稻壳炭基固体酸催化剂的制备及其催化酯化反应性能

以热解稻壳炭为原料, 浓硫酸为磺化剂制备了固体酸催化剂. 采用X射线衍射、X射线光电子能谱、元素分析、孔结构分析和热重-质谱联用等手段对其进行了表征. 以油酸和甲醇的酯化为探针反应, 考察了磺化温度和时间对催化剂活性的影响, 探讨了反应条件对油酸转化率的影响, 并对所制催化剂的稳定性进行了研究. 结果表明, 制备该催化剂的适宜磺化温度和时间分别为90℃和0.25 h, 在该条件下制得的催化剂为无定形碳结构, 磺酸基密度为0.7 mmol/g. 该催化剂表现出较高的催化酯化反应活性, 在催化剂用量为5%、甲醇/油酸摩尔比为4、酯化温度和时间分别为110℃和2 h的条件下, 油酸的酯化率可达98.7%. 该催化剂具有较好的稳定性, 经7次连续反应后, 油酸的酯化率仍可达96.0%.

Preparation of solid acid catalyst from rice husk char and its catalytic performance in esterification

A sulfonated carbon-based solid acid catalyst was prepared by sulfonating rice husk char with concentrated sulfuric acid. The as-prepared catalyst was characterized using X-ray diffraction, X-ray photoelectron spectroscopy, ultimate analysis, specific surface area analysis, and thermogravimetry-mass spectrometry. The effects of the sulfonation temperature and time on the catalytic performance were investigated using the esterification of oleic acid and methanol as the probe reaction. The effects of the reaction conditions on the esterification catalyzed by sulfonated rice husk char were also studied. The stability of the catalyst was examined. The results showed that 90℃ and 0.25 h were suitable sulfonation temperature and time, respectively. The catalyst prepared under these conditions had an amorphous carbon structure with a sulfonic group concentration of 0.7 mmol/g. It exhibited high catalytic performance. The conversion of oleic acid was 98.7% under the optimal reaction conditions with a catalyst amount of 5%, a methanol to oleic acid molar ratio of 4:1, and a reaction temperature and time of 110℃ and 2 h, respectively. The esterification conversion still reached 96.0% after seven cycles of successive reuse, which indicated that the catalyst stability was excellent.