WO2009155785A1

WO2009155785A1 - Method for preparation of biodiesel and glycerol from microalgal oil

Info

Publication number: WO2009155785A1
Application number: PCT/CN2009/000665
Authority: WO
Inventors: 石蕾; 张惠敏; 刘敏胜
Original assignee: 新奥科技发展有限公司
Priority date: 2008-06-27
Filing date: 2009-06-18
Publication date: 2009-12-30
Also published as: CN101613618B; CN101613618A

Abstract

A method for preparation of biodiesel and glycerol from microalgal oil can include the technologies of extracting microalgal oil, transesterification reaction, producing high purity and high performance biodiesel, and recovering byproduct glycerol effectively. The method has the advantages of simple process, high efficiency, low cost, high quality, and environment friendly. The method is easy to apply to industry, which has good industrial application value.

Description

Method for preparing biodiesel and glycerol by using microalgae oil as raw material

The invention belongs to the fields of bioengineering and clean energy, and relates to a method for preparing biodiesel and glycerin by using microalgae oil as raw material, and is a complete method for preparing biodiesel and glycerin. Background technique

In recent years, due to the rise in oil prices, the emergence of energy crises, and the pollution of gasoline, which affects human health, people's eyes are once again concentrated on renewable bio-energy.

Biodiesel is mainly composed of fatty acid methyl esters, which are biodegradable, non-toxic, low in sewage and rich in raw materials. Therefore, it is an environmentally friendly green fuel with a very broad prospect. Due to the high cost, long growth cycle and environmental constraints, the prices of biodiesel are higher or closer to traditional diesel. The ideal raw material for industrial preparation of biodiesel should be high in yield and low in cost. Among the many biomasses, algae have the characteristics of high photosynthesis efficiency, strong environmental adaptability, short growth cycle and enthalpy of biological production. In addition, through cultivation, considerable oil content can be obtained from microalgae, and directly from microalgae. The extracted oil and fat components are similar to vegetable oils, so algae is a good material for preparing biodiesel.

At present, the method commonly used in the biodiesel industry is transesterification. Various natural vegetable oils, animal fats and microalgae oils, and waste oils from the food industry can be used as raw materials for transesterification to produce biodiesel. Alcohols for transesterification include methanol. , lower alcohols such as ethanol, the most commonly used of which is methanol. Under the action of a catalyst (acid, base or enzyme), a fat exchange reaction between a fat and a lower alcohol produces a fatty acid methyl ester, and a process of separating glycerin is obtained.

Patent EP1928994, US20090077863> W02009018230 gives a general procedure for preparing biodiesel using microalgae oil, and does not give specific process steps and parameters; US2008241902 uses acid catalysis, but the temperature is 140~260'C, high energy consumption , and the equipment requirements are also high, which is not conducive to large-scale production; US5354878 process steps are cumbersome, production costs are low, and because the microalgae algae oil fatty acid content is higher than other vegetable oils, the base catalysis mentioned above is not suitable for microalgae Oil to prepare biodiesel. This patent not only gives specific process steps and parameters, but also has low reaction temperature, low equipment requirements, and simple process steps. It is specifically suitable for the preparation of biodiesel from microalgae oil.

The invention integrates the microalgae oil extraction technology, the transesterification reaction technology, the high purity and high performance biodiesel technology and the effective recovery by-product glycerin technology, and combines the specific process conditions to propose a microalgae oil as the original A method for the complete preparation of biodiesel and glycerol. Summary of the invention

The invention relates to a method for preparing comprehensive utilization of biodiesel and glycerol by using microalgae oil as raw material, and the preparation process is as follows:

a. Adding organic solvent to extract oil in microalgae: The microalgae used in this step can be obtained by various collection methods known at present, such as centrifugation or sedimentation; microalgae can be common algae, generally selected from: Dunaliella salina

Freshwater or seawater microalgae such as (Dunaliella salina sp.), Chlorella sp., and Myrmecia incise. The microalgae in the present invention can be obtained by an ordinary culture method, or can be commercially available, and can also be wet algae or dried microalgae;

The algae used in this step may be, for example, wet algae having a water content of between 80% and 96% by weight, or algae after ordinary drying (e.g., air drying). In the case of dry algae, the organic solvent may be directly added for extraction, and the mass ratio of the algae: organic solvent is 1:1 to 10. In the case of wet algae collected by centrifugation, a small amount of water may be added to suspend the wet algae. Therefore, the water and the organic solvent are added in a ratio of algae (wet algae):water:organic solvent mass ratio of 1:1 to 5:1 to 10, and the microalgae oil is extracted by shaking, and after standing for a while, the supernatant liquid is obtained. Oil extract. The organic solvent is recovered by atmospheric distillation and used for cyclic extraction. The atmospheric distillation temperature is 70~100'C;

The organic solvent used for extracting the oil and fat is a mixture of one or more of n-hexane, chloroform and methanol, and the organic solvent is generally preferably hexamethylene. Alga: water: organic solvent mass ratio is preferably 1: 2: 3;

b. The microalgae oil and small alcohol are added to the reactor, and the small molecule alcohol is selected from one or a mixture of methanol and ethanol. The molar ratio of the alcohol to the microalgae oil is 30 to 60: 1. The reaction is carried out under the action of a catalyst (acid, alkali or enzyme), and generally 98% concentrated sulfuric acid having the same weight as the weight of the raw material oil is used as a catalyst to start the reaction, and the dropwise addition is completed. Continue to react for a certain period of time. The reaction temperature is 20 to 100 ° C, and the reaction time is 3 to l lh.

When the reaction, the small molecule alcohol is generally excessive, the molar ratio of alcohol to oil is 30~60: 1, the reaction temperature is 70'C, and the reaction time is 4h, the higher crude oil yield of diesel can be obtained, reaching 80% or more. In terms of cost, solvent recovery, and energy consumption, the alcohol is preferably methanol in the reaction, and the molar ratio of the alcohol to oil is preferably 40:1.

The reaction temperature is above 50 ° C, the molar ratio of alcohol to oil is 40: 1, and the reaction time is 4 h to obtain a higher yield of crude biodiesel, which is 80% or more. Therefore, the reaction temperature is preferably 50'C to 100 °C. . When the reaction temperature is 50 ° C ~ 100 ° C, the temperature change has little effect on the crude biodiesel yield. Therefore, from the perspectives of cost, energy consumption, equipment requirements, etc., the reaction temperature is about 70 ° C. .

In the case where the molar ratio of alcohol to oil is 40: 1, and the reaction temperature is 7 (TC, the reaction time exceeds 8 hours, the obtained organism The yield of the crude diesel oil is more than 90%. Therefore, the reaction time should be 8 hours or more. When the reaction time is 8 to 9 hours, the yield of the crude biodiesel obtained is higher, reaching 93% or more. Therefore, the reaction time is preferably 8 ~9h _; With the extension of reaction time, the yield of crude biodiesel showed a slow decline. When the reaction time is 9h, the crude biodiesel yield is 96%, so the reaction time is most preferably 9 hours;

c the above reaction product is allowed to stand layered, the upper layer is a crude product, and the lower layer is a crude glycerin layer;

d 095 MPa (gauge pressure) minus 0. 09〜0. 095 MPa (gauge pressure) reduction of the crude product obtained after the water is washed to a pH value of about 7 or so. Press distillation, collecting fractions with a liquidus temperature of 180 to 280 ° C, to obtain biodiesel fine, the color is light yellow. The black, viscous heavy fraction obtained after the distillation of the crude biodiesel is plant pitch and can be used as an industrial use for casting binders.

Preferably, after the step d, the lower layer is firstly distilled to remove alcohol, and then neutralized, dehydrated, and filtered to obtain by-product glycerin. The alcohol is recovered and dehydrated and can be recycled as a transesterification solvent.

The feature of this method is -

(1) The organic solvent extraction method is used to extract the oil and fat in the microalgae as the raw material oil for biodiesel production, which solves the problems caused by the high cost, long growth period and environmental constraints of other raw material oils.

(2) Biodiesel was prepared by transesterification method, and the molar ratio of alcohol to oil, reaction temperature, reaction time and other conditions were optimized, and the method of vacuum distillation was carried out to finally obtain high-yield and high-quality biodiesel.

(3) After a series of treatments, the by-product glycerin is obtained, which has certain industrial value.

(4) The organic solvent used can be recycled and reused. The heavy fraction material left in the distillation of biodiesel - plant asphalt also has certain industrial uses.

The present invention has the following advantages over other methods of preparing biodiesel and glycerol:

1) The present invention uses microalgae oil as a raw material, and the oil extraction method is simple and easy to control, and the obtained oil and fat component is similar to the vegetable oil, and can be directly used as a raw material for biodiesel preparation.

2) The organic solvent used in the present invention can be distilled and recycled, and recycled, which not only reduces the production cost, but also reduces environmental pollution.

3) The invention integrates microalgae oil extraction technology, transesterification reaction technology, production of high-purity and high-performance bio-diesel technology and effective recovery by-product glycerin technology to obtain a complete method for preparing biodiesel and glycerol by using microalgae oil.

4) The biodiesel and glycerin obtained by the invention have high purity and high industrial value. DRAWINGS Figure 1 is a process flow diagram of the present invention;

Figure 2 is a gas chromatogram analysis diagram described in Examples 2 to 5;

Figure 3 is a schematic diagram showing the change of biodiesel yield under different molar ratios of alcohol to oil;

Figure 4 is a schematic diagram showing the change of biodiesel yield under different temperature conditions;

Figure 5 is a schematic diagram showing the change in biodiesel yield under different reaction time conditions. detailed description

The invention provides a method for preparing comprehensive utilization of biodiesel and glycerin by using microalgae oil as raw material.

Example 1 : Extraction of microalgae oil by organic solvent extraction

Freshwater or seawater microalgae such as Dunaliella salina, Chlorella, and nicked algae (purchased from UTEX (The University of Texas at Austin; US)) were collected by centrifugation, and the medium used for the culture was Erdschreiber's Medium (Duradium salina). Spirulina Medium, BG-11 Medium, References: Esra IMAMOGLU, Fazilet VARDAR SU AN, Meltem CONK DALAY, International Journal of Natural and Engineering Sciences 1 (3): 05-09, 2007) Then, the algae collected by centrifugation: water: n-hexane is added in a ratio of 1:2:3, water and n-hexane are added, and the microalgae oil is extracted by shaking, and after standing for a while, the upper liquid is a fat extract, and the upper layer is taken. The liquid is distilled at a normal pressure of 70 to 100 ° C to obtain a microalgae oil (the main component of the gas chromatographic analysis is a fatty acid methyl ester, and the content is 80% or more), and the distilled hexamidine is recycled and used.

Example 2~5: Effect of different alcohol-oil molar ratio on the yield of microalgae biodiesel

The reaction conditions are as follows: the molar ratio of alcohol to oil is 30: 1, 40: 1, 50: 60: 1, and the reaction temperature is 70 °C. Catalyst 98% concentrated sulfuric acid is 100% (based on the weight of the raw material grease). Reaction time 4h.

The Dunaliella salina microalgae oil and methanol prepared in Example 1 were placed in a four-necked flask, and the catalyst concentrated sulfuric acid was added dropwise from a constant pressure dropping funnel, and the four-necked bottle was sealed, stirred, and refluxed. The four-neck bottle is heated by an oil bath. After the completion of the reaction, the upper and lower layers were separated in a separatory funnel to obtain a crude product and a crude glycerin layer, which were treated by distillation or the like to obtain a biodiesel product and glycerin. Methanol is recycled and can be recycled.

When the upper crude product is distilled, at least the pressure is reduced to 2 kPa or less, and the distilled portion between 160 and 280 ° C is collected as a biodiesel product, and the residue is a heavy fraction, which is a plant asphalt.

The crude product and the distillation product were analyzed by gas chromatography as the main component of the fatty acid methyl ester, similar to the biodiesel component prepared from vegetable oil (see the gas chromatographic analysis shown in Figure 2 and Table 1 below, Table 2).

Yield (purity)%=determined fatty acid methyl ester content (g) *100%/theoretical fatty acid methyl ester content (g) Calculation of theoretical fatty acid methyl esters:

According to the principle of reaction

CataJ st

CH ₂ -OOC-R 3ROH → R _r COO-R* + H ₂ 0 ci ooc- Ri Rj-COO- ' CH OH

Catalyst I

CH-OOC-R ₂ 3ROH s ,-COO-R* + CH-OH

I

CH.-OOC-R, Rj-COO R' CI OH

Alcohol E v> Glycerol Whether it is lmol triglyceride or fatty acid, it reacts with lower alcohol to produce 1 mol of fatty acid methyl ester. The difference in quality is not significant. Therefore, it can be inferred that if the methyl esterification reaction is complete, the organic solvent is extracted. The microalgae oil monthly mass = theoretically the fatty acid methyl ester mass. ' Table 1. Gas chromatographic analysis of microalgae oil report

Sample Name: *ENN3 Sample Notes - Submitted: April 26, 2009 11:34:53 Injection Date: April 26, 2009 11:40:59

GC description: GC6820 - SN: CN10807013 Signal description: FID1 B, Post detector method: Alginate methyl ester (internal standard) Recently modified time - April 25, 2009 14:30:54 Table 2. Internal Standard Report

Biodiesel composition and quality produced by the method of the present invention and bio-firewood produced by other vegetable oils The oil is similar.

In the reaction, the small molecule alcohol should be excessive, and the molar ratio of alcohol to oil is 30~60:1, which can obtain higher crude oil yield of diesel oil, which is more than 80%. Therefore, in terms of cost, solvent recovery and energy consumption, alcohol in reaction The class is methanol, and the ratio of alcohol to oil is more suitable at 40:1 (as shown in Figure 3).

Examples 6 to 14: Effect of different reaction temperatures on the yield of microalgae biodiesel

The reaction conditions were as follows: molar ratio of alcohol to oil 40: 1, reaction time 4 h. Temperatures are 20 ° C, 30 ° C, 40 ° C,

50 ° C, 60 ° C, . 70 ° C, 80 ° C, 90 ° C, 100 ° C, catalyst 98% concentrated sulfuric acid is 100% (based on the weight of the raw material grease).

When the reaction temperature is above 7CTC, a higher yield of crude biodiesel can be obtained, which is more than 80%. When 70'C~100'C, the temperature change has little effect on the crude biodiesel yield. Therefore, considering the cost, energy consumption, equipment requirements, etc., the reaction condition is 70 °C (Figure 4). Shown). Example 15: Effect of different reaction times on the yield of microalgae biodiesel

The reaction conditions are as follows: molar ratio of alcohol to oil 40: 1, reaction temperature 70. C. Catalyst 98% concentrated sulfuric acid is 100% (based on the weight of the raw material grease).

The Dunaliella salina microalgae oil and methanol prepared in Example 1 were placed in a four-necked flask, and the catalyst concentrated sulfuric acid was added dropwise from a constant pressure dropping funnel, and the four-necked bottle was sealed, stirred, and refluxed. The four-neck bottle is heated by an oil bath. After the completion of the reaction, the upper and lower layers were separated in a separatory funnel to obtain a crude product and a crude glycerin layer, which were treated by distillation or the like to obtain biodiesel and glycerin. Methanol is recycled and can be recycled.

When the reaction time is 8~9h, the yield of the crude biodiesel obtained is higher, reaching more than 93%. As the reaction time prolonged, the yield of crude biodiesel showed a slow downward trend. At a reaction time of 9 h, the crude biodiesel yield was the highest, at 96% (as shown in Figure 5).

The above experimental results show that the microalgae can be directly subjected to transesterification after extracting the oil by organic solvent extraction. The optimum reaction conditions for the transesterification reaction are 70'C, 9h, 100% feedstock amount of catalyst (98% concentrated sulfuric acid) and alcohol to oil molar ratio of 40:1. Under this condition, the crude biodiesel yield is as high as 96%.

It has been found through research that the components of the different microalgae oils described in the present invention are substantially similar, and the experimental results obtained are obtained. The same, so the above reaction preferred conditions apply to various microalgae oils and fats.

The crude biodiesel is distilled under reduced pressure, and a fraction having a liquidus temperature of 180 to 280 Torr is collected to obtain a biodiesel product in a pale yellow color. The black, viscous heavy fraction remaining after distillation, called plant asphalt, can be used as an industrial use for casting binders. After the lower layer is treated by distillation, neutralization, dehydration, filtration, etc., a by-product glycerin is obtained, and the organic solvent used can be distilled and recycled for recycling.

Claims

Rights request

A method for preparing biodiesel and glycerol using microalgae oil as a raw material, comprising the steps of:

a. adding organic solvent to extract the oil in the microalgae, and recovering the organic solvent by atmospheric distillation;

b. adding microalgae oil and small alcohols into the reactor, and adding a catalyst to start the reaction;

d. After the obtained crude product is washed with water, a part of the alcohol and water dissolved therein are removed by atmospheric distillation to obtain a crude biodiesel; and then distilled under reduced pressure to obtain a biodiesel product, and the heavy fraction is left after distillation.

2. A method of preparing biodiesel and glycerol according to claim 1, wherein, after step d., the method further comprises the steps of:

e. The lower layer is firstly distilled to remove alcohol, then neutralized, dehydrated and filtered to obtain glycerin; the alcohol can be recycled as a transesterification solvent after being recovered and dehydrated.

The method for preparing biodiesel and glycerin according to claim 1, wherein the microalgae is selected from the group consisting of Dunaliella salina sp., Chlorella sp., and Myrmecia. Incise) such as freshwater or seawater microalgae.

The method for preparing biodiesel and glycerin according to claim 1, wherein in step a., water is added in a ratio of alga:water:organic solvent by mass ratio of 1:1 to 5:1 to 10; And the organic solvent, the microalgae oil is extracted by shaking, and the supernatant liquid is allowed to stand to obtain the oil extract.

The method for preparing biodiesel and glycerin according to claim 1, wherein in the step a., the oil extract is distilled under normal pressure to obtain microalgae oil, and the organic solvent is recovered for cyclic extraction.

The method for preparing biodiesel and glycerin according to claim 1, wherein in the step b., the small molecule alcohol is excessive, and the molar ratio of the alcohol to the oil is 30 to 60:1.

7. Process for the preparation of biodiesel and glycerol according to claim 6, characterized in that the alcohol is methanol and the molar ratio of alcohol to oil is 40:1.

8. The method of preparing biodiesel and glycerin according to claim 1, wherein in the step b., the catalyst is concentrated sulfuric acid.

The method for preparing biodiesel and glycerin according to claim 1, wherein in the step b., the reaction temperature is 20 to 100 ° C, and the reaction time is 3 to l lh.

The method for producing biodiesel and glycerin according to claim 9, wherein the reaction temperature is 70 ° C, the reaction time is 9 hours, and the molar ratio of the alcohol to oil is 40:1.

The method for producing biodiesel and glycerin according to claim 1, wherein in the step d., the crude product is washed with water until the pH of the washing liquid is close to about 7.

The method for preparing biodiesel and glycerin according to claim 11, wherein in step d., the washed crude neutral product is distilled under normal pressure to remove a part of the alcohol and water dissolved therein. The crude biodiesel is obtained, and then distilled under reduced pressure to collect a liquidus temperature of 180~28 (TC fraction, which is a biodiesel product.

13. The method for preparing biodiesel and glycerin according to claim 1, wherein in step d., the black, viscous heavy fraction obtained after distillation of the crude biodiesel is plant pitch, which can be used as a casting paste. It is used in industrial applications such as cement.

The method of producing biodiesel and glycerin according to claim 2, wherein the microalgae is Dunaliella, and the organic solvent is hexamethylene.

The method for producing biodiesel and glycerin according to claim 14, wherein the microalgae, water and hexamethylene are added in a mass ratio of 1:2:3.