Degrees of polymerization (DP) and DP distribution of dilute acid-hydrolyzed products of alkali-treated native and regenerated celluloses

Abstract

Three groups of cellulose II samples, 20% NaOH-treated native celluloses (M-native celluloses), commercial regenerated celluloses and those treated with 20% NaOH (M-regenerated celluloses), were subjected to dilute acid hydrolysis at 105°C to obtain so-called leveling-off degrees of polymerization (LODP). Molecular mass parameters of the acidhydrolyzed products were analyzed by SEC-MALLS using 1% LiCl/DMAc as an eluent. The LODP values were in the order of M-native celluloses % M-regenerated celluloses [ regenerated celluloses. The LODP values of M-regenerated celluloses are 1.5-1.7 times as much as those of the regenerated celluloses; the cellulose II crystallites in regenerated celluloses increase in size to the longitudinal direction by the alkali treatment and the successive acid hydrolysis at 105°C. This increase in the longitudinal crystal sizes might primarily occur during acid hydrolysis. All the acid-hydrolyzed products had bimodal SEC elution patterns, i.e. the predominant high-molecular-mass and minor low-molecular-mass components, the latter of which corresponded to DP 20.

Analyzing cellulose degree of polymerization and its relevancy to cellulosic ethanol

“…80 Table 6 summarizes some of the samples analyzed by SEC-MALLS with their respective DP values. [80][81][82] Th e samples were dissolved in 8% LiCl/DMI. As shown in Table 6, the samples include native cellulose, such as cotton lint cellulose, algal cellulose, and bacterial cellulose, and a variety of bleached and unbleached pulps (kraft or sulfi te).…”

“…82 Tencel and Bemliese were mercerized (M) (alkalitreated) with 20% NaOH, and acid hydrolyzed in 1 M HCl at . 90 In all likelihood, as our knowledge of ionic liquids grows, especially in regards to the solubilization of biomass, these new solvents will assume greater importance for DP analysis of cellulosic biomass.…”

Preparation and Analysis of Cello- and Xylooligosaccharides

“…According to Isogai et al [100], higher cellooligomers can be isolated from cellulosic starting materials by performing the hydrolysis reaction in a heterogeneous state, exploiting the fact that when celluloses are hydrolyzed in dilute acids at high temperatures they display a rapid and drastic decrease in chain length until they reach a constant value, referred to as the level-off degree of polymerization (LODP) [101]. This LODP behavior is thought to be related to the size of the crystalline zones along the cellulose fiber and is therefore dependent on the species and tissue from which the cellulose originates [102].…”

“…This LODP behavior is thought to be related to the size of the crystalline zones along the cellulose fiber and is therefore dependent on the species and tissue from which the cellulose originates [102]. When alkali-treated native and regenerated celluloses were subject to hydrolysis with 1 M HCl solutions at 105 C for 3 h, the degraded samples (regardless of their origin) showed bimodal size exclusion chromatography (SEC) elution patterns, indicating the presence of a predominant high molecular mass fraction and a minor low molecular mass fraction [100]. The DP values of the former ranged from 35 to about 100; those of the minor fraction from 18 to 24.…”

“…However, as can be demonstrated, the separation performance decreases with a decline in DP, indicating the particular difficulty of analyzing cellooligosaccharides with a DP between 10 and 50. Isogai et al [100] prepared cellooligomers by dilute HCl hydrolysis that had DPs of 18-24 and 35-100 (depending on the DP of the cellulose used). The authors also used SEC to characterize the hydrolyzates.…”