FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
A PROCESS FOR OBTAINING ALPHA-CELLULOSE;
GODAVARI BIOREFINERIES LIMITED, A
COMPANY INCORPORATED UNDER THE
INDIAN COMPANIES ACT, 1956, WHOSE
ADDRESS IS 45/47, SOMAIYA
BHAVAN.M.G.ROAD, MUMBAI- 400001, MAHARASHTRA, INDIA
THE FOLLOWING SPECIFICATION
PARTICULARLY DESCRIBES THE
INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

Field of the Invention
The present invention relates to a process for obtaining alpha-cellulose. More particularly the present invention relates to a process for obtaining the alpha-cellulose with high molecular weight.
Background of the Invention
Cellulose is one of the few high volume renewable feedstocks used on a large scale by the chemical industry. Over 1.5 billion pounds of highly pure cellulose are used annually to produce food additives, fibers, paper and textiles. Recently, the cellulose is also used to produce the high end product such as specialty chemicals and plastics. Due to environment concerns the production of biodegradable products from cellulose is becoming popular. For producing biodegradable products for example plastic and polymerized derivatives, cellulose needs to be of requisite properties the most important ones are high purity and very high molecular weight. The usual source of cellulose is lignocellulosic materials. There are number of processes which have been developed, by and large with the objective of producing cellulosic pulp suitable for use in the paper and textile industries. For such applications the important criteria for quality of cellulose include whiteness index, fibre length and strength of cellulose. However, these methods are not suitable for providing cellulose particularly alpha-cellulose with very high purity and having extremely high molecular weight.
Summary of the Invention
Accordingly, in one aspect the present invention is directed to provide a process for obtaining alpha-cellulose with high molecular weight and purity suitable for converting into biodegradable derivatives.

In an embodiment, the present invention provides a process for obtaining alpha-cellulose comprising steps of:
-pulping pretreated lignocellulosic material with alkali, sulfite and anthraquinone at a temperature of atleast 120 oC and holding time of atleast 15 minutes for solubilizing lignin component by converting into lignosulfonates;
-washing and screening the pulp for separating lignosulfonates an d removing residual impurities;
- bleaching the washed pulp;
-separating the fibrous organic residue and washing to obtain the pulp containing atleast 92% alpha-cellulose having high molecular weight in the range of 10,00,000-25,00,000.
In another aspect the present invention is directed to provide an alpha-cellulose with very high molecular weight and purity suitable for converting alpha-cellulose into biodegradable derivatives.
In one embodiment, the present invention provides alpha - cellulose of atleast 92% having high molecular weight in the range of 10,00,000-25,00,000
Detailed Description
The present invention relates to the process for obtaining alpha-cellulose with high molecular weight and purity and the alpha-cellulose produced by the process of the present invention, with high molecular weight and purity suitable for converting into biodegradable derivatives for example plastics and polymers.

In one of the embodiments, the present invention provides a process for obtaining alpha-cellulose with high molecular weight and purity in which process comprises:
-pulping pretreated lignocellulosic material with alkali, sulfite and anthraquinone at a temperature of atleast 120 °C and holding time of atleast 15 minutes for solubilizing lignin component by converting into lignosulfonates;
-washing and screening the pulp for separating lignosulfonates and removing residual impurities;
- bleaching the washed pulp;
-separating the fibrous organic residue and washing to obtain the pulp containing atleast 92% α-cellulose having high molecular weight in the range of 10,00,000-25,00,000.
Representative "lignocellulosic material" includes any type of lignocellulosic material comprising cellulose, such as but not limited to non-woody-plant lignocellulosic material, wooden material, agricultural wastes, forestry residues, paper-production sludge, waste-water-treatment sludge, corn fiber from wet and dry mill corn ethanol plants, and sugar-processing residues.
In a non-limiting example, the lignocellulosic material can include, but is not limited to, grass, selected from but not limiting to switch grass, cord grass, rye grass, reed canary grass, miscanthus, or a combination thereof; sugar-processing residues, selected from but not limited to sugar cane bagasse; agricultural wastes, selected from but not limited to rice straw, rice hulls, barley straw, corn cobs, wheat straw, canola straw, oat straw, oat hulls, and corn fiber; stover, selected from but not limited to soybean stover, corn stover; and forestry wastes, selected from but not limited to recycled wood pulp fiber, sawdust, hardwood, softwood, or any combination thereof. One of the exemplary lignocellulosic material processed as per the process of the present invention is sugar cane bagasse, preferably the dipithed one.

Lignocellulosic materials are composed of mainly cellulose, hemicellulose, and lignin. Generally, a lignocellulosic material, on a dry basis, may contain about 50% (w/w) cellulose, about 30% (w/w) hemicellulose, and about 20% (w/w) lignin. The lignocellulosic material can be of lower cellulose content, for example, containing 20% (w/w) cellulose.
The pretreatment of the lignocellulosic material may be carried out by subjecting the lignocellulosic raw material to a suitable step to dissociate the hemicellulose-cellulose-lignin complex and removing the hemicellulose.
The conventional treatment of lignocellulosic material includes acidic or basic hydrolysis. Acids or bases used are strong acids and bases which unfortunately, promote undesirable side reactions such as lignin condensation and depolymerization of hemicellulose/cellulose causing cellulose degradation. Cellulose degradation not only reduces the yield and quality of recovered pulp but it also creates the condition in which condensation of lignin with the products of cellulose degradation occurs, thereby degrading the quality of recovered fractions. Besides, for improving the accessibility of lignocellulosic materials and effective fragmentation, acidic or basic hydrolysis is carried out in presence of steam. An example of such a thermochemical process is described in Spanish patent ES87/6829, which uses steam at a temperature of 200-250 degree centigrade in a hermetically sealed reactor to treat previously ground lignocellulosic material. It is reported that the best results can be achieved with 210-240 degree centigrade for holding the material for 4-16 minutes. Other reported prehydrolysis temperature is between 155-170 degree centigrade and the hold time is 90-170 minutes. Thus, such acid hydrolysis steps are required to be carried out in presence of strong acids, at very high temperatures requiring very lengthy hold time making the process very costly due to high energy consumption and also further degrading the quality of the cellulose.

Other type of thermochemical treatment includes a sudden depressurization of the reactor, called steam explosion treatment. However, such known steam explosion treatment also requires very high cooking temperature, lengthy hold time and in so me instances, the pretreatment protocol incorporates varying concentrations of a catalytic agent (e.g. acid).
Prior to subjecting to the steam treatment, the lignocellulosic material may be subjected to a mechanical treatment, such as crushing, mashing or the like, thereby allowing the easy infiltration of steam and other chemicals during further processing into the cellulose raw materials and improving the desired effect to be achieved. Lignocellulosic material may also be saturated with water prior to subjecting to steam treatment to remove silica.
In accordance with the present invention in one of the embodiment, the pretreatment involves treating lignocellulosic raw material in contact with high pressure steam at temperature in the range 190°C - 200°C for atleast 2 minutes for hydrolyzing and solubilizing the hemicellulose, separating the solubilized hemicellulose and washing the undissolved fibrous organic biomass with hot soft water to give the pretreated lignocellulosic material. The evaporation (concentrating) of the water from the solubilized hemicellulose fraction gives the Hemicellulose, It was surprisingly found that very short hold time of 2-4 minutes was enough for the requisite separation of hemicellulose and provided desired quality of pre-treated material. The percentage of hemicellulose separated in the form of xylans is in the range of about 18-22% on weight basis.
In one embodiment the pretreated lignocellulosic material is subjected to pulping by cooking the pre-treated pulp with sodium sulfite Na2So3, Sodium carbonate Na2CO3 and Sodium Hydroxide (NaOH) in presence of anthraquinone at temperatures in the range 125-180°C for atleast 15 minutes, preferably for 15-45 minutes to solubilize all the lignin component mainly into lignosulfonates. The cooked pulp is then washed with water to remove adhering lignosulfonates and other impurities. Such washed and cooked pulp is

screened to remove shives. The lignosulfonates obtained after separating cooked pulp can be in the range of 16-18 % on weight basis.
In the pulping step the sodium sulfite (Na2SO3) may be employed in an amount of about 5% - 25% as Na2O, preferably, 10% - 15% by weight. Sodium carbonate (Na2CO3) may be employed in the range of about 0.1% -10% as Na2O, preferably 0.5% - 5% by weight. Sodium Hydroxide (NaOH) may be used in the range of about 0.25% -15% as Na2O, preferably in the range of about 0.5% - 5% by weight. Anthraquinone may be employed in the range of about 0.01% - 0.3%, preferably in the range of about 0.01% to 0.2% by weight.
After pulping by cooking, washing and screening for removing residual uncooked impurities, the bleaching of pulp is carried out. The residual lignin is a major contributing factor as an impurity, hence it must be removed. The chemicals used in bleaching in the process of the present invention effectively remove residual lignin and also dissolved extractives contained in the pulp (e.g. resin).
In one embodiment of the present invention the bleaching of the pulp is carried out in multiple steps and the pulp is washed between them. The Multi-step bleaching gives the best results regarding both quality and economy and it also addresses environment concerns over chlorinated organic by products from elemental chlorine and its derivatives. Due to such multi-stage bleaching process the AOX (Adsorable organic hallide) load can be achieved around 0.5 kg/BDMT of pulp and it also helps to achieve the better pulp properties.
In one embodiment of the present invention the multi-step bleaching comprises of following steps carried out under defined conditions of temperature, pH and time duration:

i) treating the washed pulp obtained from pulping step with active bleaching agent, followed by washing;
ii) treating the washed pulp of (i) with alkali and washing;
iii) treating the washed pulp of (ii) with active bleaching agent and washing.
The active bleaching agent that may be used may be selected from the group consisting of but not limited to chlorine dioxide, hypochlorite, sodium chlorite, hydrogen peroxide, ozone or the like. The alkali used may be sodium hydroxide.
The concentrations of the active bleaching agent and alkali to be employed in the above step (i) to (iii) may be about 0.1% -10 %, preferably active bleaching agent may be about 2% - 5% by weight and alkali may be about 3% -5% by weight.
The above bleaching steps are carried out under various conditions of temperature, pH and for a desired time duration. The temperature in step (i) may be atleast 50 degree centigrade and in step (ii) and step (iii) the temperature may be atleast 70 degree centigrade. The duration for which the step (i) may be carried out is atleast 30 minutes, preferably about 30 minutes to 60 minutes, step (ii) may be carried out for the duration of atleast 60 minutes, preferably about 60 minutes to 120 minutes and step (iii) may be carried out for atleast 90 minutes, preferably about 150 minutes to 180 minutes. The pH in step (i) may be atleast 2, in step (ii) it may be atleast 10 and in step (iii) it may be atleast 3.
The yield of alpha - cellulose obtained is atleast 30%, preferably more than 35%. The alpha-cellulose obtained by the process of the present invention has high purity of atleast 92%. The molecular weight of the alpha - cellulose obtained is very high in the range of 10,00,000-25,00,000. Hereto followed processes have not known to achieve such high yield, purity and particularly high molecular weight of alpha-cellulose suitable for conversion into cellulose derivatives for biodegradable materials for example plastics and polymers. It is the

first time that the inventors of the present invention have been able to obtain alpha-cellulose with such high molecular weight and purity by the process of the present invention involving shorter duration of pre-treatment and further processing, milder conditions of temperature than conventionally known processes using much lesser concentrations of chemical reagents used.
Alpha-cellulose with high molecular weight and purity can be readily converted into high end products like biodegradable cellulose derivatives for example plastics and other polymeric materials. Additionally, hemicellulose (xylan) 18 -22 % and 16-18 % lignosulfonates obtained by the process of the present invention can be further converted into industrially useful products, rendering the process commercially cost effective.
Thus, the process according to the present invention is extremely useful for effective utilization of natural resources and waste material and converting them into high demand high value commodities.
The present invention will be illustrated by following non-limiting examples: EXAMPLES
Example 1
6.0 Kg dry of Sugarcane bagasse containing 4-5% pith was saturated with water to remove silica content and charged into the steam explosion reactor. Steam was charged into this reactor at pressure of 18-20.0 Kg/cm2, and temperature was maintained about 190-195° C. for 4.0 minutes, after that steam pressure was released into the atmosphere, so that the bagasse was "exploded" into fine particles. Solid mass was washed with hot water and 1.2

kg of hemicellulose (xylan) was separated by evaporating the water. Hemicellulose obtained was analysed to a monomeric xylose, arabinose, glucose, fructose and unidentified sugar after hydrolysis by HPLC (high performance liquid'chromatography). A 4,8 Kg of the steam exploded material was pulped by cooking with 1.3 kg sodium sulfite, 0.211 kg sodium carbonate, 0.082 Kg sodium hydroxide and 10 grams anthraquinone in 500 K L Hastelloy reactor for about 30 minutes and temperature of about 160 degree. The cooked pulp was washed well with hot soft water. The filtrate contained 1.1 Kg lignosulfonates. Washed cooked pulp was screened to remove shives 2.43 Kg pulp obtained after screening was bleached with 31 gm sodium chlorite in first stage for 60 minutes at 60 degree centigrade at pH 2.6, followed by alkali extraction with 58 gm sodium hydroxide for 120 minutes, at temperature 70 degree centigrade at pH 10.9 and treatment with 12 gm sodium chlorite for 180 minutes, at 70 degree centigrade, at pH 3.2 in subsequent stage. The final bleached pulp was air dried. The final cellulose pulp obtained was 2.4 kg with 85 % brightness (Photo Volt) and alpha cellulose content of 94 % with molecular weight of 21,00,000.
Example 2
12 Kg dry of Sugarcane bagasse containing 4-5% pith was saturated with water to remove silica content and charged into the steam explosron reactor. Steam was charged into this reactor at pressure of 18-20.0 Kg/cm2, and temperature was maintained about 190-195° C. for 4.0 minutes, after that steam pressure was released into the atmosphere, so that the bagasse was "exploded" into fine particles. Solid mass was washed with hot water and 2.6 kg of hemicellulose (xylan) was separated by evaporating the water. Hemicellulose obtained was analysed to a monomeric xylose, arabinose, glucose, fructose and unidentified sugar after hydrolysis by HPLC (high performance liquid chromatography). A 9.4 Kg of the steam exploded material was pulped by cooking with 2.561 kg sodium sulfite, 0.419 kg sodium carbonate, 0.163 Kg sodium hydroxide and 25 grams anthraquinone in 500 K L Hastelloy reactor for about 30 minutes and temperature of about 160 degree. The cooked pulp was washed well with hot soft water. The filtrate contained 25 Kg lignosulfonates. Washed cooked pulp was screened to remove shives 4.70 Kg pulp obtained after screening was bleached with 68 gm sodium chlorite in first stage for 60 minutes at 60 degree centigrade at

pH 2.8, followed by alkali extraction with 94 gm sodium hydroxide for 120 minutes, at temperature 70 degree centigrade at pH 11.1 and treatment with 28 gm sodium chlorite for 180 minutes, at 70 degree centigrade, at pH 3.2 in subsequent stage. The final bleached pulp was air dried. The final cellulose pulp obtained was 4.8 kg with 88 % brightness (Photo Volt) and alpha cellulose content of 94.3 % with molecular weight of 22,00,000.
Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. It is to be understood that the invention is not limited to these precise processes and embodiments and that changes may be made to the same without departing from the spirit and scope of the invention and the same will be construed to be within the scope of the present invention as defined by the appended claims.

We Claim:
1. A process for obtaining alpha-cellulose with high molecular weight and purity
comprising steps of:
(a) pulping pretreated lignocellulosic material with sulfite, alkali and anthraquinone at a temperature of atleast 120 °C and holding time of atleast 15 minutes for solubilizing lignin component by converting into lingnosulfontes;
(b) washing and screening the pulp for separating lingnosulfontes and removing residual impurities;
(c) bleaching the washed pulp;
(d) separating the fibrous organic residue and washing to obtain the pulp containing atleast 92% alpha - cellulose having high molecular weight in the range of 10,00,000-25,00,000.

2. The process as claimed in claim 1, wherein the lignocellulosic material is selected from but not limiting to grass, sugar-processing residues, agricultural wastes, stover, and forestry wastes.
3. The process as claimed in claim 2, wherein the sugar-processing residue material is sugar cane bagasse, preferably the dipithed sugar cane bagasse.
4. The process as claimed in claim 1, wherein the pre-treated ligoncellulosic material is obtained by treating lignocellulosic raw material in contact with high pressure steam at temperature in the range 190°C - 200°C for atleast 2 minutes, separating the solubilized hemicellulose and washing the undissolved fibrous organic biomass with hot soft water to give the pretreated lignocellulosic material.
5. The process as claimed in claim 1, wherein the sulfite is sodium sulfite (Na2S03) employed in an amount of 10%-15% by weight as Na20, alkali includes sodium carbonate (Na2C03) employed from 0.5% - 5% by weight and sodium Hydroxide (NaOH) in the range of 0.5% -5% by weight as Na20.

6. The process as claimed in claim 1, wherein the anthraquinone is employed in the range of 0.01% - 0.3%, preferably in the range of about 0.01% - 0.2% by weight.
7. The process as claimed in claim 1, wherein the bleaching is carried out by multi-step bleaching process carried out under defined conditions of temperature, pH and time duration comprising steps of:

(a) treating the washed pulp obtained from pulping step with active bleaching agent, followed by washing;
(b) treating the washed pulp of (i) with alkali and washing;
(c) treating the washed pulp of (ii) with active bleaching agent and washing.

8. The process as claimed in claim 7, wherein the active bleaching agent is selected from the group consisting of but not limited to chlorine dioxide, hypochlorite, sodium chlorite, hydrogen peroxide and ozone.
9. The process as claimed in claim 7, wherein the alkali is sodium hydroxide.
10. The process as claimed in claim 7, wherein the active bleaching agent in step (a) to (c) is used in the concentration of 2%-5% by weight.
11. The process as claimed in claim 7, wherein the alkali in step (a) to (c) is used in the concentration of 3%-5% by weight.
12. The process as claimed in claim 7, wherein the temperature in step (a) is atleast 50 degree centigrade and in step (b) and step (c) is atleast 70 degree centigrade.
13. The process as claimed in claim 7, wherein the duration for which the step (a) is carried out is for 30 minutes - 60 minutes, step (b) is carried out for 60 minutes -120 minutes and step (c) is carried out for 150 minutes -180 minutes.

14. The process as claimed in claim 7, wherein the pH in step (a) is atleast 2, in step (b) it is atleast 10 and in step (c) it is atleast 6.
15. An alpha - cellulose as obtained by process of claim 1-14, having high molecular weight in the range of 10,00,000-25,00,000 and purity of atleast 92%.