Surface and structural characterization of CexZr1-xO2 CEZIRENCAT mixed oxides as potential three-way catalyst promoters

Colón, G.; Pijolat, Michèle; Valdivieso, Françoise; Vidal, Hilario; Kašpar, Jan; Finocchio, Elisabetta; Daturi, Marco; Binet, Claude; Lavalley, Jean‐Claude; Baker, Richard T.; Bernal, S.

doi:10.1039/a807680d

Cited by 199 publications

(149 citation statements)

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“…The slight shift to the right of the main (111) peak indicates a decrease of the lattice parameter due to Zr incorporation. The shift provides evidence of the formation of a solid solution that has been associated with superior catalytic properties by Colon et al (1998). Formation of a separate ZrO 2 phase is thought to be undesirable for a desulfurization sorbent.…”

Section: Xrd and Tem Characterizationmentioning

confidence: 99%

“…Colon et al (1998) state that the addition of ZrO 2 enhances the oxygen mobility within the crystal and improves the catalyst thermal stability at 1000 o C. Zamar et al (1995) Hori et al (1998) report an increase in reversibly stored oxygen by a factor of 1.7-2.5 for phase separated CeO 2 -ZrO 2 compared to CeO 2 alone, and by a factor 0f 3 to 5 for solid solutions of CeO 2 -ZrO 2 . The optimum Zr concentration was 25 mol%, but performance was relatively insensitive to Zr loading between 15 mol% and 50 mol%.…”

Section: Ceria-zirconia Catalyst Researchmentioning

confidence: 99%

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High Efficiency Desulfurization of Synthesis Gas

Yi¹,

Mukherjee²,

Podlaha³

et al. 2004

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Mixed metal oxides containing ceria and zirconia have been studied as high temperature desulfurization sorbents with the objective of achieving the DOE Vision 21 target of 1 ppmv or less H 2 S in the product gas. The research was justified by recent results in this laboratory that showed that reduced CeO 2 , designated CeO n (1.5 < n < 2.0), is capable of achieving the 1 ppmv target in highly reducing gas atmospheres. The addition of ZrO 2 has improved the performance of oxidation catalysts and three-way automotive catalysts containing CeO 2 , and was postulated to have similar beneficial effects on CeO 2 desulfurization sorbents.An electrochemical method for synthesizing CeO 2 -ZrO 2 mixtures was developed and the products were characterized by XRD and TEM during year 01. Nanocrystalline particles having a diameter of about 5 nm and containing from approximately 10 mol% to 80 mol% ZrO 2 were prepared. XRD analysis showed the product to be a solid solution at low ZrO 2 contents with a separate ZrO 2 phase emerging at higher ZrO 2 levels. Unfortunately, the quantity of CeO 2 -ZrO 2 that could be prepared electrochemically was too small to permit desulfurization testing.Also during year 01 a laboratory-scale fixed-bed reactor was constructed for desulfurization testing. All components of the reactor and analytical systems that were exposed to low concentrations of H 2 S were constructed of quartz, Teflon, or silcosteel. Reactor product gas composition as a function of time was determined using a Varian 3800 gas chromatograph equipped with a pulsed flame photometric detector (PFPD) for measuring low H 2 S concentrations from approximately 0.1 to 10 ppmv, and a thermal conductivity detector (TCD) for higher concentrations of H 2 S.Larger quantities of CeO 2 -ZrO 2 mixtures from other sources, including mixtures prepared in this laboratory using a coprecipitation procedure, were obtained. Much of the work during year 02 consisted of characterization and desulfurization testing of materials obtained from commercial sources. Most of the commercial CeO 2 and CeO 2 -ZrO 2 materials were capable of reducing H 2 S concentration from 5000 ppmv in highly reducing feed gas to less than 1 ppmv in the product gas. However, to properly evaluate the effect of ZrO 2 addition on desulfurization capability, the physical properties of the sorbent must be similar. That is, a CeO 2 -ZrO 2 mixture from source A would not necessarily be superior to pure CeO 2 from source B if the properties of the pure CeO 2 were superior. Therefore, research during year 03 concentrated on CeO 2 and CeO 2 -ZrO 2 mixtures prepared in this laboratory using a coprecipitation procedure. The structural properties of these sorbents were similar and the effect of ZrO 2 addition could better be separated from the structural effects.X-ray diffraction tests of the sorbents prepared in house confirmed the formation of a solid solution of ZrO 2 in CeO 2 . Crystallite sizes ranged from 12.7 to 18.8 nm and surface areas from 75 to 85 m 2 /g. Reduction tests us...

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Section: Xrd and Tem Characterizationmentioning

confidence: 99%

Section: Ceria-zirconia Catalyst Researchmentioning

confidence: 99%

High Efficiency Desulfurization of Synthesis Gas

Yi¹,

Mukherjee²,

Podlaha³

et al. 2004

View full text Add to dashboard Cite

show abstract

“…Even without reduction, the solid solutions appear to evolve with high temperature aging. For example it has been reported that partial demixing of the solution occurs across the composition range upon aging at 1473 K and that new phases of approximate composition Ce 0.8 Zr 0.2 O 2 and Ce 0.12 Zr 0.88 O 2 form, although surface enrichment of neither of the elements is observed [58].…”

Section: Ceria and Mixed Metal Cerium Oxidesmentioning

confidence: 99%

Summary report : direct approaches for recycling carbon dioxide into synthetic fuel.

Allendorf

Ambrosini²,

Diver³

et al. 2009

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“…The slight shift to the right of the main (111) peak indicates a decrease of the lattice parameter due to Zr incorporation. The shift provides evidence of the formation of a solid solution, that has been associated with superior catalytic properties Colon et al (1998). Formation of a separate ZrO 2 phase is undesirable from a catalytic perspective.…”

Section: Xrd and Tem Characterizationmentioning

confidence: 99%

High Efficiency Desulfurization of Synthesis Gas

Mukherjee¹,

Yi²,

Podlaha³

et al. 2001

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Mixed metal oxides containing CeO 2 and ZrO 2 are being studied as high temperature desulfurization sorbents capable of achieving the DOE Vision 21 target of 1 ppmv of less H 2 S. The research is justified by recent results in this laboratory that showed that reduced CeO 2 , designated CeO n (1.5 < n < 2.0), is capable of achieving the 1 ppmv target in highly reducing gas atmospheres. The addition of ZrO 2 has improved the performance of oxidation catalysts and three-way automotive catalysts containing CeO 2 , and should have similar beneficial effects on CeO 2 desulfurization sorbents.An electrochemical method for synthesizing CeO 2 -ZrO 2 has been developed and the products have been characterized by XRD and TEM during year 01. Nanocrystalline particles having a diameter of about 5 nm and containing from approximately 10 mol% to 80 mol% ZrO 2 have been prepared. XRD showed the product to be a solid solution at low ZrO 2 contents with a separate ZrO 2 phase emerging at higher ZrO 2 levels. Phase separation did not occur when the solid solutions were heat treated at 700 o C.A flow reactor system constructed of quartz and teflon has been constructed, and a gas chromatograph equipped with a pulsed flame photometric detector (PFPD) suitable for measuring sub-ppmv levels of H2S has been purchased with LSU matching funds. Preliminary desulfurization tests using commercial CeO 2 and CeO 2 -ZrO 2 in highly reducing gas compositions has confirmed that CeO 2 -ZrO 2 is more effective than CeO 2 in removing H 2 S. At 700 o C the product H 2 S concentration using CeO 2 -ZrO 2 sorbent was near the 0.1 ppmv PFPD detection limit during the prebreakthrough period.ii EXECUTIVE SUMMARYThe recently released DOE Vision 21 program requires much more stringent control of H 2 S concentration in coal-derived synthesis gas. Previous target levels of about 20 ppmv H 2 S suitable for electric power generation using an integrated gasification combined cycle process (IGCC) have been replaced by H 2 S targets of 1 ppmv or less required for fuel cell and other catalytic processes.Zinc-based sorbents developed for IGCC applications are not capable of achieving the Vision 21 target at high temperatures. Reduced cerium oxide, CeO n (1.5 < n < 2.0) has recently been shown to be capable of reducing H 2 S to less than 1ppmv at temperatures near 700 o C, but only in gas atmospheres having considerable greater reducing power than typical coal-derived gases. Related research in oxidation catalysis and three-way automotive catalysis has shown that performance has been improved by the addition of ZrO 2 to the CeO 2 . The reasons given for the improved performance, including increased oxygen exchange capacity, should also result in improved desulfurization performance.This research project consists of two major activities -the electrochemical synthesis and characterization of CeO 2 -ZrO 2 materials, and high temperature desulfurization tests using CeO 2 -ZrO 2 sorbents. Nanocrystalline powders of approximately 5 nm grain diameter and containin...

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Surface and structural characterization of CexZr1-xO2 CEZIRENCAT mixed oxides as potential three-way catalyst promoters

Cited by 199 publications

References 20 publications

High Efficiency Desulfurization of Synthesis Gas

High Efficiency Desulfurization of Synthesis Gas

Summary report : direct approaches for recycling carbon dioxide into synthetic fuel.

High Efficiency Desulfurization of Synthesis Gas

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