Abstract Nanostructured calcium oxides supported onto biochar obtained by pyrolysis of avocado seeds were prepared, characterized and successfully used as catalysts to produce biodiesel from waste oils. The effect of increasing calcium load (5, 10 and 20 wt%) was investigated. Elemental analysis, FTIR, XRD, SEM, BET, acid and basic sites were used to characterize the resulting carbon-based calcium oxides. Supported systems efficiently promoted the transesterification of oil with methanol, but differently from calcium oxide, they were easily recoverable and reusable for three cycles without any loss of activity. Kinetic data were better fitted by a pseudo-second order model with an activation energy of 39.9 kJ mol−1. Thermodynamic parameters of activation energy were also determined for the transesterification reaction ( Δ ‡ G: 98.68-106.08 kJ mol−1, Δ ‡ H: 37.05 kJ mol−1 and Δ ‡ S: 0.185 kJ mol−1 K). Finally, reaction conditions were optimized using the desirability function applied on the response surface methodology analysis of a Box–Behnken factorial design of experiments. By carrying out the reaction at 99.5 °C for 5 h with 7.3 wt% of catalyst and a molar ratio of methanol to oil of 15.6, a FAME content over 96% was achieved. Even starting from waste cooking oil, final biodiesel was conform to the main EN14214 specifications.

中文翻译：

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负载在生物炭上的纳米结构氧化钙的合成和表征及其作为生物柴油生产催化剂的应用

摘要 制备、表征了鳄梨种子热解获得的生物炭上负载的纳米结构氧化钙，并成功用作催化剂以从废油中生产生物柴油。研究了增加钙负荷（5、10 和 20 重量%）的影响。元素分析、FTIR、XRD、SEM、BET、酸和碱位用于表征所得碳基氧化钙。支撑系统有效地促进了油与甲醇的酯交换，但与氧化钙不同的是，它们很容易回收和重复使用三个循环而不会损失任何活性。动力学数据更适合于具有 39.9 kJ mol-1 活化能的伪二阶模型。还确定了酯交换反应的活化能热力学参数（Δ‡ G：98.68-106。08 kJ mol-1，Δ ‡ H：37.05 kJ mol-1 和 Δ ‡ S：0.185 kJ mol-1 K）。最后，使用适用于 Box-Behnken 实验设计的响应面方法分析的合意性函数优化反应条件。通过在 99.5 °C 下用 7.3 wt% 的催化剂和 15.6 的甲醇与油的摩尔比进行反应 5 h，实现了超过 96% 的 FAME 含量。即使从废食用油开始，最终的生物柴油也符合主要的 EN14214 规范。实现了超过 96% 的 FAME 含量。即使从废食用油开始，最终的生物柴油也符合主要的 EN14214 规范。实现了超过 96% 的 FAME 含量。即使从废食用油开始，最终的生物柴油也符合主要的 EN14214 规范。