pH‐Regulated Refinement of Pore Size in Carbon Spheres for Size‐Sieving of Gaseous C8, C6 and C3 Hydrocarbon Pairs

Abstract

AbstractSelective separation of industrial important C8, C6 and C3 hydrocarbon pairs by physisorbents can greatly reduce the energy intensity related to the currently used cryogenic distillation techniques. The achievement of size‐sieving based on carbonaceous materials is desirable, but commonly hindered by the random structure of carbons often with a broad pore size distribution. Herein, a pH‐regulated pre‐condensation strategy was introduced to control the carbon pore architecture by the sp2/sp3 hybridization of precursor. The lower pH value during pre‐condensation of glucose facilitates the growth of aromatic nanodomains, rearrangement of stacked layers and a concomitant transition from sp3‐C to sp2‐C. The subsequent pyrolysis endows the pore size manipulated from 6.8 to 4.8 Å and narrowly distributed over a range of 0.2 Å. The refined pores enable effective size‐sieving of C8, C6 and C3 hydrocarbon pairs with high separation factor of 1.9 and 4.9 for C8 xylene (X) isomers para‐X/meta‐X and para‐X/ortho‐X, respectively, 5.1 for C6 alkane isomers n‐hexane/3‐methylpentane, and 22.0 for C3H6/C3H8. The excellent separation performance based‐on size exclusion effect is validated by static adsorption isotherms and dynamic breakthrough experiments. This synthesis strategy provides a means of exploring advanced carbonaceous materials with controlled hybridized structure and pore sizes for challenging separation needs.