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| Hydrolysis Products Analysis of Polysaccharides of Anthocephalus Indicus Kraft Pulp and Oxygen Treated Pulp Samples | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Paper Id :
16958 Submission Date :
2023-01-10 Acceptance Date :
2023-01-22 Publication Date :
2023-01-23
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| Abstract |
The Polysaccharides chemistry of the alkaline delignification / pulping process involves several complicated reactions. The recent progress in polysaccharide chemistry, in general, has facilities the understanding of the change in Polysaccharides during the pulping process. The initial reaction between alkaline pulping liquor and polysaccharides is a salvation of the hydroxyl group by the hydroxyl ions and water. At the same time the carboxyl groups of the uronic acid are neutralized, and the carboxylate groups are solvated, the salvation results in considerable swelling of the cell wall, facilitates the penetration and diffusion of the pulping liquor and subsequently dissolves out the easily accessible low molecular weight Polysaccharides.
In the present investigation, attempts have been made to understand the behavior of Anthocephalus indicus wood and pulps polysaccharides during alkaline pulping and oxygen treatment during bleaching. Holocellulose was isolated from wood, unbleached, and oxygen-treated pulps of Anthocephalus indicus and subjected to acid hydrolysis for knowing the sugar composition. Analysis of hydrolysis products was performed on gas-liquid chromatography. Acid hydrolysis of holocellulose of Anthocephalus indicus wood, unbleached pulps produced using 12 % and 14 % alkali during pulping, corresponding to kappa number 36.49 and 24.76 and oxygen treated pulps was carried out. Rhamanose, arabinose,xylose, mannose, glucose were identified.
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| Keywords | Anthocephalus Indicus, Delignification, Polysaccharides, Holocellulose. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Introduction |
The polysaccharides composition of bleached and unbleached pulp and paper is an important parameter for the characterization of their chemical and physical properties (Sundberg et.al 2003, Willfor et.al 2005a,b 2009) The alkaline delignification/pulping process involves a number of complicated reactions. The initial reaction between alkaline pulping liquor and polysaccharides is a salvation of the hydroxyl group by the hydroxyl ions and water. At the same time, the carboxyl group of the uronic acid is neutralized and the carboxylate groups are solvated, the salvation results in considerable swelling of the cell wall, which facilitates the penetration and diffusion of the pulping liquor (Stone 1957) and subsequently dissolves out the easily accessible low molecular weight polysaccharides. The lignocellulosic material contains a considerable amount of xylan, e.g hardwood and agricultural residues. The alkaline hydrolysis of the acetyl group also occurs at the early stage of pulping probably immediately when in contact with pulping liquor.
In the alkaline pulping the chemical degradation of the polysaccharide chain has been shown partly an alkaline hydrolysis of glycoside bonds (Corbett and Richards,1957) and partly a reaction starting at the aldehydic end groups and proceeding as a successive “ peeling off” of the terminal units under formation of iso-saccharinic and other hydroxyl acids(Kenner 1957). The peeling off proceeds until a rearrangement of the polysaccharide terminal unit to a meta saccharinic acid configuration or until the degradation reached to monomer substituted in the 2 positions, the later is the case with xylan, which is frequently substituted by methyl glucouronic acid units in the 2 positions. This is one of the reasons why xylan is fairly hot alkali resistant. However alkaline hydrolysis of the glycosidic bond at 170 oC always forms new starting points for peeling-off reactions. Thereby monosidic bonds have been found to be considerably more resistant than are glucosidic, galactosidic, and xylosidic bonds (Lindberg 1958). There are differences in the rate of hydrolysis of polysaccharides due to differences in the reactivity rate of the glycosidic linkages. The type of monosaccharide, anomer linkage neighboring activating and deactivating groups, and their positions and the hydrogen bond are major influencing factors ( Yoneda et.al 2016, will for et.al 2005).
Apart from these chemical differences in the behavior of the various polysaccharides in the alkaline pulping crystalline of cellulose being to a considerable extent is less accessible to degradation than amorphous Hemi cellulose. The later, however, degraded to liner fragments with definite crystallization tendency. The behavior of xylan during the alkaline pulping indicates that xylan loses some of its bulkier substituents at a fairly early stage where after somewhat degraded xylan is adsorbed in the fiber walls in a less accessible state that in the native form, possibly by an inter crystallization with the cellulose at the microfibril surfaces. However, the alkaline hydrolysis of acetyl groups and removal of uronic acid groups are the prerequisite for the re-precipitation of xylan as these form irregularities in the straight chain configuration of polysaccharide
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| Objective of study | In the present investigation, attempts have been made to understand the behavior of Anthocephulus indicus wood and pulps polysaccharides during alkaline pulping and oxygen treatment. The knowledge about the polysaccharides of pulp and paper samples is essential for their characterization, further processing, and understanding various properties viz tensile index, tear index, burst index, etc. As all physical properties of paper depend upon carbohydrate composition. |
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| Review of Literature | Chemically wood is comprised mainly of three macromolecular
species cellulose, hemicelluloses, and lignin. Pulps contain hemicelluloses
along with cellulose with traces of lignin. Knowledge about the polysaccharide
composition is very important in material characterization (Swiatek et.al 2020, Willfor et.al 2005a,b 2009, Sundberg et.al
2003). Polysaccharide composition is determined by acid hydrolysis and
qualitative and quantitative analysis of monomers by different analytical
methods (Nitsos et al 2019, Haykiri-Acma et al 2019, Black and Fore 1996). Cleavage of the glycosidic bonds of the
polysaccharides occurs during hydrolysis and releases the monomers of
polysaccharides. Acid hydrolysis is mostly preferred by means of sulphuric
acid, trifluoroacetic acid, etc.( Vedovatto et al 2021, Bose et.al 2009, Galant et.al 2015, Sundberg et. al 1996,
Marques et.al 2010). The main advantage of acid hydrolysis is the high
conversion, shown in the complete solubilization of the starting raw material
and commonly called “ total hydrolysis”. Substrates that are resistant to
hydrolysis because of high crystallinity or poly uronic acid are reliably
converted. |
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| Main Text |
Experimental Polysaccharides composition of wood, unbleached and
oxygen-treated pulp of Anthocephulus indicus :
Holocellulose was isolated by the standard method (Wise et.al) and subjected to
acid hydrolysis Total hydrolysis of holocellulose (
Seamen et.al,1954, Bose et.al 2009) Holocellulose (0.10 g) was weighed and transferred to a
test tube and 72 % sulphuric acid (W/W) (1ml) was added. The test tube was
placed in a water bath at 20oC and the mixture was stirred
occasionally with a glass rod to promote dissolution. After 1 hour the
hydrolysate was poured into a beaker (100ml) was diluted with distilled water
to 28ml. The beaker was covered with a glass plate was autoclaved at 120oC
for 1 hour. The resulting solution was cooled and diluted to 80ml. This
solution was neutralized by adding a suitable quantity of anion exchange resin
(IR-45,20-50 mesh). After washing the resin with distilled water (1.25 ml), the
resulting solution was evaporated to dryness in a vacuum evaporator. Finally,
water was added to give a volume of 5 ml. Reduction and acetylation (
Steward et.al 1973) To the above solution, sodium borohydride (20mg)was added
and the solution was allowed to stand for 4 hours. The sodium ions were by
adding a small amount of cation exchange resin ( Dowex 50,50-100 mesh). After standing
for 5 minutes the solution was filtered through a sintered crucible and the
resin was washed with water: ethanol (1:1 V/V) mixtures (5 X 3ml). The filtrate
and washing were collected and evaporated under a vacuum to dryness. Alditols
(reduced product), thus obtained were refluxed for 4 hours with a mixture
containing equal amounts of acetic anhydride and pyridine (2ml). The acetylated
sample was poured into ice-cold water and alditol acetates were isolated with
methylene chloride (2X10ml) methylene chloride was evaporated to get a
concentrated solution of alditol acetates thus obtained, which was
chromatographed. Gas-liquid chromatography of hydrolysis products Analysis was performed on a Perkin Elmer model 3920B chromatograph equipped with a glass column and a flame ionization detector. To facilitate the identification of individual mono sugar. CO-GC of individual mono sugar was performed and peak enhancement was noted besides comparing the retention time of individual sugar with those of the reference sample. The relative percentage of each sugar was calculated on peak area bases. |
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| Result and Discussion |
Acid hydrolysis of holocelloluse of Anthocephalus
indicus wood, unbleached pulp producing using 12 5 and 14% alkali
during pulping corresponding to kappa number 36.49 and 24.76, and
oxygen-treated pulps were carried out. Rhamnose, arabinose, xylose, mannose,
galactose, and glucose were identified by gas chromatography. In each case, the
relative percentage of glucose was exceptionally high as compared to another
constituent (Table- 1). It is expected that a major portion of the glucose
might have been generated from the cellulose while hemicelluloses may have
contributed for a small portion. The relative percentage of xylose was higher except for
glucose as compared to other neutral sugar. It was 21.42 % for wood, 14.62 %,
and 13.57% for unbleached pulps produced using 12 5 and 14% alkali during
pulping and it was 12.63 % and 11.20 % for respective oxygen-treated pulps.
These data reveal that the main hemicelluloses of Anthocephalus
indicus was xylan, presence of other monomers viz. Rhamnose,
arabinose, mannose, galactose, and glucose indicated the presence of other
hemicelluloses in minor quantities along with a substantial amount of
cellulose. Comparison of Sugar Composition of Wood, unbleached
pulps, and Oxygen treated pulps Results recorded for the sugar composition of Anthocephalus
indicus wood holocellulose revealed that wood contains a comparatively
higher amount of xylose (21.42%) as compared to 14.62 % and 13.57% for
unbleached pulps producing using 12 % and 14% alkali during pulping. It was
further decreased to 12.63 % and 11.20 % for respective oxygen-treated pulps,
suggesting that during the course of pulping the hemicelluloses , xylose might
have undergone chemical degradation leading to a decrease in relative
percentage. xylose in pulp and further degradation during oxygen treatment. The
relative percentage of rhamnose 0.54, 0.25, 0.20, traces and traces, arabinose
1.05, 0.40, 0.27, traces and traces mannose 2.14, 1.55, 1.50,1.48 and1.42,
galactose 2.37, 1.89, 1.80, 1.72 and 1.50 and glucose 72.48, 81.29, 82.66,
84.07 and 85.55 for wood dust, unbleached pulps producing using 12 % and
14% alkali during pulping and their oxygen treated pulps respectively. The
descending trend in the relative percentage of these mono sugar except glucose
which exhibited ascending trend indicated that almost all the hemicelluloses
suffered degradation during pulping and subsequent oxygen treatment stage.
Ascending trend exhibited by the glucose may be attributed to the more
resistant nature of cellulose during pulping and subsequent oxygen treatment
stage as compared to hemicelluloses. A perusal of data for the ratio of xylose to other of
mono sugar revealed that the xylose to rabinose ratio was increased while
xylose to mannose and xylose to galactose ratio was decreased on pulping and
subsequent oxygen treatment ( Table-2). These results indicated that perhaps
rahaminose and arabinose-containing hemicelluloses are more labile to degradation
during pulping and subsequent oxygen treatment stages as compared to main
hemicelluloses xylan. While hemicelluloses containing mannose and galactose are
comparatively more resistant to alkaline degradation and even in the subsequent
oxygen treatment stage. The decreasing trend in xylose to glucose may be due to
the more resistant nature of cellulose during pulping and subsequent oxygen
treatment stage. Table 1 Sugar composition of Anthocephalus
indicus wood, unbleached and oxygen-treated pulps
Table 2 Ratio of Xylose to
other mono-sugar
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| Conclusion |
Characterization of the acid hydrolysis product of holocellulose of Anthocephalus indicus concluded that xylan is the hemicelluloses that are labile to degradation during pulping and subsequent oxygen treatment. However, hemicelluloses containing rhamnose and arabinose are comparatively more labile to degradation while hemicelluloses containing mannose and galactose are comparatively more resistant to degradation as compared to xylan during pulping and subsequent oxygen treatment. |
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