Direct water thermolysis

The possibility to transform directly a high-temperature thermal source to chemical energy makes quite attractive the water thermolysis process. This approach represents a direct route for conversion of heat associated with a primary source into hydrogen without intermediate steps the constraint is that theoretically attractive efficiency can be obtained only if primary sources producing high-temperature energy are used. 

We hoped to define conditions that would allow us to use toluene as solvent for the reaction. The toluene solution of 8 could be taken directly into the dehydrogenation following distillation to remove water and alcohol solvents. The boiling point of toluene was suitable for the thermolysis but silylation in toluene was very slow. 

In contrast to the situation on flash pyrolysis, methyleneoxophosphoranes generated by thermolysis or photolysis in the presence of protic nucleophiles can be directly trapped to form corresponding derivatives of phosphinic acid (17- 19) however, the possibility of competing insertion of carbenes into the H/X bond of the additives is always present, giving phosphine oxides with X in the a-position (16- 18). Reaction branching at the carbene 16 was first observed on photolysis of 7 in water 13) and prompted detailed investigations on the phosphorylcarbene/ methyleneoxophosphorane rearrangement. 

In a process called direct thermolysis, at a high enough temperature thermal energy is sufficient to split water into hydrogen and oxygen. Only one reaction is involved in this process, that of equation (2.3.1). In Fig. 2.6, if the input water and output gas mixture are at the same temperature To, the minimum work input required to effect water splitting at temperature Tr can be written [60]... 

Solvent-free uncatalyzed amidations of acids occurred readily under microwave conditions when conducted with a slight excess of either amine or acid (1.5 equiv). The pathways involved thermolysis of the previously formed ammonium salts (acid-base equilibrium) and proceeded by nucleophilic attack of the amine on the carbonyl moiety of the acid, with removal of water. This procedure was extended to the preparation of functionalized tartramides directly from amines and tartaric acid under solvent-free conditions and microwave activation (Scheme 10). By conventional heating, yields were lower even after 16 h. 

Thermochemical production of hydrogen involves the separation of water into hydrogen and oxygen through chemical reactions at high temperatures. Ideally, water can be separated directly (thermolysis) however this process requires temperatures in excess of 2 500°C. 

Since a direct thermolysis of water, which requires temperatures of > 2500 °C, is not practicable under normal circumstances, the splitting process is subdivided into different partial reactions, either one running on a lower temperature level. The principle is given by the following cycle ... 

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