Limitations of proton-conducting materials as supports for Pt-catalyzed ethane dehydrogenation in membrane reactors

Olefin formation via non-oxidative dehydrogenation of light alkanes is limited by thermodynamic equilibrium. A possible strategy to increase olefin yields aims at removing H 2 from the reaction zone using ceramic proton-conducting membranes. An attractive proposition is to deposit the catalyst directly onto the proton-conducting material to optimize hydrogen transport. To test this concept a Pt dehydrogenation catalyst was deposited onto lanthanum tungstate (LWO) and barium zirconium cerium yttrium (BZCY) oxides, which are prototypical materials in proton-conducting ceramics. The performance of Pt/LWO and Pt/BZCY was compared to a conventional Pt/ZnAl 2 O 4 dehydrogenation catalyst in the non-oxidative dehydrogenation of ethane. The ethylene selectivity on Pt/LWO and Pt/BZCY was much lower than for Pt/ZnAl 2 O 4 , at the cost of a higher methane selectivity. Methane formation is possibly boosted by C-C cleavage on Lewis acid sites of the LWO and BZCY supports. These acid sites originate from the presence of oxygen vacancies in LWO and BZCY. Additionally, Pt/LWO deactivated rapidly in dry atmospheres, due to Pt sintering. This sintering, however, was suppressed when cofeeding steam. The presence of steam, unfortunately, further decreased ethylene selectivity for Pt/LWO. The Pt/BZCY system was comparably stable relative to Pt/LWO, which was attributed to relatively strong interactions between Pt and the Ba in the support. Implementing proton-conducting materials, like LWO and BZCY, as catalyst supports requires significant improvements to compete with the conventional Pt/ZnAl 2 O 4 catalyst. Addressing this issue will be key to enable large-scale implementation of proton ceramic catalytic membrane reactors for alkane dehydrogenation. ● Proton-conducting supports enhance C-C cleavage in Pt-based ethane dehydrogenation. ● Pt sinters in catalyst systems in which Pt is supported onto proton-conducting materials. ● Cofeeding steam suppresses Pt sintering in Pt-catalyzed ethane dehydrogenation.