水热法制备Ni/CeO2-Al2O3及催化乙炔选择性加氢

Preparation of Ni/CeO2-Al2O3 by hydrothermal method and catalytic selective hydrogenation of acetylene

摘要:

采用水热法制备不同CeO2质量分数（x%）的xCeO2-Al2O3载体，再采用初湿浸渍法制备Ni质量分数2%的Ni/xCeO2-Al2O3，通过乙炔选择性加氢制乙烯反应，结合XRD、SEM、H2-TPR、BET、XPS、NH3-TPD、TG等表征手段对Ni/xCeO2-Al2O3进行评价。结果表明，CeO2质量分数5%制备的Ni/5CeO2-Al2O3，表现出最佳的催化性能，在280 ℃的反应温度下，乙炔转化率为99.7%，乙烯选择性为94.9%。Ni/5CeO2-Al2O3具有最大的比表面积（164.2 m2/g）和孔径（7.2 nm），以及适当的氧空位含量〔9.20%，以Ce3+/(Ce3++Ce4+)计，下同〕。CeO2的添加减弱了Ni/Al的强相互作用，减少了惰性NiAl2O4尖晶石相的生成，有效提升了催化剂的活性、选择性和稳定性。在30 h的反应时间内，乙炔转化率下降至90%，原因在于反应过程中造成的碳沉积降低了Ni/5CeO2-Al2O3的比表面积（151.5 m2/g）和孔径（6.6 nm）。

Abstract:

Selective hydrogenation of acetylene is a key process in the ethylene industry to remove acetylene impurities and obtain high-quality ethylene products. The development of highly active and selective catalyst for acetylene hydrogenation, which are green and economical, is currently a hot and difficult research topic in this field. In this paper, xCeO2-Al2O3 supports with different CeO2 additions were synthesized by hydrothermal method and evaluated experimentally. The results showed that 2Ni/5CeO2-Al2O3 exhibited excellent catalytic performance with 99.7% conversion and 94.9% selectivity at 280℃ compared with the catalyst without CeO2 addition. However, the excess CeO2 would reduce the specific surface area and pore volume of the catalyst, block the catalyst pores, and affect the dispersion of Ni species on the surface, which in turn would affect the reaction performance of the catalyst. The catalyst samples were characterized by XRD, H2-TPR, SEM, BET, XPS, NH3-TPD and TG. The excellent performance was found to be mainly attributed to the addition of CeO2 attenuating the strong Ni-Al interactions and reducing the generation of inert NiAl2O4 spinel phases, which effectively enhanced the activity, selectivity and stability of the catalyst.