Improved facile synthesis of mesoporous SBA-15-CTA using citric acid under mild conditions

Abstract

Unlike being traditionally synthesized in HCl intermediates, in this study, well-ordered 2D hexagonal mesoporous silica (SBA-15) was developed under moderate polycarboxylic acid (e.g. citric acid or oxalic acid) medium without introducing inorganic salts and mineral acids. The key synthesis factors such as the type and concentration of polycarboxylic acids, preparation temperature and crystallization time are systemically studied. It was found that the amount of carboxyl groups inside the organic acid molecules plays a critical role in synthesizing high-quality mesoporous silica products owing to their bridging effects on both nonionic copolymer micelles and silica precursors. The more carboxyl groups the organic acid possesses, the less dosage of organic acid will be used. The citric acid concentration can be as low as 0.0010 molL-1 (pH ​> ​3) for forming the high quality SBA-15-CTA materials (CTA stands for the material prepared under citric acid medium) their microstructure and rod-like particle size can be tailored by varying the acid type and preparation conditions. As-synthesized SBA-15-CTA supported Ni catalysts showed a good potential for dry reforming of methane (DRM) reaction with much less coke formation at 700 ​°C. The synthesis strategy for mesoporous silica under moderate organic acid medium demonstrates a promising prospect for other mesoporous materials preparation and utilizations in catalysis, selective adsorptions, drug delivery, and so on.