Abstract
For the first time, experimental and simulation studies were carried out to determine the mechanisms of catalyst formation for the targeted synthesis of carbon nanotubes. The geometry of the molecular system of a solution of the initial components of a Ni/MgO catalyst has been calculated and modeled using the molecular mechanics method. During the catalyst preparation, ionic complexes were formed, the core of which comprised amino acetic acid molecules held by hydrogen bonds. The structure and properties of the catalytic system depended on the effect and state of these ionic complexes, making possible to explain the observed effects in the process of catalyst formation. The treatment of a solution of Ni/0.3 MgO catalyst in a microwave field (2.45 GHz) promoted the formation of the most efficient catalyst for almost 2 times increased selectivity and productivity for the synthesis of CNTs. A microwave field was a controlling factor for the specified catalytic characteristics, ensuring the directed synthesis of CNTs by the method of gas-phase chemical deposition. This method resulted in the synthesis of carbon nanotubes with an outer diameter of 15–60 nm and a degree of defectiveness (ID/G) of ~ 0.9–1.4. The method is economic for the preparation of CNTs of the desired dimension. The prepared CNTs were used for packing gas chromatographic column, which performed well for separating a mixture of propane, butane, and atmospheric air. The reported method may be used to prepare CNTs of required properties for a variety of applications.
Graphical abstract