Abstract Low-cost biodiesel was successfully produced through esterification of palm fatty acid distillate over corncob residue-derived heterogeneous solid acid catalyst. The sulfonated functionalized carbon derived from corncob was synthesized via hydrothermal carbonization followed by chemical activation using concentrated sulfuric acid. This technique allows efficient carbonization process and able to maintain active polar species of the catalyst hence effectively improves the acid strength of prepared catalyst. The esterification of palm fatty acid distillate over HTC-S catalyst was optimized via the one-variable-at-a-time technique, and 92% free fatty acid conversion with a biodiesel yield of 85% was achieved at optimum conditions of 2 h reaction time, 70 °C reaction temperature, 3 wt% catalyst loading, and 15:1 methanol-to-oil molar ratio. Various of catalyst regeneration techniques have been studied and sulfuric acid treatment is found to be the most effective approach for restoring the active sites for spent HTC-S catalyst in comparison to washing solvent and thermal treatment. The HTC-S catalyst regenerated via sulfuric acid treatment is capable to convert PFAD to biodiesel with free fatty acid conversion >90% for two consecutive cycles. The synthesized PFAD-derived biodiesel has complied with the international biodiesel standard ASTM D6751.

中文翻译：

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通过水热合成路线磺化碳衍生玉米芯残渣用于棕榈脂肪酸馏出物的酯化

摘要 在玉米芯渣衍生的非均相固体酸催化剂上，将棕榈脂肪酸馏分酯化，成功制备低成本生物柴油。源自玉米芯的磺化官能化碳是通过水热碳化合成的，然后使用浓硫酸进行化学活化。该技术允许有效的碳化过程并能够保持催化剂的活性极性物质，从而有效地提高所制备催化剂的酸强度。棕榈脂肪酸馏分在HTC-S催化剂上的酯化反应通过一次一变技术优化，在2 h反应的最佳条件下，游离脂肪酸转化率为92%，生物柴油产率为85%时间、70 °C 反应温度、3 wt% 催化剂负载量和 15:1 的甲醇与油摩尔比。已经研究了各种催化剂再生技术，发现与洗涤溶剂和热处理相比，硫酸处理是恢复用过的 HTC-S 催化剂活性位点的最有效方法。通过硫酸处理再生的 HTC-S 催化剂能够连续两个循环将 PFAD 转化为生物柴油，游离脂肪酸转化率 >90%。合成的PFAD衍生生物柴油符合国际生物柴油标准ASTM D6751。通过硫酸处理再生的 HTC-S 催化剂能够连续两个循环将 PFAD 转化为生物柴油，游离脂肪酸转化率 >90%。合成的PFAD衍生生物柴油符合国际生物柴油标准ASTM D6751。通过硫酸处理再生的 HTC-S 催化剂能够连续两个循环将 PFAD 转化为生物柴油，游离脂肪酸转化率 >90%。合成的PFAD衍生生物柴油符合国际生物柴油标准ASTM D6751。