Boosting the Characterization of Heterogeneous Catalysts for H2O2 Direct Synthesis by Infrared Spectroscopy

Abstract

Infrared (IR) spectroscopy is among the most powerful spectroscopic techniques available for the morphological and physico-chemical characterization of catalytic systems, since it provides information on (i) the surface sites at an atomic level, (ii) the nature and structure of the surface or adsorbed species, as well as (iii) the strength of the chemical bonds and (iv) the reaction mechanism. In this review, an overview of the main contributions that have been determined, starting from IR absorption spectroscopy studies of catalytic systems for H2O2 direct synthesis, is given. Which kind of information can be extracted from IR data? IR spectroscopy detects the vibrational transitions induced in a material by interaction with an electromagnetic field in the IR range. To be IR active, a change in the dipole moment of the species must occur, according to well-defined selection rules. The discussion will be focused on the advancing research in the use of probe molecules to identify (and possibly, quantify) specific catalytic sites. The experiments that will be presented and discussed have been carried out mainly in the mid-IR frequency range, between approximately 700 and 4000 cm−1, in which most of the molecular vibrations absorb light. Some challenging possibilities of utilizing IR spectroscopy for future characterization have also been envisaged.

Characterization and in vivo assay of chitosan alginate microencapsulation to deliver the combination of HBcAg and HBsAg as a hepatitis B oral vaccine candidate

“…Chitosan alginate has strong peaks at 3,565-3,400, 1,651-1,643, and 1,072 cm -1 , respectively 23,26 . The FTIR spectrum in the range of 2,170-2,000 cm -1 shows linear CO bonds 27 . The shifting peak from 1,610 to 1,643 cm -1 was due to the overlap between chitosan amide group and carboxyl alginate 23 .…”

“…The band at 3,390-3,340 cm -1 indicates a vibrational strain of hydroxyl group with an increase of band's shape, which overlaps the hydroxyl group of amines in the presence of an intermolecular hydrogen bond in line with previous study 23,26 . Another spectrum at 2,138-2,135 cm -1 acts as a vibrational strain of linear CO 27 . The presence of absorption bands at 1,652-1,643 cm -1 originates from C=O vibration of amide group, whereas the C-O bonds in chemical structures are evidenced by the presence of peaks in fingerprint region at 1,070 cm -1 23,26 .…”

Worthwhile Relevance of Infrared Spectroscopy in Characterization of Samples and Concept of Infrared Spectroscopy-Based Synchrotron Radiation

“…e interferometer consists of a moving mirror which changes the IR light distribution when it passes through the sample [27,28]. e resulting signal called, "interferogram," is recorded directly, signifying the light output as a function of mirror position [29].…”

An Insight into the Role of Reactant Structure Effect in Pd/C Catalysed Aldehyde Hydrogenation

“…Some techniques allow studying the interaction between a molecule and the catalyst surface, as for example FT-IR spectroscopy of probe molecules [ 2 ] that are able to adsorb on specific sites which can subsequently be detected, identified and quantified, based on the intensity and position of the absorption band. Busca et al [ 3 ], for example, studied the adsorption of formaldehyde on different oxides (TiO 2 , ZrO 2 , Al 2 O 3 ) by FT-IR.…”