Evolved Gas Analysis by Infrared Spectroscopy

Abstract

The analytical applications of the evolved gas analysis (EGA) performed by infrared spectroscopy, for the period extending from 2005 to 2009, are collected in this review. By this technique, the nature of volatile products released by a substance subjected to a controlled temperature program are on-line determined, with the possibility to prove a supposed reaction, either under isothermal or under heating conditions.     

Evolved Gas Analysis by Mass Spectrometry

Abstract

The analytical applications of the evolved gas analyses (EGAs) performed by mass spectrometry for the period extending from 2005 to 2010 are collected in this review. By EGA, the nature of volatile products released by a substance subjected to a controlled temperature program are determined on-line, with the possibility to prove a supposed reaction either under isothermal or under heating conditions.     

Mass spectrometry for evolved gas analysis: An update

Advances in evolved gas analysis (EGA) techniques are periodically reported by our group to provide useful examples of their applications in many different fields. It is actually recognized that anytime is requested a correct interpretation of the thermally induced reaction mechanism, involving the formation of gaseous species, it is strongly recommended the characterization of the evolved products. In this review, recent applications of mass spectrometry for EGA (EGA–MS), selected among those published in 2016 and 2017, are reported to show how the characterization of the nature of volatile products released by a substance subjected to a controlled temperature program allows to prove a supposed reaction, either under isothermal or under heating conditions.     

Mass Spectrometry Coupled to Thermogravimetry (TG-MS) for Evolved Gas Characterization: A Review.

INTRODUCTION

Combining thermal analysis (TA) with gas-analykal techniques significantly enhances the possibilities for correctly interpreting the mechanism of thermally induced reactions, which involve the formation of gaseous species. Several techniques can be used for evolved gas analysis (EGA), ranging from simple, non-specific detection to the more elaborate multidimensional/multifunctional methods, such as gas chromatography (GC), infrared spectroscopy (IR) or mass spectrometry (MS), for gas detection and analysis [1]. While the GC methods were used as early as the 1960s [2], EGA by FTIR was described much later and was used for the analysis of pyrolytic and combustion products. Presently, there are several commercial FTIR systems available that can be coupled to a thermogravimetric analyzer (TGA), and a broad range of applications have been investigated by this important hyphenated technique [3].     

FTIR-evolved gas analysis in recent thermoanalytical investigations

Several analytical instruments (like pyrolyzers, thermobalances, differential thermal analyzers, or calorimeters, and sometimes simply temperature-controlled reactors) can be on-line coupled to infrared spectrometers to perform evolved gas analysis (EGA). Advances in EGA techniques are currently proposed by the scientific literature because the possibility to on-line detect the nature of the released gases or vapors has become fundamental to proving a supposed reaction, either under isothermal or under heating conditions. In this review, recent analytical applications of evolved gas analysis performed by infrared spectroscopy (EGA-IR), selected among those published in the years 2013 to 2015, are collected.     

Fourier Transform Infrared Evolved Gas Analysis (FT-IR-EGA)

Abstract

Since their commercial introduction, Fourier transform infrared spectrophotometers have enabled a variety of new infrared applications not possible or practical with other spectrophotometers. One such application—evolved gas analysis (EGA)—has received relatively little attention although its potential is quite significant. Within this text, a discussion of the background of Fourier transform infrared evolved gas analysis (FT-IR-EGA), the experimental considerations of this technique, and some application areas for this technique will be presented. Because of the small number of references on this technique and its use, the predominant portion of the latter two topics will be based upon activities within our laboratory at Philip Morris.     

Raman Spectrum of the Fluorination Products of RbC1

Abstract

Compounds with high fluorinating capacity are obtained when rubidium and cesium chlorides are fluorinated in a stream of elemental fluorine. Best results are obtained when the, temperature is kept in the range of 140–170°C. These products were first assumed to be polyfluorides, MF₃, of Rb and Cs ¹. It was later assumed by various researchers ² that the products are really tetrafluorohalates of Rb and Cs, formulated as MC1F₄. One of the authors was himself involved in the problem of trying to establish the structure of these products. It is, however, a very difficult problem since pure products giving constant analytical results were not obtained. During the fluorination process, which is an exothermic one, enough heat is evolved to melt the reaction medium and the temperature rises above that needed to decompose the products. It is therefore impossible to obtain reliable analytical data, the products being a mixture of regular fluorides, MF, and the active, fluorinating, ones. No final proof has therefore been found for the C1F^? ₄ structure.     

IR Study of the Pressure Induced Solid State DI- and Polymerization in 1,3-butadiene

The pressure induced chemical reaction of butadiene was studied in the crystal phase by means of FTIR spectroscopy using a Membrane Diamond Anvil Cell (DAC). Two different reaction products, vinylcyclohexene (dimerization) and trans-polybutadiene (polymerization), were obtained. The phase diagram of butadiene was investigated and the existence of an orientationally disordered phase, between the liquid and the ordered solid phase, was identified. The analysis of the time evolution of the integrated absorption of the product bands provides information on the reaction mechanisms. Distinct models are necessary to explain the polymer and the dimer formation.     

Wastes Treatment: Hydrothermal electrolytic oxidation of wastewater

Abstract

Electrochemical evolution of hydrogen gas, oxygen gas and chlorine at the electrodes is the usual reaction in conventional electrolysis of aqueous salt solution. However, here we demonstrate that the electrolysis governing reaction in hydrothermal solutions is different from the electrolysis performed at atmospheric pressure and temperatures up to 100°C. Experimental electrolytic reaction of aqueous salt solution carried out inside a sealed 300-mL batch autoclave showed that; accumulation of hydrogen gas, oxygen gas and chlorine is highly suppressed under hydrothermal (250°C and 7 MPa) conditions. We have also observed that, when organics are present in the aqueous salt solution being hydrothermally electrolyzed, an effective oxidation of organics is accomplished. Furthermore, for hydrothermal electrolytic oxidation (HEO) with oxygen gas added, experimentally observed TOC removal profile demonstrates apparent anodic oxidation electrical current efficiency of almost 200% for highconcentrated acetic acid solutions.     

A novel determination of activation quantities and reaction order(s) for the hydrothermal destruction and its applications

Abstract

A novel determination method of activation quantities and reaction order(s) of hydro-thermal reactions was developed in order to achieve economically, easily and speedily research and development of new hydrothermal plants. This method is called the NIT method (abbreviation of ‘Nonisothemal method’) in the case of a batch reactor and the F-NIT method (abbreviation of ‘nonisothermal method for flow reactor’) in the case of a plugged flow reactor. The main merit of the NIT method (or the F-NIT method) is to give access to the determination of activation quantities and/or reaction orders by measuring the changes in amount of chemical species under nonisothermal conditions.

After summary of the recently published NIT method, the newly F-NIT method is described briefly. Then the two types of hydrothermal fluids (hydrothermal steam and supercritical/subcritical water) are applied to the destruction of phenol under nonisothermal conditions. The activation quantities can be obtained at once by use of these methods and are compared with the reported values in the scWO.     

The Possible Contribution of Isotope Effects on Ester- and Aldol Condensations to Isotope Discriminations and Isotopic Patterns of Natural Compounds

Abstract

Acetyl-CoA provides the C-2-units for the formation of many secondary compounds. The primary pattern of this intermediate is originating from glucose, further modifications are introduced by isotope effects on the pyruvate-dehydrogenase-reaction and on ester- and aldol-reactions in the course of the biosynthesis of secondary products. The overlap of these various effects is demonstrated through the pattern of some natural products.

The partial pattern of limonene and pulegone, respectively, products from different origin are not identical, this is interpreted as a consequence of individual relative contributions of the above mentioned effects in the plants in question.

On the other hand the distinct relative depletion in a position of sinigrin, a glucosinolate from Brassica nigra, originating from CH₃ of acetate can be assigned to an isotope effect of the aldol reaction between a precursor and acetyl-CoA. An corresponding depletion has been measured in position 5 of citrate. Therefore the kinetic isotope effect on the citrate synthase reaction is studied in vitro at present.     

A Ketene Intermediate in 3-Cyclopentenone Photolysis : Matrix-Isolation and Gas Phase Experiments

Abstract

Photolysis experiments are performed at λ  230 nm on argon matrix-isolated and on gas phase 3-cyclopentenone ( 1 ); in both cases, a ketene intermediate (KE) is detected (FT-IR spectra : 2121–2126 cm^?1 in argon matrix; 2066–2210 cm^?1 in gas phase). 1,3-butadiene ( 2 ) and carbon monoxide are the reaction products. Two first-order consecutive photochemical processes occur 1 ^k1 > KE ^k2 > 2 + CO with k₁ = 1.7 10–2 s^?1 and k₂ = 2.4 10–2 s^?1.     

The Interpretation of Infrared Spectra: Published Reference Sources

INTRODUCTION

Historically, infrared spectroscopy made its debut as an analytical tool during World War II. At that time it was used for quality control by several major chemical manufacturing companies. The instrumentation, which was essentially home-made, was adapted for the quantitative measurements of components in polymeric and petroleum products. In the 1950s, with the introduction of gas chromatographic instrumentation, infrared spectroscopy gradually fell out of favor as a quantitative tool. As a result, the emphasis switched to qualitative analysis. This was a natural role for infrared spectroscopy because of the significant amount of unique structural and chemical/physical information that is intrinsically available from the spectrum. The resultant increase in the use of infrared spectroscopy, as a qualitative tool, was aided by the influx of new, commercial instrumentation introduced during the 1950s - including lower priced, easy to use instruments for routine analysis. Much of the published work for the next two decades focused on the identification and characterization of materials and the development of correlations between the measured spectrum and molecular structure and chemical functionality.     

Modeling extinction in forced opposed-flow smolder

We address a discrepancy between smolder extinction theory and experimental work regarding whether extinction can occur under oxygen-depleted conditions. Single heterogeneous (solid/gas) reaction models that model the complex reaction process of smoldering with a single reaction predict extinction for large head winds only when oxygen remains (fuel-limited smolder). Experimental evidence, however, shows that oxygen concentrations are essentially zero for smolder waves close to the extinction limit. We consider a two-step sequential reaction scheme in which the solid fuel is converted to char, which also reacts with oxygen to produce ash. This generic scheme leads to extinction with oxygen depletion. The model suggests that oxygen depletion is caused by the second reaction while extinction is driven by the first. Solid fuel must be completely converted to char for extinction to occur while oxygen consumption in the secondary reaction induces oxygen depletion. Spatial separation of the localized reactions is predicted to increase with head wind as a precursor to extinction.     

Determination of Heavy Metal Accumulation in Plant Samples by Spectrometric Techniques in Turkey

Abstract:

Heavy metals are significant and extremely persistent environmental pollutants and their toxicity is a problem of increasing significance for ecological, nutritional, and environmental reasons. Biomonitoring methods are gaining more importance because they allow for prediction, detection, and control of potential environmental hazards caused by heavy metal pollution. The objective of the present study was to collect and analyze research on heavy metal accumulation in plant samples using spectrometric detection techniques in Turkey published between 2003 and 2013. Five main criteria were predetermined to limit the study and better portray the studies on heavy metal accumulation using plant samples in Turkey. These criteria were as follows: studies aiming to determine heavy metal accumulation levels, studies sampling plant species growing at various localities in Turkey, studies using spectrometric detection techniques, studies published as journal articles, and studies undertaken between 2003 and 2013. Consequently, 47 studies that satisfied all criteria were considered and selected for this investigation. A content analysis method was used for the review and analysis of the selected studies. The results of the review analysis were grouped under three categories and the findings obtained in this scope were presented.     

Harmonic and Intermodulation Performance of Fabry-Perot Intensity Modulator

Abstract

In this article, a mathematical model for the transfer function of the Fabry-Perot intensity modulator is presented. The model, basically a cosine-series function, can be used to obtain closed-form expressions for the amplitudes of the harmonic and intermodulation products of the Fabry-Perot intensity modulator driven by a multi-frequency radio frequency voltage. The special case of a Fabry-Perot intensity modulator driven by an equal-amplitude two-frequency radio frequency voltage is considered in detail, and the results are compared, whenever possible, with previously published experimental and numerically obtained results.     

Ion bombardment induced amorphous layers on single crystal stainless steel-a combined rutherford backscattering and transmission electron microscopy study

Abstract

Decomposition reactions of NaClO₃, KClO₃, and KIO₄ induced by 3 keV Ar⁺ ions and 1254 eV X-rays are investigated by X-ray photoelectron spectroscopy (XPS). The reactions lead to the formation of binary halides with preferential losses of oxygen. The decomposition pattern, monitored at the various stages of reaction, indicates almost direct changeover to the final products with only a few intermediate species formed. Product abundancies are compared for the ion, X-ray, and electron induced reactions and discussed in relation to the various radiation induced reaction mechanisms.     

Pressure dependence of the reversible hydrolysis of thiazolium salts

Abstract

The hydrolysis of thiazolium salts is studied under varying pressures between 0.1 and 85 MPa. Activation and reaction volumes are obtained for different reaction steps. The results confirm the reaction scheme, where the thiazolium cation forms a pseudobase by addition of an hydroxide ion. The pseudobase can be protonated or can form a ring-opened species, which can further be deprotonated.     

Recent Progress in Chemiluminescence for Gas Analysis

Abstract

Chemiluminescence is frequently used as a powerful analytical tool for gas analysis. In this mini-review with 102 references, we summarize the recent advances in chemiluminescence-based analytical methodologies and their application in gas/volatile species analysis, mainly including applications of ozone-induced chemiluminescence, cataluminescence-based gas sensors and arrays, and dielectric barrier discharge–induced chemiluminescence for gas analysis. Efforts in the innovation of the methodologies, the exploration of new sensing materials, and the mechanism studies are discussed in detail.     

Platinized Magnesium as Reducing Agent for Hydrogen Isotope Analysis

Abstract

Platinized magnesium has recently been proposed as a new reducing agent for the conversion of small quantities of water to hydrogen in a flame-sealed borosilicate glass tube at 400°C for isotopic analysis. The reagent, Mg-Pt, in contrast to zinc can be prepared in every laboratory by coating a magnesium granulate with a thin layer of platinum by reaction with H₂PtCl₆·6H₂O dissolved in acetone-ether mixture. Excellent reproducibility of the isotope ratios in hydrogen gas prepared from water samples has been obtained using 4 μl of water and 120 mg of the reagent.