Selective catalytic reduction of NO with C1–C3 reductants over solvothermally prepared Ga2O3–Al2O3 catalysts: Effects of water vapor and hydrocarbon uptake

Miyahara, Yuki; Takahashi, Masaru; Masuda, Takeo; Imamura, Seiichiro; Kanai, Hiroyoshi; Iwamoto, Satoshi; Watanabe, Tsunenori; Inoue, Masashi

doi:10.1016/j.apcatb.2008.04.005

Cited by 26 publications

(17 citation statements)

References 32 publications

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“…This material was later investigated by MacDonald et al, and several possible hexagonal space groups were suggested on the basis of systematic absences in powder X-ray diffraction (XRD) patterns, and other new ternary phases also reported. More recent work by Inoue and co-workers on the Ga–Al–O system used solvothermal synthesis to prepare γ-Ga 2– x Al x O 3 defect spinels. − These mixed-metal γ-Ga 2– x Al x O 3 spinels have been explored for some catalysis applications, including their use in the selective catalytic reduction (SCR) of NO by methane, ,− dehydrogenation of propane, , and dimethyl ether steam re-forming . γ-Ga 2 O 3 supported on γ-Al 2 O 3 has been applied for photocatalysis …”

Section: Introductionmentioning

confidence: 99%

Synthesis and Polymorphism of Mixed Aluminum–Gallium Oxides

et al. 2020

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The synthesis of a new solid solution of the oxyhydroxide Ga 5−x Al x O 7 (OH) is investigated via solvothermal reaction between gallium acetylacetonate and aluminum isopropoxide in 1,4-butanediol at 240 °C. A limited compositional range of 0 ≤ x ≤ 1.5 is produced, with the hexagonal unit cell parameters refined from powder X-ray diffraction (XRD) showing a linear contraction in unit cell volume with an increase in Al content. Solid-state 27 Al and 71 Ga nuclear magnetic resonance (NMR) spectroscopies show a strong preference for Ga to occupy the tetrahedral sites and Al to occupy the octahedral sites. Using isopropanol as the solvent, γ-Ga 2−x Al x O 3 defect spinel solid solutions with x ≤ 1.8 can be prepared at 240 °C in 24 h. These materials are nanocrystalline, as evidenced by their broad diffraction profiles; however, the refined cubic lattice parameter shows a linear relationship with the Ga:Al content, and solid-state NMR spectroscopy again shows a preference for Al to occupy the octahedral sites. Thermal decomposition of Ga 5−x Al x O 7 (OH) occurs via poorly ordered materials that resemble ε-Ga 2−x Al x O 3 and κ-Ga 2−x Al x O 3 , but γ-Ga 2−x Al x O 3 transforms above 750 °C to monoclinic β-Ga 2−x Al x O 3 for 0 ≤ x ≤ 1.3 and to hexagonal α-Ga 2−x Al x O 3 for x = 1.8, with intermediate compositions of 1.3 < x < 1.8 giving mixtures of the αand β-polymorphs. Solid-state NMR spectroscopy shows only the expected octahedral Al for α-Ga 2−x Al x O 3 , and for β-Ga 2−x Al x O 3 , the ∼1:2 tetrahedral:octahedral Al ratio is in good agreement with the results of Rietveld analysis of the average structures against powder XRD data. Relative energies calculated by periodic density functional theory confirm that there is an ∼5.2 kJ mol −1 penalty for tetrahedral rather than octahedral Al in Ga 5−x Al x O 7 (OH), whereas this penalty is much smaller (∼2.0 kJ mol −1 ) for β-Ga 2−x Al x O 3 , in good qualitative agreement with the experimental NMR spectra.

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Section: Introductionmentioning

confidence: 99%

Synthesis and Polymorphism of Mixed Aluminum–Gallium Oxides

et al. 2020

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“…Al) = 0.50) is the largest (7.2 nm). In the previous paper, we showed that the catalyst with small crystallite size is easily affected by water formed by CH 4 -SCR [9,13], and therefore large crystallite size of this catalyst is one of the reasons for the relatively high activity of this catalyst under the wet conditions.…”

Section: Catalytic Performance Of the C-ga 2 O 3 -Al 2 O 3 Solidmentioning

confidence: 98%

“…The Ga 2 O 3 -Al 2 O 3 solid solutions prepared from the AACH-AGCH solid solutions had large mode pore-diameters. Since water adsorbed on the surface of micropores cannot be easily removed inhibiting the reaction [13], large pore diameter of the catalyst can moderate the inhibitory effect of water. Therefore, the Ga 2 O 3 -Al 2 O 3 catalyst with Ga/(Ga ?…”

Section: Catalytic Performance Of the C-ga 2 O 3 -Al 2 O 3 Solidmentioning

confidence: 99%

Synthesis of Ga2O3–Al2O3 Catalysts by a Coprecipitation Method for CH4-SCR of NO

et al. 2009

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Synthesis of the c-Ga 2 O 3 -Al 2 O 3 solid solutions by the coprecipitation method was examined. Precipitates were obtained by adding at once an aqueous solution of aluminum and gallium nitrates to an excess base solution (reverse strike precipitation). The precipitates were calcined at 700°C to give c-Ga 2 O 3 -Al 2 O 3 solid solutions. When an ammonium carbonate solution was used as the precipitant, ammonium aluminum carbonate hydroxide (ammonium dawsonite, AACH)-ammonium gallium carbonate hydroxide (AGCH) solid solutions were obtained. Calcination of the AACH-AGCH solid solutions at 700°C gave the c-Ga 2 O 3 -Al 2 O 3 solid solutions which exhibited high activity for selective catalytic reduction of NO with methane.

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“…Haneda et al reported that Ga 2 O 3 -Al 2 O 3 prepared by a sol-gel method has high performance for the SCR of NO x with propene [12]. Previously, we reported that for CH 4 -SCR of NO, the c-Ga 2 O 3 -Al 2 O 3 solid solution catalysts prepared by the solvothermal method showed higher performance than the catalysts prepared by impregnation of the Ga component on c-alumina [13][14][15]. Diethylenetriamine was found to be the best solvent for the solvothermal synthesis of the c-Ga 2 O 3 -Al 2 O 3 catalyst having high performance under both wet and dry conditions [13].…”

Section: Introductionmentioning

confidence: 93%

Enhancement of the Activities of γ-Ga2O3–Al2O3 Catalysts for Methane-SCR of NO by Treatment with NH3

et al. 2011

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The precursor particles for c-Ga 2 O 3 -Al 2 O 3 solid solutions were prepared by the coprecipitation method from aqueous solutions of Ga(NO 3 ) 3 and Al(NO 3 ) 3 with (NH 4 ) 2 CO 3 as a precipitant. The c-Ga 2 O 3 -Al 2 O 3 solid solutions were obtained by calcination of the precursor at 700°C. In this paper, the performance of the catalysts treated with NH 3 was investigated for the selective catalytic reduction (SCR) of NO with methane as a reducing agent, and it was found that c-Ga 2 O 3 -Al 2 O 3 catalysts treated with NH 3 and subsequently annealed in air showed higher activities than the c-Ga 2 O 3 -Al 2 O 3 catalysts without NH 3 treatment. NH 3 treatment of the catalyst caused partial rearrangement of Ga 3? and Al 3? ions and increased the population of tetrahedral Ga 3? ions in the defective spinel structure.

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Selective catalytic reduction of NO with C1–C3 reductants over solvothermally prepared Ga2O3–Al2O3 catalysts: Effects of water vapor and hydrocarbon uptake

Cited by 26 publications

References 32 publications

Synthesis and Polymorphism of Mixed Aluminum–Gallium Oxides

Synthesis and Polymorphism of Mixed Aluminum–Gallium Oxides

Synthesis of Ga2O3–Al2O3 Catalysts by a Coprecipitation Method for CH4-SCR of NO

Enhancement of the Activities of γ-Ga2O3–Al2O3 Catalysts for Methane-SCR of NO by Treatment with NH3

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