Walczak Michał, Lemanowicz Marcin, Dziuba Krzysztof, Kubica Robert
Grupa Azoty Zakłady Azotowe Puławy S.A., 24-110 Puławy, Poland.
Department of Chemical Engineering and Process Design, Faculty of Chemistry, Silesian University of Technology, ul. ks. M. Strzody 7, 44-100 Gliwice, Poland.
Materials (Basel). 2023 Aug 24;16(17):5795. doi: 10.3390/ma16175795.
The industrial production of melamine is carried out by the thermal decomposition of urea in two technological processes, using high or low pressure. The reaction may be accompanied by the formation of undesirable byproducts, oxoaminotriazines, and so-called polycondensates, mainly melam, melem, and melon, as well as their hydrates and adducts. Their presence leads to the deterioration of the quality of the final product and may lead to the release of troublesome deposits inside the apparatus of the product's separation node. With the limited possibility of controlling the crystallization of the byproducts of the process, improving the technological process requires the precise determination of the composition of the separated insoluble reaction byproducts, which is the main objective of this work. This work presents the results of qualitative and quantitative analyses of the composition of deposits sampled in the technological process of melamine production. The full characterization of the deposits was performed using inductively coupled plasma optical emission spectroscopy (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS) techniques. The elemental analysis (EA) of carbon, hydrogen, and nitrogen allowed us to obtain characteristic C/H, C/N, and H/N ratios. X-ray diffraction (XRD) and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy were also performed to confirm the obtained data. In addition, the morphology of the solid byproducts of the reaction was investigated, and the characteristics of the structures were determined using a scanning electron microscope. The elemental composition was investigated using scanning electron microscopy and the energy-dispersive X-ray spectroscopy (SEM-EDS) technique. The key finding of this research is that about 95% of the deposits are a mixture of melem and melem hydrate. The soluble part of the deposits contains melamine, urea, and oxyaminotriazines, as well as trace inorganic impurities.
三聚氰胺的工业生产是通过尿素在两个工艺过程中进行热分解来实现的，采用高压或低压。该反应可能伴随着不良副产物、氧代氨基三嗪以及所谓的缩聚物（主要是蜜胺、三聚氰二胺和三聚氰三胺）及其水合物和加合物的形成。它们的存在会导致最终产品质量下降，并可能导致产品分离节点设备内部出现麻烦的沉积物。由于控制该过程副产物结晶的可能性有限，改进工艺流程需要精确测定分离出的不溶性反应副产物的组成，这是本工作的主要目标。本文介绍了三聚氰胺生产工艺过程中采集的沉积物组成的定性和定量分析结果。使用电感耦合等离子体发射光谱法（ICP - OES）和电感耦合等离子体质谱法（ICP - MS）技术对沉积物进行了全面表征。通过对碳、氢和氮的元素分析（EA），我们获得了特征性的C/H、C/N和H/N比值。还进行了X射线衍射（XRD）和衰减全反射傅里叶变换红外（ATR - FTIR）光谱分析以确认所得数据。此外，研究了反应固体副产物的形态，并使用扫描电子显微镜确定了结构特征。使用扫描电子显微镜和能量色散X射线光谱法（SEM - EDS）技术研究了元素组成。本研究的关键发现是，约95%的沉积物是三聚氰二胺和三聚氰二胺水合物的混合物。沉积物的可溶部分包含三聚氰胺、尿素、氧代氨基三嗪以及微量无机杂质。
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