摘要
分别采用超临界甲醇流体、浓硝酸氧化、浓硝酸结合超临界甲醇流体等不同手段对椰壳活性炭进行了表面处理,用N2物理吸附、Boehm滴定、X光电子能谱仪(XPS)、电感耦合等离子原子发射光谱分析(ICP)、透射电镜(TEM)等手段研究了处理方法对活性炭表面孔结构及表面基团的影响;并以活性炭为载体,三氯化钌为活性前驱体,采用等容水浸渍法制备了钌炭催化剂,以葡萄糖加氢生产山梨醇为模型反应对制备的钌基催化剂的催化活性进行了评价.结果表明:各种处理方法对活性炭的比表面、孔径等孔结构性能影响不大;但超临界甲醇处理活性炭可明显减少活性炭表面含氧酸性基团的含量,尤其是羧基等不稳定基团的含量;而硝酸处理活性炭则可大幅度提高活性炭表面含氧酸性基团的含量,尤其是羧基等不稳定基团的含量增加更大.ICP分析结果表明:超临界甲醇处理活性炭并不改变活性炭样品对钌的吸附量,但硝酸氧化处理活性炭却能明显提高样品对钌的吸附能力.活性炭表面的这些含氧基团虽然有利于钌离子的吸附,但却不利于钌在活性炭表面的分散.由于超临界甲醇流体处理活性炭时的表面反应及萃取作用,可有效清除活性炭表面的不稳定含氧酸性基团,避免还原过程中钌的迁移聚集,使负载钌的分散度提高,有利于增强钌与活性炭间的相互作用,使钌部分缺失电子,钌的结合能升高;可明显提高负载钌炭催化剂葡萄糖催化加氢的活性.
Activated carbon （AC） was modified by supercritical methanol （scCH3OH） treatment,HNO3 oxidation,and HNO3 oxidation in combination with scCH3OH treatment.The pristine and modified AC samples were characterized by N2 physisorption,Boehm titration,X-ray photoelectron spectroscopy （XPS）,inductively coupled plasma atomic emission spectroscopy （ICP-AES）,and transmission electron microscopy （TEM）.These modifications did not significantly change the surface area and the pore size distribution of the AC.ScCH3OH treatment decreased the density of surface acidic groups,especially carboxylic groups.However,HNO3 oxidation increased the density of surface acidic groups.ICP analysis revealed that the scCH3OH modified sample had a similar adsorptive capacity for ruthenium as the original AC,while the AC oxidized with HNO3 had the highest adsorptive capacity of all samples tested.Ru/AC catalysts were prepared with RuCl3 solution impregnation on the four aforementioned AC supports.The as-prepared catalysts were characterized by TEM,XPS and examined for their effectiveness in D-glucose hydrogenation as well.The modifications drastically affected the properties of the activated carbons and the catalysts loaded on them.The dispersion of ruthenium after impregnation was highly dependent on the density of surface acidic groups.The AC sample treated by scCH3OH,which contained a lower amount of surface acidic complexes,showed the highest dispersion of ruthenium.The XPS results showed that the scCH3OH modification enhanced the interaction between AC and Ru.The Ru/AC-scCH3OH catalyst showed the highest activity for hydrogenation of D-glucose;producing a reaction rate 1.56 times higher than that produced by Ru/AC.
出处
《物理化学学报》
SCIE
CAS
CSCD
北大核心
2012年第1期177-183,共7页
Acta Physico-Chimica Sinica
基金
supported by the National Natural Science Foundation of China(50955010)~~
关键词
表面改性
活性炭
钌基催化剂
表面含氧基团
氢化
Surface modification
Activated carbon
Ruthenium catalyst
Surface oxygen containing group
Hydrogenation
