镧改性Cu/SiO2催化剂的乙酸甲酯高效加氢催化性能研究

Catalytic performance of La-modified Cu/SiO2 in the hydrogenation of methyl acetate

  • 摘要: 采用蒸氨法制备了镧(La)改性的负载型铜硅(Cu/SiO2)催化剂,并对其乙酸甲酯(MeOAc)气相加氢制乙醇(EtOH)的催化性能进行了研究。采用N2吸附-脱附(N2 adsorption-desorption)、X射线粉末衍射(XRD)、电感耦合等离子体发射光谱(ICP-OES)、氢气程序升温还原(H2-TPR)、傅里叶红外光谱(FT-IR)、高分辨透射电镜(HRTEM)、光电子能谱(XPS)和原子发射光谱仪(AES)等手段对催化剂进行了的表征,发现La物种的加入产生了较多的层状硅酸铜,增强了Cu和La物种之间的相互作用。La物种的加入在结构方面提高了催化剂的比表面积,降低了铜物种的粒径,提高了铜物种的分散度;在电子还原调控方面提高了Cu+的含量,增强了催化剂吸附酰基和甲氧基的能力。与未改性的Cu/SiO2催化剂相比,镧改性后Cu/SiO2催化剂的乙酸甲酯加氢性能得到大幅提升;其中La掺杂量0.5%的Cu/SiO2催化剂表现出最佳的催化性能,乙酸甲酯转化率达98.5%,乙醇的总收率为97.0%。

     

    Abstract: A series of Cu/SiO2 catalysts modified with lanthanum (La) (30Cu-nLa/SiO2, n=0, 0.5, 1 and 2) were synthesized using the ethanol (EtOH)-assisted ammonia-evaporation method; their catalytic performance in the gas-phase hydrogenation of methyl acetate (MeOAc) to produce ethanol (EtOH) was investigated. The results indicate that the catalytic performance of Cu/SiO2 can be greatly enhanced by La modification. In particular, the 30Cu-0.5La/SiO2 catalyst exhibits excellent performance in the MeOAc hydrogenation; under 230 °C, 2 MPa H2, an LHSV of 2 h−1 and an H2/MeOAc molar ratio of 20, the MeOAc conversion reaches 98.5%, with a total EtOH yield of 97.0%. The N2-sorption, XRD, ICP-OES, H2-TPR, FT-IR, TEM, XPS, and AES characterization results reveal that the introduced La metal has a strong interaction with Cu, which can promote the dispersion of the copper species on the SiO2 support. Moreover, the content of Cu+ is increased significantly, which can enhance the electronic interaction with MeOAc via the acyl and methoxide groups and thus promote the hydrogenation of MeOAc to EtOH.

     

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