Oxidation and Reduction Processes During NO x Removal with Corona-Induced Nonthermal Plasma

In this paper, the NO-to-NO ₂ conversion in various gaseous mixtures is experimentally investigated. Streamer coronas are produced with a dc-superimposed high-frequency ac power supply (10–60 kHz). According to NO _x removal experiments in N ₂ +NO _x and N ₂ +O ₂ +NO _x gaseous mixtures, it is supposed that the reverse reaction NO ₂ +ONO+O ₂ may not only limit NO ₂ production in N ₂ +NO _x mixtures, but also increase the energy cost for NO removal. Oxygen could significantly suppress reduction reactions and enhance oxidation processes. The reduction reactions, such as N+NON ₂ +O, induce negligible NO removal provided the O ₂ concentration is larger than 3.6%. With adding H ₂ O into the reactor, the produced NO ₂ per unit removed NO can be significantly reduced due to NO ₂ oxidation. NH ₃ injection could also significantly decrease the produced NO ₂ via NH and NH ₂ - related reduction reactions. Almost 100% of NO ₂ can be removed in gaseous mixtures of N ₂ +O ₂ +H ₂ O+NO ₂ with negligible NO production.     

Simultaneous removal of NO and SO<Subscript>2</Subscript> in a plasma reactor packed with TiO<Subscript>2</Subscript>-coated glass beads

We analyzed the dielectric pellet bed discharge-photocatalyst hybrid process for NO and SO₂ removal. A cylindrical-wire type discharge reactor was packed with glass beads as dielectric pellets and the plasmas were generated by dielectric pellet bed discharge. The TiO₂ photocatalysts were coated onto the glass beads by the dip-coating method and were activated by the light from discharge. Experiments were carried out for three cases: NO removal only, SO₂ removal only, and simultaneous NO and SO₂ removal. As the voltage applied to the plasma reactor increased, or as the residence time increased, the NO and SO₂ removal efficiencies increased. With increasing initial NO and SO₂ concentrations, the NO and SO₂ removal efficiencies decrease. The removal efficiencies for simultaneous NO and SO₂ removal are lower than those for NO only or SO₂ only.     

Interaction Between Two Similar Plane Parallel Double Layers for (NH4)2Fe(SO4)2 or (NH4)2Cu(SO4)2 Type Complex Salt Electrolytes at Positive Surface Potential

Interaction energies between two similar plane parallel double layers for (NH₄)₂Fe(SO₄)₂ or (NH₄)₂Cu(SO₄)₂ type complex salt electrolytes at positive surface potential were expanded in a power series and accurate numeral results were given for 0.1 ≤ y _e  < y ₀ ≤ 20. The general expressions were given for the interaction energies of A _ν +B _ν′ +C_ν? type complex salt electrolytes at y > 0. The interaction energies for simple salts NaCl, CaCl₂, Na₂SO₄, FeCl₃, Na₃PO₄, Mg₃(PO₄)₂, Al₂(SO₄)₃, and complex salts (NH₄)₂Fe(SO₄)₂ or (NH₄)₂Cu(SO₄)₂ at y ₀ = 1 were compared. There was hardly difference between these simple salts and this complex salt for the interaction energies. The interaction energy for complex salt (NH₄)₂Fe(SO₄)₂ was close to that for simple salt Na₃PO₄.

Supplemental files are available for this article. Go to the publisher's online edition of the Journal of Dispersion Science and Technology to view the free supplemental file.     

The compounds KAs4O6 X (X=Cl,Br, I) and NH4As4O6 X (X=Br,I): Hydrothermal syntheses and structure determinations

The crystal structures of five isotypic hexagonal compounds with general formulaMAs₄O₆ X [M=K, NH₄;X=Cl, Br, I; space group: P622;Z=1] were determined from 370 single crystal X-ray data and refined toR values <0.05. The structure type is characterized by neutral charged [As₂O₃] sheets arranged parallel (00.1). The As atoms of neighbouring two sheets point to each other and the sheets are combined by interlayeredM andX atoms, respectively. TheM atoms are coordinated to twelve oxygen atoms, theX atoms are coordinated to twelve arsenic atoms. In both cases the coordination polyhedron is a hexagonal prism. The compounds were synthesized by thermal treatments of cubic As₂O₃ and potassium or ammonium haloids in a saturated aqueous solution of potassium acetate resp. ammonia [500 K, saturation vapour pressure].

---

Die Verbindungen KAs₄O₆ X (X=Cl, Br, I) und NH₄As₄O₆ X (X=Br, I): Hydrothermalsynthese und Strukturbestimmung

Zusammenfassung Die Kristallstrukturen der fünf isotypen hexagonalen Verbindungen mit der allgemeinen FormelMAs₄O₆ X [M=K, NH₄;X=Cl, Br, I; Raumgruppe: P622;Z=1] wurden anhand von 370 Einkristall-Röntgendaten bestimmt und aufR-Werte <0.05 verfeinert. Der Strukturtyp ist ausgezeichnet durch neutrale [As₂O₃]-Schichten, die parallel (00.1) angeordnet sind. Die As-Atome zweier benachbarter Schichten weisen jeweils aufeinander zu, und die Schichten selbst werden durch zwischengelagerteM- bzw.X-Atome verbunden. DieM-Atome werden jeweils von zwölf O-Atomen, dieX-Atome von zwölf As-Atomen umgeben. Das Koordinationspolyeder ist in beiden Fällen ein hexagonales Primsa. Die einzelnen Verbindungen wurden unter Hydrothermalbedingungen aus kubischem As₂O₃ und dem jeweiligen Kalium- oder Ammoniumhalogenid in einer gesättigten wäßrigen Lösung von Kaliumacetat bzw. Ammoniak synthetisiert (500 K, Sättigungsdampfdruck).

     

Breakdown of the Rule of “Linearity of Water Isoactivity Lines” in a System Containing Solid Solutions

Osmotic coefficients of water have been measured isopiestically for the entire region of homogeneous ternary solutions for the Rb₂SO₄- (NH₄)₂SO₄-H₂O system at 25°C. One might expect that water isoactivity lines should be straight since this system involves a continuous series of solid solutions. The related systems (K₂SO₄-Rb₂SO₄-H₂O and (K₂SO₄- (NH₄)₂ SO₄-H₂O) obey the linearity of water isoactivity lines rule. Contrary to expectations, the (Rb₂SO₄-(NH₄)₂-SO₄-H₂O appears to be the first water–salt system containing continuous solid solutions in which the mentioned rule is not obeyed.     

Removal of SO2 from Gas Streams by Oxidation using Plasma-Generated Hydroxyl Radicals

The key problem for the removal of SO₂ by electrical discharge methods is how to obtain the hydroxyl radicals at high concentration and large production rates. With the micro-gap discharge method, O₂ and H₂O in simulated gas streams (N₂/O₂/H₂O/SO₂) are ionized into a large number of OH^. radicals to oxidize SO₂ into SO₃ which reacts with H₂O forming H₂SO₄ droplets at 120 °C in the absence of any catalyst or absorbent. The droplets are captured with an electrostatic precipitator. As a result, conversion of SO₂ to primarily H₂SO₄ is limited by the generation of OH^. radicals. By increasing the reduced field and concentrations of O₂ and H₂O, the amount of OH^. radicals increase resulting in more removal of SO₂ from gas streams. The removal efficiency of SO₂ reaches 100% when the residence time is only 0.74 s. Therefore, a new gas-phase oxidation method for removal of SO₂ without NH₃ additive is found.     

Strukturelle Abwandlungen an partiell silylierten Kohlenhydraten mittels Triphenylphosphan/Azodicarbonsäurediethylester, 4. Mitt.: Transformationen an Mannose und Galaktose

Reaction of methyl -D-galactopyranoside (1) with two equivalents oft-butyldimethylchlorosilane yields methyl 2,6-bis-O-(tBDMSi)--D-galactopyranoside (1 b), methyl 3,6-bis-O-(tBDMSi)--D-galactopyranoside (1 c) and methyl 4,6-bis-O-(tBDMSi)--D-galactopyranoside (1 d). Likewise methyl -D-mannopyranoside (6) affords methyl 2,6-bis-O-(tBDMSi)--D-mannopyranoside (6 d) and methyl 3,6-bis-O-(tBDMSi)--D-mannopyranoside (6 b), which can be isomerised withTPP/DEAD to methyl 4,6-bis-O-(tBDMSi)--D-mannopyranoside (6 f). Methyl 6-O-(tBDMSi)--D-galactopyranoside (1 a) and methyl 6-O-(tBDMSi)--D-mannopyranoside (6 a) can be prepared from1 or6 with one equivalent oft-butyldimethylchlorosilane.Without an external nucleophile the sugar derivatives1 a and1 b react withTPP/DEAD to form the 3,4-carbonato--D-galactopyranosides1 h and1 i and the 3,4-carbonato-2-O-ethoxycarbonyl--D-galactoside (1 j). In contrast to the formation of the compound1 i by means ofTPP/DEAD the reaction of1 a withTPP and Di-t-butyl-azodicarboxylate (DTBAD) yields the 2,3-anhydro--D-taloside (4 b) and only a small amount of1 i. The epoxide4 b can be cleaved withp-nitrobenzoylchloride/pyridine to the 3-chloro-3-deoxy-2,6-di-O-p-nitrobenzoyl--D-idoside (5). Reaction of1 c and1 d withTPP/DEAD yields the 2,3-anhydro--D-gulopyranoside (2), which can be transformed with NaN₃/NH₄Cl to the 2-azido-2-deoxy--D-idopyranoside (3).Likewise6 a and6 d can be converted to the 3,4-anhydro--D-talosides (7 a and7 b). Reaction of7 b or6 d withTPP/DEAD/NH₃ leads to 3,4-anhydro-2-azido-2-deoxy--D-galactopyranoside (8) and 3-azido-3-deoxy--D-altropyranoside (10), resp.The epoxide7 b is opened with NaN₃/NH₄Cl to the 4-azido-4-deoxymannosides (11 a and11 c) and the 3-azido-3-deoxy--D-idopyranoside (12), while the epoxide8 affords the 2,4-di-azido-2,4-dideoxy--D-glucopyranoside (9).Structures were elucidated by¹H-NMR-analysis of the corresponding acetates.

H. H. Brandstetter undE. Zbiral, Helv., im Druck.     

Micropore filling of NO,SO2, NH3, and CO2 onα-FeOOH dispersed activated carbon fibers

Adsorption isotherms of NO, SO₂, NH₃, and CO₂ on-FeOOH dispersed activated carbon fibers at 303 K were examined to determine the role of surface modification in micropore filling. The parameters on micropore structures were obtained from both nitrogen adsorption at 77 K and benzene adsorption at 303 K; both isotherms were of BDDTI type and gave the same micropore volume. The preoxidation conditions of ACF, prior to the deposition of-FeOOH against the NO adsorptivity were examined. The dispersion of-FeOOH on ACF was effective in enhancement of micropore filling, irrespective of the adsorbate molecule. We determined the degree of volume filling for each gas by the use of a DR plot. The modified DR plot for an NO gas, of which the critical temperature was much lower than 303 K, was proposed. The degree of volume filling for various gases was correlated with the deviation of each boiling point from 303 K and with the van der Waalsa constant.     

Heats of solution and neutralization ofLewis acids and bases in acetic anhydride

Heats solution of someLewis acids and bases in acetic anhydride have been determined and the following order of their relative strengths is proposed: SbCl₅>SO₃>SnCl₄>TiCl₄>AsCl₃ and piperidine> n-butylamine>potassium acetate>sodium acetate -picoline>quinoline. Heats neutralization of theseLewis acids and bases in acetic anhydride suggest that the major enthalpy change in these neutralization reactions is due to the combination of a proton and the (CH₂COOCOCH₃)-ion, resulting in the formation of acetic anhydride.

---

Lösungs- und Neutralisationswärmen von Lewis-Säuren und-Basen in Essigsäureanhydrid

Zusammenfassung Es wurden die Lösungswärmen einigerLewis-Säuren in Essigsäureanhydrid bestimmt und folgende Reihung nach ihrer relativen Stärke vorgeschlagen: SbCl₅>SO₃>SnCl₄>TiCl₄>AsCl₃ und Piperidin> n-Butylamin>KAc>NaAc-Picolin>Chinolin. Die Neutralisationswärmen dieserLewis-Säuren und-Basen legen nahe, daß der Hauptanteil daran auf die Reaktion eines Protons mit (CH₂–COOCOCH₃)-zurückzuführen ist.

     

Error of Atomic Charges Derived from Electrostatic Potential

The purpose of this article is to show that CHELP, CHELPG, and Merz and Kollman undergo error for the charge on atoms of HCOO^– (H₂O) _n for n = 1 6. We also demonstrate that the CHELP, CHELPG, and Merz and Kollman show error for the tendency toward change in the charges on carbons for CH₃NH⁺ ₃ (CH₃)₂NH⁺ ₂ (CH₃)₃NH⁺ (CH₃)₄N⁺.     

Trinuclear metal(III) trifluoroacetates

Hydrated and anhydrous trinuclear metal(III) trifluoroacetates of Cr and Fe were prepared by reaction of freshly precipitated metal oxides with trifluoroacetic acid, while manganese analogs by acid exchange. IR data show the presence of bidentate trifluoroacetate groups. The diffuse reflectance spectra suggest octahedral environment around metals.Mössbauer spectra show that iron atoms in the compounds are high spin hexacoordinated; two types of iron sites are suggested in hydrated iron compound. Low magnetic moment of chromium and iron compounds indicate antiferromagnetic coupling. Th anhydrous compounds decompose in single step with the evolution of (CF₃CO)₂O.M ₃O(O₂CCF₃)₇ form complexes [M ₃O(O₂CCF₃)₆·3Py]⁺ [O₂CCF₃]^– with pyridine.

---

Dreikernige Metall(III)-Trifluoracetate

Zusammenfassung Es wurden hydratisierte und wasserfreie dreikernige Metall(III)-Trifluoracetate von Cr und Fe mittels der Reaktion von frisch gefälltem Metalloxid und Trifluoressigsäure dargestellt; die Mangan-Analogen wurden über Säure-Austausch gewonnen. Die IR-Daten zeigen die Präsenz von zweizähnigen Trifluoracetat-Gruppen an. Die diffuse-reflectance-Spektren sprechen für eine octahedrale Umgebung rund um das Metall. DieMössbauer-Spektren zeigen, daß die Eisenatome in den entsprechenden Verbindungen high-spin hexakoordiniert sind; dabei werden in den hydratisierten Eisenverbindungen zwei Typen von Eisenatomen gezeigt. Ein niederes magnetisches Moment der Chrom- und Eisen-Verbindungen zeigen eine antiferromagnetische Kopplung an. Die wasserfreien Verbindungen zersetzen sich in einem einzigen Schritt unter Entwicklung von (CF₃CO)₂O. Mit Pyridin bilden die VerbindungenM ₃O(O₂CCF₃)₇ die Komplexe [M ₃O(O₂CCF₃)₆·3Py]⁺ [O₂CCF₃]^–.

     

NH3-SCR脱硝催化剂抗硫性能的研究进展

氮氧化物(NO_x)是一种重要的大气污染物, 它造成严重的环境问题, 同时威胁人类健康. 以钢铁烧结烟气为代表的固定源和以柴油机尾气为代表的移动源是氮氧化物的主要来源. 氨气选择性催化还原法(NH₃-SCR)是目前最有效且应用最广泛的NO_x脱除技术. 然而, 无论是固定源还是移动源上NH₃-SCR催化剂, 都不可避免地会被SO₂毒化, 造成催化剂失活, 限制了NH₃-SCR技术的进一步应用. 因此, 研究NH₃-SCR催化剂的SO₂中毒机制以及提高催化剂的抗硫性能至关重要. 我们对固定源脱硝的金属氧化物和移动源上脱硝的Cu基分子筛这两类不同催化剂体系的SO₂中毒机制的研究进展进行了介绍, 并对这两种催化剂上提高抗硫性能改性方法的研究进展进行了评述, 为未来的研究提供了参考.     

A monitor for atmospheric sulphur dioxide,based on enrichment of SO2 by a polydispersive water aerosol

A monitor for continuous analysis of sulphur dioxide in the atmosphere at the ppb v/v level (1 ppb v/v = 2.62 g/m³ SO₂) is described. The apparatus operates on the principle of equilibrium accumulation of sulphur dioxide from the air by a polydispersive water aerosol which continuously transfers SO₂ from an air-flow of l/min into microlitre volumes of water condensate. High sensitivity (1 ppb v/v), low relative error (± 5% at 4 ppb v/v SO₂), high selectivity (CO₂ does not interfere at a concentration of 2 × 10³ ppm v/v, interference by NO _x and H₂S is acceptably low), and low response delay (10 s) are provided by a compact coupling of the enrichment procedure with conductivity detection of SO₂ in the film of water aerosol condensate formed directly on the wire-gauze sensor. The reliability of the method has been studied under simulated conditions, with spectrophotometric method as reference. The analyser is computer-controlled, and the detector response is processed on-line and displayed (as g/m³) in real-time on a screen or is transmitted telemetrically to a control centre. It is portable and suitable for use in both stationary and moving locations.The paper is dedicated to the 65th anniversary of the birthday of Prof. Josef F. K. Huber     

Removal of SO2 and the simultaneous removal of SO2 and NO from simulated flue gas streams using dielectric barrier discharge plasmas

A gas-phase oxidation method using dielectric barrier discharges (DBDs) has been developed to remove SO₂ and to simultaneously remove SO₂ and NO from gas streams that are similar to gas streams generated by the combustion of fossil fuels. SO₂ and NO removal efficiencies are evaluated as a function of applied voltage, temperature, and concentrations of SO₂, NO, H₂O_(g), and NH3. With constant H₂O_(g) concentration, both SO₂ and NO removal efficiencies increase with increasing temperature from 100 to 160°C. At 160°C with 15% by volume H₂0_(g), more than 95% of the NO and 32% of the S0₂ are simultaneously removed from the gas stream. Injection of NH₃ into the gas stream caused an increase in S0₂ removal efficiency to essentially 100%. These results indicate that DBD plasmas have the potential to simultaneously remove SO₂ and NO from gas streams generated by large-scale fossil fuel combustors.     

The catalytic effects of various third molecules on reaction channels of weakly bound complex CO2HF systems in the vapor phase

In this investigation, reaction channels of weakly bound complexes CO₂HF, CO₂HFH₂O, CO₂HFNH₃, CO₂HFCH₃OH, CO₂HFNH₂CH₃, CO₂HFNH(CH₃)₂ and CO₂HFN(CH₃)₃ systems were studied at the B3LYP/6-311++G(3df,2pd) level. The conformers of syn-fluoroformic acid or syn-fluoroformic acid plus a third molecule (H₂O, NH₃, CH₃OH, NH₂CH₃, NH(CH₃)₂ or N(CH₃)₃) were found to be more stable than the conformers of the related anti-fluoroformic acid or anti-fluoroformic acid plus a third molecule (H₂O, NH₃, CH₃OH, NH₂CH₃, NH(CH₃)₂ or N(CH₃)₃). However, the weakly bound complexes were found to be more stable than either the related syn- and anti- type fluoroformic acid or the acid plus third molecule (H₂O, NH₃, CH₃OH, NH₂CH₃, NH(CH₃)₂ or N(CH₃)₃) conformers. They decomposed into CO₂+HF, CO₂+H₃OF, CO₂+NH₄F, CO₂+(CH₃)OH₂F, CO₂+NH₃(CH₃)F, CO₂+NH₂(CH₃)₂F, or CO₂+NH(CH₃)₃F combined molecular systems. The weakly bound complexes have seven reaction channels, each of which includes weakly bound complexes and their related systems. Moreover, each reaction channel includes two transition state structures. The transition state between the weakly bound complex and anti-fluoroformic acid type structure (T₁₃) is significantly higher than that of internal rotation (T₂₃) between the syn- and anti-FCO₂H (or FCO₂HH₂O, FCO₂HNH₃, FCO₂HCH₃OH, FCO₂HNH₂CH₃, FCO₂HNH(CH₃)₂, or FCO₂HN(CH₃)₃) structures. However, adding the third molecule H₂O, NH₃, CH₃OH, NH₂CH₃, NH(CH₃)₂ or N(CH₃)₃ can significantly reduce the activation energy of T₁₃. The catalytic strengths of the third molecules are predicted to follow the order H₂O<NH₃<CH₃OH<.NH₂CH₃<NH(CH₃)₂<N(CH₃)₃.     

PbCu3(OH)(NO3)(SeO3)3·1/2H2O und Pb2Cu3O2(NO3)2(SeO3)2: Synthese und Kristallstrukturuntersuchung

Crystals of PbCu₃(OH)(NO₃)(SeO₃)₃·1/2H₂O [a=7.761(3)Å,b=9.478(4)Å,c=9.514(4)Å, =66.94(2)°, =69.83(2)°, =81.83(2)°, space group P ,Z=2] and Pb₂Cu₃O₂(NO₃)₂(SeO₃)₂ [a=5.884(2)Å,b=12.186(3)Å,c=19.371(4)Å, space group Cmc2₁,Z=4] were synthesized under hydrothermal conditions. Their crystal structures were refined with three-dimensional X-ray data toR _w=0.033 resp. 0.055. In PbCu₃(OH)(NO₃)(SeO₃)₃·1/2H₂O the Cu atoms are [4+1] and [4+2] coordinated and via SeO₃ groups a three-dimensional atomic arrangement is built up. In Pb₂Cu₃O₂(NO₃)₂(SeO₃)₂ there are sheets, which are connected only via Pb-O bonds ranging from 2.98 Å to 3.16 Å.

     

Effect of the structure of frozen solutions of H2SO4 on radiothermoluminescence

A pronounced effect of structural heterogeneity (cracks) of glass-like solutions of 4.9M H₂SO₄ on their radiothermoluminescence (RTL) was found. In perfect glasses one RTL peak was observed at 115 K. Additional luminescence peaks appeared at 165, 195, and 240 K in glasses having cracks. The effect observed was explained by elevated thermal stability of the SO₄ ^– radical stabilized on the surface of sulfuric acid crystal hydrates: H₂SO₄ · 4H₂O and H₂SO₄· 6.5H₂O.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1566–1568, June, 1996.     

Untersuchungen der Hydroxylammonium-Fluorozirconate(IV)

Summary Hydroxylammonium fluorozirconates have been investigated. Two new microcristalline phases have been isolated from aqueous solutions: (NH₃OH)₂ZrF₆ (1) and (NH₃OH)₃ZrF₇ (2). The crystals were prepared by slow evaporation of the solution of NH₂OH, Zr, and HF. Different compositions of the crystals were achieved by varying the molar ratios of the components. They were characterized by thermal analysis, vibrational spectroscopy, and structure (single crystal x-ray methods). (NH₃OH)₂ZrF₆ (1) crystallizes triclinic, P (No.: 2),a=7.400(2),b=7.609(2),c=7.887(2) Å, =57.29(3)°, =62.16(3)°, =67.83(2)°. (NH₃OH)₃ZrF₇ (2) crystallizes triclinic, P (No.: 2),a=7.128(1),b=7.989(1),c=8.888(1) Å, =109.72(1)°, =91.01(1)°, =104.27(1)°.

     

Syntheses and crystal structures of NH4Ag2(AsS2)3 and (NH4)5Ag16(AsS4)7 with a discussion of (NH4)Sx polyhedra

Summary The atomic arrangements within the structures of NH₄Ag₂(AsS₂)₃ [a=9.557(2),b=7.414(2),c=16.29(1) Å; =91.30(5)°; space group P2₁/n;R(F)=0.042] and (NH₄)₅Ag₁₆(AsS₄)₇ [a=64.49(6),b=6.471(2),c=12.806(4) Å; =95.47(5)°; space group Cc;R(F)=0.073] were determined from single crystal X-ray data. In these two compounds the coordination spheres of the Ag atoms are quite different. In NH₄Ag₂(AsS₂)₃, the Ag atoms exhibit a [2+2]- and a [3+1]-coordination to S atoms up to 3.3 Å and with Ag atom neighbours at 2.93 Å and 3.05 Å respectively. In (NH₄)₅Ag₁₆(AsS₄)₇, the Ag atoms are — with one exception- [4] coordinated (Ag-S<3.3 Å) and the distances to further Ag atom neighbours are greater than 3.1 Å. NH₄Ag₂(AsS₂)₃ represents an ordered cyclo-thioarsenate(III) with three-membered As₃S₆ rings, (NH₄)₅Ag₁₆(AsS₄)₇ a neso-thioarsenate(V) with two split Ag atom positions. Both compounds were synthesized under moderate hydrothermal conditions.

---

Synthesen und Kristallstrukturen von NH₄Ag₂(AsS₂)₃ und (NH₄)₅Ag₁₆(AsS₄)₇ mit einer Diskussion über (NH₄)S_x Polyeder

Zusammenfassung Die Atomanordnungen in den Strukturen von NH₄Ag₂(AsS₂)₃ [a=9.557(2),b=7.414(2),c=16.29(1) Å; =91.30(5)°; Raumgruppe P2₁/n;R(F)=0.042] und (NH₄)₅Ag₁₆(AsS₄)₇ [a=64.49(6),b=6.471(2),c=12.806(4) Å; =95.47(5)°; Raumgruppe Cc;R(F)=0.073] wurden anhand von röntgenographischen Einkristalldaten bestimmt. In diesen beiden Verbindungen sind die Koordinationsverhältnisse um die Ag-Atome sehr unterschiedlich. In NH₄Ag₂(AsS₂)₃ besitzen die Ag-Atome bis 3.3 Å eine [2+2]- und [3+1]-Koordination durch S-Atome mit weiteren Ag-Atomen bei 2.93 Å und 3.05 Å. In (NH₄)₅Ag₁₆(AsS₄)₇ sind die Ag-Atome mit einer Ausnahme [4]-koordiniert (Ag-S < 3.3 Å), und die Abstände zu weiteren Ag-Atomen sind größer als 3.1 Å. NH₄Ag₂(AsS₂)₃ stellt ein geordnetes Cyclothioarsenat(III) mit dreigliedrigen As₃S₆-Ringen dar, (NH₄)₅Ag₁₆(AsS₄)₇ ein Nesothioarsenat (V) mit zwei aufgespaltenen Ag-Positionen. Beide Verbindungen wurden unter mäßigen Hydrothermalbedingungen synthetisiert.

     

Evaluation of Energy Utilization Efficiencies for SO2 and NO Removal by Pulsed Corona Discharge Process

Pulsed corona discharge process was applied to the removal of sulfur dioxide and nitrogen oxides from simulated flue gas. The energy transfer efficiency of the pulse generation circuit and the energy utilization efficiencies for SO ₂ and NO removal are evaluated and discussed. When the pulse-forming capacitance was five times larger than the geometric capacitance of the reactor, the energy utilization efficiency was maximized, and the energy requirements for NO and SO ₂ removal could be lowered. With regard to radical utilization efficiency, producing small amounts of radicals frequently was found to be more advantageous than producing large amounts of radicals less frequently. Removal efficiency of SO ₂ increased with the applied peak voltage, but the energy utilization efficiency was nearly independent of the peak voltage when the peak field intensity was high enough to induce corona discharge (above 10 kV cm ^–1 in this system).