Divanadium substituted keggin [PV 2 W 10 O 40 ] on non-reducible supports-Al 2 O 3 and SiO 2 : synthesis, characterizati
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Divanadium substituted keggin [PV2W10O40] on non‑reducible supports‑Al2O3 and SiO2: synthesis, characterization, and catalytic properties for oxidative dehydrogenation of propane José C. Orozco, et al. [full author details at the end of the article] Received: 12 August 2020 / Accepted: 18 October 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract Molecular metal oxide cluster, K5[α-1,2-PV2W10O40] (PV2W10), was found to have intrinsic catalytic activity for the oxidative dehydrogenation of propane with high selectivity (> 80%) to propylene at low propane conversion (0.3%). Synthesis of dispersed PV2W10 in non-reducible supports, γ-Al2O3 and SiO2, was done by incipient wetness impregnation. The supported catalysts were characterized by IR, Raman spectroscopy, nitrogen adsorption, x-ray powder diffraction (PXRD), elemental analysis, hydrogen temperature-programmed reduction (H2–TPR), and ammonia temperature-programmed desorption (NH3–TPD). Catalytic testing of the supported PV2W10 at equimolar cluster concentration revealed that when supported in γ-Al2O3 it is more active (sevenfold increase in propane conversion) but in SiO2 it is more selective to propylene (94%). The observed performance was due to both an increase in reducibility and higher concentration of strong acid sites for PV2W10 supported in γ-Al2O3 versus S iO2. Lastly, PV2W10 was shown to remain intact under reaction conditions indicating its thermal and oxidative stability. Graphic abstract
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s1114 4-020-01893-7) contains supplementary material, which is available to authorized users.
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Reaction Kinetics, Mechanisms and Catalysis
Keywords Polyoxometalates · Alkanes · Alkenes · Dehydrogenation · Supported catalysts
Introduction Propylene is an essential building block in our modern world where 67% of its consumption is used for the production of polypropylene, 7% is used to make propylene oxide, 6% for acrylonitrile, and 5% for acrylic acid among many other bulk chemicals [1]. The annual global demand for propylene is about 103 million tons and is projected to increase by about 5% per year while the production of propylene is estimated to rise only to 19 million tons per year [2]. In order to satiate the global demand, propylene is produced commercially via steam cracking of petroleum at elevated temperatures (> 800 ºC) but there now exists commercial dehydrogenation of paraffins processes to produce propylene among other light olefins. However, two of the most important propane dehydrogenation processes, Catofin (CB&I Lummus) and Oleflex (UOP), rely on utilizing environmentally unfriendly supported chromia catalysts and expensive platinum catalysts, respectively, operated at high temperatures (> 500 °C) via non-oxidative dehydrogenation of propane (NODHP) [2, 3]. NODHP suffers from being an endothermic process with thermodynamic restrictions on alkane conversions and the undesirable byproduct, coke. For the re
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