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Monitoring the Heat Flow in Mechanochemical Reactions

Despite recent advances in real-time and in situ monitoring techniques, 1, 2 a major unknown in the study of mechanochemical milling reaction is the evolution and influence of temperature on reaction mechanisms and kinetics – a prerequisite for mechanistic understanding of these reactions.3 Here, we describe high- precision reaction temperature profiles of mechanochemical reactions derived from tandem in situ temperature monitoring and synchrotron powder X-ray diffraction. Numerical simulations of the observed temperature profiles revealed that the heat flow generated by dissipative friction processes within a vessel have a dominant influence on the temperature profile of the milling assembly and finally, on the steady state temperature. While temperature profiles correlate with changes in the reaction mixture composition, contribution of the reaction enthalpy to temperature profiles is, in general, significantly lower or even negligible compared to frictional heating. Our results reveal the sensitivity of global temperature to milling and vice-versa as well as emphasise the importance of temperature monitoring for mechanistic understanding of milling reactions.

Mechanochemistry ; in situ synchrotron diffraction monitoring, MOF materials ; heat-flow monitoring ; temperature fluctuations

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