Method for preparing high-performance molecular sieve membrane through ion exchange at melting state

[0047] Example 1 Li-SAPO-34 molecular sieve membrane was prepared by immersing in 1wt% lithium nitrate acetone solution and performing ion exchange in air at 300°C for 8 hours

[0048] Step 1: Add 2.46 g of deionized water to 31.13 g of tetraethylammonium hydroxide solution (TEAOH, 35 wt%), then weigh 7.56 g of aluminum isopropoxide and add it to the aforementioned solution, and stir at room temperature for 2-3 hours; then Add dropwise 1.665g silica sol (40wt%), stir 1 hour; Finally slowly add dropwise 8.53g phosphoric acid solution (H 3 PO 4 , 85wt%), stirred overnight. Microwave heating was used for crystallization at 180°C for 7 hours. After the product was taken out, it was centrifuged, washed with deionized water, and dried to obtain SAPO-34 molecular sieve seed crystals. SEM images of SAPO-34 molecular sieve seed crystals, such as figure 1 As shown, the seed crystal is a flaky crystal of 300×300×100 nm. The XRD pattern of SAPO-34 molecular sieve seed crystal, such as

[0063] Example 2 Soak in 1wt% potassium acetate aqueous solution, and prepare K-SAPO-34 molecular sieve membrane by ion exchange in 300°C air for 8 hours

[0064] The difference from Example 1 is that in Step 5, the molecular sieve membrane tube obtained in Step 4 was soaked in 1 wt% potassium acetate aqueous solution for 3 minutes, and dried at room temperature. All the other steps are the same as in Example 1. The seed crystals used are flaky crystals with a size of 300×300×100 nm. Figure 5 It is the SEM picture of the molecular sieve membrane after ion exchange, such as Figure 5 As shown, it can be seen that ion exchange has no significant effect on the morphology of the membrane.

[0065] CO 2 / CH 4 The gas separation test method is the same as in Example 1, and the test results are shown in Table 3. Molecular sieve membrane CO after ion exchange 2 / CH 4 The separation selectivity of the mixed gas is 60, which is respectively increased by 33% compared with that b

[0070] Example 3 Soak in 1wt% sodium nitrate aqueous solution, ion exchange in air at 310°C for 8 hours to prepare Na-SAPO-34 molecular sieve membrane

[0071] The difference from Example 1 is that in step 5, the molecular sieve membrane tube obtained in step 4 was soaked in 1 wt% sodium nitrate aqueous solution for 3 minutes, and dried at room temperature. The roasting temperature in step 4 is 310 ℃. All the other steps are the same as in Example 1. The seed crystals used are flaky crystals with a size of 300×300×100 nm.

[0072] CO 2 / CH 4 The gas separation test method is the same as in Example 1, and the test results are shown in Table 4. Molecular sieve membrane CO after ion exchange 2 / CH 4 The separation selectivity of the mixed gas is 63, which is respectively increased by 29% compared with that before the exchange.

[0073] Table 4 CO of Example 3 2 / CH 4 Gas Separation Test Results

[0074]

[0075] Note: The pressure difference between the feed side