Taming microwave plasma to beat thermodynamics in CO2 dissociation

Gerard van Rooij, D.C.M. van den Bekerom, N.P. (Nicolaas) Harder, den, T. (Teofil) Minea, G. Berden, W.A. Bongers, R.A.H. Engeln, M.F. Graswinckel, E. Zoethout, M.C.M. van de Sanden

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Abstract

The strong non-equilibrium conditions provided by the plasma phase offer the opportunity to beat traditional thermal process energy efficiencies via preferential excitation of molecular vibrations. Simple molecular physics considerations are presented to explain potential dissociation pathways in plasma and their effect on energy efficiency. A common microwave reactor approach is evaluated experimentally with Rayleigh scattering and Fourier transform infrared spectroscopy to assess gas temperatures (exceeding 104 K) and conversion degrees (up to 30%), respectively. The results are interpreted on a basis of estimates of the plasma dynamics obtained with electron energy distribution functions calculated with a Boltzmann solver. It indicates that the intrinsic electron energies are higher than is favorable for preferential vibrational excitation due to dissociative excitation, which causes thermodynamic equilibrium chemistry to dominate. The highest observed energy efficiencies of 45% indicate that non-equilibrium dynamics had been at play. A novel approach involving additives of low ionization potential to tailor the electron energies to the vibrational excitation regime is proposed
LanguageEnglish
Pages233-248
Number of pages16
JournalFaraday Discussions
Volume183
DOIs
StatePublished - 1 Dec 2015

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Energy efficiency
synchronism
Microwaves
Thermodynamics
dissociation
Plasmas
microwaves
thermodynamics
Electrons
Molecular physics
Molecular vibrations
excitation
Rayleigh scattering
Ionization potential
electron energy
molecular physics
plasma dynamics
nonequilibrium conditions
Distribution functions
thermodynamic equilibrium

Cite this

van Rooij, G., van den Bekerom, D. C. M., Harder, den, N. P. N., Minea, T. T., Berden, G., Bongers, W. A., ... van de Sanden, M. C. M. (2015). Taming microwave plasma to beat thermodynamics in CO2 dissociation. Faraday Discussions, 183, 233-248. DOI: 10.1039/C5FD00045A
van Rooij, Gerard ; van den Bekerom, D.C.M. ; Harder, den, N.P. (Nicolaas) ; Minea, T. (Teofil) ; Berden, G. ; Bongers, W.A. ; Engeln, R.A.H. ; Graswinckel, M.F. ; Zoethout, E. ; van de Sanden, M.C.M./ Taming microwave plasma to beat thermodynamics in CO2 dissociation. In: Faraday Discussions. 2015 ; Vol. 183. pp. 233-248
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van Rooij, G, van den Bekerom, DCM, Harder, den, NPN, Minea, TT, Berden, G, Bongers, WA, Engeln, RAH, Graswinckel, MF, Zoethout, E & van de Sanden, MCM 2015, 'Taming microwave plasma to beat thermodynamics in CO2 dissociation' Faraday Discussions, vol. 183, pp. 233-248. DOI: 10.1039/C5FD00045A

Taming microwave plasma to beat thermodynamics in CO2 dissociation. / van Rooij, Gerard; van den Bekerom, D.C.M.; Harder, den, N.P. (Nicolaas); Minea, T. (Teofil); Berden, G.; Bongers, W.A.; Engeln, R.A.H.; Graswinckel, M.F.; Zoethout, E.; van de Sanden, M.C.M.

In: Faraday Discussions, Vol. 183, 01.12.2015, p. 233-248.

Research output: Contribution to journalArticleAcademicpeer-review

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T1 - Taming microwave plasma to beat thermodynamics in CO2 dissociation

AU - van Rooij,Gerard

AU - van den Bekerom,D.C.M.

AU - Harder, den,N.P. (Nicolaas)

AU - Minea,T. (Teofil)

AU - Berden,G.

AU - Bongers,W.A.

AU - Engeln,R.A.H.

AU - Graswinckel,M.F.

AU - Zoethout,E.

AU - van de Sanden,M.C.M.

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AB - The strong non-equilibrium conditions provided by the plasma phase offer the opportunity to beat traditional thermal process energy efficiencies via preferential excitation of molecular vibrations. Simple molecular physics considerations are presented to explain potential dissociation pathways in plasma and their effect on energy efficiency. A common microwave reactor approach is evaluated experimentally with Rayleigh scattering and Fourier transform infrared spectroscopy to assess gas temperatures (exceeding 104 K) and conversion degrees (up to 30%), respectively. The results are interpreted on a basis of estimates of the plasma dynamics obtained with electron energy distribution functions calculated with a Boltzmann solver. It indicates that the intrinsic electron energies are higher than is favorable for preferential vibrational excitation due to dissociative excitation, which causes thermodynamic equilibrium chemistry to dominate. The highest observed energy efficiencies of 45% indicate that non-equilibrium dynamics had been at play. A novel approach involving additives of low ionization potential to tailor the electron energies to the vibrational excitation regime is proposed

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van Rooij G, van den Bekerom DCM, Harder, den NPN, Minea TT, Berden G, Bongers WA et al. Taming microwave plasma to beat thermodynamics in CO2 dissociation. Faraday Discussions. 2015 Dec 1;183:233-248. Available from, DOI: 10.1039/C5FD00045A