2017

Part 1 concerns non-thermal plasma (NTP) techniques, which offer a green route for catalyst preparation and modification. The report describes the techniques with examples. Non thermal plasmas (plasmas with gas temperature of 298 – 473 K and electron temperature up to 10000 K) are applied to prepare supported metal catalysts, as well as to modify the catalyst surface and to regenerate coked catalysts. NPT treatments can increase particle dispersion and metal-support interaction, enrich the catalyst surface with the active element, remove the preparation precursor, reduce the oxidized particles, and increase the acidity of the catalyst.

Part 2 concerns thermal plasma applications for catalysts preparation. Thermal plasmas (up to 15000 K) are obtained via direct current arcs (dc/plasma jet arc) or via radiofrequency arc discharges. In Conventional Plasma Spray, solids injected into the plasma jet via a gas carrier, get heated up to melting and then impact the target surface or cool down forming powders. Suspension plasma spray is used to deposit powders onto supports as thin layers. An alternative method to produce agglomerated or nano powders and coatings is the Solution Precursors Plasma Spray method. The arc plasma deposition (APD) processes is a method to prepare metal supported catalysts with nano-sized particle distribution.

Part 3 concerns quantitative modelling the most relevant phenomena that occur in a non-thermal plasma (NTP) discharge, with and without a ceramic media. There are two main categories of reactors for exposing a packed-bed catalyst to non-thermal plasma: one-stage plasma reactors (Direct Barrier Discharge reactor and the Pin-to-Plate reactor) and two-stage plasma reactors. The synergistic effect of NTP on catalysis can be positive (VOC abatement, NOx reduction, decoking) or negative (Fischer Tropsch, steam reforming). The possible effects of plasma on the catalyst are discussed, followed by a kinetics and reactor model.

2017

A trickle bed reactor model and calculation method are presented that allow simulating partial external and internal wetting. Additional mass transfer terms are to be included in the gas, liquid and solid phase species continuity equations. Furthermore, the presence of both gas and liquid in the catalyst has to be accounted for. The calculation of the external partial wetting requires the definition of a critical film thickness.
Gas volume fraction inside the catalyst particles can be calculated without additional model equations provided that the total pressure inside the catalyst is equal to the bulk total pressure. The approach is illustrated with a case study.

2016

This report is the result of the continuation on the work on ‘Objective versus ‘Subjective’ Function Minimization’ and ‘Data fitting: best practices’ and aims at how to obtain a ‘good’ experimental dataset. Data validation and conditioning are very important, though frequently undervalued, activities. The report is divided into two major sections: data treatment to interpretable information and design considerations. In most cases the normalization approach preferred over the one based on measured flow rates, after having verified the mass and element balances over the reactor. The file ‘Data Reconciliation – examples 5-6.xlsx’ is an appendix.

2016

Review of multi-scale approaches (methods) for bridging the huge differences in time scale (from micro to meso to macro) by exploring different methods, best practice, and gaps & needs. Intraphase transport is coupled with reaction using (i) generalized Thiele modulus, or (ii) 1D + 1D approach, or (iii) multi-region approach (microkinetics + rate equations). Hierarchical multiscale approaches for fundamental analysis of complex systems. The review finishes with an illustration concerning the comparison between rate-equation and microkinetic modeling for CH4 steam-reforming over a Rh catalyst in which the water-gas shift reaction is not always equilibrated.

2016

The center manifold methodology allows to reduce the dimension of the state spaces when analysing a bifurcation of a dynamic system. It is applied to predict the dynamic behaviour of an industrial reactor when it starts to run away. The center manifold methodology goes a step beyond the Linear Stability Analysis by including the local nonlinear behaviour of the system and this approach is particularly important when encountering Hopf bifurcations (thermal runaway). For the complex LCO hydrotreating reactor model, the reduction leads to a precise criterion that determines whether a limit cycle exists and an algebraic formula is capable of predicting the deviation of the state variables from the operating point.

2015

An approach to reconcile the observed reaction kinetics at gas and liquid phase conditions has been investigated for reaction mixtures exhibiting a pronounced thermodynamic non-ideality, i.e., the esterification of acetic acid with methanol. Activity coefficients up to 2.5 were estimated (NRTL) for methanol. The reaction order for methanol in the gas phase was between 0.05 and -0.53, but in the liquid phase 1.0. The kinetic model is based on an Eley-Rideal mechanism. From the kinetic modeling it was found that due to pronounced differences in catalyst occupancies, the enthalpy of the surface species is affected by the transition from G to L phase. This is accounted for by an excess enthalpy estimated by regression.

2015

Literature review on developments in in-situ/operando techniques for studying reaction kinetics, changes in oxidation state and phase composition especially during redox reactions including the state of the art and new characterization techniques. Techniques to characterise catalyst surface phase transitions in redox reactions are SXRD (surface x-ray diffr.), XAS (x-ray abs. spectr.), infrared techniques including FTIR and DRIFTS, UV-Vis, STM, and DP-ETEM (differentially pumped-environmental TEM). These techniques are normally coupled with analytical devices such as GC and/or MS to obtain kinetic information.

2015

Review on microwave techniques and plasma technology related with reaction engineering and possible process intensification. Microwave energy and various microwave instruments. Interaction with homo- and heterogeneous reactions, observed phenomena, design of microwave-assisted reactors. Unanswered questions and outlook. Fundamentals of reactions with plasmas. Plasma generation techniques and types of plasmas. Application to chemistry including heterogeneous catalysts. Personal perspective on applications and scale-up of plasmas.

2015

Report on establishing a systematic methodology for the kinetic modeling of chemical reactions from experimental kinetic data, resulting in adequate kinetic models with a combined sound physical meaning and statistical significance. A practical example (n-hexane hydroisomerization) is used to illustrate the discussed techniques. Assumptions in regression analysis, (weighted) sum of squares, background of significance tests and statistics, and more.

2014

Comprehensive review of the hydrocracking process starting from the commercialization in the 60’s up to the present.
Focus on conventional ideal bifunctional reaction mechanism (acid catalyzed steps and quasi-equilibrated (de)hydrogenation on the metal). Various catalyst configurations were reviewed.
Lumped, discrete lumped, and continuous lumped model have been developed, as well as more structure-oriented lumping and single-event kinetics.