Structure And Characterization Of Complexes Formed Of Ca²⁺ And Coal Active Group

As basic research on the theory about inhibition technology for spontaneous coal combustion is not adequate, the quantum chemistry theory is used to study the basic theory about inhibition technology for preventing spontaneous coal combustion from microcosmic view for the first time. With B3LYP/6-3llG density functional theory, the process of forming coordination chemical bond and ligand between active groups of coal including N, P, S and inhibitor is studied and characterized by infrared spectrum and thermogravimetry experiment. The theory of inhibition mechanism for preventing spontaneous coal combustion is founded. The core content is that coordination chemical bond and ligand are formed between active groups including N, P, S, O, etc in organic macromolecule and low molecular weight compounds of coal and metal ions in inhibitor, which decrease the reaction activity between oxygen and active groups. It is a breakthrough of traditional theory and academic view that water film, separating oxygen, is formed on coal surface after strong salts absorb water. It also fills the gaps in field of studying inhibition mechanism for preventing coal spontaneous combustion. The main research contents and achievements are as follows:Through infrared spectrum experimental study and quantum chemistry calculation, based on the molecular structure model of coal, with B3LYP/6-3llG density functional theory, structure model and frontier orbital figure of coal molecule after simplification are obtained and determine that active groups like -NH2, -PH2, and–SH in coal molecule have high chemical activity and therefore are easy to loss electron and form coordination bond with metal ions, making spontaneous coal combustion happened easily.The process of forming coordination chemical bond and coordination compound between active groups of coal molecule and ions Ca²⁺ is studied. After calculating and analyzing natural bond orbital, net charge population and natural electron configuration, strong interaction energy between lone pair electrons of atoms N, P, S in coal molecule and ions Ca²⁺ and unoccupied orbital is discovered. Meanwhile, atomic orbital of ions Ca²⁺ gets part of feedback electrons from ligand and deviates its apparent charge, which illustrate that coordination bond is formed between Ca²⁺ and N, P, S in ligand.After analyzing stabilization energy and frontier orbital energy level, it is obtained that four-coordination compounds forming from Ca²⁺ and active groups N is the most stable, so does the two-coordination compounds forming from Ca²⁺ and active group P, S.Coordination compounds forming from coal and Ca²⁺are synthesized and characterized by infrared spectrum and thermogravimetry experiment. Infrared spectrum characterization indicates that peak area values of -CH2-NH2, -CH2-S-, -CH2-P- are changed and peak position is undertook einstein shift and hypo chromatic shift. Thermogravimetry experiment indicates that ignition activation energy rises at large after inhibitor is added into the coal, which illustrate that coordination compounds are formed from active group in coal and Ca²⁺ and therefore decrease the activation of reaction between oxygen and coal.