Abstract Solid acid catalyst (SAC) was synthesized via direct treatment of cacao shells (CS) with concentrated sulfuric acid at varying temperature (80, 100, 120 °C) and time (4, 6, 8 h) settings. The synthesized catalysts were found to have sulfonic acid density ranging from 0.6326 to 0.8500 mmol SO3H/g dry CS-SAC and total acid density from 6.0509 to 7.1165 mmol H+/g dry CS-SAC. The catalytic activity is dependent on the sulfonic acid density of the catalyst. Catalyst synthesized at 120 °C for 6 h showed the highest sulfonic acid density (0.85 mmol SO3H/g catalyst) corresponding to highest catalytic activity (5.73 mmol OA converted/mmol SO3H·h) and a conversion of ∼39% after a fixed reaction time of 4 h and carried out at 65 °C. Conversions of up to 76% could be achieved after 24 h. The catalyst was reused for 4 cycles and was able to retain 78% of its catalytic activity from the 2nd to the 4th cycle. Direct sulfonation may be an alternative to conventional synthesis process.

中文翻译：

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可可壳直接磺化合成油酸与甲醇酯化的固体酸催化剂

摘要 通过在不同温度（80、100、120°C）和时间（4、6、8小时）设置下用浓硫酸直接处理可可壳（CS）合成固体酸催化剂（SAC）。发现合成的催化剂的磺酸密度范围为 0.6326 至 0.8500 mmol SO3H/g 干 CS-SAC，总酸密度范围为 6.0509 至 7.1165 mmol H+/g 干 CS-SAC。催化活性取决于催化剂的磺酸密度。在 120 °C 下合成 6 h 的催化剂显示出最高的磺酸密度（0.85 mmol SO3H/g 催化剂），对应于最高的催化活性（5.73 mmol OA 转化率/mmol SO3H·h）和固定反应后的转化率约为 39% 4 小时，在 65 °C 下进行。24 小时后可实现高达 76% 的转化率。该催化剂重复使用 4 次循环后，从第 2 次到第 4 次循环仍能保持 78% 的催化活性。直接磺化可能是常规合成方法的替代方法。