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Acid hydrolysis
About: Acid hydrolysis is a research topic. Over the lifetime, 5640 publications have been published within this topic receiving 123998 citations.
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TL;DR: In this article, a rapid, high-yield process was proposed to obtain an aqueous stable colloid suspension of cellulose nanocrystals/whiskers. But the results of the process were limited by the concentration of MCC and sulfuric acid, the hydrolysis time and temperature, and ultrasonic treatment time.
Abstract: The objective of this work was to find a rapid, high-yield process to obtain an aqueous stable colloid suspension of cellulose nanocrystals/whiskers. Large quantities are required since these whiskers are designed to be extruded into polymers in the production of nano-biocomposites. Microcrystalline cellulose (MCC), derived from Norway spruce (Picea abies), was used as the starting material. The processing parameters have been optimized by using response surface methodology. The factors that varied during the process were the concentration of MCC and sulfuric acid, the hydrolysis time and temperature, and the ultrasonic treatment time. Responses measured were the median size of the cellulose particles/whiskers and yield. The surface charge as calculated from conductometric titration, microscopic examinations (optical and transmission electron microscopy), and observation of birefringence were also investigated in order to determine the outcome (efficiency) of the process. With a sulfuric acid concentration of 63.5% (w/w), it was possible to obtain cellulose nanocrystals/whiskers with a length between 200 and 400 nm and a width less than 10 nm in approximately 2 h with a yield of 30% (of initial weight).
1,251 citations
TL;DR: In this paper, a biphasic system was used to produce 5-hydroxymethylfurfural (HMF) and furfural derivatives from renewable biomass-derived carbohydrates.
1,097 citations
TL;DR: For more accurate comparison of different pretreatment methods it is necessary to improve the assessment methods under real process conditions, as the various pret treatment methods give different types of materials.
Abstract: Second-generation bioethanol produced from various lignocellulosic materials, such as wood, agricultural or forest residues, has the potential to be a valuable substitute for, or a complement to, gasoline. One of the crucial steps in the ethanol production is the hydrolysis of the hemicellulose and cellulose to monomer sugars. The most promising method for hydrolysis of cellulose to glucose is by use of enzymes, i.e. cellulases. However, in order to make the raw material accessible to the enzymes some kind of pretreatment is necessary. During the last few years a large number of pretreatment methods have been developed, comprising methods working at low pH, i.e. acid based, medium pH (without addition of catalysts), and high pH, i.e. with a base as catalyst. Many methods have been shown to result in high sugar yields, above 90% of theoretical for agricultural residues, especially for corn stover. For more recalcitrant materials, e.g. softwood, acid hydrolysis and steam pretreatment with acid catalyst seem to be the methods that can be used to obtain high sugar and ethanol yields. However, for more accurate comparison of different pretreatment methods it is necessary to improve the assessment methods under real process conditions. The whole process must be considered when a performance evaluation is to be made, as the various pretreatment methods give different types of materials. (Hemicellulose sugars can be obtained either in the liquid as monomer or oligomer sugars, or in the solid material to various extents; lignin can be either in the liquid or remain in the solid part; the composition and amount/concentration of possible inhibitory compounds also vary.) This will affect how the enzymatic hydrolysis should be performed (e.g. with or without hemicellulases), how the lignin is recovered and also the use of the lignin co-product.
996 citations
TL;DR: The periodate-resorcinol method was substantially more sensitive than the resorcinl procedure, was not affected by lipids, amino acids, or sugars, and could be used to detect free or glycosidically bound sialic acids on paper chromatograms.
969 citations
TL;DR: It is demonstrated here that only low pH reaction conditions favor the deamination of N-sulfated D-glucosamine residues; the reaction proceeds very slowly at pH 3.5 or above and at room temperature solutions of nitrous acid lose one-fourth to one-third of their capacity to deaminate amino sugars in 1 h at all pHs.
Abstract: In the reactions used to break heparin down to mono- and oligosaccharides, androsugars are formed at two stages. The first of these is the well-known cleavage of heparin with nitrous acid to convert the N-sulfated D-glucosamines to anhydro-D-mannose residues; this reaction has been studied in detail. It is demonstrated here that only low pH (less than 2.5) reaction conditions favor the deamination of N-sulfated D-glucosamine residues; the reaction proceeds very slowly at pH 3.5 or above. On the other hand, N-unsubstituted amino sugars are deaminated at a maximum rate at pH 4 with markedly reduced rates at pH2 or pH6. At room temperature solutions of nitrous acid lose one-fourth to one-third of their capacity to deaminate amino sugars in 1 h at all pHs. A low pH nitrous acid reagent which will convert heparin quantitatively to its deamination products in 10 min at room temperature is described, and a comparison of the effectiveness of this reagent with other commonly used nitrous acid reagents is presented. It is also shown that conditions used for acid hydrolysis of heparin convert approximately one-fourth of the L-iduronosyluronic acid 2-sulfate residues to a 2,5-anhydrouronic acid. This product is an artifact of the reaction conditions, and its formation represents one of several pathways followed in the acid-catalyzed cleavage of the glycosidic bond of the sulfated L-idosyluronic acid residues.
856 citations