A Review of BTEM Analysis for Catalytic Studies and a Recent Homogeneous Catalytic Example

Abstract

In situ spectroscopic measurements of homogeneous catalytic reactions have become much more widely used. This is particularly true for FTIR, Raman, and NMR spectroscopic measurements. Although the instrumental and experimental advances have been quite noteworthy, less attention has been focused on the corresponding signal processing and numerical issues. In the present review, pure component spectral reconstruction using FTIR spectroscopy and band-target entropy minimization (BTEM) is emphasized. In a typical BTEM analysis, a set of hundreds or thousands of reaction spectra are acquired from a series of experimental runs and then analyzed together. The resulting set of pure component spectral estimates are obtained without any a priori information such as spectral libraries, and therefore, BTEM analysis is particularly suitable for the analysis of new reactions in exploratory studies. In the present review, the hydroformylation of alkenes using a mixed rhodium-rhenium carbonyl system is given as an example.

Operandomonitoring of mechanisms and deactivation of molecular catalysts

“…A different approach named band-target entropy minimization (BTEM) was developed to face these issues, with implementation in in situ spectroscopic investigations. 98,104,105 BTEM is based on the subsequent reconstruction of pure component spectra by singular value decomposition of the original data set according to eqn (2):…”

“…99 BTEM has the additional advantage of not requiring initial estimates of the number of species present, which helps the elucidation of complex reaction mechanisms. 21,105 Recently, a comparison between MCR-ALS and BTEM was published, where the authors implement the use of these techniques separately and jointly to mass and UV-Vis spectra as well as Raman images. The conclusion reached is that the two methods performed well in all cases, although MCR-ALS performed better for UV-vis spectra and was more robust to noise.…”

“…Section 3) and also the provision of illustrative application examples thereof. 105,134,135 With regard to catalyst deactivation, the group investigated the influence of alkynes 136 and dienes 137 on the unmodified Rh 4 (CO) 12 hydroformylation catalyst. Being more reactive towards the catalyst, these typical alkene feedstock impurities block the catalytic activity for alkene hydroformylation.…”

Hydroformylation

“…For an accurate analysis of single IR bands of a single component in mixtures of compounds, programs for spectra deconvolution are required. High quality algorithms for this purpose were developed by the groups of Garland (BTEM, band-target entropy minimization) [53] and Neymeyr (PCD, pure component spectral recovery) [54].…”

Simultaneous Infrared Spectroscopy, Raman Spectroscopy and Luminescence Sensing: A Multi-Spectroscopic Analyti-cal Platform

“…'Gold standard' methods such as mass spectrometry, X-ray absorption spectroscopic methods (i.e., X-ray absorption near edge structure (XANES) or extended X-ray absorption fine structure (EXAFS)) or magnetic resonance spectroscopic methods (i.e., electron para-magnetic resonance (EPR), and NMR) were applied for studying several types of catalytic and (bio-)chemical reactions in the liquid phase, yet are in part limited by extended measurement times and lack in compactness and robustness for integration. 23,24,34 Especially 2D data correlation methods benefit from the combination of orthogonal techniques. As a relatively young research field introduced by Noda in 1993, homoand heterospectral 2D correlation techniques have evolved into effective and powerful tools for extracting spectroscopic information from complex data sets and minute molecular changes.…”