CN102585039B - Extraction separation method of hemicellulose - Google Patents

Abstract

The invention discloses a method for extracting and separating hemicellulose. Firstly, the raw material is pretreated, decolorized and flocculated with an alkaline solution, and then centrifuged and filtered to obtain a hemicellulose product; the flocculant and organic solvent used in the method of the invention The amount of organic solvent is less, and the amount of organic solvent is only 1/3 of the amount of organic solvent in the traditional method. At the same time, the precipitation rate of hemicellulose can reach more than 75% of the hemicellulose content in the raw material, which can greatly reduce the separation of hemicellulose cost.

Description

A kind of extraction separation method of hemicellulose

technical field

The invention relates to a method for extracting and separating hemicellulose, which belongs to the field of comprehensive utilization of biomass resources.

Background technique

Hemicellulose mainly refers to a class of non-cellulose carbohydrates that are closely related to lignin in plant cell walls. It is one of the three main components of plants. The content in coniferous wood is 25%-35%, and in hardwood The content is 18%-22%, while the content in Gramineae is 16%-25%. According to statistics, there are as many as 3.5×10 ¹⁰ tons of hemicellulose produced in the world every year, which is the second renewable resource in nature. However, in the traditional field of plant resource development, such as the pulp and paper industry, hemicellulose is mostly used With the alkali recovery system, it is directly burned as low-value waste, but this treatment method does not fully utilize the value of hemicellulose and lignin, and directly burning it to obtain heat energy is only the primary utilization method , especially the calorific value of hemicellulose (13.6MJ/Kg) is much smaller than that of lignin (27.1MJ/Kg), so it is not reasonable to obtain heat energy by combustion.

With the transformation of people's resource utilization mode and the development of biomass resource development technology, the development of hemicellulose products has shown great potential. Especially with the proposal of the development concept of biomass resources, how to make full use of hemicellulose has become one of the keys to its utilization, and related technologies have always been concerned. Such as using hemicellulose as raw materials for the preparation of levulinate, 1,2-propanediol (non-toxic antifreeze), 1,3-propanediol, fiber-polymer composite materials, biofuels, chemicals, etc., to replace related petrochemical products. If these transformational studies can be successfully realized, hemicellulose will become a high value-added product, and its value will be increased several times or dozens of times.

Although the value of hemicellulose has been re-identified by people, most of its research and development are still in the experimental research stage, and its large-scale development and application are still difficult to put into practice, which is mainly related to its own physical and chemical properties and separation and extraction methods. Relationship.

In addition to the restriction of raw materials on the application of hemicellulose, the extraction and separation technology of hemicellulose is another important factor affecting its development. The traditional separation method of hemicellulose mainly uses the polymer properties of hemicellulose to separate it directly from pulping waste liquid. In the alkaline pulping waste liquid, Venter J.S.M and Hannes Sihtola mixed the equal volume of ethanol with the concentrated waste liquid to precipitate hemicellulose from the waste liquid. In the sulfite pulping waste liquor, Yoshikatsu Ikari adjusted the pH value of the waste liquor to neutral, and then added a certain volume of water-soluble organic solvent, such as acetone, to separate hemicellulose from the waste liquor. The method of directly separating hemicellulose has the characteristics of simple operation and economy, but the hemicellulose separated by this method contains more impurities, especially accompanied by more lignin or lignosulfonate precipitation. Moreover, the use of methanol to separate hemicellulose also has safety issues.

Compared with the development of hemicellulose extraction, the separation of hemicellulose is relatively backward. The traditional hemicellulose separation still uses the organic solvent precipitation method. This method is simple to operate, but the separation efficiency of hemicellulose is relatively low. The separation purity is low, the total sugar content is generally less than 50%, and there is often a certain amount of lignin or lignosulfonate in hemicellulose. The existence of these impurities increases the difficulty of subsequent purification operations such as ethanol reprecipitation, ion exchange, and chromatography. In addition, there are certain difficulties in the recovery of ethanol. It can be seen from the experiment that during the precipitation of each kilogram of polysaccharide, ethanol

The consumption of hemicellulose is about 50-60 kg, while the recovery rate of ethanol is about 30%, pushing up the production cost of hemicellulose.

Contents of the invention

The purpose of the present invention is to provide a hemicellulose flocculation extraction and separation method on the basis of traditional hemicellulose extraction.

Technical scheme of the present invention is as follows:

(1) Use alkaline solution to extract semi-cellulose-containing raw materials, the solid-to-liquid ratio is 1:6-15 (add 6-15ml of alkaline solution per 100g of raw material), and the mixture is reacted at 50-90°C for 2- 6h, make the hemicellulose extract;

(2) After filtering the above-mentioned hemicellulose extract, remove the impurities, adjust the pH value to 4.0-6.0, and stir and react at room temperature for 20-35min;

(3) Add activated carbon of 30-60% of the hemicellulose solution mass to the hemicellulose extract after adjusting the pH value for decolorization, after standing for 20-30min, filter, remove impurities, and collect the filtrate;

(4) Add hemicellulose flocculant to the hemicellulose filtrate after activated carbon treatment at a stirring speed of 300-700rpm

And the organic solvent of 72-94% filtrate volume, carry out flocculation extraction to hemicellulose, the addition amount of flocculant is 0.01-0.08% of filtrate quality, stirring reaction 10-30min;

(5) After the flocculation reaction is completed, the hemicellulose extract is centrifuged at 3500-5000rpm for 15-20min, filtered and dried at 45°C to obtain the hemicellulose product.

The alkali solution in the present invention is NaOH or KOH solution with a mass percentage concentration of 15-40%.

The hemicellulose flocculant in the present invention is a high molecular weight polymer, one of anionic flocculant and inorganic flocculant or a mixture of anionic flocculant and inorganic flocculant in a ratio of 1-7:1.

The high molecular weight polymer in the present invention is commercially available polychitosan or cationic starch containing active amino groups.

The anionic flocculant in the present invention is one of commercially available sodium dodecylbenzenesulfonate, high molecular weight anionic polyacrylamide, and cetyltrimethylammonium bromide.

In the present invention, the inorganic flocculant is a commercially available polyaluminum or polyiron inorganic salt complex capable of ionizing strong positive charges in water.

In the present invention, the polyaluminum or polyferric inorganic salt complex is one of polyaluminum chloride, polyferric chloride and polyaluminum sulfate.

In the present invention, the organic solvent is one or a mixture of two in any proportion among ethanol, methanol and acetone.

The filtrate after activated carbon treatment in the present invention can be assisted by ultrasonic treatment at the same time during flocculation extraction, under the conditions of ultrasonic power of 200-400w and frequency of 28-57Hz, ultrasonic treatment for 8-15min. the

The raw materials used for extracting hemicellulose in the present invention are all plant fiber materials containing hemicellulose.

The present invention adopts the flocculation method combined with organic solvent for the first time in the separation of hemicellulose, which reduces the usage of organic solvent by 1/3, thereby significantly reducing the separation cost of bagasse hemicellulose.

Detailed ways

The present invention will be described in further detail below in conjunction with the examples, but the protection scope of the present invention is not limited to the content.

Embodiment 1: the extraction and separation method of this hemicellulose, concrete steps are as follows:

(1) The bagasse was extracted with NaOH solution with a mass percentage concentration of 15%, and the bagasse and alkali solution were reacted for 5 hours at a solid-to-liquid ratio of 1:8 and a temperature of 75°C to obtain a hemicellulose extract;

(2) After the hemicellulose extract is filtered to remove impurities, put it in a reaction vessel with a stirring device, adjust the pH value of the filtrate to 5.5 with 2mol/L hydrochloric acid and sodium hydroxide, and stir at room temperature for 20 minutes;

(3) Add activated carbon particles with 30% of the mass of the hemicellulose solution to the stirred hemicellulose solution, let it stand for 20 minutes, filter, and collect the filtrate;

(4) Add 0.01% cetyltrimethylammonium bromide of filtrate mass and 87% ethanol of filtrate volume to the filtrate after activated carbon treatment at a stirring speed of 300rpm to flocculate and extract hemicellulose, and stir to react 20min;

(5) After the flocculation reaction is completed, centrifuge the hemicellulose extract at 5000rpm for 20min, filter and dry at 45°C, and 84% of the hemicellulose in the raw material can be precipitated.

Embodiment 2: the extraction and separation method of this hemicellulose, concrete steps are as follows:

(1) Use KOH solution with a mass percentage concentration of 30% to extract the waste liquor from the kraft cooking process of Simao pine, and react bagasse and alkali solution at a solid-liquid ratio of 1:15 at a temperature of 50°C for 2 hours to obtain Hemicellulose extract;

(2) After the hemicellulose extract is filtered to remove impurities, put it in a reaction vessel with a stirring device, adjust the pH value of the filtrate to 4.5 with 2mol/L hydrochloric acid and sodium hydroxide, and stir at room temperature for 30 minutes;

(3) Add activated carbon particles with 50% of the mass of the hemicellulose solution to the stirred hemicellulose solution, react for 25 minutes, filter, and collect the filtrate;

(4) The activated carbon treated filtrate was added with a mixture of 0.06% of the filtrate mass of anionic polyacrylamide-polyferric chloride (2:1) and 72% of the filtrate volume of ethanol/methanol (V _B /V _A =3:7), flocculation extraction of hemicellulose, stirring for 30min;

(5) After the flocculation reaction is completed, centrifuge the hemicellulose extract at 4000rpm for 15min, filter and dry at 45°C, and 89% of the hemicellulose in the raw material can be precipitated.

Embodiment 3: the extraction and separation method of this hemicellulose, concrete steps are as follows:

(1) The bagasse was extracted with a 40% NaOH solution by mass percentage, the solid-liquid ratio of the bagasse and the alkali solution was 1:6, and the mixture was reacted at 90°C for 4 hours to obtain a hemicellulose extract;

(2) After the hemicellulose extract is filtered to remove impurities, put it in a reaction vessel with a stirring device, adjust the pH value of the filtrate to 6 with 2mol/L hydrochloric acid and sodium hydroxide, and stir at room temperature for 35 minutes;

(3) Add activated carbon particles with a mass of 60% of the hemicellulose solution to the stirred hemicellulose solution, react for 30 minutes, filter, and collect the filtrate;

(4) The activated carbon-treated filtrate was subjected to ultrasonic-assisted flocculation at a stirring speed of 700rpm. The ultrasonic conditions were: power 400w, frequency 57Hz, time 15min. Under the above conditions, add 0.02% hexadecane of the filtrate mass Trimethylammonium bromide and 80% ethanol/acetone (V _B /V _C =6:4) of the filtrate volume are used for flocculation extraction of hemicellulose;

(5) After the flocculation reaction is completed, centrifuge the hemicellulose extract at 3500rpm for 20min, filter and dry at 45°C, and 92% of the hemicellulose in the raw material can be precipitated.

Embodiment 4: the extraction and separation method of this hemicellulose, concrete steps are as follows:

(1) The poplar wood was leached with 40% NaOH solution by mass percentage, the solid-liquid ratio of poplar wood and alkali solution was 1:9, and the mixture was reacted at 85°C for 6 hours to obtain hemicellulose extract;

(2) After the hemicellulose extract is filtered to remove impurities, put it in a reaction vessel with a stirring device, adjust the pH value of the filtrate to 4 with 2mol/L hydrochloric acid and sodium hydroxide, and stir at room temperature for 25 minutes;

(3) Add activated carbon particles with 40% mass of the hemicellulose solution to the stirred hemicellulose solution, react for 20 minutes, filter, and collect the filtrate;

(4) The filtrate treated with activated carbon was subjected to ultrasonic-assisted flocculation at a stirring speed of 600rpm. The ultrasonic conditions were: power 200w, frequency 28Hz, time 8min. Under the above conditions, add 0.03% of the filtrate mass containing active amino Cationic starch and filtrate volume 94% methanol/acetone (V _A /V _C =4:6) are used for flocculation extraction of hemicellulose;

(5) After the flocculation reaction is completed, centrifuge the hemicellulose extract at 4500rpm for 18min, filter and dry at 45°C, and 81% of the hemicellulose in the raw material can be precipitated.

Claims (3)

1. an extraction and separation method for hemicellulose, is characterized in that carrying out as follows:

(1) adopting alkaline solution to carrying out lixiviate processing containing hemicellulose raw material, is 1:6-15 in solid-to-liquid ratio, and temperature is to react 2-6h under the condition of 50-90 DEG C, makes hemicellulose extract;

(2) after hemicellulose extract filters, regulate the pH value of filtrate to 4-6, at room temperature stir 20-35min;

(3) in the hemicellulose solution regulating after pH value, add the gac of hemicellulose solution quality 30-60%, leave standstill after 20-30min, filter collection filtrate;

(4) filtrate after activated carbon treatment is under the stirring velocity of 300-700rpm, add the organic solvent of hemicellulose flocculation agent and 72-94% filtrate volume, to the hemicellulose extraction of flocculating, the addition of flocculation agent is the 0.01-0.08% of filtrate quality, stirring reaction 10-30min;

(5) after flocculation reaction completes, under the rotating speed of 3500-5000rpm, to the centrifugal 15-20min of hemicellulose extract, filter and 45 DEG C be dried, obtain the product of hemicellulose;

Wherein said hemicellulose flocculation agent is the mixture a kind of or that be made up of in 1-7:1 ratio anionic flocculant and inorganic flocculating agent in high-molecular weight polymer, anionic flocculant, inorganic flocculating agent;

Described high-molecular weight polymer is poly-chitose or the cationic starch that contains active amino;

Described anionic flocculant is the one in Sodium dodecylbenzene sulfonate, anionic polyacrylamide;

Described inorganic flocculating agent is poly-aluminium or the Polyferric Sulfate inorganic salt complex compound that can ionize out strong positive charge in water;

The NaOH of the mass percent concentration 15-40% of described alkaline solution or KOH solution;

Described poly-aluminium or Polyferric Sulfate inorganic salt complex compound are polymerize aluminum chloride, and poly-ferric chloride is a kind of in polyaluminium sulfate.

2. the extraction and separation method of hemicellulose according to claim 1, is characterized in that: organic solvent is the mixed solution of one or both any ratios in ethanol, methyl alcohol and acetone.

3. the extraction and separation method of hemicellulose according to claim 1, it is characterized in that: when the filtrate after activated carbon treatment is extracted in flocculation, adopt Sonication assisted treatment, ultrasonic power is 200-400w simultaneously, frequency is under the condition of 28-57Hz, supersound process 8-15min.