Chemical and petrochemical applications

Oxidising aromatics to phenols, quinones, anhydrides and acids is a key petrochemical route for the dye, plastics and pharmaceutical industries. Conditions depend on the oxidant (oxygen, potassium permanganate, potassium chlorate and others), the catalyst (transition metals, metal complexes, enzymes and nanomaterials), temperature and pressure. The cavitation reactor improves the rate and selectivity of these reactions through intense mixing and localised conditions.

Ethylene oxide and water are fed to the reactor with a catalyst such as potassium hydroxide and converted to ethylene glycol under the pressure, temperature and turbulence of cavitation; the product is then purified by distillation. Advantages: higher yield, shorter reaction time, better quality and lower energy use.

Undecomposed emulsifiers in pesticides harm the environment. With the cavitation reactor the emulsifier is fully decomposed and the active ingredient placed in the intended phase, usually aqueous; two-phase stability rises, production cost falls and shelf life increases.

A fluid–gas mixture enters the reactor through a nozzle, and hydrodynamic shocks, localised pressure and temperature and intense turbulence reduce particles to the nano range. In pharmaceuticals this improves solubility and absorption; in food it improves rheology, emulsion stability and shelf life.

Monomer is fed with catalyst and solvent, and a polymer of controlled molecular weight and low polydispersity index results. Uses include packaging films, nano-coatings, soft rubbers, adhesives, epoxy resins and medical plastics. Advantages: lower production cost, time and energy, and better quality.

Breaking up mineral particles and agglomerates in leaching solutions, flotation reagents and slurries; more exposed surface, better reaction efficiency and lower reagent consumption. For mineral processing, the particle type and size, solution pH and temperature and the operating parameters are assessed before implementation.

Heat is produced in the bulk of the liquid with no hot surface. In chemical synthesis the reaction energy is supplied without an external heating system; in wastewater treatment, localised heating and pressure break down organic and inorganic pollutants such as pesticides, dyes and pharmaceuticals.

The uniform heating of the cavitation reactor allows purification at a lower bulk temperature:

• Thermal decomposition of impurities by localised high temperature
• Mechanical breakdown of impurities by shear forces, with better mass transfer
• Separation of impurities from solid particle surfaces by shock waves (de-agglomeration)
• Oxidation of organic impurities by the radicals produced

Examples: phenol removal from wastewater, isolation of metal nanoparticles from surfactant-laden solutions, purification of clays, decolourisation of sugar syrups, separation of lignin and cellulose from biomass.

High cooling rates, shear forces, localised pressure and uniform mixing complete nucleation and crystallisation in a fraction of a second. Rapid precipitation of calcium carbonate, barium sulfate, magnesium hydroxide and the like can replace conventional dryers; crystallisation of organic molecules, dyes and pharmaceuticals, synthesis of monodisperse nanoparticles, and production of nano-emulsions and nano-dispersions are further uses.

Polymer-modified bitumen has a higher softening point and modulus, better low-temperature workability and a longer life, and is used in asphalt paving, waterproofing, coatings and metal-pipe wrapping. The cavitation reactor disperses the polymer (plastomers, elastomers, crumb rubber) uniformly in the bitumen through intense mixing and high shear, cutting processing time against high-shear milling and ultrasonication and saving energy.

Steps: pre-heating of bitumen and modifier, pre-mixing, cavitation, cooling and testing. Polymer type and dose, compatibilisers and the cavitation parameters are optimised for each product. This application is registered in our name with WIPO and has been executed for manufacturing companies. To be completed: patent number and references