Modified alkene separation adsorbent and its preparation method

Abstract

The present invention provides a modified alkene separation adsorbent and a preparation method thereof. The preparation method includes the following steps: Step S1, subjecting waste molecular sieves to aluminum dissolution treatment and silicon dissolution treatment in sequence to obtain an aluminum-rich solution and a silicon-rich solution; Step S2, subjecting the raw materials including the aluminum-rich solution, the silicon-rich solution and seeds to gelation treatment, aging treatment and hydrothermal crystallization treatment in sequence to obtain 13X molecular sieves; Step S3, subjecting the raw materials including the 13X molecular sieves and a carbon source solution to impregnation treatment and calcination treatment in sequence to obtain carbon-coated 13X molecular sieves; and Step S4, mixing the carbon-coated 13X molecular sieves and a silicon source solution and then performing hydrothermal reaction, first calcination treatment, zinc deposition treatment, reduction treatment and second calcination treatment in sequence to obtain the modified alkene separation adsorbent. The modified alkene separation adsorbent has high selectivity and separation efficiency in the separation of olefins and alkanes.

Description

Technical Field

[0001] The present invention relates to the technical field of molecular sieve separation adsorbents, and more particularly, to a modified alkene-alkane separation adsorbent and a preparation method thereof. Background Art

[0002] As important chemical raw materials, olefins play an important role in the processes of synthesizing rubber, plastics and other chemical products. Olefins usually coexist with alkanes in petrochemical products, and the effective separation of olefins and alkanes is a key step in the chemical production process. At present, the adsorption separation method is widely used in the separation of olefins and alkanes due to its advantages such as low energy consumption and simple operation. 13X molecular sieve is regarded as a promising alkene-alkane separation adsorbent due to its excellent adsorption performance and thermal stability. However, there is still room for improvement in the specificity and adsorption capacity of traditional 13X molecular sieve in the separation of olefins and alkanes. Summary of the Invention

[0003] The main object of the present invention is to provide a modified alkene-alkane separation adsorbent and a preparation method thereof, so as to solve the problem that the selectivity and separation efficiency of 13X molecular sieve in the separation of olefins and alkanes are relatively low in the prior art.

[0004] To achieve the above object, according to one aspect of the present invention, there is provided a preparation method of a modified alkene-alkane separation adsorbent, the preparation method comprising the following steps: Step S1, subjecting waste molecular sieve to aluminum dissolution treatment and silicon dissolution treatment in sequence to obtain an aluminum-rich solution and a silicon-rich solution; Step S2, subjecting the raw materials including the aluminum-rich solution, the silicon-rich solution and seeds to gelation treatment, aging treatment and hydrothermal crystallization treatment in sequence to obtain 13X molecular sieve; Step S3, subjecting the raw materials including 13X molecular sieve and a carbon source solution to impregnation treatment and calcination treatment in sequence to obtain carbon-coated 13X molecular sieve; and Step S4, mixing the carbon-coated 13X molecular sieve and a silicon source solution and then subjecting them to hydrothermal reaction, first calcination treatment, zinc deposition treatment, reduction treatment and second calcination treatment in sequence to obtain a modified alkene-alkane separation adsorbent.

[0005] Further, in the above step S3, the temperature of the impregnation treatment is 20-30°C; and / or, the time of the impregnation treatment is 6-24 h; and / or, the mass ratio of 13X molecular sieve to the volume of the carbon source solution is 400-600:1 g / L; and / or, the molar concentration of the carbon source solution is 0.05-0.2 mol / L; and / or, the solute in the carbon source solution is selected from any one or more of benzene, furan and furfural; and / or, the solvent in the carbon source solution is ethanol and / or N,N-dimethylformamide; and / or, the temperature of the calcination treatment is 600-900°C; and / or, the time of the calcination treatment is 2-4 h.

[0006] Further, in the above step S2, the 13X molecular sieve contains silicon element and aluminum element, and the molar ratio of silicon element to aluminum element is 2.2 - 2.9:1; and / or, the pore volume of the 13X molecular sieve is 0.3 - 0.5 cm 3 / g; and / or, the specific surface area of the 13X molecular sieve is 700 - 950 m 2 / g.

[0007] Further, the above seed crystal contains SiO2, Al2O3, Na2O and H2O, wherein the molar ratio of SiO2 to Al2O3 is 0.01 - 2.5:1, and the molar ratio of Na2O, H2O to SiO2 is 0.01 - 4.0:1.0 - 40.0:1.

[0008] Further, the above step S2 includes: step S21, subjecting the aluminum-rich solution and the silicon-rich solution to gelation treatment to obtain a first gel; step S22, successively subjecting the first gel and the seed crystal to aging treatment and hydrothermal crystallization treatment to obtain the 13X molecular sieve; wherein, the first gel contains SiO2, Al2O3, Na2O and H2O, wherein the molar ratio of SiO2 to Al2O3 is 0.5 - 6.0:1, and the molar ratio of Na2O, H2O to SiO2 is 0.5 - 6.0:10 - 100:1; preferably, the mass ratio of the seed crystal to the first gel is 5 - 20:100; and / or, the temperature of the aging treatment is 20 - 100 °C, and the time of the aging treatment is 0.1 - 24 h; and / or, the temperature of the hydrothermal crystallization treatment is 60 - 105 °C, and the time of the hydrothermal crystallization treatment is 0.1 - 36 h.

[0009] Further, the above preparation method further includes: the preparation process of the seed crystal, and the preparation process includes: stirring and mixing the raw materials including an aluminum source, a second silicon source and water to obtain a second gel; adjusting the pH value of the second gel to 8.5 - 12.5 and then performing two-stage hydrothermal crystallization treatment to obtain the seed crystal; wherein, the stirring and mixing rate is 200 - 800 rpm; and / or, the stirring and mixing temperature is 20 - 100 °C; and / or, the stirring and mixing time is 0.1 - 24 h; and / or, the second silicon source is selected from any one or more of silica sol, tetraethyl orthosilicate, macroporous silica gel, silicon powder; and / or, the aluminum source is selected from any one or more of sodium aluminate, pseudo-boehmite, aluminum sulfate, aluminum nitrate.

[0010] Further, the above two-stage hydrothermal crystallization treatment includes the first-stage hydrothermal crystallization treatment and the second-stage hydrothermal crystallization treatment performed successively; wherein, the temperature of the first-stage hydrothermal crystallization treatment is 20 - 60 °C; and / or, the time of the first-stage hydrothermal crystallization treatment is 4 - 24 h; and / or, the temperature of the second-stage hydrothermal crystallization treatment is 80 - 120 °C; and / or, the time of the second-stage hydrothermal crystallization treatment is 6 - 48 h.

[0011] Further, the above preparation method further includes a process of pre-treating the waste molecular sieve, and the pre-treatment process includes: sintering a mixture including the waste molecular sieve and a sodium salt to obtain a sintered product; sequentially performing aluminum dissolution treatment and solid-liquid separation on the sintered product with an acidic solution to obtain an aluminum-rich solution and a residue; sequentially performing silicon dissolution treatment and solid-liquid separation on the residue with an alkaline solution to obtain a silicon-rich solution; wherein, the mass ratio of the waste molecular sieve to the sodium salt is 1:0.5 - 5; and / or, the temperature of the sintering treatment is 550 - 800 °C; and / or, the time of the sintering treatment is 60 - 120 min.

[0012] Further, the above acidic solution is a monobasic acid solution, and the mass fraction of the monobasic acid solution is 10 - 35%; and / or, the monobasic acid is hydrochloric acid and / or nitric acid; and / or, the alkaline solution includes a monobasic base and water, and the mass ratio of the residue, the monobasic base and water is 1.5 - 100:40 - 60:50 - 400; and / or, the monobasic base is NaOH and / or KOH; and / or, the waste molecular sieve is selected from any one or more of waste HZSM-5 molecular sieve catalysts, waste MTO catalysts, fly ash, waste FCC catalysts, waste VOC adsorbents; and / or, the sodium salt is Na2SO4 and / or NaCO3.

[0013] According to another aspect of the present invention, a modified alkene separation adsorbent is provided, and the modified alkene separation adsorbent is prepared by the above-mentioned preparation method.

[0014] Applying the technical solution of the present application, step S3 of the present application optimizes the structure of the 13X molecular sieve to form carbon-coated 13X molecular sieve, and this structure helps to improve the mechanical strength and thermal stability of the molecular sieve. And in this process, the structure of the 13X molecular sieve has been optimized to a great extent, and the carbon-coated 13X molecular sieve has certain parameters such as specific surface area and porosity. Therefore, the modified alkene separation adsorbent prepared from the carbon-coated 13X molecular sieve has high selectivity, high adsorption capacity and easy regeneration performance. Applying this modified alkene separation adsorbent to the separation of olefins and alkanes helps to improve the separation efficiency of olefins and alkanes. In addition, on the one hand, the 13X molecular sieve prepared from waste catalysts in steps S1 and S2 of the present application realizes waste utilization and reduces the cost of preparing the 13X molecular sieve. On the other hand, the 13X molecular sieve prepared by the method of the present application has characteristics such as a high silicon-aluminum ratio, a large pore volume and specific surface area, and regular morphology, which helps to improve the utilization rate of the silicon source of the 13X molecular sieve, provide more adsorption sites for the separation process of alkanes and olefins, and improve the flow and diffusion performance of alkene molecules inside the molecular sieve, thereby improving the separation efficiency and separation effect of alkanes and olefins. Detailed Embodiments

[0015] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments may be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0016] As analyzed in the background art of the present application, there is a problem in the prior art that the selectivity and separation efficiency of 13X molecular sieve in the separation of olefins and paraffins are relatively low. To solve this problem, the present application provides a modified olefin-paraffin separation adsorbent and its preparation method.

[0017] In a typical embodiment of the present application, a preparation method of a modified olefin-paraffin separation adsorbent is provided. The preparation method includes the following steps: Step S1, successively performing aluminum dissolution treatment and silicon dissolution treatment on waste molecular sieve to obtain an aluminum-rich solution and a silicon-rich solution; Step S2, successively subjecting the raw materials including the aluminum-rich solution, the silicon-rich solution and seeds to gelation treatment, aging treatment, and hydrothermal crystallization treatment to obtain 13X molecular sieve; Step S3, successively subjecting the raw materials including 13X molecular sieve and carbon source solution to impregnation treatment and calcination treatment to obtain carbon-coated 13X molecular sieve; and Step S4, mixing the carbon-coated 13X molecular sieve and silicon source solution and then successively performing hydrothermal reaction, first calcination treatment, zinc deposition treatment, reduction treatment and second calcination treatment to obtain a modified olefin-paraffin separation adsorbent.

[0018] Step S3 of the present application optimizes the structure of 13X molecular sieve to form carbon-coated 13X molecular sieve, and this structure helps to improve the mechanical strength and thermal stability of the molecular sieve. And in this process, the structure of 13X molecular sieve has been optimized to a great extent, and the carbon-coated 13X molecular sieve has parameters such as a certain range of specific surface area and porosity. Therefore, the modified olefin-paraffin separation adsorbent prepared from the carbon-coated 13X molecular sieve has high selectivity, high adsorption capacity and easy regeneration performance. Applying this modified olefin-paraffin separation adsorbent to the separation of olefins and paraffins helps to improve the separation efficiency of olefins and paraffins. In addition, the 13X molecular sieve prepared from waste catalyst as the raw material in Steps S1 and S2 of the present application realizes waste utilization on the one hand and reduces the cost of preparing 13X molecular sieve on the other hand. Moreover, the 13X molecular sieve prepared by the method of the present application has characteristics such as a high silicon-aluminum ratio, a large pore volume and specific surface area, and regular morphology, which helps to improve the utilization rate of the silicon source of the 13X molecular sieve, provide more adsorption sites for the separation process of paraffins and olefins, and improve the flow and diffusion performance of olefin-paraffin molecules inside the molecular sieve, thereby improving the separation efficiency and separation effect of paraffins and olefins.

[0019] In an embodiment of the present application, in the above step S3, the temperature of the impregnation treatment is 20-30°C; and / or, the time of the impregnation treatment is 24-48 h; and / or, the mass ratio of the 13X molecular sieve to the volume of the carbon source solution is 400-600:1 g / L; and / or, the molar concentration of the carbon source solution is 0.05-0.2 mol / L; and / or, the solute in the carbon source solution is selected from any one or more of benzene, furan, and furfural; and / or, the solvent in the carbon source solution is ethanol and / or N,N-dimethylformamide; and / or, the temperature of the calcination treatment is 600-900°C; and / or, the time of the calcination treatment is 2-4 h.

[0020] Preferably controlling the temperature, time, and the mass ratio of the 13X molecular sieve to the volume of the carbon source solution within the above ranges helps to control the thickness of the finally formed carbon coating layer, thereby helping to further improve the selectivity, adsorption capacity, and regeneration performance of the modified alkene separation adsorbent. Preferably controlling the type of the carbon source solution within the above range helps to form a carbon-coated 13X molecular sieve with a larger specific surface area. Preferably controlling the temperature and time of the calcination treatment within the above ranges helps to improve the formation efficiency of the carbon coating layer.

[0021] In an embodiment of the present application, in the above step S2, the 13X molecular sieve contains silicon and aluminum elements, and the molar ratio of the silicon element to the aluminum element is 2.2-2.9:1; and / or, the pore volume of the 13X molecular sieve is 0.3-0.5 cm 3 / g; and / or, the specific surface area of the 13X molecular sieve is 700-950 m 2 / g.

[0022] Preferably, through steps S1 and S2 of the present application, the prepared 13X molecular sieve has the above properties. Among them, preferably, the molar ratio of the silicon element to the aluminum element within the above range helps to improve the utilization rate of the silicon source in the raw materials; preferably, the pore volume and specific surface area of the 13X molecular sieve within the above ranges help to provide more adsorption sites for the separation process of alkanes and alkenes, and are beneficial to improving the flow and diffusion performance of alkane molecules and alkene molecules inside the molecular sieve.

[0023] In order to promote the formation of the 13X molecular sieve framework structure and improve its stability, in an embodiment of the present application, preferably, the above seed crystal contains SiO2, Al2O3, Na2O, and H2O, wherein the molar ratio of SiO2 to Al2O3 is 0.01-2.5:1, and the molar ratio of Na2O, H2O to SiO2 is 0.01-4.0:1.0-40.0:1.

[0024] To further promote the smooth formation of the 13X molecular sieve structure, in one embodiment of the present application, it is preferred that the above step S2 includes: step S21, subjecting the aluminum-rich solution and the silicon-rich solution to gelation treatment to obtain a first gel; step S22, successively subjecting the first gel and the seed crystal to aging treatment and hydrothermal crystallization treatment to obtain the 13X molecular sieve; wherein, the first gel contains SiO2, Al2O3, Na2O and H2O, and the molar ratio of SiO2 to Al2O3 is 0.5 to 6.0:1, and the molar ratio of Na2O, H2O to SiO2 is 0.5 to 6.0:10 to 100:1; preferably, the mass ratio of the seed crystal to the first gel is 5 to 20:100; and / or, the temperature of the aging treatment is 20 to 100 °C, and the time of the aging treatment is 0.1 to 24 h; and / or, the temperature of the hydrothermal crystallization treatment is 60 to 105 °C, and the time of the hydrothermal crystallization treatment is 0.1 to 36 h.

[0025] In addition, it is preferred that the aging process is carried out under stirring.

[0026] To promote the formation of the 13X molecular sieve crystals, in one embodiment of the present application, it is preferred that the above preparation method further includes: a process for preparing the seed crystal, and the preparation process includes: stirring and mixing raw materials including an aluminum source, a second silicon source and water to obtain a second gel; adjusting the pH value of the second gel to 8.5 to 12.5 and then performing two-stage hydrothermal crystallization treatment to obtain the seed crystal; wherein, the stirring and mixing rate is 200 to 800 rpm; and / or, the stirring and mixing temperature is 20 to 100 °C; and / or, the stirring and mixing time is 0.1 to 24 h; and / or, the second silicon source is selected from any one or more of silica sol, tetraethyl orthosilicate, macroporous silica gel, silicon powder; and / or, the aluminum source is selected from any one or more of sodium aluminate, pseudo-boehmite, aluminum sulfate, aluminum nitrate.

[0027] To improve the crystallization degree of the 13X molecular sieve, in one embodiment of the present application, it is preferred that the above two-stage hydrothermal crystallization treatment includes a first-stage hydrothermal crystallization treatment and a second-stage hydrothermal crystallization treatment carried out in sequence; wherein, the temperature of the first-stage hydrothermal crystallization treatment is 20 to 60 °C; and / or, the time of the first-stage hydrothermal crystallization treatment is 4 to 24 h; and / or, the temperature of the second-stage hydrothermal crystallization treatment is 80 to 120 °C; and / or, the time of the second-stage hydrothermal crystallization treatment is 6 to 48 h.

[0028] In addition, in order to further improve the mixing effect of the aluminum source, silicon source and water, the specific steps of preferably stirring and mixing the above aluminum source, second silicon source and water raw materials include: stirring and mixing the silicon source and water at a temperature of 20-60°C for a time of 0.1-12 h and at a rotation speed of 200-800 rpm to obtain a silicon-containing solution with a concentration of 28%-99 wt%; stirring and mixing the aluminum source and water at a temperature of 20-60°C for a time of 0.1-12 h and at a rotation speed of 200-800 rpm to obtain an aluminum-containing solution with a concentration of 28%-99 wt%, and stirring and mixing the silicon-containing solution and the aluminum-containing solution to obtain a second gel.

[0029] Preferably, the method for adjusting the pH value of the second gel is to slowly add a solid base or an aqueous solution of a base to the second gel; preferably, the base is sodium hydroxide and / or potassium hydroxide. Preferably, after the hydrothermal crystallization treatment in step S22, the reaction product needs to be filtered and washed until neutral, and then dried at 80-120°C until there is no obvious weight loss to obtain 13X molecular sieve.

[0030] In order to remove impurities such as moisture and carbon deposition in the waste molecular sieve, and further reduce the preparation cost of the 13X molecular sieve and increase the pore volume and specific surface area of the 13X molecular sieve, in one embodiment of the present application, preferably, the above preparation method further includes a process of pretreating the waste molecular sieve, and the pretreatment process includes: sintering a mixture including the waste molecular sieve and a sodium salt to obtain a sintered product; sequentially performing aluminum dissolution treatment and solid-liquid separation on the sintered product with an acidic solution to obtain an aluminum-rich solution and a residue; sequentially performing silicon dissolution treatment and solid-liquid separation on the residue with an alkaline solution to obtain a silicon-rich solution; wherein, the mass ratio of the waste molecular sieve to the sodium salt is 1:0.5-5; and / or, the sintering temperature is 550-800°C; and / or, the sintering time is 60-120 min.

[0031] In order to further reduce the preparation cost of the 13X molecular sieve and increase the pore volume and specific surface area of the 13X molecular sieve, in one embodiment of the present application, preferably, the above acidic solution is a monobasic acid solution with a mass fraction of 10-35%; and / or, the monobasic acid is hydrochloric acid and / or nitric acid; and / or, the alkaline solution includes a monobasic base and water, and the mass ratio of the residue, the monobasic base and water is 1.5-100:40-60:50-400; and / or, the monobasic base is NaOH and / or KOH; and / or, the waste molecular sieve is selected from any one or more of waste HZSM-5 molecular sieve catalysts, waste MTO catalysts, fly ash, waste FCC catalysts, waste VOC adsorbents; and / or, the sodium salt is Na2SO4 and / or NaCO3.

[0032] In addition, preferably, the size of the waste molecular sieve is less than 200 mesh.

[0033] In another typical embodiment of the present application, a modified alkene separation adsorbent is provided, and the modified alkene separation adsorbent is prepared by the aforementioned preparation method.

[0034] The modified alkene separation adsorbent obtained by the preparation method of the present application has high activity, high selectivity, high adsorption capacity, high diffusion performance and easy regeneration performance. Applying the modified alkene separation adsorbent to the separation of olefins and alkanes helps to improve the separation efficiency of olefins and alkanes.

[0035] In addition, in order to improve the preparation effect and efficiency of the modified alkene separation adsorbent, in an embodiment of the present application, it is preferably in the above step S4 that after mixing the carbon-coated 13X molecular sieve and the silicon source solution, a hydrothermal reaction and a first calcination treatment are carried out in sequence. The product after the first calcination treatment is immersed in a zinc-containing solution for 18 - 22 h for zinc deposition treatment, and the product after the zinc deposition treatment is put into a reduction solution to react for 5 - 8 h for reduction treatment; the product after the reduction treatment is subjected to a second calcination treatment to obtain the modified alkene separation adsorbent.

[0036] Preferably, the temperature of the above hydrothermal reaction is 60 - 80 °C, and the time of the hydrothermal reaction is 6 - 10 h; the temperature of the first calcination treatment is 550 - 800 °C, and the time of the first calcination treatment is 3 - 10 h; the temperature of the second calcination treatment is 500 - 800 °C, and the time of the second calcination treatment is 4 - 10 h;

[0037] Preferably, the concentration of the above zinc-containing solution is 38 - 55 g / L, and / or the concentration of the reduction solution is 14 - 25 g / L;

[0038] Preferably, the above zinc-containing solution is a zinc nitrate solution; the reduction solution is a sodium borohydride solution; the silicon source solution is a tetraethyl orthosilicate solution.

[0039] The beneficial effects of the present application will be further described below in conjunction with examples.

[0040] Example 1

[0041] (1) Dissolve 21.0 g of silica sol (mass fraction 30%) in 36.0 g of deionized water. After pre-treating at 25 °C for 1 hour in a closed reaction kettle, a silicon-containing material is obtained. Dissolve 24 g of aluminum sulfate in 18.0 g of deionized water and stir at 25 °C for 1 h to obtain an aluminum-containing material. Slowly add the aluminum-containing material to the silicon-containing material (the dropping rate is completed in 0.8 h), continue to stir at 60 °C for 8 h, and the stirring and mixing rate is 500 rpm to obtain a mixture gel. Dissolve 6.74 g of sodium hydroxide in 36 g of deionized water dispersion and add it to the mixture gel until the pH value is 12 to obtain a gelled slurried solution. Place it in a hydrothermal reaction kettle and perform two-stage temperature-controlled crystallization. The first-stage crystallization temperature is 40 °C and the time is 12 hours. The second-stage crystallization temperature is 95 °C and the time is 24 hours to obtain 13X seeds (where the molar ratio of each component is: SiO2 / Al2O3 = 1.5:1, Na2O / SiO2 = 1.6:1, H2O / SiO2 = 32:1).

[0042] (2) Grind fly ash to 100 mesh. After uniformly mixing the ground fly ash and NaCO3 in a mass ratio of 1:2.5, sinter at 700 °C for 90 min. Dissolve the sintered product with 25% hydrochloric acid by mass, and filter to obtain an aluminum-rich solution and a residue. Stir and mix the residue, NaOH, and H2O in a mass ratio of 50:50:200 evenly, and filter to obtain a silicon-rich solution. According to the molar ratio SiO2 / Al2O3 = 3.0:1, Na2O / SiO2 = 3.0:1, H2O / SiO2 = 50:1, weigh the silicon-rich solution and the aluminum-rich solution for proportioning to obtain a gelled mother liquor.

[0043] (3) Based on the mass of the gelled mother liquor being 100%, add a solution containing 13X molecular sieve seeds with a mass of 15% to the gelled mother liquor prepared in step (2), age at 60 °C for 12 h, and then perform hydrothermal crystallization at 80 °C for 12 h. Filter, wash the hydrothermal seeds to neutrality, and dry to constant weight at 100 °C to obtain 13X molecular sieve, where the molar ratio of silicon element and aluminum element in the 13X molecular sieve is 2.57:1; the pore volume of the 13X molecular sieve is 0.461 cm 3 / g, the specific surface area of the 13X molecular sieve is 897 m 2 / g, the average pore diameter of the 13X molecular sieve is 0.91 nm, and the proportion of mesopores and macropores is 72.56%.

[0044] (4) Immerse the 13X molecular sieve in the carbon source solution at a temperature of 25 °C for 24 h. Under an argon atmosphere, heat the impregnated 13X molecular sieve to 750 °C for calcination for 3 hours to obtain carbon-coated 13X molecular sieve; wherein, the solute of the carbon source solution is furfural, the solvent is N,N-dimethylformamide, the mass ratio of the 13X molecular sieve to the volume of the carbon source solution is 500:1 g / L, and the molar concentration of the carbon source solution is 0.1 mol / L.

[0045] (5) Take 50 g of the carbon-coated 13X molecular sieve and put it into 1 L of an aqueous solution of tetraethyl orthosilicate with a volume ratio of 0.5% for mixing. Hydrothermally react the mixed solution at 60 °C for 6 hours. Filter, wash, and dry the reacted solution in sequence to obtain a solid. Calcinate the solid at 550 °C for 3 hours to obtain the calcined solid; dissolve 45 g of zinc nitrate in 1 L of deionized water to form an aqueous zinc nitrate solution. Add 30 g of the calcined solid to the aqueous zinc nitrate solution to form a mixed solution. Let the mixed solution stand for 20 hours, and then filter, wash, and dry the standing mixed solution in sequence to obtain a solid. Dissolve 20 g of NaBH4 in 1 L of deionized water to form an aqueous NaBH4 solution. Add 25 g of the solid to the aqueous NaBH4 solution and react for 6 hours. Filter, wash, and dry the reacted solution to obtain a solid. Finally, calcinate the solid in an air atmosphere at 500 °C for 4 hours and vacuum dry it at room temperature for 24 hours to obtain the modified alkene separation adsorbent.

[0046] Example 2

[0047] The difference from Example 1 is that: (1) Dissolve 1 g of silicon powder in 18 g of deionized water, and after pretreatment at 25 °C for 1 hour in a closed reaction kettle, obtain a silicon-containing material; at the same time, dissolve 12 g of aluminum nitrate in 18.0 g of deionized water and stir at 35 °C for 1 hour to prepare an aluminum-containing material. Slowly add the prepared aluminum-containing material dropwise to the silicon-containing material (the dropping rate is completed in 0.6 h), and continue to stir at 50 °C for 6 hours to obtain a mixture gel; dissolve 2 g of sodium hydroxide in 36 g of deionized water to obtain a dispersion, and add it to the mixture gel until the pH value is 11.8 to obtain a gel slurry solution, and then transfer it to a hydrothermal reaction kettle to perform a two-stage temperature-controlled crystallization process: the first-stage crystallization temperature is set at 50 °C for 14 hours; the second-stage crystallization temperature is controlled at 100 °C for 18 hours to obtain 13X crystal seeds (where the molar ratio of each component is: SiO2 / Al2O3 = 0.6:1, Na2O / SiO2 = 3:1, H2O / SiO2 = 20:1).

[0048] (2) Grind the waste HZSM-5 molecular sieve catalyst to 100 mesh. After mixing the ground Z-5 molecular sieve catalyst and NaCO3 evenly at a mass ratio of 1:0.5, calcine them at 550 °C for 60 min, dissolve the calcined product with 35% nitric acid by mass fraction, and filter to obtain an aluminum-rich solution and a residue; Stir and mix the residue, NaOH, and H2O evenly at a mass ratio of 5:40:50, and filter to obtain a silicon-rich solution; According to the molar ratio SiO2 / Al2O3 = 0.5:1, Na2O / SiO2 = 0.5:1, H2O / SiO2 = 10:1, weigh the silicon-rich solution and the aluminum-rich solution for proportioning to obtain a gel-like mother liquor.

[0049] (3) Based on the mass of the gel-like mother liquor being 100%, add a solution containing 13X molecular sieve seeds with a mass of 5% to the gel-like mother liquor prepared in step (2), age at 20 °C for 0.1 h, then carry out hydrothermal crystallization at 60 °C for 0.1 h. Filter, wash the hydrothermal seeds to neutrality, and dry them to constant weight at 80 °C to obtain 13X molecular sieve, where the molar ratio of silicon element to aluminum element in the 13X molecular sieve is 2.32:1; The pore volume of the 13X molecular sieve is 0.453 cm 3 / g, the specific surface area of the 13X molecular sieve is 886 m 2 / g, the average pore diameter of the 13X molecular sieve is 0.83 nm, and the proportion of mesopores and macropores is 70.24%.

[0050] (4) Immerse the 13X molecular sieve in the carbon source solution at an immersion temperature of 25 °C for 6 h. Under an argon atmosphere, heat the immersed 13X molecular sieve to 600 °C for calcination for 2 hours to obtain carbon-coated 13X molecular sieve; Among them, the solute of the carbon source solution is benzene, the solvent is ethanol, the mass ratio of the 13X molecular sieve to the volume of the carbon source solution is 500:1 g / L, and the molar concentration of the carbon source solution is 0.1 mol / L.

[0051] (5) Take 50 g of carbon-coated 13X molecular sieve and put it into 1 L of an aqueous solution of tetraethyl orthosilicate with a volume ratio of 0.5%, and mix. Hydrothermally react the mixed solution at 60 °C for 6 hours. Filter, wash, and dry the reacted solution in sequence to obtain a solid. Calcinate the solid at 550 °C for 3 hours to obtain a calcined solid; dissolve 45 g of zinc nitrate in 1 L of deionized water to form an aqueous zinc nitrate solution, add 30 g of the calcined solid to the aqueous zinc nitrate solution to form a mixed solution, let the mixed solution stand for 20 hours, and then filter, wash, and dry the standing mixed solution in sequence to obtain a solid. Dissolve 20 g of NaBH4 in 1 L of deionized water to form an aqueous NaBH4 solution, add 25 g of the solid to the aqueous NaBH4 solution, react for 6 hours, filter, wash, and dry the reacted solution to obtain a solid. Finally, calcinate the solid in an air atmosphere at 500 °C for 4 hours and vacuum dry it at room temperature for 24 hours to obtain a modified alkene separation adsorbent.

[0052] Example 3

[0053] The difference from Example 1 is that: (1) Dissolve 0.17 g of silicon powder in 6 g of deionized water, and pretreat it at 25 °C for 1 hour in a closed reactor to obtain a silicon-containing material; at the same time, dissolve 12 g of aluminum nitrate in 18.0 g of deionized water and stir it at 35 °C for 1 hour to prepare an aluminum-containing material solution. Slowly add the aluminum-containing material to the silicon-containing material (the dropping rate is completed in 1 h), and stir at 100 °C for 24 hours to obtain a mixture gel; dissolve 0.9 g of sodium hydroxide in 6 g of deionized water to prepare a dispersion, and add it to the mixture gel until the pH value is 12.5 to obtain a gelled slurry solution, and then transfer it to a hydrothermal reactor for two-stage crystallization. First, crystallize at 60 °C for 24 hours, and then raise the temperature to 120 °C for a crystallization reaction of 48 hours to obtain 13X seeds (where the molar ratio of each component is: SiO2 / Al2O3 = 0.1:1, Na2O / SiO2 = 4:1, H2O / SiO2 = 1:1).

[0054] (2) Grind the waste MTO catalyst to 100 mesh, mix the ground waste MTO catalyst and NaCO3 evenly according to a mass ratio of 1:5, then calcine at 800 °C for 120 min, dissolve the calcined product with 10% nitric acid by mass, and filter to obtain an aluminum-rich solution and a residue; stir and mix the residue, NaOH, and H2O evenly according to a mass ratio of 100:60:400, and filter to obtain a silicon-rich solution; according to the molar ratio SiO2 / Al2O3 = 6.0:1, Na2O / SiO2 = 6.0:1, H2O / SiO2 = 100:1, weigh the silicon-rich solution and the aluminum-rich solution for proportioning to obtain a gelled mother liquor.

[0055] (3) Based on the mass of the gel-like mother liquor being 100%, into the gel-like mother liquor prepared in step (2), a solution containing 13X molecular sieve seeds with a mass of 20% is added, aged at 100 °C for 24 h, and then subjected to hydrothermal crystallization at 105 °C for 36 h. The hydrothermal seeds are filtered, washed until neutral, and dried to constant weight at 120 °C to obtain 13X molecular sieve, where the molar ratio of silicon element to aluminum element in the 13X molecular sieve is 2.2:1; the pore volume of the 13X molecular sieve is 0.427 cm 3 / g, the specific surface area of the 13X molecular sieve is 844 m 2 / g, the average pore diameter of the 13X molecular sieve is 0.78 nm, and the proportion of mesopores and macropores is 68.31%, and finally a modified alkene separation adsorbent is obtained.

[0056] Example 4

[0057] The difference from Example 1 is that (1) 14.650 g of tetraethyl orthosilicate and 36 g of deionized water are mixed at a volume ratio of 1:1, and after pretreatment at 25 °C for 1 hour in a closed reaction kettle, a silicon-containing material is obtained. At the same time, 12 g of aluminum nitrate is dissolved in 18.0 g of deionized water and stirred at 35 °C for 1 hour to obtain an aluminum-containing material. Then, the aluminum-containing material is gradually added dropwise to the silicon-containing material (the dropping rate is completed in 0.5 hour), and mixed and stirred at 20 °C for 0.1 hour to prepare a mixture gel; 0.56 g of sodium hydroxide is dissolved in 6 g of deionized water as a dispersion liquid, and slowly poured into the mixture gel until the pH value is 8.5 to obtain a gel slurrying solution, which is then transferred to a hydrothermal reaction kettle for staged crystallization reaction: first, the crystallization temperature is set at 20 °C for 4 hours; then it is raised to 80 °C and the crystallization is maintained for 6 hours to obtain 13X seeds (where the molar ratio of each component is: SiO2 / Al2O3 = 2.5:1, Na2O / SiO2 = 0.1:1, H2O / SiO2 = 40:1), and finally a modified alkene separation adsorbent is obtained, where the molar ratio of silicon element to aluminum element in the 13X molecular sieve is 2.9:1; the pore volume of the 13X molecular sieve is 0.431 cm 3 / g, the specific surface area of the 13X molecular sieve is 851 m 2 / g, the average pore diameter of the 13X molecular sieve is 0.81 nm, and the proportion of mesopores and macropores is 69.21%.

[0058] Example 5

[0059] The difference from Example 1 is that the impregnation temperature is 20 °C, the impregnation time is 24 h, the mass ratio of the 13X molecular sieve to the volume of the carbon source solution is 600:1 g / L, and the molar concentration of the carbon source solution is 0.05 mol / L, and finally a modified alkene separation adsorbent is obtained.

[0060] Example 6

[0061] The difference from Example 1 is that the temperature of the impregnation treatment is 30 °C, the time of the impregnation treatment is 6 h, the mass ratio of the 13X molecular sieve to the volume of the carbon source solution is 400:1 g / L, the molar concentration of the carbon source solution is 0.2 mol / L, and finally a modified alkene separation adsorbent is obtained.

[0062] Example 7

[0063] The difference from Example 1 is that the temperature of the impregnation treatment is 40 °C, the time of the impregnation treatment is 5 h, the mass ratio of the 13X molecular sieve to the volume of the carbon source solution is 300:1 g / L, the molar concentration of the carbon source solution is 0.3 mol / L, and finally a modified alkene separation adsorbent is obtained.

[0064] Example 8

[0065] The difference from Example 1 is that the temperature of the calcination treatment is 900 °C, the time of the calcination treatment is 2 h, and finally a modified alkene separation adsorbent is obtained.

[0066] Example 9

[0067] The difference from Example 1 is that the temperature of the calcination treatment is 600 °C, the time of the calcination treatment is 4 h, and finally a modified alkene separation adsorbent is obtained.

[0068] Example 10

[0069] The difference from Example 1 is that the temperature of the calcination treatment is 1000 °C, the time of the calcination treatment is 5 h, and finally a modified alkene separation adsorbent is obtained.

[0070] Comparative Example 1

[0071] The difference from Example 1 is that the 13X molecular sieve is directly used for the preparation of the alkene separation adsorbent, and finally an alkene separation adsorbent is obtained.

[0072] Testing method

[0073] A fixed-bed adsorption experiment was carried out on the alkene separation adsorbents obtained in the above examples and comparative examples: An alkene mixture (including C6, C7, and C8 components, with an olefin content of 60%) was passed through a fixed bed containing the adsorbent (the mass ratio of the adsorbent to the alkene mixture was 1:10), and the change in the concentration of the alkene mixture passing through the bed layer was monitored to determine the adsorption performance of the adsorbent for a specific alkene mixture. The results of the olefin selectivity and olefin purity are shown in Table 1.

[0074] Table 1

[0075]

[0076] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0077] Step S3 of the present application optimizes the structure of 13X molecular sieve to form carbon-coated 13X molecular sieve. This structure helps to improve the mechanical strength and thermal stability of the molecular sieve. And during this process, the structure of 13X molecular sieve is optimized to a great extent, and the carbon-coated 13X molecular sieve has parameters such as a certain range of specific surface area and porosity. Therefore, the modified alkene / alkane separation adsorbent prepared from the carbon-coated 13X molecular sieve has high selectivity, high adsorption capacity and easy regeneration performance. Applying this modified alkene / alkane separation adsorbent to the separation of olefins and alkanes helps to improve the separation efficiency of olefins and alkanes. In addition, on the one hand, the 13X molecular sieve prepared from waste catalyst as raw material in steps S1 and S2 of the present application realizes waste utilization and reduces the cost of preparing 13X molecular sieve. On the other hand, the 13X molecular sieve prepared by the method of the present application has characteristics such as a high silicon-aluminum ratio, a large pore volume and specific surface area, and regular morphology, which helps to improve the utilization rate of the silicon source of the 13X molecular sieve, provide more adsorption sites for the separation process of alkanes and olefins, and improve the flow and diffusion performance of alkene / alkane molecules inside the molecular sieve, thereby improving the separation efficiency and separation effect of alkanes and olefins.

[0078] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a modified alkane-olefin separation adsorbent, characterized in that: The preparation method comprises the following steps: Step S1, subjecting the waste catalyst to aluminum dissolution treatment and silicon dissolution treatment in sequence to obtain aluminum-rich liquid and silicon-rich liquid; Step S2, subjecting the raw materials including the aluminum-rich liquid, the silicon-rich liquid and the seed crystal to gelation treatment, aging treatment and hydrothermal crystallization treatment in sequence to obtain a 13X molecular sieve; Step S3, subjecting the raw materials including the 13X molecular sieve and the carbon source solution to an impregnation treatment and a calcination treatment in sequence to obtain a carbon-coated 13X molecular sieve; and Step S4, mixing the carbon-coated 13X molecular sieve and the silicon source solution, and sequentially performing a hydrothermal reaction, a first calcination treatment, a zinc deposition treatment, a reduction treatment, and a second calcination treatment to obtain a modified alkane-alkene separation adsorbent; In the step S2, the 13X molecular sieve contains silicon and aluminum, and the molar ratio of the silicon to the aluminum is 2.2-2.9:1; The pore volume of the 13X molecular sieve is 0.3-0.5 cm 3 / g; the specific surface area of ​​the 13X molecular sieve is 700~950m 2 / g; In step S3, the immersion temperature is 20-30° C. and the immersion time is 6-24 hours. The ratio of the mass of the 13X molecular sieve to the volume of the carbon source solution is 400-600:1 g / L; The molar concentration of the carbon source solution is 0.05-0.2 mol / L; The waste catalyst is waste molecular sieve and / or fly ash.

2. The preparation method according to claim 1, characterized in that: The solute in the carbon source solution is selected from any one or more of benzene, furan and furfural; and / or the solvent in the carbon source solution is ethanol and / or N,N-dimethylformamide; And / or, the temperature of the calcination treatment is 600-900° C.; and / or, the time of the calcination treatment is 2-4 hours.

3. The preparation method according to claim 1 or 2, characterized in that: The seed crystals contain SiO2, Al2O3, Na2O and H2O, wherein the molar ratio of the SiO2 to the Al2O3 is 0.01-2.5:1, and the molar ratio of the Na2O, the H2O and the SiO2 is 0.01-4.0:1.0-40.0:

1.

4. The preparation method according to claim 1 or 2, characterized in that: The step S2 comprises: Step S21, performing the gelation treatment on the aluminum-rich liquid and the silicon-rich liquid to obtain a first gel; Step S22, subjecting the first gel and the seed crystal to the aging treatment and the hydrothermal crystallization treatment in sequence to obtain the 13X molecular sieve; The first gel comprises SiO2, Al2O3, Na2O and H2O, wherein the molar ratio of the SiO2 to the Al2O3 is 0.5-6.0:1, and the molar ratio of the Na2O, the H2O and the SiO2 is 0.5-6.0:10-100:1; And / or, the temperature of the aging treatment is 20~100°C, and the time of the aging treatment is 0.1~24h; and / or, the temperature of the hydrothermal crystallization treatment is 60~105°C, and the time of the hydrothermal crystallization treatment is 0.1~36h.

5. The preparation method according to claim 4, characterized in that: The mass ratio of the seed crystal to the first gel is 5-20:

100.

6. The preparation method according to claim 1 or 2, characterized in that: The preparation method further comprises: The preparation process of the seed crystal comprises: Stirring and mixing raw materials including an aluminum source, a second silicon source and water to obtain a second gel; Adjusting the pH value of the second gel to 8.5-12.5 and then performing two-stage hydrothermal crystallization treatment to obtain the seed crystal; Wherein, the stirring and mixing speed is 200-800 rpm; and / or, the stirring and mixing temperature is 20-100° C.; and / or, the stirring and mixing time is 0.1-24 h; And / or, the second silicon source is selected from any one or more of silica sol, tetraethyl orthosilicate, macroporous silica gel, and silicon powder; And / or, the aluminum source is selected from any one or more of sodium aluminate, pseudo-boehmite, aluminum sulfate, and aluminum nitrate.

7. The preparation method according to claim 6, characterized in that: The two-stage hydrothermal crystallization treatment includes a first stage hydrothermal crystallization treatment and a second stage hydrothermal crystallization treatment performed sequentially; Wherein, the temperature of the first hydrothermal crystallization treatment is 20-60°C; and / or, the time of the first hydrothermal crystallization treatment is 4-24h; And / or, the temperature of the second hydrothermal crystallization treatment is 80-120° C.; and / or, the time of the second hydrothermal crystallization treatment is 6-48 hours.

8. The preparation method according to claim 1 or 2, characterized in that: The preparation method further comprises a process of pre-treating the waste catalyst, and the pre-treatment process comprises: sintering the mixture including the waste catalyst and the sodium salt to obtain a sintered product; The sintered product is sequentially subjected to the aluminum dissolving treatment and solid-liquid separation using an acidic solution to obtain the aluminum-rich liquid and residue; Using an alkaline solution to sequentially perform the silicon dissolving treatment and solid-liquid separation on the residue to obtain the silicon-rich liquid; Wherein, the mass ratio of the waste catalyst to the sodium salt is 1:0.5-5; and / or, the temperature of the sintering treatment is 550-800° C.; and / or, the time of the sintering treatment is 60-120 min.

9. The preparation method according to claim 8, characterized in that: The acidic solution is a monoprotic acid solution, and the mass fraction of the monoprotic acid solution is 10-35%; and / or the monoprotic acid is hydrochloric acid and / or nitric acid; And / or, the alkaline solution comprises a monobasic alkali and water, and the mass ratio of the residue, the monobasic alkali and the water is 1.5-100:40-60:50-400; and / or, the monobasic alkali is NaOH and / or KOH; And / or, the waste molecular sieve is selected from any one or more of waste HZSM-5 molecular sieve catalyst, waste MTO catalyst, and waste FCC catalyst; And / or, the sodium salt is Na2SO4 and / or NaCO3.

10. A modified alkane-olefin separation adsorbent, characterized in that: The modified alkane-olefin separation adsorbent is prepared by the preparation method described in any one of claims 1 to 9.

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