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Direct reduction of sulfur dioxide t...

Zhu, Tianli.

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Direct reduction of sulfur dioxide to elemental sulfur by methane and partial oxidation of methane to syngas on ceria-based catalysts.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Direct reduction of sulfur dioxide to elemental sulfur by methane and partial oxidation of methane to syngas on ceria-based catalysts./
Author:	Zhu, Tianli.
Description:	210 p.
Notes:	Source: Dissertation Abstracts International, Volume: 61-03, Section: B, page: 1534.
Contained By:	Dissertation Abstracts International61-03B.
Subject:	Chemical engineering. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=9965412
ISBN:	9780599700017

Direct reduction of sulfur dioxide to elemental sulfur by methane and partial oxidation of methane to syngas on ceria-based catalysts.
Zhu, Tianli.

Direct reduction of sulfur dioxide to elemental sulfur by methane and partial oxidation of methane to syngas on ceria-based catalysts. - 210 p.

Source: Dissertation Abstracts International, Volume: 61-03, Section: B, page: 1534.

Thesis (Ph.D.)--Tufts University, 2000.

Single-stage catalytic reduction of SO2 to elemental sulfur is a promising technology for the treatment of SO2-laden gas streams. In this thesis, the catalytic reduction of SO2 to elemental sulfur by methane at atmospheric pressure was studied over ceria-based catalysts. The catalysts were prepared by urea coprecipitation/gelation and incipient wetness impregnation. H2- and CH4-TPR were used to characterize the catalyst reduction properties. The catalyst structure was examined by XRD, STEM/EDS and YPS. The catalyst activity/selectivity studies were complemented by SO2 uptake experiments and by reduction of the pre-sulfated catalysts in methane, both isothermally and in the TPR mode.

ISBN: 9780599700017Subjects--Topical Terms:

560457
Chemical engineering.

Direct reduction of sulfur dioxide to elemental sulfur by methane and partial oxidation of methane to syngas on ceria-based catalysts.
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245 1 0 $a Direct reduction of sulfur dioxide to elemental sulfur by methane and partial oxidation of methane to syngas on ceria-based catalysts.
300 $a 210 p.
500 $a Source: Dissertation Abstracts International, Volume: 61-03, Section: B, page: 1534.
500 $a Adviser: Maria Flytzani-Stephanopoulos.
502 $a Thesis (Ph.D.)--Tufts University, 2000.
520 $a Single-stage catalytic reduction of SO2 to elemental sulfur is a promising technology for the treatment of SO2-laden gas streams. In this thesis, the catalytic reduction of SO2 to elemental sulfur by methane at atmospheric pressure was studied over ceria-based catalysts. The catalysts were prepared by urea coprecipitation/gelation and incipient wetness impregnation. H2- and CH4-TPR were used to characterize the catalyst reduction properties. The catalyst structure was examined by XRD, STEM/EDS and YPS. The catalyst activity/selectivity studies were complemented by SO2 uptake experiments and by reduction of the pre-sulfated catalysts in methane, both isothermally and in the TPR mode.
520 $a Ceria-based catalysts are active for SO2 reduction by methane to elemental sulfur in the temperature range 550--750°C. At temperatures below &sim;550°C the catalyst surface is capped by SO2. Activation of CH4 on these surfaces is initiated after sulfate decomposition. The working catalyst surface is partially sulfated even under fuel-rich conditions. CH4-TPR and isothermal CH4 reduction of pre-sulfated catalysts suggest that the reaction light-off coincides with the threshold temperature for sulfate decomposition. The addition of 5 at% copper into La-doped ceria, Ce(La)Ox, improved dramatically both the wet activity of the latter as well as its selectivity to elemental sulfur under fuel-rich conditions. Nickel addition, on the other hand, favored the partial oxidation of methane, and decreased the selectivity to sulfur.
520 $a The reaction kinetics and mechanism of the SO2 reduction by methane to elemental sulfur are discussed within the redox framework. Creation of surface oxygen vacancies by methane is followed by SO2 giving off its oxygens to fill the vacancies and produce sulfur. The activation energy is 188 kJ/mol. The rate of partial oxidation of methane by SO2 to H2S over the 1wt%Cu-1wt%La/CeO2 catalyst was also measured. The rate of H2S formation is negligible at dry conditions, but increased at wet conditions due to the participation of the water-gas-shift reaction.
520 $a The partial oxidation of methane to syngas was also studied in this work over Ni-containing ceria with nickel content of 5, 10 and 20 at% at atmospheric pressure. All catalysts in the as-prepared state showed similar activity and CO selectivity at T ≥ 550°C. Catalyst pre-reduction was not required. Reaction mixtures were dilute, containing 3 mol% CH4 and 1.5 mol% O2. Methane conversion and CO selectivity approached their respective thermodynamic equilibrium values above 550°C. The H2/CO ratio was equal to 2 at T > 600°C. Over the range 0.54 to 0.04 g.s/cm 3 (STP), contact time effects were absent in partial oxidation of methane over 5 at% Ni-Ce(La)Ox. This catalyst, comprising highly dispersed nickel oxide in ceria, showed excellent resistance to carbon deposition and stable performance during 100h-on-stream at 650°C. On the other hand, high-content (>10 at%) nickel in ceria, comprising both dispersed nickel and bulk nickel oxide particles, was unstable even after shorter time-on-stream; carbon deposition was clearly the cause of this performance instability. The high activity and stability of 5at%Ni-Ce(La)Ox for POM were correlated with the high reducibility and oxygen mobility of this material.
590 $a School code: 0234.
650 4 $a Chemical engineering. $3 560457
650 4 $a Inorganic chemistry. $3 3173556
690 $a 0542
690 $a 0488
710 2 $a Tufts University. $3 1017847
773 0 $t Dissertation Abstracts International $g 61-03B.
790 $a 0234
791 $a Ph.D.
792 $a 2000
793 $a English
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=9965412