scholarly journals The Effect of CO Partial Pressure on Important Kinetic Parameters of Methanation Reaction on Co-Based FTS Catalyst Studied by SSITKA-MS and Operando DRIFTS-MS Techniques

Catalysts ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 583
Author(s):  
Michalis A. Vasiliades ◽  
Konstantina K. Kyprianou ◽  
Nilenindran S. Govender ◽  
Ashriti Govender ◽  
Renier Crous ◽  
...  
Keyword(s):  
Partial Pressure ◽  
Kinetic Parameters ◽  
Elevated Temperatures ◽  
Linear Type ◽  
Carbonaceous Species ◽  
Methanation Reaction ◽  
Adsorbed Co ◽  
Temperature Programmed ◽  
Diffuse Reflectance Infrared ◽  
Isotopic Transient Kinetic Analysis

A 20 wt% Co-0.05 wt% Pt/γ-Al2O3 catalyst was investigated to obtain a fundamental understanding of the effect of CO partial pressure (constant H2 partial pressure) on important kinetic parameters of the methanation reaction (x vol% CO/25 vol% H2, x = 3, 5 and 7) by performing advanced transient isotopic and operando diffuse reflectance infrared Fourier transform spectroscopy–mass spectrometry (DRIFTS-MS) experiments. Steady State Isotopic Transient Kinetic Analysis (SSITKA) experiments conducted at 1.2 bar, 230 °C after 5 h in CO/H2 revealed that the surface coverages, θCO and θCHx and the mean residence times, τCO, and τCHx (s) of the reversibly adsorbed CO-s and active CHx-s (Cα) intermediates leading to CH4, respectively, increased with increasing CO partial pressure. On the contrary, the apparent activity (keff, s−1) of CHx-s intermediates, turnover frequency (TOF, s−1) of methanation reaction, and the CH4-selectivity (SCH4, %) were found to decrease. Transient isothermal hydrogenation (TIH) following the SSITKA step-gas switch provided important information regarding the reactivity and concentration of active (Cα) and inactive -CxHy (Cβ) carbonaceous species formed after 5 h in the CO/H2 reaction. The latter Cβ species were readily hydrogenated at 230 °C in 50%H2/Ar. The surface coverage of Cβ was found to vary only slightly with increasing CO partial pressure. Temperature-programmed hydrogenation (TPH) following SSITKA and TIH revealed that other types of inactive carbonaceous species (Cγ) were formed during Fischer-Tropsch Synthesis (FTS) and hydrogenated at elevated temperatures (250–550 °C). The amount of Cγ was found to significantly increase with increasing CO partial pressure. All carbonaceous species hydrogenated during TIH and TPH revealed large differences in their kinetics of hydrogenation with respect to the CO partial pressure in the CO/H2 reaction mixture. Operando DRIFTS-MS transient isothermal hydrogenation of adsorbed CO-s formed after 2 h in 5 vol% CO/25 vol% H2/Ar at 200 °C coupled with kinetic modeling (H-assisted CO hydrogenation) provided information regarding the relative reactivity (keff) for CH4 formation of the two kinds of linear-type adsorbed CO-s on the cobalt surface.

Kinetics of temperature-programmed reactivation of a hydrodesulphurization catalyst

1983 ◽  
Vol 48 (12) ◽  
pp. 3340-3355 ◽  
Author(s):  
Pavel Fott ◽  
Pavel Šebesta
Keyword(s):  
Carbon Dioxide ◽  
Thermal Analysis ◽  
Differential Thermal Analysis ◽  
Thin Layer ◽  
Kinetic Parameters ◽  
Diffusion Region ◽  
Reaction Heat ◽  
Gaseous Products ◽  
Temperature Programmed ◽  
Kinetics Of

The kinetic parameters of reactivation of a carbonized hydrodesulphurization (HDS) catalyst by air were evaluated from combined thermogravimetric (TG) and differential thermal analysis (DTA) data. In addition, the gaseous products leaving a temperature-programmed reactor with a thin layer of catalyst were analyzed chromatographically. Two exothermic processes were found to take part in the reactivation, and their kinetics were described by 1st order equations. In the first process (180-400 °C), sulphur in Co and Mo sulphides is oxidized to sulphur dioxide; in the second process (300-540 °C), in which the essential portion of heat is produced, the deposited carbon is oxidized to give predominantly carbon dioxide. If the reaction heat is not removed efficiently enough, ignition of the catalyst takes place, which is associated with a transition to the diffusion region. The application of the obtained kinetic parameters to modelling a temperature-programmed reactivation is illustrated on the case of a single particle.

scholarly journals Effect of CO2 partial pressure on dry reforming of ethanol for hydrogen production

2018 ◽  
Vol 1 (1) ◽  
pp. 6-10
Author(s):  
Fahim Fayaz ◽  
Ahmad Ziad Sulaiman ◽  
Sharanjit Singh ◽  
Sweeta Akbari
Keyword(s):  
Partial Pressure ◽  
Fixed Bed ◽  
Dry Reforming ◽  
Fixed Bed Reactor ◽  
Bet Surface Area ◽  
Impregnation Method ◽  
X Ray Diffraction ◽  
Co2 Partial Pressure ◽  
Temperature Programmed ◽  
Al2o3 Catalyst

The effect of CO2 partial pressure on ethanol dry reforming was evaluated over 5%Ce-10%Co/Al2O3 catalyst at = PCO2 = 20-50 kPa, PC2H5OH = 20 kPa, reaction temperature of 973 K under atmospheric pressure. The catalyst was prepared by using impregnation method and tested in a fixed-bed reactor. X-ray diffraction measurements studied the formation of Co3O4, spinel CoAl2O4 and CeO2, phases on surface of 5%Ce-10%Co/Al2O3 catalyst. CeO2, CoO and Co3O4 oxides were obtained during temperature–programmed calcination. Ce-promoted 10%Co/Al2O3 catalyst possessed high BET surface area of 137.35 m2 g-1. C2H5OH and CO2 conversions was improved with increasing CO2 partial pressure from 20-50 kPa whilst the optimal selectivity of H2 and CO was achieved at 50 kPa.

Tensile Properties and Creep Behavior of SiC-Based Fibers under Various Oxygen Partial Pressures

2005 ◽  
Vol 475-479 ◽  
pp. 1333-1336 ◽  
Author(s):  
Jan Ji Sha ◽  
J.S. Park ◽  
Tatsuya Hinoki ◽  
Akira Kohyama ◽  
J. Yu
Keyword(s):  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Tensile Properties ◽  
Creep Behavior ◽  
Elevated Temperatures ◽  
Low Oxygen ◽  
X Ray Diffraction ◽  
Sic Fibers ◽  
Partial Pressures ◽  
Ar Gas

Three kinds of atmospheres (air, highly-pure Ar and ultra highly-pure Ar gas) with different oxygen partial pressures were applied to investigate the tensile properties and creep behavior of SiC fibers such as Hi-NicalonTM and TyrannoTM-SA. These fibers were annealed and crept at elevated temperatures ranging from1273-1773 K in such environments. After annealing at 1773 K, the room temperature tensile strengths of SiC-based fibers decreased with decreasing the oxygen partial pressure and the near stoichiometric fiber TyrannoTM-SA shows excellent strength retention. At temperatures above the 1573 K, the creep resistance of SiC fibers evaluated by bending stress relaxation (BSR) method under high oxygen partial pressure was lower than that of in low oxygen partial pressure. The microstructural features on these fibers were examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD).

scholarly journals An alternative approach to kinetic analysis of temperature-programmed reaction data

RSC Advances ◽  
2018 ◽  
Vol 8 (6) ◽  
pp. 3286-3295 ◽  
Author(s):  
A. S. Portnyagin ◽  
A. P. Golikov ◽  
V. A. Drozd ◽  
V. A. Avramenko
Keyword(s):  
Particle Size ◽  
Kinetic Analysis ◽  
Kinetic Parameters ◽  
Isothermal Reaction ◽  
Alternative Approach ◽  
Reaction Data ◽  
Temperature Programmed ◽  
Temperature Programmed Reaction

Presented method of kinetic analysis of non-isothermal reaction data provides precise kinetic parameters for different materials with different morphology and particle size.

scholarly journals Effect of Zirconia Polymorph on Vapor-Phase Ketonization of Propionic Acid

Catalysts ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 768 ◽  
Author(s):  
Shuang Ding ◽  
Jiankang Zhao ◽  
Qiang Yu
Keyword(s):  
Propionic Acid ◽  
Vapor Phase ◽  
Surface Concentration ◽  
X Ray Diffraction ◽  
In Situ Drifts ◽  
X Ray ◽  
Surface Intermediates ◽  
Temperature Programmed ◽  
Diffuse Reflectance Infrared

Vapor-phase ketonization of propionic acid derived from biomass was studied at 300–375 °C over ZrO2 with different zirconia polymorph. The tetragonal ZrO2 (t-ZrO2) are more active than monoclinic ZrO2 (m-ZrO2). The results of characterizations from X-ray diffraction (XRD) and Raman suggest m-ZrO2 and t-ZrO2 are synthesized by the solvothermal method. NH3 and CO2 temperature-programmed desorption (NH3-TPD and CO2-TPD) measurements show that there were more medium-strength Lewis acid base sites with lower coordination exposed on m-ZrO2 relative to t-ZrO2, increasing the adsorption strength of propionic acid. The in situ DRIFTS (Diffuse reflectance infrared Fourier transform spectroscopy) of adsorbed propionic acid under ketonization reaction reveal that as the most abundant surface intermediates, the monodentate propionates are more active than bidentate propionates. In comparison with m-ZrO2, the t-ZrO2 surface favors monodentate adsorption over bidentate adsorption. Additionally, the adsorption strength of monodentate propionate is weaker on t-ZrO2. These differences in adsorption configuration and adsorption strength of propionic acid are affected by the zirconia structure. The higher surface concentration and weaker adsorption strength of monodentate propionates contribute to the higher ketonization rate in the steady state.

Synthesis of highly reactive polyisobutylene by catalytic chain transfer in hexanes at elevated temperatures; determination of the kinetic parameters

2017 ◽  
Vol 8 (18) ◽  
pp. 2852-2859 ◽  
Author(s):  
Tota Rajasekhar ◽  
Jack Emert ◽  
Rudolf Faust
Keyword(s):  
Kinetic Parameters ◽  
Rate Constants ◽  
Chain Transfer ◽  
Elevated Temperatures ◽  
Polymerization Rate ◽  
Carbenium Ions ◽  
Catalytic Chain Transfer ◽  
Highly Reactive Polyisobutylene ◽  
Increasing Temperature

The rate constants of activation/deactivation for dormant oxonium/active carbenium ions have been measured and related to the increasing polymerization rate with increasing temperature.

scholarly journals New Insight into the In Situ SO2 Poisoning Mechanism over Cu-SSZ-13 for the Selective Catalytic Reduction of NOx with NH3

Catalysts ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1391
Author(s):  
Yu Qiu ◽  
Chi Fan ◽  
Changcheng Sun ◽  
Hongchang Zhu ◽  
Wentian Yi ◽  
...  
Keyword(s):  
Selective Catalytic Reduction ◽  
Active Sites ◽  
Catalytic Reduction ◽  
Zeolite Catalysts ◽  
So2 Poisoning ◽  
Negative Effect ◽  
Temperature Programmed ◽  
Diffuse Reflectance Infrared ◽  
Sulfate Species

To reveal the nature of SO2 poisoning over Cu-SSZ-13 catalyst under actual exhaust conditions, the catalyst was pretreated at 200 and 500 °C in a flow containing NH3, NO, O2, SO2, and H2O. Brunner−Emmet−Teller (BET), X-ray diffraction(XRD), thermo gravimetric analyzer (TGA), ultraviolet Raman spectroscopy (UV Raman), temperature-programmed reduction with H2 (H2-TPR), temperature-programmed desorption of NO+O2 (NO+O2-TPD), NH3-TPD, in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS), and an activity test were utilized to monitor the changes of Cu-SSZ-13 before and after in situ SO2 poisoning. According to the characterization results, the types and generated amount of sulfated species were directly related to poisoning temperature. Three sulfate species, including (NH4)2SO4, CuSO4, and Al2(SO4)3, were found to form on CZ-S-200, while only the latter two sulfate species were observed over CZ-S-500. Furthermore, SO2 poisoning had a negative effect on low-temperature selective catalytic reduction (SCR) activity, which was mainly due to the sulfation of active sites, including Z2Cu, ZCuOH, and Si-O(H)-Al. In contrast, SO2 poisoning had a positive effect on high-temperature SCR activity, owing to the inhibition of the NH3 oxidation reaction. The above findings may be a useful guideline to design excellent SO2-resistant Cu-based zeolite catalysts.

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