TPD study of catalyst surface acidity

1989 ◽  
Vol 39 (1) ◽  
pp. 137-140 ◽  
Author(s):  
A. T. Shakhtakhtinskaya ◽  
Z. M. Mamedova ◽  
Sh. F. Mutallibova ◽  
S. Z. Alieva ◽  
R. G. Mardzhanova
Keyword(s):  
Catalyst Surface ◽  
Surface Acidity

Rhenium-promoted Pt/WO3/ZrO2: an efficient catalyst for aqueous glycerol hydrogenolysis under reduced H2 pressure

RSC Advances ◽  
2016 ◽  
Vol 6 (89) ◽  
pp. 86663-86672 ◽  
Author(s):  
Qing Tong ◽  
Anyi Zong ◽  
Wei Gong ◽  
Lei Yu ◽  
Yining Fan
Keyword(s):  
Catalyst Surface ◽  
Surface Acidity ◽  
Efficient Catalyst ◽  
Glycerol Conversion ◽  
Glycerol Hydrogenolysis

Re improved the dispersion of Pt in Pt/WO3/ZrO2 and enhanced the catalyst surface acidity. Pt–Re/WO3/ZrO2 afforded glycerol conversion >99% and C3 alcohol selectivity >95%. The reactions were performed under reduced H2 pressure.

Molybdenum oxide modified HZSM-5 catalyst: Surface acidity and catalytic performance for the dehydration of aqueous ethanol

2011 ◽  
Vol 396 (1-2) ◽  
pp. 8-13 ◽  
Author(s):  
Yuwang Han ◽  
Cuiyun Lu ◽  
Dongsheng Xu ◽  
Yelong Zhang ◽  
Yi Hu ◽  
...  
Keyword(s):  
Molybdenum Oxide ◽  
Aqueous Ethanol ◽  
Catalyst Surface ◽  
Surface Acidity ◽  
Catalytic Performance

Modeling the Electrical Double Layer to Understand the Reaction Environment in a CO2 Electrocatalytic System

2019 ◽  
Author(s):  
Divya Bohra ◽  
Jehanzeb Chaudhry ◽  
Thomas Burdyny ◽  
Evgeny Pidko ◽  
wilson smith
Keyword(s):  
Electric Field ◽  
Double Layer ◽  
Electrical Double Layer ◽  
Surface Reaction ◽  
Catalyst Surface ◽  
Local Reaction ◽  
Reaction Diffusion ◽  
Alkali Metal Cations ◽  
Applied Potential ◽  
Critical Aspect

<p>The environment of a CO<sub>2</sub> electroreduction (CO<sub>2</sub>ER) catalyst is intimately coupled with the surface reaction energetics and is therefore a critical aspect of the overall system performance. The immediate reaction environment of the electrocatalyst constitutes the electrical double layer (EDL) which extends a few nanometers into the electrolyte and screens the surface charge density. In this study, we resolve the species concentrations and potential profiles in the EDL of a CO<sub>2</sub>ER system by self-consistently solving the migration, diffusion and reaction phenomena using the generalized modified Poisson-Nernst-Planck (GMPNP) equations which include the effect of volume exclusion due to the solvated size of solution species. We demonstrate that the concentration of solvated cations builds at the outer Helmholtz plane (OHP) with increasing applied potential until the steric limit is reached. The formation of the EDL is expected to have important consequences for the transport of the CO<sub>2</sub> molecule to the catalyst surface. The electric field in the EDL diminishes the pH in the first 5 nm from the OHP, with an accumulation of protons and a concomitant depletion of hydroxide ions. This is a considerable departure from the results obtained using reaction-diffusion models where migration is ignored. Finally, we use the GMPNP model to compare the nature of the EDL for different alkali metal cations to show the effect of solvated size and polarization of water on the resultant electric field. Our results establish the significance of the EDL and electrostatic forces in defining the local reaction environment of CO<sub>2</sub> electrocatalysts.</p>

The effect of composition of cobalt-molybdenum catalysts on their surface acidity and isomerisation activity

1980 ◽  
Vol 45 (3) ◽  
pp. 697-702 ◽  
Author(s):  
Vlastimil Vyskočil ◽  
Miroslav Zdražil
Keyword(s):  
Chromatographic Method ◽  
Surface Acidity ◽  
Parallel Reaction ◽  
Molybdenum Catalysts ◽  
The Difference ◽  
Kinetics Of ◽  
Alumina Catalysts

Kinetics of isomerisation of cyclohexene to methylcyclopentene proceeding as parallel reaction to hydrogenation of cyclohexene to cyclohexane on cobalt-molybdenum catalysts of different composition has been measured. The surface acidity of these catalysts was estimated from the difference in the adsorption of toluene and heptane which was measured by chromatographic method. In a series of catalysts containing molybdenum the acidity parallels isomerisation activity. Cobalt on alumina catalysts and alumina itself have greater acidity but exhibit lower isomerisation activity compared to the catalysts containing molybdenum.

Hydrogenation-dehydrogenation and cleavage functions of hydrorefining catalysts studied by the reaction of tetrahydrothiophene

1986 ◽  
Vol 51 (12) ◽  
pp. 2770-2780 ◽  
Author(s):  
Alexandra Drahorádová ◽  
Miroslav Zdražil
Keyword(s):  
Activated Carbon ◽  
Catalyst Surface ◽  
Bond Cleavage ◽  
Unsaturated Hydrocarbons ◽  
Cleavage Reactions

The reaction of tetrahydrothiophene in a stream of nitrogen was used to study the relations between dehydrogenation and C-S cleavage reactions on sulphided Co-Mo/Al2O3 catalysts. The course of the reaction was compared for Co-Mo catalysts supported on alumina and activated carbon, for alumina alone as well as for a Pt/C catalyst. The effect of substitution of nitrogen for hydrogen, of the addition of water to the feed, of pre-sulphidation of catalysts and their deactivation by coking on the rate and selectivity of the reaction were also investigated. The results showed that hydrogenation-dehydrogenation and dehydrosulphurization activity of the sulphide catalysts have the same origin. Hydrogen accelerates dehydrosulphurization on the sulphide catalysts by removing sulphur and unsaturated hydrocarbons formed on catalyst surface by C-S bond cleavage reactions.

Physicochemical and Catalytic Properties of Spinels Formed by Solid-Solid Interaction Between Fe2O3and V2O5

1996 ◽  
Vol 61 (8) ◽  
pp. 1131-1140 ◽  
Author(s):  
Abd El-Aziz Ahmed Said
Keyword(s):  
Vanadium Oxide ◽  
Active Sites ◽  
Catalyst Surface ◽  
Catalytic Properties ◽  
Flow System ◽  
Oxide Catalysts ◽  
X Ray Diffraction ◽  
Selective Catalyst ◽  
X Ray ◽  
Solid Catalysts

Vanadium oxide catalysts doped or mixed with 1-50 mole % Fe3+ ions were prepared. The structure of the original samples and those calcined from 200 up to 500 °C were characterized by TG, DTA, IR and X-ray diffraction. The SBET values and texture of the solid catalysts were investigated. The catalytic dehydration-dehydrogenation of isopropanol was carried out at 200 °C using a flow system. The results obtained showed an observable decrease in the activity of V2O5 on the addition of Fe3+ ions. Moreover, Fe2V4O13 is the more active and selective catalyst than FeVO4 spinels. The results were correlated with the active sites created on the catalyst surface.

scholarly journals Post-Plasma Catalysis for Trichloroethylene Abatement with Ce-Doped Birnessite Downstream DC Corona Discharge Reactor

Catalysts ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 946
Author(s):  
Grêce Abdallah ◽  
Jean-Marc Giraudon ◽  
Rim Bitar ◽  
Nathalie De Geyter ◽  
Rino Morent ◽  
...  
Keyword(s):  
Corona Discharge ◽  
Active Oxygen Species ◽  
Surface Acidity ◽  
Good Stability ◽  
Ozone Decomposition ◽  
Moist Air ◽  
Plasma Catalysis ◽  
Dry Air ◽  
Water Tolerance ◽  
By Products

Trichloroethylene (TCE) removal was investigated in a post-plasma catalysis (PPC) configuration in nearly dry air (RH = 0.7%) and moist air (RH = 15%), using, for non-thermal plasma (NTP), a 10-pin-to-plate negative DC corona discharge and, for PPC, Ce0.01Mn as a catalyst, calcined at 400 °C (Ce0.01Mn-400) or treated with nitric acid (Ce0.01Mn-AT). One of the key points was to take advantage of the ozone emitted from NTP as a potential source of active oxygen species for further oxidation, at a very low temperature (100 °C), of untreated TCE and of potential gaseous hazardous by-products from the NTP. The plasma-assisted Ce0.01Mn-AT catalyst presented the best CO2 yield in dry air, with minimization of the formation of gaseous chlorinated by-products. This result was attributed to the high level of oxygen vacancies with a higher amount of Mn3+, improved specific surface area and strong surface acidity. These features also allow the promotion of ozone decomposition efficiency. Both catalysts exhibited good stability towards chlorine. Ce0.01Mn-AT tested in moist air (RH = 15%) showed good stability as a function of time, indicating good water tolerance also.

scholarly journals Insight into the Promoting Role of Er Modification on SO2 Resistance for NH3-SCR at Low Temperature over FeMn/TiO2 Catalysts

Catalysts ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 618
Author(s):  
Huan Du ◽  
Zhitao Han ◽  
Xitian Wu ◽  
Chenglong Li ◽  
Yu Gao ◽  
...  
Keyword(s):  
Low Temperature ◽  
Catalyst Surface ◽  
Impregnation Method ◽  
In Situ Drifts ◽  
Tio2 Catalyst ◽  
Nh3 Scr ◽  
Nh3 Adsorption ◽  
So2 Resistance ◽  
Fast Scr

Er-modified FeMn/TiO2 catalysts were prepared through the wet impregnation method, and their NH3-SCR activities were tested. The results showed that Er modification could obviously promote SO2 resistance of FeMn/TiO2 catalysts at a low temperature. The promoting effect and mechanism were explored in detail using various techniques, such as BET, XRD, H2-TPR, XPS, TG, and in-situ DRIFTS. The characterization results indicated that Er modification on FeMn/TiO2 catalysts could increase the Mn4+ concentration and surface chemisorbed labile oxygen ratio, which was favorable for NO oxidation to NO2, further accelerating low-temperature SCR activity through the “fast SCR” reaction. As fast SCR reaction could accelerate the consumption of adsorbed NH3 species, it would benefit to restrain the competitive adsorption of SO2 and limit the reaction between adsorbed SO2 and NH3 species. XPS results indicated that ammonium sulfates and Mn sulfates formed were found on Er-modified FeMn/TiO2 catalyst surface seemed much less than those on FeMn/TiO2 catalyst surface, suggested that Er modification was helpful for reducing the generation or deposition of sulfate salts on the catalyst surface. According to in-situ DRIFTS the results of, the presence of SO2 in feeding gas imposed a stronger impact on the NO adsorption than NH3 adsorption on Lewis acid sites of Er-modified FeMn/TiO2 catalysts, gradually making NH3-SCR reaction to proceed in E–R mechanism rather than L–H mechanism. DRIFTS.

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