•Ni/Mo ratio determines acidity, dispersion and phosphide phase.•There is an electron transfer from Ni to Mo.•Catalyst activity and product distribution can be tuned by altering Ni/Mo ratio.•Catalyst ...with Ni/Mo ratio of 1 shows particular performance.
SiO2-supported Ni2P, MoP and Ni–Mo bimetallic phosphides with different Ni/Mo ratios were investigated for the deoxygenation of methyl laurate to C11 and C12 hydrocarbons. They were characterized by means of N2 sorption, X-ray diffraction, transmission electron microscope, CO chemisorption, X-ray photoelectron spectroscopy and NH3 temperature-programmed desorption. In the Ni–Mo bimetallic phosphide, the NiMoP2 phase was formed apart from Ni2P and MoP, and the incorporation of Mo into Ni2P took place. These led to an interaction between Ni and Mo via the electron transfer from Ni to Mo. In addition, the increase in the Ni/Mo ratio tended to reduce the phosphide dispersion and catalyst acidity. In the deoxygenation, the turnover frequency of methyl laurate and the C11/C12 ratio tended to increase as the Ni/Mo ratio increased (apart from Ni/Mo ratio of 1). This is related to not only the different catalytic roles of Ni and Mo sites but also the interaction between Ni and Mo and the phosphide dispersion. In all, the C11/C12 ratio can be regulated by altering the Ni/Mo ratio. The catalyst acidity obviously affected the distributions of the oxygenated intermediates.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Mesoporous silica is a class of silica material with a large specific surface area, high specific pore volume and meso-sized pores. These properties make mesoporous silica a good choice of support in ...heterogenous catalysis. In this review, we discuss the functionalization of mesoporous silica, preparations of mesoporous silica supported catalysts and their typical applications in heterogenous catalysis. We highlight the introduction of different functionalities over mesoporous silica and their cooperation to achieve the catalytic turnover. Both the advantages and disadvantages of mesoporous silica as a support in these applications are compared, such as regulating the particle size distribution, dispersion of active species and interaction between active species-support. The review aims to summarize the recent progress on mesoporous silica related catalytic applications and provide valuable insight into the rational design of efficient catalysts.
Mesoporous silica is a class of silica material with a large specific surface area, high specific pore volume and meso-sized pores.
The hydrodeoxygenation (HDO) of biomass-derived oxygenates to fuels is an effective way to reduce the negative environmental impact resulting from the dependence on fossil energy. However, the ...complexity in the feedstock compositions (
e.g.
acids, phenols, esters) and the presence of large amounts of water, cause significant challenges to the design of HDO catalysts. Nickel and nickel-based bimetallic catalysts have been extensively investigated for HDO due to their high activity and low price over the past years. Lots of valuable information about the structure of catalysts (
e.g.
active sites, synergy among various sites) and HDO reactions (
e.g.
reaction routes, kinetics) has been found. In this mini-review, we first summarize the preparation methods of nickel and nickel based bimetallic catalysts and the strategies to improve the HDO performance. The mechanisms and kinetics on HDO of typical oxygenates (aromatic oxygenates, furanic compounds, carboxylic acids and esters) over different catalysts are compared to reveal how the synergistic effects among different functionalities enhance the HDO performance. Solvent effects, the mutual influence among oxygenates and HDO of raw feedstocks over nickel and nickel-based bimetallic catalysts are discussed as well. Finally, we recommend several directions for further research on nickel and nickel-based bimetallic catalysts for HDO reactions.
The hydrodeoxygenation (HDO) of biomass-derived oxygenates to fuels is an effective way to reduce the negative environmental impact resulting from dependence on fossil energy.
The current study reports LaFe1−xNixO3−δ redox catalysts as flexible oxygen or carbon carriers for CO2 utilization and tunable production of syngas at relatively low temperatures (∼700 °C), in the ...context of a hybrid redox process. Specifically, perovskite-structured LaFe1−xNixO3−δ with seven different compositions (x = 0.4–1) were prepared and investigated. Cyclic experiments under alternating methane and CO2 flows indicated that all the samples exhibited favorable reactive performance: CH4 and CO2 conversions varied between 85% and 98% and 70–88%, respectively. While H2/CO ratio from Fe-rich redox catalysts was ~2.3:1 in the methane conversion step, Ni-rich catalysts produced a concentrated (~ 93.7 vol%) hydrogen stream via methane cracking. The flexibility of LaFe1−xNixO3−δ to produce syngas (or hydrogen) with tunable compositions was found to be governed by the iron/nickel (Fe/Ni) ratio. Redox catalysts with higher Fe contents act as a lattice oxygen carrier via chemical looping partial oxidation (CLPOx) of methane whereas those with higher Ni contents function as a carbon carrier via chemical looping methane cracking (CLMC) scheme. XRD analysis and temperature-programmed reactions revealed that both types of catalysts involve the formation of La2O3 and Ni0 /Ni-Fe phases under the methane environment. The ability to re-incorporate La2O3 and Ni/Fe into a perovskite structure gives rise to oxygen-carrying capacity whereas stable Ni0 or Ni/Fe phases would catalyze methane cracking without lattice oxygen exchange in the reaction cycles. Temperature programmed oxidation and Raman spectroscopy indicated the presence of graphitic and amorphous carbon species, which were effectively gasified by CO2 to produce concentrated CO. Stability tests over LaFe0.5Ni0.5O3 and LaNiO3 revealed that the redox performance was stable over a span of 50 cycles.
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•LaFe1−xNixO3−δ facilitates tunable production of syngas with CO2 utilization.•Tuning the Fe:Ni ratio changes the catalyst functionality and reaction pathway.•Excellent CH4 and CO2 conversions were observed at 700 oC.•Inherently separated H2 and CO streams were produced via the carbon carrier route.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The current study reports LaFe1–xNixO3–δ redox catalysts as flexible oxygen or carbon carriers for CO2 utilization and tunable production of syngas at relatively low temperatures (~700 °C), in the ...context of a hybrid redox process. Specifically, perovskite-structured LaFe1–xNixO3–δ with seven different compositions (x = 0.4–1) were prepared and investigated. Cyclic experiments under alternating methane and CO2 flows indicated that all the samples exhibited favorable reactive performance: CH4 and CO2 conversions varied between 85% and 98% and 70–88%, respectively. While H2/CO ratio from Fe-rich redox catalysts was ~2.3:1 in the methane conversion step, Ni-rich catalysts produced a concentrated (~ 93.7 vol%) hydrogen stream via methane cracking. The flexibility of LaFe1–xNixO3–δ to produce syngas (or hydrogen) with tunable compositions was found to be governed by the iron/nickel (Fe/Ni) ratio. Redox catalysts with higher Fe contents act as a lattice oxygen carrier via chemical looping partial oxidation (CLPOx) of methane whereas those with higher Ni contents function as a carbon carrier via chemical looping methane cracking (CLMC) scheme. XRD analysis and temperature-programmed reactions revealed that both types of catalysts involve the formation of La2O3 and Ni0 /Ni-Fe phases under the methane environment. The ability to re-incorporate La2O3 and Ni/Fe into a perovskite structure gives rise to oxygen-carrying capacity whereas stable Ni0 or Ni/Fe phases would catalyze methane cracking without lattice oxygen exchange in the reaction cycles. Here, temperature programmed oxidation and Raman spectroscopy indicated the presence of graphitic and amorphous carbon species, which were effectively gasified by CO2 to produce concentrated CO. Stability tests over LaFe0.5Ni0.5O3 and LaNiO3 revealed that the redox performance was stable over a span of 50 cycles.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Liquid organic hydrogen carriers (LOHCs) have been considered as a promising technique for hydrogen storage and transportation. In this study, we investigated the impacts of Pt size on the catalytic ...performance of Pt/Al
2
O
3
catalysts for the abstraction of H
2
via
dehydrogenation of methylcyclohexane (MCH), one of the most desired LOHC candidates. As the Pt loading increases from 0.05% to 5%, Pt species transition from nanoclusters to well-defined nanoparticles with the Pt size increasing from ∼0.7 nm to 1.7 nm. During MCH dehydrogenation, the turnover frequency (TOF) displays a volcano dependence on the Pt size, as the 0.1% Pt/Al
2
O
3
sample with medium Pt size exhibits the highest atomic efficiency. Furthermore, the catalyst stability of Pt/Al
2
O
3
samples is also dependent on the Pt size with the small Pt size in the 0.05% Pt/Al
2
O
3
sample leading to fast catalyst deactivation due to the accumulation of coke on the Pt active sites. In summary, this study underscores the importance of Pt size to the activity and stability of Pt/Al
2
O
3
in MCH dehydrogenation, providing new insights into the catalyst design for LOHC applications.
Liquid organic hydrogen carriers (LOHCs) have been considered as a promising technique for hydrogen storage and transportation. In this study, we investigated the impacts of Pt size on the catalytic ...performance of Pt/Al
2
O
3
catalysts for the abstraction of H
2
via
dehydrogenation of methylcyclohexane (MCH), one of the most desired LOHC candidates. As the Pt loading increases from 0.05% to 5%, Pt species transition from nanoclusters to well-defined nanoparticles with the Pt size increasing from ∼0.7 nm to 1.7 nm. During MCH dehydrogenation, the turnover frequency (TOF) displays a volcano dependence on the Pt size, as the 0.1% Pt/Al
2
O
3
sample with medium Pt size exhibits the highest atomic efficiency. Furthermore, the catalyst stability of Pt/Al
2
O
3
samples is also dependent on the Pt size with the small Pt size in the 0.05% Pt/Al
2
O
3
sample leading to fast catalyst deactivation due to the accumulation of coke on the Pt active sites. In summary, this study underscores the importance of Pt size to the activity and stability of Pt/Al
2
O
3
in MCH dehydrogenation, providing new insights into the catalyst design for LOHC applications.
A volcano trend is observed for the intrinsic activity of Pt/Al
2
O
3
catalysts in methylcyclohexane dehydrogenation.
Liquid organic hydrogen carriers (LOHCs) have been considered as a promising technique for hydrogen storage and transportation. In this study, we investigated the impacts of Pt size on the catalytic ...performance of Pt/Al2O3 catalysts for the abstraction of H2via dehydrogenation of methylcyclohexane (MCH), one of the most desired LOHC candidates. As the Pt loading increases from 0.05% to 5%, Pt species transition from nanoclusters to well-defined nanoparticles with the Pt size increasing from ∼0.7 nm to 1.7 nm. During MCH dehydrogenation, the turnover frequency (TOF) displays a volcano dependence on the Pt size, as the 0.1% Pt/Al2O3 sample with medium Pt size exhibits the highest atomic efficiency. Furthermore, the catalyst stability of Pt/Al2O3 samples is also dependent on the Pt size with the small Pt size in the 0.05% Pt/Al2O3 sample leading to fast catalyst deactivation due to the accumulation of coke on the Pt active sites. In summary, this study underscores the importance of Pt size to the activity and stability of Pt/Al2O3 in MCH dehydrogenation, providing new insights into the catalyst design for LOHC applications.
