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ZnO-based catalysts are promising for nonoxidative propane dehydrogenation (PDH) to propene owing to their low cost and environmental friendliness but experience serious loss of the active component because of the reduction of ZnO to metallic Zn that evaporates. Here, we demonstrate that MgO-modified ZnO x /silicalite-1 materials prepared through one-pot hydrothermal method are active, selective, and durable in the PDH reaction. The undesired loss of Zn could also be successfully suppressed without negative effect on the PDH performance owing to a strong interaction between Mg2+ and ZnO x , as concluded from the results of X-ray photoelectron and Fourier-transform infrared spectroscopic measurements as well as temperature-programmed reduction with CO. X-ray absorption spectroscopy revealed that atomically dispersed Zn2+ sites are responsible for PDH. Using an industrially relevant feed with 40 vol % propane, propene selectivity between 88 and 95% at propane conversion between 15 and 32% was achieved over six PDH/oxidative regeneration cycles lasting for about 20 h on stream at 550 °C without loss in the initial activity, while some deactivation occurred after longer (up to about 60 h) time on stream. The deactivation (caused by Zn loss) constant of Mg-modified ZnO x /silicalite-1 considering the 2nd and 20th cycles is more than 3 times lower than that of its Mg-free counterpart.

SummaryNon-oxidative propane dehydrogenation (PDH) is an attractive reaction from both an industrial and a scientific viewpoint because it allows direct large-scale production of propene and fundamental analysis of C-H activation respectively. The main challenges are related to achieving high activity, selectivity, and on-stream stability of environment-friendly and cost-efficient catalysts without non-noble metals. Here, we describe an approach for the preparation of supported ultrasmall ZnO nanoparticles (2–4 nm, ZnO NPs) for high-temperature applications. The approach consists of encapsulation of NPs into a nitrogen-doped carbon (NC) layer in situ grown from zeolitic imidazolate framework-8 on a Silicalite-1 support. The NC layer was established to control the size of ZnO NPs and to hinder their loss to a large extent at high temperatures. The designed catalysts exhibited high activity, selectivity, and on-stream stability in PDH. Propene selectivity of about 90% at 44.4% propane conversion was achieved at 600°C after nearly 6 h on stream.

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NH2-UiO-66(Zr) materials with structural defects, prepared by simply controlling the synthesis temperature, exhibit significantly enhanced activities in photocatalytic CO2 reduction.

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