Abstract
The syntheses of various chemical compounds require heating. The intrinsic release of heat in exothermic processes is a valuable heat source that is not effectively used in many reactions. In this work, we assessed the released heat during the hydrolysis of an energy-rich compound, calcium carbide, and explored the possibility of its usage. Temperature profiles of carbide hydrolysis were recorded, and it was found that the heat release depended on the cosolvent and water/solvent ratio. Thus, the release of heat can be controlled and adjusted. To monitor the released heat, a special tube-in-tube reactor was assembled using joining part 3D-printed with nylon. The thermal effect of the reaction was estimated using a thermoimaging IR monitor. It was found that the kinetics of heat release are different when using mixtures of water with different solvents, and the maximum achievable temperature depends on the type of solvent and the amount of water and carbide. The possibility of using the heat released during carbide hydrolysis to initiate a chemical reaction was tested using a hydrothiolation reaction—the nucleophilic addition of thiols to acetylene. In a model experiment, the yield of the desired product with the use of heat from carbide hydrolysis was 89%, compared to 30% in this intrinsic heating, which was neglected.
Highlights
Chemical reactions may proceed with heat release, with heat consumption, or nearly thermoneutral [1,2]
Concerning novelty, we demonstrate for the first time that, by using cosolvents, it is possible to control the temperature profile to a substantial degree and to achieve the best heat release
We have demonstrated that calcium carbide can be successfully used as a source of gaseous acetylene and as a heat source
Summary
Chemical reactions may proceed with heat release (exothermic), with heat consumption (endothermic), or nearly thermoneutral [1,2]. In the first case, which is typical for many synthetic targets, additional heat is required. Some amount of heat may be released upon a reaction of energy-rich components of the reaction. Rather often, this heat remains unused or even requires extra energy for freezing. It is a very common case to supply or remove heat at each step individually, resulting in double power consumption (i.e., power for freezing in one stage and heating in another stage). The design of energy-economic processes is scarcely developed
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