Method for producing biodiesel from waste oil

Abstract

The invention discloses a method for producing biodiesel from waste oil and belongs to the field of biodiesel preparation. The invention relates to an innovative photocatalytic decarboxylation process using an acridine photocatalyst, which is used for producing second-generation biodiesel using waste oil as a raw material. According to the method, a microchannel continuous flow technology can be combined and used, and the product can be obtained with excellent yield and high selectivity.

Description

Technical Field

[0001] The present invention belongs to the field of biodiesel production, and particularly relates to a method for producing biodiesel from waste oils and fats. Background Art

[0002] In recent years, many studies have attempted to convert non-renewable energy into sustainable energy, such as electricity, clean hydrogen and its derivatives, as well as renewable energy such as wind energy, solar energy and biofuels. Among these alternatives, biodiesel has been the focus of attention for decades due to its good combustion performance, good low-temperature starting performance, good lubrication performance, high safety performance and other advantages. Compared with petrochemical diesel, its emissions of CO 2 and SO 2 are relatively low, and it also has the advantages of green renewable, efficient, clean combustion and biodegradable. Therefore, it is regarded as one of the most promising candidate energy sources to replace fossil fuels and provide energy for the world.

[0003] Traditional biodiesel production methods, such as thermal catalysis and hydrotreating, usually require high temperatures (200 °C to 700 °C) or high pressures and consume a large amount of hydrogen. This not only increases the consumption of energy and materials, but also does not meet the requirements of sustainable development. Since the chlorine-containing solvents used in the reaction process will produce a large amount of harmful gases, such as hydrogen chloride, during production, it causes serious pollution to the environment. At the same time, there are also problems such as the need for solvent separation after the reaction. Therefore, in view of the above problems, the present technology uses inexpensive and small amounts of acridine-based catalysts and alkanes as solvents for a photocatalytic reaction with mild conditions, without the need for solvent separation and post-treatment, and can achieve a relatively high photocatalytic reaction efficiency. In addition, waste cooking oil is used as the preferred raw material for its production. It can not only solve the waste treatment problem, but also realize the recycling of resources, meeting the requirements of sustainable development. Summary of the Invention

[0004] The present invention provides a method for producing biodiesel from waste oils and fats in view of the problems existing in the prior art. The present invention uses an innovative photocatalytic decarboxylation process with an acridine photocatalyst for the production of second-generation biodiesel from waste oils and fats. This method can also be combined with a microchannel continuous flow technology to obtain products with excellent yields and high selectivity.

[0005] The method for producing biodiesel from waste oils and fats according to the present invention comprises the following steps:

[0006] Mix the free fatty acids obtained by hydrolyzing waste oils and fats, an acridine photosensitizer, a hydrogen transfer reagent and a solvent, and carry out a decarboxylation reaction under an inert gas atmosphere and under light irradiation conditions to obtain second-generation biodiesel.

[0007] The structural general formula of the acridine photosensitizer is as follows:

[0008]

[0009] Among them, R 1 represents H, phenyl or substituted phenyl, and the substituent is alkyl or alkoxy. R 2 and R 3 represent H or alkyl.

[0010] Furthermore, the acridine photosensitizer is preferably a compound with the following structure:

[0011]

[0012] More preferably, it is Acr4.

[0013] The hydrogen transfer reagent includes, but is not limited to, the following compounds:

[0014]

[0015] Furthermore, p - tolyl mercaptan is preferred.

[0016] The solvent includes, but is not limited to, dichloromethane, methanol, acetone, methyl ethyl ketone, n - hexane, N,N - dimethylformamide, diethyl carbonate or γ - valerolactone. n - hexane is preferred.

[0017] The inert gas includes, but is not limited to, argon, nitrogen, carbon dioxide. Argon or nitrogen is preferred.

[0018] In this embodiment, the molar ratio of the substrate fatty acid to the acridine photosensitizer is 100:1 - 1:1, preferably 30:1 - 5:1.

[0019] In this embodiment, the molar ratio of the substrate fatty acid to the hydrogen transfer reagent is 100:1 - 1:1, preferably 100:1 - 20:1.

[0020] In this embodiment, the concentration of the substrate fatty acid is 0.1 - 0.5 mol / L, preferably 0.2 - 0.3 mol / L.

[0021] In this embodiment, the reaction temperature is 10 - 100 °C, preferably 20 - 45 °C; the reaction light wavelength is 380 nm - 460 nm, preferably 400 - 420 nm.

[0022] The substrate fatty acid is preferably a saturated fatty acid.

[0023] The present invention adopts an acridine photocatalyst combined with a microchannel continuous flow technology. Through a photocatalytic decarboxylation process, waste oils and fats are efficiently converted into second-generation alkane-based biodiesel under mild conditions, achieving high yields and high selectivities. This process not only optimizes the production process, reduces energy consumption and environmental burden, but also greatly improves the production efficiency and economic feasibility of biodiesel, opening up a new way for the resource utilization of waste oils and fats.

[0024] The present invention has the following advantages: high apparent quantum efficiency, using a non-metallic catalyst, solvent-free separation and post-treatment, high product yield, short reaction time and mild conditions. Brief Description of the Drawings

[0025] Figure 1 It is a schematic diagram of the preparation process of the present invention. Detailed Embodiments

[0026] The technical solution of the present invention will be further analyzed and described below through specific examples.

[0027] Example 1:

[0028] The waste oils and fats are first pretreated, and the specific operation steps are as follows: First, the food residues in the oil are carefully filtered to ensure the removal of any impurities or unwanted particles, thereby improving the purity of the subsequent products. After filtration, an excessive amount of NaOH is added to the oil. The purpose is to initiate a saponification reaction, in which the triglycerides in the oil are converted into sodium fatty acid salts and glycerol. After the reaction is completed, the mixture is thoroughly stirred to ensure uniform distribution of the reactants and products. After stirring, H 2 SO 4 is introduced into the mixture for acidification. This step reverses the saponification reaction and releases the fatty acids from the sodium salt form. Subsequently, the acidified mixture is washed with distilled water. The washing process helps to remove residual impurities, such as excessive NaOH, glycerol and any other water-soluble compounds. Then the mixture is separated into two layers: an aqueous layer containing impurities and an organic layer rich in fatty acids. The organic layer is collected and dried to remove residual moisture.

[0029] Example 2:

[0030]

[0031] 0.08 g (0.4 mmol) of dodecanoic acid, 0.016 mmol (4 mol%) of Acr4, and 0.004 mmol (1 mol%) of PhS3 are added to a 10 ml Schlenk tube, and then 2 ml of n-hexane is added under an Ar atmosphere. At room temperature, the reaction system is irradiated with light at 400 nm for 12 hours. After the reaction is completed, dodecane is added as an internal standard, and then analyzed by gas chromatography. The yield of undecane > 99%, and the conversion rate of dodecanoic acid > 99%.

[0032] Examples 3 - 6:

[0033] The operation process is similar to that of Example 1, except that Acr4 is replaced with different acridine photosensitizers, and the reaction effects are shown in Table 1 below.

[0034]

[0035] Examples 7 - 9:

[0036] The operation process is similar to that of Example 1, except that PhS3 is replaced with different hydrogen transfer reagents, and the reaction effects are shown in Table 2 below.

[0037]

[0038] Examples 10 - 14:

[0039] The operation process is similar to that of Example 1, except that dodecanoic acid is replaced with different fatty acids, and the reaction effects are shown in Table 3 below.

[0040]

[0041] Example 15:

[0042] The waste oil and fat are first pretreated to obtain free fatty acids. Take 1.388 g of free fatty acids and put them into a round-bottom flask, then add 4 mol% of Acr4 and 1 mol% of PhS3. Under an argon atmosphere, add 25 ml of n-hexane solvent, and then carry out a continuous flow reaction. Purge the bottle with an argon balloon for 15 min. Then use a peristaltic pump to pump the reaction mixture into a 3 mL microchannel reaction plate at a flow rate of 10 mL / min. The reaction mixture is retained in the microchannel reaction plate for 60 minutes under irradiation by a 400 nm LED (600 mW·cm -2 ). After the reaction is completed, dodecane is added as an internal standard, and the yield of the target product is determined by gas chromatography to be >90%.

Claims

1. A method for producing biodiesel from waste oils and fats, characterized in that The steps include: The free fatty acids obtained by hydrolyzing waste oil, acridine photosensitizer, hydrogen transfer reagent and solvent are mixed, and decarboxylation reaction is carried out under light conditions in an inert gas atmosphere to obtain the second generation biodiesel; The general structural formula of the acridine photosensitizer is as follows: ； Wherein, R1 represents H, phenyl or substituted phenyl, the substituent is alkyl or alkoxy, and R2 and R3 are independently represented by H or alkyl.

2. The method according to claim 1, characterized in that The acridine photosensitizer is selected from the compounds with the following structures: 。 3. The method according to claim 1, characterized in that The acridine photosensitizer is: 。 4. The method according to claim 1, characterized in that The hydrogen transfer reagents include but are not limited to the following compounds: 。 5. The method according to claim 4, characterized in that: The hydrogen transfer reagent is p-toluene thiophenol.

6. The method according to claim 1, characterized in that: The solvent includes, but is not limited to, alkanes, halogenated alkanes, ketones, alcohols, and ester solvents.

7. The method according to claim 6, characterized in that: The solvent is an alkane solvent.

8. The method according to claim 1, characterized in that: The reaction temperature is 10-100° C., the reaction light wavelength is 380 nm-460 nm, and the inert gas includes but is not limited to argon, nitrogen or carbon dioxide.

9. The method according to claim 8, characterized in that: The reaction temperature is 20-45° C., the reaction light wavelength is 400-420 nm, and the inert gas is argon or nitrogen.

10. The method according to claim 1, characterized in that: The reaction was carried out in a continuous flow manner using a microchannel photoreactor.

Images