Optimized Preparation And CO₂ Adsorption Performance Of SSZ-13

Because of its unique eight-membered ring pore structure and the arrangement of cations in the structure,SSZ-13 molecular sieve has a higher affinity for carbon dioxide than other gases,so it attracts more attention than other porous materials for CO₂ adsorption.However,the expensive template and long preparation time limit the industrial production of SSZ-13.At present,there have been many studies on optimizing the preparation method of SSZ-13molecular sieve to reduce the industrial production threshold of SSZ-13 molecular sieve.Multi-stage pore molecular sieves and hollow molecular sieves have received close attention because of their unique structure,which can solve the problem of low diffusion efficiency of macromolecules in micropores.However,the synthesis of multi-stage molecular sieves or hollow molecular sieves is difficult.At present,multi-pore SSZ-13 molecular sieves have been prepared by adding a mesoporous template to the synthesis system,but studies on hollow SSZ-13 molecular sieves are rare.Considering that the aluminum atom provided by the aluminum source is one of the basic atoms of the zeolite framework,and the research on the hollow SSZ-13 molecular sieve is less,this paper has done the following work:?1?Using aluminum isopropoxide as the Al source,it was found that the synthesis rate of the product did not change significantly,but the crystal morphology changed from a traditional cubic shape to a spheroid composed of cubic crystal stacks.On this basis,the effect of aging time on the product was investigated,and it was found that as the aging time increased,the stack-up assembly phenomenon became more obvious.When the aging time reached 12 h,the specific surface area of the product increased to 647.85 m²/g compared with the traditional574.91 m²/g.?2?During the synthesis of SSZ-13,by using aluminum nitrate and aluminum sulfate as Al sources,inorganic oxygen-containing anions were introduced into the synthesis system,and the reaction time was shortened to 72 h and 40 h,respectively.Its crystals conform to the unconventional growth mode,and assembled from small unit crystals into large crystals.And extending the reaction time,aging time and adding fluoride ions can introduce a multi-stage pore structure on the surface of the molecular sieve.When aging for 24 h,reaction for 4 d,and the amount of fluorine added was 0.05?F/Si?,the sample had the best multi-stage pore structure.The SSZ-13 molecular sieve with an added amount of 0.1 has the best CO₂ adsorption performance.The adsorption amount at the 0.25 bar is 2.74 mmol/g,which is 54.8%higher than that of the SSZ-13 prepared by the traditional method;at 4.55 at 1 bar mmol/g,which is20.4%higher than the molecular sieve prepared by the traditional method.?3?In the synthesis process,aging was performed with ultrasound and induced by adding seeds.A hollow structure was successfully introduced into the SSZ-13 molecular sieve.The effects of the amount of seed added and the ultrasonic time on the product were investigated.When the amount of seed added was 0.5 wt%and the ultrasonic time was 60 min,the sample was a hollow cubic crystal with a diameter of 50 nm.The specific surface area reached 791.50m²/g and the mesoporous ratio was 66.3%.The samples were tested for CO₂ adsorption performance at 273 K.It was found that when the seed addition amount is 0.5 wt%,the adsorption capacity of the sample for CO₂ is better than that of the microporous SSZ-13molecular sieve prepared by the traditional method,whether under low pressure or high pressure.When the adsorption pressure is 0.27 bar,the adsorption amount reaches 2.53 mmol/g,which is higher than 1.83 mmol/g of SSZ-13 prepared by the traditional method.At the same time,it was found that the change in ultrasonic time had a limited effect on the amount of CO₂adsorbed.Among them,the ultrasonic SSZ-13 molecular sieve had the highest adsorption capacity at 1 bar,reaching 4.24 mmol/g.