Acidic pulp

Although acidic pulping methods have largely been displaced over the past 50 years by neutral and alkaline processes, there is still a significant amount carried out. Acid sulfite pulping uses combinations of sulfur dioxide and water at high temperatures and pressures. An appropriate base is used to control the pH and, although usually acidic, it is possible to perform these reactions at neutral or even alkaline pH. The most active nucleophile present is the bisulfite ion,... 

The effect of chemical delignification on the carbohydrate fraction is predominantly that of pH, and it is important therefore to consider separately degradation in alkali and in acidic pulping systems. 

Figure 3.19 The hydrolysis of carbohydrate during acid pulping.

Nonconventional pulping methods such as solvent pulping, acid pulping, and biopulping are discussed in subsection 10.9.1. 

The oxidative procedures involve alkaline nitrobenzene, nitric acid, and molecular oxygen under acidic, neutral, and mildly alkaline conditions. Dilute nitric acid solutions were used under the conditions of the nitric acid pulping process. The analytical procedures which have been developed include gas-liquid chromatography (GLC) for quantitative analy-... 

Roll Est. Loss, Folds/hr xio-o (28.9° C) Acidity Pulp a-Cellulose Recycled Fiber... 

Davies JL, Nakatsubo F, Murakami K, Umezawa T (1987) Organic acid pulping of wood IV Reactions of arylglycerol fi guaiacyl ethers Mokuzai Gakkaishi 33 478-486 Deobald LA, Crawford DL (1987) Activities of cellulase and other extracellular enzymes during lignin solubilization by Streptomyces vindosporus Appl Microbiol Biotechnol 26 158-163... 

Ede RM, Brunow G (1989) Formic acid/peroxyformic acid pulping II Synthesis of 3 aryl 2,3 dihydro 7 methoxy-2-benzofuranmethanols - model compounds for lignin acidolysis products Holzforschung 43 127-129... 

Davies JL, Nakatsubo F, Murakami K, Umezawa T (1987) Organic acid pulping of wood. IV. 

The baobab fruit pulp is probably the most important foodstuff. It can be dissolved in water or milk. The hquid is then used as a drink, a sauce, a fermenting agent in local brewing, or as a substitute for cream of tartar in baking. The fruit pulp has a very high vitamin C content and is a rich source of calcium. The acidic pulp is rich in pectin, contains a high amount of carbohydrate, is low in protein, and extremely low in fat. Nevertheless, the fruit pulp can be considered as a rich source of amino acids and linoleic acid. It contains a very low amount of a-hnolenic acid and iron. 

Sulfide emissions may of course be bypassed altogether by a change of the pulping process to avoid the use of sulfide [49]. Both the old soda process and nitric acid pulping suffer from the inferior strength properties of the pulps produced. Use of anthraquinone with basically a soda pulping procedure could put this alternative on a more competitive basis, but has not been adopted [50]. So this is not a practical option. 

Kubo, S. Uraki, Y. Sano, Y. Preparation of carbon fibers from softwood lignin by atmospheric acetic acid pulping. Carbon 1998, 36 (7-8), 1119-1124. 

Production of alkylated celluloses requires material free of other polysaccharides, so dissolving pulps , produced under acid pulping conditions which remove... 

Darmstadt, W. J., and Tomlinson, G. H. (1960). Magnesia Base Pulping and Recovery, Presented before the Acid Pulp Session of TAPPI, February, 23. The Babcock Wilcox Company Bulletin BR-751. 

The acid pulping process uses sodium bisulfite or magnesium bisulfite in a pulp digester at a pH of 3. Type 316 stainless steel is normally used as a minimum alloy because the sulfur dioxide can be converted into sulfuric acid. Sulfuric acid can corrode the stainless steel depending on the pH, temperatiire, and pressure of the system. SCC has been observed in the HAZ of weldments in the pulp digesters in the presence of sodium hydroxide. Because of SCC susceptibility of the austenitic stainless steels, duplex stainless steel 2205 is often used in pressure vessels and tanks. 

Organosolv lignin obtained with a mixed formic and acetic acids pulping technique [9] is bound to present a number of formylated and acetylated phenolic and aliphatic hydroxyl groups. The results in Table 1 confirm this by the evidence of esterification by formyl and acetyl groups mainly of the aliphatic but also of the phenolic... 

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