Tiziana Zerlia

Fourier transform-infrared study of the adsorption of unsaturated and aromatic hydrocarbons on the surface of α-Fe2O3. Part III. Toluene, ethylbenzene and styrene

IR spectra of toluene, ethylbenzene and styrene adsorbed on pressed discs of hematite between room temperature and 400°C are described. Mechanisms of adsorption and transformation are discussed and compared with those reported on the basis of kinetic measurements of ethylbenzene dehydrogenation on iron oxide catalysts.AbstractПриводятся ИК спектры толуола, этилбензола и стирола, адсорбированных на прессованных дисках гематита в интервале от комнатной температуры до 400 °C. Механизм адсорбции и превращений обсуждается и сравнивается с механизмом, сообщенным, исходя из кинетических измерений дегидрирования этилбензола на катализаторе окиси железа.

Depth Profile Study of Large-Sized Coal Samples by Fourier Transform Infrared Photoacoustic Spectroscopy

A multidisciplinary approach is demonstrated to elucidate coal weathering at a molecular level. Fourier Transform Infrared Photoacoustic Spectroscopy (FT-IR/PAS) provides a technique for a compositional depth profile of coal by simply varying the modulation frequency (mirror velocity) of the light impinging upon the solid surface. In order that the potential of this technique in this field could be evaluated, large-sized coal samples were examined. The PA difference spectra obtained from the spectra taken at different modulation frequencies (i.e., different depths), on a sample aged in air, demonstrate the appearance of negative features in the CH infrared absorption which are indicative of a coal alteration. Therefore, different coal layers can be distinguished by FT-IR/PAS. The application of the same technique to the study of a coal sample heated in air at 200°C allows the detection of different oxidation mechanisms operating inside and outside the coal. Although quantitative results are difficult to obtain, the technique can be successfully proposed for a qualitative description of coal weathering.

Fourier transform-infrared study of the adsorption of unsaturated and aromatic hydrocarbons on the surface of α-Fe2O3: I. Ethylene

Benzene adsorption on α-Fe2O3 in the temperature range 300–673 K has been studied. Two different molecular adsorbed forms can be distinguished due to their spectroscopic behavior and the different equilibrium pressures needed for their formation. The more stable form, in which the benzene molecule is π-bonded on exposed metal cations, slowly transforms at room temperature into combustion products. This process is inhibited by the presence on the surface of the second form of adsorbed benzene.

Asphaltenes determination in heavy petroleum products by partial least squares analysis of u.v. data

Abstract The u.v. parameters obtained from the u.v. spectra of several petroleum samples (including crude oils, commercial fuel oils, straight run and visbreaking residues) have been used for the determination of asphaltenes content. Partial least squares (PLS) in latent variables has been used to correlate the u.v. parameters to the IP-143 asphaltenes content. A set of samples (homogeneous on the basis of their u.v. parameters), including the greater part of the commercial fuel oils and visbreaking residues, has been singled out by PLS analysis. For petroleum products belonging to this class, the asphaltenes content can be derived with a maximum error comparable to the precision of the IP-143 precipitation method.

Fourier transform infrared photoacoustic spectroscopy of raw coal

Abstract Photoacoustic Fourier transform infrared (PA-FT-i.r.) spectrometry was employed to examine raw coal containing 13–64 wt%, daf volatile matter (VM). Sample preparation for i.r. examination was the same as for ASTM proximate analysis. Technological and spectroscopic information on representative samples were obtained. PA scan time is longer than for conventional FT-i.r. operation; however sample preparation is faster and easier. The time-consuming KBr pellet technique, possibly affecting coal structure, is avoided. The i.r. absorption in the OH, NH, CH ar and CH x ,al regions may allow the determination of VM for both high- and low-rank coal. Some differences between present PA and diffuse reflectance spectra of raw coal from the literature are discussed.

Stability-related tests on visbreaking residues obtained at increasing severity

Abstract Xylene-equivalent (XE) and sediment by hot filtration (‘Sediment’) are often used to characterize instability of petroleum thermal residues. Nine visbreaking (VB) residues obtained at increasing severity from the same feedstock were studied to explain the significance of these characteristics in the light of the chemical changes induced by the VB process. The results indicate two different severity-related relations between XE (and Sediment) and chemical composition, at low and high severity: under mild process conditions the instability (XE) increases as the asphaltene content decreases, whereas the opposite trend is found at high severity. These opposing trends can be explained in the light of the VB chemistry and shed light on the different mechanisms governing the peptization state of asphaltenes under mild and severe process conditions. Sediment, constant at low severity, starts to increase only when condensation reactions involving asphaltenes occur. Thus Sediment, which unlike XE cannot be adjusted with a suitable diluent fuel, plays a key role in evaluation of the stability of thermal residues: high Sediment, in the absence of inorganic or coke-like material, would be concomitant with storage problems, whatever the XE level.

A new approach to determination of saturates in heavy petroleum products

Abstract The method of partial least-squares modelling in latent variables is used to relate the u.v. spectral parameters to the saturates content of heavy petroleum products without the need for prior deasphalting or chromatography. Statistical evaluation and results are presented for reference aromatic mixtures, artificial samples and actual petroleum fractions.

Fourier Transform Infrared Spectrometer Coupled with Electrothermal Atomizer for High-Temperature Vapor-Phase Investigations

An electrothermal atomizer is employed to vaporize solid samples of pigments at temperatures ranging from 150°C to 1000°C The evolution of vapors is followed by Fourier transform infrared spectrometry (FT-IR) The atomizer acts at the same time as vapor supplier and vapor holder This coupling allows the investigation in situ of vaporization or pyrolysis phenomena avoiding the use of heated transfer pipes The pigments examined in this study show various vapor-phase behaviors Some pigments vaporize without appreciable decomposition at temperatures from 400°C to 950°C, while other pigments investigated decompose during the heating and originate pyrolysis products whose evolution is monitored continuously by the FT-IR spectrometer

FT-IR/PAS investigation of solid fuels and catalysts

Coal and catalysts are examples of substances of great technical importance, whose knowledge has advanced for many years empirically. They are considered as disordered and complex materials. FT-IR/PAS suggests models closer to the real systems as the samples can be examined “as they are”: coal with the same sampling procedure as for ASTM analysis and catalysts “during catalysis” without manipulation. Some examples are reported.