Plasma Catalytic Conversion of CH4 to Alkanes, Olefins and H2 in a Packed Bed DBD Reactor

Mohammadreza Taheraslani,Han Gardeniers

doi:10.3390/pr8070774

Abstract

Methane is activated at ambient conditions in a dielectric barrier discharge (DBD) plasma reactor packed with Pd/γ-alumina catalyst containing different loadings of Pd (0.5, 1, 5 wt%). Results indicate that the presence of Pd on γ-alumina substantially abates the formation of deposits, leads to a notable increase in the production of alkanes and olefins and additionally improves the energy efficiency compared to those obtained for the non-packed reactor and the bare γ-alumina packed reactor. A low amount of Pd (0.5 and 1 wt%) favors achieving a higher production of olefins (mainly C2H4 and C3H6) and a higher yield of H2. Increasing Pd loading to 5 wt% promotes the interaction of H2 and olefins, which consequently intensifies the successive hydrogenation of unsaturated compounds, thus incurring a higher production of alkanes (mainly C2H6 and C3H8). The substantial abatement of the deposits is ascribed to the role of Palladium in moderating the strength of the electric and shifting the reaction pathways, in the way that hydrogenation reactions of deposits’ precursors become faster than their deposition on the catalyst.

Highlights

Non-thermal plasma techniques have extensively been employed for the production of value-added products, including hydrogen, hydrocarbons, oxygenates and aromatics, at ambient conditions [1]
The plasma provides the required energy for activation of the stable molecule by breaking the bond (e.g., C-H for methane activation) and generates a pool of radicals, which can react with the catalyst, as the medium that is capable of conducting the interaction among radicals, selectively shifting reaction pathways towards more value-added products
Plasma generates CHx fragments and H radicals, for which their successive recombination and interactions lead to the formation of higher hydrocarbons and hydrogen, while deposits form as the by-product

Summary

Introduction

Non-thermal plasma techniques have extensively been employed for the production of value-added products, including hydrogen, hydrocarbons, oxygenates (e.g., methanol) and aromatics, at ambient conditions [1]. In a plasma–catalyst hybrid system, reactive plasma species (e.g., radicals) can interact with the catalyst, which can influence the reaction pathways and the selectivity of the desired products [3,4,5,6,7,8,9,10,11,12,13]. The plasma provides the required energy for activation of the stable molecule by breaking the bond (e.g., C-H for methane activation) and generates a pool of radicals, which can react with the catalyst, as the medium that is capable of conducting the interaction among radicals, selectively shifting reaction pathways towards more value-added products. Several catalyst-supports, such as alumina, silica and titania [7,14,15], with or without metals, such as Pt, Ni, Cu and Ru, were utilized for conversion of methane via a non-oxidative route in combination with dielectric barrier discharge (DBD) plasma

Methods

Results

Conclusion