Work

Effects of Acetylene and Hydrogen Cofeeding in Microwave Plasma Methane Pyrolysis

Year: 2026

Type: article

Abstract: High Resolution Image Download MS PowerPoint Slide Methane pyrolysis offers low-carbon hydrogen production by decomposing CH 4 into H 2 and solid carbon. However, the formation of stable hydrocarbon intermediates, particularly acetylene (C 2 H 2 ), can limit the overall conversion efficiency and associated carbon-emission benefits. In this work, C 2 H 2 cofeeding and combined C 2 H 2 and H 2 cofeeding were investigated in a microwave plasma reactor to emulate product recirculation and evaluate their impact on process performance and carbon formation. Experiments were conducted over microwave powers of 1.1–2.5 kW with C 2 H 2 feed fractions ranging from 0 to 100%. Three distinct operational regimes were identified based on normalized energy input (NEI). At low NEI (<1), H 2 selectivity remained constant up to 50% C 2 H 2 before decreasing sharply due to preferential CH 4 decomposition. At high NEI (>2), efficient conversion of both species was measured, resulting in a linear decrease in H 2 selectivity with increasing C 2 H 2 fraction. Intermediate NEI values (1–1.8) exhibited transitional behavior, characterized by a gradual selectivity decay beyond 20% C 2 H 2 . Combined C 2 H 2 and H 2 cofeeding reduced total hydrocarbon conversion by up to 20 percentage points and decreased H 2 selectivity while increasing C 2 H 4 selectivity to as high as 23%, consistent with equilibrium shifts favoring reverse reactions. Carbon characteristics were strongly influenced by cofeeding. C 2 H 2 addition increased primary particle sizes from 50–70 nm to 100–200 nm, while combined C 2 H 2 and H 2 cofeeding yielded particles as large as 0.5–1 μm. Surface areas increased from ∼100 m 2 /g to 400–550 m 2 /g with C 2 H 2, accompanied by an increase in microporosity. While cofeeding does not improve the overall reactivity, C 2 H 2 incorporation enables tunable carbon morphology and porosity, offering pathways to produce amorphous carbon with varying properties within a single reactor system.

Source: Energy & Fuels

DOI: 10.1021/acs.energyfuels.6c00877

Authors: Gregory G. Facas, Ilva Lazdiņa, Nora Schüller, Paweł P. Ziemiański, Panayotis Dimopoulos Eggenschwiler

Institutions: Swiss Federal Laboratories for Materials Science and Technology, Paul Scherrer Institute

Language: English

Topic: Catalysts for Methane Reforming

Subfield: Catalysis

Field: Chemical Engineering

Domain: Physical Sciences

SDGs: Affordable and clean energy, Climate action

Open Access status: hybrid

Estimated APC paid: $4,500