Synthesis of a novel spherical granular microporous carbon with exceptional propylene sieving performance over propane

The development of new spherical granular carbon materials with excellent selectivity for the separation of propylene (C3H6) and propane (C3H8) is of great importance in the petrochemical industry, but remains a significant challenge due to the closely similar molecular sizes and physical property of propylene and propane. Herein, we present a novel approach to fabricate binder-free granular carbon materials exhibiting outstanding selectivity towards C3H6, while also elucidating the evolution of pore structure during the preparation process of these carbon materials. A mixture of starch and molasses was selected as carbon source, and subsequently, novel spherical granular carbon materials (SGCs) were successfully fabricated through the processes of rolling forming, pyrolysis activation and carbonization. The resulting samples were characterized and tested for separation of C3H6 and C3H8. These samples exhibit exceptional selectivity toward C3H6. Its C3H6/C3H8 selectivity reaches as high as 33.6 with C3H6 uptake of 2.21 mmol/g at 298 K and 100 kPa. Breakthrough experiments confirmed its excellent dynamical separation performance, achieving complete separation of C3H6/C3H8 binary mixtures. In addition, the evolutionary mechanism of the pore structure in the samples SGCs is elucidated, revealing that the microstructure of starch-based carbon materials gradually evolves towards graphitization at elevated temperature, causing shrinkage of pores at sub-angstrom level. This work presents a distinctive and promising approach for fabricating spherical granular carbon materials, and the resulting samples SGCs demonstrate great potential for industrial applications in separation of C3H6 and C3H8.