Preparation and characterization of carbamoylethyl hemicelluloses

Abstract

Abstract:The reaction of hemicelluloses, isolated from wheat straw, with acrylamide in alkaline aqueous solution was investigated. The degree of substitution (DS, up to 0.65) of the products could be obtained by adjusting the molar ratios of reagent to xylose unit in hemicelluloses (1.0-10.0) and the molar ratios of catalyst to xylose unit in hemicelluloses (0.5-1.6). Changes in the structure of hemicelluloses were verified by FT-IR and 1 H and 13 C NMR spectroscopies. The results showed that carbamoylethyl groups surely were grafted onto the main chain of hemicelluloses. Moreover, it was also found that the saponification of carbamoylethyl groups to carboxyl groups occurred in alkaline medium. The behavior of modified hemicelluloses was monitored by means of thermo gravimetry (TG) and differential thermal analysis (TGA). It was found that the products had a lower thermal stability than the native hemicelluloses.

Characteristics of the Coagulate Obtained During the Process of Model Wastewater Treatment

“…The chemical shifts at 168.4 ppm represents the C-6 of glucuronic acid residues [19]. The presence of quantities of associated lignin was identified by one weak signal at 182.0 ppm, which originates from the carbonyl group in associated lignin [20].…”

Fractional isolation and structural characterization of hemicellulosic polymers from Caragana sinica

“…In these conditions, carbohydrates are less damaged and delignification is more efficient. However, the chemical structures of lignin and hemicelluloses from shrubs like Caragana sinica are different and less studied compared with sugarcane bagasse [19] and wheat straw [20] in our previous research works. Moreover, the presence of hydroxycinnamic acids, such as p-coumaric and ferulic acids, in the cell walls results in a more difficult characterization of the two polymers from lignocellulosic biomass [21].…”