by Brooke Kuei
Ethylene is one of the most important chemicals produced worldwide, serving as the fundamental building block for everyday materials like plastics, antifreeze, and solvents. Despite its widespread use, the production of ethylene always generates small amounts of acetylene, an impurity that can disrupt downstream catalysts and compromise product quality if it is not carefully removed.
This issue is typically addressed through selective semihydrogenation, adding hydrogen to convert the acetylene into ethylene. The challenge is that the reaction must go far enough to remove as much acetylene as possible—without continuing too far and converting ethylene into ethane. For decades, this delicate balance has relied on precious metal catalysts that are not only costly, but still can’t control the reaction with complete precision.
In a recent paper published in Nature Communications, researchers from Oak Ridge National Laboratory (ORNL) and the Advanced Light Source (ALS) developed a metal-free boron nitride catalyst that converts acetylene impurities into ethylene with greater than 98% selectivity. Soft x-ray spectroscopy at ALS Beamlines 8.0.1 and 7.3.1 played a key role in revealing the atomic-scale origins of this high performance.
“The challenge is removing tiny amounts of acetylene from ethylene without destroying the ethylene itself,” said Zhenzhen Yang, a researcher at ORNL and co-corresponding author on the study. “The beauty of our boron nitride system is that we can achieve very high selectivity without over reduction.”
ALS measurements showed that the key to this performance lies in atomic-scale defects. Although boron nitride is a ceramic that is normally considered chemically inert, the researchers created a unique form of boron nitride through flux reconstruction, a processing method that reorganizes a disordered material into an ordered structure while creating chemically active defects.
Understanding how this process unfolds was possible through x-ray methods capable of probing light elements at the atomic scale. “The ALS was critical because soft x-ray spectroscopy is uniquely sensitive to light elements like boron and nitrogen,” said ALS Senior Scientist Jinghua Guo. “ALS measurements allowed us to directly see the formation of defect sites and link those atomic-scale changes to the catalyst’s exceptional selectivity.”
The spectroscopy measurements revealed the complete removal of boron–oxygen species and the transformation of the material from an amorphous state to a crystalline structure. These results confirmed that heating the material reorganizes the boron nitride into tiny crystalline sheets containing chemically active boron and nitrogen atoms. At the same time, the process removes unwanted impurities such as oxygen and carbon.
“By using a flux reconstruction process, we transformed boron nitride from an inert ceramic into a crystalline material filled with clean, well-defined defects that act as active sites for catalysis,” said Tao Wang, one of the lead authors and a researcher at ORNL. These defects convert acetylene impurities into ethylene without reacting further to create ethane.
Looking ahead, the team is exploring other applications of defect-engineered boron nitride, such as hydrogen storage, and opportunities for industrial scale-up of their flux reconstruction process for metal-free catalysts.
T. Wang, K.M. Siniard, M. Li, F. Polo-Garzon, J. Liu, Z. Zhuo, J. Guo, A.S. Ivanov, T. Kobayashi, K. Tan, S. Amagbor, A.A. Maruf, J. Kelber, S. Yang, H. Song, D. Jiang, G. Duscher, Z. Yang, and S. Dai, “Selective semihydrogenation of acetylene in ethylene using defect-rich boron nitride catalyst from flux reconstruction,” Nat. Commun. 16, 9948 (2025), doi:10.1038/s41467-025-64886-x.