A method for synthesizing branched fatty acid methyl esters from epoxidized fatty acid methyl esters using a sulfonated biochar catalyst

Abstract

The application discloses a method for synthesizing branched fatty acid methyl ester by catalyzing epoxidized fatty acid methyl ester by sulfonated biochar, and specifically comprises the following steps: uniformly mixing a catalyst, epoxidized fatty acid methyl ester and C1-C10 alkyl alcohol, stirring and reacting under the protection of nitrogen at an oil bath temperature of 80-140 DEG C for 3-7 h, removing the catalyst through filtration, removing the C1-C10 alkyl alcohol through rotary evaporation, and finally obtaining branched fatty acid methyl ester. The catalyst used in the application has good catalytic performance, the reaction condition is mild, there are no problems such as equipment corrosion and wastewater treatment, the reaction product has strong oxidation resistance, and the product can be applied to bio-based lubricating oil.

Description

Technical Field

[0001] This invention relates to the fields of renewable energy, lubricating oil base oil, and surfactants, and specifically to a method for synthesizing branched-chain fatty acid methyl esters by catalysis of sulfonated biochar. Background Technology

[0002] In recent years, the consumption of lubricating oil has been increasing year by year, placing different demands on its performance, low biodegradability, and non-toxicity. Improper disposal of waste edible oils can lead to serious environmental disasters. Using waste edible oils as raw materials and agricultural waste as catalysts to produce high-value-added chemicals such as bio-based lubricating oils not only turns waste into treasure but also reduces the cost of urban pollutant and rural waste treatment, promoting sustainable resource development. Because epoxide fatty acid methyl esters contain epoxy bonds and lack branching in their molecular structure, their thermal stability and low-temperature fluidity do not meet the requirements of lubricating oils. However, by adding branching to natural oils through chemical modification, the modified vegetable oils can meet the requirements for lubricating oil base oils in terms of thermal stability, oxidative stability, and lubricity.

[0003] Epoxy fatty acid methyl esters contain epoxide bonds, making them more chemically reactive than C=C bonds. Under acid catalysis, they can undergo ring-opening reactions with various nucleophiles. The ring-opening reaction process is as follows: In an acidic environment, the oxygen atom in the epoxide bond reacts with H... + The combination of positive charges causes adjacent carbon atoms to become positively charged, and the CO on one side of the epoxide bond breaks. The O atom of the hydroxyl group in the alcohol then attacks the C cation to form a CO bond, removing the H atom. + The final product is obtained. Currently, inorganic acids are often used as catalysts in epoxy-ring-opening reactions because they have the advantage of short reaction times, but they also have problems such as complex post-processing and high equipment requirements.

[0004] Summary of the Invention

[0005] To address the aforementioned technical problems in the existing technology, this invention provides a method for synthesizing branched-chain fatty acid methyl esters by catalysis of sulfonated biochar.

[0006] The technical solution adopted in this invention is as follows:

[0007] A method for synthesizing branched-chain fatty acid methyl esters via sulfonated biochar catalysis involves using sulfonated biochar-based solid acid as a catalyst, employing sulfonated biochar as a raw material, and mixing the catalyst, sulfonated fatty acid methyl ester, and C1-C10 alkyl alcohols uniformly. The mixture is then stirred under oil bath heating to induce an epoxide ring-opening reaction. After the reaction, the catalyst is removed by filtration. The filtrate is washed with distilled water and then subjected to rotary evaporation to remove moisture and unreacted C1-C10 alkyl alcohol raw materials, yielding the product, branched-chain fatty acid methyl esters. The epoxide ring-opening reaction is as follows:

[0008]

[0009] In the formula, R is a C1-C10 alkyl group.

[0010] Furthermore, the preparation method of the sulfonated biochar-based solid acid catalyst is as follows: biomass is placed in a muffle furnace and pyrolyzed in an air atmosphere to form biochar, and then the biochar is immersed in concentrated sulfuric acid and heated and stirred for sulfonation reaction. The product is washed with hot deionized water and then dried to complete the preparation. The biomass is algae, corn cob, or corn cob with hemicellulose removed.

[0011] Furthermore, the pyrolysis temperature is 280-320℃, and the pyrolysis time is 2-4 hours.

[0012] Furthermore, the concentrated sulfuric acid has a mass concentration of 95-98%, the sulfonation reaction temperature is 75-85°C, and the reaction time is 3-5 hours.

[0013] Furthermore, the molar ratio of C1-C10 alkyl alcohol to epoxy fatty acid methyl ester is 3-7:1, preferably 5:1; the amount of biochar-based solid acid catalyst added is 11-15 wt% of the mass of epoxy fatty acid methyl ester, preferably 13%.

[0014] Furthermore, the reaction temperature for the epoxy ring-opening reaction is 80-140℃, preferably 120℃, and the reaction time is 3-7h, preferably 6h.

[0015] Furthermore, the C1-C10 alkyl alcohol is 2-ethylhexanol or 1-butanol.

[0016] By employing the above-described technology, the beneficial effects achieved by this invention are as follows:

[0017] 1) This invention uses epoxidized fatty acid methyl esters and 2-ethylhexanol or 1-butanol as raw materials, and biochar-based solid acids as catalysts to prepare and synthesize branched fatty acid methyl esters. This reaction has the advantages of readily available raw materials, easy separation and recovery of catalysts, short reaction time, mild reaction conditions, and high conversion rate.

[0018] 2) The solid acid catalyst provided by the present invention has the advantages of superior catalytic performance, high selectivity, reusability of the catalyst and simple post-processing of the product, and is an ideal ring-opening catalyst for epoxy greases.

[0019] 3) The reaction conditions for the epoxide-ring-opening reaction are related to the acidity of the catalyst, while the biochar solid acid provided by this invention has a unique graphene-like carbon structure and a pH value comparable to concentrated sulfuric acid. Acidity is due to the effect of acidic oxygen-containing functional groups (OH and COOH groups) on the SO3H groups in sulfonated biochar. The OH and COOH groups decrease the electron cloud density of the π-π conjugated system of the biochar, thus indirectly affecting the charge density of the SO3H groups and increasing the H content within the SO3H groups. + The release effect is enhanced, and the loading strength of SO3H groups is strengthened, resulting in better catalytic performance compared to other SO3H supported catalysts. The preparation of branched-chain fatty acid methyl esters via a biochar solid acid catalytic ring-opening method using epoxy fatty acid methyl esters is significant for the industrialization of ester-based lubricants due to the mild reaction conditions and short reaction time of the epoxy-ring-opening method. Detailed Implementation

[0020] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0021] The corn cobs used in this embodiment of the invention, after removing hemicellulose, were purchased from Zhejiang Huakang Pharmaceutical Co., Ltd. They are waste products obtained from the deep processing of corn cobs into xylitol, after removing hemicellulose. The concentrated sulfuric acid has a mass fraction of 95-98%.

[0022] The epoxy ring-opening reaction involved in this embodiment of the invention is as follows:

[0023]

[0024] In the formula, R is 2-ethylhexyl or 1-butyl.

[0025] Example 1:

[0026] Corn cobs with unremoved hemicellulose were pyrolyzed in a muffle furnace at 300℃ for 3 hours to obtain biochar. Concentrated sulfuric acid was mixed with the pyrolyzed biochar at a ratio of 15 ml: 1 g, and the mixture was stirred in an oil bath at 80℃ for 4 hours. The product was then filtered, the residue was washed with hot deionized water, and dried to obtain a biochar-based solid acid catalyst. 2.0 g of epoxy fatty acid methyl ester, 0.26 g of the biochar-based solid acid catalyst, and 3.5 g of 2-ethylhexanol were added at a 5:1 alcohol-to-oil molar ratio. After thorough mixing, the mixture was stirred in an oil bath at 120℃ for 6 hours. After the reaction, the reaction mixture was filtered, washed with distilled water, and the water was removed by rotary evaporation to obtain branched-chain fatty acid methyl esters (methyl 9-(2-ethylhexoxy)-10-hydroxystearate and methyl 9-hydroxy-10-(2-ethylhexoxy)stearate).

[0027] Example 2:

[0028] Hemicellulose-removed corn cobs were pyrolyzed in a muffle furnace at 300℃ for 3 hours to obtain biochar. Concentrated sulfuric acid was mixed with the pyrolyzed biochar at a ratio of 15 ml: 1 g, and the mixture was stirred in an oil bath at 80℃ for 4 hours. The product was then filtered, the residue was washed with hot deionized water, and dried to obtain a biochar-based solid acid catalyst. 2.0 g of epoxy fatty acid methyl ester, 0.26 g of the biochar-based solid acid catalyst, and 3.5 g of 2-ethylhexanol were added at a 5:1 alcohol-to-oil molar ratio. After thorough mixing, the mixture was stirred in an oil bath at 120℃ for 6 hours. After the reaction, the reaction mixture was filtered, washed with distilled water, and the water was removed by rotary evaporation to obtain branched-chain fatty acid methyl esters (methyl 9-(2-ethylhexoxy)-10-hydroxystearate and methyl 9-hydroxy-10-(2-ethylhexoxy)stearate).

[0029] Example 3:

[0030] Copper diatoms were pyrolyzed in a muffle furnace at 300℃ for 3 hours to obtain biochar. Concentrated sulfuric acid was mixed with the pyrolyzed biochar at a ratio of 15 ml: 1 g, and the mixture was stirred in an oil bath at 80℃ for 4 hours. The product was then filtered, the filter residue was washed with hot deionized water, and dried to obtain a biochar-based solid acid catalyst. 2.0 g of epoxy fatty acid methyl ester, 0.26 g of the biochar-based solid acid catalyst, and 3.5 g of 2-ethylhexanol were added according to an alcohol-to-oil molar ratio of 5:1. After thorough mixing, the mixture was stirred in an oil bath at 120℃ for 6 hours. After the reaction was complete, the reaction mixture was filtered, washed with distilled water, and the water was removed by rotary evaporation to obtain branched-chain fatty acid methyl esters (methyl 9-(2-ethylhexoxy)-10-hydroxystearate and methyl 9-hydroxy-10-(2-ethylhexoxy)stearate).

[0031] Example 4:

[0032] Hemicellulose-removed corn cobs were pyrolyzed in a muffle furnace at 300℃ for 3 hours to obtain biochar. Concentrated sulfuric acid was mixed with the pyrolyzed biochar at a ratio of 15 ml: 1 g, and the mixture was stirred in an oil bath at 80℃ for 4 hours. The product was then filtered, the residue was washed with hot deionized water, and dried to obtain a biochar-based solid acid catalyst. 2.0 g of epoxy fatty acid methyl ester, 0.26 g of the biochar-based solid acid catalyst, and 1.4 g of 1-butanol were added at a 3:1 molar ratio of alcohol to oil. After thorough mixing, the mixture was stirred in an oil bath at 110℃ for 4 hours. After the reaction, the reaction mixture was filtered, washed with distilled water, and the water was removed by rotary evaporation to obtain branched-chain fatty acid methyl esters (methyl 9-butoxy-10-hydroxystearate and methyl 9-hydroxy-10-butoxystearate).

[0033] Example 5:

[0034] Hemicellulose-removed corn cobs were pyrolyzed in a muffle furnace at 300℃ for 3 hours to obtain biochar. Concentrated sulfuric acid was mixed with the pyrolyzed biochar at a ratio of 15 ml: 1 g, and the mixture was stirred in an oil bath at 80℃ for 4 hours. The product was then filtered, the residue was washed with hot deionized water, and dried to obtain a biochar-based solid acid catalyst. 2.0 g of epoxy fatty acid methyl ester, 0.26 g of the biochar-based solid acid catalyst, and 3.3 g of 1-butanol were added according to an alcohol-to-oil molar ratio of 7:1. After thorough mixing, the mixture was stirred in an oil bath at 110℃ for 4 hours. After the reaction was complete, the reaction mixture was filtered, washed with distilled water, and the water was removed by rotary evaporation to obtain branched-chain fatty acid methyl esters (methyl 9-butoxy-10-hydroxystearate and methyl 9-hydroxy-10-butoxystearate).

[0035] Example 6:

[0036] Corn cobs with hemicellulose removed were pyrolyzed in a muffle furnace at 300℃ for 3 hours to obtain biochar. Concentrated sulfuric acid was mixed with the pyrolyzed biochar at a ratio of 15 ml: 1 g, and the mixture was stirred in an oil bath at 80℃ for 4 hours. The product was then filtered, the residue was washed with hot deionized water, and dried to obtain a biochar-based solid acid catalyst. 2.0 g of epoxy fatty acid methyl ester, 0.26 g of the biochar-based solid acid catalyst, and 2.5 g of 2-ethylhexanol were added according to an alcohol-to-oil molar ratio of 3:1. After thorough mixing, the mixture was stirred in an oil bath at 120℃ for 6 hours. After the reaction, the reaction mixture was filtered, washed with distilled water, and the water was removed by rotary evaporation to obtain branched-chain fatty acid methyl esters (methyl 9-(2-ethylhexoxy)-10-hydroxystearate and methyl 9-hydroxy-10-(2-ethylhexoxy)stearate).

[0037] Example 7:

[0038] Hemicellulose-removed corn cobs were pyrolyzed in a muffle furnace at 300℃ for 3 hours to obtain biochar. Concentrated sulfuric acid was mixed with the pyrolyzed biochar at a ratio of 15 ml: 1 g, and the mixture was stirred in an oil bath at 80℃ for 4 hours. The product was then filtered, the residue was washed with hot deionized water, and dried to obtain a biochar-based solid acid catalyst. 2.0 g of epoxy fatty acid methyl ester, 0.26 g of the biochar-based solid acid catalyst, and 5.8 g of 2-ethylhexanol were added according to an alcohol-to-oil molar ratio of 7:1. After thorough mixing, the mixture was stirred in an oil bath at 120℃ for 6 hours. After the reaction, the reaction mixture was filtered, washed with distilled water, and the water was removed by rotary evaporation to obtain branched-chain fatty acid methyl esters (methyl 9-(2-ethylhexoxy)-10-hydroxystearate and methyl 9-hydroxy-10-(2-ethylhexoxy)stearate).

[0039] Example 8:

[0040] Hemicellulose-removed corn cobs were pyrolyzed in a muffle furnace at 300℃ for 3 hours to obtain biochar. Concentrated sulfuric acid was mixed with the pyrolyzed biochar at a ratio of 15 ml: 1 g, and the mixture was stirred in an oil bath at 80℃ for 4 hours. The product was then filtered, the residue was washed with hot deionized water, and dried to obtain a biochar-based solid acid catalyst. 2.0 g of epoxy fatty acid methyl ester, 0.18 g of the biochar-based solid acid catalyst, and 3.5 g of 2-ethylhexanol were added at a 5:1 molar ratio of alcohol to oil. After thorough mixing, the mixture was stirred in an oil bath at 120℃ for 6 hours. After the reaction, the reaction mixture was filtered, washed with distilled water, and the water was removed by rotary evaporation to obtain branched-chain fatty acid methyl esters (methyl 9-(2-ethylhexoxy)-10-hydroxystearate and methyl 9-hydroxy-10-(2-ethylhexoxy)stearate).

[0041] Example 9:

[0042] Corn cobs with hemicellulose removed were pyrolyzed in a muffle furnace at 300℃ for 3 hours to obtain biochar. Concentrated sulfuric acid was mixed with the pyrolyzed biochar at a ratio of 15 ml: 1 g, and the mixture was stirred in an oil bath at 80℃ for 4 hours. The product was then filtered, the residue was washed with hot deionized water, and dried to obtain a biochar-based solid acid catalyst. 2.0 g of epoxy fatty acid methyl ester, 0.34 g of the biochar-based solid acid catalyst, and 3.5 g of 2-ethylhexanol were added at a 5:1 molar ratio of alcohol to oil. After thorough mixing, the mixture was stirred in an oil bath at 120℃ for 6 hours. After the reaction, the reaction mixture was filtered, washed with distilled water, and the water was removed by rotary evaporation to obtain branched-chain fatty acid methyl esters (methyl 9-(2-ethylhexoxy)-10-hydroxystearate and methyl 9-hydroxy-10-(2-ethylhexoxy)stearate).

[0043] Example 10:

[0044] Corn cobs with hemicellulose removed were pyrolyzed in a muffle furnace at 300℃ for 3 hours to obtain biochar. Concentrated sulfuric acid was mixed with the pyrolyzed biochar at a ratio of 15 ml: 1 g, and the mixture was stirred in an oil bath at 80℃ for 4 hours. The product was then filtered, the residue was washed with hot deionized water, and dried to obtain a biochar-based solid acid catalyst. 2.0 g of epoxy fatty acid methyl ester, 0.26 g of the biochar-based solid acid catalyst, and 3.5 g of 2-ethylhexanol were added at a 5:1 molar ratio of alcohol to oil. After thorough mixing, the mixture was stirred in an oil bath at 80℃ for 6 hours. After the reaction, the reaction mixture was filtered, washed with distilled water, and the water was removed by rotary evaporation to obtain branched-chain fatty acid methyl esters (methyl 9-(2-ethylhexoxy)-10-hydroxystearate and methyl 9-hydroxy-10-(2-ethylhexoxy)stearate).

[0045] Example 11:

[0046] Hemicellulose-removed corn cobs were pyrolyzed in a muffle furnace at 300℃ for 3 hours to obtain biochar. Concentrated sulfuric acid was mixed with the pyrolyzed biochar at a ratio of 15 ml: 1 g, and the mixture was stirred in an oil bath at 80℃ for 4 hours. The product was then filtered, the residue was washed with hot deionized water, and dried to obtain a biochar-based solid acid catalyst. 2.0 g of epoxy fatty acid methyl ester, 0.26 g of the biochar-based solid acid catalyst, and 3.5 g of 2-ethylhexanol were added according to an alcohol-to-oil molar ratio of 5:1. After thorough mixing, the mixture was stirred in an oil bath at 140℃ for 6 hours. After the reaction, the reaction mixture was filtered, washed with distilled water, and the water was removed by rotary evaporation to obtain branched-chain fatty acid methyl esters (methyl 9-(2-ethylhexoxy)-10-hydroxystearate and methyl 9-hydroxy-10-(2-ethylhexoxy)stearate).

[0047] Example 12:

[0048] Hemicellulose-removed corn cobs were pyrolyzed in a muffle furnace at 300℃ for 3 hours to obtain biochar. Concentrated sulfuric acid was mixed with the pyrolyzed biochar at a ratio of 15 ml: 1 g, and the mixture was stirred in an oil bath at 80℃ for 4 hours. The product was then filtered, the residue was washed with hot deionized water, and dried to obtain a biochar-based solid acid catalyst. 2.0 g of epoxy fatty acid methyl ester, 0.26 g of the biochar-based solid acid catalyst, and 3.5 g of 2-ethylhexanol were added according to an alcohol-to-oil molar ratio of 5:1. After thorough mixing, the mixture was stirred in an oil bath at 120℃ for 3 hours. After the reaction, the reaction mixture was filtered, washed with distilled water, and the water was removed by rotary evaporation to obtain branched-chain fatty acid methyl esters (methyl 9-(2-ethylhexoxy)-10-hydroxystearate and methyl 9-hydroxy-10-(2-ethylhexoxy)stearate).

[0049] Example 13:

[0050] Corn cobs with hemicellulose removed were pyrolyzed in a muffle furnace at 300℃ for 3 hours to obtain biochar. Concentrated sulfuric acid was mixed with the pyrolyzed biochar at a ratio of 15 ml: 1 g, and the mixture was stirred in an oil bath at 70℃ for 4 hours. The product was then filtered, the residue was washed with hot deionized water, and dried to obtain a biochar-based solid acid catalyst. 2.0 g of epoxy fatty acid methyl ester, 0.26 g of the biochar-based solid acid catalyst, and 3.5 g of 2-ethylhexanol were added according to an alcohol-to-oil molar ratio of 5:1. After thorough mixing, the mixture was stirred in an oil bath at 120℃ for 7 hours. After the reaction, the reaction mixture was filtered, washed with distilled water, and the water was removed by rotary evaporation to obtain branched-chain fatty acid methyl esters (methyl 9-(2-ethylhexoxy)-10-hydroxystearate and methyl 9-hydroxy-10-(2-ethylhexoxy)stearate).

[0051] The epoxy values ​​of the raw materials and products in Examples 1-13 were determined, and their conversion rates were calculated. The reaction selectivity of the reaction products was analyzed using a Shimadzu GC-2014 (DB-5 capillary column, FID detector). The reaction selectivity was calculated using formula (1). This reaction showed few side reactions and good selectivity. The determined reaction selectivity was >99%.

[0052]

[0053] In the formula:

[0054] X represents the amount of branched-chain fatty acid methyl ester;

[0055] X0 represents the amount of epoxidized fatty acid methyl ester.

[0056]

[0057] In addition to the embodiments described above, the present invention may have other implementations. All technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by the present invention.

Claims

1. A method for synthesizing branched-chain fatty acid methyl esters from epoxy fatty acid methyl esters catalyzed by sulfonated biochar, characterized in that... Using epoxidized fatty acid methyl ester as raw material and sulfonated biochar-based solid acid as catalyst, the catalyst, epoxidized fatty acid methyl ester, and C1-C10 alkyl alcohol are mixed evenly and stirred under oil bath heating to carry out an epoxidation ring-opening reaction. After the reaction, the catalyst is removed by filtration, and the filtrate is washed with distilled water and then evaporated by rotary evaporation to remove water and unreacted C1-C10 alkyl alcohol raw material, thereby obtaining the product branched fatty acid methyl ester; wherein, the epoxidation ring-opening reaction is as follows: ； In the formula, R is a C1-C10 alkyl group; The preparation method of the sulfonated biochar-based solid acid catalyst is as follows: biomass is placed in a muffle furnace and pyrolyzed in an air atmosphere to form biochar. Then, the biochar is immersed in concentrated sulfuric acid and heated and stirred to react with sulfonation. The product is washed with hot deionized water and dried to complete the preparation. The biomass is corn cob with hemicellulose removed. The pyrolysis temperature is 280-320℃, and the pyrolysis time is 2-4 hours. The concentrated sulfuric acid has a mass concentration of 95-98%, the sulfonation reaction temperature is 75-85℃, and the reaction time is 3-5 hours. The molar ratio of C1-C10 alkyl alcohols to epoxy fatty acid methyl esters is 3-7:1; the dosage of biochar-based solid acid catalyst is 11-15 wt% of the mass of epoxy fatty acid methyl esters.

2. The method for synthesizing branched-chain fatty acid methyl esters by catalysis of sulfonated biochar as described in claim 1, characterized in that... The molar ratio of C1-C10 alkyl alcohols to epoxy fatty acid methyl esters is 5:1; the amount of biochar-based solid acid catalyst added is 13% of the mass of epoxy fatty acid methyl esters.

3. The method for synthesizing branched-chain fatty acid methyl esters by catalysis of sulfonated biochar as described in claim 1, characterized in that... The reaction temperature for the epoxy ring-opening reaction is 80-140℃, and the reaction time is 3-7h.

4. The method for synthesizing branched-chain fatty acid methyl esters by catalysis of sulfonated biochar as described in claim 3, characterized in that... The reaction temperature for the epoxy ring-opening reaction is 120℃, and the reaction time is 6 hours.

5. The method for synthesizing branched-chain fatty acid methyl esters by catalysis of sulfonated biochar as described in claim 1, characterized in that... The C1-C10 alkyl alcohol is 2-ethylhexanol or 1-butanol.

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