Desenvolvimento de protótipos de reatores para extração de óleos essenciais assistidos por micro-ondas (2,45 GHZ)

Abstract

The use of plants as therapeutic resources for the treatment of "body and soul" afflictions, goes back to humanity itself. In some ethnic groups it is the only therapeutic resource available, including the use of essential oils (OE), which, in addition to having numerous industrial applications, is used in alternative medicine and aromatherapy. Brazil has an enormous animal and vegetal biodiversity, among these plants there are many that produce OE. There are several methods for extracting these OE, conventional, and more recently, microwave assisted methods. OE commercially available microwave extraction equipment is faster and more efficient, delivering results that are comparable to conventional ones, with about a fifth of the time. However these equipments are basically adapted furnaces, that is, they use multimode cavities to propagate the waves. With a single-mode cavity, the efficiency of the microwaves would be much higher, but this type of cavity must meet the so-called boundary conditions (imposed by the matrix used), and respect the dimensions related to them, which are calculated from the dielectric permittivity of material. The measurements of the dielectric properties of Cymbopogum (Nardus or Winterianus), Eucalyptus sp, Piper aduncum and Piper hispidinervum, with dry plants (without addition of water) and in mixtures with water (1: 1) were performed. With the aid of software, SOLCOND, the dimensions (cavity and sample diameter) optimized for a single-mode cylindrical reactor were calculated. According to these calculations, the best single-mode reactor would be operating in transverse electric mode at 2.45GHz. However, since the calculated dimensions were very small (from 3 to 115 mm) and the physical characteristics of the sample, a single-mode reactor would only be viable if it worked in a continuous flow, but the passage of the sample by the reactor would be a complicated task and would make it impractical to expand of scale (from bench to pilot or industrial). In this way, a batch reactor, microwave assisted, multimode and operating at 2.45GHz was machined. The efficiency of extraction was greater than 70% in 30min for power of 2400W, and in other potencies, the efficiency of extraction was greater than 70% in 30min for power of 2400W, compared to hydrodistillation (for 3h) the extraction efficiency was, on average, over 62%, besides the time saving around 83%. The use of microwave assisted reactors for extraction of OE, even using a multimode cavity, is a very interesting alternative, since the extractions occur in times inferiors, with yields and efficiency comparable to the conventional methods, besides the saving of water and energy , without loss of OE quality.