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For the conversion of CO 2 into fuels and chemical feedstocks, hybrid gas/liquid-fed electrochemical flow reactors provide advantages in selectivity and production rates over traditional liquid phase reactors. However, fundamental questions remain about how to optimize conditions to produce desired products. Using an alkaline electrolyte to suppress hydrogen formation and a gas diffusion electrode catalyst composed of copper nanoparticles on carbon nanospikes, we investigate how hydrocarbon product selectivity in the CO 2 reduction reaction in hybrid reactors depends on three experimentally controllable parameters: (1) supply of dry or humidified CO 2 gas, (2) applied potential, and (3) electrolyte temperature. Changing from dry to humidified CO 2 dramatically alters product selectivity from C 2 products ethanol and acetic acid to ethylene and C 1 products formic acid and methane. Water vapor evidently influences product selectivity of reactions that occur on the gas-facing side of the catalyst by adding a source of protons that alters reaction pathways and intermediates.
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Pt3Mn/SiO2 + ZSM-5 Bifunctional Catalyst for Ethane Dehydroaromatization
Ethane dehydroaromatization (EDA) is a potentially attractive process for converting ethane to valuable aromatics such as benzene, toluene, and xylene (BTX). In this study, a Pt3Mn/SiO2 + ZSM-5 bifunctional catalyst was used to investigate the effect of dehydrogenation and the Brønsted acid catalyst ratio, hydrogen partial pressure, and reaction temperature on the product distributions for EDA. Pt3Mn/SiO2 + ZSM-5 with a 1/1 weight ratio showed the highest ethane conversion rate and BTX formation rate. Ethylene is initially formed by dehydrogenation by the Pt3Mn catalyst, which undergoes secondary reactions on ZSM-5, forming C3+ reaction intermediates. The latter form final products of CH4 and BTX. At conversions from 15 to 30%, the BTX selectivities are 82–90%. For all bifunctional catalysts, the ethane conversion significantly exceeds the ethane–ethylene equilibrium conversion due to reaction to secondary products. Low H2 partial pressures did not significantly alter the product selectivity or conversion. However, higher H2 partial pressures resulted in increased methane and decreased BTX selectivity. The excess hydrogen saturated the olefin intermediates to form alkanes, which produced methane by monomolecular cracking on ZSM-5. With an increasing reaction temperature from 550 °C to 650 °C, the benzene selectivity increased, while the highest BTX selectivity was obtained at 600 to 650 °C.
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- Award ID(s):
- 2045013
- PAR ID:
- 10667914
- Publisher / Repository:
- Catalysts
- Date Published:
- Journal Name:
- Catalysts
- Volume:
- 14
- Issue:
- 6
- ISSN:
- 2073-4344
- Page Range / eLocation ID:
- 365
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.3390/catal14060365
