Tailoring MgO-based supported Rh catalysts for purification of gas streams from phenol

K. Polychronopoulou; K. Giannakopoulos; A. M. Efstathiou

doi:10.1016/j.apcatb.2011.10.019

Tailoring MgO-based supported Rh catalysts for purification of gas streams from phenol

K. Polychronopoulou, K. Giannakopoulos, A. M. Efstathiou

Mechanical & Nuclear Engineering

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Abstract

The present work is focused on the sol-gel synthesis, characterization and catalytic performance evaluation of novel Mg-Ce-Zr-O-based mixed oxides supported Rh catalysts for the purification of H₂-rich gas streams from phenol through steam reforming in the 575-730°C range. Phenol is used as a model compound of tars, the former being one of the main constituents of tars formed during steam gasification and pyrolysis of biomass. Novel Rh catalysts (0.1wt%) supported on Mg-Ce-Zr-O-based mixed oxides modified by alkaline-earth, rare earth, and transition metal ions, having the general formula Mg-Ce-Zr-X-O (where X stands for La, Sr, Ba, Ca and Zn) were systematically studied. The physicochemical properties of the catalysts were evaluated using complementary bulk and surface characterization techniques, such as BET, XPS, in situ XRD, TEM/SAED and SEM/EDX. Transient techniques including H₂-TPR, TPD-CO₂ and TPD-NH₃ were employed in order to characterize redox behavior, surface basicity, and surface acidity of support, respectively. Among the catalysts examined, a 0.1wt% Rh/40Mg-20Ce-20Zr-20La-O was found to exhibit the highest hydrogen product yield, specific H₂ production rate (μmol/m²min), and the lowest CO/CO₂ product ratio (575-730°C), even when compared to a Ni-based commercial steam reforming of tars catalyst. At 655°C, a H₂ yield of ∼95% and a specific reaction rate of 100μmolH₂/m²min were obtained for a feed containing 0.5vol% phenol and 40vol% H₂O at a gas hourly space velocity of ∼80,000h^-1. This activity behavior is correlated with the largest concentration of basic sites and labile oxygen species (μmol/m²), and also with the largest acid/base site ratio present in the 40Mg-20Ce-20Zr-20La-O support composition. Steam was also found to be an efficient reagent for the removal of carbonaceous deposits (e.g., C_xH_y) formed on the catalyst surface during phenol steam reforming. The H/C atom compositional ratio of the carbonaceous deposits was found to depend on reaction temperature.

Original language	British English
Pages (from-to)	360-375
Number of pages	16
Journal	Applied Catalysis B: Environmental
Volume	111-112
DOIs	https://doi.org/10.1016/j.apcatb.2011.10.019
State	Published - 12 Jan 2012

Keywords

High resolution transmission electron microscopy
In situ XRD
MgO-based solid supports
Phenol steam reforming
Supported Rh catalysts
X-ray photoelectron spectroscopy

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10.1016/j.apcatb.2011.10.019

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title = "Tailoring MgO-based supported Rh catalysts for purification of gas streams from phenol",

abstract = "The present work is focused on the sol-gel synthesis, characterization and catalytic performance evaluation of novel Mg-Ce-Zr-O-based mixed oxides supported Rh catalysts for the purification of H2-rich gas streams from phenol through steam reforming in the 575-730°C range. Phenol is used as a model compound of tars, the former being one of the main constituents of tars formed during steam gasification and pyrolysis of biomass. Novel Rh catalysts (0.1wt%) supported on Mg-Ce-Zr-O-based mixed oxides modified by alkaline-earth, rare earth, and transition metal ions, having the general formula Mg-Ce-Zr-X-O (where X stands for La, Sr, Ba, Ca and Zn) were systematically studied. The physicochemical properties of the catalysts were evaluated using complementary bulk and surface characterization techniques, such as BET, XPS, in situ XRD, TEM/SAED and SEM/EDX. Transient techniques including H2-TPR, TPD-CO2 and TPD-NH3 were employed in order to characterize redox behavior, surface basicity, and surface acidity of support, respectively. Among the catalysts examined, a 0.1wt% Rh/40Mg-20Ce-20Zr-20La-O was found to exhibit the highest hydrogen product yield, specific H2 production rate (μmol/m2min), and the lowest CO/CO2 product ratio (575-730°C), even when compared to a Ni-based commercial steam reforming of tars catalyst. At 655°C, a H2 yield of ∼95% and a specific reaction rate of 100μmolH2/m2min were obtained for a feed containing 0.5vol% phenol and 40vol% H2O at a gas hourly space velocity of ∼80,000h-1. This activity behavior is correlated with the largest concentration of basic sites and labile oxygen species (μmol/m2), and also with the largest acid/base site ratio present in the 40Mg-20Ce-20Zr-20La-O support composition. Steam was also found to be an efficient reagent for the removal of carbonaceous deposits (e.g., CxHy) formed on the catalyst surface during phenol steam reforming. The H/C atom compositional ratio of the carbonaceous deposits was found to depend on reaction temperature.",

keywords = "High resolution transmission electron microscopy, In situ XRD, MgO-based solid supports, Phenol steam reforming, Supported Rh catalysts, X-ray photoelectron spectroscopy",

author = "K. Polychronopoulou and K. Giannakopoulos and Efstathiou, {A. M.}",

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doi = "10.1016/j.apcatb.2011.10.019",

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AU - Giannakopoulos, K.

AU - Efstathiou, A. M.

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Y1 - 2012/1/12

N2 - The present work is focused on the sol-gel synthesis, characterization and catalytic performance evaluation of novel Mg-Ce-Zr-O-based mixed oxides supported Rh catalysts for the purification of H2-rich gas streams from phenol through steam reforming in the 575-730°C range. Phenol is used as a model compound of tars, the former being one of the main constituents of tars formed during steam gasification and pyrolysis of biomass. Novel Rh catalysts (0.1wt%) supported on Mg-Ce-Zr-O-based mixed oxides modified by alkaline-earth, rare earth, and transition metal ions, having the general formula Mg-Ce-Zr-X-O (where X stands for La, Sr, Ba, Ca and Zn) were systematically studied. The physicochemical properties of the catalysts were evaluated using complementary bulk and surface characterization techniques, such as BET, XPS, in situ XRD, TEM/SAED and SEM/EDX. Transient techniques including H2-TPR, TPD-CO2 and TPD-NH3 were employed in order to characterize redox behavior, surface basicity, and surface acidity of support, respectively. Among the catalysts examined, a 0.1wt% Rh/40Mg-20Ce-20Zr-20La-O was found to exhibit the highest hydrogen product yield, specific H2 production rate (μmol/m2min), and the lowest CO/CO2 product ratio (575-730°C), even when compared to a Ni-based commercial steam reforming of tars catalyst. At 655°C, a H2 yield of ∼95% and a specific reaction rate of 100μmolH2/m2min were obtained for a feed containing 0.5vol% phenol and 40vol% H2O at a gas hourly space velocity of ∼80,000h-1. This activity behavior is correlated with the largest concentration of basic sites and labile oxygen species (μmol/m2), and also with the largest acid/base site ratio present in the 40Mg-20Ce-20Zr-20La-O support composition. Steam was also found to be an efficient reagent for the removal of carbonaceous deposits (e.g., CxHy) formed on the catalyst surface during phenol steam reforming. The H/C atom compositional ratio of the carbonaceous deposits was found to depend on reaction temperature.

AB - The present work is focused on the sol-gel synthesis, characterization and catalytic performance evaluation of novel Mg-Ce-Zr-O-based mixed oxides supported Rh catalysts for the purification of H2-rich gas streams from phenol through steam reforming in the 575-730°C range. Phenol is used as a model compound of tars, the former being one of the main constituents of tars formed during steam gasification and pyrolysis of biomass. Novel Rh catalysts (0.1wt%) supported on Mg-Ce-Zr-O-based mixed oxides modified by alkaline-earth, rare earth, and transition metal ions, having the general formula Mg-Ce-Zr-X-O (where X stands for La, Sr, Ba, Ca and Zn) were systematically studied. The physicochemical properties of the catalysts were evaluated using complementary bulk and surface characterization techniques, such as BET, XPS, in situ XRD, TEM/SAED and SEM/EDX. Transient techniques including H2-TPR, TPD-CO2 and TPD-NH3 were employed in order to characterize redox behavior, surface basicity, and surface acidity of support, respectively. Among the catalysts examined, a 0.1wt% Rh/40Mg-20Ce-20Zr-20La-O was found to exhibit the highest hydrogen product yield, specific H2 production rate (μmol/m2min), and the lowest CO/CO2 product ratio (575-730°C), even when compared to a Ni-based commercial steam reforming of tars catalyst. At 655°C, a H2 yield of ∼95% and a specific reaction rate of 100μmolH2/m2min were obtained for a feed containing 0.5vol% phenol and 40vol% H2O at a gas hourly space velocity of ∼80,000h-1. This activity behavior is correlated with the largest concentration of basic sites and labile oxygen species (μmol/m2), and also with the largest acid/base site ratio present in the 40Mg-20Ce-20Zr-20La-O support composition. Steam was also found to be an efficient reagent for the removal of carbonaceous deposits (e.g., CxHy) formed on the catalyst surface during phenol steam reforming. The H/C atom compositional ratio of the carbonaceous deposits was found to depend on reaction temperature.

KW - High resolution transmission electron microscopy

KW - In situ XRD

KW - MgO-based solid supports

KW - Phenol steam reforming

KW - Supported Rh catalysts

KW - X-ray photoelectron spectroscopy

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VL - 111-112

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JO - Applied Catalysis B: Environmental

JF - Applied Catalysis B: Environmental

ER -

Tailoring MgO-based supported Rh catalysts for purification of gas streams from phenol

Abstract

Keywords

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