材料期刊网

在Y分子筛上浸渍0.1 wt% Pd和0.1–0.5 wt% Ni,用X射线衍射表征了该催化剂的结晶度,用透射电镜测得平均金属粒径.催化剂中Pd和Ni的化学态用X射线光电子能谱测定,其酸性则用氨-程序升温脱附进行了表征,发现一些酸位被Ni2+离子交换.采用程序升温还原表征了HY分子筛负载的Pd, Ni和Pd-Ni催化剂的还原性能.正癸烷加氢异构化反应在200–450 oC和1 atm条件下进行.结果发现,当0.1 wt% Pd/HY中Ni添加量增至0.3 wt%时,正癸烷转化率和异构化选择性增加.单支链和双支链异构体选择性的增加表明该反应遵循质子化环丙烷中间体机理. Ni添加量超过阈值导致活性和异构化选择性急剧下降.综上可见,双金属催化剂更有利于选择性生成双支链异构体,其辛烷值更高.

Metal‐loaded zeolite catalysts were synthesized and examined in the hydroisomerization of n‐decane. Specifically, zeolite Y was impregnated with 0.1 wt% Pd and varying amounts of Ni (0.1–0.5 wt%). The crystallinity of the metal‐loaded catalysts was characterized by X‐ray diffraction, and the average metal particle size was determined by transmission electron microscopy. The states of Pd and Ni were identified by X‐ray photoelectron spectroscopy. Ammonia tempera‐ture‐programmed desorption analysis revealed the occurrence of ion‐exchange of some of the cata‐lyst acid sites with Ni2+. The reducibility of the HY zeolite‐supported Pd, Ni, and Pd‐Ni catalysts was studied by temperature‐programmed reduction. The hydroisomerization of n‐decane over the pre‐pared catalyst was conducted at 200–450 °C under 1 atm. Ni addition of up to 0.3 wt%over 0.1 wt%Pd/HY enhanced the n‐decane conversion and isomerization product selectivity. The improved selectivity of the mono‐and dibranched isomers suggested the occurrence of a protonated cyclo‐propane intermediate mechanism. However, further Ni addition above 0.3 wt%considerably re‐duced the activity and isomerization selectivity. The bimetallic catalysts were more selective toward the formation of dibranched isomers, i.e., those containing a higher octane number.