Effects of particle size on CO 2 reduction and discharge characteristics in a packed bed plasma reactor

Butterworth, Tom; Elder, Rachael H.; Allen, Ray

doi:10.1016/j.cej.2016.02.047

Cited by 137 publications

(120 citation statements)

References 24 publications

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“…The same phenomenon is also observed in PBRs packed with high dielectric constant materials [21], and with surface discharge plasmas such as plasma actuators [33]. This behaviour can be accounted for by considering the physical interpretation of the Q-V plot shape and its relationship to the behaviour of the plasma in the reactor.…”

Section: Interpretation Of Almond Shaped Q-v Plotsmentioning

confidence: 90%

“…In our previous work, we applied an alternative equivalent circuit developed by Peeters et al to packed bed reactors where we quantified and demonstrated the impact of partial discharging [21]. In this article, with the SPR, it is possible to add a plot of the partial discharging coefficient, alpha, to the voltage-power profile of each material.…”

Section: Relationship Between Plasma Behaviour and Alpha Coefficient mentioning

confidence: 99%

“…The yttria stabilized zirconia (YSZ-CoorsTek), CaTiO 3 (Catal International), BaTiO 3 (Catal International) and SiO 2 (Aigma Aldrich) are dense, with a very low porosity, whilst the Al 2 O 3 (Sigma-Aldrich) used is highly porous. The dielectric constant of the BaTiO 3 has been experimentally tested using an LCR meter, and found to have a value of 4000 [21]. The other materials are assumed to take their values described in literature.…”

Section: Materials Propertiesmentioning

confidence: 99%

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Plasma-catalyst interaction studied in a single pellet DBD reactor: dielectric constant effect on plasma dynamics

Butterworth

Allen

2017

Plasma Sources Sci. Technol.

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A novel single dielectric pellet DBD that is designed to facilitate studying the interaction between plasmas and catalysts is presented. The influence of material dielectric constant on plasma dynamics across a range of applied voltages is determined through the use of electrical characterisation combined with videos of the discharge. Different discharge modes in nitrogen are observed and their behaviour is characterised. A particular focus is given to the phenomenon known as 'partial discharging'. This is where incomplete plasma formation occurs between the electrodes of the reactor, which may have implications for the fair testing of catalysts in packed bed reactors. Additionally, the occurrence of an 'almond shaped' QV plot in the event of pointto-point discharging in PBRs is explained. This work provides easily implemented analytical techniques that can be applied to understand the behaviour of plasmas within packed bed DBD reactors.

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Section: Interpretation Of Almond Shaped Q-v Plotsmentioning

confidence: 90%

Section: Relationship Between Plasma Behaviour and Alpha Coefficient mentioning

confidence: 99%

Section: Materials Propertiesmentioning

confidence: 99%

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Plasma-catalyst interaction studied in a single pellet DBD reactor: dielectric constant effect on plasma dynamics

Butterworth

Allen

2017

Plasma Sources Sci. Technol.

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“…The reactor was chosen because of its large volume, which facilitates diagnostic measurements. Furthermore, the reactor does not require packing with catalyst or inert particles, and thus complicated interactions with the bed, which obfuscate fundamental interpretations of reaction rates, were avoided . It will be demonstrated that the steady state is nominally independent of the initial feed speciation provided the relative amounts of different elements are held constant, and that superlocal equilibrium state is fundamentally different than the local equilibrium state at the background temperature.…”

Section: Introductionmentioning

confidence: 99%

Superlocal chemical reaction equilibrium in low temperature plasma

Üner

Thimsen

2020

AIChE Journal

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Low temperature plasmas (LTP) are a unique class of open-driven systems in which chemical reactions are unpredictable using established concepts. The terminal state of chemical reactions in LTP, termed the superlocal equilibrium state, is hypothesized to be defined by a proposed set of state variables. Using a LTP reactor wherein the state variables have been measured, it is shown that CO 2 spontaneously splits and the effluent speciation is independent of the influent speciation if the state variables are held constant and the residence time is long. CO 2 conversion at long residence times, which is expected to be nominally zero from equilibrium thermodynamics, can be as high as 70% in the LTP. The employed low pressure plasma reactor (P = 10 mbar) had a similar volume, productivity, and energy efficiency compared to an atmospheric pressure dielectric barrier discharge reactor, thanks to reaction rates that were three orders of magnitude faster. K E Y W O R D SCO 2 splitting, low-pressure reactor, low-temperature plasma, plasma chemistry, superlocal equilibrium 1 | INTRODUCTION A major challenge currently facing chemical engineering is the development of processes to transform CO 2 into platform chemicals from which valuable materials can be synthesized, with the goal of removing the greenhouse gas from the atmosphere. CO 2 is a relatively inert species that must be activated before it can react. Activation can be accomplished by photocatalysis, 1-3 electrochemistry, 4-7 raising the gas to high temperature, 8 or using low temperature plasma, [9][10][11] which is a partially ionized gas. Of these activation methods, plasma has a combination of desirable traits that stands out from the others: high-energy efficiency 12 (up to 90%), high reaction rates at the laboratory scale (approximately 1 t m −3 hr −1 ), and the possibility of low background gas temperature for compatibility with temperature-sensitive molecules. The synthesis of platform chemicals from CO 2 will likely require sophisticated reaction engineering. A major challenge preventing engineering of reactions between CO 2 and other molecules such as CH 4 or H 2 O in low temperature plasma is that one cannot make the local equilibrium assumption, 13 and consequently, practical methods to predict the direction and maximum extent of chemical reactions have not been forthcoming.The concept of thermodynamic equilibrium is generally used to predict the direction of chemical reactions and theoretical maxima for conversion and yield. In flow systems, which are intrinsically not at equilibrium, 14 the local equilibrium assumption 15 is often used for process modeling. One aspect of the local equilibrium assumption is that at given location in space, one can describe a single temperature, which is defined as T = ∂U ∂S À Á x , where U is internal energy, S is entropy, and the partial derivative is taken at constant work displacement x. Nonequilibrium systems can then be modeled using temperature gradients and the associated heat fluxes. 16 Such approaches for modeli...

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“…Close coupling of plasmas with heterogeneous catalysts presents many advantages,i ncluding the possibility of opening up alternative reaction pathways from the plasmagenerated species [13] and structural changes of the active phase due to the plasma;however,the activation mechanism depends on many factors including the type of catalyst, reactants,r eaction conditions. [3,4,[18][19][20][21] Thep resent study demonstrates that areversible exothermic reaction of significant industrial importance can be performed at close to room temperature using heterogeneous catalysis and dielectricbarrier discharge (DBD) plasma activation;a nd thus overcoming the equilibrium limitations whilst maintaining high catalytic activity.…”

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confidence: 99%

Non‐Thermal Plasma Activation of Gold‐Based Catalysts for Low‐Temperature Water–Gas Shift Catalysis

et al. 2017

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Non‐thermal plasma activation has been used to enable low‐temperature water‐gas shift over a Au/CeZrO4 catalyst. The activity obtained was comparable with that attained by heating the catalyst to 180 °C providing an opportunity for the hydrogen production to be obtained under conditions where the thermodynamic limitations are minimal. Using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), structural changes associated with the gold nanoparticles in the catalyst have been observed which are not found under thermal activation indicating a weakening of the Au−CO bond and a change in the mechanism of deactivation.

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Effects of particle size on CO 2 reduction and discharge characteristics in a packed bed plasma reactor

Cited by 137 publications

References 24 publications

Plasma-catalyst interaction studied in a single pellet DBD reactor: dielectric constant effect on plasma dynamics

Plasma-catalyst interaction studied in a single pellet DBD reactor: dielectric constant effect on plasma dynamics

Superlocal chemical reaction equilibrium in low temperature plasma

Non‐Thermal Plasma Activation of Gold‐Based Catalysts for Low‐Temperature Water–Gas Shift Catalysis

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