TY - JOUR
T1 - In Situ X-ray Photoelectron Spectroscopy Detects Multiple Active Sites Involved in the Selective Anaerobic Oxidation of Methane in Copper-Exchanged Zeolites
AU - Artiglia, Luca
AU - Sushkevich, Vitaly L.
AU - Palagin, Dennis
AU - Knorpp, Amy J.
AU - Roy, Kanak
AU - Van Bokhoven, Jeroen A.
PY - 2019/8/2
Y1 - 2019/8/2
N2 - A direct route to convert methane into high-value commodities, such as methanol, with high selectivity is one of the primary challenges in modern chemistry. Copper-exchanged zeolites show remarkable selectivity in the chemical looping process. Although multiple copper species have been proposed as active, an in situ spectroscopic investigation is difficult, because of their similar fingerprints. We used ambient pressure X-ray photoelectron spectroscopy to investigate an actual powder sample. We could discriminate between different types of active species involved in the conversion of methane to methanol over two different copper-exchanged zeolites, namely, mordenite and mazzite. After activation at 400 °C in oxygen, we followed the reaction in situ at 200 °C, switching from methane to water, and followed by a second cycle with anaerobic activation. Our experimental results, combined with theoretical calculations, prove that Cu(II) sites bound to extra-framework oxygen are involved in the reaction, and that their structure, formation, and stabilization depend on the type of zeolite and on the Si/Al ratio. ©
AB - A direct route to convert methane into high-value commodities, such as methanol, with high selectivity is one of the primary challenges in modern chemistry. Copper-exchanged zeolites show remarkable selectivity in the chemical looping process. Although multiple copper species have been proposed as active, an in situ spectroscopic investigation is difficult, because of their similar fingerprints. We used ambient pressure X-ray photoelectron spectroscopy to investigate an actual powder sample. We could discriminate between different types of active species involved in the conversion of methane to methanol over two different copper-exchanged zeolites, namely, mordenite and mazzite. After activation at 400 °C in oxygen, we followed the reaction in situ at 200 °C, switching from methane to water, and followed by a second cycle with anaerobic activation. Our experimental results, combined with theoretical calculations, prove that Cu(II) sites bound to extra-framework oxygen are involved in the reaction, and that their structure, formation, and stabilization depend on the type of zeolite and on the Si/Al ratio. ©
KW - active sites
KW - ambient pressure X-ray photoelectron spectroscopy
KW - copper zeolites
KW - density functional theory
KW - infrared spectroscopy
KW - methane to methanol
UR - http://www.scopus.com/inward/record.url?scp=85071164455&partnerID=8YFLogxK
U2 - 10.1021/acscatal.9b01223
DO - 10.1021/acscatal.9b01223
M3 - Article
AN - SCOPUS:85071164455
SN - 2155-5435
VL - 9
SP - 6728
EP - 6737
JO - ACS Catalysis
JF - ACS Catalysis
IS - 8
ER -