The behavior of ash elements of wood in the process of acid hydrolysis of wood

Abstract

Mineral substances, in addition to their great physiological significance in the development of plants, have a significant effect on the processes of chemical and thermochemical processing of wood. In particular, this is important when carrying out acidic hydrolytic processes of the carbohydrate complex and associated processes of acid neutralization with ash elements of plant materials. The study of the behavior of ash elements of wood in the process of acid hydrolysis of wood was the goal of this work. It was shown in the work that the ash substances of birch wood are easily extracted with water and weak acid solutions at room temperature. At the same time, water-soluble substances make up 42.4%, and acid-soluble ones – 63.6% of the total ash content in wood. Analysis of the ability of ash substances of birch wood to neutralize acid showed that complete neutralization is – 72.5 mg-eq/kg dry weight (3.55 g of sulfuric acid per 1 kg of wood); after water extraction – 34.0 mEq/kg, and after extraction with acid solutions – 9.4-13.6 mEq/kg. When carrying out hemicellulose hydrolysis of birch wood, more than 85% of the mass of ash elements of the wood is removed, including more than 85% of calcium salts, 90% of magnesium salts, 90% of phosphorus and 63% of potassium. At the same time, the neutralizing ability of ash was 62.4 mg-eq/kg of dry weight (3.1 g of sulfuric acid per 1 kg of wood). The mode of low-acid hemicellulose hydrolysis of wood, selected on the basis of the data obtained, under the condition of 50% neutralization of sulfuric acid with ash elements (6.25 g/kg of dry raw materials). Showed significantly better indicators in terms of the rate of hydrolysis, the content of monosaccharides and the color of the extract in comparison with autohydrolysis.