reactions rate reaction phase liquid

The gap

Supporting evidence — 3 representative gaps

• Kinetics of primary mechanochemical covalent-bond-forming reactions (2024) · doi

  of these hot-spots have been hypothesized to be >1000 K (ref. 74) and to last for a few milliseconds before dissipating,75 and it is further hypothesized that these increases in temperature provide the energy to overcome the reaction activation barrier. The hot spot theory, however, has been questioned by recent investigated the phase experimental studies. Delogu et al. transition of metals and metal oxides under milling.76 These metals and metal oxides can undergo transitions between different structures under thermal activation. For example, the face-centered cubic a-phase of Ca transforms into the body- centered cubic b-phase at 720 K, while CuI g-phase undergoes structural phase transitions, rst to a b-phase and then to a a- phase structure at 650 and 672 K, respectively. However, no changes in phase were detected during milling of these mate- rials even though the temperatures required for this conversion in both cases could presumably be accessed under hot-spot conditions. The recent development of mechanochemical reactors with the ability to control temperature precisely77 or monitor temperature in situ78 have also been used to test the hot-spot theory. The experiments revealed that the mechanical impact occurring within the reactor can increase temperature, but these increases are closer to 10 °C.79 It is worth noting, however, that these experiments may be insensitive to sharp rises in local temperatures at the site of impact from ball collisions. To measure the temperature of the balls, since the temperature rise during the milling that are hypothesized to be the result of ball-to-ball, ball-to-powder, and ball-to-wall colli- sions, Gerasimov et al. used calorimetric techniques to estimate the local temperatures of the balls during the milling, and found the temperatures as high as 600 °C can occur on the surface of the balls.80 As such, the roles of localized hot-spots and temperature spikes on increasing the rates of reactions remains unresolved but suggest that increased temperature could have a role in increasing reaction rates. However, because the activation here remains thermal, the transition state ener- gies and structures would not differ from those that arise under typical thermal activation, and, as such, hot-spot theory does not account for changes in selectivities that occur in mecha- nochemical reactions. Mixing efficiency theory Butyagin divided mechanochemical reactions into two groups based on their kinetics.19 In the rst case, the rate of the mechanochemical process is determined by the rate of the primary chemical reaction that is under a constant eld of mechanical stress. Mechanical energy is absorbed quickly when a constant stress is applied, and the stress is distributed evenly along the reaction system. In this model, the dependence of reaction rate on external stress should be dened mainly by the characteristics of the primary chemical reaction. The second class of reactions consist of a multistep process, inv

  Keywords: temperature phase reaction ball activation spot theory milling temperatures reactions stress hypothesized thermal mechanochemical mechanical
• Packed Bed Microreactors for Sustainable Chemistry and Process Development (2025) · doi

  The complex hydrodynamics of gas–liquid–solid reactions are unavoidable when using a packed bed microreactor, presenting a challenge that needs to be addressed in kinetic studies.

  Keywords: complex hydrodynamics liquid solid reactions unavoidable using packed microreactor presenting challenge needs addressed kinetic
• Packed Bed Microreactors for Sustainable Chemistry and Process Development (2025) · doi

  Limited hydrogen diffusion rate in liquid-phase systems compared to vapor-phase reactions needs further investigation to improve reaction performance in gas–liquid–solid systems.

  Keywords: liquid phase systems limited hydrogen diffusion rate compared vapor reactions needs further investigation improve reaction