Challenges and Solutions to Scalable Testing of Catalysts for Converting Syngas to Chemicals and Fuels
Dr. Anton J. Nagy1* (underline presenting author) and Prof. Dr. T. Turek2
1ILS-Integrated Lab Solutions GmbH, Berlin (Germany)
2TU Clausthal, Institut für Chemische und Elektrochemische Verfahrenstechnik,
Clausthal-Zellerfeld (Germany)
*anton.nagy@integratedlabsolutions.com
Introduction
The recent increase in availability of short chain alkanes derived from the US Fracking gas initiative combined with worldwide recognition of the need to reduce CO2 emissions to mitigate climate change has resulted in ever-increased interest in converting synthesis gas to chemicals and/or fuels. This presentation will highlight a number of new systems developed by ILS for performing such tests and also provide real-life examples of pitfalls to avoid in GTL catalyst testing.
GTL Types
Fischer Tropsch
Fischer Tropsch catalyst for low-temperaure cobalt-catalyzed FT are done industrially in either parallel fixed-bed reactors or bubble-column reactors. At the lab scale there serious challenges in testing these catalysts1. We will address a number of these issues in the presentation pointing out a number of practicable solutions including:
Figure 1. Example Data for Long-Term Parallel FT Testing
1. Isothermicity issues: Despite what is often published we have found that even small-diamter, SiC thinned catalysts tested with 2mm inner diameters show deviation from true temperature.
2. Axial Oxidation Gradients: Product water formed during reaction results in oxidation of the lower catalyst bed and potential falsification of results
3. Slurry CSTR. Vs. Fixed-Bed: The rapid response of small fixed-bed lab reactors makes them powerful tools for studying process variations that only appear after long time-on-streams in larger s lurry reactors.
4. Pore-diffusion limitations: Fixed-bed reactor testing of high-alpha FT catalysts almost all exhibit pore-diffusion limitations. This can be overcome by operating reactors at similar conversion levels as long as product spectrums are similar.
CO2/CO Methanation
CO and CO2 methanation are already industrially-relevant processes used for example for converting syngas generated from coal to clean fuels for city power and fuel requirements.
Challenges in high-throughput testing of extremely effective nickel-based methanation catalysts will be shown. For example; the need to operate at extremely high flowrates to obtain data far enough from thermodynamic equilibrium.
Methanation catalysts for use as energy storage via hydrogenation of CO and CO2 using green-powered electrolysis units is a very exciting topic at the moment. These catalysts are exposed to large swings in redox atmosphere as the availability of H2 varies as a function of the electricity available.
The ILS-Berty internal recycle reactor
is a next-generation Berty derived from the exclusive licensing agreement that
ILS has with the Friedrich-Alexander-University in Erlangen, Germany. The use
of a novel, electromagnet makes possible stirring rates of 10.000rpm and
completely eliminates the need for an external motor with rotating parts. The
high speeds and lack of moving parts ensures a broader pressure operating
regime and virtually no downtime. This is particularly advantageous for
high-temperature, low-to-medium pressure gas-phase reactions.
Figure 2. Instationary CO2 Methanation in ILS Berty Reactor
Recent data from the Turek group isusing a Berty-type CSTR from ILS to study the instationary methanation kinetics of CO2. The pulse RTD results clearly show the ideal backmixing of the ILS Berty reactor. Initial transient kinetic studies performed for CO2 methanation in the CSTR show the transient kinetic behavior to be very different than that predicted by more traditional steady-state models.
Methanol Synthesis
Methanol synthesis is a reaction of
major industrial relevance. We will present the modern high-throughput
fixed-bed methanol synthesis testing units provided by ILS which allow
independent temperature control in order to do rapid parallel kinetic testing.
The ability to have temperature control on the order of +/-0,5°C was critical
for these units which have been in operation at Clariant for over 10 years now.
Challenges like carbonyl poisoning and effective measurement of
low-concentrations of byproducts will be addressed.
Figure 3. Results of 16-Paralle Methanol Synthesis Catalyst Testing2
References
1. Sie S.T., Miniaturization of hydroprocessing catalyst testing systems: Theory and practice, AICHE Journal, , Vol 42, Issue 12, Dec 1996
2. Dissertation. T. Henkel, Modellierung von Reaktion und Stofftransport in geformten Katalysatoren am Beispiel der Methanolsynthese, TU Munich 2011
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