Pd/CeO₂ Catalysts Prepared by Solvent-free Mechanochemical Route for Methane Abatement in Natural Gas Fueled Vehicles

Abstract

The increasing diffusion of alternative mobility solutions, ranging from electric technologies to natural gas fueled vehicles (NGVs), has led to a progressive life-cycle analysis approach of their environmental impact in terms of greenhouse gases (GHGs) emissions. This new approach prompted a careful design of the NGVs catalytic aftertreatment system in order to minimize the catalytic converter carbon footprint as well as the unburned methane emissions at tailpipe. Here, a series of Pd/CeO2 methane oxidation catalysts were prepared by an environmentally friendly solvent-free method and compared to the commercial wet-synthesized state-of-the-art catalysts. Their application in NGVs aftertreatment systems was evaluated by testing powder catalysts and coated monolith cores for CH4 oxidation and steam reforming, which are the main methane abatement reactions occurring in a three-way catalyst (TWC) under lean and rich conditions, respectively. Pd/CeO2 catalysts prepared by mechanochemical synthesis initially displayed superior activity compared to their counterpart obtained by conventional wet impregnation, especially under lean oxidation conditions, but appeared less resistant to the industrial aging process after core washcoating. Lambda sweep experiments carried out under full gas composition proved that, despite needing further optimization in the washcoating and aging processes, the developed mild milling synthesis procedure is a viable way for the production of Pd/CeO2 based catalysts for natural gas TWCs.

The Dehydrogenation of H‐S Bond into Sulfur Species on Supported Pd Single Atoms Allows Highly Selective and Sensitive Hydrogen Sulfide Detection

“…The supported metal catalysts in heterogenous catalysis [ 1,2 ] have always been the focus of research in many fields, such as petrochemical industry, [ 3,4 ] energy storage and conversion, [ 5,6 ] gas sensors, [ 7–10 ] abatement of emissions, [ 11,12 ] etc. Specially, the catalytic behavior of supported metal catalysts is highly dependent on their shapes, sizes, constituent, as well as metal‐support interaction.…”

Decoupling the Chemical and Mechanical Strain Effect on Steering the CO2 Activation over CeO2-Based Oxides: An Experimental and DFT Approach

“…For the continuous stirred-tank reactor (CSTR) behavior considered in this study, the transient rates (μmol/g s) of 16 O 18 O­(g) (eq ) and 16 O 2 (g) (eq ) formation were calculated …”

“…In eqs and , F T is the total molar flow rate (mol/s) of the feed gas stream, y 16 O 18 O , y 16 O 2 , and y Kr are the mole fractions of 16 O 18 O, 16 O 2 , and Kr at the outlet of the CSTR microreactor, respectively, N T is the total number of moles in the CSTR reactor, and W is the sample’s mass (20 mg) . The total rate of 16 O exchange with 18 O and R ( 16 O) (mol 16 O g –1 s –1 ) and the transient evolution of the amount of 16 O and N ( 16 O) (mol 16 O g –1 ) were estimated based on 16 O-material balance eqs and where Z i is the dimensionless response of gaseous species i , y i is the mole fraction of gaseous species i , y ( 16 O 2 ) ( t = 0) is the mole fraction before the step-gas switch (2 vol %), and y f ( 16 O 18 O) is the mole fraction of 16 O 18 O­(g) present in the 2 mol % 18 O 2 /Ar/He feed gas mixture used …”

“…For instance, in the preparation of ceria-based catalysts, the latter used for environmental and energy applications has been reported in many review articles using mechanochemical methods . Demonstration of the superiority of Pd/CeO 2 ball-milled catalysts for the methane oxidation reaction at low temperature, above 95% conversion, over the traditional wet impregnation catalysts has been discussed by Trovarelli’s research group even at conditions which are challenging for the particular reaction. , Furthermore, there is extensive literature on the impact of different types of external stimuli on thin films of ceria; for example, the electrochemomechanical effect has been reported by Lubomirsky and his colleagues , to produce stress that can potentially deteriorate them. , Furthermore, strain engineering has been reported to increase the CT and electronic conductivity . However, the effect of applying compressive or tensile stress on doped ternary ceria (111) surfaces has not being comprehensively investigated in the literature yet in the context of steering of its catalytic chemistry and adsorption behavior.…”

Preparation and electrochemical inhibition properties of Ce3+-photomodified zinc phosphate materials

“…[18][19][20] Cerium has been more widely reported as a corrosion inhibitor and is very effective in the protection of magnesium-aluminum alloys. [21][22][23] This is attributed to its ability to produce stable cerium oxide and cerium hydroxide that blocks the cathodic reaction site, thereby reducing the corrosion reaction rate. 24,25 The combined action of cerium and organophosphates has been proposed, and tris(bis(2-ethylhexyl)) cerium phosphate, 26 dibutyl cerium a Key Laboratory for Advanced Materials, School of Chemistry and Molecular phosphate, 27 and dibutyl cerium phosphate 28 have been shown to have significant effects in inhibiting corrosion of aluminum alloys.…”