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Synthesis Of Biodiesel In Supercritical FluidsRathore, Vivek 05 1900 (has links)
Alternative fuels are becoming important due to diminishing fossil fuel reserves and the
environmental hazards associated with exhaust gases. Biodiesel is an attractive alternative fuel because it is environmentally friendly and can be synthesized from edible/non-edible oils. Though several methods are available for synthesis, transesterification is the preferred route for biodiesel synthesis. The current techniques for transesterification of the oils to biodiesel are based on acid/alkali catalysis. However, these methods do not work for oils with high free fatty acid content and also require an additional downstream step for separation of catalyst from the product.
In this work, we investigate the synthesis of biodiesel by two techniques: in
supercritical methanol and ethanol without any catalyst; in supercritical carbon dioxide
using enzyme as catalyst. In the first technique, the transesterification of refined grade edible oil like sunflower oil, palm oil and groundnut oil, and crude non-edible oils like Pongamia pinnata and Jatropha curcas was investigated in supercritical methanol and ethanol without using any catalyst from 200 oC to 400 oC at 200 bar. The variables affecting the conversion during transesterification, such as molar ratio of alcohol to oil, temperature and time were investigated in supercritical methanol and ethanol. The conversion to biodiesel increased from 30-40% at a molar ratio of 10 to 80-85% at a molar ratio of 45 to 50. Very high conversions (96-97%) were obtained in supercritical methanol and ethanol within 30 minutes at 350 oC. The kinetics of the reaction was modeled, the rate coefficients and activation energies were determined.
As an enzymatic transesterification in organic solvents is mass transfer limited,
supercritical fluids are found to be a better alternative because of their gas like
diffusivity. Among potentially interesting solvents for enzymatic synthesis, carbon
dioxide is the most obvious choice in supercritical fluids, because it is non-toxic, nonflammable and easily available. Because the products and the enzyme do not dissolve in carbon dioxide at room conditions, separation can easily be achieved by reduction of pressure Thus, the enzymatic transesterification for production of biodiesel in supercritical fluids under mild conditions is of commercial interest. Therefore, biodiesel was synthesized using immobilized enzyme (Lipase, Novozym-435) in supercritical carbon dioxide. The effect of reaction variables like temperature, molar ratio, enzyme loading and kinetics of the reaction was investigated. The conversion to biodiesel was found to be lower in supercritical carbon dioxide than that in supercritical alcohol.
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Catalisadores heterogêneos suportados em carvão ativado destinados à síntese de biodiesel de óleo de algodão. / Heterogeneous catalysts supported in activated carbon destined to the synthesis of biodiesel of cotton oil.MENEZES, Janaina Moreira de. 23 March 2018 (has links)
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Previous issue date: 2015 / Diante de uma demanda crescente por energia no mundo e o aumento da poluição atmosférica causada pelo uso de combustíveis fósseis, a busca por fontes de energia renováveis vem crescendo consideravelmente. O processo utilizado pelas usinas de biodiesel emprega catalisadores homogêneos básicos, que apesar de conduzir a elevados rendimentos requer óleos altamente refinados e necessita de etapas de purificação do produto final o que vem a contribuir para um alto custo de produção. Partindo desta premissa, busca-se desenvolver um catalisador heterogêneo de baixo custo que simplifique o processo de produção, que seja estável e forneça altas conversões em temperaturas brandas de reação. Desta forma, o presente trabalho teve como objetivo preparar catalisadores metálicos suportados em carvão ativado
comercial e aplicá-los na produção de biodiesel metílico e etílico a partir do óleo de algodão degomado e neutralizado, avaliando a conversão em ésteres. Os catalisadores foram preparados pelo método de impregnação úmida na concentração de 5% em massa. Foram caracterizados pelas técnicas de DRX, FRX, IFTR, MEV, titulação de Boehm e análise textural. Testes preliminares identificaram que o catalisador molibdênio ofereceu os melhores resultados na reação simultânea de esterificação/transesterificação metílica e etílica, com conversão de 43 % e 40 % respectivamente. Uma vez selecionado o catalisador este foi aplicado em um planejamento fatorial 23 para verificar o efeito das variáveis: temperatura de reação (80-160 °C), razão molar óleo:álcool (1:6 a 1:12) e concentração de catalisador (1 a 3 %); sob a resposta teor de ésteres. Verificou-se que a temperatura foi a variável de maior influência e atua de forma positiva nas reações de éster/transesterificação, conduzindo a conversão de 91 % em teor de ésteres. A partir de análise das superfícies de resposta, verificou-se que as condições ótimas de operação que conduzem a uma maior conversão em ésteres seriam: temperatura de 160 °C, razão molar óleo:álcool de 1:13 e concentração de catalisador de 3,2 %. Os resultados do ensaio de reuso mostrou que o catalisador pode ser reutilizado de forma consecutiva atingindo bons resultados, observou-se um decaimento de apenas 7 % no teor de éster ao ser reutilizado no 3° ciclo. O acompanhamento cinético demonstrou que com 5 horas de reação nas melhores condições reacionais é possível alcançar um teor de éster de 96,3 %. / Faced with a growing demand for energy in the world and the increase of air pollution caused
by the use of fóssil fuels, the search for renewable energy sources has grown considerably.
The processused in biodiesel plants use basic homogeneous catalysts, although they lead to
high yields, this requires highly refined oil sand purification steps of the final product which
is contribute to a high production cost. Starting from this premise, we seek to develop a lowcost
heterogeneous catalyst to simplify the production process, which could best able and
provides high conversions under mild reaction temperatures. Thus, this study aimed to
prepare metal catalysts supported on activated carbono and apply them in the production of
methyl and ethyl biodiesel using degummed and neutralized cottonseed oil, in batch reactor
with agitation, evaluating the conversion into esters. The catalysts were prepared by wet
impregnation at a mass concentration of 5%. They were characterized by techniques of DRX,
FRX, IFTR, MEV, Boehm tritation and textural analysis. Preliminary tests identified that the
molybdenum catalyst offered the best results in the simultaneous reaction of methyl and ethyl
ester/transesterification, with conversion of 43% and 40% respectively. Once selected the
catalyst, this was applied to a 23 factorial design to determine the effect of variables: reaction
temperature (80-160°C), molar ratio oil:alcohol (1:6 to 1:12) and catalyst concentration (1 to
3%); and the response variable was ester content. And it was found that the temperature
variable was the greatest influence and acts positively on the ester/transesterification
reactions, leading to 91% conversion in ester content. From analysis of response surfaces, it
was found that the optimal operating conditions leading to a higher conversion to esters are:
temperature 160°C oil molar ratio: 1:13 alcohol and catalyst concentration 3,2%. The results
of the recycle showed that reuse of the catalyst can be reused consecutively achieving good results, there was a decay of only 7% in the ester content to be reused in the 3rd cycle. The kinetic monitoring demonstrated that 5 hours of reaction with the best reaction conditions it is possible to achieve a 97.3% ester content.
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Biodiesel de óleo de fritura via hidroesterificação utilizando vermiculita como catalisador heterogêneo. / Biodiesel from frying oil via hydroesterification using vermiculite as a heterogeneous catalyst.LACERDA, José Gorete Pedroza de. 14 May 2018 (has links)
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Previous issue date: 2018-03-05 / Este trabalho investigar a síntese do biodiesel proveniente do óleo de fritura através da reação de hidroesterificação, utilizando como suporte catalítico heterogêneo, a vermiculita. A hidrólise foi efetuada em reator de autoclave numa temperatura de 300 ºC por 3 h, e em seguida, a esterificação foi realizada sob razão molar do álcool etílico/ácido graxo na proporção 6:1, na presença de 5% do catalisador em relação à massa do óleo. Tanto o biodiesel e o óleo de fritura foram caracterizados por meio de parâmetros físico-químico, térmicos e por espectrofotometria de absorção na região do UV-Visível com fins de melhor compreensão. O rendimento reacional em relação à massa do óleo de fritura residual para o biodiesel foi de 66,65%. A curva termogravimétrica referente ao biodiesel apresentou duas etapas de decomposição, sendo a primeira etapa com 83,1% de perda de massa, indicando a conversão em monoacilglicerideos, e a segunda com 14,3% de perda de massa, atribuída a presença de traços de diacilglicerídeos e/ou triacilglicerídeos não convertida em ésteres de ácidos graxos etílicos. Os espectros de absorção na região do infravermelho confirmaram a presença dos ésteres de ácidos graxos etílicos em 1749,7 cm-1, no entanto, também verificou presença de banda vibracional correspondente ao estiramento do grupo OH, em 3600 a 3300 cm-1, confirmando presença de umidade e/ou a não conversão total da hidrólise de glicerídeos. Por fim, este trabalho demonstrou ser satisfatório em termos de conversão, embora requeira um estudo mais aprofundado, manipulando as condições reacionais. / This study aimed to investigate the synthesis of biodiesel from frying oil through the
hydroesterification reaction, using as heterogeneous catalytic support – vermiculite. Both the
biodiesel obtained and the raw material (frying oil) were characterized by physical-chemical,
thermal and absorption spectrophotometry in the UV-Visible region for better understanding.
The synthesis of biodiesel by hydroesterification involved two steps: hydrolysis and
esterification, whereby the residual frying oil was subjected to the step of hydrolysis in an
autoclave reactor at a temperature of 300 ° C for 03 hours. After the hydrolysis, the glycerin
was removed and the fatty acids generated were subjected to the esterification step and
processed under the following conditions: 6: 1 molar ratio of the ethyl alcohol / fatty acid in
the presence of 5% of the catalyst (vermiculite) relative to the mass of the oil. Subsequently,
the mixture was subjected to the stirring process and transferred to the autoclave reactor at
200°C for 01 hour. After that, the mixture was decanted for 2 hours and the phases were
separated. The dense phase – biodiesel – was characterized according to the standards of the
National Agency for Petroleum, Natural Gas and Biofuel. Thus, the reaction yield in relation
to the initial mass of the residual frying oil for biodiesel was 66.65%. It is suggested that this
yield was compromised by the acidity of the obtained biodiesel (0.61mg KOH/g),
contributing to the release of the free fatty acids in the medium. Regarding the thermal study,
the thermogravimetric curves showed that biodiesel is more volatile compared to the frying
oil and presented two stages of decomposition: the first probably corresponding to the ethyl
ester volatilization, with 83.1% of mass loss, indicating the conversion to
monoacylglycerides; and the second stage with 14.3% of mass loss, attributed to the presence
of diacylglyceride and/or triacylglyceride traces not converted to esters of ethyl fatty acids.
The absorption spectra in the infrared region confirmed the presence of the strongly acidic
fatty acid esters of 1749.7 cm-1; however, the presence of medium-sized vibrational band,
corresponding to OH group stretching, is also present at 3600 to 3300cm-1, corroborating the
thermal and physicochemical profile, confirming the presence of moisture and/or total nonconversion
of glyceride hydrolysis. Finally, according to the results presented, this study
proved to be feasible in terms of conversion, although it requires further investigation,
manipulating the reactional conditions.
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