CO₂ Capture Using Double Times Amine Modified Layered Double Hydroxide As Adsorbents

Layered double hydroxide is a kind of promising CO₂ adsorption material,and it has advantages of high adsorption selectivity,wide adsorption temperature range and fast adsorption and desorption rate.However,the lower adsorption capability severely limits its further industrial application.The amount of amine loading can be effectively increased by amine modification and then improve the CO₂ adsorption capacity of the layered double hydroxides.At present,the common modified methods such as Anionic surfactant route and exfoliation route have bottlenecks.It was difficult to further increase the amine loading of the layered double hydroxide.Therefore,in order to improve the loading of the layered double hydroxides and obtain an excellent CO₂ adsorbing material,double times modification was put forward,and a series of double times amine modified layered double hydroxides were prepared,the physical and chemical properties of these materials have been studied,using SEM,FT-IR,XRD,BET,EA and TG.And the adsorption of these materials was also studied by thermogravimetric analysis.ASPEN ADSORPTION software was used to simulate the adsorption process.This paper contains the main contents and results as follows:?1?The effects of the kinds of anionic surfactants and aminosilane,mount of aminosilan,replacement with Ni and addition of deionized water on the amine loading of double times amine modified layered double hydroxides have been studied.The results show that the amine loading was higher with a small surfactant anion intermolecular.The double times amine modified layered double hydroxides have a higher amine loading,as the amine modifier is N-aminoethy-?-aminopropyltrim ethoxysilane.With the increase of the amount of aminosilane,the amine loading of the layered double hydroxides increased.As Mg is gradually replaced by Ni,the amine loading of the layered double hydroxides reduced.The deionized water was introduced in the exfoliation process,with the increase of the amount of deionized water,the amine loading of the layered double hydroxides increased first and then decreased.And the Mg-Al 0.30 N1 prepared under the condition that the amount of deionized water is 0.30 m L/g,the anionic surfactant is sodium dodecylsulfonate and the aminosilane is 3-aminopropyltrimethoxysilane has the largest amine loading,that is 8.30 mmol/g.?2?The effects of amine loading,adsorption temperature and adsorption pressure on the adsorption performance of double times amine modified Mg-Al LDH,the recycle ability and adsorption mechanism have been studied.The results show that upon exfoliation process,with no deionized water adding,aminosilane is attached to the surface of the laminate via Si-O bonds,the adsorption capacity and initial adsorption rate of the adsorbents increased as the amine loading increased.The maximum CO₂ adsorption capacity and initial adsorption rate were 2.26 mmol/g and 0.32 mmol/?g · min?respectively when the loading of Mg-Al N2 was 6.20 mmol/g.Upon exfoliation process,deionized water was introduced,the aminosilane connection to the surface of the board via the Si-O-Si bonds,with the increase of the amine loading,the CO₂ adsorption capacity increased first and then decreased,and the initial adsorption rate of CO₂ decreased.For Mg-Al N2,the CO₂ adsorption capacity was up to 2.55 mmol/g when the amine loading was 7.06 mmol/g.The CO₂ adsorption capacity weakened with the increase of temperature,at 30? to 90? of the temperature.The CO₂ adsorption capacity enhanced with the increase of CO₂ partial pressure,at 0 to 0.1 MPa of the pressure.The performance of the adsorbent remained after cycle five times,showing good re-use performance.The CO₂ adsorption performance of double times amine modified layered double hydroxides belonged to Chemical adsorption.The Pseudo-second-order model matched CO₂ adsorption kinetics,and the adsorption mechanism is consistent with the mechanism of zwitterion.?3?The process of adsorption was simulated with ASPEN ADSORPTION.The breakthrough time of the CO₂ is 3000 s,with the pressure increases,the breakthrough time extended.Controlling the adsorption desorption time,different adsorption effects could be achieved.This work provided experimental and theoretical basis for exploiting CO₂ adsorbents with good CO₂ adsorption performance,have certain significance on developing environment friendly,efficient and economical CO₂ capture technology.