Blowing in the tube

The method is based on the use of silica-supported metal-precursors for each element of the targeted intermetallic compound. The team chose platinum–zinc alloys to begin with, and accordingly prepared Pt/SiO₂ and ZnO/SiO₂ precursors via incipient wetness impregnation. Such precursors are physically mixed and heated under hydrogen atmosphere in a flow reactor (pictured, panel a), with a stepped thermal profile. At a temperature between 170–350 °C platinum is first reduced under the reactive environment and forms a nucleation site (pictured, panel b). Thus, an increase in temperature to above 350 °C triggers the reduction of the ZnO with the simultaneous migration of mobile zinc atoms to the Pt seed, forming an ordered intermetallic PtZn alloy. Optimization of the synthesis parameters guided by spectroscopic characterization resulted in the formation of an alloy with a specific composition — PtZn_1.4/SiO₂. This material proved to be a very active catalyst for the dehydrogenation of propane to propylene, showing high selectivity under industrially relevant conditions. Thanks to a straightforward regeneration approach, the catalyst was also able to achieve a very good durability for over 1,300 h on stream. The team also extended this atomic gas-migration approach to the preparation of other intermetallic catalysts competent for propane dehydrogenation, including platinum–gallium and plating–indium.

The generality of the method, together with the possibility of preparing ordered structures, make this atomic gas-migration approach an interesting tool for the catalysis community. The successful preparation of intermetallic alloys active for other gas–solid reactions as well as the ability to scale up the synthesis of the desired material remain as questions for future studies to demonstrate the ultimate potential of this synthetic strategy.