A team of Japanese researchers has created an ultrastable, selective catalyst to dehydrogenate propane without deactivating it, even at temperatures of over 600 degrees Celsius (1112 degrees Fahrenheit). This is a required process to develop the main petrochemical substance known as propylene.
Reaction temperatures of over 600 degrees Celsius (1112 degrees Fahrenheit) are required to get enough propylene yields, but under these challenging circumstances, serious catalyst deactivation is necessary because of the carbon disposition and/or sintering. Catalysts in conventional applications, therefore, has to be regenerated either in a continuous manner or in short periods, which makes the process rather ineffective and expensive.
In the new study, the team of researchers, including a master’s student Yuki Nakaya and Associate Professor Shinya Furukawa at Hokkaido University‘s Institute for Catalysis, geared towards the intermetallics (PtGa) of platinum (Pt) and gallium (Ga), which have interesting characteristics and structures.
PtGa has high thermal stability, and its mechanism doesn’t alter, even under extremely high temperatures. It also has two types of catalytic sites on its surfaces, a site with three Pt atoms – Pt3 – and one with a single-atom-like isolated site – Pt1.
The team theorized that if the Pt3 sites, which promote carbon deposition besides generating propylene, are disabled to enable only Pt1 sites to operate, the catalyst will be ultrastable and able to prevent carbon deposition. The scientists tried different metals and catalyst synthesis techniques in order to maintain only Pt1 site function.
A Cheaper Process
The newly-created catalyst – PtGa-Pb/SiO2 – which is silica-supported produced by adding lead (Pb) to the surface of PTGa, shows no deactivation when dehydrogenating propane heats at 600 degrees Celsius (1112 degrees Fahrenheit). The catalyst kept the initial conversion rate of 30 percent for 96 hours after the reaction began, which is considerably more stable than practical catalysts.
Propylene selectivity is about 99.6 percent with a couple of side reactions, such as carbon deposition. The outcome showed that this particular catalyst offers the world’s best performance at temperatures of 580 degrees Celsius (1076 degrees Fahrenheit) or higher. Moreover, its life span is more than twice as long as the initial record for longevity for such catalysts.
In addition, the catalyst can be manufactured as cheaply as practical catalysts. Their structural examination confirmed Pt3 sites, not Pt1 sites, were covered and disabled by Pb.
“Our finding could lead to a more efficient and cheaper industrial process to produce propylene from propane without the need for catalyst regeneration—which is far superior in selectivity and stability than conventional ones,” says Furukawa. “Moreover, this method could be applicable to dehydrogenation of other lower alkanes such as ethane and isobutane, thus contributing to the petrochemical industry’s development.”
The research has been published in the prestigious journal Nature Communications.