Liquid organic hydrogen carriers (LOHC) are interesting hydrogen vectors which can exploit existing infrastructure. Specifically, N-heterocyclic compounds are attractive due to lower dehydrogenation enthalpy than homocyclic ones and demand a viable palladium catalyst to guarantee high dehydrogenation activity at low temperatures and stability in recycle runs. Here, we employ one-pot solvent deficient precipitation yielding a mesoporous palladium-alumina. The prepared catalyst system offers higher hydrogen release capability by 20% than conventional palladium/γ-Al2O3 in the dehydrogenation of four different N-heterocyclic compounds at or below 250 °C. Futhermore, it shows negligible activity loss up to five consecutive runs for perhydro 2-(n-methylbenzyl)pyridine and perhydro 2-methylindole. Such dehydrogenation performance is caused by the solvent deficient environment that restricts palladium mobility by contiguous alumina particles and produces well-dispersed palladium phase with a higher density of (111) plane. Therefore, the reported synthesis method may contribute to the production of innovative dehydrogenation catalysts for LOHC compounds.
Catalyst
stability in the hydrodeoxygenation of vegetable oils
is one of the big challenges for practical production of bio-jet fuel.
Particularly, supported Pt catalysts are known to show activity decay
because of Pt sintering and coking. Herein, we report superior long-term
stability of the Pt catalyst in the hydrodeoxygenation of palm oil
by using the mesoporous γ-Al2O3 (MA) support
synthesized by solvent-deficient precipitation (SDP). When the MA
was prepared with a molar ratio of water to aluminum isopropoxide
being five, the space-time yield of the Pt catalyst was maintained
at ca. 6.09 mol kg–1 h–1 for over
80 h, which was much better than those of the other Pt catalysts.
This result was attributed to the two properties such as well-developed
mesopores of a larger diameter than 20 nm in the fresh MA and strong
metal–support interaction of Pt/MA. Therefore, the SDP method
could endow the alumina support with textural and chemical benefits
for stable performance. Furthermore, the hydrodeoxygenated palm oil
was converted into paraffinic hydrocarbons mainly ranging from C8 to C15 with an iso- /n-paraffin ratio of ca. 6.8, perfectly meeting the standard
specifications of bio-jet fuel.
The oxidative cyanation of tertiary amines by using the less‐toxic ethyl cyanoformate as the cyanating agent was achieved over heterogeneous iron‐exchanged molybdophosphoric acid (FeMPA) supported on a niobia catalyst under mild reaction conditions. The catalyst not only showed exceptional activity with variety of tertiary amines but also exhibited consistent activity upon reuse.
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