Hielscher Ultrasonics discusses how sonochemistry ultrasound devices can boost chemical reactions.
According to the company, it is a known fact that for - most chemical reactions - heat is required and that reactions proceed approximately twice as fast with a temperature increase of 10C to 15C.
In recent decades, the range of technical possibilities for heat input into liquids has been extended.
Aside from the traditional heating methods, microwave and ultrasound technologies have become established techniques.
While all of these forms of energy finally result in heating, physical and chemical reactions are observed during a few of these heating processes so that they can be used for specific applications.
If ultrasonic irradiation is applied to liquids, this kinetic energy is converted by friction partly into heat.
However, if amplitudes and acceleration are high enough, the phenomenon of so-called cavitation occurs.
The liquid bursts and vacuum bubbles are generated during the alternating high-pressure and low-pressure cycles.
When these small bubbles cannot absorb anymore energy, they implode during a high-pressure cycle so that pressures of up to 1,000 bar, shock waves and liquid jets of up to 400km/h are reached locally.
These highly intense forces, caused by ultrasonic cavitation, take effect to the enclosing droplets and particles.
The main objective of power ultrasonics consists in the use of cavitational forces; the heating is, mostly, a welcome side effect.
Cavitation and the effects described above cause interparticular collision, according to Hielscher.
Existing bondings are broken, and particles are dispersed and deagglomerated.
By that, new bonding can occur.
The reaction time is reduced thanks to the very fine, intensive mixing and dispersing of particles and droplets.
The larger the overall surface area of all reacting particles will be, the faster and more efficient a process will run.
This is achieved thanks to the particle size reduction and the break-up of agglomerates in suspensions or by the shearing of droplets in emulsions.
By ultrasonication, particles and droplets in micron and nano size can be achieved easily.
A further effect of ultrasonic irradiation is the permanent cleaning of the catalysts, so they offer a larger active surface area whereby the amount of added catalyst can be reduced.
Aside from the catalytic speed-up, ultrasonication initiates reactions that are either not achieved, as a result of the input of other energy forms, or just hardly obtained.
In the last few years, Hielscher has investigated and developed ultrasound technology in order to offer customers a range of ultrasonic processors for applications in the laboratory and in industry.
The company can advise its customers on manifold sonochemical reactions, such as precipitation, homogeneous and heterogeneous catalysis, crystallisation, the sonochemistry of polymers or the transesterification of oil and fat to biodiesel.
In the laboratory, it is not only important to reduce processing time and cost but also to ensure speedy analysis results.
For the quality control of production processes, it is important to react as promptly as possible.
Accordingly, Hielscher offers ultrasonic devices with manifold accessories not only for fast sample preparation in the laboratory, such as the handheld or stand-mounted homogenisers or the recirculating Sonostep, but also for the in-line sonication of large-volume streams for industrial production.
For example, the company's UIP1000hd bench-top, 1,000W, 20kHz processor is capable of sonicating liquids in flow mode with a flow rate of between 0.5 litres per minute and 4.0 litres per minute, depending on the specific process.
Hielscher's UIP16000, a powerful ultrasound device, processes between 12m/hr and 50m/hr.
All industrial devices are simple to handle and operate; built at full industrial grade, they can be operated 24 hours a day.
As the ultrasonic units can be installed as clusters, there is virtually no processing limit.
Hielscher supplies turnkey systems including ultrasound generators, transducers, sonotrodes, flow cells, electronic controls, sound protection devices and explosion-proof solutions.