Support Shape Effect in Metal Oxide Catalysis: Ceria-Nanoshape-Supported Vanadia Catalysts for Oxidative Dehydrogenation of Isobutane

The support effect has long been an intriguing topic in catalysis research. With the advancement of nanomaterial synthesis, the availability of faceted oxide nanocrystals provides the opportunity to gain unprecedented insights into the support effect by employing these well-structured nanocrystals. In this Letter, we show by utilizing ceria nanoshapes as supports for vanadium oxide that the shape of the support poses a profound effect on the catalytic performance of metal oxide catalysts. Specifically, the activation energy of VO_<i>x</i>/CeO₂ catalysts in oxidative dehydrogenation of isobutane was found to be dependent on the shape of ceria support, rods < octahedra, closely related to the surface oxygen vacancy formation energy and the numbe of defects of the two ceria supports with different crystallographic surface planes

Molybdenum Carbides, Active and <i>In Situ</i> Regenerable Catalysts in Hydroprocessing of Fast Pyrolysis Bio-Oil

This paper describes properties of molybdenum carbides as a potential catalyst for fast pyrolysis bio-oil hydroprocessing. Currently, high catalyst cost, short catalyst lifetime, and lack of effective regeneration methods are hampering the development of this otherwise attractive renewable hydrocarbon technology. A series of metal-doped bulk Mo carbides were synthesized, characterized, and evaluated in sequential low-temperature stabilization and high-temperature deoxygenation of a pine-derived bio-oil. During a typical 60 h run, Mo carbides were capable of upgrading raw bio-oil to a level suitable for direct insertion into the current hydrocarbon infrastructure with residual oxygen content and total acid number of upgraded oils below 2 wt % and 0.01 mg KOH g^–1, respectively. The performance was shown to be sensitive to the type of metal dopant, Ni-doped Mo carbides outperforming Co-, Cu-, or Ca-doped counterparts; a higher Ni loading led to a superior catalytic performance. No bulk oxidation or other significant structural changes were observed. Besides the structural robustness, another attractive property of Mo carbides was <i>in situ</i> regenerability. The effectiveness of regeneration was demonstrated by successfully carrying out four consecutive 60 h runs with a reductive decoking between two adjacent runs. These results strongly suggest that Mo carbides are a good catalyst candidate which could lead to a significant cost reduction in hydroprocessing bio-oils. We highlight areas for future research which will be needed to further understand carbide structure–function relationships and help design practical bio-oil upgrading catalysts based on Mo carbides