The Experts below are selected from a list of 237 Experts worldwide ranked by ideXlab platform
Weikang Yuan - One of the best experts on this subject based on the ideXlab platform.
-
kinetics of selective hydrogenation of pyrolysis gasoline over an Egg Shell catalyst
Chemical Engineering Science, 2010Co-Authors: Zhiming Zhou, Tianying Zeng, Zhenmin Cheng, Weikang YuanAbstract:Abstract The kinetics of liquid-phase selective hydrogenation of pyrolysis gasoline over a commercial Egg-Shell catalyst was investigated in a stirred semi-batch reactor in the absence of external transport limitations. Experimental observations showed that competitive hydrogenation between monoolefins and diolefins was noticeable, and that the reaction rates of diolefins were much faster than those of monoolefins. A Langmuir–Hinshelwood-type reaction mechanism was proposed for the reaction system, and then a rigorous diffusion-reaction mathematical model was developed. For the Egg-Shell catalyst particle, the diffusion and reaction of species were described separately in two distinct regions, i.e., the outer active region, where both diffusion and reaction occurred, and the inner inertia region, where only diffusion happened. The kinetic and adsorption parameters were estimated from the diffusion-reaction model with the experimental data. The model was able to describe the experimental observations very well. The simulation results showed that significant concentration gradients existed inside the Egg-Shell catalyst, which revealed that the influence of the internal diffusion resistances on the reaction kinetics was considerable.
Fazhi Zhang - One of the best experts on this subject based on the ideXlab platform.
-
an Egg Shell type ni al2o3 catalyst derived from layered double hydroxides precursor for selective hydrogenation of pyrolysis gasoline
Applied Catalysis A-general, 2013Co-Authors: Rushi Li, Yixuan Yang, Jiali Chen, Fazhi ZhangAbstract:Abstract Egg-Shell type catalysts, in which a thin layer of catalytically active component is distributed on the outer surface of the support particle, have been theoretically and experimentally proved to be useful in processes where the reaction has a very high rate and the intraparticle diffusion becomes the limiting step. Herein we report the preparation of an Egg-Shell Al 2 O 3 -supported nickel (Ni/Al 2 O 3 ) catalyst derived from layered double hydroxides (LDHs) precursor, and its catalytic performance for selective hydrogenation of pyrolysis gasoline (PyGas), an important by-product of ethylene industry from thermal decomposition of heavier oil fractions, which was carried out in the liquid phase. Firstly, a Ni 2+ Al 3+ -containing LDHs (NiAl-LDHs) precursor was in situ grown on the surface of γ-Al 2 O 3 spheres by using a diluted ammonia solution as precipitator. Then, Egg-Shell Al 2 O 3 -supported nickel oxide (NiO/Al 2 O 3 ) sample with NiO crystallites highly dispersed on the external edge of the Al 2 O 3 support was obtained after calcination at 450 °C. The experimental study of selective hydrogenation of styrene (PyGas model 1 ) for revealing the intrinsic hydrogenation kinetics was carried out in a batch reactor at 60 °C using the Egg-Shell Ni/Al 2 O 3 catalyst (denoted LP-Ni/Al 2 O 3 ; LP is expressed as layered precursor) fabricated by subsequent ex situ presufidation and final H 2 reduction at 500 °C of the NiO/Al 2 O 3 sample. In addition, an Ni/Al 2 O 3 catalyst with uniform distribution of Ni in the catalyst was prepared by a conventional wet impregnation method (denoted IM-Ni/Al 2 O 3 ; IM is expressed as impregnation method) with the consistent Ni loading amounts and given into the consideration for comparison. The estimated effectiveness factor ( η ) of the LP-Ni/Al 2 O 3 catalyst was higher than that of the IM-Ni/Al 2 O 3 one, demonstrating the catalyst with Egg-Shell structure has a lower intraparticule mass transfer resistance. The catalytic hydrogenation activities of both Ni-based catalysts were further evaluated by selective hydrogenation of diolefins (PyGas model 2 ), along with selective hydrogenation of PyGas model 1 , in a micro-flow reactor. The Egg-Shell Ni/Al 2 O 3 catalyst derived from LDHs precursor exhibited a superior catalytic hydrogenation performance, which mainly be due to Ni metal being deposited on the Al 2 O 3 support in a much thinner outer layer, as well as a smaller average size of nickel particles with stronger interaction between the nickel species and support. Several characterization techniques including powder X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), low temperature N 2 adsorption–desorption, X-ray photoelectron spectroscopy (XPS), and temperature programmed reduction of hydrogen (TPR)/temperature programmed desorption of hydrogen (H 2 -TPD) were adopted to investigate the physical–chemical properties of the two supported Ni catalysts in detail.
Zhiming Zhou - One of the best experts on this subject based on the ideXlab platform.
-
kinetics of selective hydrogenation of pyrolysis gasoline over an Egg Shell catalyst
Chemical Engineering Science, 2010Co-Authors: Zhiming Zhou, Tianying Zeng, Zhenmin Cheng, Weikang YuanAbstract:Abstract The kinetics of liquid-phase selective hydrogenation of pyrolysis gasoline over a commercial Egg-Shell catalyst was investigated in a stirred semi-batch reactor in the absence of external transport limitations. Experimental observations showed that competitive hydrogenation between monoolefins and diolefins was noticeable, and that the reaction rates of diolefins were much faster than those of monoolefins. A Langmuir–Hinshelwood-type reaction mechanism was proposed for the reaction system, and then a rigorous diffusion-reaction mathematical model was developed. For the Egg-Shell catalyst particle, the diffusion and reaction of species were described separately in two distinct regions, i.e., the outer active region, where both diffusion and reaction occurred, and the inner inertia region, where only diffusion happened. The kinetic and adsorption parameters were estimated from the diffusion-reaction model with the experimental data. The model was able to describe the experimental observations very well. The simulation results showed that significant concentration gradients existed inside the Egg-Shell catalyst, which revealed that the influence of the internal diffusion resistances on the reaction kinetics was considerable.
Xiaobin Wang - One of the best experts on this subject based on the ideXlab platform.
-
preparation and performance of ts 1 sio2 Egg Shell catalysts
Chemical Engineering Journal, 2011Co-Authors: Xiaobin Wang, Xiongfu Zhang, Yao Wang, Jinqu Wang, Hung Lai Ho, King Lun YeungAbstract:A monolayer of zeolite nanoparticles was deposited uniformly on SiO2 beads’ surface by a new seeding method based on the combined use of organic linker and dip-coating procedure. The seeds were transformed into a well-intergrown TS-1 zeolite film and characterizations by SEM and XRD indicated that the film has a preferred (0 1 1) orientation. EDXS, XPS and UV–vis spectroscopies confirmed the successful preparation of Egg-Shell TS-1/SiO2 catalysts. Thin Shell catalysts (i.e., <11 μm) were more active for styrene oxidation. Conversion reaction rate of 8.9 mmol g−1 h−1 and turnover frequency of 28 h−1 were obtained with aromatic aldehydes (i.e., benzaldehyde and phenyl acetaldehyde) being the main products. Greater mass transfer resistance made thick Shell catalysts less efficient with lower specific conversion rate of 6.9 mmol g−1 h−1 and turnover frequency of 25 h−1. Also, the extra-framework titanium resulting from the longer synthesis led to poorer selectivity. Egg-Shell TS-1/SiO2 catalyst beads were shown to be resistant to attrition and were easier to separate and recover from reaction.
Rushi Li - One of the best experts on this subject based on the ideXlab platform.
-
an Egg Shell type ni al2o3 catalyst derived from layered double hydroxides precursor for selective hydrogenation of pyrolysis gasoline
Applied Catalysis A-general, 2013Co-Authors: Rushi Li, Yixuan Yang, Jiali Chen, Fazhi ZhangAbstract:Abstract Egg-Shell type catalysts, in which a thin layer of catalytically active component is distributed on the outer surface of the support particle, have been theoretically and experimentally proved to be useful in processes where the reaction has a very high rate and the intraparticle diffusion becomes the limiting step. Herein we report the preparation of an Egg-Shell Al 2 O 3 -supported nickel (Ni/Al 2 O 3 ) catalyst derived from layered double hydroxides (LDHs) precursor, and its catalytic performance for selective hydrogenation of pyrolysis gasoline (PyGas), an important by-product of ethylene industry from thermal decomposition of heavier oil fractions, which was carried out in the liquid phase. Firstly, a Ni 2+ Al 3+ -containing LDHs (NiAl-LDHs) precursor was in situ grown on the surface of γ-Al 2 O 3 spheres by using a diluted ammonia solution as precipitator. Then, Egg-Shell Al 2 O 3 -supported nickel oxide (NiO/Al 2 O 3 ) sample with NiO crystallites highly dispersed on the external edge of the Al 2 O 3 support was obtained after calcination at 450 °C. The experimental study of selective hydrogenation of styrene (PyGas model 1 ) for revealing the intrinsic hydrogenation kinetics was carried out in a batch reactor at 60 °C using the Egg-Shell Ni/Al 2 O 3 catalyst (denoted LP-Ni/Al 2 O 3 ; LP is expressed as layered precursor) fabricated by subsequent ex situ presufidation and final H 2 reduction at 500 °C of the NiO/Al 2 O 3 sample. In addition, an Ni/Al 2 O 3 catalyst with uniform distribution of Ni in the catalyst was prepared by a conventional wet impregnation method (denoted IM-Ni/Al 2 O 3 ; IM is expressed as impregnation method) with the consistent Ni loading amounts and given into the consideration for comparison. The estimated effectiveness factor ( η ) of the LP-Ni/Al 2 O 3 catalyst was higher than that of the IM-Ni/Al 2 O 3 one, demonstrating the catalyst with Egg-Shell structure has a lower intraparticule mass transfer resistance. The catalytic hydrogenation activities of both Ni-based catalysts were further evaluated by selective hydrogenation of diolefins (PyGas model 2 ), along with selective hydrogenation of PyGas model 1 , in a micro-flow reactor. The Egg-Shell Ni/Al 2 O 3 catalyst derived from LDHs precursor exhibited a superior catalytic hydrogenation performance, which mainly be due to Ni metal being deposited on the Al 2 O 3 support in a much thinner outer layer, as well as a smaller average size of nickel particles with stronger interaction between the nickel species and support. Several characterization techniques including powder X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), low temperature N 2 adsorption–desorption, X-ray photoelectron spectroscopy (XPS), and temperature programmed reduction of hydrogen (TPR)/temperature programmed desorption of hydrogen (H 2 -TPD) were adopted to investigate the physical–chemical properties of the two supported Ni catalysts in detail.