Hielscher Ultrasound Technology

Improved Fischer-Tropsch Catalysts with Sonication

Improved Synthesis of Fischer-Tropsch Catalysts with Ultrasound: Ultrasonic treatment of catalyst particles is used for several purposes. Ultrasonic synthesis helps to create modified or functionalized nano-particles, which have a high catalytic activity. Spent and poisoned catalysts can be easily and fast recovered by an ultrasonic surface treatment, which removes inactivating fouling from the catalyst. Finally, ultrasonic deagglomeration and dispersion results in a uniform, mono-disperse distribution of catalyst particles to ensure a high active particle surface and mass transfer for optimum catalytic conversion.

Ultrasonic Effects on Catalyst

High power ultrasound is well-known for its positive influence on chemical reactions. When intense ultrasound waves are introduced into a liquid medium acoustic cavitation is generated. Ultrasonic cavitation produces locally extreme conditions with very high temperatures of up to 5,000K, pressures of approx. 2,000atm, and liquid jets of up to 280m/s velocity. The phenomenon of acoustic cavitation and its effects on chemical processes is known under the term sonochemistry.
A common application of ultrasonics is the preparation of heterogeneous catalysts: the ultrasound cavitation forces activate catalyst’s surface area as cavitational erosion generates unpassivated, highly reactive surfaces. Furthermore, mass transfer is significantly improved by the turbulent liquid streaming. The high particle collision caused by acoustic cavitation removes surface oxide coatings of powder particles resulting in the reactivation of the catalyst surface.

Ultrasonic Preparation of Fischer-Tropsch Catalysts

The Fischer-Tropsch process contains several chemical reactions that convert a mixture of carbon monoxide and hydrogen into liquid hydrocarbons. For Fischer-Tropsch synthesis, a variety of catalysts can be used, but most frequently used are the transition metals cobalt, iron, and ruthenium. The high temperature Fischer-Tropsch synthesis is operated with iron catalyst.
As Fischer-Tropsch catalysts are susceptible to catalyst poisoning by sulfur-containing compounds, the ultrasonic reactivation is of great importance to maintain full catalytic activity and selectivity.

Advantages of Ultrasonic Catalyst Synthesis

  • Precipitation or crystallization
  • (Nano-) Particles with well-controlled size and shape
  • Modified and functionalized surface properties
  • Synthesis of doped or core-shell particles
  • Mesoporous structuring

Ultrasonic Synthesis of Core-Shell Catalysts

Core–shell nanostructures are nanoparticles encapsulated and protected by an outer shell that isolates the nanoparticles and prevents their migration and coalescence during the catalytic reactions

Pirola et al. (2010) have prepared silica-supported iron-based Fischer-Tropsch catalysts with high loading of active metal. In their study is shown that the ultrasonically assisted impregnation of the silica support improves the metal deposition and increases the catalyst activity. The results of the Fischer-Tropsch synthesis have indicated the catalysts prepared by ultrasonication as the most efficient, particularly when ultrasonic impregnation is performed in argon atmosphere.

UIP2000hdT - 2kW ultrasonicator for liquid-solid processes.

UIP2000hdT – 2kW powerful ultrasonicator to treat nano-particles.

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Ultrasonic Catalyst Reactivation

Ultrasonic particle surface treatment is a rapid and facile method to regenerate and reactivate spent and poisoned catalysts. The regenerability of the catalyst allows for its reactivation and reuse and is thereby an economical and environmental-friendly process step.
Ultrasonic particle treatment removes inactivating fouling and impurities from the catalyst particle, which block sites for catalytic reaction. The ultrasonic treatment gives the catalyst particle a surface jet wash, thereby removing depositions from the catalytically active site. After ultrasonication, catalyst activity is restored to the same effectiveness as fresh catalyst. Furthermore, sonication breaks agglomerates and provides a homogeneous, uniform distribution of mono-dispersed particles, which increases the particle surface area and thereby the active catalytic site. Hence, ultrasonic catalyst recovery yields in regenerated catalysts with a high active surface area for improved mass transfer.
Ultrasonic catalyst regeneration works for mineral and metal particles, (meso-)porous particles and nanocomposites.

High Performance Ultrasonic Systems for Sonochemistry

Ultrasonic processor UIP4000hdT, a 4kW powerful ultrasonic reactorHielscher Ultrasonics’ industrial ultrasonic processors can deliver very high amplitudes. Amplitudes of up to 200µm can be easily continuously run in 24/7 operation. For even higher amplitudes, customized ultrasonic sonotrodes are available. The robustness of Hielscher’s ultrasonic equipment allows for 24/7 operation at heavy duty and in demanding environments.
Our customers are satisfied by the outstanding robustness and reliability of Hielscher Ultrasonic’s systems. The installation in fields of heavy-duty application, demanding environments and 24/7 operation ensure efficient and economical processing. Ultrasonic process intensification reduces processing time and achieves better results, i.e. higher quality, higher yields, innovative products.
The table below gives you an indication of the approximate processing capacity of our ultrasonicators:

Batch Volume Flow Rate Recommended Devices
0.5 to 1.5mL n.a. VialTweeter
1 to 500mL 10 to 200mL/min UP100H
10 to 2000mL 20 to 400mL/min UP200Ht, UP400St
0.1 to 20L 0.2 to 4L/min UIP2000hdT
10 to 100L 2 to 10L/min UIP4000hdT
n.a. 10 to 100L/min UIP16000
n.a. larger cluster of UIP16000

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Literature/References

  • Hajdu Viktória; Prekob Ádám; Muránszky Gábor; Kocserha István; Kónya Zoltán; Fiser Béla; Viskolcz Béla; Vanyorek László (2020): Catalytic activity of maghemite supported palladium catalyst in nitrobenzene hydrogenation. Reaction Kinetics, Mechanisms and Catalysis 2020.
  • Pirola, C.; Bianchi, C.L.; Di Michele, A.; Diodati, P.; Boffito, D.; Ragaini, V. (2010): Ultrasound and microwave assisted synthesis of high loading Fe-supported Fischer–Tropsch catalysts. Ultrasonics Sonochemistry, Vol.17/3, 2010, 610-616.
  • Suslick, K. S.; Skrabalak, S. E. (2008): Sonocatalysis. In: Handbook of Heterogeneous Catalysis. 8, 2008, 2007–2017.
  • Suslick, K.S. (1998): Kirk-Othmer Encyclopedia of Chemical Technology; 4th Ed. J. Wiley & Sons: New York, Vol. 26, 1998, 517-541.
  • Suslick, K.S.; Hyeon, T.; Fang, M.; Cichowlas, A. A. (1995): Sonochemical synthesis of nanostructured catalysts. Materials Science and Engineering A204, 1995, 186-192.



Facts Worth Knowing

Applications of Fischer-Tropsch Catalysts

The Fischer–Tropsch synthesis is a category of catalytic processes that are be applied in the production of fuels and chemicals from synthesis gas (mixture of CO and H2), which can be
derived from natural gas, coal, or biomass the Fischer-Tropsch process, a transition metal-containing catalyst is used to produce hydrocarbons from the very basic starting materials hydrogen and carbon monoxide, which can be derived from various carbon-containing resources such as coal, natural gas, biomass, and even waste.