CaO对Pt/C催化硬脂酸脱羧反应性能的影响

Effect of CaO on decarboxylation of stearic acid over Pt/C catalyst

以硬脂酸(C17H35COOH)脱羧为探针反应,研究了亚临界水中CaO对Pt/C催化脱羧反应性能的影响。实验表明,CaO可以促进脱羧反应,对十七烷选择性没有影响。CaO/硬脂酸物质的量比为0.5时,在330℃反应1 h,硬脂酸转化率由未添加CaO时的46.06%提高到66.99%。硬脂酸催化脱羧的最佳反应温度为350℃,高于这一温度时,烷基链上碳碳键断裂的副反应增加,导致十七烷选择性降低。亚临界水中硬脂酸脱羧反应符合一级动力学,建立的动力学方程可以较好地预测不同反应条件下十七烷的产率。根据实验结果推测,氧化钙与硬脂酸反应生成硬脂酸钙,催化剂表面的吸附态羧酸盐增加,从而提高了脱羧反应的速率。

The effects of CaO addition and temperature on decarboxylation of stearic acid over Pt/C catalyst in subcritical water were investigated.The conversion of stearic acid increased dramatically,while the selectivity to heptadecane hardly changed with the addition of CaO.At 330 ℃ the conversion of stearic acid reached a maximum with Ca/stearic mol ratio of 0.5.Moreover,Pt/C catalyzed decarboxylation of stearic acid in subcritical water exhibited first-order kinetics.It was proposed that dissociative stearic acid was adsorbed on Pt/C catalyst,forming surface octadecanoate species and adsorbed H.The C-C bond dissociated via H insertion,resulting in the formation of heptadecane and CO2.The addition of CaO promoted the dissociation of stearic acid.As a result,the amount of adsorbed octadecanoate increased and the reaction was accelerated.