MIT-HOL kerdes [1397]: fempor dezoxidalas (redukalas)
Omikk Tajekoztatas
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2000. Jún. 6., K, 14:03:11 CEST
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2 Complete Record
DIALOG No: 05305755 EI Monthly No: EIP99064707389
Title: Direct reduction of SO//2 to elemental sulfur by methane over ceria-based
catalysts
Author: Zhu, Tianli; Dreher, Andreas; Flytzani-Stephanopoulos, Maria
Corporate Source: Tufts Univ, Medford, MA, USA
Source: Applied Catalysis B:Environmental v 21 n 2 1999. p 103-120
Publication Year: 1999
CODEN: ACBEE3 ISSN: 0926-3373
Language: English
Document Type: JA; (Journal Article) Treatment Code: X; (Experimental)
Abstract: The catalytic reduction of SO//2 to elemental sulfur by methane was
studied over ceria-based catalysts. Both La-doped and undoped ceria were found to
catalyze the SO//2 reduction by CH//4 in the temperature range of 550-750 degree C at
atmospheric pressure and with feed gases containing a molar ratio of CH//4/SO//2
equals 0.5-3. At temperatures below approximately 550 degree C, the catalyst surface
is capped by SO//2. The reaction light-off coincides with the threshold temperature
for sulfate decomposition. Various SO//2/CH//4/H//2O gas mixtures were used to study
the catalyst activity and selectivity to elemental sulfur. The incorporation of
nickel and copper improves the wet activity of Ce(La)Ox catalysts. Also, the
addition of a low amount (5 at.%) of copper or nickel into La-doped ceria, Ce(La)Ox,
had a markedly different effect on the catalyst selectivity under fuel-rich
conditions. The Cu-Ce(La)Ox catalyst has higher selectivity to elemental sulfur and
complete oxidation products (H//2O, CO//2), while Ni-Ce(La)Ox favors the formation of
H//2S and partial oxidation products (CO). The catalyst activity/selectivity studies
were complemented by SO//2 uptake experiments and by reduction of the as-prepared and
pre-sulfated catalysts in methane, both isothermally and in the TPR mode. The
initial rate of reduction of pre-sulfated catalysts with methane is similar for
Ce(La)Ox, Cu-Ce(La)Ox and Ni-Ce(La)Ox in the temperature range of 500-700 degree C.
Activation of methane on these surfaces requires partial sulfate decomposition.
(Author abstract) 41 Refs.
Descriptors: *Sulfur dioxide; Reduction; Catalysis; Methane; Cerium compounds;
Copper; Nickel; Catalyst activity; Catalyst selectivity; Oxidation
Identifiers: Cerium oxide; Temperature-programmed reduction (TPR)
EI Classification Codes:
804.2 (Inorganic Components); 802.2 (Chemical Reactions); 804.1 (Organic
Components); 544.1 (Copper); 548.1 (Nickel)
804 (Chemical Products); 802 (Chemical Apparatus & Plants); 544 (Copper &
Alloys); 548 (Nickel & Alloys); 803 (Chemical Agents & Basic Industrial Chemicals)
5 Complete Record
DIALOG No: 05276185 EI Monthly No: EIP99034609781
Title: Direct conversion of SO//2 to elemental sulfur
Author: Oehlberg, Richard J.; Nelson, Sidney G.; Cianciolo, Brian C.
Corporate Source: Sorbent Technologies Corp, Twinsburg, OH, USA
Conference Title: Proceedings of the 1998 91st Annual Meeting & Exposition of the
Air & Waste Management Association
Conference Location: San Diego, CA, USA Conference Date: 19980614-19980618
Source: Proceedings of the Air & Waste Management Association's Annual Meeting &
Exhibition 1998. Air & Waste Management Assoc, Pittsburgh, PA, USA. 12pp 98-RP93B.01
Publication Year: 1998
CODEN: PAMEE5
Language: English
Conference Number: 49496
Document Type: CA; (Conference Article) Treatment Code: G; (General Review)
Abstract: Gas streams containing concentrated levels of SO//2 are common in many
regenerable flue-gas desulfurization (FGD) processes, in gas-treatment systems
associated with coal gasification processes, and in hydrocarbon treatment processes.
Generally, the most desirable sulfur by-product is elemental sulfur. In the past, a
modified Claus process was usually the method employed to convert SO//2 to elemental
sulfur. The Claus process, however, involves multiple reactors in series, is
relatively expensive, consumes significant energy, and does not go to completion,
which means that a tail gas treatment plant and other facilities are required. For
over five years, Sorbent Technologies Corporation has been developing and scaling up
a simpler, less-costly process for converting SO//2-rich gases directly to elemental
sulfur. The process is based on a new SO//2-to-elemental sulfur catalyst. The
simple technology operates at typical coal gasification temperatures and can use
natural gas (reformed methane) or other typical process gases for SO//2 reduction.
This new direct-to-sulfur process was recently tested at the Federal Energy
Technology Center's advanced Copper Oxide Process FGD pilot plant in Pittsburgh. A
skid-mounted test unit was placed after the copper oxide regenerator, where it turned
the high-concentration SO//2 off-gas directly into elemental sulfur. This paper
discusses the chemistry involved in the new technology, traces its development, and
presents the results achieved in various pilot plant tests. (Author abstract)
Descriptors: *Sulfur dioxide; Sulfur; Desulfurization; Coal gasification; Natural
gas
Identifiers: Elemental sulfur; Regenerable flue gas desulfurization
EI Classification Codes:
804.2 (Inorganic Components); 802.2 (Chemical Reactions)
804 (Chemical Products); 802 (Chemical Apparatus & Plants); 522 (Gas Fuels)
6 Complete Record
DIALOG No: 05250536 EI Monthly No: EIP99034601220
Title: IR spectroscopy study of CO and NO//x adsorption on a Cu/Zr-HMS catalyst
Author: Hadjiivanov, K.; Dimitrov, L.
Corporate Source: Bulgarian Acad of Sciences, Sofia, Bulg
Source: Microporous and Mesoporous Materials v 27 n 1 Jan 1999. p 49-56
Publication Year: 1999
CODEN: 003088 ISSN: 1387-1811
Language: English
Document Type: JA; (Journal Article) Treatment Code: X; (Experimental)
Abstract: The adsorption of CO, NO and NO//2 and the co-adsorption of CO plus NO
and NO plus O//2 on Cu/Zr-HMS have been investigated by infrared spectroscopy.
Carbon monoxide and nitrogen monoxide are adsorbed selectively on Cu** plus and
Cu**2** plus cations, respectively. Owing to back pi -donation, the Cu** plus -CO
complexes [nu (CO) at 2132 cm** minus **1] are relatively stable towards evacuation
and water vapor treatment. On the contrary, the Cu**2** plus -NO nitrosyls [nu (NO)
at 1888 cm** minus **1] are easily decomposed during evacuation. Adsorption of NO//2
and co-adsorption of NO and O//2 cause the formation of weakly adsorbed N//2O//4 (a
band at 1740-1730 cm** minus **1) and N//2O//3 (bands at 1904 and 1540 cm** minus
**1) as well as strongly bound nitrates (bands at 1620-1550 cm** minus **1). The
latter possess a high oxidation ability, oxidizing NO at room temperature and
methane at 200 degree C. The results obtained show that the coordination state of
copper ions in Cu/Zr-HMS is closer to their state in Cu/SiO//2 and Cu/Al//2O//3 than
to that in Cu-ZSM-5, which is due to the absence of strongly acidic OH groups in Zr-
HMS. (Author abstract) 49 Refs.
Descriptors: *Catalysts; Gas adsorption; Carbon monoxide; Nitrogen oxides; Oxygen;
Copper; Zirconium; Catalyst selectivity; Catalyst supports; Oxidation
Identifiers: Selective catalytic reduction
EI Classification Codes:
802.3 (Chemical Operations); 804.2 (Inorganic Components); 544.1 (Copper); 549.3
(Others, including Bismuth, Boron, Cadmium, Cobalt, Mercury, Niobium, Selenium,
Silicon, Tellurium & Zirconium)
803 (Chemical Agents & Basic Industrial Chemicals); 804 (Chemical Products); 802
(Chemical Apparatus & Plants); 544 (Copper & Alloys); 549 (Nonferrous Metals &
Alloys)
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