The oxidative dehydrogenation of propane is an attractive reaction for propylene production, but the overoxidation leads to low propylene selectivity at considerable propane conversions. Here, we report the oxidative dehydrogenation of propane by oxygen in the presence of hydrogen chloride. CeO2 was found to be an efficient catalyst for the conversion of propane to propylene by (O2 + HCl). The reaction was structure-sensitive, and the catalytic behavior depended on the exposed facet of CeO2 nanocrystals. The nanorod exposing {110} and {100} facets showed the highest activity, whereas the nanocube enclosed by {100} facets was the most selective for propylene formation. The modification of CeO2 nanorods by NiO increased both propane conversion and propylene selectivity. A propylene selectivity of 80% was achieved at propane conversion of 69% over an 8 wt % NiO–CeO2 catalyst at 773 K, offering a single-pass propylene yield of 55%. No significant catalyst deactivation was observed in 100 h of reaction. HCl played a pivotal role in the selective formation of propylene, and more than 95% of HCl could be recovered after the reaction. The structure–property correlation indicates that the surface oxygen vacancy and the surface chloride coverage are two crucial factors determining the activity and selectivity. The mechanistic studies suggest that the peroxide species (O2 2–) formed by adsorption of O2 on surface oxygen vacancies may activate chloride, generating a radical-like active chlorine species. The active chlorine species accounts for the activation of C–H bond of propane, forming propylene as a major product.

This study shows a high prevalence rate of dry eye syndrome in elderly Tibetans, representing an important health problem.

Highly efficient photocatalytic reduction of 4-nitroaniline to p-phenylenediamine over a commercial CdS photocatalyst was observed under visible light irradiation (λ ≥ 420 nm) in water. The conversion of 4-nitroaniline and the selectivity of p-phenylenediamine were ∼100% and ∼98% after 9 min of visible light irradiation, respectively. The photoreduction efficiency of 4-nitroaniline over the CdS photocatalyst remained above 95% in the 5th cycle of testing. Its photocatalytic activity was much higher than those of nitrogen-doped TiO 2 and commercial TiO 2 photocatalysts. Further experimental results revealed that the ammonium formate and N 2 atmosphere were indispensable for the photocatalytic reduction of 4-nitroaniline over the CdS photocatalyst. On the basis of the results of electron spin resonance, photoexcited electrons and •CO 2 − radicals were detected in the present system. These species had strong reductive powers, and were therefore able to efficiently reduce 4-nitroaniline to p-phenylenediamine. † Electronic supplementary information (ESI) available: GC-MS spectra of the reaction solution before and after the reaction; MS patterns for the compounds at different retention times; photoreduction efficiencies of 4-NA over CdS powders under different visible light irradiation; UV-vis spectral changes of 4-NA aqueous solution under visible light irradiation (λ ≥ 420 nm) in the presence of HCO 2 NH 4 upon purging with N 2 ; DMPO spin-trapping ESR spectra of the CdS suspension and the HCO 2 NH 4 aqueous solution under visible light irradiation. See

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