Monitoring of N-doped organic xerogels pyrolysis by TG–MS
Monitoring of N-doped organic xerogels pyrolysis by TG–MS
复制标题
通过TG-MS 监测氮掺杂有机干凝胶的热解
DOI：
10.1007/s10973-012-2923-0
复制
发表时间：
2013
影响因子：
4.4
通讯作者：
V. Slovák
中科院分区：
文献类型：
--
作者：
P. Veselá;V. Slovák
用热重-质谱法研究了由不同含氮前驱体制备的含氮有机干凝胶的热解过程，确定了热解过程分为三个步骤。第一步(直到CCA。250摄氏度)被解释为水分损失(湿度，毛孔中固定的水分)，在某些情况下被解释为甲醛损失。第二步与挥发性物质的演化(CCA)有关。250-450°C)，主要释放NH3、CO2和三聚氰胺(M)或尿素的分解产物。在这一步骤中还检测到了反应/孔隙水和甲醛。热解的第三阶段(450-1000℃)归因于碳化反应，此时NH3、CO2、反应/孔隙水和M分解产物仍在继续释放。这伴随着H_2和3-羟基吡啶的演化。在热重测试的基础上，发现有机干凝胶缩合时间越长，催化剂用量越大，炭化产物的产率越高。此外，掺氮碳干凝胶对铅(II)的吸附实验证明，干凝胶的吸附性能与热解过程中的氮损失之间存在一定的关系。当样品中只含有氨基时，它们在热解过程中以氨的形式丢失，吸附能力较低，而N-前驱体芳环中的氮保留在结构中，导致吸附容量增大。
Pyrolysis of N-doped organic xerogels prepared from different N-containing precursors has been studied by TG–MS. The pyrolytic process has been ascertained to consist of three steps. The first step (up to cca. 250 °C) has been interpreted as water loss (humidity, fixed water from pores) and in some cases as formaldehyde loss. The second step has been connected with volatile substances evolution (cca. 250–450 °C) with predominant release of NH3, CO2and products of melamine (M) or urea decomposition. Reaction/pore water and formaldehyde have also been detected in this step. The third step of pyrolysis (450–1,000 °C) has been ascribed to carbonization reaction when the other releases of NH3, CO2, reaction/pore water and M decomposition products have continued. This was accompanied with evolution of H2and 3-hydroxypyridine. On the basis of TG measurements, it was found that increasing time of condensation of organic xerogels and amount of used catalyst lead to higher yield of carbonaceous products. In addition, adsorption experiments of Pb(II) on N-doped carbon xerogels proved that relationship between adsorption properties of xerogels and nitrogen loss during pyrolysis exists. When the sample contains only amino groups, they are lost during pyrolysis as ammonia and the adsorption ability is low, while nitrogen comprised in the aromatic rings of N-precursors stays in the structure and causes enlarging of adsorption capacity.