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Featured researches published by T. Verdejo.


Journal of Analytical and Applied Pyrolysis | 1994

Pyrolysis derivatization of humic substances 1. Pyrolysis of fulvic acids in the presence of tetramethylammonium hydroxide

Fernandez Martin; F.J. González-Vila; J.C. del Río; T. Verdejo

Abstract Humic Acids (HAs) extracted from soils of very different origin have been analyzed by pyrolysis in the presence of tetramethylammonium hydroxide. The thermal degradation products consisted mainly of aliphatic series such as fatty acids methyl esters and α,ω-methoxy fatty acid methyl esters. Triterpenoid compounds with ursane, oleanane and hopane skeletons were also detected in several samples. Aromatic units derived from lignin moieties were also detected although in minor amounts and corresponded mainly to guaiacyl and syringyl units. This procedure seems to release the more labile, aliphatic moieties attached to the aromatic nuclei of the HA structure.


Journal of Analytical and Applied Pyrolysis | 1995

Thermally assisted hydrolysis and alkylation of lignins in the presence of tetra-alkylammonium hydroxides

Fernandez Martin; J.C. del Río; F.J. González-Vila; T. Verdejo

Three different milled lignins isolated from bamboo, pine and beech, corresponding to the three different structural groups, have been subjected to pyrolysis in the presence of tetramethylammonium hydroxide (TMAH) and tetrabutylammonium hydroxide (TBAH). Pyrolysis of the lignins in the presence of TMAH releases the methyl esters and methyl ethers of the different lignin monomers. Several moieties bearing carboxylic acid groups, not previously detected using pyrolytic techniques, could be released from the three lignins, suggesting that the presence of these moieties in the lignin structure have been underestimated.


Organic Geochemistry | 1994

Characterization of humic acids from low-rank coals by 13C-NMR and pyrolysis-methylation. Formation of benzenecarboxylic acid moieties during the coalification process

J.C. del Río; F.J. González-Vila; Fernandez Martin; T. Verdejo

Abstraet--Humic acid (HA) fractions isolated from a peat and lignite deposit were studied by CP/MAS ~3C-NMR and pyrolysis-methylation. Loss of carbohydrates, removal of methoxyls and formation of catechols during the coalification process was evident. Pyrolysis-methylation released a great variety of components, the lignin-derived monomers being the most prominent. A very striking feature was the release of benzenecarboxylic moieties after pyrolysis-methylation which have not been observed previously by pyrolytic techniques. These moieties were released in higher amounts from the lignite HA, suggesting that the content in carboxylic groups increase with coalification, at least up to the lignite stage. Oxidation of the C-3 side chain of the lignin structure would produce these benzenecarboxylic acids and benzylic ketones.


Journal of Chromatography A | 1996

Pyrolytic alkylation-gas chromatography-mass spectrometry of model polymers Further insights into the mechanism and scope of the technique

F.J. González-Vila; J.C. del Río; Fernandez Martin; T. Verdejo

The mechanism of the high-temperature hydrolysis and alkylation with tetraalkylammonium hydroxides of bio- and geopolymers has been approached mainly by studying the behaviour of single standard compounds. In the present work, we have applied this technique to three polymers of known structure, i.e. suberin, polycitraconic acid (PCA) and a lignin dehydrogenase polymer (DHP), related respectively to natural polyesters, fulvic acids and lignins, in order to get new insight into the reaction mechanism. As further application of the technique, the case study of the lignin signature during the coalification process has been analyzed by pyrolysis-butylation of humic acids extracted from two peat and lignite samples.


Organic Geochemistry | 1995

Chemical structural investigation of asphaltenes and kerogens by pyrolysis-methylation

J.C. del Río; Fernandez Martin; F.J. González-Vila; T. Verdejo

Molecular characterization of kerogen and asphaltene fractions isolated from three oil shales taken from the Puertollano deposit has been carried out by pyrolysis-methylation. Long-chain n-alkanes, n-alk-l-enes, long-chain carboxylic acid methyl esters and aromatic compounds were the major thermal degradation products obtained for both kerogen and asphaltene fractions. Different monomeric and dimeric lignin-derived compounds were also released. The use of pyrolysis-methylation provides additional information about the chemical structural composition of the macromolecular organic matter comprising kerogens and asphaltenes at a molecular level, to that gained from conventional pyrolysis. The chemical structures of the released products indicate that considerable amounts of functionalized compounds are bound to the macromolecular structure of asphaltenes and kerogens via ester and ether linkages.


Journal of Analytical and Applied Pyrolysis | 2001

Experimental reappraisal of flash pyrolysis and low-temperature thermally assisted hydrolysis and methylation using tetramethylammonium hydroxide for the molecular characterization of humic acids

Fernandez Martin; G. Almendros; F.J. González-Vila; T. Verdejo

Abstract In this study, thermal degradation products of humic acids (HAs) from widely different origins and compositions obtained by either on-line flash pyrolysis at 500°C or off-line, low-temperature (270°C) thermally assisted hydrolysis and methylation (THM) using tetramethylammonium hydroxyde (TMAH) have been compared. Both methods yielded phenols, methoxyphenols, benzenecarboxylic acids, alkanoic acids and hydrocarbons, but their relative amounts differed among the samples and for each sample depending on the degradation method. In relative quantitative terms, and when compared with the results obtained by 13 C NMR, it was observed that the use of TMAH led to an ‘aliphatic enhancement’, the extent inversely depending of temperature. Our results indicate that thermal degradations based on reactions at 500 and 270°C should be considered as distinct techniques, providing independent structural information in the analysis of HAs. It is suggested that transesterification and base-catalysed hydrolysis reactions occurring at a sub-pyrolysis temperature could be a successful method of mild, low-temperature alkaline degradation, but it is not sufficient for obtaining stoichiometrically representative information on the molecular assemblages of the HA structure.


Chemosphere | 1995

Accumulation of hydrophobic compounds in the soil lipidic and humic fractions as result of a long term land treatment with olive oil mill effluents (alpechin)

F.J. González-Vila; T. Verdejo; J.C. del Río; Fernandez Martin

Land treatment with high loading rates of olive oil mill effluents (alpechin) results in the quantitative increase of the lipidic fraction of the soil upper layer and in significative alterations in the lipid compositions of both the soil upper layer and the subsoil. GC-MS analysis of the lipidic fractions before and after the treatments showed the preferential accumulation of some hydrophobic components of the wastewater. These compounds were also retained by the humic acid (HA) fractions as seen by Pyrolysis-GC-MS.


Journal of Analytical and Applied Pyrolysis | 1997

Application of analytical pyrolysis to the characterization of Eucalyptus extractives and pitch deposits from a pulp mill

F.J. González-Vila; Ana Gutiérrez; Fernandez Martin; T. Verdejo

Abstract It has been demonstrated that both conventional flash pyrolysis and thermally assisted hydrolysis and alkylation (THA) in the presence of tetramethylammonium hydroxide (TMAH), enable the detection of some important components of wood extractives (WE) from Eucalyptus globulus. These are released by thermoevaporation from the acetone extracts and easily identified by GC-MS. On the other hand, Py-GC-MS with and without TMAH has proven to be a very useful technique for a rapid characterization of pitch deposits both from the machine area and from TCF end-pulp from E. globulus. In spite of the low ratio analyte/matrix in the second case, the pyrograms from the pitch-enriched pulp samples showed a satisfactory reproducibility, and some significative pyrolysis compounds arising exclusively from the pitch deposit were also evident, although their specific origin could not be unambiguously determined.


International Journal of Environmental Analytical Chemistry | 1992

Characterization of wastes from olive and sugarbeet processing industries and effects of their application upon the organic fraction of agricultural soils

F.J. González-Vila; T. Verdejo; Fernandez Martin

The lipidic fraction compositions of both concentrated vinasses, a by-product of the sugar industry, and a compost made basically from olive oil vegetation waters (alpechin) were studied. The alpechin lipids are composed mainly by series of n-alkanes and lineal and branched fatty acids, whereas the major lipids in vinasses were n-alkanes, n-alkanols and acetals. Concentrations and composition of lipids in both materials do not seem of concern (...)


Journal of Chromatography A | 1992

Extraction of bituminous material from fossil organic matter using liquid carbon dioxide under liquid-vapour equilibrium conditions

Fernandez Martin; T. Verdejo; F.J. González-Vila

Abstract Extracts from a peat, a low-rank coal and a bituminous oil shale obtained with liquid carbon dioxide were studied by capillary gas chromatography-mass spectrometry and compared with those obtained by Soxhlet extraction with n -hexane. Although the extraction yields with liquid carbon dioxide were lower, the composition of the extracts, comprising mainly a large variety of linear and cyclic hydrocarbons, was similar in both cases. Owing to the advantages of the liquid carbon dioxide extraction regarding speed, cleanliness and mildness of the extraction conditions, it seems to be an adequate procedure, coupled with gas chromatography-mass spectrometry, to study the biomaker composition of sedimentary organic matter.

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F.J. González-Vila

Spanish National Research Council

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Fernandez Martin

Spanish National Research Council

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J.C. del Río

Spanish National Research Council

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G. Almendros

Spanish National Research Council

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Ana Gutiérrez

Spanish National Research Council

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