Semi cellulose (hemicellulose) is composed of several different types: Monosaccharide
A heterogeneous polymer, the sugar is five carbon sugar and six carbon sugar, including sugar, xylose and galactose in Arabia. Hemicellulose xylan accounted for 50% of the total in the woody tissue, it combined on the surface of cellulose micro fibers, and connected with each other. These fibers constitute a connected hard cell network.
Hemicellulose brief introduction Plant cell wall
A small interstitial cellulose fiber gel polysaccharide group removed Pectin
Outside of the material, which is The primary wall
The main component of. Including glucose, xylose
, Arabia sugar
And galactose etc., Monosaccharide
Among the polymers respectively covalent bond
, hydrogen bond
, ether and ester linkages, and they Extensin
And other structural protein, enzyme, cellulose and wall pectin
A cell wall with certain hardness and elasticity, and has stable chemical structure. It is from the total cellulose
In general the polysaccharide components 17.5%NaOH and 24%KOH extracted, and there is no specific chemical structure of the corresponding. Alkali extraction liquor with acetic acid neutralization precipitation is part of hemicellulose A with ethanol supernate is part of hemicellulose B. As an important polysaccharide in Xylan
, Arabia xylan
, Grape Mannan
, Arabia galactosan
Hemicellulose with hydrophilic properties, which will cause the cell wall swelling, with elastic fiber. In the sheet forming process for fiber structure and inter fiber Binding force
. Therefore, the influence of the adding of hemicellulose adsorbed on the surface of fibers, have influence on the strength of paper. pulp
Retain or join in favor of Hemicellulose beating
This is because, more easily than cellulose hemicellulose hydration swelling, hemicellulose adsorption to cellulose, increase the fiber swelling and elastic grinding, instead of being cut off the fine fiber, it can reduce the strength of pulp beating energy consumption, get ideal.
Hemicellulose executive summary
Hemicellulose (hemicellulose): refers to the plant cell wall and symbiosis, soluble cellulose alkali
In case of acid liquid, after much more easy to that part of the hydrolysis of plant cellulose polysaccharide. A plant usually contains several by two or three Sugar
Semi cellulose, the chemical structure of the same. The hemicellulose content of tree stems, branches, roots and bark and composition is also different. Therefore, hemicellulose is the name for a class of substances.
A sugar based hemicellulose are D- based, D- based, xylose mannose D glucose, D- galactose, L- Arabia, 4-O- -D- glycosyl methyl glucuronide, D- galacturonic acid group and D- glucuronide, L- and a small amount of rhamnose, fucose and L-. Hemicellulose is mainly divided into three categories, namely poly xylose
Class, poly and poly saccharide grape Mannan Galactose
Grape nectar sugar.
Hemicellulose The technology of sugar
1,4- is the -D beta pyranose form xylose backbone, with 4 - methyl - oxygen pyranose glucuronic acid polysaccharide chains. Its structure is as follows:
Type X beta beta -D- pyran type xylosyl; (H3CO) 4GA 4- - pyran type oxygen methyl glucuronide; hardwood A and B are oxygen acetyl; softwood A alpha -L- furan type Arabia sugar, B hydroxyl.
Hardwood and Gramineae
Hemicellulose grass is mainly this kind of polysaccharide, polysaccharide in Gramineae hemicellulose, often also contain L furan glycosyl as a branch connection in Arabia polyxylose backbone. How many different plants with branched chain.
Hemicellulose Poly grape nectar sugar
D is composed of mannose glucopyranose base and pyranose base with 1,4- beta type connection into the main chain. Another kind of grape sugar and galactose mannose D - galactopyranose base with branched chain in the form of 1,6- alpha mannose type connection number of D- - and D - pyran type glucopyranose base is on the main chain, their structures are as follows:
Poly grape mannose structure
Type G beta beta -D - glucopyranose base; M beta beta -D was mannose pyranose radical; hardwood A and B are hydroxyl groups; softwood A alpha -D - galactopyranose base, B acetyl oxygen.
Softwood hemicellulose with poly galactose mannose carbohydrate based grape. Based on the main chain and glucose mannose
Based on the molecular ratio for different kinds of wood between 1:1 to 1:2 changes. Most of the average wood hemicellulose The degree of polymerization
No chemical bond between cellulose and hemicellulose, hydrogen bonding and inter Vander Wa Alsley
Hemicellulose and lignin
May connect with benzyl ether in the form of lignin carbohydrate complex formation, for example:
Hemicellulose widely exists in plants, containing 15% ~ 20% softwood, hardwood and grasses containing from 15% to 35%, but its distribution for plant species, maturity, and earlywood cell types and morphological parts are different. for example Softwood
The main hemicellulose is poly Galactose
Grape sugar and nectar, hardwood and grasses is the technology of sugar; softwood and hardwood timber radial
Cells containing more than cell and fiber cell tube technology in sugar; softwood cell Secondary wall
The middle leaves, sugar content is the lowest in the secondary wall and the inner layer is high, and the distribution of poly ctose grape sugar dew on the contrary.
The chemical pulping process any plant material, at the same time in the delignification of hemicellulose can occur or acidic hydrolysis, alkaline hydrolysis, peeling reaction and oxidation reaction, while hemicellulose dissolution and cooking can be adsorbed on the deposition of pulp, but will lose a certain number, greatly influence the properties of semi cellulose and residue the pulp, it can increase the pulp tensile strength, elastic modulus and transparency, but had no effect on the tear strength. In the business Cellulose derivatives
With the pulp when required to remove hemicellulose as far as possible.
The industrial utilization of hemicellulose is developing, pulping waste liquor can be extracted and yeast, yeast 10% Ribonucleic acid
Then, derived for single phosphate guanosine and inosine monophosphate, can be used as Flavoring agent
Or, anticancer agents antiviral
Agent. Law is the first use of forest chemicals organic acid
The fiber raw material pretreatment hydrolysis
Still, the hydrolysis residue can not pre pulping, quality and hydrolysis of pulp comparable to that from the hydrolysate could be isolated from the pentose and hexose components, the xylose
After treatment. xylitol
That can be used as sweetener, plasticizer, surface active agent for acid; xylose An adhesive
; polyxylose sulfate can be used as anticoagulants.
Hemicellulose alcohol fermentation is the use of biological technology, the plant fiber raw materials for producing ethanol renewable, has been a hot topic of international concern. This project is based on the Corn Cob core as raw materials by dilute acid hydrolysis of hemicellulose into the Pentose
Further, fermentation alcohol
. The overall level of China initiative, the international advanced. This technology in the success of the test will be to promote the development of the China alcohol industry, are of great significance to resolve the problem of humanity will face the energy crisis, food shortage and environmental pollution etc..
Hemicellulose Effect of cigarette paper
Hemicellulose is wood pulp
One of the main components, and are connected by 1, 4 - beta glycosidic bond glucose consisting of cellulose, hemicellulose by various carbohydrates and sugars and pentose. In addition, Monosaccharide
Connection between are very different.
The purpose of this study is to investigate the difference of hemicellulose content in a variety of wood pulp, and the influence of these differences on the thermal properties of the pulp and paper of cigarette. In order to determine the content of hemicellulose pulp, semi cellulose by 18% NaOH
The solution extraction, then adjust the precipitation of pH to 7. After the separation, by 100 to 200 DEG C for heat extraction and in the range of 300 ~ 700 DEG C within the pyrolysis experiment, the thermal properties of hemicellulose obtained from various pulp were studied.
In order to analyze the composition of carbohydrates, semi cellulose Three fluorine acetic acid
Hydrolysis. use Ion exchange chromatography
For sugar analysis, using pulse current
The test results showed that there were significant differences between the different pulp. Half cellulose, wood pulp can be divided into three categories: long, short cellulose pulp and wood pulp cellulose pulp plant. The content and composition of pulp hemicelluloses have differences, these differences determine the thermal properties of pulp and thermal properties of cigarette paper.
Hemicellulose Extraction method
from Plant fiber
The method of hemicellulose extraction, the steps are: plant fiber, alkali and water mixed into the reaction kettle with stirring device and the heating system, will Reaction kettle
The temperature rose to 35 to 85 DEG C, while the speed of 300rpm ~ 2000rpm, 10s ~ 10min mixing, filtering or by conventional methods centrifugal
The supernatant or filtrate, extracting hemicellulose; to extract hemicellulose into the 2 to 3 times the volume of 80% to 95% ethanol soluble hemicelluloses, conventional filtration, collecting product and drying, half cellulose. The concentration of the method of the invention of the reactants reactant extraction method requires a concentration higher than water, use a lot of water does not require extraction, significantly reduces the cost of extraction.