Microporosity development in phenolic resin-based mesoporous carbons for enhancing CO_2 adsorption at ambient conditions

摘要

Soft-templating method was used to prepare mesoporous carbons. The synthesis in the presence of hydrochloric and citric acids involved resorcinol and formaldehyde as carbon precursors and triblock copolymer Pluronic F127 as a template. The as-synthesized samples underwent carbonization in flowing nitrogen at various temperatures; namely 600 ℃, 700 ℃ and 800 ℃. Two routes were used to develop microporosity in the mesoporous carbons studied. The first one involved introduction of tetraethyl orthosilicate to the reaction system. After silica dissolution with NaOH, an increase in microporosity was observed. The second method, chemical activation with KOH at 700℃, was explored as an alternative approach to create microporosity. It is noteworthy that the TEOS addition not only led to the development of microporosity but also to some improvement of mesoporosity. The post-synthesis KOH activation resulted in more significant increase in the microporosity as compared to the samples obtained by TEOS-assisted synthesis. The mesopore volume was somewhat lower for activated carbons as compared to that in mesoporous carbons. Both methods resulted in micro-mesoporous carbons with good adsorption properties; for instance, in the case of carbons prepared in the presence of TEOS, the best sample exhibited BET surface area of 1463 m~2/g and the total pore volume of 1.31 cm~3/g. For the KOH activated carbons the best adsorption parameters were as follows: the specific surface area = 1906 m~2/g, and the total pore volume = 0.98 cm~3/g. Both procedures used for microporosity development afforded carbons with good adsorption properties that can be useful for applications such as CO_2 adsorption, air and water purification.