CN1626621A - New method for producing biology diesel oil from vegetable oil - Google Patents

Abstract

The invention aims to propose a new method for producing biodiesel from vegetable oil, which relates to the fields of renewable energy technology and environmental protection. The general catalytic method to produce biodiesel has a long reaction time, complex post-treatment process and high cost. The invention proposes a new method for producing biodiesel from vegetable oil, which is characterized in that vegetable oil and small molecular alcohols are used as reactants, co-solvent is added, transesterification is carried out under supercritical conditions, and fatty acid glyceride is converted into fatty acid Small molecule alcohol esters, namely biodiesel, yield products with good properties. The addition of a co-solvent in the reaction process not only strengthens the mutual solubility of vegetable oil and small molecule alcohol, accelerates the reaction rate, and greatly shortens the reaction time; it also reduces the critical point of small molecule alcohol, reduces the reaction temperature and pressure, and makes the reaction in It is easy to implement in industrial production and has good industrial application value. The production process is environmentally friendly and has no pollutant discharge.

Description

A new method to produce biodiesel from vegetable oil

(1) Technical field

The invention relates to the technical fields of environmental protection and renewable energy. Specifically, it refers to a method for producing biodiesel through transesterification of vegetable oil under supercritical conditions.

(2) Background technology

At present, biodiesel is mainly produced by catalyzing the transesterification reaction of animal and vegetable oils and some short-chain alcohols (methanol, ethanol, etc.) in the presence of a catalyst. Depending on the catalyst used, catalytic methods mainly include chemical catalysis and enzymatic catalysis.

The chemical catalysis method uses acid or alkali catalysts. Although the reaction conditions are mild, there are some shortcomings that cannot be eliminated by themselves: such as complex process, many post-processing procedures, large loss, high cost, acid and alkali in the production process severely corrode the equipment and affect product quality. , easy to cause secondary pollution and so on. Patent CN1374370A uses acidified vegetable oil and sewer oil as raw materials for vegetation biodiesel, and the reaction time is long, which takes 4-8 hours; after the esterification reaction, it needs to be filtered, distilled, and the catalyst is removed. The post-treatment is complicated and the product loss is large. CN1412278A adopts the method of acidifying waste animal and vegetable oil to produce biodiesel, and after the esterification reaction, processes such as decolorization and catalyst removal are required. The reaction time is long and the post-processing is complicated.

Due to the limitations of the enzyme itself, the enzymatic method is easily inactivated by the toxicity of methanol and ethanol, and the activity is greatly affected by the environment; and the by-product glycerol is easy to attach to the surface of the enzyme during the reaction, hindering the reaction from continuing, the conversion rate is low, and a large amount of organic solvents are used. Not only the cost is high, but also causes environmental pollution, which limits its application.

The production of biodiesel by the supercritical method does not require any catalyst, and has the advantages of fast reaction speed, simple post-treatment process, low cost, high yield, and environmental friendliness. At present, the supercritical method is in the emerging stage of research and is receiving widespread attention. Its limitation lies in the high reaction temperature and pressure conditions when only vegetable oil reacts with small molecule alcohols.

(3) Contents of the invention

The object of the present invention is to propose a new method for producing biodiesel from vegetable oil, which is characterized in that: take vegetable oil and small molecule alcohols as reactants, add co-solvent, carry out transesterification under supercritical conditions, and convert fatty acid glyceride Converted into small molecule alcohol esters of fatty acids (ie biodiesel). Wherein, the molar ratio of small molecular alcohol plant: vegetable oil is 3-45: 1, and after 4-30 minutes of reaction, biodiesel is produced, and its production process and process conditions are:

1) Place the reaction raw materials and co-solvent in a high-pressure reactor with automatic temperature control and heat to 200-350°C.

2) Control the reaction pressure at 10-30Mpa.

3) The temperature control reaction is completed after 4-30 minutes, and the final product of the reaction is separated to produce the finished biodiesel.

The vegetable oil is one or more of soybean oil, transgenic soybean oil, rapeseed oil, transgenic rapeseed oil, castor oil, tung oil, palm oil, peanut oil, sunflower oil, waste edible oil (including two )mixture.

The small molecule alcohol is one or a mixture of methanol and ethanol.

The co-solvent is one or a mixture of two or more (including two) of carbon dioxide, small molecule hydrocarbons, small molecule oxygen-containing compounds, and small molecule nitrogen-containing compounds.

Compared with other methods for producing biodiesel, the present invention has advantages and beneficial effects:

1) No catalyst is needed in the transesterification process of the present invention, the post-treatment process is greatly reduced, the reaction process is simple and easy to control, and the cost is reduced.

2) The invention is environmentally friendly, and no pollutants are discharged during the production process.

3) The addition of the co-solvent in the reaction process of the present invention not only strengthens the mutual solubility of vegetable oil and small molecule alcohol, makes small molecule alcohol form a single-phase system with vegetable oil under supercritical conditions, thereby accelerating the reaction rate and greatly shortening the reaction time; and The critical point of the small molecule alcohol is lowered so that it can reach a supercritical state at a lower temperature and lower pressure, and the reaction temperature and pressure are lowered, so that the reaction is easy to realize in industrial production and has good industrial application value.

4) The small molecular alcohol isolated at the end of the reaction of the present invention can be purified and reused repeatedly, and the isolated crude glycerin is refined to obtain finished product pure glycerin or used for other industrial production (such as saponification, etc.). The co-solvent added in the reaction can also be processed and reused.

(4) Specific implementation methods

The present invention is a new method for producing biodiesel from vegetable oil, which is characterized in that vegetable oil and small molecule alcohols are used as reactants, co-solvent is added, transesterification is carried out under supercritical conditions, and fatty acid glyceride is converted into fatty acid Small molecule alcohol esters (i.e. biodiesel). Wherein, the molar ratio of small molecular alcohol: vegetable oil is 3-45: 1, and after 4-30 minutes of reaction, biodiesel is produced, and its production process and process conditions are:

1) The reaction raw materials and co-solvent are placed in a high-pressure reactor with automatic temperature control and heated to 200-350°C;

2) Control the reaction pressure at 10-30Mpa.

3) The temperature control reaction is completed after 4-30 minutes, and the final product of the reaction is separated to produce the finished biodiesel.

The vegetable oil is one or more of soybean oil, transgenic soybean oil, rapeseed oil, transgenic rapeseed oil, castor oil, tung oil, palm oil, peanut oil, sunflower oil, waste edible oil (including two )mixture.

The small molecule alcohol is one or a mixture of methanol and ethanol.

The co-solvent is one or a mixture of two or more (including two) of carbon dioxide, small molecule hydrocarbons, small molecule oxygen-containing compounds, and small molecule nitrogen-containing compounds.

Below in conjunction with embodiment, the present invention is described in further detail.

Embodiment one

Put 58.1 g of soybean oil and 70.5 g of methanol into the autoclave, seal the autoclave and replace the air in the autoclave with inert gas, and add 36 g of co-solvent CO ₂ . The pressure and temperature of the reactor are monitored in real time by instruments. The autoclave is heated by an external heater, and the temperature in the autoclave is monitored by Fe and Cu-Ni alloy thermocouples. Adjust the voltage to reach 300°C within 30 minutes, control ±5°C, and complete the transesterification reaction within 25 minutes. Finally, it was transferred to a water bath to stop the reaction.

After the reaction, discharge gas, pour the mixture in the autoclave into the collector, and wash the autoclave with methanol. The product to be treated was settled for 60 minutes and separated into three layers, the uppermost layer being methanol phase, which was separated. The remaining two layers were separated and distilled at 60-80°C for 30 minutes respectively, and the remaining methanol was evaporated, and the mass of the residue was weighed, and analyzed by high performance liquid chromatography (column length 25cm, diameter 4.6mm, 40°C, 1.0ml /min Methanol is the sample solvent, the injection volume is 20ul), and the identified products are vegetable oil methyl ester (biodiesel) and glycerol. Determination of product quality: 57.2 grams of vegetable oil methyl ester, 6 grams of glycerin, the calculated reaction yield reached 98%.

The quality and performance of the resulting biodiesel product are tested as follows: viscosity 2.8-6csl (20°C), similar to 2# diesel, calorific value 10000kcal/kg, flash point≮85, cetane number 54, ash 0.001% The performance test of the internal combustion engine shows that the power generated by the combustion of biodiesel is slightly lower than that of 2# diesel, and the concentration of smoke, CO and unburned hydrocarbons are reduced. It is a renewable and environmentally friendly alternative fuel for fossil diesel .

Embodiment two

Put 58.1 grams of transgenic soybean oil and 89.7 grams of methanol into a high-pressure reactor, seal the reactor and replace the air in the reactor with an inert gas, and add 24 grams of short-chain alkanes with less than 3 carbons as a co-solvent. The pressure and temperature of the reactor are monitored in real time by instruments. The autoclave is heated by an external heater, and the voltage is adjusted to reach 270°C within 30 minutes, controlled at ±5°C, and the transesterification reaction is completed within 30 minutes. Finally, it was transferred to a water bath to stop the reaction.

After the reaction, discharge gas, pour the mixture in the autoclave into the collector, and wash the autoclave with methanol. The product to be treated was settled for 60 minutes and separated into three layers, the uppermost layer being methanol phase, which was separated. The remaining two layers were separated and distilled at 60-80° C. for 30 minutes, the remaining methanol was distilled off, and the mass of the residue was weighed. Using high-performance liquid chromatography analysis, the products were identified as vegetable oil methyl ester (biodiesel) and glycerol. Determination of product quality: 58.2 grams of vegetable oil methyl ester, 6 grams of glycerin, the calculated reaction yield reached 99.5%. The quality and performance of the resulting biodiesel product are the same as in Example 1.

Embodiment three

Put 58.1 grams of pretreated waste cooking oil and 51.3 grams of methanol into the autoclave, seal the autoclave and replace the air in the autoclave with an inert gas, and add 32 grams of co-solvent propane. The pressure and temperature of the reactor are monitored in real time by instruments. The autoclave is heated by an external heater, and the voltage is adjusted to reach 285°C within 30 minutes, controlled at ±5°C, and the transesterification reaction is completed within 30 minutes. Finally, it was transferred to a water bath to stop the reaction.

After the reaction, discharge gas, pour the mixture in the autoclave into the collector, and wash the autoclave with methanol. The product to be treated was settled for 60 minutes and separated into three layers, the uppermost layer being methanol phase, which was separated. The remaining two layers were separated and distilled at 60-80° C. for 30 minutes, the remaining methanol was distilled off, and the mass of the residue was weighed. Using high-performance liquid chromatography analysis, the products were identified as vegetable oil methyl ester (biodiesel) and glycerol. Determination of product quality: 46.3 grams of vegetable oil methyl ester, 4.7 grams of glycerin. The quality and performance of the resulting biodiesel product are the same as in Example 1.

Embodiment four

Put 58.5 g of pretreated peanut oil and 76.9 g of methanol into the autoclave, seal the autoclave, replace the air in the autoclave with inert gas, and add 24 g of co-solvent CO ₂ . The pressure and temperature of the reactor are monitored in real time by instruments. The autoclave is heated by an external heater, and the voltage is adjusted to reach 330°C within 30 minutes, controlled at ±5°C, and the transesterification reaction is completed within 20 minutes. Finally, it was transferred to a water bath to stop the reaction.

After the reaction, discharge gas, pour the mixture in the autoclave into the collector, and wash the autoclave with methanol. The product to be treated was settled for 60 minutes and separated into three layers, the uppermost layer being methanol phase, which was separated. The remaining two layers were separated and distilled at 60-80° C. for 30 minutes, the remaining methanol was distilled off, and the mass of the residue was weighed. Using high-performance liquid chromatography analysis, the products were identified as vegetable oil methyl ester (biodiesel) and glycerol. Determination of product quality: 56.3 grams of vegetable oil methyl ester, 5.7 grams of glycerin, and the calculated reaction yield is more than 97%. The quality and performance of the resulting biodiesel product are the same as in Example 1.

Claims (6)

1. A method for preparing biodiesel, characterized in that: take vegetable oil and small molecule alcohols as reactant, add co-solvent, carry out transesterification reaction under supercritical conditions, fatty acid glyceride is converted into fatty acid small molecule alcohol ester , i.e. biodiesel; wherein, the molar ratio of small molecule alcohol: vegetable oil is 3-45: 1, and after 4-30 minutes of reaction, biodiesel is produced, and its production process and process conditions are: 1) Place the reaction raw materials and co-solvent in a high-pressure reactor with automatic temperature control and heat to 200-350°C; 2) Control the reaction pressure at 10-30Mpa; 3) The temperature control reaction is completed after 4-30 minutes, and the final product of the reaction is separated to produce the finished biodiesel. 2. The method for preparing biodiesel according to claim 1, characterized in that: no catalyst is needed in the reaction process. 3. the method for preparing biodiesel according to claim 1 is characterized in that: described vegetable oil is soybean oil, transgenic soybean oil, rapeseed oil, transgenic rapeseed oil, castor oil, tung oil, palm oil, peanut oil, One or more mixtures of sunflower oil and waste cooking oil. 4. The method for preparing biodiesel according to claim 1, characterized in that: the small molecule alcohol is one or a mixture of methanol and ethanol. 5. The method for preparing biodiesel according to claim 1, characterized in that: the co-solvent is one or more of carbon dioxide, small molecule hydrocarbons, small molecule oxygen-containing compounds, small molecule nitrogen-containing compounds mixture. 6. the method for preparing biodiesel according to claim 1 is characterized in that: the small molecule alcohol that separates when described reaction finishes can be reused through purification, and the crude glycerol that separates is refined and obtains finished product pure glycerol or with In other industrial production, such as saponification, etc.