Sulfonate group combustion

Methods of determining the sulfonate content of lignin fall into two main classes those typified by conductometric titration, in which sulfonate content is measured directly and those, as represented by combustion/ion chromatography, which measure the sulfur content and assume that all the sulfur is present as sulfonate groups is approximate in many ultra-high-yield sulfite pulps (Katz et al. 1984) but may lead to large errors (Samuelson and Westlin 1947, 1948, Regestad and Samuelson 1958, Schoon 1961, Janson and Sjostrom 1966, Katz et al. 1984). 

Under normal PEMFC operation conditions (<95 C), thermal degradation of membrane ionomer is generally of little concern. Sulfonate groups in PFS A ionomer decompose at approximately 280-300°C (St Pierre et al. 2000). Thermal decomposition of membranes by local combustion can become a potential pathway leading to membrane failures, especially when a pinhole is formed (Aoki et al. 2006a). By exchange of the proton for potassium ion, the thermal stability of Nafion is enhanced (Wilkie et al. 1991). So a heavily contaminated MEA can potentially slow down catastrophic failures. On the other hand, the required contamination level can be so high that the conductivity suffers to an unacceptable level. 

The formation of sulfones, followed by elimination of sulfur as sulfuric acid, has been proposed as a means of removing the organic sulfur from coal prior to combustion. Unfortunately, the formation of a sulfone from sulfur in a thiophene group is rather difficult. However, up to 40% of the organic sulfur in bituminous coal can be removed when the coal is subjected to 1000 psi air at 200°C (390°F) for 1 h, implying that there exists within the coal an appreciable fraction of nonthiophene sulfur from which sulfuric acid is produced ... 

Heavy-duty (HD) additives keep solid combustion and oxidation products in suspension, thus avoiding deposits on metal surfaces, sludge formation and corrosive wear by neutralizing acidic decomposition products. Detergents, some of them RR-based, have sulfonate, hydroxy and/or carboxyl groups and usually contain metal ions or amine functions. More modem HD additives are based on methacrylates of fatty alcohols (Cn-ig), copolymerized with diethylaminoethyl methacrylate (9 1), vinylpyrollidone, N-vinylpyridine and hy-droxyethyl methacrylate. These ash-free dispersants may act also as VI improvers. Extreme-pressure (EP) additives ... 

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