Domingos Anderson Kurunczi, Saad Emir Bolzani, Wilhelm Helena Maria, Ramos Luiz Pereira
Centro de Pesquisa em Química Aplicada (CEPESQ), Department of Chemistry, Federal University of Paraná - UFPR, Curitiba, PR, Brazil.
Bioresour Technol. 2008 Apr;99(6):1837-45. doi: 10.1016/j.biortech.2007.03.063. Epub 2007 Jun 12.
Raphanus sativus (L. Var) is a perennial plant of the Brassicaceae (or Cruciferae) family whose oil has not been investigated in detail for biodiesel production, particularly when ethanol is used as the alcoholysis agent. In this work, response surface methodology (RSM) was used to determine the optimum condition for the ethanolysis of R. sativus crude oil. Three process variables were evaluated at two levels (2(3) experimental design): the ethanol:oil molar ratio (6:1 and 12:1), the catalyst concentration in relation to oil mass (0.4 and 0.8 wt% NaOH) and the alcoholysis temperature (45 and 65 degrees C). When the experimental results were tentatively adjusted by linear regression, only 58.15% of its total variance was explained. Therefore, a quadratic model was investigated to improve the poor predictability of the linear model. To apply the quadratic model, the 2(3) experimental design had to be expanded to a circumscribed central composite design. This allowed the development of a response surface that was able to predict 97.75% of the total variance of the system. Validation was obtained by performing one ethanolysis experiment at the conditions predicted by the model (38 degrees C, ethanol:oil molar ratio of 11.7:1 and 0.6 wt% NaOH). The resulting ester yield (104.10 wt% or 99.10% of the theoretical yield of 105.04 wt%) was shown to be the highest among all conditions tested in this study. The second ethanolysis stage of the best RSM product required 50% less ethanol and 90% less catalyst consumption. The amount of ethyl esters obtained after this procedure reached 94.5% of the theoretical yield. The resulting ethyl esters were shown to comply with most of the Brazilian biodiesel specification parameters except for oxidation stability. Addition of 500 ppm of BHT to the esters, however, complied with the specification target of 6h. The application of 2 wt% Magnesol after the second ethanolysis stage eliminated the need for water washing and helped generate a final product with less unreacted glycerides.
萝卜（L. Var）是十字花科的一种多年生植物，其油尚未针对生物柴油生产进行详细研究，特别是当乙醇用作醇解剂时。在这项工作中，采用响应面法（RSM）来确定萝卜原油醇解的最佳条件。在两个水平（2(3)实验设计）下评估了三个工艺变量：乙醇与油的摩尔比（6:1和12:1）、相对于油质量的催化剂浓度（0.4和0.8 wt% NaOH）以及醇解温度（45和65℃）。当通过线性回归初步调整实验结果时，仅解释了其总方差的58.15%。因此，研究了二次模型以改善线性模型较差的预测能力。为了应用二次模型，2(3)实验设计必须扩展为外切中心复合设计。这使得能够开发出一个响应面，该响应面能够预测系统总方差的97.7%。通过在模型预测的条件（38℃、乙醇与油的摩尔比为11.7:1和0.6 wt% NaOH）下进行一次醇解实验获得了验证。所得酯产率（104.10 wt%或理论产率105.04 wt%的99.10%）在本研究测试的所有条件中显示为最高。最佳RSM产物的第二个醇解阶段所需乙醇减少50%，催化剂消耗减少90%。此步骤后获得的乙酯量达到理论产率的94.5%。所得乙酯除氧化稳定性外，显示符合巴西生物柴油规格的大多数参数。然而，向酯中添加500 ppm的BHT符合6小时的规格目标。在第二个醇解阶段后应用2 wt%的硅酸镁消除了水洗的需要，并有助于生成未反应甘油酯较少的最终产物。
