Spectroscopy based process monitoring

Near-infrared (NIR) spectroscopy has been successfully used to monitor compositional changes during powder mixing of sugar, flour, and cornmeal, by intermittently scanning the mixture with diffuse reflectance spectroscopy. The chemical similarities between the powder components were overcome using multi-variate, multi-component calibration techniques such as partial least squares (PLS) and principal component analysis (PCA) to separate the spectral features of the individual components. PLS calibration models were developed for each component using their characteristic spectral features within the 1100∼2500 nm region especially the combination region between 2100∼2500 nm. The PLS calibration results of each component showed excellent correlation with the reference data. Mathematical procedures based on Fourier-transform, principal component analysis, dissimilarity, and the Gram-Schmidt orthogonalization were developed to monitor the homogeneity of the powder mixture during mixing.; A continuous method was also developed for the continuous conversion of n-butyl-ethanolamine to the corresponding nitramine, n-(2-nitroxyethyl)butylnitramine. Semi-batch and continuous production of n-(2-nitroxyethyl)butylnitramine were performed to investigate the influence of the process parameters such as relative amounts of nitric acid, acetic anhydride, and n-butyl-ethanolamine, and types of drying agents (acetic anhydride vs. sulfuric acid), on the conversion of the amine. Experiments were also performed leading to an understanding of the underlying nitration mechanism.; The data shows that the extent of nitration is dependent on the relative amounts of nitric acid, acetic anhydride, and n-butyl-ethanolamine. The crude reaction yield passes through a maximum with increasing nitric acid, acetic anhydride, and both nitration reaction temperatures. Extent of nitration is also dependent on the temperature of both the first and second nitration reactions, and on whether sulfuric acid and/or acetic anhydride is used as a drying agent. Experimental observations supports the postulate that chloride catalyzed nitration is a self-sustained chain reaction that propagates through the chloronitramine intermediate. Based on the above findings, a detailed double-nitration mechanism is proposed that includes nitration of the chloronitramine intermediate as the main nitration step.; The feasibility of using NIR spectroscopy to monitor composition changes of the reactants and products in the production of n-(2-nitroxyethyl)butylnitramine was investigated. PLS calibration models were developed to monitor compositional changes during nitration.