Stability and Deactivation Behavior of Cuprous Acetylide Containing Catalysts in Reppe Ethynylation

Reppe’s ethynylation of formaldehyde uses coal-based acetylene to produce commercially valuable 1,4-butynediol with a silica-supported copper oxide-bismuth oxide catalyst. Cuprous acetylide (Cu2C2) is generally accepted to be the catalytically active phase, which is formed in situ from the CuO-Bi2O3/SiO2 pre-catalyst under ethynylation conditions. The catalytic performance and stability of this sensitive Cu2C2 phase are evaluated by long-term experiments (up to 240 h) and by catalyst recycling (10 cycles of 22 h). Powder X-ray diffraction and Raman spectroscopy are found to be the best and the only applicable analytical tools for qualitative evaluation of Cu2C2’s crystallinity, purity, and morphology during in situ formation and for phase transformations during the ethynylation. They were continuously correlated with the catalytic performance (1,4-butynediol yield determined by gas chromatography). No catalyst deactivation was observed, indicating outstanding catalyst stability. Observed structural changes within the active Cu2C2 phase have obviously limited influence on the catalytic cycle and performance.