Sulfur, thermodynamic data

The thermodynamic properties of sulfur trioxide, and of the oxidation reaction of sulfur dioxide are summarized in Tables 3 and 4, respectively. Thermodynamic data from Reference 49 are beheved to be more accurate than those of Reference 48 at temperatures below about 435°C. 

Flame Temperature. The adiabatic flame temperature, or theoretical flame temperature, is the maximum temperature attained by the products when the reaction goes to completion and the heat fiberated during the reaction is used to raise the temperature of the products. Flame temperatures, as a function of the equivalence ratio, are usually calculated from thermodynamic data when a fuel is burned adiabaticaHy with air. To calculate the adiabatic flame temperature (AFT) without dissociation, for lean to stoichiometric mixtures, complete combustion is assumed. This implies that the products of combustion contain only carbon dioxide, water, nitrogen, oxygen, and sulfur dioxide. 

Sulfur dioxide hydrate, thermodynamic data and lattice constants, 8 Sulfur hexafluoride (SFa), hydrate, 22, 47... 

Thermodynamic data suggest that P -alumina is stable in sulfur and that Na20-rich //"-alumina maybe unstable to some degree. In the latter event, depletion of Na20 from / " -alumina according to Eq. (5) would result in a surface layer resistant to further corrosion. A significant corrosion reaction does occur be-... 

This paper surveys the field of methanation from fundamentals through commercial application. Thermodynamic data are used to predict the effects of temperature, pressure, number of equilibrium reaction stages, and feed composition on methane yield. Mechanisms and proposed kinetic equations are reviewed. These equations cannot prove any one mechanism however, they give insight on relative catalyst activity and rate-controlling steps. Derivation of kinetic equations from the temperature profile in an adiabatic flow system is illustrated. Various catalysts and their preparation are discussed. Nickel seems best nickel catalysts apparently have active sites with AF 3 kcal which accounts for observed poisoning by sulfur and steam. Carbon laydown is thermodynamically possible in a methanator, but it can be avoided kinetically by proper catalyst selection. Proposed commercial methanation systems are reviewed. 

Sulfur. It is not readily predictable from existing thermodynamic data that sulfur would be a poison of nickel catalysts. The action of sulfur is undoubtedly through the reaction of hydrogen sulfide with nickel, according to ... 

Seby F, Potin-Gautier M, Giffaut E, Borge G, Donard OFX (2001) A critical review of thermodynamic data for selenium species at 25 °C. Chem Geol 171 173-194 Ball S, Milne J (1995) Studies on the interaction of selenite and selenium with sulfur donors. Part 3. Sulfite. Can J Chem 73 716-724... 

The sulfur dioxide enters the reactor with an initial concentration of 10% by volume, the remainder being air. At the exit of the first bed, the temperature is 620°C. Assume ideal gas behavior, the reactor operates at 1 bar and R = 8.3145 kJ-Kr -lonoD1. Assume air to be 21% 02 and 79% N2. Thermodynamic data at standard conditions at 298.15 K are given in Table 6.186. 

Table 6.18 Thermodynamic data at standard conditions and 298.15 K for sulfuric acid production.

Tables 3 and 4 contain values of the log water activity and log sulfuric acid activity in molarity units. These can be obtained at any temperature by using the polynomial coefficients supplied by Zeleznik,45 which are based on all of the preexisting thermodynamic data obtained for this medium. The numbers were converted to the molarity scale using the conversion formula given in Robinson and Stokes 46 Molarity-based water activities are given for HCIO4 in Tables 5 and 6. These are calculated from data obtained at 25°C by Pearce and Nelson,17...

Only a few thermodynamic data on cyclic selenium sulfides are available. The appearance potential of gaseous SeS, (9.3 0.2 eV) is by 0.25 eV lower than that of but 0.7 eV higher than that of SCg The enthalpy of mixing of liquid sulfur and selenium is positive throughout the composition range at temperatures of 345 to 460 °C. Obviously the reaction... 

Collections of fundamental and thermodynamic data can be found in an earlier review [158] and in standard resources [13, 14]. However, due to the reactivity of iodine there are many less common or more reactive forms of iodine that have been less well characterized. For example, a blue 12 cation, a brown I3+, or a green I5+ cation are formed in concentrated sulfuric acid and 1+ is stabilized in donor environments such as pyridine [159]. So-called hypervalent iodine reagents have been developed as a versatile oxidation tool in organic synthesis and often iodine derivatives are employed as electron transfer catalysts. Some fundamental thermodynamic data and typical applications of iodine are summarized in Scheme 5. 

Experimental thermodynamic data have been reported for dibenzo-l,4-thiazino[3,2-/ ][l,4]thiazine 166 <1997MI565> compared to the corresponding oxazinooxazine, replacement of oxygen by sulfur increases ring strain. Crystallographic data show that the nitrogen centres in 166 are /7-periplanar <1994JCM458>. 

A wide range of ligands of the type RXCH2C02H where R = alkyl, alkenyl or aryl and X = S, Se or Te have been reacted with silver ions and thermodynamic data for some representative examples are given in Table 49.358,359 The silver-selenium complexes were found to be more stable than their silver-sulfur analogues as a result of both larger favourable enthalpy and smaller unfavourable entropy changes. 

Thermodynamic data for the formation of Ag(TSC)3 are given in Table 58.437 Based on the similarity of the stability of this complex and the analogous thiourea complex, the ligand was proposed to be monodentate. The IR spectra of [Ag2(TSC)3](NC>3)2438 and of Ag(TSC)Cl439 were also interpreted in terms of silver-sulfur bonding only. 

High temperature thermodynamic data are available only for three sulfites calcium, potassium, and sodium. Most sulfites are fairly unstable, decomposing at relatively low temperatures. The decomposition reactions are not always exactly known, with diverse decomposition products, including sulfur, being reported. There are two major decomposition reactions (1) decomposition to the oxide and S02, and (2) oxidation-reduction (disproportionation) to the sulfate and oxide and S02, i.e.,... 

In practice, thermodynamic data such as heats and free energies of formation of surface sulfides are very difficult to obtain, mainly because quantitative measurements must be made of adsorbed and gas-phase sulfur at extremely low concentrations. Only during the last decade has the develop-... 

Only a limited amount of thermodynamic data are available for 2-D sulfides of metals other than nickel. Data reported for Ag (57), Co (252), Cu (255), Fe (252, 154), Mo (255, 255), Ru (256), and Pt (84, 85) indicate that the heats of sulfur adsorption are generally 20-40% larger than the heats of formation of the most stable bulk sulfides. Indeed, Benard et al. (255) have shown a linear correlation between the heats of adsorption of sulfur and the... 

As demonstrated in the case of H2S on Ni, thermodynamic data such as AG° and A//ad are of great value in understanding the extent and reversibility of sulfur poisioning. Clearly, more thermodynamic data for adsorption of sulfur are needed for important metals of catalytic interest such as Co, Fe, Mo, Pd, Pt, Re, Rh, Ru, etc. Since sulfur adsorption on Co, Pd, Rh, and Ru... 

Three alternative mechanisms were proposed based only on the thermodynamic data (403). All of these assumed distinct functions for each flavin and interaction between the flavins. They also assumed that electrons would be transferred to cytochrome P-450 one at a time this has been shown to be the case with cytochromes P-450 that receive electoons from iron-sulfur proteins rather than from the flavoprotein directly (or through the indirect mediation of lipid) (405, 406). One of these mechanisms (403) is shown below. It seems to fit best with the kinetic data determined for the lipase-solubilized reductase (345, 398). In this scheme, SH is a hydroxylatable substrate and SOH its hydroxylated product, and Fli and FU are the high potential and low potential flavins, respectively. 

Given in the literature are vapor pressure data for acetaldehyde and its aqueous solutions (1—3) vapor—liquid equilibria data for acetaldehyde—ethylene oxide [75-21-8] (1), acetaldehyde—methanol [67-56-1] (4), sulfur dioxide [7446-09-5]— acetaldehyde—water (5), acetaldehyde—water—methanol (6) the azeotropes of acetaldehyde—butane [106-97-8] and acetaldehyde—ethyl ether (7) solubility data for acetaldehyde—water—methane [74-82-8] (8), acetaldehyde—methane (9) densities and refractive indexes of acetaldehyde for temperatures 0—20°C (2) compressibility and viscosity at high pressure (10) thermodynamic data (11—13) pressure—enthalpy diagram for acetaldehyde (14) specific gravities of acetaldehyde—paraldehyde and acetaldehyde—acetaldol mixtures at 20/20°C vs composition (7) boiling point vs composition of acetaldehyde—water at 101.3 kPa (1 atm) and integral heat of solution of acetaldehyde in water at 11°C (7). 

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