The determination of active filter aid adsorption sites by temperature-programmed desorption

1994 ◽  
Vol 71 (2) ◽  
pp. 189-194 ◽  
Author(s):  
Z. Y. Zhu ◽  
R. A. Yates ◽  
J. D. Caldwell
Keyword(s):  
Temperature Programmed Desorption ◽  
Active Filter ◽  
Adsorption Sites ◽  
Temperature Programmed ◽  
Filter Aid

Chemisorption of CO on Au/TiOx/Pt(111) Model Catalysts with Different Stoichiometry and Defectivity

2008 ◽  
Vol 8 (7) ◽  
pp. 3595-3602 ◽  
Author(s):  
Luca Artiglia ◽  
Gian Andrea Rizzi ◽  
Francesco Sedona ◽  
Stefano Agnoli ◽  
Gaetano Granozzi
Keyword(s):  
Ultrathin Films ◽  
Au Nanoparticles ◽  
Temperature Programmed Desorption ◽  
Model Catalysts ◽  
Desorption Peak ◽  
Adsorption Sites ◽  
Ordered Array ◽  
Temperature Programmed ◽  
A Minor ◽  
Minor Extent

Au/TiOx/Pt(111) model catalysts were prepared starting from well characterized TiOx/Pt(111) ultrathin films, according to an established procedure consisting in a reactive evaporation of Ti, subsequent thermal treatment in O2 or in UHV, and final deposition of submonolayer quantities of Au. Temperature Programmed Desorption measurements were performed to compare the interaction of CO in the case of two reduced TiOx/Pt(111) substrates (indicated as w-TiOx and w′-TiOx, being the former characterized by an ordered array of defects that can act as template for the deposition of a stable array of Au nanoparticles), with the case of a stoichiometric rect′-TiO2/Pt(111) substrate. It was found that in all cases CO is molecularly adsorbed and two different desorption peaks are detected: one at ≈140 K corresponding to CO desorption from less active adsorption sites (terraces) of the Au nanoparticles and one at ≈200 K corresponding to CO desorption from Au nanoparticles step sites. After annealing at 770 K, the high temperature CO desorption peak is still present in the case of the defective reduced w-TiOx phase, supporting the good templating and stabilizing effect of such phase. On the rect′-TiO2 stoichiometric phase, the CO uptake decreases after annealing but only to a minor extent.

Determination of ion-exchanged Co2+ cation in Co-ZSM-5 by temperature-programmed desorption

1997 ◽  
Vol 12 (1-3) ◽  
pp. 21-24 ◽  
Author(s):  
Chul Wee Lee ◽  
Paul Joe Chong ◽  
Young Chul Lee ◽  
Chong Shik Chin ◽  
Larry Kevan
Keyword(s):  
Temperature Programmed Desorption ◽  
Temperature Programmed

Dynamics of Surface Segregation During InGaAs Mbe

1995 ◽  
Vol 379 ◽  
Author(s):  
Keith R. Evans ◽  
R. Kaspi ◽  
J.E. Ehret ◽  
M. Skowronski
Keyword(s):  
Quantum Wells ◽  
Molecular Beam ◽  
Surface Segregation ◽  
Temperature Programmed Desorption ◽  
Molecular Beam Epitaxy Growth ◽  
Ingaas Layer ◽  
Temperature Dependent ◽  
Bottom Interface ◽  
Temperature Programmed

ABSTRACTThe dynamics of In surface segregation during molecular beam epitaxy growth of In.22Ga.78As/GaAs quantum wells (QWs) are studied by temperature-programmed desorption (TPD). The TPD spectra show two In peaks: a low temperature (low-T5) peak and a high temperature (high-T5) peak, which arise from desorption of surface segregated In and dissociation of the underlying InGaAs lattice, respectively. Integration of the low-Ts peak provides quantitative determination of the surface segregated In population ΘIn, as a function of InGaAs layer thickness, incident arsenic dimer flux [(Fi(As2)], InGaAs growth temperature, and GaAs cap thickness. The surface segregated In population ΘIn, is observed to grow with InGaAs thickness, until reaching a temperature-dependent steady state value between 1.0 and 2.0 monolayers after approximately ten monolayers of growth, and then decays during GaAs overlayer growth. The variation of ΘIn with thickness closely mimics the resulting vertical composition profile, which is characterized by an In-depleted bottom interface and segregation of In into the GaAs cap. Based on these results, a sequence of: 1) In predeposition, 2) InGaAs growth, and 3) thermal desorption of Eh is proposed to produce a more square InGaAs/GaAs QW than can be obtained by more standard MBE approaches.

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