Temperature-programmed surface

The second part of this work will be dedicated to the start of the game what are the pieces motions How can the adsorbed molecules react on the surface and among all the playground, where does the real action take place This is the so-called in situ approach for which techniques such as temperature-programmed surface reaction (TPSR) or transient analysis by pulse injection have been developed. 

Abstract A three-function catalyst model for hydrocarbon SCR of NOx is described, based on experimental evidence for each function, during temperature-programmed surface reactions (TPSR). 

The thermal stability of NOx adsorbed species and their reactivity in the presence of gaseous reductant molecules was addressed by thermal decomposition in He (TPD) or by heating in flowing H2/He mixtures [temperature-programmed surface reaction (TPSR)], respectively. In these cases, after NOx adsorption and He purge at the adsorption temperature (300 100oC), the samples were cooled to RT under flowing He. Then the samples were heated at 15°C/min up to 500-600°C in He (TPD) or in He + H2 (2000 ppm) (H2-TPSR). 

In this work, an attempt is made to show the role of the different metal species present in Co and Co/Pd based FER zeolites, using UV-Vis and H2-TPR experiments, coupled with Temperature Programmed Surface Reaction (TPSR) tests. 

Catalytic runs were carried out in a U-type quartz reactor, under Temperature Programmed Surface Reaction (TPSR) conditions (GHSV= 45000 h"1). The sample was pre-treated in flowing argon from room temperature (RT) to 500 °C, using a heating rate of 5 °C min"1, and kept at 500 °C for lh. Further details are also given elsewhere [19]. 

Using a temperature-programmed surface reaction (TPSR) technique, Li et al. (154) showed that this complete oxidation of methane took place on the NiO catalyst during the CHfOi reaction. Weng et al. (145) used in situ microprobe Raman and in situ time-resolved IR spectroscopies to obtain a relationship between the state of the catalyst and the reaction mechanism. These authors showed that RuC>2 in the Ru/SiC>2 catalyst formed easily at 873 K in the presence of a CH4/02/Ar (2/1/45, molar) mixture and that the dominant pathway to synthesis gas was by the sequence of total oxidation of CH4 followed by reforming of the unconverted CH4 by C02 and H20. Thus, these results indicate that the oxidation of methane takes place principally by the combustion mechanism on the oxidized form of this catalyst. 

Temperature-Programmed Surface Reaction (TPSR) Experiments at 800 Torr. Pretreated and preoxidized silver exhibited no reactivity toward an ethylene/argon mixture at reaction temperatures (443 - 543 K) and atmospheric pressures (750-800 torr). The desorption spectrum of a pretreated sample showed no evidence of oxygen desorption when the sample was heated in vacuo to 673 K. These... 

Fig. 5.3. Arrhenius plot for temperature programmed surface reaction ln(rate) as a function of 1/T, for the reaction of a pre-adsorbed CO in the flow of H2. Promoted and unpromoted Rh/Si02...

The amount of carbon deposited was measured and the temperature programmed surface... 

The apparent activation energy of both reactions was found to decrease when they were carried out over the doped Rh catalysts. The decrease was found to be about 20 kJ moP for the CO/H2 reaction and 25-30 kJ moP for the CO2/H2 reaction, almost independent of the dopant content in the Ti02 support. Doped Rh catalysts also exhibited superior stability with time on stream in both reactions. While the activity of the undoped Rh catalyst declined by about 30-50% in the first 3 h on stream, the activity of the doped catalysts remained practically constant even after 4—5h on stream. This implies that carbon deposition is retarted on doped catalysts, a phenomenon also investigated by temperature programmed surface reaction techniques [107]. 

Shown in Figures 3 and 4 are the results of temperature programmed surface reaction on an iron, 1% Cu/Fe, and 2.5% Cu/Fe catalysts following 24 h of reaction in synthesis gas (H2/CO=0.7). The TSPR behavior of the two copper-containing catalysts was quite similar. The major difference was between the copper-containing and the iron-only catalyst. Less CH carbon is formed on the iron-only eatalyst, and the substantial amount of graphitic carbon formed on the iron-only catalyst is considerably less reactive. Also, the more copper in the catalyst, the more... 

Figure 3. Temperature programmed surface reaction of 3 catalysts following FT synthesis for 24 h at 215°C and 16 atm. TPSR reduction carried out to 550°C.

Figure 5. Temperature programmed surface reaction of 1% Cu/Fe catalyst following reaction at 215°C and 270°C...

J.G. McCarty, P.Y. Hou, D. Sheridan, and H. Wise, Reactivity of Surface Carbon on Nickel Catalysts Temperature-Programmed Surface Reaction with Hydrogen and Water, in Coke Formation on Metal Surfaces, eds. L.G. Albright and R.T.K. Baker, American Chemical Society, Washington D.C., 1982, p. 253. 

Temperature-programmed surface reaction (TPSR). Measurements were performed in a flow apparatus with a BALZERS quadrupolar mass spectrometer to monitor effluent products versus temperature. Samples of 300 mg were used in each measurement. The gases employed were He (99.9%) and mixtures 4% NH3/He, 1% NO/He and 5% 02/He. TPSR measurements were obtained after NH3 adsorption at 70°C under continuous flow until base line stabilization. The reactor was heated to 500°C at 20°C/min and kept at this... 

Reactivity of Surface Carbon on Nickel Catalysts Temperature-Programmed Surface Reaction with Hydrogen and Water... 

The nature of the carbon deposits formed on an alumina-supported nickel catalyst have been characterized by their reactivity with H2 and H 0 during temperature-programmed surface reaction (TPSR). 

In a previous study (9 ) we used temperature-programmed surface reaction (TPSR) with 1 atm hydrogen to determine the... 

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