Process for removing h2s from natural gas at high pressures by means of a psa process

Description

1 / 19 “PROCESS FOR REMOVING H2S FROM NATURAL GAS AT HIGH PRESSURES BY MEANS OF A PSA PROCESS” Field of Invention

[001] The present invention relates to an application of high Si / Al ratio NaY zeolite in the removal of hydrogen sulfide (H2S) present in dry or wet natural gas by Pressure Swing Adsorption (PSA) process. Specifically, NaY zeolite with a Si / Al ratio > 2.6 is presented as a partially regenerable adsorbent in the removal of H2S when subjected to a PSA process intended for the removal of acid gases from natural gas from pre-salt wells, producing a purified natural gas stream at high pressure. Description of the State of the Art

[002] Interest in natural gas and its products has grown in recent years because it is a clean and safe fossil fuel compared to others. In the Brazilian market, however, the price of natural gas for industries is almost 5 times higher than that practiced in the American market. A large part of the responsibility for the high price of natural gas is due to the fact that it has a high exploration cost.

[003] In Brazil, offshore oil production is predominantly in the pre-salt polygon. The costs of natural gas exploration in this modality are very high, as the producing wells are located far from the coast, at great exploration depths, and may contain considerable amounts of acidic gases such as carbon dioxide (CO2) and hydrogen sulfide (H2S), among others, meaning that this gas, without proper treatment, does not meet the specifications for use, transport, and storage.

[004] The volume of natural gas to be processed is very large, and if it also contains a high quantity of contaminants, then the processing cost will be even higher (ARAÚJO, OQF et al. “Comparative analysis of separation technologies for processing carbon dioxide rich natural gas in ultradeepwater oil fields”. Journal of Cleaner Production, v. 155, p. 12-22, 2017). A Petition 870210107103, dated 11 / 19 / 2021, p. 19 / 46 2 / 19 The permitted amount of H2S in commercially sold natural gas is only 10 mg rrr3 (National Petroleum Agency. “ANP Resolution No. 16, of 17.6.2008”). Therefore, the removal of H2S is extremely necessary.

[005] Thus, there is a need for raw gas purification to meet established standards and specifications, however, the classic processes currently employed contribute significantly to increasing the final price of the product. Therefore, research into more efficient natural gas purification technologies is becoming an increasingly growing necessity in order to meet the needs of contemporary society.

[006] For the removal of acid gases CO2 and H2S, solvent absorption, cryogenic distillation, membrane separation and adsorption processes, or combinations of these methods can be used (KIDNAY, AJ; PARRISH, WR “Fundamentals of Natural Gas Processing”, CRC Press, 2006). Although PSA removal of acid gases from natural gas is not a readily available technology, it is a highly competitive emerging technology compared to membrane technology, as it allows for ease of automation, as well as enabling adsorbent regeneration and high efficiency in treating streams with low contaminant concentrations, where membranes fail.

[007] The use of amine-based absorption technologies has as its main disadvantage the high operational costs related to the regeneration of the liquid stream, a fact that is not necessary in a PSA process.

[008] The main disadvantage of using iron oxides is that H2S is removed from the gas stream, irreversibly producing a solid waste containing iron sulfide, in addition to causing a significant environmental impact because this solid is pyrophoric. Furthermore, the recurring replacement of the solid represents a high cost, which can be avoided by using a regenerable solid in a Pressure Swing Adsorption (PSA) process, since the regeneration of the adsorbent solid occurs in situ. In this sense, the material Petition 870210107103, dated 11 / 19 / 2021, page 20 / 46 3 / 19 The adsorbent must prove to be stable in the face of the separation process in continuous operation.

[009] Adsorption units should preferably allow for the regeneration of the solid used in contaminant removal. This regeneration can be achieved by changing the total operating pressure, through the PSA process.

[0010] Faujasite-type zeolites interact strongly with H2S, potentially promoting H2S chemisorption and making the regeneration process more costly. However, NaY zeolites with a Si / Al ratio greater than 2.6 exhibit reversible adsorption. Even if a portion of H2S remains trapped in this adsorbent, there is still a high capacity for capturing H2S, with the possibility of removing the adsorbed portion of H2S by reducing the absolute pressure.

[0011] In addition to allowing the gas to meet market specifications, removing contaminants from natural gas is important for the maintenance of pipelines and process equipment, since acidic gases such as CO2 and H2S contribute to corrosion in the presence of moisture, reducing the lifespan of this equipment and increasing the cost of the production process.

[0012] Regarding the different natural gas purification processes mentioned above, it is also worth highlighting that technologies based on amine absorption, such as Selexol™ and Rectisol™, can be used to remove H2S from a natural gas stream; however, they have the disadvantages of high installation and operating costs, as well as high energy consumption. Even in integrated absorption technologies, heating of the regenerating material may be necessary. An example is found in patent BR 112015000151-3 A2. In this invention, it is proposed to separate CO2 from a stream containing hydrocarbons, CO2, and H2S through an absorption process involving solvents integrated into a Claus process. Another example is patent document EP1480733A1, which describes a combined adsorption and absorption process for the removal of H2S and mercaptans from Petition 870210107103, dated 11 / 19 / 2021, page 21 / 46 4 / 19 a natural gas stream. The current patent application differs from the aforementioned inventions because it presents the application of NaY zeolite in an adsorption-based process, more specifically a PSA process. The adsorbent exhibits partial regeneration when the operating pressure is modulated, allowing in situ regeneration.

[0013] An example of an absorption technology integrated with another is presented in patent BR 102017001342-1 A2. In the document, water is used as a solvent in the removal of H2S from a gas stream. The H2S retained in the solvent is removed in a reactive adsorption bed in an oxycatalyst. Thus, in addition to an absorption column, it is necessary to use a column containing the oxycatalyst and equipment for drying the desulfurized gas stream. The present invention uses only NaY zeolite arranged in an adsorption bed. In this configuration, a dry natural gas stream free of H2S is produced.

[0014] The most prominent technologies based on the use of iron oxide (FexOy) are IRON SPONGE and SULFATREAT. In IRON SPONGE technology, hydrated iron oxide is supported on wood chips, while in SULFATREAT technology, mixed iron oxide particles supported on a ceramic matrix are used. In these technologies, H2S is removed from the gas stream, irreversibly producing a solid waste containing iron sulfide (Dl FELICE, R.; PAGLIAI, P. (2015). “Prediction of the onset of rupture of a mixture of dilute H2S and dry gas when treated with commercial sorbent sulfatreat”. Biomass and Bioenergy, v. 74, p. 244-252). The main disadvantage of these technologies is the high cost of transporting the solid, which must be replaced periodically.

[0015] Patent EP1234947B1 proposes the removal of H2S and / or CO2 from a crude oil or natural gas stream by using iron nanoparticles deposited in fractures present in oil wells. The present invention, on the other hand, proposes the use of a NaY zeolite with a Si / Al ratio > 2.6 for the removal of H2S from a natural gas stream. Furthermore, the Petition 870210107103, dated 11 / 19 / 2021, p. 22 / 46 5 / 19 NaY zeolite is arranged in a stainless steel column, forming a packed bed. In this configuration, the NaY zeolite can be partially regenerated in situ, allowing its use without periodic replacement.

[0016] In addition to reactive adsorption on oxides, the main continuous separation processes based on adsorption involve the modulation of pressure (Pressure Swing Adsorption, PSA), temperature (Temperature Swing Adsorption, TSA), vacuum pressure (Vaccum Swing Adsorption, VSA) or combinations thereof. In the case of PSA, several configurations are possible, allowing the use of two or more adsorption beds, in single or multiple pressurization and depressurization steps.

[0017] PSA technology has several applications: hydrogen purification; separation of atmospheric air components; CO2 removal from gas streams; and purification of noble gases. This technology is associated with low energy consumption when compared to other technologies (GRANDE, CA “Advances in Pressure Swing Adsorption for Gas Separation”, ISRN Chemical Engineering, 2012, p.1-13).

[0018] In PSA technology, a high-pressure gas stream containing the contaminant to be removed is allowed to pass through an adsorbent solid, which selectively captures this contaminant, producing a decontaminated stream. Adsorption must be fully or partially reversible, allowing for the total or partial removal of the adsorbed component by decreasing the total pressure. In this sense, the choice of adsorbent is essential in the PSA separation process. The adsorbent must have mechanical resistance to withstand frequent pressurization and depressurization, as well as a high contaminant removal capacity and the possibility of regeneration to extend its service life in the process.

[0019] Patent AU2012223485 presents a process apparatus for removing CO2 and H2S from natural gas by means of a fast-cycle pressure swing adsorption (PSA) process. While the document prioritizes describing the apparatus Petition 870210107103, dated 11 / 19 / 2021, p. 23 / 46 6 / 19 of a process in which the removal of acidic gases occurs, the present invention presents NaY zeolite with a Si / Al ratio > 2.6, a commercially available material that has a high capacity for removing H2S and that maintains this high removal capacity for several adsorption / desorption cycles, when desorption occurs by reducing the total pressure.

[0020] Document WO2012 / 138910 A2 presents a methodology for the preparation of mesoporous and / or mesostructured materials by modifying zeolites with a low Si / Al ratio. More specifically, it describes methodologies for the preparation of mesoporous and / or mesostructured materials by means of structure modification followed by a mesopore introduction process.

[0021] Document W02008143825 describes a process for removing CO2, N2, and H2S from a gas mixture using a PSA process. The adsorbent used has 20% or less of open pore volume in the meso- and macropore regions. The invention described in document BR 112019002106-0 A2 presents a PSA process for removing water from a gas stream containing hydrocarbons using a zeolite 3A as an adsorbent. The invention described in document AU2012223560B2 describes the removal of H2S by means of a generic cyclic adsorption / desorption process, limited to two beds. In another document, AU2012259377B2, a modular equipment is described for carrying out a cyclic adsorption process, in which each module has 5 adsorption beds and an equalization tank. Neither of these documents specifies the use of regenerative NaY zeolite, which can be applied in PSA processes.

[0022] The invention described in patent AU2012259377B2 presents equipment that removes multiple contaminants from natural gas (H2S, heavy hydrocarbons, CO2 and H2O, mercaptans and mercury) by means of adsorption in a bed containing multiple layers of adsorbent material (molecular sieves, silica gel, zeolites, MOFs, non-regenerative material and combinations), arranged in a specific order. Furthermore, regeneration Petition 870210107103, dated 11 / 19 / 2021, page 24 / 46 7 / 19 of the adsorbent materials is absorbed by passing clean gas with or without an increase in operating temperature.

[0023] In none of the aforementioned patent documents is NaY zeolite with a Si / Al ratio > 2.6 specified as a partially regenerable adsorbent material for the adsorption of H2S from natural gas, being regenerated by decreasing the total operating pressure. The proposed invention, on the other hand, aims at removing H2S from natural gas using NaY zeolite with a Si / Al ratio > 2.6 with regenerative capacity.

[0024] Ultra-stabilized zeolite Y, containing rare earth cations and in acidic form, is a material known in the petroleum industry, being used in petroleum refining, in catalytic cracking units, promoting increased yield in gasoline and diesel (BHATIA, S. “Zeolite Catalysis: Principles and Applications”, CRC Press, Inc., Boca Raton, Florida, 1990). Zeolite Y, especially in its sodium form, does not have catalytic cracking activity, however, it exhibits a high capacity for capturing H2S.

[0025] It was evidenced in the article by KARGE, HG; RASKÓ, J. (1978) “Hydrogen sulfide adsorption on faujasite-type zeolites with systematically varied Si-Al ratios”. Journal of Colloid And Interface Science, v. 64, n. 3, p. 522-532, that the first H2S molecules that adsorb onto NaY zeolite do so in a dissociative manner and that this dissociation becomes less and less evident as the Si / Al ratio increases to levels above 2.6.

[0026] The article by LUTZ, W.; SEIDEL, A; BODDENBERG, B. (1998) “On the formation of COS from H2S and CO2 in the presence of zeolite / salt compounds”. Adsorption Science and Technology, v. 16, p. 577-581, evaluates the conversion of H2S and CO2 into COS in NaY and NaX zeolites. It was found that NaY zeolite, which has a higher Si / Al ratio, has a lower conversion of H2S into COS than NaX zeolite. According to the authors, at Si / Al ratios > 2.43, Na+ cations from the supercavities of the zeolite structure are not available to H2S and CO2 molecules, which reduces activity at short contact times. Petition 870210107103, dated 11 / 19 / 2021, p. 25 / 46 8 / 19

[0027] Recently, in OLIVEIRA, LH et al. (2019) “H2S adsorption on NaY zeolite”, Microporous and Mesoporous Materials, v. 284, p. 247-257, it was verified that NaY zeolite with a Si / Al ratio of 2.8 exhibits a highly favorable H2S adsorption isotherm, with high capture capacity, and with desorption hysteresis, since a residual amount of H2S remained adsorbed on the solid during the desorption step. This amount was 2.4034, 1.8027 and 1.0184 mol kg-1 at temperatures of 20, 30 and 40 °C, respectively. Despite this, the adsorbent still showed a high capacity for capturing H2S at 39.90 bar, with values ​​of 6.8095, 6.5195, and 6.0302 mol kg-1 at 20, 30, and 40°C, respectively.

[0028] The aforementioned articles show that NaY zeolite has a high capacity for capturing H2S. Furthermore, it is verified that a portion of the retained H2S is removed during the desorption step, demonstrating that the adsorbent is partially regenerative. This possibility of partial regeneration is explained by the fact that the adsorbent is a NaY zeolite with a Si / Al ratio > 2.6, which has a reduced capacity to dissociate H2S molecules, minimizing the amount chemisorbed. It is therefore suggested that this adsorbent has great potential for use in a PSA process.

[0029] While the high capture capacity suggests great potential for using the material in cyclic adsorption processes, the high adsorbate-adsorbent interaction, indicated by the highly favorable H2S adsorption isotherm, on the other hand, suggests low potential for this type of process, as it may make it impossible to remove the adsorbate by dropping the working pressure.

[0030] This fact, in turn, would render the solid ineffective in future adsorption cycles, eventually being replaced by a new load of adsorbate-free solid, ultimately resulting in a costly process with low implementation viability. Therefore, to verify the potential of NaY zeolite with a Si / Al ratio > 2.6 in a cyclic adsorption process, it is necessary to carry out experiments under conditions closer to those of a Petition 870210107103, dated 11 / 19 / 2021, page 26 / 46 9 / 19 PSA process, since it is not evident from this article whether, under cyclic conditions, the NaY zeolite actually exhibits regenerative behavior, and also whether there is degradation of the material in the face of consecutive cyclic adsorption / desorption processes.

[0031] On the other hand, the present invention proposes the use of NaY zeolite with a Si / Al ratio > 2.6 as a regenerable material for the adsorption of H2S present in natural gas. Regeneration of the material is possible by reducing the absolute pressure from the operating pressure, preferably 51 bar, to atmospheric pressure. The use of this regenerable material would imply a reduction in the need to replace the adsorbent solid in offshore gas extraction platforms, allowing for a lower-cost purification process. Thus, no structural modifications to the solid are proposed, but rather the use of NaY zeolite with a Si / Al ratio greater than 2.6, which has a reduced capacity to dissociate H2S molecules, a fact that increases the regenerative capacity of the adsorbent solid.

[0032] The article by GEORGIADIS, AG; CHARISIOU, ND; GOULA, M. A. (2020) “Hydrogen sulfide removal from various industrial gases: a review of the most promising adsorption materials”, Catalysts, v. 10, doi: 10.3390 / catal10050521, presents a review of promising solid materials for H2S removal from industrial gaseous effluents. Among the various studies presented in this review article, it is pertinent to highlight that in the article by SIGOT, L; DUCOM, G.; GERMAIN, P. (2016) “Hydrogen sulfide (H2S) adsorption on zeolite (Z): Retention Mechanism”, Chern. Eng. J. v. 287, p. 47-53, a mechanism for the interaction of H2S with 13X zeolite in the presence of water and with increasing temperature is proposed. The mechanism suggests the dissolution and dissociation of H2S in the water contained in the pores of the zeolite, followed by the formation of elemental sulfur and the possibility of polymerization with increasing temperature.On the other hand, the present invention proposes a new use for NaY zeolite with a Si / Al ratio. Petition 870210107103, dated 11 / 19 / 2021, p. 27 / 46 10 / 19 greater than 2.6, in a PSA process, for the removal of H2S from a natural gas stream. The process allows for the partial regeneration of zeolite in situ.

[0033] In the work of BÜLOW, M.; LUTZ, W.; SUCKOW, M. (1999) “The mutual transformation of hydrogen sulfide and carbonyl sulfide and its role for gas desulfurization processes with zeolite molecular sieve sorbents”, Stud. Surf. Sci. Catal., v. 120, p. 301-345, LTA and FAU type zeolites with low Si / Al ratio are studied for H2S removal in the presence of CO2 and the effect of COS formation in simulated PTSA adsorption and desorption cycles, the latter heated, is evaluated. It was verified that COS formation is not suppressed by modifying the zeolite structure or by means of ion exchange; however, H2S removal is possible by using processes with shorter cycle times, such as the PSA process. The present invention also proposes a PSA process; however, the adsorbent solid used is NaY zeolite with a Si / Al ratio > 2.6.Experiments conducted with this zeolite revealed a high capacity for capturing H2S, stability of the amount captured in subsequent cycles, and high structural stability against the adsorption of this corrosive compound. These aspects reveal the excellent use of NaY zeolite with a Si / Al ratio > 2.6 in the process of removing H2S from natural gas through a PSA process.

[0034] The article by TOMADAKIS, M. M. et al. (2011) “Pressure balance adsorption separation of H2S from CO2 with 4A, 5A and 13X molecular sieves”, set. Sci. Technol., v. 46, p. 428-433, evaluates the separation capacity of binary mixtures containing very high concentrations of H2S and CO2 by means of PSA processes using zeolites 4A, 5A and 13X. It was verified that a high CO2 production capacity was obtained when using zeolites 5A and 4A, with the latter still showing high capacity when regenerated. However, the present invention uses NaY zeolite with a Si / Al ratio greater than 2.6 for the removal of H2S from natural gas by means of a PSA process. Petition 870210107103, dated 11 / 19 / 2021, p. 28 / 46 11 / 19

[0035] The publications cited above reflect the importance of the H2S removal process and reinforce the use of NaY zeolite as an adsorbent material. However, unlike what has already been shown in the literature, and thus with the aim of solving these problems, the present invention was developed by using NaY zeolite with a high Si / Al ratio in a cyclic adsorption process for the selective removal of a natural gas stream. Regeneration of the material is possible by reducing the absolute pressure from the operating pressure to atmospheric pressure. The use of this regenerable material implies a reduction in the need to replace the adsorbent solid in offshore gas extraction platforms, allowing for a reduction in the cost of the purification process.

[0036] In summary, the present invention offers advantages such as reducing costs associated with transporting tons of iron oxide to oil platforms, since in situ regeneration is possible, as the NaY zeolite allows several consecutive adsorption and desorption cycles to be performed before being replaced (if necessary), reducing the need for constant transport.

[0037] Furthermore, the present invention avoids exposure to and handling of a pyrophoric material, currently produced during the desulfurization process with Sulfatreat®, during the discharge of the exhausted adsorption bed. Brief Description of the Invention

[0038] The present invention relates to a process for removing H2S from natural gas at high pressures by means of a PSA process, in which NaY zeolite with a Si / Al ratio > 2.6 is used as a regenerable material for the adsorption of H2S present in natural gas. Regeneration of the material is possible by reducing the absolute pressure from the operating pressure, preferably 51 bar, to atmospheric pressure. The use of this regenerable material implies a reduction in the need for adsorbent replacement in offshore gas extraction platforms, allowing for a reduction in the cost of the purification process. Petition 870210107103, dated 11 / 19 / 2021, page 29 / 46 12 / 19

[0039] The main application involves the removal of H2S from a natural gas stream, which is at high pressure, producing natural gas at high pressures, with the specification of the H2S content through pressure modulated adsorption (PSA) processes. Therefore, potential consumer markets are oil and gas exploration companies. Brief Description of the Drawings

[0040] The present invention will be described in more detail below, with reference to the attached figures which, in a schematic and non-limiting way of the inventive scope, represent examples of its embodiment, wherein: - Figure 1 illustrates the flowchart of the high-pressure adsorption equipment, which was used to evaluate the potential application of NaY zeolite with a Si / Al ratio greater than 2.6 in H2S adsorption, showing: pressurization gas (1) and adsorbate (2); syringe pump (3); micrometer valve at the inlet (4) and outlet (8) of the adsorption bed; adsorption bed (5); mass flow meter (6); vacuum pump (7); 6-way electric valve (9); gas chromatograph (10); and exhaust fan (11); Figure 2 illustrates the H2S breakdown curves in NaY zeolite obtained in the adsorption / desorption cycles; Figure 3 shows a graph containing the amounts of H2S adsorbed in each adsorption cycle; - Figure 4 illustrates (a) the X-ray diffractogram of NaY zeolite, measured before the adsorption and desorption cycles, and (b) the X-ray diffractogram measured after the adsorption / desorption cycles; Figure 5 illustrates adsorption tests performed in the first stage, showing the breakthrough curves for cycles 1 to 5; Figure 6 shows the amount of FteS absorbed / kg of zeolite per cycle; Figure 7 shows the adsorption of the CFU+CCte+FteS+He mixture. Petition 870210107103, dated 11 / 19 / 2021, pp. 30 / 46 13 / 19 Detailed Description of the Invention

[0041] The process for removing H2S from natural gas at high pressures by means of a PSA process, as described by the invention, comprises the following steps: a) To promote contact between a natural gas stream containing H2S and particles of the zeolite adsorbent NaY with a Si / Al ratio > 2.6; b) Pressurization at a pressure of 20 to 80 bar and a temperature of 25 to 70°C; c) Adsorption at constant pressure between 20 and 80 bar and at a temperature of 25 to 70 °C; d) Depressurization from 0.9 to 1.1 bar, at a temperature of 25 to 70°C; e) Purging using H2S-free gas, at a temperature of 25 to 70°C.

[0042] Steps b and c are preferably conducted at a pressure of 51 bar and a temperature of 30°C. Step d is preferably conducted at a pressure of 1 bar and a temperature of 30°C. The natural gas stream for the PSA process has a content of up to 50,000 ppmv of H2S (5.0 % mol.mol·1H2S), noting that the outlet natural gas has an H2S content of less than 5 ppmv.

[0043] Consecutive adsorption and desorption tests were performed in a high-pressure adsorption module, which is illustrated in FIGURE 1. This module allows pressurizing gases (1) or adsorbate (2) to be fed into a syringe pump (3), which controls the gas pressure at the bed inlet (5).The module also features a micrometer valve (4), which allows pressurization control at the bed inlet (5), when necessary; an adsorption bed (5), which allows accommodation of the adsorbent solid; a mass flow meter (6); a vacuum pump (7); a micrometer valve at the bed outlet (8), allowing volumetric flow control at the outlet; a 6-way electrical valve (9), allowing injection. Petition 870210107103, dated 11 / 19 / 2021, page 31 / 46 14 / 19 periodic portions of the effluent gas from the adsorption bed; a gas chromatograph (10), equipped with a thermal conductivity detector (TCD). The effluent gases are conducted to the exhaust (11).

[0044] The invention presents a novel application of NaY zeolite with a Si / Al ratio > 2.6, namely, the removal of hydrogen sulfide from a natural gas stream at pressures of 20 to 80 bar, for the production of gas practically free of H2S at high pressures. The material exhibits partial regenerability in this process when the total operating pressure is reduced to atmospheric pressure. Therefore, the material can be used in a fixed bed for an extended period. Thus, its main advantage is the possibility of regenerating the NaY zeolite in the process equipment, i.e., in situ, eliminating or reducing the exchange of solid material, a process that is very costly in offshore operations. EXAMPLES:

[0045] The following examples are presented to illustrate some particular embodiments of the present invention and should not be interpreted as limiting it.

[0046] To prove the use of NaY zeolite with Si / Al ratio > 2.6 as a regenerable material for H2S adsorption in PSA processes, the following steps for preparing binder-free NaY zeolite particles in H2S adsorption / desorption cycles were carried out as described below. Example 1: Preparation of binder-free NaY zeolite particles.

[0047] The NaY zeolite used, with a Si / Al ratio of 2.8, in powder form, was pelletized in an 8-ton press for 5 minutes. The resulting pellet was crushed and classified using sieves. The content retained between sieves with 65 and 100 mesh was collected, resulting in an average particle diameter of 0.1810 mm. The solid was inserted into the adsorption bed (5) of FIGURE 1. Example 2: Adsorption of He + H2S.

[0048] Consecutive adsorption and desorption tests were performed in a high-pressure adsorption module, which is illustrated in FIGURE 1. This Petition 870210107103, dated 11 / 19 / 2021, pp. 32 / 46 Module 15 / 19 allows pressurizing gases (1) or adsorbate (2) to be fed into a syringe pump (3), which controls the gas pressure at the bed inlet (5). The module also has a micrometer valve (4), which allows pressurization control at the bed inlet (5) when necessary; an adsorption bed (5), which allows accommodation of the adsorbent solid; a mass flow meter (6); a vacuum pump (7); a micrometer valve at the bed outlet (8), allowing control of the volumetric flow rate at the outlet; a 6-way electrical valve (9), allowing periodic injection of portions of the effluent gas from the adsorption bed; a gas chromatograph (10), equipped with a thermal conductivity detector (TCD). The effluent gases are exhausted (11). The tests followed the steps described below: a) Prior to adsorption, a heat treatment aimed at removing water was employed. Initially, helium was flowed at ambient pressure with a flow rate of 50 mL min⁻¹, at a temperature of 300°C, achieved by means of a heating ramp of 10°C min⁻¹. Subsequently, a vacuum was created in the system using a vacuum pump (7). This step lasted 6 hours and was performed only before the first adsorption cycle; b) After the activation procedure, consecutive adsorption / desorption cycles were performed following the sequence of events: Pressurization, Adsorption, Depressurization, and Purging. I. In the pressurization stage, the bed was pressurized to an absolute pressure of 51 bar and a temperature of 30°C. II. In the adsorption stage, a mixture of 4.96 % mol.mol·1 of H2S in 95.04 % of He was passed through the bed (5) at a flow rate of 100 NmL.min⁻¹; III. In the desorption stage, the bed was depressurized from an absolute pressure of 51 bar to an absolute pressure of 1 bar; Petition 870210107103, dated 11 / 19 / 2021, pp. 33 / 46 16 / 19 IV. In the purge stage, He was fed at 100 NmL.min⁻¹, at a total pressure of 1 bar, for 30 min; c) At the end of the purging stage, a new pressurization was performed and the cycle was repeated. In total, the procedure was repeated 15 times; d) The gas composition at the bed outlet was calculated by integrating the peaks detected by the TCD and then applying the external standard method for quantification.

[0049] As shown in FIGURE 2, it can be seen that the breakthrough curves of cycles 2 to 15 are shifted from the curve of cycle 1, for shorter retention times, indicating a decrease in the H2S capture capacity.

[0050] The calculation of the absolute amount adsorbed in each cycle, performed by means of a material balance applied in each adsorption step, reveals that in the first adsorption run the material has the capacity to remove 6.59 mol of H2S per kg of NaY zeolite. In subsequent cycles, this amount reduced, on average, by 25.8%, to 4.89 mol of H2S per kg of NaY zeolite. Despite the reduction, this value remained stable in subsequent cycles, as indicated by FIGURE 3.

[0051] X-ray diffractometry performed on the material before (FIGURE 4 (a)) and after (FIGURE 4 (b)) the H2S adsorption / desorption cycles showed no significant difference. The characteristic peaks of the NaY zeolite (12 to 19) do not show horizontal displacement and have practically the same shape and intensity. In fact, the application of the method described by ASTM D39619 - “Standard Test Method for Determination of Relative X-ray Diffraction Intensities of Faujasite-Type Zeolite-Containing Materials”, indicates a low reduction in crystallinity. The zeolite subjected to the adsorption and desorption cycles showed 96.2% of the crystallinity of the starting zeolite. This fact reveals that the material's structure was not severely affected by prolonged contact with H2S, which proves the stability of the adsorbent solid against consecutive H2S adsorption. Petition 870210107103, dated 11 / 19 / 2021, pp. 34 / 46 17 / 19 Example 3: Adsorption of CH4 + CO2 + H2S.

[0052] Another adsorption test was conducted to verify if the adsorbent material was selective to H2S even in the presence of CH4 and CO2 gases, the main components of natural gas. This test was carried out in two stages. In Stage 1, 5 adsorption and desorption cycles of H2S + He gas were performed, allowing the chemisorption of H2S. In Stage 2, 2 adsorption and desorption cycles of gas containing CH4 + CO2 + H2S + He were performed, allowing the evaluation of the adsorption selectivity of H2S in relation to CH4 and CO2.

[0053] Step 1 was conducted in accordance with the procedures described below: a) A heat treatment was employed to remove the water contained in the adsorbent material. Initially, helium was flowed at ambient pressure with a flow rate of 50 mL.min⁻¹, at a temperature of 300°C, reached by means of a heating ramp of 10°C.min⁻¹. Then, a vacuum was created in the system using a vacuum pump (7). This procedure lasted 6 hours and was performed only before the first adsorption cycle; b) After the activation procedure, consecutive adsorption / desorption cycles were performed following the sequence of events: Pressurization, Adsorption, Depressurization, and Purging. I. In the pressurization process, the bed was pressurized to an absolute pressure of 51 bar and a temperature of 30°C; II. In the adsorption process, a mixture of 4.96 % mol mol·1 of H2S in 95.04 % of He was passed through the bed (5) at a flow rate of 300 NmL.min⁻¹; III. In the desorption process, the bed was depressurized from an absolute pressure of 51 bar to an absolute pressure of 1 bar; IV. In the purging process, He was fed at 300 NmL.min⁻¹, at a total pressure of 1 bar, for 30 min. Petition 870210107103, dated 11 / 19 / 2021, pp. 35 / 46 18 / 19 c) At the end of the purging process, a new pressurization was performed and the cycle was repeated. This procedure was repeated 5 times.

[0054] In Stage 2, the adsorption / desorption tests of ChU+CCte+hhS+He were conducted following the sequence of events: Pressurization, Adsorption, Depressurization and Purging. a) In the pressurization process, the bed was pressurized to an absolute pressure of 51 bar and a temperature of 30°C; b) In the adsorption process, a mixture containing 27.6 mol.mol⁻¹ CPU, 16.9 mol.mol⁻¹ CO₂, 1.98 mol.mol⁻¹ H₂S and 53.5 mol.mol⁻¹ He was passed through bed (5) at a flow rate of 400 NmL.min⁻¹. o) In the desorption process, the bed was depressurized from an absolute pressure of 51 bar to an absolute pressure of 1 bar; d) In the purging process, He was fed at 400 NmL.min⁻¹ at a total pressure of 1 bar for 30 min.

[0055] At the end of the purge stage, new pressurization was carried out and the cycle was repeated.

[0056] The gas composition at the bed outlet was calculated by integrating the peaks detected by the TCD and then applying the external standard method for quantification.

[0057] With regard to the adsorption tests carried out in the first stage, as shown in FIGURE 5, the breakthrough curves of cycles 1 to 5 practically coincide, suggesting that there is little change in the amount adsorbed from one cycle to another.

[0058] The calculation of the absolute amount adsorbed in each cycle, performed using a material balance applied at each adsorption stage, reveals that in the first adsorption run, the material has the capacity to remove 5.92 mol of H2S per kg of NaY zeolite. In subsequent cycles, this amount reduced, on average, by 25.5%, to 4.47 mol of H2S per kg of NaY zeolite. Despite Petition 870210107103, dated 11 / 19 / 2021, pp. 36 / 46 19 / 19 of the reduction, this value remained stable in subsequent cycles, as shown in FIGURE 6.

[0059] Regarding the adsorption of the CFU+CCte+FbS+He mixture, FIGURE 7 shows that the breakthrough curves of CFU and CO2 precede the breakthrough curve of H2S, revealing that CFU and CO2 efflux from the adsorption bed before H2S. It is observed that a free stream of H2S is produced for a time of 32.2 minutes in the first cycle and 37.7 minutes in the second cycle.

[0060] The breakdown curves of CFU and CO2 exhibit the roll-up effect, i.e., their concentrations at the outlet exceed their respective initial concentrations (Li, G., Xiao, P., Xu, D., & Webley, PA (2011). Dual mode roll-up effect in multicomponent non-isothermal adsorption processes with multilayered bed packing. In Chemical Engineering Science (Vol. 66, Issue 9, pp. 1825-1834). Elsevier BV. https: / / doi.Org / 10.1016 / j.ces.2011.01.023). This phenomenon is generally related to the displacement of one component by the other due to different affinities with the solid surface. In this context, it is suggested that both CFU and CO2 are displaced by H2S.

[0061] The high amount of capture verified, the stability of the amount captured in subsequent cycles, even with prolonged contact with H2S at very high concentrations, combined with the high stability of the structure in the adsorption of this corrosive compound, make NaY zeolite a promising adsorbent for removing H2S contained in natural gas, at high pressures, through a PSA process.

[0062] It should be noted that, although the present invention has been described with respect to the attached drawings, it may undergo modifications and adaptations by those skilled in the art, depending on the specific situation, but provided that it is within the inventive scope defined herein. Petition 870210107103, dated 11 / 19 / 2021, pp. 37 / 46

Claims

1 / 1 Claims 1. PROCESS FOR REMOVING H2S FROM NATURAL GAS AT HIGH PRESSURES BY MEANS OF A PSA PROCESS, characterized by comprising the following steps: a) Promoting contact of a natural gas stream containing H2S with particles of the zeolite adsorbent NaY; b) Pressurization at a pressure of 20 to 80 bar and a temperature of 25 to 70 °C; c) Adsorption at constant pressure between 20 and 80 bar and a temperature of 25 to 70 °C; d) Depressurization from 0.9 to 1.1 bar, at a temperature of 25 to 70 °C; e) Purging using H2S-free gas, at a temperature of 25 to 70 °C, in which the zeolite NaY has an average particle diameter of 0.1810 mm.

2. PROCESS, according to claim 1, characterized by the NaY zeolite having a Si / Al ratio equal to or greater than 2.

6.

3. PROCESS, according to claim 1, characterized in that steps b and c are preferably carried out at a pressure of 51 bar and a temperature of 30 °C.

4. PROCESS, according to claim 1, characterized in that step d is preferably carried out at a pressure of 1 bar and a temperature of 30 °C. Petition 870260063788, dated 06 / 29 / 2026, pp. 42 / 43

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