2 research outputs found
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<sub><i>x</i></sub>/CeO<sub>2</sub> 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<sup>–1</sup>, 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