Examinando por Autor "Martos, C."

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Assessment of different methods to determine the total wax content of crude oils
(ACS, 2012-10-05) Robustillo, M.D.; Martos, C.; Espada, J.J.; Coto, B.
Wax formation by temperature decrease is a serious issue in the petroleum industry, since it makes the production difficult and can lead to important economic losses. As a result, a large effort has been made in order to predict the occurrence of this phenomenon as accurately as possible. Thermodynamic models are commonly used to predict the main parameters involved in the wax precipitation process. Models with wide basis require as most common input information the n-paraffin distribution and the total wax content (C20+ fraction). The aim of this work is to check the capabilities of different experimental techniques to determine the C20+ content of different crude oils. For that purpose, High Temperature Gas Chromatography (HTGC) and Differential Scanning Calorimetry (DSC) analyses (direct analysis of the raw crude oil) were used, showing reasonable agreement. Likewise, the wax precipitation of the raw crude oils was performed to obtain the direct C20+ content. Such experiments lead to clearly higher values than those obtained by HTGC and DSC analyses because of the presence of trapped crude oil in the precipitated solid. After that porosity correction carried out by 1H-NMR, DSC and sequential elution chromatography techniques, the obtained results indicate that both 1H-NMR, DSC analyses yield more consistent results. An empirical correlation was developed to determine the C20+ content from the API gravity and the pour point of the selected crude oils. The correlation was applied to a number of crude oils, obtaining a reasonable agreement between experimental and calculated C20+ values, which shows that the validity of that correlation is wider than previous unreliable equations.
Synthesis of Fe304-based catalysts for the high temperature water gas shift reaction
(ELSEVIER, 2009) Martos, C.; Dufour, J.; Ruiz, A.
The water gas shift reaction is an essential process to adjust the CO/H2 ratio in the industrial production of hydrogen. FeCr catalysts have been widely used in this reaction at high temperature but have environmental and safety concerns related to chromium content. In this work the replacement of chromium by molybdenum in magnetite-based catalysts is studied. The materials were prepared by oxidation-precipitation and wet impregnation and they were characterized using X-ray powder diffraction, X-ray fluorescence, transmission electron microscopy and temperature programmed reduction. Specific surface areas of samples were also measured. The results obtained indicate that molybdenum increases thermal stability of the magnetite active phase and prevents metallic iron formation during the reaction. The oxidation-precipitation method allows obtaining the material directly in the active phase and molybdenum is incorporated into magnetite lattice.