Ultrastable Catalyst Could Lead to More Efficient and Cheaper Production of Propylene From Propane

On the surface of the newly developed catalyst (PtGa-Pb/SiO2), Pt1 sites remain exposed to facilitate catalytic reaction while Pt3 sites (and Ga3 sites) shown with triangles are blocked by Pb. (Yuki Nakaya, et al., Nature Communications, June 5, 2020).
Credit: Yuki Nakaya, et al., Nature Communications, June 5, 2020

A group of Japanese scientists has developed an ultrastable, selective catalyst to dehydrogenate propane — an essential process to produce the key petrochemical substance of propylene — without deactivation, even at temperatures of more than 600°C.

Propylene is an important raw material for plastics, synthetic rubber, surfactants, dyes and pharmaceuticals. In recent years, there has been an increased demand for propylene produced from cheaper, shale-originated propane. Reaction temperatures of more than 600°C are necessary to obtain sufficient propylene yields, but under these harsh conditions, severe catalyst deactivation is inevitable due to carbon deposition and/or sintering. Catalysts in practical use, therefore, must be regenerated either continuously or in short cycles, making the process inefficient and costly.

In the present study, the group, including a master’s student Yuki Nakaya and Associate Professor Shinya Furukawa at Hokkaido University’s Institute for Catalysis, focused on the intermetallics (PtGa) of platinum (Pt) and gallium (Ga), which have unique properties and structures. PtGa has a high thermal stability and its structure does not change even under high temperatures. It is also known to have two kinds of catalytic sites on its surface: a site with three Pt atoms (Pt3 site) and one with single-atom-like isolated Pt (Pt1 site).

The group hypothesized that if the Pt3 sites — which facilitates carbon deposition in addition to producing propylene — is disabled to allow only the Pt1 sites to function, the catalyst will be ultrastable and also able to prevent carbon deposition. The group tried various metals and catalyst synthesis methods to make only the Pt1 site function.

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