Modified molecular sieve for adsorbing and removing thioether and preparation method thereof

Abstract

The invention relates to a modified molecular sieve for adsorption removal of thioether and a preparation method thereof, and belongs to the technical field of adsorbents, the preparation method of the modified molecular sieve for adsorption removal of thioether comprises two steps of preparation of a tin-cobalt modified molecular sieve and alkali treatment; the penetrating sulfur capacity of the modified molecular sieve for adsorbing and removing thioether is 39-45mg / g at the air speed of 5h <-1 >, 34-38mg / g at the air speed of 8h <-1 > and 30-36mg / g at the air speed of 12h <-1 >.

Description

Technical Field

[0001] The present invention relates to a modified molecular sieve for adsorbing and removing thioether and a preparation method thereof, belonging to the technical field of adsorbents. Background Art

[0002] In the petroleum refining industry, in order to solve the problem of excessive sulfides in high-sulfur crude oil, the catalytic combination unit often adopts the "double removal" process to remove hydrogen sulfide and mercaptan in liquefied petroleum gas. However, the "double removal process" cannot remove thioether. Therefore, the excessive total sulfur, ammonia nitrogen content and COD in catalytic cracking sewage have become the primary problems that need to be solved urgently. Thioether is mainly dimethyl disulfide, which is a typical organic sulfur gas with a foul smell. When its content in the air reaches one part per billion, it will produce an odor, and its toxicity cannot be underestimated. At present, the main methods for removing thioether are hydrodesulfurization, selective oxidation desulfurization and adsorption desulfurization. Among them, hydrodesulfurization requires continuous cyclic hydrogenation and has relatively high operating pressure and temperature. Selective catalytic oxidation desulfurization has relatively strict requirements for reaction conditions and the operation process is relatively complex. While adsorption desulfurization can be operated at normal temperature and pressure and can deeply remove organic sulfides. Therefore, the adsorption desulfurization technology has attracted great attention from countries around the world. However, the development of adsorbents with high adsorption capacity is still the focus and difficulty of the adsorption desulfurization technology. Especially for adsorbents for deep adsorption and removal of dimethyl disulfide, because the dimethyl disulfide molecule has a linear structure, its acidity and polarity are weaker than those of mercaptan. In addition, the relative molecular mass and kinetic diameter of dimethyl disulfide are relatively large, and it is difficult for general adsorbents to quickly adsorb dimethyl disulfide molecules. Therefore, it is difficult to deeply and thoroughly remove dimethyl disulfide at a high liquid or gas space velocity. In order to meet the need for deep removal of dimethyl disulfide, a large number of modification studies have been carried out on ordinary solid adsorbents, such as modified activated carbon, modified activated silica and modified molecular sieve, etc. Among them, the adsorption effect of the modified molecular sieve is relatively good, which has attracted wide attention in the industrial and academic circles.

[0003] Chinese patent CN116492980A discloses a dimethyl sulfide adsorbent and its preparation method and application. The adsorbent includes zeolite molecular sieve and metal ions, and the molecular formula is HM[(AlO2)x(SiO2)y]·zH2O, wherein M is a metal ion, y / x is the silicon-aluminum ratio of the zeolite molecular sieve, and z is zero or a positive number; the metal ions include zero or more alkaline earth metal ions, and silver ions. The adsorbent is obtained by using a metal-modified zeolite molecular sieve. The active sites of the adsorbent obtained by metal modification are increased, the adsorption effect of the adsorbent on low-concentration dimethyl sulfide in the indoor environment is improved, and the deep removal of dimethyl sulfide by the zeolite molecular sieve is achieved. The dimethyl sulfide adsorbent prepared by this patent is only suitable for the removal of trace dimethyl sulfide at very low air velocity, and is relatively effective for the deep removal of trace dimethyl sulfide indoors, but the removal effect of a large amount of dimethyl sulfide in industrial gas or liquid oil is very poor, especially under industrial operating conditions at high air velocity, the modified molecular sieve in this patent is difficult to meet.

[0004] Chinese patent CN119657077A discloses a preparation and application method of a modified activated carbon adsorbent for removing sulfide compounds from styrene. The activated carbon adsorbent is characterized in that the activated carbon is modified by a compounding method of an acid and a metal ion, the acid is selected from one of sulfuric acid, nitric acid and hydrochloric acid, the concentration is between 1 and 7 mol / L, and the metal ion is selected from Cu 2+ , Fe 3+ 、Zn 2+ One of them has a metal ion loading of 0.1wt%~20wt% of the activated carbon; the application method is to use the modified activated carbon as an adsorbent, and in an intermittent reactor at 30°C, the sulfide is adsorbed by σ complexation to achieve the purpose of removing sulfide compounds in styrene. The adsorbent does not adsorb styrene. When adsorbed at 30°C, it is not easy to cause styrene to oligomerize and will not cause styrene loss. Its static sulfur capacity is increased from 2.5mg / g before modification to 25mg / g after modification. The modified activated carbon adsorbent obtained by this patent has a relatively low sulfur capacity, poor desulfurization performance, and can only be used for the removal of sulfide compounds in styrene in a targeted manner, and has a narrow applicability.

[0005] From the above, we can see that the adsorbents used for deep adsorption and removal of sulfide still have significant disadvantages such as low sulfur capacity, poor desulfurization effect and difficulty in use under high-space-velocity industrial operating conditions. Therefore, there is an urgent need to develop a modified adsorbent with high sulfur capacity, high adsorption performance, suitable for industrial high-space-velocity operating conditions and capable of deep adsorption and removal of sulfide. Summary of the invention

[0006] Aiming at the deficiencies of the above-mentioned existing technologies, the present invention provides a modified molecular sieve for adsorbing and removing thioethers and a preparation method thereof, achieving the following invention objectives: preparing a modified molecular sieve adsorbent with high sulfur capacity, high adsorption performance, suitable for industrial high airspeed operation conditions and capable of deeply adsorbing and removing thioethers.

[0007] To achieve the above invention objectives, the present invention adopts the following technical solutions: A modified molecular sieve for adsorbing and removing thioethers and a preparation method thereof. The breakthrough sulfur capacity of the modified molecular sieve for adsorbing and removing thioethers is 39 - 45 mg / g at a space velocity of 5 h -1 space velocity, 34 - 38 mg / g at a space velocity of 8 h -1 space velocity, and 30 - 36 mg / g at a space velocity of 12 h -1 space velocity; The preparation method of the modified molecular sieve for adsorbing and removing thioethers includes two steps: preparing a tin-cobalt modified molecular sieve and alkali treatment; The following is a further improvement of the above technical solution: Step 1, preparing a tin-cobalt modified molecular sieve Add deionized water, cobalt stannate, silicon source, aluminum source, sodium hydroxide, composite template agent, and structure guiding agent into a mixing kettle. After vigorously stirring and mixing evenly, reduce the stirring rate. After stirring into a gel, quickly transfer the gel to a reaction kettle with a polytetrafluoroethylene inner liner, heat up to the crystallization temperature, keep the temperature constant for crystallization. After crystallization is completed, cool and discharge the material, carry out suction filtration and separation. The separated solid is washed, dried, and then put into a muffle furnace for roasting. After roasting is completed, cool to room temperature to obtain the tin-cobalt modified molecular sieve; The silicon source is one of silica sol, fumed silica, sodium silicate, potassium silicate, tetraethyl orthosilicate or a mixture composed of any two or more of them in any mass ratio; The aluminum source is one of aluminum isopropoxide, pseudo-boehmite, sodium meta-aluminate or a mixture composed of any two or more of them in any mass ratio; The composite template agent is a mixture of ammonium phytate and biuret; The mass ratio of ammonium phytate to biuret is 20 - 53:90; The structure guiding agent is an amino-terminated hyperbranched polyamide; The number average molecular weight of the amino-terminated hyperbranched polyamide is 240 - 600 g / mol; The mass ratio of deionized water, cobalt stannate, silicon source, aluminum source, sodium hydroxide, composite template agent, and structure guiding agent is 270 - 520:20 - 65:70 - 190:70 - 230:25 - 60:3 - 15:2 - 7; For the vigorous stirring and mixing, the stirring rate is 2000 - 5000 revolutions per minute; Reduce the stirring rate, and the stirring rate is reduced to 1000 - 1500 revolutions per minute; The crystallization temperature is 150 - 230 °C; When the crystallization is completed, the crystallization time is 33 - 64 h; For the washing, wash the solid with deionized water until the pH value of the washing liquid is 7.2 - 7.8; For the drying, the drying temperature is 80 - 100 °C, and the drying time is 14 - 25 h; For the calcination, the calcination temperature is 430 - 520 °C, and the calcination time is 4 - 9 h.

[0008] Step 2: Alkali treatment Add the tin-cobalt modified molecular sieve, deionized water, and composite alkali into the reaction kettle, heat up and keep the temperature constant at 90 - 130 °C under closed conditions, stir and react for 3 - 6 hours, then cool to room temperature, discharge and filter, and then obtain the modified molecular sieve after washing with water and drying; The composite alkali is composed of tetramethylguanidine, N,N-diethylhydroxylamine, and urea compounds; The urea compound is semicarbazide, N-methylurea, 1,1-dimethylurea, or a mixture composed of two or more of them in any mass ratio; The mass ratio of tetramethylguanidine, N,N-diethylhydroxylamine, and urea compound is 30 - 70:4 - 12:10 - 40; The mass ratio of the tin-cobalt modified molecular sieve, deionized water, and composite alkali is 35 - 60:180 - 440:10 - 25; For the stirring reaction, the stirring rate is 500 - 1100 revolutions per minute; For the washing with water, wash the solid with deionized water until the pH value of the washing liquid is 7.3 - 7.7; For the drying, the drying temperature is 90 - 110 °C, and the drying time is 15 - 24 h.

[0009] Compared with the prior art, the present invention has the following beneficial effects: 1. In the process of preparing the molecular sieve of the present invention, a composite template agent composed of ammonium phytate and biuret and a structure-directing agent, terminal amino hyperbranched polyamide, are added. Among them, ammonium phytate and biuret, during the formation of the molecular sieve, affect the crystallization process of silicate and aluminosilicate radicals through two effects of ionic complexation adsorption and negative charge induction of nitrogen atoms, thereby regulating the formation process of the internal pores of the molecular sieve. At the same time, the ordered arrangement of the structure-directing agent, terminal amino hyperbranched polyamide, during the high-temperature crystallization process will induce the formation of a multi-level pore size distribution inside the molecular sieve, thereby endowing the molecular sieve with a more comprehensive multi-level adsorption performance, and finally promoting the strong adsorption of dimethyldisulfide by the modified molecular sieve; 2. In the preparation process of the molecular sieve of the present invention, two heteroatoms, tin and cobalt, are introduced. The charge numbers of tin and cobalt are relatively large, and their atomic radii are also relatively large, resulting in a very strong negative charge adsorption effect. Therefore, it is easy to have a charge adsorption complexation with the sulfur element in dimethyl disulfide. So, the two heteroatoms of tin and cobalt will greatly improve the adsorption capacity of the molecular sieve for thioether; 3. The present invention uses a composite base composed of tetramethylguanidine, N,N - diethylhydroxylamine, and urea compounds to carry out alkali etching treatment on the molecular sieve, increasing the roughness of the surface of the internal pores of the molecular sieve, correspondingly increasing the specific surface area, and the rough inner surface can form more adsorption sites, thereby increasing the adsorption amount of dimethyl disulfide. Macroscopically, it shows a significant increase in the breakthrough sulfur capacity. In addition, the composite base treatment can also avoid the drawback of excessive etching of the internal structure of the molecular sieve by inorganic bases such as sodium hydroxide. Therefore, while increasing the adsorption performance, the composite base will also maximize the avoidance of the uncontrollable excessive etching of the internal pores of the molecular sieve by inorganic strong bases; 4. The modified molecular sieve for adsorbing and removing thioether obtained in the present invention has a breakthrough sulfur capacity of 39 - 45 mg / g at a space velocity of 5 h -1 and 34 - 38 mg / g at a space velocity of 8 h -1 and 30 - 36 mg / g at a space velocity of 12 h. -1 Description of the Drawings

[0010] Figure 1 It is a scanning electron microscope photograph of the modified molecular sieve for adsorbing and removing thioether obtained in Example 1, with its cross - section magnified 100,000 times; Figure 2 It is a scanning electron microscope photograph of the modified molecular sieve for adsorbing and removing thioether obtained in Example 2, with its cross - section magnified 100,000 times; Figure 3 It is a scanning electron microscope photograph of the modified molecular sieve for adsorbing and removing thioether obtained in Comparative Example 1, with its cross - section magnified 100,000 times. Detailed Embodiments

[0011] The following are the preferred embodiments of the present invention. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention and are not used to limit the present invention.

[0012] Example 1: A preparation method of a modified molecular sieve for adsorbing and removing thioether Step 1. Prepare a tin - cobalt modified molecular sieve Deionized water, cobalt stannate, silicon source, aluminum source, sodium hydroxide, composite template agent, and structure-directing agent are added to a mixing kettle. After vigorously stirring and mixing evenly, the stirring rate is reduced. After stirring into a gel-like substance, the gel-like substance is quickly transferred to a reaction kettle with a polytetrafluoroethylene lining, heated to the crystallization temperature, and crystallized at a constant temperature. After crystallization is completed, it is cooled and discharged, and separated by suction filtration. The separated solid is washed and dried, and then placed in a muffle furnace for roasting. After roasting is completed, it is cooled to room temperature to obtain tin-cobalt modified molecular sieve; The silicon source is silica sol; The aluminum source is aluminum isopropoxide; The composite template agent is a mixture of ammonium phytate and biuret; The mass ratio of ammonium phytate to biuret is 44:90; The structure-directing agent is amino-terminated hyperbranched polyamide; The number-average molecular weight of the amino-terminated hyperbranched polyamide is 400 g / mol; The mass ratio of deionized water, cobalt stannate, silicon source, aluminum source, sodium hydroxide, composite template agent, and structure-directing agent is 360:45:110:130:45:11:5; For the vigorous stirring and mixing, the stirring rate is 4000 revolutions per minute; For the reduction of the stirring rate, the stirring rate is reduced to 1200 revolutions per minute; The crystallization temperature is 190 °C; For the completion of crystallization, the crystallization time is 55 h; For the washing, the solid is washed with deionized water until the pH value of the wash liquor is 7.7; For the drying, the drying temperature is 95 °C and the drying time is 19 h; For the roasting, the roasting temperature is 460 °C and the roasting time is 7 h.

[0013] Step 2, alkali treatment The tin-cobalt modified molecular sieve, deionized water, and composite alkali are added to a reaction kettle. Under closed conditions, it is heated and kept at a constant temperature of 110 °C, stirred and reacted for 5 hours, then cooled to room temperature, discharged and filtered, and then washed with water and dried to obtain the modified molecular sieve; The composite alkali is composed of tetramethylguanidine, N,N-diethylhydroxylamine, and urea compound; The urea compound is semicarbazide; The mass ratio of tetramethylguanidine, N,N-diethylhydroxylamine, and urea compound is 55:8:30; The mass ratio of the tin-cobalt modified molecular sieve, deionized water, and composite alkali is 50:350:16; For the stirring reaction, the stirring rate is 900 revolutions per minute; The water washing is to wash the solid with deionized water until the pH value of the washing liquid is 7.6; The drying is carried out at a drying temperature of 105 °C for 19 h.

[0014] Example 2: A preparation method of a modified molecular sieve for adsorbing and removing thioether Step 1: Prepare a tin-cobalt modified molecular sieve Add deionized water, cobalt stannate, silicon source, aluminum source, sodium hydroxide, composite template agent, and structure guiding agent into a mixing kettle. After vigorously stirring and mixing evenly, reduce the stirring rate. After stirring into a gel, quickly transfer the gel to a reaction kettle with a polytetrafluoroethylene inner lining, heat up to the crystallization temperature, and carry out constant-temperature crystallization. After the crystallization is completed, cool and discharge the material, carry out suction filtration and separation. The separated solid is washed and dried, and then put into a muffle furnace for roasting. After the roasting is completed, cool to room temperature to obtain the tin-cobalt modified molecular sieve; The silicon source is fumed silica; The aluminum source is pseudo-boehmite; The composite template agent is a mixture of ammonium phytate and biuret; The mass ratio of ammonium phytate to biuret is 20:90; The structure guiding agent is amino-terminated hyperbranched polyamide; The number average molecular weight of the amino-terminated hyperbranched polyamide is 240 g / mol; The mass ratio of deionized water, cobalt stannate, silicon source, aluminum source, sodium hydroxide, composite template agent, and structure guiding agent is 270:20:70:70:25:3:2; For the vigorous stirring and mixing, the stirring rate is 2000 revolutions per minute; For the reduction of the stirring rate, the stirring rate is reduced to 1000 revolutions per minute; The crystallization temperature is 150 °C; When the crystallization is completed, the crystallization time is 33 h; The washing is to wash the solid with deionized water until the pH value of the washing liquid is 7.2; The drying is carried out at a drying temperature of 80 °C for 14 h; The roasting is carried out at a roasting temperature of 430 °C for 4 h.

[0015] Step 2: Alkali treatment Add the tin-cobalt modified molecular sieve, deionized water, and composite alkali into a reaction kettle. Under closed conditions, heat up and keep the temperature at 90 °C, stir and react for 3 hours, then cool to room temperature, discharge and filter, and then obtain the modified molecular sieve after washing with water and drying; The composite alkali is composed of tetramethylguanidine, N,N-diethylhydroxylamine, and urea compound; The urea compound is N-methylurea; The mass ratio of the tetramethylguanidine, N,N-diethylhydroxylamine, and urea compound is 30:4:10; The mass ratio of the tin-cobalt modified molecular sieve, deionized water, and composite base is 35:180:10; For the stirring reaction, the stirring rate is 500 revolutions per minute; For the water washing, the solid is washed with deionized water until the pH value of the washing liquid is 7.3; For the drying, the drying temperature is 90 °C and the drying time is 15 h.

[0016] Example 3: A preparation method of a modified molecular sieve for adsorbing and removing thioether Step 1: Prepare a tin-cobalt modified molecular sieve Add deionized water, cobalt stannate, silicon source, aluminum source, sodium hydroxide, composite template agent, and structure guiding agent into a mixing kettle. After vigorously stirring and mixing evenly, reduce the stirring rate. After stirring into a gel-like substance, quickly transfer the gel-like substance to a reaction kettle with a polytetrafluoroethylene lining, heat up to the crystallization temperature, keep the temperature constant for crystallization. After the crystallization is completed, cool and discharge the material, perform suction filtration and separation. The separated solid is washed and dried, then put into a muffle furnace for roasting. After the roasting is completed, cool to room temperature to obtain the tin-cobalt modified molecular sieve; The silicon source is sodium silicate; The aluminum source is sodium aluminate; The composite template agent is a mixture of ammonium phytate and biuret; The mass ratio of the ammonium phytate and biuret is 53:90; The structure guiding agent is an amino-terminated hyperbranched polyamide; The number average molecular weight of the amino-terminated hyperbranched polyamide is 600 g / mol; The mass ratio of the deionized water, cobalt stannate, silicon source, aluminum source, sodium hydroxide, composite template agent, and structure guiding agent is 520:65:190:230:60:15:7; For the vigorous stirring and mixing, the stirring rate is 5000 revolutions per minute; For the reduction of the stirring rate, the stirring rate is reduced to 1500 revolutions per minute; The crystallization temperature is 230 °C; When the crystallization is completed, the crystallization time is 64 h; For the washing, the solid is washed with deionized water until the pH value of the washing liquid is 7.8; For the drying, the drying temperature is 100 °C and the drying time is 25 h; For the roasting, the roasting temperature is 520 °C and the roasting time is 9 h.

[0017] Step 2: Alkali treatment Add the tin-cobalt modified molecular sieve, deionized water, and composite base into a reaction kettle. Under closed conditions, heat up and maintain a constant temperature of 130 °C, stir and react for 6 hours, then cool to room temperature, discharge and filter, and then obtain the modified molecular sieve after washing with water and drying. The composite base is composed of tetramethylguanidine, N,N-diethylhydroxylamine, and a urea compound. The urea compound is 1,1-dimethylurea. The mass ratio of the tetramethylguanidine, N,N-diethylhydroxylamine, and urea compound is 70:12:40. The mass ratio of the tin-cobalt modified molecular sieve, deionized water, and composite base is 60:440:25. For the stirring reaction, the stirring rate is 1100 revolutions per minute. For the water washing, wash the solid with deionized water until the pH value of the washing liquid is 7.7. For the drying, the drying temperature is 110 °C and the drying time is 24 h.

[0018] Example 4: A preparation method of a modified molecular sieve for adsorbing and removing thioether Step 1: Prepare the tin-cobalt modified molecular sieve The silicon source is potassium silicate. Other operations are the same as in Example 1. The operation of Step 2 is the same as in Example 1.

[0019] Example 5: A preparation method of a modified molecular sieve for adsorbing and removing thioether Step 1: Prepare the tin-cobalt modified molecular sieve The silicon source is tetraethyl orthosilicate. Other operations are the same as in Example 1. The operation of Step 2 is the same as in Example 1.

[0020] Comparative Example 1: Based on Example 1, in Step 1 of preparing the tin-cobalt modified molecular sieve, without adding the structure-directing agent, replace 5 parts of the structure-directing agent with 5 parts of deionized water equally. The specific operation is as follows: Step 1: Prepare the slurry Replace 5 parts of the structure-directing agent with 5 parts of deionized water equally, and other operations are the same as in Example 1. The operation of Step 2 is the same as in Example 1.

[0021] Comparative Example 2: Based on Example 1, in Step 1 of preparing the tin-cobalt modified molecular sieve, without adding cobalt stannate, replace 45 parts of cobalt stannate with 45 parts of deionized water equally. The specific operation is as follows: Step 1: Prepare the slurry Replace 45 parts of cobalt stannate with 45 parts of deionized water equally, and other operations are the same as in Example 1. The operation of Step 2 is the same as that of Example 1.

[0022] Comparative Example 3: Based on Example 1, in Step 2 and the alkali treatment, 16 parts of the composite alkali were equally replaced with 16 parts of sodium hydroxide. The specific operation is as follows: The operation of Step 1 is the same as that of Example 1; Step 2, alkali treatment 16 parts of the composite alkali were equally replaced with 16 parts of sodium hydroxide, and other operations were the same as those of Example 1.

[0023] Performance test: The modified molecular sieves for adsorbing and removing thioether obtained in Examples 1, 2, 3, 4, 5 and Comparative Examples 1, 2, 3 were loaded into a fixed adsorption bed with an inner diameter of φ8 mm × 100 mm (diameter × length). Dimethyl disulfide was added to a mixed solvent of n-hexane and 1-hexene to prepare a simulated oil with a sulfur content of 2000 mg / kg. Under normal temperature and pressure and a liquid hourly space velocity of 5 h -1 、8 h -1 、12 h -1 the adsorption desulfurization performance was tested. The sulfur content of the liquid at the outlet of the fixed adsorption bed was monitored in real time. When the sulfur content of the liquid at the outlet was higher than 1 mg / kg, it was regarded as breakthrough. At this time, the value obtained by dividing the total sulfur amount adsorbed by the modified molecular sieve in the fixed adsorption bed by the total mass of the modified molecular sieve was recorded as the breakthrough sulfur capacity, that is, the maximum adsorption capacity of dimethyl disulfide corresponding to when the liquid passing through the modified molecular sieve penetrated a sulfur content of 1 mg / kg; The test results are shown in Table 1: Table 1

[0024] From the test data in Table 1, it can be seen that in Examples 1-5 at a space velocity of 5 h -1 、8 h -1 、12 h -1Under the above conditions, the breakthrough sulfur capacity is above 30 mg / g, indicating that the modified molecular sieve for adsorbing and removing thioether obtained in the present invention has a high sulfur capacity, high adsorption performance, and is very suitable for deep adsorption and removal of thioether under the industrial high air velocity operating conditions. In Comparative Example 1, no structure-directing agent was added, and the breakthrough sulfur capacity of Comparative Example 1 dropped sharply to the range of 6 - 25 mg / g, indicating that the structure-directing agent has a very significant impact on the internal pore distribution and specific surface area of the modified molecular sieve. Without the structure-directing agent, it may be difficult to form hierarchical pores inside the molecular sieve, resulting in a serious decline in adsorption performance. In Comparative Example 2, cobalt stannate was not added, and the breakthrough sulfur capacity of Comparative Example 2 also decreased significantly, which may be because the two elements of tin and cobalt have a very significant promoting effect on the adsorption of sulfur elements by the molecular sieve. In Comparative Example 3, the composite base was replaced with sodium hydroxide during the alkali treatment operation, and the breakthrough sulfur capacity of Comparative Example 3 was significantly lower than that of Example 1, indicating that the composite base system designed in the present invention can more effectively etch the surface of the internal pores of the molecular sieve, increase the alkalinity of the internal pore surface, and thus can greatly improve the adsorption capacity of the molecular sieve for dimethyl disulfide, and can also avoid the problem of over-etching of the molecular sieve caused by a single inorganic strong base such as sodium hydroxide.

[0025] attachment Figure 1 attachment Figure 2 and attachment Figure 3 are the scanning electron microscope photos of the modified molecular sieves for adsorbing and removing thioether obtained in Example 1, Example 2, and Comparative Example 1 respectively, with a magnification of 100,000 times for the cross-section. Nanoscale pores and holes inside the molecular sieve can be clearly seen in all three attached figures, and the inner surface of the pores or holes is relatively rough, which may be caused by etching with the composite base. Carefully comparing attachment Figure 1 attachment Figure 2 with attachment Figure 3 , it can be seen that the number of pores or holes in attachment Figure 1 and attachment Figure 2 is significantly more than that in attachment Figure 3 attachment Figure 3 . The number of pores or holes in attachment Figure 1 is significantly less, and the cross-section is relatively dense. Moreover, the sizes of the pores or holes in attachment Figure 2 show a relatively regular multi-level distribution, while in attachment Figure 3 , there is no sign of such a regular distribution, which may be because no structure-directing agent was added in Comparative Example 1, and it is impossible to form an internal pore diameter with a multi-level distribution during the synthesis of the molecular sieve.

[0026] The above is only the preferred specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A preparation method of a modified molecular sieve for adsorbing and removing thioether, characterized in that: The preparation method of the modified molecular sieve for adsorbing and removing thioether includes two steps: preparing a tin-cobalt modified molecular sieve and alkali treatment; For the preparation of the tin-cobalt modified molecular sieve, deionized water, cobalt stannate, a silicon source, an aluminum source, sodium hydroxide, a composite template agent, and a structure-directing agent are added to a mixing kettle. After vigorously stirring and mixing evenly, the stirring rate is reduced. After stirring into a gel-like substance, the gel-like substance is quickly transferred to a reaction kettle with a polytetrafluoroethylene lining, heated to the crystallization temperature, and crystallized at a constant temperature. After the crystallization is completed, it is cooled and discharged, filtered and separated. The separated solid is washed, dried, and then placed in a muffle furnace for roasting. After the roasting is completed, it is cooled to room temperature to obtain the tin-cobalt modified molecular sieve; The silicon source is one of silica sol, fumed silica, sodium silicate, potassium silicate, tetraethyl orthosilicate, or a mixture composed of any two or more of them in any mass ratio; The aluminum source is one of aluminum isopropoxide, pseudo-boehmite, sodium metaaluminate, or a mixture composed of any two or more of them in any mass ratio; The composite template agent is a mixture of ammonium phytate and biuret; The structure-directing agent is an amino-terminated hyperbranched polyamide; The number-average molecular weight of the amino-terminated hyperbranched polyamide is 240 - 600 g / mol; For the alkali treatment, the tin-cobalt modified molecular sieve, deionized water, and a composite alkali are added to a reaction kettle. Under a closed condition, it is heated and kept at 90 - 130 °C, stirred and reacted for 3 - 6 hours, then cooled to room temperature, discharged and filtered, and then washed with water and dried to obtain the modified molecular sieve; The composite alkali is composed of tetramethylguanidine, N,N-diethylhydroxylamine, and a urea compound; The urea compound is one of semicarbazide, N-methylurea, 1,1-dimethylurea, or a mixture composed of two or more of them in any mass ratio.

2. The preparation method of the modified molecular sieve for adsorbing and removing thioether according to claim 1, characterized in that: The mass ratio of ammonium phytate to biuret is 20 - 53:90; The mass ratio of deionized water, cobalt stannate, the silicon source, the aluminum source, sodium hydroxide, the composite template agent, and the structure-directing agent is 270 - 520:20 - 65:70 - 190:70 - 230:25 - 60:3 - 15:2 - 7.

3. The preparation method of the modified molecular sieve for adsorbing and removing thioether according to claim 1, characterized in that: The mass ratio of tetramethylguanidine, N,N-diethylhydroxylamine, and the urea compound is 30 - 70:4 - 12:10 - 40.

4. The preparation method of the modified molecular sieve for adsorbing and removing thioether according to claim 1, characterized in that: The mass ratio of the tin-cobalt modified molecular sieve, deionized water, and the composite alkali is 35 - 60:180 - 440:10 - 25.

5. The modified molecular sieve for adsorbing and removing thioether prepared by the preparation method according to any one of claims 1 - 4, characterized in that: The modified molecular sieve for adsorptive removal of thioether has a breakthrough sulfur capacity of 39-45 mg / g at a space velocity of 5 h -1 and 34-38 mg / g at a space velocity of 8 h -1 and 30-36 mg / g at a space velocity of 12 h -1 and 30-36 mg / g at a space velocity of 12 h

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