Automated potentiometric determination of sulfur functional groups in fossil fuels

Abstract

A fully extended description is given of an automated setup to monltor H,S continuously in a sensltlve, qualitative, and quantltatlve way. H,S Is led by a stream of N, Into an alkallne solution and is contlnuousty determlned as S2-by a potentiometric detectlon system. The H,S detection system has been applied to the temperature-programmed reduction (TPR) of fossil fuel samples. The TPR procedure conslsts of the nonIsothermal heating of a sample in a reducing atmosphere, In order to liberate the different sulfur functional groups as H,S at dlscrete temperature ranges.

Studies of the soluble part of oxidised coals

“…Un%rtunately, the sulphur recovered (Table 2) from the samples is very low, which permits drawing only approximate qualitative conclusions. The low values of sulphur recovery are a consequence of the fact that the H2S %rmed in the process of analysis combines with some inorganic coal components [23,24] or are due to the presence of some highly stable thiophenic species [13]. However the main reason %r such a low AP TPR sulphur recovery is the release of sulphur in the %rm of species other than H2S (mainly SO2, but also some small amounts of volatile thiols and thiophenes including its methyl and ethyl substituted derivatives) [19,25], which can not be recorded by the potentiometric detection system of the AP TPR.…”

“…Total sulphur content was determined by the micro method using thiorine as an indicator [15,16]. The AP TPR analysis was performed according to a procedure described earlier [13], using 40 mg of sample mixed with 60 mg of silica. The hydrogen flow rate was 50 cm3/min, and the temperature was increased at a rate of 5 ~ from 20 1000 ~ The H2S formed at a given temperature was carried by H2 gas out of the system, dissolved in an appropriate basic buffer, and quantified by an S 2-ion selective electrode.…”

“…The oxidised sulphur containing species are analysed by Atmospheric Pressure Temperature Programmed Reduction (AP TPR) [13]. The oxidation products are also studied by Fourier Transform Infrared Spectroscopy (FTIR).…”

Development of a Temperature Programmed Identification Technique to Characterize the Organic Sulphur Functional Groups in Coal

“…It should be noted that at this stage there are only three main groups left behind i.e., pyrite, complex thiophenes and inorganic sulphates. The oxidation temperature ranges as found by [16][17][18][19][20][21][22] for the evolution of SO 2 for these three groups are pyrite (250-380 • C), complex thiophenes (450-600 • C), and inorganic sulphates (above 650 • C), respectively.…”

“…Using Mequinenza lignite, different researchers [16][17][18][19][20][21] used different techniques to study various organic sulphur groups. Table 1 shows the results of these studies.…”