硼酸催化炭气凝胶的制备

Preparation of carbon aerogels using boric acid as catalyst

以苯酚、间甲酚和糠醛为原料,正丙醇作为溶剂,硼酸作为催化剂,通过溶胶-凝胶反应、超临界正己烷干燥以及高温炭化得到了炭气凝胶,并利用扫描电镜、N2吸附、傅立叶变换红外光谱和热重分析等表征手段对所制备的有机气凝胶及其炭气凝胶进行了表征,考察总反应物浓度对有机气凝胶及其炭气凝胶结构的影响。实验结果表明:所制备的炭气凝胶主要是大孔,随着总反应物浓度的增加,炭气凝胶的结构出现拐点现象,低浓度下形成炭气凝胶时,凝胶粒子大,硼氧化物在炭化过程中逸出难,得率高,硼含量高,微孔孔容可忽略,比表面积低;而高浓度下形成炭气凝胶时,凝胶粒子小,硼氧化物在炭化过程中逸出容易,得率低,硼含量低,微孔孔容和比表面积显著大。

Carbon aerogels were prepared by the sol-gel polycondensation of phenol,m-cresol and furfural by boric acid catalyst in a 1-propanol solution,followed by supercritical n-hexane drying and carbonization.The aerogels were characterized by infrared spectroscopy,N2 adsorption,scanning electron microscopy and thermogravimetry.The effects of total reactant concentrations on properties of the carbon aerogels were investigated.It was found that as-synthesized carbon aerogels were rich in macropores with their ratios over 95%.There was a critical phenomenon found for the structure of carbon aerogels with increasing the total reactant concentrations.When the total reactant concentrations was low,the particles that formed gels were large,carbonization yields were high,boron contents in carbon aerogels were high,micropore volumes were negligible and BET surface areas were low.While the total reactant concentrations was high,all of the properties were reversed.This critical phenomenon may be related to the capability to release boron oxides during carbonization.