Effect of the extent of reduction of V2O5 on the adsorption of propylene and the oxidative dehydrogenation of propane to give propylene on V2O5 and V2O5/TiO2-SiO2

Abstract

An increase in the propylene output in the oxidative dehydration of propane on V 2 O 5 /TiO 2 -SiO 2 was observed after prior reduction of V 2 O 5 in the reaction mixture to V 2 O 4 , which reduces the destructive chemisorption of propylene. A low titanium dioxide content in TiO 2 -SiO 2 hinders the deep reduction of V 2 O 5 to V 2 O 3 , which reduces the conversion of propane. Key words: propylene adsorption, vanadium oxide, oxidative dehydrogenation of propane.The oxidative dehydration (ODH) of propane to give propylene is currently the subject of extensive investigation in work designed to replace the high-temperature dehydrogenation of propane, which requires the periodic regeneration of the coked Cr 2 O 3 /Al 2 O 3 catalyst in the air by dehydrogenation in the presence of oxygen in the reaction mixture [1, 2]. The search for propane ODH catalysts has been undertaken in many laboratories but the results obtained so far do not hold industrial interest. The best propane yields are 35 mole % and have been obtained on vanadium-containing oxide systems on supports, which have a significant effect on the properties of the active phase [3,4].The dehydrogenation of propane in the presence of oxygen may be seen as a combination of two reactions [5]: the reversible endothermal removal of hydrogen C 3 H 8 « C 3 H 6 + H 2 , DH = 124.3 kJ/mol and the exothermal oxidation of hydrogen H 2 + 0.5O 2 ® H 2 O, DH = -241.8 kJ/mol, which shifts the equilibrium of the first reaction toward the formation of propylene.

Poisoning Effects of HCl on MOx‐WO3/TiO2(M=Mn, Ce and V) Catalysts for Selective Catalytic Reduction of NOxby NH3

“…[25] Since the high oxygen state V (V 5 + /4 + ) was attributed to hard Lewis acid, it was difficult to combine with weak Lewis basic (Cl À ) to form the strong bind, resulting in NH 4 Cl being difficult to exist on VW/Ti catalyst with large quantities. [26] The results were consistent with XPS.…”

“…Because CeO x has more oxygen vacancies, it might provide more anchor sites for NH 4 Cl, leading to the accumulation of NH 4 Cl on CeW/Ti catalyst surface [25] . Since the high oxygen state V (V 5+/4+ ) was attributed to hard Lewis acid, it was difficult to combine with weak Lewis basic (Cl − ) to form the strong bind, resulting in NH 4 Cl being difficult to exist on VW/Ti catalyst with large quantities [26] . The results were consistent with XPS.…”

The role of lattice oxygen in the oxidative dehydrogenation of ethane on alumina-supported vanadium oxide

“…5 Alternatively, ethene adsorption could occur via interaction with Lewis acid centers, such as V 5+ , V 4+ , and V 3+ . Evidence for ethene and propene adsorption on V cations has been presented by Che et al 27 and Red'kina et al, 28 respectively. As the oxidation state of V cations decreases, their ionic radius increases together with the number of electrons in the 3d orbital.…”