论文部分内容阅读
用Ｒａｍ ａｎ、ＸＲＤ、ＳＥＭ 等技术， 研究了Ｐｄ－Ｂ／ＳｉＯ２ 非晶态合金的晶化过程及其对催化活性的影响． 研究发现， Ｐｄ２＋ 能高度分散在ＳｉＯ２ 载体上， 并与载体发生作用． 但Ｐｄ－Ｂ合金在载体上形成颗粒微细的原子簇． 温度低于６７３ Ｋ时， 这些原子簇在ＳｉＯ２ 载体上呈非晶态结构， 并随着温度的增加而发生团聚． 温度高于６７３ Ｋ时， Ｐｄ－Ｂ合金发生晶化并分相， 活性比表面积和催化活性随温度增加而下降． 由于Ｐｄ 是催化活性物种， 因此Ｂ的促进作用主要归因于其与Ｐｄ 合金化作用形成对加氢有利的非晶态结构和表面电子态； 载体ＳｉＯ２ 对Ｐｄ－Ｂ非晶态合金的分散作用， 不仅有利于提高催化剂的比表面积， 而且可改善非晶态合金的热稳定性．
The crystallization process of Pd-B / SiO2 amorphous alloy and its effect on the catalytic activity were studied by Ram an, XRD, SEM and other techniques. The study found that, Pd2 + can be highly dispersed in the SiO2 carrier, and with the carrier role. However, the Pd-B alloy forms clusters of fine particles on the support. At temperatures below 673 K, these clusters are amorphous on the SiO2 support and agglomerate with increasing temperature. When the temperature is higher than 673 K, the Pd-B alloy crystallizes and separates, and the specific surface area and catalytic activity decrease with increasing temperature. Since Pd is a catalytically active species, the promoting effect of B is mainly attributed to its alloying with Pd to form an amorphous structure and surface electronic state favorable for hydrogenation; the dispersion of the carrier SiO2 on the Pd-B amorphous alloy , Not only help to improve the specific surface area of the catalyst, but also improve the thermal stability of the amorphous alloy.