Thermal desorption of gases

Redhead, P. A.

doi:10.1016/0042-207x(62)90978-8

Cited by 3,428 publications

(1,540 citation statements)

References 12 publications

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“…The major contribution to base adsorption in all cases was due to uptake by Brønsted acid sites (Table 1) with the relative percentages of this mode of adsorption being 72, 59 and 72% for ZSM-5 (25), (36) and (135), respectively. At 128 °C, the relative percentages are 88, 77% for ZSM-5 (25) and (36) respectively.…”

Section: Characterizationmentioning

confidence: 99%

“…Redhead [25] proposed a method for desorption profile analysis based on the analysis of maximum temperatures. An assumption of the order of desorption must be made first.…”

Section: Effect Of Heating Ratementioning

confidence: 99%

“…Two approaches were used to simulate TPD profiles: (i) the Redhead method [25] and (ii) the detailed elementary step model. The desorption profile was firstly deconvoluted and analysed using the Redhead method.…”

Section: Desorption Profile Modelmentioning

confidence: 99%

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Mechanistic Insights into the Desorption of Methanol and Dimethyl Ether Over ZSM-5 Catalysts

et al. 2017

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The desorption of methanol and dimethyl ether has been studied over fresh and hydrocarbon-occluded ZSM-5 catalysts with Si/Al ratios of 25, 36 and 135 using a temporal analysis of products reactor. The catalysts were characterized by XRD, SEM, N 2 physisorption and pyridine FT-IR. The crystal size increases with Si/Al ratio from 0.10 to 0.78 µm. The kinetic parameters were obtained using the Redhead method and a plug flow reactor model with coupled convection, adsorption and desorption steps. ZSM-5 catalysts with Si/Al ratios of 25 and 36 exhibit three adsorption sites (low, medium, and high temperature sites), while there is no difference between medium and high temperature sites at a Si/Al ratio of 135. Molecular adsorption on the low temperature site and dissociative adsorption on the medium and high temperature sites give a good match between experiment and the plug flow reactor model. The DME desorption activation energy was systematically higher than that of methanol. Adsorption stoichiometry shows that methanol and DME form clusters onto the binding sites. When non-activated re-adsorption is accounted for, a local equilibrium is reached only on the low and medium temperature binding sites. No differences were observed, other than in site densities, when extracting the kinetic parameters for fresh and activated ZSM-5 catalysts at full coverage. Graphical AbstractElectronic supplementary material The online version of this article (https://doi

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Section: Characterizationmentioning

confidence: 99%

“…Redhead [25] proposed a method for desorption profile analysis based on the analysis of maximum temperatures. An assumption of the order of desorption must be made first.…”

Section: Effect Of Heating Ratementioning

confidence: 99%

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Mechanistic Insights into the Desorption of Methanol and Dimethyl Ether Over ZSM-5 Catalysts

et al. 2017

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“…Each TPD spectrum, expressed in number of molecules coming off the surface per unit time, are known to follow the Polanyi-Wigner equation: 27 …”

Section: Analysis By Direct Inversion Of Tpd Curvesmentioning

confidence: 99%

Changes in the morphology of interstellar ice analogues after hydrogen atom exposure

Accolla

Congiu

Dulieu

et al. 2011

Phys. Chem. Chem. Phys.

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The morphology of water ice in the interstellar medium is still an open question. Although accretion of gaseous water could not be the only possible origin of the observed icy mantles covering dust grains in cold molecular clouds, it is well known that water accreted from the gas phase on surfaces kept at 10 K forms ice films that exhibit a very high porosity. It is also known that in the dark clouds H2 formation occurs on the icy surface of dust grains and that part of the energy (4.48 eV) released when adsorbed atoms react to form H2 is deposited in the ice. The experimental study described in the present work focuses on how relevant changes of the ice morphology result from atomic hydrogen exposure and subsequent recombination. Using the temperature-programmed desorption (TPD) technique and a method of inversion analysis of TPD spectra, we show that there is an exponential decrease in the porosity of the amorphous water ice sample following D-atom irradiation. This decrease is inversely proportional to the thickness of the ice and has a value of φ0 = 2 × 10 16 D-atoms cm -2 per layer of H2O. We also use a model which confirms that the binding sites on the porous ice are destroyed regardless of their energy depth, and that the reduction of the porosity corresponds in fact to a reduction of the effective area. This reduction appears to be compatible with the fraction of D 2 formation energy transferred to the porous ice network. Under interstellar conditions, this effect is likely to be efficient and, together with other compaction processes, provides a good argument to believe that interstellar ice is amorphous and non-porous. 1.IntroductionAmorphous solid water (ASW) is reputed to be the most abundant form of water in the Universe, thanks to its propensity for forming, molecule after molecule, as a deposit on interstellar dust particles. 1,2 The accretion of icy mantles (predominantly constituted by ASW) on silicate and carbonaceous dust grains takes place in interstellar molecular clouds. Some of them are cold (~10 K) and dense (10 4 -10 6 cm -3 ) regions where gaseous species heavier than hydrogen and helium freeze out onto the grains. Beside H2O and CO, other species constitute the inventory of icy mantles such as CO2, CH3OH, CH4, H2CO and NH3, 3,4 as a result of the gasgrain interactions occurring on the surface of interstellar dust. The most important and abundant molecular species as well, H2, is formed likewise thanks to reactions occurring on amorphous water ice in molecular clouds 5,6 . In addition, a significant fraction of the gas phase species is constituted by atomic hydrogen whose abundance is mostly governed by the destruction of H2 due to cosmic rays. It has been evaluated that, in dense clouds, the average number density ratio of atomic hydrogen component compared to the molecular one is ~ 0.1%. 7 In a dark cloud, atomic hydrogen thus represents the third most abundant gas-phase species, after H2 and He.Along with atoms and molecules available in the gas-phase and the condensed/adsorbed speci...

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“…We do not entirely rule out this possibility. If it is the case, one can roughly estimate the upper limit of the molecular adsorption energy as ∼0.25 eV from the absence of a distinct desorption peak down to 90 K and the general relation 30 E des ∼ 31 kT p between the desorption activation energy (E des ) and the peak temperature (T p ) for firstorder desorption.…”

Section: Resultsmentioning

confidence: 99%

Interaction of D₂ with Ti-Adsorbed Polyaniline and Implication for Hydrogen Storage

Kim

et al. 2008

J. Phys. Chem. B

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Interaction of D 2 with Ti-adsorbed polyaniline (PANI) and TiO 2 at low Ti coverages has been investigated by temperature programmed desorption, Auger electron spectroscopy, and H 2 -D 2 exchange in a high pressure cell. In contrast to recent DFT calculations (Lee et al. Phys. ReV. Lett. 2006, 97, 56104-56107) that have shown a multiple number of molecular hydrogen chemisorption on Ti-decorated PANI, only 0.52 D 2 molecules per Ti atomically adsorb on Ti-deposited PANI at 87 K at a nominal Ti coverage of 2 ML. Broad TPD spectra of D 2 , HD, and H 2 were observed, which showed a common peak at 250 K and another isotopedependent peak at higher temperature. Ti deposited on TiO 2 forms clusters with a size distribution at 87 K, on which D 2 atomically adsorbs. As the Ti coverage increases, the D 2 desorption peak gradually shifts from 200 to 260 K and the number of D 2 molecules adsorbed per Ti also increases from 0.26 at 0.1 ML to 0.87 at 2 ML. We attribute this to the fact that D 2 adsorbs on larger clusters with a greater adsorption energy. TPD spectra of D 2 desorbing from Ti (2 ML)/PANI and Ti (1 ML)/TiO 2 look very similar to each other. This led us to conclude that Ti also adsorbs on PANI in clusters. We suggest that no molecular D 2 adsorption on Ti/PANI at 87 K is due to a reduced electron backdonation ability of Ti upon clustering. The small number of adsorbed D 2 per Ti on both substrates was ascribed to irreVersible D 2 adsorption only on relatively large Ti clusters, while D 2 adsorbs reVersibly on small clusters. This was indirectly confirmed by the observation that continuous H 2 -D 2 isotope exchange occurs to produce HD on Ti/PANI as well as on Ti/TiO 2 at 106 K in a high pressure cell at 5.7 mTorr. Desorption mechanisms involving H atom abstraction from PANI by Ti clusters are proposed to account for the complex isotope-dependent TPD spectra. Implication of the present results for hydrogen storage based on Ti-dispersed polymers is briefly addressed.

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Thermal desorption of gases

Cited by 3,428 publications

References 12 publications

Mechanistic Insights into the Desorption of Methanol and Dimethyl Ether Over ZSM-5 Catalysts

Mechanistic Insights into the Desorption of Methanol and Dimethyl Ether Over ZSM-5 Catalysts

Changes in the morphology of interstellar ice analogues after hydrogen atom exposure

Interaction of D₂ with Ti-Adsorbed Polyaniline and Implication for Hydrogen Storage

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Thermal desorption of gases

Cited by 3,428 publications

References 12 publications

Mechanistic Insights into the Desorption of Methanol and Dimethyl Ether Over ZSM-5 Catalysts

Mechanistic Insights into the Desorption of Methanol and Dimethyl Ether Over ZSM-5 Catalysts

Changes in the morphology of interstellar ice analogues after hydrogen atom exposure

Interaction of D2 with Ti-Adsorbed Polyaniline and Implication for Hydrogen Storage

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Interaction of D₂ with Ti-Adsorbed Polyaniline and Implication for Hydrogen Storage