No description available.

No description available.

Tese de doutoramento. Ciências de Engenharia. Faculdade de Engenharia. Universidade do Porto. 2005

A simple process to obtain onion oil by direct solvent extraction was proposed. Several solvents commonly utilized in the food industry were tested for their selectivity in the extraction of the oil of onion. Diethyl ether and methylene chloride appeared to be the most suitable solvents for the extraction operation. The direct solvent extraction method produced a yield of onion oil approximately seven times higher than the yield obtained by the steaim distillation method. A process of fermentation of the ground raw onions was used prior to the solvent extraction operation. This produced an improvement in the onion oil yield of 60% over the normal solvent extraction method. In order to determine the quality of the onion oil obtained, refractive index, specific gravity, melting point, and sulfur content were determined. Sulfur content in the onion oil obtained by the method proposed here had one-third (weight basis) of the sulfur content of commercial onion oil. Two organoleptic evaluations were conducted for commercial onion oil and for the onion oil obtained by direct solvent extraction: odor threshold determination and comparative flavor evaluation. The commercial onion oil showed a lower threshold concentration (1.6 ppb) than the onion oil obtained in the laboratory (8.4 ppb). With respect to the comparative flavor tests, the test panels did not detect a statistically significant difference between the flavor of commercial onion oil and the oil obtained by the method proposed here. / Graduation date: 1982

No description available.

A novel technique of direct copper precipitation from a loaded chelating extractant using hydrogen in an autoclave (pressure hydrogen stripping) was studied. In its simplest form, the reaction is given by / {CuL(,2)}(,org) + H(,2)(g) (--->) 2{HL}(,org) + Cu(s). / Kelex 100 (Sherex Chemical Co. - commercial solvent extraction reagent), an alkylated derivative of 8-hydroxyquinoline was used as the basis of the present investigation and represents HL in the above equation. / Two types of experiments were carried out: (a) those designed to study the chemical and thermal response of the extractant at high temperature and hydrogen pressures and (b) those which describe the chemistry and kinetics of hydrogen stripping. / The extractant was found to exhibit excellent chemical stability up to 573 K (300(DEGREES)C) and 2.76 MPa (400 psi) hydrogen in the absence of copper. Its chemical stability was somewhat reduced when loaded with copper. In the latter case, some limited hydrogenation of the quinoline nucleus of the extractant and some of the impurities present (furoquinolines) was observed. The chemical stability of the extractant was found to be enhanced when at least 0.52 M of a long-chain alcohol (decanol) was added to the organic solvent (0.4 M Kelex/kerosene). A slow thermal dissociation of the copper chelate was found to take place within the experimental temperature range studied (443 to 488 K). This resulted in copper precipitation and organic regeneration. / Copper in a powder form was found to precipitate rapidly from loaded Kelex 100/decanol/kerosene solvents by reaction with hydrogen at pressures between 0.52 and 4.00 MPa (75 and 580 psi) and temperatures from 443 to 488 K (170 to 215(DEGREES)C). The overall process has heterogeneous characteristics. Nuclei are provided through slow thermal dissociation of the copper chelate. The freshly produced metallic copper, acting autocatalytically accelerates the precipitation kinetics. Reduction of the Cu(II) chelate to Cu(I) complex appears to be the rate controlling step. / In addition to temperature and pressure, the effects of seeding, agitation, copper concentration, ligand concentration and copper chelate age were investigated. Some physical and chemical properties of the copper powder product were also determined.

No description available.

No description available.

Thesis (PhD)--University of South Australia, 1997

Thesis (M.S.)--Virginia Polytechnic Institute, 1965. / Vita. Abstract. Includes bibliographical references (leaves 34-36). Also available via the Internet.