TWI576423B - Process for producing biodiesel - Google Patents

Description

Method for producing biodiesel

The present invention provides a method of converting a neutral lipid-containing feedstock into biodiesel under subcritical conditions.

In view of the growing energy crisis and environmental problems, the world has been looking for clean alternative energy sources for some time. Biodiesel is formed by transesterification and/or esterification of oils and fats, and is a kind of renewable energy. Because biodiesel has low pollution, non-toxicity and biodegradability, it meets economic and environmental considerations and has become a recognized clean alternative energy source.

At present, the industrial production of quality diesel oil is mainly based on refined vegetable oil (the main component is triglyceride). After sodium or potassium hydroxide is used as a catalyst and methanol is transesterified, fatty acid methyl ester is obtained. , also known as biodiesel. This process is not suitable for the use of low quality oils containing high levels of free fatty acids and water, such as waste cooking oil (Lotero et al., 2005; Vicente et al., 2004). When such a low-quality oil is used as a raw material and a commercialized alkali process is used to produce a quality diesel oil, a pretreatment step is required to remove the moisture and free fatty acids in the raw material oil. Water and free fatty acids in the reaction consume alkali catalysts via the saponification reaction and thus reduce the yield of biodiesel. In particular, in the washing process after completion of the reaction, the mixture of soap, fatty acid methyl ester and unreacted material forms emulsification, resulting in a decrease in the quality of the product biodiesel (Marulanda et al., 2010). As the price of vegetable oil continues to rise, the inability to use low-cost feedstock oil has become a major drawback of traditional processes. This disadvantage can be overcome by the use of solid catalysts that can tolerate high levels of free fatty acid feedstock oil (Shu et al., 2010; Zhang et al., 2010). However, due to the mass transfer resistance between the liquid reactant and the solid catalyst, the activity of the solid catalyst is low (Tan et al., 2010).

The recent production of quality diesel in a supercritical state is considered to be a process that can overcome the shortcomings of conventional homogeneous catalyst processes. In the supercritical state, the feedstock oil and methanol become a single phase to achieve complete mixing, so high conversion (>95%) can be achieved in a few minutes without the need for a catalyst. In particular, the presence of water and free fatty acids does not affect the conversion of biodiesel because transesterification of triglycerides occurs simultaneously with esterification of free fatty acids (Ayhan, 2009; He et al., 2007). Therefore, this process can use low-priced oils containing high levels of water and free fatty acids as raw materials.

The critical temperature and critical pressure of methanol are 240 ° C and 8.09 MPa. However, due to the presence of glycerides and free fatty acids, temperatures and pressures well above 240 ° C and 8.09 MPa must be used in the so-called "production of diesel fuel in supercritical methanol". High temperature (300 to 350) in the early studies of oil-alcohol transesterification in supercritical alcohols (Anitescu et al., 2008; Ayhan, 2009; Kasim et al., 2009; Varma and Madras, 2006) °C), high pressure (20 to 35 MPa) and high alcohol oil molar ratio (40:1 to 42:1). By using a co-solvent such as hexane, carbon dioxide and propane, and a non-homogeneous catalyst such as calcium oxide, the operating temperature, pressure and alcohol molar ratio can be reduced to 250 to 280 ° C, 15 to 20 MPa, respectively. 24:1 to 30:1. However, the aforementioned temperatures and pressures are still quite high, and the use of co-solvents is not conducive to environmental protection and purity of product-based diesel (Laosiripojana et al., 2010; Trentin et al., 2011). Since the raw material is produced in a supercritical state, the raw material needs to be heated to a very high temperature and a very high pressure. After the reaction is completed, the product needs to be lowered to room temperature and normal pressure, so that the production of the quality diesel in the supercritical state is regarded as An energy intensive program (Tan and Lee, 2011).

Subcritical water is an environmentally friendly technology widely used in applications such as extraction, hydrolysis, and wet oxidation of organic materials. It is known to those skilled in the art that any water between about 100 ° C and about 374 ° C is said to be subcritical water as long as a sufficient pressure is applied to bring it into a liquid state, i.e., the applied pressure is at least The saturated vapor pressure of water at this temperature. When water is used as the extraction solvent, its dielectric constant is the most important property. The dielectric constant of water is 80 at room temperature and drops to 27 when the temperature rises to 250 ° C, which is approximately equal to the dielectric constant of ethanol at room temperature. In recent years, many studies have explored the hydrolysis or biodegradation of biomass or carbohydrates into useful compounds by subcritical water (Holliday et al., 1997; Khuwijitjaru et al., 2004; Quitain et al., 2002). . In addition, subcritical water treatment can also be used to increase the amount of extractable lipid in activated sludge (Huynh et al., 2010).

In view of the above, the present invention provides a method for producing mass diesel in a subcritical state, the method of the present invention can produce quality diesel at a lower temperature and pressure than the supercritical methanol process, and due to the method of the present invention There is no need to use a catalyst, so separation and purification of the product becomes simpler, so the present invention can reduce operating and equipment costs.

In the present invention, a solution formed from a fat or oil raw material, water, and methanol is reacted in a subcritical state to produce a quality diesel oil. Therefore, the present invention produces a quality diesel fuel in a relatively simple manner without using a conventional acid or alkali catalyst and without consuming a large amount of energy.

The solution of the invention is mixed with water and methanol, so the boiling point of the formed solution should be between the boiling point of methanol (64.7 ° C) and the boiling point of water (100 ° C), and the critical temperature should also be between the critical temperature of methanol (240). °C) is between the critical temperature of water (374 °C).

The object of the present invention is to provide a method for producing quality diesel oil by adding a raw material containing neutral lipids with water and methanol to a closed reactor, and heating to raise the temperature of the reactor to about 100 ° C. Between about 240 ° C (preferably in the temperature range of about 120 ° C to about 230 ° C), and the pressure in the reactor is at least the saturated vapor pressure of the solution at this temperature, and the reaction is carried out for a suitable time to obtain biodiesel.

In general, the longer the reaction time, the higher the conversion rate of the reaction. Thus, for those of ordinary skill in the art to which the present invention pertains, it is possible to determine an appropriate reaction time depending on the reaction temperature.

With regard to the saturated vapor pressure of the solution in the reactor, it is possible for those of ordinary skill in the art to carry out appropriate experiments according to methods well known in the art to obtain saturation of the solution in the reactor at a specific temperature. Vapor pressure; and after further consideration of its needs (eg, reaction cost or reaction time), the appropriate reaction pressure is determined as long as the pressure is at least the saturated vapor pressure of the solution at that temperature.

In the method of the present invention, the oil and fat raw material used is a neutral lipid-containing material. The raw material, preferably, the weight ratio of the neutral lipid-containing raw material to water ranges from 1:0.01 to 1:10.

Preferably, in the process of the invention, the weight ratio of methanol to water used ranges from 3:1 to 500:1.

In the method of the present invention, the neutral lipid comprises triglyceride, diglyceride, monoglyceride and free fatty acid.

In the method of the present invention, the neutral lipid-containing raw material used may be derived from any substance containing a neutral lipid, for example, it may be selected from the group consisting of finely braked vegetable oil, waste edible oil, rice bran, activated sludge, yeast, micro. a group of algae and mixtures thereof.

Preferably, in the process of the invention, the reactor temperature ranges between about 120 ° C and 230 ° C.

In the process of the present invention, sulfuric acid may optionally be added to the reactor to participate in the reaction, wherein the ratio of the sulfuric acid to the reaction mixture preferably ranges from 1:1000 to 1:10000 g/mL.

Compared with the commercial alkali catalyst process, the method of the invention does not need a catalyst, so not only the fine brake vegetable oil but also a low-priced oil containing more water and free fatty acid, such as waste edible oil, can be used, and the invention is used. The method can directly use raw materials containing neutral lipids, such as rice bran and activated sludge, without pre-treatment of the raw materials, such as oil extraction. Since no catalyst is used, in the present invention, separation and purification of the product becomes relatively simple.

Compared to the supercritical methanol process that does not require a catalyst, since the supercritical methanol process requires very high temperatures and pressures (about 300 to 350 ° C and about 20 to 35 MPa, respectively), even if a cosolvent is added, the supercritical Methanol process still A relatively high temperature (about 250 to 280 ° C) and a pressure (about 15 to 20 MPa) are required. In contrast, the process of the present invention can be carried out at any temperature greater than about 100 ° C and less than about 240 ° C, and the pressure in the reactor is at least the saturated vapor pressure of the solution at that temperature; preferably, the present invention The process can be carried out at any temperature from about 120 to 230 ° C, and the pressure in the reactor is also at least the saturated vapor pressure of the solution at that temperature. Therefore, the operation and equipment costs required for the process of the present invention will be lower than the supercritical methanol process.

The invention is further illustrated by the following examples, which are not intended to limit the scope of the present invention, and any modifications and variations which may be obtained without departing from the spirit of the invention are the invention. range.

Example 1

1 g of commercially available soybean oil was added, and 30 ml of methanol and 0.05 ml of water were added, and the mixture was reacted at 175 ° C, 35 bar (3.5 MPa) for 4 hours. After removing water and methanol, the composition of the product is as follows: fatty acid methyl ester (96.38%), triglyceride (0.02%), diglyceride (0.03%), monoglyceride (0.72%), free fatty acid ( <0.01%), others (2.85%).

Example 2

1 g of commercially available soybean oil was added, and 30 ml of methanol and 0.05 ml of water were added, and the mixture was reacted at 200 ° C, 45 bar (4.5 MPa) for 2 hours. After removing water and methanol, the composition of the product is as follows: fatty acid methyl ester (85.88%), triglyceride (2.01%), diglyceride (3.09%), monoglyceride (8.46%), tour From fatty acids (<0.01%), others (0.56%).

Example 3

0.9 g of commercially available edible soybean oil, 0.1 g of palmitic acid, 30 ml of methanol, 0.05 ml of water and trace sulfuric acid (the ratio of the reaction mixture to sulfuric acid is about 1:0.0005 g/mL), at 175 ° C, The reaction was carried out for 2 hours at 35 bar (3.5 Map). After removing water and methanol, the composition of the product is as follows: fatty acid methyl ester (94.17%), triglyceride (<0.01%), diglyceride (<0.01%), monoglyceride (1.50%), free Fatty acid (0.21%), others (4.12%).

Example 4

1 g of activated sludge containing 83% of water was added, and 5 ml of methanol was added thereto, and the mixture was reacted at 175 ° C, 35 bar (3.5 MPa) for 8 hours. After removing water, methanol and solid residues, the composition of the product is as follows: fatty acid methyl ester (80.89%), free fatty acid (15.52%), others (3.59%); fatty acid methyl ester available per gram of dry activated sludge The amount is 0.45 grams. If the reaction time is extended to 24 hours, the composition of the product is as follows: fatty acid methyl ester (89.43%), free fatty acid (5.75%), others (4.82%); the amount of fatty acid methyl ester available per gram of dry activated sludge It is 0.46 grams.

Example 5

1 g of Yarrowia lipolytica Po1g was added, and 30 ml of methanol and 0.5 ml of water were added, and the mixture was reacted at 175 ° C, 35 bar (3.5 MPa) for 8 hours. After removal of water, methanol and solid residue, the composition of the product was as follows: fatty acid methyl ester (92.18%), triglyceride (2.25%), diglyceride (2.39%), monoglyceride (2.30%) The free fatty acid (0.13%) and others (0.75%) have a fatty acid methyl ester amount of 0.38 g per gram of dry yeast.

Example 6

1 g of Chlorella vulgaris biomass containing 80% of water was added to 4 ml of methanol, and reacted at 175 ° C, 35 bar (3.5 MPa) for 4 hours. After removal of water, methanol and solid residue, the composition of the product was as follows: fatty acid methyl ester (89.71%), triglyceride (1.01%), diglyceride (2.30%), monoglyceride (5.43%) , free fatty acid (1.48%), the amount of fatty acid methyl ester per gram of dry microalgae is 0.29 grams.

The following patent claims are intended to define the scope of the invention. It should be understood that the obvious modifications and equivalents that can be achieved by those skilled in the art based on the disclosure of the present invention are also intended to be within the scope of the invention.

Claims (8)

A method for producing a quality diesel oil by adding a raw material containing neutral lipids with water and methanol to a closed reactor, heating to raise the temperature of the reactor to between about 100 ° C and about 240 ° C, and in the reactor The pressure system is at least the saturated vapor pressure of the solution at the temperature, and the reaction is carried out for a suitable time to obtain biodiesel. The method of claim 1, wherein the neutral lipid comprises triglyceride, diglyceride, monoglyceride, and free fatty acid. The method of claim 1, wherein the raw material is selected from the group consisting of fine brake vegetable oil, waste cooking oil, rice bran, activated sludge, yeast, microalgae, and combinations thereof. The method of claim 1, wherein the heating raises the reactor temperature to between about 120 ° C and about 230 ° C. The method of claim 1, wherein the weight ratio of methanol to water ranges from 3:1 to 500:1. The method of claim 1, wherein the neutral lipid-containing material to water weight ratio ranges from 1:0.01 to 1:10. As in the method of claim 1, it is further added with sulfuric acid to participate in the reaction in the reactor. The method of claim 1, wherein the ratio of the sulfuric acid to the reaction mixture ranges from 1:1000 to 1:10000 g/mL.