Abstract
Carbon dioxide (CO2) hydrogenation to value-added molecules is an attractive way to reduce CO2 emission via upgrading. Herein, non-thermal plasma (NTP) activated CO2 hydrogenation over Ru/MgAl layered double hydroxide (LDH) catalysts was performed. The catalysis under the NTP conditions enabled significantly higher CO2 conversions (∼85 %) and CH4 yield (∼84 %) at relatively low temperatures compared with the conventional thermally activated catalysis. Regarding the catalyst preparation, it was found that the reduction temperature can affect the chemical state of the metal and metal-support interaction significantly, and thus altering the activity of the catalysts in NTP-driven catalytic CO2 hydrogenation. A kinetic study revealed that the NTP-catalysis has a lower activation energy (at ∼21 kJ mol−1) than that of the thermal catalysis (ca. 82 kJ mol−1), due to the alternative pathways enabled by NTP, which was confirmed by the comparative in situ diffuse reflectance infrared Fourier (DRIFTS) coupled with mass spectrometry (MS) characterisation of the catalytic systems.
Highlights
Catalytic hydrogenation of carbon dioxide (CO2) is an appealing way to produce fuels and chemical building blocks such as methane (CH4) and methanol
The performance of the 2.5 % Ru/MgAl catalysts in non-thermal plasma (NTP)-activated CO2 hydrogenation was studied in reference to the control experiments
The hybrid NTP-catalyst system for CO2 hydrogenation has been investigated in a dielectric-barrier-discharge (DBD) reactor combined with Ru supported on the MgAl layered double hydroxide (LDH) catalysts, in which 85 % CO2 conversion and 84 % CH4 yield can be achieved at 6.5 kV
Summary
Catalytic hydrogenation of carbon dioxide (CO2) is an appealing way to produce fuels and chemical building blocks such as methane (CH4) and methanol. Non-thermal plasma (NTP) dissociates and activates gaseous species to produce a variety of active electrons, ions and radicals, being able to participate in surface reactions over a catalyst under relatively mild conditions (i.e. atmospheric pressure and low bulk temperatures < ∼200 °C) compared to the conventional thermally activated catalysis [11,12]. NTP-assisted catalytic CO2 hydrogenation over Ni/Al2O3 catalysts has been demonstrated, in which the conversion of CO2 was improved significantly (by 60 % compared to the NTP-promoted gas-phase reactions) at ∼150 °C [16]. NTP-catalysis systems were investigated in situ using a combined DRIFTS-mass spectrometry (MS), in which the dynamics of surface species during the NTP-activated CO2 hydrogenation provide useful information to allow the development of reaction mechanism of the system under study
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