Pine, acidic hemicelluloses

Xyloisosaccharinic acid [2,4-dihydroxy-2-(hydroxymethyl)butanoic acid] is one of the major, alkaline-degradation products of wood xylan, in particular, that of birch. The disaccharide, 2-O-D-xylopyranosyl-L-arabinose, which was isolated as a hydrolysis product of corn-cob hemicellulose, is readily degraded at 100° in 15 mM Ca(OH)2 to acidic products, primarily saccharinic acids. Xylan oligosaccharides from corn-cob hemicellulose produced 2,4-dihydroxy-2-(hydroxymethyl)buta-noic acid when exposed to 0.02 M Ca(OH)2 at 25°. However, it was noted that the xylan, itself, was stable at 100° in Af NaOH. The major acidic component of the hemicellulose fraction of slash pine Pinus el-liotti) after acid hydrolysis was identified as 4-O-methyl-D-glucuronic... 

The basic experiment that demonstrated the effects of molecular ordering is a rather simple one. Southern pine chips were delignified using the acid chlorite process at 60°C, then extracted with caustic solutions to remove the hemicelluloses. The pulp was then divided into two batches. One was used as a control the other was immersed in distilled water inside stainless steel vessels and heated through the temperature cycle of a typical kraft cook. During this cycle, the pulp was held at 170°C for approximately 2 h. The two batches of pulp were then used to make handsheets, and their papermaking properties were compared. 

Further studies on hemicelluloses of hardwoods have shown that these may exhibit a considerable range in the content of xylan and 0-methylhexuronic anhydride. In a recent review of hemicelluloses, Wise suggests that hardwood hemicelluloses may have a rather simple, architectural pattern, consisting predominantly of n-xylose units and smaller amounts of 0-methyluronic acid units. Softwood hemicelluloses also contain this fundamental structural unit consisting of a mono-O-methyluronic acid in combination with n-xylose units. In the case of pine, this fundamental unit may be associated with a part of the maiuian. ... 

Wise and RatlilF extracted slash pine Pinus caribaea) chlorite holocellulose at 20° with increasing concentrations of aqueous potassium hydroxide. In the range of 2 to 10% potassium hydroxide, the larger part of the hemicelluloses dissolved. Thereafter, less material dissolved, and above 16% potassium hydroxide, the weight of residue remained constant. The hemicelluloses could be recovered quantitatively by acidification of the alkaline extracts with acetic acid, followed by precipitation with an excess of ethanol. For the practical purposes of analysis, Wise and Ratliff chose to divide the... 

Acid-catalysed depolymerisation of cellulose and hemicellulose in pine wood using [C2mim][Cl] produces a range of water-soluble products such as monosaccharides, oligosaccharides, furfural and hydroxymethylfurfural, with 97% conversion of cellulose after 2 hours at 120 °C [210], Maximum yields of 11% monosaccharides, 3% hydroxymethylfurfural and 0.5% furfural were reported, however, separation of products was acknowledged to be a major problem for practical application, considering the polarity of both the products and the ionic liquid. 

Within the GC detectable range, we identified the different composition of the liquid products from the various origins by using a GC-MS analysis. The liquid products from Kraft pine lignin contain mainly guaiacol and methyl dehydroabietate. The liquid products from oat hull, hardwood, and switchgrass contain acetic acid, 1-hydroxy-2-propanone, and/ or furfural, which are the products of hemicellulose and cellulose. This further confirms that these three materials contain hemicellulose and cellulose. The liquid products have only two to three component differences from one biomass species to another. But the composition distributions are quite different among species (Table 4). So the composition of liquid products depends on the type of raw materials. 

Acetic acid, formic acid and ievulinic acid are the most common carboxylic acids found in the hydrolyzates. Acetic acid is not only a by-product of hydrolysis (45) but is also a well-known by-product in fermentation (46). Acetic acid is mainly formed from acetylated sugars in the hemicellulose, which are cleaved off already at mild hydrolysis conditions. Therefore, die acetic acid yield in the hydrolysis does not significantly depend on the severity of the hydrolysis process (2). Hydrolysis of hardwoods (alder, aspen and birch) at 198-234°C, 0.5 g/1 H2SO4, and 33% wood dry materials for 7 min resulted in approximately 10 g/l acetic acid, whereas the hydrolysis of softwoods (pine and spruce) produced 3 g/1 acetic acid at similar conditions (2). 

Isol. from partial acid hydrolysates of gum chagual (Puya spp.) and the hemicelluloses from corn hulls, wheat straw, wheat bran and maritime pine (Pinus pinaster). Amorph. -hlOl (88) (H2O). 

C12H22O11 342.299 Structural unit in the glucomannans of plant hemicelluloses. Isol. from the partial acid hydrolysates of the glucomannans from Amorphophallus spp., white spruce (Pinus glauca), western hemlock (Tsuga heterophylla), red maple (Acer rubrum), eastern white pine (Pinus strobus), larch (Larix decidua), jack pine (Pinus bank-siana) and from Narcissus tazetta from hemicelluloses of lobolly pine (Pinus taeda) and in trace amounts from the acetolysates of the a-celluloses from white birch (Betula papyrifera) and slash pine... 

C12H20O11 340.283 Isol. from partial acid hydrolysates of maritime pine Pinus pinaster), birch (Betula verrucosa) and Scandinavian spruce (Picea abies) hemicelluloses. 

Isol. from the partial acid hydrolysates of white spruce (Picea glauca), western hemlock (Tsuga heterophylla), jute fibre, maritime pine (Pinus pinaster), aspen (Populus tremuloides) hemicelluloses. 

Wood pulp (kraft pulp) from a mixture of spruce and pine was supplied from Sddra Cell Tofte, Norway. It is composed of eellulose and hemicellulose. The pulp was dissolved in trifluoroacetie acid (TEA) to a concentration of 1 wt%. The disso-... 

---