Abstract
H2 production through dry reforming of methane (DRM) is a hot topic amidst growing environmental and atom-economy concerns. Loading Ni-based reducible mixed oxide systems onto a thermally stable support is a reliable approach for obtaining catalysts of good dispersion and high stability. Herein, NiO was dispersed over MOx-modified-γ-Al2O3 (M = Ti, Mo, Si, or W; x = 2 or 3) through incipient wetness impregnation followed by calcination. The obtained catalyst systems were characterized by infrared, ultraviolet–visible, and X-ray photoelectron spectroscopies, and H2 temperature-programmed reduction. The mentioned synthetic procedure afforded the proper nucleation of different NiO-containing mixed oxides and/or interacting-NiO species. With different modifiers, the interaction of NiO with the γ-Al2O3 support was found to change, the Ni2+ environment was reformed exclusively, and the tendency of NiO species to undergo reduction was modified greatly. Catalyst systems 5Ni3MAl (M = Si, W) comprised a variety of species, whereby NiO interacted with the modifier and the support (e.g., NiSiO3, NiAl2O4, and NiWO3). These two catalyst systems displayed equal efficiency, >70% H2 yield at 800 °C, and were thermally stable for up to 420 min on stream. 5Ni3SiAl catalyst regained nearly all its activity during regeneration for up to two cycles.
Highlights
Hydrogen (H2) is a green energy source
An increased fraction of species whereby Ni interacted with MoOx (i.e., NiMoO4) caused the catalyst to increase in stability and resulted in >45% H2 yield of the dry reforming of methane (DRM) reaction at 700 ◦C
The IR spectra of 5Ni3SiAl and 5Ni3WAl were characterized by vibrational frequencies due to a variety species, whereby NiO interacted with the modifier or the support. 5Ni3SiAl comprised species, whereby NiO interacted with the modifier to form NiSiO3 and with the support to produce NiAl2O4, much like 5Ni3WAl comprised species, whereby NiO interacted with the modifier to form NiWO4 and with the support to form NiAl2O4
Summary
Hydrogen (H2) is a green energy source. Biomass pyrolysis and biomass gasification have always been environmentally questionable approaches to hydrogen production; the implementation of these methods renders H2 isolation and purification quite difficult, as the desired product associates with many side-products [3]. A more convenient approach is hydrogen production from compounds such as ethanol [4], glycerol [5], glucose [6], starch, and catechol [7], by steam or thermal reforming over a heterogeneous catalyst. Environmental concerns and the high demand for atom-economies have driven the development of hydrogen production methods, relying on clean sources, such as water splitting, thermal reforming of methane, stream reforming of methane, and CO2 (dry) reforming of methane (DRM) [8,9]. DRM in particular, has drawn great deal of attention globally because it fulfils the goal of hydrogen production while raising hope for the reduction of the atmospheric concentrations of carbon dioxide and methane, the two gases whose emissions are most responsible for global warming
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