Sulfuric acid lignin, contents

Determination of Lignin Content. Lignin content in plants (wood) is determined by direct or indirect methods (21). The direct method includes measurement of acid-insoluble (ie, Klason) lignin after digesting wood with 72% sulfuric acid to solubilize carbohydrates (22). The Klason lignin contents of representative lignifted materials are shown in Table 2. 

In order to separate lignin from carbohydrates, stronger reagents were used in the expts of Friese et al ( Refs 9 12) for the nitration of wood pulp, namely normal mixed acids. In this way nitrolignin with a higher N content was obtained. When nitric-sulfuric acids (1 2 ratio) were used, a prod contg 8.45% N was obtained with a yield of 55%... 

The CASH process was developed by cooperation between Canada, the USA and Sweden. In this method, hydrolysis occurs in two steps with dilute sulfuric acid at a temperature around 200 °C (pressure 8-25 bar) and the fermentation of sugars by yeast to ethanol. It has been shown that by using SO2 and dilute sulfuric acid in two steps, this increases the sugar and ethanol yield, since the amount of inhibitors such as furfural is decreased. The process was developed for raw materials such as sawdust and other residues from trees. The ethanol yield is about 30% of the energy in the raw material and there are also by-products, with up to 40% of the energy content in solid form (lignin), which can be used as biofuel. 

Fate of Ammonium Ion During Lignin Phenolation. Aliquots (1-5 g) of the reaction products were then diluted with water (200 mL) and analyzed for their ammonium ion content. The procedure comprised treatment with an aqueous solution of NaOH (20% w/v, 100 mL), distillation with collection of the distillate (175 mL) in an aqueous solution of boric acid (4% w/v, 50 mL), and titration with a standard solution of sulfuric acid. The results obtained are compiled in Table I. 

Wet Chemistry and Chromatography. For the analysis of wood, the Klason lignin test, performed in concentrated sulfuric acid, is the accepted method for the determination of lignin content. We performed similar tests using also trifluoroacetic acid (TFA), the results of which are almost identical to those of the Klason tests. TFA has the advantage of allowing further analysis of the saccharides in the acid soluble fraction, as it can easily be evaporated from the solution. 

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