Combustion sulfur preparation

Combustion of Sulfur. For most chemical process appHcations requiring sulfur dioxide gas or sulfurous acid, sulfur dioxide is prepared by the burning of sulfur or pyrite [1309-36-0], FeS2. A variety of sulfur and pyrite burners have been developed for sulfuric acid and for the pulp (qv) and paper (qv) iadustries, which produce and immediately consume about 90% of the captive sulfur dioxide produced ia the United States. Information on the European sulfur-to-sulfuric acid technology (with emphasis on Lurgi) is available (255). 

An important criticism of the use of combustion trains is that combustion is not site specific, that is all atoms in the analyte end up in the gas transferred to the IRMS. For studies of carbon isotope effects this is invariably C02. The question is especially important for carbon isotope analysis because analyte molecules of interest usually contain several different kinds of carbon atoms and therefore combustion methods average or dilute the IE s of interest. Should site specific isotope ratios be required another method of sample preparation (usually much more tedious) is necessary. Combustion methods, however, are frequently used to study nitrogen and sulfur IE s because many organic molecules are singly substituted with these atoms. Obviously, oxygen isotope effects cannot be determined using combustion trains because external oxygen is employed. Rather some type of pyrolytic sample preparation is required. 

For the extraction of sulfates and total sulfur a suitable acid and reducing agent, such as tin(II)-phosphoric acid (the Kiba solution of Sasaki et al. 1979) is needed. The direct thermal reduction of sulfate to SO2 has been described by Holt and Engelkemeier (1970) and Coleman and Moore (1978). Ueda and Sakai (1984) described a method in which sulfate and sulfide disseminated in rocks are converted to SO2 and H2S simultaneously, but analyzed separately. With the introduction of on-line combustion methods (Giesemann et al. 1994), multistep off-line preparations can be reduced to one single preparation step, namely the combustion in an elemental analyzer. Sample preparations have become less dependent on possibly fractionating wet-chemical extraction steps and less time-consuming. 

Esterification Reactions. The use of solid acids provides a practical substitute for homogeneous acid catalysts commonly employed to prepare alkyl esters. The use of homogeneous acid catalysts, such as sulfuric acid, and p-toluene- or methane-sulfonic acids, generally results in sulfur contamination of the final product, which upon combustion yield compounds that are known pollutants. 

Oil of vitriol was prepared by heating a natural vitriol, most typically green (iron) vitriol. This yielded sulfur trioxide which combined with the moisture of the air to give a fairly concentrated sulfuric acid. The name, oil of vitriol, was derived from its source, and from its viscous nature. Acid (or spirit) of sulfur was made by the combustion of common sulfur, the sulfur dioxide produced reacted with the moisture and the oxygen of the atmosphere to give a much more dilute solution of the same acid, mixed with some unoxidized sulfur dioxide. 

Catalyst Poisons. Synthesis gas prepared by the partial combustion of sweet natural gas can be charged to the reactors directly without purification. However, synthesis gas containing more than 0.1 grain of sulfur per 100 cubic feet must be purified before use over fluidized iron catalysts. Other catalyst poisons are known, such as chlorine (14), but they are not likely to be encountered in the natural gas to gasoline process. 

ZnO (c). The heat of solution of unfused zinc oxide in aqueous hydrochloric acid was measured by Favre and Silbermann,3 Hess,10 Maier, Parks, Hablutzel, and Webster,1 and Maier, Parks, and Anderson.1 Apparently, the heat of solution of unfused zinc oxide is independent of the manner of its preparation. These data yield, for ZnO (c,unfused), Qf=83.5. Ditte, de Forcrand8-9>40141,42 and Marignac1 measured the heat of solution of zinc oxide in aqueous sulfuric acid. Their data yield, for ZnO (c, unfused), Qf=83.7, and for ZnO (c, fused), Qf=85.5. See also Woods,1 Berthelot,141-142 and Theis.1 Parr and Moose1 measured the heat of combustion of zinc to form fused zinc oxide to be 85.2. See also the old values of Dulong,1 Andrews,14 15 and Despretz.2... 

Infrared absorption is one of three standard test methods for sulfur in the analysis sample of coal and coke using high-temperature tube furnace combustion methods (ASTM D-4239). Determination of sulfur is, by definition, part of the ultimate analysis of coal (Chapter 4), but sulfur analysis by the infrared method is also used to serve a number of interests evaluation of coal preparation, evaluation of potential sulfur emissions from coal combustion or conversion processes, and evaluation of the coal quality in relation to contract specifications, as well as other scientific purposes. Infrared analysis provides a reliable, rapid method for determining the concentration of sulfur in coal and is especially applicable when results must be obtained rapidly for the successful completion of industrial, beneficiation, trade, or other evaluations. 

Selenium dioxide, unlike sulfur dioxide, is not readily prepared by direct combination of the elements. The best methods depend upon combustion of selenium in the presence of nitrogen dioxide1 or oxidation of selenium by nitric acid.2 The first method includes purification by sublimation the second gives a pure product only if the selenium is pure or if the product is sublimed. 

Metallic rhenium, prepared by the reduction of either potassium perrhenate (see synthesis 60A) or ammonium perrhenate (see synthesis 60B), is placed in a previously ignited porcelain boat and inserted in a pyrex combustion tube of the type shown in Fig. 31. All air in the train is displaced with nitrogen that has been passed through alkaline pyrogallol A and sulfuric acid B. 

Preparation ofnitrosylsulfuric acid from nitrous gases obtained from combustion of ammonia and sulfuric acid ... 

Nitroguanidine (NQ) was first prepared by Jousselin in 1887 (Fig. 1.3). However, during WWI and WWII it only found limited use, for example in formulations with AN in grenades for mortars. In more recent days NQ has been used as a component in triple-base propellants together with NC and NG. One advantage of the triple-base propellants is that unlike double-base propellants the muzzle flash is reduced. The introduction of about 50 % of NQ to a propellant composition also results in a reduction of the combustion temperature and consequently reduced erosion and increased lifetime of the gun. NQ can be prepared from dicyandiamide and ammonium nitrate via guanidinium nitrate which is dehydrated with sulfuric acid under the formation of NQ ... 

However, this reaction is very slow in the absence of a catalyst. One of the mysteries during early research on air pollution was how the sulfur dioxide produced from the combustion of sulfur-containing fuels is so rapidly converted to sulfur trioxide in the atmosphere. It is now known that dust and other particles can act as heterogeneous catalysts for this process (see Section 15.9). In the preparation of sulfur trioxide for the manufacture of sulfuric acid, either platinum metal or vanadium(V) oxide (V205) is used as a catalyst, and the reaction is carried out at approximately 500°C, even though this temperature decreases the value of the equilibrium constant for this exothermic reaction. 

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