Preparation of Pd/SiO2 Catalysts by a Simple Dry Ball-Milling Method for Lean Methane Oxidation and Probe of the State of Active Pd Species

A series of Pd/SiO2 catalysts were prepared with different Pd precursors by a dry ball-milling method and used in the catalytic oxidation of lean methane at low temperature. The effect of Pd precursors on the catalytic performance was investigated and the state of the most active Pd species was probed. The results indicate that dry ball-milling is a simple but rather effective method to prepare the Pd/SiO2 catalysts for lean methane oxidation, and palladium acetylacetonate is an ideal precursor to obtain a highly active Pd/SiO2-Acac catalyst with well- and stably dispersed Pd species, owing to the tight contact between acetylacetonate and Si–OH on the SiO2 support. Besides the size and dispersion of Pd particles, the oxidation state of Pd species also plays a crucial role in determining the catalytic activity of Pd/SiO2 in lean methane oxidation at low temperature. A non-monotonic dependence of the catalytic activity on the Pd oxidation state is observed. The activity of various Pd species follows the order of PdOx >> Pd > PdO; the PdOx/SiO2-Acac catalysts (in particular for PdO0.82/SiO2-Acac when x = 0.82) exhibit much higher activity in lean methane oxidation at low temperature than Pd/SiO2-Acac and PdO/SiO2-Acac. The catalytic activity of PdOx/SiO2 may degrade during the methane oxidation due to the gradual transformation of PdOx to PdO in the oxygen-rich ambiance; however, such degradation is reversible and the activity of a degraded Pd/SiO2 catalyst can be recovered through a redox treatment to regain the PdOx species. This work helps to foster a better understanding of the relationship between the structure and performance of supported Pd catalysts by clarifying the state of active Pd species, which should be beneficial to the design of an active catalyst in lean methane oxidation at low temperature.

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Catalytic activity of oxide-supported Pd catalysts on a honeycomb for low-temperature methane oxidation

Applied Catalysis A General ◽

10.1016/s0926-860x(02)00387-3 ◽

2003 ◽

Vol 239 (1-2) ◽

pp. 169-179 ◽

Cited By ~ 26

Author(s):

Ryuji Kikuchi ◽

Shingo Maeda ◽

Kazunari Sasaki ◽

Stefan Wennerström ◽

Yasushi Ozawa ◽

...

Keyword(s):

Catalytic Activity ◽

Low Temperature ◽

Methane Oxidation ◽

Pd Catalysts ◽

Supported Pd Catalysts ◽

Supported Pd

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Direct fabrication of anatase/activated carbon nano-hybrid materials by hydrothermal with ball milling method at low temperature

Journal of Materials Science ◽

10.1007/s10853-006-7408-8 ◽

2006 ◽

Vol 41 (5) ◽

pp. 1363-1368 ◽

Cited By ~ 1

Author(s):

N. Sakamoto ◽

T. Fujino ◽

T. Watanabe ◽

M. Yoshimura

Keyword(s):

Activated Carbon ◽

Low Temperature ◽

Ball Milling ◽

Hybrid Materials ◽

Direct Fabrication ◽

Milling Method

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Preparation of Ni/ZrO2/SiO2 Catalyst and its Application in Hydrogenation of CO2 to Methane

Materials Science Forum ◽

10.4028/www.scientific.net/msf.1001.79 ◽

2020 ◽

Vol 1001 ◽

pp. 79-83

Author(s):

Zhen Xing Han ◽

Si Xi Guo ◽

Kai Ming Li ◽

Bing Yao ◽

Ming Song ◽

...

Keyword(s):

Catalytic Activity ◽

Low Temperature ◽

Catalytic Performance ◽

Experimental Results ◽

Impregnation Method ◽

Energy And Environment ◽

Supported Ni ◽

Hydrogenation Of Co

The hydrogenation of CO2 to CH4 can realize the utilization of CO2, which has an important implications to both the energy and environment. As a result of the low catalytic activity of the supported Ni/SiO2 catalyst, the ZrO2 is added to improve its catalytic performance by the impregnation method. The experimental results show that ZrO2 is an effective promoter to enhance the low-temperature catalytic activity of Ni/SiO2 catalyst.

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Enhanced Performance of Bimetallic Co-Pd Catalysts Prepared by Mechanical Alloying

Metals ◽

10.3390/met9030335 ◽

2019 ◽

Vol 9 (3) ◽

pp. 335

Author(s):

Steven Knauss ◽

Laura Guevara ◽

Mark Atwater

Keyword(s):

Catalytic Activity ◽

Mechanical Alloying ◽

Ball Milling ◽

Bimetallic Catalysts ◽

Reactant Ratio ◽

Pd Catalysts ◽

Close Proximity ◽

Intermediate Time ◽

Underlying Mechanisms ◽

Co Precipitation

Bimetallic catalysts can provide enhanced performance, and Co-based catalysts in particular have been studied in various respects for their activity in the deposition of carbon nanofibers (CNFs). The majority of studies on CNF catalysis use co-precipitation to create alloys, but recent work has demonstrated the suitability of mechanical alloying (MA) by ball milling to reduce cost and increase catalytic activity. This work establishes the unique ability of MA to control the microstructure to produce bimetallic composites, which retain distinct metallic phases that improve catalytic activity. It is demonstrated that Co-Pd alloys reach a maximum in catalytic activity at an intermediate time of mechanical activation, where 30 min of milling outperformed samples milled for 5, 15, 60, and 240 min at a reaction temperature of 550 °C and a 1:4 C2H4:H2 reactant ratio. This indicates there is benefit to retaining the metals in distinct phases in close proximity. Ball milling provides a relatively simple and scalable method to achieve these unique microstructures, and in the optimal condition tested here, the activity toward carbon deposition is increased fourfold over prior work. Furthermore, the minimum temperature for deposition is also reduced. The characteristics of these materials, the effects of milling and annealing, and the underlying mechanisms of deposition are discussed.

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Self-oscillations during methane oxidation over Pd/Al 2 O 3 : Variations of Pd oxidation state and their effect on Pd catalytic activity

Applied Catalysis A General ◽

10.1016/j.apcata.2016.04.024 ◽

2016 ◽

Vol 522 ◽

pp. 40-44 ◽

Cited By ~ 11

Author(s):

V.Yu. Bychkov ◽

Yu.P. Tulenin ◽

M.M. Slinko ◽

A.K. Khudorozhkov ◽

V.I. Bukhtiyarov ◽

...

Keyword(s):

Catalytic Activity ◽

Methane Oxidation ◽

Oxidation State

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Bimetallic Cooperativity with a 2-Phosphinoimidazole-Derived Pd(II) Dimer Enables Naphthalene Synthesis via dimeric Pd(III) Catalysis

10.26434/chemrxiv.13010528 ◽

2020 ◽

Author(s):

Chloe C. Ence ◽

S. Hadi Nazari ◽

Mariur Rodriguez Moreno ◽

Manase F. Matu ◽

Samantha G. Kulka ◽

...

Keyword(s):

Catalytic Activity ◽

Dft Calculations ◽

Oxidation State ◽

Methyl Ketone ◽

Methyl Ketones ◽

Mechanistic Studies ◽

High Oxidation State ◽

Pd Catalysts ◽

Silver Triflate ◽

High Oxidation

We report the synthesis of bimetallic Pd(I) and Pd(II) complexes scaffolded on bidentate 2-phosphinoimidazole ligands. These complexes display unique catalytic activity and enable the expeditious formation of 1,3-disubstituted naphthalenes via an unprecedented coupling of aryl iodides and methyl ketones in the presence of silver triflate. Excellent substrate scope for naphthalene formation is also demonstrated. Mechanistic studies suggest that the transformation proceeds via Pd-catalyzed arylation of a methyl ketone, followed by cyclization with a second equivalent of ketone. Importantly, this ketone arylation processes occurs under oxidizing conditions, suggesting involvement of higher oxidation state dimeric Pd catalysts. Based on experiments and DFT calculations, we propose a mechanism involving high oxidation state Pd(III) bimetallic catalysis. These new bimetallic complexes possess reactivity that is not seen with monometallic Pd catalysts and we confirm the importance of the palladium catalyst for both arylation and cyclization for naphthalene formation.

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The Enhanced Performance of N-Modified Activated Carbon Promoted with Ce in Selective Catalytic Reduction of NOx with NH3

Catalysts ◽

10.3390/catal10121423 ◽

2020 ◽

Vol 10 (12) ◽

pp. 1423

Author(s):

Marwa Saad ◽

Agnieszka Szymaszek ◽

Anna Białas ◽

Bogdan Samojeden ◽

Monika Motak

Keyword(s):

Catalytic Activity ◽

Activated Carbon ◽

Low Temperature ◽

Selective Catalytic Reduction ◽

Catalytic Reduction ◽

Catalytic Performance ◽

Reduction Mechanism ◽

Modified Activated Carbon ◽

Oxidation Reduction ◽

Reduction Of Nox

The goal of the study was to modify activated carbon (AC) with nitrogen groups and ceria and to test the obtained materials in low temperature selective catalytic reduction of nitrogen oxides. For that purpose, the starting AC was oxidized with HNO3 of various concentrations, modified with urea and doped with 0.5 wt.% of Ce. It was observed that the increased concentration of acid influenced the catalytic activity, since textural and surface chemistry of activated carbon was changed. The most active sample was that modified with 14 M HNO3 and it reached 96% of NO conversion at 300 °C. Additionally, the addition of Ce improved the catalytic performance of modified AC, and NO was reduced according to oxidation–reduction mechanism, characteristic for supported metal oxides. Nevertheless, the samples promoted with Ce emitted significantly higher amount of CO2 comparing to the non-promoted ones.

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