锆粉对高氯酸钾热分解反应的影响

为研究平均粒径1μm的锆粉(Zr)对高氯酸钾(KClO_4)各步热分解反应的影响,通过X射线光电子能谱(XPS)和热重分析(TG/DTG)研究了纯KClO_4和质量比为50∶50的Zr/KClO_4两种体系的热分解过程。XPS结果表明,锆粉的加入促进了KClO_4第一步热分解生成KClO_3的可逆反应平衡向右移动。利用线性拟合方法求解了两步热分解过程的动力学三因子,计算结果表明,加入小粒径锆粉后第一步热分解的活化能降低,指前因子增大,最可几机理函数由G(α)=-ln(1-α)]~(3/4)变为G(α)=-ln(1-α),热爆炸临界温度由587.7℃降至516.9℃;第二步热分解活化能升高,指前因子不变,最可几机理函数均为G(α)=-ln(1-α)。因此,锆粉的加入促进了KClO_4的第一步热分解,增加了反应的活性位点,使反应更易进行,提高了反应速率,但同时锆粉表面被氧化为氧化锆,作为惰性物质掺杂于KClO_4和KClO_3之间,使得第二步热分解的表观活化能升高,但其不参与反应,不改变反应机理

Effect of Zirconium Powder on Thermal Decomposition of KClO4

In order to investigate the effect of fine zirconium powder with diameter of 1 μm on the reaction mechanism of KClO4 during thermal decomposition, TG/DTG and X-ray photoelectron spectroscopy (XPS) analysis were applied to determine the thermal behavior of KClO4 and Zr/KClO4 (50∶50).The result of XPS shows that the addition of KClO4 promoted the reversible chemical reaction equilibrium of KClO4.Linear regression was used to determine the kinetic triplet.The calculation result shows that the activation energy declined while the pre-exponential factor increased and the mechanism function shifted from G(α)=-ln(1-α)]3/4 to G(α)=-ln(1-α), the critical temperature of thermal explosion declined from 587.7 ℃ to 516.9 ℃ for the first decomposition stage.As for the second one, the activation energy increased while the pre-exponential factor hardly changed and the mechanism function remains G(α)=-ln(1-α).Thus it can be inferred that zirconium accelerated the first thermal decomposition step of KClO4, increased the number of active sites and made it easier to happen, but became inert substance since it was oxidized to ZrO2 and that was the reason of the increment of the activation energy and the invariant of the mechanism function.