催化学报
催化學報
최화학보
CHINESE JOURNAL OF CATALYSIS
2014年
8期
1418-1427
,共10页
鲍洪亮%孙雪平%姜政%黄宇营%王建强
鮑洪亮%孫雪平%薑政%黃宇營%王建彊
포홍량%손설평%강정%황우영%왕건강
铑%锰%纳米粒子%X射线吸收近边结构%扩展X射线吸收精细结构
銠%錳%納米粒子%X射線吸收近邊結構%擴展X射線吸收精細結構
로%맹%납미입자%X사선흡수근변결구%확전X사선흡수정세결구
Rhodium%Manganese%Nanoparticle X-ray absorption near-edge spectroscopy%Extended X-ray absorption fine structure spectroscopy
利用X射线吸收谱技术研究了负载于多壁碳纳米管内的Rh-Mn纳米粒子在不同气氛和温度下的结构.结果表明, Rh-Mn粒子在空气中是由氧化铑团簇和混合锰氧化物组成.经过氢气在300°C下还原后,混合锰氧化物种转化成MnO.而氧化铑团簇在He气氛下当温度达到250°C时就会发生分解而形成金属铑团簇.对形成的铑团簇用H2或CO进行热处理,发现其分散性随温度升高而提高;同时, X射线吸收谱实验没有观察到Mn和Rh之间存在显著的相互作用,助剂Mn的主要作用是提高了Rh的分散性.
利用X射線吸收譜技術研究瞭負載于多壁碳納米管內的Rh-Mn納米粒子在不同氣氛和溫度下的結構.結果錶明, Rh-Mn粒子在空氣中是由氧化銠糰簇和混閤錳氧化物組成.經過氫氣在300°C下還原後,混閤錳氧化物種轉化成MnO.而氧化銠糰簇在He氣氛下噹溫度達到250°C時就會髮生分解而形成金屬銠糰簇.對形成的銠糰簇用H2或CO進行熱處理,髮現其分散性隨溫度升高而提高;同時, X射線吸收譜實驗沒有觀察到Mn和Rh之間存在顯著的相互作用,助劑Mn的主要作用是提高瞭Rh的分散性.
이용X사선흡수보기술연구료부재우다벽탄납미관내적Rh-Mn납미입자재불동기분화온도하적결구.결과표명, Rh-Mn입자재공기중시유양화로단족화혼합맹양화물조성.경과경기재300°C하환원후,혼합맹양화물충전화성MnO.이양화로단족재He기분하당온도체도250°C시취회발생분해이형성금속로단족.대형성적로단족용H2혹CO진행열처리,발현기분산성수온도승고이제고;동시, X사선흡수보실험몰유관찰도Mn화Rh지간존재현저적상호작용,조제Mn적주요작용시제고료Rh적분산성.
Supported Rh-based catalysts such as Rh-Mn nanoparticles (NPs) have potential use in the synthe-sis of ethanol from syngas. The structure of Rh-Mn NPs in multi-walled carbon nanotubes under different atmospheres and temperatures was studied by X-ray absorption spectroscopy (XAS). TEM images showed that the NPs dispersed in the carbon nanotubes had a uniform size of 2 nm. XAS data revealed that the Rh-Mn NPs before reduction were composed of Rh2O3 clusters and mixed Mn oxide species. After reduction in a 10%H2-90%He atmosphere, the mixed Mn oxides were con-verted into nearly pure MnO. In contrast, the Rh2O3 clusters were easily decomposed to metallic Rh clusters even under a He atmosphere at 250 °C. The Rh clusters remained in the metal state under the next reduction atmosphere, but their dispersion in the Rh-Mn NPs increased with increasing temperature. No significant Mn-Rh or Mn-O-Rh interaction in the reduced NPs was observed in the extended X-ray absorption fine structure analysis. The results showed that there was no interaction between the MnO particles and Rh clusters and the role of the Mn promoter was mainly to improve Rh dispersion.