CN113186233A - Preparation method of biodiesel - Google Patents
Preparation method of biodiesel Download PDFInfo
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- CN113186233A CN113186233A CN202110474358.8A CN202110474358A CN113186233A CN 113186233 A CN113186233 A CN 113186233A CN 202110474358 A CN202110474358 A CN 202110474358A CN 113186233 A CN113186233 A CN 113186233A
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Abstract
The invention provides a preparation method of biodiesel, and belongs to the technical field of pretreatment of municipal sludge. Adjusting the pH value of the municipal sludge to 2-3 to obtain pretreated sludge; adjusting the pH value of the pretreated sludge to 5.5-6.5, and mixing with crude glycerol to obtain a mixed material, wherein the C/N of the mixed material is 70-100; inoculating grease yeast on the mixed material, and then performing fermentation culture to obtain a fermentation product; sequentially carrying out solid-liquid separation and chloroform-methanol extraction on the fermentation product to obtain microbial oil; and (3) carrying out methyl esterification reaction on the microbial oil and the methanol sulfate solution to obtain the biodiesel. According to the invention, the pH value of the municipal sludge is adjusted to 2-3 to obtain the pretreated sludge, so that the breaking of organic macromolecules in the municipal sludge is promoted, the biodegradability of the pretreated sludge is enhanced, the C/N of the mixed material is controlled to be 70-100 by using crude glycerol, the content of microbial oil obtained by culture is higher, and the yield of final biodiesel is further improved.
Description
Technical Field
The invention relates to the technical field of pretreatment of municipal sludge, in particular to a preparation method of biodiesel.
Background
Biodiesel, as a green energy source, has nearly the same properties as diesel fuel. The residual sludge contains lipids synthesized by various oil-producing microorganisms and lipids absorbed from sewage, and is a cheap and easily-obtained oil raw material for synthesizing biodiesel. Research has shown that sludge has great potential as a raw material for synthesizing biodiesel. At present, the preparation of the biodiesel by utilizing the excess sludge mainly comprises the following three ways: firstly, directly extracting grease from excess sludge to prepare biodiesel; secondly, strengthening the fermentation culture mode of producing the grease by using the excess sludge by the oil-producing microorganisms; thirdly, the excess sludge is used as the culture medium of the oil-producing microorganism to inoculate the oil-rich microorganism to produce the grease.
The most suitable carbon source required for the growth of most microorganisms is glucose, the glucose is the most researched and widely applied carbon source which is efficient in cell growth and oil synthesis, and the oil-producing yeast utilizes the glucose to produce the oil with the oil content of more than 60 wt%.
The prior art for preparing biodiesel by using sludge and glucose has the problem of low yield of biodiesel.
Disclosure of Invention
In view of the above, the present invention aims to provide a method for preparing biodiesel. The preparation method provided by the invention utilizes the co-fermentation of the crude glycerol and the municipal sludge to produce the oil, the municipal sludge is pretreated, and the yield of the biodiesel is high.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a preparation method of biodiesel, which comprises the following steps:
adjusting the pH value of the municipal sludge to 2-3 to obtain pretreated sludge;
adjusting the pH value of the pretreated sludge to 5.5-6.5, and mixing the pretreated sludge with crude glycerol to obtain a mixed material, wherein the C/N of the mixed material is 70-100;
inoculating grease yeast on the mixed material, and then performing fermentation culture to obtain a fermentation product;
sequentially carrying out solid-liquid separation and chloroform-methanol extraction on the fermentation product to obtain microbial oil;
and mixing the microbial oil, a methanol sulfate solution and a solvent to perform a methyl esterification reaction to obtain the biodiesel.
Preferably, the inoculation amount of the grease yeast is 5-15%.
Preferably, the inoculation amount of the grease yeast is 10%.
Preferably, the temperature of the fermentation culture is 26-28 ℃, the fermentation culture is carried out under the condition of stirring, and the rotation speed of the stirring is 150-200 rpm.
Preferably, the C/N of the mixed material is 80.
Preferably, the temperature of the methyl esterification reaction is 50-60 ℃ and the time is 10-12 h.
Preferably, the extractant used in the chloroform-methanol method is a mixed solution of chloroform and methanol, and the volume ratio of the chloroform to the methanol in the mixed solution is 2: 1.
Preferably, the volume ratio of the fermentation product to the mixed solution is 1: 1-2: 1.
Preferably, the volume ratio of the microbial oil to the methanol sulfate solution is 2:0.7, and the mass percentage of sulfuric acid in the methanol sulfate solution is 5%.
Preferably, the methyl esterification reaction is followed by extracting the obtained methyl esterification reaction product with n-hexane, and then filtering the obtained upper layer with a 0.45 μm organic membrane.
The invention provides a preparation method of biodiesel, which comprises the following steps: adjusting the pH value of the municipal sludge to 2-3 to obtain pretreated sludge; adjusting the pH value of the pretreated sludge to 5.5-6.5, and mixing the pretreated sludge with crude glycerol to obtain a mixed material, wherein the C/N of the mixed material is 70-100; inoculating grease yeast on the mixed material, and then performing fermentation culture to obtain a fermentation product; sequentially carrying out solid-liquid separation and chloroform-methanol extraction on the fermentation product to obtain microbial oil; and mixing the microbial oil, a methanol sulfate solution and a solvent to perform a methyl esterification reaction to obtain the biodiesel.
According to the invention, the pH value of the municipal sludge is adjusted to 2-3 to obtain the pretreated sludge, so that the breaking of organic macromolecules in the municipal sludge is promoted, the biodegradability of the pretreated sludge is enhanced, the C/N of the mixed material is controlled to be 70-100 by using crude glycerol, the content of microbial oil obtained by culture is higher, and the yield of final biodiesel is further improved. And the crude glycerol is used as a carbon source for culturing the oil-producing microorganisms, thereby not only solving the problem of treatment and disposal of the crude glycerol, but also solving the problem of high production cost caused by the carbon source required by the production of microbial oil,
drawings
FIG. 1 shows the accumulation of microbial oils in example 1;
FIG. 2 shows the accumulation of lipids in experiment group 1 in example 1 with glucose added;
FIG. 3 shows the accumulation of lipids in experiment group 2 in example 1 with glucose added;
FIG. 4 shows the accumulation of lipids in experiment group 3 in example 1 with glucose added;
FIG. 5 shows the carbon source consumption of experiment 1 in example 1 with glucose added;
FIG. 6 shows the carbon source consumption of experiment group 2 in which glucose was added in example 1;
FIG. 7 shows the carbon source consumption of experiment group 3 in which glucose was added in example 1;
FIG. 8 shows the change of oil accumulation in the case of treatment at pH 2 for 1 hour with glycerol added under the pretreatment conditions of example 1;
FIG. 9 shows the change of oil accumulation when glycerin is added after 7 hours of treatment under the pretreatment condition of pH 1 in example 1;
FIG. 10 is a graph showing the composition and content of fatty acid methyl esters in each experimental group in example 1.
Detailed Description
The invention provides a preparation method of biodiesel, which comprises the following steps:
adjusting the pH value of the municipal sludge to 2-3 to obtain pretreated sludge;
adjusting the pH value of the pretreated sludge to 5.5-6.5, and mixing the pretreated sludge with crude glycerol to obtain a mixed material, wherein the C/N of the mixed material is 70-100;
inoculating grease yeast on the mixed material, and then performing fermentation culture to obtain a fermentation product;
sequentially carrying out solid-liquid separation and chloroform-methanol extraction on the fermentation product to obtain microbial oil;
and mixing the microbial oil, a methanol sulfate solution and a solvent to perform a methyl esterification reaction to obtain the biodiesel.
The method adjusts the pH value of the municipal sludge to 2-3 to obtain the pretreated sludge. The source of the municipal sludge is not particularly limited in the present invention, and any source known to those skilled in the art may be used.
The pH value of the municipal sludge is preferably adjusted by using a 12mol/L hydrochloric acid solution, the dosage of the hydrochloric acid solution is not particularly limited, and the pH value of the pretreated sludge can be ensured to be 2-3.
After the pretreated sludge is obtained, the pretreated sludge is preferably oscillated, the oscillating rotation speed is preferably 150r/min, the oscillating time is preferably 21h, and the oscillating is preferably carried out in a constant temperature oscillator.
After the pretreated sludge is obtained, the pH value of the pretreated sludge is adjusted to 5.5-6.5, and then the pretreated sludge is mixed with crude glycerol to obtain a mixed material, wherein the C/N of the mixed material is 70-100.
The pH value of the pretreated sludge is preferably adjusted by using 1mol/L sodium hydroxide solution, the dosage of the sodium hydroxide solution is not specially limited, and the pH value can be adjusted to be 5.5-6.5.
In the present invention, the pH value of the pretreated sludge is preferably adjusted to 6.
The source of the crude glycerol is not particularly limited in the present invention, and any source known to those skilled in the art can be used, specifically, a by-product from the methyl esterification of fats and oils and methanol to produce biodiesel.
In the present invention, the mass content of glycerin in the crude glycerin is preferably 30 to 85%, and more preferably 80%.
The use amount of the crude glycerol is not specially limited, and the C/N of the mixed material can be ensured to be 70-100. In the present invention, the C/N of the mixed material is preferably 80.
After the mixed material is obtained, the oil yeast is inoculated on the mixed material and then fermentation culture is carried out to obtain a fermentation product.
In the present invention, the inoculation amount of the oleaginous yeast is preferably 5 to 15%, more preferably 10%.
In the invention, the temperature of the fermentation culture is preferably 26-28 ℃, the fermentation culture is preferably carried out under the condition of stirring, and the rotation speed of the stirring is preferably 150-200 rpm, and more preferably 180 rpm.
In the fermentation culture process, the fermentation product is preferably sampled every 24 hours or every 12 hours, and the biomass and the accumulated amount of grease in the fermentation culture process are respectively measured.
In the present invention, the method for measuring biomass preferably comprises the steps of:
10mL of the fermentation product was centrifuged and the resulting solid was dried at 105 ℃ to constant weight. In the present invention, the rotation speed of the centrifugal treatment is preferably 4000r/min, and the time is preferably 15 minutes.
In the present invention, the biomass is constant weight per 10mL, and the unit of the biomass is preferably g/L.
In the present invention, the oil accumulation amount is the oil content after extraction/biomass at the same volume, and when the oil content does not rise any more, the fermentation culture is terminated.
After a fermentation product is obtained, the invention sequentially carries out solid-liquid separation and chloroform-methanol extraction on the fermentation product to obtain the microbial oil.
In the invention, the solid-liquid separation is preferably centrifugation, the rotation speed of the centrifugation is preferably 4000r/min, and the time is preferably 10 min.
In the present invention, the extractant used in the chloroform-methanol extraction is preferably a mixture of chloroform and methanol, and the volume ratio of chloroform to methanol in the mixture is preferably 2:1 or 1: 1.
In the invention, the volume ratio of the fermentation product to the mixed liquid is preferably 1: 1-2: 1.
In the present invention, glass beads are preferably added at the time of the chloroform-methanol extraction, and the diameter of the glass beads is preferably 2 mm.
In the present invention, the number of times of the chloroform-methanol extraction is preferably 2.
In the invention, the chloroform-methanol extraction is preferably carried out under the condition of oscillation, the rotation speed of the oscillation is preferably 2000r/min, and the time is preferably 30 min.
In the present invention, the chloroform-methanol extraction process preferably comprises the steps of:
centrifuging the fermentation product for 10min at 4000r/min, performing first extraction on microbial oil by adopting a chloroform-methanol method on wet sludge of a first lower layer obtained by the first centrifugation, adding glass beads into the wet sludge of the first lower layer, adding an extracting agent with a volume ratio of chloroform to methanol of 2:1, oscillating, mixing an obtained oscillating system with a NaCl solution, centrifuging at the rotating speed of 4000r/min for 5min to obtain a first bottom chloroform layer containing the microbial oil, and extracting the first bottom chloroform layer containing the microbial oil to weighed M1(g) Discarding methanol and a water layer, centrifuging the rest solid part for 10min at 4000r/min for the second time, performing second extraction on the microbial oil by adopting a chloroform-methanol method on the wet sludge of the lower layer obtained by the second centrifugation, adding glass beads into the wet sludge of the second lower layer, adding an extracting agent with the volume ratio of chloroform to methanol being 1:1, oscillating, mixing the obtained oscillating system with a NaCl solution, centrifuging at the rotating speed of 4000r/min for 5min to obtain a second bottom chloroform layer containing the microbial oil, mixing the first bottom chloroform layer containing the microbial oil and the second bottom chloroform layer containing the microbial oil, and volatilizing the obtained container phase with the mixed phase in an oven at 80 ℃ to constant weight M2(g) The method for calculating the yield of the microbial oil is shown as a formula (1), and the formula for calculating the content of the microbial oil is shown as a formula (2):
C＝W/MLSS×100％ (2)
in the formula M1-weight (g) after drying to constant weight in the container at 105 ℃;
M2-the weight (g) of the container with the mixed phase after drying at 80 ℃ to constant weight;
v-volume of sludge (mL);
w-microbial oil yield (g/L);
c-microbial oil content (%);
MLSS-suspended solids concentration in g/L in sludge.
After the microbial oil is obtained, the microbial oil, a methanol sulfate solution and a solvent are mixed for methyl esterification reaction to obtain the biodiesel.
In the invention, the methyl esterification reaction is preferably carried out at the temperature of 50-60 ℃ for 10-12 h.
In the invention, the volume ratio of the microbial oil to the methanol sulfate solution is preferably 2:0.7, and the mass percentage of sulfuric acid in the methanol sulfate solution is preferably 5%.
In the present invention, the solvent is preferably n-hexane.
In the invention, preferably, the microbial oil is dissolved by normal hexane, and then a methanol sulfate solution is added for methyl esterification reaction. The method has no special limitation on the dosage of the normal hexane, and can ensure that the microbial oil is completely dissolved.
In the present invention, the methyl esterification reaction preferably further comprises extracting the obtained methyl esterification reaction product with n-hexane, and then filtering the obtained upper layer with a 0.45 μm organic membrane.
In the present invention, the number of n-hexane extractions is preferably 3, and the amount of n-hexane used in each extraction is not particularly limited.
After the upper layer is filtered by using a 0.45 mu m organic membrane, the invention preferably performs gas chromatography (GC-FID) detection on the obtained filtrate to determine the composition of the biodiesel and the content of each component.
In the present invention, the detection conditions for the gas chromatography (GC-FID) detection are preferably: the used biodiesel standard is 37 kinds of fatty acid methyl ester mixed standard (NU-CHEK-PREP, INC. USA), and is purchased from Shanghai' an spectral experiment science and technology, Inc.; the model of the gas chromatograph is Agilent-7890A, and the specific parameters are set as follows: the chromatographic column is HP-5(30m multiplied by 0.32mm multiplied by 0.25 mu m, Agilent-19091J-413), and the detector is a hydrogen flame ion detector; a sample inlet: the flow is not split, and the flow rate of tail gas blowing nitrogen is 15 mL/min; ③ sample injector: the sample injection volume is 1.0 mu L; column box temperature-rising program: maintaining the initial temperature of the column box for 1min at 5min, heating to 130 deg.C at 10 deg.C/min, heating to 200 deg.C at 4 deg.C/min, heating to 220 deg.C at 3 deg.C/min, and heating to 270 deg.C at 5 deg.C/min; flow rates of hydrogen, air and nitrogen are respectively 30mL/min, 300mL/min and 25 mL/min; sixthly, the inlet temperature is 200 ℃, and the temperature of the FID detector is 270 ℃.
In order to further illustrate the present invention, the following examples are given to describe the preparation method of biodiesel according to the present invention in detail, but they should not be construed as limiting the scope of the present invention.
Example 1
The embodiment provides a method for preparing biodiesel from crude glycerol and municipal sludge, which comprises the following steps:
the sludge used in the experiment is sludge from a sewage treatment plant in the south, and the basic properties of the sludge are shown in table 1. The oleaginous microorganism (grease yeast) used in the test needs to grow and propagate by using sludge, a heterotrophic oleaginous microorganism, namely saccharomyces starkeyi, which is purchased from the China center for industrial microorganism culture collection management is selected, the growth conditions of the oleaginous yeast (grease yeast) are shown in Table 2, and the oleaginous yeast (grease yeast) is cultured by using a YPD culture medium.
TABLE 1 basic Properties of the sludge
TABLE 2 growth conditions of oleaginous yeast
S1: comparison of different pretreatment conditions: the method comprises the steps of treating sludge by adopting acid heat, adjusting the pH value of the sludge to 1, 2, 3, 4, 5 and 6 by using 1mol/L hydrochloric acid and 12mol/L hydrochloric acid respectively, setting blank control groups (the pH value of the sludge is 6.6-6.9), setting the temperature to room temperature, 60 ℃, 70 ℃ and 80 ℃ respectively, oscillating the sludge for 21 hours at a constant temperature oscillator at a rotating speed of 150r/min, sampling the sludge for 1, 3, 7, 13 and 21 hours respectively, and measuring SCOD, TN, protein and polysaccharide indexes. The pretreatment conditions are favorable for improving the property of the sludge and increasing the SCOD when the sludge is treated for 1, 7 and 13 hours under the conditions that the pH is 2 (room temperature), 1 (room temperature) or 3(60 ℃).
S2: under the condition of no external carbon source, the accumulation conditions of the oil-producing yeast grease under the condition of three better acid-heat pretreatment screened by S1 are as follows: and (3) dividing the mixture into three groups according to pretreatment conditions, simultaneously inoculating oleaginous yeasts into the three groups, wherein the oleaginous yeasts are 10% (v/v), sampling culture solution every 24h, and observing the accumulation condition of sludge grease. Experimental grouping is shown in table 3.
TABLE 3 sludge pretreatment conditions and name of Experimental group
Before culturing the oil-producing yeast by using the sludge as a substrate, the pH values of the pretreated sludge and the sludge which is not pretreated at room temperature are adjusted to 6 by using 1mol/L sodium hydroxide, good conditions are created for microbial growth and oil accumulation, and the oil accumulation condition of the oil-producing yeast is observed, as shown in figure 1. It can be seen that the pH value is 2 (room temperature), and the grease accumulation condition is better when the treatment is carried out for 1 h.
S3: determining the optimal C/N ratio under the condition of glucose as an external carbon source: after different pretreatments, the C/N of the sludge is respectively adjusted to 60, 80 and 100, 2 parallel samples are respectively taken after every 24h sampling, and the oil accumulation condition is determined, as shown in figures 2-4, wherein figure 2 is the oil accumulation condition of an experiment group 1 with glucose added, figure 3 is the oil accumulation condition of the experiment group 2 with glucose added, figure 4 is the oil accumulation condition of an experiment group 3 with glucose added, and compared with the oil accumulation conditions under different C/N conditions, the oil accumulation amount is the highest in the C/N80 condition, and the oil accumulation amount in the C/N100 condition is the next.
S4: carbon source utilization: the method comprises the steps of taking pretreated sludge as a substrate, adding a certain amount of glucose according to the C/N conditions of different pretreated sludge to adjust the C/N to be 60, 80 and 100, inoculating 10% of oil-producing yeast, culturing in a constant-temperature shaking incubator (28 ℃, 180r/min), sampling every 24 hours, and showing the utilization condition of a carbon source in the culture process as shown in figures 5-7. Wherein fig. 5 is a carbon source consumption situation of the experiment group 1 with glucose added, fig. 6 is a carbon source consumption situation of the experiment group 2 with glucose added, and fig. 7 is a carbon source consumption situation of the experiment group 3 with glucose added, and it can be seen from fig. 5 to 7 that SCOD is consumed rapidly in the first 48 hours and then slowly. When the pretreatment condition is that the pH is 2 for 1 hour, the utilization rate of the carbon source in the sludge is the highest, which can reach 97 percent, and the pH is 1. When comparing different C/N effects, the carbon source utilization was found to be most complete at C/N100, followed by the efficiency of C/N80 utilization.
S5: microbial oil production from different substrates: selecting pH, treating the sludge for 1h under the pretreatment conditions that the pH value is 2 and the pH value is 1 and treating for 7h, and adjusting the C/N of the sludge to 80 by using crude glycerol and pure glycerol respectively. In different culture systems, sampling every 12h, taking 2 parallel samples from each sample, extracting microbial oil by adopting a chloroform-methanol method, and determining the oil accumulation amount by adopting a gravimetric method, wherein the specific steps are as follows:
centrifuging 30mL of fermentation product at 4000r/min for 10min, pouring out the supernatant obtained by centrifugation, storing the supernatant for measuring SCOD, N and P, and extracting and measuring the grease by adopting a chloroform-methanol method. Adding glass beads (diameter of 2mm) into the wet sludge at the lower layer, adding 30mL of chloroform-methanol solution (2: 1, v/v), then placing into an oscillator for oscillation at 2000r/min for 30min, adding 5mL of NaCl solution into a centrifuge tube after oscillation is finished, then centrifuging at the rotation speed of 4000r/min for 5min, and extracting the chloroform layer at the bottom layer to weighed M after centrifugation is finished1(g) In the container (2). Removing the upper layer of methanol-water mixture based on the first extraction, adding 20mL of chloroform-methanol solution into the solid in the centrifuge tubePlacing the solution (1: 1, v/v), then placing into an oscillator for oscillation, 2000r/min, 15min, adding 5mL NaCl solution into a centrifuge tube after oscillation is finished, centrifuging for 5min at 4000r/min, extracting the upper chloroform layer into the container in the first step, placing the container containing the chloroform layer into an oven, and volatilizing at 80 ℃ to constant weight M2(g) Extracting the oil to obtain two parallel samples, wherein the calculation method of the oil yield is shown as a formula (1), and the calculation formula of the content of the microbial oil is shown as a formula (2):
C＝W/MLSS×100％ (2)
in the formula M1-weight (g) after drying to constant weight in the container at 105 ℃;
M2-the weight (g) of the container with the mixed phase after drying at 80 ℃ to constant weight;
v-volume of sludge (mL);
w-microbial oil yield (g/L);
c-microbial oil content (%);
MLSS-suspended solids concentration in g/L in sludge.
The change of the oil content in each culture system during the culture process is shown in fig. 8-9, wherein fig. 8 is the change of the oil accumulation when the pretreatment condition pH value is 2 for 1 hour and glycerol is added, and fig. 9 is the change of the oil accumulation when the pretreatment condition pH value is 1 for 7 hours and glycerol is added. As can be seen from FIGS. 8 to 9, in different culture systems, the change of the microbial oil content shows a tendency of increasing first and then decreasing, after the sludge is pretreated for 1 hour at a pH value of 2 and 7 hours at a pH value of 1, crude glycerol and pure glycerol are respectively used as external carbon sources, wherein the microbial oil content reaches the highest value near 60 hours, and is respectively 46 wt%, 40 wt%, 54 wt% and 38 wt%, which are 2.1, 1.9, 2.2 and 1.9 times of the initial content. Therefore, the microbial oil accumulation amount is higher when the crude glycerol is used as an external carbon source than when the pure glycerol is used as a substrate, and the oil production effect is good when the crude glycerol is used as the external carbon source.
S6: biodiesel component analysis: the method comprises the steps of performing methyl esterification on microbial oil extracted from a culture system with carbon sources of glucose, crude glycerol and pure glycerol to prepare biodiesel, adding 10.5mL of 5% methanol sulfate solution into the microbial oil extracted from 30mL of sludge, performing methyl esterification reaction in water bath at 55 ℃ for 12h, repeatedly extracting with n-hexane for 3 times, oscillating and standing to enable the methanol and the n-hexane to be layered, filtering the upper n-hexane layer with an organic membrane of 0.45 mu m, and using the filtered solution for the on-machine detection of gas chromatography (GC-FID).
The biodiesel standard used in the gas chromatography (GC-FID) measurement is a mixture of 37 fatty acid methyl esters (NU-CHEK-PREP, INC. USA) and purchased from Shanghai' an spectral laboratory science and technology, Inc. The model of the gas chromatography is Agilent-7890A, and the specific parameters are set as follows: the chromatographic column is HP-5(30m multiplied by 0.32mm multiplied by 0.25 mu m, Agilent-19091J-413), and the detector is a hydrogen flame ion detector; a sample inlet: the flow is not split, and the flow rate of tail gas blowing nitrogen is 15 mL/min; ③ sample injector: the sample injection volume is 1.0 mu L; column box temperature-rising program: maintaining the initial temperature of the column box for 1min at 5min, heating to 130 deg.C at 10 deg.C/min, heating to 200 deg.C at 4 deg.C/min, heating to 220 deg.C at 3 deg.C/min, and heating to 270 deg.C at 5 deg.C/min; flow rates of hydrogen, air and nitrogen are respectively 30mL/min, 300mL/min and 25 mL/min; sixthly, the inlet temperature is 200 ℃, and the temperature of the FID detector is 270 ℃.
The fatty acid methyl ester composition is shown in FIG. 10. After the sludge is pretreated by acid with the pH value of 1 and the pH value of 2, the stearic acid (C18: 0) in the sludge is respectively increased from the initial 18.82 wt% to 34.14 wt% and 38.59 wt%.
When glucose, pure glycerol and crude glycerol are used as different external carbon sources, after a certain period of culture, the ratio of palmitic acid (C16: 0) to stearic acid (C18: 0) in the fatty acid methyl ester is 12.7-18.74 wt%, and the ratio of stearic acid (C18: 0) to stearic acid is 17.44-40.27 wt% respectively. The ideal biodiesel mainly comprises C18, and the content of C18 in fatty acid methyl ester is increased, which indicates that the prepared biodiesel is ideal.
The foregoing is merely a preferred embodiment of the invention and is not intended to limit the invention in any manner. It should be noted that, for those skilled in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be construed as the protection scope of the present invention.
Claims (10)
1. The preparation method of the biodiesel is characterized by comprising the following steps:
adjusting the pH value of the municipal sludge to 2-3 to obtain pretreated sludge;
adjusting the pH value of the pretreated sludge to 5.5-6.5, and mixing the pretreated sludge with crude glycerol to obtain a mixed material, wherein the C/N of the mixed material is 70-100;
inoculating grease yeast on the mixed material, and then performing fermentation culture to obtain a fermentation product;
sequentially carrying out solid-liquid separation and chloroform-methanol extraction on the fermentation product to obtain microbial oil;
and mixing the microbial oil, a methanol sulfate solution and a solvent to perform a methyl esterification reaction to obtain the biodiesel.
2. The method according to claim 1, wherein the amount of the inoculated oleaginous yeast is 5 to 15%.
3. The method according to claim 1 or 2, wherein the amount of the inoculated oleaginous yeast is 10%.
4. The method according to claim 1, wherein the fermentation culture is carried out at a temperature of 26 to 28 ℃ under stirring at a rotation speed of 150 to 200 rpm.
5. The method of claim 1, wherein the mixture has a C/N of 80.
6. The preparation method according to claim 1, wherein the temperature of the methyl esterification reaction is 50-60 ℃ and the time is 10-12 h.
7. The method according to claim 1, wherein the extractant used in the chloroform-methanol extraction is a mixture of chloroform and methanol, and the volume ratio of chloroform to methanol in the mixture is 2: 1.
8. The method according to claim 7, wherein the volume ratio of the fermentation product to the mixed solution is 1:1 to 2: 1.
9. The method according to claim 1, wherein the volume ratio of the microbial oil to the methanol sulfate solution is 2:0.7, and the mass percentage of sulfuric acid in the methanol sulfate solution is 5%.
10. The method according to claim 1 or 6, wherein the methyl esterification reaction is followed by extracting the resulting methyl esterification reaction product with n-hexane and then filtering the resulting upper layer with a 0.45 μm organic membrane.
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| CN (1) | CN113186233A (en) |
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| CN103923685A (en) * | 2014-05-09 | 2014-07-16 | 北京师范大学 | Method for preparing biodiesel through activated sludge |
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| CN103923685A (en) * | 2014-05-09 | 2014-07-16 | 北京师范大学 | Method for preparing biodiesel through activated sludge |
| CN105219419A (en) * | 2015-10-20 | 2016-01-06 | 上海应用技术学院 | A kind of method adopting mud to prepare biofuel |
| CA2945507A1 (en) * | 2016-10-14 | 2018-04-14 | Institut National De La Recherche Scientifique | Process for hydrogen production from glycerol |
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