High Specific Surface Area Two-Dimensional Hexagonal Boron Nitride And Its Application In Oxidative Dehydrogenation Of Propane

Recently,two-dimensional hexagonal boron nitride(h-BN)with graphene-like structure has received extensive attention in the field of catalysis.In particular,many recent studies have found that h-BN had excellent catalytic performance in the oxidative dehydrogenation(ODH)of light alkanes,which can effectively inhibit the deep oxidation of alkanes and alkenes.Compared with traditional vanadium-based catalysts,the yield of olefins is greatly increased over h-BN catalyst.However,under the harsh reaction conditions of ODH of light alkanes,agglomeration of the h-BN catalyst tends to occur due to its unstable structure,leading to drastically reduced specific surface area and inferior catalytic performance.To mitigate this issue,we attempted to modify the defective sites of h-BN using metal ion in order to obtain highly stable h-BN for the ODH of propane at harsh reaction conditions,i.e.,high temperature,high oxygen and water vapor content.This dissertation is divided into three parts as follows.First,synthesis conditions of h-BN with high specific surface area were systematically investigated.The results show that the h-BN with a specific surface area as high as 1034 m2/g can be successfully synthesized at 950 ℃ using a wet chemical method.However,in the presence of oxygen or water vapor,the structure of h-BN is destroyed,resulting in a dramatic decreasing of the specific surface area.Meanwhile,compared with water as a solvent,h-BN can maintain a high specific surface area when alcohol is used as a solvent.Second,aming to obtain highly stable h-BN for the ODH of propane at harsh reaction conditions,the strategy to repair defective sites of h-BN by nickle ions were invesitaged.The results indicate that h-BN modified by Ni ions(named as NiOx@h-BN)is quite stable even after treatment by oxygen or water vapor at 550 °C.The activity of ODH of propane over the NiOx@h-BN is higher than that over h-BN.The experiments using temperature-programmed oxidation(TPO),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS)and UV-visible diffuse reflectance spectroscopy(UV-vis),were performed and the results indicate that Ni ions can occupy the defect sites of the h-BN,which successfully suppresses the attack by oxygen or water vapor on the defect sites of the h-BN,leading to enhanced stability of h-BN under harsh conditions.Finally,a brief summary was made on the knowledge learned in both the synthesis of the h-BN and its stabilization.Outlooks about the future studies are also proposed.