Carbon nanotubes (CNTs) have excellent catalytic activity in liquid phase reaction, especially in aerobic oxidation of cumene. In previous work, the conversion of cumene was 41.8% and the selectivity of cumene hydroperoxide was 71.5%, which was catalyzed by CNTs. But a small amount of impurity Zn2+ totally blocked up the aerobic oxidation of cumene that catalyzed by CNTs, which is an unexpected discovery. By analyzing the catalytic mechanism of CNTs, the inhibition effect of Zn2+ is locked on the abstraction of H atom from cumene. The inhibition of Zn2+ is confirmed in two effects by density functional theory (DFT) calculations. Firstly, due to the strongly coordination of active oxygen species (ROS) by Zn2+, the energy barrier of initial reaction increases to 1.90 eV, which is nearly 4 times higher than that of the only ROS promoted-process. Secondly, the interaction of Zn2+ and RO· or ROO· to inhibits the chain propagation reaction of free radicals. This work precisely demonstrates that the inhibition effect of Zn2+ on initial reaction of cumene. The most significant thing is that the effect of metallic heteroatoms is not negligible in organic oxidation reaction.
As an efficient approach to high-purity hydrogen, the sorption-enhanced steam reforming (SESR) is usually highly energy-intensive. Herein, the sorbent decarbonation was conducted in the presence of O2 to enable the exothermic reaction between CaO and cobalt oxides to form calcium cobaltate (CCO). By utilizing CCO as oxygen carrier (OC), the chemical looping methane combustion (CLMC) was employed prior to the SESR of glycerol (SESRG). The CCO was pre-reduced to generate a multi-functional material composed of metallic Co catalysts and CaO sorbent, which can significantly improve the H2 yield from SESRG. With a simple Pt-doped CCO acting as pre-catalyst, CO2 sorbent and OC, we realized 70% CH4 conversion and 96 vol.% H2 with 120% yield for 20 cycles. The promoting effects of Pt towards CH4 conversion and H2 production were rationalized by CH4-TPR, XPS, SEM and TEM. Our results demonstrate the feasibility of process integration and intensification enabled by multi-functional materials.