Sulfite lignins

Sulfite-bisulfite-metabisulfite-sulfurous acid system, 23 672 Sulfite ester, 23 651 Sulfite lignins, 75 15-18 Sulfite oxidation kLaL measurement method, 75 679... 

Commercial lignosulfonates (also called lignin sulfonates and sulfite lignins) are by-products of the treatment of pulp. One of the methods of isolating and purifying them is to add excess slaked lime to spent sulfite liquor. This precipitates calcium lignosulfonates, which are removed by filtration [32.29]. 

Sulfide of sodium. See Sodium polysulfide Sulfinylbis (methane). See Dimethyl sulfoxide Sulfinyl chloride. SeeThionyl chloride Sulfiram. See Tetraethylthiuram sulfide Sulfisomezole. See Sulfamethoxazole Sulfite lignin. See Lignin sulfonate Sulfoacetic acid, 1-dodecyl ester, sodium salt Sulfoacetic acid dodecyl ester S-sodium salt. See Sodium lauryl sulfoacetate 2-Sulfoanthraquinone sodium salt. See Sodium 2-anthraquinone sulfonate Sulfobenzide. See Diphenyl sulfone o-Sulfobenzimide o-Sulfobenzoic acid imide. See Saccharin... 

Poly (lignosulfonic acid) Sulfite lignin Definition A metallic sulfonate salt... 

Uses Surfactant for mineral processing copper/zinc flotation collector Sulfinylbis (methane). See Dimethyl sulfoxide Sulfite lignin. See Lignin suKonate... 

Substitution Reactions on Side Chains. Because the benzyl carbon is the most reactive site on the propanoid side chain, many substitution reactions occur at this position. Typically, substitution reactions occur by attack of a nucleophilic reagent on a benzyl carbon present in the form of a carbonium ion or a methine group in a quinonemethide stmeture. In a reversal of the ether cleavage reactions described, benzyl alcohols and ethers may be transformed to alkyl or aryl ethers by acid-catalyzed etherifications or transetherifications with alcohol or phenol. The conversion of a benzyl alcohol or ether to a sulfonic acid group is among the most important side chain modification reactions because it is essential to the solubilization of lignin in the sulfite pulping process (17). 

The aromatic rings of kraft lignins can be sulfonated to varying degrees with sodium sulfite at high temperatures (150—200°C) or sulfomethylated with formaldehyde and sulfite at low temperatures (<100° C). Oxidative sulfonation with oxygen and sulfite is also possible. 

Further Modifications. There have been attempts to improve the pulp strength and decrease the energy requirement of the groundwood process by the addition of chemicals, eg, sodium carbonate or sodium sulfite. Although some benefits can be obtained, the additional costs and chemical disposal problems have not been justified. Presteaming of wood is practiced in Europe to add moisture and to soften the lignin, which is especially advantageous for certain hardwoods. 

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