No abstract

The microscopic quantum effect, spherical morphology, and fast mass transfer properties render nanosized porous carbon spheres (NPCSs, <100 nm) of great utilitarian value in numerous applications, including catalysis. However, the preparation of monodisperse NPCSs was typically low output and high cost due to their large surface energy along with nanosized particles. In this study, we designed a high-yield hydrothermal carbonization process of soluble starch with the aid of poly-(diallyldimethylammonium chloride) to fabricate monodisperse carbonaceous spheres with a tunable nanosize of 43−97 nm. This synthesis still functioned well at starch concentrations as high as 520 g/L and in a 10-fold extended experiment with a yield of 49.1 g. The proposed methodology showed good versatility among various biomass-based carbon sources, including glucose, maltose, glucan, potato starch, barley starch, and corn starch. The subsequent static-air calcinations could facilely introduce rich mesoporosity onto nanosized carbonaceous spheres. N-Hydroxyphthalimide (NHPI) covalently anchored on NPCSs were first prepared as heterogeneous catalysts by polyamidamine dendrimer-based quaternization and amidate modification with 4-carboxyl-NHPI. These dendrimeric NPCSs contributed to the high NHPI loading (6.09 mmol/g). The synergistic effects between the loaded NHPI and the quaternized dendrimer afforded 45% conversion and 72% selectivity in the catalytic oxidation of ethylbenzene into acetophenone at 95 °C under 1 atm O 2 for 16 h, which was superior to the performance of unsupported NHPI. This anchored NHPI demonstrated good catalytic oxidation performance for various hydrocarbons and favorable reusability in a nine-run test. Their positively charged surface could prevent nanocatalyst agglomeration during the catalytic process. The nonmetal system, sustainable high-yield nanocarrier material, and high-loading active catalyst with good reusability are the advantages of the designed catalysis.