Titulo corto: Biodiesel de aceite residual de cocina Titulo en ingles: Characterization of Biodiesel obtained from waste cooking Resumen Se realizo un analisis fisico y quimico a cada uno de los siguientes tipos de aceite: desechado proveniente de asaderos de pollo, usado de hogares y fresco adquirido en el mercado local de la ciudad de Florencia, Caqueta (Colombia). Se evaluaron los siguientes parametros: Peso especifico, indice de yodo, indice de saponificacion, indice de refraccion, humedad y materia volatil, punto de fusion, impurezas insolubles, indice de acidez, coeficiente especifico de extincion valores K232 y K270, color y prueba de Kreiss. Igualmente se evaluaron los espectros UV-VIS de los tres tipos de aceite estudiados. Se ensayaron siete diferentes tipos de catalizadores para la reaccion de transesterificacion manteniendo en todos los casos la proporcion de catalizador: aceite 38:190 (v/v), tiempo de reaccion (2h) y temperatura de reaccion (60°C). Se lograron rendimientos de biodiesel de 75.8% de aceite desechado usando KOH 1,269%p/v/MeOH 99%; 87.50% de aceite usado con KOH 0,537%p/v/MeOH 99% y 86.60% de aceite fresco usando KOH 0,457%p/v/MeOH 99%. Al biodiesel obtenido en cada caso se le determino peso especifico, indice de refraccion, humedad y materia volatil, cenizas sulfatadas, carbon residual, corrosion a la lamina de cobre y perfil de acidos grasos. En todos los casos hubo predominio de acido palmitico, acido oleico y acido estearico en los aceites usados y desechados. Del analisis por cromatografia de gases acoplada a espectrometria de masas se pudo establecer que el contenido total de esteres metilicos de acidos grasos es del 98,38% para el biodiesel de aceite desechado; 99,53% para el biodiesel de aceite usado y 97, 69% para el biodiesel de aceite fresco. Palabras clave: aceite residual de cocina; biodiesel; acidos grasos; transesterificacion Abstract Aphysical and chemical analysis was carried outin the following types of oils: waste oil taken from chicken steakhouses, waste oil from houses and clean oil from the local market at Florencia, Caqueta (Colombia). The following parameters were evaluated: specific weight, iodine value, saponification value, refractive index, moisture and volatile matter, melting point, insoluble impurities,acidity index, specific coefficient extinction of K232 and K270 values, color and Kreiss test. Also, the UV-VIS spectra for the three types of oil studied were evaluated. Seven different types of catalysts for the transesterification reaction were tested, maintaining the same ratio of catalyst for all cases: oil 38:190(v/v), reaction time (2 h) and reaction temperature (60 °C). biodiesel performancesof 75.8% with disposedo,using KOH 1.269%w/v/99%MeOH; 87.50% wasted oil with KOH 0.537% w/v/99%MeOH and 86.60% fresh oil using KOH 0.457% w/v/MeOH99%were achieved. For the biodiesel obtained, in each case, the specific gravity, refractive index, moisture and volatile matter, sulfated ash, carbon residue, corrosion to the copper foil and fatty acid profile were determined. In all cases, there was a predominance of palmitic, stearic and oleic acids in the usedand disposedoils. From the chromatography gases analysis with the mass spectrometry was established that the total content of methyl esters of fatty acids was 98.38 % for biodiesel taken from waste oil; 99.53% for biodiesel t from wasted oil and 97,69% for biodiesel from clean oil. Key words: biodiesel; fatty acids; transesterification; wasted cooking oils .