Process and operation steps of preparing fatty acid from methyl ester

Fatty acid methyl ester is the raw material of widely used surfactant (SAA). Two kinds of surfactants can be produced from fatty acid methyl ester, one is to produce fatty acid methyl ester sulfonate (MES) through sulfonation and neutralization, and the other is to produce fatty alcohol through hydrogenation. 57% of fatty alcohols in the world are produced by fatty acid methyl esters, and 43% are produced by fatty acids. Alcohol ether (AE) is produced by ethoxylation of fatty alcohol, and alcohol ether sulfate (AES) is produced by sulfonation and neutralization of AE. Fatty alcohol can also be sulfonated and neutralized to produce primary alkyl sulfate (PAS). Therefore, fatty acid methyl ester is the raw material and intermediate of SAA such as MES, AE, AES and PAS. The supply of oil, fatty alcohol, fatty acid methyl ester and other raw materials determines the efficiency of SAA production. The production of fatty acid methyl esters is very important for the industrial production of fatty acid derivatives, because most of fatty acid methyl esters are used as intermediate raw materials for the production of many oil chemical products, such as alkanolamide, sucrose ester, etc. The production of fatty acid methyl esters in the world from 1970 to 2000 is shown in Table 1. Table 1 World production of fatty acid methyl esters from 1970 to 2000 [1] (10000 tons) countries or regions from 1970 to 1988 from 1995 to 2000 from the United States - 11 17.519 Western Europe - 18 21.524 Asia - 17 18 20 other countries and regions - 22.53, a total of 18 48 59.566 From Table 1, it can be seen that the average annual growth rate of world fatty acid methyl esters from 1970 to 1988 was 4.2%. It is predicted that the growth rate will reach 4.7% in the future. In recent years, fatty acid methyl esters have made new progress in the production process, in the preparation of non-ionic surfactants and anionic surfactants, and in the saponification process. The author will mainly introduce the new method of methyl ester saponification, the new process of MES production, the new development of methyl ester ethoxylation to ether ester n-SAA and the catalytic amination of methyl ester to fatty amine. 1. There are three methods to produce soap base (65%~70% anhydrous soap) by methyl ester saponification method (ES method): fat direct saponification method, fatty acid neutralization and fatty acid methyl ester saponification. The first two methods are commonly used in the soap industry. The production of soap by methyl ester method is the latest technology at present, and high-quality soap can be obtained [2]. The new process flow of ES method is shown in Figure 1. This method includes: pre-esterification of free fatty acids; Transesterification of oil; Saponification of methyl ester and recovery of glycerol and methanol. The chemical reactions in each step are as follows: (1) esterification reaction RCOOH+CH3OH → RCOOCH3+H2O (2) transesterification reaction (3) saponification reaction RCOOCH3+NaOH → RCOONa+CH3OH 1 - esterification tower; 2 - transesterification tower; 3 - Separator; 4 - saponification unit separator; 5 - Methanol recovery unit; 6 - Purification tower. Fig. 1 Process flow diagram of ES method. 1.1 Esterified oil containing free fatty acid will inhibit the catalytic action of alkali in the next esterification process, so the free fatty acid will be converted into methyl ester by esterification method. The process is characterized by the use of special resin as catalyst. The grease containing free fatty acid is mixed with methanol and converted into methyl ester continuously through a packed column containing resin catalyst. The low temperature reaction at 60 ℃ prevents the degradation of raw oil. The use of fixed bed catalytic reaction eliminates the necessary procedures for catalyst filtration and separation. 1.2 Ester exchange reaction of oils and fats The pretreated oils and fats are combined with methanol, and a small amount of NaOH is added as a catalyst. The ester exchange reaction is carried out at 60 ℃ and normal pressure, which can produce methyl ester. Due to the chemical balance, the conversion rate of oil to methyl ester in one-step method is only 96%. When the chemical equilibrium is removed, a two-step reaction is adopted, that is, the glycerol generated in the initial reaction is continuously removed through a specially designed separator, so that the transesterification reaction continues, and the conversion rate can reach more than 99%. On the other hand, soap is generated due to the action of alkali catalyst. Pigment and other impurities are mixed in a small amount of soap to produce a dark brown separation layer, which is separated from the ester layer during the separation operation. Through this refining, light-colored methyl ester can be obtained with high conversion. The transesterification reaction is the most important step in the methyl ester saponification process. 1.3 Saponification reaction of fatty acid methyl ester Add methyl ester and alkali solution in a constant proportion to the saponifier, and react quickly at 100 ℃. The methanol regenerated in the reaction is recovered in the alcohol recovery unit, and the saponification rate of this method is up to 99%. A pure soap is thus prepared. 1.4 Glycerol/methanol recovery The lower layer discharged from the separator contains methanol, glycerin, soap and water. The methanol is recovered in the methanol recovery tower, and the waste water discharged is sweet water. This sweet water is treated with sulfuric acid to obtain 70% crude glycerol, and the dark oil layer produced is accumulated with impurities. Dark oil layer is used to make low-grade soap, and the recovered methanol needs to be distilled and reused. The advantage of ES method is that methyl ester/soap with good color can be prepared with high yield. Due to the low processing temperature, the degradation of oil and methyl ester and the refining of methyl ester during the transesterification reaction are prevented, so the quality of soap is stable. The recovered glycerol has a high mass fraction (more than 70%) and a high yield. No corrosion to equipment. When methyl ester is used as an intermediate, it is stable in the storage tank, has low melting point and is easier to handle than fatty acids. 2　 α- Sulfonate（ α- SF) New production process α- As a detergent raw material, SF has excellent characteristics such as hard water resistance, emulsification and solubilization, biodegradability and so on, and soon attracted the attention of detergent manufacturers worldwide. C18, C12 and C16 saturated fatty acid methyl esters obtained from butter, coconut oil and palm oil were selected. The reaction mechanism and preparation methods have been developed for a long time. but α- SF has never been used as the main SAA like LAS and AS. The reason is that it is difficult to realize industrial scale production with good color and few side reactions. In view of the above problems, Lion Company of Japan recently proposed to solve industrial production α- SF should take the following technical measures [3]: ① Use a membrane isothermal (TO) reactor to make the sulfonation reaction mild. ② Apply new bleaching technology, improve color and inhibit side reaction products（ α- Disodium sulfonate). ③ In the production process of granular detergent, it can be inhibited by combining with ultra-concentrated detergent α- SF hydrolyzed into α- Disodium sulfonate. 2.1 The sulfonation reaction of fatty acid methyl ester is first added to 1mol SO3, and then α After further addition of SO3 at position, after the intermediate composed of 2 mol SO3 and 1 mol ester, the initial addition of 1 mol SO3 is removed to obtain α- SF。 The SO3 removal step is the reaction rate control step. If the ester is 1mol, SO31.1~1.5mol or slightly excess is required. In order to make the reaction complete, membrane reactor is used. The sulfonation reaction of methyl ester is characterized by significant coloring of the sulfonate. In order to make the reaction mild and uniform, and to obtain products with good color, bleaching is required after sulfonation. 2.2 The TO isothermal reactor with mild and uniform sulfonation reaction is characterized by: ① introducing an air curtain between the liquid film and SO3 gas, that is, in the later stage of the reaction of SO3 and air mixture, introducing cold air (or non-active gas that can be cooled) from another inlet, the amount of which is 2 to 12 times the amount of SO3 and air mixture, and absorbing the reaction heat in parallel flow to control the diffusion rate of SO3 gas; ② The liquid film thickness is uniform through non-continuous trough distributor to reach the maximum temperature at the initial stage of the reaction, so that the reaction can be carried out isothermal, and the product with good color can be obtained. In order to prevent color deterioration, the reaction conditions in the tubular reactor can be improved. The key is how to make the liquid membrane reaction in the first stage mild and uniform. α- The TO reactor used in SF sulfonation reaction can reduce the deterioration of color and significantly inhibit the formation of trace impurities during high-temperature reaction. 2.3 The new technology of esterification and bleaching at the same time usually uses sodium hypochlorite and hydrogen peroxide as surfactants, but α- In SF, not only the bleaching is not sufficient, but also about 70% of the water soluble and cleaning performance is not ideal due to the end ester bond breaking α- SF disodium salt by-product. Lion Company of Japan has developed a bleaching technology in the presence of excessive methanol. When hydrogen peroxide and methanol are added at the same time, the ester bond is not broken, and the bleaching effect is significantly improved than before α- SF has the same good color as LAS and AOS. It can be considered that after the application of this esterification simultaneous bleaching method and new bleaching technology, industrial scale production α- SF becomes possible. The methanol used in the bleaching process will also help to reduce the α- The viscosity of SF prevents hydrolysis due to excessive alkali α- Disodium sulfonate, producing high concentration α- Sulfonate. 2.4 Inhibition of hydrolysis in detergent production α- SF is generated by hydrolysis in the presence of alkali α- SF disodium salt. Will α- SF and concentrated detergent are spray in the spray drying tower, although they have certain hydrolysis inhibition effect, it is difficult to make products and hydrolysis occurs due to moisture absorption. In order to prevent subsequent hydrolysis, it is necessary to increase the relative density of detergent particles. The spray drying particles are hollow and thin spheres. In recent years, the concentrated laundry powder, which is dominant in the world, has a full interior. Because of its small surface area per unit weight, the moisture absorption rate is reduced to 1/5, which can basically inhibit hydrolysis. From 1953, Weil et al α- After more than 40 years of research and development, SF was finally developed by Lion Corporation of Japan in 1991 α- The granular detergent with SF as the main component was officially put into production. 　　 α- SF is based on renewable natural resources as the initial raw material α- SF also has washing power at low concentration, so the amount of detergent used in production can be reduced than before. In addition, facing the 21st century, considering resources and environmental protection, α- SF has a bright application prospect [4]. Preparation of new n-SAA ethoxylated fatty acid methyl ester by ethoxylation of fatty acid methyl ester is a known ether-ester n-SAA. For example, ethoxylated stearic acid stearic ester is used as emulsifier, dispersant or oil phase regulator in cosmetics and industrial products. Ethoxylated methyl laurate is used as a wetting agent. Alcohol ethoxylates and fatty acid ethoxylates are typical ethylene oxide (EO) - based n-SAA, which can be easily obtained by directly reacting with EO through one of the active hydrogen in its molecule in the presence of alkaline or acidic catalysts, but these catalysts cannot be directly reacted with fatty acid methyl esters without active hydrogen. Two common methods for the synthesis of ethoxylated fatty acid methyl ester (EFMe) are known. One method is to synthesize EFMe through ethylene glycol and methyl ester. Another method is to synthesize EFMe through fatty acid ethoxylate. These two methods require two steps of reaction at high temperature/high pressure, and produce a large number of by-products, such as diester and PEG. If a new synthetic method is developed to directly add EO to fatty acid methyl ester, EFMen-SAA can be easily obtained from natural oils. The author introduces a new method of producing EFMe using a new solid catalyst and the properties of EFMe obtained by this method [5]. Preparation method: put methyl laurate and catalyst into a stainless steel autoclave with stirring, and replace the air in the autoclave with nitrogen. The mixture is heated to 180 ℃ under stirring, and EO is added to the autoclave under atmospheric pressure. The temperature is kept at 180 ℃ and the pressure is 0.3MPa. Stop feeding when the required amount of EO is added. EFMe is obtained by aging, cooling, filtering and removing catalyst. Recently, ethoxylates with narrow EO distribution and some new catalysts have been developed. Catalysts suitable for the ethoxylation of fatty acids have been used for the ethoxylation of fatty acid methyl esters. The modified magnesium oxide catalyst has sufficient reactivity to improve the direct addition of fatty acid methyl ester without active hydrogen to EO. The amount of unreacted fatty acid methyl ester depends on the average EO addition number and decreases with the increase of EO addition number. EFMe is almost uniform monoester obtained by the new synthesis method. The properties of EFMe as n-SAA are shown in Table 3. Table 3 EFMe characteristics EFMe methyl laurate BRE1) average EO addition number of lauryl alcohol 6 10 15 6 hydrophile-lipophilic equilibrium 11 13 15 11 critical micelle concentration (25 ℃)/(mol. L-1) 10-210-210-210-210-2 10-2 surface tension（ × 10-5, 25 ℃)/(N.cm-1) 30 31 32 35 wetting force (25 ℃)/(S.min-1) 9 10 14 10 solubilization（ × 10-6, 25 ℃) 21 17 12 6 foam (25 ℃, start)/mm 40 63 79 foam (25 ℃, 5min later)/mm 16 25 50 55 1) is a general alcohol ethoxylate. From the comparison of EO distribution characteristics of methyl ethoxylaurate (C12. Me-nEO) and ethoxylauryl alcohol (C12OH. 6EO) in Table 3, it can be seen that the critical micelle concentration, surface tension and wetting force of EFMe are almost identical with BRE. The starting compounds of amination of fatty acid methyl ester to primary amine and tertiary amine amination are different, and the requirements for catalyst performance are very different. At present, among the various process routes for the preparation of fatty amines, the most competitive and difficult is the atmospheric catalytic amination route of methyl ester. At present, France has conquered this route - the high-pressure catalytic amination process route, but no company in the world can completely overcome the technical problem of atmospheric catalytic amination of methyl ester. It is reported that the conversion rate of atmospheric catalytic amination is only about 40%. On the basis of experimental exploration and combined with the preparation experience of branched chain alcohol catalytic amination catalyst, China has obtained a catalytic amination conversion of 73% under atmospheric pressure, and has made good progress. However, there is still a large gap between this achievement and the level of industrialization [6]. In foreign countries, the catalytic amination of fatty acid methyl ester to produce primary amine and tertiary amine in one step is carried out under a certain pressure: this method can obtain primary amine or tertiary amine in one step, but there has not been any report of industrialization. Recently, there are reports of a two-step method to produce primary amine and secondary amine from methyl ester as raw material by generating fatty nitrile and then hydrogenation [7]. The reaction formula is as follows: its process flow is shown in Figure 2. Figure 2 Schematic diagram of the two-step process flow of methyl ester ammoniation and hydrogenation to produce C22 primary amine The yield of C22 nitrile hydrogenation to C22 primary amine increases with the increase of catalyst dosage, ammonia partial pressure and water dosage. The general dosage is controlled at 0.5%~2.5%, the hydrogen pressure is 1.6~4.0 MPa, and the ammonia pressure is 1.2~2.0 MPa; The mass fraction of C22 nitrile is between 90% and 95%, and the final mass fraction of C22 primary amine product can reach more than 98%. Advanced fatty amines are widely used in industry and high-tech industries. In particular, saturated C22 primary amine has special effect as anti-corrosion and anti-algae adhesion agent on marine ships. It can be used as antifriction agent for secondary rotation of nuclear power plant in the atomic energy industry. 5 Conclusion Before the era of "synthetic detergent", natural oil was closely related to the oldest and widely used anionic surfactant soap. Due to the development of oil chemistry and the development of many SAA production processes, the use of fatty acid methyl ester intermediate products to produce SAA and soap from oil has opened up an effective way with higher added value for the production of SAA products. The boiling point of methyl ester is lower than that of corresponding fatty acids (30 ℃ lower on average), so the energy consumption can be reduced when methyl ester is distilled. In addition, the chemical stability of methyl ester is better than that of fatty acid, especially the color is not easy to change when heating, and it is also very stable to oxidation, and methyl ester is less corrosive than fatty acid. Therefore, not only is fatty acid methyl ester suitable as the raw material of SAA, but also the development and application of fatty acid methyl ester based SAA will become increasingly important in the future.

Donald Montecalvo Follow

Fatty acid methyl ester is the raw material of widely used surfactant (SAA). Two kinds of surfactants can be produced from fatty acid methyl ester, one is to produce fatty acid methyl ester sulfonate (MES) through sulfonation and neutralization, and the other is to produce fatty alcohol through hydrogenation. 57% of fatty alcohols in the world are produced by fatty acid methyl esters, and 43% are produced by fatty acids. Alcohol ether (AE) is produced by ethoxylation of fatty alcohol, and alcohol ether sulfate (AES) is produced by sulfonation and neutralization of AE. Fatty alcohol can also be sulfonated and neutralized to produce primary alkyl sulfate (PAS). Therefore, fatty acid methyl ester is the raw material and intermediate of SAA such as MES, AE, AES and PAS. The supply of oil, fatty alcohol, fatty acid methyl ester and other raw materials determines the efficiency of SAA production. The production of fatty acid methyl esters is very important for the industrial production of fatty acid derivatives, because most of fatty acid methyl esters are used as intermediate raw materials for the production of many oil chemical products, such as alkanolamide, sucrose ester, etc. The production of fatty acid methyl esters in the world from 1970 to 2000 is shown in Table 1. Table 1 World production of fatty acid methyl esters from 1970 to 2000 [1] (10000 tons) countries or regions from 1970 to 1988 from 1995 to 2000 from the United States - 11 17.519 Western Europe - 18 21.524 Asia - 17 18 20 other countries and regions - 22.53, a total of 18 48 59.566 From Table 1, it can be seen that the average annual growth rate of world fatty acid methyl esters from 1970 to 1988 was 4.2%. It is predicted that the growth rate will reach 4.7% in the future. In recent years, fatty acid methyl esters have made new progress in the production process, in the preparation of non-ionic surfactants and anionic surfactants, and in the saponification process. The author will mainly introduce the new method of methyl ester saponification, the new process of MES production, the new development of methyl ester ethoxylation to ether ester n-SAA and the catalytic amination of methyl ester to fatty amine. 1. There are three methods to produce soap base (65%~70% anhydrous soap) by methyl ester saponification method (ES method): fat direct saponification method, fatty acid neutralization and fatty acid methyl ester saponification. The first two methods are commonly used in the soap industry. The production of soap by methyl ester method is the latest technology at present, and high-quality soap can be obtained [2]. The new process flow of ES method is shown in Figure 1. This method includes: pre-esterification of free fatty acids; Transesterification of oil; Saponification of methyl ester and recovery of glycerol and methanol. The chemical reactions in each step are as follows: (1) esterification reaction RCOOH+CH3OH → RCOOCH3+H2O (2) transesterification reaction (3) saponification reaction RCOOCH3+NaOH → RCOONa+CH3OH 1 - esterification tower; 2 - transesterification tower; 3 - Separator; 4 - saponification unit separator; 5 - Methanol recovery unit; 6 - Purification tower. Fig. 1 Process flow diagram of ES method. 1.1 Esterified oil containing free fatty acid will inhibit the catalytic action of alkali in the next esterification process, so the free fatty acid will be converted into methyl ester by esterification method. The process is characterized by the use of special resin as catalyst. The grease containing free fatty acid is mixed with methanol and converted into methyl ester continuously through a packed column containing resin catalyst. The low temperature reaction at 60 ℃ prevents the degradation of raw oil. The use of fixed bed catalytic reaction eliminates the necessary procedures for catalyst filtration and separation. 1.2 Ester exchange reaction of oils and fats The pretreated oils and fats are combined with methanol, and a small amount of NaOH is added as a catalyst. The ester exchange reaction is carried out at 60 ℃ and normal pressure, which can produce methyl ester. Due to the chemical balance, the conversion rate of oil to methyl ester in one-step method is only 96%. When the chemical equilibrium is removed, a two-step reaction is adopted, that is, the glycerol generated in the initial reaction is continuously removed through a specially designed separator, so that the transesterification reaction continues, and the conversion rate can reach more than 99%. On the other hand, soap is generated due to the action of alkali catalyst. Pigment and other impurities are mixed in a small amount of soap to produce a dark brown separation layer, which is separated from the ester layer during the separation operation. Through this refining, light-colored methyl ester can be obtained with high conversion. The transesterification reaction is the most important step in the methyl ester saponification process. 1.3 Saponification reaction of fatty acid methyl ester Add methyl ester and alkali solution in a constant proportion to the saponifier, and react quickly at 100 ℃. The methanol regenerated in the reaction is recovered in the alcohol recovery unit, and the saponification rate of this method is up to 99%. A pure soap is thus prepared. 1.4 Glycerol/methanol recovery The lower layer discharged from the separator contains methanol, glycerin, soap and water. The methanol is recovered in the methanol recovery tower, and the waste water discharged is sweet water. This sweet water is treated with sulfuric acid to obtain 70% crude glycerol, and the dark oil layer produced is accumulated with impurities. Dark oil layer is used to make low-grade soap, and the recovered methanol needs to be distilled and reused. The advantage of ES method is that methyl ester/soap with good color can be prepared with high yield. Due to the low processing temperature, the degradation of oil and methyl ester and the refining of methyl ester during the transesterification reaction are prevented, so the quality of soap is stable. The recovered glycerol has a high mass fraction (more than 70%) and a high yield. No corrosion to equipment. When methyl ester is used as an intermediate, it is stable in the storage tank, has low melting point and is easier to handle than fatty acids. 2　 α- Sulfonate（ α- SF) New production process α- As a detergent raw material, SF has excellent characteristics such as hard water resistance, emulsification and solubilization, biodegradability and so on, and soon attracted the attention of detergent manufacturers worldwide. C18, C12 and C16 saturated fatty acid methyl esters obtained from butter, coconut oil and palm oil were selected. The reaction mechanism and preparation methods have been developed for a long time. but α- SF has never been used as the main SAA like LAS and AS. The reason is that it is difficult to realize industrial scale production with good color and few side reactions. In view of the above problems, Lion Company of Japan recently proposed to solve industrial production α- SF should take the following technical measures [3]: ① Use a membrane isothermal (TO) reactor to make the sulfonation reaction mild. ② Apply new bleaching technology, improve color and inhibit side reaction products（ α- Disodium sulfonate). ③ In the production process of granular detergent, it can be inhibited by combining with ultra-concentrated detergent α- SF hydrolyzed into α- Disodium sulfonate. 2.1 The sulfonation reaction of fatty acid methyl ester is first added to 1mol SO3, and then α After further addition of SO3 at position, after the intermediate composed of 2 mol SO3 and 1 mol ester, the initial addition of 1 mol SO3 is removed to obtain α- SF。 The SO3 removal step is the reaction rate control step. If the ester is 1mol, SO31.1~1.5mol or slightly excess is required. In order to make the reaction complete, membrane reactor is used. The sulfonation reaction of methyl ester is characterized by significant coloring of the sulfonate. In order to make the reaction mild and uniform, and to obtain products with good color, bleaching is required after sulfonation. 2.2 The TO isothermal reactor with mild and uniform sulfonation reaction is characterized by: ① introducing an air curtain between the liquid film and SO3 gas, that is, in the later stage of the reaction of SO3 and air mixture, introducing cold air (or non-active gas that can be cooled) from another inlet, the amount of which is 2 to 12 times the amount of SO3 and air mixture, and absorbing the reaction heat in parallel flow to control the diffusion rate of SO3 gas; ② The liquid film thickness is uniform through non-continuous trough distributor to reach the maximum temperature at the initial stage of the reaction, so that the reaction can be carried out isothermal, and the product with good color can be obtained. In order to prevent color deterioration, the reaction conditions in the tubular reactor can be improved. The key is how to make the liquid membrane reaction in the first stage mild and uniform. α- The TO reactor used in SF sulfonation reaction can reduce the deterioration of color and significantly inhibit the formation of trace impurities during high-temperature reaction. 2.3 The new technology of esterification and bleaching at the same time usually uses sodium hypochlorite and hydrogen peroxide as surfactants, but α- In SF, not only the bleaching is not sufficient, but also about 70% of the water soluble and cleaning performance is not ideal due to the end ester bond breaking α- SF disodium salt by-product. Lion Company of Japan has developed a bleaching technology in the presence of excessive methanol. When hydrogen peroxide and methanol are added at the same time, the ester bond is not broken, and the bleaching effect is significantly improved than before α- SF has the same good color as LAS and AOS. It can be considered that after the application of this esterification simultaneous bleaching method and new bleaching technology, industrial scale production α- SF becomes possible. The methanol used in the bleaching process will also help to reduce the α- The viscosity of SF prevents hydrolysis due to excessive alkali α- Disodium sulfonate, producing high concentration α- Sulfonate. 2.4 Inhibition of hydrolysis in detergent production α- SF is generated by hydrolysis in the presence of alkali α- SF disodium salt. Will α- SF and concentrated detergent are spray in the spray drying tower, although they have certain hydrolysis inhibition effect, it is difficult to make products and hydrolysis occurs due to moisture absorption. In order to prevent subsequent hydrolysis, it is necessary to increase the relative density of detergent particles. The spray drying particles are hollow and thin spheres. In recent years, the concentrated laundry powder, which is dominant in the world, has a full interior. Because of its small surface area per unit weight, the moisture absorption rate is reduced to 1/5, which can basically inhibit hydrolysis. From 1953, Weil et al α- After more than 40 years of research and development, SF was finally developed by Lion Corporation of Japan in 1991 α- The granular detergent with SF as the main component was officially put into production. 　　 α- SF is based on renewable natural resources as the initial raw material α- SF also has washing power at low concentration, so the amount of detergent used in production can be reduced than before. In addition, facing the 21st century, considering resources and environmental protection, α- SF has a bright application prospect [4]. Preparation of new n-SAA ethoxylated fatty acid methyl ester by ethoxylation of fatty acid methyl ester is a known ether-ester n-SAA. For example, ethoxylated stearic acid stearic ester is used as emulsifier, dispersant or oil phase regulator in cosmetics and industrial products. Ethoxylated methyl laurate is used as a wetting agent. Alcohol ethoxylates and fatty acid ethoxylates are typical ethylene oxide (EO) - based n-SAA, which can be easily obtained by directly reacting with EO through one of the active hydrogen in its molecule in the presence of alkaline or acidic catalysts, but these catalysts cannot be directly reacted with fatty acid methyl esters without active hydrogen. Two common methods for the synthesis of ethoxylated fatty acid methyl ester (EFMe) are known. One method is to synthesize EFMe through ethylene glycol and methyl ester. Another method is to synthesize EFMe through fatty acid ethoxylate. These two methods require two steps of reaction at high temperature/high pressure, and produce a large number of by-products, such as diester and PEG. If a new synthetic method is developed to directly add EO to fatty acid methyl ester, EFMen-SAA can be easily obtained from natural oils. The author introduces a new method of producing EFMe using a new solid catalyst and the properties of EFMe obtained by this method [5]. Preparation method: put methyl laurate and catalyst into a stainless steel autoclave with stirring, and replace the air in the autoclave with nitrogen. The mixture is heated to 180 ℃ under stirring, and EO is added to the autoclave under atmospheric pressure. The temperature is kept at 180 ℃ and the pressure is 0.3MPa. Stop feeding when the required amount of EO is added. EFMe is obtained by aging, cooling, filtering and removing catalyst. Recently, ethoxylates with narrow EO distribution and some new catalysts have been developed. Catalysts suitable for the ethoxylation of fatty acids have been used for the ethoxylation of fatty acid methyl esters. The modified magnesium oxide catalyst has sufficient reactivity to improve the direct addition of fatty acid methyl ester without active hydrogen to EO. The amount of unreacted fatty acid methyl ester depends on the average EO addition number and decreases with the increase of EO addition number. EFMe is almost uniform monoester obtained by the new synthesis method. The properties of EFMe as n-SAA are shown in Table 3. Table 3 EFMe characteristics EFMe methyl laurate BRE1) average EO addition number of lauryl alcohol 6 10 15 6 hydrophile-lipophilic equilibrium 11 13 15 11 critical micelle concentration (25 ℃)/(mol. L-1) 10-210-210-210-210-2 10-2 surface tension（ × 10-5, 25 ℃)/(N.cm-1) 30 31 32 35 wetting force (25 ℃)/(S.min-1) 9 10 14 10 solubilization（ × 10-6, 25 ℃) 21 17 12 6 foam (25 ℃, start)/mm 40 63 79 foam (25 ℃, 5min later)/mm 16 25 50 55 1) is a general alcohol ethoxylate. From the comparison of EO distribution characteristics of methyl ethoxylaurate (C12. Me-nEO) and ethoxylauryl alcohol (C12OH. 6EO) in Table 3, it can be seen that the critical micelle concentration, surface tension and wetting force of EFMe are almost identical with BRE. The starting compounds of amination of fatty acid methyl ester to primary amine and tertiary amine amination are different, and the requirements for catalyst performance are very different. At present, among the various process routes for the preparation of fatty amines, the most competitive and difficult is the atmospheric catalytic amination route of methyl ester. At present, France has conquered this route - the high-pressure catalytic amination process route, but no company in the world can completely overcome the technical problem of atmospheric catalytic amination of methyl ester. It is reported that the conversion rate of atmospheric catalytic amination is only about 40%. On the basis of experimental exploration and combined with the preparation experience of branched chain alcohol catalytic amination catalyst, China has obtained a catalytic amination conversion of 73% under atmospheric pressure, and has made good progress. However, there is still a large gap between this achievement and the level of industrialization [6]. In foreign countries, the catalytic amination of fatty acid methyl ester to produce primary amine and tertiary amine in one step is carried out under a certain pressure: this method can obtain primary amine or tertiary amine in one step, but there has not been any report of industrialization. Recently, there are reports of a two-step method to produce primary amine and secondary amine from methyl ester as raw material by generating fatty nitrile and then hydrogenation [7]. The reaction formula is as follows: its process flow is shown in Figure 2. Figure 2 Schematic diagram of the two-step process flow of methyl ester ammoniation and hydrogenation to produce C22 primary amine The yield of C22 nitrile hydrogenation to C22 primary amine increases with the increase of catalyst dosage, ammonia partial pressure and water dosage. The general dosage is controlled at 0.5%~2.5%, the hydrogen pressure is 1.6~4.0 MPa, and the ammonia pressure is 1.2~2.0 MPa; The mass fraction of C22 nitrile is between 90% and 95%, and the final mass fraction of C22 primary amine product can reach more than 98%. Advanced fatty amines are widely used in industry and high-tech industries. In particular, saturated C22 primary amine has special effect as anti-corrosion and anti-algae adhesion agent on marine ships. It can be used as antifriction agent for secondary rotation of nuclear power plant in the atomic energy industry. 5 Conclusion Before the era of "synthetic detergent", natural oil was closely related to the oldest and widely used anionic surfactant soap. Due to the development of oil chemistry and the development of many SAA production processes, the use of fatty acid methyl ester intermediate products to produce SAA and soap from oil has opened up an effective way with higher added value for the production of SAA products. The boiling point of methyl ester is lower than that of corresponding fatty acids (30 ℃ lower on average), so the energy consumption can be reduced when methyl ester is distilled. In addition, the chemical stability of methyl ester is better than that of fatty acid, especially the color is not easy to change when heating, and it is also very stable to oxidation, and methyl ester is less corrosive than fatty acid. Therefore, not only is fatty acid methyl ester suitable as the raw material of SAA, but also the development and application of fatty acid methyl ester based SAA will become increasingly important in the future.More

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