Liquid Metals as Robust Reaction Media for Ethane Dehydrogenation

Ethylene, a major building block in the chemical industry, is predominantly produced via steam cracking, a noncatalytic process where ethane (or naphtha) is mixed with steam and thermally dehydrogenated at ∼850 °C. While this process is commercially widely deployed, it faces significant challenges including coking of the reactor and large CO2 emissions due to the high-temperature operation and large steam cofeed. The present work evaluated the use of liquid metals as alternate, robust reaction media to address these challenges. Using bismuth-based liquid metal systems, we demonstrate via a combination of experimental studies and kinetic simulations that pure bismuth exhibits minimal catalytic activity but functions as a highly effective integrated coke separator that enables ethylene yields that exceed commercial steam cracking while entirely eliminating the need for steam. This results in more than 30% savings in process energy, enabling a reduction in global CO2 emissions from ethylene production by 39 million tons of CO2,eq per year. The unique robustness of this system against deactivation via coking is confirmed by intentionally increasing coke formation via alloying Bi with 5 wt % Ni and demonstrating stable operation for at least 100 h time-on-stream. This liquid NiBi system shows 5 orders of magnitude reduction in deactivation rate compared to a conventional solid 5 wt % Ni/SiO2 catalyst, which deactivates within minutes. These results suggest new avenues for catalytic and noncatalytic ethane dehydrogenation and related reactions by exploiting the exceptional resilience of liquid metal systems in heavily coke-forming environments, lowering energy intensity and carbon footprint for hydrocarbon processing.