铁催化硬脂酸选择性氢化制硬脂醇

Iron-Catalyzed Selective Hydrogenation of Stearic Acid to Stearyl Alcohol

长链脂肪酸是一种重要的生物质原料,其氢化制备的脂肪醇由于用途广泛以及市场价值不断增长,近年来引起了人们的广泛关注.报道了一例使用非均相铁催化硬脂酸选择性加氢制备硬脂醇的实例.与其他非贵金属元素(如钴和镍)相比,铁在地壳中的丰度高出3000~30000倍,价格仅为20~150分之一,因此该方法更经济,更有吸引力.催化剂是通过将铁和氮掺杂碳前驱体同时热解到氧化铝载体上制备的.制备催化剂时最佳热解温度为900℃,最佳铁的质量分数为20%.反应最佳反应温度为320℃,最佳氢气压力为4 MPa.产物随时间分布曲线表明硬脂酸在0.5 h内迅速转化为硬脂醇,收率为88.6%. 4 h后逐渐转化为十八烷,收率为90%.

The utilization of sustainable resources such as biomass to produce fuels and chemicals has recently attracted significant attention due to the depletion of fossil reserves, increasing energy demand, and growing environmental concerns. Long-chain fatty acids, which are major constituents of plant oil, are important feedstock for biorefinery. Besides producing well-known biodiesels, the hydrogenation of fatty acids to fatty alcohols has recently drawn significant attention due to the versatility and growing market value of fatty alcohols. An example of heterogenous iron-catalyzed selective hydrogenation of stearic acid to stearyl alcohol is reported. Comparing with other reported non-noble metal centers, such as Co and Ni, Fe is 3000~30000 times more abundant and 20~150 times cheaper, thus making our method more economic and attractive. The iron catalyst was prepared by simultaneous pyrolysis of iron precursor [Fe(acac)3] and nitrogen-doped carbon precursor(melamine) onto alumina, bearing Fe3C active phase and nitrogen-doped carbon-alumina hybrid support. The optimization of preparation parameter showed that the optimal pyrolysis temperature is 900 ℃, while the best mass fraction of iron is 20%. The replacement of Fe(acac)3 with Fe(NO3)3 led to inferior catalytic performance, which was due to undesired redox reaction between NO3- and melamine during pyrolysis that hampered the reaction between Fe and melamine to form Fe3C active phase. Instead, hercynite phase became the predominant phase. The exploration of reaction parameter showed that the optimal reaction temperature is 320 ℃, and the best H2 pressure is 4 MPa. The time course for stearic acid conversion shows that stearic acid was rapidly converted into stearyl alcohol with yield of 88.6% within 0.5 h, and then gradually converted into octadecane with yield of 90% at 4 h. The unsatisfactory stability of the iron catalyst is probably due to the decomposition of Fe3C active phase to metallic Fe phase during recycling tests.