Current Progress on Methods and Technologies for Catalytic Methane Activation at Low Temperatures

Abstract

Methane (CH₄ ) is an attractive energy source and important greenhouse gas. Therefore, from the economic and environmental point of view, scientists are working hard to activate and convert CH₄ into various products or less harmful gas at low-temperature. Although the inert nature of CH bonds requires high dissociation energy at high temperatures, the efforts of researchers have demonstrated the feasibility of catalysts to activate CH₄ at low temperatures. In this review, the efficient catalysts designed to reduce the CH₄ oxidation temperature and improve conversion efficiencies are described. First, noble metals and transition metal-based catalysts are summarized for activating CH₄ in temperatures ranging from 50 to 500 °C. After that, the partial oxidation of CH₄ at relatively low temperatures, including thermocatalysis in the liquid phase, photocatalysis, electrocatalysis, and nonthermal plasma technologies, is briefly discussed. Finally, the challenges and perspectives are presented to provide a systematic guideline for designing and synthesizing the highly efficient catalysts in the complete/partial oxidation of CH₄ at low temperatures.

Keywords: CH bond activation; low-temperature; methane activation; noble metal-based catalysts; transition metal-based catalysts.

Figure 1

A summary of methods and technologies for catalytic CH₄ oxidation at low temperatures.

Figure 2

Supports for Pd‐based catalysts for CH₄ oxidation at low temperatures.

Figure 3

a) TOFs versus CH₄‐TPR peak temperature for 7 nm Pd supported on different metal oxides. Reproduced with permission.^{[ 49 ]} Copyright 2020, American Chemistry Society. b) CH₄ oxidation performance per total Pd molar at 350 °C. Reproduced with permission.^{[ 50 ]} Copyright 2020, American Chemistry Society. Temperature‐dependent of CH₄ combustion over various catalysts. c) Pd/NA‐Al₂O₃. Reproduced under the terms of the Creative Commons Attribution 4.0 International License.^{[ 33 ]} Copyright 2022, The Authors, published by Springer Nature. d) Pd/Al₂O₃ after steam (600 °C), O₂–H₂, and CO–O₂–H₂ pretreatments. Reproduced with permission.^{[ 57 ]} Copyright 2021, AAAS. e) Cross‐linked assembly Pd active phases stabilized by NA‐Al₂O₃ at 1000 °C in the air. Reproduced under the terms of the Creative Commons Attribution 4.0 International License.^{[ 33 ]} Copyright 2022, The Authors, published by Springer Nature.

Figure 4

Structures and morphologies of the CeO₂ and Co₃O₄ supports. a–c) Low‐magnification HADDF–STEM images of CeO₂‐oct (111), CeO₂‐cube (100), and CeO₂‐rod. d–f) Atomic structure of CeO₂‐oct (111), CeO₂‐cube (100), and CeO₂‐rod. Reproduced with permission.^{[ 71 ]} Copyright 2021, American Chemistry Society. g) TEM of Co₃O₄‐C, SEM of h) Co₃O₄‐F, i) Co₃O₄‐P, and j) Co₃O₄‐R. Reproduced with permission.^{[ 85 ]} Copyright 2017, Elsevier. TEM images of k) Co₃O₄, l) Pd–Co₃O₄, m) Pd/Co₃O₄, and n) Pd@Co₃O₄ catalysts. PdO particle size distributions of o) Pd–Co₃O₄, p) Pd/Co₃O_4, and q) Pd@Co₃O₄ catalysts. Reproduced with permission.^{[ 88 ]} Copyright 2021, Elsevier.

Figure 5

XPS a) Zr 3d spectra and b) O 1s spectra of the different. Reproduced with permission.^{[ 91 ]} Copyright 2019, Elsevier. c) Change in the catalytic activity of the Pd/ZrO₂(x) in the CH₄ oxidation reaction with time on stream in 10 vol% water vapors at 500. d) Reduction characteristics of the Pd/ZrO₂ catalysts as exhibited by CH₄‐TPR. Reproduced with permission.^{[ 93 ]} Copyright 2018, Elsevier.

Figure 6

CH₄ conversion as a function of temperature over a) Pd/CZ catalysts. Reproduced with permission.^{[ 45 ]} Copyright 2021, Elsevier. b) 0.23 wt% Pd/SiO₂–ZrO₂ catalyst and the 0.23 wt% Pd/ZrO₂ catalyst. Reproduced with permission.^{[ 111 ]} Copyright 2017, Royal Society of Chemistry. c) PdO/Co₃O₄ before and after coating CeO₂. Reproduced with permission.^{[ 132 ]} Copyright 2019, Wiley‐VCH. d) CH₄ conversion over Co₂NiO₄ and Pd–Co₂NiO₄ catalysts. Reproduced with permission.^{[ 134 ]} Copyright 2021, Elsevier. e) Reaction mechanism of PdO/Co₃O₄ and PdO/CeO₂‐x/Co₃O₄ toward catalytic CH₄ combustion. Reproduced with permission.^{[ 132 ]} Copyright 2019, Wiley‐VCH.

Figure 7

a) Illustration of the 1.0Pd/mod‐HfO₂ synthesis process, b) proposed mechanism for the oxidation of CH₄ over 1.0Pd/mod‐HfO₂. Reproduced with permission.^{[ 135 ]} Copyright 2020, American Chemistry Society. c) Galvanic deposition procedure. Reproduced with permission.^{[ 147 ]} Copyright 2020, Royal Society of Chemistry. d) Proposed mechanism for CH₄ oxidation over Co₂MnO₄ and Pd–Co₂MnO₄ catalysts. Reproduced with permission.^{[ 145 ]} Copyright 2020, Elsevier. e) The proposed reaction pathway over the GD‐Pd/ NiCo₂O₄ catalyst. Reproduced with permission.^{[ 147 ]} Copyright 2020, Royal Society of Chemistry.

Figure 8

CH₄ combustion over a) catalyst prepared on different zeolite supports. Reproduced with permission.^{[ 167 ]} Copyright 2020, Royal Society of Chemistry. b) H‐ZSM‐5 and Pd‐containing MFI zeolites. Reaction conditions: 1% CH₄, 5% O₂, He balance, GHSV = 60 000 h⁻¹. Reproduced with permission.^{[ 186 ]} Copyright 2021, Elsevier. c) Pd/Al₂O₃ and various Pd/mordenite catalysts, and d) 65 h stability test without regeneration. Reproduced under the terms of the Creative Commons Attribution 4.0 International License.^{[ 163 ]} Copyright 2018, The Authors, published by Springer Nature.

Figure 9

a) The activity and b) stability test of various catalysts in wet condition. Reproduced with permission.^{[ 197 ]} Copyright 2021, Elsevier. c) T₅₀ and T₉₀ of CH₄ combustion over Pd(0.5)Co(x)/BEA, Co(1.0)/ BEA, and Pd(1.0)/BEA catalysts. d) Arrhenius plot and apparent activation energies for CH₄ combustion over Pd(0.5)Co(x)/BEA and Pd(1.0)/BEA catalysts. e) Structures of Co/BEA and Pd/BEA. Reproduced with permission.^{[ 198 ]} Copyright 2021, American Chemistry.

Figure 10

a) The preparation process for Pd/HAP catalysts using an ion‐exchange period of 5, 10, and 20 h. b) CH₄ conversion over the different Pd/HAP catalysts, c) resistance of Pd/HAP‐5 toward 5 vol% CO₂ and 5 vol% H₂O or 7 vol% H₂O in CH₄ combustion at 450 °C. Reproduced with permission.^{[ 202 ]} Copyright 2020, Elsevier. d) Proposed scheme for Pd species distribution. Reproduced with permission.^{[ 203 ]} Copyright 2020, Elsevier.

Figure 11

a) Performance indicators and b) stability measurement at 350 °C for Pd‐supported on HNTs catalysts. Reproduced with permission.^{[ 206 ]} Copyright 2021, Elsevier. c) Synthesis of Pd/HNTs‐600‐CTAB catalyst with Pd nanoparticles inside the tube, d) CH₄ combustion over different catalysts, and e) stability tests with and without H₂O. Reproduced with permission.^{[ 207 ]} Copyright 2020, American Chemistry Society.

Figure 12

CH₄ conversion as a function of time on stream over a) Pd–Pt/Al₂O₃ and b) Pt–Pt/CZ in the presence of 12% H₂O and 5 ppm SO₂. Reproduced with permission.^{[ 225 ]} Copyright 2020, Elsevier. c) AC‐STEM images of 2Pt@CeO₂ synthesized through atom trapping showing single atoms of Pt. d) AC‐STEM image of Pd deposited on 2Pt@CeO₂ ((1Pd/2Pt@CeO₂), e) light‐off curves of CH₄ oxidation without water vapor over different catalysts, f) comparison of different catalysts for CH₄ combustion at 500 °C in 4% H₂O demonstrating the outstanding ability of 1Pd/2Pt@CeO₂ in wet conditions. Reproduced with permission.^{[ 221 ]} Copyright 2021, Springer Nature.

Figure 13

CH₄ conversion on a) 2 wt% Rh/ZSM‐5 and b) 2 wt% Pd/ZSM‐5 under CH₄ + O₂ (red), CH₄ + O₂ + H₂O (blue), CH₄ + O₂ + SO₂ (green), and CH₄ + O₂ + H₂O + SO₂ (black) conditions. (2500 ppm CH₄, 10 vol% O₂, 5 vol% H₂O, 20 ppm SO₂, and N₂. GHSV = 150 000 N mL (g_cat h)⁻¹. Reproduced with permission.^{[ 235 ]} Copyright 2020, American Chemistry Society. c) Au–Pd–3.61CoO/3DOM as a reaction time in the absence or presence of 5.0 vol% water vapor at 340 °C and d) Au–Pd–3.61CoO/3DOM as a function of the reaction time in the presence of different water vapor. Reproduced with permission.^{[ 251 ]} Copyright 2017, American Chemistry Society.

Figure 14

a) H₂‐TPR and b) O₂‐TPD patterns of Co₃O₄ catalysts synthesized with different cobalt precursors. Reproduced under the terms of the Creative Commons CC‐BY license.^{[ 268 ]} Copyright 2020, Royal Society of Chemistry. c) Arrhenius plots. Reproduced with permission.^{[ 270 ]} Copyright 2021, Royal Society of Chemistry. d) Catalytic activity in CH₄ oxidation as a function of the reaction temperature. Reproduced with permission.^{[ 277 ]} Copyright 2019, Elsevier.

Figure 15

a) Ni/Co oxides prepared with varying Ni/Co ratios. Reproduced with permission.^{[ 287 ]} Copyright 2019, Wiley‐VCH. b) Ni/Co with different Ni atomic fractions. Reproduced with permission.^{[ 290 ]} Copyright 2015, Springer Nature. c) Synthesis diagram of the Co–In‐x nanoparticles via a modified precipitation method. d) Cyclic and long‐term stability tests over Co₃O₄ and Co–In‐0.2 catalyst under 5 vol% moisture conditions. Reproduced with permission.^{[ 289 ]} Copyright 2020, American Chemistry Society. e) Co–Ce–O composite oxide catalysts. Reproduced with permission.^{[ 294 ]} Copyright 2016, Elsevier. f) Energy barriers for the activation of the first C—H bond in CH₄ on different surfaces. Reproduced with permission.^{[ 274 ]} Copyright 2020, Elsevier.

Figure 16

TEM images of a) α‐MnO₂, b) β‐MnO₂, c) Meso‐MnO₂, and d) α‐Mn₂O₃. Structural depictions of e) α‐MnO₂, f) β‐MnO₂, g) Meso‐MnO₂, and h) α‐Mn₂O₃. i) CH₄ oxidation as a function of temperature and j) effect of 9.5 vol% H₂O and 10%CO₂ on CH₄ oxidation at 475 °C in α‐MnO₂. Reproduced with permission.^{[ 297 ]} Copyright 2018, Elsevier. k) Catalytic stability over the BaO–MnO _x catalysts with various Ba contents at 450 °C and l) the effect of H₂O over the BaO(10)–MnO _x catalyst calcined at 500 °C for CH₄ stability. Reproduced with permission.^{[ 303 ]} Copyright 2021, Elsevier.

Figure 17

a) Stability tests of NiO NPs and NiO‐SPP with TEM images after the tests. Scale bar: 50 nm. (reaction temperature 500 °C; 0.2% CH₄, 15% H₂O, and 1 ppm of SO₂. Reproduced with permission.^{[ 309 ]} Copyright 2021, American Chemistry Society. The relation between the CH₄ conversion rates (reaction at 280 °C) over Ni1– xZr _x O₂–δ nanocatalysts with desorbed the amount of b) NH₃ and c) CO₂. Reproduced with permission.^{[ 323 ]} Copyright 2021, American Chemistry Society.

Figure 18

a) The effects of reaction time on CH₄ conversion (Conv.), CH₃OH selectivity (Sel.), CH₃OH productivity (Prod.), and H₂O₂ concentration in water solution over AuPd@ZSM‐5 catalysts. Reproduced with permission.^{[ 340 ]} Copyright 2020, AAAS. b) Activation free energies ΔG′ = of C—H bond breaking of CH₄ and CH₃OH. Reproduced with permission.^{[ 367 ]} Copyright 2021, Elsevier. c) Reaction pathway of direct CH₄ to CH₃OH using H₂O₂ (a) or O₂/H₂ mixture gases oxidants. Reproduced with permission.^{[ 371 ]} Copyright 2020, Elsevier. d) Proposed mechanism for CH₄ oxidation in the presence of H₂O₂ and molecular O₂. Reproduced with permission.^{[ 369 ]} Copyright 2017, AAAS.

Figure 19

a) Time course of product yields under simulated sunlight irradiation with 0.1 wt% Au/ZnO at room temperature, light source: solar simulator (AM 1.5G), and light intensity 100 mW cm⁻². Reproduced with permission.^{[ 382 ]} Copyright 2019, American Chemistry Society. Methanol yields b) for a series of metal‐modified TiO₂ samples after 3 h of full arc irradiation. Reproduced with permission.^{[ 389 ]} Copyright 2018, Springer Nature. c) Reaction mechanism for photooxidation of CH₄ using quantum‐sized bismuth vanadate. Reproduced with permission.^{[ 396 ]} Copyright 2021, Springer Nature. d) Schematic of a Cu–single‐atom Ru surface alloy catalyst with the dry reforming reactants and products shown on the left. e) CH₄ conversion by photocatalysis (blue) and thermocatalysis (red). Filled and unfilled circles are two different batches of measurements, while dashed and solid lines are visual guides. Reproduced with permission.^{[ 400 ]} Copyright 2020, Springer Nature.

Figure 20

a) CH₄ electrochemical oxidation by ZrO₂:CuO _x hybrid catalyst. Reproduced with permission.^{[ 422 ]} Copyright 2020, Elsevier. b) MS for CH₃OH from an electrolyte containing ¹⁸CO₃ ²⁻ (top panel). The CH₃OH contains ¹⁸O and ¹⁶O calculated as 38% and 62%, respectively. Typical MS for CH₃OH (bottom panel). Reproduced with permission.^{[ 426 ]} Copyright 2021, American Chemistry Society. c) The structural information of the catalyst and a proposed mechanism d) a potential energy surface.^{[ 418 ]} e) Illustration of electrooxidation of CH₄ to ethanol and methanol on the NiO/Ni interface at ambient temperature. Reproduced with permission.^{[ 415 ]} Copyright 2018, American Chemistry Society.

Figure 21

DBD system showing reaction between CH₄ and H₂O for methanol production. Reproduced under the terms of the Creative Commons Attribution 4.0 International License.^{[ 440 ]} Copyright 2022, The Authors, published by Springer Nature. Effect of DBD packing on b) CH₄ conversions. Reproduced with permission.^{[ 444 ]} Copyright 2016, American Chemistry Society. c) On energy efficiency and CH₄. d) Principal reaction routes in plasma‐aided catalytic DRM. Products are depicted in black (or green), whereas intermediates are indicated in gray. The color of metastable Ar is blue. Reproduced with permission.^{[ 456 ]} Copyright 2020, Elsevier. e) Proposed mechanistic pathways for the production of methanol using plasma on the Fe/γ‐Al₂O₃ surface. Reproduced with permission.^{[ 458 ]} Copyright 2021, Elsevier.