HDC in Chemical Processes
HDC has been effectively used for the synthesis of many chemicals such as biodiesel, polymeric substance (low molecular weight), organic chemicals, and thermal cracking of heavier petroleum crude into low molecular weight distillates. HDC can drive many chemical reactions such as oxidation reactions, breakdown of higher molecular weight compounds into smaller molecules, hydrolysis of edible oil, and transesterification reactions.
Reactions associated with solid catalysts can also be intensified under the mechanical effects of cavitation. The catalyst gets activated because of the increased surface area and porosity as a result of asymmetric cavity collapse on the surface of catalyst.
In chemical industries, many important chemicals such as alcohols, carboxylic acids, phenol, quinones, and acetone are produced by the oxidation of aldehydes, ketones, and alkylarenes. These oxidation reactions are conducted in the presence of catalyst and require high temperature and high-pressure conditions.
Most of the oxidation reactions are initiated by the attack of free radicals, which is generated by a catalyst. Metal oxides are normally used as a catalyst for the oxidation reactions such as vanadium pentoxide (V2O5), CuO-impregnated mesoporous silica (CuO/SiO2), Pt/Al2O3, etc. The reaction yield highly depends on the catalyst activity, and highspeed agitation is required to generate sufficiently high interfacial area. In addition, heat needs to be supplied to maintain the required reaction temperature and reaction rates.
In the reactor, it is very important to impart the energy at the intermolecular level and reaction interfaces. In conventional processes, most of the energy is wasted in created turbulence in the bulk of the liquid and only a part of the supplied energy is used for reaction purposes.
The advantages of HC reactor over conventional reactors is that the reactions can be conducted more efficiently at ambient conditions using HC and at a lower cost. The cavities generated in HC are capable of delivering the energy at microlevel because of their small sizes and the hot spots provide the energy at the required molecular level. Some reactions that have been tried successfully:
Production of aryl carboxylic acid by the oxidation of alkylarenes in the presence of aqueous KMnO4 .
The oxidation of toluene by aqueous KMnO4.
Hydrolysis of vegetable oils.
Depolymerization of biopolymers such as chitosan, guar gum, etc..
Crude oil upgradation, to reduce the chain length of waxy oils.