Catalytic Performance And Thermal Analysis Kinetics Of Pyrazine Carboxylic Acid Heterometallic Complexes For AP Decomposition

Respecting the disadvantages of heterogeneous mixing and uncontrollable ratio of composite bimetallic oxide combustion catalysts,this thesis aims to synthesize a molecular-scale controllable heteronuclear bimetallic combustion catalyst.The previous work of our research group showed that the four metal coordination polymers formed by Co,Fe,Ni,Zn and 5-methyl-2-pyrazinecarboxylic acid are heterocrystals with each other.Based on this,the use of pyridine the oxazine carboxylic acid contains both coordinating N atoms and coordinating O atoms,connecting two different metal ions in the same crystal lattice.In this paper,28 kinds of heterometallic coordination polymers,which are mutually heteromorphic,are synthesized.They were characterized by infrared spectroscopy（IR）,powder X-ray diffraction（PXRD）,inductively coupled plasma mass spectrometry（ICP-MS）,and scanning electron microscopy（SEM）to determine their structures.The performance of the above coordination polymers in catalyzing the thermal decomposition of ammonium perchlorate（AP）was studied by differential scanning calorimetry（DSC）.Among them,the catalytic effect of Fe_0.75Ni_0.25（2-mpac）₂（H₂O）₂was especially prominent.The apparent activation energy Ea and pre-exponential factor A were calculated,and parameters such as activation enthalpy,activation entropy and Gibbs free energy were further estimated.The specific content and research conclusions are as follows:1.28 kinds of heteronuclear bimetallic coordination polymers were obtained by coordinating any two of the four metal ions of Co,Fe,Ni and Zn with5-methyl-2-pyrazinecarboxylic acid:Co_xNi_y（2-mpac）₂（H₂O）₂（x and y are 0.25,0.33,0.5,0.67,0.75,and x+y=1）Fe_xNi_y（2-mpac）₂（H₂O）₂（x and y are 0.25,0.33,0.5,0.67,0.75,and x+y=1）Fe_xCo_y（2-mpac）₂（H₂O）₂（x and y are 0.25,0.33,0.5,0.67,0.75,and x+y=1）Zn_xFe_y（2-mpac）₂（H₂O）₂（x and y are 0.25,0.33,0.5,0.67,0.75,and x+y=1）Zn_xCo_y（2-mpac）₂（H₂O）₂（x and y are 0.25,0.33,0.5,0.67,0.75,and x+y=1）.(The zinc-nickel combination is composed of Zn_0.75Ni_0.5（2-mpac）₂（H₂O）₂,Zn_0.33Ni_0.67（2-mpac）₂（H₂O）₂and Zn_0.67Ni_0.33（2-mpac）₂H₂O)₂.The structural analysis shows that in the above heterometallic coordination polymers,the coordination configuration of the metal atoms is a distorted octahedron.Two5-methyl-2-pyrazinecarboxylic acid ligands provide a carboxyl O atom and an ortho-aromatic N atom,respectively,which coordinate with the metal central atom in a chelating coordination mode to form two stable pentagonal rings of members,constituting the equatorial plane of the octahedron.2.Four kinds of single-metal coordination polymers and 28 cases of hetero-metal coordination polymers were used to study the catalytic thermal decomposition performance of AP by DSC.The results show that the catalytic combustion performance of bimetallic coordination polymers for AP is generally better than that of single metal coordination polymers.Among the bimetallic coordination polymers,the performance of Fe_0.75Ni_0.25（2-mpac）₂（H₂O）₂is particularly outstanding,which not only advances the high temperature decomposition peak temperature to 302℃,but also eliminates the original endotherm at 242℃peak,the low-temperature decomposition peak was advanced to 240.2℃,and the heat release was also increased from 7.63 m W·mg^-1to 18.89 m W·mg^-1,an increase of nearly 2.5 times.3.The DSC curves of pure AP and Fe_0.75Ni_0.25（2-mpac）₂（H₂O）₂as combustion catalyst were tested respectively under different heating rate conditions(5℃·min^-1and10℃·min^-1,15℃·min^-1,20℃·min^-1four groups were taken in this paper.),the apparent activation energy Ea was calculated by the Kissinger method,the Ozawa method and the Starink method,with（1/_）×10³as the abscissa,ln（β/_<sup>2）is plotted on the ordinate,and Ea and A can be obtained according to the slope and intercept of the straight line.Then,using the Arrhenius equation,the reaction rate constants at the two peak temperatures of the high temperature decomposition peak and the low temperature decomposition peak are obtained.k,further estimate the thermodynamic parameters such as activation enthalpy,activation entropy,Gibbs free energy,and further illustrate that Fe_0.75Ni_0.25（2-mpac）₂（H₂O）₂has a great effect on the thermal decomposition of AP from the perspective of thermal analysis kinetics Excellent catalytic performance.Studies and calculations show that the catalytic performance of heterometallic coordination polymers is generally better than that of single metal coordination polymers in catalyzing the thermal decomposition of AP,indicating that the emergence of multiple metal catalytic active centers can further improve the catalytic decomposition efficiency of AP..