Infrared spectroscopy oxidation monitoring

Although acetone was a major product, it was not observed by infrared spectroscopy. Flowing helium/acetone over the catalyst at room temperature gave a prominent carbonyl band at 1723 cm 1 (not show here). In this study, a DRIFTS (diffuse reflectance infrared Fourier transform spectroscopy) cell was placed in front of a fixed reactor DRIFTS only monitored the adsorbed and gaseous species in the front end of the catalyst bed. The absence of acetone s carbonyl IR band in Figure 3 and its presence in the reactor effluent suggest the following possibilities (i) acetone formation from partial oxidation is slower than epoxidation to form PO and/or (ii) acetone is produced from a secondary reaction of PO. 

In reviews on formic acid decomposition, Mars and coworkers194,198 wrote that the formation and decomposition of formate anions were monitored by infrared spectroscopy. These studies were carried out by Fahrenfort, Sachtler, and coworkers188,193 for the case of formates on metals produced by formic acid adsorption—Cu, Ni, Pd, Rh, Pt, and Zn and in the case of metal oxides, Hirota et al. investigated ZnO,187,189,190,197 while Scholten et al. studied MgO.199,200 The infrared... 

The oxidation was studied in an 11-mm diameter Pyrex flow tube at temperatures of 200-600°C by Heicklen and Knight.77 The cold, 02-C2F4 mixtures (10-200 torr total pressure) flowed through the 60-cm long hot zone, and the products were monitored by infrared spectroscopy at the... 

IR monitoring of oxidation process. Monitoring lubricants by infrared spectroscopy is a well established technique. The infrared spectra of oxidized (used) engine oil samples can be split into three parts (a) above 1900 cm 1, (b) 1900 to 1500 cm 1, and (c) below 1500 cm"1. The spectral changes in the region between 1900 to 1500 cm 1 in commercial automotive oils (SAE 10W/40, API service SE) operated in a Toyota 20R engine over a 8000 km period were evaluated (Coates and Setti, 1984). Major absorptions bands (1900 to 1500 cm 1) of the spectra are [cm 1] 1732 (oxidation, carbonyl esters), 1710 (oxidation, carbonyl ketones/acids), 1629 (nitrate esters), 1605 (carboxylates) of used oils. 

Dealuminated M-Y zeolites (Si/Al = 4.22 M NH4, Li, Na, K, Cs) were prepared using the dealumination method developed by Skeels and Breck and the conventional ion exchange technique. These materials were characterised by infrared spectroscopy (IR) with and without pyridine adsorption, temperature-programmed desorption (t.p.d.) of ammonia. X-ray difiracto-metry (XRD) and differential thermoanalysis (DTA). They were used for encapsulation of Mo(CO)5. Subsequent decarbonylation and ammonia decomposition was monitored by mass spectrometry (MS) as a function of temperature. The oxidation numbers of entrapped molybdenum as well as the ability for ammonia decomposition were correlated to the overall acidity of the materials. It was found that the oxidation number decreased with the overall acidity (density and/or strength of Bronsted and Lewis acidity). Reduced acidity facilitated ammonia decomposition. 

Fourier-transform infrared spectroscopy (FTIR) and pH measurements are the techniques most often adapted for in-line IPC. pH measurements are used for reactions that are run in water or have an aqueous component, e.g., an aqueous extraction. FTIR is especially good for monitoring continuous reactions [12] and reactions that would be dramatically changed by exposure to the atmosphere and temperature of the laboratory. Suitable reactions include low-temperature reactions, reactions run under pressure, reactions with gaseous or toxic materials (e.g., ethylene oxide), and reactions run under inert atmosphere. Further advantages of in-line assays are that no samples need to be prepared, and assay results can be generated within minutes. 

Infrared spectroscopy is used for the analysis of almost all the fractions and products of crude oil. However, in the last century, a very interesting purpose of the infrared spectroscopy has been developed. It is the dynamic monitoring of the changes in the structure of lubricating oils as it undergoes degradation. Many processes such as oxidation or polycondensation in oils can be studied by infrared spectroscopy. 

These oxidation reactions are readily monitored by following isocyanide stretching vibrations by infrared spectroscopy. The energy of this vibration increases by about 40 cm for oxidation of Rh(I) to Rh(II). For comparison, the oxidation of mononuclear Rh(I) complexes to Rh(III) species results in an 80cm increase in the energy of the isocyanide stretching vibration. 

Both chemical and physical processes take place during calcination and activation. Ligand decomposition from the metal complex can be monitored with in situ vibrational spectroscopy, for example, using diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS). In the case of a transition metal ion, the metal oxidation state can be tracked as a function of time and temperature using in situ UV-vis spectroscopy. Finally, the formation of metal clusters and nanoparticles can be monitored using XRD, similar to that described for the synthesis of silicalite-1. 

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