Influence of Different Birnessite Interlayer Alkali Cations on Catalytic Oxidation of Soot and Light Hydrocarbons

Tomasz Jakubek,Camillo Hudy,Andrzej Kotarba,Stan Golunski,Paweł Stelmachowski,Ewa Nowicka

doi:10.3390/catal10050507

Tomasz Jakubek, Camillo Hudy + Show 4 more

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https://doi.org/10.3390/catal10050507

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Abstract

A series of layered birnessite (AMn4O8) catalysts containing different alkali cations (A = H+, Li+, Na+, K+, Rb+, or Cs+) was synthesized. The materials were thoroughly characterized using X-ray diffraction, X-ray fluorescence, X-ray photoelectron spectroscopy, Raman spectroscopy, specific surface area analysis, work function, thermogravimetry/differential scanning calorimetry, and transmission electron microscopy. The catalytic activity in soot combustion in different reaction modes was investigated (tight contact, loose contact, loose contact with NO addition). The activity in the oxidation of light hydrocarbons was evaluated by tests with methane and propane. The obtained results revealed that alkali-promoted manganese oxides are highly catalytically active in oxidative reactions. In soot combustion, the reaction temperature window was shifted by 195 °C, 205 °C, and 90 °C in tight, loose + NO, and loose contact conditions against uncatalyzed oxidation, respectively. The catalysts were similarly active in hydrocarbon combustion, achieving a 40% methane conversion at 600 °C and a total propane conversion at ~450 °C. It was illustrated that the difference in activity between tight and loose contacts can be successfully bridged in the presence of NO due to its facile transformation into NO2 over birnessite. The particular activity of birnessite with H+ cations paves the road for the further development of the active phase, aiming at alternative catalytic systems for efficient soot, light hydrocarbons, and volatile organic compounds removal in the conditions present in combustion engine exhaust gases.

Highlights

Carbon-derived fuels play a major role in energy conversion applications, despite current efforts to replace them with more sustainable sources
The examination of the patterns reveals the pureness of the prepared materials, as no other reflexes, apart from those assignable diffraction patterns reveals the pureness of the prepared materials, as no other reflexes, apart from to birnessite, are present
The 2Θ value of this reflex determines the separation of the layers phase, which is influenced by the introduced alkali cations

Summary

Introduction

Carbon-derived fuels play a major role in energy conversion applications, despite current efforts to replace them with more sustainable sources They are used both in the energy and transportation sectors, where pyrolysis or the incomplete combustion of carbon-based fuels occurs regularly, leading to the emission of cancerogenic and mutagenic pollutants. Among these are soot, light hydrocarbons (methane, propane), volatile organic compounds (VOCs), and polyaromatic hydrocarbons (PAH), which are associated with the formation of smog and are harmful to human welfare [1,2,3,4]. Long-term exposure to soot particles can lead to many illnesses, including cancero illnesses, including cancero and mutagenic changes or lung and heart problems [5,6,7]. The materials’ reactivity towards VOCs oxidation can be gauged by VOCs oxidation can be gauged by testing catalysts in the combustion of light hydrocarbons, as they testing catalysts in the combustion of light hydrocarbons, as they are thermodynamically more stable are thermodynamically more stable and more difficult to activate

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