Documents disponibles écrits par cet auteur

Hydrodechlorination of chlorobenzene over silica-supported nickel phosphide catalysts / Xuguang Liu in Industrial & engineering chemistry research, Vol. 47 n°15 (Août 2008) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 47 n°15 (Août 2008) . - p. 5362–5368 Titre : Hydrodechlorination of chlorobenzene over silica-supported nickel phosphide catalysts Type de document : texte imprimé Auteurs : Xuguang Liu, Auteur ; Jixiang Chen, Auteur ; Jiyan Zhang, Auteur Année de publication : 2008 Article en page(s) : p. 5362–5368 Note générale : Bibliogr. p. 5367-5368 Langues : Anglais (eng) Mots-clés : Chlorobenzene  --  hydrodechlorination;  Nickel  phosphate  catalysts Résumé : Silica-supported Ni3P, Ni12P5, and Ni2P catalysts were prepared by the temperature-programmed reduction method from nickel phosphate precursors. A Ni/SiO2 catalyst was also prepared as a reference. The effect of the initial Ni/P molar ratio in the precursor on the catalyst structure and hydrodechlorination performance was investigated. The physicochemical properties of the catalysts were characterized by means of N2 adsorption, hydrogen temperature-programmed reduction, X-ray diffraction, X-ray photoelectron spectroscopy, ultraviolet and visible spectroscopy, hydrogen temperature-programmed desorption, and inductively coupled plasma spectroscopy. The catalyst activities in the hydrodechlorination of chlorobenzene were evaluated in a fixed-bed reactor at atmospheric pressure. The silica-supported nickel phosphides exhibited superior hydrodechlorination activities to that of supported nickel. This can be attributed to the special physicochemical properties of nickel phosphides and a great amount of spillover hydrogen species. In nickel phosphides, there is a small amount of electron transfer from Ni to P, leading to a small positive charge on Ni. This favors a weakening of the interaction between chlorine and nickel sites, as well as between adsorbed hydrogen species and nickel phosphides. The “ensemble effect” of P is also beneficial in decreasing the coverage of chlorine on nickel sites. Because of the reduced interaction between adsorbed hydrogen species and nickel phosphides, the energy barrier of the hydrogen spillover on the silica-supported nickel phosphide catalysts decreases, which accounts for the increased amount of spillover hydrogen species on the catalyst surface. Spillover hydrogen species not only promote the hydrogenolysis of the C−Cl bond, but also favor the removal of chlorine ions from the surface of the catalysts. Hydrodechlorination over the nickel phosphide catalysts is characterized by a reaction induction period that becomes longer with increasing phosphorus content in the catalyst precursor. This is related to the blocking of active sites by excess phosphorus. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie7017542 [article] Hydrodechlorination of chlorobenzene over silica-supported nickel phosphide catalysts [texte imprimé] / Xuguang Liu, Auteur ; Jixiang Chen, Auteur ; Jiyan Zhang, Auteur . - 2008 . - p. 5362–5368. Bibliogr. p. 5367-5368 Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 n°15 (Août 2008) . - p. 5362–5368 Mots-clés : Chlorobenzene  --  hydrodechlorination;  Nickel  phosphate  catalysts Résumé : Silica-supported Ni3P, Ni12P5, and Ni2P catalysts were prepared by the temperature-programmed reduction method from nickel phosphate precursors. A Ni/SiO2 catalyst was also prepared as a reference. The effect of the initial Ni/P molar ratio in the precursor on the catalyst structure and hydrodechlorination performance was investigated. The physicochemical properties of the catalysts were characterized by means of N2 adsorption, hydrogen temperature-programmed reduction, X-ray diffraction, X-ray photoelectron spectroscopy, ultraviolet and visible spectroscopy, hydrogen temperature-programmed desorption, and inductively coupled plasma spectroscopy. The catalyst activities in the hydrodechlorination of chlorobenzene were evaluated in a fixed-bed reactor at atmospheric pressure. The silica-supported nickel phosphides exhibited superior hydrodechlorination activities to that of supported nickel. This can be attributed to the special physicochemical properties of nickel phosphides and a great amount of spillover hydrogen species. In nickel phosphides, there is a small amount of electron transfer from Ni to P, leading to a small positive charge on Ni. This favors a weakening of the interaction between chlorine and nickel sites, as well as between adsorbed hydrogen species and nickel phosphides. The “ensemble effect” of P is also beneficial in decreasing the coverage of chlorine on nickel sites. Because of the reduced interaction between adsorbed hydrogen species and nickel phosphides, the energy barrier of the hydrogen spillover on the silica-supported nickel phosphide catalysts decreases, which accounts for the increased amount of spillover hydrogen species on the catalyst surface. Spillover hydrogen species not only promote the hydrogenolysis of the C−Cl bond, but also favor the removal of chlorine ions from the surface of the catalysts. Hydrodechlorination over the nickel phosphide catalysts is characterized by a reaction induction period that becomes longer with increasing phosphorus content in the catalyst precursor. This is related to the blocking of active sites by excess phosphorus. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie7017542

Influence of supports on structure and performance of nickel phosphide catalysts for hydrodechlorination of chlorobenzene / Jixiang Chen in Industrial & engineering chemistry research, Vol. 48 N° 8 (Avril 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 8 (Avril 2009) . - pp. 3812–3819 Titre : Influence of supports on structure and performance of nickel phosphide catalysts for hydrodechlorination of chlorobenzene Type de document : texte imprimé Auteurs : Jixiang Chen, Auteur ; Shaojun Zhou, Auteur ; Donghui Ci, Auteur Année de publication : 2009 Article en page(s) : pp. 3812–3819 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Phosphide  catalysts  N2  adsorption−desorption  Hydrogen  temperature-programmed  reduction  X-ray  diffraction  X-ray  photoelectron  spectroscopy Résumé : SiO2, TiO2, γ-Al2O3, and HY zeolite supported phosphide catalysts were prepared by the hydrogen temperature-programmed reduction method from phosphate precursors. The physicochemical properties of the catalysts were characterized by means of N2 adsorption−desorption, hydrogen temperature-programmed reduction, X-ray diffraction, X-ray photoelectron spectroscopy, hydrogen temperature-programmed desorption, inductively coupled plasma atomic emission spectroscopy, energy-dispersion X-ray spectroscopy, and thermal gravimetric analysis. The catalyst performance in the hydrodechlorination of chlorobenzene was evaluated in a fixed-bed reactor at atmospheric pressure. It has been found that the support property remarkably affects the formation of nickel phosphides. With the same Ni/P molar ratio (about 0.7) in the precursors, Ni2P is prepared on SiO2 and TiO2; however, Ni and Ni3P form on γ-Al2O3 and Ni and Ni12P5 form on HY. This phenomenon is attributed to some phosphorus reacting with γ-Al2O3 and HY to form AlPO4, and the phosphorus reacting with nickel is scarce. Under identical reaction conditions, the hydrodechlorination performance of the catalysts decrease in the order of SiO2-supported N2P, γ-Al2O3-supported Ni−Ni3P, TiO2-supported N2P, and HY-supported Ni−Ni12P5. The catalyst performance is closely related to the properties of active phases and hydrogen species. Nickel phosphides have better performance than metallic nickel due to the electron deficiency of nickel, and the spilt-over hydrogen species also contribute to the hydrogenolysis of C−Cl bond. The chlorobenzene conversion exceeds 99% over SiO2-supported Ni2P during 130 h at 573 K. The excellent performance is ascribed to the strong poison resistance of Ni2P to chlorine and the abundant hydrogen species. TiO2-supported N2P and HY-supported Ni−Ni12P5 have good initial activities; however, their deactivation is remarkable, especially HY-supported Ni−Ni12P5. Their deactivation is mainly owing to the carbonous deposition. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8018643 [article] Influence of supports on structure and performance of nickel phosphide catalysts for hydrodechlorination of chlorobenzene [texte imprimé] / Jixiang Chen, Auteur ; Shaojun Zhou, Auteur ; Donghui Ci, Auteur . - 2009 . - pp. 3812–3819. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 8 (Avril 2009) . - pp. 3812–3819 Mots-clés : Phosphide  catalysts  N2  adsorption−desorption  Hydrogen  temperature-programmed  reduction  X-ray  diffraction  X-ray  photoelectron  spectroscopy Résumé : SiO2, TiO2, γ-Al2O3, and HY zeolite supported phosphide catalysts were prepared by the hydrogen temperature-programmed reduction method from phosphate precursors. The physicochemical properties of the catalysts were characterized by means of N2 adsorption−desorption, hydrogen temperature-programmed reduction, X-ray diffraction, X-ray photoelectron spectroscopy, hydrogen temperature-programmed desorption, inductively coupled plasma atomic emission spectroscopy, energy-dispersion X-ray spectroscopy, and thermal gravimetric analysis. The catalyst performance in the hydrodechlorination of chlorobenzene was evaluated in a fixed-bed reactor at atmospheric pressure. It has been found that the support property remarkably affects the formation of nickel phosphides. With the same Ni/P molar ratio (about 0.7) in the precursors, Ni2P is prepared on SiO2 and TiO2; however, Ni and Ni3P form on γ-Al2O3 and Ni and Ni12P5 form on HY. This phenomenon is attributed to some phosphorus reacting with γ-Al2O3 and HY to form AlPO4, and the phosphorus reacting with nickel is scarce. Under identical reaction conditions, the hydrodechlorination performance of the catalysts decrease in the order of SiO2-supported N2P, γ-Al2O3-supported Ni−Ni3P, TiO2-supported N2P, and HY-supported Ni−Ni12P5. The catalyst performance is closely related to the properties of active phases and hydrogen species. Nickel phosphides have better performance than metallic nickel due to the electron deficiency of nickel, and the spilt-over hydrogen species also contribute to the hydrogenolysis of C−Cl bond. The chlorobenzene conversion exceeds 99% over SiO2-supported Ni2P during 130 h at 573 K. The excellent performance is ascribed to the strong poison resistance of Ni2P to chlorine and the abundant hydrogen species. TiO2-supported N2P and HY-supported Ni−Ni12P5 have good initial activities; however, their deactivation is remarkable, especially HY-supported Ni−Ni12P5. Their deactivation is mainly owing to the carbonous deposition. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8018643

Preparation, characterization, and performance of HMS-supported Ni catalysts for hydrodechlorination of chorobenzene / Jixiang Chen in Industrial & engineering chemistry research, Vol. 48 N° 8 (Avril 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 8 (Avril 2009) . - pp. 3802–3811 Titre : Preparation, characterization, and performance of HMS-supported Ni catalysts for hydrodechlorination of chorobenzene Type de document : texte imprimé Auteurs : Jixiang Chen, Auteur ; Jianjun Zhou, Auteur ; Rijie Wang, Auteur Année de publication : 2009 Article en page(s) : pp. 3802–3811 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : HMS-supported  Ni  catalysts  Hydrodechlorination  N2  adsorption  X-ray  diffraction Résumé : HMS-supported Ni catalysts were prepared by the direct synthesis and the impregnation method. In the direct synthesis, the effect of nickel content and pH value of the preparation system on the catalyst structure and hydrodechlorination performance was systematically investigated. The physicochemical properties of the catalysts were characterized by means of N2 adsorption, hydrogen temperature-programmed reduction, low- and wide-angle X-ray diffraction, hydrogen chemisorption, hydrogen temperature-programmed desorption, transmission electron microscope, and atomic absorption spectroscopy. The catalyst activity in the hydrodechlorination of chlorobenzene was evaluated in a fixed-bed reactor at atmospheric pressure. For the n%Ni(m%)-HMS samples prepared by the direct synthesis method, BET surface area, pore volume, and the pore (2∼5 nm) diameter decrease with increasing Ni content, and the mesostructures becomes worse. When the nickel content exceeds 7.0 wt%, the sample with mesostructures cannot be prepared. This is attributed to the decrease of pH value in the preparation system and the embedment of Ni2+ in the SiO2 matrix. Ni2+ ions highly disperse in the n%Ni(m%)-HMS samples and mainly exist as nickel silicate. After reduction at 450∼650 °C, the metallic nickel particles in n%Ni(m%)-HMS uniformly distribute at about 3 nm. However, for the im−4.1%Ni/HMS sample prepared by the impregnation method, the metallic nickel particles are much larger than those of n%Ni(m%)-HMS. In the hydrodechlorination of chlorobenzene, the n%Ni(m%)-HMS samples show higher activities than im−4.1%Ni/HMS, which can be attributed to the strong interaction between small metallic nickel particles and the support, a greater amount of spilt-over hydrogen, and the acidity of nickel silicate. When the nickel content exceeds 5.9 wt % and the reduction temperature is above 450 °C, there is no remarkable difference in chlorobenzene conversion for n%Ni(m%)-HMS samples. This is perhaps related to the intraparticle mass transfer limitation. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801792h [article] Preparation, characterization, and performance of HMS-supported Ni catalysts for hydrodechlorination of chorobenzene [texte imprimé] / Jixiang Chen, Auteur ; Jianjun Zhou, Auteur ; Rijie Wang, Auteur . - 2009 . - pp. 3802–3811. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 8 (Avril 2009) . - pp. 3802–3811 Mots-clés : HMS-supported  Ni  catalysts  Hydrodechlorination  N2  adsorption  X-ray  diffraction Résumé : HMS-supported Ni catalysts were prepared by the direct synthesis and the impregnation method. In the direct synthesis, the effect of nickel content and pH value of the preparation system on the catalyst structure and hydrodechlorination performance was systematically investigated. The physicochemical properties of the catalysts were characterized by means of N2 adsorption, hydrogen temperature-programmed reduction, low- and wide-angle X-ray diffraction, hydrogen chemisorption, hydrogen temperature-programmed desorption, transmission electron microscope, and atomic absorption spectroscopy. The catalyst activity in the hydrodechlorination of chlorobenzene was evaluated in a fixed-bed reactor at atmospheric pressure. For the n%Ni(m%)-HMS samples prepared by the direct synthesis method, BET surface area, pore volume, and the pore (2∼5 nm) diameter decrease with increasing Ni content, and the mesostructures becomes worse. When the nickel content exceeds 7.0 wt%, the sample with mesostructures cannot be prepared. This is attributed to the decrease of pH value in the preparation system and the embedment of Ni2+ in the SiO2 matrix. Ni2+ ions highly disperse in the n%Ni(m%)-HMS samples and mainly exist as nickel silicate. After reduction at 450∼650 °C, the metallic nickel particles in n%Ni(m%)-HMS uniformly distribute at about 3 nm. However, for the im−4.1%Ni/HMS sample prepared by the impregnation method, the metallic nickel particles are much larger than those of n%Ni(m%)-HMS. In the hydrodechlorination of chlorobenzene, the n%Ni(m%)-HMS samples show higher activities than im−4.1%Ni/HMS, which can be attributed to the strong interaction between small metallic nickel particles and the support, a greater amount of spilt-over hydrogen, and the acidity of nickel silicate. When the nickel content exceeds 5.9 wt % and the reduction temperature is above 450 °C, there is no remarkable difference in chlorobenzene conversion for n%Ni(m%)-HMS samples. This is perhaps related to the intraparticle mass transfer limitation. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801792h