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Chin Kui Cheng - One of the best experts on this subject based on the ideXlab platform.
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Synthesis and characterization of a La-Ni/α-Al2O3 catalyst and its use in pyrolysis of glycerol to syngas
Renewable Energy, 2019Co-Authors: Mohd Nasir Nor Shahirah, Jolius Gimbun, Su Shiung Lam, Chin Kui ChengAbstract:Abstract The current paper reports on the kinetics of syngas production from glycerol catalytic pyrolysis over Ni/α-Al2O3 catalyst promoted by lanthanum. The 3 wt%La-20 wt%Ni/77 wt%α-Al2O3 catalyst was synthesized and its physiochemical properties were characterized. The BET specific surface area was 2.20 m2.g−1, which was 0.11 m2.g−1 larger than the unpromoted Ni/α-Al2O3 catalyst. Significantly, the BET results were supported by the FESEM image which showed that the promoted catalyst has smaller particle size compared to the unpromoted catalyst. The NH3 and CO2-TPD analyses indicates that the catalyst has net acidity with acid:base ratio of 1.12. Catalytic pyrolysis was performed in a 10 mm-ID stainless steel fixed bed reactor with reaction temperatures set at 973, 1023 and 1073 K, employing a weight-hourly-space-velocity (WHSV) of 4.5 × 104 ml g−1 h−1. From reaction studies, the highest glycerol conversion (XG) value was 36.96% at 1073 K. The resulting syngas has H2:CO ratios always lower than 2.0. Subsequently, mechanistic studies indicate that the catalytic glycerol pyrolysis occurred on single catalytic site via Associative Adsorption, with molecular surface reaction as the rate-determining step.
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Renewable syngas production from thermal cracking of glycerol over praseodymium-promoted Ni/Al2O3 catalyst
Applied Thermal Engineering, 2017Co-Authors: Mohd Nasir Nor Shahirah, Jolius Gimbun, Su Shiung Lam, Bamidele Victor Ayodele, Chin Kui ChengAbstract:Abstract In this study, the kinetics of glycerol pyrolysis over a 3wt%Pr-20wt%Ni/77wt%α-Al 2 O 3 catalyst was investigated. The catalyst was synthesized via wet-impregnation method and was characterized using temperature-programmed calcination (TPC), temperature-programmed reduction (TPR), N 2 -physisorption, FESEM imaging, X-ray diffraction and CO 2 -/NH 3 -temperature-programmed desorption (TPD). The catalytic activity of the as-synthesized 3 wt% Pr-Ni/α-Al 2 O 3 catalyst was evaluated in a stainless steel fixed bed reactor at temperatures that ranged from 973 K to 1073 K and a weight-hourly-space-velocity (WHSV) of 4.5 × 10 4 ml g −1 h −1 under the atmospheric condition. The main gaseous products from catalytic glycerol pyrolysis were H 2 , CO, CO 2 and CH 4 (descending ranking) with the highest H 2 formation rate and H 2 yield of 0.02593 mol g cat −1 s −1 and 29.04%, respectively. The analysis of the kinetic data obtained from the glycerol pyrolysis showed activation energy of 37.36 kJ mol −1 . Based on the mechanistic modeling, it can be deduced that the rate determining step of the glycerol pyrolysis was via a single site Associative Adsorption with molecular surface reaction as the rate-determining step.
Stephen C. Parker - One of the best experts on this subject based on the ideXlab platform.
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atomistic simulation of the dissociative Adsorption of water on calcite surfaces
Journal of Physical Chemistry B, 2003Co-Authors: Sebastien Kerisit, Stephen C. Parker, J H HardingAbstract:Atomistic simulation methods have been used to model the interaction of water with the {1014} calcite surface and the energetics for the removal of carbonate groups in the presence of water. Electronic structure calculations show that Associative Adsorption of water is the energetically favored mode of Adsorption on the {1014} surface, that water is strongly bound to the surface, and that the atom-based simulations reproduce the energetics of Adsorption. The use of atom-based molecular dynamics techniques on the calcite−water interface found that water loses its hydrogen-bond network when adsorbing on the surface and that it causes an oscillation of water density in the vicinity of the surface. Finally, we considered a possible reaction of the surface with water that would account for the presence of OH groups as observed experimentally on surfaces and would also constitute an initial step in the dissolution process. Our calculations suggest that carbonate groups at some step edges and low-index surface...
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Density functional theory calculations of Adsorption of water at calcium oxide and calcium fluoride surfaces
Surface Science, 2000Co-Authors: N. H. De Leeuw, Stephen C. Parker, John A. Purton, Graeme W. Watson, Georg KresseAbstract:Abstract Electronic structure calculations using the density functional theory (DFT) within the generalized-gradient approximation and ultra-soft pseudopotentials have been used to investigate the Adsorption of water on the main cleavage planes of CaO and CaF2. The calculated structural parameters are found to be in good agreement with experiment. The unhydrated surfaces show negligible ionic relaxation from bulk termination due to the minimal distortion of the electron density in the surface layer. Electron density plots show both crystals to be strongly ionic. We found on both mineral surfaces that Associative Adsorption of water is energetically preferred. Water molecules which were initially dissociatively adsorbed, recombined to form Associatively adsorbed species. The water molecules are adsorbed by their oxygen ion to surface calcium ions, but electron density plots show strong interactions between surface anions and hydrogen atoms. The calculated hydration energies of approximately 70 kJ mol−1 on the CaO {100} surface and 41–53 kJ mol−1 on the CaF2 {111} surface indicate physisorption on both surfaces.
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Modeling the Surface Structure and Reactivity of Pyrite: Introducing a Potential Model for FeS2
The Journal of Physical Chemistry B, 2000Co-Authors: N. H. De Leeuw, Stephen C. Parker, H. M. Sithole, Phuti E. NgoepeAbstract:Atomistic simulation techniques are used to investigate the surface structure, stability and reactivity of pyrite. We introduce a potential model for FeS2 which reproduces experimental structural parameters, elastic constants and hydration energies of pyrite. We modeled the {100}, {110}, and {111} surfaces of pyrite and calculated the {100} surface to be the most stable and to show little surface relaxation, in agreement with experiment. The surfaces were hydrated by Associative Adsorption of water molecules which stabilized all three surfaces, especially the unstable {111} surface. The calculated Adsorption energy of −47 kJ mol-1 for water on the {100} surface agrees well with an Adsorption energy of −42 kJ mol-1, determined for the stoichiometric (100) surface by temperature-programmed desorption.1 Adsorption of water molecules at surface sites of lower coordination (four- or three- coordinated) showed increased reactivity of these sites. We calculated an increase in Adsorption energy of 50−60 kJ mol-1 ...
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Modeling the Surface Structure and Stability of α-Quartz
The Journal of Physical Chemistry B, 1999Co-Authors: Nora H. De Leeuw, And F. Manon Higgins, Stephen C. ParkerAbstract:Atomistic simulation techniques were employed to model the {0001}, {1010}, {1011}, and {1011} surfaces of α-quartz. The effect of Associative and dissociative Adsorption of water onto the surface structure is studied, and it is found that Associative Adsorption of water onto the {1011} surface induces the formation of Si−O−Si bridges, similar to those found on the very stable unhydrated {0001} surface. Dissociative Adsorption of water is energetically favorable on all four surfaces, and hydration energies agree with experiment. Surface H+ ions were replaced by Na+ ions in two consecutive steps. Replacing only half the surface H+ ions by Na+ ions is energetically favorable, but when all H+ ions are replaced, the surface energies and hence stabilities of the four surfaces diverge widely, which has implications for the crystal morphology. On the {1011} surface Na−O−Na bridges are formed, which has a stabilizing effect.
Georges Calas - One of the best experts on this subject based on the ideXlab platform.
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First principles study of water Adsorption on the (100) surface of zircon: Implications for zircon dissolution
American Mineralogist, 2001Co-Authors: Etienne Balan, Francesco Mauri, Jean-pierre Muller, Georges CalasAbstract:We have studied the interaction of aqueous species with the (100) face of zircon using first-principles quantum mechanical calculations. Adsorption energy of molecular water on the Zr Lewis site is 1.27 eV per molecule, whereas the energy of dissociative Adsorption is only 0.84 eV per molecule. Thus, the non-dissociative Adsorption of water is strongly preferred with respect to the dissociative Adsorption on the (100) face of zircon. Such behavior, which is related to the weak ability of the surface structure to relax, is changed by a 5% increase of the surface cell parameters. From our theoretical results, we propose that the exceptional resistance of zircon to dissolution may be related to the strong acidity of the Zr-O-Si bridging O atoms, which promotes the Associative Adsorption of water on the (100) surface of zircon.
Jolius Gimbun - One of the best experts on this subject based on the ideXlab platform.
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Synthesis and characterization of a La-Ni/α-Al2O3 catalyst and its use in pyrolysis of glycerol to syngas
Renewable Energy, 2019Co-Authors: Mohd Nasir Nor Shahirah, Jolius Gimbun, Su Shiung Lam, Chin Kui ChengAbstract:Abstract The current paper reports on the kinetics of syngas production from glycerol catalytic pyrolysis over Ni/α-Al2O3 catalyst promoted by lanthanum. The 3 wt%La-20 wt%Ni/77 wt%α-Al2O3 catalyst was synthesized and its physiochemical properties were characterized. The BET specific surface area was 2.20 m2.g−1, which was 0.11 m2.g−1 larger than the unpromoted Ni/α-Al2O3 catalyst. Significantly, the BET results were supported by the FESEM image which showed that the promoted catalyst has smaller particle size compared to the unpromoted catalyst. The NH3 and CO2-TPD analyses indicates that the catalyst has net acidity with acid:base ratio of 1.12. Catalytic pyrolysis was performed in a 10 mm-ID stainless steel fixed bed reactor with reaction temperatures set at 973, 1023 and 1073 K, employing a weight-hourly-space-velocity (WHSV) of 4.5 × 104 ml g−1 h−1. From reaction studies, the highest glycerol conversion (XG) value was 36.96% at 1073 K. The resulting syngas has H2:CO ratios always lower than 2.0. Subsequently, mechanistic studies indicate that the catalytic glycerol pyrolysis occurred on single catalytic site via Associative Adsorption, with molecular surface reaction as the rate-determining step.
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Synthesis and characterization of a La Ni/α-Al2O3catalyst and its use in pyrolysis of glycerol to syngas
'Elsevier BV', 2019Co-Authors: Nor Shahirah, Mohd Nasir, Jolius Gimbun, Lam, Su Shiung, Ng, Yun Hau, Cheng C. K.Abstract:The current paper reports on the kinetics of syngas production from glycerolcatalytic pyrolysis over Ni/α-Al2O3 catalyst promoted by lanthanum. The 3 wt%La-20 wt%Ni/77 wt%α-Al2O3 catalyst was synthesized and its physiochemical properties were characterized. The BET specific surface area was 2.20 m2.g−1, which was 0.11 m2.g−1 larger than the unpromoted Ni/α-Al2O3 catalyst. Significantly, the BET results were supported by the FESEM image which showed that the promoted catalyst has smaller particle size compared to the unpromoted catalyst. The NH3 and CO2-TPD analyses indicates that the catalyst has net acidity with acid:base ratio of 1.12. Catalytic pyrolysis was performed in a 10 mm-ID stainless steel fixed bed reactor with reaction temperatures set at 973, 1023 and 1073 K, employing a weight-hourly-space-velocity (WHSV) of 4.5 × 104 ml g−1 h−1. From reaction studies, the highest glycerol conversion (XG) value was 36.96% at 1073 K. The resulting syngas has H2:CO ratios always lower than 2.0. Subsequently, mechanistic studies indicate that the catalytic glycerol pyrolysis occurred on single catalytic site via Associative Adsorption, with molecular surface reaction as the rate-determining step
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Renewable syngas production from thermal cracking of glycerol over praseodymium-promoted Ni/Al2O3 catalyst
Applied Thermal Engineering, 2017Co-Authors: Mohd Nasir Nor Shahirah, Jolius Gimbun, Su Shiung Lam, Bamidele Victor Ayodele, Chin Kui ChengAbstract:Abstract In this study, the kinetics of glycerol pyrolysis over a 3wt%Pr-20wt%Ni/77wt%α-Al 2 O 3 catalyst was investigated. The catalyst was synthesized via wet-impregnation method and was characterized using temperature-programmed calcination (TPC), temperature-programmed reduction (TPR), N 2 -physisorption, FESEM imaging, X-ray diffraction and CO 2 -/NH 3 -temperature-programmed desorption (TPD). The catalytic activity of the as-synthesized 3 wt% Pr-Ni/α-Al 2 O 3 catalyst was evaluated in a stainless steel fixed bed reactor at temperatures that ranged from 973 K to 1073 K and a weight-hourly-space-velocity (WHSV) of 4.5 × 10 4 ml g −1 h −1 under the atmospheric condition. The main gaseous products from catalytic glycerol pyrolysis were H 2 , CO, CO 2 and CH 4 (descending ranking) with the highest H 2 formation rate and H 2 yield of 0.02593 mol g cat −1 s −1 and 29.04%, respectively. The analysis of the kinetic data obtained from the glycerol pyrolysis showed activation energy of 37.36 kJ mol −1 . Based on the mechanistic modeling, it can be deduced that the rate determining step of the glycerol pyrolysis was via a single site Associative Adsorption with molecular surface reaction as the rate-determining step.
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A Study on the Kinetics of Syngas Production from Glycerol over Alumina-Supported Samarium-Nickel Catalyst
'Elsevier BV', 2016Co-Authors: Nor Shahirah, Mohd Nasir, Jolius Gimbun, Ng, Yun Hau, Sureena Abdullah, Cheng C. K.Abstract:The current paper reports on the kinetics of syngas production from glycerol pyrolysis over the alumina-supported nickel catalyst that was promoted with samarium, a rare earth element. The catalysts were synthesized via wet-impregnation method and its physicochemical properties were subsequently characterized. Reaction studies were performed in a 10 mm-ID stainless steel fixed bed reactor with reaction temperatures maintained at 973, 1023 and 1073 K, respectively, employing weight-hourly-space-velocity of 4.5�104 ml g-�1 h-�1. The textural property examination showed that BET specific surface area was 2.09 m2 g-�1 for the unpromoted catalyst while the samarium promoted catalyst has 2.68 m2 g-�1. Interestingly, the results were supported by the FESEM images which showed that the promoted catalyst has smaller particle size compared to the unpromoted catalyst. Furthermore, the NH3- and CO2-TPD analyses proved that the strong and weak acid-basic sites were present. During glycerol pyrolysis, the syngas was produced directly from the glycerol decomposition. This has created H2:CO ratios that were always lower than 2.0, which is suitable for Fischer-Tropsch synthesis. The activation energy based on power law modeling for the unpromoted catalyst was 35.8 kJ mol-�1 and 23.4 kJ mol-�1 for Sm-promoted catalyst with reaction order 1.20 and 1.10, respectively. Experimental data were also fitted to the LangmuireHinshelwood model. Upon subjected to both statistical and thermodynamics consistency criteria, it can be conclusively proved that single-site mechanisms with Associative Adsorption of glycerol best describe the glycerol pyrolysis over both unpromoted and Sm promoted catalyst in the current work, with regression coefficient values of more than 0.9
Mohd Nasir Nor Shahirah - One of the best experts on this subject based on the ideXlab platform.
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Synthesis and characterization of a La-Ni/α-Al2O3 catalyst and its use in pyrolysis of glycerol to syngas
Renewable Energy, 2019Co-Authors: Mohd Nasir Nor Shahirah, Jolius Gimbun, Su Shiung Lam, Chin Kui ChengAbstract:Abstract The current paper reports on the kinetics of syngas production from glycerol catalytic pyrolysis over Ni/α-Al2O3 catalyst promoted by lanthanum. The 3 wt%La-20 wt%Ni/77 wt%α-Al2O3 catalyst was synthesized and its physiochemical properties were characterized. The BET specific surface area was 2.20 m2.g−1, which was 0.11 m2.g−1 larger than the unpromoted Ni/α-Al2O3 catalyst. Significantly, the BET results were supported by the FESEM image which showed that the promoted catalyst has smaller particle size compared to the unpromoted catalyst. The NH3 and CO2-TPD analyses indicates that the catalyst has net acidity with acid:base ratio of 1.12. Catalytic pyrolysis was performed in a 10 mm-ID stainless steel fixed bed reactor with reaction temperatures set at 973, 1023 and 1073 K, employing a weight-hourly-space-velocity (WHSV) of 4.5 × 104 ml g−1 h−1. From reaction studies, the highest glycerol conversion (XG) value was 36.96% at 1073 K. The resulting syngas has H2:CO ratios always lower than 2.0. Subsequently, mechanistic studies indicate that the catalytic glycerol pyrolysis occurred on single catalytic site via Associative Adsorption, with molecular surface reaction as the rate-determining step.
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Renewable syngas production from thermal cracking of glycerol over praseodymium-promoted Ni/Al2O3 catalyst
Applied Thermal Engineering, 2017Co-Authors: Mohd Nasir Nor Shahirah, Jolius Gimbun, Su Shiung Lam, Bamidele Victor Ayodele, Chin Kui ChengAbstract:Abstract In this study, the kinetics of glycerol pyrolysis over a 3wt%Pr-20wt%Ni/77wt%α-Al 2 O 3 catalyst was investigated. The catalyst was synthesized via wet-impregnation method and was characterized using temperature-programmed calcination (TPC), temperature-programmed reduction (TPR), N 2 -physisorption, FESEM imaging, X-ray diffraction and CO 2 -/NH 3 -temperature-programmed desorption (TPD). The catalytic activity of the as-synthesized 3 wt% Pr-Ni/α-Al 2 O 3 catalyst was evaluated in a stainless steel fixed bed reactor at temperatures that ranged from 973 K to 1073 K and a weight-hourly-space-velocity (WHSV) of 4.5 × 10 4 ml g −1 h −1 under the atmospheric condition. The main gaseous products from catalytic glycerol pyrolysis were H 2 , CO, CO 2 and CH 4 (descending ranking) with the highest H 2 formation rate and H 2 yield of 0.02593 mol g cat −1 s −1 and 29.04%, respectively. The analysis of the kinetic data obtained from the glycerol pyrolysis showed activation energy of 37.36 kJ mol −1 . Based on the mechanistic modeling, it can be deduced that the rate determining step of the glycerol pyrolysis was via a single site Associative Adsorption with molecular surface reaction as the rate-determining step.
