A Zn-MOR molecular sieve and its application in adsorbing and separating CO2 in low-carbon hydrocarbons

Abstract

The present invention provides a Zn-MOR molecular sieve and its adsorption and separation of CO in low-carbon hydrocarbons 2 applications, especially CO 2 / C 2 H 2 Application of difficult-to-separate systems. The present invention mixes zinc salt, sodium aluminate, sodium hydroxide, silicon source and water, and hydrothermally crystallizes the obtained gel to obtain zinc-containing MOR heteroatom molecular sieve. The synthesis process is simple and the product cost is low. It is the first to achieve CO 2 / C 2 H 2 Capturing CO 2 Molecular sieve materials, Zn-MOR molecular sieve has high selective adsorption of CO in low carbon hydrocarbons. 2 performance, can be applied to CO 2 / C 2 H 2 separation.

Description

Technical Field

[0001] The present invention provides a Zn-MOR molecular sieve and its application in the adsorption and separation of CO2 in low-carbon hydrocarbons, especially in a CO2 / C2H2 difficult-to-separate system. Background Art

[0002] During the secondary processing of crude oil, coal and natural gas, various industrial stream gases containing CO2 are generated, such as the product gas containing CO2 in the preparation of acetylene from natural gas, the cracking tail gas containing CO2 from the catalyst cracking of the refinery and the by-product refinery dry gas containing CO2, and the tail gas containing CO2 generated by the combustion of thermal coal in power plants. Among them, the separation of CO2 / C2H2 is the most challenging.

[0003] In the prior art, CN106633091A discloses a dual-penetration metal organic framework material for efficient selective separation and adsorption of CO2 / C2H2 and C2H2 / CH4 and a preparation method thereof, which uses 1,3,5-tribromobenzene, ethyl acrylate, anhydrous potassium carbonate, and tetrabutylammonium bromide to perform cross-coupling reaction to prepare MOF materials. Although the prepared MOF material has high CO2 / C2H2 and C2H2 / CH4 selective separation and adsorption, its preparation cost is high and the method is complicated, and it is not suitable for large-scale promotion. At present, molecular sieves are widely used adsorption materials in the field of adsorption and separation, but there are few molecular sieves used in CO2 / C2H2 systems, and their adsorption capacity is limited, making it difficult to achieve high selective adsorption and removal of CO2 by molecular sieves in industrial streams.

[0004] Therefore, in order to obtain a molecular sieve having high selectivity for systems in low-carbon hydrocarbons and at the same time having adsorption separation performance that can highly selectively remove low-content CO2 in low-carbon hydrocarbons, the present invention is specially proposed. Summary of the invention

[0005] The present invention provides a Zn-MOR molecular sieve and its application in adsorbing and separating CO2 in low-carbon hydrocarbons. The technical solution adopted by the present invention is:

[0006] Step 1: Mix zinc salt, sodium aluminate, sodium hydroxide, silicon source and water to obtain a gel;

[0007] Step 2: putting the prepared gel into a reactor for hydrothermal crystallization;

[0008] Step 3: Take out the block product obtained from the reactor, filter it, air dry it naturally, and then put it into an oven to dry;

[0009] Step 4: After drying, the obtained solid block is taken out, which is the prepared Zn-MOR molecular sieve;

[0010] Further, in step 1, the effective ingredients of the gel are calculated as zinc salt, SiO2, Al2O3, Na2O and H2O;

[0011] The molar ratio of the zinc salt to SiO2 is 1:10-800;

[0012] The molar ratio of SiO2 to Al2O3 is 20-25:1;

[0013] The molar ratio of sodium hydroxide to sodium aluminate is 4 to 6:1;

[0014] The molar ratio of H2O to sodium aluminate is 200-250:1;

[0015] Furthermore, the zinc salt in step 1 can be zinc chloride, zinc nitrate, zinc oxide, or zinc hydroxide;

[0016] Furthermore, in step 1, the silicon source may be one or more of silica sol, white carbon black, and sodium silicate;

[0017] Further, in step 2, the hydrothermal crystallization temperature is controlled at 170-190°C;

[0018] Further, in step 2, the hydrothermal crystallization time is controlled within 3-11 days;

[0019] Furthermore, the natural air drying time in step 3 is 12 to 24 hours, and the drying temperature in the oven is 60 to 120° C., and the drying time is 8 to 12 hours.

[0020] Due to the adoption of the above technical solution, the beneficial effects achieved by the present invention are as follows:

[0021] The MOR molecular sieve prepared by the present invention has good crystallinity and high purity; it is the first molecular sieve material that realizes CO2 capture by CO2 / C2H2, so that the modified MOR molecular sieve has high selective adsorption and separation of CO2 in low-carbon hydrocarbons, especially in CO2 / C2H2 difficult-to-separate systems, and can purify industrial streams of carbon-containing systems; the Zn-MOR molecular sieve prepared by the present invention has a simple synthesis process without the use of templates, a simple method, easy-to-obtain raw materials, low cost, and environmental protection advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Example 1-9 XRD patterns of MOR molecular sieves with different Zn / Si ratios prepared using zinc chloride as zinc salt;

[0023] Figure 2 Comparative Example 1-4 XRD patterns of MOR molecular sieves prepared using zinc nitrate, zinc oxide, and zinc hydroxide as zinc salts;

[0024] Figure 3Examples 1, 2, 4, 5, and 7 show CO2 adsorption isotherms of MOR molecular sieves with different Zn / Si ratios prepared using zinc chloride as the zinc salt;

[0025] Figure 4 Examples 1, 2, 4, 5, and 7 show C2H2 adsorption isotherms of MOR molecular sieves with different Zn / Si ratios prepared using zinc chloride as the zinc salt;

[0026] Figure 5 Comparative Example 1: Multi-component attachment isotherm of conventional MOR molecular sieve without adding zinc salt;

[0027] Figure 6 Example 7 Multi-component adsorption isotherm of MOR molecular sieve with a Zn / Si=50 ratio prepared using zinc chloride as zinc salt;

[0028] Figure 7 The breakthrough curve of the MOR molecular sieve prepared with zinc chloride as the zinc salt in Example 7 for removing CO2 from an industrial stream of CO2 / C2H2, wherein the adsorption-desorption flow ratio is 3:10;

[0029] Figure 8 The breakthrough curve of the MOR molecular sieve prepared by using zinc chloride as the zinc salt in Example 7 for removing CO2 from an industrial stream of CO2 / C2H2, wherein the adsorption-desorption flow ratio is 10:10;

[0030] Fig. 9 This is the breakthrough curve of the MOR molecular sieve prepared with zinc chloride as the zinc salt in Example 7 for removing CO2 in an industrial stream of N2 / CO2;

[0031] Fig.10 This is the breakthrough curve of the MOR molecular sieve prepared with zinc chloride as the zinc salt in Example 7 for removing CO2 from an industrial stream of CO2 / low-carbon hydrocarbons;

[0032] Fig.11 This is the breakthrough curve of the MOR molecular sieve prepared with zinc chloride as the zinc salt in Example 7 for removing CO2 in an industrial stream of CO2 / N2 / H2 / low-carbon hydrocarbons. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention is described in detail below in conjunction with specific embodiments and experimental data. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0034] The present invention provides a zinc-containing heteroatom molecular sieve, a preparation method and its application in the adsorption and separation of CO2 in low-carbon hydrocarbons, especially in the CO2 / C2H2 difficult-to-separate system. The specific preparation steps are:

[0035] Step 1: Mix zinc salt, sodium aluminate, sodium hydroxide, silicon source and water to obtain a gel;

[0036] Step 2: putting the prepared gel into a reactor for hydrothermal crystallization;

[0037] Step 3: Take out the block product obtained from the reactor, filter it, air dry it naturally, and then put it into an oven to dry;

[0038] Step 4: After drying, the obtained solid block is taken out, which is the prepared Zn-MOR molecular sieve;

[0039] Furthermore, in step 1, the effective ingredients of the gel are calculated as ZnCl2, SiO2, Al2O3, Na2O and H2O.

[0040] The molar ratio of the zinc salt to SiO2 is 1:10-800;

[0041] The molar ratio of SiO2 to Al2O3 is 20-25:1;

[0042] The molar ratio of sodium hydroxide to sodium aluminate is 4 to 6:1;

[0043] The molar ratio of H2O to sodium aluminate is 200-250:1;

[0044] Furthermore, the zinc salt in step 1 can be zinc chloride, zinc nitrate, zinc oxide, or zinc hydroxide;

[0045] Preferably, in step 1, zinc chloride is selected as the zinc salt;

[0046] Furthermore, in step 1, the silicon source may be one or more of silica sol, white carbon black, and sodium silicate;

[0047] Preferably, in step 1, the silicon source is selected from silica sol as the silicon source;

[0048] Furthermore, in step 2, the hydrothermal crystallization temperature is controlled at 170-190°C.

[0049] Further, in step 2, the hydrothermal crystallization time is controlled within 3-11 days, preferably 5-8 days;

[0050] Furthermore, the natural air drying time in step 3 is 12 to 24 hours, preferably 12 to 16 hours, the drying temperature in the oven is 60 to 120° C., preferably 80 to 100° C., and the time is 8 to 12 hours.

[0051] In some specific embodiments, in step 1, the aging time is controlled to be 3-6 hours, and the temperature can be room temperature;

[0052] In some specific embodiments, in step 1, care should be taken to avoid the formation of lumps during the stirring of the prepared gel.

[0053] Example 1

[0054] Add 0.9475g of sodium hydroxide and 0.5075g of sodium aluminate to 23.53g of deionized water, stir evenly, slowly add 0.012g of zinc chloride, and then slowly add 14.186g of 30wt% silica sol, stir for 4h and then perform hydrothermal crystallization, filter and dry to obtain the product.

[0055] Example 2

[0056] Add 0.9475g of sodium hydroxide and 0.5075g of sodium aluminate to 23.53g of deionized water, stir evenly, slowly add 0.024g of zinc chloride, and then slowly add 14.186g of 30wt% silica sol, stir for 4h and then perform hydrothermal crystallization, filter and dry to obtain the product.

[0057] Example 3

[0058] Add 0.9475g of sodium hydroxide and 0.5075g of sodium aluminate to 23.53g of deionized water, stir evenly, slowly add 0.032g of zinc chloride, and then slowly add 14.186g of 30wt% silica sol, stir for 4h and then perform hydrothermal crystallization, filter and dry to obtain the product.

[0059] Example 4

[0060] Add 0.9475g of sodium hydroxide and 0.5075g of sodium aluminate to 23.53g of deionized water, stir evenly, slowly add 0.048g of zinc chloride, and then slowly add 14.186g of 30wt% silica sol, stir for 4h and then perform hydrothermal crystallization, filter and dry to obtain the product.

[0061] Example 5

[0062] Add 0.9475g of sodium hydroxide and 0.5075g of sodium aluminate to 23.53g of deionized water, stir evenly, slowly add 0.096g of zinc chloride, and then slowly add 14.186g of 30wt% silica sol, stir for 4h and then perform hydrothermal crystallization, filter and dry to obtain the product.

[0063] Example 6

[0064] Add 0.9475g of sodium hydroxide and 0.5075g of sodium aluminate to 23.53g of deionized water, stir evenly, slowly add 0.1284g of zinc chloride, and then slowly add 14.186g of 30wt% silica sol, stir for 4h, then perform hydrothermal crystallization, filter and dry to obtain the product.

[0065] Example 7

[0066] Add 0.9475g of sodium hydroxide and 0.5075g of sodium aluminate to 23.53g of deionized water, stir evenly, slowly add 0.1926g of zinc chloride, and then slowly add 14.186g of 30wt% silica sol, stir for 4h, then perform hydrothermal crystallization, filter and dry to obtain the product.

[0067] Example 8

[0068] Add 0.9475g of sodium hydroxide and 0.5075g of sodium aluminate to 23.53g of deionized water, stir evenly, then slowly add 0.3853g of zinc chloride, and then slowly add 14.186g of 30wt% silica sol, stir for 4h, then perform hydrothermal crystallization, filter and dry to obtain the product.

[0069] Example 9

[0070] Add 0.9475g of sodium hydroxide and 0.5075g of sodium aluminate to 23.53g of deionized water, stir evenly, slowly add 0.9632g of zinc chloride, and then slowly add 14.186g of 30wt% silica sol, stir for 4h and then perform hydrothermal crystallization, filter and dry to obtain the product.

[0071] Comparative Example 1

[0072] 0.9475 g of sodium hydroxide and 0.5075 g of sodium aluminate were added to 23.53 g of deionized water, and stirred evenly. Then, 14.186 g of 30 wt% silica sol was slowly added, and stirred for 4 hours, and then hydrothermal crystallization was performed. The product was obtained by filtering and drying.

[0073] Comparative Example 2

[0074] Add 0.9475g of sodium hydroxide and 0.5075g of sodium aluminate to 23.53g of deionized water, stir evenly, slowly add 0.4213g of zinc nitrate hexahydrate, and then slowly add 14.186g of 30wt% silica sol, stir for 4h, then perform hydrothermal crystallization, filter and dry to obtain the product.

[0075] Comparative Example 3

[0076] Add 0.9475g of sodium hydroxide and 0.5075g of sodium aluminate to 23.53g of deionized water, stir evenly, then slowly add 0.1152g of zinc oxide, and then slowly add 14.186g of 30wt% silica sol, stir for 4h, then perform hydrothermal crystallization, filter and dry to obtain the product.

[0077] Comparative Example 4

[0078] Add 0.9475g of sodium hydroxide and 0.5075g of sodium aluminate to 23.53g of deionized water, stir evenly, then slowly add 0.1408g of zinc hydroxide, and then slowly add 14.186g of 30wt% silica sol, stir for 4h, then perform hydrothermal crystallization, filter and dry to obtain the product.

[0079] XRD characterization was performed on all embodiments and control examples. Embodiments 1, 2, 4, 5, and 7 were preferably selected to perform adsorption isotherm tests on CO2 and C2H2 at 298K. Comparative Example 1 was preferably selected to perform multi-component adsorption isotherm tests. Embodiment 7 was preferably selected to perform multi-component adsorption isotherm tests and penetration experiment tests.

[0080] Table 2 Test gas composition

[0081]

[0082]

[0083] The MOR molecular sieve of Example 7 was used to conduct a breakthrough experiment on the removal of CO2 from an industrial stream. Figure 7-11 It can be seen that the MOR molecular sieve prepared in the present invention has a much lower adsorption selectivity for hydrocarbon gases in a carbon dioxide / hydrocarbon mixture than for CO2, and thus can perform highly selective adsorption separation of CO2 in a CO2 / C2H2 difficult-to-separate system.

Claims

1. Application of Zn-MOR molecular sieve for adsorption and separation of CO2 in low-carbon hydrocarbons, characterized in that: The Zn-MOR molecular sieve is used for adsorption and separation of CO2 / C2H2; The preparation method of the Zn-MOR molecular sieve comprises the following steps: Step 1: Mix zinc salt, sodium aluminate, sodium hydroxide, silicon source and water to obtain a gel; Step 2: putting the prepared gel into a reactor for hydrothermal crystallization; Step 3: Take out the block product obtained from the reactor, filter it, air dry it naturally, and then put it into an oven to dry; Step 4: After drying, the obtained solid block is taken out, which is the prepared Zn-MOR molecular sieve; The zinc salt in step 1 is any one of zinc chloride, zinc nitrate, zinc oxide and zinc hydroxide; the silicon source is one or more of silica sol, white carbon black and sodium silicate; The effective ingredients of the gel include zinc salt, SiO2, Al2O3, Na2O and H2O; The molar ratio of the zinc salt to SiO2 is 1:10-800; The molar ratio of SiO2 to Al2O3 is 20-25:1; The molar ratio of sodium hydroxide to sodium aluminate is 4 to 6:1; The molar ratio of H2O to sodium aluminate is 200-250:1; In the step 2, the temperature of the hydrothermal crystallization is controlled at 170-190°C.

2. The use of a Zn-MOR molecular sieve for adsorption and separation of CO2 in light hydrocarbons as claimed in claim 1, characterized in that: In step 2, the hydrothermal crystallization time is controlled within 3-11 days.

3. The use of a Zn-MOR molecular sieve for adsorption and separation of CO2 in light hydrocarbons according to claim 1, characterized in that: The natural air drying time in step 3 is 12 to 24 hours, the oven drying temperature is 60 to 120° C., and the oven drying time is 8 to 12 hours.

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