cerium oxide usually shows two peaks, where the first starts above 500°C and the second above 800°C. The peak at the lower temperature is related to the reduction of surface ceria (CeC), while the one formed at higher temperatures refers to the reduction of bulk CeC to Ce2O3. These peaks can be correlated with the first and last peaks of the support. The appearance of the peak at 690°C can be attributed to surface niobium species. The highest peak temperature (950°C) may also reflect a contribution from the reduction of bulk niobium.Analysis of the reduction profile obtained for the catalyst also revealed the possible formation of different cobalt species resulting from interaction with the support.

[0024]

[0022] Given the limitations present in the current state of the art, the present invention aimed at developing a catalyst that could replace traditional catalysts, such as Fe-Cr, enabling the use of more energy-efficient operating conditions and at a lower cost compared to materials with noble metals in their composition.

[0025] Summary of the invention

[0026]

[0023] In a first embodiment, the present invention describes a process for producing a chromium-free supported catalyst.

[0027]

[0024] In a second embodiment, the present invention describes the catalyst obtained by the process. The catalyst of the invention consists of Co (Cobalt), supported on the mixed oxide Nb2Os-CeO2 (Niobium and Cerium), with the potential to replace traditional catalysts, such as Fe-Cr, and which presents a lower cost than catalysts based on noble metals.

[0028]

[0025] In a third embodiment, the present invention describes the use of said catalyst in a WGS reaction. More specifically, the catalyst of the invention can be used, for example, in various hydrogen generation units based on steam reforming technology, where High Temperature Shift (HTS) catalysts could be applied to maximize hydrogen production.

[0029]

[0026] These objectives and advantages of the invention are described in more detail in the following sections. Brief description of the Figures

[0030]

[0027] In order to make the invention easier to understand, the following Figures, which accompany this report and form an integral part thereof, are presented by way of illustration, but without intending to limit the invention.

[0031]

[0028] Figure 1 shows the diffractogram obtained by XRD analysis for the mixed oxide CeO2-Nb2Oõ compared to the diffractograms for the oxides of Cerium and Niobium.

[0032]

[0029] Figure 2 shows the diffractogram obtained by XRD analysis for the mixed oxide Nb2Oõ-CeO2 compared to the diffractograms for the oxides of Cerium and Niobium.

[0033]

[0030] Figure 3 shows the diffractogram obtained with a longer analysis time for the mixed oxide Nb2Os-CeO2, highlighting the position of the diffraction peaks.

[0034]

[0031] Figure 4 shows the graph of the reduction profiles of the Nb2Os-CeO2 support and the Co / Nb2Os-CeO2 catalyst.

[0035]

[0032] Figure 5 shows the deconvolution graph of the hydrogen consumption peaks by the Co / Nb2O5-CeO2 catalyst.

[0036]

[0033] Figure 6 shows the graph of the results of the catalytic test at 400°C with 200 mg of sample and a feed stream of 100 ml / min composed of 5% H2, 15% CO, 5% CO2, 20% H2O and 55% N2, being TOF (Turnover Frequency) x time (h).

[0037] Detailed description of the invention

[0038]

[0034] In general terms, the present invention describes a Co (Cobalt) catalyst supported on the mixed oxide Nb2Os-CeO2 (Niobium and Cerium), and its support, which is prepared as follows:

[0039]

[0035] Support Preparation: The mixed oxide Nb2Os-CeO2 (Niobium and Cerium) was synthesized by the co-precipitation method. Solutions of niobium ammonium oxalate (CBMM) and cerium nitrate hexahydrate (Sigma-Aldrich) were prepared, with the appropriate mass of each reagent to ensure the desired final CeO2 / Nb2Os ratio. These solutions were mixed and stirred using a magnetic stirring plate (IKA C-MAG HS 7).

[0036] The mixture of solutions was kept under stirring at room temperature (25°C), and its pH was constantly monitored using a benchtop pH meter. Initially, the pH value was 1 and the solution was white and cloudy. An ammonium hydroxide solution was added dropwise for precipitation, and at the end of the precipitation, the solution had a pH of 9.8 and a yellow color.The precipitate was filtered and washed with deionized water, dried in an oven at 120°C for 24 h, and finally calcined at 500°C for 2 h at a rate of 10°C / min.

[0040]

[0037] Catalyst Preparation: The addition of the active cobalt phase was carried out by dry impregnation. A solution of the precursor Co(NO3)6H2O was prepared, resulting in a nominal Co content of 10% w / w for the final catalyst. The support was placed in a porcelain mortar, and 0.41 mL / g of the precursor solution was added using a Pasteur pipette. During this process, the drops were distributed on the support to homogenize the deposition of the active phase on the solid, aiming for better metallic dispersion in the final catalyst. After impregnation, the material was dried in an oven at 120°C for 24 hours and then calcined at 500°C (10°C / min) for 2 hours.

[0041] Experimental composition of the catalyst

[0042]

[0038] Energy Dispersive X-ray Spectroscopy (EDX) analysis was employed to determine the mass composition of the obtained catalyst. An energy dispersive X-ray fluorescence spectrometer (Shimadzu EDX-700 model), equipped with a rhodium (Rh) X-ray tube, was used for the analyses. The results can be seen in Table I below.

[0043] Table I: Concentrate composition (%m / m) obtained by EDX analysis. Evidence of solid solution formation for support.

[0044]

[0039] X-ray Diffraction (XRD) experiments were performed on the Rigaku Miniflex II diffractometer. The diffractogram obtained by varying the angle (20) from 10° to 90°, with a step of 0.05° and a speed of 1° / min for the CeO2-Nb2O2 support showed only peaks referring to CeO2, with a crystalline (cubic) phase, as shown in Figure 1, in comparison to the pure oxides of Niobium (Nb2O2) and Cerium (CeC).

[0045]

[0040] It can be seen from Figure 2 that the Nb2Os-CeO2 support showed only peaks referring to cubic cerium (JCPDS 4-0593). As the EDX analysis of this oxide confirmed that niobium is present in the material in significant amounts (Table I), a new XRD analysis was also performed for this support to better understand the result, since niobium could be highly dispersed, making it difficult to obtain its diffraction peaks under the conditions previously used. In this new analysis, the scanning range, speed and step were reduced to a range of 15° to 60°, 0.25° / min and 0.02°, respectively. Even with the new analytical conditions, the diffractogram presented in Figure 3 showed only peaks derived from cerium oxide, as can be observed by comparison with the analyses of pure niobium and cerium oxides also presented in Figure 3. Although the diffractogram for Nb2O5 also shows a peak at 28.6 s, the absence of other high-intensity peaks, such as 22, 6 e and 36, 8 e , indicates that the peak obtained for the Nb2Oõ-CeO2 support is associated with CeC .

[0046]

[0041] It is also possible to observe in Figure 3 that the diffraction peaks obtained for the Nb2Os-CeO2 oxide are shifted relative to those of the Cerium oxide, from 20 = 28.3°, 32.8°, 47.3° and 56.2° to 20 = 28.6°, 33.2°, 47.6° and 56.4°. This shift, according to the article Sour water-gas shift reaction over Pt / CeZrO2 catalysts, published in 2015, may indicate that Niobium cations were introduced into the crystalline structure of Cerium, as observed analogously for Ceria and Zirconia oxides. The addition of a cation to the Cerium crystalline lattice causes an elastic deformation of the material, resulting in changes in the spatial plane of the lattice and consequently in new values ​​of 20 for the diffraction peaks.

[0047] Evaluation of possible species in the catalyst after activation.

[0048]

[0042] The mixed oxide (support) Nb2Os-CeO2 showed three hydrogen consumption regions, with maxima at approximately 515°C, 690°C, and 950°C, as can be seen in Figure 4. The reduction profile of pure cerium oxide usually presents two peaks, where the first begins above 500°C and the second above 800°C, as reported in the article "The effect of ceria content on the performance of Pt / CeO / AlO2 catalysts in the partial oxidation of methane," published in 2005. The peak at the lower temperature is related to the reduction of surface cerium, while the one formed at higher temperatures refers to the reduction of bulk CeC to Ce2O3. These peaks can be correlated with the first and last peaks of the support. The peak at the highest temperature may also show a contribution from the reduction of bulk niobium.

[0049]

[0043] The appearance of the peak at 690°C can be attributed to surface Niobium species, according to the article CeO2-Nb2Os mixed oxide catalysts: Preparation, characterization and catalytic activity in fructose dehydration reaction, published in 2012. Impregnation with Cobalt promoted a decrease in the maximum reduction temperatures of all species related to the support.

[0050]

[0044] It has been observed that the presence of transition metals promotes the reduction of CeO2, which corresponds to a lower reduction temperature of surface cerium through the spillover of H2 from the metallic particles of the active phase to CeO2, as suggested in the article Copper-based catalysts for water gas shift reaction: Influence of support on their catalytic activity, published in 2009. According to the article Fischer-Tropsch Synthesis on Anchored Co / Nb2Os / Al2O3 Catalysts: The Nature of the Surface and the Effect on Chain Growth, published in 2006, it is also possible that partial reduction of niobium occurs in contact with the metal.

[0051]

[0045] In Figure 4 it is also possible to verify that for the active phase of the catalyst, there is the formation of two reduction peaks, which is frequently reported in the literature. The lower temperature peak is associated with the reduction of CO2O3 to CoO and the second peak corresponds to the reduction of Co 2+to metallic Cobalt, this type of Cobalt may originate from the first reduction of CO2O3, as well as from Co(II) pre-existing in the catalyst and which exhibits a strong interaction with the support, as described in the article Fischer-Tropsch Synthesis on Anchored Co / Ni^Os / AC Catalysts: The Nature of the Surface and the Effect on Chain Growth, published in 2006.

[0052]

[0046] In Figure 5, it is possible to verify the deconvolution of the hydrogen consumption peaks of the catalyst of the present invention. The sum of the first four peaks, P1 (a), P1 (b), P1 (c) and P2(d) results in a degree of Cobalt reduction of 97%, which denotes that the others are related to the support. This greater number of peaks referring to Cobalt in the catalyst of the invention may indicate different species of Cobalt formed by the interaction with the support, as well as more diverse particle sizes.

[0053] Catalytic Evaluation

[0054]

[0047] The catalytic activity evaluation of the product developed in the present invention was carried out on an automated Microactivity Effi unit, model MAEPGL1 M6 from PID. The effluent analysis was performed on a Shimadzu GC-2030N gas chromatograph, equipped with a carboxen 1010 column and a barrier discharge ionization detector (BID).

[0055]

[0048] For the reaction, a fixed-bed quartz reactor was used containing approximately 200 mg of catalyst diluted in silicon carbide (Sigma-Aldrich), in a 1:1 ratio. Prior to the catalytic activity test, the catalyst was dried at 150°C (10 e C / min) with He (30 mL / min) for 30 min and subsequently reduced with H2 (30 ml / min) at 500°C (10°C / min) for 1 h.

[0056]

[0049] The reaction feedstock consisted of 5% H2, 15% CO, 5% CO2 and 20% H2O %v / v, with 55% N2 for balance, totaling 100 ml / min. The water vapor was fed through an Eldex HPLC pump, which drew distilled water from a reservoir pressurized to 0.5 MPa.

[0057]

[0050] The temperature of the reaction system, with the exception of the reactor heating furnace, was maintained at 200°C to avoid water condensation points. The catalytic activity test to assess stability was performed at 400°C for approximately 18 h. A catalytic test was also performed at 450°C for approximately 4 h with fresh catalyst, previously dried and activated under the same conditions described above, to assess the average initial activity.

[0058]

[0051] The average activity of the Co / Ce02-Nb2O5 catalyst was compared to other commonly used catalytic systems in the HTS range, and to catalysts based on Cobalt and Molybdenum, as shown in Table II. The HTS COM 1 and HTS COM 2 materials refer to commercial catalysts.

[0059]

[0052] The other materials listed in Table II, with the exception of the catalyst of the present invention, were evaluated in a homemade catalytic unit used prior to the acquisition of the automated unit, but under the same test conditions, such as temperature, catalyst mass, and feedstock composition. The homemade unit consisted of temperature controllers for the line and furnace, mass flow controllers for gases with a digital panel for defining the opening of the solenoid valves, 3-way valves for gas selection, and 2-way valves for directing the flow path. Water vapor was fed by introducing the (dry) gases into a saturator containing distilled water, maintained at 60°C. The effluent analysis was performed on a Shimadzu gas chromatograph, model 2014, equipped with a Carboxen 1010 column and a thermal conductivity detector (TCD) and a flame ionization detector (FID); however, only the TCD was used for the analyses.The reactions were also conducted in a fixed-bed quartz reactor, just like in the automated unit.

[0060]

[0053] The catalyst developed by the present invention showed an unexpected result, as can be seen from the excellent catalytic performance in the gas-water displacement reaction, far superior to the commercial reference catalysts, as can also be seen in Table II.

[0061] Table II: Average forward reaction rates obtained at 400°C (a) or 450°C (b) with a feed stream of 100 ml / min composed of 5% H2, 15% CO, 5% CO2, 20% H2O and 55% N2.

[0062]

[0054] The developed catalyst, with a mass composition of CeO2: 65.75%, Nb2O5: 18.02%, Co: 13.83% and Impurities: 2.40% (Table I), shows higher activity than the other catalysts in Table II.

[0055] In addition to Table II, the data in Figure 6 stand out, showing the results of TOF - Turnover Frequency, which denotes the stability of the catalyst in the evaluation.

[0063]

[0056] The catalyst of the present invention can be successfully used in water-gas shift reactions (WGS). More specifically, it can be used in hydrogen generation units based on steam reforming technology, where high temperature shift (HTS) catalysts could be applied.

[0064] Advantages of the Catalyst

[0065]

[0057] Regarding the advantages presented by the developed catalyst, it can be said that it has an active phase composed of transition metal, with a lower cost than catalysts based on noble metal.

[0066]

[0058] Furthermore, the catalyst of the invention does not require additional steps beyond activation with H2 at 500°C to exhibit activity, such as a sulfidation step or activation with more rigorous control.

[0067]

[0059] The catalyst of the invention exhibits greater initial activity, enabling a longer campaign time than catalysts currently available on a commercial scale.

[0068]

[0060] The catalyst of the invention also contributes to increasing the lifespan of subsequent catalysts used in various industrial processes, such as in ammonia synthesis and hydrogenation reactions, as they are deactivated or have their activity reduced in the presence of CO.

[0069]

[0061] Regarding reliability, the use of catalysts with higher activity, such as the one developed by the present invention, can allow the unit to operate with longer campaign times.

[0070]

[0062] Regarding health and safety, it is known that 0 Cr, in its hexavalent form, is a corrosive and irritating agent to the human body, being toxic to the kidneys and potentially causing tumors. Inhalation of Chromium VI, for example, in addition to causing severe respiratory irritation, is recognized as a human carcinogen. Therefore, hexavalent Chromium is found on most national and international lists of highly toxic materials, for which strict control procedures are applied.

[0071]

[0063] The form found in the commercial HTS catalyst before activation is precisely as hexavalent chromium, therefore the use of catalysts without this element in their composition is highly recommended and in this way, the catalyst of the present would meet this restriction.

[0072]

[0064] Regarding the environment, the developed catalyst exhibits greater activity without the need for Chromium for its stabilization, thus reducing the environmental impact of the process, both in terms of use and disposal of the material after the campaign ends.

[0073]

[0065] Those skilled in the art will appreciate the knowledge presented here and will be able to reproduce the invention in the forms presented and in other variants, covered within the scope of the appended claims.

Claims

CLAIMS 1. A process for producing a chromium-free supported catalyst for use in gas-water shift reactions, characterized by the following steps: preparation of the support, in which the mixed oxide Nb2Os-CeO2 is synthesized by the co-precipitation method, using solutions of niobium ammonium oxalate and cerium nitrate hexahydrate; and preparation of the catalyst, in which the addition of the active phase of Cobalt is carried out by dry impregnation, using a solution of the precursor Co(NO)3.6H20.

2. Production process according to claim 1, characterized in that, in the support preparation step, the solutions are mixed and kept under magnetic stirring at room temperature (25°C), and the pH is constantly monitored until it reaches a pH of 9.8 and a yellow color.

3. Production process according to claim 2, characterized in that the precipitate is filtered and washed with deionized water, dried in an oven at 120°C for 24 h, and calcined at 500°C for 2 h at a rate of 10°C / min.

4. Production process according to claim 1, characterized in that, in the catalyst preparation step, 0.41 mL / g of the precursor solution is added to the support using a Pasteur pipette.

5. Production process according to claim 4, characterized in that, after impregnation, the material is dried in an oven at 120°C for 24 hours and calcined at 500°C (10°C / min) for 2 hours.

6. Chromium-free supported catalyst, obtained by the process as described in any one of claims 1 to 5, characterized in that the catalyst is Co supported on the mixed oxide Nb2Os-CeO2, with a nominal Co content of 10% w / w in the catalyst, and having the following mass composition: CeO2 = 65.75%; Nb2Os = 18.02%; Co = 13.83%; and Impurities = 2.40%; and containing a support formed by a solid solution for which only diffraction peaks associated with ceria are observed (20 = 28.6°, 33.2°, 47.6° and 56.4°), however with a shift relative to pure ceria oxide (20 = 28.3°, 32.8°, 47.3° and 56.2°).

7. Use of the catalyst, as described in claim 6, characterized by being used in high-temperature gas-water displacement reactions, in the range of 350 to 500°C.

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