WO2012021056A1

WO2012021056A1 - A method of producing microcrystalline cellulose from biomass

Info

Publication number: WO2012021056A1
Application number: PCT/MY2011/000184
Authority: WO
Inventors: Mat Soon Rosnah; Abdul Aziz Astimar; Wan Hassan Wan Hassamudin
Original assignee: Malaysian Palm Oil Board (Mpob); Top, Gapor, Md., A., B.
Priority date: 2010-08-09
Filing date: 2011-08-09
Publication date: 2012-02-16
Also published as: CN103261232B; WO2012021056A8; MY151341A; CN103261232A

Abstract

A method of producing microcrystalline cellulose comprising the step of chlorinating pretreated fibers of empty fruit bunches of oil palm which have reduced oil content to acquire holocellulose followed by an alkaline extraction of said holocellulose to produce alpha-cellulose. The alpha-cellulose is then treated with an acid to form a hydrolysate mixture. Neutralizing the hydrolysate mixture affords microcrystalline cellulose.

Description

A METHOD OF PRODUCING MICROCRYSTALLINE CELLULOSE FROM

BIOMASS

FIELD OF INVENTION

5The present invention relates to a method of producing microcrystalline from a biomass waste. In more specific, the disclosed method employs a pre-treatment process to prepare the biomass in a preferred form to facilitate microcrystalline production.

BACKGROUND OF THE INVENTION

lOOil palm empty fruit bunches (EFB) are abundantly and readily available renewable organic materials generated at the palm oil mills. Due to the pressure arising from ever-increasing demand of biomass utilization, an innovative effort to develop products with value addition from the empty fruit bunch is highly desirable. EFB can be considered as a valuable biomass residue which can be converted not only into energy (which is currently its major use), but

15also as a raw material for products of higher value such as panels, composites, fine chemicals, pulp and paper as well as compost and bio-fertilizer.

Studies have shown that oil palm fibre comprises lignocellulosic biochemical components which are largely made up of 18-23% (w/w) lignin, 35% (w/w) cellulose and 25% (w/w) 0hemicellulose. Cellulose, which can be obtained in the pure form from cotton, or extracted from lignocellulosic material, is a value-added compound that is being used in a wide range of industries. It is the major constituent of pulp and paper products, and is also being utilized as a starting material for the production of regenerated fibres such as rayon, carboxymethylcellulose, microcrystalline cellulose and other cellulose derivatives, especially 5esters and ethers. Microcrystalline cellulose (MCC) has many applications in structural composites, pharmaceuticals, food, paper, etc. In addition, it is a naturally derived stabilizer, texturing agent and fat replacer.

United States Patent. No. 3,954,727 issued to Toshkov et.al. describes the preparation of 0microcrystalline cellulose by hydrolyzing cellulose containing about 92% alpha-cellulose with 1% sulphuric acid and the acid hydrolysis being performed at the same time as the chemical de-aggregating of the materials. The described process uses pure cellulose or a lignocellulosic material as the starting material. Another United States Patent No. 4,063,018 issued to Hanna et al. describes the production of microcrystalline cellulose by reactive 5extrusion that the raw material is fed through an extruder in the presence of basic aqueous solution so as to break down the lignocellulosic complex into lignin, hemicellulose and cellulose.

SUMMARY OF THE INVENTION

lOThe present invention aims to provide a method to produce microcrystalline cellulose using biomass waste from oil milling industry. In more specific, the disclosed invention employs a pre-treatment process to convert the biomass waste into alpha cellulose facilitating the production of microcrystalline cellulose.

15 Another object of the disclosed invention is to provide a cost saving method to produce microcrystalline cellulose. Empty fruit bunches, which is a waste disposal from palm oil milling and can be acquired at a much lower price compared to other cellulosic sources, is used in the present invention.

20Still another object of the present invention is to disclose a method of recycling disposal waste from oil palm milling to value-added product.

At least one of the preceding objects is met, in whole or in part, by the present invention, in which one of the embodiments of the present invention is a method of producing

25microcrystalline comprising the step of subjecting pretreated fibers of empty fruit brunches and/or pressed palm fibers of oil palm to chlorination process to acquire holocellulose; subjecting the holocellulose to alkaline extraction to produce alpha-cellulose; hydrolyzing the alpha-cellulose with an acid to form a hydrolysate mixture; neutralizing the hydrolysate mixture; and acquiring the microcrystalline from the hydrolysate mixture, characterized in

30that the pretreated fibers is deoiled. In one embodiment, this invention relates to the production of microcrystalline cellulose from oil palm empty fruit bunch fibres by hydrolyzing the alpha-cellulose acquired from oil palm empty fruit bunch fibres with diluted sulphuric acid, in an autoclave at temperature rangingfrom 12 to 132°C, with selected time of reactions.

In another aspect, the pretreated fibers is deoiled via removing the oil residue from the fibers using a solvent extraction process. Preferably, the solvent extraction process uses hexane for dissolving and removing the oil residues from the fibers.

Another aspect of the present invention has the pretreated fibers ground to smaller pieces prior to the solvent extraction process.

Another aspect of the disclosed method has the chlorination process conducted by reactingthe pretreated fibers with acetic acid and sodium chlorite in an aqueous medium at 40°C to 95°C.

The present invention may further comprise the steps of washing and drying the acquired microcrystalline, and optionally alkalinizing the washed microcrystalline and bleaching thealkalinized microcrystalline cellulose to produce refined microcrystalline cellulose.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is the fourier transform spectroscopy of the obtained microcrystalline which has not undergone bleaching; and

Figure 2 is the fourier transform spectroscopy of the obtained microcrystalline which has not undergone bleaching.

DETAILED DESCRIPTION OF THE INVENTION One skilled in the art will readily appreciate that the present invention is well adapted to carry out the objects and obtain the ends and advantages mentioned, as well as those inherent therein. The embodiment describes herein is not intended as limitations on the scope of the invention.

5

The present invention is a method of producing microcrystalline comprising the step of subjecting pretreated fibers of empty fruit brunches and/or pressed palm fibers of oil palm to chlorination process to acquire holocellulose; subjecting the holocellulose to alkaline extraction to produce alpha-cellulose; hydrolyzing the alpha-cellulose with an acid to form a lOhydrolysate mixture; neutralizing the hydrolysate mixture; and acquiring the microcrystalline from the hydrolysate mixture, characterized in that the pretreated fibers is deoiled. It was found by the inventors of the present invention that the fibers from EFB can only be used for microcrystalline cellulose synthesis with the oil residue removed. The oil residue retained in the fiber content of the EFB are impurities which can interfere the chlorination and hydrolysis

15processes in the synthesis of microcrystalline. Thus, the oil residue can significantly affect yield and purity of the produced microcrystalline cellulose.

According to the preferred embodiment, the pretreated fibers is deoiled via removing the oil residue from the fibers using a solvent extraction process. The solvent used in the extraction

20process dissolves the oil residues retained in the matrix of the EFB fibers without physically damage the fibers and leaving the cellulosic materials in the EFB intact for the subsequent processes. Any oil dissolving organic solvent can be used in the disclosed method to dissolve the oil residue. Yet, preferably, non-toxic solvent such as hexane is employed in the solvent extraction process for dissolving and removing the oil residues from the fibers. In more

25 specific, oil constitutes about 5 to 10% of the EFB weight, is removed from the fibres by solvent extraction, preferably using hexane.

To enhance the efficiency of oil removal, preferably the pretreated fibers are ground to smaller pieces prior to the solvent extraction process. The ground fibers provide larger 30surface area to contact with the solvent effectively dissolving the oil residues. Any known method or technologies in the field capable of reducing the fiber size can be employed in the present invention, though physical cutting and grinding tools are more preferably used.

The EFB normally contains about 18% to 23% lignin which has to be removed as well before 5proceeding to the delignification step. The chlorination process, as in setting forth, is involved in the disclosed method aiming to remove the lignin content in the fibers. The chlorination process is performed by reacting the pretreated fibers with acetic acid and sodium chlorite in an aqueous medium at 40°C to 95°C. In this process, part of the impurities, lignin, is removed leaving only holocellulose. The alpha-cellulose content in the lOholocellulose is an essential ingredient for subsequent processes to produce microcrystalline cellulose.

The holocellulose is then proceeded to alkaline extraction process to further rid the hemicellulose contained in the holocellulose. Preferably, but not limited to, sodium hydroxide 15solution is utilized to remove the hemicellulose. Specifically, the holocellulose is immersed into the basic solution which dissolves the hemicellulose in the leaving insoluble cellulose or pulp constituted majorly of alpha-cellulose which contain about 0.7% to 1.5% of lignin.

The alpha-cellulose is then going through the hydrolyzing step to form the hydrolysate 20mixture. Particularly, amorphous regions of microfibrils of the pulp is dissolved in the hydrolysis process while leaving the microcrystalline cellulose fraction intact. Pursuant to the preferred embodiment, a mineral acid is used as the agent to hydrolyze and dissolve amorphous region to produce the microcrystalline cellulose. To enhance the hydrolysis efficiency, the reaction occurs under a positive pressure at a temperature of 100°C to 150°C. 25In one embodiment, autoclave machine can be used to carry out the reaction under the preferred condition. For example, the cellulose or pulp is autoclaved together with the acidic solution at temperature of 110-132 °C for 1 hour to 2 hours. The duration and yield of the hydrolysis greatly depends on the volume of the pulp to be hydrolyzed and acidity of the solution as well as the condition. Preferably, sulfuric acid solution of 0.5 to 1.5% is used in 30the disclosed method, while a suitable basic material is employed in the process to neutralize the acidic solution. The pressure during the reaction is preferably maintained in the range of 2 to 5 bars.

Subsequently, the produced microcrystalline cellulose is cleaned by the steps of washing and 5drying the acquired microcrystalline without subjecting the microcrystalline cellulose to bleaching. Distilled water can be the washing medium to wash away the impurities and chemical residues to produce crude microcrystalline cellulose. Further, de-aggregation process may be performed onto the dried microcrystalline cellulose before it is actually used. lOStill another embodiment of the present invention comprises the steps of washing the acquired microcrystalline; alkalinizing the washed microcrystalline and bleaching the alkalinized microcrystalline cellulose to produce refined microcrystalline cellulose. More specifically, the washed microcrystalline cellulose is turned basic using an alkalizing agent such as sodium hydroxide solution, potassium hydroxide solution, sodium carbonate solution

15and the like instead of being dried. Following the alkalizing step, the alkalinized microcrystalline cellulose is bleached using a bleaching agent, preferably hydrogen peroxide. The bleached microcrystalline cellulose is further washed to remove the chemical residues and impurities followed by drying and/or de-aggregation by using a mechanical grinder to produce refined microcrystalline cellulose.

0

The produced microcrystalline cellulose of the disclosed method preferably has pH of about 6.5 - 7.3, water soluble substances of about 0.1% - 0.4% and loss on drying of less than 6% for both bleached and non-bleached microcrystalline cellulose. 5The following example is intended to further illustrate the invention, without any intent for the invention to be limited to the specific embodiments described therein.

Example 1

About 6 g of grounded EFB strands were treated with hexane to remove the residual oil. The 0oil-free fibres were then subjected to chlorination process for lignin by mixing the fibres with distilled water, 4.0 ml acetic acid and 7.0 g sodium chlorite at 70°C for 4 h. Finally, the holocellulose produced was subjected to alkaline extraction, using 70 ml each of 17.5% and 8.3% sodium hydroxide solution. Then 2 g of alpha-cellulose produced was shredded and immersed in 1% sulphuric acid to form cellulose-acid mixture. The mixture was then 5autoclaved at uniform temperature of 132°C. The reaction pressure was maintained at 2 bar and the reaction was carried out for 60 minutes. Afterwards the hydrolysate was cooled and neutralized. The microcrystalline cellulose was separated from the hydrolysate, washed and dried. Finally the microcrystalline cellulose is subjected to mechanical de-aggregation. The structural properties of the microcrystalline cellulose prepared were recorded by Perkin lOElmer Fourier Transformed Infrared Spectrometer (FTIR) Spectrum One. The infrared spectrum of microcrystalline prepared was identical to that of the commercial MCC which showed comparable presence of C-O-C, C-C, O-H, and C-H bands. Figure 1 shows the fourier transform spectroscopy of the obtained microcrystalline which has not undergone bleaching.

15

Example 2

About 6 g of grounded EFB strands were treated with hexane to remove the residual oil. The oil-free fibres were then subjected to chlorination process for lignin by mixing the fibres with distilled water, 4.0 ml acetic acid and 7.0 g sodium chlorite at 70°C for 4 h. Finally, the

20holocellulose produced was subjected to alkaline extraction, using 70 ml each of 17.5% and 8.3% sodium hydroxide solution. Then 2 g of alpha-cellulose produced was shredded and immersed in 1% sulphuric acid to form cellulose-acid mixture. The mixture was then autoclaved at uniform temperature of 132°C. The reaction pressure was maintained at 2 bar and the reaction was carried out for 60 minutes. In the next stage, the microcrystalline

25cellulose was separated from the hydrolysate and washed. The washed microcrystalline cellulose was diluted with water, and then alkalized with sodium hydroxide solution. Further it was bleached with hydrogen peroxide at a temperature of 90°C. The suspension was filtered, washed and dried. Finally the microcrystalline cellulose is subjected to mechanical de-aggregation. Figure 2 shows the fourier transform spectroscopy of the obtained

30microcrystalline which has not undergone bleaching. Example 3

The MCC products from example 1 and example 2 exhibit the following properties:

Properties Value

pH 6.5 - 7.3

Water soluble 0.1% - 0.4%

substance

Loss on drying Less than 6%

All MCC products from example 1 and example 2 show typical infrared spectra profile of MCC with the occurrence of peaks at 3316-3318 cm ¹, 2891-2892 cm ¹, 1158 cm ¹, 1024- 1025 cm^"1 and 894 cm^"1 which belong to intermolecular and intramolecular O-H bonds, C-Hbonds, C-C bonds, C-O-C linkage of the anhydrous repeating units and β-glycosidic linkages, respectively.

In determining the properties of the microcrystalline cellulose derived from oil palm empty fruit bunch, several test procedures were employed in accordance to the Resolution OENO9/2002 test method; including determination of pH, water soluble substances and loss on drying. The results show the pH is about 6.5 - 7.3, water soluble substances are about 0.1% - 0.4% and the loss on drying of less than 6%.

Claims

1. A method of producing microcrystalline comprising the step of

subjecting pretreated fibers of empty fruit brunches and/or pressed palm fibers of oil palm to chlorination process to acquire holocellulose;

subjecting the holocellulose to alkaline extraction to produce alpha-cellulose;

hydrolyzing the alpha-cellulose with an acid to form a hydrolysate mixture;

neutralizing the hydrolysate mixture; and

acquiring the microcrystalline from the hydrolysate mixture, characterized in that the pretreated fibers is deoiled.

2. A method of claim 1, wherein the pretreated fibers is deoiled via removing the oil residue from the fibers using a solvent extraction process.

3. A method of claim 2, wherein the solvent extraction process uses hexane for dissolving and removing the oil residues from the fibers.

4. A method of claim 2, wherein the pretreated fibers are ground to smaller pieces prior to the solvent extraction process.

5. A method of claim 1, wherein the chlorination process is conducted by reacting the pretreated fibers with acetic acid and sodium chloride in an aqueous medium at 40°C to 95°C.

6. A method of claim 1 , wherein the hydrolyzing step to form the hydrolysate mixture is performed under positive pressure at a temperature of 100°C to 150°C.

7. A method of claim 1 further comprising the steps of washing and drying the acquired microcrystalline to produce crude microcrystalline cellulose.

8. A method of claim 1 further comprising the steps of washing the acquired microcrystalline; alkalinizing the washed microcrystalline and bleaching the alkalinized microcrystalline cellulose to produce refined microcrystalline cellulose.