Flow Toolkit for Measuring Reaction Enthalpy and Application to Highly Exothermic Synthesis of Alkylaluminoxanes

Abstract

We present a flow strategy to characterize reaction enthalpy and showcase the application in synthesis of alkylaluminoxanes from the fast and exothermic alkylaluminum hydrolysis. Our platform mainly encompasses a three-dimensional printed micromixer and a tubular reactor in an adiabatic vacuum box, aided by a thermal imaging camera to record temperature profiles. The temperature increase at steady state is used to calculate the released heat, which is further decoupled to quantify the reaction enthalpy and enthalpy of mixing. We validate the concept with the classic neutralization reaction between sulfuric acid and sodium hydroxide, with less than 2% deviation from theoretical values. In application, we determine the exothermic reaction enthalpy and the endothermic enthalpy of mixing to be −143.13 and +7.66 kJ/mol for triisobutylaluminum hydrolysis and −164.63 and +5.03 kJ/mol for trimethylaluminum hydrolysis, respectively. The presented platform, on the one hand, yields new insights into the microreactor scale-up for alkylaluminoxane synthesis and, on the other hand, can be readily used to measure reaction enthalpies of other reactions.

Thermal characterization of highly exothermic flash chemistry in a continuous flow calorimeter

“…37 Moreover, reaction temperatures cannot be controlled and calorimetry at low temperatures is difficult or even impossible for this type of calorimeter. 34,36…”

“…• Energy balance based on measurements with an infrared camera. [33][34][35][36][37] Infrared thermometry is a non-intrusive method to record the complete temperature profile of the area of interest. 35 Zhang et al developed a microsystem integrated with an infrared camera to measure the reaction enthalpy.…”

“…37 Moreover, reaction temperatures cannot be controlled and calorimetry at low temperatures is difficult or even impossible for this type of calorimeter. 34,36 • Heat flow measurements with thermoelectric elements. 25,26,[38][39][40][41][42][43][44][45][46] Seebeck elements can be used to directly measure the heat flux with high sensitivity and resolution.…”

Densely Packed Chemical Synthesis Equipment by 3D Spatial Design and Additive Manufacturing: Acetylene Generation Cartridge

“…The miniaturization of chemical equipment is an important approach that can reduce the required spatial area and therefore increase the efficiency of the use of laboratory space . Recently, there has been rapid progress in the miniaturization of analytical instruments and diagnostic tools, while the equipment for organic synthesis benefits from the implementation of flow reactors . Three-dimensional (3D) printing provides flexible solutions in the fields of catalysis, fine chemicals, drug synthesis, chemical analysis, and nanomaterial preparation, among many other directions.…”

A two-stage flow strategy for the synthesis of isobutyl-modified methylaluminoxane

“…Alkylaluminoxanes are synthesized conventionally via partial hydrolytic reactions of alkylaluminums in largevolume batch reactors with a very low yield. 10 Alkylaluminums are pyrophoric and violently reactive with water, 11,12 bringing big challenges in process control and safe operation during reaction. If the temperature and amount of water were poorly controlled, the hydrolysis of alkylaluminums would become utterly unsafe with more byproduct formation, further reducing the yield of alkylaluminoxanes.…”