Optimized Chemical Reactor Efficiency by High-Power Ultrasonication

Ultrasonication is well known to intensify and/or initiate chemical reactions. Therefore, the integration of high-performance ultrasound is considered as reliable tool to promote chemical reactors for improved reaction outcomes. Hielscher Ultrasonics offers various reactor solutions to tweak your chemical process. Learn how ultrasound can improve your chemical reactor!

How Does Power Ultrasound Improve Chemical Reactors?

The integration of one or more ultrasonic probes (sonotrodes) allows to couple powerful ultrasound waves into the chemical reactor. Intense ultrasonication of liquids and slurries not only create strong turbulences due to acoustic vibration but is known for multiple effects, which are defined under the term “sonochemistry”.

What is Sonochemistry? How Does it Promote Reactions?

High-intensity ultrasound / high-power ultrasound is applied to chemical systems in order to initiate and/or promote reactions, improve conversion rate and yields or to switch reaction pathways. The physical phenomenon responsible for sonochemical effects is acoustic cavitation. When high-intensity ultrasound waves are coupled into a liquid medium, the waves travel through the liquid creating alternating low pressure (rarefaction) and high pressure (compression) cycles. During the low pressure / rarefaction, minute vacuum bubbles arise in the liquid, which grow over several pressure cycles until the vacuum bubble reaches a point where it cannot absorb any further energy. At the point of maximum bubble growth, the bubble implodes violently during a high pressure cycle. During the implosive bubble collapse, the phenomenon of cavitation can be observed. Ultrasonic cavitation creates so called “hot spots,” which are characterized by extreme conditions such as temperature of up to ∼5000 K with very high heating/cooling rates of > 1000 K s^-1, pressures of up to ∼1000 bar as well as respective temperature and pressure differentials. The liquid or slurry is heavily agitated by liquid jets and shear forces.

The chemical effects (e.g., the formation of radical species, flexing of molecules etc.) and physical / physico-mechanical effects of sonochemistry are successfully applied to numerous chemical reactions such as organic catalysis, organocatalytic reactions, phase transfer reactions, nanoparticle synthesis, precipitation / crystallization, sol-gel reactions, Suzuki coupling, Diels-Alder reactions, Mannich reactions, Michael addition, Wurtz-type coupling and many others. Sonochemically promoted reactions often show a significantly increased conversion rate, higher yields, accelerated reaction, more complete reaction, can be used with milder solvents under ambient conditions, create less unwanted by-products and contribute due to its high efficiency to green chemistry.

Ultrasound-Driven Chemical Batch Reactors

The integration of ultrasonicators into open or closed batch reactors is a commonly applied technique to accelerate reactions in laboratories, pilot plants and production facilities. Depending on the vessel size, geometry and the chemical reaction system, one or multiple sonotrodes can be integrated into the batch reactor. Ultrasonication is also often used to improve continuously stirred reactors (CSTR).

Ultrasonic Semi-Batch Reactors: Of course, sonication can be also integrated into semi-batch reactors. For semi-batch systems, one chemical reactant is loaded into the reactor, whilst a second chemical is added at a continuous flow rate (for instance, at a slow feed to prevent side reactions) getting combined in the ultrasonic hot spot. Alternatively, a product of a chemical reaction, which results from the reaction in the reactor is continuously removed, e.g., synthesized precipitates or crystals, or an intermediate of end product that can be removed due to phase separation.

Ultrasonically-Agitated Chemical Flow-through Reactor

In a flow-through reactor, also known as flow cell or inline reactor, the reactants are feed through one or multiple feeding ports into the reaction chamber, where the chemical reaction happens. After a certain retention time that is needed for a specific reaction to occur, the medium is continuously discharged from he reactor. Ultrasonic flow cells and inline reactors allow for an uninterrupted production of product, which is only dependent on the continuous supply of the reagents.

High-Performance Chemical Sono-Reactors

Hielscher Ultrasonics is your trusted manufacturer for sono-chemical reactors and high-performance ultrasonic equipment that can reliably improve your chemical reaction. Hielscher Ultrasonics product range includes various types and classes of laboratory and industrial large-scale sonoreactors for batch and flow-through mode. With Hielscher high-performance probe-type ultrasonication, multiple advances – such as improved reaction rate, more complete conversion, higher yields, precise reaction control, and excellent overall efficiency – are reliably achieved in batch and flow-through reactors. Designed for high-performance and robustness, Hielscher ultrasonicators and sono-reactors can be installed for the use with harsh chemicals, in demanding environments and heavy-duty applications.
Hielscher ultrasonic reactors are designed with focus of a uniform ultrasonic irradiation of the medium so that the acoustic pressure field can expand evenly. Meeting this requirement improves the overall efficiency of the sonochemical reaction since the ultrasound achieves highest process intensification.

The product range covers compact laboratory ultrasonicators for R&D, powerful bench-top and pilot ultrasonic systems as well as fully-industrial grade equipment for large volume production. This allows for risk-free feasibility testing on small scale and the subsequent completely linear scale-up to larger volumes.

Precise Sonication Control

The digital colour display and the smart software with remote browser control and automatic data protocolling on an integrated SD-card allow for sophisticated setting and monitoring of the ultrasonic parameters in the sono-chemical reactor.
The beauty of sonochemically driven reactions is the efficiency that can be reliably achieved via process optimization. Optimum ultrasonic amplitude, ultrasound power input, temperature and pressure can be determined for each particular reaction. This allows to find the ideal sonication parameters so that optimum reaction results and efficiency are achieved.

Temperature Control

All our digital ultrasonicators are equipped with a pluggable temperature sensor for continuous temperature monitoring, which can be inserted into the liquid for constant measuring of the bulk temperature. Sophisticated software allows the setting of a temperature range. When the temperature limit is exceeded, the ultrasonicator automatically pauses until the temperature in the liquid has lowered to a certain set point and starts automatically sonicating again. All temperature measurements as well as other important ultrasonic process data are automatically recorded on a built-in SD card and can be revised easily for process control.
Sonochemical reactors from Hielscher are available with cooling jackets. Additionally, heat exchangers and chiller units can be connected to ensure the desired process temperature.

Readily Available Components to Assemble the Ideal Chemical Reactor

The large portfolio of readily available ultrasonic devices, probes (sonotrodes), boosters horns, batch reactors and flow cells as well as numerous additional accessories allow to configure the ideal ultrasonic-chemical reactor (sono-reactor) for your specific process.
All equipment is already optimized for uniform distribution of acoustic cavitation and stable flow patterns, which are the most important design aspects to obtain homogeneous, reliable results in an ultrasonically agitated chemical reactor.
Unwanted oxidation can be avoided by purging the reactor with an inert gas, e.g. nitrogen blanket.

Customized Solutions for Your Chemical Reactor

Whilst Hielscher offers various batch and inline reactor solution in various sizes and geometries, made from stainless steel or glass, we are glad to manufacture your special chemical reactor vessel considering the analysis and design fundamentals of your specific process requirements. With a long-time experienced team of engineers and technical developers, we design your chemical reactor meeting your demands. For instance, size, material, geometry, feeding and discharging ports, number of ultrasonic probes etc. can be designed in order to make the ideal ultrasonically-promoted chemical reactor for your chemical process.

The table below gives you an indication of the approximate processing capacity of our ultrasonicators: