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Peyman Bigdeli - One of the best experts on this subject based on the ideXlab platform.
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Pd‐Ag/α‐Al2O3 Catalyst Deactivation in Acetylene Selective Hydrogenation Process
Chemical Engineering & Technology, 2016Co-Authors: Maryam Takht Ravanchi, Maryam Rahimi Fard, Siavash Fadaeerayeni, Saeed Sahebdelfar, Peyman BigdeliAbstract:The selective hydrogenation of acetylene to ethylene over Pd-Ag/α-Al2O3 Catalysts prepared by different impregnation/reduction methods was studied. The best catalytic performance was achieved with the sample prepared by sequential impregnation. A kinetic model based on first order in acetylene and 0.5th order in hydrogen for the main reaction and second-order independent decay law for Catalyst Deactivation was used to fit the conversion time data and to obtain quantitative assessment of Catalyst performances. Fair fits were observed from which the reaction and Deactivation rate constants were evaluated. Coke deposition amounts showed a good correlation with Catalyst Deactivation rate constants, indicating that coke formation should be the main cause of Catalyst Deactivation.
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Pd-Ag/α-Al2O3 Catalyst Deactivation in Acetylene Selective Hydrogenation Process
Chemical Engineering and Technology, 2016Co-Authors: Maryam Takht Ravanchi, Maryam Rahimi Fard, Siavash Fadaeerayeni, Saeed Sahebdelfar, Peyman BigdeliAbstract:The selective hydrogenation of acetylene to ethylene over Pd-Ag/α-Al2O3 Catalysts prepared by different impregnation/reduction methods was studied. The best catalytic performance was achieved with the sample prepared by sequential impregnation. A kinetic model based on first order in acetylene and 0.5th order in hydrogen for the main reaction and second-order independent decay law for Catalyst Deactivation was used to fit the conversion time data and to obtain quantitative assessment of Catalyst performances. Fair fits were observed from which the reaction and Deactivation rate constants were evaluated. Coke deposition amounts showed a good correlation with Catalyst Deactivation rate constants, indicating that coke formation should be the main cause of Catalyst Deactivation.
Maryam Takht Ravanchi - One of the best experts on this subject based on the ideXlab platform.
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Pd‐Ag/α‐Al2O3 Catalyst Deactivation in Acetylene Selective Hydrogenation Process
Chemical Engineering & Technology, 2016Co-Authors: Maryam Takht Ravanchi, Maryam Rahimi Fard, Siavash Fadaeerayeni, Saeed Sahebdelfar, Peyman BigdeliAbstract:The selective hydrogenation of acetylene to ethylene over Pd-Ag/α-Al2O3 Catalysts prepared by different impregnation/reduction methods was studied. The best catalytic performance was achieved with the sample prepared by sequential impregnation. A kinetic model based on first order in acetylene and 0.5th order in hydrogen for the main reaction and second-order independent decay law for Catalyst Deactivation was used to fit the conversion time data and to obtain quantitative assessment of Catalyst performances. Fair fits were observed from which the reaction and Deactivation rate constants were evaluated. Coke deposition amounts showed a good correlation with Catalyst Deactivation rate constants, indicating that coke formation should be the main cause of Catalyst Deactivation.
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Pd-Ag/α-Al2O3 Catalyst Deactivation in Acetylene Selective Hydrogenation Process
Chemical Engineering and Technology, 2016Co-Authors: Maryam Takht Ravanchi, Maryam Rahimi Fard, Siavash Fadaeerayeni, Saeed Sahebdelfar, Peyman BigdeliAbstract:The selective hydrogenation of acetylene to ethylene over Pd-Ag/α-Al2O3 Catalysts prepared by different impregnation/reduction methods was studied. The best catalytic performance was achieved with the sample prepared by sequential impregnation. A kinetic model based on first order in acetylene and 0.5th order in hydrogen for the main reaction and second-order independent decay law for Catalyst Deactivation was used to fit the conversion time data and to obtain quantitative assessment of Catalyst performances. Fair fits were observed from which the reaction and Deactivation rate constants were evaluated. Coke deposition amounts showed a good correlation with Catalyst Deactivation rate constants, indicating that coke formation should be the main cause of Catalyst Deactivation.
Kevin J. Smith - One of the best experts on this subject based on the ideXlab platform.
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Catalyst Deactivation in Slurry-Phase Residue Hydroconversion
Energy & Fuels, 2013Co-Authors: Hooman Rezaei, Kevin J. SmithAbstract:MoS2 Catalysts used in slurry-phase hydroconversion of bitumen deactivate when the solid coke–Catalyst recovered from the product is recycled in a semi-batch reactor operated at high residue conversion (445 °C and 13.8 MPa H2). The Catalyst Deactivation, manifested by an increasing coke yield, is dependent upon the MoS2 concentration in the recycled coke–Catalyst and the age of the coke in the reactor. Characterization data show significant changes in the chemical and physical properties of the coke when recycled under hydroconversion conditions. In particular, with increased recycling, the coke becomes more graphitic with a decreased H/C ratio and an increased aromatic/aliphatic carbon ratio. Model ex situ coke aging experiments, conducted in He at 700 °C for 15 h, were used to confirm that changes in the chemical properties of the recovered coke determined the extent of Catalyst Deactivation, whereas morphological changes were less important. On the basis of these results, a model of the Catalyst deacti...
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Carbon Formation Thresholds and Catalyst Deactivation During CH4 Decomposition on Supported Co and Ni Catalysts
Catalysis Letters, 2004Co-Authors: Yi Zhang, Kevin J. SmithAbstract:Carbon deposition during catalytic CH4 decomposition (CH2↔C+2H2), occurs at a given reaction temperature when KM < KM*, where KM* is the carbon formation threshold defined as the value of KM = (PH22/PCH4) at which the net rate of carbon deposition is zero (Snoeck et al., J. Catal. 169 (1997) 240). Carbon deposition can produce encapsulating carbon that results in Catalyst Deactivation, or filamentous carbon that ensures stable Catalyst activity for extended periods of time. In the present study, the rate of Catalyst Deactivation during CH4 decomposition at 773 K on supported Co and Ni Catalysts decreased as KM increased. A filamentous carbon formation threshold KMf is therefore defined as the value of KM at which the rate of Catalyst Deactivation equals zero as a consequence of filamentous carbon formation. Results presented herein demonstrate that stable activity and filamentous carbon formation during CH4 decomposition on supported Ni and Co Catalysts can be guaranteed by choosing KM such that the inequality KMf < KM < KM* is satisfied, whereas if KM < KMf < KM*, encapsulating carbon accompanied by Catalyst Deactivation occurs.
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Carbon Formation Thresholds and Catalyst Deactivation During CH_4 Decomposition on Supported Co and Ni Catalysts
Catalysis Letters, 2004Co-Authors: Yi Zhang, Kevin J. SmithAbstract:Carbon deposition during catalytic CH_4 decomposition (CH_2↔C+2H_2), occurs at a given reaction temperature when K _M < K _M ^*, where K _M ^* is the carbon formation threshold defined as the value of K_M = (P _H2 ^2 /PCH_4) at which the net rate of carbon deposition is zero (Snoeck et al. , J. Catal. 169 (1997) 240). Carbon deposition can produce encapsulating carbon that results in Catalyst Deactivation, or filamentous carbon that ensures stable Catalyst activity for extended periods of time. In the present study, the rate of Catalyst Deactivation during CH_4 decomposition at 773 K on supported Co and Ni Catalysts decreased as K _M increased. A filamentous carbon formation threshold K _M ^f is therefore defined as the value of K _M at which the rate of Catalyst Deactivation equals zero as a consequence of filamentous carbon formation. Results presented herein demonstrate that stable activity and filamentous carbon formation during CH_4 decomposition on supported Ni and Co Catalysts can be guaranteed by choosing K _M such that the inequality K _M ^f < K _M < K _M ^* is satisfied, whereas if K _M < K _M ^f < K _M ^*, encapsulating carbon accompanied by Catalyst Deactivation occurs.
Steven D Phillips - One of the best experts on this subject based on the ideXlab platform.
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evaluation of Catalyst Deactivation during catalytic steam reforming of biomass derived syngas
Industrial & Engineering Chemistry Research, 2005Co-Authors: Richard L. Bain, Stefan R. Czernik, Calvin J. Feik, Richard J French, David Charles Dayton, Daniel Carpenter, Kimberly A Magrinibair, Steven D PhillipsAbstract:Mitigation of tars produced during biomass gasification continues to be a technical barrier to developing systems. This effort combined the measurement of tar-reforming Catalyst Deactivation kinetics and the production of syngas in a pilot-scale biomass gasification system at a single steady-state condition with mixed woods, producing a gas with an H2-to-CO ratio of 2 and 13% methane. A slipstream from this process was introduced into a bench-scale 5.25 cm diameter fluidized-bed Catalyst reactor charged with an alkali-promoted Ni-based/Al2O3 Catalyst. Catalyst conversion tests were performed at a constant space time and five temperatures from 775 to 875 °C. The initial Catalyst-reforming activity for all measured components (benzene, toluene, naphthalene, and total tars) except light hydrocarbons was 100%. The residual steady-state conversion of tar ranged from 96.6% at 875 °C to 70.5% at 775 °C. Residual steady-state conversions at 875 °C for benzene and methane were 81% and 32%, respectively. Catalytic Deactivation models with residual activity were developed and evaluated based on experimentally measured changes in conversion efficiencies as a function of time on stream for the catalytic reforming of tars, benzene, methane, and ethane. Both first- and second-order models were evaluated for the reforming reaction and for Catalyst Deactivation. Comparison of experimental and modeling results showed that the reforming reactions were adequately modeled by either first-order or second-order global kinetic expressions. However, second-order kinetics resulted in negative activation energies for Deactivation. Activation energies were determined for firstorder reforming reactions and Catalyst Deactivation. For reforming, the representative activation energies were 32 kJ/g‚mol for ethane, 19 kJ/g‚mol for tars, 45 kJ/g‚mol for tars plus benzene, and 8-9 kJ/g‚mol for benzene and toluene. For Catalyst Deactivation, representative activation energies were 146 kJ/g‚mol for ethane, 121 kJ/g‚mol for tars plus benzene, 74 kJ/g‚mol for benzene, and 19 kJ/g‚mol for total tars. Methane was also modeled by a second-order reaction, with an activation energy of 18.6 kJ/g‚mol and a Catalyst Deactivation energy of 5.8 kJ/g‚mol.
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Evaluation of Catalyst Deactivation during catalytic steam reforming of biomass-derived syngas
Industrial and Engineering Chemistry Research, 2005Co-Authors: Richard L. Bain, Kimberly A. Magrini-bair, Stefan R. Czernik, Daniel L. Carpenter, Calvin J. Feik, Richard J French, David Charles Dayton, Steven D PhillipsAbstract:Mitigation of tars produced during biomass gasification continues to be a technical barrier to developing systems. This effort combined the measurement of tar-reforming Catalyst Deactivation kinetics and the production of syngas in a pilot-scale biomass gasification system at a single steady-state condition with mixed woods, producing a gas with an H \n 2-to-CO ratio of 2 and 13% methane. A slipstream from this process was introduced into a bench-scale 5.25 cm diameter fluidized-bed Catalyst reactor charged with an alkali-promoted Ni-based/Al \n 2O \n 3 Catalyst. Catalyst conversion tests were performed at a constant space time and five temperatures from 775 to 875°C. The initial Catalyst-reforming activity for all measured components (benzene, toluene, naphthalene, and total tars) except light hydrocarbons was 100%. The residual steady-state conversion of tar ranged from 96.6% at 875°C to 70.5% at 775°C. Residual steady-state conversions at 875°C for benzene and methane were 81% and 32%, respectively. Catalytic Deactivation models with residual activity were developed and evaluated based on experimentally measured changes in conversion efficiencies as a function of time on stream for the catalytic reforming of tars, benzene, methane, and ethane. Both first-and second-order models were evaluated for the reforming reaction and for Catalyst Deactivation. Comparison of experimental and modeling results showed that the reforming reactions were adequately modeled by either first-order or second-order global kinetic expressions. However, second-order kinetics resulted in negative activation energies for Deactivation. Activation energies were determined for first-order reforming reactions and Catalyst Deactivation. For reforming, the representative activation energies were 32 kJ/g·mol for ethane, 19 kJ/g·mol for tars, 45 kJ/g·mol for tars plus benzene, and 8-9 kJ/g·mol for benzene and toluene. For Catalyst Deactivation, representative activation energies were 146 kJ/g·mol for ethane, 121 kJ/g·mol for tars plus benzene, 74 kJ/g·mol for benzene, and 19 kJ/g·mol for total tars. Methane was also modeled by a second-order reaction, with an activation energy of 18.6 kJ/g·mol and a Catalyst Deactivation energy of 5.8 kJ/g·mol. © 2005 American Chemical Society.
Maryam Rahimi Fard - One of the best experts on this subject based on the ideXlab platform.
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Pd‐Ag/α‐Al2O3 Catalyst Deactivation in Acetylene Selective Hydrogenation Process
Chemical Engineering & Technology, 2016Co-Authors: Maryam Takht Ravanchi, Maryam Rahimi Fard, Siavash Fadaeerayeni, Saeed Sahebdelfar, Peyman BigdeliAbstract:The selective hydrogenation of acetylene to ethylene over Pd-Ag/α-Al2O3 Catalysts prepared by different impregnation/reduction methods was studied. The best catalytic performance was achieved with the sample prepared by sequential impregnation. A kinetic model based on first order in acetylene and 0.5th order in hydrogen for the main reaction and second-order independent decay law for Catalyst Deactivation was used to fit the conversion time data and to obtain quantitative assessment of Catalyst performances. Fair fits were observed from which the reaction and Deactivation rate constants were evaluated. Coke deposition amounts showed a good correlation with Catalyst Deactivation rate constants, indicating that coke formation should be the main cause of Catalyst Deactivation.
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Pd-Ag/α-Al2O3 Catalyst Deactivation in Acetylene Selective Hydrogenation Process
Chemical Engineering and Technology, 2016Co-Authors: Maryam Takht Ravanchi, Maryam Rahimi Fard, Siavash Fadaeerayeni, Saeed Sahebdelfar, Peyman BigdeliAbstract:The selective hydrogenation of acetylene to ethylene over Pd-Ag/α-Al2O3 Catalysts prepared by different impregnation/reduction methods was studied. The best catalytic performance was achieved with the sample prepared by sequential impregnation. A kinetic model based on first order in acetylene and 0.5th order in hydrogen for the main reaction and second-order independent decay law for Catalyst Deactivation was used to fit the conversion time data and to obtain quantitative assessment of Catalyst performances. Fair fits were observed from which the reaction and Deactivation rate constants were evaluated. Coke deposition amounts showed a good correlation with Catalyst Deactivation rate constants, indicating that coke formation should be the main cause of Catalyst Deactivation.