Síntese de ésteres emolientes em sistema livre de solvente utilizando lipases imobilizadas

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Química, Florianópolis, 2019A utilização de catalisadores enzimáticos são uma alternativa aos catalisadores químicos, pois podem ajudar a obter produtos com menor impacto ambiental, considerados sustentáveis dentro do conceito da química verde. Neste trabalho, avaliou-se a viabilidade de produção dos ésteres estearato de benzila e oleato de etilenoglicol, ésteres emolientes utilizados na formulação principalmente de cosméticos, a partir da reação de esterificação enzimática, utilizando lipases comerciais imobilizadas em sistema livre de solvente. A síntese de oleato de etilenoglicol foi realizada a partir do ácido oleico e do álcool monoetilenoglicol utilizando a lipase comercial Candida antarctica (NS 88011) como catalisador. A síntese do estearato de benzila foi realizada a partir do ácido esteárico e o álcool benzílico utilizando principalmente a lipase comercial Candida antarctica Novozym 435®. A síntese de oleato de etilenoglicol foi estudada por meio de planejamento experimental, utilizando as variáveis temperatura (40-70 oC), razão molar entre o ácido e o álcool (1:2, 1:4, 1:6) e agitação (200-600 rpm). Além disso, realizou-se ensaios cinéticos com diferentes concentrações de derivado enzimático e teste de reúso. Diferentes enzimas comerciais (Novozym 435®, Lipozyme RMIM, Lipozyme TLIM e NS 88011) foram testadas na síntese de estearato de benzila, sendo que ensaio cinético foi realizado para diferentes razões molares de reagentes para o derivado Novozym 435®. Foi possível produzir o éster oleato de etilenoglicol e também estearato de benzila com excesso de álcool em sistema livre de solventes com conversão praticamente total para o oleato de etilenoglico e acima de 90% para o estearato de benzila. A cinética da reação de síntese de oleato de etilenoglicol apresentou duas fases: a primeira em que as velocidades e os níveis de conversão atingidos dependem da concentração do derivado enzimático e a segunda em que a inibição atingida na primeira fase cessa e há uma retomada da reação com velocidades inferiores. A temperatura mostrou ser a variável mais importante para atingir-se altas conversões da reação de esterificação de oleato de etilenoglicol e foi possível reutilizar o catalisador enzimático lipase NS 88011 com conversões similares em dois ciclos de 48 h. Utilizando a enzimas Novozym 435® obteve-se o éster estearato de benzila em sistema livre de solvente com conversão 95% em 6 h de reação, sendo que o excesso de álcool em relação ao ácido, acima de 5:1, prejudicam a cinética da reação, mas não influenciam a conversão final.Abstract: The use of enzymatic catalysts is an alternative to chemical catalysts, since they can help to obtain products with less environmental impact, considered sustainable within the concept of green chemistry. In this work, the viability of the production of the benzyl stearate esters and ethylene glycol oleate, emollients esters used in the formulation of cosmetics mainly, from the enzymatic esterification reaction, was evaluated using commercial lipases immobilized in a solvent-free system. Synthesis of ethylene glycol oleate was performed from oleic acid and alcohol monoethyleneglycol using the commercial lipase Candida antarctica (NS 88011) as the catalyst. The synthesis of benzyl stearate was performed using stearic acid and benzyl alcohol using mainly the commercial lipase Candida antarctica Novozym 435®. The synthesis of ethylene glycol oleate was studied by means of experimental design, using the variables temperature (40-70 ºC), molar ratio of acid to alcohol (1:2, 1:4, 1:6) and stirring (200-600 rpm). In addition, kinetic assays were performed with different concentrations of enzyme derivative and re-test. Different commercial enzymes (Novozym 435®, Lipozyme RMIM, Lipozyme TLIM and NS 88011) were tested in the synthesis of benzyl stearate, and kinetic assay was performed for different molar ratios of reagents for the Novozym 435® derivative. It was possible to produce the oleate ester of ethylene glycol and also benzyl stearate with excess alcohol in a solvent-free system with practically total conversion to ethylene glycol oleate and above 90% for benzyl stearate. The kinetics of the ethylene glycol oleate synthesis reaction had two phases: the first where the rates and the conversion levels reached depend on the concentration of the enzymatic derivative and the second where the inhibition reached in the first phase ceases and there is a recovery of the reaction with lower speeds. The temperature showed to be the most important variable to achieve high conversions of the esterification reaction of ethylene glycol oleate and it was possible to reuse the enzymatic catalase NS 88011 lipase with similar conversions in two 48 h cycles. Using the enzymes Novozym 435®, the benzyl stearate ester was obtained in a solvent-free system with a conversion of 95% in 6 hours of reaction, with excess alcohol over 5:1, harming the kinetics of the reaction, but do not influence the final conversion

Photocatalytic activity of ceramic tiles coated with titania supported on kaolinite

Titania is an established photocatalytic material. The dispersion of titania nanoparticles on kaolinite particles as carrier and support precursor, TiO2-kao, has been studied to avoid losses in photocatalytic efficiency once fired by single-fired porcelain tile route. The photocatalyst was prepared using the hydrolytic sol-gel route. A commercial titania, P25, was used as a reference TiO2. The samples were fast fired at 800, 1015, 1100, and 1185 °C. Degradation of methylene blue was used to assess the photocatalytic performance. TiO2-kao and P25 applied to unglazed plates fired at 800 °C yielded ∼65% degradation, ∼50% due to photocatalysis, and ∼15% due to photolysis. P25 samples retained ∼10% of their photoactivity after firing at 1185 °C, TiO2-kao retained 80%. TiO2-kao on glazed tiles fired at 1185 °C retained 30% photoactivity. The photocatalytic losses in the glazed sample were due to the reduction in contact area caused by particle encapsulation in the glass layer

Enzymatic esterification of stearic acid and ethanol for ethyl stearate production

Ethyl stearate is an ester obtained by the esterification of stearic acid and ethanol. Esters are organic substances that can be found in nature and it is of great importance pharmaceutical industry, perfumes, polymers, cosmetics and in the food industry. Ethyl stearate is widely used in the perfume industry in fragrances in small concentrations, and can also be used as artificial flavoring, generally as additives to enhance the aroma of a drink or a food. This study aimed to evaluate the enzymatic synthesis of ethyl stearate in a free-solvent system. For the synthesis the effect of the agitation of 150 at 250 rpm and molar ratio between the substrates of 1:1 at 1:7 (acid:alcohol) was evaluated since the temperature (60 °C) and enzyme concentration (1%, wt of acid) were kept constant. Commercial ipases Novozym 435 and NS 88011 were tested and Novozym 435 showed better performance (82% conversion) for the synthesis of ethyl stearate. The highest conversion (92%) in ethyl stearate in the optimized condition was obtained at molar ratio of 1:5, 60 °C, 200 rpm of agitation, enzyme concentration of 1 wt%, 24 h of reaction and addition of alcohol fractionated in three portions in the first hours of reaction. This study also evaluated the possibility of reuse of the biocatalyst, obtaining satisfactory results of 60% in three cycles

Enzymatic synthesis of butyl stearate in solvent-free system

Butyl stearate is an ester obtained by the esterification of stearic acid and butanol, which is used a solvent and spreading agent for creams and creamy lotions. It has been important for the cosmetics industry as it often acts as substitute for mineral and vegetable oils. It also has emollient properties, having the advantage of not leaving the greasy sensation on the skin and providing the sensation of softness. Considering the importance of this ester, this work aimed to evaluate the enzymatic production of butyl stearate. All experiments for the production of this ester were conducted in an orbital shaker, varying the agitation of 150 at 250 rpm and substrates molar ratio of 1:1 at 1:7 (acid:alcohol), while the temperature (60 °C) and enzyme concentration (1%, wt of acid) were kept constant. First, two immobilized commercial enzymes were tested (Novozym 435 and NS 88011), where the enzyme that gave the best results (conversion of 84%) was the Novozym 435. So, the optimization of butyl stearate production was performed using Novozym 435. The best result, conversion of 92%, was observed in the condition of 60 °C, substrates molar ratio of 1:2, 1 wt% of the enzyme, 200 rpm and with the addition of alcohol fractionated in three portions in the first hours of reaction. The biocatalyst reuse was also evaluated, leading to satisfactory results, 70% of conversion after five cycles of use