Direct Epoxidation of Propylene over Stabilized Cu⁺ Surface Sites on Titanium‐Modified Cu₂O

Abstract

Direct propylene epoxidation by O2 is a challenging reaction because of the strong tendency for complete combustion. Results from the current study demonstrate that by generating highly dispersed and stabilized Cu(+) active sites in a TiCuOx mixed oxide the epoxidation selectivity can be tuned. The TiCuOx surface anchors the key surface intermediate, an oxametallacycle, leading to higher selectivity for epoxidation of propylene.

Water-assisted oxygen activation during selective oxidation reactions

“…The ideal process for PO production, which is analogous to ethylene epoxidation over silver catalysts, is the selective epoxidation of propylene with molecular O 2 : C 3 H 6 + ½O 2 ! C 3 H 6 O [46,47]. This goal, however, has not yet been achieved and is considered by some as a Holy Grail in catalysis [34].…”

Correlation between Copper Oxide Particle Size and Selectivity towards Propylene Oxide in Selective Oxidation of Propene

“…Nanostructured SBA-15 was synthesized using the method reported by Zhao et al [19] 16.2 g of triblock copolymer (P123, Aldrich) were dissolved in a mixture of 293.6 g water and 8.8 g concentrated HCl.…”

“…While all three metal catalysts can form PO with gaseous oxygen as oxidant, currently only gold and silver can form PO with a good selectivity using a mixture of oxygen and hydrogen ,,. In contrast to silver and gold metal catalysts, both metallic Cu and cationic Cu + species are active epoxidation species in copper catalysts ,. Valence of active copper species is crucial, considering copper oxide can be used as epoxidation catalyst without reductive pretreatment.…”

“…[9,17,18] In contrast to silver and gold metal catalysts, both metallic Cu and cationic Cu + species are active epoxidation species in copper catalysts. [9,19] Valence of active copper species is crucial, considering copper oxide can be used as epoxidation catalyst without reductive pretreatment. Hence, active species need to form under reaction conditions.…”

Über den Technologiewandel in der Propylenoxid‐Herstellung

“…Bekanntlich wird Ethylen in der Gasphase an einem Silberkatalysator mit Luftsauerstoff epoxidiert . Die analoge Umsetzung von Propylen ist aufgrund der Eigenschaften der Allylgruppe nicht möglich: Oxidationsreaktionen setzen durch Abstraktion eines Protons an der CH 3 ‐Gruppe des Propylens an, so dass nahezu ausschließlich CO 2 erhalten wird (oder andere Oxidationsprodukte wie Acrolein, Acrylsäure, Propionsäure,…) . Kupfer‐, Silber‐ oder Gold‐Katalysatoren liegen im derzeitigen Fokus, da sie unter bestimmten Reaktionsbedingungen geeignete Selektivitäten durch Unterdrückung der C‐H‐Aktivierung zeigen können .…”