(4ag) Rational Design of the Heterogeneous Catalysts and Their Opportunities in Renewable Fuels

Abstract:

A
sustainable economy requires the development of alternative energy to replace
the energy based on fossil fuels, thus the hydrogen production and the biomass conversion
attract a lot of research attentions recently to make the world sustainable. 
The objective of the research is to develop novel catalysts and processes for
the hydrogen production and the upgrading biomass-derived oxygenated compounds
to useful chemicals and fuels.  The nanoparticle impregnation method was
developed to prepare supported nanopartilce (np) catalysts with controlled
particle sizes and composition.  And these np catalysts were applied for the
non-oxidative dehydrogenation of methane for the production of CO_x-free
hydrogen and sequestering carbon as potentially value-added by-product carbon
nanotubes (CNTs).  Monosized Fe_0.65Ni_0.35
oxide nanoparticles with an average particle size of 9 nm were prepared by
thermal decomposition of an Fe, Ni oleate-surfactant complex in octadecene
under reflux; these nanoparticles were dispersed onto a Mg(Al)O support to form
a Fe-Ni np/Mg(Al)O catalyst.  Compared with the Fe-Ni IW/Mg(Al)O catalyst, the
nanoparticle catalyst was more easily reduced and exhibited enhanced methane
dehydrogenation and 5 times longer life-times.  Each reduced Fe-Ni nanoparticle
functioned as an active site for the growth of CNTs.  An invar-like Fe-Ni-C
alloy phase is believed to be more active phase for methane dehydrogenation
than Fe-Ni austenitic phase, Fe metal and metastable Fe-C carbides.  Another
effort was the combination of computational and experimental approaches to
design shape selective solid base catalysts for the liquid phase furaldehydes
condensations with ketones, where the zeolites with desired pore structures and
sizes were nitrided in ammonia at the elevated temperatures to replace the
bridging oxygens to lower electronegativity nitrogens for the generation of the
strong basic sites.  In one of these
researches, the nitrogen-substituted NaY showed comparable catalytic activity
to MgO-ZrO₂, but higher selectivity to furadehyde acetone monomer
product, indicating the shape selective significance of nitrogen-substituted NaY. 
The combination of advanced material synthesis with computation,
characterization, temperature programmed surface reactions, and kinetic studies
provide a useful tool to rational design heterogeneous catalysts.

Keywords:  Non-oxidative methane dehydrogenation; monodispersed
nanoparticles; nanoparticle catalysts; solid base catalysts;
nitrogen-substituted zeolites