ABSTRACT

	The present doctoral thesis presents a study on the synthesis and characterization of materials based in metal transition oxide as catalyst in the partial oxidation of hydrogen sulphide to sulphur. Specifically, the synthesis of V-containing catalysts (bulk, supported or incorporated in a bronze as Mo and/or W bronzes) has been studied.

	Firstly, a study over vanadium oxide has been realized (bulk, supported, partially reduced and dope with alkali metal). The physic-chemical characterizations of catalysts have been determined by using several spectroscopic techniques (i.e. XRS, Raman, IR, RD-UV-vis, TPR-H2). Combination of catalytic and characterization results have allowed us to identify that the best activity, sulphur selectivity and stability is due at the presence of V2O5 crystallites.
	On the other hand, the characterization of catalysts after the catalytic test shows a selective transformation from V2O5 to V4O9 crystallites. The study of catalytic properties of this crystalline phase shows that is active, selective and stable in the partial oxidation of H2S. Moreover, this activity can be improved by sodium addition.
	Although, V4O9 could be the active phase, this can be formed as a result of the partial reduction/reoxidation of the materials during the reactions and later characterization. So, different experiments were carried out in operando conditions (Raman spectroscopy) and in-situ (XAS and Raman spectroscopy). These results confirm that V2O5 crystallites are selectively transformed in V4O9 crystallites during the partial oxidation of H2S to sulphur. It may be the case that, the presence of V5+-O-V4+ pairs are responsible of redox mechanism.
	Later, the Mo and/or W bronzes, in which have incorporated vanadium atoms, have been studied to know the activity properties of Men+-O-V4+ pairs (Me = Mo and/or W and n+ = 5 or 6). Thus, a study on the synthesis, characterization and catalytic activity of bronzes with different crystalline phase (orthorhombic, hexagonal, and pentagonal) has been realized. The results show that the composition and crystalline phase have an important effect in the activity properties. Moreover, the higher activity corresponds to the catalysts with empty framework positions. These materials have both acid and redox properties, so the catalytic activity depends on reducibility and acid sites in the catalysts.
	Therefore, tungsten and vanadium materials with hexagonal structure and empty framework positions have been synthesized. These catalysts have both acid and redox properties. They are active, selective and stable in the partial oxidation of H2S to sulphur.
	Finally, a study of catalytic activity of W-V-O bronzes in an interesting industry’s reaction as oxideshydration of glycerol into acrylic acid has been studied. The results showed that these catalysts have both acid and redox properties, proving that both sites are active in the oxideshydration of glycerol into acrylic acid.