十氢十硼酸双四乙基铵热分解特性及其动力学参数

为了解十氢十硼酸双四乙基铵(BHN-10)热分解特性及反应动力学,采用同步热分析-红外质谱联用技术(TG-DSC-MS-FTIR)及热裂解原位池-傅里叶变换红外光谱联用技术(FTIR)对BHN-10热分解过程中间产物和最终产物进行分析;使用Kissinger和Ozawa方法计算两个热分解阶段的动力学参数,并利用Coats-Redfern法拟合得到反应动力学方程。结果表明,BHN-10热分解第一阶段和第二阶段的活化能分别为150.9 kJ/mol和161.7 kJ/mol;第一阶段受随机成核和核增长机理控制,第二阶段遵从幂级数法则(Mampel power);两阶段的动力学机理函数分别为G(α)=-ln(1-α)]1/3(n=3)和G(α)=α1/4;BHN-10热分解反应第一阶段质量损失2.9%,与理论脱氢质量损失相一致,此阶段发生B10H2-10的脱氢产生氢气和非晶态硼的过程,在热分解第一阶段会生成熔融分解型的中间产物四乙基铵阳离子;第二步反应质量损失39.4%,接近第二阶段气体质量损失的计算值43.4%,是四乙基铵阳离子上的质子转移并通过Hoffman消除反应生成乙烯和Et3N,Et3N进一步分解为C 2H 6、NH3、H2和碳单质。

Thermal Decomposition Characteristics and Kinetic Parameters of Tetraethylammonium Decahydrodecaborate

To explore the thermal decomposition characteristics and reaction kinetics of tetraethylammonium decahydrodecaborate(BHN-10),the intermediate and final products of the thermal decomposition process were analyzed by combined solid reaction cell in-situ and FTIR,TG-DSC-MS-FTIR simultaneous techniques.The kinetic parameters of the two decomposition stages were calculated by the Kissinger′s and Ozawa′s methods,and the reaction kinetic equations were obtained by Coats-Redfern method.The results show that the activation energies of the first and second stages of BHN-10 thermal decomposition are 150.9 kJ/mol and 161.7 kJ/mol,respectively.The first stage is controlled by the mechanism of random nucleation and nuclear growth,in which the most probable mechanism function is G(α)=-ln(1-α)]^1/3(n=3).The second stage follows the Mampel power and the most probable mechanism function is G(α)=α^1/4.The mass loss in the first stage of the thermal decomposition reaction is 2.9%,which is consistent with the theoretical dehydrogenation mass loss.At this stage,the dehydrogenation of B10 H2-10 produces amorphous form of boron and hydrogen.BHN-10 can produce a melt-decomposable intermediate product during the first decomposition process.The mass loss in the second stage is 39.4%,close to the calculated value of gas mass loss in the second stage 43.4%,which is proton transfer on a tetraethylammonium cation to form ethylene and Et 3N through Hoffman elimination reaction,and Et 3N is further decomposed into C2H6,NH3,H2 and carbon.