梅氏譜圖之廻歸分析及其在鐵觸媒成份分析上之應用

Regression Analysis of Mössbauer Spectra and Its Applications in Analysis of Iron Catalysts

李志甫(Jyh-Fu Lee,) ； 李敏達(Min-Dar Lee) ； 鄭伯昆(Poh-Kun Tseng)

《化學》 45卷2期 (1987/06) Pp. 50-57

https://doi.org/10.6623/chem.1987013

摘要

本文首先對於梅氏譜圖建立模式，以利數值的分析，其次介紹一迴歸技術，以迭代法求得非線性模式之最適參數值，爲求易於收斂及結果之合乎物理意義，復考慮各種限制之加入，文末並對計算機系統及執行效率有所探討。迴歸分析之成效提高了梅氏光譜在鑑定樣品成份與定量方面的應用價值，以一氧化碳氫化所用的鐵觸媒爲例，通以330°C之氫氣流進行12小時的還原後，除大部分的金屬鐵外，尙有少許Fe_2O_4存在，而在反應(320℃及140 psig) 80小時後，觸媒成份則包括Fe_3O_4與x-Fe_5C_2，其中Fe_3O_4之含量較反應前爲多，此一發現顯示在催化作用的同時，觸媒本身不但逐漸碳化，亦有被氧化的傾向。

並列摘要

A model for numerical analysis of Mossbauer spectra is first established and then the regression technique is developed for using iteration method to evaluate the optimum parameters in the nonlinear model. In order to attain the point of convergence with ease and obtain the results with physical significance , several constraints can be incorporated in the computer program optionally. Finally, the computer system and its performance are also discussed. The use of regression analys is in the resolution of Mossbauer spectra has greatly increased its applications in qualitative and quantitative analyses. For example. the studies of Mossbauer spectra of iron catalysts for CO hydrogenation show that even the catalyst is reduced in H 2 stream at 330°C for 12 hours , there still exists a small amount of Fe_3O_4 besides the fully reduced metallic iron phase. After being subjected to reaction for 80 hours at 320°C and 140 psig . the catalyst is found to be composed of Fe_3O_4 and χ-Fe_5C_2, in which the amount of Fe_3O_4 is larger than that observed in the fresh reduced state. From these observations , it is confirmed that iron catalyst is oxidized as well as carburized gradually during the CO hydrogenation.