An Orders‐of‐Magnitude Increase in the Rate of the Solid‐Catalyzed CO Oxidation by In Situ Ball Milling

Abstract

Shaken, not stirred: CO oxidation was carried out continuously in a shaker ball mill. During milling, the reaction rate increases dramatically, but drops rapidly to zero when the mill is stopped. Compared to a conventional experiment in a plug‐flow reactor, the rate of a ball‐mill reaction catalyzed by Cr2O3 is three orders of magnitude higher at room temperature and one order of magnitude higher at 100°C.

Temperature progression in a mixer ball mill

“…One option is the integration of milling pauses to the milling cycle that allow a cooling down of the milling beakers, but also increase the total reaction time [10,17,18]. Technical solutions for a temperature-controlled milling are: cryogenic milling, where the beakers are cooled with liquid nitrogen [19]; water cooling of the vessels [5] and of the milling beaker holder [20]; (forced) air cooling [21]; use of heating tapes [22]; the application of double-walled milling beakers, which are equipped with an inlet and outlet for a circulating liquid that can be tempered by a thermostat [23][24][25].…”

Metal-catalyzed organic reactions using mechanochemistry

“…This view is supported by the recently described designs for continuous mechanochemical manufacturing, pioneered by Amgen, 105 and for mechanochemical gas-solid reactions, described by the Schüth group. 106 …”

Oscillatory combustion of propene during in situ mechanical activation of solid catalysts

“…The 25-ml tungsten carbide milling vial and the respective milling balls (d = 10 mm) were obtained from RETSCH and modified. All milling vials were equipped with a gas inlet and outlet via Swagelok fittings, with a cone at the gas outlet in order to prevent loss of catalyst by acting as a cyclone filter similar to the one previously described [14]. The milling vessels were additionally equipped with a wireless temperature sensor for measuring the vessel temperature or a thermocouple at the gas outlet for measuring the temperature inside the milling vessel.…”

“…CO 2 methanation was the first example in which the potential of in situ ball milling in heterogeneously catalyzed reactions was explored [13]. Recently, we showed that the in situ ball milling activation of a catalyst can lead to activity increases of a solid catalyst by several orders of magnitude during CO oxidation [14]. Also unusual selectivities have been observed during in situ ball milling catalysis [15].…”