Preparation And CO₂ Capture Performance Of Amine Modified Layered Double Hydroxide

Layered double hydroxide?LDH?is a kind of promising CO₂ adsorbent with high adsorption selectivity and wide adsorption temperature range,but its adsorption capacity is relatively low.Amine modification of LDH can significantly improve its CO₂ adsorption performance.In this paper,the application of the composite modification route is extended and the method is improved.CuMgAl-LDH has the prospect of photocatalytic conversion of CO₂ to CH₃OH.In this paper,a series of amine modified Cu_xMg_3-xAl-LDH was prepared by composite modification route,and the process parameters such as Cu²⁺ratio and aminosilane dosage were investigated.In addition,qualitative analysis of photocatalytic conversion of CO₂ before and after modification was carried out.This work aims to provide a basis for the preparation of CO₂ adsorption-catalytic coupling CuMgAl-LDH materials from adsorption.The results show that the composite modification route is suitable for Cu-Mg-Al trimetal system.When x=1 and the amount of aminosilane is 5g,the adsorption capacity of CuMgAl-N?5?can reach 1.94 mmol?g^-1;When x=1.25,The large amount of aminosilane grafting and the increase in distortion due to the Cu²⁺Jahn-Teller effect make the stability of the system seriously degrade,Severe aminosilane polymerization occurred on the surface of 1.25CuMgAl-N,and its CO₂ adsorption performance also decreased significantly;The composite amine modified CuMgAl-LDH has good cycle regeneration performance and and can separate CO₂/N₂ simulated power plant flue gas in fixed bed.CuMgAl-N can photocatalytic reduction of CO₂ to CH₃OH,and its performance is better than before modification.As a two-time modification method,the composite modification route has obvious shortcomings such as long time-consuming,high energy consumption and serious environmental pollution.Based on the previous research,an ultrasound-assisted amine modification route was proposed in this paper.MgAl-LDH was prepared in one step by adding ultrasonic to the anionic surfactant-mediated route.The effects of ultrasonic intensity,anionic surfactant type,aminosilane species and other factors on the surface morphology and CO₂ adsorption properties of the material were investigated.This work aims to improve the composite modification route.Studies have shown that a certain intensity of ultrasonic assisted treatment can significantly improve the surface morphology of the material,while increasing the free amino group content on the surface and reducing the protonated amino group content,which not only benefits the physical adsorption of CO₂,but also provides more site for chemical adsorption;When the anionic surfactant is sodium dodecyl sulfate,the modifier is N-aminoethyl-?-aminopropyltrimethoxysilane,and the ultrasonic intensity is 195 W,the obtained UL30-LDH has the largest CO₂.Adsorption capacity 1.65 mmol?g^-1,Which is 50.0%higher than Conv-LDH without ultrasound assistance.Excessive ultrasonic assisted strength may cause large-area fracture of the LDH layer,and the CO₂ adsorption performance of the material also decreases significantly.This work provided experimental and theoretical basis for exploiting CO₂adsorbents with good CO₂ adsorption performance,and has certain significance on developing environment friendly,efficient and economical CO₂ capture-conversion technology.