A direct alkaline hydrothermal method was used to synthesize mono- and bimetallic Ni and Cu on mesoporous silica (m-SiO2) as catalysts for the hydrogenation of furfural (FAL) to cyclopentanone (CPO). The catalysts were characterized by XRD, FTIR, H2-TPR, SEM, TEM, HR-TEM, XPS, ICP, BET, and CHN analysis. The results demonstrate that the addition of Cu metal improved the reducibility of Ni catalysts and revealed Ni-Cu alloy formation over m-SiO2. Furthermore, XPS and FTIR results reveal that the silanol groups on the catalyst surface play an important role in the ring rearrangement of furfuryl alcohol. Hence, the effect of silanol groups in the FOL rearrangement was studied in detail. Among the catalysts at fixed metal loading of 20 wt.%, Ni5Cu15/m-SiO2 catalyzed the formation of CPO as the main product due to the synergy of Ni-Cu alloy and surface silanol groups. Ni5Cu15 supported on a commercial mesoporous silica (Ni5Cu15/C-SiO2) showed inferior performance compared with the Ni5Cu15/m-SiO2 catalyst for the FAL hydrogenation. Reaction temperature and time were also optimized for the enhanced CPO yield over Ni5Cu15/m-SiO2. The Ni5Cu15/m-SiO2 catalyst is durable, as demonstrated by stability tests over multiple reuses. This effective and flexible NixCuy on m-SiO2 catalyst provides an effective candidate for efficient upgrading of furanics in selective hydrogenation reactions.
The interaction between active metal centers and supports
can be
tailored by the judicious combination of morphologically specific
metal nanoparticles and metal oxide supports such that the efficacy
of the catalysts could be enhanced for practical suitability. Herein,
structurally engineered spherical silver nanoparticles (AgNPs) were
decorated on manganese oxide nanorods (MnO2NRs), and their
catalytic efficacy toward complete oxidation of propane has been explored.
It was observed that 1 wt % Ag-loaded catalysts (1Ag/MnO2NRs) exhibited the highest catalytic activity, where the temperatures
required for the oxidation of 10% (T
10%), 50% (T
50%), and 90% (T
90%) of propane were 130, 160, and 190 °C, respectively,
with apparent activation energy as low as 42.73 kJ mol–1. Strong metal–support interaction between AgNPs and MnO2NRs leads to an increase in the oxygen vacancies and activation
of surface oxygen. A series of investigations including X-ray photoelectron
spectroscopy, temperature-programmed desorption by oxygen, temperature-programmed
reduction by hydrogen, and in situ DRIFTS were carried out in an effort
to establish the mechanistic pathway, and it could be concluded that
the 1Ag/MnO2NR has substantiated impressive catalytic activity
through Mars–van–Krevelen mechanism. Furthermore, 1Ag/MnO2NR has demonstrated remarkable activity and stability when
compared with the current benchmark catalysts and thus can be considered
as a proficient catalyst toward total oxidation of propane from industrial
exhausts.
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