Preferential Carbon Monoxide Oxidation over Copper‐Based Catalysts under In Situ Ball Milling

Abstract

In situ ball milling of solid catalysts is a promising yet almost unexplored concept for boosting catalytic performance. The continuous preferential oxidation of CO (CO-PROX) under in situ ball milling of Cu-based catalysts such as Cu/Cr O is presented. At temperatures as low as -40 °C, considerable activity and more than 95 % selectivity were achieved. A negative apparent activation energy was observed, which is attributed to the mechanically induced generation and subsequent thermal healing of short-lived surface defects. In situ ball milling at sub-zero temperatures resulted in an increase of the CO oxidation rate by roughly 4 orders of magnitude. This drastic and highly selective enhancement of CO oxidation showcases the potential of in situ ball milling in heterogeneous catalysis.

Milling Down to Nanometers: A General Process for the Direct Dry Synthesis of Supported Metal Catalysts

“…Them odification of the milling capsules has been described previously. [12,13] Milling was performed under different atmospheres,s ee the Supporting Information for details.…”

“…[10,11] Milling during the catalytic reaction itself can lead to an increase in reaction rates by several orders of magnitude. [12][13][14] There are also scattered results in the literature that for specific cases the milling of metal compounds,a ccompanied or followed by reduction reactions,c an be used to produce supported catalysts. [15,16] In one publication, as one of three alternative synthetic processes,e lemental silver was used as precursor of high-activity Ag/g-Al 2 O 3 particles synthesized by ball milling.…”

Mechanochemistry for Synthesis

“…[27] This provides an enclosed environment in which the additive and milling conditions are controllable and can include milling frequency,time,light, [31,32] temperature, [33] and gas (Figure 1c-h). [34] As the liquid can accelerate or enable reactions that do not proceed by neat milling, LAGoffers the mechanochemist apowerful method to optimize solid-state reactions.…”

“…Setups for milling with:f)temperature control; [33] g) irradiation [31] and h) gases. [34] Panels (e), (f), (g) are adapted from Refs. [33,31] and [34].…”

Hydroformylation of Alkenes in a Planetary Ball Mill: From Additive‐Controlled Reactivity to Supramolecular Control of Regioselectivity

“…1min) via supramolecular means,t he reactant (tosylimidazole) being included into the CD cavity. [20,21] Reported herein is the ball-milled Rh-catalyzed hydroformylation of alkenes to the corresponding aldehydes under CO/ H 2 pressure in the presence of saccharide additives such as methyl-a-d-glucopyranoside (1a), acyclicd extrins (1b,m altodextrins 6D,d egree of polymerization = 20) [22] and CDs of different cavity size (1c-e,F igure 1). [19] On the basis of the aforementioned results,w es ought to assess the potential of CDs to control both the chemo-and regioselectivity of the hydroformylation reaction under CO/H 2 pressure under mechanochemical activation.…”