Activation energy distribution in temperature-programmed desorption: modeling and application to the soot oxygen system

1990 ◽  
Vol 4 (3) ◽  
pp. 296-302 ◽  
Author(s):  
Zhiyou Du ◽  
Adel F. Sarofim ◽  
John P. Longwell
Keyword(s):  
Activation Energy ◽  
Energy Distribution ◽  
Temperature Programmed Desorption ◽  
Oxygen System ◽  
Temperature Programmed

MONTE CARLO SIMULATION OF TEMPERATURE-PROGRAMMED DESORPTION CO/Cu(110) AND CO2/Cu(100) SYSTEMS

2004 ◽  
Vol 11 (02) ◽  
pp. 137-143 ◽  
Author(s):  
KH. ZAKERI ◽  
A. DASHTI
Keyword(s):  
Activation Energy ◽  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Excellent Agreement ◽  
Temperature Programmed Desorption ◽  
High Order ◽  
Kinetics And Mechanism ◽  
Lateral Interaction ◽  
Desorption Rate ◽  
Temperature Programmed

In this investigation, we have studied the kinetics and mechanism of desorption of CO from the Cu (110) surface using a new Monte Carlo simulation and putting emphasis on high order lateral interaction. According to our simulated TPD spectra, for β=10 K/s the maximum desorption rate occurs at Tm=218.6 K. Furthermore, analysis of simulated TPD spectra of CO desorption shows that it is strongly lateral-interactive and results an activation energy of CO desorption from Cu (110) that is Ed=66.6 Kj/mol. These simulated results are compared with other reported results and show excellent agreement. After that we have investigated the kinetics and mechanism of desorption of CO 2 from the Cu (100) surface using a Monte Carlo simulation. According to our simulated TPD spectra, for β=0.5 K/s the maximum desorption rate occurs at Tm=89.7 K. Analysis of simulated TPD spectra of CO 2 desorption shows that it is not strongly lateral-interactive and results in an activation energy of CO desorption from Cu (100) that is Ed=25.2 Kj/mol. Finally, the CO / Cu (110) system is compared with the CO 2/ Cu (100) system.

Thermal Stability of Z-Type Perfluoro Poly Ether Lubricant Polymers: A Combined Thermogravimetric and Temperature Programmed Desorption Study

2003 ◽  
Author(s):  
Paul M. Jones ◽  
Lei Li ◽  
Yiao-Tee Hsia
Keyword(s):  
Activation Energy ◽  
Thermal Stability ◽  
Temperature Programmed Desorption ◽  
Kcal Mole ◽  
Three Samples ◽  
Desorption Study ◽  
Polymer Decomposition ◽  
Temperature Programmed ◽  
Decomposition Chemistry ◽  
Thermal Stability Of

The thermal stability of Zdol 4000, 7800 and Ztetraol perfluoropolyethers (PFPE) have been studied in both the bulk with thermogravimetric analysis (TGA) and in thin film form with temperature programmed desorption spectroscopy (TPD). The TGA results have been interpreted to yield an evaporation activation energy for both Zdol 4000 (13 kcal/mole) and Zdol 7800 (19 kcal/mole). A larger activation energy is also found for all three samples investigated that is consistent with polymer decomposition (22, 27 and 21 kcal/mole respectively). The TPD threshold has been found to be approximately similar all three samples (∼500 K). The temperature of decomposition was also found to be similar for all three samples and was dominated by the CF2O+ mass fragment at ∼660 K. Two desorption maximums were observed for both Zdol 4000 and Ztetraol indicating the similarity in their decomposition chemistry. In contrast only one desorption peak was observed from Zdol 7800 (675 K). A CF3+ fragment was not observed in any of the TPD spectra indicating the absence an acidic decomposition path for all of the Fomblin Z polymers studied.

Application of temperature-programmed desorption to surfaces with physically adsorbed species

1968 ◽  
Vol 46 (6) ◽  
pp. 1033-1036 ◽  
Author(s):  
H. P. Schreiber ◽  
A. G. MacKinnon
Keyword(s):  
Activation Energy ◽  
Acetic Acid ◽  
Chain Length ◽  
High Stability ◽  
Temperature Programmed Desorption ◽  
Adsorbed Species ◽  
Pigment Surface ◽  
Temperature Programmed ◽  
Activation Energy Of Desorption ◽  
Very High

Temperature-programmed desorption has been applied to physisorbed aliphatic alcohols and acids on a rutile pigment surface. Reproducible desorption chromatograms for a series of alcohol adsorbates indicate that the same sites are involved in adsorbing the series and that the adsorbate orientation from the surface deviates progressively from normal as the chain length increases. The data also infer a reduction in the activation energy of desorption with increasing chain length. Acid adsorbates also generate reproducible chromatograms, those for formic and acetic acid showing characteristic peaks near 300 °C. The reason for the very high stability of these adsorbates has not yet been resolved.

KINETIC AND REACTIVE PROPERTIES OF ETHYLENE ON CLEAN AND HYDROGEN-COVERED Pd(111)

2003 ◽  
Vol 10 (06) ◽  
pp. 909-916 ◽  
Author(s):  
L. BURKHOLDER ◽  
D. STACCHIOLA ◽  
W. T. TYSOE
Keyword(s):  
Activation Energy ◽  
Infrared Spectroscopy ◽  
Temperature Programmed Desorption ◽  
Molecular Adsorption ◽  
Lateral Interactions ◽  
Ethylene Adsorption ◽  
Reflection Absorption Infrared Spectroscopy ◽  
Temperature Programmed ◽  
Ethane Formation ◽  
Reactive Properties

Several molecular adsorption states are identified following ethylene adsorption on clean and hydrogen-covered Pd(111) using temperature-programmed desorption (TPD) and reflection absorption infrared spectroscopy (RAIRS). Di-σ-bonded ethylene forms on clean Pd(111) desorbing with an activation energy of 80 kJ/mol at low coverages. The strong intermolecular lateral interactions considerably reduce the desorption temperature at higher coverages. Π-bonded ethylene is formed on hydrogen-covered Pd(111), where the proportion of π-bonded species increases with hydrogen coverage. This species converts to the more stable di-σ-bonded species on heating. Ethane formation is detected in TPD from hydrogen-precovered Pd(111), which is predominantly formed by reaction with π-bonded ethylene.

Adsorption and Desorption Kinetics for Chlorosilanes on Si(111) 7×7

1990 ◽  
Vol 204 ◽  
Author(s):  
P. Gupta ◽  
P.A. Coon ◽  
B.G. Koehler ◽  
M.L. Wise ◽  
S.M. George
Keyword(s):  
Activation Energy ◽  
Surface Coverage ◽  
Temperature Programmed Desorption ◽  
Desorption Kinetics ◽  
Sticking Coefficient ◽  
Temperature Dependent ◽  
Adsorption And Desorption ◽  
Desorption Activation Energy ◽  
Temperature Programmed ◽  
Sticking Coefficients

ABSTRACTThe adsorption and desorption kinetics for SiCl4 and SiCl2H2 on Si(111) 7×7 were studied using laser-induced thermal desorption (LITD) and temperature programmed desorption (TPD) techniques. Both LITD and TPD experiments monitored SiCl2 as the main desorption product at 950 K at all coverages of SiCl4 and SiCl2H2 on Si(111) 7×7.HC1 desorption at 850 K and H2 desorption at 810 K were also observed following SiCl2H2 adsorption. Isothermal LITD measurements of SiCl4 and SiCl2H2) adsorption on Si(111) 7×7 revealed that the initial reactive sticking coefficient decreased with increasing surface temperature for both molecules. The temperature-dependent sticking coefficients were consistent with precursor-mediated adsorption kinetics. Isothermal LITD studies of SiC12 desorption revealed second-order SiCl2 desorption kinetics. The desorption kinetics were characterizedby a desorption activation energy of Ed = 67 kcal/mol and a preexponential of vd = 3.2 cm2/s. TPD studies observed that the HCI desorption yield decreased relative to H2 and SiCl2 desorption as a function of surface coverage following SiCl2H2 exposure. These results indicate that when more hydrogen desorbs as H2 at higher coverages, The remaining chlorine is forced to desorb as SiCl 2.

Adsorption of Styrene on Hydrochloric Acid-Modified Sepiolite

2012 ◽  
Vol 518-523 ◽  
pp. 2058-2063
Author(s):  
Zhao Du ◽  
Bin Bin Yang ◽  
Er Hong Duan ◽  
Bin Guo
Keyword(s):  
Activation Energy ◽  
Hydrochloric Acid ◽  
Surface Area ◽  
Temperature Programmed Desorption ◽  
Micropore Volume ◽  
Breakthrough Curves ◽  
Adsorption Capacities ◽  
Desorption Activation Energy ◽  
Temperature Programmed ◽  
Fixed Beds

In this work, the breakthrough curves of styrene in fixed beds packed separately with hydrochloric acid-modified sepiolite were determined. And the Temperature Programmed Desorption (TPD) method is applied to research the desorption activation energy on modified sepiolite and untreated sepiolite. The results showed that in compared with the original sepiolite, the hydrochloric acid-modified sepiolite had more surface basic groups, pore volume and higher surface area so that their adsorption capacities of styrene were improved. The sepiolite modified with 12% hydrochloric acid solution had more micropore volume and higher surface area than the other modified sepiolite, and thus its adsorption capacity of styrene was the highest. The activation energy for desorption of styrene on the modified is higher than on the original sepiolite, this show that using hydrochloric acid modified sepiolite can enhance its adsorption of styrene.

The Reaction of NH3 With TiN: Implications for CVD

1995 ◽  
Vol 410 ◽  
Author(s):  
Michelle T. Schulberg ◽  
Mark D. Allendorf ◽  
Duane A. Outka
Keyword(s):  
Activation Energy ◽  
Chemical Vapor Deposition ◽  
Reaction Temperature ◽  
Vapor Deposition ◽  
High Probability ◽  
Film Growth ◽  
Chemical Vapor ◽  
Temperature Programmed Desorption ◽  
Surface Sites ◽  
Temperature Programmed

ABSTRACTSince NH3 is an important component of TiN chemical vapor deposition (CVD) processes, understanding the NH3/TiN surface interaction is crucial to developing a model for the overall reaction. Temperature programmed desorption experiments show that NH3 adsorbs molecularly on amorphous TiN surfaces. Chemisorption occurs at only ∼5% of the surface sites, with an activation energy for desorption of 24 kcal/mol. The sticking probability into this state is 0.06 at 100 K. In addition, NH3 adsorbs with high probability into a multilayer state with an activation energy for desorption of 7.3 kcal/mol, similar to that found in other systems. NH3 does not dissociate on TiN. Under CVD conditions, however, the reactivity of NH3 on TiN may increase and surface reactions may play a part in film growth.

Adsorption and Decomposition of Trimethylarsenic on GaAs(100)

1988 ◽  
Vol 131 ◽  
Author(s):  
J. R. Creighton
Keyword(s):  
Activation Energy ◽  
Electron Irradiation ◽  
Electron Spectroscopy ◽  
Auger Electron ◽  
Temperature Programmed Desorption ◽  
Methyl Radicals ◽  
Arsenic Compounds ◽  
Group V ◽  
Desorption Activation Energy ◽  
Temperature Programmed

ABSTRACTAlkylated arsenic compounds have shown some promise as alternatives to arsine as the group-V source gas for GaAs MOCVD. However, little is known about the fundamental chemical interactions of these compounds with the GaAs surface. We have investigated the adsorption and reactivity of trimethylarsenic (TMAs) on GaAs(100) using temperature programmed desorption (TPD), Auger electron spectroscopy, and LEED. For the exposures and temperatures studied, TMAs did not pyrolytically decompose on the GaAs(100). TPD results indicate that TMAs chemisorbs, apparently non-dissociatively, and desorbs ≅330 K. Multilayers of TMAs desorb ≅140–160 K. Exposure of adsorbed TMAs to 70 eV electrons results in irreversible decomposition of the molecule. After electron irradiation, TPD shows that methyl radicals desorb at 660 K, which corresponds to a desorption activation energy of ≅40 kcal/mol. At higher temperatures, As2, H2, C2H2, and a smaller amount of methyl radicals desorb, and a small coverage of carbon remains on the surface.

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