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Product temperature, effect from wood

Acid hydrolysis of the polysaccharide portion of wood will release lignin but also causes major condensation reactions in the product(2l). These reactions can be minimized by using 41 wt. percent hydrochloric acid in place of other mineral acids but some condensation reactions still occur(22). This is not an effective method by which to obtain unaltered lignin. On the other hand, lignin can be solvent extracted from wood at temperature of 175°C using solvent mixtures such as 50/50 by volume water/1,4-dioxacyclohexane(23) Changes in lignin under these conditions appear to be minor. [Pg.178]

Most experimental results reported in literature were obtained using commercially available activated carbons. A few other studies were carried out with self synthesized activated carbons derived from different natural organic materials. The preparation of activated carbons consists of two main stages termed carbonization and activation, and the choice of conditions under which these processes are carried out, gives practically infinite number of combinations. The temperature, time and atmosphere (the nature of the gas or gas mixture, and its pressure or flow rate) are the main variables. Moreover, different additives can be added before or between these processes to modify the final product. Wood and coal are the most common precursors, but sorption properties of activated carbons derived from other materials, e.g. coconut shells or plum kernels can be also found in literature. Although the precursor material certainly has some effect on the adsorption properties of activated carbon, these properties are chiefly defined by the conditions of thermal treatment and purification vide infra). Therefore statements like, "activated carbon from coconut shells has higher affinity to certain adsorbate than activated carbon from wood" are misleading and they should be avoided. [Pg.710]

Extraction of hemiceUulose is a complex process that alters or degrades hemiceUulose in some manner (11,138). Alkaline reagents that break hydrogen bonds are the most effective solvents but they de-estetify and initiate -elimination reactions. Polar solvents such as DMSO and dimethylformamide are more specific and are used to extract partiaUy acetylated polymers from milled wood or holoceUulose (11,139). Solvent mixtures of increasing solvent power are employed in a sequential manner (138) and advantage is taken of the different behavior of various alkaUes and alkaline complexes under different experimental conditions of extraction, concentration, and temperature (4,140). Some sequences for these elaborate extraction schemes have been summarized (138,139) and an experimenter should optimize them for the material involved and the desired end product (102). [Pg.33]

Helmut Orth first reported the use of laetones to accelerate phenolic resole cure in 1957 [161]. A year later, Orth discovered that this effect could be extended to aliphatic esters as well [162], Despite the dramatic nature of the acceleration seen, Orth s observations were not applied in industry for a decade. In 1967, Sumitomo and BASF applied esters to soil grouting and wood uses [133,163, 164]. Neither of these applications were commercially successful, however, and commercial success would not occur until 1980 when Borden introduced ester-cured sand binders for foundry [165]. This technology was highly successful in UK and spread to the US, where it was applied immediately to foundry in 1981 and eventually to wood products in 1990 [119,166-173]. Esters are capable of reducing the gel times of resoles from several weeks to less than 30 s at room temperature. Both gaseous and liquid esters are applicable [119,166]. [Pg.916]

Figures 6.5 to 6.7 show the effect of temperature on yields of + paraffins obtained from biomass samples by pyrolysis. As can be seen in Figs. 6.5 to 6.7, the percentage of + paraffins in gaseous products obtained from the samples of hazelnut shell, tea waste and spmce wood increased, while the final pyrolysis temperature was increased from 700 to 950 K. Figures 6.5 to 6.7 show the effect of temperature on yields of + paraffins obtained from biomass samples by pyrolysis. As can be seen in Figs. 6.5 to 6.7, the percentage of + paraffins in gaseous products obtained from the samples of hazelnut shell, tea waste and spmce wood increased, while the final pyrolysis temperature was increased from 700 to 950 K.

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See also in sourсe #XX -- [ Pg.74 ]




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