Selective Catalytic Epoxidation-Hydration of α-Pinene with Hydrogen Peroxide to Sobrerol by Durable Ammonium Phosphotungstate Immobilized on Imidazolized Activated Carbon.

It is presented that the activated carbon was carboxylated with hydrogen peroxide and then acylated with 2-methylimidazole to prepare the porous carbon support with a surface imidazolated modification. Through the adsorption of phosphotungstic acid on the fundamental site of an imidazolyl group and then adjusting the acid strength with the ammonia molecule, a catalytic carbon material immobilized with ammonium phosphotungstate (AC-COIMO-NH4PW) was obtained, which was used to catalyze a one-pot reaction of convenient α-pinene and hydrogen peroxide to sobrerol. The bifunctional active site originated from the dual property of ammonium phosphotungstate, as the oxidant and acid presenting a cooperatively catalytic performance, which effectively catalyzes the tandem epoxidation-isomerization-hydration of α-pinene to sobrerol, in which the solvent effect of catalysis simultaneously exists. The sobrerol selectivity was significantly improved after the acid strength weakening by ammonia. Monomolecular chemical bonding and anchoring of ammonium phosphotungstate at the basic site prevented the loss of the active catalytic species, and the recovered catalyst showed excellent catalytic stability in reuse. Using acetonitrile as the solvent at 40 °C for 4 h, the conversion of α-pinene could reach 90.6%, and the selectivity of sobrerol was 40.5%. The results of five cycles show that the catalyst presents excellent stability due to the tight immobilization of ammonium phosphotungstate bonding on the imidazolized activated carbon, based on which a catalytic-cycle mechanism is proposed for the tandem reaction.

Improvement and regeneration of Co-B amorphous alloy nanowires for the selective hydrogenation of cinnamaldehyde.

One-dimensional Co-B amorphous alloy nanowires (NWs) were prepared using surfactant as a template and were treated with plasma to study the effect of different treatment times on the essential physical and chemical properties of the catalyst. The study showed that plasma with a certain amount of strength will not change the morphology and amorphous structure of the NWs within the chosen treatment time. It could, however, modify the electronic structure and active sites of the catalyst surface, increase its specific surface area and H2 adsorption capacity, and also improve the selective hydrogenation performance of cinnamaldehyde. Most of all, plasma treatment could also play an important role in the reuse of catalysts. After several recycling reactions, plasma treatment on Co-B amorphous alloy NWs could regenerate their high catalytic activity. This work provides a novel method for preserving the high catalytic activity and stability of amorphous alloy nanomaterials, as well as for increasing their reusability.