Research On Molecular Sieve Monolithic Structural Forming For CO₂ Adsorption

Because of the low cost,excellent chemical and thermal stability,they have good application prospects in CO₂adsorption and separation.However,molecular sieves are all powder structures,which cannot be directly applied in engineering,and require integral structural molding.The water column forming method has the characteristics of rapid ball formation,uniform product size,mild forming conditions and green environmental protection.In this paper,molecular sieve spherical particles with suitable strength and high CO₂adsorption efficiency were prepared by alginate water column molding method.The main work is as follows:（1）Based on sodium alginate water column forming method,Na Y and Na X spherical molecular sieves were prepared.The effects of gelation time,calcium ion mass fraction in the gel solution,sodium alginate（SA）content in the slurry,and molecular sieve content in the slurry on the pellet forming process,sphericity,strength,and CO₂adsorption were explored.When the gel time is 12 h,the mass fraction of calcium ions in the gel solution is 2%,the SA content in the slurry is 1.0%,and the Na Y content in the slurry is 12.5%,the strength of the prepared Na Y spherical particles is 12.6 N,CO₂The adsorption capacity is 29.37 m L/g（25°C,0.1 bar）,82%of the adsorption capacity of the original Na Y powder is retained,and the water absorption rate is 338.82 m L/g（25°C,40%relative humidity）.When the SA content in the slurry is 1.2%,and the Na X content in the slurry is 12.5%,the strength of the spherical particles prepared is 13.9 N,and the CO₂adsorption capacity is 48.57 m L/g（25°C,0.1 bar）,retain 89%of the adsorption capacity of Na X powder,and the water absorption rate is 330.60 m L/g（25°C,40%relative humidity）.Studies have shown that Na X molecular sieves are more suitable for forming with sodium alginate water column,and the spherical particles have the characteristics of high strength,good sphericity and high CO₂adsorption performance retention.（2）Based on sodium alginate assisted water column forming method,good stability Na X spherical molecular sieves were prepared.The effects of binder type and addition amount on the properties of spherical particles were explored.When the binder is silica sol and the addition amount is 40%,the strength of spherical particles prepared is 10.3 N,the CO₂adsorption capacity is 20.83 m L/g（25°C,0.1 bar）,and the water absorption rate is 176.47 m L/g（25°C,40%relative humidity）.Studies have shown that the spherical particles prepared by this method have better stability.Compared with the Na X spherical particles prepared by the sodium alginate water column molding method,although the water absorption rate has also decreased significantly,the CO₂adsorption has decreased more.（3）Modified molecular sieves were prepared by introducing sodium fluoride and organic amine,and spherical particles were prepared by sodium alginate water column forming method.The effects of adding sodium fluoride and organic amines on the CO₂adsorption performance of molecular sieves under different alkalinity were explored.The prepared modified molecular sieve had a CO₂adsorption capacity of 57.86 m L/g at 25°C and 0.1 bar.At40%relative humidity,the water absorption capacity is 288.83 m L/g.The spherical particles prepared by modified molecular sieves have a CO₂adsorption capacity of 49.26 m L/g at 25°C and 0.1 bar,and a water absorption rate of 310.31 m L/g at 40%relative humidity.Studies have shown that compared with Na X molecular sieve,modified molecular sieve has a5.5%increase in adsorption capacity and a 9.4%decrease in water absorption rate.Compared with Na X spherical particles,the adsorption capacity of carbon dioxide is increased by 1.5%,and the H₂O absorption capacity is decreased by 6.0%.