CN104449788A - Method for preparing micro-algal oil by microalgae hydro-thermal liquefaction - Google Patents

Abstract

The invention discloses a method for preparing microalgae oil by hydrothermal liquefaction of microalgae. The steps include: 1) breeding and collecting microalgae, adding them to a hydrothermal reaction kettle, and mixing with deionized water to form a solid-liquid ratio of 1-50g:100ml 2) Seal the hydrothermal reaction kettle, drain the air in the kettle, raise the temperature to 180-450°C under stirring, and keep it for 10-180min; 3) Cool, collect the reaction product, and extract it with an organic solvent , separate and filter the organic phase, and remove the organic solvent to obtain microalgae oil. The present invention uses microalgae as raw material and adopts a mild and controllable hydrothermal reaction system to prepare microalgae oil, which not only reduces the energy consumption and cost of the reaction system, but also improves the calorific value and yield of the prepared microalgae oil, making the The eutrophic algae waste in the water body has realized resource utilization.

Description

Method for preparing microalgae oil by hydrothermal liquefaction of microalgae

technical field

The invention relates to the technical field of biomass energy, in particular to a method for preparing microalgae oil by hydrothermally liquefying microalgae.

Background technique

With the development of the economy and the improvement of people's living standards, the demand for energy is increasing day by day. At the same time, the fossil fuels represented by coal and oil are becoming increasingly exhausted, and the extensive use of fossil fuels will inevitably bring about problems such as the greenhouse effect. How to break the bottleneck of energy depletion and environmental pollution is a major issue facing all mankind. Renewable energy represented by biomass energy has attracted widespread attention because of its environmental friendliness and renewable characteristics.

Biomass energy, as a clean and renewable energy, can realize the closed cycle of carbon during its utilization, thereby reducing the emission of CO ₂ to the atmosphere and effectively reducing the effect of greenhouse gases. At present, the development and utilization of biomass energy is mostly concentrated on terrestrial biomass, mainly lignocellulosic raw materials such as straw and wood. The reaction process mostly uses high temperature (>500°C) pyrolysis to convert biomass raw materials into liquid fuel bio-oil. However, the woody biomass raw material has the disadvantages of slow growth cycle, large land occupation, low biomass and great seasonal influence, and the pyrolysis process requires a high temperature and the raw material needs to be dried in advance, and the obtained bio-oil contains oxygen High volume and unstable properties.

Microalgae is a kind of aquatic plant, which has the characteristics of short growth cycle, high carbon sequestration efficiency, strong reproductive ability, easy cultivation, and tolerance to extreme environments. Microalgae are rich in carbohydrates, proteins, fats, etc., do not contain lignin, and can be pyrolyzed at a lower temperature. The obtained microalgae oil is more stable and calorific than those prepared from lignocellulose raw materials Bio-oil is more advantageous.

The Chinese invention patent with the publication number CN1446883A proposes a method for rapidly pyrolyzing microalgae to prepare biofuels, and the Chinese invention patent application with the application number 01136699.0 also uses microalgae as a raw material for pyrolysis to prepare oil and gas fuels. The high-temperature pyrolysis conversion method is adopted. Since the water content of the microalgae is above 90%, the algae needs to be dried after collection, and the microalgae is prepared into algae powder, so the energy consumption is relatively large. The Chinese invention patent application with the application number 200910054288.X proposes a method for preparing liquid fuel by hydrothermal liquefaction of microalgae, but this method needs to be flushed with high-pressure N ₂ , which requires high equipment.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for preparing microalgae oil by hydrothermal liquefaction of microalgae, which has low energy consumption, low requirements on equipment, and the prepared microalgae oil has high stability, calorific value and yield.

In order to solve the above-mentioned technical problems, the method for preparing microalgae oil by hydrothermal liquefaction of microalgae of the present invention comprises:

1) Cultivate and collect microalgae, add them to a hydrothermal reactor, and mix with deionized water to form a microalgae liquid with a solid-to-liquid ratio of 1-50g:100ml;

2) Seal the hydrothermal reaction kettle, drain the air in the hydrothermal reaction kettle, and then raise the temperature to 180-450°C under stirring, and keep it for 10-180min;

3) Cool the hydrothermal reaction kettle, collect the reaction product, and extract and extract with an organic solvent, then separate and filter the organic phase, remove the organic solvent, and obtain microalgae oil.

The microalgae are seawater or freshwater microalgae with high water content, including chlorella, spirulina, cyanobacteria, salina, enteromorpha and the like.

In step 1), one or more of NaOH, KOH, K ₂ CO ₃ , and Na ₂ CO ₃ can be added to the reaction system as an additive, and the mass percentage concentration of the additive solution is 0-10.0%.

In step 3), the organic solvent used for extraction can be one or more of organic solvents such as dichloromethane, chloroform, and carbon tetrachloride.

The present invention uses microalgae as raw material and adopts a mild and controllable hydrothermal reaction system to prepare microalgae oil. Compared with the existing preparation method of microalgae oil, it has the following advantages and beneficial effects:

1. The raw material does not need to be dried, and the microalgae can be liquefied directly after simple concentration and collection, and the temperature of the hydrothermal process is very low, so the energy consumption is small, and the calorific value and yield of the obtained microalgae oil are high.

2. There are many varieties of microalgae that can be used as raw materials, and the microalgae itself has the advantages of fast growth and reproduction, easy localization, and small land occupation area. It can make full use of ponds, coastal waters, tidal flats, wetlands, etc. for large-scale artificial Farming, which can reduce the cost of raw materials.

3. It can effectively treat algae pollutant wastes that cause eutrophication of water bodies and realize their resource utilization. At the same time, the microalgae reproduction process can also achieve efficient biological fixation, chemical conversion and closed carbon cycle of _CO2 .

4. The liquid phase products, solid residues and gas phase components (mainly CO ₂ ) obtained from the reaction can be recycled and comprehensively utilized. Among them, liquid phase products and gas phase components can be recycled for microalgae cultivation, and solid phase residues rich in C, N and other elements can be used for barren soil improvement.

Description of drawings

Fig. 1 is a schematic flow chart of the method for preparing microalgae oil by hydrothermal liquefaction of microalgae according to the present invention.

Detailed ways

In order to have a more specific understanding of the technical content, characteristics and effects of the present invention, now in conjunction with the accompanying drawings, the present invention is described in detail as follows:

Example 1

Using microalgae as raw materials, take 20g of microalgae and 150ml of distilled water and put them into a 300ml high-pressure reactor, and stir to prepare microalgae slurry. Seal the reaction kettle, drain the air in the kettle with _N2 , turn on the heating switch, set the stirring speed to 200r/min, start to heat up to 300℃ at a rate of about 4℃/min, keep it for 30min, turn off the heating switch immediately, and cool to At room temperature, the generated gas was collected, the reaction mixture was taken out by opening the kettle, the inner wall of the reaction kettle and the stirrer were cleaned with CH ₂ Cl ₂ , and the mixture was extracted. The extract was separated, the CH ₂ Cl ₂ phase was filtered with a Buchner funnel, and the CH ₂ Cl ₂ was recovered by distillation under reduced pressure to obtain microalgae oil.

The yield of microalgae oil was 23.00%, and the calorific value was 35.81KJ/g. The water-soluble phase product can be recycled for microalgae cultivation after certain treatment, and the remaining solid-phase algae residue can be used for soil improvement after drying, and the CO ₂ in the gas generated during the hydrothermal liquefaction process can be recycled for microalgae cultivation .

Example 2

Using microalgae as raw material, take 20g of microalgae and 200ml of distilled water into a 300ml autoclave, stir to prepare microalgae slurry. Seal the reaction kettle, drain the air in the kettle with _N2 , turn on the heating switch, set the stirring speed at 200r/min, start to heat up to 320℃ at a rate of about 4℃/min, keep it for 30min, turn off the heating switch immediately, and cool to At room temperature, the generated gas was collected, the reaction mixture was taken out by opening the kettle, the inner wall of the reaction kettle and the stirrer were cleaned with CH ₂ Cl ₂ , and the mixture was extracted. The extract was separated, the CH ₂ Cl ₂ phase was filtered with a Buchner funnel, and the CH ₂ Cl ₂ was recovered by distillation under reduced pressure to obtain microalgae oil.

The yield of microalgae oil is 30.62%, and the calorific value is 32.34KJ/g. The water-soluble phase product can be recycled for microalgae cultivation after certain treatment, and the remaining solid-phase algae residue can be used for soil improvement after drying, and the CO ₂ in the gas generated during the hydrothermal liquefaction process can be recycled for microalgae cultivation .

Example 3

Using microalgae as raw material, take 20g of microalgae and 200ml of NaOH solution with a concentration of 5.0%, put them into a 300ml high-pressure reactor, and stir to prepare a microalgae slurry. Seal the reaction kettle, drain the air in the kettle with _N2 , turn on the heating switch, set the stirring speed to 200r/min, start to heat up to 300℃ at a rate of about 4℃/min, keep it for 30min, turn off the heating switch immediately, and cool to room temperature , collect the generated gas, open the kettle to take out the reaction mixture, clean the inner wall of the reaction kettle and the stirrer with CH ₂ Cl ₂ , and extract the mixture. The extract was separated, the CH ₂ Cl ₂ phase was filtered with a Buchner funnel, and the CH ₂ Cl ₂ was recovered by distillation under reduced pressure to obtain microalgae oil.

The yield of microalgae oil is 32.83%, and the calorific value is 30.53KJ/g. The water-soluble phase product can be recycled for microalgae cultivation after certain treatment, and the remaining solid-phase algae residue can be used for soil improvement after drying, and the CO ₂ in the gas generated during the hydrothermal liquefaction process can be recycled for microalgae cultivation .

Claims (5)

1. The method for preparing microalgae oil by hydrothermal liquefaction of microalgae, is characterized in that, the steps comprise: 1) Cultivate and collect microalgae, add them to a hydrothermal reactor, and mix with deionized water to form a microalgae liquid with a solid-to-liquid ratio of 1-50g:100ml; 2) Seal the hydrothermal reaction kettle, drain the air in the hydrothermal reaction kettle, and then raise the temperature to 180-450°C under stirring, and keep it for 10-180min; 3) Cool the hydrothermal reaction kettle, collect the reaction product, and extract and extract with an organic solvent, then separate and filter the organic phase, remove the organic solvent, and obtain microalgae oil. 2. The method according to claim 1, wherein the microalgae are seawater or freshwater microalgae with high water content, including Chlorella, Spirulina, Cyanobacteria, Salina, Enteromorpha. 3. The method according to claim 1, characterized in that, in step 1), one or more of NaOH, KOH, K ₂ CO ₃ , Na ₂ CO ₃ is added to the reaction system as an additive. 4. The method according to claim 3, characterized in that, the solution mass percent concentration of the additive is 0-10.0%. 5. The method according to claim 1, characterized in that, in step 3), the organic solvent used for extraction comprises a mixed solution of one or more of dichloromethane, chloroform, and carbon tetrachloride.