This review describes the history and development of plasma-assisted catalysis focussing mainly on the use of atmospheric pressure, non-thermal plasma. It identifies the various interactions between the plasma and the catalyst that can modify and activate the catalytic surface and also describes how the catalyst affects the properties of the discharge. Techniques for in situ diagnostics of species adsorbed onto the surface and present in the gas-phase over a range of timescales are described. The effect of temperature on plasma–catalysis can assist in determining differences between thermal catalysis and plasma-activated catalysis and focuses on the meaning of temperature in a system involving non-equilibrium plasma. It can also help to develop an understanding of the gas-phase and surface mechanism of the plasma–catalysis at a molecular level. Our current state of knowledge and ignorance is highlighted and future directions suggested.

http://iopscience.iop.org/article/10.1088/0022-3727/49/24/243001/pdf

Plasma–catalysis: the known knowns, the known unknowns and the unknown unknowns

Plasma catalysis is gaining increasing interest for various gas conversion applications, such as CO2 conversion into value-added chemicals and fuels, CH4 activation into hydrogen, higher hydrocarbons or oxygenates, and NH3 synthesis Other applications are already more established, such as for air pollution control, eg volatile organic compound remediation, particulate matter and NOx removal In addition, plasma is also very promising for catalyst synthesis and treatment Plasma catalysis clearly has benefits over 'conventional' catalysis, as outlined in the Introduction However, a better insight into the underlying physical and chemical processes is crucial This can be obtained by experiments applying diagnostics, studying both the chemical processes at the catalyst surface and the physicochemical mechanisms of plasma-catalyst interactions, as well as by computer modeling The key challenge is to design cost-effective, highly active and stable catalysts tailored to the plasma environment Therefore, insight from thermal catalysis as well as electro- and photocatalysis is crucial All these aspects are covered in this Roadmap paper, written by specialists in their field, presenting the state-of-the-art, the current and future challenges, as well as the advances in science and technology needed to meet these challenges

/pdf/the-2020-plasma-catalysis-roadmap-4nij6g176p.pdf

The 2020 plasma catalysis roadmap

Catalyst preparation with plasmas is increasingly attracting interest A plasma is a partially ionized gas, consisting of electrons, ions, molecules, radicals, photons, and excited species, which are all active species for catalyst preparation and treatment Under the influence of plasma, nucleation and crystal growth in catalyst preparation can be very different from those in the conventional thermal approach Some thermodynamically unfavorable reactions can easily take place with plasmas Compounds such as sulfides, nitrides, and phosphides that are produced under harsh conditions can be synthesized by plasma under mild conditions Plasmas can produce catalysts with smaller particle sizes and controllable structure Plasma is also a facile tool for reduction, oxidation, doping, etching, coating, alloy formation, surface treatment, and surface cleaning in a simple and direct way A rapid and convenient plasma template removal has thus been established for zeolite synthesis It can operate at room tempera

Catalyst Preparation with Plasmas: How Does It Work?

Blood plasma separation is vital in the field of diagnostics and health care. Due to the inherent advantages obtained in the transition to microscale, the recent trend in these fields is a rapid shift towards the miniaturization of complex macro processes. Plasma separation in microdevices is one such process which has received extensive attention from researchers globally. Blood plasma separation techniques based on microfluidic platforms can be broadly classified into two categories. While active techniques utilize external force fields for separation, the passive techniques are dependent on biophysical effects, cell behavior, hydrodynamic forces and channel geometry for blood plasma separation. In general, passive separation methods are favored in comparison to active methods because they tend to avoid design complexities and are relatively easy to integrate with biosensors; additionally they are cost effective. Here we review passive separation techniques demonstrating separation and blood behavior at microscale. We present an extensive review of relevant biophysical laws, along with experimental details of various passive separation techniques and devices exploiting these physical effects. The relative performances, and the advantages and disadvantages of microdevices discussed in the literature, are compared and future challenges are brought about.

https://iopscience.iop.org/article/10.1088/0960-1317/25/8/083001/pdf

Passive blood plasma separation at the microscale: a review of design principles and microdevices

CO2 hydrogenation to methanol is a promising process for CO2 conversion and utilization. Despite a well-developed route for CO hydrogenation to methanol, the use of CO2 as a feedstock for methanol synthesis remains underexplored, and one of its major challenges is high reaction pressure (usually 30–300 atm). In this work, atmospheric pressure and room temperature (∼30 °C) synthesis of methanol from CO2 and H2 has been successfully achieved using a dielectric barrier discharge (DBD) with and without a catalyst. The methanol production was strongly dependent on the plasma reactor setup; the DBD reactor with a special water-electrode design showed the highest reaction performance in terms of the conversion of CO2 and methanol yield. The combination of the plasma with Cu/γ-Al2O3 or Pt/γ-Al2O3 catalyst significantly enhanced the CO2 conversion and methanol yield compared to the plasma hydrogenation of CO2 without a catalyst. The maximum methanol yield of 11.3% and methanol selectivity of 53.7% were achieved ov...

Atmospheric Pressure and Room Temperature Synthesis of Methanol through Plasma-Catalytic Hydrogenation of CO2

The current paper reports on a newly developed DRIFTS-MS system for the investigation of non-thermal plasma (NTP) assisted heterogeneously catalyzed reactions. Specifically, this methodology has been utilized to investigate the surface changes during the NTP-activated hydrocarbon selective catalytic reduction (HC-SCR) deNOx reaction over a silver-based catalyst at ambient temperature using simulated diesel fuels (toluene and n-octane). The experimental setup and the methods used to investigate the plasma activation operating with helium as the carrier gas in order to examine low-temperature reactions are described. The technique has identified the importance, even at low temperatures, of isocyanate species in the HC-SCR deNOx reaction as well as the critical role of water in the formation of N2.

Probing a Non-Thermal Plasma Activated Heterogeneously Catalyzed Reaction Using in Situ DRIFTS-MS

Hydrogenation of vegetable oils is an important process in the food industry
because of its widespread application to produce margarines, shortenings, and other
food components. Supercritical technology has proven to be a reliable alternative to
conventional hydrogenation process because not only the trans isomer levels can be
reduced, but also offers a clean, economic and environmental friendly process.
Computational Fluid Dynamics (CFD) modeling applied to the supercritical hydrogenation reaction can be useful in visualizing and understanding the mass transfer phenomena involved. CFD is applied to the study of the catalytic hydrogenation of sunflower oil in the presence of a supercritical solvent. A mix of sunflower oil, hydrogen and supercritical propane (used as a solvent) is the flowing fluid. Their transport properties at high pressure are incorporated within a CFD commercial code in order to estimate them online within the simulation process. A 2D CFD model of a single Pd-based catalyst pellet is presented. Intra-particle and surface concentration profiles and surface mass fluxes for all species present in the mixture (oil triglycerides and hydrogen) are obtained and compared against experimental results. Different temperatures, flow velocities and particle sizes are studied and external and internal
mass transfer phenomena are analyzed. External mass transfer coefficients for hydrogen and oil triglycerides are obtained and a correlation for estimating them is presented.

/pdf/single-and-two-phase-flows-on-chemical-and-biomedical-tulu4qswvd.pdf

Single and Two-Phase Flows on Chemical and Biomedical Engineering

https://pureadmin.qub.ac.uk/ws/files/200399364/202001_23_DRIFTS_CH4Oxi_NTP_clean_25733_.pdf

Cristina-Elena Stere

Papers

Probing a Non-Thermal Plasma Activated Heterogeneously Catalyzed Reaction Using in Situ DRIFTS-MS

Single and Two-Phase Flows on Chemical and Biomedical Engineering

A design of a fixed bed plasma DRIFTS cell for studying the NTP-assisted heterogeneously catalysed reactions

Spacims-Probing the Internal Behaviour of 3D Structured Materials