Showing papers by "Changhai Liang published in 2001"
TL;DR: In this paper, the authors investigated ammonia synthesis over ruthenium catalysts supported on different carbon materials using Ba or K compounds as promoters and found that the larger particles of Ru on the carbon supports are more active for ammonia synthesis in terms of TOF value.
Abstract: Ammonia synthesis over ruthenium catalysts supported on different carbon materials using Ba or K compounds as promoters has been investigated. Ba(NO3)(2), KOH, and KNO3 are used as the promoter or promoter precursor, and activated carbon (AC), activated carbon fiber (ACF). and carbon molecular sieve (CMS) are used as the support. The activity measurement for ammonia synthesis was carried out in a flow micro-reactor under mild conditions: 350-450 degreesC and 3.0 MPa. Results show that KOH promoter was more effective than KNO3. and that Ba(NO3)(2) was the most effective promoter among the three. The roles of promoters can be divided into the electronic modification of ruthenium, the neutralization of surface functional groups on the carbon support and the ruthenium precursor. The catalyst with AC as the support gave the highest ammonia concentration in the effluent among the supports used, while the catalyst with ACF as the support showed the highest turnover-frequency (TOF) value. It seems that the larger particles of Ru on the carbon supports are more active for ammonia synthesis in terms of TOF value. (C) 2001 Elsevier Science B.V. All rights reserved.
160 citations
TL;DR: In this paper, the reduction of the promoted catalysts was investigated in detail, and it was suggested that H2 spillover effect on the Ru/AC catalyst significantly promoted the reduction and conversion of the promoter precursors.
Abstract: Ru/AC catalysts promoted with nitrates of alkali metals, alkali earth metals and rare earth metals precursors were prepared by impregnation method and characterized by temperature-programmed reduction (TPR), differential thermal analysis (DTA) and chemisorption. The addition of promoters in the Ru/AC catalyst considerably improves the TOF of ammonia synthesis. The reduction of the promoted catalysts was investigated in detail. The promoter precursor can be reduced at much lower temperatures in the presence of Ru than that in the absence of Ru. It is suggested that H2 spillover effect on the Ru/AC catalyst significantly promotes the reduction of the promoter precursors, and the hydrogen spills over from Ru to the remote nitrate through the carbon surface. The promoter precursors were converted to hydroxides or oxides under reaction condition.
17 citations
TL;DR: In this article, the surface enhanced Raman scattering (SERS) of xanthopterin adsorbed on colloidal silver was measured and the Raman spectrum calculated by the density functional theory method was also obtained.
Abstract: Surface-enhanced Raman scattering (SERS) of xanthopterin adsorbed on colloidal silver was measured and the Raman spectrum calculated by the density functional theory method was also obtained. Xanthopterin can be detected down to 5 X 10(-9) m and the enhancement of the scattering intensity is at least 10(5)-fold. Xanthopterin molecules are adsorbed flatly on the surface of the Ag particles. This study shows that SERS could be another prospective method for the detection of pterines. Copyright (C) 2001 John Wiley Sons, Ltd.
16 citations