摘要
实验室制备氨基甲酸铵时易出现原料气体混合比例失衡,以及原料气体流量大小与干燥程度未知、不受控等问题,导致氨基甲酸铵制备实验效率较低。该文基于可视化与可操作性原则,设计了制备氨基甲酸铵固体的实验装置与实验方法。基于傅里叶变换红外光谱(FTIR)和X射线衍射(XRD)表征,确认了改进方法可制备氨基甲酸铵,场发射扫描电镜(SEM)成像结果表明用改进方法制备的氨基甲酸铵具有相对较优的分散度。用改进方法制备的氨基甲酸铵固体分解速率快于商品化氨基甲酸铵,且平衡分解反应的化学热力学函数与文献报道值相近,相对误差±5.5%以内。改进方法具有可靠的一致性,实验条件下氨基甲酸铵制备反应的平均产率为2.12 g/min,产率变异系数为2.83%。该改进实验方法实现了固体氨基甲酸铵的高效、快速制备,提高了实验教学效果。
[Objective]The decomposition of solid ammonium carbamate(AC)serves as a pivotal case study for the kinetic and thermodynamic analyses of multiphase chemical reactions.Traditional methods for synthesizing AC in the laboratory face significant challenges,including①difficulty maintaining precise control over the mixing ratio and flow rate of raw gases due to airflow fluctuations and②complexity associated with quantitatively assessing the dryness of feed gases.This research employs a visual operational technique to regulate the mixture ratio and moisture level of feed gases,thereby ensuring the precise and effective synthesis of AC in the laboratory.[Methods]A specialized experimental apparatus and methodology for synthesizing AC were developed.This technique employed check valves extensively to ensure the unidirectional flow of feed gases through the pipelines,thereby preventing clogs caused by the formation of solid products from gas intermixing.A metering pump dynamically adjusted the ammonia solution feed rate to precisely control NH_(3)(gas)production while maintaining a constant CO_(2)(gas)flow rate,thereby preventing fluctuations in the mixing ratio and flow rates of NH_(3) and CO_(2) gases.The gas flowmeters and humidity meters monitored the flow rates and moisture levels of CO_(2) and NH_(3) gases,respectively,thereby finely controlling experimental processes for preparing solid AC.Solid AC synthesized via the improved experiment(H-AC)and commercial AC(C-AC)were characterized using Fourier transform infrared(FTIR)spectroscopy,X-ray diffraction(XRD),and scanning electron microscopy(SEM).To evaluate the performance of the improved experimental method,the decomposition pressures and equilibrium decomposition pressures of H-AC and C-AC were experimentally determined,and the chemical thermodynamic functions of the equilibrium decomposition reaction were calculated.The stability and consistency of the improved method were also investigated via repeated experiments and a comparative analysis with the traditional method.[Results]The improved method for preparing AC successfully eliminated airflow fluctuations in the feed gases.Real-time rendering clearly displayed the flow rates and moisture levels of CO_(2)(gas)and NH_(3)(gas),facilitating precise and controllable mixing reactions to synthesize solid AC.FTIR characterization confirmed the consistency of the vibrational peak positions,intensities,and shapes in the FTIR spectra of H-AC and Treated C-AC(C-AC ground into powder)with previously reported data,verifying the formation of AC along with XRD results.SEM analyses revealed that H-AC exhibited better dispersion than Treated C-AC.The experimental results indicated that the order of decomposition pressure was H-AC>Treated C-AC>C-AC at 25℃,clearly demonstrating that the decomposition rate of solid AC correlated with the morphological distribution of samples.The equilibrium decomposition pressures of H-AC at temperatures of 20,25,30,35,40,45,and 50℃closely matched the reported values,with the chemical thermodynamic functions of the equilibrium decomposition reaction also aligning.Most relative errors were within±3%,except for one case,whose error was approximately-5.5%compared to a literature value.Notably,the relative error obtained in comparison with theoretical values was-3.7%.It was confirmed that the improved method demonstrated reasonable consistency,with an average production rate and coefficient of variation of 2.12 g/min and 2.83%,respectively.At the same time,shortening the storage time could improve the decomposition rate of solid AC.[Conclusions]From the perspective of experimental technology,a laboratory apparatus for the preparation of solid AC was developed.Concurrently,the corresponding experimental methodology was established.This advancement addresses limitations inherent in traditional laboratory preparation methods,facilitating the efficient and rapid production of solid AC.Additionally,it provides technical support and theoretical guidance for experimental teaching and significantly improves the effectiveness of experimental teaching.
作者
储诚普
王红
梁秋霞
强根荣
CHU Chengpu;WANG Hong;LIANG Qiuxia;QIANG Genrong(National Demonstration Center for Experimental Chemistry and Chemical Engineering Education,Zhejiang University of Technology,Hangzhou 310014,China)
出处
《实验技术与管理》
北大核心
2025年第5期161-168,共8页
Experimental Technology and Management
基金
2024年教育部实验教学和教学实验室建设研究项目(SYJX2024-068)。
关键词
氨基甲酸铵
制备方法
分解压
化学热力学
实验技术
ammonium carbamate
preparation method
decompression pressure
chemical thermodynamics
experimental technology
