Plasma-Catalytic Reforming of Naphthalene and Toluene as Biomass Tar over Honeycomb Catalysts in a Gliding Arc Reactor

Abstract

Biomass gasification is a promising and sustainable process to produce renewable and CO 2 -neutral syngas (H 2 and CO). However, the contamination of syngas with tar is one of the major challenges to limit the deployment of biomass gasification on a commercial scale. Here, we propose a hybrid plasma-catalytic system for steam reforming of tar compounds over honeycomb-based catalysts in a gliding arc discharge (GAD) reactor. The reaction performances were evaluated using the blank substrate and coated catalytic materials (γ-Al 2 O 3 and Ni/γ-Al 2 O 3 ). Compared with the plasma alone process, introducing the honeycomb materials in GAD prolonged the residence time of reactant molecules for collision with plasma reactive species to promote their conversions. The presence of Ni/γ-Al 2 O 3 gave the best performance with the high conversion of toluene (86.3%) and naphthalene (75.5%) and yield of H 2 (35.0%) and CO (49.1%), while greatly inhibiting the formation of byproducts. The corresponding highest overall energy efficiency of 50.9 g/kWh was achieved, which was 35.4% higher than that in the plasma alone process. Characterization of the used catalyst and long-term running indicated that the honeycomb material coated with Ni/γ-Al 2 O 3 had strong carbon resistance and excellent stability. The superior catalytic performance of Ni/γ-Al 2 O 3 can be mainly ascribed to the large specific surface area and the in situ reduction of nickel oxide species in the reaction process, which promoted the interaction between plasma reactive species and catalysts and generated the plasma-catalysis synergy.

Tar Formation in Gasification Systems: A Holistic Review of Remediation Approaches and Removal Methods

“…In recent times, plasma combined with catalysts (plasma catalysis) has also been explored for tar reduction to get a synergetic effect. The integration of nonthermal plasma and catalysts can enhance the overall efficiency and effectiveness of tar removal. ,,,,,,,− On one hand, plasma can aid the regeneration of catalysts, increasing the life span of the catalysts . On the other hand, the catalyst can provide selective tar decomposition, since plasma is nonselective in treating the tar compounds because it can collide and react with any chemical species. ,, Plasma catalysis can support lowering the operating temperatures, leading to energy savings, and reduced operational costs. , Further research and development efforts are needed to optimize the combination of these technologies, including catalyst selection, plasma reactor design, and operating conditions, to maximize the synergistic benefits and enhance the overall efficiency of removal of tar from gasification-derived syngas.…”

“…The integration of nonthermal plasma and catalysts can enhance the overall efficiency and effectiveness of tar removal. ,,,,,,,− On one hand, plasma can aid the regeneration of catalysts, increasing the life span of the catalysts . On the other hand, the catalyst can provide selective tar decomposition, since plasma is nonselective in treating the tar compounds because it can collide and react with any chemical species. ,, Plasma catalysis can support lowering the operating temperatures, leading to energy savings, and reduced operational costs. , Further research and development efforts are needed to optimize the combination of these technologies, including catalyst selection, plasma reactor design, and operating conditions, to maximize the synergistic benefits and enhance the overall efficiency of removal of tar from gasification-derived syngas. Typical plasma sources attempted for tar destruction include corona, dielectric barrier discharge, gliding arc, and spark/glow discharge, including microwave and radio frequency discharge systems, which are considered as nonthermal plasmas. ,,, Tar resulting from gasification consists of a blend of aromatic compounds.…”

Plasma Catalysis for Hydrogen Production: A Bright Future for Decarbonization

“…This improved performance was attributed to the improved reducibility of the Ni/Co alloy, which led to better reactant conversion and minimized the formation of byproducts . More recently, the same research group explored the use of a honeycomb material comprising a blank substrate and a coated catalyst material (γ-Al 2 O 3 and Ni/γ-Al 2 O 3 ) for converting the mixed biomass tar (naphthalene and toluene) in a GAD plasma reactor . A higher energy yield of 50.9 g/kWh and better catalyst stability against coke deposition was obtained .…”

Plasma catalytic technology for CH4 and CO2 conversion: A review highlighting fluidized‐bed plasma reactor

“…The interaction flux of the plasma can be enhanced to some extent via reactor miniaturization (Figure 4b) [65,69] and rotating GAD (Figure 4c) [70][71][72] . Honeycomb catalysts are also coupled with GAD discharge to strengthen the plasma-catalyst interaction (Figure 4d) [66,73] . However, a large proportion of plasma may not interact with the catalyst because of PPC; gas-phase reactions dominate the reaction path in most cases, as demonstrated by Zhu et al [70] and Lin et al [74] .…”

“…(a) Catalyst‐free two‐dimensional gliding arc discharge (GAD) (reproduced with permission [ 64 ] , Copyright 2020, Elsevier), (b) alternate current (AC) microsized GAD (reproduced with permission [ 65 ] , Copyright 2009, Elsevier), (c) rotating GAD (reproduced with permission [ 62 ] , Copyright 2021, Elsevier), and (d) GAD combined with honeycomb catalyst (reproduced with permission [ 66 ] , Copyright 2022, ACS Publications). RGA, rotating gliding arc.…”