CN1699516A - Process for preparing bio-diesel-oil by using microalgae fat - Google Patents

Abstract

The invention discloses a method for preparing biodiesel from microalgae oil, which belongs to the field of bioengineering and energy. A certain amount of methanol is added to microalgae oil, heated to a certain temperature, and reacted to generate biodiesel under the action of an acid catalyst. The density of microalgae biodiesel is 0.864kgl ^-1 , the viscosity is 5.2×10 ^-4 (40℃), and the calorific value is as high as 41MJ kg ^-1 , which are comparable to traditional diesel oil. This technology provides a basic and scientific basis for the final use of biological and engineering technology to produce renewable energy and solve environmental pollution problems, and has good application and market demand.

Description

Method for preparing biodiesel from microalgae oil

technical field

The invention belongs to the field of bioengineering and energy, and relates to a method for preparing biodiesel from microalgae oil.

Background technique

Biodiesel, or fatty acid methyl ester, is a biodegradable, non-toxic renewable energy source. Due to the depletion of oil resources and the strengthening of environmental regulations, countries around the world are actively developing and producing biodiesel. Since 1988, many European countries have used biodiesel as an alternative to conventional diesel. However, due to the higher cost of raw materials, the price of biodiesel is higher than that of traditional diesel. Therefore, it is a general trend to choose suitable and low-cost vegetable oil resources to actively develop and produce biodiesel.

Algae have the characteristics of high photosynthetic efficiency, strong environmental adaptability, short growth cycle, and high biological yield, so algae are good materials for preparing bio-oil fuels. Heterotrophic growth can not only improve growth efficiency, but also facilitate the accumulation of certain metabolites such as lipids in algal cells, and obtain microalgae with high fat content, thereby reducing the cost of biomass production and oil production. However, the current research on biodiesel production basically focuses on vegetable oils such as soybean oil, sunflower oil, and rapeseed, and there is no report on the preparation of biodiesel from heterotrophic microalgae oil. The most commonly used method for producing biodiesel is transesterification, that is, adding a certain amount of methanol to vegetable oil, heating it to a certain temperature, and reacting with a catalyst (acid, alkali or enzyme) to generate fatty acid methyl ester, and separating out by-products Glycerin process. Integrating this transesterification reaction technology with heterotrophic transformation cell engineering technology, we proposed a method to produce high-quality biodiesel from heterotrophic algae oil. The research results show that the biodiesel equivalent to traditional diesel can be obtained through acid-catalyzed transesterification by using heterotrophic algae oil, and its application value is higher.

Contents of the invention

The object of the present invention is to provide a kind of method utilizing microalgae oil to prepare biodiesel, it is characterized in that: described biodiesel utilizes microalgae oil to obtain by transesterification; Its preparation process is:

(1) collect microalgae, then dry and make algae powder;

(2) Utilize vegetable oil method to extract microalgae oil from algae flour;

(3) Transesterification reaction: add methanol with an alcohol-to-oil molar ratio of 25:1 to 84:1 to the microalgae oil, heat it to 30°C to 90°C, and react under the catalysis of concentrated sulfuric acid to generate fatty acid methyl ester, which is biodiesel , and the by-product glycerol is separated.

The beneficial effects of the present invention are: 1. High-quality biodiesel can be obtained through transesterification by utilizing microalgae oil, and its characteristics are equivalent to those of traditional fossil diesel. 2. It has good application and market demand.

Description of drawings

Figure 1(a)(b) is a schematic diagram of the change of biodiesel yield under different temperature and catalyst conditions.

Figure 2(a)(b) is a schematic diagram of the influence of different alcohol-oil molar ratios on the yield and density of microalgae biodiesel.

Fig. 3 is a diagram showing the change of the density of the reaction product (biodiesel) with time under the condition of different molar ratios of alcohol to oil.

Detailed ways

The invention provides a method for preparing biodiesel from microalgae oil. The preparation of its biodiesel is obtained by transesterification with microalgae oil, and its preparation process is as follows:

(1) collect microalgae, then dry and make algae powder;

(2) Utilize vegetable oil method to extract microalgae oil from algae flour;

(3) Transesterification reaction: Add methanol with an alcohol-to-oil molar ratio of 25:1 to 84:1 to the microalgae oil, heat it to 30°C to 90°C, and under the action of concentrated sulfuric acid catalyst, the product generated by the reaction is passed through petroleum ether and Washing with water, centrifuging to take the organic phase, evaporating the organic solvent and drying to obtain biodiesel. The reaction produces fatty acid methyl ester, ie biodiesel, and the by-product glycerin is separated.

Figure 1(a)(b) and Figure 2(a)(b) show the biodiesel yield and density changes under different temperature and catalyst conditions. Through the optimization of transesterification reaction conditions, higher oil yield can be obtained. High-quality biodiesel can be obtained through transesterification using microalgae oil. The density of microalgal biodiesel is 0.864kg l ^-1 , the viscosity is 5.2×10 ^-4 (40°C), and the calorific value is as high as 41MJ kg ^-1 . These characteristics are comparable to traditional diesel, and have good application prospects.

Examples are given below for description.

The influence of embodiment one different reaction temperature and catalyst consumption on microalgae biodiesel yield and density

The reaction conditions are: 30:1 molar ratio of alcohol to oil, the rotating speed of the shaker is 160 rpm, and the reaction time is 5 hours. The temperatures are 30°C, 50°C, and 90°C, respectively; the amount of catalyst _H2SO4 is 25%, 50%, 60% _, and 100% (based on the weight of raw oil).

Higher yield of biodiesel can be obtained at 50℃, while lower density biodiesel can be obtained at 90℃. Under the same temperature conditions, when the amount of catalyst is 100% of the raw oil, biodiesel with lower density can be obtained. The biodiesel with the lowest density (0.862) was obtained at 90°C and the catalyst dosage was 100% of the raw oil.

Under the condition that the amount of catalyst is 100% of the raw oil, there is no great difference in the yield and density at 30°C and 50°C. The yields of biodiesel at 30°C and 50°C were 56% and 58%, respectively, and the densities of biodiesel at 30°C and 50°C were 0.878 and 0.875, respectively (as shown in Figure 1). Therefore, from the perspective of cost reduction, the acid-catalyzed transesterification reaction conditions of microalgae oils and fats are 30°C, 100% of the amount of raw material oil catalyst dosage is more appropriate.

Example 2 Effects of different alcohol-oil molar ratios on microalgae biodiesel yield and density

The reaction conditions are as follows: temperature 30° C., shaker rotation speed 160 rpm, catalyst H ₂ SO ₄ dosage 100% (based on the weight of raw oil), and reaction time 7 hours.

Comparing the effects of six different molar ratios of alcohol to oil on the product ratio and its density, a higher yield of biodiesel can be obtained when the molar ratio of alcohol to oil is 45:1 and 56:1, which are 68% and 63%, respectively. Under the conditions of these two molar ratios of alcohol to oil, not only a higher yield of biodiesel, but also a low density biodiesel was obtained. The densities of biodiesel obtained when the molar ratio of alcohol to oil was 45:1 and 56:1 were 0.873 and 0.864, respectively. Biodiesel with a lower density (0.878) can also be obtained when the molar ratio of alcohol to oil is 30:1 (as shown in Figure 2).

The variation of the density of the reaction product (biodiesel) over time under the conditions of embodiment three different alcohol-to-oil molar ratios

Reaction condition is: temperature 30 ℃, shaker rotating speed 160rpm, catalyst H ₂ SO _The dosage is 100% (based on the weight of raw material oil)

The density of biodiesel obtained when the molar ratio of alcohol to oil was 25:1, 70:1 and 84:1 was higher, and the subsequent separation was inconvenient when the amount of methanol was too large. Under the conditions of 30:1, 45:1 and 56:1 molar ratio of alcohol to oil, the densities of biodiesel products gradually decreased with the prolongation of reaction time. However, when the molar ratio of alcohol to oil was 56:1, the density of the biodiesel product dropped to the lowest point in the shortest time of 4 hours, and biodiesel with a density of 0.864 was obtained; while the molar ratio of alcohol to oil was 30:1 and 45:1 , It takes 5-7 hours for its product density to reach the lowest level (as shown in Figure 3).

The above experimental results show that the optimum reaction conditions for the acid-catalyzed transesterification of microalgae oils and fats should be 30°C, a catalyst dosage of 100% feedstock oil, and an alcohol-oil molar ratio of 56:1; under these conditions, within 4 hours High quality biodiesel with a density of 0.864 can be obtained.

Claims (1)

1. a method utilizing microalgae oil to prepare biodiesel is characterized in that: described biodiesel utilizes microalgae oil to obtain by transesterification; Its preparation process is: (1) collect microalgae, then dry and make algae powder; (2) Utilize vegetable oil method to extract microalgae oil from algae flour; (3) Transesterification reaction: add methanol with an alcohol-to-oil molar ratio of 25:1 to 84:1 to the microalgae oil, heat it to 30°C to 90°C, and react under the catalysis of concentrated sulfuric acid to generate fatty acid methyl ester, which is biodiesel , and the by-product glycerol is separated.

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