Controlled Preparation Of Hollow Carbon Spheres And There Application In CO₂ Adsorption

The porous carbon materials have attracted much attention due to their high specific surface area, large pore volume, low density, good thermal stability and chemical inertness, good electrical conductivity and reproducibility. Particularly, the hollow carbon spheres?HCSs?, as one of attractive materials, have been extensively developed in wide range of drug delivery, adsorption separation, catalysis, electrode materials, and energy storage. Recently, it was found that the structural performance such as morphology, surface structure, size and so on have important influences on the adsorption performance. Therefore, the research on HCSs with a controllable morphologies and structures have received rapidly growing interest and remained a great chal enge.In this thesis, the monodisperse HCSs were synthesized using hard template, meanwhile, the influence of the preparation parameters on HCSs, including the amount of carbon precursor, the dosage of ammonia, the adding of tetraethoxysilane?TEOS?, the template size, and the surface chemical properties were investigated in detail. Moreover, the performances on the adsorption capacity of the CO₂ of the resultant HCSs were eluciated. The research contents and main conclusions are as follows:1. The HCSs were prepared using silica?Si O2? solid spheres as hard templates synthesized according to St?ber method, resorcinol and formaldehyde as carbon precursor, through sol- gel method combining with high temperature carbonization. HCSs with controllable shell thickness?7-80 nm? were evaluated through changing the concentration of the ammonia solution or R/F during the sol- gel process. Moreover, the as-synthesized HCSs as an adsorbent for CO₂ capture were preliminary investigated. The results ind icated that the adsorption capacity of CO₂ increased with the increasing in the shell thickness of HCSs, and when the shell thickness of about 80 nm, the adsorption capacity can up to 2.50 mmol/g?273K, 1atm?.2. In the above synthetic process, the TEOS was added and then through silicon etching. Through this procedure, HCSs with abundant extra pores, high surface area and micropore volume were prepared. Therefore, by modulating the concentration of TEOS, The specific surface area obtained adjustable?390-1376 m2/g? and a micropore volume controllable?0.19-0.53 cm3/g? of HCSs. The CO₂ adsorption amount can up to 2.63 mmol/g?273K, 1atm?, which was higher than HCSs without TEOS?1.80 mmol/g?. In addition, different size of s Si O2 could effectively regulating HCSs cavity size?65-255 nm?, the CO₂ adsorption results showed that when the template s Si O2 particle size was of 211 nm, the obtained HCS cavity was 180 nm, and possessed the highest CO₂ adsorption capacity?2.63 mmol/g at 273 K, 1 atm?.3. To further enhance the CO₂ adsorption performance, Mg O was employed to modify the surface of HCSs, with Mg?CH3COOH?2·4H2O as the magnesium source, a series of Mg O/HCS compound materials with different Mg O content could be prepared by dipping method. Although, the surface area and pore volum decreased as the increasing of Mg O content, the CO₂ adsorption ability increased as high as 3.6 mmol/g, indicated that the alkaline modification was important in the CO₂ capture.4. Samples were characterized by a variety of methods, such as X- ray diffraction?XRD?, high-resolution scanning electron microscopy?SEM?, transmission electron microscopy?TEM?, nitrogen adsorption-desorption, fourier transform- infrared spectroscopy?FT-IR?, gas adsorption instrument.