阅读说明：本技术 一种茶油饼粕制备生物柴油的方法 (Method for preparing biodiesel from tea oil cake meal ) 是由 张涛 唐艳萍 陈勇 李艳 于 2021-08-26 设计创作，主要内容包括：本发明公开了一种茶油饼粕制备生物柴油的方法,包括以下步骤：1)油脂提取；2)浓缩,得到毛茶油；3)萃取法降酸,回收有机溶剂,得到脱酸茶油；4)将脱酸茶油和有机溶剂采用硅胶干燥剂吸附脱水,得到干燥后的脱酸茶油；5)酯交换反应；6)分液,得到粗级产品；7)水洗干燥,得到生物柴油粗品；8)分子蒸馏,得到生物柴油。本发明采用茶油饼粕制备生物柴油的过程中,先采用有机溶剂萃取毛茶油中的游离脂肪酸,再将脱酸茶油进行吸附脱水后进行酯交换反应,避免了原料油脂水解造成游离脂肪酸含量的增加,有效防止了催化剂与游离脂肪酸发生皂化反应,提高催化剂的催化效果,进而缩短了生物柴油的制备时间,提高了生物柴油的制备效率和得率。(The invention discloses a method for preparing biodiesel from tea oil cake meal, which comprises the following steps: 1) extracting oil; 2) concentrating to obtain crude tea oil; 3) reducing acid by an extraction method, and recovering an organic solvent to obtain deacidified tea oil; 4) adsorbing and dehydrating the deacidified tea oil and the organic solvent by using a silica gel drying agent to obtain dried deacidified tea oil; 5) performing ester exchange reaction; 6) separating liquid to obtain a coarse-grade product; 7) washing and drying to obtain a crude product of the biodiesel; 8) molecular distillation to obtain the biodiesel. In the process of preparing the biodiesel by adopting the tea oil cake meal, the organic solvent is adopted to extract free fatty acid in the crude tea oil, and then the deacidified tea oil is subjected to adsorption dehydration and then subjected to ester exchange reaction, so that the increase of the content of the free fatty acid caused by hydrolysis of raw material oil is avoided, the saponification reaction of the catalyst and the free fatty acid is effectively prevented, the catalytic effect of the catalyst is improved, the preparation time of the biodiesel is further shortened, and the preparation efficiency and the yield of the biodiesel are improved.)

1. A method for preparing biodiesel from tea oil cake meal is characterized by comprising the following steps: the method comprises the following steps: 1) extracting oil; 2) concentrating to obtain crude tea oil; 3) reducing acid by an extraction method, and recovering an organic solvent to obtain deacidified tea oil; 4) adsorbing and dehydrating the deacidified tea oil and the organic solvent by using a silica gel drying agent to obtain dried deacidified tea oil; 5) performing ester exchange reaction; 6) separating liquid to obtain a coarse-grade product; 7) washing and drying to obtain a crude product of the biodiesel; 8) and (5) performing molecular distillation to obtain the purified light yellow transparent biodiesel.

2. The method for preparing biodiesel according to claim 1, wherein the method comprises the following steps: the specific operation steps of the step 1) are as follows: a) crushing the tea oil cake dregs, sieving and drying for later use; b) extracting the tea oil in the crushed tea seed cake with petroleum ether, and collecting the tea oil for later use after the extraction is finished.

3. The method for preparing biodiesel according to claim 1, wherein the method comprises the following steps: the specific operation steps of the step 3) are as follows: adding an organic solvent into the raw tea oil obtained in the step 2) for extraction while stirring, standing and layering the solution after extraction is finished, wherein the upper layer is the organic solvent and free fatty acid, and the lower layer is deacidified tea oil, and recovering the organic solvent for later use.

4. The method for preparing biodiesel according to claim 3, wherein the method comprises the following steps: the volume ratio of the organic solvent added into the raw tea oil to the raw tea oil is 2: 1-4: 1, the organic solvent is absolute methanol.

5. The method for preparing biodiesel according to claim 1, wherein the method comprises the following steps: the specific operation steps of the step 4) are as follows: and adding a silica gel drying agent into the deacidified tea oil for drying, and drying the recovered organic solvent by using the silica gel drying agent after passing through a rotary evaporator for ester exchange reaction.

6. The method for preparing biodiesel according to claim 1, wherein the method comprises the following steps: the specific operation steps of the step 5) are as follows: the organic solvent after the adsorption and dehydration treatment in the step 4) is mixed according to the mass ratio of 4: 1-10: 1 adding the obtained dried deacidified tea oil, adding a KOH catalyst, reacting under stirring at constant temperature, and recovering excessive organic solvent after the reaction is finished.

7. The method for preparing biodiesel according to claim 6, wherein the method comprises the following steps: the dosage of the KOH catalyst is 0.2 to 1.5 percent of the mass of the dried deacidified tea oil.

8. The method for preparing biodiesel according to claim 6, wherein the method comprises the following steps: the reaction temperature of the organic solvent after dehydration and the dried deacidified tea oil is 50-90 ℃, and the reaction time is 60-180 min.

9. The method for preparing biodiesel according to claim 1, wherein the method comprises the following steps: the specific operation steps of the step 7) are as follows: a. adding hot soft water into the coarse product, washing with water, slowly vibrating to make the materials fully contact, standing, layering, discharging the lower water layer, repeating the above washing steps for 2-4 times, and collecting the upper oil phase; b. transferring the oil phase to a rotary evaporator, and dehydrating and drying to obtain a crude biodiesel for later use.

10. The method for preparing biodiesel according to claim 1, wherein the method comprises the following steps: the specific operation steps of the step 8) are as follows: a) putting the crude biodiesel into a first-stage film evaporator to evaporate the crude biodiesel, and collecting light components; b) and (3) placing the light component into a wiped film type molecular distiller for molecular distillation, and collecting the light phase component to obtain the purified light yellow transparent biodiesel.

Technical Field

The invention relates to the technical field of biodiesel preparation, in particular to a method for preparing biodiesel from tea oil cake meal.

Background

Tea oil, also known as tea seed oil and camellia oil, is obtained from seeds of camellia oleifera trees in the family of theaceae and is a unique woody oil in China. China has rich oil tea resources, the area of an oil tea forest accounts for more than 80% of the area of woody edible oil plants, and the oil tea forest is widely distributed in hilly areas of 17 provinces in south, and most areas are Guangxi, Hunan, Jiangxi, Yunnan and the like.

The tea oil contains a large amount of unsaturated fatty acid, has a low freezing point and is very favorable for being converted into biodiesel. The pressed tea oil cake pulp generally contains 7-10% of residues, the residual oil is extracted by a solvent extraction method, and the edible oil residual in the solvent has potential safety hazard to human bodies. The tea oil cake residual oil is edible, the methyl ester is relatively low, and the application of the tea oil cake residual oil in the production of biodiesel is an excellent utilization way. With the attention of the country to the development of the oil tea at present, the total yield of the oil tea continuously shows an upward trend, and the content of the oil tea cake pulp is rapidly increased, so that a good raw material source is provided for the production of the biodiesel.

With the rapid increase of the demand of petroleum resources in China and the small total amount of petroleum resources in China, the supply gap is larger and larger. At present, the supply of petroleum resources in China is changed from domestic guarantee to import satisfaction, and the condition endangers the energy safety of the country, so that the search for petroleum alternative energy is reluctant under the background. Biodiesel is a clean renewable energy source, is favored by China as a future diesel substitute, and the preparation method of the biodiesel gradually receives wide attention and research, such as:

patent application No. CN201210295262.6 discloses a method for preparing biodiesel by using cottonseed oil soapstock as a raw material, which comprises the following steps: 1) placing a 250mL three-neck flask in a heating jacket, and installing a stirrer, a condenser and a thermometer; 2) adding fatty matter and methanol, adding catalyst, stirring, heating and refluxing; 3) removing methanol from the product, washing the product to be neutral, heating and dehydrating the product, and sampling the product; 4) and (3) measuring the acid value of the sample, adding a deacidification agent according to the measured acid amount, performing suction filtration to obtain a crude product, and performing reduced pressure distillation on the crude product to obtain the mixed fatty acid methyl ester.

In the preparation method of the biodiesel, the catalyst and the methanol are directly added into the raw materials for transesterification, and then the steps of separation and deacidification are carried out, wherein the deacidification treatment is carried out after the transesterification, because the raw materials do not carry out dehydration and deacidification treatment, the raw materials contain water and free fatty acid, when the transesterification is carried out, the water in the raw materials can hydrolyze grease to generate fatty acid and glycerin, the generated fatty acid and the free fatty acid contained in the raw materials can have saponification reaction with the catalyst to generate a large amount of fatty soap, so that most of the catalyst is consumed, the catalytic effect is reduced, the viscosity of a reaction system is increased, the separation of the glycerin is not facilitated, and the preparation efficiency and the yield of the biodiesel are reduced.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: overcomes the defects of the prior art, and provides a method for preparing biological tea oil from tea oil cake meal with simple preparation method and high biodiesel yield.

The technical scheme adopted by the invention for solving the technical problems is as follows: a method for preparing biodiesel from tea oil cake meal comprises the following steps: 1) extracting oil; 2) concentrating to obtain crude tea oil; 3) reducing acid by an extraction method, and recovering an organic solvent to obtain deacidified tea oil; 4) adsorbing and dehydrating the deacidified tea oil and the organic solvent by using a silica gel drying agent to obtain dried deacidified tea oil; 5) performing ester exchange reaction; 6) separating liquid to obtain a coarse-grade product; 7) washing and drying to obtain a crude product of the biodiesel; 8) and (5) performing molecular distillation to obtain the purified light yellow transparent biodiesel.

In the process of preparing the biodiesel, the extraction method is adopted to extract the fatty acid in the raw tea oil, and the deacidified tea oil is subjected to ester exchange reaction after being subjected to adsorption and dehydration, so that the reaction of free fatty acid and a catalyst is effectively avoided, the catalytic effect and the preparation efficiency of the biodiesel are increased, and the yield of the biodiesel is improved.

Further, the specific operation steps of step 1) are as follows: a) crushing the tea oil cake dregs, sieving and drying for later use; b) extracting the tea oil in the crushed tea seed cake with petroleum ether, and collecting the tea oil for later use after the extraction is finished.

Further, the tea oil cake dregs are crushed and then screened by a 60-mesh sieve, the drying temperature is 75 ℃, the extraction temperature when the tea oil is extracted by the petroleum ether is 65-80 ℃, and the extraction time is 8-10 h.

Further, the specific operation steps of step 2) are as follows: concentrating the tea oil obtained in the step 1) by using a rotary evaporator, and collecting crude tea oil for later use after petroleum ether is completely separated;

further, the specific operation steps of step 3) are as follows: adding an organic solvent into the raw tea oil obtained in the step 2) for extraction while stirring, standing and layering the solution after extraction is finished, wherein the upper layer is the organic solvent and free fatty acid, and the lower layer is deacidified tea oil, and recovering the organic solvent for later use.

Further, the volume ratio of the organic solvent added into the raw tea oil to the raw tea oil is 2: 1-4: 1, the organic solvent is absolute methanol.

Preferably, the volume ratio of the organic solvent to the raw tea oil added into the raw tea oil is 3: the acid value can be reduced to be within 1.5mg (KOH)/g by adopting the organic solvent extraction method in the application.

Further, in the step 3), the stirring speed is 600r/min to 800r/min, the extraction time is 10 min to 30min, and the extraction times are 3 times.

Further, the specific operation steps of step 4) are as follows: and adding a silica gel drying agent into the deacidified tea oil for drying treatment to achieve a dehydration effect, and drying the recovered organic solvent by using the silica gel drying agent after passing through a rotary evaporator for use in an ester exchange reaction.

The organic solvent is subjected to rotary evaporation treatment and drying and then recycled for use in the ester exchange reaction, so that the use amount of the organic solvent is reduced, the preparation components of the biodiesel are effectively saved, and the drying process adopts silica gel drying agent drying treatment without introducing other reagents, and has the advantages of safety, no toxicity and environmental protection.

Further, the specific operation steps of step 5) are as follows: the organic solvent after the adsorption and dehydration treatment in the step 4) is mixed according to the mass ratio of 4: 1-10: 1 adding the obtained dried deacidified tea oil, adding a KOH catalyst, reacting under stirring at constant temperature, and recovering excessive organic solvent after the reaction is finished.

Preferably, the mass ratio of the organic solvent after adsorption and dehydration to the deacidified tea oil after drying is 6: 1..

Further, the stirring speed in the step 5) is 600 r/min.

Further, the dosage of the KOH catalyst is 0.2 to 1.5 percent of the mass of the dried deacidified tea oil.

Preferably, the amount of the KOH catalyst is 0.6 percent of the mass of the dried deacidified tea oil.

Further, the reaction temperature of the organic solvent after the dehydration treatment and the dried deacidified tea oil is 50-90 ℃, and the reaction time is 60-180 min.

Preferably, the reaction temperature of the organic solvent after the dehydration treatment and the dried deacidified tea oil is 70 ℃, and the reaction time is 90 min.

Further, the specific operation steps of step 6) are as follows: cooling the reaction product obtained in the step 5) to below 40 ℃, pouring the reaction product into a separating funnel, standing for layering, and collecting an upper oil phase to obtain a coarse product for later use.

Further, the specific operation steps of step 7) are as follows: a. adding 10% hot soft water at 75 deg.C into the coarse product, washing with water, slowly vibrating to make the materials contact sufficiently, standing, layering, discharging lower water layer, repeating the above washing steps for 2-4 times, and collecting upper oil phase; b. transferring the oil phase to a rotary evaporator, and dehydrating and drying to obtain a crude biodiesel for later use.

Further, the specific operation steps of step 8) are as follows: a) because the crude biodiesel prepared in the step 7) contains trace moisture, soluble gas, methanol and other volatile components, in order to prevent the volatile components from entering a molecular still and causing the material to explode under the influence of high vacuum, thereby influencing the distillation process, a first-stage film evaporator is firstly adopted to evaporate the trace moisture, methanol, soluble gas and other volatile components in the crude biodiesel, and light components are collected; b) and then the light component is placed in a wiped film type molecular distiller for molecular distillation, and the light phase component is collected, thus obtaining the purified light yellow transparent biodiesel.

Further, the technological parameters of the first-stage thin film evaporator for evaporation are as follows: the vacuum degree is-0.097 MPa, the temperature is 100 ℃, and the rotating speed of the rotor is 150-300 rpm; the technological parameters of the wiped film type molecular distiller for molecular distillation are as follows: the vacuum degree is 20Pa, the inlet temperature is 170 ℃, and the outlet temperature is 150 ℃.

The method for preparing the biodiesel from the tea oil cake meal has the beneficial effects that:

(1) in the process of preparing the biodiesel by adopting the tea oil cake, the organic solvent is adopted to extract free fatty acid in the crude tea oil, and then the deacidified tea oil is subjected to adsorption dehydration and then subjected to ester exchange reaction, so that the increase of the content of the free fatty acid caused by hydrolysis of raw material oil is avoided, the saponification reaction of the catalyst and the free fatty acid is effectively prevented, the catalytic effect of the catalyst is improved, the preparation time of the biodiesel is further shortened, and the preparation efficiency and yield of the biodiesel are improved;

(2) the organic solvent obtained after the acid reduction treatment of the raw tea oil by adopting the organic solvent extraction method can be recycled for ester exchange reaction, so that the use amount of the organic solvent is reduced, and the use cost of the reagent for preparing the biodiesel is effectively saved; the deacidified tea oil is awakened, dehydrated and dried by a silica gel drying agent, and other reagents are not introduced, so that the deacidified tea oil has the advantages of safety, no toxicity, no harm and no pollution;

(3) the method for preparing the biodiesel by adopting the tea oil cake pulp has the advantages of economy, environmental friendliness, simple preparation method, high conversion rate of the prepared biodiesel, high quality standard meeting the quality standard of the biodiesel S50, improved utilization value of the tea oil cake pulp and expanded application range of byproducts in the preparation process of the tea oil.

Drawings

FIG. 1 is a schematic view of the process for preparing biodiesel according to the present invention;

FIG. 2-is the effect of catalyst usage on biodiesel yield;

FIG. 3-is the effect of alcohol oil mass ratio on biodiesel yield;

FIG. 4-is the effect of reaction temperature on biodiesel yield;

FIG. 5-is a graph showing the effect of reaction time on biodiesel yield.

Detailed Description

The invention is further illustrated with reference to the following figures and examples, which are not intended to limit the scope of the invention in any way.

Example 1

A method for preparing biodiesel from tea oil cake meal comprises the following steps:

1) oil extraction: a) crushing the tea oil cake meal into small particles by using a high-speed crusher, and sieving the small particles by using a 60-mesh sieve; sieving, and oven drying at 75 deg.C to constant weight; b) extracting the tea oil in the tea seed cake by using petroleum ether by using a Soxhlet extraction method, wherein the extraction conditions are as follows: extracting at 70 deg.C for 8 hr, and collecting oleum Camelliae after extraction;

2) concentration: concentrating the obtained tea oil by using a rotary evaporator, and collecting crude tea oil for later use after petroleum ether is completely separated;

3) reducing acid by an extraction method: placing the obtained crude tea oil into a conical flask, adding anhydrous methanol at the ratio of solvent volume to tea oil volume of 3:1 at normal temperature, and extracting at stirring speed of 600r/min for 20 min; after extraction, transferring the solution into a separating funnel, standing and layering, wherein the upper layer is organic solvent and free fatty acid, the lower layer is deacidified tea oil, the organic solvent (anhydrous methanol) is recovered for later use, and the acid value of the obtained deacidified tea oil is measured to obtain the measurement result of 1.0mg (KOH)/g;

4) silica gel drying agent adsorption dehydration: adding a silica gel drying agent into the deacidified tea oil for drying so as to achieve the dehydration effect; evaporating the recovered organic solvent (anhydrous methanol) by a rotary evaporator, and drying by using a silica gel drying agent for ester exchange reaction;

5) ester exchange reaction: adding the dried anhydrous methanol and the deacidified tea oil obtained in the step 4) into a three-neck flask according to the mass ratio of 6:1, adding a catalyst KOH according to 0.6% of the dried deacidified tea oil, reacting for 90min at the temperature of 70 ℃ under the condition of stirring speed of 600r/min, and recovering excessive anhydrous methanol after the reaction is finished;

6) liquid separation: cooling the reaction product after the ester exchange reaction in the step 5) to below 40 ℃, pouring the reaction product into a separating funnel, standing and layering the reaction product, and collecting the upper oil phase to obtain a coarse product for later use;

7) washing and drying: a. transferring the coarse product into a separating funnel, adding 10% hot soft water at 75 deg.C, slowly vibrating to make the materials fully contact, standing, discharging the lower water layer after obvious layering occurs, repeating the above steps for 2 times, and collecting the upper oil phase; b. transferring the oil phase substance to a rotary evaporator, and dehydrating and drying to obtain a crude biodiesel for later use;

8) molecular distillation: a. firstly, putting the crude biodiesel into a first-stage film evaporator for evaporation, and collecting light components, wherein the evaporation process parameters are as follows: the vacuum degree is-0.097 MPa, the temperature is 100 ℃, and the rotor rotation speed is 150-; b. then putting the light component into a wiped film type molecular distiller for molecular distillation, wherein the technological parameters of the molecular distillation are as follows: the vacuum degree is 20Pa, the inlet temperature is 170 ℃, the outlet temperature is 150 ℃, and the light phase component is collected, thus obtaining the purified light yellow transparent biodiesel.

The technological process chart of the method for preparing the biodiesel by adopting the tea oil cake is shown in figure 1, the indexes of the prepared biodiesel, such as density, viscosity, lightning, cold filter plugging point, sulfur content, acid value and the like, are measured, the detection result is shown in table 1, the experimental detection values are within the qualified range by comparing the quality standard of the biodiesel S50, namely the biodiesel prepared by adopting the method meets the quality standard of the biodiesel S50.

TABLE 1 comparison of the results of biodiesel measurements with standard values

Example 2

A method for preparing biodiesel from tea oil cake meal comprises the following steps:

1) oil extraction: a) crushing the tea oil cake meal into small particles by using a high-speed crusher, and sieving the small particles by using a 60-mesh sieve; sieving, and oven drying at 75 deg.C to constant weight; b) extracting the tea oil in the tea seed cake by using petroleum ether by using a Soxhlet extraction method, wherein the extraction conditions are as follows: extracting at 70 deg.C for 8 hr, and collecting oleum Camelliae after extraction;

2) concentration: concentrating the obtained tea oil by using a rotary evaporator, and collecting crude tea oil for later use after petroleum ether is completely separated;

3) reducing acid by an extraction method: placing the obtained crude tea oil into a conical flask, adding anhydrous methanol at the ratio of solvent volume to tea oil volume of 3:1 at normal temperature, and extracting at stirring speed of 600r/min for 20 min; after extraction, transferring the solution into a separating funnel, standing and layering, wherein the upper layer is an organic solvent and free fatty acid, the lower layer is deacidified tea oil, and the organic solvent (anhydrous methanol) is recovered for later use;

4) silica gel drying agent adsorption dehydration: adding a silica gel drying agent into the deacidified tea oil for drying so as to achieve the dehydration effect; evaporating the recovered organic solvent (anhydrous methanol) by a rotary evaporator, and drying by using a silica gel drying agent for ester exchange reaction;

5) ester exchange reaction: adding the dried anhydrous methanol and deacidified tea oil obtained in the step 4) into a three-neck flask according to the mass ratio of 7:1, adding a catalyst KOH according to 0.8% of the dried deacidified tea oil, reacting for 90min at the temperature of 80 ℃ under the condition of stirring speed of 600r/min, and recovering excessive anhydrous methanol after the reaction is finished;

6) liquid separation: cooling the reaction product after the ester exchange reaction in the step 5) to below 40 ℃, pouring the reaction product into a separating funnel, standing and layering the reaction product, and collecting the upper oil phase to obtain a coarse product for later use;

7) washing and drying: a. transferring the coarse product into a separating funnel, adding 10% hot soft water at 75 deg.C, slowly vibrating to make the materials fully contact, standing, discharging the lower water layer after obvious layering occurs, repeating the above steps for 2 times, and collecting the upper oil phase; b. transferring the oil phase substance to a rotary evaporator, and dehydrating and drying to obtain a crude biodiesel for later use;

8) molecular distillation: a. firstly, putting the crude biodiesel into a first-stage film evaporator for evaporation, and collecting light components, wherein the evaporation process parameters are as follows: the vacuum degree is-0.097 MPa, the temperature is 100 ℃, and the rotor rotation speed is 150-; b. then putting the light component into a wiped film type molecular distiller for molecular distillation, wherein the technological parameters of the molecular distillation are as follows: the vacuum degree is 20Pa, the inlet temperature is 170 ℃, the outlet temperature is 150 ℃, and the light phase component is collected, thus obtaining the purified light yellow transparent biodiesel.

Experimental example 1 optimization experiment of KOH catalyst amount

In this experimental example 1, the method of preparing biodiesel according to example 1 was adopted, and in the step 5) of transesterification, the reaction temperature was 70 ℃, the reaction time was 90min, and the mass ratio of the dried anhydrous methanol to the deacidified tea oil was 6:1, using KOH as a catalyst, and investigating the influence of the addition of different KOH catalysts on the yield of biodiesel, the experimental results are shown in FIG. 2.

The results from fig. 2 show that: when the KOH concentration is 0.2-0.6%, the yield of the biodiesel shows an upward trend, and after the KOH concentration is 0.6%, the yield of the biodiesel shows a downward trend. Therefore, in the ester exchange process, KOH and free fatty acid are subjected to neutralization reaction firstly, and part of KOH does not perform catalytic reaction, so that the yield of the biodiesel is low; along with the increase of the addition amount of the catalyst, the catalytic effect is enhanced, so that the yield of the biodiesel is obviously improved; as the amount of alkali is increased, saponification reaction is caused to generate fatty acid soap, and the viscosity of reactants is increased due to the presence of the fatty acid soap, so that the separation difficulty of products is increased, and the yield of the biodiesel is influenced finally.

Example 3

This example differs from example 1 in that: the mass ratio of the anhydrous methanol to the deacidified tea oil in the step 5) is as follows: 10: 1, the using amount of the KOH catalyst is 1.5 percent, the reaction temperature is 90 ℃, and the reaction time is 180 min.

Example 4

This example differs from example 1 in that: the mass ratio of the anhydrous methanol to the deacidified tea oil in the step 5) is as follows: 4:1, the using amount of the KOH catalyst is 0.2 percent, the reaction temperature is 50 ℃, and the reaction time is 60 min.

Comparative example 1

The method for preparing the biodiesel by adopting the tea oil cake pulp comprises the following steps:

1) extracting oil; 2) concentrating to obtain crude tea oil; 3) ester exchange reaction: adding anhydrous methanol and raw tea oil into a three-neck flask according to the mass ratio of 6:1, adding a catalyst KOH according to 0.6% of the mass of the raw tea oil, reacting for 90min at the temperature of 70 ℃ under the condition of stirring speed of 600r/min, and recovering excessive anhydrous methanol after the reaction is finished; 4) separating liquid to obtain a coarse-grade product; 5) washing and drying to obtain a crude product of the biodiesel; 6) anhydrous methanol is added into the mixture according to the volume ratio of 3:1, adding the mixture into a crude product of the biological tea oil for extraction, wherein the stirring speed is 600r/min, and the extraction time is 20 min; after extraction, transferring the solution into a separating funnel, standing and layering, wherein the upper layer is an organic solvent and free fatty acid, and the lower layer is a crude product; 7) molecular distillation to obtain the biodiesel.

The specific operation steps corresponding to each step are the same as those in embodiment 1.

Comparative example 2

This comparative example differs from example 1 in that: this comparative example does not include step 4) of example 1), and the deacidified tea oil obtained by deacidification in step 3) is directly subjected to transesterification with anhydrous methanol in step 5).

Comparative example 3

This comparative example differs from example 1 in that: the comparative example does not comprise the step 3) in the example 1), and the tea oil is directly subjected to dehydration adsorption in the step 4) by adopting the crude tea oil in the example 1.

The present invention measured the yield of biodiesel produced in examples 1-4 and comparative examples 1-3, and the results are shown in Table 2:

TABLE 2 biodiesel yield in examples 1-4 and comparative examples 1-3

As can be seen from Table 2, the yields of biodiesel prepared in comparative examples 1-3 were lower than those of example 1, indicating that the yield of biodiesel could be significantly improved by the method of the present invention.

Experimental example 2 optimization experiment of mass ratio of anhydrous methanol to deacidified tea oil

In the experimental example 2, the method of example 1 for preparing biodiesel was adopted, and in the step 5) of ester exchange reaction, the mass ratio of anhydrous methanol and deacidified tea oil was used as a research object under the conditions that the reaction temperature was 70 ℃, the reaction time was 90min, and the dosage of KOH catalyst was 0.6%, so as to research the influence of the mass ratio of anhydrous methanol and deacidified tea oil (i.e., alcohol-oil mass ratio) on the yield of biodiesel, and the experimental results are shown in fig. 3.

As can be seen from FIG. 3, when the mass ratio of the anhydrous methanol to the deacidified tea oil is 4:1-6:1, the yield of the biodiesel is obviously increased along with the increase of the ratio, and when the mass ratio is 6:1-8:1, the yield of the biodiesel is not obviously increased and shows a slow descending trend when the ratio reaches 9: 1. This is probably because the concentration of deacidified tea oil in the reactants was decreased with the increase of the amount of anhydrous methanol added, thereby causing the reaction rate to be decreased. Considering saving the cost of preparing the biodiesel, the mass ratio of 6:1 preparing the biodiesel.

Experimental example 3 optimization experiment of reaction temperature in transesterification reaction

In this experimental example 3, the method of preparing biodiesel according to example 1 was adopted, and in the transesterification reaction of step 5), the mass ratio of anhydrous methanol to deacidified tea oil was set to 6:1, the reaction time is 90min, the KOH catalyst dosage is 0.6%, the reaction temperature is taken as a research object, the influence of different reaction temperatures on the yield of the biodiesel is researched, and the experimental result is shown in figure 4.

It can be shown from fig. 4 that the increase of the biodiesel yield is insignificant when the reaction temperature is 40 ℃ to 60 ℃, and the biodiesel yield reaches a maximum value when the reaction temperature is 70 ℃, and then gradually decreases as the temperature increases.

Experimental example 4 optimization experiment of reaction time in transesterification reaction

In this experimental example 4, the method of preparing biodiesel according to example 1 was adopted, and in the transesterification reaction of step 5), the mass ratio of anhydrous methanol to deacidified tea oil was set to 6:1, under the conditions that the reaction temperature is 70 ℃ and the dosage of the KOH catalyst is 0.6 percent, the reaction time is taken as a research object, the influence of different reaction times on the yield of the biodiesel is researched, and the experimental result is shown in figure 5.

From FIG. 5, it can be shown that when the reaction time is 60-90min, the yield of biodiesel is obviously increased along with the increase of the reaction time; when the reaction time is 90-180min, the change trend of the yield of the biodiesel is relatively gentle, and the yield of the biodiesel has a slight trend of decreasing. This may be that, as the reaction time is prolonged, side reactions occur, so that the degree of reverse reaction of fatty acid methyl esters increases, thereby reducing the yield of biodiesel.

Although the present invention has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.