Pd/HZSM-5催化剂上正庚烷异构化反应特性的研究

STUDY OF ISOMERIZATION OF n-HEPTANE OVER Pd/HZSM-5 CATALYSTS

以正庚烷为模型化合物,利用微反-色谱方法考察分子筛硅铝比、晶粒大小以及贵金属Pd负载量对Pd/HZSM-5催化剂上正庚烷异构化反应特性的影响。结果表明:随着硅铝比的增大,酸性中心数目减少,正庚烷转化率降低,异构化选择性提高;分子筛的晶粒大小对载体酸性和外比表面积的影响不大,使其对Pd/ZSM-5催化剂上正庚烷异构化反应的影响较小;负载Pd后,正庚烷转化率和异构化活性显著提高,当Pd负载量(w)超过0.4%时,催化剂的金属功能与酸性功能达到平衡,正庚烷转化率及异构化活性不再发生明显变化。

The isomerization reaction of n-heptane over Pd/HZSM-5 bifunctional catalyst was studied.The effect of Si/Al ratio,crystal size and Pd loading on the reaction were investigated by micro-reactor-chromatograph system.The results showed that as the Si/Al ratio increases,the number of acid sites and the conversion of n-heptane decrease,however the isomerization selectivity of the catalyst is improved.Being the little effect of grain size of ZSM-5 molecular sieve on external surface area and acidity of the carrier,it has little influence on the isomerization performance of Pd/HZSM-5 catalysts.Loading Pd leads the conversion of n-heptane and isomerization activity improved significantly.However,when the Pd loading exceeds 0.4%,the metal function and acid function of catalyst reaches equilibrium state,and the conversion of n-heptane and isomerization activity no longer change significantly.