Highly Selective Catalyst Composition for Efficient Ethylene Oxide Production

Background

Ethylene oxide (EO) is a high-volume chemical used extensively to produce major chemicals and myriad consumer products. In 2020, the global production of EO reached 29 million metric tons, and the market is expected to grow. The epoxidation of ethylene by molecular oxygen to produce EO occurs ubiquitously over Ag based heterogeneous catalysts, and the best performance observed in patents and academic research approaches or just exceeds 90% selectivity to EO, CO2 being the other, unwanted byproduct. This process has an uncommonly low single pass conversion in industrial chemistry and requires the reactants and products to be separated and recycled in an uncommonly large recycle stream into the entrance of the reactor to create a continuous process. The separation and recycle steps are extremely energy intensive, inspiring decades of efforts to efficiently improve EO selectivity and conversion. Because of the scale of this process, improving EO selectivity by even a few percent would represent a substantial improvement to the costs, energy usage, and CO2 emissions involved in EO production.

Description

Researchers at UC Santa Barbara, Tufts University, and Tulane University have invented a heterogeneous catalyst formulation that has >90% selectivity toward EO formation from gas phase ethylene and oxygen, at high ethylene conversions up to 12%. This technology marks the first instance of Ni-doped Ag single-atom alloy nanoparticles, which are supported on inert alumina. Ni atoms dispersed in the Ag nanoparticles suppress the generation of unselective oxygen species (responsible for CO2) leading to the formation of EO over the undesired product, carbon dioxide. The high selectivity at relatively a high conversion also suggests that the nature of the oxygen species on the NiAg catalyst mitigates the unwanted secondary reaction of EO combustion. Because catalysts are changed in EO-producing plants every 1-3 years, this catalyst has the potential to serve as a drop-in replacement for current catalyst technologies, creating an impactful operational advantage with minimal lead time to implementation. Furthermore, the catalyst has shown synergistic operation with conventional Cl promoters but has not been optimized with industrial supports or other common promoters (Cs, Re, Mo, etc.) suggesting room for further improvement in performance.

Advantages

• Achieves >90% selectivity toward EO formation from gas phase ethylene and oxygen, at high ethylene conversions up to 12%
• Simplifies implementation as a drop-in replacement for conventional catalysts
• Sets a course for further optimization with more reactor testing

Applications

• Industrial Chemistry
• Ethylene Oxide (EO) production

Patent Status

Patent Pending