(453h) Ethane Oxidative Dehydrogenation By CO2 over Stable Csru/CeO2 Catalyst

Accompanied by the development of modern industry, the demand for light olefins including ethylene, propylene, butene, and butadiene continues to increase. Light olefins are important intermediates for the production of polymers (polyethylene, polypropylene, etc.) and rubber (styrene butadiene rubber, polybutadiene rubber, etc.). Currently, the primary process to produce light olefins is based on steam cracking of petroleum liquids such as naphtha and distillate fuel oil. It is an energy-intensive process, requiring high operating temperatures (750-850℃) and pressure (1.0-4.5 MPa). As the feedstock becomes lighter, the product distribution is shifted to ethylene.

Besides petroleum liquids, ethane is a promising feedstock for ethylene production by steam cracking. Oxidative dehydrogenation (ODH) of ethane by CO₂ is an energy-efficient way of utilizing abundant shale gas while mitigating greenhouse gas impact.

In this study, oxidative and non-oxidative dehydrogenation (EDH) of ethane were investigated and compared over Cs-promoted Ru/CeO₂ catalyst. The presence of CO₂ improved the ethane conversion to ethylene and led to the formation of C₃ and C₄ olefins as well (Figure 1).The olefin selectivity and yields in ODH were affected by reaction variables including CO₂/C₂H₆ ratio, temperature, and feed rate. The CsRu/CeO₂ catalyst exhibited excellent stability in the ODH reaction. Mechanistically, the interaction between Cs and Ru with ceria in the crystalline structure facilitated reduction and oxidation cycles. It was postulated that in the oxidation cycle, Ce³⁺ had a strong tendency to react with CO₂ to form Ce⁴⁺, causing C=O bond scission, whereas in the reduction cycle, Ce⁴⁺ was reduced by hydrogen during ethane dehydrogenation to form Ce³⁺. The redox cycle can be repeated during the ODH reaction keeping the catalyst active. Furthermore, in the ODH reaction, the CsRu/CeO₂ catalyst exhibited resistance to carbon deposition, evidenced by the carbon balance measurement.