Pd-Pb/SiO_2催化高浓度乙烯基乙炔加氢合成丁二烯

Hydrogenation of high-concentration monovinylacetylene for butadiene production over Pd-Pb/SiO_2 catalysts

研究了硅胶负载钯铅双金属催化剂催化高浓度乙烯基乙炔加氢合成丁二烯过程。结果表明,加入适量的铅可起到分隔钯纳米粒子,阻碍钯纳米粒子团聚的作用,从而提高催化剂的催化活性,最佳Pb/Pd摩尔比为0.2。继续提高Pb/Pd摩尔比时,会生成铅钯合金相,造成催化剂活性降低。X射线光电子能谱结果表明,催化剂的催化活性与Pd 3d的电子结合能呈正相关关系。制备催化剂过程中,还原温度对催化剂的结构和催化性能影响显著。在350℃下还原得到的催化剂中金属氧化物还原不彻底,催化剂活性较低;还原温度为450℃时,则会引起钯纳米粒子烧结,造成催化剂的催化活性和对丁二烯的选择性同时降低;催化剂的最佳还原温度为400℃。在40℃催化乙烯基乙炔反应40 h后,积炭造成催化剂的孔道堵塞,催化剂失活。因此,需要进一步开展改善催化剂的抗积炭能力和使用寿命方面的研究。

The hydrogenation of high-concentration monovinylacetylene over silica supported Pd-Pb bimetallic catalysts was investigated. It showed that the appropriate presence of Pb can prevent Pd nanoparticles from aggregation, hence facilitated the improvement of catalytic activity, i.e. the optimal molar ratio of Pb to Pd of 0.2. With the molar ratio of Pb to Pd above 0.2, Pd-Pb alloy can be formed, which causes catalytic activity loss. The positive correlation between the catalytic activity and the electron bonding energy of Pd 3d was manifested by X-ray photoelectron spectra. The temperature for PdO reduction exhibited a remarkable influence on the structure and the activity of the catalysts. The PdO reduction at 350℃ of the catalyst was incomplete thus with low activity. At 450℃ of the reduction temperature, it caused Pd nanoparticle sintering, hence with low activity and low butadiene selectivity. As a result, the optimal reduction temperature was 400℃. After 40 h, the catalyst was deactivated due to the blockage of pore by coke formation on catalyst surface. Subsequently, the improvement of anti-coking ability and the lifetime of the catalyst will be of interest.