Research Progress in Catalytic Total Oxidation of Methane

doi:10.15541/jim20230117

Abstract

Abstract:

Methane is the second greenhouse gas contributing greatly to global warming, about 80 times of CO₂. Considering background of global warming and atmospheric methane growth, to catalyze total oxidation of atmospheric methane is of great importance to mitigate greenhouse effects and slow this global warming. However, catalytic oxidation of methane has always been a big challenge due to its high structural stability. In this article, research progress in total oxidation of methane under thermal-, photo- and photothermal-catalysis was reviewed. High temperature in thermal catalysis increases the energy loss and accelerates the deactivation of catalysts speedingly. Therefore, development of catalysts that oxidize methane under moderate temperatures is the main research interests. Photocatalysis provides a way to eliminate methane at ambient conditions with the assistance of solar energy, but the reaction rates are lower than that in thermal catalysis. It is worth mentioning that photothermal catalysis, developed in recent years, can achieve efficiently catalytic total oxidation of methane under mild conditions, showing a high potential application prospect. This article reviews development of three modes of catalysis, analyzes their different reaction mechanisms, advantages and disadvantages under different reaction conditions. Finally, prospects and challenges of this catalytic total oxidation are pointed out, which is expected to provide references for future research on this field.

Key words: catalytic oxidation of methane, thermal catalysis, photocatalysis, photothermal catalysis, review

CLC Number:

O643

SUN Chen, ZHAO Kunfeng, YI Zhiguo. Research Progress in Catalytic Total Oxidation of Methane[J]. Journal of Inorganic Materials, 2023, 38(11): 1245-1256.

Figures/Tables 11

Fig. 1 Summary of catalyst properties for the total oxidation of methane by thermal catalysis[17]

Fig. 2 Performance tests and theoretical calculations of catalysts[28] (a) Light-off curves and T50 values of Pd/Al2O3 after O2 (600 ℃), O2-H2, steam (600 ℃), and steam-O2 pretreatments; (b) GB density statistical histogram of laser-generated Pd/Al2O3 and Pd/Al2O3 after steam (600 ℃) and O2-H2 pretreatments; (c, d) Calculated free energy diagrams for breaking the first C-H bond in CH4 on PdO(101) and PdO(110), respectively. Reprinted from Ref. [28] with permission, Copyright 2021 AAAS

Fig. 3 Proposed model for the CH4 dissociative adsorption over Pt0−Pt4+ dipoles saturated with chemisorbtion oxygen atoms[30] (a) Reactants: CH4 in the gas phase and 1% Pt/Cr2O3; (b) CH4 polarization by Pt0−Pt4+ site and formation of a transition state; (c) Abstraction of the first hydrogen on the adsorbed CH4 molecule

Table 1 Comparison of properties of catalysts for total oxidation of methane by thermal catalysis

Catalyst	T_c^*/℃	E_a/(kJ·mol^-1)	Feed gas	GHSV/(mL·g^-1·h^-1)	Stability	Ref.
Pd-Ce@SiO₂	T₁₀₀=350	100.4	1% CH₄, 21% O₂, bal. N₂	36000	25 h	[39]
Pd/TiO₂	T₉₉=370	83.1	1% CH₄, 10% O₂, bal. N₂	30000	4 cycles	[40]
Pd/Na-MOR	T₅₀=335	75	1% CH₄, 4% O₂, bal. N₂	70000	90 h	[41]
Pd-Pt/CeO₂	T₅₀=325	74	680 μg/mL CH₄, 14% O₂, 5% CO₂, bal. N₂	300000	12 h^#	[42]
Au/Al₂O₃	T₅₀=480	73	0.8% CH₄, 3.2% O₂, bal. He,	15000	/	[32]
Rh/ZrO₂	T₅₀=400	/	1% CH₄, 2% O₂, bal. He	15000	/	[31]
Ir/TiO₂-H	T₅₀=267	55.5	1% CH₄, 20% O₂, bal. N₂	30000	50 h	[43]
Ag/MnLaO₃	T₅₀=580	74	2% CH₄, 98% air	12000	/	[44]
Pt/Cr₂O₃	T₅₀=350	/	0.2% CH₄, 10% O₂, bal. N₂	30000	/	[30]
MgO	T₅₀=225	/	1% CH₄, 99% air	6000	70 h	[45]
LaCoO₃	T₅₀=470	/	0.8% CH₄, 5% O₂, bal. N₂	60000	/	[46]
NiCo₂O₄	T₁₀₀=350	/	5% CH₄, 25% O₂, bal. Ar	24000	48 h^#	[47]
La_0.6Sr_0.4MnO₃	T₅₀=566	56.6	2% CH₄, 20% O₂, bal. N₂	30000	/	[48]
CoAlO_x/CeO₂	T₅₀=415	92.2	10% CH₄, 25% O₂, bal. Ar	24000	50 h	[49]

Fig. 4 (a) Schematic diagram of methane activation over semiconductor-based photocatalysts[1]; (b) Schematic diagram of band structures of commonly used semiconductors and redox potentials of different reactants[55]

Fig. 5 Application of ZnO-based semiconductor in photocatalytic total oxidation of methane (a) Time evolution of photocatalytic total oxidation of methane over 0.1% Ag-decorated ZnO nanocatalysts at different CH4 concentrations[56] (Reprinted from Ref. [56] with permission, Copyright 2016 Springer Nature); (b) Time evolution of photocatalytic total oxidation of methaneover various catalysts with a CH4 input of 100 μL/L[58] (Reprinted from Ref. [58] with permission, Copyright 2019 Royal Society of Chemistry); (c) Catalytic activity of total oxidation of methane (top) and the crystal morphology (bottom) of a ZnO nanosheet and nanorod[59] (Reprinted from Ref. [59] with permission, Copyright 2019 American Chemical Society)

Fig. 6 Ga2O3/AC photocatalytic total oxidation of methane and schematic diagram of oxidation mechanism[60] (a) Recycled test of photocatalytic oxidation of CH4 over 15% Ga2O3/AC; (b) Proposed mechanism for photocatalytic oxidation of CH4 over Ga2O3/AC composites. Reprinted from Ref. [60] with permission, Copyright 2017 Royal Society of Chemistry

Fig. 7 Adsorption energy calculations of surface methane and DFT calculation of different TiO2 [61] (a1-a3) Most stable adsorption configurations of CH4 on (a1) anatase TiO2(001)-(1×4), (a2) anatase TiO2(100)-(1×2), and (a3) anatase TiO2(101) surfaces. Gray and red balls represent Ti and O atoms, respectively; (b1, b2, c1,c2, d1, d2) Calculated PDOS of (b1) bare and (b2) CH4-adsorbed anatase TiO2(001)-(1×4) surfaces, (c1) bare and (c2) CH4-adsorbed anatase TiO2(100)-(12) surfaces, and (d1) bare and (d2) CH4-adsorbed anatase TiO2-(101) surfaces. Reprinted from Ref. 61 with permission, Copyright 2022 American Chemical Society

Table 2 Comparison of performances of photocatalysts for total oxidation of methane by photocatalysis

Catalyst	Reaction conditions	Yield/(μmol·h^-1)	Ref.
TiO₂	Batch reactor, 3×10⁵Pa CH₄, Xe lamp, RT	1.1	[62]
TiO₂	Batch reactor, 2×10⁶Pa CH₄, 5 bar O₂, Xe lamp, RT	23	[63]
ZnO	Batch reactor, 1×10⁵Pa, 250 μg/mL CH₄ in air, Xe lamp, RT	2	[59]
Ag/ZnO	Batch reactor, 1×10⁵Pa, 250 μg/mL CH₄, Xe lamp, RT	22	[56]
CuO/ZnO	Batch reactor, 1×10⁵Pa, 100 μg/mL CH₄, Xe lamp, RT	4	[58]
Au-CeO₂/ZnO	Batch reactor, 1×10⁵Pa, 250 μg/mL CH₄, Xe lamp, RT	0.6	[57]
Ag/AgCl	Batch reactor, 1×10⁵Pa, 500 μg/mL CH₄, Xe lamp, RT	5.4	[64]
SrCO₃/SrTiO₃	Batch reactor, 1×10⁵Pa, 200 μg/mL CH₄, Xe lamp, RT	0.8	[65]
BiVO₄	Batch reactor, 1×10⁵Pa, 20 μg/mL CH₄, visible light, RT	0.05	[66]

Fig. 8 Tests of ZnO/LSCO photocatalysis and photothermal cocatalysis for methane total oxidation[70] (a) Temperature profiles on these monolithic catalysts under irradiation of Xe lamp; (b) CH4 photothermal conversions over these monolithic catalysts under Xe lamp irradiation; (c) Comparison of CH4 conversion for ZnO/LSCO under Xe lamp irradiation and direct thermal heating (furnace) at the same temperature; (d) Activity comparison of methane oxidation with previous studies by normalized reaction rate constant. Reprinted from Ref. [70] with permission, Copyright 2008 American Chemical Society

Fig. 9 HPMC photothermal co-catalyzed methane total oxidation performance (a, b) and its mechanism (c)[71] (a) Cycling stability test of HPMC; (b) Methane conversion measured at 200 ℃ with different optical power (OPD); (c) Reaction mechanism of HPMC catalyzed methane combustion. Reprinted from Ref. [71] with permission, Copyright 2021 Wiley

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