KR20160046522A

KR20160046522A - Methods for Integrated Usage of Rice husks

Info

Publication number: KR20160046522A
Application number: KR1020140142514A
Authority: KR
Inventors: 한종인; 송동수; 김일국; 서영환; 박승빈
Original assignee: 한국과학기술원
Priority date: 2014-10-21
Filing date: 2014-10-21
Publication date: 2016-04-29

Abstract

The present invention relates to a method for integrally utilizing rice hulls, more particularly, to a method of pretreating rice hulls using sodium carbonate which can be obtained from a carbon dioxide capture process to increase the availability of cellulose, To convert monosaccharide such as glucose to liquefied residual rice husks in an unused glycation process to produce a bio-oil having an increased calorific value and to produce silica by carbonizing the bio-tea obtained as a by- And how to utilize them integrally. According to the present invention, by converting the organic matter component and the inorganic matter constituting the rice husk into the high value-added product, it can contribute to the increase of recycling of resources, the improvement of profitability of the domestic rice farming and related rice gravel processing plant.

Description

Methods for Integrated Usage of Rice husks

The present invention relates to a method for integrally utilizing rice husk. More specifically, the present invention relates to a method for integrally utilizing rice husk, which comprises pretreating rice hulls using sodium carbonate, glycosylating the pretreated rice hulls with an enzyme to convert them into monosaccharides, The present invention also relates to a method of utilizing chrysanthemum to produce silica by carbonizing the obtained bio-tea.

One of the global trends toward high oil prices and global warming is energy that can replace oil. One of the leading alternative energy sources is biofuels. Biofuels are energy obtained by using biomass as a raw material, and they are obtained by direct combustion, alcohol fermentation, methane fermentation, and the like. Among these biofuels, bioethanol, a fuel that can replace gasoline, is spreading very rapidly. Conventionally, bioethanol can be obtained from the first generation biomass such as sugarcane and corn, and can be used as an automobile fuel, either mixed with gasoline or independently, and is being regarded as a representative renewable alternative energy in addition to biodiesel and biobutanol. However, there has been a question of food ethics in producing fuel using first-generation biomass.

Woody biomass, one of the biomass that can produce such biofuels, is used in all organic matter that can be used for renewable energy such as crops, wood, waste wood or by-products, grass, residual fiber, rice husks, rice straw, It is a lignocellulosic resource consisting of lignin, mainly woody plants and herbaceous plants and includes products derived therefrom or waste thereof, such as wood, waste wood, paper and the like. Woody biomass is a non-edible plant and has a low raw material cost and is emerging as a major raw material for biofuels.

The most costly and challenging process in the process of producing biofuels from woody biomass is pre-treatment and saccharification. The woody biomass pretreatment process decomposes cellulosic or hemicelluloses of woody biomass to individual monomers (such as glucan or xylan) and separates them from lignin. The glycosylation yields of the Poplar needle and the non-pretreated specimens after steam explosion (Steam Explosion) were 90% and 15%, respectively (Grous et al. , Enzyme Microb. Technol. 8: 274-280, 1986), and the saccharification yields of the untreated and untreated turfgrass were 93% and 16%, respectively, according to Ammonia Fiber Explosion (AFEX) method (Alizadeh et al. , Appl. Biochem. Biotechnol. 124: 113-1141, 2005). The pretreatment process is indispensable in producing biofuels using woody biomass.

Woody biomass preprocessing technology is a chemical pretreatment that reacts with acid pretreatment such as mechanical pretreatment, steam pretreatment, steam explosion, acid or alkali, oxidizing substance to reduce particle size and crystallization .

However, the woody biomass pretreatment method as described above is difficult to produce biofuels by using pretreatment methods, because the high operating cost and the low yield of biofuel according to the high installation cost and the severe reaction conditions (high temperature and pressure) . In order to solve these problems, studies are being conducted to reduce operational costs, and as it has been recognized that wastewater treatment is an important part of economical efficiency in the woody bioethanol production process, studies on solvent recovery and reuse have been actively conducted .

One of the woody pretreatment methods that could be a potential candidate from this point of view is the alkali pretreatment. Alkali salts used in alkaline pretreatment include basic substances such as sodium hydroxide and potassium hydroxide. Recently, however, the use of substances such as sodium carbonate and potassium carbonate, which are obtained by collecting carbon dioxide in the basic substance, To improve the low energy density. These basic materials can be reused, which has the advantage of lowering the process cost.

On the other hand, there is a direct liquefaction (or hydrothermal liquefaction) method as one of the methods for producing high value-added products by treating biomass. This is a technology to convert biomass such as woody, sewage sludge, and manure into pyrolysis at the high temperature and high pressure in the reactor simultaneously with the hydrogenation process. To produce a biomass-derived oil that is a liquid non-tactical oil. As a by-product obtained at this time, biochar and some tar can be obtained. Such an example has been disclosed in Patent Application No. 10-2008-0127852 for a process for producing bio-ethanol using algae, but there is no mention of utilization of bio-tea.

In addition, materials such as rice hulls or rice straw absorb and accumulate silica, which is a unique characteristic of rice, in the form of silicic acid, which is used to protect rice from the outside environment. (Present in the form of ash). As a method of utilizing the silica, the silica contained in the rice husks is utilized in Korean Patent Registration No. 10-0396457 and Patent Application No. 10-2013-0060297. However, (Lignin, hemicellulose, cellulose), which is a carbon source, is not utilized.

In order to utilize both the organic and inorganic components contained in the rice husk, the present inventors used sodium carbonate as a pretreatment for rice husk, one of the woody biomass resources, and converted the pretreated rice husk into a monosaccharide such as glucose , An integrated utilization method of rice hulls for producing crystalline silica by liquefying the residual rice husks of the saccharification process to produce bio oil, and carbonizing the obtained bio-tea in a high temperature atmosphere.

Korean Patent Application No. 10-2008-0127852 Korean Patent Registration No. 10-0396457 Korean Patent Application No. 10-2013-0060297

Grous et al., Enzyme Microb. Technol., 8: 274-280, 1986. Alizadeh et al., Appl. Biochem. Biotechnol., 124: 113-1141, 2005.

In order to solve the above problems, the present invention utilizes both organic and inorganic materials constituting rice hulls, and confirmed that it can be converted into monosaccharide (glucose), bio oil and silica from rice hulls.

Therefore, the present invention provides a method for effectively utilizing the components constituting rice hulls.

The present invention also provides glucose, bio-oil and silica produced using this method.

In order to accomplish the above object, the present invention provides a method for preparing rice hulls, comprising the steps of: (a) pretreating rice hulls using sodium carbonate; (b) adding an enzyme to the pretreated rice husk to convert it to a monosaccharide; (c) liquefying residual rice husks in the step (b) to produce a bio-oil; And (d) carbonizing the bio-char obtained in the step (c) to produce silica.

The present invention also provides a monosaccharide, bio oil and silica produced by the integrated utilization of the rice hulls.

According to the present invention, it is possible to effectively utilize the entire organic and inorganic components constituting the rice husk without reaction wastes, and bio-oils including monosaccharides such as glucose and fatty acids and phenol can be obtained from organic matters, It is possible to obtain silica, which is an inorganic substance. In particular, since sodium carbonate that can be obtained from the carbon dioxide capture process can be utilized using sodium hydroxide, the amount of generated carbon dioxide can be reduced as a result, and sodium carbonate used as a catalyst can be reused.

1 is a SEM photograph of a rice husk used in the present invention. Fig. 1 (a) is a rice husk without pretreatment, Fig. 1 (b) is a rice husk pretreated with sodium carbonate as a catalyst, and Fig. 1 (c) is a mechanical crushing rice husk as a control.
2 is a GC / MS result of the bio-oil obtained by liquefying the residual rice husks in the step of converting the pretreated rice husk into an enzyme by adding an enzyme.
FIG. 3A is a photograph of bio-oil obtained in the liquefaction step of residual rice hulls dispersed in a solvent, and FIG. 3B is a photograph of bio-hyphae obtained in the liquefaction step of residual rice husks.
Fig. 4A is the result of XRD analysis of the silica obtained by carbonization of the bio-tea to remove the carbon component, and Fig. 4B is the result of silica obtained by carbonizing the rice hull as a control.
Fig. 5 is a photograph of silica derived from rice hulls. Fig. 5A is a photograph of silica obtained by carbonization of bio-tea to remove carbon components, and Fig. 5B is a photograph of silica obtained by direct carbonization of rice husk as a control group.

The present invention relates to a process for producing rice hulls, comprising the steps of: (a) pretreating rice hulls using sodium carbonate; (b) adding an enzyme to the pretreated rice husk to convert it to a monosaccharide; (c) liquefying residual rice husks in the step (b) to produce a bio-oil; And (d) carbonizing the bio-char obtained in the step (c) to produce silica.

The step (a) is a step of pretreating rice hulls using sodium carbonate. The sodium carbonate used in the present invention may be obtained by adding carbon dioxide to a sodium hydroxide (NaOH) solution produced during the carbon dioxide capture process, You can contribute.

In the present invention, hemicellulose and lignin constituting the rice husk were decomposed when the rice hull was introduced using sodium carbonate, and it was confirmed that this can be used in the pretreatment step of step (a). Although sodium hydroxide, potassium hydroxide, sodium carbonate and ammonium solutions are mainly used as alkaline solutions in the case of the rice husk pretreatment using a substance showing alkalinity in general, in the present invention, it is possible to obtain from the sodium hydroxide which is supplied at relatively low cost, Sodium carbonate was used for the pretreatment.

In the present invention, the rice husk was added to a sodium carbonate solution to perform the pretreatment. The rice husk was added at 10% (w / v), and pretreatment was carried out at a temperature range of 100 to 160 ° C., a sodium carbonate concentration of 1 to 3% (w / v) and a time of 15 to 45 minutes. A microwave reactor, an infrared ray reactor, an oil bath, or the like can be used. In the present invention, an oil bath is used.

Through the pretreatment process, it was confirmed that hemicellulose and lignin constituting rice husk were partially decomposed and removed in a liquid state, and at the same time, the content of cellulose was increased. The pretreated rice hulls showed up to 10% higher cellulosic content than that of the untreated rice hulls, and it was confirmed that lignin was removed by up to 20%.

In the step (b), the enzyme is added to the pretreated rice husk to convert it to a monosaccharide. The polysaccharide is converted into a monosaccharide by an enzyme, and the cellulose is converted into a monosaccharide glucose. Is performed at 30 to 70 DEG C, preferably at 40 to 60 DEG C, in order to effectively perform saccharification with an enzyme. In order to effectively convert the polysaccharide into a monosaccharide, the saccharification time is 24 to 96 hours, preferably 48 to 72 hours. In one embodiment of the present invention, the saccharification process is performed for 72 hours.

(c) is a step of liquefying under high pressure conditions to utilize the components of the residual rice husk of the saccharification step (step (b)), thereby converting the carbon components remaining in the residual rice husk into bio oil. Liquefaction is also called liquefaction. The liquefaction is performed at a temperature range of 250 to 350 ° C. for 10 to 40 minutes. In order to increase the separation efficiency of the bio-oil, an organic phase may be further added to perform a reaction with a two- have. In order to increase the efficiency of the reaction, a catalyst may be additionally added, and a weak base material such as sodium carbonate, ammonium carbonate or potassium carbonate or a metal-based material such as iron oxide, iron chloride, aluminum oxide or aluminum chloride may be used. Sodium carbonate was used as a catalyst in an amount of 1 to 3% (w / v), preferably 2% (w / v) of sodium carbonate.

The step (d) carries out the step (c) to obtain the silica constituting the rice husk, and carbonizing the remaining bio-char to obtain the residual silica. The temperature for carbonizing is sufficient to remove all of the residual carbon content of the rice husk. In one embodiment of the present invention, the temperature for carbonization is in the range of 500 to 800 DEG C, preferably 550 to 600 DEG C for about 1 to 3 hours Lt; / RTI > to obtain silica.

Hereinafter, the present invention will be described in more detail with reference to Examples.

5 g of rice hull was charged into a reactor composed of Teflon and the concentration of sodium carbonate aqueous solution was adjusted to 1 to 3% and the solid solution ratio was adjusted to 1/10 (rice husk / sodium carbonate solution) at a temperature of 100 to 160 ° C The rice husk pre-treatment was performed for 45 minutes. Rice hulls were obtained from rice threshed at the rice paddy fields in Daejeon area, washed with distilled water and dried at room temperature. The composition ratio of the rice husk used in the present invention is as follows. Glucan (glucan) is composed of 26.7%, xylan (xylan) 16.2%, lignin (lignin) 32.3%, chaff material (ash, the main component SiO ₂₎ 13.1%.

Table 1 below shows the result of partial rupture of hemicellulose and lignin constituting the rice husks due to the pretreatment as a result of performing the rice husk pretreatment under various conditions. As a result of the saccharification test for 72 hours at a reaction temperature of 50 ° C, pH 4.8 (citric acid solution buffer) and a liquid ratio of 1:20, the pretreatment of rice straw was 45.7% (Table 1). Table 2 shows the results of increasing the BET surface area of rice hulls through the pretreatment. 1B is a SEM photograph of a sodium rice pretreated rice husk, FIG. 1C is a SEM photograph of a rice husk mechanically pulverized as a control, and FIG. 1C is a SEM photograph of a rice husk mechanically pulverized as a control. It can be confirmed that the use of rice husk is increased by a chemical method.

turn
Reaction conditions
Composition ratio (%)
Saccharification Efficiency (%)
Na ₂ CO ₃ (%) Temperature (℃) Time (min) Glucan Xylian Lignin One One 100 30 30.2 19.4 28.0 21.0 2 One 130 30 35.5 20.7 24.4 28.0 3 One 160 30 34.4 20.4 25.9 22.5 4 2 100 15 28.8 20.1 27.2 25.8 5 2 100 30 34.8 21.9 26.5 33.9 6 2 100 45 32.7 20.7 25.0 22.7 7 2 130 15 34.9 21.9 26.1 33.9 8 2 130 30 37.6 22.1 24.5 45.7 9 2 130 45 34.2 22.4 24.3 35.5 10 2 160 15 33.4 21.6 25.8 28.4 11 2 160 30 36.9 20.2 25.7 40.3 12 2 160 45 36.1 19.8 23.6 32.6 13 3 100 30 32.0 23.9 26.3 29.2 14 3 130 30 36.0 21.6 24.9 37.7 15 3 160 30 35.1 20.6 23.2 37.0 Control group 26.7 16.2 32.3

BET surface area (m ² / g) Unprocessed rice husk 0.88 Pretreated rice husk 1.43 Rice chaff after enzyme saccharification 1.32

Example 2. Saccharification Process Preparation of bio-oil by liquefaction of residual rice hulls

As a method for utilizing the carbon content of the remaining rice husks remaining in the saccharification process of the Example 1, bio-oil was prepared by liquefaction.

The reaction was carried out by adding 5 g of 5% (w / v) sodium carbonate as a reaction catalyst to a Teflon reactor at a solid ratio of 1:10 to a solvent (distilled water: 2-butanol = 1: 1) The reaction conditions were set at 300 ^° C at a heating rate of 10 ^° C / min for 20 minutes. The remaining rice hull was left in the same conditions as in Example 1 (Na ₂ CO ₃ 2% (w / v), reaction temperature 130 ^° C, reaction time 30 minutes) .

The temperature of the reactor was lowered to room temperature, and the liquid component and the solid component were separated. The 2-butanol component was used to effectively separate the bio-oil, and the bio-oil component derived from the rice husk was separated using the density difference. The separated bio-oil was analyzed by GC / MS (Gas Chromatograph / Mass spectrophotometry gas chromatograph / mass spectrometer). The results are shown in Table 3 below. 2 shows GC / MS results of the bio-oil obtained by this example. 3 (a) is a bio-oil (upper layer) obtained by the present invention, and Fig. 3 (b) is a bio-char obtained after producing a bio-oil.

5 g of residual rice husk was carbonized to obtain 1.507 g of biocha (rice husk conversion rate 69.86%), and the yield of bio oil was 18.5%. The other part was discharged as steam. The components of the residual rice husk were partially decomposed in the supercritical condition, and the compounds as shown in Table 3 were obtained as monosaccharide. When the relative area is 1% or more, the compound is shown in Table 3 below, and the relative area is calculated by the area represented by the specific compound for the entire GC / MS area. Bio-oil was mainly composed of phenol compounds, followed by ether compounds.

The calorific value of the bio-oil is calculated according to the Dulong formula and is shown in Table 4 below. The heat of the rice husk was 15.15 MJ / kg, whereas the amount of heat of the bio-oil was 27.64 MJ / kg. Especially, the content of oxygen and oxygen decreased to 2/3 level.

Calorific value (MJ / kg) = 0.3383C + 1.442 ((H) - (O / 8))

sample
Elemental content (% by weight)
H / C one consumption
O / C one consumption
Heat output (MJ / kg)
C H N O chaff 40.16 5.38 0.48 54.01 1.61 1.01 15.15 Bio Oil 49.53 12.05 2.41 36.01 2.92 0.54 27.64

Example 3. Carbonization of bio-tea to obtain residual silica

To obtain the silica contained in the bio-tea obtained in Example 2, the bio-tea was carbonized to carbonize the residual carbon component to remove it. Silicon was obtained by carbonization at 570 ^° C for 1 hour. 1.5 g of carbon was carbonized to obtain 0.597 g of silica. From the XRD analysis, quartz SiO ₂ was obtained. FIG. 4A shows the XRD analysis of the silica obtained by this example, and FIG. 4B shows the amorphous SiO ₂ as a result of the XRD analysis of the silica obtained by carbonizing the rice hull as a control group.

Table 5 below shows the purity of about 99.64% as a result of ICP-MS of the silica obtained by this example.

element Content (ppm) Al 67.47 B 18.68 Ba 1.71 Ca 241.3 Co 0.74 Cr 86.98 K 41.81 Li 319.3 Mg 37.06 Mn 95.41 Na 2572 Ni 72.85 P 49.85 Sr 0.67 Ti 3.06 V 0.19 Zn 19.06

Claims

(a) pretreating rice hulls using sodium carbonate; (b) adding an enzyme to the pretreated rice husk to convert it to a monosaccharide; (c) liquefying residual rice husks in the step (b) to produce a bio-oil; And (d) carbonizing the bio-char obtained in the step (c) to produce silica.

The method according to claim 1, wherein the concentration of the aqueous solution of sodium carbonate in step (a) is 1 to 10% by weight.

The method of claim 1, wherein the solid ratio of the rice husks and sodium carbonate aqueous solution introduced into the step (a) is 1: 5-20.

The method according to claim 1, wherein the reaction temperature of step (a) is 100 to 160 ^° C.

The method of claim 1, wherein the reaction time of step (a) is 10 to 60 minutes.

The method of claim 1, wherein the monosaccharide is glucose.

The method of claim 1, wherein step (b) is performed for 12 to 96 hours.

The method of claim 1, wherein the reaction temperature of step (c) is performed at 250 to 350 ^° C.

A monosaccharide, bio-oil and silica, produced by the method of claim 1.