活性炭负载的Co-Mo催化剂的加氢脱硫性能Ⅰ.活性炭载体与γAl_2O_3的对比

Activated Carbon-Supported Co-Mo Catalyst for HydrodesulfurizationⅠ. Comparison of Activated Carbon and Alumina Supports

用XRD ,TPR和XPS技术对Co Mo/AC(活性炭 )和Co Mo/γ Al2 O3 催化剂进行了表征 ,并以二苯并噻吩HDS反应评价了催化剂的活性 .在不同温度下处理的催化剂 ,其活性组分高度分散在活性炭表面 ,未检测到明显的Mo和Co物种 .在Co Mo/AC催化剂中 ,表面物种的还原温度低于Co Mo/γ Al2 O3 的还原温度 .在 2 6 0℃下处理的Co Mo/AC催化剂 ,其表面Mo是高价态的Mo(Ⅵ ) ,在 5 0 0℃下处理的Co Mo/AC催化剂 ,其表面存在Mo(Ⅴ )和Mo(Ⅵ )两种价态 .硫化态CoMoS/AC催化剂中存在Mo(Ⅳ )和Mo(Ⅴ )两种低价态的Mo物种 ,而S主要以S2 -2 和S2 -的形式存在于MoS2 和MoO3 S2 -中 ,还有部分高价态的S6+ .在硫化态CoMoS/γ Al2 O3 催化剂中 ,Mo主要以Mo(Ⅴ )和Mo(Ⅵ )两种状态存在 ,而S主要以S2 -2 或S2 -的形式存在于MoO2 S2 -和MoO3 S2 -中 ,还有部分高价态的S6+ .活性评价结果表明 ,n(Co) /n(Mo) =0 7的Co Mo/AC的活性高于Co Mo/γ Al2 O3 的活性 ,而其他Co/Mo比的Co Mo/AC的活性低于Co Mo/γ Al2 O3 的活性 .

The XRD, TPR and XPS techniques were used to characterize the Co-Mo/AC (activated carbon) and Co-Mo/γ-Al 2O 3 catalysts prepared by impregnation. The activity and selectivity of the catalysts for HDS of dibenzothiophene were evaluated. All the active phases were well dispersed on the surface of AC support irrespective of treatment temperature and Co/Mo ratio. The active species on AC support were reduced at lower temperatures than those on γ-Al 2O 3 support. Only Mo(Ⅵ) species existed on the surface of oxidized Co-Mo/γ-Al 2O 3 catalyst, whereas, Mo(Ⅴ) and Mo(Ⅵ) species co-existed on the surface of oxidized Co-Mo/AC catalyst. As for the sulfided Co-Mo catalyst, low valence state Mo(Ⅳ) species in the form of MoS 2 along with partially reduced Mo(Ⅴ) species in the form of MoO 3S 2- and/or MoO 2S 2- were detected on the surface of CoMoS/AC catalyst. By comparison, low valence Mo(Ⅳ) was absent on the surface of sulfided CoMoS/γ-Al 2O 3. Similarly, the Mo(Ⅴ) species in the form of MoO 3S 2- and/or MoO 2S 2- were detected, but there still was a fraction of unreduced high valence state Mo(Ⅳ) on the surface of sulfided CoMoS/γ-Al 2O 3. The Mo(Ⅳ) species in the form of MoS 2 were more easily formed on the surface of Co-Mo/AC than on Co-Mo/γ-Al 2O 3. Co-Mo/AC ( n(Co)/ n(Mo)=0 7) possessed higher activity than Co-Mo/γ-Al 2O 3 whereas the Co-Mo/AC samples with other Co/Mo ratios were less active than Co-Mo/γ-Al 2O 3.