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Alkali Promotion in the Formation of CH 4 from CO 2 and Renewably Produced H 2 over Supported Ni Catalysts
Author(s) -
Vogt Charlotte,
Wijten Jochem,
Madeira Chantal Leal,
Kerkenaar Oscar,
Xu Kangming,
Holzinger Rupert,
Monai Matteo,
Weckhuysen Bert M.
Publication year - 2020
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.202000327
Subject(s) - methanation , catalysis , chemistry , desorption , electrolysis of water , inorganic chemistry , electrolysis , chemical engineering , organic chemistry , adsorption , electrode , engineering , electrolyte
In Power‐to‐Methane (PtM) plants, the renewable electricity supply can be stabilized by using green electrons to produce H 2 via H 2 O electrolysis, which is subsequently used to hydrogenate CO 2 into CH 4 . In this work PtM is studied in a cascade fashion, from simulated solar light to methane production in an all‐in‐one setup, which was newly developed for this work. This setup was used to assess the effects of H 2 stream purity on the activity of Ni/SiO 2 catalysts in CO 2 methanation. An activity effect in downstream methanation is shown to be onset by aerosols that evolve from the electrochemical splitting of water. Small amounts of K are shown to affect CH 4 production positively, but only if they are deposited in situ, via KOH aerosols. K‐doped Ni/SiO 2 catalysts prepared in an ex situ manner, by impregnation with a KOH solution, showed a decrease in activity, while the same amount of KOH was deposited. Operando FT‐IR spectroscopy reveals that increased back‐donation to CO‐containing intermediates and carbonates formation likely causes catalyst deactivation in ex situ samples as often reported in literature for Ni/SiO 2 catalysts. The mechanism for in situ promotion is either an increased rate in the hydrogenation of CH x (X=0–3) fragments, or a more facile water formation or desorption as CO‐containing reaction intermediates are unaffected by in situ promotion. These results are relevant to PtM from a fundamental standpoint explaining the effect of potassium on nickel methanation, but also from a practical standpoint as the presented effect of in situ promotion is difficult to achieve via standard synthesis methods.