Pretreated lignocellulose biomass and preparation method thereof

Abstract

The invention relates to the technical field of biological fermentation, and discloses a pretreated lignocellulose biomass and a preparation method thereof, the pretreated lignocellulose biomass comprises 35-65% of water, 10-25% of cellulose, 0.5-4% of hemicellulose, 8-16% of lignin, 3-10% of sugar, 0.1-5% of an inhibitor, 1-5% of inorganic acid and / or organic acid, and 0.01-5% of ash. The pretreated lignocellulose biomass provided by the invention has the characteristics of high sugar content, low ash content, low inhibitor content and the like, and is beneficial to subsequent enzymolysis and fermentation.

Description

Technical Field

[0001] The invention relates to the technical field of biological fermentation, and in particular to a pretreated lignocellulose biomass and a preparation method thereof. Background Art

[0002] Lignocellulosic raw materials are one of the most abundant renewable resources in the world. They have a complex structure and are mainly composed of cellulose, hemicellulose and lignin. Cellulose and hemicellulose can be hydrolyzed and used in the biorefining process based on sugar. However, cellulose is tightly wrapped by the network structure formed by hemicellulose and lignin through covalent bonds, thus forming a stubborn and dense structure. Therefore, before the bioconversion of lignocellulosic raw materials, they must be pretreated to break the network structure of hemicellulose and lignin to expose cellulose, further reduce the degree of polymerization and crystallinity of cellulose, and improve the enzyme accessibility and enzymatic efficiency of cellulose. Therefore, the pretreatment process plays a vital role in the development of the biorefining industry using lignocellulose as raw material.

[0003] At present, the pretreatment methods for lignocellulose raw materials mainly include physical method, chemical method, physicochemical method and biological method, including grinding method, alkali treatment method, organic solvent method, wet oxidation method, ammonia fiber expansion method, microwave treatment method, biological method, etc. The principles of different pretreatment methods are different, but the overall treatment is difficult, and the straw materials after pretreatment generally have problems such as high ash content and high inhibitor content, which seriously affect the subsequent enzymatic hydrolysis and fermentation effects. Summary of the invention

[0004] In order to solve the above problems existing in the prior art, the first aspect of the present invention provides a pretreated lignocellulosic biomass, comprising 35-65% moisture, 10-25% cellulose, 0.5-4% hemicellulose, 8-16% lignin, 3-10% sugar, 0.1-5% inhibitor, 1-5% inorganic acid and / or organic acid, 0.01-5% ash; the percentages are percentages relative to the total mass of the pretreated lignocellulosic biomass.

[0005] As a preferred embodiment of the present invention, it includes 35-50% moisture, 15-25% cellulose, 1-3% hemicellulose, 8-12% lignin, 5-10% sugar, 0.1-2% inhibitor, 1-3% inorganic acid and / or organic acid, and 0.01-3% ash.

[0006] In one embodiment, the moisture content of the pretreated lignocellulosic biomass is 35-40%.

[0007] In one embodiment, the inhibitor content of the pretreated lignocellulosic biomass is 0.1-1.5%.

[0008] In one embodiment, the ash content of the pretreated lignocellulosic biomass is 0.01-2%.

[0009] In one embodiment, the sugars include glucose, xylose, and optionally arabinose.

[0010] In one embodiment, the inhibitor includes one or a combination of acetic acid, furfural, hydroxymethylfurfural and phenolic compounds.

[0011] In one embodiment, the organic acid includes one or a combination of lactic acid, citric acid, formic acid, acetic acid, oxalic acid, propionic acid and pyruvic acid.

[0012] In one embodiment, the inorganic acid includes one or a combination of sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid and hydrofluoric acid.

[0013] In one embodiment, the bulk density of the pretreated lignocellulosic biomass is 0.3-0.5 t / m 3 , more preferably 0.4-0.5t / m 3 .

[0014] In one embodiment, the pH value of the pretreated lignocellulosic biomass is ≤4, further ≤3.5, preferably 2-3.

[0015] In one embodiment, the combustion value of the pretreated lignocellulosic biomass is 2000-3500 kcal / kg.

[0016] In one embodiment, the volatile matter of the pretreated lignocellulosic biomass is ≤8 wt %, further ≤5 wt %, preferably 2-4 wt %.

[0017] The second aspect of the present invention provides a method for preparing pretreated lignocellulosic biomass, the method comprising: mixing a lignocellulosic raw material with an acid solution; (1) firstly increasing the pressure of the mixed system to 0-0.2 MPa (gauge pressure) by steam, and then increasing the temperature to 100-130°C and maintaining the temperature for 0.5-1 min; (2) continuing to increase the temperature of the mixed system to 170-200°C and the pressure to 0.8-1.6 MPa by steam, and pretreating at the temperature and pressure for 2-10 min to obtain the pretreated lignocellulosic biomass.

[0018] The pretreated lignocellulosic biomass has the definitions as described above.

[0019] In one embodiment, the mass ratio of the lignocellulosic raw material to the acid solution is 1:(0.1-1.0), further 1:(0.3-0.8).

[0020] In one embodiment, the acid solution includes one or a combination of sulfuric acid solution, hydrochloric acid solution, phosphoric acid solution, nitric acid solution and hydrofluoric acid solution.

[0021] In one embodiment, the concentration of the acid solution is 2-10 wt %.

[0022] As a preferred embodiment of the present invention, in step (1), the mixed system is first heated to a set temperature (i.e., 100-130° C.), and further to 110-120° C., by means of programmed temperature increase using steam.

[0023] Preferably, the heating rate is controlled to be 10-30°C / min, more preferably 15-25°C / min.

[0024] As a preferred embodiment of the present invention, in step (2), the mixed system is continuously heated to a set temperature (i.e., 170-200° C.), and further to 180-190° C., by means of programmed temperature increase using steam.

[0025] Preferably, the heating rate is controlled to be 20-50°C / min, more preferably 30-45°C / min.

[0026] In one embodiment, the pretreatment time is 3-7 min.

[0027] In one embodiment, the lignocellulosic raw material includes, but is not limited to, one or more of corn straw, wheat straw, bagasse, rice straw, cotton straw, rape straw, sorghum stalk, wood chips, waste paper, willow branches and jatropha seed shells.

[0028] Compared with the prior art, the present invention has the following technical effects:

[0029] The pretreated lignocellulosic biomass provided by the present invention has the characteristics of high sugar content, low ash content, low inhibitor content, etc., which is beneficial to subsequent enzymatic hydrolysis and fermentation.

[0030] In addition, the lignocellulosic biomass prepared by the present invention has a high calorific value and low volatile matter, and can be used as a renewable new energy source to replace fossil fuels, further broadening the use scenarios and value of the pretreated lignocellulosic biomass. DETAILED DESCRIPTION

[0031] The present invention will be described in detail below by way of examples. In the following examples, unless otherwise specified, all the raw materials used can be obtained from commercial channels.

[0032] (1) The contents of cellulose, hemicellulose, lignin, sugars, inhibitors, inorganic acids and / or organic acids in the pretreated corn stover were determined by high performance liquid chromatography.

[0033] (2) Ash content detection method: Referring to GB / T212-2001 standard, weigh a certain amount of air-dried sample, put it into a muffle furnace, heat it to 815±10℃ at a certain speed, and burn it until the mass is constant. The percentage of the mass of the residue to the mass of the sample is taken as the ash content of the sample.

[0034] Ash content = {mass of residue (g) / mass of sample (g)}*100%.

[0035] (3) Moisture detection method: The moisture content of the pretreated corn stalks was determined according to the drying method in GB / T5009.3-2016. A certain amount of stalk sample was weighed and placed in an oven at 105°C for 2 h to a constant mass. The percentage of the reduced mass to the mass of the sample was taken as the moisture content.

[0036] Moisture percentage = {mass loss of sample after drying (g) / mass of sample (g)} * 100%.

[0037] (4) pH determination: The pretreated lignocellulosic biomass was crushed to a particle size of 10 mm, then mixed evenly with water at a mass ratio of 1:10, and extracted at 30° C. for 2 h. The pH value of the extract was measured.

[0038] (5) Volatile matter detection method: Referring to GB / T212-2001 standard, a certain amount of air-dried sample is weighed and placed in a covered crucible. It is then heated at 900±10℃ in an air-tight state for 7 min. The percentage of volatile matter is the percentage of the reduced mass to the mass of the sample minus the moisture content of the sample.

[0039] Volatile content = {mass loss of sample after heating (g) / mass of sample (g) * 100%} - moisture content of air-dried sample (%).

[0040] (6) The combustion value of pretreated corn straw was measured with reference to GB / T 213-2008 and other standards.

[0041] Examples 1A to 1C

[0042] Corn stalks are mixed with a sulfuric acid solution (with a concentration of 9 wt%), and (1) the pressure of the mixed system is first increased to 0.07 MPa (gauge pressure) by steam at a heating rate of 20°C / min, and the temperature is maintained at 100°C for 0.5 min; (2) the temperature of the mixed system is continued to be increased to 180°C and the pressure is increased to 1.5 MPa by steam at a heating rate of 25°C / min, and pretreated at this temperature and pressure for 5 min, and then the stalks are exhausted, depressurized and cooled, and the pretreated corn stalks are discharged and cooled for use.

[0043] Among them, the mass ratios of corn stalks to acid solution in Examples 1A to 1C and Comparative Example 1 are different (see Table 1).

[0044] The performance of the pretreated corn stalks obtained in Examples 1A to 1C and Comparative Example 1 was measured. The results are shown in Table 1. Among them, sugars include glucose, xylose, etc.; inhibitors include acetic acid, furfural, hydroxymethylfurfural, phenolic compounds, etc.; organic acids include lactic acid, citric acid, formic acid, acetic acid, oxalic acid, propionic acid, pyruvic acid, etc.; inorganic acids include sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid, hydrofluoric acid, etc.

[0045] Table 1

[0046]

[0047] From the results in Table 1, it can be seen that the present invention controls the mass ratio of corn stalks to sulfuric acid solution within an appropriate range, and the sugar content of the pretreated lignocellulosic biomass is relatively high, the content of inhibitors, inorganic acids and / or organic acids is low, and it has the characteristics of high combustion value, low ash content and volatile matter content. In Comparative Example 1, due to the excessive amount of acid solution added, the sugar content of the pretreated lignocellulosic biomass decreased, and the content of inhibitors, inorganic acids and / or organic acids increased, which is not conducive to subsequent enzymatic hydrolysis and fermentation, and a large amount of acid will cause more serious corrosion to the equipment.

[0048] Examples 2A to 2C

[0049] Corn stalks were mixed with sulfuric acid solution (9 wt %), with the mass ratio of corn stalks to sulfuric acid solution (8 wt %) being 1:0.5. (1) the pressure of the mixed system was first increased to 0.07 MPa (gauge pressure) by steam at a heating rate of 20°C / min, and the temperature was maintained at T1 for 0.5 min. (2) the temperature of the mixed system was continued to be increased to T2 and the pressure was increased to 1.5 MPa by steam at a heating rate of 40°C / min, and pretreated at this temperature and pressure for a period of time, then the exhaust gas was exhausted, the pressure was reduced and the temperature was lowered, and the pretreated corn stalks were discharged and cooled for use.

[0050] Among them, T1, T2 and pretreatment time are different in Examples 2A to 2C and Comparative Example 2 (see Table 2).

[0051] The performance of the pretreated corn stalks obtained in Examples 2A to 2C and Comparative Example 2 was measured. The results are shown in Table 2. The specific compositions of sugars, inhibitors, organic acids and inorganic acids are the same as those in Example 1.

[0052] Table 2

[0053]

[0054] From the results in Table 2, it can be seen that the present invention controls the pretreatment temperature and time within an appropriate range, and the sugar content in the obtained pretreated lignocellulosic biomass is higher, and the content of inhibitors, ash and volatile matter is significantly reduced, which is beneficial to subsequent enzymatic hydrolysis and fermentation. However, when the pretreatment time is too long or too short, and the temperature is too high or too low, the obtained pretreated lignocellulosic biomass is not conducive to enzymatic hydrolysis and fermentation, and the higher the pretreatment cost, the higher the equipment requirements.

[0055] Examples 3A to 3C

[0056] Corn stalks were mixed with sulfuric acid solution, with the mass ratio of corn stalks to sulfuric acid solution (concentration of 8 wt%) being 1:0.5. (1) the pressure of the mixed system was first raised to 0.07 MPa (gauge pressure) using steam, and the temperature was raised to 110°C and maintained for 0.5 min. (2) the temperature of the mixed system was continued to be raised to 180°C and the pressure was raised to 1.5 MPa using steam, and pretreated at this temperature and pressure for 5 min, then the gas was exhausted, the pressure was reduced and the temperature was lowered, and the pretreated corn stalks were discharged and cooled for use.

[0057] Among them, in Examples 3A to 3C and Comparative Example 3, the heating rates of steps (1) and (2) are different (see Table 3).

[0058] The performance of the pretreated corn stalks obtained in Examples 3A to 3C and Comparative Example 3 was measured. The results are shown in Table 3. The specific compositions of sugars, inhibitors, organic acids and inorganic acids are the same as those in Example 1.

[0059] Table 3

[0060]

[0061]

[0062] From the results in Table 3, it can be seen that the present invention has a better straw pretreatment effect by controlling the heating rate within an appropriate range, more hemicellulose is converted into sugars, and the inhibitor, ash and volatile matter contents of the obtained pretreated lignocellulosic biomass are lower.

[0063] Example 4

[0064] Corn straw is mixed with sulfuric acid solution, and the mass ratio of corn straw to sulfuric acid solution (concentration of 8 wt%) is 1:0.5. (1) The pressure of the mixed system is first increased to 0.07 MPa (gauge pressure) by steam at a heating rate of 20°C / min, and the temperature is maintained at 110°C for 0.5 min. (2) The temperature of the mixed system is continued to be increased to 200°C and the pressure is increased to 1.5 MPa by steam at a heating rate of 25°C / min. The mixed system is pretreated at this temperature and pressure for 5 min, and the gas is exhausted, the pressure is reduced and the temperature is lowered. The pretreated corn straw is discharged and cooled for standby use.

[0065] In Comparative Example 4, the temperature of the mixed system was raised to 200° C. and the pressure was raised to 1.5 MPa by using steam at a heating rate of 25° C. / min. The pretreatment was carried out at this temperature and pressure for 5 minutes. Other conditions were the same as those in Example 1.

[0066] The performance of the pretreated corn stalks obtained in Example 4 and Comparative Example 4 was measured. The results are shown in Table 4. The specific compositions of sugar, inhibitor, organic acid and inorganic acid are the same as those in Example 1.

[0067] Table 4

[0068]

[0069] From the results in Table 4, it can be seen that the pretreatment process provided by the present invention can better convert the hemicellulose in the lignocellulosic raw material into sugars, and the content of inhibitors, inorganic acids and / or organic acids is relatively low, which is more conducive to subsequent enzymatic hydrolysis and fermentation. The obtained pretreated lignocellulosic biomass has the characteristics of low ash content, low volatile matter content, high calorific value, etc., and can be used as a renewable new energy source with wide use value.

[0070] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A pretreated lignocellulosic biomass, characterized in that: It comprises 35-65% moisture, 10-25% cellulose, 0.5-4% hemicellulose, 8-16% lignin, 3-10% sugar, 0.1-5% inhibitor, 1-5% inorganic acid and / or organic acid, and 0.01-5% ash; the percentages are relative to the total mass of the pretreated lignocellulosic biomass.

2. The pretreated lignocellulosic biomass according to claim 1, characterized in that It contains 35-50% moisture, 15-25% cellulose, 1-3% hemicellulose, 8-12% lignin, 5-10% sugar, 0.1-2% inhibitor, 1-3% inorganic acid and / or organic acid, and 0.01-3% ash; Further, the moisture content of the lignocellulosic biomass after the pretreatment is 35-40%; Further, the inhibitor content of the lignocellulosic biomass after the pretreatment is 0.1-1.5%; Furthermore, the ash content of the lignocellulosic biomass after the pretreatment is 0.01-2%.

3. The pretreated lignocellulosic biomass according to claim 1, characterized in that The sugars include glucose, xylose and optionally arabinose; and / or, The inhibitor comprises one or a combination of acetic acid, furfural, hydroxymethylfurfural and phenolic compounds; and / or, The organic acid comprises one or a combination of lactic acid, citric acid, formic acid, acetic acid, oxalic acid, propionic acid and pyruvic acid; and / or, The inorganic acid includes one or a combination of sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid and hydrofluoric acid.

4. The pretreated lignocellulosic biomass according to claim 1, characterized in that The bulk density of the pretreated lignocellulosic biomass is 0.3-0.5 t / m 3 , more preferably 0.4-0.5t / m 3 and / or, The pH value of the pretreated lignocellulosic biomass is ≤4, further ≤3.5, preferably 2-3.

5. The pretreated lignocellulosic biomass according to claim 1, characterized in that The combustion value of the pretreated lignocellulosic biomass is 2000-3500 kcal / kg; and / or The volatile matter of the pretreated lignocellulosic biomass is ≤8wt%, further ≤5wt%, preferably 2-4wt%.

6. A method for preparing pretreated lignocellulosic biomass, characterized in that: The method comprises: mixing a lignocellulose raw material with an acid solution; (1) firstly increasing the pressure of the mixed system to 0-0.2 MPa (gauge pressure) by steam, and then increasing the temperature to 100-130° C. and maintaining the temperature for 0.5-1 min; and (2) continuing to increase the temperature of the mixed system to 170-200° C. and the pressure to 0.8-1.6 MPa by steam, and pretreating at the temperature and pressure for 2-10 min.

7. The method according to claim 6, characterized in that The mass ratio of the lignocellulose raw material to the acid solution is 1:(0.1-1.0), further 1:(0.3-0.8).

8. The method according to claim 6, characterized in that The acid solution includes one or a combination of sulfuric acid solution, hydrochloric acid solution, phosphoric acid solution, nitric acid solution and hydrofluoric acid solution; and / or the concentration of the acid solution is 2-10wt%.

9. The method according to claim 6, characterized in that In step (1), the mixed system is heated to a set temperature in a programmed temperature-raising manner, further 110-120° C.; preferably, the heating rate is controlled to be 10-30° C. / min, more preferably 15-25° C. / min; And / or, in step (2), the temperature of the mixed system is continued to be raised to a set temperature by programmed temperature increase, further to 180-190°C; preferably, the heating rate is controlled to be 20-50°C / min, more preferably 30-45°C / min; And / or, the pretreatment time is 3-7 min.

10. The method according to claim 6, characterized in that The lignocellulosic raw materials include, but are not limited to, one or more of corn straw, wheat straw, bagasse, rice straw, cotton straw, rape straw, sorghum stalk, wood chips, waste paper, willow branches and jatropha seed shells.

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