Influence of Molybdenum Loadings on the Properties of MoO3/Zirconia Catalysts

Abstract

An ideal hydroisomerisation reaction is expected to take place over a bifunctional catalyst, in which a balance between the number of metal sites and acid sites might lead to an optimal performance. In order to assess this relationship and the implications for n-heptane hydroisomerisation, various loadings of molybdenum oxide (1-10 wt%) were impregnated on zirconia with a view to producing samples with a range of acid and metal-like properties. The nature and amounts of the acid sites were determined using quantitative FTIR of pyridine adsorption, while the metal-like properties were determined using CO chemisorption. It was observed that zirconia alone contained only Lewis acid sites (1440 cm −1), while addition of MoO 3 generated Brønsted acidity (1536 cm −1). The ratio of Brønsted to Lewis acid sites increased with loadings. Similarly, the amounts of CO taken up by the samples increased with MoO 3 loadings; hence, the addition of MoO 3 resulted in an improved metal like behaviour. The ratio of Brønsted acid to metal-like sites were found to range between 0.009 and 1.180 on going from 1 to 10 wt% MoO 3. The materials were used for n-heptane hydroconversion. The sample with the highest amount of Brønsted acid site, which also consumed the highest amount of CO showed the highest activity. Hence, it could be concluded that the addition of MoO 3 improves the Brønsted acid to metal-like site ratio, which resulted in a pronounced improvement in the activity of the samples.

Production of Propanediols through In Situ Glycerol Hydrogenolysis via Aqueous Phase Reforming: A Review

“…From the list of promoters used, Co and Mo have the potential to generate high amounts of Brønsted acid sites, which are beneficial to increase the selectivity for 1,3-propanediol [42]. The addition of Mo also resulted in increased activity, as the ratio of Brønsted acid to metal-like sites increased [149]. Mo is compatible with noble metals and is able to reduce the coke formation of bulk Ni and other noble metals [150].…”

Extraction of Silica from Different Solid Wastes and Its Application as Catalyst Support for Vapour Phase Oxidation of Aromatic Hydrocarbon

“…Many scientists have attempted to reduce this drawback by incorporating molybdenum onto a wide variety of solid supports by adopting different methodology via impregnation, sol-gel, MoO2(acac)2 anchoring and thermal spreading [33][34][35]. Several support materials have been used such as SnO2 [36], Al2O3 [37], SiO2 [38], ZrO2 [39], MoV heteropoly acid (HPA) [40], classical supported catalysts [41,42] and various types of mesoporous silica i.e. MCM-41 [43], SBA-15 [44] and have also been used as support materials.…”