A novel hydrodeoxygenation catalytic system, Ni2P/SBA-15,
has been synthesized by temperature-programmed reduction of a nickel
phosphate precursor impregnated in the mesostructured silica support.
The formation of this active phase was verified by X-ray diffraction,
whereas the study by transmission electron microscopy revealed that
the catalyst is mainly constituted of nickel phosphide particles of
relatively uniform size dispersed within the SBA-15 channels. Both
Ni2P/SBA-15 and a reference Ni/SBA-15 catalyst were tested
for the hydrodeoxygenation of methyl oleate (C17H33–COO–CH3) in a fixed-bed continuous flow
reactor. This compound was used as a convenient surrogate of triglyceride
molecules present in vegetable oils that following catalytic hydrotreating
yields n-alkanes as the main products. In the whole
range of pressure studied (3–40 bar) and for temperatures higher
than 290 °C, both systems achieve more than 80% ester conversion
at 20 h–1 WHSV, although the Ni/SBA-15 catalyst
presents a slightly higher activity. Overall, higher pressure and
lower temperature and space velocity favors the formation of C18 hydrocarbon, which is the preferred product in terms of
carbon atom economy. Nevertheless, under all the assayed conditions,
the n-C18/n-C17 ratio was remarkably higher for Ni2P/SBA-15 than for
Ni/SBA-15 catalysts. On the basis of these results, it can be concluded
that both deoxygenation and decarboxylation occur simultaneously over
the Ni2P catalyst, whereas decarboxylation and cracking
are the prevailing processes over the Ni catalyst. Owing to these
high yields of long-chain paraffins, Ni2P/SBA-15 can be
considered as a very promising catalyst for the production of green
diesel.
Despite nearly 40 years of research on CO 2 photocatalytic reduction and the increasing number of works dealing with this application, there are still many unknowns on the mechanistic aspect of the reaction.Perspective pubs.acs.org/JPCL
First direct images of cobalt nanoparticles covered by a few atomic layers thick TiO(x) moieties after reduction treatment of a Co/TiO(2) system with the simultaneous formation of Co-O-Ti bonds confirm the development of the SMSI decoration effect.
Activation
of ultraviolet (UV) energy bandgap semiconductors for
solar fuel production using visible light as energy source is one
of the most challenging tasks in the artificial photosynthesis field.
Triplet–triplet annihilation (TTA) based on photon upconversion
(UC) generates frequently high energy (i.e., UV) from lower energy
(visible). Thus, an efficient and appropriate TTA-UC system can successfully
use visible light to power a photoelectrochemical cell using TiO2, leading to photovoltages, photocurrents, and photoelectrocatalytic
hydrogen production. Here, for the first time, visible-to-UV TTA-UC
is demonstrated to be a useful strategy for performing artificial
photosynthesis processes by means of UV energy bandgap semiconductors.
The geometric, electronic and magnetic properties of the three metallic cobalt phases: hcp(alpha), fcc(beta), and epsilon(epsilon) have been theoretically studied using periodic density functional calculations with generalized gradient approximation (GGA) and plane wave basis set. These results have been compared with those obtained with GGA+U approach which have shown a noticeable improvement with regard to experimental data. For instance, the cohesive energy values predicted by GGA are overestimated by approximately 25%, whereas GGA+U underestimate them by 14%-17%. On the other hand, magnetic moment values are underestimated in GGA while are overestimated for GGA+U approach by almost the same amount. Besides, the introduction of U parameter gives rise to an electronic redistribution in the d-band structure, which leads to variations in the magnetic properties. Moreover, a higher attention has been paid in the study of the electronic and magnetic properties of the epsilon-phase that has not described previously. These studies show that this phase possesses special properties that could lead to an unusual behavior in magnetic or catalytic applications.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.