Catalyst for low-temperature hydrolysis of carbonyl sulfide and preparation method thereof

Abstract

The embodiment of the invention provides a catalyst for low-temperature hydrolysis of carbonyl sulfide and a preparation method of the catalyst, and belongs to the technical field of desulfurization. The preparation method comprises the following steps: by taking gamma-Al2O3 as an active carrier and ionic liquid consisting of organic cations and halogen anions as a promoter, loading the ionic liquid on the surface of the gamma-Al2O3 to form a catalyst; under the assistant catalysis effect of organic cations, one part of aluminum sites on the surface of gamma-Al2O3 of the catalyst and halogen anions form covalent bonds or ionic bonds, and the other part of aluminum sites adsorb H2O and enable the H2O to be dissociated continuously to generate alkaline hydroxyl for hydrolyzing carbonyl sulfide. According to the catalyst disclosed by the invention, the reaction temperature for hydrolyzing carbonyl sulfide is reduced to be below 100 DEG C, and meanwhile, the catalyst has the carbonyl sulfide hydrolysis conversion rate of over 80 percent and the hydrogen sulfide selectivity of over 90 percent.

Description

Technical Field

[0001] The invention belongs to the technical field of desulfurization, and particularly relates to a catalyst for low-temperature hydrolysis of carbonyl sulfide and a preparation method thereof. Background Art

[0002] Carbonyl sulfide is widely present in blast furnace gas, natural gas, petroleum gas and Claus tail gas. It is a colorless, smelly and harmful gas. The presence of carbonyl sulfide not only seriously pollutes the environment and harms human health, but also has an adverse effect on the stability of downstream catalysts.

[0003] Carbonyl sulfide is generally treated by hydrolysis, in which metal oxides, hydrotalcite-derived mixed metal oxides, carbon-based porous materials, etc. are usually used as catalysts.

[0004] Among metal oxide catalysts, γ-Al2O3 has high catalytic activity and stability, but it requires a higher hydrolysis reaction temperature, usually higher than 150°C or even 200°C to show strong catalytic activity. The higher the hydrolysis reaction temperature, the more thermodynamic restrictions there are in the hydrolysis process, and the higher energy consumption reduces economic efficiency.

[0005] Other catalysts (such as layered double hydroxide-derived mixed metal oxides, carbon-based porous materials, etc.) can achieve strong catalytic activity below 100°C, but as the hydrolysis reaction continues, the catalytic activity will gradually decrease or even become inactivated due to problems such as the reduction of surfactants or pore blockage, resulting in poor stability of these catalysts, inability to adapt to industrial applications, and poor economic efficiency.

[0006] In view of this, a new catalyst for low-temperature hydrolysis of carbonyl sulfide and a preparation method thereof are needed to completely or partially solve the above problems. Summary of the invention

[0007] In order to solve at least one aspect of the above problems and defects in the prior art, the embodiments of the present invention provide a catalyst for low-temperature hydrolysis of carbonyl sulfide and a preparation method thereof, by loading an ionic liquid composed of organic cations and halogen anions as a catalyst promoter onto the surface of γ-Al2O3, so that the reaction temperature of hydrolysis of carbonyl sulfide is reduced to below 100°C, and at the same time, the carbonyl sulfide hydrolysis conversion rate exceeds 80% and the hydrogen sulfide selectivity exceeds 90%. The technical solution is as follows:

[0008] According to one aspect of an embodiment of the present invention, a method for preparing a catalyst for low-temperature hydrolysis of carbonyl sulfide is provided.

[0009] The preparation method comprises: using γ-Al2O3 as an active carrier, using an ionic liquid composed of organic cations and halogen anions as a catalyst promoter, and loading the ionic liquid on the surface of γ-Al2O3 to form a catalyst; under the catalyst promoter action of the organic cation, a part of the aluminum sites on the surface of the γ-Al2O3 of the catalyst forms a covalent bond or an ionic bond with the halogen anion, and the other part adsorbs H2O and causes it to continuously dissociate to generate alkaline hydroxyl groups for hydrolyzing carbonyl sulfide.

[0010] In some embodiments, specifically, Al in the tetrahedral gap formed by O located on the surface of γ-Al2O3 forms a covalent bond or an ionic bond with a halogen anion, and the bond length of the covalent bond or the ionic bond ranges from 2 to 2.5 angstroms; Al in the octahedral gap formed by O located on the surface of γ-Al2O3 is used to adsorb H2O and generate basic hydroxyl groups after dissociation and coordination.

[0011] In some embodiments, the halogen anion forms a covalent bond or an ionic bond with Al in the tetrahedral gap, specifically through the long chain group of the organic cation.

[0012] In some embodiments, the organic cation is alternatively a tetraalkyl quaternary phosphonium salt ion or a tetraalkyl quaternary ammonium salt ion.

[0013] In some embodiments, specifically, the steps of the preparation method specifically include:

[0014] Pseudo-boehmite is placed in a muffle furnace and calcined to obtain γ-Al2O3;

[0015] Using a solvent to dissolve an ionic liquid composed of organic cations and halogen anions to obtain an ionic solution;

[0016] γ-Al2O3 was added into the ionic solution and the ionic liquid was loaded onto the surface of γ-Al2O3 by ultrasonic impregnation;

[0017] The γ-Al2O3 loaded with ionic liquid is allowed to stand for 12 to 24 hours and then placed in a drying oven at a drying temperature of 60 to 90° C. for 12 to 24 hours to obtain a catalyst for low-temperature hydrolysis of carbonyl sulfide.

[0018] In some embodiments, further, the calcination temperature ranges from 550 to 650° C., and the calcination time ranges from 2 to 6 hours.

[0019] In some embodiments, further, based on the mass of γ-Al2O3, the mass fraction of the ionic liquid ranges from 3% to 20%; the solvent is any one of anhydrous methanol, anhydrous ethanol, acetone and water, or a combination thereof.

[0020] In some embodiments, further, the ultrasonic impregnation is to add γ-Al2O3 to the ionic solution and then subject the obtained mixture to ultrasonic treatment in an ultrasonic cleaning machine for 1 to 3 hours.

[0021] In some embodiments, preferably, tetrabutylphosphine chloride is used as an ionic liquid to load the catalyst obtained by loading the catalyst onto the surface of γ-Al2O3 in a fixed bed reactor at a concentration of 500 to 1000 mg / m 3 The carbonyl sulfide is subjected to a hydrolysis catalytic reaction for 36 hours or more, and a carbonyl sulfide hydrolysis conversion rate of 90% or more and a hydrogen sulfide selectivity of 95% or more are obtained at a catalytic reaction temperature of 50-70°C.

[0022] According to another aspect of the embodiments of the present invention, a catalyst for low-temperature hydrolysis of carbonyl sulfide is provided.

[0023] The catalyst is obtained by using the preparation method described in the above aspects. The catalyst has a carbonyl sulfide hydrolysis conversion rate of greater than or equal to 80% and a hydrogen sulfide selectivity of greater than or equal to 90% at a catalytic reaction temperature of 50-70°C.

[0024] The catalyst for low-temperature hydrolysis of carbonyl sulfide and the preparation method thereof provided by the embodiments of the present invention have at least one or part of the following advantages:

[0025] (1) The catalyst for low-temperature hydrolysis of carbonyl sulfide and the preparation method thereof provided in the embodiments of the present invention are characterized in that an ionic liquid composed of organic cations and halogen anions is loaded onto the surface of γ-Al2O3 as a catalyst promoter, so that the reaction temperature of hydrolysis of carbonyl sulfide is reduced to below 100°C, and the carbonyl sulfide hydrolysis conversion rate is more than 80% and the hydrogen sulfide selectivity is more than 90%;

[0026] (2) The catalyst for low-temperature hydrolysis of carbonyl sulfide and the preparation method thereof provided in the embodiments of the present invention can control the tendency of halogen anions to form covalent bonds or ionic bonds with Al in the tetrahedral gaps through the catalytic effect of organic cations, thereby freeing up more Al in the octahedral gaps for continuous adsorption of H2O and causing H2O to undergo alkaline dissociation to continuously generate alkaline hydroxyl groups for hydrolysis of carbonyl sulfide;

[0027] (3) The catalyst for low-temperature hydrolysis of carbonyl sulfide and the preparation method thereof provided in the embodiments of the present invention further reduce the dissociation energy required for alkaline dissociation of H2O adsorbed by Al in the octahedral interstices by forming covalent bonds or ionic bonds between halogen anions and Al in the tetrahedral interstices, thereby reducing the temperature required for the hydrolysis reaction;

[0028] (4) The catalyst for low-temperature hydrolysis of carbonyl sulfide provided by the embodiments of the present invention and the preparation method thereof can further improve the carbonyl sulfide hydrolysis conversion rate to greater than or equal to 90% at a catalytic reaction temperature of 50 to 70° C. by using tetrabutylphosphonium chloride as an ionic liquid, and the hydrogen sulfide selectivity is improved to greater than or equal to 95%;

[0029] (5) The catalyst for low-temperature hydrolysis of carbonyl sulfide and the preparation method thereof provided in the embodiments of the present invention use an ultrasonic impregnation method to load the ionic liquid onto the surface of γ-Al2O3. Since the vapor pressure of the ionic liquid is almost negligible, the ionic liquid is not easily lost during the preparation process and the catalytic hydrolysis reaction, thereby improving the low-temperature stability of the catalyst;

[0030] (6) The catalyst for low-temperature hydrolysis of carbonyl sulfide and the preparation method thereof provided in the embodiments of the present invention use conventional processes such as muffle furnace calcination and ultrasonic impregnation. The preparation method is simple and can be widely used in the fields of steel, petrochemical, natural gas, etc. to remove carbonyl sulfide. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] These and / or other aspects and advantages of the present invention will become apparent and readily understood from the following description of the preferred embodiments in conjunction with the accompanying drawings, in which:

[0032] Figure 1 A comparison curve diagram of the carbonyl sulfide hydrolysis conversion rates of Examples 1-3 and Comparative Examples 1-5 according to the present invention;

[0033] Figure 2 A comparison curve diagram of hydrogen sulfide selectivity in carbonyl sulfide hydrolysis reactions according to Examples 1-3 of the present invention and Comparative Examples 1-5;

[0034] Figure 3 is a P element distribution map of catalyst A according to Example 1 of the present invention;

[0035] Figure 4 is a Cl element distribution map of catalyst A according to Example 1 of the present invention;

[0036] Figure 5 A comparison diagram of characteristic X-ray diffraction characteristic peak curves of Example 1, Comparative Example 1 and Comparative Example 2 according to the present invention;

[0037] Figure 6 A schematic diagram of a simulated structure of catalyst A constructed by density functional theory (DFT) calculation according to Example 1 of the present invention;

[0038] Figure 7This is a comparison diagram of the dissociation energy curves required for alkaline dissociation of H2O adsorbed by Al in the octahedral gaps on the surfaces of Catalysts A and E obtained by DFT calculation according to Example 1 of the present invention and Comparative Example 2. DETAILED DESCRIPTION

[0039] The technical solution of the present invention is further specifically described below by examples and in conjunction with the accompanying drawings. In the specification, the same or similar reference numerals indicate the same or similar components. The following description of the embodiments of the present invention with reference to the accompanying drawings is intended to explain the overall inventive concept of the present invention and should not be construed as a limitation of the present invention.

[0040] In recent years, the hydrolysis method for treating carbonyl sulfide has received increasing attention, mainly because the hydrolysis method has low comprehensive energy consumption and higher economic efficiency. In particular, low-temperature hydrolysis, the lower the temperature at which the catalytic reaction is achieved, the less thermodynamic constraints the hydrolysis process is subject to.

[0041] The reaction of hydrolyzing carbonyl sulfide is a basic catalytic reaction. When γ-Al2O3 is used as a catalyst, the basic hydroxyl groups on the surface of γ-Al2O3 can be increased by adjusting the conditions of the catalytic reaction, thereby enhancing the catalytic activity of γ-Al2O3 through these basic hydroxyl groups. The basic reaction formula for hydrolyzing carbonyl sulfide (COS) is: COS+H2O←→CO2+H2S.

[0042] When the temperature of the hydrolysis reaction is low (for example, below 100°C), the catalytic activity of γ-Al2O3 is low, and it is difficult to provide sufficient energy to break the OH bond of H2O, resulting in the dissociation of H2O on the surface of γ-Al2O3 being very difficult. The number of basic hydroxyl groups on the surface of γ-Al2O3 is very limited, resulting in the inability to continuously obtain basic hydroxyl groups, which also limits the conversion rate of carbonyl sulfide hydrolysis.

[0043] Therefore, the embodiment of the present invention proposes a novel γ-Al2O3 catalyst and a preparation method thereof, which are used to solve the problem of low activity of γ-Al2O3 catalyst under low-temperature hydrolysis conditions (temperature below 100°C). Specifically, the preparation method uses γ-Al2O3 as an active carrier, an ionic liquid composed of organic cations and halogen anions as a promoter, and loads the ionic liquid on the surface of γ-Al2O3 to form a catalyst; under the promotion of organic cations, a part of the aluminum sites on the surface of γ-Al2O3 of the catalyst forms a covalent bond or an ionic bond with the halogen anion, and the other part adsorbs H2O and causes it to continuously dissociate to generate alkaline hydroxyl for hydrolysis of carbonyl sulfide.

[0044] In one example, the steps of the preparation method specifically include:

[0045] Step S100: placing pseudo-boehmite in a muffle furnace and calcining to obtain γ-Al2O3;

[0046] Step S200: using a solvent to dissolve an ionic liquid composed of organic cations and halogen anions to obtain an ionic solution;

[0047] Step S300: adding γ-Al2O3 to the ionic solution obtained in step S200 and loading the ionic liquid onto the surface of γ-Al2O3 by ultrasonic impregnation;

[0048] Step S400: The γ-Al2O3 loaded with the ionic liquid is placed in a drying oven at a drying temperature of 60 to 90° C. for 12 to 24 hours to obtain a catalyst for low-temperature hydrolysis of carbonyl sulfide.

[0049] In one example, when the active carrier γ-Al2O3 of the catalyst is obtained by step S100, the pseudo-boehmite can alternatively use a finished product, or can be obtained by treating the raw material by, for example, a precipitation method or a sol-gel method. After obtaining the pseudo-boehmite, γ-Al2O3 is prepared by calcining it under appropriate calcination conditions. Preferably, γ-Al2O3 is obtained by calcining the finished pseudo-boehmite in a muffle furnace.

[0050] Furthermore, through a large number of experimental accumulations and empirical references, in order to obtain the best catalytic activity of the catalyst, the carbonyl sulfide hydrolysis conversion rate of the hydrolysis catalytic reaction, and the hydrogen sulfide selectivity, the environmental conditions during the calcination process are also controlled. Specifically, the calcination temperature ranges from 550 to 650° C., and the calcination time ranges from 2 to 6 hours.

[0051] In one example, the catalyst promoter (ionic liquid) is loaded onto the active carrier (γ-Al2O3) to form a substrate of the catalyst through steps S200 and S300. The components of the ionic liquid mainly include organic cations and halogen anions. Alternatively, the organic cation can select a quaternary phosphonium salt or a quaternary ammonium salt, and the halogen anion can select chlorine, bromine, fluorine, iodine, etc. Through previous experimental experience, preferably, one of tetraalkylphosphonium chloride, tetraalkylammonium chloride, and tetraalkylammonium fluoride is selected when preparing the catalyst of each embodiment of the present invention.

[0052] Those skilled in the art will understand that ionic liquids as promoters will directly affect the catalytic activity of the catalyst. The basic principle is that the organic cations in the ionic liquids control the tendency of the halogen anions to interact with the Al in the tetrahedral gaps formed by O on the surface of γ-Al2O3 through the binding effect of their long-chain groups, so that the aluminum sites in the octahedral gaps formed by O are more used to continuously adsorb H2O and continuously dissociate it to generate basic hydroxyl groups. Therefore, in theory, as long as the organic cations have a positive effect on the process of γ-Al2O3 generating basic hydroxyl groups and the structure or chain length of their long-chain groups are suitable, they can be combined with halogen anions to form ionic liquid promoters. This example only provides some illustrative examples, and those skilled in the art should not be understood as a limitation of the present invention.

[0053] In one example, after selecting a suitable ionic liquid catalyst promoter, it is also necessary to adjust the ratio of the ionic liquid catalyst promoter to the active carrier. Alternatively, based on the mass of γ-Al2O3, the mass fraction of the ionic liquid ranges from 3% to 20%, that is, after determining the mass of γ-Al2O3, the mass of the ionic liquid is 3% to 20% of the mass of γ-Al2O3. Preferably, the mass fraction of the ionic liquid ranges from 5% to 15%.

[0054] After determining the mass fraction of the ionic liquid, a common solvent can be used to dissolve the ionic liquid before performing the ultrasonic impregnation process of step S300. Wherein, depending on the specific composition of the ionic liquid and the corresponding solubility characteristics, the solvent can alternatively use an organic solvent with a smaller molecular weight (such as anhydrous methanol, anhydrous ethanol, acetone, etc.), or water can also be used. Further alternatively, when an organic solvent is needed, one of the organic solvents can be used, or a mixture of two, three or more thereof can be used as the organic solvent. Preferably, anhydrous methanol or anhydrous ethanol is used.

[0055] In one example, preferably, the ionic liquid is loaded onto the surface of γ-Al2O3 using ultrasonic impregnation. Specifically, the ionic liquid is dissolved in a solvent and then added to γ-Al2O3 to form a mixed solution, and the mixed solution is ultrasonically treated in an ultrasonic cleaning machine for 1 to 3 hours. Compared with the traditional impregnation method, during the ultrasonic treatment process, the ultrasonic wave has a strong cavitation effect, which can produce a high temperature and high pressure physical state locally, so that the ionic liquid has good dispersibility on the surface of γ-Al2O3, improves its distribution uniformity, and effectively ensures the stability of the catalyst.

[0056] In one example, during the preparation process, it is necessary to control the loading of the ionic liquid on the surface of γ-Al2O3 to not more than 20%. The amount of loading will affect the generation of basic hydroxyl groups. For example, too little loading (less than 3%) will limit the catalytic effect of the ionic liquid. For another example, as the loading increases, it will have some adverse effects on the surface structure of the catalyst. Specifically, too high a loading (more than 20%) will significantly reduce the specific surface area and pore volume of the catalyst, resulting in limited exposure of active sites, which in turn hinders the process of H2O dissociating into basic hydroxyl groups, resulting in a decrease in catalyst activity.

[0057] After step S100 to step S400, and by adjusting specific parameters in the preparation process (such as roasting conditions, the ratio of the catalyst promoter to the active carrier, ultrasonic impregnation conditions, drying conditions, etc.), an ionic liquid-modified γ-Al2O3-based catalyst can be obtained. The catalyst can achieve efficient catalytic hydrolysis of carbonyl sulfide at a low-temperature hydrolysis temperature (at least below 100° C., and each embodiment of the present invention can further reduce the low-temperature hydrolysis temperature to 50-70° C.), and maintain a high selectivity for hydrogen sulfide. The catalyst also has high stability and is not easy to deactivate.

[0058] In one example, based on experimental experience, theoretical simulation and calculation are used in combination with detection equipment (such as X-ray detection equipment, scanning electron microscope equipment, etc.) to obtain characterization of the microstructure of the catalyst and conduct further analysis. The catalyst prepared through steps S100 to S400 can achieve low-temperature hydrolysis of carbonyl sulfide at 50 to 70°C. The mechanism mainly includes two aspects. On the one hand, Al in the majority of tetrahedral gaps on the surface of γ-Al2O3 selects to form covalent bonds or ionic bonds with halogen anions, which makes Al in the majority of octahedral gaps on the surface of γ-Al2O3 vacated and used to adsorb H2O and dissociate and coordinate to generate basic hydroxyl groups. On the other hand, the appropriate length of the long-chain group of the organic cation has a binding effect on the halogen anions, so that most halogen anions form covalent bonds or ionic bonds with Al in the majority of tetrahedral gaps.

[0059] Regarding the first aspect of the above mechanism analysis, specifically, the aluminum sites on the surface of γ-Al2O3 are tetrahedral gaps and octahedral gaps formed by O. The Al of γ-Al2O3 is randomly distributed in the tetrahedral gaps and octahedral gaps formed by O. Under the binding effect of the organic cations of the ionic liquid, during the ultrasonic impregnation process, most of the halogen anions are controlled to form covalent bonds or ionic bonds with the Al located in the tetrahedral gaps. Further detection and characterization by X-ray equipment showed that the bond length of the covalent bond or ionic bond ranged from 2 to 2.5 angstroms (2×10 -10 ~2.5×10 -10 When chloride ions are used, the bond length is generally kept around 2.25 angstroms.

[0060] Further, the covalent bond or ionic bond formed by the halogen anion and the Al in the tetrahedral gap is a bond structure with higher stability. For example, when using fluoride ions, since the fluoride ions have strong electronegativity, the electrons they carry will be offset to one side of the Al ions to affect the electron cloud structure distribution or electron cloud density distribution of the Al ions, so it is easier to form a stable ionic bond. For another example, when using chloride ions and bromide ions, since their electronegativity is not as strong as that of fluoride ions, the positive and negative electrons are balanced when contacting with Al ions, so it is easier to form a stable covalent bond. Whether it is an ionic bond or a covalent bond, the smaller its bond length is, the greater its bond strength is, that is, there is a strong bond strength between the halogen anion and the Al in the tetrahedral gap, and once the load is difficult to disengage, the Al in the tetrahedral gap is stably occupied, thereby vacating the Al in the octahedral gap.

[0061] Furthermore, since Al is also an adsorption site for H2O, if H2O is adsorbed on Al in the tetrahedral interstices, the hydroxyl groups after H2O dissociates and coordinates will show stronger acidity. On the contrary, if H2O is adsorbed on Al in the octahedral interstices, the hydroxyl groups after H2O dissociates and coordinates will show stronger basicity. In other words, if more H2O is adsorbed on Al in the octahedral interstices, more basic hydroxyl groups can be obtained, and the continuously generated basic hydroxyl groups can continuously catalyze the hydrolysis of carbonyl sulfide. Therefore, the vacated Al in the octahedral interstices just provides a path for more H2O to be adsorbed on Al in the octahedral interstices, thereby continuously providing basic hydroxyl groups by continuously adsorbing H2O and dissociating it, and ensuring that γ-Al2O3 has a high catalytic activity even under low temperature conditions.

[0062] Regarding the second aspect of the above mechanism analysis, specifically, the organic cation is actually an ionic group, which is a long-chain group with a certain chain length. Taking the alkyl long chain in tetraalkylphosphonium chloride, tetraalkylammonium chloride or tetraalkylammonium fluoride as an example, the longer the alkyl long chain, the higher its activity. In some experiments, the halogen anion is kept unchanged and the cation is replaced by NH4 + Later, when NH4Cl is loaded on the surface of γ-Al2O3, for example, the catalytic activity of the catalyst finally obtained is lower than that of using only γ-Al2O3 as a catalyst. From a mechanistic analysis, the long-chain group structure of the organic cation can produce a special binding effect on the halogen anion, thereby controlling the activity path of the halogen anion, such as controlling the halogen anion to be loaded on the Al in the tetrahedral gap of γ-Al2O3.

[0063] Furthermore, although the long-chain groups of organic cations have a positive promoting effect on the catalytic activity of the catalyst. However, the chain length of its long-chain groups is not the longer the better, but there is a suitable chain length. In some experiments, when the alkyl organic cations are replaced with phenyl organic cations with larger molecular groups, better or the same catalytic activity as when the alkyl organic cations are used cannot be obtained. The main reason for this is that the molecular groups are too large, making it difficult for such organic cations to enter the pores on the surface of γ-Al2O3 even during the ultrasonic impregnation process, and thus it cannot achieve its role as a catalyst promoter. Instead, it hinders the effective loading of the ionic liquid, and then hinders the increase in the number of basic hydroxyl groups, and it is impossible to achieve enhanced catalyst activity. On the other hand, the long-chain groups of organic cations that are too large may also destroy the Al-O bonds of γ-Al2O3 itself, thereby destroying the bulk structure of γ-Al2O3.

[0064] In one example, according to step S100-step S400 of the preparation method, tetrabutylphosphine chloride (TBuPC), tetrabutylammonium chloride (TBuAF) and tetrapropylammonium chloride (TPAC) are loaded on the surface of γ-Al2O3 to obtain corresponding catalysts, which are marked as catalyst A (TBuPC / γ-Al2O3), catalyst B (TBuAF / γ-Al2O3) and catalyst C (TPAC / γ-Al2O3). The specific preparation and experimental test process are described in detail by the following Examples 1-3.

[0065] Example 1

[0066] Catalyst A (TBuPC / γ-Al2O3) was prepared according to step S100 to step S400.

[0067] (1) Pseudo-boehmite is placed in a muffle furnace and calcined to obtain γ-Al2O3 at a temperature of 550°C for 5 hours;

[0068] (2) Weigh 0.20 g of tetrabutylphosphine chloride (TBuPC) and dissolve it in 5 mL of anhydrous ethanol to obtain an ionic liquid solution, weigh 2 g of the γ-Al2O3 prepared in (1) and add it to the ionic liquid solution to obtain a mixture;

[0069] (3) subjecting the mixture obtained in (2) to ultrasonic treatment in an ultrasonic cleaning machine for 1 hour to complete ultrasonic immersion;

[0070] (4) The mixture was allowed to stand at room temperature for 12 hours, and then placed in a forced air drying oven and dried at 90° C. for 12 hours to obtain catalyst A (TBuPC / γ-Al 2 O 3 ).

[0071] The catalyst A was placed in a fixed bed reactor for experimental testing of low-temperature hydrolysis of carbonyl sulfide. Specifically, 0.3 g of catalyst A was weighed, crushed and sieved to form a 40-60 mesh catalyst A powder, and the catalyst A powder was loaded into a 6 mm quartz tube reactor. The reaction temperature was set to 60°C, and the mixed gas of carbonyl sulfide and N2 was first passed into a bubbler. The bubbler was controlled to a temperature of 25°C through a water bath to form a raw gas to be treated that carried water vapor. Then the raw gas to be treated that carried water vapor was passed into a quartz tube reactor containing catalyst A. The reaction time was set to 36 hours, and the concentration of carbonyl sulfide in the raw gas ranged from 500 to 1000 mg / m 3 The volume space velocity setting range is 20000-30000 / h. Preferably, in each embodiment (including comparative example), the volume space velocity is set to 25000 / h.

[0072] See also Figure 1 , showing the curve of carbonyl sulfide hydrolysis conversion rate of the corresponding catalyst obtained in each example (including comparative example) in the hydrolysis catalytic experiment. And see Figure 2 , showing Figure 1 The curve of the selectivity of each catalyst corresponding to each embodiment (including comparative example) in the hydrolysis catalytic experiment to the hydrolysis product hydrogen sulfide. Figure 1 and Figure 2 It can be seen from the curve of catalyst A obtained in Example 1 that during the 36-hour continuous catalytic hydrolysis reaction, catalyst A always maintained a high level of catalytic activity. Under the reaction temperature condition of 60° C., the carbonyl sulfide hydrolysis conversion rate exceeded 95%, the hydrogen sulfide selectivity exceeded 98%, and no deactivation was shown within 36 hours.

[0073] Example 2

[0074] Catalyst B (TBuAF / γ-Al2O3) was prepared according to step S100 to step S400.

[0075] (1) calcining pseudo-boehmite in a muffle furnace to obtain γ-Al2O3 at a temperature of 650°C for 2 hours;

[0076] (2) Weigh 0.30 g of tetrabutylammonium fluoride (TBuAF) and dissolve it in 5 mL of water to obtain an ionic liquid solution, weigh 2 g of the γ-Al2O3 prepared in (1) and add it to the ionic liquid solution to obtain a mixture;

[0077] (3) ultrasonically immersing the mixture obtained in (2) in an ultrasonic cleaning machine for 2 hours;

[0078] (4) The mixture was allowed to stand at room temperature for 24 hours, and then placed in a forced air drying oven and dried at 60° C. for 24 hours to obtain catalyst B (TBuAF / γ-Al 2 O 3 ).

[0079] The catalyst B was placed in a fixed bed reactor for experimental testing of low-temperature hydrolysis of carbonyl sulfide. Specifically, 0.3 g of catalyst B was weighed, crushed and sieved to form a 40-60 mesh catalyst B powder, and the catalyst B powder was loaded into a 6 mm quartz tube reactor. The reaction temperature was set to 50°C, and the mixed gas of carbonyl sulfide and N2 was first passed into a bubbler. The bubbler was controlled to a temperature of 40°C by a water bath to form a raw gas to be treated that carried water vapor. Then the raw gas to be treated that carried water vapor was passed into a quartz tube reactor containing catalyst B. The reaction time was set to 36 hours, and the concentration of carbonyl sulfide in the raw gas ranged from 500 to 1000 mg / m 3 , the volume space velocity was set to 25000 / h.

[0080] Combination Figure 1 and Figure 2 It can be seen from the curve of Catalyst B obtained in Example 2 that during the 36-hour continuous catalytic hydrolysis reaction, Catalyst B always maintained a high level of catalytic activity. Under the reaction temperature condition of 50°C, the carbonyl sulfide hydrolysis conversion rate exceeded 80%, the hydrogen sulfide selectivity exceeded 95%, and no deactivation was shown within 36 hours.

[0081] Example 3

[0082] Catalyst C (TPAC / γ-Al2O3) was prepared according to step S100 to step S400.

[0083] (1) calcining pseudo-boehmite in a muffle furnace to obtain γ-Al2O3 at a temperature of 600°C for 3 hours;

[0084] (2) Weigh 0.06 g of tetrapropylammonium chloride (TPAC) and dissolve it in 5 mL of anhydrous methanol to obtain an ionic liquid solution, weigh 2 g of the γ-Al2O3 prepared in (1) and add it to the ionic liquid solution to obtain a mixture;

[0085] (3) subjecting the mixture obtained in (2) to ultrasonic treatment in an ultrasonic cleaning machine for 3 hours to complete ultrasonic impregnation;

[0086] (4) The mixture was allowed to stand at room temperature for 12 hours, and then placed in a forced air drying oven and dried at 80° C. for 12 hours to obtain catalyst C (TPAC / γ-Al 2 O 3 ).

[0087] The catalyst C was placed in a fixed bed reactor for experimental testing of low-temperature hydrolysis of carbonyl sulfide. Specifically, 0.3 g of catalyst C was weighed, crushed and sieved to form a 40-60 mesh catalyst C powder, and the catalyst C powder was loaded into a 6 mm quartz tube reactor. The reaction temperature was set to 70°C, and the mixed gas of carbonyl sulfide and N2 was first passed into a bubbler. The bubbler was controlled to a temperature of 40°C through a water bath to form a raw gas to be treated that carried water vapor. Then the raw gas to be treated that carried water vapor was passed into a quartz tube reactor containing catalyst C. The reaction time was set to 36 hours, and the concentration of carbonyl sulfide in the raw gas ranged from 500 to 1000 mg / m 3 , the volume space velocity was set to 25000 / h.

[0088] Combination Figure 1 and Figure 2 It can be seen from the curve of Catalyst C obtained in Example 3 that during the 36-hour continuous catalytic hydrolysis reaction, Catalyst C always maintained a high level of catalytic activity. Under the reaction temperature condition of 70°C, the carbonyl sulfide hydrolysis conversion rate reached 95%, the hydrogen sulfide selectivity reached 95%, and no deactivation was shown within 36 hours.

[0089] Among the catalysts A, B and C prepared using the three catalyst promoters of Examples 1 to 3, the catalyst A of Example 1 has the best catalytic effect of low-temperature hydrolysis (the carbonyl sulfide hydrolysis conversion rate is the highest and the hydrogen sulfide selectivity is also the highest). Therefore, taking Example 1 as an example, the microstructure of catalyst A is further characterized by a scanning electron microscope. Specifically, see Figure 3 and Figure 4 , respectively showing the distribution mapping of P element (from organic cations) and Cl element (from halogen anions) on the surface of catalyst A. Figure 3 and Figure 4 As shown, the P element and the Cl element are evenly distributed on the surface of γ-Al2O3, indicating that tetrabutylphosphine chloride is highly dispersed on the surface of γ-Al2O3.

[0090] In one example, further, multiple groups of comparative examples are provided for comparison with Examples 1 to 3, and the experimental results further verify that the catalysts of the various embodiments of the present invention have significant and stable high-efficiency catalytic activity in the low-temperature hydrolysis of carbonyl sulfide.

[0091] Specifically, comparative examples 1-5 respectively use tetrabutylphosphine chloride (TBuPC), γ-Al2O3, titanium dioxide (T iO2) loaded tetrabutylphosphine chloride (TBuPC), γ-Al2O3 loaded tetrabutylammonium hydrogen sulfate (TBuAHS) and γ-Al2O3 loaded alkali metal salt potassium carbonate (K2CO3) to obtain the corresponding catalysts, and are marked as catalyst D (TBuPC), catalyst E (γ-Al2O3), catalyst F (TBuPC / T iO2), catalyst G (TBuAHS / γ-Al2O3) and catalyst H (K2CO3 / γ-Al2O3).

[0092] Wherein, referring to Table 1, the preparation process of the corresponding catalysts obtained in Comparative Examples 1 to 5 is shown. Referring to Table 2, the experimental results of hydrolyzing carbonyl sulfide obtained by the same experimental test as in Examples 1 to 3 are shown.

[0093] Table 1 Main preparation process of the corresponding catalysts obtained in Comparative Examples 1-5

[0094]

[0095]

[0096] Table 2 Catalytic effects of the corresponding catalysts obtained in Comparative Examples 1 to 5 in low-temperature hydrolysis of carbonyl sulfide experiments

[0097]

[0098] Combination Figure 1 and Figure 2 The catalytic effect curves of each catalyst are further analyzed. First, when comparative example 1 uses only ionic liquid tetrabutylphosphine chloride (TBuPC) as a catalyst, it can be seen from comparative experiments that it does not have the ability to catalyze the hydrolysis of carbonyl sulfide. Secondly, γ-Al2O3 itself has relatively good catalytic activity, but in the existing hydrolysis catalytic reaction, a higher hydrolysis temperature (above 150°C) is usually required to stimulate the inherent catalytic activity of γ-Al2O3. Comparative example 2 also further verifies that under low-temperature hydrolysis conditions, if only γ-Al2O3 is used as a catalyst, the catalytic activity is very low (the carbonyl sulfide hydrolysis conversion rate is only about 30%).

[0099] Therefore, when comparative examples 1 and 2 are subjected to carbonyl sulfide hydrolysis reaction under the same experimental test conditions as in Example 1, only when tetrabutylphosphine chloride (TBuPC) is loaded as a catalyst promoter on the surface of the active carrier γ-Al2O3 to form catalyst A (TBuPC / γ-Al2O3) as in Example 1, can a carbonyl sulfide hydrolysis conversion rate of more than 90% and a hydrogen sulfide selectivity of more than 90% be obtained under low-temperature hydrolysis conditions. The effect of tetrabutylphosphine chloride on the surface adsorption characteristics of γ-Al2O3 is also verified. Tetrabutylphosphine chloride effectively promotes the alkaline dissociation of H2O in γ-Al2O3, helps to continuously generate more alkaline hydroxyls on the surface of γ-Al2O3, thereby promoting the hydroxyl sulfide hydrolysis reaction to have efficient catalytic performance under low-temperature conditions.

[0100] Further, see Figure 5 , showing the characteristic X-ray diffractometer (XRD) patterns of catalyst A, catalyst D and catalyst E obtained in Example 1, Comparative Example 1 and Comparative Example 2, respectively. Figure 5 It can be seen from the three curves that the catalyst A obtained in Example 1 does not have the characteristic diffraction peak of tetrabutylphosphine chloride. Figure 3 and Figure 4 From the microscopic characterization of catalyst A shown, it can be seen that the reason why catalyst A does not show the characteristic diffraction peak of tetrabutylphosphine chloride is that tetrabutylphosphine chloride is highly uniformly dispersed on the surface of γ-Al2O3.

[0101] Recombination Figure 1 and Figure 2 The curves of the catalytic effects of the catalysts in the hydrolysis catalytic effects of Comparative Examples 3 to 5 show that the use of TiO2 instead of γ-Al2O3 in Comparative Example 3 results in the catalyst F having no catalytic effect. The reason is that the ionic liquid has selectivity for the active carrier.

[0102] Furthermore, in Comparative Example 4, tetrabutylammonium hydrogen sulfate (TBuAHS) was used instead of tetrabutylphosphine chloride (TBuPC). The acidity of tetrabutylammonium hydrogen sulfate caused the surface of γ-Al2O3 to become acidic, which in turn inhibited the formation of basic hydroxyl groups on the surface of γ-Al2O3, thereby failing to promote the low-temperature catalytic activity of γ-Al2O3.

[0103] Further, similar to the case of the NH4Cl solution mentioned above, the catalytic effect of using a traditional alkali metal salt (such as potassium carbonate K2CO3) supported on the surface of γ-Al2O3 in Comparative Example 5 is not as significant as the catalytic effect of using an ionic liquid in Examples 1 to 3, which is not conducive to the implementation of the catalyst-catalyzed carbonyl sulfide hydrolysis reaction under low-temperature hydrolysis conditions.

[0104] In one example, density functional theory (DFT) calculations were further performed to analyze the interaction between tetrabutylphosphine chloride (TBuPC) and γ-Al2O3 and the process and mechanism of promoting the dissociation of H2O from basic hydroxyl groups by taking catalyst A of Example 1 as an example.

[0105] See also Figure 6 , shows the simulated structure of catalyst A (TBuPC / γ-Al2O3) of Example 1 constructed by DFT calculation. The calculation results show that when tetrabutylphosphine chloride (TBuPC) is loaded on γ-Al2O3, the Cl ion approaches the Al in the tetrahedral gap to form a covalent bond with a bond length of 2.25 angstroms. The interaction between the organic cations and the halogen anions in the ionic liquid, especially the large steric hindrance effect formed by the two, makes Cl and Al have bonding selectivity. That is, Cl tends to form a covalent bond with Al at a specific position, for example, with Al in the tetrahedral gap on the surface of γ-Al2O3. In this way, since most of the halogen ions first occupy the Al in the tetrahedral gap, H2O can be more adsorbed on the Al in the octahedral gap on the surface of γ-Al2O3 and dissociate the basic hydroxyl group after coordination.

[0106] See also Figure 7 , shows the dissociation energy curves obtained by DFT calculation when H2O is adsorbed on the aluminum sites in the octahedral gaps on the surface of γ-Al2O3 and undergoes alkaline dissociation in catalyst A (TBuPC / γ-Al2O3) of Example 1 and catalyst E (γ-Al2O3) of Comparative Example 2.

[0107] The calculation results show that the dissociation energy of H2O at the aluminum site in the octahedral interstitial of γ-Al2O3 alone is reduced from 0.54 eV to 0.19 eV compared with γ-Al2O3 loaded with tetrabutylphosphine chloride (TBuPC) (catalyst A). In other words, the energy of alkaline dissociation of H2O in catalyst A is reduced, thereby reducing the reaction temperature of catalyst A for hydrolysis of carbonyl sulfide.

[0108] Specifically, during the hydrolysis of carbonyl sulfide, H2O can supplement -OH groups, and these basic -OH groups are the key active sites on γ-Al2O3 that catalyze the hydrolysis of carbonyl sulfide. The acidity and basicity of the -OH group are mainly determined by its net charge, which is affected by the configuration and coordination environment of the -OH group. The interaction between Cl and Al weakens the adsorption of H2O on the Al site in the tetrahedral gap, while promoting the adsorption and further dissociation of H2O on the Al site in the octahedral gap. The coordination of Al in the octahedral gap will produce more basic -OH groups, which ultimately promote the low-temperature hydrolysis of carbonyl sulfide.

[0109] The catalyst for low-temperature hydrolysis of carbonyl sulfide and the preparation method thereof provided by the embodiments of the present invention have at least one or part of the following advantages:

[0110] (1) The catalyst for low-temperature hydrolysis of carbonyl sulfide and the preparation method thereof provided in the embodiments of the present invention are characterized in that an ionic liquid composed of organic cations and halogen anions is loaded onto the surface of γ-Al2O3 as a catalyst promoter, so that the reaction temperature of hydrolysis of carbonyl sulfide is reduced to below 100°C, and the carbonyl sulfide hydrolysis conversion rate is more than 80% and the hydrogen sulfide selectivity is more than 90%;

[0111] (2) The catalyst for low-temperature hydrolysis of carbonyl sulfide provided by the embodiments of the present invention and the preparation method thereof can control the tendency of halogen anions to form covalent bonds or ionic bonds with Al in the tetrahedral gaps through the catalytic effect of organic cations, thereby freeing up more Al in the octahedral gaps for continuous adsorption of H2O and causing H2O to undergo alkaline dissociation to continuously generate alkaline hydroxyl groups for hydrolysis of carbonyl sulfide;

[0112] (3) The catalyst for low-temperature hydrolysis of carbonyl sulfide and the preparation method thereof provided in the embodiments of the present invention further reduce the dissociation energy required for alkaline dissociation of H2O adsorbed by Al in the octahedral gaps by forming covalent bonds or ionic bonds between halogen anions and Al in the tetrahedral gaps, thereby reducing the temperature required for the hydrolysis reaction;

[0113] (4) The catalyst for low-temperature hydrolysis of carbonyl sulfide provided by the embodiments of the present invention and the preparation method thereof can further improve the carbonyl sulfide hydrolysis conversion rate to greater than or equal to 90% at a catalytic reaction temperature of 50 to 70° C. by using tetrabutylphosphonium chloride as an ionic liquid, and the hydrogen sulfide selectivity is improved to greater than or equal to 95%;

[0114] (5) The catalyst for low-temperature hydrolysis of carbonyl sulfide and the preparation method thereof provided in the embodiments of the present invention use an ultrasonic impregnation method to load the ionic liquid onto the surface of γ-Al2O3. Since the vapor pressure of the ionic liquid is almost negligible, the ionic liquid is not easily lost during the preparation process and the catalytic hydrolysis reaction, thereby improving the low-temperature stability of the catalyst;

[0115] (6) The catalyst for low-temperature hydrolysis of carbonyl sulfide and the preparation method thereof provided in the embodiments of the present invention use conventional processes such as muffle furnace calcination and ultrasonic impregnation. The preparation method is simple and can be widely used in the fields of steel, petrochemical, natural gas, etc. to remove carbonyl sulfide.

[0116] Although some embodiments of the present general inventive concept have been shown and described, it will be appreciated by those skilled in the art that changes may be made to these embodiments without departing from the principles and spirit of the present general inventive concept, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for preparing a catalyst for low-temperature hydrolysis of carbonyl sulfide, characterized in that: Using γ-Al2O3 as an active carrier and an ionic liquid composed of organic cations and halogen anions as a catalyst promoter, the ionic liquid is loaded on the surface of the γ-Al2O3 to form a catalyst; Under the catalytic effect of the organic cation, a part of the aluminum sites on the surface of the γ-Al2O3 of the catalyst forms a covalent bond or an ionic bond with the halogen anion, and another part adsorbs H2O and causes it to continuously dissociate to generate alkaline hydroxyl groups for hydrolyzing carbonyl sulfide.

2. The preparation method according to claim 1, characterized in that: Al in the tetrahedral gap formed by O on the surface of the γ-Al2O3 forms a covalent bond or an ionic bond with the halogen anion, and the bond length of the covalent bond or the ionic bond ranges from 2 to 2.5 angstroms; The Al in the octahedral gap formed by O on the surface of the γ-Al2O3 is used to adsorb H2O and generate basic hydroxyl groups after dissociation and coordination.

3. The preparation method according to claim 2, characterized in that: The long-chain group of the organic cation allows the halogen anion to form a covalent bond or an ionic bond with Al in the tetrahedral gap.

4. The preparation method according to claim 3, characterized in that: The organic cation is a tetraalkyl quaternary phosphonium salt ion or a tetraalkyl quaternary ammonium salt ion.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The steps of the preparation method include: Pseudo-boehmite is placed in a muffle furnace and roasted to obtain γ-Al2O3; Using a solvent to dissolve an ionic liquid composed of organic cations and halogen anions to obtain an ionic solution; γ-Al2O3 was added into the ionic solution and the ionic liquid was loaded onto the surface of γ-Al2O3 by ultrasonic impregnation; The γ-Al2O3 loaded with ionic liquid is allowed to stand for 12 to 24 hours and then placed in a drying oven at a drying temperature of 60 to 90° C. for 12 to 24 hours to obtain a catalyst for low-temperature hydrolysis of carbonyl sulfide.

6. The preparation method according to claim 5, characterized in that: The calcination temperature ranges from 550 to 650° C., and the calcination time ranges from 2 to 6 hours.

7. The preparation method according to claim 6, characterized in that: Based on the mass of the γ-Al2O3, the mass fraction of the ionic liquid ranges from 3% to 20%; The solvent is any one of anhydrous methanol, anhydrous ethanol, acetone and water, or a combination thereof.

8. The preparation method according to claim 7, characterized in that: The ultrasonic impregnation is to add γ-Al2O3 into the ion solution to obtain a mixture and then ultrasonically treat it in an ultrasonic cleaning machine for 1 to 3 hours.

9. The preparation method according to claim 8, characterized in that: The catalyst obtained by using tetrabutylphosphine chloride as an ionic liquid loaded on the surface of γ-Al2O3 was subjected to a fixed bed reactor with a concentration of 500-1000 mg / m 3 The carbonyl sulfide is subjected to a hydrolysis catalytic reaction for 36 hours or more, and a carbonyl sulfide hydrolysis conversion rate of 90% or more and a hydrogen sulfide selectivity of 95% or more are obtained at a catalytic reaction temperature of 50-70°C.

10. A catalyst for low-temperature hydrolysis of carbonyl sulfide, obtained by the preparation method according to any one of claims 1 to 9, characterized in that: The catalyst can obtain a carbonyl sulfide hydrolysis conversion rate of greater than or equal to 80% and a hydrogen sulfide selectivity of greater than or equal to 90% at a catalytic reaction temperature of 50-70°C.

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