Optimisation studies for the esterification and transesterification of oil extracted from Croton gratissimus grains were also carried out using the Response Surface Methodology (RMS) that utilises the Central Composite Design (CCD) and the Analysis of Variance (ANOVA). A 23 full-factorial rotatable CCD for three independent variables at five levels was developed in each case, giving a total of 20 experiments needed per study. The 3 design factors chosen for study were the catalyst concentration, methanol-to-oil ratio and the reaction temperature. The values of the Acid Value of oil (in esterification) and percentage FAME yield and FAME purity (in transesterification) were taken as the responses of the designed experiments. In the optimisation of the esterification and transesterification processes, the ANOVA showed that both quadratic regression models developed were significant. The optimum operating conditions for the esterification process that could give an optimum Acid Value of 2.693 mg KOH/g of oil were found to be; 10.96 mass % SO42–/ZrO2 catalyst concentration, 27.60 methanol-to-oil ratio and 64 0C reaction temperature. In the optimisation of the transesterification process, the model revealed that the catalyst concentration and methanol-to-oil ratio were the terms that had the most influence on the % FAME yield and the % FAME purity of the final biodiesel product. From the combined regression model, it was established that optimum responses of 84.51% FAME yield and 90.66% FAME purity could be achieved when operating the transesterification process at 1.439 mass % KOH catalyst concentration, 7.472 methanol-to-oil ratio and at a temperature of 63.50 0C. Furthermore, in the two-step biodiesel synthesis, a predominantly monoclinic-phased sulphated zirconia (SO42–/ZrO2) catalyst exhibited high activity in the esterification of high Free Fatty acid oil extracted from Croton gratissimus grains. A 91% reduction in the Acid Value of the Croton gratissimus oil from 21.46 mg KOH/g of oil to 2.006 mg KOH/g of oil, well below the 4 mg KOH/g of oil maximum limit, was achieved. This resulted in the high FAME yield and purity of the biodiesel produced in the subsequent catalytic transesterification of oil using KOH.

中文翻译：

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使用硫酸氧化锆和 KOH 作为催化剂从巴豆油生产生物柴油

还使用响应面方法学 (RMS) 进行了对从巴豆提取的油的酯化和酯交换的优化研究，该方法利用了中心复合设计 (CCD) 和方差分析 (ANOVA)。在每种情况下开发了一个 23 个全因子可旋转 CCD，用于五个级别的三个自变量，每个研究总共需要 20 个实验。为研究选择的 3 个设计因素是催化剂浓度、甲醇油比和反应温度。将油的酸值（在酯化中）和 FAME 产率百分比和 FAME 纯度（在酯交换中）作为设计实验的响应。在酯化和酯交换过程的优化中，方差分析表明，开发的两个二次回归模型都很重要。酯化过程的最佳操作条件可以得到 2.693 mg KOH/g 油的最佳酸值；10.96 质量 % SO42–/ZrO2 催化剂浓度，27.60 甲醇油比和 64 0C 反应温度。在酯交换过程的优化中，模型显示催化剂浓度和甲醇油比是对最终生物柴油产品的 FAME 收率和 FAME 纯度百分比影响最大的项。根据组合回归模型，确定在 1.439 质量 % KOH 催化剂浓度下操作酯交换过程时，可以实现 84.51% FAME 产率和 90.66% FAME 纯度的最佳响应，7。472 甲醇与油的比例，温度为 63.50 0C。此外，在两步生物柴油合成中，主要是单斜相硫酸化氧化锆 (SO42–/ZrO2) 催化剂在从巴豆籽粒中提取的高游离脂肪酸油的酯化中表现出高活性。实现了巴豆油的酸值从 21.46 mg KOH/g 油降至 2.006 mg KOH/g 油的 91% 降低，远低于 4 mg KOH/g 油的最大限值。这导致在随后使用 KOH 的油催化酯交换中产生的生物柴油的高 FAME 产率和纯度。主要为单斜相的硫酸化氧化锆 (SO42–/ZrO2) 催化剂在从巴豆籽粒中提取的高游离脂肪酸油的酯化反应中表现出高活性。实现了巴豆油的酸值从 21.46 mg KOH/g 油降至 2.006 mg KOH/g 油的 91% 降低，远低于 4 mg KOH/g 油的最大限值。这导致在随后使用 KOH 的油催化酯交换中产生的生物柴油的高 FAME 产率和纯度。主要为单斜相的硫酸化氧化锆 (SO42–/ZrO2) 催化剂在从巴豆籽粒中提取的高游离脂肪酸油的酯化反应中表现出高活性。实现了巴豆油的酸值从 21.46 mg KOH/g 油降至 2.006 mg KOH/g 油的 91% 降低，远低于 4 mg KOH/g 油的最大限值。这导致在随后使用 KOH 的油催化酯交换中产生的生物柴油的高 FAME 产率和纯度。