Methods for preparing LiCa-LSX molecular sieves with mixed cations and applications thereof

A method for preparing LiCa-LSX molecular sieves with mixed cations, comprising the following steps:

• step 1 of preparing CaLSX molecular sieves:
• during the preparation of CaLSX molecular sieves, replacing all Na+ in NaLSX molecular sieves with Ca2+ by multiple times of exchange with a solution containing Ca2+ kept at room temperature, washing to remove Ca2+ and any Cl− adhered on the surface, and drying the filter cake obtained after washing to obtain CaLSX molecular sieves;
• step 2 of changing CaLSX molecular sieves to LiCa-LSX molecular sieves by exchange with Li+, with the mole percentage of Li+ in the resulting LiCa-LSX molecular sieves within a range from 2% to 5%, wherein
• during the exchange with Li+ to produce LiCa-LSX molecular sieves, a solution containing Li+ is used;
• the CaLSX molecular sieves are added in the solution containing Li+ in such an amount that the amount of starting material of Li+ is 0.15-0.3 times of that of Ca2+ contained in CaLSX raw powder;
• the exchange lasts for 0.5-2 hours, at room temperature;
• and an exchanged sample is directly filtered in vacuum without washing, and dried at normal temperature;
• and
• step 3 of activating and pre-treating the sample:
• heating, at a rate of 5-15° C./min, the sample which has been dried at normal temperature to a maximum temperature of 330-350° C., degassing for 0.5-3 hours, and naturally cooling to room temperature at the end of degassing, to obtain LiCa-LSX molecular sieves with mixed cations.