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An egg-shell type Ni/Al2O3 catalyst derived from layered double hydroxides precursor for selective hydrogenation of pyrolysis gasoline

Paper ID Volume ID Publish Year Pages File Format Full-Text
40252 45848 2013 12 PDF Available
Title
An egg-shell type Ni/Al2O3 catalyst derived from layered double hydroxides precursor for selective hydrogenation of pyrolysis gasoline
Abstract

•Egg-shell type nickel catalyst (Ni/Al2O3) has been prepared from LDHs precursor.•The confinement effect in the LDHs main layer lead to smaller nickel particles.•The egg-shell catalyst exhibited enhanced activity and stability for hydrogenation.

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 Al2O3-supported nickel (Ni/Al2O3) 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 Ni2+Al3+-containing LDHs (NiAl-LDHs) precursor was in situ grown on the surface of γ-Al2O3 spheres by using a diluted ammonia solution as precipitator. Then, egg-shell Al2O3-supported nickel oxide (NiO/Al2O3) sample with NiO crystallites highly dispersed on the external edge of the Al2O3 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/Al2O3 catalyst (denoted LP-Ni/Al2O3; LP is expressed as layered precursor) fabricated by subsequent ex situ presufidation and final H2 reduction at 500 °C of the NiO/Al2O3 sample. In addition, an Ni/Al2O3 catalyst with uniform distribution of Ni in the catalyst was prepared by a conventional wet impregnation method (denoted IM-Ni/Al2O3; 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/Al2O3 catalyst was higher than that of the IM-Ni/Al2O3 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/Al2O3 catalyst derived from LDHs precursor exhibited a superior catalytic hydrogenation performance, which mainly be due to Ni metal being deposited on the Al2O3 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 N2 adsorption–desorption, X-ray photoelectron spectroscopy (XPS), and temperature programmed reduction of hydrogen (TPR)/temperature programmed desorption of hydrogen (H2-TPD) were adopted to investigate the physical–chemical properties of the two supported Ni catalysts in detail.

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Keywords
Ethylene industry; Pyrolysis gasoline; Selective hydrogenation; Egg-shell catalyst; Layered double hydroxide
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An egg-shell type Ni/Al2O3 catalyst derived from layered double hydroxides precursor for selective hydrogenation of pyrolysis gasoline
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 468, 5 November 2013, Pages 204–215
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us