Síntese enzimática de diésteres do ácido sebácico

Abstract

Pollution and aspects of environmental conservation has gained high visibility in the global context in recent decades. In lubrication area, concern is focused on issues related to the large proportion of lubricant that is released into the environment. In this scenario, development of sustainable alternatives has been investigated, including synthesis of biolubricants. These are considered a good alternative to traditional lubricants. Synthetic esters are considered promising for the replacement of mineral-based lubricating substances because they respond to the challenges for modern engines and machines in both points, technical and environmental. Particularly esters derived from dicarboxylic acids have thermal and oxidative stability, good lubricity, are biodegradable and have a moderate cost of production. Therefore, in this work the synthesis of diesters derived from sebacic acid, a dicarboxylic acid which is obtained from the alkaline oxidation of the castor oil to obtain a biolubricant was studied. The main process parameters reported in the literature were investigated, including: type of alcoholic substrate (2-octanol, 1-octanol, 1-hexanol), type of commercial immobilized lipase (Novozym 435, Lipozyme RM IM, Lipozyme TL IM), lipaseamount (1, 3, 5, 7, 9, 11 e 13% w/w), reaction temperature (90,ºC, 100º e 110ºC), molar ratio of the substrate (razão ácido sebácico/álcool = 1:4, 1:5, 1:6, 1:7), methods of removal water produced in the reaction (using sieve molecular, application of vacuum or free evaporation) andpossibility of recovery and reuse of the biocatalyst after solvent washing (n-hexane, 2-octanol). Also was evaluated the use of homogeneous acid catalyst (sulfuric acid) in the synthesis of di-octyl sebacate, at a concentration of 0.1; 1 and 2% w / w relative to the mass of sebacic acid. The best results were obtained in the enzymatic catalysis was observed in the reactions employing molar ratio alcohol/sebacic acid equal to 5, concentration of biocatalyst Novozym 435 equal to 5% w/w and temperature of 100°C. Under these conditions, sebacic acid conversion was nearly 100% after 150 minutes of reaction, the molar fraction of the diester was 90%. Similar results were obtained in the reaction using sulfuric acid as catalyst at 2% w/w. After study the suitable reaction conditions for increased product selectivity and conversion of substrate, the biolubricant was characterized and compared with the commercial lubricants