Bifunctional catalysts, methods for making the same, and methods for adsorptive catalytic H2S removal

Abstract

The application relates to the technical field of catalysts and discloses a bifunctional catalyst, wherein the catalyst comprises a carrier and a metal active component loaded on the carrier, the carrier is modified 13X molecular sieve, and the metal active component is Fe2O3 and ZnO; wherein the content of Fe2O3 is 4-5 wt%, the content of ZnO is 2-2.5 wt%, the specific surface active site density of the catalyst is 1000-1500 / m 2 2, and the total weight of the catalyst is taken as the reference. The metal active component and the hydroxyl group on the modified 13X molecular sieve interact with each other, so that the metal active component is fixed on the pore channel; the metal active component and the molecular sieve jointly have good catalytic effects; the active site density on the specific surface is increased by adjusting the matching of the catalyst and the preparation conditions, so that the catalytic activity and selectivity of the catalyst are improved; the catalyst is a bifunctional adsorbent-catalyst which selectively adsorbs H2S and catalyzes H2S into elemental sulfur; and the adsorption desulfurization, adsorbent regeneration and sulfur recovery are integrated.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, specifically to a bifunctional catalyst and its preparation method, and a method for adsorbing and catalyzing H2S. Background Technology

[0002] Natural gas is an important clean energy source, and major countries attach great importance to its proportion in their primary energy mix. The International Energy Agency (IEA) predicts that global natural gas consumption will continue to grow over the next five years. The huge natural gas consumption market and continuously improving exploration technologies have spurred global natural gas development. However, with the vigorous exploitation of natural gas, the remaining resources are becoming increasingly of lower quality, with much of it being sulfur-containing (mainly H2S, with smaller amounts of COS, methanethiol, and other organic sulfur compounds) acidic natural gas. In fact, to obtain more natural gas and sulfur, countries such as Russia, France, Canada, the United States, and Kazakhstan began developing high-sulfur natural gas quite early on.

[0003] Adsorption desulfurization is widely used in processes such as desulfurization, fine desulfurization, and removal of organic sulfur from natural gas with low H2S content. If the natural gas H2S adsorbent used in the adsorption tower also has the function of catalyzing the conversion of H2S into elemental sulfur, multiple adsorption towers can be used simultaneously for adsorption desulfurization of natural gas and recovery of elemental sulfur from the removed H2S. The adsorption towers and sulfur recovery towers operate alternately to achieve a coupled adsorption-sulfur recovery process. Both steps of this technology have numerous industrial applications, technically meeting the requirements of desulfurized natural gas and addressing the issue of H2S treatment, ensuring that the sulfur quality after H2S conversion meets industrial sulfur standards. However, the coupling of the chemical reactions involved in the two steps presents a new challenge: finding an adsorption-catalyst that simultaneously possesses both absorption desulfurization and catalytic conversion functions. Therefore, once this new challenge is addressed, the coupled adsorption desulfurization-catalytic conversion sulfur recovery technology becomes a competitive natural gas desulfurization technology. Summary of the Invention

[0004] The purpose of this invention is to overcome the problem of poor catalyst performance in existing adsorption desulfurization-catalytic conversion sulfur recovery coupling technology, and to provide a bifunctional catalyst, its preparation method, and a method for adsorbing and catalyzing H2S.

[0005] To achieve the above objectives, a first aspect of the present invention provides a bifunctional catalyst, wherein the catalyst comprises: a support and a metal active component supported on the support, wherein the support is a modified 13X molecular sieve, and the metal active component is Fe2O3 and ZnO; wherein, based on the total weight of the catalyst, the content of Fe2O3 is 4-5 wt%, the content of ZnO is 2-2.5 wt%, and the specific surface area active site density of the catalyst is 1000-1500 sites / m². 2 .

[0006] A second aspect of the present invention provides a method for preparing a bifunctional catalyst, comprising:

[0007] (1) 13X molecular sieve was added to an alkaline solution, and after sonication and drying, modified 13X molecular sieve was obtained;

[0008] (2) The bifunctional catalyst was prepared by mixing zinc salt, iron salt and modified 13X molecular sieve, drying and calcining.

[0009] A third aspect of the present invention provides a bifunctional catalyst prepared by the preparation method described above.

[0010] A fourth aspect of the present invention provides a method for adsorbing and catalyzing H2S, wherein the method comprises: performing a desulfurization reaction on crude natural gas containing H2S in the presence of SO2 gas and a catalyst, wherein the catalyst is the bifunctional catalyst described above.

[0011] Through the above technical solution, this invention provides a bifunctional catalyst in which the metal active component interacts with the hydroxyl groups on the modified 13X molecular sieve, fixing the metal active component on the pores. The combined effect of the metal active component and the molecular sieve results in a better catalytic effect. By controlling the catalyst ratio and preparation conditions, the density of active sites on the specific surface area can be increased, thereby improving the catalytic activity and selectivity of the catalyst. Simultaneously, by limiting the specific content of the metal active component, the acidity and alkalinity of the catalyst can be adjusted. The catalyst is a bifunctional adsorbent-catalyst that selectively adsorbs H2S and simultaneously catalyzes H2S to elemental sulfur, achieving integrated adsorption desulfurization, adsorbent regeneration, and sulfur recovery. In terms of process: the integrated natural gas adsorption desulfurization and sulfur recovery process simplifies the traditional multi-equipment combination process of independent adsorption, regeneration, and acid gas sulfur recovery into a limited number of reactors, making operation convenient, saving investment, reducing energy consumption, reducing floor space, and allowing for skid-mounted installation. Detailed Implementation

[0012] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0013] The first aspect of this invention provides a bifunctional catalyst, wherein the catalyst comprises: a support and a metal active component supported on the support, wherein the support is a modified 13X molecular sieve, and the metal active component is Fe2O3 and ZnO; wherein, based on the total weight of the catalyst, the content of Fe2O3 is 4-5 wt%, the content of ZnO is 2-2.5 wt%, and the specific surface area active site density of the catalyst is 1000-1500 sites / m². 2 .

[0014] In this invention, the interaction between the active metal component and the hydroxyl groups on the modified 13X molecular sieve fixes the active metal component on the pores. The combined effect of the active metal component and the molecular sieve results in a better catalytic effect. At the same time, by limiting the specific content of the active metal component, when the content of Fe2O3 is 4-5wt% and the content of ZnO is 2-2.5wt%, the acidity and alkalinity of the catalyst can be adjusted. The resulting catalyst has the highest saturated sulfur capacity and is a bifunctional adsorbent-catalyst that selectively adsorbs H2S and simultaneously catalyzes H2S to elemental sulfur, thus realizing the integration of adsorption desulfurization, adsorbent regeneration, and sulfur recovery.

[0015] In some specific embodiments of the present invention, the modified 13X molecular sieve has a porous structure and a tunable pore size distribution. The modified 13X molecular sieve has suitable pore size and pore structure, which is more conducive to the adsorption of H2S molecules, resulting in better catalytic performance. Simultaneously, it can make the specific surface area of ​​the catalyst have an active site density of 1000-1500 sites / m². 2 .

[0016] In some specific embodiments of the present invention, the specific surface area of ​​the catalyst has an active site density of 1000-1500 sites / m². 2By adjusting the catalyst ratio and preparation conditions, the density of active sites on the specific surface area can be increased, thereby improving the catalytic activity and selectivity of the catalyst. This limitation can bring the following advantages: (1) Increased reaction rate and product selectivity: Increasing the density of active sites can increase the contact opportunities between reactants and catalysts, enhance adsorption and reaction processes, thereby accelerating the reaction rate and improving product selectivity. (2) Reduced catalyst dosage: High active site density means that less catalyst dosage can achieve the same reaction effect, thereby reducing catalyst cost. The specific surface area active site density can be determined by nitrogen adsorption-desorption measurement (BET method) of the catalyst's specific surface area and pore volume, and then the specific surface area active site density can be calculated. The specific surface area active site density is calculated by relating the specific surface area to the number of active sites in the catalyst.

[0017] In some specific embodiments of the present invention, the silicon-to-aluminum ratio of the modified 13X molecular sieve is 2-5:1. The silicon-to-aluminum ratio refers to the molar ratio of silicon to aluminum in the modified 13X molecular sieve. By adjusting the silicon-to-aluminum ratio of the modified 13X molecular sieve within this range, the chemical properties and pore structure of the molecular sieve can be changed, thereby improving the adsorption and catalytic performance of the catalyst.

[0018] In some specific embodiments of the present invention, the average particle size of the catalyst is 0.3-0.5 mm. Smaller particle size increases the contact area between the catalyst and the reactants, improving the adsorption effect. However, excessively small particles may cause a rapid decrease in the adsorption rate after penetration. Therefore, the modified 13X molecular sieve used in this invention has an average particle size of 0.3-0.5 mm, resulting in the optimal catalyst adsorption effect and achieving the best adsorption performance.

[0019] In some specific embodiments of the present invention, the specific surface area of ​​the catalyst is 300-500 m². 2 / g. This limitation can bring the following advantages: (1) The catalyst of the present invention has a higher specific surface area, which can provide more active surface area, increase the contact area between the catalyst and the reactants, and thus promote the increase of reaction rate. More active surface area provides more catalytic active sites, which can make the specific surface active site density of the catalyst 1000-1500 sites / m². 2(1) Increased adsorption and conversion capacity of the catalyst for reactants, thereby effectively improving the catalytic activity of the catalyst, achieving higher reaction conversion rate and product yield, thus improving resource utilization efficiency and reducing catalyst waste. (2) Improved reaction selectivity: The specific surface area of ​​the catalyst plays a key role in the diffusion and transport of reactant molecules. An appropriate specific surface area density can achieve a uniform distribution of reactant molecules on the catalyst surface, reducing non-uniform reactions caused by local concentration changes. This helps to improve the selectivity of the reaction, reduce the occurrence of side reactions, and thus improve the purity and quality of the product. (3) Reaction kinetic control: The regulation of specific surface area can affect the adsorption capacity of the catalyst surface and the diffusion rate of reactant molecules, thereby affecting the reaction kinetic process. By controlling the range of specific surface area, the reaction rate can be effectively controlled and regulated, making the reaction process more controllable and stable.

[0020] In some specific embodiments of the present invention, the pore volume of the catalyst is 0.3-0.5 cm. 3 / g. This limitation can bring the following advantages: (1) Effective diffusion path: An appropriate pore volume range can provide suitable pore size and pore structure, providing a good channel for the diffusion and transfer of reactant molecules. A larger pore volume can provide a wider pore size distribution, promoting the entry and exit of larger molecules into the catalyst interior, which is beneficial to the diffusion-limited reaction. (2) Enhanced catalytic activity: An increase in pore volume can increase the active surface area inside the catalyst, providing more catalytic active sites. These sites can provide more adsorption sites, enhance the interaction between reactant molecules and the catalyst, and help the catalytic reaction to proceed. In addition, a larger pore volume can also provide a larger reaction space, reduce competitive adsorption between reactants, and improve the selectivity of the catalyst. (3) Restriction of reactant molecules: An appropriate pore volume range can restrict the movement of reactant molecules inside the catalyst and reduce the occurrence of side reactions. A smaller pore volume can restrict the entry of larger molecules, thereby reducing non-selective reactions with the catalyst surface. This helps to improve the selectivity of the reaction and improve the purity and quality of the product. (4) Dispersion of reaction heat: A larger pore volume can provide more channels and pores, enhancing the catalyst's ability to disperse reaction heat. The heat generated in the catalytic reaction can be more evenly distributed inside the catalyst, avoiding the formation of local high-temperature areas, reducing the hot spot effect, and improving the stability and service life of the catalyst.

[0021] In some specific embodiments of the present invention, the pH value of the surface acidity / alkalinity of the modified 13X molecular sieve is 8-9.5. The modified 13X molecular sieve has a certain acidity / alkalinity, and the acidity / alkalinity of the catalyst surface can be adjusted by controlling the ratio of the modified 13X molecular sieve and the preparation conditions of the present invention. The role and advantages of limiting the surface acidity / alkalinity include: (1) regulating the adsorption and dissociation of reactants: appropriate acidity / alkalinity can regulate the adsorption and dissociation characteristics of reactants on the catalyst surface, which is beneficial to the reaction and the formation of transition states. (2) controlling the reaction pathway and product selectivity: different acidity / alkalinity conditions can guide different reaction pathways, affecting the product selectivity of the reaction, thereby achieving the desired reaction process and product distribution. (3) stability and lifetime: limiting the stability and lifetime of the catalyst is crucial for achieving long-term stable catalytic performance. Optimizing the catalyst ratio, support selection and surface modification can improve the stability of the catalyst and extend its lifetime. (4) improving the durability of the catalyst: a stable catalyst can maintain its catalytic activity and selectivity over a long period of time, reduce the frequency of catalyst deactivation and regeneration, and improve production efficiency and economy. (5) Reduce catalyst replacement and maintenance costs: Improved stability and lifespan can extend the catalyst's lifespan, reducing the frequency and cost of replacement and maintenance. Surface acidity and alkalinity can be analyzed by measuring the vibrational frequencies and intensities of specific molecules adsorbed on the catalyst surface using Fourier transform infrared spectroscopy (FTIR).

[0022] In some specific embodiments of the present invention, by adjusting the silica-to-alumina ratio, average particle size, specific surface area, and pore volume of the modified 13X molecular sieve, the modified 13X molecular sieve can provide a more optimized pore structure, specific surface area, and adsorption performance, thereby enhancing the interaction between the catalyst and reactants and improving the catalytic activity, selectivity, and stability of the catalyst. The modified 13X molecular sieve possesses a porous structure and a tunable pore size distribution. Through reasonable synthesis and processing methods, the existence of micropores and mesopores can be achieved, and their size and distribution can be adjusted. This porous structure and pore size distribution are beneficial for increasing the surface area, adsorption capacity, and transport rate of the catalyst, thereby improving the catalytic performance of the catalyst.

[0023] A second aspect of the present invention provides a method for preparing a bifunctional catalyst, comprising:

[0024] (1) 13X molecular sieve was added to an alkaline solution, and after sonication and drying, modified 13X molecular sieve was obtained;

[0025] (2) The bifunctional catalyst was prepared by mixing zinc salt, iron salt and modified 13X molecular sieve, drying and calcining.

[0026] In this invention, the chemical properties of 13X molecular sieve are improved by impregnation with an alkaline solution, and the OH- in the alkaline solution... -It reacts with SiO2 in the molecular sieve, causing some of the SiO2 in the molecular sieve to be eroded. The modified 13X molecular sieve has a high specific surface area and well-developed pore volume, thereby changing the original structural characteristics of the molecular sieve and increasing the adsorption performance of the catalyst. Its surface chemical properties play an important role in the removal of hydrogen sulfide and improve the desulfurization effect.

[0027] In some specific embodiments of the present invention, the modified 13X molecular sieve has a silica-to-alumina ratio of 2-5:1, an average particle size of 0.3-0.5 mm, and a specific surface area of ​​300-500 m². 2 / g, with a pore volume of 0.3-0.5cm3 / g.

[0028] In some specific embodiments of the present invention, the alkaline solution is selected from one or more of NaOH solution, KOH solution, and NH4OH.

[0029] In some specific embodiments of the present invention, the zinc salt is selected from one or more of zinc nitrate and zinc chloride.

[0030] In some specific embodiments of the present invention, the iron salt is selected from one or more of ferric nitrate and ferric chloride.

[0031] In some specific embodiments of the present invention, in step (1), the ultrasonic time is 10-20 min, the drying temperature is 80-120℃, and the drying time is 2-4 h.

[0032] In some specific embodiments of the present invention, step (2) further includes allowing the mixture to stand for 8-12 hours after mixing.

[0033] In some specific embodiments of the present invention, in step (2), the drying temperature is 120-150°C and the drying time is 3-6 hours.

[0034] In some specific embodiments of the present invention, in step (2), the calcination temperature is 300-500℃, and the calcination time is 2-4 hours. By controlling the calcination temperature and time, the pore structure and pore size distribution of the catalyst can be adjusted.

[0035] In some specific embodiments of the present invention, relative to 5-10 parts by weight of 13X molecular sieve and 10-20 mL of 25wt% alkaline solution, the zinc and iron salt solution contains 0.5-1 parts by weight of zinc salt and 1-2 parts by weight of iron salt.

[0036] A third aspect of the present invention provides a bifunctional catalyst prepared by the preparation method described above.

[0037] A fourth aspect of the present invention provides a method for adsorbing and catalyzing H2S, wherein the method comprises: performing a desulfurization reaction on crude natural gas containing H2S in the presence of SO2 gas and a catalyst, wherein the catalyst is the bifunctional catalyst described above.

[0038] In some specific embodiments of the present invention, the catalytic reaction temperature is 150-250℃ and the catalytic reaction pressure is 0.5-5MPa.

[0039] In some specific embodiments of the present invention, the ratio of n(H2S) / n(SO2) is 1-3, preferably 2.

[0040] In some specific embodiments of the present invention, the airspeed is 200-500 h. -1 The volume fraction of H2S in the crude natural gas is 1.6-2%, where space velocity refers to the rate at which gas passes through the catalyst per unit time.

[0041] The present invention will be described in detail below through embodiments.

[0042] Specific surface area and active site density determination: Nitrogen adsorption-desorption measurement (BET method) can be used to determine the specific surface area and pore volume of catalysts, and then calculate the specific surface area and active site density.

[0043] General steps for determining the density of active sites on the specific surface area of ​​a catalyst using the BET method:

[0044] (1) Preparation of catalyst samples: Catalyst samples are usually pretreated at high temperature to remove any adsorbent. This is to ensure that the sample is in a dry state.

[0045] (2) Nitrogen adsorption: The dry catalyst sample is exposed to liquid nitrogen, and then nitrogen gas is exposed to it, so that the nitrogen gas is adsorbed onto the catalyst surface.

[0046] (3) Nitrogen desorption: The catalyst sample was gradually heated while nitrogen desorption was monitored. This can be used to determine the adsorption and desorption isotherms.

[0047] (4) Data analysis: Adsorption-desorption data were analyzed using methods such as the BET equation to calculate the specific surface area and specific surface active site density of the catalyst.

[0048] The density of active sites on specific surface area is calculated by relating the specific surface area to the number of active sites in the catalyst.

[0049] Surface acidity and basicity determination: Fourier transform infrared spectroscopy (FTIR) can analyze the acidity and basicity of a catalyst by measuring the vibrational frequency and intensity of specific molecules adsorbed on the catalyst surface.

[0050] Unless otherwise specified in the following examples and comparative examples, all conditions were performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments used, unless otherwise specified, are all commercially available products.

[0051] Example 1

[0052] (1) After grinding and sieving the 13X molecular sieve, select molecular sieves with an average particle size of 0.3-0.5 mm and wash them repeatedly in deionized water until the water is clear and free of suspended matter. Then soak them in deionized water for 4 hours, filter them, and dry them in a drying oven at 105℃ for 12 hours to obtain the original sample of the pretreated 13X molecular sieve.

[0053] (2) The 13X molecular sieve after grinding and sieving was dried in a drying oven at 105℃ for 12h, and then calcined in a muffle furnace at 500℃ for 3h to obtain the pretreated 13X molecular sieve.

[0054] (3) The pretreated 13X molecular sieve was added evenly to 15 ml of 25 wt% alkaline solution, ultrasonically vibrated for 30 min and then left to stand for 1 hour. After that, it was dried in a drying oven at 105 ℃ for 12 hours to prepare the modified 13X molecular sieve.

[0055] (4) Weigh different masses of zinc nitrate and ferric nitrate, dissolve them completely in distilled water, and then add 20.0 g of modified 13X molecular sieve. Stir evenly and let stand for 24 h, then dry at 120℃ for several hours. The dried desulfurizing agent is placed in a muffle furnace at 350℃ for 2 h under N2 protection and then cooled to obtain bifunctional catalyst A1.

[0056] Based on the total weight of the catalyst, the Fe2O3 content is 4.5wt% and the ZnO content is 2.5wt%; the silicon-to-aluminum ratio of the modified 13X molecular sieve is 3:1.

[0057] Example 2

[0058] (1) After grinding and sieving the 13X molecular sieve, select molecular sieves with an average particle size of 0.3-0.5 mm and wash them repeatedly in deionized water until the water is clear and free of suspended matter. Then soak them in deionized water for 4 hours, filter them, and dry them in a drying oven at 105℃ for 12 hours to obtain the original sample of the pretreated 13X molecular sieve.

[0059] (2) The 13X molecular sieve after grinding and sieving was dried in a drying oven at 105℃ for 12h, and then calcined in a muffle furnace at 500℃ for 3h to obtain the pretreated 13X molecular sieve.

[0060] (3) The pretreated 13X molecular sieve was added to the alkaline solution in a uniform ratio, ultrasonically vibrated for 30 min and then left to stand for 1 hour. After that, it was dried in a drying oven at 105℃ for 12 hours to prepare the modified 13X molecular sieve.

[0061] (4) Weigh different masses of zinc nitrate and ferric nitrate, dissolve them completely in distilled water, and then add 20.0 g of modified 13X molecular sieve. After stirring evenly, let stand for 24 h, and then dry at 120℃ for several hours. The dried desulfurizing agent is placed in a muffle furnace at 350℃ for 2 h under N2 protection, and then cooled to obtain bifunctional catalyst A2;

[0062] Based on the total weight of the catalyst, the Fe2O3 content is 4wt%, the ZnO content is 3wt%, and the silica-alumina ratio of the modified 13X molecular sieve is 4:1.

[0063] Example 3

[0064] (1) After grinding and sieving the 13X molecular sieve, select molecular sieves with an average particle size of 0.3-0.5 mm and wash them repeatedly in deionized water until the water is clear and free of suspended matter. Then soak them in deionized water for 4 hours, filter them, and dry them in a drying oven at 105℃ for 12 hours to obtain the original sample of the pretreated 13X molecular sieve.

[0065] (2) The 13X molecular sieve after grinding and sieving was dried in a drying oven at 105℃ for 12h, and then calcined in a muffle furnace at 500℃ for 3h to obtain the pretreated 13X molecular sieve.

[0066] (3) The pretreated 13X molecular sieve was added to the alkaline solution in a uniform ratio, ultrasonically vibrated for 30 min and then left to stand for 1 hour. After that, it was dried in a drying oven at 105℃ for 12 hours to prepare the modified 13X molecular sieve.

[0067] (4) Weigh different masses of zinc nitrate and ferric nitrate, dissolve them completely in distilled water, and then add 20.0 g of modified 13X molecular sieve. After stirring evenly, let stand for 24 h, and then dry at 120℃ for several hours. The dried desulfurizing agent is placed in a muffle furnace at 350℃ for 2 h under N2 protection, and then cooled to obtain bifunctional catalyst A3;

[0068] Based on the total weight of the catalyst, the content of Fe2O3 is 5.0 wt%, the content of ZnO is 2.0 wt%, and the silica-alumina ratio of the modified 13X molecular sieve is 5:1.

[0069] Example 4

[0070] (1) After grinding and sieving the 13X molecular sieve, select molecular sieves with an average particle size of 0.4-0.6 mm and wash them repeatedly in deionized water until the water is clear and free of suspended matter. Then soak them in deionized water for 4 hours, filter them, and dry them in a drying oven at 105℃ for 12 hours to obtain the original sample of the pretreated 13X molecular sieve.

[0071] (2) The 13X molecular sieve after grinding and sieving was dried in a drying oven at 105℃ for 12h, and then calcined in a muffle furnace at 500℃ for 3h to obtain the pretreated 13X molecular sieve.

[0072] (3) The pretreated 13X molecular sieve was added to the alkaline solution in a uniform ratio, ultrasonically vibrated for 30 min and then left to stand for 1 hour. After that, it was dried in a drying oven at 105℃ for 12 hours to prepare the modified 13X molecular sieve.

[0073] (4) Weigh different masses of zinc nitrate and ferric nitrate, dissolve them completely in distilled water, and then add 20.0 g of modified 13X molecular sieve. After stirring evenly, let stand for 24 h, and then dry at 120℃ for several hours. The dried desulfurizing agent is placed in a muffle furnace at 350℃ for 2 h under N2 protection, and then subjected to subsequent cooling treatment to obtain bifunctional catalyst A4;

[0074] Based on the total weight of the catalyst, the Fe2O3 content is 4.5wt%, the ZnO content is 2.5wt%, and the silica-alumina ratio of the modified 13X molecular sieve is 3:1.

[0075] Example 5

[0076] (1) After grinding and sieving the 13X molecular sieve, select molecular sieves with an average particle size of 0.2-0.4 mm and wash them repeatedly in deionized water until the water is clear and free of suspended matter. Then soak them in deionized water for 4 hours, filter them, and dry them in a drying oven at 105℃ for 12 hours to obtain the original sample of the pretreated 13X molecular sieve.

[0077] (2) The 13X molecular sieve after grinding and sieving was dried in a drying oven at 105℃ for 12h, and then calcined in a muffle furnace at 500℃ for 3h to obtain the pretreated 13X molecular sieve.

[0078] (3) The pretreated 13X molecular sieve was added to the alkaline solution in a uniform ratio, ultrasonically vibrated for 30 min and then left to stand for 1 hour. After that, it was dried in a drying oven at 105℃ for 12 hours to prepare the modified 13X molecular sieve.

[0079] (4) Weigh different masses of zinc nitrate and ferric nitrate, dissolve them completely in distilled water, and then add 20.0 g of modified 13X molecular sieve. Stir evenly and let stand for 24 h, then dry at 120℃ for several hours. The dried desulfurizer is placed in a muffle furnace at 350℃ for 2 h under N2 protection, and then cooled to obtain bifunctional catalyst A5;

[0080] Based on the total weight of the catalyst, the Fe2O3 content is 4.5wt%, the ZnO content is 2.5wt%, and the silica-alumina ratio of the modified 13X molecular sieve is 3:1.

[0081] Example 6

[0082] (1) After grinding and sieving the 13X molecular sieve, select molecular sieves with an average particle size of 0.5-0.7 mm and wash them repeatedly in deionized water until the water is clear and free of suspended matter. Then soak them in deionized water for 4 hours, filter them, and dry them in a drying oven at 105℃ for 12 hours to obtain the original sample of the pretreated 13X molecular sieve.

[0083] (2) The 13X molecular sieve after grinding and sieving was dried in a drying oven at 105℃ for 12h, and then calcined in a muffle furnace at 500℃ for 3h to obtain the pretreated 13X molecular sieve.

[0084] (3) The pretreated 13X molecular sieve was added to the alkaline solution in a uniform ratio, ultrasonically vibrated for 30 min and then left to stand for 1 hour. After that, it was dried in a drying oven at 105℃ for 12 hours to prepare the modified 13X molecular sieve.

[0085] (4) Weigh different masses of zinc nitrate and ferric nitrate, dissolve them completely in distilled water, and then add 20.0 g of modified 13X molecular sieve. Stir evenly and let stand for 24 h, then dry at 120℃ for several hours. The dried desulfurizing agent is placed in a muffle furnace at 350℃ for 2 h under N2 protection, and then cooled to obtain bifunctional catalyst A6;

[0086] Based on the total weight of the catalyst, the Fe2O3 content is 4.5wt%, the ZnO content is 2.5wt%, and the silicon-to-aluminum ratio of the modified 13X molecular sieve is 1:1.

[0087] Example 7

[0088] (1) After grinding and sieving the 13X molecular sieve, select molecular sieves with an average particle size of 0.3-0.5 mm and wash them repeatedly in deionized water until the water is clear and free of suspended matter. Then soak them in deionized water for 4 hours, filter them, and dry them in a drying oven at 105℃ for 12 hours to obtain the original sample of the pretreated 13X molecular sieve.

[0089] (2) The 13X molecular sieve after grinding and sieving was dried in a drying oven at 105℃ for 12h, and then calcined in a muffle furnace at 500℃ for 3h to obtain the pretreated 13X molecular sieve.

[0090] (3) The pretreated 13X molecular sieve was added to the alkaline solution in a uniform ratio, ultrasonically vibrated for 30 min and then left to stand for 1 hour. After that, it was dried in a drying oven at 105℃ for 12 hours to prepare the modified 13X molecular sieve (silicon-aluminum ratio of 1:1).

[0091] (4) Weigh different masses of zinc nitrate and ferric nitrate, dissolve them completely in distilled water, and then add 20.0 g of modified 13X molecular sieve. After stirring evenly, let stand for 24 h, and then dry at 120℃ for several hours. The dried desulfurizing agent is placed in a muffle furnace at 350℃ for 2 h under N2 protection, and then cooled to obtain bifunctional catalyst A7;

[0092] Based on the total weight of the catalyst, the Fe2O3 content is 4.5wt%, the ZnO content is 2.5wt%, and the silica-alumina ratio of the modified 13X molecular sieve is 6:1.

[0093] Comparative Example 1

[0094] (1) After grinding and sieving the 10X molecular sieve, select molecular sieves with an average particle size of 0.3-0.5mm and wash them repeatedly in deionized water until the water is clear and free of suspended matter. Then soak them in deionized water for 4 hours, filter them, and dry them in a drying oven at 105℃ for 12 hours to obtain the original sample of the pretreated 13X molecular sieve.

[0095] (2) The 10X molecular sieve after grinding and sieving was dried in a drying oven at 105℃ for 12h, and then calcined in a muffle furnace at 500℃ for 3h to obtain the pretreated 10X molecular sieve.

[0096] (3) The pretreated 10X molecular sieve was added to the alkaline solution in a uniform ratio, ultrasonically vibrated for 30 min and then left to stand for 1 hour. After that, it was dried in a drying oven at 105℃ for 12 hours to prepare the modified 13X molecular sieve.

[0097] (4) Weigh different masses of zinc nitrate and ferric nitrate, dissolve them completely in distilled water, and then add 20.0 g of modified 10X molecular sieve. Stir evenly and let stand for 24 h, then dry at 120℃ for several hours. The dried desulfurizing agent is placed in a muffle furnace at 350℃ for 2 h under N2 protection and then cooled to obtain catalyst B1;

[0098] Based on the total weight of the catalyst, the Fe2O3 content is 4.5wt%, the ZnO content is 2.5wt%, and the silicon-to-aluminum ratio of the modified 10X molecular sieve is 3:1.

[0099] Comparative Example 2

[0100] (1) After grinding and sieving the 10X molecular sieve, select molecular sieves with an average particle size of 0.3-0.5 mm and wash them repeatedly in deionized water until the water is clear and free of suspended matter. Then soak them in deionized water for 4 hours, filter them, and dry them in a drying oven at 105℃ for 12 hours to obtain the original sample of the pretreated 10X molecular sieve.

[0101] (2) The 10X molecular sieve after grinding and sieving was dried in a drying oven at 105℃ for 12h, and then calcined in a muffle furnace at 500℃ for 3h to obtain the pretreated 10X molecular sieve.

[0102] (3) The pretreated 10X molecular sieve was added to the alkaline solution in a uniform ratio, ultrasonically vibrated for 30 min and then left to stand for 1 hour. After that, it was dried in a drying oven at 105℃ for 12 hours to prepare the modified 10X molecular sieve.

[0103] (4) Weigh different masses of zinc nitrate and ferric nitrate, dissolve them completely in distilled water, and then add 20.0 g of modified 10X molecular sieve. After stirring evenly, let stand for 24 h, and then dry at 120℃ for several hours. The dried desulfurizing agent is placed in a muffle furnace at 350℃ for 2 h under N2 protection, and then cooled to obtain bifunctional catalyst B2;

[0104] Based on the total weight of the catalyst, the Fe2O3 content is 4.5 wt%, the ZnO content is 4 wt%, and the silicon-to-aluminum ratio of the modified 10X molecular sieve is 3:1.

[0105] Comparative Example 3

[0106] (1) After grinding and sieving the 13X molecular sieve, select molecular sieves with an average particle size of 0.3-0.5 mm and wash them repeatedly in deionized water until the water is clear and free of suspended matter. Then soak them in deionized water for 4 hours, filter them, and dry them in a drying oven at 105℃ for 12 hours to obtain the original sample of the pretreated 13X molecular sieve.

[0107] (2) The 13X molecular sieve after grinding and sieving was dried in a drying oven at 105℃ for 12h, and then calcined in a muffle furnace at 500℃ for 3h to obtain the pretreated 13X molecular sieve.

[0108] (3) The pretreated 13X molecular sieve was added to the alkaline solution in a uniform ratio, ultrasonically vibrated for 30 min and then left to stand for 1 hour. After that, it was dried in a drying oven at 105℃ for 12 hours to prepare the modified 13X molecular sieve.

[0109] (4) Weigh different masses of zinc nitrate and ferric nitrate, dissolve them completely in distilled water, and then add 20.0 g of modified 13X molecular sieve. After stirring evenly, let stand for 24 h, and then dry at 120℃ for several hours. The dried desulfurizing agent is placed in a muffle furnace at 350℃ for 2 h under N2 protection, and then cooled to obtain bifunctional catalyst B3;

[0110] Based on the total weight of the catalyst, the Fe2O3 content is 6wt% and the ZnO content is 2.5wt%; the silicon-to-aluminum ratio of the modified 13X molecular sieve is 3:1.

[0111] Test Example 1

[0112] The testing methods for adsorbent performance are divided into static and dynamic methods. Since this experiment mixes hydrogen sulfide with various gases, the hydrogen sulfide will be adsorbed by the adsorbent when passing through the adsorption bed. Therefore, detecting the hydrogen sulfide concentration at the fixed bed outlet is an important indicator for evaluating the adsorbent's adsorption effect. When hydrogen sulfide is detected at the fixed bed outlet, it indicates that the desulfurizer has penetrated. Measurement continues until the outlet concentration reaches a certain value, at which point the measurement stops. A breakthrough curve for the adsorbent is obtained by plotting the concentration of hydrogen sulfide in the outlet gas against time.

[0113] Evaluation indicators for adsorbent desulfurization include breakthrough time, breakthrough sulfur capacity, saturated sulfur capacity, and hydrogen sulfide conversion rate.

[0114] Sulfur capacity is defined as the mass of hydrogen sulfide adsorbed per unit mass of adsorbent, typically expressed in mg / g. Sulfur capacity can be determined through calculation or by directly measuring the mass change of the adsorbent before and after adsorption. When other evaluation conditions remain constant, there is a correlation between the sulfur capacity of the adsorbent and time.

[0115] Transmission sulfur capacity: The mass of hydrogen sulfide adsorbed per unit mass of adsorbent when the hydrogen sulfide concentration at the adsorption bed outlet reaches a certain level is called the transmission sulfur capacity. Considering the safety of desulfurization adsorbents in practical applications and the generally high requirements for desulfurization efficiency, this experiment defines the time when the hydrogen sulfide concentration at the adsorption bed outlet is 1 ppm as the breakthrough time, and the sulfur capacity at this point is called the transmission sulfur capacity. The formula for calculating the transmission sulfur capacity is as follows:

[0116]

[0117] Where: q represents the sulfur penetration capacity of the adsorbent, in mg / g;

[0118] Q represents the gas flow rate, in mL / min;

[0119] T represents the penetration time, in minutes;

[0120] C0 represents the hydrogen sulfide concentration at the inlet of the adsorption bed, in mg / m³. 3 ;

[0121] CT indicates the hydrogen sulfide concentration at the adsorption bed outlet, in mg / m³. 3 ;

[0122] m represents the mass of the adsorbent before desulfurization, in grams.

[0123] The reaction stopped when the hydrogen sulfide concentration at the adsorption bed outlet was 50% of the inlet concentration. This experiment used the breakthrough sulfur capacity and breakthrough curve as important indicators for evaluating adsorption performance.

[0124] An adsorbent is loaded into a reactor, which is then filled with a bifunctional adsorbent. During continuous operation, the same reactor operates in one of three states: adsorption, regeneration, or cooling. These three states are cyclically switched to achieve continuous operation of natural gas desulfurization, sulfur recovery, and adsorbent regeneration. The feed gas used in the experiment contained 1.6% H2S by volume, with the remainder being nitrogen. The experimental pressure was 0.5 MPa, and the space velocity ratio was 450 h⁻¹. -1 The absorbent particle size is 0.4 mm, and the gas flow rate is 380 mL / min.

[0125] Following the above method, the sulfur capacity and sulfur recovery rate of the catalysts in the examples and comparative examples were tested, and the results are shown in Table 1.

[0126] Table 1

[0127]

[0128]

[0129] Table 1 (continued)

[0130]

[0131]

[0132] As can be seen from the results in Table 1, this invention provides a catalyst system based on 13X molecular sieve. By adjusting parameters such as component content, physical properties, and metal weight ratio, the catalyst performance can be optimized and adjusted.

[0133] The results of Examples 1-3 and Examples 4-5 show that adjusting the pH value of the catalyst surface can affect the performance of the catalyst. When the pH value of the catalyst surface is 8-9.5, the catalyst has better specific surface active site density, sulfur capacity and sulfur recovery rate.

[0134] The results of Examples 1 and 6-7 show that the performance of the catalyst can be affected by adjusting the silica-alumina ratio of the modified 13X molecular sieve, and the modified 13X molecular sieve with a silica-alumina ratio of 2-5:1 has a better catalytic effect.

[0135] The results of Example 1 and Comparative Example 1 show that the 13X molecular sieve of this application has better performance than other molecular sieves. The results of Comparative Examples 2-3 verify the importance of the metal weight ratio used in Example 1. Setting the metal weight ratio outside the scope of this application will lead to poor catalytic performance and a significant reduction in the density of active sites on the catalyst surface.

[0136] In summary, through the analysis of the examples and comparative examples, we can see the innovation and originality of this invention in catalyst design and performance optimization, providing new ideas and methods for research and application in the field of catalysis.

[0137] Test Example 2

[0138] The effects of the catalyst in Example 1 on sulfur recovery rate under different n(H2S) / n(SO2), pressure, and temperature were determined, and the results are shown in Tables 2-4.

[0139] Table 2. Effect of n(H2S) / n(SO2) on sulfur recovery rate

[0140] 1.7 97.4 1.8 97.5 1.9 98.2 2.0 98.5 2.1 98.0

[0141] Table 3 Effect of pressure on sulfur recovery rate YS (%)

[0142] 10 98.2 20 98.1 40 95.4 60 92.7 80 88.6 100 83.4

[0143] Table 4 Effect of temperature on sulfur recovery rate YS (%)

[0144] 150 98.5 180 98.4 210 98.2 240 98.0 270 97.7 310 97.5

[0145] Optimize the adsorbent-catalyst and adsorbent sulfur recovery process to reduce side reactions and tail gas composition. To achieve the highest sulfur recovery rate, the n(H2S) / n(SO2) ratio is maintained at approximately stoichiometric ratio 2, resulting in very low SO2 in the tail gas. Simultaneously, ensure the hydrolysis of COS and CS2; therefore, the reactor needs to be maintained at a relatively high temperature, typically controlled between 150℃ and 310℃. Optimize the adsorption process conditions. This experiment selected 13X with an intermediate particle size of 0.5-0.3 mm as the molecular sieve adsorption experimental conditions. Increasing the bed height and space velocity ratio significantly increased the breakthrough time and saturation time. When the bed height was 4 cm, the breakthrough time reached 196 min, and the breakthrough sulfur capacity was 45.3 mg / g. The desulfurization performance of the Zn-Fe / 13X adsorbent differed at three different temperatures: 20℃, 40℃, and 80℃. As the temperature increased, the desulfurization performance of the molecular sieve gradually decreased, the breakthrough time shortened, the residence time of H2S gas on the adsorbent decreased, and the adsorbent rapidly saturated after breakthrough. Regarding the optimization of sulfur recovery process conditions, to achieve the highest sulfur recovery rate, the ratio of n(H2S) / n(SO2) must be strictly controlled to around 2. Higher H2S concentrations are beneficial for improving H2S conversion rates. Sulfur recovery reactions tend to proceed at low atmospheric pressure; the higher the pressure, the worse the effect. The temperature of the catalytic reactor has a significant impact on the total sulfur recovery rate. When the reactor temperature decreases from 310℃ to 150℃, the total sulfur recovery rate of acidic gas with a 3% H2S concentration increases sequentially.

[0146] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A bifunctional catalyst, characterized in that, The catalyst comprises: a support and a metallic active component supported on the support, wherein the support is a modified 13X molecular sieve, and the metallic active component is Fe2O3 and ZnO; wherein, based on the total weight of the catalyst, the content of Fe2O3 is 4-5 wt%, the content of ZnO is 2-2.5 wt%, and the specific surface area active site density of the catalyst is 1000-1500 sites / m². 2 ; The modified 13X molecular sieve has a silica-to-alumina ratio of 2-5:1; The modified 13X molecular sieve has a surface acidity / alkalinity of pH 8-9.5; Modified 13X molecular sieve was obtained by exchanging 13X molecular sieve with an alkaline solution, followed by sonication and drying.

2. The catalyst according to claim 1, characterized in that, The catalyst has an average particle size of 0.3-0.5 mm.

3. The catalyst according to claim 1, characterized in that, The catalyst has a specific surface area of ​​300-500 m². 2 / g.

4. The catalyst according to claim 1, characterized in that, The catalyst has a pore volume of 0.3-0.5 cm³. 3 / g.

5. A method for preparing a bifunctional catalyst according to any one of claims 1-4, characterized in that, include: (1) 13X molecular sieve was exchanged with an alkaline solution, and then subjected to ultrasonication and drying to obtain modified 13X molecular sieve; (2) The modified 13X molecular sieve was mixed with zinc salt and iron salt solution, dried and calcined to prepare the bifunctional catalyst.

6. The preparation method according to claim 5, characterized in that, The modified 13X molecular sieve has an average particle size of 0.3-0.5 mm and a specific surface area of ​​300-500 m². 2 / g, pore volume 0.3-0.5 cm³ 3 / g.

7. The preparation method according to claim 5, characterized in that, The alkaline solution is selected from one or more of NaOH solution, KOH solution, and NH4OH.

8. The preparation method according to claim 5, characterized in that, The zinc salt is selected from one or more of zinc nitrate, zinc sulfate, and zinc chloride.

9. The preparation method according to claim 5, characterized in that, The iron salt is selected from one or more of ferric nitrate, ferric sulfate, and ferric chloride.

10. The preparation method according to claim 5, characterized in that, In step (1), the ultrasound time is 10-20 min, the drying temperature is 80-120℃, and the drying time is 2-4 h.

11. The preparation method according to claim 5, characterized in that, Step (2) also includes allowing the mixture to stand for 8-12 hours after mixing.

12. The preparation method according to claim 5, characterized in that, In step (2), the drying temperature is 120-150℃ and the drying time is 3-6h.

13. The preparation method according to claim 5, characterized in that, In step (2), the roasting temperature is 300-500℃ and the roasting time is 2-4h.

14. The preparation method according to any one of claims 5-13, characterized in that, The zinc and iron salt solution contains 0.5-1 parts by weight of zinc salt and 1-2 parts by weight of iron salt, relative to 5-10 parts by weight of 13X molecular sieve and 10-20 mL of 25 wt% alkaline solution.

15. A method for adsorbing and catalyzing H2S, characterized in that, The method includes: performing a desulfurization reaction on crude natural gas containing H2S in the presence of SO2 gas and a catalyst, wherein the catalyst is a bifunctional catalyst as described in any one of claims 1-4 or a bifunctional catalyst prepared by the preparation method described in any one of claims 5-14.

16. The method according to claim 15, characterized in that, The desulfurization reaction temperature is 150-250℃, and the desulfurization reaction pressure is 0.5-5MPa.

17. The method according to claim 15, characterized in that, The amount of SO2 gas introduced satisfies the molar ratio of H2S to SO2 being 1-3.

18. The method according to claim 17, characterized in that, The amount of SO2 gas introduced satisfies the molar ratio of H2S to SO2 of 2.

19. The method according to any one of claims 15-18, characterized in that, Airspeed is 200-500 h -1 The volume fraction of H2S in the crude natural gas is 1.6-2%.

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