The_Catalyst_Review_August_2023 - 19

mechanism. Interestingly, for CoN4
-(OH)TiN4[CNC] and CoN4-(OH)TiN4[Gr-Gr] systems (in Figure 3c-f), the enhancement of *OOH
adsorption induced by H-bond can even shift the PDS. As illustrated, the potential determining step (PDS) is replaced by the fourth
step of *OH departure compared to those without extra *OH. Within the change of PDS, the UL can simultaneously increase to
0.83 V and 0.96 V, both outperforming the benchmark Pt(111). Furthermore, additional H-bond assistance leads to a reduction in
ΔG*OOH
- ΔG*OH and the emergence of a new linear scaling relationship of ΔG*OOH
=ΔG*OH+2.84 eV. This proposed critical H-bond
mediation mechanism represents a significant advance in exploiting an intrinsic structural feature to improve catalytic activity. Li Y,
Yue Z, Yan H, et al. (2023). ChemSusChem, doi.org/10.1002/cssc.202300082
Enhancing Catalytic Performance with Sol-gel Hydrotalcite-derived Nickel Oxide Catalysts
for Dry Reforming of Methane: An Examination on Reactivity and Coke Formation
The CO2 reforming process converts CH4
and CO2
into synthesis gas using nickel catalysts. Although nickel is an economical catalyst,
it is sensitive to deactivation by carbon deposition. Efforts have therefore been directed to develop more sustainable catalysts.
Hydrotalcites, by virtue of their rhombohedral or hexagonal symmetry, have been shown to possess improved catalytic performance
in reforming reactions and have prompted significant interest. In this study, three types of hydrotalcites prepared by coprecipitation
(CpOxMix
of methane. The best catalyst was then characterized and tested for stability. Statistical analysis of reaction parameters was then
conducted to better understand the reaction mechanism.
The synthesized hydrotalcites exhibit nanocapsular morphology
and dispersed nickel nano-oxide particles after calcination at
500 °C. The catalysts were evaluated at 600 °C and 800 °C
for 8 hours (Table 1) and demonstrated high conversions and
varying yields, with sol-gel oxide catalysts (Sg)OxMix
showing the
best performance with the highest reactivity and controlled
coke formation at 800 °C after 14 hours of testing. Sol-gel
hydrotalcites were found to promote mixed oxides for methane
reforming and show variations in plate-like morphology due to
the hygroscopic nature of precursors and alcohol molecules in
catalyst synthesis. Memory effects were compared with direct
synthesis and coprecipitation, showing structure, behavior,
and catalytic performance differences. For instance, higher
occupancy factors for O1
vacancies were found for SgOxMix
compared to IEOxMix and CpOxMix. A detailed analysis of SgOxMix
revealed different binding energies related to oxide and
metallic nickel species. The nanospheroidal nature of the
metallic species inhibited coke deposition and avoided the
encapsulation of the metallic particles, providing evidence of
a reaction mechanism (Scheme 1) based on the activation of
CH4
The proposed reaction pathway suggests that OH groups on
the catalyst support participate in the reaction, arising from
O1s
deconvolution in MgAlNiOx
present on the catalyst surface. The reactor experienced
two experimental fluctuations with 93 %confidence, favoring
synthesis gas production with minimal coke formation and
a higher reaction rate for CO2
Table 1. Catalytic activity performance for mixed oxides
tested at 600 °C and 800 °C.
), sol-gel (SgOxMix), and ion exchange (IEOxMix) were used as precursors for NiMgAl mixed oxides and evaluated in dry reforming
Scheme 1. Reaction pathway for DMR over Nickel catalysts
derived from sol-gel hydrotalcites.
and CO, with possible contribution from oxygen vacancies
present in the support and Ni(111) lattice.
mixed oxide and other species
nanospheroidal morphology can improve coke control and reaction rate for methane and CO2
and CH4 at 800 °C. In spite of the effect of calcination temperature on catalyst stability, mixed oxides with
at low temperatures. For calcined oxides
at higher temperatures, more time for stabilization is necessary in catalytic and transient tests for samples activated at 500 °C. GonzalezCaranton
AR, Stavale F, Annese E, et al. (2023). ChemCatChem, https://doi.org/10.1002/cctc.202300280
The Catalyst Review
August 2023
19

http://www.doi.org/10.1002/cssc.202300082 https://www.doi.org/10.1002/cctc.202300280

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